Silicon Carbide Epitaxial Substrate Defect Control
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Solution Overview
Problem
Existing silicon carbide epitaxial substrates face challenges in effectively managing defects on their surfaces, particularly in suppressing the two-dimensional extension of defects during epitaxial growth, which affects 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, is manufactured using a hot wall type lateral CVD process, employing a buffer layer with a high nitrogen atom concentration formed using ammonia gas to promote step-flow growth and reduce defect extension.
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 provides a crystalline foundation for epitaxial growth, but defects on the surface extend two-dimensionally during growth, degrading device quality
Solution Approach 1:
The patent changes the crystallographic orientation parameter by using an off-cut substrate (e.g., 6° off-cut from the (0001) plane). This parameter change in the substrate orientation fundamentally alters the growth morphology, causing defects to extend in a controlled direction rather than two-dimensionally, thereby improving device quality while managing defect propagation
Solution Approach 2:
The patent transforms the defect extension from two-dimensional spreading to one-dimensional linear extension by introducing an off-cut angle. This dimensional transformation of defect propagation is achieved by changing the growth surface orientation, causing defects to extend along a specific crystallographic direction rather than spreading across the surface
2Strength
If the silicon carbide layer is grown with high thickness to improve device performance, then the structural integrity is enhanced, but defects propagate further and have greater impact
Solution Approach 1:
By changing the substrate off-cut angle parameter, the patent controls the defect extension morphology. This allows the growth of thicker silicon carbide layers with improved structural integrity while defects are constrained to extend in a controlled manner rather than spreading widely, thereby reducing their overall impact
3Ease of manufacture
If conventional epitaxial growth methods are used, then the process is simple and well-established, but defects cannot be effectively suppressed or managed
Solution Approach 1:
The patent modifies a single key parameter - the substrate off-cut angle - while maintaining conventional epitaxial growth processes. This minimal change achieves superior defect control without complicating the manufacturing process, as the off-cut substrate can be used with standard growth equipment and procedures
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
This approach effectively suppresses the two-dimensional extension of defects, enhancing the quality and performance of silicon carbide semiconductor devices by increasing the number of second defects and reducing the impact of first defects, thereby improving the substrate's structural integrity and device performance.
Implementation Method 1
a method for epitaxially growing a silicon carbide layer on a silicon carbide single-crystal substrate
Implementation Method 2
manufactured using a hot wall type lateral CVD process
Data Source
AI summary
Assuming that one or more defects satisfying relations of Formula 1 and Formula 2 are first defects, and one or more defects satisfying relations of Formula 3 and Formula 2 are second defects, where an off angle is θ°, the thickness of a silicon carbide layer in a direction perpendicular to a second main surface is W μm, the width of each of the one or more defects in a direction obtained by projecting a direction parallel to an off direction onto the second main surface is L μm, and the width of each of the one or more defects in a direction perpendicular to the off direction and parallel to the second main surface is Y μm, a value obtained by dividing the number of the second defects by the sum of the number of the first defects and the number of the second defects is greater than 0.5.