SiC Single Crystal Growth via Periodic Dopant Flow
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Solution Overview
Problem
The existing gas growth method for manufacturing silicon carbide (SiC) single crystals often results in the generation of differently-oriented crystals, which lead to defective products and increased manufacturing costs due to the need for etching to remove these crystals, thereby reducing the growth rate and yield.
Innovation Solution
A method that involves periodically and gradually increasing and decreasing the specific resistance of the SiC single crystal during growth by varying the flow rate of the dopant gas, such as nitrogen (N2), to prevent the inheritance and expansion of differently-oriented crystals without the need for etching, using a SiC single crystal manufacturing apparatus that supplies SiC raw material, carrier, and dopant gases to a seed crystal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gas growth method is used to manufacture SiC single crystal, then SiC single crystal can be grown, but differently-oriented crystals are generated leading to defective products and reduced yield
Solution Approach 1:
The patent applies periodic action by repeatedly changing the flow rate of dopant gas (N2) during the crystal growth process. This periodic variation in dopant concentration creates corresponding variations in specific resistance, which prevents the inheritance and expansion of differently-oriented crystals while maintaining continuous growth, thereby resolving the contradiction between quality and yield
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the flow rate of dopant gas to control the specific resistance of the growing SiC crystal. By varying the dopant concentration parameter during growth, the patent prevents the formation of differently-oriented crystals without stopping the growth process, thus improving both quality and yield
2Reliability
If etching is performed to remove differently-oriented crystals, then product quality improves, but growth rate decreases and manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by preventing the formation and expansion of differently-oriented crystals during the growth process itself, rather than allowing them to develop and then removing them via etching. By proactively controlling dopant flow rate to maintain specific resistance variations, the patent eliminates the need for subsequent etching operations, thereby maintaining high growth rate while ensuring quality
Solution Approach 2:
The patent converts the potentially harmful effect of dopant gas into a beneficial control mechanism. By using dopant gas flow rate variations to control specific resistance, the patent transforms what would be a simple doping process into a proactive prevention mechanism that eliminates differently-oriented crystals without requiring etching, thus avoiding the trade-off between quality improvement and growth rate reduction
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 eliminates differently-oriented crystals during growth, maintaining a high growth rate and improving product yield while reducing manufacturing costs by restricting their generation and expansion, thus ensuring higher quality SiC single crystals.
Implementation Method 1
heating and decomposing the raw material gas
Implementation Method 2
a dopant gas containing a dopant from below the pedestal
Data Source
AI summary
A silicon carbide single crystal includes a region in which a change of a specific resistance is repeated in a growth direction of the silicon carbide single crystal, and the change of the specific resistance is a gradual increase and decrease of the specific resistance. A changing range of the specific resistance may be within a range from 0.5% to 50% inclusive. A changing period of the gradual increase and decrease of the specific resistance that is repeated may be 500 μm or less in terms of a length of the silicon carbide single crystal.