Fluorinated Silicon-Oxide Passivation for Solar Cell Textures
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Solution Overview
Problem
Existing silicon-based photovoltaic device manufacturing processes face challenges in achieving efficient etching and passivation of substrates, particularly for sub-micrometer features, which affects the electrical properties and reflectivity of solar cells, as conventional methods result in low carrier lifetime and surface defects.
Innovation Solution
A dry chemical etching and passivation process using molecular fluorine as the etchant gas at atmospheric pressure, followed by in-situ oxidation to create a stable fluorinated silicon-oxide layer, ensuring the preservation of electrical properties and reducing thermal budget, all performed within a single tool without exposing the substrate to air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional etching processes are used to create surface texture, then reflectivity is reduced, but surface defects are generated that degrade electrical properties
Solution Approach 1:
The patent combines the etching step and passivation step into a single integrated process. The fluorinated etchant simultaneously etches the silicon surface to create light-trapping texture and passivates the surface by forming a fluorinated silicon-oxide layer, eliminating the need for separate etching and passivation tools and processes.
Solution Approach 2:
The patent changes the chemical parameters of the etching process by using a fluorinated etchant gas (such as SF6, CF4, or NF3) instead of conventional halogen-based etchants. This parameter change enables the etchant to provide both etching and passivation functions, creating a fluorinated surface layer that reduces recombination while maintaining electrical properties.
2Manufacturing precision
If PECVD passivation is applied to sub-micrometer features, then conformality is achieved, but carrier lifetime remains very low
Solution Approach 1:
The patent changes the chemical composition and deposition mechanism by using a fluorinated etchant that simultaneously etches and passivates. The fluorinated silicon-oxide layer formed has superior passivation properties compared to conventional PECVD layers, achieving both conformal coverage on sub-micrometer features and high carrier lifetime.
3Manufacturing precision
If multiple separate process steps are used for etching and passivation, then each step can be optimized, but the number of manufacturing steps increases
Solution Approach 1:
The patent merges two separate process steps (etching and passivation) into a single integrated step using a fluorinated etchant gas. This reduces the number of manufacturing steps from two separate tool processes to one unified process, improving productivity while maintaining the ability to optimize both functions simultaneously through parameter control.
4Illumination intensity
If sub-micron texture is created for light trapping, then surface reflectivity is reduced, but conventional passivation methods become inefficient
Solution Approach 1:
The patent changes the chemical parameters by using a fluorinated etchant that forms a fluorinated silicon-oxide layer. This layer provides superior passivation efficiency on sub-micron textured surfaces compared to conventional PECVD methods, enabling both effective light trapping and high passivation quality on sub-micrometer features.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process enhances passivation quality, reduces the number of manufacturing steps, and improves the overall efficiency of solar cells by creating a stable and efficient light-trapping nano-texture without the need for additional anti-reflective layers, while maintaining the substrate's electrical properties.
Implementation Method 1
etching the surface of the substrate with a fluoride-containing etchant gas inside the chamber
Implementation Method 2
oxidising the textured, fluorinated surface of the substrate without exposing the substrate to air
Data Source
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AI summary
A process for passivating and etching a texture on a surface of a substrate, the process comprising the steps of inserting a substrate in a reactor chamber; heating the reactor chamber and substrate; etching the substrate with an fluoride-containing etchant gas inside the chamber; and oxidising the etched surface of the substrate prior to exposing the fluorinated substrate to air or any other reactive atmosphere; wherein oxidisation of the etched surface of the substrate generates a strongly passivated and stable surface texture.