Spectral Interferometric Thickness Measurement With Airflow Control

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Solution Overview

Problem

Spectral interferometric sensors for measuring workpiece thickness are affected by the refractive index, which is influenced by temperature changes, leading to measurement errors.

Innovation Solution

An apparatus and method utilizing an enclosure with a rectifier to rectify airflow, a spectral interferometric sensor, and temperature sensors to minimize temperature fluctuations within the enclosure, ensuring accurate thickness measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a spectral interferometric sensor is used to measure workpiece thickness, then measurement precision is improved by eliminating axial misalignment and vibration-induced displacement deviations, but measurement precision deteriorates due to temperature-induced refractive index changes affecting the measurement results

Engineering Contradiction:

Improvethickness measurement precisionVSAvoidtemperature-induced refractive index changes

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The enclosure is divided into multiple zones with independent airflow control. The rectifier is segmented into multiple units that can independently rectify airflow in different regions, allowing precise control of temperature distribution within the enclosure to minimize temperature-induced refractive index changes during measurement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A rectifier is introduced as an intermediary device between the external environment and the measurement chamber. The rectifier rectifies airflow entering the enclosure, acting as a mediator to control and stabilize temperature conditions, thereby eliminating temperature-induced refractive index changes from affecting the measurement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If displacement sensors are set on the front side and back side of the workpiece to measure thickness, then device complexity is reduced with a simple design, but measurement precision deteriorates due to axis misalignment, vibration, and thermal expansion

Engineering Contradiction:

Improvemeasurement device complexityVSAvoidthickness measurement precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical displacement sensor system with a spectral interferometric sensor system. This substitution eliminates the mechanical issues of axis misalignment and vibration-induced displacement deviations while maintaining simplicity in the overall device design.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If the measurement is performed in an open environment, then ease of operation is improved, but measurement precision deteriorates due to temperature fluctuations affecting the refractive index

Engineering Contradiction:

Improvemeasurement operation easeVSAvoidthickness measurement precision

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent creates a controlled enclosure environment that acts as an inert atmosphere for the measurement process. By enclosing the measurement chamber and using a rectifier to control airflow, the system maintains stable temperature conditions that prevent refractive index changes, thereby ensuring high measurement precision while keeping the operation simple.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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

The solution enables precise thickness measurement by reducing temperature-induced errors, enhancing measurement accuracy and reliability using spectral interferometric sensors.

Implementation Method 1

measure the workpiece using a spectral interferometric sensor... the thickness can be calculated by measuring the reflected light on the front and back surfaces of the workpiece by a laser emitted from the coaxial

Methodology Applied

Scientific EffectSpectral interferometry: Interference

Implementation Method 2

a rectifier disposed inside the enclosure for rectifying airflow inside the enclosure

Methodology Applied

Scientific EffectForced convection: Forced Convection

Data Source

PatentUS20250289090A1Apparatus for measuring thickness of workpiece, method for measuring thickness of workpiece, and system for polishing workpiece

Publication Date: 2025.09.18 SUMCO CORP

AI summary

The apparatus for measuring a thickness of a workpiece of this disclosure comprises an enclosure; a measurement section disposed inside the enclosure for measuring the thickness of the workpiece; and a rectifier disposed inside the enclosure for rectifying airflow inside the enclosure, wherein the measurement section is provided with a spectral interferometric sensor. In the system for polishing a workpiece of this disclosure, the apparatus for measuring a thickness of a workpiece above is installed in each of the workpiece carry-in unit and the workpiece carry-out unit. In the method for measuring a thickness of a workpiece of this disclosure, the thickness of the workpiece is measured using a measurement section comprising a spectral interferometric sensor, the measurement section is disposed inside an enclosure, and the thickness of the workpiece is measured by the measurement section while rectifying airflow in the enclosure using a rectifier disposed inside the enclosure.