Obviousness

Obviousness Analysis of US Patent 9666732 under 35 U.S.C. § 103

To determine the obviousness of US Patent 9666732, we must consider whether the differences between the claimed invention and the prior art would have been obvious, at the time the invention was made, to a person having ordinary skill in the art (PHOSITA). This analysis follows the framework set forth in Graham v. John Deere Co., which considers the scope and content of the prior art, the differences between the prior art and the claims, the level of ordinary skill in the art, and secondary considerations of non-obviousness. The Supreme Court's decision in KSR Int'l Co. v. Teleflex Inc. further clarified that a motivation to combine prior art references is crucial and can be gleaned from various sources, including common sense, market pressure, and the desire to improve existing products or processes, even if not explicitly stated in the references themselves.

The patent US9666732 focuses on high-efficiency solar cell structures and methods of manufacture, including multifunctional layers and thermal treatments for layer formation and conversion. The priority date for US9666732 is April 21, 2009.

Prior Art References

The "Prior art keywords" listed in US9666732 include "silicon," "type," "doped," "layer," and "layers." The patent itself incorporates by reference U.S. Provisional Application No. 61/171,187, filed April 21, 2009, and PCT/US2010/123976, both related to "Method for Forming Structures in a Solar Cell," and U.S. Provisional Application No. 61/171,491, filed April 22, 2009, and PCT/US2010/031881, concerning "Localized Metal Contacts By Localized Laser Assisted Conversion Of Functional Films In Solar Cells." These references, while related to the applicant's own work, establish a baseline of knowledge in the art at or before the priority date.

Furthermore, a general understanding of solar cell technology at the time would include:

• Solar cells with various layers: The general concept of solar cells comprising a central substrate, conductive layers, antireflection layers, passivation layers, and electrodes was well-known.
• Surface Passivation: The importance of surface passivation to suppress electron and hole recombination was recognized. Dielectric layers (e.g., silicon oxide, silicon nitride) and intrinsic amorphous silicon were known for this purpose.
• Doping for junctions: The use of doping atoms to create high-low junctions or p-n junctions for carrier collection was a standard technique in semiconductor devices, including solar cells.
• Transparent Conductive Oxides (TCOs): Materials like indium tin oxide (ITO), aluminum-doped zinc oxide, and fluorine-doped tin oxide were established as transparent and conductive films for solar cell electrodes.
• CVD processes: Various Chemical Vapor Deposition (CVD) methods (PECVD, APCVD, LPCVD) were common for depositing layers in semiconductor manufacturing.
• Thermal treatment: Heat treatments were used in semiconductor fabrication for various purposes, including activating dopants, crystallizing amorphous films into polycrystalline films, and improving optical transmissivity. For example, US Patent 7,666,732 B2 (Doris et al., filed Sep. 15, 2008) describes thermal treatments in CMOS fabrication, indicating the general knowledge of such processes in semiconductor manufacturing. While Doris et al. is not directly in the solar cell art, it demonstrates the broader knowledge of thermal processing in semiconductor device manufacturing.

Obviousness Combinations and Motivations

A PHOSITA in the field of solar cell manufacturing, seeking to improve efficiency and reduce manufacturing complexity, would have been motivated to combine known elements and processes in predictable ways.

1. Combination of known layers and doping techniques with thermal treatment for crystallization and dopant activation (Claim 3 and related method claims):

• Prior Art Elements: The prior art clearly teaches solar cells with various layers, including a substrate, passivation layers, and conductive layers (e.g., layers 62, 63, 64, 65, 66, 67, 68 in FIG. 6 of US9666732). It also teaches the use of amorphous silicon-containing compounds for layers, and the general application of thermal treatment in semiconductor manufacturing for activating dopants and crystallizing films.
• Motivation to Combine: A PHOSITA would be motivated to improve the electrical and optical properties of amorphous silicon-containing layers by crystallizing them into polycrystalline films and activating dopants. Crystallization can lead to improved carrier mobility and stability, while dopant activation is essential for forming efficient junctions and conductive layers. The patent itself notes that amorphous silicon layers can be turned into polycrystalline silicon layers by thermal treatment, and this process can also activate doping atoms. The desire to achieve "high-efficiency solar cell structures and methods of manufacture" and "increased cell efficiency" would provide a strong motivation to apply known thermal treatments to amorphous silicon-containing layers to optimize their performance.
• Obviousness Argument: Combining the known practice of depositing amorphous, silicon-containing compounds in solar cells with the known technique of using heat treatment to initiate crystallization and activate doping atoms would have been obvious to a PHOSITA. The expected result would be improved electrical and optical properties, leading to higher efficiency, a well-understood goal in the art. The patent explicitly states that thermal treatment "may activate doping atoms in the compound and result in diffusion of dopant atoms into a substrate wafer to provide a high-low junction or a p-n junction." This describes a predictable application of known techniques to achieve a desired outcome in solar cell fabrication.

