Solar Cell Metal Contact Etching for Intermetallic Removal
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Solution Overview
Problem
Current solar cell manufacturing processes are inefficient, leading to suboptimal solar cell efficiency and increased costs, particularly due to the formation of intermetallics which can cause shorts and shunts in semiconductor devices.
Innovation Solution
A method involving the formation of a metal seed region with a first metal region, a barrier region, and a second metal region, followed by etching with an etchant containing an acid, an oxidizer, and chloride ions to form metal contact fingers, which can etch away intermetallics in a single bath, thereby improving the etch rate and reducing shading on solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching processes are used to form metal contact fingers, then the manufacturing process is simpler, but the etch rate of barrier regions and intermetallics is insufficient leading to formation of shorts and shunts
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition of the etchant to include specific concentrations of hydrofluoric acid (0.1-10%), nitric acid (0.1-10%), and hydrogen peroxide (0.1-10%). This chemical parameter optimization enables the etchant to effectively remove barrier regions and intermetallics at an adequate etch rate while maintaining reliability by preventing shorts and shunts.
Solution Approach 2:
The patent uses an intermediary etchant solution comprising a specific combination of hydrofluoric acid, nitric acid, and hydrogen peroxide. This intermediary chemical mixture mediates between the conflicting requirements of etch rate and reliability by providing selective removal of unwanted materials (barrier regions and intermetallics) without compromising the formation of reliable metal contact fingers.
2Reliability
If more metal regions are formed to improve electrical contact, then the electrical conductivity improves, but the shading on solar cells increases reducing light collection
Solution Approach 1:
The patent applies the taking out principle by selectively removing barrier regions and intermetallics through the specialized etching process. This extraction of unwanted materials allows for reduced metal coverage while maintaining electrical conductivity, thereby reducing shading on solar cells and improving light collection efficiency without sacrificing electrical performance.
Solution Approach 2:
The patent uses parameter changes in the etching process to achieve precise control over metal region formation. By optimizing etchant composition and processing parameters, the method enables minimal metal coverage sufficient for electrical conductivity, thus reducing shading effects and maximizing light absorption by the solar cell active areas.
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 approach enhances the etch rate of barrier regions and intermetallics, reducing the formation of shorts and shunts, and maximizes light collection by allowing for reduced shading on solar cells, thereby increasing efficiency and cost-effectiveness in solar cell production.
Implementation Method 1
etched with an etchant including an acid, an oxidizer, and chloride ions
Implementation Method 2
an etchant including an acid, an oxidizer, and chloride ions
Data Source
AI summary
Fabricating a semiconductor device can include forming a metal seed region over a substrate. The method can include forming a mask over a first portion of the metal seed region. The method can also include forming a metal region over the metal seed region and removing the mask. The method can include forming metal contact fingers on the semiconductor device, where the forming includes etching the first portion of the metal seed region with an etchant comprising an acid, an oxidizer and chloride ions.