SiC Crystal Growth Separation Plate for Defect Reduction
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Solution Overview
Problem
Current SiC sublimation crystal growth methods face challenges in achieving high-quality, large-diameter SiC substrates due to issues such as dislocations, micropipes, stacking faults, and carbon inclusions, which lead to stress and defects in the crystal.
Innovation Solution
The method involves controlling vapor transport and temperature gradients to restrict vapor transport to the central area of the growing crystal, maintaining near-zero radial temperature gradients, and using a separation plate with distinct permeability zones to filter out particulates and control the flux of sublimated source material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SiC sublimation crystal growth methods are used, then crystal growth can proceed, but dislocations, micropipes, stacking faults, and carbon inclusions occur leading to high crystal defect densities
Solution Approach 1:
The growth cell is divided into a source compartment and a crystallization compartment by a separation plate with selective permeability. This segmentation restricts vapor transport to specific pathways, controlling where vapor reaches the crystal and enabling better defect reduction while maintaining growth.
Solution Approach 2:
The separation plate has zones of different permeability (fully permeable, partially permeable, and non-permeable zones) that create localized vapor flux patterns. This local quality control directs vapor preferentially to the central area of the crystal while filtering particulates, reducing defects in critical growth regions.
2Productivity
If vapor transport is allowed to reach the entire crystal surface, then growth area is maximized, but radial temperature gradients increase causing crystal stress and defects
Solution Approach 1:
The separation plate creates localized vapor flux concentrated in the central area rather than uniform distribution across the entire crystal surface. This local quality control maintains near-zero radial temperature gradients while still achieving effective growth through controlled vapor delivery to the central region.
3Quantity of substance
If the separation plate is fully permeable to vapor, then vapor flux is maximized, but particulates from the source reach the crystal causing inclusions
Solution Approach 1:
The separation plate features spatially varying permeability with fully permeable, partially permeable, and non-permeable zones. This local quality differentiation allows vapor to pass through while blocking particulates, achieving both high vapor flux and effective filtration to prevent carbon inclusions.
Solution Approach 2:
The separation plate acts as an intermediary between the source compartment and crystallization compartment. It mediates the vapor transport process by selectively permitting vapor passage while intercepting and filtering out particulates, preventing their reach to the crystal surface.
4Device complexity
If conventional single-compartment growth cells are used, then device complexity is minimized, but control over vapor transport and temperature gradients is insufficient for large-diameter high-quality crystals
Solution Approach 1:
The growth cell is segmented into two compartments by a separation plate, adding structural complexity but enabling precise control over vapor transport pathways and temperature gradients. This segmentation allows independent optimization of source and crystallization zones for producing large-diameter high-quality crystals.
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 results in SiC single crystals with a flat or slightly convex growth interface, reduced crystal stress, and lower densities of crystal defects, enabling the production of high-quality SiC substrates with improved diameter sizes such as 100 mm, 125 mm, 150 mm, and 200 mm.
Implementation Method 1
heating the interior of the growth crucible such that the source material is heated to a sublimation temperature and the temperature gradient is sufficient to cause sublimated source material to be transported in the form of vapor to the seed crystal
Implementation Method 2
filtration of the vapor from particulates originating from the SiC source
Implementation Method 3
controlling the vapor transport and temperature gradients, wherein said transport is restricted to the central area of the growing crystal
Data Source
Figure 1~2B
Figure 3~4B
Figure 5~6
AI summary
A method and system of forming large-diameter SiC single crystals suitable for fabricating high crystal quality SiC substrates of 100, 125, 150 and 200 mm in diameter are described. The SiC single crystals are grown by a seeded sublimation technique in the presence of a shallow radial temperature gradient. During SiC sublimation growth, a flux of SiC bearing vapors filtered from carbon particulates is substantially restricted to a central area of the surface of the seed crystal by a separation plate disposed between the seed crystal and a source of the SiC bearing vapors. The separation plate includes a first, substantially vapor-permeable part surrounded by a second, substantially non vapor-permeable part. The grown crystals have a flat or slightly convex growth interface. Large-diameter SiC wafers fabricated from the grown crystals exhibit low lattice curvature and low densities of crystal defects, such as stacking faults, inclusions, micropipes and dislocations.