Reactive Ion Etching Processes for Solar Cell Fabrication

Back-contacted solar cells with enhanced efficiency using a novel metallization approach. The cells feature back-side contacts with aluminum metallization, where the aluminum content is strategically distributed between 60-20% to 12.5% in the positive and negative electrodes, respectively. This composition creates a highly conductive metallization layer while maintaining passivation properties of the silicon surface. The metallization layer is formed through a novel firing process that preserves the silicon surface quality, enabling efficient solar cell production with conventional manufacturing processes.

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A method for preparing solar cells that enables efficient copper seed layer formation for gate electrode deposition. The method involves depositing a protective gas plasma in a controlled hydrogen environment to create a thin copper seed layer on a transparent conductive film, followed by a second copper layer deposition. This sequential process enables the formation of a uniform copper seed layer suitable for subsequent gate electrode deposition, significantly improving the efficiency and quality of solar cell fabrication.

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A method for preparing solar cells that significantly enhances etching speed and reduces etching time for transparent conductive layers. The method employs a novel acid concentration strategy that maintains a controlled concentration of etching agents while achieving higher etching rates compared to conventional wet etching methods. The controlled acid concentration enables precise control over etching conditions, particularly for difficult-to-etch transparent conductive layers, while minimizing etching liquid usage and volatilization. The method enables rapid etching of transparent conductive layers, enabling faster solar cell production.

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Highly efficient back-contacted solar cell with passivated contacts that reduces recombination and improves efficiency. The cell has interdigitated electrodes on the back contacting doped regions of opposite polarity. The doping in the regions is balanced to create the opposite polarity. This eliminates the need for complex doping steps or masks on the back. The front has lower doping compared to the back. Passivation layers on front and back further reduce recombination. The cell is manufactured by depositing a polycrystalline silicon layer on a dielectric layer, locally doping the back regions, and forming passivation layers.

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Bifacial solar cells with high efficiency (>25%) achieved through a novel double-side passivated contact (TOPCon) architecture. The cells employ a novel fabrication process that enables selective patterning of poly-Si on both sides of the solar cell, while maintaining high-quality passivation. The passivation stack, comprising a thin layer of silicon nitride (SiNX:H), achieves a field inversion layer of 4 fA/cm², enabling efficient carrier collection across the front surface. This approach enables the creation of high-efficiency solar cells with reduced parasitic absorption losses compared to traditional PERC cells, while maintaining excellent passivation quality.

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Method to improve the efficiency of heterojunction solar cells by treating the intrinsic amorphous silicon (a-Si) layer with hydrogen plasma multiple times during deposition. After forming each layer of a-Si, hydrogen plasma treatment is performed before continuing with the next layer. This step is repeated multiple times during the deposition of the entire a-Si stack. The hydrogen plasma treatment improves carrier transport in the a-Si layers, which increases solar cell efficiency.

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Enhancing the etching rate of silicon nitride films in plasma processing by combining iodine heptafluoride (IF7) plasma with an inert gas. The method utilizes a plasma generated by converting IF7 into plasma to etch the silicon nitride film simultaneously with the formation of a silicon oxide film. The IF7 plasma provides high etch rates for the silicon nitride, while the oxide film acts as a sacrificial mask. This approach enables simultaneous etching of both silicon nitride and silicon oxide films at elevated etch rates.

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A novel etching method for photovoltaic cells that enables the removal of the silicon-arsenic (a-Si) transition layer through enhanced physical etching without replacing etching gases or equipment. The method employs reactive ion etching (RIE) with chlorine and sulfur hexafluoride as the etching gas, which generates reactive plasma that selectively targets and breaks through the transition layer. This approach addresses the conventional challenge of removing the transition layer through dry etching without damaging the underlying silicon.

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Method for manufacturing tandem solar cells by selectively removing pyramid-shaped defects from a crystalline silicon substrate surface through a combination of isotropic and anisotropic etching processes. The method employs a novel etching sequence that balances isotropic etching for surface roughness control with anisotropic etching for precise defect removal, enabling the formation of uniform unit layers without compromising the substrate's surface integrity.

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Etching method and application of silicon nitride in crystalline silicon solar cells, particularly for achieving low-temperature sintering and lead-free metallization. The method involves using tellurium glass as the front electrode in crystalline silicon solar cells, where tellurium glass forms a stable silver-silicon contact through oxidation. The tellurium glass powder is melted during the sintering process, forming a stable glass-oxide interface that enables the formation of a high-quality silver-silicon contact. This approach enables the use of tellurium glass in crystalline silicon solar cells, particularly for low-temperature sintering and lead-free metallization, while maintaining high efficiency and performance.

