Single-Step Wet Etch for Back Contact Multijunction Solar Cells
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Solution Overview
Problem
Conventional methods for fabricating multijunction solar cells, such as dry etching and selective wet etching, face challenges including complex etch conditions, rough sidewalls, high costs, and reduced processing throughput due to the need for multiple etchants and elaborate masking techniques, which hinder the cost-effective and efficient production of high-quality solar cells.
Innovation Solution
A single-step wet etch process using a mixture of hydrochloric acid and iodic acid is employed to etch through-wafer vias in multijunction solar cells, allowing for non-selective removal of semiconductor materials with smooth sidewalls and reduced pitting, thereby simplifying the fabrication process and improving device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching is used to etch through-wafer vias in multijunction solar cells, then the etching process can be performed, but rough sidewalls and pitting are generated on the wafer surfaces
Solution Approach 1:
The patent replaces the dry etching process (mechanical/physical removal) with a wet etching process using chemical solutions. This substitution of etching mechanism eliminates the rough sidewalls and pitting caused by dry etching, achieving smooth sidewalls and pit-free surfaces through chemical dissolution of the semiconductor materials.
Solution Approach 2:
The patent changes the etching parameters by using a specific wet etchant composition (hydrochloric acid and iodic acid in a volumetric ratio of 1:4 to 1:6) and controlling the etching temperature (20°C to 60°C). These parameter changes enable non-selective etching of all III-V semiconductor layers with uniform rates, producing smooth sidewalls without the defects associated with conventional dry etching.
2Ease of manufacture
If selective wet etching is used to etch different semiconductor materials, then specific layers can be etched selectively, but multiple etchants and elaborate masking techniques are required
Solution Approach 1:
The patent employs a universal wet etchant composition (hydrochloric acid and iodic acid mixture) that can etch all III-V semiconductor materials (GaAs, InP, InGaAs, AlGaAs, etc.) with uniform etch rates. This single etchant performs the function of multiple selective etchants, eliminating the need for elaborate masking techniques and simplifying the fabrication process while maintaining ease of manufacture.
Solution Approach 2:
The patent merges the functions of multiple selective etchants into a single wet etching process. By combining hydrochloric acid and iodic acid in specific ratios, the etchant achieves non-selective etching of all heteroepitaxial III-V semiconductor layers simultaneously, reducing the number of etching steps and masking operations required.
3Reliability
If conventional multijunction solar cell fabrication is performed, then high efficiency solar cells can be produced, but the production cost is high and processing throughput is reduced
Solution Approach 1:
The patent changes the etching parameters by using a wet etching process instead of dry etching, which enables batch processing of multiple wafers simultaneously. This parameter change increases processing throughput while maintaining the quality required for high-efficiency solar cells, thereby improving productivity without sacrificing reliability.
4Reliability
If conventional multijunction solar cell fabrication is performed, then high efficiency solar cells can be produced, but the production cost is high
Solution Approach 1:
The patent uses a universal wet etchant that simplifies the fabrication process by eliminating multiple selective etching steps and elaborate masking techniques. This reduces fabrication complexity and associated costs while maintaining the quality required for high-efficiency solar cells, thereby improving ease of manufacture without compromising reliability.
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
The single-step wet etch process enhances processing throughput, reduces costs, and ensures complete passivation of TWV walls, resulting in smoother sidewalls and improved device performance and reliability, making the solar cell production more efficient and cost-effective.
Implementation Method 1
a wet etch process that removes semiconductor materials non-selectively without major differences in etch rates between heteroepitaxial III-V semiconductor layers
Data Source
AI summary
This disclosure relates to semiconductor devices and methods for fabricating semiconductor devices. Particularly, the disclosure relates to back-contact-only multijunction solar cells and the process flows for making such solar cells, including a wet etch process that removes semiconductor materials non-selectively without major differences in etch rates between heteroepitaxial III-V semiconductor layers.