SiC Single-Crystal Growth with Local Etching for Flat Surfaces
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Solution Overview
Problem
Existing methods for manufacturing silicon carbide (SiC) single crystals face challenges in maintaining a flat growth surface and controlling internal stress, leading to crystal cracks and hindered growth of long crystals due to cumulative height differences on the growth surface.
Innovation Solution
A method and apparatus that involves supplying a silicon carbide raw material gas to a seed crystal within a heating vessel, using a first gas inlet below the seed crystal, and introducing an etching gas through a second gas inlet positioned to protrude towards the pedestal, allowing localized etching of the growth surface to reduce height differences, while maintaining high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gas growth method is used to manufacture SiC single crystal, then crystal growth is achieved, but height differences occur on the growth surface leading to internal stress and crystal cracks
Solution Approach 1:
The patent applies local quality by introducing etching gas through a gas-blowing outlet positioned at the periphery of the growth surface, enabling localized etching treatment specifically at regions with height differences while maintaining crystal growth conditions in other areas. This selective local processing resolves the contradiction by addressing surface flatness issues without halting overall crystal production.
Solution Approach 2:
The patent implements periodic action by alternating between crystal growth phases and etching phases. During growth, raw material gas is supplied to advance the crystal. When height differences develop, etching gas is introduced through the gas-blowing outlet to remove protrusions, then growth resumes. This periodic switching between growth and etching maintains surface flatness while achieving continuous crystal elongation.
2Length of moving object
If continuous crystal growth is performed, then crystal length increases, but cumulative height differences cause internal stress and prevent further growth
Solution Approach 1:
The patent applies preliminary action by proactively introducing etching gas through the gas-blowing outlet before height differences become severe enough to cause crystal cracks. The system monitors growth surface conditions and performs preventive etching to remove developing protrusions, thereby eliminating internal stress accumulations before they compromise crystal integrity and enable continued lengthening.
Solution Approach 2:
The patent implements feedback by using the information from height difference measurements to control etching gas introduction. When the growth surface develops protrusions exceeding acceptable thresholds, the system activates etching gas supply through the gas-blowing outlet to remove the excess material, then returns to growth mode. This closed-loop control maintains both crystal length and structural reliability.
3Measurement precision
If gas-blowing outlet is positioned closer to growth surface, then localized etching precision improves, but risk of affecting crystal structure increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the positioning of the gas-blowing outlet at a specific distance from the growth surface, along with adjusting etching gas flow rate and composition. These parameter optimizations enable precise localized etching of height differences while maintaining safe distances and conditions that prevent damage to the underlying crystal structure, thus resolving the contradiction between etching precision and crystal safety.
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 method and apparatus enable the growth of SiC single crystals with a controlled, flat growth surface, reducing internal stress and preventing crystal cracks, thereby enabling longer crystal growth.
Implementation Method 1
heating and decomposing the raw material gas by heating the heating vessel to 2000° C. or higher and supplying the decomposed raw material gas to the seed crystal
Implementation Method 2
a growth surface of the silicon carbide single crystal is locally etched so as to reduce a height difference by performing at least one of (i) introducing a carrier gas, which serves as an etching gas, from the first gas inlet or (ii) spraying an etching gas from a gas-blowing outlet portion
Data Source
AI summary
In a method and an apparatus for manufacturing a silicon carbide single crystal by a gas supply technique, a raw material gas of silicon carbide is introduced into a heating vessel through a first gas inlet disposed below a seed crystal placed on a pedestal, and the silicon carbide single crystal is grown on the seed crystal by heating and decomposing the raw material gas by heating the heating vessel to 2000° C. or higher and supplying the decomposed raw material gas to the seed crystal. Further, a growth surface of the silicon carbide single crystal is locally etched by spraying an etching gas from a gas-blowing outlet portion of a second gas inlet while heating the heating vessel to 2000° C. or higher. The gas-blowing outlet portion of the second gas inlet is disposed at a position protruding more than the first gas inlet toward the pedestal.