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Method for manufacturing high-efficiency crystalline silicon-based solar cells with integrated intrinsic silicon layers and conductive silicon-based layers. The method employs plasma treatment to form intrinsic silicon layers on the substrate surface during CVD processing. The plasma treatment introduces hydrogen gas into the chamber while maintaining a controlled silicon-containing gas flow, which enhances film quality and passivation while suppressing variations in conversion characteristics. The intrinsic silicon layers are formed in the valleys of the substrate texture, while the conductive silicon-based layers are formed in the valleys and mid-abdomen regions. The plasma treatment achieves controlled film thickness distribution between substrates while maintaining uniform film quality.

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Plasma etching method using a novel etchant that replaces conventional fluorinated gases with heptafluoropropyl methyl ether (HFE) gas, while maintaining the etchant's environmental benefits. The HFE gas, combined with argon (Ar) and oxygen (O2), produces a plasma etching process with improved etching characteristics for high-aspect-ratio structures, while minimizing the etchant's global warming potential. The plasma density can be controlled by adjusting the Ar flow rate, enabling the formation of anisotropic etched patterns.

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Plasma etching method using an etchant with low global warming potential (GWP) for semiconductor device manufacturing. The method employs a combination of hexafluoroisopropanol (HFIP) and argon (Ar) gases in a plasma chamber. By heating the HFIP canister to 75°C and the Ar line to 135°C, HFIP vaporizes and enters the plasma chamber, where it reacts with Ar to form an etching target. This dual-gas approach enables the formation of anisotropic etched patterns through enhanced ion bombardment, while maintaining the environmental benefits of HFIP.

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Plasma-curing of light-receiving surfaces for solar cells enhances performance and stability through a novel fabrication process. The process involves growing a phosphorous-doped oxide layer and an anti-reflective coating (ARC) layer in a plasma-enhanced chemical vapor deposition (PECVD) tool. The ARC layer is formed directly on the phosphorous-doped oxide layer, eliminating the need for intermediate layers. Plasma-induced radiation during the ARC deposition process creates a protective layer that prevents hot electron injection across the interface, thereby reducing interface wear and degradation. The plasma-cured solar cell exhibits improved front surface field (FSF) performance, enhanced UV stability, and enhanced overall solar cell efficiency compared to conventional methods.

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Etching process for III-V semiconductor materials, particularly indium phosphide (InP), that enhances aspect ratio through repeated etching cycles. The process involves three sequential steps: initial isotropic etching, followed by anisotropic etching with a passivation layer, and repeated etching cycles. This multi-step approach enables controlled removal of material from the bottom of the structure while maintaining sidewall integrity, resulting in structures with improved aspect ratios.

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A novel texturing agent for silicon wafers that enhances yield and efficiency of photovoltaic cells produced from diamond wire-cut silicon wafers. The agent combines hydrogen peroxide with a specific etching solution composition that precisely controls the etching process. The composition is optimized to maintain optimal etching conditions while minimizing the formation of undesirable amorphous silicon layers. This agent enables improved surface preparation for photovoltaic cells, resulting in higher efficiency conversion rates compared to conventional methods.

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Process for etching the surface of cadmium telluride solar cells to improve cell efficiency and appearance. The process involves selectively etching the positive side of the solar cell while maintaining the negative side intact. The etching is performed using a controlled atmosphere environment that prevents the formation of acid droplets during the etching process. This controlled environment enables precise control over the etching conditions and prevents the formation of unwanted cadmium telluride spots on the positive side of the solar cell.

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Etching silicon films using an iodine heptafluoride gas with a controlled flow ratio of basic gas. The etching process involves supplying the iodine heptafluoride gas and basic gas to the substrate while maintaining a specific flow ratio between the two gases. This controlled ratio enables precise control over the etching conditions, particularly in achieving high uniformity and suppressing roughness during the wet etching step.

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A double-sided PERC solar cell back polishing process that balances high reflectivity and uniformity. The process employs a novel approach to achieve both improved back reflectivity and reduced air bubble formation through a controlled application of a specific concentration of nitric acid (HNO3) during the back polishing step. This concentration enables optimal dielectric passivation while minimizing the formation of undesirable zebra patterns typically associated with conventional acid polishing methods. The process maintains consistent back reflectivity while reducing the production costs associated with traditional acid polishing solutions.

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A process for etching silicon wafers that combines a pretreatment step with an F2-containing gas etching process, enabling improved etch rates and reduced reflection characteristics in photovoltaic applications. The pretreatment step uses an HF-containing gas mixture to modify the silicon surface before etching with F2-containing gas, while the F2-containing gas etches the modified surface. This combined approach enables enhanced etch properties and reduced reflection characteristics compared to conventional F2-based etching methods.

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