Silicon Carbide Epitaxial Substrate Defect Control
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Solution Overview
Problem
Existing silicon carbide epitaxial substrates face challenges in suppressing the two-dimensional extension of defects, particularly threading screw dislocations and carbon inclusions, which affect the quality and performance of silicon carbide semiconductor devices.
Innovation Solution
A silicon carbide epitaxial substrate with a silicon carbide layer having a second main surface inclined at an off angle, where the ratio of second defects to the sum of first and second defects is greater than 0.5, and the use of ammonia gas in the epitaxial growth process to form a buffer layer with high nitrogen concentration, promoting step-flow growth and reducing the extension of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon carbide layer is grown on a silicon carbide single-crystal substrate, then the substrate quality is improved, but two-dimensional extension of defects such as threading screw dislocations and carbon inclusions occurs
Solution Approach 1:
The patent changes the crystal orientation parameter by using an off-cut substrate (e.g., 6° off-cut) instead of a standard {0001} oriented substrate. This parameter change in the substrate orientation suppresses the two-dimensional extension of defects during epitaxial growth, while still maintaining high substrate quality for device fabrication
Solution Approach 2:
The patent introduces a buffer layer with different local properties between the substrate and the epitaxial layer. The buffer layer has a controlled defect structure that locally manages dislocation propagation, allowing the main epitaxial layer to maintain high quality while containing defects in a specific region
2Ease of manufacture
If conventional epitaxial growth is used, then the growth process is simple, but defects extend two-dimensionally affecting device performance
Solution Approach 1:
The patent modifies the epitaxial growth parameters by controlling the temperature gradient, pressure, and gas flow conditions during growth. These parameter changes suppress defect extension while maintaining a relatively simple overall growth process that can be implemented in existing equipment
Solution Approach 2:
The patent performs preliminary surface preparation of the substrate before epitaxial growth, including cleaning and conditioning steps that prepare the surface to minimize defect formation. This preliminary action reduces the need for complex in-situ defect management during growth
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 approach effectively suppresses the two-dimensional extension of defects, improving the quality of the silicon carbide epitaxial substrate and enhancing the performance of silicon carbide semiconductor devices by increasing the number of second defects and reducing the impact of first defects.
Implementation Method 1
a method for epitaxially growing a silicon carbide layer on a silicon carbide single-crystal substrate
Implementation Method 2
the use of ammonia gas in the epitaxial growth process to form a buffer layer with high nitrogen concentration
Data Source
AI summary
It is assumed that a defect satisfying relations of Formula 1 and Formula 2 is a first defect, where an off angle is θ. It is assumed that a defect having an elongated shape when viewed in a direction perpendicular to the second main surface, and satisfying relations of Formula 3 and Formula 4 is a second defect. A value obtained by dividing the number of the second defect by the sum of the number of the first defect and the number of the second defect is greater than 0.5.