SiC Seed Crystal Spacing Member for Strain-Free Growth
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Solution Overview
Problem
Existing methods for producing silicon carbide single crystals often result in strain due to thermal stress from pedestals and interference from polycrystals, leading to crack formation and reduced quality.
Innovation Solution
A process involving a silicon carbide spacing member non-adhesively held between the pedestal and seed crystal, with a curvature-matched adhesive surface and controlled spacing to prevent polycrystal contact, using materials with matching thermal expansion coefficients to minimize stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon carbide seed crystal is affixed to a pedestal by adhering using an adhesive, then the seed crystal is securely fixed on the pedestal, but thermal stress from the pedestal based on difference in coefficients of thermal expansion imparts strain to the seed crystal, resulting in cracks in the grown single crystals
Solution Approach 1:
A spacing member made of silicon carbide is introduced as an intermediary between the pedestal and the seed crystal. This spacing member has a coefficient of thermal expansion matching that of the seed crystal, thereby mediating the thermal stress transmission and preventing strain accumulation that would otherwise occur through direct contact with the pedestal.
Solution Approach 2:
The direct contact interface between the pedestal and seed crystal is segmented by introducing the spacing member. This divides the thermal stress transmission path into separate segments: pedestal-to-spacing member and spacing member-to-seed crystal, with the latter being stress-free due to matched thermal expansion properties.
2Manufacturing precision
If a silicon carbide seed crystal is mechanically supported on a pedestal without affixing using an adhesive, then thermal stress from the pedestal is avoided, but polycrystals grow between the supporting member and the seed crystal, covering the outer periphery of single crystals and imparting stress
Solution Approach 1:
The spacing member serves as a mediator that provides mechanical support while preventing polycrystal formation. By being made of silicon carbide with matched thermal expansion properties, it creates a controlled interface that allows mechanical support without allowing unwanted polycrystal growth to reach the seed crystal.
Solution Approach 2:
The spacing member introduces a vertical dimension of separation between the supporting structure and the seed crystal. This spatial separation in the vertical dimension prevents lateral polycrystal growth from reaching the seed crystal while still providing necessary mechanical support.
3Reliability
If adhesive is used to fix the seed crystal, then secure fixation is achieved, but the adhesive and its application process add complexity to the manufacturing procedure
Solution Approach 1:
The adhesive and its application process are completely extracted from the system by using a spacing member that provides fixation through mechanical interference and friction fit. This eliminates the need for adhesives, curing processes, and associated complexity while maintaining secure fixation.
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 enables the production of strain-free, high-quality silicon carbide single crystals by avoiding thermal stress and polycrystal interference, resulting in crack-free and high-quality crystal growth.
Implementation Method 1
supplying a sublimed gas of a silicon carbide source material to the silicon carbide seed crystal arranged on a pedestal
Data Source
Figure 1
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AI summary
The process for producing silicon carbide single crystals of the present invention comprises a step for growing single crystals of silicon carbide on a silicon carbide seed crystal by supplying a sublimed gas of a silicon carbide source material to the silicon carbide seed crystal arranged on a pedestal, wherein a spacing member composed of silicon carbide is arranged between the pedestal and the silicon carbide seed crystal, the spacing member is non-adhesively held on the pedestal by a supporting member, the silicon carbide seed crystal is adhered to the surface of the spacing member on the opposite side of the pedestal, and the spacing member and the supporting member are relatively arranged so that the adhesive surface of the spacing member adhered with the silicon carbide seed crystal is separated by 5 mm or more in the vertical direction from the lowest position of the supporting member.