Hanwha Solutions Corp v. Maxeon Solar Pte Ltd

1. Case Identification

• Case #: IPR2024-01199
• Patent #: 8,878,053
• Filed: August 8, 2024
• Petitioner(s): Hanwha Solutions Corporation
• Patent Owner(s): Maxeon Solar Pte. Ltd.
• Challenged Claims: 1-20

2. Patent Overview

• Title: Solar Cell Fabrication Processes
• Brief Description: The ’053 patent discloses methods for fabricating a solar cell. The methods generally involve forming a backside junction by creating an emitter (e.g., P-type polysilicon) on the back surface of a silicon substrate of the opposite doping type (e.g., N-type), sometimes with an intervening tunnel oxide layer.

3. Grounds for Unpatentability

Ground I: Obviousness over Froitzheim and Gan - Claims 9-12, 14, and 16-20 are obvious over Froitzheim in view of Gan.

• Prior Art Relied Upon: Froitzheim (EP 1,732,142A1) and Gan (Polysilicon Emitters for Silicon Concentrator Solar Cells, IEEE Conference on Photovoltaic Specialists, 1990).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Froitzheim teaches a method of manufacturing a rear-junction solar cell with a diffused p-type emitter on the back of an n-type silicon substrate. This structure includes front contacts, a textured front surface, and passivation layers to reduce recombination. Gan teaches that solar cell performance can be improved by replacing a diffused emitter with a polysilicon emitter having a thin, thermally grown interfacial oxide layer between the emitter and the substrate. Gan’s data demonstrated this structure achieves lower recombination and contact resistance, leading to higher efficiency. Independent claim 16’s additional limitation of an oxide layer between the substrate and the polysilicon emitter is expressly taught by Gan.
  • Motivation to Combine: Petitioner contended a Person of Ordinary Skill in the Art (POSITA) would combine Gan’s high-efficiency polysilicon emitter and oxide layer structure with Froitzheim’s back-junction solar cell design. The motivation would be to apply a known technique (Gan's emitter) to improve a similar device (Froitzheim's cell) to achieve the predictable result of increased efficiency. Gan explicitly states its structure is useful for "backside contact solar cells," a known configuration.
  • Expectation of Success: A POSITA would have a reasonable expectation of success because the fabrication processes in both references are compatible, using similar thermal diffusion steps and temperature ranges. Implementing a polysilicon emitter and oxide layer were well-known, routine techniques within the skillset of a POSITA at the time.

Ground II: Obviousness over Froitzheim, Gan, and Smith - Claims 1-20 are obvious over Froitzheim, Gan, and Smith.

• Prior Art Relied Upon: Froitzheim (EP 1,732,142A1), Gan (1990 IEEE Conference paper), and Smith (Patent 6,998,288).

• Core Argument for this Ground:

  • Prior Art Mapping: This ground builds upon the combination of Froitzheim and Gan, adding Smith for its teachings on simplifying fabrication and reducing costs. Smith discloses techniques like depositing a boron-doped silicon dioxide layer as a dopant source, followed by an undoped silicon dioxide "capping layer" to enable one-sided deposition. Smith also explicitly teaches performing multiple diffusion steps "in-situ," meaning in a single loading of the wafer into a processing furnace, which "simplifies the fabrication process" and lowers costs. These teachings map onto limitations in claims 1, 7, 8, and 15 related to capping layers and in-situ processing.
  • Motivation to Combine: Petitioner argued that a POSITA, having combined Froitzheim and Gan to create a high-efficiency cell, would have been further motivated to incorporate Smith’s manufacturing techniques to simplify the process and reduce costs—a critical consideration in commercial solar cell production. Smith’s techniques for one-sided deposition and in-situ diffusion were advantageous and directly applicable to the structure resulting from the Froitzheim/Gan combination.
  • Expectation of Success: The combination involves applying known, compatible manufacturing techniques to improve a known solar cell design in a predictable way. Smith’s methods were designed to simplify standard fabrication steps and would be expected to work successfully with the processes taught by Froitzheim and Gan.

• Additional Grounds: Petitioner asserted an additional obviousness challenge (Ground III) against claims 9-20 based on the combination of Li (CN 1949545A), Gan, and Smith. This ground relied on similar motivations, with Li teaching a backside junction solar cell analogous to Froitzheim's.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial would be improper under both the General Plastics and Fintiv frameworks.
• General Plastics/§325(d): Petitioner asserted that a prior IPR filed by Canadian Solar Inc. (CSI) against a subset of claims should not bar this petition. Petitioner argued it has no relationship with CSI, this petition challenges all claims, and it was filed promptly in response to litigation initiated by the Patent Owner. Furthermore, the petition relies on prior art (Froitzheim, Gan, Li) that was not considered during the original prosecution, and its arguments based on Smith are materially different from those before the examiner.
• Fintiv: Petitioner contended that because it filed the petition expeditiously after being sued and there is no current case schedule or trial date in the parallel district court litigation, the Fintiv factors weigh against denial.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-20 of the ’053 patent as unpatentable under 35 U.S.C. §103.