Porous Biaxially Oriented SiC Substrate for Low Dislocation Density
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Solution Overview
Problem
Current SiC single crystal substrates have high dislocation densities, which negatively impact semiconductor device performance, and there is no known method to produce SiC substrates with extremely low dislocation densities.
Innovation Solution
A SiC composite substrate is developed with a biaxially oriented SiC layer that has pores, reducing defect density to 1.0×10^1/cm² or less by relaxing thermal stress and facilitating defect annihilation, thereby improving crystallinity and reducing dislocation propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SiC single crystal substrate is used, then the material can control high voltage and high electric power with small loss, but the dislocation density is high (10³ to 10⁴ cm⁻²) which negatively impacts device performance
Solution Approach 1:
The invention uses a composite structure consisting of a SiC single crystal layer combined with a biaxially oriented SiC layer. This composite substrate integrates the high voltage control capability of single crystal SiC with the low defect density of biaxially oriented SiC, achieving both reliable device performance and reduced dislocation density affecting threading defects
Solution Approach 2:
The biaxially oriented SiC layer is designed with a porous structure containing numerous small pores. This porous configuration reduces thermal stress during crystal growth and facilitates the annihilation of dislocations, particularly threading screw dislocations and basal plane dislocations, thereby reducing the density of defects reaching the surface to 1.0×10¹/cm² or less
2Manufacturing precision
If pores are introduced in the biaxially oriented SiC layer, then the defect density reaching the surface is reduced to 1.0×10¹/cm² or less, but the structural complexity increases
Solution Approach 1:
The invention intentionally introduces a porous structure in the biaxially oriented SiC layer to reduce thermal stress and facilitate defect annihilation. The pores act as sites for dislocation termination and annihilation, particularly effective for threading screw dislocations and basal plane dislocations, achieving defect density of 1.0×10¹/cm² or less at the surface
Solution Approach 2:
The composite substrate structure combines a SiC single crystal layer with a biaxially oriented SiC layer containing pores. This composite design achieves low defect density through the porous layer while maintaining the beneficial electrical properties of the single crystal layer, with the biaxial orientation providing both c-axis and a-axis alignment
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 SiC composite substrate with a biaxially oriented SiC layer achieves a significantly low defect density, enhancing the production of semiconductor and electronic devices by minimizing threading screw dislocations, basal plane dislocations, and micropipes, leading to improved electrical conductivity and reduced processing challenges.
Implementation Method 1
When the pores are present, the thermal stress generated during the formation of the biaxially oriented SiC layer may be relaxed, so that the formation of new dislocations may be prevented
Implementation Method 2
when the pores are present in the biaxially oriented SiC layer, the dislocations propagating from the SiC single crystal layer may collide with the pores and annihilate
Implementation Method 3
the stress due to the lattice mismatch is relaxed, so that the defect density may be reduced
Data Source
AI summary
A SiC composite substrate includes a SiC single crystal layer and at least one biaxially oriented SiC layer. The at least one biaxially oriented SiC layer is disposed on the SiC single crystal. In the biaxially oriented SiC layer, the SiC is oriented in both a c-axis direction and an a-axis direction. The biaxially oriented SiC layer has pores and has a density of defect reaching the surface of 1.0×101/cm2 or less.