Hanwha Solutions Corporation v REC Solar Pte Ltd
[2023] FCA 1017
•29 August 2023
FEDERAL COURT OF AUSTRALIA
Hanwha Solutions Corporation v REC Solar Pte Ltd [2023] FCA 1017
File number(s): NSD 458 of 2019 Judgment of: BURLEY J Date of judgment: 29 August 2023 Catchwords: PATENTS – patent for method for manufacturing a solar cell with a surface-passivating dielectric double layer, and corresponding solar cell – infringement – validity – claim construction
PATENTS – infringement – construction of method and product claims – no infringement found
PATENTS – validity – lack of inventive step – ss 7(2) and (3) of the Patents Act 1990 (Cth) – ground not established
PATENTS – validity – lack of fair basis – legal test – claims fairly based
PATENTS – validity – novelty – whether prior publications being patent applications and a patent anticipated claimed invention – claims 9, 11, 16 and 21 of the patent anticipated
PATENTS – validity – lack of utility – promise of the invention – whether promises met – ground not established
PATENTS – validity – lack of clarity – ground not established
PATENTS – unjustified threats – whether applicant made unjustified threats of patent infringement in breach of s 128 of the Patents Act – ground established in relation to letters of demand
CONSUMER LAW – misleading and deceptive conduct – whether respondents contravened s 18 of the Australian Consumer Law by representing that the accused products do not infringe any intellectual property rights and that the respondents are legally entitled to sell, and third parties are entitled to purchase, install and use those products – dismissed
Legislation: Competition and Consumer Act 2010 (Cth), sch 2 (Australian Consumer Law)
Intellectual Property Laws Amendment (Raising the Bar) Act 2012 (Cth)
Patents Amendment Act 2000 (Cth)
Patents Act1990 (Cth) ss 7(1), 7(2), 7(3), 18(1)(b), 18(1)(c), 40(3), 43(2), 128, sch 1 definition of “prior art base”
Evidence Act 1995 (Cth) s 136
Cases cited: Aktiebolaget Hässle v Alphapharm Pty Limited [2002] HCA 59; 212 CLR 411
Allsop Inc v Bintang Ltd [1989] FCA 428; 15 IPR 686
Apotex Pty Ltd v ICOS Corporation (No 3) [2018] FCA 1204; 135 IPR 13
Aristocrat Technologies Australia Pty Limited v Konami Australia Pty Limited [2015] FCA 735; 114 IPR 28
AstraZeneca AB v Apotex Pty Ltd [2014] FCAFC 99; 226 FCR 324
AstraZeneca AB v Apotex Pty Ltd [2015] HCA 30; 257 CLR 356
Atlantis Corporation Pty Ltd v Schindler [1997] FCA 1105; 39 IPR 29
Australian Mud Company Pty Ltd v Globaltech Corp Pty Ltd [2018] FCA 1839; 138 IPR 33
Brugger v Medic-Aid Ltd [1996] WLUK 122; RPC 635
Catnic Components v Hill & Smith Ltd [1982] RPC 183
CCOM Pty Ltd v Jeijing Pty Ltd [1994] FCA 396; 51 FCR 260
Commissioner of Patents v Emperor Sports Ltd [2006] FCAFC 26; 149 FCR 386
Electric & Musical Industries Ltd v Lissen Ltd (1939) 56 RPC 23
Flexible Steel Lacing v Beltreco [2000] FCA 890; 49 IPR 331
Flour Oxidizing Company Ltd v Carr & Co Ltd [1908] 25 RPC 428
Fresenius Medical Care Australia Pty Ltd v Gambro Pty Ltd [2005] FCAFC 220; 67 IPR 230
General Tire & Rubber Co Ltd v Firestone Tyre & Rubber Co Ltd [1971] 7 WLUK 130; [1972] RPC 457
Generic Health Pty Ltd v Bayer Pharma Aktiengesellschaft [2014] FCAFC 73; 222 FCR 336
GM Global Technology Operations LLC v S.S.S. Auto Parts Pty Ltd [2019] FCA 97; 371 ALR 1
Idenix Pharmaceuticals LLC v Gilead Sciences Pty Ltd [2017] FCAFC 196; 134 IPR 1
Insta Image Pty Ltd v KD Kanopy Australasia Pty Ltd [2008] FCAFC 139; 239 FCR 117
Jupiters Ltd v Neurizon Pty Ltd [2005] FCAFC 90; 65 IPR 86
Kauzal v Lee [1936] HCA 39; 58 CLR 670
Lido Manufacturing Co Pty Ltd v Meyers & Leslie Pty Ltd (1964) 5 FLR 443
Lockwood Security Products Pty Ltd v Doric Products Pty Ltd (No 2) [2007] HCA 21; 235 CLR 173
Lockwood Security Products Pty Ltd v Doric Products Pty Ltd [2004] HCA 58; 217 CLR 274
Merck Sharp & Dohme Corporation v Wyeth LLC (No 3) [2020] FCA 1477; 155 IPR 1
Meyers Taylor Pty Ltd v Vicarr Industries Ltd [1977] HCA 19; 137 CLR 228
NichiaCorporation v Arrow Electronics Australia Pty Ltd [2019] FCAFC 2
Olin Corporation v Super Cartridge Co Pty Ltd [1977] HCA 23; 180 CLR 236
Olin Mathieson Chemical Corporation v Biorex Laboratories Ltd [1970] RPC 157
Pharmacia LLC v Juno Pharmaceuticals Pty Ltd [2022] FCA 92; 165 IPR 200
R D Werner & Co Inc v Bailey Aluminium Products Pty Ltd [1989] FCA 57; 25 FCR 565
Radiation Limited v Galliers and Klaerr Pty Ltd [1938] HCA 17; 60 CLR 36
Rodi & Wienenberger AG v Henry Showell Ltd [1969] RPC 367
Sandvik Intellectual Property AB v Quarry Mining & Construction Equipment Pty Ltd [2017] FCAFC 138; 348 ALR 156
Sigma Pharmaceuticals (Australia) Pty Ltd v Wyeth [2011] FCAFC 132; 119 IPR 194
TCT Group Pty Ltd v Polaris IP Pty Ltd [2022] FCA 1493; 170 IPR 313
Technological Resources Pty Limited v Tettman [2019] FCA 1889; 375 ALR 185
U & I Global Trading (Australia) Pty Ltd v Tasman-Warajay Pty Ltd [1995] FCA 794; 60 FCR 26
Wellcome Foundation Ltd v VR Laboratories (Aust) Pty Ltd [1981] HCA 12; 148 CLR 262
Division: General Division Registry: New South Wales National Practice Area: Intellectual Property Sub-area: Patents and associated Statutes Number of paragraphs: 595 Date of last submission/s: 3 July 2023 Date of hearing: 12-16, 19-23 and 26-29 September, 10-14 October 2022 Counsel for the Applicants: Mr N R Murray SC with Mr D B Larish and Ms N Gollan Solicitor for the Applicants: Herbert Smith Freehills Counsel for the Respondents: Mr C Dimitriadis SC with Mr P Creighton-Selvay Solicitor for the Respondents: Gilbert + Tobin ORDERS
NSD 458 of 2019 BETWEEN: HANWHA SOLUTIONS CORPORATION (REGISTRATION NO. 10111-030935)
First Applicant
HANWHA Q CELLS AUSTRALIA PTY LTD ABN 84 141 108 590
Second Applicant
AND: REC SOLAR PTE LTD
First Respondent
SOL DISTRIBUTION PTY LTD ABN 53 146 905 286
Second Respondent
BAYWA R.E. SOLAR SYSTEMS PTY LTD ACN 614 035 620
Third Respondent
AND BETWEEN: REC SOLAR PTE LTD (and others named in the Schedule)
First Cross-Claimant
AND: HANWHA GLOBAL ASSET CORPORATION (REGISTRATION NO. 110111-1725930) (and another named in the Schedule)
First Cross-Respondent
ORDER MADE BY:
BURLEY J
DATE OF ORDER:
29 AUGUST 2023
THE COURT ORDERS THAT:
1.The parties confer and supply to the chambers of Justice Burley by 4pm on 19 September 2023 draft short minutes of order giving effect to these reasons and a proposed timetable for further steps to be taken in the proceedings.
2.Insofar as the parties are unable to agree to the terms of the draft short minutes of order referred to in order 1, the areas of disagreement should be set out in mark-up.
3.The confidential reasons for judgment be published only to those persons who have executed suitable confidentiality agreements as determined in first instance by the solicitors acting for the applicants and the respondents.
4.The non-confidential reasons, which do not include the reasons concerning patent infringement, are published without restriction.
Note: Entry of orders is dealt with in Rule 39.32 of the Federal Court Rules 2011.
PUBLIC REASONS FOR JUDGMENT
1 INTRODUCTION
[1]
1.1 The parties and the proceedings
[1]
1.2 The case asserted by Hanwha
[5]
1.3 The responsive case advanced by REC Solar
[7]
1.4 Summary of conclusions
[21]
1.5 Relevant aspects of case management of the three proceedings
[24]
2 THE LAY WITNESSES
[27]
2.1 Hanwha – the REC Solar U Cell
[27]
2.2 REC Solar
[30]
3 THE EXPERT EVIDENCE
[35]
3.1 Hanwha
[35]
3.2 REC Solar
[43]
4 THE AGREED COMMON GENERAL KNOWLEDGE
[54]
5 THE PATENT
[55]
5.1 The specification
[56]
5.2 The Claims
[83]
5.3 The nature and purpose of the claimed invention
[84]
5.4 The skilled addressee
[86]
6 CLAIM CONSTRUCTION
[92]
6.1 Introduction
[92]
6.2 “dielectric layer” in claim 9
[102]
6.2.1 The arguments
[102]
6.2.2 The expert evidence
[104]
6.2.3 Consideration
[112]
6.3 “depositing a first dielectric layer on a surface of silicon substrate”; claim 9
[121]
6.3.1 Introduction
[121]
6.3.2 The arguments
[127]
6.3.3 Consideration
[137]
6.4 “second dielectric layer on a surface of the first dielectric layer”; claims 1 and 9
[182]
6.5 “first dielectric layer comprising aluminium oxide”; claim 9
[187]
6.5.1 The submissions
[187]
6.5.2 Consideration
[189]
6.6 “… and hydrogen being embedded into the second dielectric layer”; claim 9
[194]
6.6.1 The arguments
[196]
6.6.2 Consideration
[197]
6.7 “… substantially atomically tight”; claim 10
[215]
6.8 “… second dielectric layer comprises silicon nitride”; claim 11
[216]
6.9 “… wherein the surface of the silicon substrate is passivated by hydrogen”; claim 16
[219]
6.10 “…second dielectric layer forms part of a back surface reflector”; claim 19
[222]
7 INFRINGEMENT – THE CASE AGAINST REC SOLAR
[226]
8 THE ACL CASE
[281]
9 LACK OF INVENTIVE STEP
[282]
9.1 Introduction
[282]
9.2 The evidence in chief concerning inventive step
[292]
9.2.1 Professor Weber
[292]
9.2.2 Professor Cuevas-Fernandez
[299]
9.2.3 Dr Winderbaum
[303]
9.3 The inventive step joint expert report
[305]
9.4 The disclosure of Hoex 2006
[306]
9.5 The agreed teaching from Hoex 2006
[329]
9.6 Steps 1 and 2 and the ascertainment of Hoex 2006
[330]
9.6.1 The submissions
[330]
9.6.2 Consideration of steps 1 and 2 and the ascertainment of Hoex 2006
[337]
