GaN Epitaxy Stack for Defect-Tolerant SiC Substrates
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Solution Overview
Problem
The challenge in semiconductor epitaxy is achieving high-quality epitaxy layers using silicon carbide substrates, which are in short supply due to their difficult growth and high cost, while down-grade substrates with defects result in poor epitaxy quality.
Innovation Solution
A semiconductor epitaxy structure is developed using a thinner silicon carbide substrate with a specific stacked structure between the nucleation layer and the gallium nitride buffer layer, comprising alternately stacked silicon nitride and aluminum gallium nitride layers, which reduces dislocation and improves epitaxy quality while reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a down-grade silicon carbide substrate is used instead of a prime substrate, then substrate cost is reduced and substrate availability is increased, but epitaxy quality deteriorates due to substrate defects
Solution Approach 1:
The patent introduces a stacked structure comprising alternating silicon nitride and aluminum gallium nitride layers as an intermediary between the down-grade substrate and the epitaxy layer. This intermediate structure acts as a buffer that isolates the defects from the epitaxy process, allowing the use of cheaper substrates while maintaining high epitaxy quality
Solution Approach 2:
The patent employs a composite stacked structure with alternating layers of silicon nitride and aluminum gallium nitride. This composite material approach combines the advantages of different materials to create a structure that can accommodate substrate defects while providing a high-quality interface for epitaxy growth
2Strength
If a thicker silicon carbide substrate is adopted to withstand lattice stress, then lattice stress resistance is improved, but substrate cost increases and substrate availability decreases
Solution Approach 1:
The stacked structure serves as an intermediary that manages lattice stress between the substrate and epitaxy layer, eliminating the need for thicker substrates to withstand stress. This allows the use of thinner, more affordable substrates while maintaining structural integrity
Solution Approach 2:
The patent changes the structural parameters by introducing a multi-layer stacked structure with specific thickness ratios (silicon nitride layers: 5-20 nm, aluminum gallium nitride layers: 2-10 nm). This parameter optimization provides sufficient stress resistance without requiring increased substrate thickness
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 solution effectively prevents defects from affecting the epitaxy layer, enhancing epitaxy quality and reducing substrate costs by utilizing a thinner, lower-quality silicon carbide substrate with a higher basal plane dislocation density, thereby improving the overall epitaxy process.
Implementation Method 1
The stacked structure includes a plurality of silicon nitride (SiNx) layers and a plurality of aluminum gallium nitride (AlxGa1-xN) layers alternately stacked... effectively prevents defects from affecting the epitaxy layer
Data Source
AI summary
A semiconductor epitaxy structure includes a silicon carbide substrate, a nucleation layer, a gallium nitride buffer layer, and a stacked structure. The nucleation layer is formed on the silicon carbide substrate, the gallium nitride buffer layer is disposed on the nucleation layer, and the stacked structure is formed between the nucleation layer and the gallium nitride buffer layer. The stacked structure includes: a plurality of silicon nitride (SiNx) layers and a plurality of aluminum gallium nitride (AlxGa1-xN) layers alternately stacked, wherein the first layer of the plurality of silicon nitride layers is in direct contact with the nucleation layer.