SiC Single Crystal Lattice Warp for Lower C-Surface Dislocations
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Solution Overview
Problem
Existing SiC single crystals exhibit varying basal plane dislocation densities between the Si and C surfaces, with the C surface typically having higher densities, which affects the quality of SiC substrates and epitaxial wafers.
Innovation Solution
Control the warp of the lattice surface of SiC single crystals by measuring and curving specific straight lines on the lattice surface, ensuring the center is closer to the C surface, and adhering to specific X-ray diffraction peak angle and half-width criteria to reduce basal and threading dislocation densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the SiC single crystal is grown on a C surface, then the crystal growth can proceed, but the basal plane dislocation density on the C surface becomes high
Solution Approach 1:
The patent applies parameter changes by controlling the warp curvature radius of the lattice surface (R ≤ 1000 mm) and the tilt angle (0° ≤ θ ≤ 5°) to transform the crystal growth conditions. These parameter adjustments enable the lattice surface to curve in a specific manner that directs dislocation movement toward the Si surface, thereby reducing basal plane dislocation density on the C surface while maintaining productive crystal growth.
Solution Approach 2:
The patent introduces asymmetry by creating a non-uniform lattice surface warp where the curvature radius varies across the crystal surface. This asymmetric warp pattern, combined with the tilted orientation relative to the c-axis, creates directional stress fields that asymmetrically guide dislocation propagation away from the C surface, resolving the contradiction between growth productivity and dislocation density control.
2Shape
If the external form of the SiC single crystal is controlled, then the shape can be maintained, but the warp of the lattice surface cannot be sufficiently controlled
Solution Approach 1:
The patent transitions from controlling only the external two-dimensional shape to incorporating three-dimensional lattice surface warp control. By specifying the curvature radius (R ≤ 1000 mm) and tilt angle (θ) of the lattice surface relative to the c-axis, the invention adds dimensional control parameters that directly influence dislocation behavior, enabling sufficient warp control while maintaining the required external crystal shape.
3Manufacturing precision
If the basal plane dislocation density is reduced, then the substrate quality improves, but the crystal growth conditions become more difficult to control
Solution Approach 1:
The patent implements feedback control by establishing specific measurable parameters (warp curvature radius R ≤ 1000 mm and tilt angle 0° ≤ θ ≤ 5°) that provide clear guidance for crystal growth control. These quantifiable feedback parameters enable operators to adjust growth conditions systematically to achieve the desired lattice surface warp, thereby reducing basal plane dislocation density while making the control process more manageable rather than more difficult.
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 effectively reduces basal plane dislocation and threading screw dislocation densities on the C surface, enhancing the quality of SiC substrates and epitaxial wafers by maintaining a high crystallinity and reducing defects.
Implementation Method 1
The warp of the lattice surface of the SiC single crystal changes due to the influence of internal stress that occurs during crystal growth and cooling of the SiC single crystal
Implementation Method 2
measuring a curvature of a lattice surface of a SiC single crystal; in X-ray diffraction results measured along each of the first straight line to the sixth straight line, a half width of a maximum diffraction peak of a (0004) plane at a measurement point separated by d/3 from the center
Data Source
AI summary
A SiC single crystal according to an embodiment has a lattice surface measured along each of a first straight line, a second straight line, a third straight line, a fourth straight line, a fifth straight line and a sixth straight line, which is curved in a convex shape. In the lattice surface measured along each of the first straight line, the second straight line, the third straight line, the fourth straight line, the fifth straight line and the sixth straight line, the center is located closer to a C surface than an end portion of the lattice surface measured along each of the straight lines. Each of the first straight line, the second straight line, the third straight line, the fourth straight line, the fifth straight line and the sixth straight line is a straight line passing through the center when seen in a plan view in a thickness direction and inclined by 30° each based on the center.