Movable Magnetic Poles 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 with maintaining 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
Regulating the position of the maximum gauss plane (MGP) during ingot growth in at least two stages to control the horizontal magnetic field, using an ingot puller apparatus with movable magnetic poles to maintain a consistent crystal-melt interface shape and suppress melt convection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pull speed and thermal condition are continuously adjusted to control the crystal-melt interface shape, then Perfect Silicon can be produced in an axial window of ingot growth, but the production complexity increases due to thermal condition changes during growth
Solution Approach 1:
The patent changes the magnetic field parameter (position of maximum gauss plane) in two distinct stages during ingot growth. In the first stage, the MGP is positioned at a first location optimized for initial crystal formation, and in the second stage, it is moved to a second location optimized for continued growth, allowing interface shape control without continuous adjustment of multiple thermal parameters
Solution Approach 2:
The growth process is segmented into at least two distinct stages based on ingot length or growth progress. Each stage has specific magnetic field positioning requirements, allowing the complex growth process to be divided into manageable segments with optimized control parameters for each, reducing overall process complexity
2Device complexity
If the position of the maximum gauss plane is maintained at a constant position during entire ingot growth, then the magnetic field configuration is simple, but the crystal-melt interface shape cannot be optimized for different growth stages
Solution Approach 1:
The magnetic field configuration is made dynamic by moving the maximum gauss plane to different positions during different growth stages. The MGP is positioned at a first location during initial growth and moved to a second location during subsequent growth, allowing the magnetic field to adapt to changing thermal conditions and optimize interface shape throughout the process
3Device complexity
If the magnetic poles are fixed relative to the crucible, then the apparatus structure is simpler, but the position of the maximum gauss plane cannot be regulated during ingot growth
Solution Approach 1:
The magnetic poles are made movable relative to the crucible through a translation device that can reposition them along the growth axis. This dynamic positioning capability allows the maximum gauss plane to be moved to optimal locations for different growth stages, enabling Perfect Silicon production while maintaining relatively simple apparatus structure
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 the production of high-quality 'Perfect Silicon' wafers by reducing variations in axial temperature gradients, increasing productivity, and improving yield by maintaining a constant crystal-melt interface, thereby enhancing the production of semiconductor and solar wafers.
Implementation Method 1
A horizontal magnetic field is generated within the growth chamber
Implementation Method 2
During growth of Perfect Silicon ingot in a horizontal magnetic field Czochralski process, the crystal-melt interface shape is typically concave
Implementation Method 3
A pair of magnetic poles are disposed radially outward from the crucible
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.