AlGaN Multi-Layer Buffer for Silicon Substrate Crack Reduction
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Solution Overview
Problem
The semiconductor device using a silicon substrate faces challenges due to lattice and thermal expansion coefficient mismatches with GaN-based III-V compounds, leading to stress and increased crack possibility during manufacturing.
Innovation Solution
A semiconductor structure is designed with a silicon substrate, a nucleation layer, and multiple multi-layer sets of Al-containing III-V group compounds, where the aluminum content decreases with distance from the substrate, and the first and second sub-layers have different aluminum contents, reducing stress and crack likelihood.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If silicon substrates are used for GaN-based LEDs, then thermal conductivity and electrical conduction are improved, but lattice and thermal expansion coefficient mismatches cause stress and crack possibility
Solution Approach 1:
The patent divides the interface between silicon substrate and GaN-based layer into multiple segments by inserting multi-layer sets comprising alternating high-aluminum-content and low-aluminum-content AlGaN layers. This segmentation allows gradual transition of lattice constants and thermal expansion coefficients, reducing stress concentration and preventing cracks while maintaining the thermal conductivity benefits of silicon substrates.
Solution Approach 2:
The patent changes the aluminum content parameter gradually across the multi-layer sets, with high-aluminum-content layers near the silicon substrate and low-aluminum-content layers toward the GaN-based layer. This parameter gradient enables continuous adjustment of lattice constants and thermal expansion coefficients, effectively reducing mismatch stress and improving reliability while preserving thermal conductivity.
2Reliability
If multi-layer sets with varying aluminum content are used, then stress from lattice and thermal expansion mismatches is reduced, but device structure becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the transition region into multiple alternating high-aluminum and low-aluminum AlGaN layers. This segmented structure achieves gradual parameter transition for stress reduction while maintaining a relatively simple overall architecture that can be integrated into existing LED fabrication processes.
Solution Approach 2:
The patent uses composite AlGaN multi-layer sets with different aluminum contents as an intermediate buffer structure between silicon substrate and GaN-based layer. This composite approach reduces stress through material property gradients while maintaining structural integrity and compatibility with standard semiconductor manufacturing techniques.
Data Source
AI summary
A semiconductor structure including a silicon substrate, a nucleation layer and a plurality of multi-layer sets is provided. The nucleation layer is disposed on the silicon substrate. The multi-layer sets are stacked over the nucleation layer, and each of the multi-layer sets includes a plurality of first sub-layers and a plurality of second sub-layers stacked alternately. A material of the first sub-layers and the second sub-layers includes Al-containing III-V group compound, wherein an average content of aluminum of the multi-layer sets decreases as a minimum distance between each of the multi-layer sets and the silicon substrate increases, and an aluminum content of the first sub-layers is different from an aluminum content of the second sub-layers.