Silicon Single Crystal Growth Cristobalite Dissolution
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Solution Overview
Problem
The Czochralski method for growing silicon single crystals faces issues with dislocation generation due to the exfoliation of cristobalite from quartz crucibles, and existing solutions either introduce impurities or are inefficient with repeated magnetic field applications.
Innovation Solution
A method involving a cristobalitizing step to form cristobalite on the crucible surface followed by a dissolving step to partially dissolve it, using adjustments in crucible rotations, gas flow rates, and furnace pressures, while maintaining a magnetic field, to create an ideal crucible surface state that prevents dislocation generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aluminum low concentration layer is formed on the inner surface of the quartz crucible to prevent cristobalite exfoliation, then dislocation generation is suppressed, but impurity contamination occurs in the silicon single crystal
Solution Approach 1:
The harmful aluminum impurity layer is completely removed from the crucible inner surface through dissolution in the silicon melt. The dissolution step extracts and eliminates the contaminating substance while preserving the beneficial dislocation suppression effect through controlled cristobalite formation.
Solution Approach 2:
The chemical composition of the crucible inner surface is dynamically changed through dissolution. By controlling dissolution conditions (time, temperature, melt composition), the surface transitions from containing aluminum impurities to being free of impurities while maintaining the cristobalite layer for dislocation suppression.
2Reliability
If magnetic field application is intermittently repeated to control cristobalite size, then dislocation generation is suppressed, but operational complexity and dead time increase
Solution Approach 1:
The cristobalite layer is formed in advance during the dissolution step before the actual crystal pulling begins. This preliminary formation eliminates the need for repeated intermittent magnetic field applications during crystal growth, simplifying operations and reducing dead time.
Solution Approach 2:
The magnetic field is applied continuously during the dissolution step to maintain stable cristobalite formation, eliminating the need for intermittent application. This continuous action ensures consistent cristobalite layer quality without operational interruptions.
3Object-affected harmful factors
If the cristobalite layer is completely removed from the crucible surface, then impurity contamination is eliminated, but dislocation generation increases due to direct contact between silicon melt and quartz crucible
Solution Approach 1:
The cristobalite layer is selectively formed only on the inner surface of the quartz crucible where it is needed for dislocation suppression, while the bulk crucible material remains unchanged. This localized transformation provides the protective function without affecting other system components.
Solution Approach 2:
The crucible inner surface becomes a composite structure combining the quartz substrate with a cristobalite layer. This composite structure provides both mechanical integrity and the specific protective properties needed to prevent dislocation generation while being free of aluminum impurities.
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 generation in silicon single crystals by ensuring the cristobalite is dissolved before reaching the growth interface, reducing operational errors and inefficiencies associated with previous methods.
Implementation Method 1
applying a magnetic field to the silicon melt with use of a coil
Implementation Method 2
applying a magnetic field to a silicon melt in order to suppress a convection current of a silicon melt
Implementation Method 3
melting the polycrystalline silicon in the quartz crucible with use of a heater
Implementation Method 4
a cristobalite crystal layer, which is crystalline SiO2, is formed on a SiO2/Si interface
Implementation Method 5
The quartz crucible reacts with the silicon melt, and a cristobalite crystal layer is formed
Implementation Method 6
bringing a seed crystal into contact with a melt surface of the silicon melt and pulling up the seed crystal to grow the silicon single crystal
Data Source
AI summary
There is provided a method for manufacturing a silicon single crystal, the method includes: a raw material melting step of melting polycrystalline silicon accommodated in a crucible to obtain a silicon melt; and bringing a seed crystal into contact with the silicon melt and pulling up the seed crystal to grow the silicon single crystal, wherein, after the raw material melting step and before the pulling step, there are performed: a cristobalitizing step of leaving the silicon melt at a predetermined number of rotations of the crucible with a predetermined gas flow rate and a predetermined furnace pressure to generate cristobalite while applying a magnetic field; and a dissolving step of partially dissolving the cristobalite by carrying out any one of an increase in number of rotations of the crucible, an increase in gas flow rate, and a reduction in furnace pressure beyond counterpart figures in the cristobalitizing step.