SiC Single Crystal Growth Gap Control
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Solution Overview
Problem
The challenge in producing silicon carbide single crystals is the occurrence of cracking and polytype inclusion due to the close proximity of the crystal to deposited polycrystals on the guide member, which worsens with longer crystal growth, leading to defects and reduced quality.
Innovation Solution
A method involving a gap enlargement step by maintaining a partial pressure difference of Si2C in the source gas between the inlet and outlet of the gap at 0.18 torr or less, allowing for the expansion of the gap between the silicon carbide single crystal and the polycrystal on the guide member, thereby preventing adhesion and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a guide member is used to control source gas flow for extending crystal length, then crystal length is improved, but the gap between crystal and guide member narrows causing adhesion and cracking
Solution Approach 1:
The patent applies parameter changes by controlling the partial pressure difference of Si2C between inlet and outlet of the gap. By maintaining this pressure difference at 0.18 torr or less during the gap enlargement step, the crystal surface recedes relative to the guide member, enlarging the gap and preventing adhesion while allowing continued crystal length extension.
2Object-affected harmful factors
If heat insulating material is installed on guide member outer wall to prevent adhesion, then adhesion is suppressed, but gap enlargement and defect prevention are insufficient
Solution Approach 1:
The patent replaces the thermal insulation approach with a pressure control mechanism. Instead of using heat insulating material to prevent adhesion, the invention uses precise control of Si2C partial pressure difference (0.18 torr or less) to drive gap enlargement through sublimation and recession of the crystal surface, thereby preventing both adhesion and defects.
3Reliability
If crystal growth is terminated early to avoid contact with polycrystal, then adhesion is prevented, but crystal length extension is limited
Solution Approach 1:
The patent applies preliminary action by performing a gap enlargement step before terminating crystal growth. During this step, the Si2C partial pressure difference is controlled at 0.18 torr or less to recede the crystal surface and enlarge the gap, ensuring that even when growth continues for extended periods, adhesion and defects are prevented while achieving longer crystal lengths.
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 method effectively suppresses the occurrence of cracking in silicon carbide single crystals, enabling the production of longer, higher-quality crystals with reduced defects.
Implementation Method 1
The sublimation method uses a gas containing a sublimated source to effect crystal growth on a seed crystal
Implementation Method 2
maintaining a difference, Pin−Pout, between a partial pressure Pin of Si2C in a source gas in the vicinity of an inlet of the gap D and a partial pressure Pout of Si2C in a source gas in the vicinity of an outlet of the gap D at 0.18 torr or less
Data Source
AI summary
A silicon carbide single crystal is grown by a method comprising: a single crystal growth step of growing a silicon carbide single crystal so as to not close a gap between a side surface of the silicon carbide single crystal growing on a silicon carbide seed crystal, and an inner-side surface of a guide member and a crystal deposited on the inner-side surface of the guide member; a crystal growth termination step of terminating crystal growth by temperature lowering; and a gap enlargement step, performed between the single crystal growth step and the crystal growth termination step, of enlarging the gap by maintaining a difference, Pin−Pout, between partial pressure Pin of Si2C in a source gas in the vicinity of an inlet of the gap and partial pressure Pout of Si2C in a source gas in the vicinity of an outlet of the gap at 0.18 torr or less.