SiC Epitaxial Substrate Structure for Carrot Defect Reduction
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Solution Overview
Problem
Existing silicon carbide epitaxial wafers suffer from high carrot defects, which negatively impact the yield of silicon carbide semiconductor devices.
Innovation Solution
A silicon carbide epitaxial substrate with a tilted main surface and controlled screw dislocation recesses, where the area densities of these recesses are managed to minimize defect regions, and the recesses are oriented to connect with specific polytype regions, enhancing the substrate's structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon carbide epitaxial wafer is manufactured with conventional methods, then the production process is simple, but the number of carrot defects is high
Solution Approach 1:
The epitaxial layer is divided into multiple layers with different functions: a first epitaxial layer grown on the substrate, and a second epitaxial layer grown on the first layer. This segmentation allows each layer to address specific defect types, with the first layer targeting carrot defects and the second layer providing additional defect reduction, thereby improving overall yield while managing complexity through functional division
Solution Approach 2:
The patent introduces a specific epitaxial layer configuration where the first epitaxial layer has controlled properties (thickness, composition) specifically tailored to address carrot defects originating from screw dislocations, while the second epitaxial layer provides complementary defect reduction. This local quality approach ensures that each part of the epitaxial structure is optimized for its specific function in reducing particular types of defects
2Stability of the object's composition
If the main surface is tilted relative to the {0001} plane, then the structural integrity is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a precise tilt angle parameter for the main surface relative to the {0001} plane, ranging from 0.5 degrees to 5 degrees. This parameter change optimizes the structural integrity and defect reduction effectiveness while establishing clear manufacturing specifications that balance performance improvement with fabrication feasibility
3Reliability
If the area density of the first recess is increased to 0.03/cm2 or more, then the carrot defects are reduced, but the density of screw dislocations increases
Solution Approach 1:
The patent converts the harmful effect of screw dislocations into a beneficial feature by intentionally introducing controlled screw dislocations at specific area densities (0.03/cm2 or more for the first recess). These controlled dislocations serve as nucleation sites that redirect defect formation away from carrot defects, transforming what is typically a defect source into a defect-control mechanism that improves overall device yield
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 improves the yield of silicon carbide semiconductor devices by reducing defects and optimizing the substrate's structural properties.
Implementation Method 1
a silicon carbide epitaxial layer (40) on the silicon carbide substrate (30)
Data Source
AI summary
The first area density is 0.03/cm2 or more, and a value obtained by dividing the second area density by a sum of the first area density and the second area density is 10% or less. As viewed in a direction perpendicular to the main surface, the first recess extends in a straight line along a direction inclined with respect to each of the first direction and a second direction perpendicular to the first direction, and a first-direction-side end portion of the first recess is contiguous to a 4H polytype region, and as viewed in the direction perpendicular to the main surface, the second recess extends in a straight line along a direction inclined with respect to each of the first direction and the second direction, and a first-direction-side end portion of the second recess is contiguous to a 3C polytype region.