SiC Crystal Growth via Staged Sublimation for Low Fe and Al Impurities
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Solution Overview
Problem
The use of SiC powders (Green Silicon Carbide) as a source material for growing SiC crystals results in high impurity concentrations of aluminum (Al) and iron (Fe), which degrade the quality of the grown crystals, making it difficult to achieve low impurity levels and improve semiconductor device performance.
Innovation Solution
A method involving multiple stages of growing SiC crystals, where the source material is progressively refined by crushing and washing to reduce Fe and Al concentrations, with specific size distribution and acid treatment to minimize impurities, ultimately achieving an SiC crystal with Fe concentration not higher than 0.1 ppm and Al concentration not higher than 100 ppm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SiC powders for polishing (GC) are used as source material for growing SiC crystal, then the manufacturing process is simple and cost-effective, but the impurity concentration (Fe and Al) becomes high which degrades crystal quality
Solution Approach 1:
The patent divides the crystal growth process into multiple sequential stages (first growth stage, second growth stage, third growth stage) with progressively stricter impurity control. Each stage uses source material with different impurity specifications, allowing the process to benefit from both simple manufacturing (using readily available GC powder) and high precision (achieving ultra-low impurity levels through staged refinement)
Solution Approach 2:
The patent performs preliminary purification actions on the source material before each growth stage. Specifically, the second source material is prepared by crushing and washing the first grown crystal to remove surface contaminants, and the third source material is prepared by crushing and washing the second grown crystal. This preliminary preparation removes impurities before they can be incorporated into the crystal structure
2Manufacturing precision
If multiple stages of crystal growth with source material refinement are performed, then impurity concentration is reduced and crystal quality improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent systematically changes key parameters across growth stages: source material particle size (from powder to crushed crystal), source material impurity specifications (progressively tighter controls on Fe and Al), and growth conditions (temperature, pressure, atmosphere). These parameter changes are implemented in a structured sequence that improves precision while keeping the overall process framework relatively simple
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 suppresses the lowering of SiC crystal quality due to impurities, improving micropipe density, etch pit density, and overall crystal quality, making the SiC crystals suitable for high-performance semiconductor devices.
Implementation Method 1
growing an SiC crystal by sublimating the source material through heating and precipitating an SiC crystal
Implementation Method 2
sublimating the source material through heating and precipitating an SiC crystal
Data Source
AI summary
An SiC crystal (10) has Fe concentration not higher than 0.1 ppm and Al concentration not higher than 100 ppm. A method of manufacturing an SiC crystal includes the following steps. SiC powders for polishing are prepared as a first source material (17). A first SiC crystal (11) is grown by sublimating the first source material (17) through heating and precipitating an SiC crystal. A second source material (12) is formed by crushing the first SiC crystal (11). A second SiC crystal (14) is grown by sublimating the second source material (12) through heating and precipitating an SiC crystal. Thus, an SiC crystal and a method of manufacturing an SiC crystal capable of achieving suppressed lowering in quality can be obtained.