Vitreous Silica Crucible Arc Fusing Temperature Control
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Solution Overview
Problem
The existing methods for manufacturing vitreous silica crucibles face challenges in controlling the high temperature required for fusing silica powder, leading to melt surface vibration and the generation of brown rings during silicon single crystal production, which affects the quality and yield of silicon wafers.
Innovation Solution
A method involving the precise measurement and control of the temperature during the arc fusing process of silica powder using a radiation thermometer to set a reference temperature based on a local maximum point, allowing for adjustment of the current supplied to the carbon electrodes to optimize the fused state of the crucible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the temperature of silica powder layer is not precisely controlled during arc fusing, then the manufacturing process is simpler, but brown rings and melt surface vibration occur during silicon single crystal production
Solution Approach 1:
The patent replaces complex mechanical temperature control systems with an optical measurement system (radiation thermometer) that non-contactively measures the temperature of the silica powder layer during arc fusing. This substitution enables precise temperature control without the complexity of direct thermal contact sensors in the high-temperature arc environment.
Solution Approach 2:
The patent implements a feedback control system where the radiation thermometer continuously monitors the temperature of the silica powder layer, and the measured temperature is used to adjust the arc fusing parameters in real-time. This feedback mechanism ensures the temperature remains within the optimal range to prevent brown ring formation and melt surface vibration.
2Productivity
If arc fusing temperature is too high or uneven, then silica powder fuses faster, but brown rings form on the crucible inner surface
Solution Approach 1:
The patent identifies and controls critical temperature parameters during arc fusing, maintaining the silica powder layer temperature within a specific range (1600-2000°C). By precisely controlling this temperature parameter, the process achieves both efficient fusing speed and uniform crucible inner surface without brown ring formation.
Solution Approach 2:
The radiation thermometer provides non-contactive, real-time temperature measurement of the silica powder layer, enabling precise monitoring and control of the fusing process. This optical measurement system replaces indirect temperature estimation methods, allowing for accurate maintenance of optimal fusing temperature to prevent brown rings while maintaining productivity.
3Length of moving object
If the crucible inner surface contacts silicon melt for extended periods, then larger diameter silicon crystals can be produced, but the crucible inner surface corrodes and forms brown rings
Solution Approach 1:
The patent applies preliminary action by optimizing the crucible manufacturing process before the silicon crystal pulling process. By precisely controlling the arc fusing temperature to create a uniform, defect-free vitreous silica structure, the crucible inner surface is pre-conditioned to resist corrosion and brown ring formation during extended contact with silicon melt, enabling production of larger diameter crystals.
Solution Approach 2:
The patent changes the structural parameters of the vitreous silica crucible through controlled arc fusing temperature and duration. This creates a denser, more uniform glass structure with reduced micro-defects, thereby enhancing the crucible's resistance to chemical corrosion from silicon melt during prolonged operation for large-diameter crystal growth.
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 the generation of brown rings and melt surface vibration, improving the inner surface properties of the crucible and enhancing the quality and yield of silicon single crystals.
Implementation Method 1
a process of measuring a temperature of the silica powder layer with a radiation thermometer
Implementation Method 2
an arc fusing process of arc fusing the silica powder layer by arc discharge generated from carbon electrodes
Data Source
AI summary
The present invention provides a method of manufacturing a vitreous silica crucible including: a silica powder supplying process of supplying a material silica powder into a mold for molding a crucible, to form a silica powder layer, and an arc fusing process of arc fusing the silica powder layer by arc discharge generated by carbon electrodes, wherein the arc fusing process includes processes of measuring a temperature of the silica powder layer, and controlling a vitreous silica fused state based on a reference temperature which is a temperature at a local maximum point which appears first in the arc fusing process.