Silicon Carbide Chamfer Geometry for Defect-Free Epitaxy
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Solution Overview
Problem
Conventional wafer fabrication processes face defects due to faceted growth at the edges of silicon carbide substrates, leading to reduced yield and quality issues in epitaxial layers, particularly in regions with on-axis oriented surfaces.
Innovation Solution
The method involves chamfering the silicon carbide substrate with a bevel angle chosen based on the actual tilt angle of the main surface, ensuring that normal vectors of the chamfered peripheral region differ from the basal lattice plane by less than the difference between the normal vector of the main surface and the basal lattice plane, thereby avoiding local on-axis orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional mechanical treatment is applied to substrate edges for stabilization, then mechanical stability is improved, but parasitic or defective epitaxial growth occurs due to faceted growth on mechanically treated edges
Solution Approach 1:
The patent applies different geometric configurations to different regions of the substrate edge. Specifically, it uses either a chamfer angle between 5-15 degrees or a rounded edge radius of 0.1-2 mm, depending on the local requirements. This local differentiation allows the substrate to maintain mechanical stability while avoiding faceted growth that causes defective epitaxial growth, thereby resolving the contradiction between mechanical stability and epitaxial quality.
2Reliability
If off-oriented substrates are used to achieve step-flow growth, then epitaxial layer quality is improved, but the mechanically treated edges create local on-axis oriented surfaces that generate crystalline defects
Solution Approach 1:
The patent applies preliminary geometric treatment to the substrate edges before epitaxial growth to prevent the formation of on-axis oriented surfaces. By pre-configuring the edge geometry (chamfer or rounded) to maintain off-orientation, the method prevents the generation of crystalline defects that would otherwise occur during mechanical treatment, thus maintaining epitaxial layer quality without introducing harmful factors.
3Stability of the object's composition
If standard chamfering is applied to substrate edges, then edge stability is improved, but the fixed chamfer angle may create local on-axis orientations depending on the main surface offcut angle
Solution Approach 1:
The patent introduces dynamic adaptability in edge geometry configuration by providing two alternative solutions: a chamfer angle between 5-15 degrees or a rounded edge radius of 0.1-2 mm. This dynamic approach allows the manufacturing process to adapt to different main surface offcut angles, ensuring that the edge geometry maintains off-orientation and prevents on-axis orientations regardless of the specific substrate characteristics, thereby achieving both edge stability and precise orientation control.
Data Source
AI summary
The present invention relates to a chamfered silicon carbide substrate which is essentially monocrystalline, and to a corresponding method of chamfering a silicon carbide substrate. A silicon carbide substrate according to the invention comprises a main surface (102), wherein an orientation of said main surface (102) is such that a normal vector ({right arrow over (O)}) of the main surface (102) includes a tilt angle with a normal vector ({right arrow over (N)}) of a basal lattice plane (106) of the substrate, and a chamfered peripheral region (110), wherein a surface of the chamfered peripheral region includes a bevel angle with said main surface, wherein said bevel angle is chosen so that, in more than 75% of the peripheral region, normal vectors ({right arrow over (F)}_i) of the chamfered peripheral region (110) differ from the normal vector of the basal lattice plane by less than a difference between the normal vector of the main surface and the normal vector of the basal lattice plane of the substrate.