PTAB

IPR2025-01130

JinkoSolar Holding Co Ltd v. First Solar Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: High-efficiency Solar Cell Structure and Methods of Manufacture
  • Brief Description: The ’074 patent relates to methods of fabricating high-efficiency solar cells. The claimed methods generally involve providing a silicon wafer as a central substrate, depositing an amorphous interface passivation layer followed by a doped conductive and passivating layer, and then applying a thermal treatment at 500°C or higher to crystallize the layers and facilitate dopant diffusion.

3. Grounds for Unpatentability

Ground 1: Claims 1-8 are anticipated or obvious over Tamura

  • Prior Art Relied Upon: Tamura (Japanese Application Publication No. JP1992245683).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Tamura discloses every limitation of the challenged claims. Tamura describes a method for manufacturing a solar cell by depositing an undoped amorphous silicon layer (the interface passivation layer) onto a p-type silicon substrate. It then discloses depositing a high-concentration n+ type amorphous silicon layer (the conductive and passivating layer) on the undoped layer. Petitioner asserted that Tamura’s subsequent step of heat-treating the structure at 600°C for five minutes meets the thermal treatment limitation, as it crystallizes the amorphous layers and causes dopant diffusion to form a p-n junction. Finally, Petitioner contended that Tamura’s disclosure of forming a "comb-shaped front surface electrode" after the heat treatment, which directly contacts the crystallized n+ layer, satisfies the metallization limitation of claim 1.
    • Key Aspects: Petitioner emphasized that Tamura, which was not considered during prosecution, teaches the very process claimed in the ’074 patent, including the final metallization step that was identified by the Examiner as the point of novelty.

Ground 2: Claims 1-2 and 4-8 are anticipated or obvious over Borden

  • Prior Art Relied Upon: Borden ("Polysilicon Tunnel Junctions as Alternates to Diffused Junctions," a 2008 publication).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that Borden’s method for creating solar cells maps directly onto the claims. Borden teaches growing a thin tunnel dielectric (e.g., silicon oxide) on an n-type silicon substrate, which Petitioner identified as the claimed amorphous interface passivation layer. Borden then discloses depositing a doped amorphous silicon layer over the tunnel dielectric, which Petitioner mapped to the conductive and passivating layer. Petitioner argued that Borden's subsequent rapid thermal annealing (RTA) at 1000°C meets the thermal treatment limitation, as it crystallizes the amorphous silicon into polysilicon and facilitates dopant diffusion. The final metallization step was allegedly met by Borden’s disclosure of forming front-side "Grids" and a back-side aluminum contact after the RTA step. Dependent claim limitations, such as forming an antireflective layer (claim 2) and perforation of the passivation layer (claim 4), were also allegedly disclosed.

Ground 3: Claims 3-4 are obvious over Borden in view of Kwark, Gan, or Swanson

  • Prior Art Relied Upon: Borden ("Polysilicon Tunnel Junctions..."), Kwark ("SIPOS Heterojunction Contacts to Silicon," a 1984 publication), Gan ("Polysilicon Emitters for Silicon Concentrator Solar Cells," a 1990 publication), and Swanson (Patent 5,057,439).

  • Core Argument for this Ground: This ground focused on the obviousness of dependent claims 3 and 4, which require depositing a single amorphous silicon-containing compound that is later separated into the passivation and conductive layers by thermal treatment.

    • Prior Art Mapping: Borden provides the foundational solar cell manufacturing process. The secondary references, such as Kwark, teach alternative methods for forming the passivating and conductive layers. Kwark, for instance, discloses depositing a single Semi-Insulating Polycrystalline Silicon (SIPOS) film, which is an amorphous silicon-containing compound. Upon annealing, this single SIPOS layer separates into a thin interfacial silicon oxide layer (the passivation layer) and a layer of conductive silicon microcrystallites.
    • Motivation to Combine: Petitioner argued a person of ordinary skill in the art (POSITA) would combine Kwark with Borden to simplify the manufacturing process and reduce costs. Borden teaches a two-step process of first growing a tunnel oxide and then depositing an amorphous silicon layer. A POSITA would have been motivated to replace this with Kwark’s more efficient single-step deposition of a SIPOS layer, which achieves the same layered structure after annealing. This modification would reduce process complexity and fabrication costs while achieving a superior balance between passivation and dopant control.
    • Expectation of Success: A POSITA would have a reasonable expectation of success in this combination because both Borden and Kwark utilize well-known CVD deposition techniques and thermal treatments within similar temperature ranges to achieve similar device structures. The modification was presented as a simple substitution of one known layer-formation technique for another to achieve predictable benefits.

  • Additional Grounds: Petitioner asserted an additional challenge that claims 1-8 are anticipated or obvious over Rana (Application # US 2010/0240172).

4. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-8 of the ’074 patent as unpatentable.