Method for the Follow-On Processing of a Silicon Layer with a Structure Created by Liquid-Phase Crystallization

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This invention presents a method for post-processing thin silicon layers that have been structured using liquid-phase crystallization (LPC-Si), which is primarily intended for thin-film solar cell applications. The method relies exclusively on sequential plasma-chemical processes carried out in one (or optionally two) vacuum process chambers, thus avoiding time-consuming and resource-intensive alternation with wet-chemical methods. Through plasma etching, unwanted oxide and defective material are removed; hydrogen plasma is then used for defect passivation. Optionally, a protective covering layer can be deposited, and further steps such as texturing or emitter/buffer layer additions can be integrated, all without breaking vacuum or moving the substrate between multiple systems.

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• Manufacturing high-efficiency thin-film silicon solar cells using liquid-phase crystallized silicon.
• Mass production of silicon absorber structures for photovoltaic modules on large low-cost glass substrates.
• Integrated, in-line processing lines for thin-film electronics where plasma-only processes are preferable over mixed wet/dry approaches.
• Production of solar cells and modules with improved material quality and lower production costs.
• R&D of next-generation photovoltaic devices seeking to eliminate or simplify vacuum-to-air transfer processes.

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• Reduces equipment and material costs by eliminating the need for wet-chemical processing steps and additional chambers.
• Increases throughput and production speed by enabling all steps to occur in direct sequence without interrupting the vacuum, thus minimizing substrate handling and transfer times.
• Enhances the quality and efficiency of the thin silicon absorber layers by more effectively removing defects and passivating the material within a controlled plasma environment.
• Facilitates scalable production using existing industrial plasma-enhanced chemical vapor deposition (PECVD) chambers, making it suitable for large-area substrates.
• Minimizes use of hazardous chemicals such as acids and bases as required in wet processing, improving workplace safety and environmental impact.
• Improves reproducibility and consistency of the final product due to integration and automation of all process steps within a single or limited set of process chambers.

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Patent Abstract

For solid-phase-crystallized silicon (SPC-Si) in a thin layer there are existing procedures that alternate between wet-chemical processes under atmospheric pressure and plasma-chemical processes in a vacuum. A known method uses successive plasma-enhanced method steps for the deposition, cleaning and texturing of a silicon wafer. In the case of the method according to the invention, exclusively plasma-chemical method steps are carried out in a direct sequence without interruption of the vacuum, whereby the quality of the thin silicon absorber layer (01) of liquid-phase-crystallized silicon (LPC-Si) is increased and the processing costs are lowered. Quality-reducing surface oxide (05) and defect-rich material (09) are removed by plasma-chemical etching and a defect passivation is performed by means of a hydrogen plasma. At the end of the defect passivation, a protective covering layer may be optionally deposited. The method can be carried out in one process chamber or, if a covering layer is formed, in two process chambers. The method may be concluded by the directly following deposition of an intrinsic buffer layer and/or a counterdoped emitter layer.