Single Crystal Diameter Control via Melt Sinking Speed
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Solution Overview
Problem
Current methods for determining the diameter of a single crystal during the Czochralski process, especially in the end cone region, are inefficient due to the need for camera adjustments or additional components like mirrors, leading to material waste and potential dislocations in the crystal.
Innovation Solution
A method that calculates the single crystal diameter by considering the first sinking speed of the melt, first lifting speed, mass conservation, and density differences between liquid and solid materials, allowing for precise control of the end cone formation without the need for camera adjustments or additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera is positioned outside the pulling device to measure the single crystal diameter, then the measurement can be performed, but the camera cannot capture the end cone region due to the steep angle requirement
Solution Approach 1:
The patent introduces a mirror positioned above the melt surface to redirect the optical path, allowing the camera to capture the end cone region from a different angular dimension without physically repositioning the camera inside the high-temperature zone
2Measurement precision
If a mirror is added to enable end cone diameter measurement, then measurement capability is improved, but the device complexity increases and the mirror fogs up easily
Solution Approach 1:
The patent employs a simple, easily replaceable mirror that can be quickly changed if it fogs up, treating it as a consumable component rather than a permanent fixture, thereby reducing the impact of its limitations on overall system complexity
Solution Approach 2:
The mirror serves as an intermediary optical element that enables measurement without requiring direct line-of-sight access to the end cone region, mediating between the camera and the measurement target
3Loss of substance
If the end cone is drawn with a small angle to reduce material waste, then material utilization improves, but the single crystal may detach prematurely from the melt
Solution Approach 1:
The patent uses real-time diameter measurements of the end cone to provide feedback on the pulling process, allowing dynamic adjustment of pulling parameters to maintain optimal conditions that prevent premature detachment while minimizing material waste
Solution Approach 2:
The patent dynamically changes pulling parameters such as pulling speed and temperature based on measured diameter data to optimize the balance between end cone length and crystal stability
4Measurement precision
If the camera position is changed during end cone drawing to capture smaller angles, then measurement capability improves, but additional effort is required and positioning precision is compromised
Solution Approach 1:
The patent pre-positions the camera and mirror in fixed locations before the pulling process begins, eliminating the need for dynamic repositioning during operation and ensuring consistent measurement geometry throughout the end cone drawing
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 method enables precise control of the single crystal diameter during the end cone formation, reducing material waste and preventing premature tearing, resulting in higher reproducibility and quality of the crystal rods.
Implementation Method 1
the diameter of the single crystal, which depends on the radial growth of the single crystal at the crystallization boundary
Implementation Method 2
This bright ring is a reflection from the glowing wall of the crucible containing the melt
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a method for determining a diameter (dk) of a single crystal (200) during the pulling of the single crystal (200), in particular an end-cone (210) of the single crystal (200), from a melt (230) in a crucible (130) of a device (100) for pulling the single crystal (200), wherein the diameter (dk) of the single crystal (200) is determined at a boundary surface to the melt (230), taking into account a first lowering speed (vs) of a surface (235) of the melt (230) relative to the crucible (130), a first lifting speed (vk) with which the single crystal (200) is raised relative to the crucible (130), and a conservation of mass.