9.7 Step 3 – would Hoex 2006 be regarded as relevant?
[368]
9.8 Step 4 – the limits of the teaching in Hoex 2006
[376]
9.8.1 The submissions
[376]
9.8.2 Consideration
[381]
9.9 Step 5 – a second dielectric layer?
[396]
9.9.1 The submissions
[396]
9.9.2 Consideration
[399]
9.10 Step 6 – atomic layer deposition
[406]
9.11 Consideration of inventive step
[413]
9.11.1 The relevant law
[413]
9.11.2 Analysis of lack of inventive step
[425]
9.12 Inventive step in light of Hoex 2007
[431]
10 LACK OF FAIR BASIS
[441]
10.1 Relevant law of fair basis
[441]
10.2 Ground 5 – the ALD argument
[443]
10.2.1 The submissions
[443]
10.2.2 Consideration
[447]
10.3 Grounds 6, 7 and 8 “on a surface”
[464]
11 LACK OF NOVELTY
[466]
11.1 The relevant law
[466]
11.2 Isaka
[469]
11.2.1 Introduction
[469]
11.2.2 The contested integers
[475]
11.2.3 The disclosure of Isaka
[480]
11.2.4 Consideration of Isaka
[486]
11.2.4.1 Integer 9(c) (“first dielectric layer comprising aluminium oxide”)
[486]
11.2.4.2 Integer 9(d) (thickness of the first dielectric layer)
[496]
11.2.4.3 Claims 12, 13 and 21 (thickness of the second dielectric layer)
[508]
11.2.5 Conclusion in relation to Isaka
[512]
11.3 Nakano
[513]
11.3.1 Introduction
[513]
11.3.2 The contested integers
[516]
11.3.3 The disclosure of Nakano
[517]
11.3.4 “hydrogen being embedded into the second dielectric layer” – integer 9(g)
[528]
11.3.4.1 The submissions
[528]
11.3.4.2 Consideration
[530]
11.3.5 “surface of the silicon substrate is passivated by hydrogen” – claim 16
[541]
11.3.5.1 Hanwha’s arguments
[541]
11.3.5.2 Consideration
[542]
11.3.6 Conclusion in relation to Nakano
[552]
11.4 Bhattacharyya
[553]
12 LACK OF UTILITY
[557]
12.1 Introduction
[557]
12.2 The law of inutility
[560]
12.3 The very good surface passivation argument
[561]
12.3.1 The submissions
[561]
12.3.2 Consideration
[566]
12.4 The very good optical properties argument
[570]
12.4.1 The submissions
[570]
12.4.2 Consideration
[572]
13 LACK OF CLARITY
[573]
14 UNJUSTIFID THREATS
[585]
15 CONCLUSION
[593]
ANNEXURE A
[]
BURLEY J
1. INTRODUCTION
1.1 The parties and the proceedings
These proceedings concern solar cell technology, a claim of patent infringement, a cross claim for the invalidity of the asserted claims of the patent, misleading and deceptive conduct and the making of unjustified threats of patent infringement.
Hanwha Solutions Corporation, a company incorporated in South Korea, is the registered proprietor of Australian patent No AU 2008323025, which is entitled “Method for manufacturing a solar cell with a surface-passivating dielectric double layer, and corresponding solar cell”. It and Hanwha Q CELLS Australia Pty Ltd (collectively Hanwha) are the applicants. The patent has a priority date of 14 November 2007.
Hanwha initially commenced three sets of proceedings being:
(a)NSD 394 of 2019 against LONGi Green Energy Technology Co Ltd, a company organised under the laws of the Peoples Republic of China, and three other related companies (collectively, LONGi).
(b)NSD 395 of 2019 against Jinko Solar Australia Holdings Co Pty Ltd; and
(c)NSD 458 of 2019, against REC Solar Pte Ltd, a company organised under the laws of Singapore and two other companies that REC Solar has authorised to sell products that Hanwha alleges fall within the scope of the claims of the patents, being Sol Distribution Pty Ltd and Baywa r.e. Solar Systems Pty Ltd. For convenience, I refer to these respondents collectively as REC Solar.
As matters transpired, after the hearing, but before judgment, the proceedings in (a) and (b) settled. As I explain in section 1.5 below, each of LONGi, Jinko and REC Solar co-operated in the conduct of the proceedings so that there was no unnecessary duplication in their approach to the invalidity case. The consequence was that, leaving aside the separate allegations of infringement against LONGi and Jinko, the content of the matters in controversy remained largely unchanged as a result of the settlements.
1.2 The case asserted by Hanwha
In its seventh amended statement of claim, Hanwha alleges that multiple products sold and offered for sale by or with the approval of REC Solar (REC Solar products) fall within the scope of asserted claims 12, 13, 14, 16, 17, 18, 19 and 21 of the patent. Hanwha also alleges that by reason of its infringing conduct REC Solar has falsely represented that one or more of the accused REC Solar products do not infringe any intellectual property rights and that it is legally entitled to sell and third parties are entitled to purchase, install and use those products in breach of the Australian Consumer Law being schedule 2 to the Competition and Consumer Act 2010 (Cth) (ACL claim).
REC Solar denies that the REC Solar products fall within the scope of the asserted claims and also advances a cross claim alleging that those claims are not valid.
1.3 The responsive case advanced by REC Solar
In its fourth amended particulars of invalidity REC Solar relies on lack of novelty, lack of inventive step, lack of fair basis, inutility and lack of clarity as grounds. It also contends that Hanwha made unjustified threats of patent infringement, in breach of s 128 of the Patents Act1990 (Cth). I note that the version of the Patents Act applicable to the proceedings is that following the amendments made by the Patents Amendment Act 2000 (Cth) but before those made by the Intellectual Property Laws Amendment (Raising the Bar) Act 2012 (Cth) (RTB Act).
In its Amended Consolidated Particulars of Invalidity (POI), REC Solar sets out the grounds upon which it contends that claims 9, 11-14 and 16-21 (challenged claims) ought to be revoked.
In its novelty challenge as advanced in its closing submissions, REC Solar contends that, by reason of the publication of the documents identified below, the claims identified are not novel in accordance with s 18(1)(b)(i) of the Act (grounds 1, 2 and 3):
(a)International Patent Application WO 2008/065918 A1 entitled “Solar cell and method of manufacturing the same” (Isaka) is said to invalidate claims 9, 11-14, 17-19 and 21 of the patent;
(b)US patent application 2006/0102972 A1 entitled “Optoelectronic devices, solar cells, method of making optoelectronic devices, and methods of making solar cells” (Bhattacharyya), published 18 May 2006, is said to invalidate claims 9 and 11 of the patent; and
(c)US patent 4,463,216 entitled “Solar Cell” (Nakano), published 31 July 1984, is said to invalidate claims 9, 12, 16 and 21 of the patent.
In its lack of inventive step challenge, REC Solar contends that the invention in the challenged claims is not patentable for want of an inventive step within the meaning of s 18(1)(b)(ii) of the Act by reason that a person skilled in the art in light of the common general knowledge before 14 November 2007 together with the following documents considered separately or together (ground 4):
(a)An article entitled “Ultralow surface recombination of c-Si substrates passivated by plasma-assisted atomic layer deposited Al2O3” by B. Hoex et al (Hoex 2006); and
(b)An article entitled “Excellent passivation of highly doped p-type Si surfaces by the negative-charge-dielectric Al2O3” by B. Hoex et al (Hoex 2007)
would find the invention to be obvious.
In relation to its challenge on the basis of lack of fair basis, REC Solar advances six contentions.
First, it contends that the challenged claims travel beyond the matter described in the specification in that there is no real and reasonably clear disclosure in the specification of a solar cell, or a method for manufacturing such a solar cell, having a first dielectric layer formed by means other than atomic layer deposition (ALD) (ground 5).
Secondly, it contends that if claim 9 is construed such that the “silicon substrate” may have a silicon oxide layer on its surface, then the specification does not comply with s 40(3) of the Act in that claim 9 and claims 11-14 and 16-21 when dependent on claim 9 are not fairly based on the specification (ground 6).
Thirdly, it contends that if the challenged claims encompass a solar cell or method of making such a cell with material other than aluminium oxide on a surface of the silicon substrate, those claims travel beyond the matter described in the specification (ground 7).
Fourthly, if claim 9 is construed such that it encompasses a solar cell which is not manufactured by a method which includes depositing a first dielectric layer comprising aluminium oxide on a surface of the silicon substrate, then claim 9 and claims 11-14 and 16-21 when dependent on claim 9 travel beyond the matter described in the specification (ground 8).
Fifthly, each of claims 9, 11-14, 16 and 21 travel beyond the matter described in the specification in that:
(a)Insofar as it includes a silicon substrate having a lightly doped region of conduction type n it includes a solar cell or a method of manufacturing a solar cell in which an inversion layer is induced below the passivating layer, and in which a parasitic shunt may form; and
(b)There is no real and reasonably clear disclosure of such a solar cell or method of manufacturing such a cell.
(ground 9)
Sixthly, each of the challenged claims travels beyond the matter described in the specification as the specification discloses a second dielectric layer with a high hydrogen content (of at least 1 atomic percent (at. %) preferably at least 2 at. % and more preferably at least 5 at. %) and each of those claims are not so limited (ground 10).
In ground 12, REC Solar contends that the alleged invention as claimed in the challenged claims is not a patentable invention for the purposes of s 18(1)(c) of the Patents Act for lack of utility in that those claims include solar cells containing dielectric layers that do not achieve the promise of the invention.
REC Solar contends that the specification of the patent does not comply with the requirements of s 40(3) of the Patents Act in that claims 16, and claims 17-21 to the extent that they are dependent on claim 16, are not clear and succinct because:
(a)In ground 20, the phrase “wherein the surface of the silicon substrate is passivated by hydrogen” is unclear and ambiguous and there is no workable standard for determining whether that feature is present;
(b)In ground 20A, if the phrase “hydrogen being embedded into the second dielectric layer” in claim 9 is construed so as to require a minimum concentration of hydrogen, then it is ambiguous because there is no workable standard for determining whether the feature is present.
For completeness, I note that grounds 11 and 13-19 of the POI were not pressed by REC Solar in closing submissions.
