Silicon Crystal Diameter Control via Meniscus Height
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Solution Overview
Problem
Existing methods for controlling the diameter of silicon single crystals during the Czochralski process face challenges in accurately detecting and responding to variations, leading to inconsistent crystal diameters and increased defects.
Innovation Solution
The method involves capturing images of the fusion ring using an imaging device to measure brightness distribution, detecting the liquid level and solid-liquid interface, and controlling the crystal diameter based on meniscus height, allowing for rapid and precise adjustments to the pulling speed and temperature to maintain a constant diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the diameter of the silicon single crystal is measured and feedback control is performed by changing the temperature of the silicon melt or pulling speed, then the diameter can be controlled, but it takes a long time for the diameter to approximate the set value, causing waves in the diameter and making it difficult to maintain constant diameter
Solution Approach 1:
The invention measures the meniscus height in advance as an indicator of future diameter variations. By detecting the meniscus height before the diameter deviation actually occurs and feeding back this information, the system can adjust the pulling speed proactively, preventing diameter waves rather than reacting to them after they occur.
Solution Approach 2:
The invention replaces the conventional method of directly measuring and controlling the crystal diameter with a non-contact optical measurement system that measures the meniscus height. This substitution enables faster detection and response without the mechanical inertia associated with direct diameter measurement and adjustment.
2Measurement precision
If the fusion ring is regarded as an inclined plane and the angle or diameter is measured to detect diameter variation, then diameter detection is attempted, but the interface of the fusion ring is unclear, making it difficult to accurately detect the width or diameter
Solution Approach 1:
The invention extracts and isolates the meniscus region from the complex fusion ring structure. By specifically targeting and measuring only the meniscus height rather than attempting to measure the entire fusion ring or its ambiguous interfaces, the system achieves clear and accurate detection of diameter variation indicators.
Solution Approach 2:
The invention focuses measurement on the specific local region of the meniscus rather than the entire fusion ring. The meniscus height at the contact line between the crystal and melt provides localized, high-precision information about diameter trends, avoiding the ambiguity of measuring the overall fusion ring structure.
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 early detection and rapid control of diameter variations, resulting in high-quality silicon single crystals with reduced defects and consistent cylindrical portions.
Implementation Method 1
a ring-shaped high-brightness region that is generated so as to surround the silicon single crystal at the solid-liquid interface when radiation light from the wall of a crucible is reflected to the surface of a silicon melt
Implementation Method 2
a ring-shaped high-brightness region that is generated so as to surround the silicon single crystal at the solid-liquid interface when radiation light from the wall of a crucible is reflected to the surface of a silicon melt that arises by the surface tension of the silicon single crystal during a pulling process
Data Source
AI summary
An object of the present invention is to provide a silicon single crystal pulling method of accurately controlling the diameter of a silicon single crystal, thereby obtaining a high-quality silicon single crystal with little crystal defect.According to an aspect of the present invention, the pulling step includes: capturing an image of the silicon single crystal using an imaging device; measuring the brightness distribution of a fusing ring generated in the vicinity of a solid-liquid interface between the silicon melt and the silicon single crystal for each image scan line in the image captured by the imaging device; detecting the liquid level of the silicon melt and the position of the solid-liquid interface; and controlling the diameter of the silicon single crystal on the basis of a meniscus height, which is a difference between the liquid level and the position of the solid-liquid interface.