CMP Polishing Apparatus Optical Sensor Cleaning via Transparent Liquid Flow

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Solution Overview

Problem

The abrasive grains and polishing debris in the CMP process tend to adhere to the optical sensor head, leading to inaccurate film thickness measurements due to decreased reflected light intensity.

Innovation Solution

A polishing apparatus is designed with a polishing pad having a through-hole, where a transparent liquid is supplied through the hole to create a flow that cleans the optical sensor head's light-emitting and light-receiving surfaces, preventing abrasive grains and debris from adhering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the light path is filled with transparent liquid to stabilize film thickness measurement, then measurement stability is improved, but abrasive grains and polishing debris adhere to the optical sensor head causing measurement inaccuracy

Engineering Contradiction:

Improvemeasurement stabilityVSAvoidfilm thickness measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The light path is segmented into multiple sections with transparent liquid filling only the measurement region between the optical sensor head and workpiece. The inlet passage and outlet passages are spatially separated, creating distinct zones for liquid supply, measurement, and discharge, thus stabilizing measurement while enabling debris removal.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transparent liquid is selectively applied only to the light path region where measurement occurs, rather than filling the entire polishing environment. This localized application maintains measurement stability in the critical zone while allowing other regions to handle debris removal through the outlet passages.

Inventive Principle:

Principle #3Local quality

Solution Approach 3:

The outlet passages are positioned to receive and remove abrasive grains and polishing debris before they can adhere to the optical sensor head. The continuous flow of transparent liquid creates a protective action that prevents debris accumulation on the sensor surfaces.

Inventive Principle:

Principle #9Preliminary anti-action

2Productivity

If abrasive grains and polishing debris are present in the light path, then the polishing process continues, but the optical sensor head becomes contaminated reducing reflected light intensity

Engineering Contradiction:

Improvepolishing continuityVSAvoidreflected light intensity

Core Design Contradiction:

ProductivityVSIllumination intensity

Solution Approach 1:

The transparent liquid acts as an intermediary medium between the abrasive-containing polishing environment and the optical sensor head. It allows the polishing process to continue with abrasive grains present while the liquid flow carries debris away from the sensor, maintaining light intensity through the mediating liquid barrier.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

A hydraulic system using transparent liquid flow is implemented to continuously remove abrasive grains and polishing debris from the light path region. The liquid flow through the inlet and outlet passages creates a hydraulic cleaning mechanism that maintains optical clarity without interrupting the polishing process.

Inventive Principle:

Principle #29Pneumatics and hydraulics

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 solution effectively prevents abrasive grains and debris from adhering to the optical sensor head, thereby improving the accuracy of film thickness measurements by maintaining the cleanliness of the sensor's surfaces.

Implementation Method 1

a transparent liquid is supplied through the hole to create a flow that cleans the optical sensor head's light-emitting and light-receiving surfaces

Methodology Applied

Scientific EffectFluid flow:

Implementation Method 2

direct light onto the workpiece and receive reflected light from the workpiece by an optical sensor head

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS20250041987A1Polishing apparatus

Publication Date: 2025.02.06 EBARA CORP

AI summary

A polishing apparatus includes: a polishing table configured to support a polishing pad having a through-hole; an optical film-thickness measuring system having an optical sensor head mounted to the polishing table; a transparent-liquid inlet passage configured to supply a transparent liquid to the through-hole; and a light-emitting-side transparent-liquid outlet passage and a light-receiving-side transparent-liquid outlet passage communicating with the through-hole. The optical sensor head has a light-emitting surface configured to emit light obliquely upward and a light-receiving surface configured to receive reflected light from the workpiece, and the light-emitting surface faces the light-emitting-side transparent-liquid outlet passage, and the light-receiving surface faces the light-receiving-side transparent-liquid outlet passage.