1.4 Summary of conclusions
For the reasons set out in this judgment I have found that the REC Solar products do not fall within the scope of claim 9 of the patent, and accordingly none of the asserted claims are infringed because each of the asserted claims is dependent upon claim 9. As a result, the ACL claim advanced by Hanwha, which depended on a finding of infringement, also fails. The unjustified threats claim advanced by REC Solar succeeds.
I also find that claims 9, 12, 16 and 21 are invalid for want of novelty in the light of Nakano but that otherwise the invalidity challenges advanced by REC Solar fail.
REC Solar has asserted confidentiality over much of the information concerning the make-up of the REC Solar products. Accordingly, I will not publish the infringement section of these reasons until the parties have had an opportunity to consider whether an agreed (redacted) version of that section can be released. The only orders that I will make are for the parties to confer and supply to my chambers within 21 days draft short minutes of order giving effect to these reasons, and a proposed timetable for further steps to be taken in the proceedings.
1.5 Relevant aspects of case management of the three proceedings
The proceedings were complicated and hard-fought. Prior to the settlements reached between Hanwha, LONGi and Jinko, the management of the case involved dealing with three sets of allegations of infringement concerning multiple products manufactured by each of the three sets of respondents. All parties are fierce competitors in the emerging field of solar cell production. Each maintained a high degree of confidentiality in their products and processes of manufacture.
The conduct of the proceedings is a testament to the good sense of the parties and the professionalism of their advisors. In all three of the cases, the parties consented to (or did not inordinately oppose) a number of significant case management steps that enabled the proceedings to be managed together and conducted efficiently.
The following aspects of the management of the case warrant mention:
(1)Early in the proceedings the respondents accepted that they should be permitted one substantive witness to give evidence going to questions of invalidity. This considerably eased the progress of the trial and eliminated unnecessary duplication. The invalidity expert retained by the respondents was Professor Weber, to whom I refer below.
(2)Before the preparation of evidence in chief, REC Solar, LONGi and Jinko each filed and served a Product Description of the products alleged to be infringed and a position statement of non-infringement concerning each of the impugned products. Hanwha responded with a position statement on infringement that identified any factual or legal matters in dispute arising from the respondents’ position statement.
(3)A technical primer was prepared using a process whereby, when Hanwha served its expert affidavit evidence in chief on infringement, it identified a portion that included what was intended to be an uncontroversial introduction to the relevant technology and a glossary of relevant terms at the priority date. In their expert affidavit evidence in chief on validity, the respondents identified what was also intended to be an uncontroversial portion of that affidavit that included a summary of the relevant common general knowledge to the skilled addressee before the priority date. Each side’s expert responded to these sections and then the parties jointly served and filed the primer and statement of common general knowledge, which included a mark-up indicating any areas of disagreement between them.
(4)Although each of the respondents pleaded separate particulars of invalidity, shortly before the trial they cooperated to produce one consolidated set of particulars of invalidity, thereby limiting unnecessary repetition.
(5)The parties agreed to suitable confidentiality regimes during the preparation of the proceedings to ensure that, whilst their confidential manufacturing processes were protected, sufficient disclosure was provided to the other parties to enable the legal advisors to understand how the case would run. This involved a complicated regime with multiple levels of confidentiality that required ongoing cooperation between the parties and minimal involvement by the Court.
(6)Orders were made that all issues of liability, including as to infringement, contravention of the ACL and unjustified threats under s 128 of the Patents Act, were to be determined separately and before any issues of election and quantification of pecuniary relief (including any additional damages).
(7)The respondents had divergent interests on the question of infringement. Whilst they relied on the evidence of Professor Weber in support of their grounds of invalidity, each relied upon the evidence of separate experts in support of the non-infringement defences (being Dr Glew (REC Solar), Dr Ruby (Jinko) and Professor Weber (LONGi)).
(8)Those experts who were involved in giving evidence concerning infringement issues, but who were not involved in giving evidence concerning the validity of the patent, were not invited to participate in the preparation of joint expert reports concerning validity, or the subsequent concurrent evidence sessions addressing that topic.
(9)The experts, with the assistance of a Judicial Registrar of the Court, participated in meetings prior to the hearing and produced six separate joint expert reports (JER), three concerning infringement issues (REC Solar, Jinko and LONGi JER respectively), one concerning claim construction (Construction JER) and two concerning invalidity issues (Validity JER).
(10)The oral and written evidence of the experts in all three proceedings given by Professor Weber, Dr Glew, Dr Ruby, Dr Rentsch, Professor Cuevas-Fernandez and Dr Winderbaum, including the JER, was taken as evidence in all of the proceedings.
(11)One issue arose during the course of objections to evidence, when Hanwha expressed concern that the infringement experts, in giving evidence going to construction, might be considered also to have given expert evidence relevant to the questions of fair basis and inutility of the patent. Those concerns did not arise out of any improper instructions to the experts, but rather because, naturally enough, it was necessary for each expert to construe the claims in the context of the specification as a whole, which led them to express views as to the breadth of the claims in the context of the invention disclosed as a whole. To ensure that the experts maintained the roles envisaged for them early in the proceedings, and bearing in mind that Professor Weber had separately given evidence concerning all invalidity issues, particular paragraphs identified by Hanwha were made the subject to a limitation under s 136 of the Evidence Act 1995 (Cth) to the effect that those paragraphs may not be relied upon for the purposes of the fair basis or utility challenges (as the case may be) to the validity of the patent.
2. THE LAY WITNESSES
2.1 Hanwha – the REC Solar U Cell
Magnus Garbrecht is a Senior Transmission Electron Microscopy (TEM) Manager at Sydney Microscopy & Microanalysis at the University of Sydney, specialising in aberration-corrected high-resolution TEM imaging and spectroscopy techniques in the field of materials science. He has a Diploma in Physics and a PhD in Materials Science from the Institute for Experimental and Applied Physics, Christian-Albrechts-University in Kiel, Germany. Dr Garbrecht gives evidence about TEM analysis he and Ms Pillai (see below) undertook on a sample of the REC Solar product identified as the U Cell. He was not cross-examined.
Ashalatha Indiradevi Kamalasanan Pillai is a Scanning Electron Microscopy (SEM) Specialist at Sydney Microscopy & Microanalysis at the University of Sydney. In this role, she provides technical support in SEM and Focused Ion Beam (FIB) techniques. Ms Pillai gives evidence about TEM analysis she and Dr Garbrecht undertook on a sample of the U Cell that was prepared by the use of a FIB. She was not cross-examined.
Mohanad Mursi is a Manager at the Centre for Advanced Structural Engineering in the School of Civil Engineering at the University of Sydney. He holds a PhD in Civil Engineering and a second PhD in Structural Engineering from the University of New South Wales. Dr Mursi gives evidence about work undertaken by himself and his colleagues at the Centre for Advanced Structural Engineering in relation to extracting samples of U Cells from the U solar modules for subsequent testing. He was not cross-examined.
2.2 REC Solar
Udit Sharma is a scientific fellow at Eurofins EAG Materials Science. In this role, he facilitates, manages, oversees and reports upon the testing and analysis of a range of industrial materials including in the field of solar cell technology. Mr Sharma gives evidence regarding testing undertaken by EAG of the Sing, Vina, MS, MMS and MV Cells. Mr Sharma was not cross-examined.
Jae Sung Lee, is an R&D researcher employed by REC Solar in the Cell R&D Department. In this role he is responsible for researching and developing new technology, including in the field of solar cells, and testing and analysing solar cells, including engaging external service providers to undertake testing and analysis of REC Solar products. Mr Lee gives evidence regarding testing undertaken by WinTech Nano-Technology Services Pte Ltd of the NSP and Solartec Cells. He was not cross-examined.
Shankar Gauri Sridhara is the Chief Technology Officer employed by REC Solar. Prior to this position, he joined the REC Scan Module AB division of REC in Sweden, joined the Singapore division of REC as a director of module technology in 2011, and assumed responsibility for the entirety of research and development in REC from poly-silicon to products in 2016. Dr Sridhara was responsible for preparing:
(1)REC Solar’s product description (REC-PD), which involves his interpretation of testing undertaken by WinTech of the Sing, Vina, NSP and Solartec Cells; and
(2)REC Solar’s second supplementary product description (REC-SSPD), which involves his interpretation of testing undertaken by WinTech of the MS and MMS Cells and his interpretation of testing undertaken by EAG of the MV Cell.
Dr Sridhara verifies the REC-PD and REC-SSPD relied upon by REC Solar in these proceedings, and gives evidence providing the primary sources and contemporaneous documents referred to and relied upon in the REC-PD and REC-SSPD. Dr Sridhara was cross-examined.
John Lee is a partner at Gilbert + Tobin, the solicitors acting for REC Solar. He gives evidence annexing correspondence relevant to REC Solar’s unjustified threats cross-claim. He was not cross-examined.
3. THE EXPERT EVIDENCE
3.1 Hanwha
Jochen Rentsch is Department Head, PV Production Technologies – Surfaces and Interfaces, at the Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany. He has previously provided expert evidence in relation to patent infringement proceedings in Germany between companies related to Hanwha on the one hand and companies related to the respondents on the other concerning a European patent No 2 220 689, which is related to the patent. In 2002 Dr Rentsch completed a degree in physics whereupon he began a PhD thesis entitled “Dry production technologies for crystalline silicon solar cells” at Albert-Ludwigs University in Frieburg. In 2005 he commenced working for his current employer focussing on research in solar cell and photovoltaics production technologies and in particular upon deposition and etching processes and technologies.
Dr Rentsch has given six affidavits in these proceedings which address questions of infringement and validity of the patent (excluding lack of inventive step). He participated in the preparation of the Construction JER and infringement JERs for each of the LONGi, Jinko and REC Solar infringement cases and the matching concurrent evidence sessions for each.
Andres Cuevas-Fernandez is an Emeritus Professor at the Australian National University (ANU). He has worked in the field of silicon solar cell technology since 1976. He received an undergraduate degree in telecommunications engineering at the Universidad Politecnica de Madrid in 1976 and conducted research in the area of silicon solar cells in the Laboratorio de Semiconductores to earn his PhD from the same university in 1980. He has since worked in various teaching and research positions. In July 1993 he moved to the ANU where he was the head of the School of Engineering from 2007 until 2010. He retired in April 2018 whereupon he took an appointment as Emeritus Professor.
In his affidavit Professor Cuevas-Fernandez describes himself as one of the most experienced researchers in the field of photovoltaics, having contributed to the scientific and technological advancement of silicon solar cells since 1976. He has collaborated extensively with many of the leading researchers and research institutes in the field and also with workers in industrial settings. He is a named inventor on 12 patents and patent applications. His research has almost entirely been devoted to wafer-based silicon solar cell technology.
Professor Cuevas-Fernandez gave one affidavit addressing the validity of the patent and participated in joint expert reports and concurrent evidence sessions concerning the alleged lack of inventive step in the patent.
Professor Cuevas-Fernandez participated in the preparation of the two Validity JERs concerning the obviousness case and the matching concurrent evidence sessions for each.
