Silicon Single Crystal Cooling Member for Dislocation Control
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Solution Overview
Problem
The Czochralski method for growing silicon single crystals often results in dislocations due to thermal stress, leading to poor productivity and low yield, with repeated melting and pulling causing crystal cracking and residual stresses.
Innovation Solution
A method involving the use of a cooling member to control the temperature gradient around the silicon single crystal during growth, with an ambient gas containing hydrogen, which inhibits the formation of thermal stress-induced dislocations by reducing interstitial atoms and facilitating a longer dislocation-free portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the silicon ingot is rapidly cooled to increase pull rate, then productivity is improved, but dislocations induced by thermal stress arise
Solution Approach 1:
The invention applies selective cooling to specific regions of the silicon crystal. The cooling member is positioned to cool primarily the outer peripheral portion of the crystal, while the central portion maintains a different temperature gradient. This local differentiation of thermal conditions allows the outer region to solidify with reduced dislocation formation while maintaining overall productivity.
Solution Approach 2:
The invention changes the temperature distribution parameters within the crystal by introducing a cooling member that creates a non-uniform cooling pattern. By controlling the cooling rate and temperature gradient in the outer peripheral region specifically, the patent modifies the solidification parameters to prevent dislocation formation while maintaining high pull rates.
2Manufacturing precision
If the silicon single crystal is cooled to control temperature gradient, then manufacturing precision is improved, but thermal stress increases causing dislocations
Solution Approach 1:
The cooling member is designed to apply cooling selectively to the outer peripheral portion of the silicon crystal, creating a localized temperature gradient. This local cooling approach controls the overall temperature distribution without subjecting the entire crystal to uniform thermal stress, thereby reducing dislocation formation while maintaining precise temperature gradient control.
Solution Approach 2:
The invention applies cooling action only to the outer peripheral region rather than the entire crystal. This partial cooling approach is sufficient to control the temperature gradient and prevent dislocations in the critical outer region without inducing excessive thermal stress throughout the whole crystal structure.
3Manufacturing precision
If dislocations are eliminated by repeated melting and pulling, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The cooling member is introduced during the crystal growth process itself to prevent dislocation formation in the first place, rather than requiring subsequent melting and re-pulling operations. This preliminary preventive action eliminates the need for time-consuming repeated processing cycles, thereby maintaining high productivity while achieving dislocation-free crystals.
Solution Approach 2:
The invention skips the traditional multi-cycle melting and re-pulling process by implementing dislocation prevention during the single initial growth phase. Through controlled cooling of the outer peripheral region, the method rushes through the entire process in one continuous operation, achieving both high precision and productivity.
4Loss of substance
If crystal growth is stopped to avoid wasting silicon melt, then loss of substance is reduced, but residual stress causes cracking
Solution Approach 1:
The invention changes the temperature distribution parameters during crystal growth by applying localized cooling to the outer peripheral region. This parameter modification allows the crystal to be pulled to its full intended length with controlled stress distribution, preventing both material waste and subsequent cracking from residual stresses.
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 suppresses dislocation formation, enhances productivity, and allows for the growth of high-quality silicon single crystals with extended dislocation-free regions, reducing cracking and improving yield.
Implementation Method 1
dislocations caused by thermal stresses that arise from cooling the lateral surface portion of the silicon single crystal during growth
Implementation Method 2
an ambient gas in which the silicon single crystal is grown includes a hydrogen-atom-containing substance in gaseous form
Data Source
AI summary
This method for producing silicon single crystals includes: growing a silicon single crystal by the Czochralski method while cooling at least part of the silicon single crystal under growth with a cooling member which circumferentially surrounds the silicon single crystal and has an inner contour that is coaxial with a pull axis, wherein an ambient gas in which the silicon single crystal is grown includes a hydrogen-atom-containing substance in gaseous form. This silicon single crystal is produced by the above method.