Carbon Electrode Diameter Gradient for Stable Arc Discharge
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Solution Overview
Problem
The manufacturing of large-diameter vitreous silica crucibles for semiconductor devices faces challenges with electrode vibration during arc discharge, leading to unstable arcs, deteriorated crucible characteristics, and potential electrode damage, due to increased power requirements and fume attachment.
Innovation Solution
A vitreous silica crucible manufacturing apparatus using carbon electrodes with a diameter ratio of 0.6 to 0.8 from base to tip, featuring a flat surface perpendicular to the axis and a diameter reduction portion, optimized to prevent electrode vibration and ensure stable arc generation by maintaining suitable power density and electrode strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the diameter of the carbon electrode is enlarged to prevent vibration, then electrode strength is improved, but power density deteriorates and arc output decreases
Solution Approach 1:
The electrode is designed with non-uniform diameter along its length, creating different local properties: a larger base diameter for strength and a smaller front end diameter for high power density. This gradient structure allows the electrode to simultaneously satisfy both strength requirements and power output requirements in different regions.
2Use of energy by moving object
If the processing temperature is decreased due to enlarged electrode diameter, then power consumption is reduced, but fume attaches to the upper portion of the electrode and crucible characteristics deteriorate
Solution Approach 1:
The reduced diameter at the front end creates a localized high-temperature zone with concentrated power density, ensuring sufficient temperature to prevent fume attachment and maintain crucible quality, while the overall larger electrode diameter keeps total power consumption at acceptable levels.
3Strength
If the diameter of the carbon electrode is enlarged to prevent vibration, then electrode strength is improved, but the processing temperature decreases and arc generation becomes unstable
Solution Approach 1:
The electrode design creates a concentration of power density at the front end (smaller diameter region) while maintaining overall structural strength through the larger base diameter. This localized power concentration ensures stable arc generation and consistent processing temperature, preventing the arc instability that would result from a uniformly large electrode.
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
The solution effectively prevents electrode vibration, stabilizes arc discharge, and improves crucible characteristics by maintaining a stable arc and reducing fume attachment, ensuring high-quality vitreous silica crucibles for large-diameter silicon wafer production.
Implementation Method 1
a carbon electrode is mounted above the quartz powder molded body, and the quartz deposition is heated and vitrified by arc discharge
Implementation Method 2
a plurality of carbon electrodes configured to heat and melt raw material powder by arc discharge
Data Source
AI summary
A vitreous silica crucible manufacturing apparatus includes a plurality of carbon electrodes configured to heat and melt raw material powder by arc discharge, and a value of a ratio R2/R1 of a diameter R2 of a front end of each of the carbon electrodes to a diameter R1 of a base end is set in a range of 0.6 to 0.8. Each carbon electrode has a diameter reduction portion formed at a front end position and reduced in diameter from a diameter R3 of a base end side to the diameter R2 of the front end. When a length of the diameter reduction portion is L1, the diameter of the front end is R2, the diameter of the base end is R1, an angle between the axis lines of the carbon electrodes is θ1, and X=(R1−R2)/2, a value of L1−(X/tan(θ1/2)) is set in a range of 50 to 150 mm.