Saul Winderbaum is a retired adjunct associate professor at the University of New South Wales and Director of Shamash Australia Pty Ltd. From 1984 until 1993 he worked as a process engineer in the production of microelectronic components. In 1998 he was awarded a PhD for a thesis entitled “Optical enhancements in silicon solar cells” by the University of New South Wales. Prior to commencing work on his PhD thesis, Dr Winderbaum had used Plasma-Enhanced Chemical Vapour Deposition (PECVD) extensively in microelectronics to deposit silicon nitride layers. He developed this use of PECVD in depositing silicon nitride on silicon wafers in the context of solar cells in his PhD research. In 2000 he took a position as senior scientist at BP Solar where he was responsible for modifying their manufacturing processes to establish the use of silicon nitride deposited by PECVD as an anti-reflective coating. In 2003 Dr Winderbaum became a consultant to BP and other companies in the solar cell industry.
Dr Winderbaum participated in the preparation of one Validity JER relating to the question of inventive step and the equivalent concurrent evidence session.
3.2 REC Solar
Klaus Weber is a Professor in the School of Engineering at the ANU. He was awarded a Bachelor of Electrical Engineering from the University of Adelaide in 1992 and a PhD in Engineering for a thesis entitled “Liquid phase epitaxy of silicon for thin film silicon solar cells” from the ANU in 1997. His research focussed on producing silicon films of 0.01 to 0.08 mm thickness to evaluate and demonstrate the potential of such films for use in low cost, high efficiency silicon solar cells.
From 1998 until 2014 he conducted research at the ANU. During his time as a post-doctoral fellow at ANU, he worked in collaboration with Boral Energy (later called Origin Energy) on a technique that he had assisted in developing (called “epilift”) to detach thin silicon films from the substrate on which they were formed. He continued this research from 1998 until 2001, which included trying to scale it up for industrial use. Also in collaboration with Origin Energy, from 2000 to 2001 Professor Weber assisted in the development of a new technology for the fabrication of thin silicon solar cells which became the subject of several patents. From 2002 to 2014 Professor Weber continued to work on developing this technology. From 2001 to 2007 Professor Weber was also involved in researching various properties of low pressure chemical vapour deposition (LPCVD) silicon nitride for use in solar cells.
Professor Weber has published over 140 papers and is a named inventor on 14 patents or patent applications, most of which pre-date the priority date. In his oral evidence he accepted that he was a leading figure in solar cell research who was doing original, cutting-edge research and who, when pressed, accepted that he was “moderately inventive”.
Professor Weber gave evidence relevant to the validity of the patent and the question of infringement in relation to the alleged infringement by the LONGi products. He participated in the preparation of the Construction JER, the LONGi infringement JER and the Validity JER and he gave concurrent evidence in sessions concerning these topics.
Alexander David Glew is a materials scientist and mechanical engineer. His academic credentials include a Bachelor of Science and a Masters of Science in Mechanical Engineering from the University of California, Berkeley received respectively in 1985 and 1987, a Master of Science in Materials Science and Engineering from Stanford University in 1995 and a PhD in Materials Science and Engineering from Stanford University in 2003. The subject of his doctoral dissertation related to PECVD of dielectric films.
Dr Glew worked from 1987 until 1997 for Applied Materials Inc, a company that manufactures the equipment used to make semiconductors and sells that equipment to companies who make semiconductors. He had various roles within the company, with particular emphasis on chemical vapour deposition, a process involving the mixing of two or more gasses in a process reactor or chamber and having them meet on the surface of a substrate to deposit a thin film which, in the semiconductor or solar industry, would be 2 to 3 nanometres (nm) or less. In 1997 he left Applied Materials and became the president of his own company, Glew Engineering, which provides consulting services to various technology or engineering areas, including chemical vapour deposition technology. He has assisted component suppliers and equipment suppliers on various projects including in relation to gas panel design, integrated circuits failures and semiconductor equipment failures. His company’s practice includes multi-physics finite element analysis.
In his first affidavits, Dr Glew was provided a review of the patent and was asked to consider whether the REC Solar Multi Sing, Multi Vina, NSP and Solartec Cells fall within claims 9, 11-14 and 16-21 of the patent and to respond to the evidence of Dr Rentsch. In his second affidavit he was asked to consider whether three additional solar cells, referred to as the MS, MMS and MV cells infringed those claims and respond to further evidence from Dr Rentsch. In his third affidavit, Dr Glew was asked to consider whether the U Cell fell within the claims and to respond to further evidence from Dr Rentsch. In his fourth affidavit, Dr Glew was provided with certain documents annexed to the affidavit of Mr Lee concerning testing performed by WinTech on the Solartec and NSP products.
Dr Glew participated in the preparation of the Construction JER and the REC Solar infringement JER.
Douglas Scott Ruby is a consultant in the photovoltaics industry. He studied physics in university and was awarded a Bachelor of Science from the Massachusetts Institute of Technology in 1978 and was awarded a Masters and PhD from the University of Illinois specialising in semiconductor physics in 1980 and 1985 respectively. After his PhD, he worked for Sandia National Laboratories as a researcher from 1985 until 2008 working in its photovoltaics solar cell research division where he focussed on devising methods and procedures which could be employed in solar cell manufacturing to make solar cells more efficient or less expensive to manufacture. In about 1999, Dr Ruby became the leader of his division’s photovoltaic cell development team, managing seven researchers including in work directed towards improving surface passivation and reducing surface reflectance.
In his first affidavit Dr Ruby gave his views as to the disclosure of the patent and the construction of the claims and expressed views concerning the alleged infringement of certain claims by the Jinko products (which are not relevant to the present proceedings). In his second affidavit he provided some clarification of a point made in his first affidavit.
Dr Ruby was involved in the preparation of the Construction JER and the Jinko infringement JER and gave concurrent evidence in sessions concerning those topics.
4. THE AGREED COMMON GENERAL KNOWLEDGE
Annexure A to this judgment consists of parts of the primer and agreed common general knowledge document provided by the parties. It was prepared as a result of an iterative process. It arises from a combination of the evidence of Dr Rentsch and Professor Weber insofar as it provides an explanation of some relevant background concepts, and a combination of evidence of Professor Weber and Professor Cuevas-Fernandez insofar as it concerns matters going to common general knowledge relevant to the question of whether or not the invention claimed involves an inventive step. It has been edited to address more central aspects of the technology. To the extent that the parties did not agree on its content, Annexure A includes my findings as to the common general knowledge. It is recommended reading for those not familiar with the technology in the patent.
5. THE PATENT
The patent relates to the production of a more efficient solar cell using a double dielectric layer stack that reduces recombination losses by increasing surface passivation. The specification is to be understood in the light of the common general knowledge of the persons skilled in the art, including the information set out in Annexure A.
5.1 The specification
The patent is entitled “Method for manufacturing a solar cell with a surface-passivating dielectric double layer, and corresponding solar cell” and the field of the invention is described in the same terms.
The Background of the Invention first provides a reference to the technology (page 1 line 20):
A key requirement for achieving high degrees of efficiency in solar cells is very effective suppression of surface recombination losses. For this purpose, the surface of solar cells should be passivated as effectively as possible, so that charge carrier pairs which are generated inside the solar cell by incident light and which diffuse to the surfaces of the solar cell substrate do not recombine at the solar cell surface, so that they would no longer be available to help improve the efficiency of the solar cell.
The Background then identifies four relevant approaches to the problem present in the prior art and difficulties said to arise from that art.
The first approach, which is said to arise in laboratory solar cells but not to be in general use in the industrial manufacture of solar cells, is the growing of silicon dioxide at a high temperature (greater than 900 °C). However, this not only adds expenditure in solar cell processing but also has a further difficulty in that high temperature oxidation can lead the more economical multicrystalline silicon to experience “a considerable reduction in material quality” in that the charge carrier lifetime is reduced and thus the wafter has losses in efficiency.
The second approach is referred to as a low-temperature alternative, which is surface passivation using amorphous silicon nitride or silicon carbide which can be prepared at temperatures of 300-400 °C by PECVD. The specification provides references to two publications, one by T. Lauinger et al, and another by I. Martin et al. It says that the dielectric layers produced in this way can be used only to a limited degree for large-area, high efficiency solar cells because they contain a high density of “pinholes”, being small holes or pores in the layer, so that they may not have good insulating properties. A further problem with this approach is said to be that (page 2 line 18):
… their passivating effect is based largely on a very high positive charge density within the dielectric layers that can lead, during the passivation of the back of the solar cell if a p-type silicon wafers are used, for example, to the formation of an inversion layer via which an additional leakage current of minority charge carriers can flow away from the base of the solar cell to the back contacts (what is known as a “parasitic shunt”). On highly doped p+ silicon surfaces, silicon nitride can even lead, on account of the high positive charge density, to depassivation compared to an unpassivated p+ surface.
The third approach is using amorphous silicon layers which can also be produced by PECVD at very low coating temperatures of typically greater than 250 °C. While very good surface passivation was achieved (page 3 lines 7-14):
… the surface-passivating property of amorphous silicon layers of this type may be very susceptible to temperature treatments. In current-day industrial solar cell processes, the metal coating is in many cases carried out by means of screen printing technology, the last process step typically being a firing of the contacts in a continuous infrared furnace at temperatures of between approx. 800 °C and 900 °C. Although the solar cell is exposed to these high temperatures only for a few seconds, this firing step can lead to considerable degradation of the passivating effect of the amorphous silicon layers.
The fourth approach is using aluminium oxide layers which are deposited by means of ALD at about 200 °C, for example, and then tempered at about 425 °C. Using this approach, whilst good passivating results are said to have been achieved, only a single molecular layer is generally deposited on the substrate surface within each deposition cycle.
As a deposition cycle typically lasts about 0.5 to 4 seconds (s), correspondingly low deposition rates are obtained. The deposition of aluminium oxide layers at a thickness which is suitable for use as an antireflection layer or as a back reflector therefore requires deposition durations which have in the past shown a use of such layers in industrially produced solar cells to be commercially disadvantageous.
The Summary of the Invention then observes that there may be a need for a solar cell and a method for manufacturing in which on the one hand, good passivation of the surface of the solar cell can be achieved and, on the other hand (page 4 lines 1-3):
… the above-mentioned drawbacks of conventional surface-passivating layers can be at least partially avoided. In particular, it should be possible to produce solar cells displaying very good surface passivation in an economical, industrially viable manner.
The specification describes a first aspect of the invention (page 4 line 6 to page 5 line 18):
According to a first aspect of the present invention, a method is proposed for manufacturing a silicon solar cell, including the following steps: providing a silicon substrate; depositing a first dielectric layer on a surface of the silicon substrate by means of atomic layer deposition, wherein the first dielectric layer comprises aluminium oxide; and depositing a second dielectric layer on a surface of the first dielectric layer, the materials of the first and the second dielectric layer differing and hydrogen being embedded into the second dielectric layer.
