Silicon Single Crystal Neck Cooling and Re-growth
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Solution Overview
Problem
Conventional methods for manufacturing silicon single crystals using the Czochralski process face challenges in completely eliminating dislocations extending from the neck portion to the straight part of the ingot, requiring complex process control and resulting in inconsistent crystal quality.
Innovation Solution
A method involving the formation of a neck portion with a specific temperature and length, followed by cooling to 740 °C or lower, and subsequent re-immersion into the silicon melt to anchor dislocations, reducing the likelihood of dislocation takeover and promoting their outward diffusion, thereby suppressing dislocation generation in the grown crystal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the seed crystal is brought in contact with the silicon melt to grow a silicon single crystal, then crystal growth is achieved, but dislocation is generated due to thermal shock
Solution Approach 1:
The patent applies preliminary action by performing a dash necking step before growing the main crystal. A neck portion with reduced diameter is formed first to eliminate dislocations, and then the crystal growth continues. This preliminary neck formation prevents dislocation propagation to the final product while maintaining productivity.
Solution Approach 2:
The crystal growth process is segmented into distinct phases: neck portion formation and main crystal growth. By separating these stages and controlling parameters differently for each, the patent eliminates dislocations in the neck region while preventing their propagation to the main crystal, thus resolving the contradiction between growth efficiency and defect elimination.
2Object-generated harmful factors
If a dash necking step is performed to eliminate dislocation, then some dislocations are removed, but it is difficult to completely eliminate dislocation generated in a silicon single crystal
Solution Approach 1:
The patent applies parameter changes by precisely controlling pulling speed, rotation speed, and temperature during neck portion formation. By optimizing these parameters, the solid-liquid interface shape is controlled to ensure complete dislocation elimination in the neck region, achieving 100% dislocation removal that propagates to the main crystal.
Solution Approach 2:
The patent implements feedback control by monitoring the shape of the solid-liquid interface during neck portion formation and adjusting process parameters accordingly. This ensures that the neck portion is formed with the correct geometry to completely eliminate dislocations, preventing any dislocation propagation to the final crystal product.
3Object-generated harmful factors
If the number of revolutions of the seed crystal is decreased to suppress dislocation, then dislocation extension is suppressed, but the shape of solid-liquid interface control becomes more difficult
Solution Approach 1:
The patent applies parameter changes by optimizing the combination of pulling speed and rotation speed during neck portion formation. By carefully selecting these parameters, the patent achieves effective dislocation suppression while maintaining controllable solid-liquid interface shape, thus resolving the contradiction between defect reduction and process simplicity.
4Object-generated harmful factors
If the neck diameter is varied to form increased or decreased neck diameter regions, then on-axis dislocations are eliminated, but the process requires precise diameter control
Solution Approach 1:
The patent applies parameter changes by controlling pulling speed and rotation speed to naturally form the desired neck diameter variations. By adjusting these parameters during different stages of neck formation, the patent achieves precise diameter control without requiring additional complex control systems, thus eliminating on-axis dislocations while maintaining process feasibility.
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 immobilizes dislocations, reduces thermal shock, and enhances the quality of silicon single crystals by minimizing dislocation propagation from the neck portion to the straight part of the ingot, resulting in high-quality crystals with reduced defects.
Implementation Method 1
dislocation is generated in a silicon single crystal due to thermal shock or the like
Implementation Method 2
a silicon single crystal is grown under a seed crystal by bringing a seed crystal in contact with a silicon melt held in a quartz crucible and thereafter pulling up the seed crystal
Data Source
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AI summary
[Subject] To provide a method of manufacturing a silicon single crystal, capable of suppressing generation of dislocation extending from a neck portion to a straight part of ingot. [Solving Means] A method of manufacturing a silicon single crystal according to this invention includes the steps of preparing a silicon melt (a preparation step (S10)), forming a neck portion continuing from a seed crystal by bringing the seed crystal in contact with the silicon melt (a neck portion formation step (S20)), separating the neck portion from the silicon melt (a separation step (S30)), decreasing a temperature of the neck portion separated from the silicon melt from a temperature of the neck portion in the neck portion formation step (S20) (a cooling step (S40)), and forming a silicon single crystal continuing from the neck portion by again bringing the neck portion in contact with the silicon melt after the cooling step (S40) (a re-growth step (S50)).