Silicon Carbide Powder for Sublimation Recrystallization
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Solution Overview
Problem
Existing methods for producing silicon carbide single crystals using sublimation recrystallization struggle with low productivity and high impurity content due to sublimation rate limitations and particle size issues, which hinder the growth of large-sized crystals with minimal impurities.
Innovation Solution
A silicon carbide powder with a Blaine specific surface area of 250 cm²/g to 1,000 cm²/g and a particle size distribution of 50 vol% or more in the range of 0.70 mm to 3.00 mm, composed of aggregated primary particles, is used as a raw material, allowing for high sublimation rates and reduced impurity incorporation during the sublimation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional silicon carbide powder with large particle size is used in sublimation recrystallization, then the sublimation rate is low, but using smaller particle size increases sublimation rate while causing excessive impurity incorporation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution (50-700 μm with specific d50 values) and Blaine specific surface area (250-1000 cm²/g) of the silicon carbide powder. This optimization balances the sublimation rate and impurity incorporation, resolving the contradiction between productivity and manufacturing precision.
2Volume of moving object
If the sublimation process is extended to grow larger crystals, then the crystal size increases, but the production time and energy consumption increase significantly
Solution Approach 1:
The patent optimizes the particle size distribution parameters to achieve a balanced sublimation rate that enables efficient growth of large-sized crystals (100 mm diameter or more) while controlling production time and energy consumption through precise parameter control.
3Manufacturing precision
If high pressure is applied during sublimation to reduce impurity sublimation, then impurity content decreases, but the sublimation rate is suppressed
Solution Approach 1:
The patent resolves this contradiction by optimizing the particle size distribution and specific surface area parameters, which enable the process to achieve both high sublimation rate and low impurity content even under high pressure conditions through enhanced heat and mass transfer efficiency.
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 enhances the growth rate and purity of silicon carbide single crystals, reducing energy costs and production time while minimizing impurity incorporation, enabling the growth of large-sized crystals with low residual material, thus improving overall productivity.
Implementation Method 1
there has been known a sublimation recrystallization method (i.e. modified Lely method) involving sublimating a silicon carbide powder serving as a raw material under a high temperature condition of 2,000°C or more
Data Source
Figure 1~2
AI summary
Provided is a silicon carbide powder which, when used as a raw material in a sublimation recrystallization method, enables an improvement in productivity of a silicon carbide single crystal by virtue of exhibiting a high sublimation rate and allowing a small amount of silicon carbide to remain without being sublimated, and enables an increase in size of the silicon carbide single crystal (for example, a single crystal wafer). The silicon carbide powder has a Blaine specific surface area of from 250 cm2/g to 1, 000 cm2/g and has a ratio of a silicon carbide powder having a particle size of more than 0.70 mm and 3.00 mm or less of 50 vol% or more with respect to a total amount of the silicon carbide powder. When a silicon carbide powder (5) accommodated in a crucible (1) is heated to be sublimated, a silicon carbide single crystal (6) is formed on a seed crystal (4) provided on an undersurface of a lid (3).