Single Crystal Diameter Measurement via Fusion Ring Projection

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Solution Overview

Problem

The existing methods for measuring the diameter of a single crystal during the Czochralski process are inaccurate due to the reliance on visual conversion coefficients, leading to potential errors in crystal diameter control.

Innovation Solution

A single crystal manufacturing apparatus and method that uses a camera to photograph the fusion ring at the melt-crystal boundary, projects and converts the image onto a reference plane, and calculates the crystal diameter based on the shape of the fusion ring, eliminating the need for conversion coefficients and improving measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a diameter conversion coefficient is used to convert pixel values to actual diameter units, then the measurement process is simple, but the measurement accuracy deteriorates due to conversion errors

Engineering Contradiction:

Improvemeasurement process simplicityVSAvoiddiameter measurement accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical/optical measurement system (camera imaging) with a mathematical calculation system. Instead of using a camera to directly measure diameter and then converting pixels to physical units, the system calculates the diameter mathematically from the image data, eliminating the need for conversion coefficients and their associated errors.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates a mathematical model (copy) of the physical measurement process. Rather than directly measuring the physical diameter, it creates a computational representation of the diameter calculation that can be performed entirely through mathematical operations on image data, bypassing the need for physical calibration.

Inventive Principle:

Principle #26Copying

2Device complexity

If visual measurement methods are used to determine crystal diameter, then the equipment is simple, but the reliability of diameter control deteriorates due to measurement errors

Engineering Contradiction:

Improvemeasurement equipment simplicityVSAvoiddiameter control reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent replaces the mechanical measurement approach (visual inspection and camera imaging) with a computational approach. The system substitutes physical measurement devices with mathematical algorithms that calculate diameter from image data, improving reliability by eliminating human visual errors and camera calibration issues.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements a feedback mechanism where the calculated diameter is continuously compared with target values, and the crystal growth parameters are adjusted accordingly. This closed-loop control system improves reliability by automatically correcting measurement and control errors in real-time.

Inventive Principle:

Principle #23Feedback

3Manufacturing precision

If the single crystal diameter is made larger to ensure sufficient wafer size, then the wafer production is guaranteed, but the grinding allowance increases and manufacturing economy deteriorates

Engineering Contradiction:

Improvewafer size guaranteeVSAvoidgrinding allowance waste

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent enables precise control of the crystal diameter parameter during growth. By accurately measuring and controlling the diameter in real-time, the system can grow crystals with diameters optimized for the target wafer size, minimizing excess material that would require grinding removal while ensuring sufficient size for wafer production.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces rough visual estimation of crystal diameter with precise mathematical calculation, enabling tighter control of the crystal growth process. This precision allows the crystal diameter to be controlled within narrower tolerances, reducing the need for excessive grinding allowance while guaranteeing sufficient wafer size.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 precise calculation and control of the single crystal diameter during the pull-up process, enhancing measurement accuracy and reducing errors, thereby improving the yield of silicon single crystals.

Implementation Method 1

a camera (18) for photographing a fusion ring generated at the boundary between the melt and the single crystal

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS20230220583A1Single crystal production apparatus and single crystal production method

Publication Date: 2023.07.13 SUMCO CORP

AI summary

A single crystal manufacturing apparatus 10 according to the present invention is provided with a single crystal puller pulling up a single crystal 15 from a melt 13, a camera 18 photographing a fusion ring generated at the boundary between the melt 13 and the single crystal 15 and an computer 24 processing a photographed image taken by the camera 18. The computer 24 projects and converts the fusion ring appearing in the photographed image taken by the camera 18 on a reference plane corresponding to the liquid level position of the melt based on an installation angle and a focal length of the camera and calculates a diameter of the single crystal 15 from a shape of the fusion ring on the reference plane.