This first aspect of the present invention may be regarded as being based on the following idea: a method is specified for manufacturing silicon solar cells with a dielectric passivating layer for reducing surface recombination losses. The dielectric passivating layer is composed of two partial layers, of a very thin aluminium oxide-containing layer, which is formed by atomic layer deposition (ALD), and also of a thicker layer made of silicon oxide, silicon nitride or silicon carbide, for example, which can be deposited on the aluminium oxide layer by means of plasma enhanced chemical vapour deposition (PECVD), for example.
The dielectric double layer produced in the method according to the first aspect allows the passivation of both high and low-doped regions of the solar cell surface of conduction type p or n. It is possible to allow stable passivation which retains its passivating properties even after a firing step in the temperature range of 800-900 °C for burning-in of metal contacts. At the same time, the dielectric passivating layer can also have advantageous optical properties, i.e for application to the front of the solar cell, the layer can serve as an effective antireflection layer; during application to the back of the solar cell, the passivating layer can form, together with metal coating over the entire area of the back, an effective mirror for photons with energies close to the silicon band gap in order to improve what is known as “light trapping”, i.e. the trapping of light by multiple internal reflection, in the solar cell. Furthermore, the negative effect of “parasitic shunting”, which is known from silicon nitride, can be avoided for rear surface passivation on standard solar cell semiconductor material of conduction type p.
In a passage much emphasised by the parties, the specification continues (page 5 lines 10-16):
The key to understanding the outstanding passivating effect and tempering stability of the stack layer according to the invention may be identified in the combination of the Si/Al2O3 interface, which is ideally atomically flat and is produced as a matter of course during the ALD process, and the highly hydrogenous SiOx, SiNx or SiCx layers, such as are formed during the PECVD process, for example. A part of the hydrogen from the PECVD-deposited layers can diffuse through the ultrathin Al2O3 layer and passivate unsaturated silicon bonds at the interface to the silicon.
(Emphasis added)
The reference above to the “Si/Al2O3 interface” is to the point of interaction between the previously described silicon wafer and the very thin aluminium oxide layer.
The specification then continues by describing features, details and possible advantages of embodiments of the manufacturing method. This commences by noting that the silicon substrate “may be a thin monocrystalline or multicrystalline silicon wafer or else a silicon thin wafer”. The specification notes that the front of the solar cell substrate that faces the incident light (sun) may be coated, in which case the second dielectric layer is applied preferably as an antireflection layer, which is at a thickness at which negative interferences occur for the incident and reflected light. This may be from about 50 to 150 nm in thickness. Alternatively, the back may be coated, in which case the second dielectric layer is embodied as a “back surface reflector” so that light which penetrates the entire solar cell is for the most part reflected at that surface and thus passes through the solar cell substrate a further time.
In a further passage that gave rise to considerable debate in submissions, the specification describes that the first dielectric layer may be applied by reference to three steps, first a cleaning of the silicon substrate (page 6 lines 6-12):
Before the depositing of the first dielectric layer, the surface of the silicon substrate can be thoroughly cleaned, so that no contamination remains thereon that might disturb the subsequently deposited dielectric layer. In particular, the surface of the silicon substrate can be slightly etched away, for example in a solution which on the one hand contains an oxidising agent and which on the other hand contains hydrofluoric acid (HF) which etches away the oxidised silicon oxide. A suitable cleaning method known in the production of solar cells is for example what is known as RCA cleaning.
The next step in one embodiment is the application of the aluminium containing layer (page 6 line 15 to page 7 line 4):
According to one embodiment of the method according to the invention, for the atomic layer deposition of the first dielectric layer, the silicon substrate is firstly flushed with an aluminium-containing compound comprising at least one of the components Al(CH3)3, AlCl3, Al(CH3)2Cl and (CH3)2(C2H5)N:AlH3, so that an aluminium-containing layer is deposited on the surface of the silicon substrate. Subsequently, the aluminium-containing layer is oxidised to higher valency in an oxygen-containing atmosphere.
During the flushing of the silicon substrate with the aluminium-containing compound, the aluminium-containing compound can cling to the silicon surface at the points at which it enters into contact with the silicon surface. A chemical reaction with the silicon surface can occur; this is also referred to as chemisorption. In the best of cases, this can lead to the formation of a monomolecular layer made up of molecules of the aluminium-containing compound. It may be advantageous in this regard that this molecular layer can be almost perfectly tight, i.e. on correct selection of the processing parameters, such as duration and temperature during flushing, the entire silicon surface is covered with molecules of the aluminium-containing compound. This allows the subsequently produced first dielectric layer to be substantially atomically or molecularly tight.
The third step is the oxidation of the aluminium containing oxide (page 7 lines 6-16):
In a subsequent processing step, the previously deposited molecular layer of the aluminium-containing compound is oxidised to higher valency. This can take place for example by flushing with oxygen or an oxygen-containing gas. In order to speed up the chemical reactions, the oxygen can be provided in the form of a high-energy O2 plasma (plasma enhanced deposition) …
The specification provides that the process can be repeated several times in order to achieve a sufficient thickness of the aluminium oxide layer, with the entire sequential deposition process being carried out in a common chamber.
The specification then says (page 8 line 1):
An essential advantage of the atomic layer deposition is the fact that the entire substrate surface is coated uniformly. The deposition takes place irrespective of the geometry of the substrate surface, i.e. it is conform to the surface. The first dielectric layer is therefore deposited at the same thickness all over. This is beneficial in particular in surface-textured solar cells or in solar cells with channels which are intended to electrically contact the front with the back of the solar cell (what are known as EWT (emitter wrap through) solar cells), as passivation of the entire relevant solar cell surface can be ensured.
The specification then turns to the second dielectric layer. It provides that in one embodiment of the method, the second dielectric layer comprises silicon nitride, silicon oxide and/or silicon carbide each of which is said to display very good optical properties. In addition, dielectric layers made of these materials can also contain a high hydrogen content which can help further passivate the solar cell. It goes on to say that, in one embodiment, the second dielectric layer is produced by means of a PECVD method using reactants such as silane, dinitrogen oxide, carbon dioxide, ammonia and/or methane, which are reacted by igniting a plasma and can produce high-quality dielectric layers which are made of silicon nitride, silicon oxide or silicon carbide and can in addition have a high hydrogen content, that content being preferably at least 1 at. % and more preferably at least 5 at. %. The specification explains (page 8 lines 25 to page 9 line 2):
The embedded hydrogen can diffuse at least in part through the first dielectric layer positioned there below and contribute to passivation there by saturating free bonds of the silicon (“dangling bonds”). It has been found that this contribution can even be still higher than in the case in which a hydrogen-containing dielectric is deposited directly on a silicon surface.
The specification explains that a high temperature step (preferably above 800 °C) after depositing the second dielectric layer not only can be used to fire metal contacts which were printed onto the solar cell surface beforehand, but also has the advantage that hydrogen in the second dielectric layer can easily diffuse at elevated temperatures through the first dielectric layer and saturate bonds of the silicon that are still free which can lead to a further improvement in the passivating effect.
The specification then turns to the second aspect of the invention and describes a solar cell product in the following terms at page 9 line 28 to page 10 line 11:
According to a second aspect of the present invention, a solar cell is proposed comprising a silicon substrate; a first dielectric layer comprising aluminium oxide on a surface of the silicon substrate; and a second dielectric layer on a surface of the first dielectric layer, the materials of the first and the second dielectric layer differing and hydrogen being embedded into the second dielectric layer.
It should be noted that the embodiments, features and advantages of the invention have been described mainly in relation to the manufacturing method according to the invention. However, a person skilled in the art will recognise both from the foregoing and from the subsequent description that, unless otherwise indicated, the embodiments and features of the invention are also transferable by analogy to the solar cell according to the invention. In particular, the features of the various embodiments may also be combined with one another in any desired manner.
The specification then provides a summary of how it is that the invention so described is distinguished from the prior art known methods before turning to a Brief Description of one drawing and a Detailed Description of Embodiments (page 10 line 13 to page 11 line 6):
In summary, the method or the solar cell according to aspects and embodiments of the present invention is distinguished from previously known methods for the surface passivation of crystalline silicon solar cells or solar cells coated in this way inter alia in terms of the following points:
(i) very good surface passivation, such as is necessary for achieving high degrees of solar cell efficiency, can be achieved even after a firing step in the temperature range of 800-900 °C;
(ii) both low and high doped n- and p-type silicon surfaces can be passivated very effectively;
(iii) on account of the high negative charge density in the Al2O3 layer on p-type silicon, no inversion layer is induced below the passivating layer in the silicon, allowing the harmful effect of a "parasitic shunt" to be substantially avoided;
(iv) the layers contain no pinholes;
(v) it is possible to achieve in a simple manner very good optical properties of the layer system that can be adapted very easily to the requirements of the solar cell by way of the thickness and the composition of the, for example PECVD-deposited, layer, so that the layer system can for example be embodied as an antireflection layer on the front of the solar cell or as an infrared reflector on the back of the solar cell in combination with a metal coating over the entire surface of the passivating layer.
The Detailed Description refers to Figure 1, which illustrates schematically a solar cell according to one embodiment of the invention including a silicon wafer 1, aluminium oxide thin layer 3, metal contacts 7, 9 and silicon oxide thin layer 5.
In the Detailed Description of Embodiments, a manufacturing method is described. In it, a silicon wafer, into which an emitter on a surface was diffused beforehand and the surface of which was “cleaned thoroughly”, is introduced into an evacuated coating chamber and an aluminium-containing compound is fed into the chamber as a reactant. Chemisorption causes the molecules of the reactant to be deposited on the silicon surface until the surface is saturated and non-chemisorbed molecules of the reactant are removed from the chamber with a flushing gas such as nitrogen. Then an O2 plasma is ignited above the silicon surface to be passivated (or in a separate chamber) and the oxygen radicals react with the chemisorbed molecules to form Al2O3. In the best of cases, a monomolecular aluminium oxide layer is formed and the cycle is repeated until the desired thickness is reached using the ALD coating process about 40 or 50 times.
Two variants of ALD are described. The first is “plasma-assisted ALD”. The second is “thermal ALD”. In relation to the latter, the specification says (page 12 lines 27 to page 13 line 1):
Alternatively, the Al2O3 thin layer 3 can also be deposited by means of thermal ALD, as described in the literature in M. Ritala et al., Atomic layer deposition of oxide thin films with meal alkoxides as oxygen sources, Science 288, 319-321 (2000), for example.
The specification next provides that the Al2O3 thin layer which is deposited on the silicon wafer is subsequently coated in a PECVD reactor with a silicon oxide thin layer in a continuous process at a high deposition rate and then metal contacts are applied, for example, by screen printing on the front and back of the coated silicon substrate, and fired-in in a continuous furnace at about 700-900 °C.
