SiC Ingot Impurity Control for Basal Plane Dislocation Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing large-area high-quality single-crystal silicon carbide (SiC) substrates are hindered by high basal plane dislocation densities, which degrade the reliability of SiC devices due to thermal stress during crystal growth, and existing solutions have limited effectiveness in minimizing thermal stress.
Innovation Solution
A single-crystal SiC ingot with controlled concentrations of donor-type and acceptor-type impurities, where the donor-type impurity concentration is higher than the acceptor-type, specifically in the range of 2 x 10^18 cm^-3 to 6 x 10^20 cm^-3, to inhibit basal plane dislocation slipping, thereby reducing dislocation density and maintaining low resistivity suitable for power devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If single-crystal SiC is grown by the modified Lely process using a seed crystal, then crystal growth rate and polytype control are improved, but basal plane dislocation density increases due to thermal stress during growth
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentration ratio of donor-type to acceptor-type impurities in the range of 10^-6 to 10^-2, and by controlling the crystal growth rate within 0.1 to 10 μm/h. These parameter optimizations reduce thermal stress effects during growth, thereby reducing basal plane dislocation density while maintaining good crystal growth control and reproducibility.
2Productivity
If the crystal growth rate is increased to improve productivity, then production efficiency is improved, but thermal stress increases causing more basal plane dislocations
Solution Approach 1:
The patent optimizes the crystal growth rate parameter within the specific range of 0.1 to 10 μm/h, balancing productivity with quality. This controlled growth rate parameter prevents excessive thermal stress accumulation while maintaining efficient production, thereby reducing basal plane dislocation density without sacrificing too much productivity.
3Reliability
If impurity concentration is increased to control resistivity, then electrical properties are improved, but crystal quality deteriorates due to increased defects
Solution Approach 1:
The patent applies parameter changes by optimizing the impurity concentration ratio (donor-type to acceptor-type) within 10^-6 to 10^-2 and controlling absolute impurity concentrations within 10^16 to 10^20 cm^-3. This balanced impurity control achieves the desired resistivity for electrical functionality while preventing excessive defect formation, thereby maintaining crystal quality.
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 approach results in a significant reduction of basal plane dislocation density to 1 x 10^4 cm^-2 or less, enabling the production of high-quality substrates and epitaxial wafers with improved electrical and optical properties, suitable for high-frequency and high-breakdown-voltage electronic devices.
Implementation Method 1
heated to 2000 to 2400 °C... A temperature gradient is established during the heating so as to make the temperature of the seed crystal slightly lower than the temperature of the feedstock powder. Owing to its concentration gradient (produced by the temperature gradient), the sublimated feedstock is dispersed toward and transported to the seed crystal.
Implementation Method 2
Single crystal growth occurs when the feedstock gas reaching the seed crystal recrystallizes on the seed crystal.
Implementation Method 3
Single crystal growth occurs when the feedstock gas reaching the seed crystal recrystallizes on the seed crystal.
Implementation Method 4
Owing to its concentration gradient (produced by the temperature gradient), the sublimated feedstock is dispersed toward and transported to the seed crystal.
Data Source
Figure 1~2
AI summary
The present invention provides a single-crystal silicon carbide ingot capable of providing a good-quality substrate low in dislocation defects, and a substrate and epitaxial wafer obtained therefrom. It is a single-crystal silicon carbide ingot comprising single-crystal silicon carbide which contains donor-type impurity at a concentration of 2 x 1018 cm-3 to 6 x 1020 cm-3 and acceptor-type impurity at a concentration of 1 x 1018 cm-3 to 5.99 x 1020 cm-3 and wherein the concentration of the donor-type impurity is greater than the concentration of the acceptor-type impurity and the difference is 1 x 1018 cm-3 to 5.99 x 1020 cm-3, and a substrate and epitaxial wafer obtained therefrom.