Silicon Melt Surface Position Control via Optical Imaging
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Solution Overview
Problem
Current methods for producing silicon single crystals using the Czochralski method face challenges in precisely controlling the surface position of the silicon melt during crystal pulling, leading to inconsistent defect distribution and difficulty in achieving homogeneous crystal properties across the wafer plane.
Innovation Solution
An apparatus and method utilizing an imaging device to capture images of the heat shield and the silicon melt, calculating the melt surface position through the spacing between real and mirror images, and adjusting the crucible position to maintain precise control of the thermal gradient, allowing for real-time monitoring and correction of the melt surface position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface position of silicon melt is not precisely controlled during crystal pulling, then the V/G ratio cannot be accurately controlled, but this leads to inconsistent defect distribution and non-homogeneous crystal properties
Solution Approach 1:
The patent implements a feedback control system where the imaging device continuously monitors the melt surface position, the calculation unit processes the image data to determine the surface position, and the control unit adjusts the crucible position accordingly. This closed-loop feedback mechanism ensures accurate and homogeneous crystal properties by dynamically maintaining the correct V/G ratio throughout the pulling process.
Solution Approach 2:
The patent replaces traditional mechanical measurement methods with an optical imaging system. Instead of using physical probes or direct contact measurement devices, the system uses an imaging device to capture images of the melt surface, calculates position information from the images, and controls the crucible based on this calculated data. This substitution improves measurement precision without mechanical interference.
2Productivity
If traditional measurement methods are used for melt surface position, then the measurement process is complex and time-consuming, but this reduces production efficiency
Solution Approach 1:
The patent replaces complex mechanical measurement systems with an optical imaging and computational system. The imaging device captures images, and the calculation unit automatically processes these images to determine surface position, eliminating the need for complex mechanical measurement apparatus and manual measurement procedures, thereby improving productivity.
Solution Approach 2:
The system performs self-measurement and self-control. The imaging device automatically captures the melt surface, the calculation unit automatically processes the images to calculate surface position, and the control unit automatically adjusts the crucible position. This automated self-service process eliminates manual intervention and reduces system complexity while maintaining high measurement precision.
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 enables accurate control of the V/G ratio, ensuring the production of high-quality silicon single crystals with defect-free regions, improving the homogeneity of crystal properties and yield.
Implementation Method 1
an imaging device that takes an image of a region including a surface of the silicon melt from a direction that is inclined with a predetermined angle about a pulling axis of the silicon single crystal
Data Source
AI summary
A method of producing a silicon single crystal is provided. The method may include taking a real image of a heat shield including a circular opening and a mirror image of the heat shield reflected on a surface of the silicon melt, measuring a spacing between the real image and the mirror image, calculating a position of the surface of the silicon melt, taking an image of a bright zone that appears in a vicinity of an interface between the silicon melt and the silicon single crystal, calculating a position of the surface of the silicon melt based on a center position of the silicon single crystal determined from the image of the bright zone, and controlling the position of the surface of the silicon melt during a pulling of the silicon single crystal while referring to data of the calculated positions of the surface of the silicon melt.