SiC Crystal Growth Insulation Segmentation
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Solution Overview
Problem
The production of high-quality SiC bulk single crystals using sublimation growth is hindered by deviations from ideal rotational symmetry due to thermal field asymmetries, leading to crystal defects and reduced yields, as well as high costs and material loss from asymmetric crystal structures.
Innovation Solution
A method involving a cultivation crucible surrounded by rotationally symmetrical thermal insulation with concentrically arranged partial insulation cylinders, each with density deviations controlled to within 10% of the average density, to create a practically ideal rotationally symmetrical temperature field, ensuring symmetrical SiC bulk single crystal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thermal insulation with imperfect rotational symmetry is used, then the crystal growth process is simpler and cheaper, but the crystal geometry deviates from ideal rotational symmetry leading to defects
Solution Approach 1:
The thermal insulation is divided into multiple separate insulation elements arranged in a circular pattern around the crystal growth chamber. Each insulation element can be independently manufactured and positioned, allowing the overall structure to achieve rotational symmetry through proper arrangement rather than requiring each individual component to be perfectly symmetric. This segmentation enables high manufacturing precision while keeping individual component complexity low.
Solution Approach 2:
The patent deliberately introduces asymmetric features into the insulation structure, specifically positioning heating elements and insulation components with controlled asymmetric arrangements. By carefully designing these asymmetric positions and densities, the patent compensates for inherent asymmetries in the heating system, ultimately achieving symmetric thermal fields and crystal growth. This applies asymmetry as a means to achieve symmetry in the final outcome.
2Manufacturing precision
If the growth crucible is continuously rotated to average out thermal asymmetries, then crystal rotational symmetry improves, but vibrations cause crystal defects and carbon inclusions
Solution Approach 1:
The patent positions heating elements and insulation components in specific asymmetric arrangements around the crystal growth chamber. By carefully controlling the density and position of these asymmetrically placed components, the patent creates a thermally symmetric environment without requiring mechanical rotation. This eliminates vibrations and carbon inclusion risks while achieving the desired crystal rotational symmetry.
3Productivity
If higher quality SiC bulk single crystals are produced with perfect rotational symmetry, then material loss decreases and yield increases, but the production process becomes more complex and costly
Solution Approach 1:
The thermal insulation system is segmented into multiple independent elements that can be manufactured using standard processes and then arranged in a circular pattern. This segmentation allows for easier manufacturing and assembly compared to creating a single complex symmetric structure, thereby reducing overall production complexity and cost while achieving high yield through improved crystal quality.
Solution Approach 2:
The patent adjusts parameters such as the number, position, and thermal properties of insulation elements to optimize crystal growth symmetry. By changing these parameters systematically, the patent achieves high-quality crystal production with improved yield while managing production complexity through parameter optimization rather than structural complexity.
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 high-quality, rotationally symmetrical SiC bulk single crystals with reduced material loss and increased yield, minimizing defects and costs by maintaining uniform thermal insulation and growth symmetry.
Implementation Method 1
During cultivation, an SiC growth gas phase is generated there by means of sublimation of the SiC source material
Implementation Method 2
the at least one SiC bulk single crystal grows by means of deposition from the SiC growth gas phase on the at least one SiC seed crystal
Implementation Method 3
Before the start of cultivation, the cultivation crucible is surrounded by a rotationally symmetrical insulation, in particular thermal insulation
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The process serves to produce a bulk SiC single crystal (2) wherein a SiC seed crystal (8) is arranged in a crystal growth region (5) of a growth vessel (3), and SiC source material (6) is introduced into a SiC storage region (4), and the bulk SiC single crystal (2) grows by deposition from a SiC growth gas phase (9). The growth vessel (3) is surrounded by a rotationally symmetric insulation (10) extending axially in the direction of a central longitudinal axis (14), which has at least two concentrically arranged and nested insulation partial cylinders (19, 20), wherein the insulation (10) is fictitiously divided into insulation ring segments, which in turn are fictitiously divided into volume elements, and each insulation ring segment has a mean insulation ring segment density.The insulating cylinder sections (19, 20) are selected and positioned relative to each other such that each volume element of the respective insulating ring segment has a volume element density that deviates by no more than 10% from the mean insulating ring segment density of the respective insulating ring segment (29). Each volume element extends axially over an axial element length equal to an axial segment length of the insulating ring segment, which is up to 50 mm, circumferentially over an outer tangential element length of up to 50 mm, and radially over the sum of all wall thicknesses (D1, D2) of the insulating cylinder sections (19, 20).