Silicon Melt Level Control via Heat Shield Reflection
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Solution Overview
Problem
Conventional methods for accurately measuring the melt level position of silicon melt during silicon single crystal pulling are hindered by variations in seed crystal length, crucible rotation, and inconsistent gas flow, leading to gap variations that affect oxygen concentration and defect distribution in the crystal, resulting in inconsistent crystal quality and yield.
Innovation Solution
A silicon single crystal manufacturing apparatus and method utilizing an imaging device to capture images of the melt level and heat shield, calculating the melt level position by analyzing the distance between real and mirror images of the heat shield, and regulating the gap value to maintain precise control over the V/G ratio and oxygen concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to measure melt level position, then the measurement process is simple, but the measurement precision is low due to variations in seed crystal length, crucible rotation, and gas flow
Solution Approach 1:
A mirror is introduced as an intermediary element placed at the melt level position. The imaging device captures images of both the heat shield and its mirror reflection on the melt surface. By measuring the distance between the heat shield and its mirror image, the melt level position can be calculated with high precision without direct contact with the melt, thus avoiding contamination while achieving accurate measurement.
Solution Approach 2:
The mirror creates a virtual copy (reflection) of the heat shield at the melt level. Instead of directly measuring the melt surface which is affected by variations, the system measures the position of the reflected image which provides a stable reference. The distance between the real heat shield and its mirror image directly indicates the melt level position.
2Manufacturing precision
If the gap value between heat shield and melt level is not controlled, then the device operation is simple, but the manufacturing precision of crystal quality deteriorates due to oxygen concentration variations and defect distribution
Solution Approach 1:
The system continuously monitors the melt level position by capturing images and calculating the distance between the heat shield and its mirror image. This real-time feedback information is used to automatically adjust the crucible position or heat shield position to maintain the optimal gap value, ensuring consistent crystal quality without requiring manual intervention.
Solution Approach 2:
The manual or mechanical adjustment of gap value is replaced by an automated optical measurement and control system. The imaging device and calculating unit automatically determine the melt level position, and the control system adjusts the gap value accordingly, replacing complex mechanical adjustment operations with automated optical-mechanical integration.
3Measurement precision
If visual observation method is used to set distance between melt level and heat shield, then the operation is simple, but the measurement precision is insufficient leading to gap variations
Solution Approach 1:
The imaging device continuously captures images of the heat shield and its mirror reflection throughout the crystal pulling process. The calculating unit continuously processes these images to track changes in melt level position, enabling real-time measurement and regulation without interrupting the production process, thus maintaining high precision while minimizing time loss.
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 accurate measurement and regulation of the melt level position, reducing gap variations and improving the controllability of oxygen concentration, leading to the production of high-quality silicon single crystals with consistent defect-free regions and enhanced production yield.
Implementation Method 1
calculating unit that calculates a melt level position of the silicon melt based on a distance between the real image and the mirror image
Data Source
AI summary
A silicon single crystal manufacturing method in which the distance between the heat shield and the melt level of the melt can be regulated in a high precision. The real image includes at least the circular opening of the heat shield provided in such a way that the heat shield covers a part of the melt level of the silicon melt. The mirror image is a reflected image of the heat shield on the surface of the silicon melt. Based on the distance between the obtained real image and the mirror image, the melt level position of the silicon melt is computed, and the distance between the heat shield and the melt level position is regulated.