Magnetic Pole Positioning for Stable Silicon Ingot Interface Control
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Solution Overview
Problem
Existing methods for producing single crystal silicon ingots in a horizontal magnetic field Czochralski process struggle to maintain a constant crystal-melt interface shape due to thermal condition changes during ingot growth, complicating the production of high-quality 'Perfect Silicon' wafers.
Innovation Solution
Regulate the position of the maximum gauss plane (MGP) during ingot growth in at least two stages to control the horizontal magnetic field, using a pair of magnetic poles disposed radially outward from the crucible, and adjust their position relative to the melt surface to maintain a constant crystal-melt interface shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal condition is controlled by adjusting gap between melt surface and reflector and controlling bottom heater, then crystal-melt interface shape can be controlled, but control becomes complicated and Perfect Silicon can be produced only in an axial window of ingot growth
Solution Approach 1:
The patent changes the parameter being controlled from thermal conditions (gap distance, heater power) to magnetic field position. By moving the maximum gauss plane (MGP) axially during ingot growth, the crystal-melt interface shape is controlled directly through magnetic field effects rather than through complex thermal adjustments, simplifying the control mechanism while maintaining precision.
2Manufacturing precision
If pull speed and thermal condition are adjusted continuously to control crystal-melt interface shape, then Perfect Silicon can be produced, but production is limited to an axial window of ingot growth
Solution Approach 1:
The patent employs dynamic adjustment of the magnetic field position by moving the MGP axially during ingot growth. This dynamic control allows the system to maintain optimal crystal-melt interface shape throughout the entire growth process, extending the Perfect Silicon production window beyond the limited axial region achievable with static thermal control methods.
3Manufacturing precision
If horizontal magnetic field is applied to control crystal-melt interface, then interface shape can be influenced, but position of maximum gauss plane varies during ingot growth
Solution Approach 1:
The patent implements feedback control by monitoring the position of the maximum gauss plane (MGP) and adjusting the magnetic field position accordingly. Sensors detect MGP position variations during ingot growth, and the system responds by moving the magnetic field to maintain the desired position, ensuring stable crystal-melt interface control throughout the growth process.
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 allows for consistent control of the crystal-melt interface, reducing variations in axial gradient and oxygen incorporation, thereby increasing the production of high-quality 'Perfect Silicon' wafers and improving yield and productivity.
Implementation Method 1
A horizontal magnetic field is generated within the growth chamber. The position of a maximum gauss plane during formation of a constant diameter portion of the silicon ingot is regulated
Data Source
AI summary
Methods for producing a silicon ingot in which a horizontal magnetic field is generated are disclosed. The magnet position is controlled in at least two stages of ingot growth. The magnetic poles may be at a first position during the first stage of ingot growth and lowered to a second position in a second stage of ingot growth. By controlling the magnet position, the crystal-melt interface shape may be relatively more consistent.