Silicon Carbide Ingot Nitrogen Gradient Control
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Solution Overview
Problem
Existing methods for producing silicon carbide ingots struggle to sufficiently suppress crack generation due to stress and strain caused by nitrogen atom concentration gradients during crystal growth, leading to defects in the ingot and subsequent substrates.
Innovation Solution
A silicon carbide ingot with a nitrogen-doped layer grown on a seed substrate, where the layer thickness is 15 mm or more and the nitrogen atom concentration gradient in the growth direction is reduced to 5×10^17 atoms/cm^4 or less, and the flow rates of carrier and nitrogen gases are adjusted to satisfy specific ratios during crystal growth to minimize stress and strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the silicon carbide layer is increased to 15 mm or more, then the ingot can provide sufficient material for substrate production, but the concentration gradient of nitrogen atoms increases leading to stress and strain that facilitates crack generation
Solution Approach 1:
The patent changes the concentration parameter of nitrogen atoms by controlling the nitrogen gas flow rate during crystal growth. By maintaining the nitrogen atom concentration gradient at 5×10^17 atoms/cm^4 or less throughout the thick silicon carbide layer (15 mm or more), the patent achieves uniform distribution that prevents stress concentration and crack generation, thus resolving the contradiction between layer thickness and crack resistance
Solution Approach 2:
The patent employs periodic adjustment of the nitrogen gas flow rate during the crystal growth process. By controlling the nitrogen supply in a periodic manner that maintains consistent concentration distribution, the patent achieves uniform nitrogen atom distribution in the thick layer, preventing stress accumulation and crack formation while ensuring sufficient layer thickness
2Reliability
If the concentration gradient of nitrogen atoms is reduced to suppress stress and strain, then crack generation is suppressed, but the uniform distribution becomes difficult to achieve in thick layers
Solution Approach 1:
The patent implements feedback control by monitoring the nitrogen atom concentration distribution during crystal growth and adjusting the nitrogen gas flow rate accordingly. This feedback mechanism ensures that the concentration gradient remains at 5×10^17 atoms/cm^4 or less throughout the silicon carbide layer, achieving both crack resistance and concentration uniformity even in thick layers
Solution Approach 2:
The patent precisely controls the concentration parameter of nitrogen atoms by adjusting the nitrogen gas flow rate during growth. By maintaining the concentration gradient within the specified limit, the patent achieves uniform distribution that simultaneously provides crack resistance and manufacturing precision
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 effectively reduces stress and strain in the ingot, suppressing crack generation and enabling the production of high-quality silicon carbide substrates with reduced defects, even when cutting the ingot.
Implementation Method 1
growing a silicon carbide single crystal on a seed substrate using a sublimation-recrystallization method
Implementation Method 2
a silicon carbide layer grown on the seed substrate and containing nitrogen atoms
Data Source
AI summary
An ingot in which generation of crack is sufficiently suppressed is obtained. The ingot includes: a seed substrate formed of silicon carbide; and a silicon carbide layer grown on the seed substrate and containing nitrogen atoms. The silicon carbide layer has a thickness of 15 mm or more in a growth direction. In the silicon carbide layer, a concentration gradient of the nitrogen atoms in the growth direction is 5×1017 atoms/cm4 or less.