Silicon Carbide Crystal Growth via Crucible Deceleration
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Solution Overview
Problem
The challenge in producing high-quality silicon carbide crystals using the solution growth method lies in generating an upward flow towards the seed crystal, which is difficult to achieve, affecting the quality of the crystal grown.
Innovation Solution
A method involving the rotational deceleration of both the crucible and seed crystal while in contact with a silicon solvent containing carbon, facilitating an upward flow and enhancing carbon delivery to the seed crystal's surface for improved crystal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seed crystal and crucible are rotated at constant speeds during solution growth, then the crystal growth process can be maintained stably, but an upward flow toward the seed crystal cannot be generated effectively, resulting in poor crystal quality
Solution Approach 1:
The patent applies dynamics by changing the rotation speeds of the crucible and seed crystal dynamically during the growth process. Specifically, the rotation speeds are adjusted in multiple stages: initially rotating at higher speeds to generate centrifugal force, then reducing speeds to create an upward flow toward the seed crystal. This dynamic speed adjustment allows the system to achieve both stable growth conditions and effective material transport, resolving the contradiction between stability and crystal quality.
Solution Approach 2:
The patent changes the rotational speed parameters of both the crucible and seed crystal during the growth process. By varying these parameters in a controlled manner - starting with higher speeds and then reducing them - the system generates the desired upward flow pattern. This parameter change enables effective carbon and silicon transport to the seed crystal surface while maintaining overall process stability, thereby improving crystal quality without sacrificing growth reliability.
2Manufacturing precision
If rotation speeds are reduced to generate upward flow, then carbon delivery to the seed crystal improves, but the time required to establish effective flow patterns increases
Solution Approach 1:
The patent applies preliminary action by first rotating the crucible and seed crystal at higher speeds before reducing to growth speeds. This initial high-speed rotation pre-establishes the solution circulation patterns and prepares the system for the subsequent upward flow phase. By performing this preparatory action, the system minimizes the time needed to establish effective flow patterns when growth speeds are achieved, thereby reducing the overall time loss while improving carbon delivery efficiency.
Solution Approach 2:
The patent employs periodic action through multi-stage rotation speed adjustments. The system alternates between higher rotation speeds for flow generation and lower speeds for controlled growth, creating a periodic pattern of speed variation. This periodic modulation allows the system to efficiently establish flow patterns during high-speed phases while maintaining effective carbon delivery during low-speed phases, optimizing both time utilization and delivery efficiency.
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 allows for the easy generation of an upward flow, enriching the carbon and silicon vicinity, resulting in the growth of high-quality silicon carbide crystals with enhanced crystal growth rates and reduced dislocation or micropipe formation.
Implementation Method 1
rotation of the seed crystal is decelerated after rotation of the crucible is decelerated, so that an upward flow toward the seed crystal can be generated easily in the solution
Data Source
AI summary
A method for producing a crystal, according to the present invention, where the lower surface of a seed crystal which is rotatably arranged and made of silicon carbide is brought into contact with a solution of silicon solvent containing carbon in a crucible which is rotatably arranged and the seed crystal is pulled up and a crystal of silicon carbide is grown from the solution on the lower surface of the seed crystal, comprising the steps of bringing the lower surface of the seed crystal into contact with the solution in a contact step, rotating the seed crystal in a seed crystal rotation step, rotating the crucible in a crucible rotation step, and stopping rotation of the crucible, while the seed crystal is rotated in the state in which the lower surface of the seed crystal is in contact with the solution, in a deceleration step.