The specification concludes with the following (page 13 lines 19 to page 14 line 11):
In summary and in other words, aspects of the present invention may be described as follows:
A method is proposed for forming a stack layer, the stack layer consisting of two partial layers:
(i) a very thin (for example ≤ 10nm) aluminium oxide thin layer formed by atomic layer deposition (ALD) from an aluminium-consisting gas (for example trimethylaluminium AL3)3), and also
(ii) a thicker (> 30nm) silicon oxide-containing thin layer which can be formed, for example by means of plasma enhanced chemical vapour deposition (PECVD), from the gases silane (SiH4) and dinitrogen oxide (N2O)) or carbon dioxide (CO2).
The second layer may also be, instead of a silicon oxide thin layer, a silicon nitride-containing thin layer formed from the gases silane (SiH4) and ammonia (NH4) by means of PECVD, or a silicon carbide-containing thin layer formed from the gases silane (CkH4) and methane (CH4). The thin layers made of silicon oxide, silicon nitride or silicon carbide, which are deposited by means of PECVD, have a very high hydrogen content (for example > 5 at. %) and therefore serve as a source of hydrogen during a firing step in the temperature range of 700-900 °C. The hydrogen diffuses through the ultrathin Al2O3 layer and passivates unsaturated silicon bonds (“dangling bonds”) at the Si/Al2O3 interface, leading to very good surface passivation after the firing step. In this way, the combination according to the invention of the two known deposition methods, ALD and PECVD, allows the formation of a firing-stable passivating layer which is optimally suitable for solar cells.
5.2 The Claims
Below are the claims of the invention, into which integer letters have been added to claims 1 and 9 for convenience. The parties proceeded on the basis that the numbers in parentheses, which appear in the claims of the patent, identify aspects of the invention identified in figure 1.
1.(a) Method for manufacturing a silicon solar cell, including the following steps:
(b) providing a silicon substrate (1);
(c) depositing a first dielectric layer (3) on a surface of the silicon substrate by means of atomic layer deposition, wherein the first dielectric layer comprises aluminium oxide; and
(d) depositing a second dielectric layer (5) on a surface of the first dielectric layer (3), the materials of the first and the second dielectric layer differing and hydrogen being embedded into the second dielectric layer.
2. Method according to claim 1, wherein, for depositing the first dielectric layer, the silicon substrate is firstly flushed with an aluminium-containing compound comprising at least one of the components Al(CH3)3, AlCl3, Al(CH3)2Cl and (CH3)2(C2H5)N:AlH3, so that an aluminium-containing layer is deposited on the surface of the silicon substrate, and wherein the aluminium-containing layer is subsequently oxidised to higher valency in an oxygen-containing atmosphere.
3. Method according to one of claims 1 or 2, wherein the second dielectric layer comprises a material selected from the group comprising silicon nitride, silicon oxide and silicon carbide.
4. Method according to one of claims 1 to 3, wherein the second dielectric layer is manufactured by means of a PECVD method.
5. Method according to one of claims 1 to 4, wherein the second dielectric layer is deposited in such a way that it has a hydrogen content of at least 1 at. %, preferably at least 2 at. % and more preferably at least 5 at. %.
6. Method according to one of claims 1 to 5, wherein a high-temperature step is carried out at temperatures above 600 °C preferably above 700 °C and more preferably above 800 °C, after the depositing of the second dielectric layer.
7. Method according to one of claims 1 to 6, wherein the first dielectric layer is deposited at a thickness of less than 50 nm, preferably less than 30 nm and more preferably less than 10 nm.
8. Method according to one of claims 1 to 7, wherein the second dielectric layer is deposited at a thickness of more than 50 nm, preferably more than 100 nm and more preferably more than 150 nm.
9. (a) Solar cell comprising:
(b) a silicon substrate (1):
(c) a first dielectric layer (3) comprising aluminium oxide on a surface of the silicon substrate (1)(d) wherein the first dielectric layer has a thickness of less than 50nm, preferably less than 30 nm and more preferably less than 10 nm;
(e) a second dielectric layer (5) on a surface of the first dielectric layer (3), (f) the materials of the first and second dielectric layer differing (g) and hydrogen being embedded into the second dielectric layer.
10. Solar cell according to claim 9 wherein the first dielectric layer is deposited by means of atomic layer deposition, so that it is substantially atomically tight.
11. Solar cell according to claim 9 or 10 wherein the second dielectric layer comprises silicon nitride.
12. Solar cell according to one of claims 9 to 11, wherein the second dielectric layer has a thickness of more than 50 nm, preferably more than 100nm and more preferably more than 150 nm.
13. Solar cell according to any one of claims 9 to 12, wherein the second dielectric layer has a thickness of more than 100 nm.
14. Solar cell according to any one of claims 9 to 13, further comprising a plurality of metal contacts, wherein the metal contacts pass through the first dielectric layer and the second dielectric layer.
16. Solar cell according to any one of claims 9 to 14, wherein the surface of the silicon substrate is passivated by hydrogen.
17.Solar cell according to any one of claims 9 to 16, wherein the first dielectric layer passivates a region of the silicon substrate of conduction type p.
18.Solar cell according to claim 17, wherein the surface of the silicon substrate is at the back of the solar cell.
19.Solar cell according to claim 18 wherein the second dielectric layer forms part of a back surface reflector.
20.Solar cell according to claim 19, wherein the back surface reflector further comprises a metal coating over a back surface of the second dielectric layer.
21.Solar cell according to any one of claims 9 to 20, wherein the thickness of the first dielectric layer is more than about 2 nm.
22.Solar cell manufactured using a method according to one of the preceding claims 1 to 8.
5.3 The nature and purpose of the claimed invention
The experts aptly summarise in the Construction JER that the purpose of the claimed invention is to provide temperature-stable passivation of surfaces of silicon solar cells, while avoiding some of the drawbacks of surface passivation methods known at the time. They agree that the nature of the claimed invention is the use of a high temperature stable dielectric stack consisting of a thin layer of aluminium oxide, which has a high density of negative charge, and a thicker layer of a different dielectric material that contains hydrogen, which is released upon annealing, further contributing to the surface passivation and to its thermal resilience.
It may be noted, however, that the patent does not disclose or describe a completed solar cell. It relates to, and describes, an aspect of a solar cell involving the double dielectric layers of the claims which are useful for passivating the surface of the silicon substrate. As the five experts involved in the preparation of the Construction JER agreed, being Dr Rentsch, Professor Cuevas-Fernandez, Professsor Weber, Dr Ruby and Dr Glew (construction experts), further work would have been required in the development of equipment and processes suitable for photovoltaics manufacturing in particular in relation to the use of ALD in the method claimed.
5.4 The skilled addressee
Skilled addressees are those likely to have a practical interest in the subject matter of the invention: Catnic Components v Hill & Smith Ltd [1982] RPC 183 at 242 (Diplock LJ). There may be more than a single person with such an interest, and the notional skilled reader to whom the document is addressed may not be a single person but a team, whose combined skills would normally be employed in that art in interpreting and carrying into effect instructions such as those which are contained in the document to be construed: General Tire & Rubber Co v Firestone Tyre & Rubber Co Ltd [1971] 7 WLUK 130; [1972] RPC 457 at 485 (Sachs LJ). Put another way, the skilled addressee is a notional person who may have an interest in using the products or methods of the invention, making the products of the invention, or making products used to carry out the methods of the invention either alone or in collaboration with others having such an interest: Aristocrat Technologies Australia Pty Limited v Konami Australia Pty Limited [2015] FCA 735; 114 IPR 28 at [26] (Nicholas J); Pharmacia LLC v Juno Pharmaceuticals Pty Ltd [2022] FCA 92; 165 IPR 200 at [111] (Burley J).
The patent is broadly directed to a method for manufacturing a solar cell and a solar cell with a surface passivating dielectric double layer, being a two dielectric layer stack, the first of which comprises aluminium oxide.
Hanwha submits that the person skilled in the art should be limited to a person who is qualified and experienced in using solar cell manufacturing processes in commercial or industrial settings. REC Solar submits that the relevant person skilled in the art is somewhat broader, contending that to take the disclosure of the patent and implement it industrially would have required the work of a notional team, consisting of industry participants but also researchers and equipment manufacturers.
In my view the patent is addressed to persons having a good understanding of silicon solar cell technology used by the photovoltaics industry. They would have at least an undergraduate degree in a relevant field such as science or engineering and have either research or industry experience working in the field whether in an applied research institution working on photovoltaics research or working in industry. Although Hanwha submits that the skilled addressee is to be confined to a person working in industry, I consider that description to be too confined. Whilst it is true that in parts the patent refers to a solar cell in its completed state, it is notable that the first problem identified in the specification is of the prior art in the form of the use of high temperature steps used in the production of laboratory solar cells, which are not in general use in industrially produced solar cells. Furthermore, the experts agreed in the Construction JER that the patent provides a general guide to the implementation of the invention but significant work would have been required to determine which technique was most suitable for the design of equipment and processes for industrial use. This would have involved collaboration between equipment manufacturers (such as in the use of ALD equipment) or research institutions or both. In this regard, the evidence going to the background and experience of Professors Rentsch, Weber and Cuevas-Fernandez supports the view that academic researchers in the field were engaged in considerable collaboration with industry. Furthermore, Dr Winderbaum’s experience indicates that those in industry are likely to collaborate with those working in research institutions in making developments in solar cell technology.
Accordingly, where I refer below to the person skilled in the art or the skilled worker, that construct refers to persons who are researchers in academia focussed on photovoltaic cells in the context of solar cell design and/or workers in industry who are engaged in the manufacture of such solar cells. I find that workers in academia and industry worked in close collaboration and as such would readily work in a team on the development of products.
In this regard, I consider that each of Professors Weber, Professor Cuevas-Fernandez, Dr Rentsch and Dr Winderbaum fall within the description of the skilled worker. Dr Glew, with his background and experience in the supply of equipment used for the manufacture of silicon chips, is less squarely within the field, although his experience as a supplier to solar cell manufacturers, his depth of knowledge in the field as a materials scientist experienced in the use of PECVD of dielectric films and his obvious understanding of the intricacies of the technology underlying the disclosure of the patent is such that I find that his evidence is of some assistance.
6. CLAIM CONSTRUCTION
6.1 Introduction
The claim construction issues in the proceeding largely, but not exclusively, concern claims 1 and 9. They arise for various reasons. Several concern non-infringement arguments, others arise in the context of novelty arguments and others are relevant to points arising from allegations of inutility or non-compliance with s 40 of the Patents Act. It is appropriate to address all construction issues separately and before turning to the these arguments, or, as the authorities say, “as if the infringer had never been born”; CCOM Pty Ltd v Jeijing Pty Ltd [1994] FCA 396; 51 FCR 260 at 267-268 (Spender, Gummow and Heerey J); Pharmacia LLC at [117] (Burley J).
