Silicon Carbide Wafer Doping Ratio for Uniform High Resistivity
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Solution Overview
Problem
The fabrication of silicon carbide wafers with high resistivity is hindered by uneven resistivity distribution and difficulty in controlling doping concentrations and purity, which affects their performance in semiconductor applications.
Innovation Solution
A method involving the introduction of vanadium and nitrogen gases in a specific proportional relationship during the crystal growth process, where the vanadium to nitrogen concentration ratio (V:N) is controlled between 2:1 to 10:1, and the silicon carbide wafers are grown using a seed crystal and raw materials in a reactor, ensuring a high percentage of the wafer area has resistivity greater than 10^12 Ω·cm, with etch pit and micropipe densities minimized.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to fabricate silicon carbide wafers with high resistivity, then resistivity can be increased, but resistivity distribution becomes uneven and doping concentration control becomes difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratio of vanadium to nitrogen concentration (V:N ratio between 2:1 to 10:1) and adjusting absolute doping concentrations within specific ranges (nitrogen: 10^16 to 9.9×10^16 atom/cm³, vanadium: 10^17 to 9×10^17 atom/cm³). This systematic parameter optimization resolves the contradiction by achieving both uniform resistivity distribution (>85% of wafer area with resistivity >10^12 Ω·cm) and reliable doping concentration control through defined concentration ranges.
2Reliability
If doping concentration is increased to achieve high resistivity, then resistivity increases, but purity control becomes difficult
Solution Approach 1:
The patent resolves this contradiction by changing the parameter of doping concentration to specific optimal ranges rather than simply increasing it. By setting nitrogen concentration at 10^16 to 9.9×10^16 atom/cm³ and vanadium concentration at 10^17 to 9×10^17 atom/cm³ with a V:N ratio of 2:1 to 10:1, the method achieves high resistivity (>10^12 Ω·cm in >85% of wafer area) while maintaining purity control through defined concentration boundaries.
3Reliability
If high vanadium concentration is used to achieve high resistivity, then resistivity improves, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies the doping process by changing the parameter approach from controlling multiple independent variables to controlling a single key parameter: the V:N ratio. By specifying that vanadium to nitrogen concentration ratio should be between 2:1 to 10:1, along with absolute concentration ranges, the method achieves high resistivity while reducing manufacturing complexity through parameter coupling rather than independent control of multiple doping elements.
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 silicon carbide wafers with uniform high resistivity and controlled purity, enhancing their performance and stability, as demonstrated by experimental results showing over 85% to 100% of the wafer area achieving the desired resistivity levels.
Implementation Method 1
Argon gas and vanadium gas are introduced into the reactor. The reactor and the raw material are heated to form a silicon carbide material on the seed crystal.
Implementation Method 2
The reactor and the raw material are heated to form a silicon carbide material on the seed crystal.
Data Source
AI summary
A silicon carbide wafer and a method of fabricating the same are provided. In the silicon carbide wafer, a ratio (V:N) of a vanadium concentration to a nitrogen concentration is in a range of 2:1 to 10:1, and a portion of the silicon carbide wafer having a resistivity greater than 1012 Ω·cm accounts for more than 85% of an entire wafer area of the silicon carbide wafer.