Saddle-Shaped Superconducting Coils for Single-Crystal Oxygen Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional single-crystal pulling methods face challenges in achieving low oxygen concentration and uniform magnetic field distribution, leading to growth striations and inadequate oxygen reduction in semiconductor crystals, particularly for high-demand applications like power devices and image sensors.
Innovation Solution
A single-crystal pulling apparatus with saddle-shaped superconducting coils arranged in a horizontal plane, where the center angle between coil axes is between 100° and 120°, generates a strong orthogonal magnetic field component near the crucible's cross-section perpendicular to the X-axis, balancing flow velocities and reducing oxygen concentration by prolonging oxygen elution time and increasing evaporation from the melt surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cylindrical superconducting coils are used, then the magnetic field can be generated, but the magnetic field distribution is non-uniform and heat convection cannot be effectively suppressed
Solution Approach 1:
The patent employs saddle-shaped superconducting coils with specific curvature radii (R1 for the arc shape, R2 for the cross-sectional shape) to generate a uniform horizontal magnetic field. The curved geometry of the coils, particularly the arc-shaped arrangement around the crucible, creates a magnetic field that is uniform across the melt region, effectively suppressing heat convection while maintaining manageable device complexity through standardized curved coil designs.
2Reliability
If the number of superconducting coils is increased to improve magnetic field uniformity, then heat convection suppression improves, but the device complexity and cost increase
Solution Approach 1:
The patent uses an asymmetric arrangement of two pairs of saddle-shaped coils positioned at specific angles (100-120 degrees between coil axes) to achieve uniform magnetic field distribution. This asymmetric angular positioning, combined with the specific saddle shape geometry, creates optimal magnetic field uniformity and heat convection suppression with only two pairs of coils, avoiding the need for more numerous coils that would increase device complexity and cost.
3Manufacturing precision
If the coil arrangement is optimized for magnetic field uniformity, then single crystal quality improves, but the ease of manufacture and maintenance decreases
Solution Approach 1:
The saddle-shaped coils with defined curvature radii (R1 and R2) provide a standardized geometric form that balances manufacturing precision with ease of fabrication. The arc-shaped configuration naturally conforms to the cylindrical crucible geometry, simplifying alignment and installation while achieving the required magnetic field uniformity for high-quality single crystal growth. The repetitive saddle shape across two pairs of coils allows for modular manufacturing and assembly.
4Quantity of substance
If the center angle between coil axes is changed to optimize oxygen reduction, then oxygen concentration decreases, but the magnetic field generation efficiency may be affected
Solution Approach 1:
The patent optimizes the center angle between coil axes to fall within 100-120 degrees, a specific parameter range that simultaneously achieves effective oxygen reduction through prolonged elution time and maintains efficient magnetic field generation. This angular parameter optimization, combined with the saddle-shaped geometry parameters (R1, R2), creates a configuration where the magnetic field distribution maximizes oxygen removal from the melt while minimizing energy consumption for field generation.
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 apparatus significantly reduces oxygen concentration in the single crystal and suppresses growth striations, allowing for the production of high-quality crystals with controlled oxygen levels, enhancing magnetic field generation efficiency and facilitating easier coil arrangement and maintenance.
Implementation Method 1
applying a horizontal magnetic field to the molten semiconductor raw material by energization to the superconducting coils to suppress convection of the molten semiconductor raw material in the crucible
Implementation Method 2
the semiconductor raw material, which is the melt, receives motion-suppressing power by lines of magnetic force produced by energization to the superconducting coils
Implementation Method 3
generates a strong orthogonal magnetic field component near the crucible's cross-section perpendicular to the X-axis
Implementation Method 4
a heater for heating and melting a semiconductor raw material in the crucible is provided around the crucible in the pulling furnace
Implementation Method 5
a small helium refrigerator for cooling a first radiation shield and a second radiation shield contained in the cylindrical vacuum container
Data Source
AI summary
A single-crystal pulling apparatus including: a pulling furnace having a central axis; and a magnetic field generation device arranged around the pulling furnace and having superconducting coils, the apparatus applying a horizontal magnetic field to the molten semiconductor raw material, two coil axes in the two pairs of the superconducting coils are included in a single horizontal plane, and when a direction of lines of magnetic force at the central axis of the pulling furnace in the horizontal plane is determined as an X axis, a center angle α having the X axis between the two coil axes is 100 degrees or more and 120 degrees or less. This makes it possible to reduce the height of the coils, to raise the magnetic field center close to the melt surface of the semiconductor raw material, and to obtain a single crystal having a lower oxygen concentration than conventional single crystals.