The matters addressed below concern the proper meaning of the following terms in claim 9:
(1)“dielectric layer”;
(2)“depositing a first dielectric layer on a surface of the silicon substrate”;
(3)“depositing a second dielectric layer on a surface of the first dielectric layer”;
(4)“first dielectric layer comprising aluminium oxide”;
(5)“and hydrogen being embedded into the second dielectric layer”.
Additional disputes arise from the following terms in claims dependent on claim 9 being:
(6)“substantially atomically tight” in claim 10;
(7)“second dielectric layer comprises silicon nitride” in claim 11;
(8)“wherein the surface of the silicon substrate is passivated by hydrogen” in claim 16; and
(9)“second dielectric layer forms part of a back surface reflector” in claim 19.
For convenience, I reproduce claim 9 with integers marked as letters:
(a) Solar cell comprising:
(b) a silicon substrate (1):
(c) a first dielectric layer (3) comprising aluminium oxide on a surface of the silicon substrate (1)(d) wherein the first dielectric layer has a thickness of less than 50nm, preferably less than 30nm and more preferably less than 10nm;
(e) a second dielectric layer (5) on a surface of the first dielectric layer (3), (f) the materials of the first and second dielectric layer differing (g) and hydrogen being embedded into the second dielectric layer.
Integers (c) and (d) identify a dielectric layer with a number of relevant characteristics including: that it must be a “first” dielectric layer; that it must be “on a surface of the silicon substrate”; that it must “comprise” aluminium oxide; and that it must have a maximum thickness. Integers (e), (f) and (g) identify further characteristics that a further dielectric layer must have including: that it be a “second” dielectric layer; that it be “on a surface of the first dielectric layer”; that it be of materials differing from the first dielectric layer; and that hydrogen be embedded into it.
The construction experts gave evidence in chief going to construction of the patent. Each participated in the preparation of Construction JER and each gave concurrent evidence addressing these issues. Their evidence was of considerable assistance in clarifying aspects of the disputed common general knowledge relevant to questions of construction, explaining the technology and identifying the meaning of terms and phrases used in the patent.
As a matter of context, it may be noted that the infringement allegations against LONGi and Jinko included that claim 1 and some of its dependent claims had been infringed. Validity challenges advanced by LONGi and Jinko (but not REC Solar) also raised questions of construction concerning claim 1 and some of its dependent claims. As a result of the settlement of the LONGi and Jinko proceedings, it is not strictly necessary to consider these questions. However, the parties in closing submissions (including REC Solar) often developed their construction arguments by reference to all of the claims in suit, including claim 1. At the time, that was a logical course to take. In addressing the construction issues relevant to claims 9 and its dependent claims in this judgment, I necessarily address the arguments as presented by the parties at trial, which for the most part first addressed the equivalent construction question in relation to claim 1 and then submitted that the same or equivalent word or phrase had the same meaning in claim 9.
Claim construction is, of course, a matter for the Court, although it is aided by the evidence of experts who can assist as to the way in which the hypothetical skilled reader would understand the claims having regard to the common general knowledge as at the priority date. In broad terms, the task of the Court is put itself in the position of the skilled addressee and, with the aid of the background knowledge in the field, to construe the language of each claim, which has been deliberately chosen by the patentee, as it sits in the context of the specification as a whole.
Although many cases have referred to the principles applicable to claim construction, one convenient authority that summarises key aspects of those principles is Jupiters Ltd v Neurizon Pty Ltd [2005] FCAFC 90; 65 IPR 86 at [67] where Hill, Finn and Gyles JJ said:
(i)the proper construction of a specification is a matter of law: Décor Corp Pty Ltd v Dart Industries Inc (1988) 13 IPR 385 at 400;
(ii)a patent specification should be given a purposive, not a purely literal, construction: Flexible Steel Lacing Company v Beltreco Ltd (2000) 49 IPR 331 at [81]; and it is not to be read in the abstract but is to be construed in the light of the common general knowledge and the art before the priority date: Kimberley-Clark Australia Pty Ltd v Arico Trading International Pty Ltd (2001) 207 CLR 1 at [24];
(iii)the words used in a specification are to be given the meaning which the normal person skilled in the art would attach to them, having regard to his or her own general knowledge and to what is disclosed in the body of the specification: Décor Corp Pty Ltd at 391;
(iv)while the claims are to be construed in the context of the specification as a whole, it is not legitimate to narrow or expand the boundaries of monopoly as fixed by the words of a claim by adding to those words glosses drawn from other parts of the specification, although terms in the claim which are unclear may be defined by reference to the body of the specification: Kimberley-Clark v Arico at [15]; Welch Perrin & Co Pty Ltd v Worrel (1961) 106 CLR 588 at 610; Interlego AG v Toltoys Pty Ltd (1973) 130 CLR 461 at 478; the body of a specification cannot be used to change a clear claim for one subject matter into a claim for another and different subject matter: Electric & Musical Industries Ltd v Lissen Ltd [1938] 56 RPC 23 at 39;
(v)experts can give evidence on the meaning which those skilled in the art would give to technical or scientific terms and phrases and on unusual or special meanings to be given by skilled addressees to words which might otherwise bear their ordinary meaning: Sartas No 1 Pty Ltd v Koukourou & Partners Pty Ltd (1994) 30 IPR 479 at 485-486; the Court is to place itself in the position of some person acquainted with the surrounding circumstances as to the state of the art and manufacture at the time (Kimberley-Clark v Arico at [24]); and
(vi)it is for the Court, not for any witness however expert, to construe the specification; Sartas No 1 Pty Ltd, at 485-486.
(63)The properties of the silicon nitride film deposited by PECVD are sensitive to the parameters used. Therefore, a standard approach is to optimise the parameters used in the PECVD process in order to obtain a silicon nitride film having the desired optical and electronic/passivation properties. This is an iterative process involving the optimisation of the parameters as a whole. In general, the process to optimise the parameters involves routine and well-established experimental and statistical methods.
3. Structure of silicon solar cells and modules
3.1 Silicon solar cell structure
(64)As at November 2007 the structure of a silicon solar cell was designed to achieve the following:
(a)trap energy from photons within the solar cell;
(b)create excess electrons and holes within the solar cell in order to produce a voltage;
(c)facilitate movement of electrons (i.e. current) to the electron contact and hole current to the hole contact; and
(d)transfer electrons from the solar cell to a circuit, so that electric current can be used outside the solar cell.
(65)These aims could potentially be achieved in a number of different ways, each of which is focused on maximising the yield (of electrical energy) from the solar cell (for example, increasing the absorption properties of the cell) while minimising losses (for example, reducing recombination).
(66)As at November 2007, in general, most commercially available, silicon solar cells had the following structure:
(a)a p-type crystalline silicon substrate. This was either a single crystalline (monocrystalline) wafer or (more commonly) a multicrystalline wafer. Single-crystalline silicon was formed using the Czochralski method, which involves melting silicon in a cylindrical container, rotating the container continuously while simultaneously drawing the silicon out of the melt. The silicon crystallises and forms a single crystal that is then cut into wafers using a wire-sawing process. As at November 2007, multicrystalline silicon wafers, which were cheaper to produce than single crystalline wafers, were produced by a casting process that involves melting silicon in a quartz crucible lined with silicon nitride, then allowing the silicon to cool carefully so that it crystallises. The silicon substrate used in conventional, commercially available silicon solar cells was textured on the front and the rear.
(b)a phosphorus diffused (n-type) front emitter in the silicon substrate. This provides a high electron concentration (typically, 1020 cm-3) near the front surface of the silicon.
(c)a dielectric layer of PECVD silicon nitride on the top (sun-facing) surface of the silicon substrate to provide surface passivation (subject to the matters discussed in paragraph 25 above) and an antireflection coating.
(d)front metal contacts. As at November 2007, the metal contacts in a solar cell were essential to allow current to flow from the cell to the external electric circuit. They collect photo-generated electrons that have made their way to the n-type emitter. As at November 2007, the front metal contacts were typically formed by a screen printing process. This involves a metal paste being squeezed across a screen so that it leaves a pattern on the surface of the silicon cell. The metal paste is then fired in a step, which reaches a maximum temperature of approximately 800-900°C, and which causes the metal paste to burn its way through any films on the surface of the silicon substrate such that the metal can make contact with the silicon wafer. This process is usually referred to as firing, or “fire-through” metallisation. Direct contact between the metal and the silicon wafer results in electrical conductivity. The front contacts are formed in strips so as to minimise the number of photons that are absorbed or reflected by the metal and therefore do not reach the silicon wafer.
(e)a back metal contact forming a heavily doped p-type region at the rear of the silicon substrate. As at November 2007, the back metal contact of most commercially available, silicon solar cells typically covered essentially the entire surface area of the rear of the solar cell. The back metal contact was typically formed from an aluminium paste, which formed an alloy with the underlying silicon during the same firing process mentioned above. This produced a region several microns thick of aluminium doped silicon in the silicon substrate. Aluminium is a p-type dopant and, like boron, is located in Group III in the Periodic Table of the elements. This provides a high concentration of holes in comparison to the concentration of electrons at the rear of the silicon wafer (that is, a heavily doped p-type surface at the rear of the silicon substrate). Such an imbalance between electron and hole concentrations at the rear of the cell can help to reduce the recombination of excess carriers in that location. In addition, heavy doping reduces the resistance of the electrical contact of the silicon to the metal. The back layer also acts as a reflector to an extent, and reflects some of the sunlight back into the silicon, as I discussed in paragraph 39 above. The heavily doped p+ region was frequently referred to as the back surface field, or BSF, region. Figure 7 below schematically illustrates the general structure of a conventional, commercially available, silicon solar cell as at November 2007. Although it is not labelled in Figure 7, the dielectric layer on the sun-facing surface of the silicon wafer as at November 2007 was silicon nitride (as set out above).
Figure 7: Schematic illustration of the structure of a conventional single crystal silicon solar cell.
(67)The conventional, commercially available silicon solar cell, as at November 2007, of the structure described above is referred to below as a Conventional Solar Cell. This solar cell design is also generally referred to by Skilled Persons in the Field as a back surface field, or BSF, solar cell.
(68)Another family of solar cell structures that was well known to Skilled Persons in the Field, was the Passivated Emitter and Rear Cell (PERC). PERC cells were being researched in laboratories but were not commercialised at that time. PERC cells were developed by the University of New South Wales well prior to November 2007. In these solar cells, the front side is the same as described above for Conventional Solar Cells. However, the rear side of a PERC cell as at November 2007 was, and still is today, mostly covered with a passivating dielectric, with local openings in the dielectric layer for the metal contacts. The entire rear surface was then usually covered with a metal. The PERC structure provides improved rear surface passivation, allowing higher voltages and currents to be achieved. It also improves the reflective properties of the rear, allowing a further boost in the current. Figure 8 below provides a schematic illustration of the general structure of the rear of a PERC cell, shown with silicon oxide as the rear dielectric layer and the metal contacts as “point” contacts.
