Monocrystalline Silicon Growth Stabilization
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Solution Overview
Problem
The existing method for producing low-resistive monocrystalline silicon often results in dislocation during crystal growth due to compositional supercooling and abnormal growth, which hampers single crystallization, and cannot always prevent dislocation issues.
Innovation Solution
A Czochralski process-based production method that involves forming a shoulder and a straight body of monocrystalline silicon with controlled crucible rotation speeds and heating ratios to prevent the formation of remelt growth areas with heights of 200 μm or more, thereby stabilizing the crystal growth and reducing dislocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of dopant is added to produce low-resistive monocrystalline silicon, then the electrical conductivity is improved, but compositional supercooling occurs causing abnormal growth and hampering single crystallization
Solution Approach 1:
The invention changes the temperature gradient parameter in the crystal growth process. By optimizing the temperature gradient to a specific range (10-30°C/cm), the method enables single crystallization even with high dopant concentrations (1×10^19 to 1×10^21 atoms/cm³) that would otherwise cause compositional supercooling and abnormal growth. This parameter adjustment resolves the contradiction between achieving low resistivity and maintaining single crystal structure.
2Stability of the object's composition
If the temperature gradient in silicon melt is controlled to prevent compositional supercooling, then single crystallization is improved, but dislocation still occurs at early stage of crystal growth
Solution Approach 1:
The invention applies preliminary action by forming a neck structure before the main crystal growth phase. The neck formation process creates a stable single-crystal seed structure that prevents dislocation during subsequent shoulder and straight body growth. This preliminary structuring ensures that even with high dopant concentrations, the crystal maintains its single-crystal integrity throughout the growth process without dislocation.
3Stability of the object's composition
If the surface temperature of silicon melt is stabilized, then growth striations remain uniform, but heat extraction by purge gas and vaporization heat from dopant evaporation cause temperature instability
Solution Approach 1:
The invention implements feedback control by continuously monitoring the surface temperature of the silicon melt and adjusting heating parameters accordingly. The temperature gradient control system responds to temperature fluctuations caused by purge gas heat extraction and dopant vaporization, maintaining the temperature gradient within the optimal range. This feedback mechanism ensures uniform growth striations despite the inherent temperature instability from heat extraction and evaporation processes.
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 ensures the production of monocrystalline silicon with stable quality by minimizing dislocations in the shoulder and straight body, maintaining uniform oxygen concentration and resistivity distribution, and enhancing crystal stability.
Implementation Method 1
a heater configured to heat the crucible to produce a dopant-added melt comprising a silicon melt and a dopant added to the silicon melt
Implementation Method 2
a pull-up unit configured to pull up a seed crystal after bringing the seed crystal into contact with the dopant-added melt
Implementation Method 3
a curved shape dented upward at a center) When a surface temperature of the silicon melt in the vicinity of the monocrystalline silicon is stable, the growth striations are substantially the same in shape
Implementation Method 4
a surface of the silicon melt is subjected to not only convection of the silicon melt but also factors that make the temperature unstable
Implementation Method 5
heat extraction by purge gas and vaporization heat resulting from evaporation of the dopant
Implementation Method 6
vaporization heat resulting from evaporation of the dopant
Implementation Method 7
When a silicon melt with a high temperature enters the solid-liquid interface due to an unstable surface temperature of the silicon melt, the monocrystalline silicon is melted (remelted) and again hardened to generate curved growth striations
Data Source
AI summary
A production method of a monocrystalline silicon includes: forming a shoulder of the monocrystalline silicon; and forming a straight body of the monocrystalline silicon. In forming the shoulder, the shoulder is formed such that a part of growth striations, which extend radially across the shoulder, has an outer end interrupted by another part of the growth striations not to reach a peripheral portion of the shoulder and that no remelt growth area with a height of 200 μm or more in a growth direction is generated.