SiC Monocrystal Growth via Seed Nucleation for Dislocation Control
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Solution Overview
Problem
Current methods for producing SiC volume monocrystals by sublimation growth result in high screw dislocation densities, leading to reduced quality and increased costs due to crystal defects, and existing solutions do not adequately address the need for low, homogeneous dislocation distribution across SiC substrates.
Innovation Solution
A method involving the examination and treatment of the SiC seed crystal to generate nucleation centers on the growth surface, where screw dislocations can be compensated, reducing the screw dislocation density through recombination and achieving a homogeneous distribution across the SiC volume monocrystal and subsequent substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sublimation growth method is used to produce SiC volume monocrystal, then production cost and time are reduced, but screw dislocation density increases leading to reduced crystal quality
Solution Approach 1:
The patent applies preliminary action by treating the seed crystal surface before growth to generate nucleation centers. The seed crystal undergoes surface treatment (chemical etching or mechanical polishing) prior to sublimation growth, which creates controlled nucleation sites that guide dislocation behavior during subsequent crystal growth, thereby preventing high dislocation density in the final product while maintaining production efficiency
Solution Approach 2:
The patent employs parameter changes by controlling growth conditions including temperature gradients, pressure, and growth rate. By optimizing these parameters during sublimation growth, the method achieves low screw dislocation density without requiring excessively slow growth rates, thus resolving the contradiction between crystal quality and production efficiency
2Manufacturing precision
If two-stage growth process is used to reduce screw dislocations in edge region, then local dislocation density in edge region decreases, but overall homogeneous low dislocation density is not achieved
Solution Approach 1:
The patent applies local quality by creating non-uniform nucleation center distribution on the seed crystal surface. Different regions of the seed crystal receive different treatments or have different nucleation center densities, which guides the formation of compensation dislocations in specific locations to achieve homogeneous overall distribution of low dislocation density in the grown crystal
Solution Approach 2:
The patent implements feedback by monitoring dislocation behavior during growth and adjusting growth parameters accordingly. The growth process incorporates real-time observation of crystal structure development, allowing dynamic adjustment of temperature, pressure, or growth rate to maintain homogeneous low dislocation density throughout the crystal volume
3Productivity
If seed crystal with high screw dislocation density is used, then growth rate is maintained, but crystal quality deteriorates due to dislocation propagation
Solution Approach 1:
The patent converts the harmful effect of screw dislocations into a beneficial mechanism by promoting the formation of compensation dislocations. The original screw dislocations in the seed crystal trigger the nucleation of compensation dislocations with opposite Burgers vectors, which annihilate the harmful dislocations and transform them into a quality-improving mechanism while maintaining normal growth rates
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 method effectively reduces screw dislocation density and achieves a homogeneous distribution, resulting in high-quality SiC substrates suitable for semiconductor and high-frequency components, improving yield and reducing production costs.
Implementation Method 1
by means of sublimation of the SiC source material and by means of transport of the sublimated gaseous components into the crystal growth region
Implementation Method 2
an SiC volume monocrystal grows on the SiC seed crystal by means of deposition from the SiC growth gas phase
Implementation Method 3
the SiC seed crystal is treated at the growth surface before the start of growth, so that nucleation centers are generated in each seed segment
Data Source
AI summary
A SiC volume monocrystal is produced by sublimation growth. An SiC seed crystal is placed in a crystal growth region of a growing crucible and SiC source material is introduced into an SiC storage region. During growth, at a growth temperature of up to 2,400° C. and a growth pressure between 0.1 mbar and 100 mbar, an SiC growth gas phase is generated by sublimation of the SiC source material and by transport of the sublimated gaseous components into the crystal growth region, where an SiC volume monocrystal grows by deposition from the SiC growth gas phase on the SiC seed crystal. Prior to the start of growth, the SiC seed crystal is examined at the growth surface for the presence of seed screw dislocations, nucleation centers are generated, wherein the nucleation centers are starting points for at least one compensation screw dislocation during the growth carried out subsequently.