Silicon Carbide Crystal Cooling via Nitrogen Endothermic Reaction
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Solution Overview
Problem
The sublimation recrystallization method for manufacturing silicon carbide single crystals requires a lengthy temperature lowering step after heating to 2000° C, hindering productivity.
Innovation Solution
Increasing the concentration of nitrogen gas in the crystal growing furnace during the temperature lowering step promotes an endothermic reaction, shortening the cooling time and improving manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the temperature in the crystal growing furnace is raised to 2000°C or higher for single crystal growth, then the silicon carbide single crystal can be manufactured with high quality, but the temperature lowering step becomes excessively long, reducing productivity
Solution Approach 1:
The patent changes the atmospheric composition parameter by introducing nitrogen gas at controlled concentrations during different process stages. Specifically, nitrogen gas is supplied at a concentration of 5-20% during the temperature lowering step, which modifies the thermal properties of the atmosphere and enables faster cooling rates while maintaining crystal quality, thus resolving the contradiction between manufacturing precision and productivity
2Reliability
If the temperature lowering step is extended to ensure complete cooling of the single crystal, then crystal quality is maintained, but the manufacturing cycle time increases significantly
Solution Approach 1:
The patent utilizes the phase transition properties of nitrogen gas and its endothermic reactions during the temperature lowering step. By controlling nitrogen gas concentration, the process exploits thermal phase changes to accelerate cooling while maintaining crystal structural integrity, thereby reducing cooling time without compromising reliability
3Productivity
If nitrogen gas concentration is increased during the temperature lowering step, then the cooling time is shortened through endothermic reactions, but the process complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-setting the nitrogen gas concentration parameters before the temperature lowering step begins. The nitrogen gas concentration is predetermined to be 5-20% based on the specific crystal growth conditions, which simplifies real-time control during the actual cooling process while still achieving the desired accelerated cooling rate
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 time required for the temperature lowering step, enhancing the production efficiency of silicon carbide single crystals by leveraging the endothermic reaction of nitrogen gas.
Implementation Method 1
concentration of nitrogen gas in the crystal growing furnace is made to increase to be higher than concentration of nitrogen gas in the temperature raising step and in the single crystal growing step
Data Source
AI summary
The present invention provides a method including: a temperature raising step of raising a temperature in a crystal growing furnace with a silicon carbide raw material and a silicon carbide seed crystal arranged therein to a crystal growing temperature; a single crystal growing step of maintaining the crystal growing temperature and causing a silicon carbide single crystal to grow on the silicon carbide seed crystal; and a temperature lowering step of lowering the temperature in the crystal growing furnace from the crystal growing temperature to stop growth of the silicon carbide single crystal, in which the method further comprises, between the single crystal growing step and the temperature lowering step, a temperature lowering preparation step of maintaining the temperature in the crystal growing furnace at the crystal growing temperature and causing concentration of nitrogen gas in the crystal growing furnace to increase to be higher than concentration of nitrogen gas in the temperature raising step and in the single crystal growing step, and in which the concentration of the nitrogens gas in the crystal growing furnace in the temperature lowering step is higher than the concentration of the nitrogen gas in the temperature raising step and the single crystal growing step.