2. Combination of separate passivation and conductive layers into a multifunctional layer via heat treatment (Claims related to multifunctional films, e.g., layers 93a, 97a):

• Prior Art Elements: The patent explicitly states that "Multifunctional layers provide combined functions of passivation, transparency, sufficient conductivity for vertical carrier flow, the junction, and/or varying degrees of anti-reflectivity." The prior art would have included individual layers for passivation (e.g., silicon oxide, silicon nitride, intrinsic amorphous silicon), transparency, conductivity (e.g., TCOs, doped silicon), and antireflection.
• Motivation to Combine: A PHOSITA would be motivated to simplify manufacturing processes and potentially enhance performance by combining the functions of multiple layers into a single "multifunctional film." The patent highlights that "high-volume manufacturing is generally considered to attain a high degree of cost-effectiveness and efficiency if the number of manufacturing steps, and the complexity of each step, can be minimized." This provides a clear motivation to reduce the number of distinct layers if possible. The patent also teaches that a layer deposited in a single process can "split into two (or more) layers" during thermal treatment, for example, incorporating oxygen in an amorphous deposited layer to form a thin oxide at the silicon interface while the rest crystallizes and dopants activate.
• Obviousness Argument: Given the motivation to reduce manufacturing steps and improve efficiency, a PHOSITA would have sought ways to achieve multiple functions with fewer layers. The idea of using a thermal treatment to induce a single deposited film to form both a passivating interface and a doped polycrystalline layer (as described in the patent) would be an obvious solution, especially if the starting amorphous silicon-containing compounds are known to be capable of such transformation and contain necessary doping elements or oxygen. This is a predictable outcome of optimizing film deposition and annealing processes. The specific examples provided in the patent for multifunctional layers, such as n-type amorphous or polycrystalline silicon carbides/nitrides, silicon, and diamond-like carbon, indicate that these are known materials capable of being doped and formed into various structures.

3. Integration of embedded electrodes for stress reduction (Claims related to FIGS. 16 and 17):

• Prior Art Elements: The patent introduces solar cells with metal electrodes embedded in a glass or other laminating films that are compressed or bonded to the cell. The electrodes make contact on top of the outer layers without penetrating underlying layers. The prior art for solar cells would include traditional metallization directly deposited onto the cell.
• Motivation to Combine: The patent explicitly states that embedding electrodes in glass or laminating films "has the benefit that the metal does not need to be deposited directly onto the cell itself, thereby eliminating a typical source of film stress which can cause cell bowing." This is particularly useful for "very large area wafers, such as thin-film silicon sheets and/or very thin wafers." A PHOSITA would be motivated to address known manufacturing challenges such as film stress and bowing, especially as solar cells become larger and thinner. Improving the "manufacturing in a cost effective manner" would lead a PHOSITA to consider alternative, less stressful contact methods.
• Obviousness Argument: The problems of film stress and cell bowing in thin-film or large-area solar cells would have been well-known to a PHOSITA. Seeking methods to mitigate these issues, a PHOSITA would have considered alternative electrode application techniques that avoid direct deposition and its associated stress. The concept of using pre-formed electrodes embedded in a laminating material, which then contact the cell surface upon bonding, would be an obvious solution given the desire to reduce stress and improve manufacturing yield for large, thin wafers. The use of "anisotropic conducting films (ACF), conductive epoxies, or spring-like contact probes" to enhance electrical conductivity between embedded electrodes and outer layers is also a collection of known conductive interfacing solutions.

In summary, the advancements claimed in US9666732, while contributing to solar cell efficiency and manufacturing, appear to stem from predictable combinations and optimizations of existing solar cell components and fabrication techniques. The motivations for these combinations are clearly articulated within the patent itself, focusing on increased efficiency, reduced manufacturing complexity, and addressing known issues like film stress.