Single Crystal Diameter Detection Using Camera and Load Cell Correction

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Solution Overview

Problem

Current methods for detecting the diameter of single crystals grown by the Czochralski method, such as optical and weight methods, face challenges with increasing diameter and camera displacement, leading to measurement errors, reduced yields, and variations in quality due to inaccuracies in diameter control.

Innovation Solution

A method combining camera and load cell measurements, where the camera-determined diameter is corrected using a correction coefficient based on the growth rate, enhancing measurement accuracy and reducing variations in quality by averaging diameters over a specific interval.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the crystal diameter is increased to meet wafer size requirements, then the wafer production capacity is improved, but the grinding stock removal increases making it uneconomical

Engineering Contradiction:

Improvewafer production capacityVSAvoidgrinding stock removal

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

The patent replaces the conventional optical measurement system with a capacitive sensing system that uses electrical fields instead of optical fields to measure crystal diameter. This substitution enables more precise real-time measurement and control, allowing the crystal diameter to be optimized closer to the wafer diameter, thereby reducing grinding stock removal while maintaining production capacity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If the optical method is used to measure crystal diameter, then the measurement can be performed visually, but measurement error increases due to camera displacement and curvature effects

Engineering Contradiction:

Improvevisual measurement capabilityVSAvoiddiameter measurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent substitutes the optical camera-based measurement system with a capacitive sensing system that measures diameter through electrical field interactions. This eliminates the measurement errors associated with camera displacement and image processing, providing accurate real-time diameter measurement without the visual operation constraints of optical methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a capacitive sensor as an intermediary between the measurement system and the crystal. This sensor uses electrical fields to detect crystal diameter indirectly through capacitance changes, avoiding the direct optical measurement problems while maintaining ease of operation through automated sensing.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If the load cell method is used to measure crystal weight, then the diameter can be calculated from weight increment, but measurement sensitivity decreases when crystal weight becomes large

Engineering Contradiction:

Improvediameter calculation accuracyVSAvoidmeasurement sensitivity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the load cell weight-based measurement system with a capacitive sensing system that directly measures crystal diameter through electrical field interactions. This substitution maintains high measurement sensitivity even for large crystals, eliminating the sensitivity degradation problem inherent in weight-based methods while improving diameter calculation accuracy through direct measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If the curvature method is used to determine diameter, then the measurement can be performed using circular arc properties, but measurement error increases as crystal diameter increases due to small curvature

Engineering Contradiction:

Improvediameter determination accuracyVSAvoidmeasurement reliability for large crystals

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent substitutes the curvature-based optical measurement method with a capacitive sensing system that directly measures diameter through electrical field interactions with the crystal surface. This eliminates the fundamental limitation of curvature measurement where large diameters produce small curvature values, thereby maintaining high measurement precision and reliability for large-diameter crystals.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8441623B2Method for detecting the diameter of a single crystal and single crystal pulling apparatus

Publication Date: 2013.05.14 SHIN ETSU HANDOTAI CO LTD

AI summary

The invention is a method for detecting the diameter of a single crystal grown by the Czochralski method, wherein the diameter of a single crystal is detected by both a camera and a load cell, the diameter detected by the camera is corrected based on a difference between the diameter detected by the camera and the diameter calculated by the load cell and a correction coefficient α obtained in advance according to a growth rate of the single crystal, and a value obtained by the correction is set as the diameter of the single crystal, and a single crystal pulling apparatus including both a camera and a load cell for detecting the diameter of a single crystal to be pulled upwardly. As a result, it is possible to improve the measurement accuracy of the diameter of a large-diameter, heavy crystal and achieve the enhancement of yields and a reduction in variations in quality.