Shield Member Heat Capacity Gradient for SiC Crystal Growth
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Solution Overview
Problem
Conventional shielding plates in silicon carbide single crystal growth apparatuses result in non-uniform surface temperatures, leading to thermal stress and poor crystal quality due to uneven heating from both the raw material and the vessel wall, making it difficult to produce high-quality, large-diameter crystals.
Innovation Solution
A shield member with increasing heat capacity from the center to the periphery, comprising multiple ring members with varying thickness and inner diameters, is placed between the raw material storage and substrate to correct non-uniform heating, ensuring the center is heated harder than the periphery, thereby reducing radial temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional shielding plate with uniform thickness is used, then the structure is simple and easy to manufacture, but the surface temperature becomes non-uniform leading to thermal stress and poor crystal quality
Solution Approach 1:
The shielding plate is designed with non-uniform thickness where the thickness increases from the center toward the periphery. This local variation in thickness creates corresponding variations in heat capacity, allowing different regions of the shielding plate to have different thermal characteristics. Specifically, the periphery has higher heat capacity to compensate for stronger heating from the vessel wall, while the center has lower heat capacity to avoid excessive heating, thereby achieving uniform temperature distribution across the substrate.
2Manufacturing precision
If the shielding plate thickness increases from center to periphery, then temperature distribution becomes uniform, but the device complexity increases
Solution Approach 1:
The shielding plate is divided into multiple ring-shaped segments arranged concentrically, with each ring having a different thickness. This segmentation allows the complex non-uniform thickness profile to be constructed from simpler individual ring components that can be manufactured separately and then assembled together, reducing the difficulty of fabricating the complete shielding plate with varying thickness.
3Reliability
If a simple shielding plate is used, then the device is easy to manufacture, but thermal stress causes crack and dislocation reducing crystal quality
Solution Approach 1:
The physical parameter of the shielding plate being modified is its thickness, which is varied continuously or in steps from the center toward the periphery. This parameter change results in corresponding changes in heat capacity across different regions of the shielding plate, creating a temperature distribution that is uniform across the substrate surface and thereby eliminating thermal stress that would cause crack and dislocation.
4Temperature
If the shielding plate is made thicker at the periphery, then the heat capacity increases to compensate for peripheral heating, but the overall device complexity increases
Solution Approach 1:
The shielding plate is designed with asymmetric thickness distribution where the thickness is not uniform across the plate but instead varies systematically from the center toward the periphery. This asymmetric configuration is intentionally created to compensate for the symmetric heating pattern from the vessel wall, with the periphery being thicker to handle the stronger heating in that region, thereby achieving symmetric temperature uniformity across the substrate.
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 configuration achieves a more uniform temperature distribution across the substrate, enabling the growth of high-quality, large-diameter silicon carbide single crystals by mitigating thermal stress and maintaining a flat growing surface.
Implementation Method 1
a heating apparatus positioned at outer periphery of the vessel for growing a crystal, thereby sublimating the raw material from the raw material storage part to grow single crystal of the raw material onto the substrate
Implementation Method 2
the shielding plate receives the radiant heat from the raw material to be heated, and emits the radiant heat to the seed crystal or the growing crystal
Data Source
AI summary
Provided is a shield member and an apparatus for growing a single crystal equipped with the shield member. Such a shield member includes: a vessel for growing the single crystal; a raw material storage part positioned at a lower portion of the vessel for growing the single crystal; a substrate supporting part, positioned above the raw material storage part to support the substrate; and a heating apparatus positioned at a an outer periphery of the vessel for growing the single crystal, thereby sublimating the raw material from the raw material storage part to grow the single crystal of the raw material onto the substrate, in which a plurality of permeation holes through which the raw material gas passes is formed. The shield member is configured such that the heat capacity thereof increases from the center to the outer periphery.