SiC Monocrystal Thermal Post-Treatment Radial Gradient
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Solution Overview
Problem
Current thermal post-treatment methods for SiC volume monocrystals do not effectively reduce mechanical stresses, leading to defects such as bow and warp in substrates, which negatively impact the quality of epitaxial layers and semiconductor components.
Innovation Solution
A method involving a thermal post-treatment process with a continuously increasing radial thermal gradient, achieved by surrounding the SiC volume monocrystal with free space for heat exchange via free heat radiation on at least two boundary surfaces, mobilizing dislocations to reduce stress and improve substrate geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an isothermal temperature field is used during thermal post-treatment, then the temperature difference is minimized (maximum 2 K), but the mechanical stresses are only partially relieved
Solution Approach 1:
The patent applies local quality by creating different temperature conditions in different regions of the SiC volume monocrystal. Specifically, it uses an inhomogeneous temperature field with a radial temperature gradient where the outer region is heated to a higher temperature (T2) than the inner region (T1), with T2-T1 ranging from 50 K to 200 K. This localized temperature differentiation enables effective stress relief by mobilizing dislocations in the high-temperature outer region while maintaining controlled thermal conditions throughout the crystal.
2Stability of the object's composition
If the SiC volume monocrystal is completely embedded in SiC powder, then thermal coupling is improved, but the temperature field becomes too homogeneous and stress relief is insufficient
Solution Approach 1:
The patent applies local quality by creating different temperature conditions in different regions of the SiC volume monocrystal. Specifically, it uses an inhomogeneous temperature field with a radial temperature gradient where the outer region is heated to a higher temperature (T2) than the inner region (T1), with T2-T1 ranging from 50 K to 200 K. This localized temperature differentiation enables effective stress relief by mobilizing dislocations in the high-temperature outer region while maintaining controlled thermal conditions throughout the crystal.
Solution Approach 2:
The patent applies segmentation by dividing the temperature field into distinct radial zones: an inner region with temperature T1 and an outer region with higher temperature T2. This segmentation of the thermal field allows different parts of the monocrystal to experience different thermal conditions, with the outer region undergoing more intense heating to mobilize dislocations and relieve stresses, while the inner region maintains a more moderate temperature.
3Manufacturing precision
If axial temperature gradient is applied during post-treatment, then the geometry of substrates is improved, but radial stresses are not effectively addressed
Solution Approach 1:
The patent applies inversion by reversing the conventional approach of using axial temperature gradients. Instead, it implements a radial temperature gradient where the temperature varies in the radial direction (from center to outer surface) rather than in the axial direction. This inverted approach targets the radial mechanical stresses directly by creating a temperature difference between the outer and inner regions, thereby mobilizing dislocations and relieving stresses that were previously unaddressed by axial gradient methods.
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 effectively minimizes mechanical stresses and improves the geometry of SiC substrates, leading to higher quality epitaxial layers and reduced defects in semiconductor components.
Implementation Method 1
a heat exchange of the SiC volume monocrystal with a free space surrounding it takes place by means of free heat radiation on at least two of the three boundary surfaces
Data Source
AI summary
Thermal post-treatment of a silicon carbide (SiC) volume monocrystal which has a substantially cylindrical basic shape with a crystal length in an axial direction, a crystal diameter in a radial direction, a crystal central longitudinal axis extending in the axial direction, and with three boundary surfaces, namely, a bottom surface, a top surface and a circumferential edge surface. The SiC volume monocrystal is brought to a post-treatment temperature in order to reduce mechanical stresses present in the SiC volume monocrystal after completion of the previous growth, wherein an inhomogeneous temperature profile with a radial thermal gradient is set in the SiC volume monocrystal, which rises continuously from the crystal central longitudinal axis to the circumferential edge surface, and a heat exchange of the SiC volume monocrystal with a surrounding free space takes place via free heat radiation on at least two of the three boundary surfaces.