SiC Seed Crystal Step Bunching for Dislocation Reduction
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Solution Overview
Problem
The physical vapor transport method for growing silicon carbide single-crystal ingots results in an increase in dislocation density at the interface of the seed crystal and the grown crystal, leading to a region with high dislocation density that persists until a certain growth height, which hinders the production of high-quality SiC single-crystal wafers.
Innovation Solution
Forming step bunching with heights of 10 µm to 1 mm and spans of 200 µm to 1 mm on the growth face of the seed crystal, using the solution growth method to create an off-angle of 0.5° to 10°, and then employing the physical vapor transport method to grow the silicon carbide single crystal, thereby reducing the threading screw dislocation density from the initial stage of growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the physical vapor transport method is used to grow silicon carbide single crystal, then large size SiC single crystals can be produced, but the threading screw dislocation density increases at the interface region
Solution Approach 1:
The invention applies preliminary action by forming step bunching structures on the seed crystal surface before the main crystal growth process. These pre-formed steps serve to redirect dislocations away from the growth interface, preventing the formation of high-density threading screw dislocations in the initial growth region. The step bunching is created in advance to modify the growth dynamics from the very beginning of crystal formation.
Solution Approach 2:
The invention changes the surface morphology parameter of the seed crystal by introducing step bunching with specific height and span parameters. This structural parameter change alters the dislocation behavior at the growth interface, causing threading screw dislocations to be redirected toward basal plane dislocations instead of propagating vertically through the crystal. The specific parameters of step height and span are optimized to achieve effective dislocation redirection.
2Speed
If conventional physical vapor transport growth is used, then crystal growth can proceed, but a high dislocation density region persists until certain growth height
Solution Approach 1:
The invention applies local quality by creating non-uniform step bunching structures at specific locations on the seed crystal surface. These localized step structures concentrate the dislocation redirection effect at the growth interface, while the bulk crystal growth continues at normal rates. This allows the crystal to maintain overall good quality while specifically addressing the dislocation problem at the critical interface region where devices will be fabricated.
3Manufacturing precision
If step bunching is formed on seed crystal, then threading screw dislocation density is reduced, but additional processing steps are required
Solution Approach 1:
The invention merges the step bunching formation process with the seed crystal preparation process. Instead of treating them as separate operations, the step bunching is formed as an integral part of the seed crystal fabrication, utilizing the same epitaxial growth technique. This integration reduces the number of distinct processing steps while achieving the dual benefit of seed crystal preparation and dislocation control.
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 significantly reduces the threading screw dislocation density along the growth height, allowing for the production of high-quality SiC single-crystal wafers suitable for devices from the initial stage, improving the yield and quality of SiC single-crystal ingots.
Implementation Method 1
growing a silicon carbide single crystal on a growth face of a seed crystal consisting of a silicon carbide single crystal by a physical vapor transport method
Implementation Method 2
an SiC material for sublimation is placed in a crucible, a seed crystal consisting of an SiC single crystal is attached to a lid of the crucible, and the material is made to sublimate to thereby grow an SiC single crystal on the seed crystal by recrystallization
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
The present invention provides a method of raising the rate of reduction of the dislocation density accompanying growth of an SiC single crystal to counter the increase in the threading screw dislocations formed near the interface of the seed crystal and grown SiC single crystal and thereby produce an SiC single-crystal ingot with a small threading screw dislocation density from the initial stage of growth. The present invention is a method for producing a silicon carbide single-crystal ingot growing a silicon carbide single crystal on a growth face of a seed crystal consisting of a silicon carbide single crystal by a physical vapor transport method so as to produce a silicon carbide single-crystal ingot, the method for producing a silicon carbide single-crystal ingot comprising forming step bunching with heights of steps of 10 µm to 1 mm and spans of terraces of 200 µm to 1 mm on the growth face of the seed crystal and making the silicon carbide single crystal grow on the growth face of the seed crystal by the physical vapor transport method.