SiC Crystal Growth Pressure Control for Dislocation Reduction
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Solution Overview
Problem
Current methods for growing silicon carbide (SiC) single crystals face challenges in achieving both high quality and increased growth rate, as higher raw material flow rates deteriorate yield and crystal quality, and high dislocation density hinders the production of high-precision devices.
Innovation Solution
The method involves controlling the total pressure of the supply gas to 40 kPa or more within a heating container while maintaining the SiC source gas flow rate at a target flow rate, increasing partial pressures near the crystal surface without raising the raw material flow rate, thereby reducing dislocation density and enhancing growth rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the raw material flow rate is increased to enhance the growth rate of SiC single crystal, then the growth rate is improved, but the crystal quality deteriorates due to gas core formation and increased dislocation density
Solution Approach 1:
The patent changes the total pressure parameter of the supply gas to 40 kPa or more while maintaining the SiC source gas flow rate at a target flow rate. This parameter change allows increasing the partial pressure of SiC source gas near the crystal surface without proportionally increasing the overall flow rate, thereby improving growth rate while avoiding gas core formation and maintaining crystal quality
Solution Approach 2:
The patent introduces a pressure dimension control mechanism by controlling the total pressure of supply gas independently from the flow rate. This creates a new control dimension where partial pressure near the crystal surface can be optimized separately from the overall gas flow rate, resolving the contradiction between growth rate and crystal quality
2Productivity
If the total pressure of supply gas is increased to increase partial pressure near crystal surface, then the growth rate is enhanced, but the dislocation density increases reducing crystal quality
Solution Approach 1:
The patent optimizes the total pressure parameter to 40 kPa or more, which is a specific threshold value that balances two competing requirements: providing sufficient partial pressure near the crystal surface to enhance growth rate, while preventing excessive pressure that would lead to increased dislocation density and reduced crystal quality
3Productivity
If the SiC source gas flow rate is increased to improve growth rate, then the productivity is enhanced, but the raw material yield deteriorates
Solution Approach 1:
The patent changes the control strategy from directly increasing flow rate to controlling total pressure at 40 kPa or more while maintaining flow rate at a target level. This allows the partial pressure of SiC source gas near the crystal surface to be increased through pressure control rather than flow rate increase, improving growth rate while maintaining raw material yield
Solution Approach 2:
The total pressure of supply gas acts as an intermediary parameter that mediates between flow rate control and partial pressure near the crystal surface. By controlling total pressure independently, the system can achieve high partial pressure for fast growth without proportionally increasing overall gas consumption, thus improving raw material yield
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 results in a high-quality SiC single crystal with reduced dislocation density, suitable for high-voltage power devices, by suppressing gas core formation and maintaining efficient raw material yield and crystal quality.
Implementation Method 1
In the sublimation method, a SiC raw material gas is supplied to a seed crystal by sublimating the SiC raw material in a crucible
Implementation Method 2
growing a SiC single crystal on a surface of the seed crystal by supplying a supply gas containing a SiC source gas to the surface of the seed crystal while heating the reaction chamber
Data Source
AI summary
A method of producing a silicon carbide single crystal includes: arranging a seed crystal in a heating container that defines a reaction chamber; and growing a silicon carbide single crystal on a surface of the seed crystal by supplying a supply gas containing a silicon carbide raw material gas while heating the reaction chamber. In the growing of the silicon carbide single crystal, the silicon carbide single crystal is grown by controlling a total pressure of the supply gas, which is an internal pressure of the heating container, to 40 kPa or more while controlling a flow rate of the silicon carbide raw material gas to a target value.