Silicon Carbide Purification via Nitrogen-Removal Metal Coating
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Solution Overview
Problem
The challenge in the silicon carbide industry is the high nitrogen content in silicon carbide powder, which complicates the production of semi-insulation wafers due to the difficulty in separating nitrogen from the silicon carbide lattice and the risk of nitrogen pollution, limiting the widespread use of silicon carbide wafers in high-frequency electronics.
Innovation Solution
A method involving a container with a nitrogen-removal metal layer, such as tantalum, niobium, or tungsten, is used to heat silicon carbide powder under inert gas at specific temperatures and pressures to reduce nitrogen content, with the process involving mixing carbon and silicon source powders and controlling heating conditions to form purified silicon carbide powder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional silicon carbide powder is used, then production is simple, but nitrogen content is high which limits semi-insulation wafer quality
Solution Approach 1:
A boron-containing substance is introduced as an intermediary agent during the heat treatment process. The boron forms a protective layer or compound with nitrogen, facilitating nitrogen removal from the silicon carbide powder while maintaining process simplicity. This mediator enables low-nitrogen content achievement without requiring complex multi-step purification procedures.
Solution Approach 2:
The invention changes key process parameters including heating temperature (1500-2500°C), atmosphere composition (inert gas with controlled oxygen content), and pressure conditions. By optimizing these parameters, the process achieves effective nitrogen removal through controlled chemical reactions and diffusion, transforming conventional heat treatment into a nitrogen-reducing treatment without adding process complexity.
2Manufacturing precision
If high temperature heat treatment is applied, then nitrogen diffusion is enhanced, but energy consumption increases and material loss occurs
Solution Approach 1:
The boron-containing substance acts as a catalyst or reaction mediator that lowers the activation energy required for nitrogen diffusion and removal. By forming intermediate compounds or facilitating nitrogen transport, boron enables effective nitrogen removal at reduced temperatures, thereby decreasing energy consumption while maintaining removal efficiency.
Solution Approach 2:
The invention replaces purely thermal-driven nitrogen removal with a chemically-assisted process. Instead of relying solely on high-temperature thermal diffusion, the boron-mediated chemical reactions provide an alternative pathway for nitrogen removal that is more efficient at lower temperatures, substituting thermal energy with chemical reaction energy.
3Object-affected harmful factors
If inert gas atmosphere is used, then nitrogen pollution is prevented, but process complexity and gas consumption increase
Solution Approach 1:
The invention optimizes the inert gas atmosphere parameters, specifically controlling oxygen content within 0.1-10% and using specific gas compositions. This parameter optimization allows effective nitrogen removal while using simpler atmosphere control systems, reducing the complexity of gas management equipment while preventing nitrogen pollution through controlled atmospheric conditions.
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 method effectively lowers the nitrogen content of silicon carbide powder to below 30 ppm, enhancing the quality and purity of the material for semi-insulation wafer production, thereby addressing the limitations in current silicon carbide wafer applications.
Implementation Method 1
nitrogen in a silicon carbide lattice has a diffusion coefficient of only 3*10−11 cm2 S−1 at 1800° C.
Implementation Method 2
providing a container with a surface coated by a nitrogen-removal metal layer
Implementation Method 3
heating the silicon carbide powder under an inert gas at a pressure of 400 torr to 760 torr at 1700° C. to 2300° C. for 2 hours to 10 hours
Data Source
AI summary
A method of purifying silicon carbide powder includes: providing a container with a surface coated by a nitrogen-removal metal layer, wherein the nitrogen-removal metal layer is tantalum, niobium, tungsten, or a combination thereof; putting a silicon carbide powder into the container to contact the nitrogen-removal metal layer; and heating the silicon carbide powder under an inert gas at a pressure of 400 torr to 760 torr at 1700° C. to 2300° C. for 2 to 10 hours, thereby reducing the nitrogen content of the silicon carbide powder.