4H-SiC Substrate Orientation for Crack Reduction
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Solution Overview
Problem
Silicon carbide (SiC) substrates are prone to cracking during mechanical processing due to their high brittleness and anisotropic mechanical properties, leading to significant waste and increased processing costs and time, as existing methods fail to account for crystallographic orientation and stress reduction effectively.
Innovation Solution
A monocrystalline 4H—SiC substrate with a specific crystal structure orientation, where the lattice is tilted to ensure a minimum number of parallel cleavage planes intersect a line segment on the lateral surface, distributing mechanical forces evenly and reducing the likelihood of cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard mechanical processing methods are used on SiC substrates, then processing can be completed with conventional equipment and procedures, but cracks and fissures occur along cleavage planes leading to material damage and reduced yield
Solution Approach 1:
The patent changes the crystallographic orientation parameter of the SiC substrate from conventional orientations to a specific orientation where the c-axis is tilted by 10-20 degrees relative to the substrate normal. This parameter change in crystal orientation causes the cleavage planes to intersect the substrate surface at angles that distribute mechanical stresses across multiple planes, preventing crack propagation along single cleavage planes and significantly improving mechanical robustness during processing.
2Productivity
If SiC substrates are processed with radial forces applied perpendicular to the outer diameter, then standard grinding and polishing operations can be performed, but the probability of cracking along cleavage planes increases leading to fissures and reduced yield
Solution Approach 1:
The patent modifies the crystal orientation parameter by tilting the c-axis 10-20 degrees from the substrate normal, which changes the spatial arrangement of cleavage planes. This causes radial mechanical forces during standard processing to intersect multiple cleavage planes at oblique angles rather than being concentrated on single planes, distributing the stress and reducing cracking susceptibility while maintaining compatibility with conventional processing methods.
3Reliability
If the crystal structure is oriented to reduce cracking, then mechanical robustness improves, but the substrate orientation must be precisely controlled during production
Solution Approach 1:
The patent specifies a quantitative orientation parameter range (c-axis tilt of 10-20 degrees) that provides optimal crack resistance. This defined parameter range enables precise control during crystal growth and substrate fabrication, allowing manufacturers to achieve the desired mechanical robustness through controlled orientation while maintaining reproducibility and quality consistency across production batches.
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 orientation significantly reduces the occurrence of cracks during mechanical processing, enhancing the mechanical robustness of SiC substrates without compromising epitaxial layer quality or increasing processing costs and time.
Implementation Method 1
the lattice is tilted to ensure a minimum number of parallel cleavage planes intersect a line segment on the lateral surface, distributing mechanical forces evenly and reducing the likelihood of cracking
Data Source
AI summary
The present invention provides monocrystalline 4H—SiC substrates having a specific orientation of its crystal structure which is set such as to reduce or even eliminate the occurrence of cracks or fissures during mechanical processing, and method of producing same. The monocrystalline 4H—SiC substrate, which has a longitudinal axis and an at least partially curved lateral surface parallel to said longitudinal axis, is characterized in that the crystal structure of the 4H—SiC substrate is oriented with respect to the longitudinal axis such that at each position on the lateral surface of the semi-finished product there is a line segment which is intersected by at least a predetermined minimum number of parallel cleavage planes of the {1010} form per unit length, wherein the line segment is defined by a plane tangent to the lateral surface at said position.