Figure 8: Schematic diagram of the rear of a PERC cell (the front, sun-facing surface of the cell is not shown).
(69)As at November 2007, Skilled Persons in the Field were aware that a particular type of PERC cell was a PERL (Passivated Emitter and Rear Locally doped) silicon solar cell. PERL cells were also developed by the University of New South Wales prior to November 2007 and held the efficiency record for crystalline silicon for some time. In a PERL cell, most of the front and rear surfaces of the silicon are passivated by a dielectric film, except for the regions where electrical contact is made. The silicon regions underneath the rear contacts are heavily doped while the silicon regions underneath the dielectric are not. The general structure of a PERL cell as at November 2007, shown with an oxide film as the front and rear dielectric, is schematically illustrated in Figure 9 below. It is worth noting that other acronyms were also in use at the time to refer to the same type of solar cell structure; for example, the Fraunhofer Institute used the terms Local Back Surface Field (LBSF), since they used aluminium doping to form the local p+ regions.
Figure 9: Schematic diagram of the general structure of a PERL cell.
(70)A number of other solar cell structures were well known by other Skilled Persons in the Field:
(a)Interdigitated Back Contact solar cells (IBCs). These solar cells do not have any contacts on the front (sun-facing surface) of the solar cell. In an IBC cell, the emitter covers part (but not all) of the rear surface. The contacts to the p and n regions of the cell alternate along the rear surface to form an interdigitated finger pattern. The general structure of an IBC cell as at November 2007 is schematically illustrated in Figure 10 below.
Figure 10: Schematic diagram of the structure of an interdigitated back contact solar cell.
(b)Heterojunction solar cells. These were developed in Japan and relied on the use of doped amorphous silicon to create a pn junction. Heterojunction cells generally do not employ diffusions. Heterojunction cells are based upon amorphous silicon, which was at November 2007, and also is today, the dominant heterojunction cell technology. They employ undoped, heavily doped n-type and heavily doped p-type amorphous silicon layers to create the contact regions for the n and p contacts. The general structure of a heterojunction cell as at November 2007 is schematically illustrated in Figure 11 below.
Figure 11: Schematic illustration of the general structure of a heterojunction cell.
(71)Prior to November 2007, silicon solar cells were also being developed and researched that featured more than one dielectric film on the front surface of the silicon. Such dielectric stacks could be used to further improve the optical and/or electronic properties of the solar cell. The use of stacks in semiconductor research, including silicon solar cell research, was generally well known to Skilled Persons in the Field as at November 2007. Prior to 2007, an example of the use of a stack in photovoltaics research was the use of stacks consisting of a thin layer of intrinsic (undoped) amorphous silicon combined with a thicker layer of doped amorphous silicon on top of a silicon wafer to create a high efficiency heterojunction solar cell. In this case, the intrinsic amorphous silicon layer serves primarily to ensure good surface passivation, while the doped amorphous silicon layer ensures good carrier transport. Yet another layer, of a conductive transparent material such as indium tin oxide, is needed on top of the doped amorphous silicon layers to provide lateral conductivity and antireflection.
(72)The final structure of a particular stack was as at November 2007, often a product of experimentation, modelling and analysis, with different techniques and materials, depending upon a number of considerations, which must be weighed against each other.
3.2 Solar Modules
(73)Solar modules, also known as solar panels, include many individual solar cells that are electrically interconnected. As at November 2007, a solar module typically consisted of a glass coversheet, an encapsulant material (e.g. ethyl vinyl acetate (EVA)), the electrically connected solar cells, a rear sheet of suitable material such as tedlar (a plastic material chosen for its properties in terms of providing a degree of electrical insulation and environmental protection), a frame and a junction box. The structure of a typical solar module as at November 2007 (without the frame and junction box) is schematically illustrated in Figure 12 below.
Figure 12: A typical solar module structure shown without the frame or junction box.
4. Solar cell manufacturing process
(74)As at November 2007, most Conventional Solar Cells were made from either a multi-crystalline or single crystal p-type silicon wafer. The first step was the formation of the silicon wafer. This was achieved by producing a silicon ingot formed from molten silicon, which was then sliced into thin wafers. In the case of a single crystal p-type Czochralski silicon wafer, the first step in manufacturing a silicon solar cell was to remove any damage caused to the silicon wafer from the sawing process used during its preparation from an ingot. Such damage consisted of defects in the near-surface region of the wafer, which could result in increased recombination and would therefore be detrimental to the performance of the cell (that is, its efficiency) if they were not removed. The removal of this damage involved etching the surface of the silicon wafer with an aqueous alkaline solution containing sodium hydroxide or potassium hydroxide and various additives. The etching process removed some of the silicon over the entire wafer surface on both sides of the wafer. In addition, it resulted in the formation of randomly positioned pyramids of varying sizes on the front and rear of the silicon substrate. In the case of a multicrystalline wafer, which was more common, the first steps were similar but not identical, as this was done with using a mixture of hydrofluoric acid (HF) and nitric acid (HNO3) and did not produce pyramidal textures. The front (sun-facing) side of the wafer was then subjected to texturing. This process was used to roughen the surface of the wafer, which improves its optical properties (ie, the amount of light it absorbs).
(75)Following the alkaline etch, the wafer was cleaned to ensure a bare silicon wafer surface that was, as far as possible, free of metallic contaminants and any oxide that had developed during the cleaning steps themselves or on exposure of the silicon wafer to air. Any such oxide that formed was typically a few nanometres thick. The cleaning process used could vary but, when done in industry, typically involved rinsing the silicon wafer in deionised water (high purity water, from which metallic ions and other organic and inorganic contaminants have been removed) to remove as much of the etching solution as possible; immersing the wafer in hydrochloric acid solution or sulphuric acid solution, which may have contained other additives; conducting a further rinse of the wafer in deionised water; immersing the wafer in hydrofluoric acid; conducting a further rinse in deionised water; and finally drying the wafer in hot air.
(76)The next step was a phosphorus diffusion to create regions of n-type silicon to form an n-type phosphorus emitter and pn junction. This process typically involved placing the silicon wafers vertically in a quartz boat which was then placed in a furnace tube heated to a temperature of between about 800-900 °C. A nitrogen carrier gas was bubbled through phosphorus oxychloride (POCl3), resulting in gaseous phosphorus oxychloride, which was then mixed with oxygen and injected into the furnace tube. This resulted in the deposition of phosphorus pentoxide (P2O5) onto the wafer surface. During a subsequent step, the temperature in the furnace was increased to about 900-950 °C. This drove the phosphorus in the P2O5 into the silicon wafer. Alternatively, industrial manufacturers used a conveyor belt furnace to achieve the phosphorus diffusion from a phosphorus containing layer previously deposited on the wafers.
(77)The diffusion process resulted in a phosphosilicate glass on the front surfaces of the wafer. This was typically removed by etching the wafer in hydrofluoric acid. The wafers were subsequently removed from the furnace and a “phosphorus glass” layer that is formed during the diffusion process was removed. This typically involved immersing the wafer in a solution containing hydrofluoric acid.
(78)Removal of the phosphorus glass could be evidenced by the lack of any film of solution forming on the wafer surface when it was pulled out of the solution. This effect is due to the bare surface of the silicon wafer being hydrophobic.
(79)The diffusion process also occurred on all sides of the wafer. As such, in some cases the rear side of the wafer was then etched away using a mixture of HF and nitric acid (HNO3) to remove the n-type region. Typically this would be done with the same tool as was used to remove the phosphosilicate glass. However, single-sided etching processes were relatively difficult to control, and because in the process of the formation of the back surface field the silicon surface containing the phosphorous diffusion was dissolved in the aluminium, it was not critical to remove the n-type doping completely from the rear side. As such, in some cases this step was not done. It was, however, more important to remove any “wraparound” n-type doping on the other sides of the wafer (ie, any n-type region running from the front to the back of the wafer). At the Relevant Date, this was commonly done by laser cutting a trench around the edge of the wafer.
(80)The antireflection coating, a layer of silicon nitride, was deposited on the front side of the wafer. This was generally done by way of PECVD. The next step was the deposition of a film of silicon nitride on the side of the wafer with the diffusion (the front side), which was usually conducted using a PECVD process, as discussed in paragraph 60-61 above. At November 2007, the typical thickness of the PECVD silicon nitride film deposited on the front side of a silicon solar cell was approximately 70-80 nm.
(81)Following the deposition of the silicon nitride film, the next step was to screen print a silver paste on the front side of the wafer to form the metal fingers (front metal contacts). That was followed by a drying step to remove most of the organic solvents from the paste. An aluminium silver paste was then screen printed onto the rear of the wafer to form the rear busbars (regions that could be soldered to for the purpose of attaching ribbons when producing solar cell modules). A further drying step then occurred. An aluminium paste was then screen printed over the rear surface of the wafer, to form the rear side metal contact, followed by another drying step.
(82)The next step in the process was a firing of the wafer. In this step, the wafers moved through a furnace that consisted of several heating zones, the temperature of which could be independently controlled. By adjusting the heat intensity and the speed at which the wafers moved through the furnace, the temporal temperature profile that the wafers experienced could be controlled. Temperatures of a maximum of approximately 800-900 °C were typically used in the firing step, although the peak temperature was only maintained for a short period of time (several seconds). The entire firing step generally lasted around a minute in length.
(83)This process was used to form the contact between the front and rear contacts and the silicon wafer, although in the case of the rear contact, this also drives the aluminium into the rear surface of the wafer. The firing step also has other effects on the structure of the solar cell. At the front surface, the firing step burned the metal contacts (fingers) through the silicon nitride film so that the metal contacted the silicon wafer and reacted with the silicon wafer surface. The metal pastes used to form the contacts have ingredients that enable the paste to etch through the antireflection coating during the firing step. This resulted in electrical contact between the silicon wafer surface and the metal layer. At the rear surface, the firing process resulted in an alloying of the aluminium with the silicon to produce a silicon layer that was heavily doped with aluminium. This produced an electrical contact between the silicon substrate and the rear metal and provided a degree of surface passivation to the rear surface.
(84)The firing process would also release hydrogen from the silicon nitride film, some of which diffused into the bulk of the wafer where it could help to passivate defects and some of which diffused to the silicon/silicon nitride interface to passivate interface defects. In the case of multicrystalline silicon wafers, such bulk hydrogenation was regarded as an important advantage of using PECVD to deposit the silicon nitride layer.
(85)The cells were then tested by measuring the current/voltage curve to obtain the efficiency and were sorted according to their performance (efficiency).
SCHEDULE OF PARTIES
NSD 458 of 2019 Cross-Claimants
Second Cross-Claimant:
SOL DISTRIBUTION PTY LTD ABN 53 146 905 286
Third Cross-Claimant:
BAYWA R.E. SOLAR SYSTEMS PTY LTD ACN 614 035 620
Cross-Respondents
Second Cross-Respondent
HANWHA SOLUTIONS CORPORATION (REGISTRATION NO. 110111-0360935)
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