Silicon Melt Surface Height Calculation via Dual CCD Diameter Measurement
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Solution Overview
Problem
Conventional methods for calculating the height position of a silicon melt surface during silicon single crystal pulling using the Czochralski method are inaccurate due to deformation of the quartz crucible and variations in crystal diameter, leading to inconsistent crystal quality.
Innovation Solution
A method utilizing CCD cameras to measure the first and second crystal diameters, allowing for real-time calculation of the silicon melt surface height position during crystal pulling, enabling precise control of the crucible height and temperature gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the height position of silicon melt surface is measured before crystal pulling and control is performed based on the measured position, then the measurement process is simple, but the actual height position varies during crystal pulling due to crucible deformation and diameter changes, leading to poor manufacturing precision
Solution Approach 1:
The patent performs preliminary measurement of the crystal diameter at the melt surface position before crystal pulling begins. This preliminary measurement value is then used as a reference to calculate the melt surface height during crystal pulling by comparing with real-time diameter measurements, enabling dynamic height control without direct measurement
Solution Approach 2:
The patent replaces direct mechanical/optical measurement of the melt surface height with an indirect calculation method. Instead of measuring height directly, the system measures crystal diameter changes and calculates the corresponding height position, substituting a difficult measurement with an easier one that can be performed during the pulling process
2Device complexity
If the height position of silicon melt surface is controlled to be fixed based on pre-measured data, then the control system is simple, but the actual position varies during pulling due to crucible deformation, leading to inconsistent crystal quality
Solution Approach 1:
The patent implements a feedback control mechanism where the real-time crystal diameter measured during pulling is compared with the preliminary measured diameter. The difference in diameter values provides feedback information that is used to calculate and adjust the actual melt surface height position, ensuring continuous correction during the pulling process
Solution Approach 2:
The system performs preliminary measurement of crystal diameter at the melt surface before pulling begins. This preliminary data serves as a baseline for subsequent calculations, allowing the system to determine height position changes during pulling by comparing real-time measurements against this reference
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 highly accurate control of the silicon melt surface height, resulting in stable production of high-quality silicon single crystals with desired defect regions.
Implementation Method 1
a first crystal diameter measured from a fusion ring on a boundary of the silicon melt and the silicon single crystal by using a CCD camera
Data Source
AI summary
A method for calculating a height position of a silicon melt surface at the time of pulling a CZ silicon single crystal is disclosed, including: obtaining a first crystal diameter measured from a fusion ring on a boundary of the silicon melt and the silicon single crystal by using a CCD camera installed at an arbitrary angle relative to the silicon single crystal, and a second crystal diameter measured by using two CCD cameras installed parallel to both ends of a crystal diameter of the silicon single crystal; and calculating the height position of the silicon melt surface in the crucible during pulling of the silicon single crystal from a difference between the first crystal diameter and the second crystal diameter. As a result, a method for enabling further accurately calculating a height position of a silicon melt surface at the time of pulling a silicon single crystal is provided.