SiC Ingot Growth via Raw Material Flow Factor Control
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Solution Overview
Problem
Conventional methods for growing silicon carbide (SiC) ingots using physical vapor transport (PVT) do not effectively control the flowability of raw material powders under changing temperature and pressure conditions, leading to defects such as micropipe defects, basal plane dislocations, and non-uniform crystal growth.
Innovation Solution
A composition of raw material powder with a flow factor of 5 to 35 and a specific particle size distribution (D50 of 10 μm to 800 μm) is used, which exhibits a 5% to 18% change in internal friction angle upon compression, ensuring uniform sublimation and minimizing defects during the growth of 4H SiC ingots with a caliber of 4 inches or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional raw material powders are used in PVT method, then the ingot growth rate is achieved, but the flowability control under changing temperature and pressure is poor leading to defects
Solution Approach 1:
The patent applies parameter changes by controlling the flow factor of raw material powder within a specific range (5-35) and adjusting particle size distribution (D50: 10-800 μm). These parameter optimizations ensure stable sublimation behavior and uniform material flow under changing temperature and pressure conditions during PVT growth, preventing defects while maintaining high growth rates
Solution Approach 2:
The patent implements preliminary action by pre-characterizing and selecting raw material powders with specific flow factors and particle size distributions before the growth process. This preliminary preparation ensures that the material exhibits appropriate flow behavior and sublimation characteristics when subjected to temperature and pressure changes, thereby preventing defects before they occur
2Reliability
If aggregated material in granulated form is used, then flowability is improved, but uniform sublimation and defect reduction are not sufficiently achieved
Solution Approach 1:
The patent applies local quality by optimizing specific properties of the raw material powder including flow factor (5-35), particle size distribution (D50: 10-800 μm), and morphology. This localized optimization of material characteristics ensures both improved flowability and uniform sublimation behavior, resolving the contradiction between these two requirements
Solution Approach 2:
The patent implements dynamics by selecting materials with appropriate flow factors that allow the powder to adapt its flow behavior under changing process conditions. The dynamic flow characteristics enable the material to maintain uniform sublimation despite temperature and pressure variations, achieving both good flowability and uniformity
3Productivity
If large diameter single crystal ingots are manufactured, then productivity is improved, but defects such as micropipe defects and basal plane dislocations increase
Solution Approach 1:
The patent applies parameter changes by optimizing the flow factor (5-35) and particle size distribution (D50: 10-800 μm) of raw material powder. These parameter optimizations enable stable and uniform sublimation during the growth of large diameter ingots, preventing the formation of micropipe defects and basal plane dislocations even at increased scales
Solution Approach 2:
The patent implements preliminary action by pre-selecting and characterizing raw materials with specific flow properties before growth. This preliminary preparation ensures that when growing large diameter ingots, the material will sublime uniformly throughout the entire volume, preventing defects before they can form during the scaling-up process
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 produces SiC ingots with excellent crystallinity and reduced surface pits, facilitating the growth of high-quality SiC wafers with minimal defects and improved processing characteristics.
Implementation Method 1
sublimating the composition such that the SiC ingot grows from the plurality of seed crystal
Data Source
AI summary
A method for preparing a SiC ingot includes loading a composition of a raw material comprising a carbon source and a silicon source into a reactor; placing a plurality of seed crystal on one side of the reactor spaced apart from the composition; and sublimating the composition such that the SiC ingot grows from the plurality of seed crystal. A flow factor of the composition may be 5 to 35.