SiC Crystal Loading Device with Tilted Seed
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Solution Overview
Problem
The challenge in silicon carbide (SiC) crystal growth by physical vapor transport is the high probability of polytype transformation, which affects the yield and quality of the crystal due to facet-related polymorph transformation and supersaturation issues during the growth process.
Innovation Solution
A crystal raw material loading device with a unique bearing unit arrangement and a seed crystal bearing device that inclines the seed crystal, creating a convex growth interface and controlling the temperature gradient to reduce the probability of polytype transformation, includes a crucible with an induction heating coil and a porous plate to manage the growth atmosphere and temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the SiC powder is sublimated at high temperature (above 2100°C) to form crystal, then the crystal growth rate is improved, but the probability of polytype transformation increases due to high supersaturation in the growth atmosphere
Solution Approach 1:
The growth atmosphere is segmented into multiple zones with different supersaturation levels. The bearing units create regions where the atmosphere transitions from high supersaturation near the raw material to lower supersaturation at the growth interface, allowing high growth rates without excessive polytype transformation risk
Solution Approach 2:
Different regions of the growth atmosphere are given different qualities - the region near the raw material has high supersaturation for rapid material supply, while the region at the growth interface maintains lower supersaturation to prevent polytype transformation. The bearing units locally modify the atmosphere distribution to achieve this gradient
2Device complexity
If the seed crystal is placed horizontally on the crucible cover, then the device structure is simple, but the facet effect causes non-uniform impurity concentration and increases polytype transformation risk
Solution Approach 1:
The seed crystal is positioned asymmetrically relative to the crucible cover, with one end elevated by bearing units. This asymmetric placement creates a tilted growth interface that eliminates the facet effect, ensuring uniform impurity concentration and reducing polytype transformation probability while maintaining relatively simple device structure
3Reliability
If the bearing units are arranged to create convex growth interface, then the polytype transformation is reduced, but the device structure becomes more complex
Solution Approach 1:
The bearing unit arrangement is segmented into multiple units positioned at different locations and heights. This segmentation allows creation of the convex growth interface through a modular structure rather than a single complex component, making the system more manageable and maintainable
Solution Approach 2:
The bearing units utilize the vertical dimension by elevating one end of the seed crystal, transforming a two-dimensional horizontal placement into a three-dimensional tilted configuration. This dimensional change creates the convex growth interface needed to reduce polytype transformation while keeping the structural modification relatively simple
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
The solution effectively reduces the probability of polytype transformation, improving the yield and quality of silicon carbide crystal growth by maintaining an unsaturated growth atmosphere and increasing the nucleation free energy, resulting in higher-quality crystal production.
Implementation Method 1
PVT uses medium frequency induction heating and high density graphite crucible as heating body
Implementation Method 2
the SiC powder must be sublimated directly into Si (SI), Si2C (SIC), SiC (t 25) (SIC) and other gases at a temperature above 2100° C.
Implementation Method 3
the physical vapor transport method is the most mature, which is adopted by most research institutions and companies in the world
Implementation Method 4
By adjusting the heat preservation layer on the outside of the crucible, the temperature in the SiC raw material zone is higher than that in the top crucible cover. Then, the SiC powder must be sublimated directly into Si (SI), Si2C (SIC), SiC (t 25) (SIC) and other gases at a temperature above 2100° C. and a low pressure environment, and then transferred from the high temperature region to the seed crystal in the lower temperature region along the temperature gradient
Implementation Method 5
A crystal raw material loading device with a unique bearing unit arrangement and a seed crystal bearing device that inclines the seed crystal, creating a convex growth interface and controlling the temperature gradient to reduce the probability of polytype transformation, includes a crucible with an induction heating coil and a porous plate to manage the growth atmosphere and temperature distribution
Data Source
AI summary
A crystal raw material loading device and a crystal growth device includes a plurality of bearing units which are arranged adjacent to each other horizontally in turn, and the multiple bearing units include a first bearing unit arranged at one end of a small plane far away from the seed crystal bearing device. Along the direction from one end of the small plane far away from the seed crystal to one end of the small plane close to the seed crystal, from the first bearing unit to the bearing unit on the side of the small plane close to the seed crystal, the height of the raw material that can be carried by each bearing unit is reduced in turn.