Polishing Apparatus Imaging via Liquid Fill

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Solution Overview

Problem

The existing polishing apparatuses struggle to capture clear images of the substrate's periphery during the polishing process due to the adherence of polishing liquids to the imaging device's lens, leading to inaccurate detection of the polishing end point.

Innovation Solution

A polishing apparatus equipped with a stage-rotating mechanism, a polishing head, an image-capturing device, and a liquid ejector that uses a light-transmissive liquid to fill the space between the substrate and the imaging element, ensuring clear visibility by preventing liquid and particle attachment on the imaging device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polishing liquid is supplied to the bevel portion during polishing, then the wafer surface is protected from contamination by particles, but the polishing liquid adheres to the objective lens of the imaging device, making it difficult to capture a clear image

Engineering Contradiction:

Improveprotection of wafer surface from contaminationVSAvoidclarity of image for polishing end point detection

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The imaging system is divided into separate optical paths: one for capturing the bevel portion (through the polishing tape) and another for monitoring the wafer surface. The objective lens is positioned to observe only through the transparent polishing tape, isolating it from direct exposure to polishing liquid while maintaining imaging capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transparent polishing tape serves as an intermediary medium that allows optical transmission from the bevel portion to the objective lens while blocking direct contact between polishing liquid and the lens. The tape acts as a protective barrier that maintains both imaging quality and contamination protection

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the objective lens is positioned close to the bevel portion for clear imaging, then image quality improves, but polishing liquid and particles adhere to the lens, degrading image quality

Engineering Contradiction:

Improveimage quality for end point detectionVSAvoidadhesion of polishing liquid and particles to lens

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The observation function is segmented into two pathways: direct observation of the bevel portion through the transparent polishing tape, and indirect observation of the wafer surface. This segmentation allows the objective lens to be positioned for optimal bevel imaging while the polishing liquid is directed away from the lens by the tape barrier

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transparent polishing tape functions as a flexible thin film barrier that permits optical transmission while physically blocking polishing liquid and particles from reaching the objective lens. The tape's transparency maintains imaging quality while its physical presence prevents contamination

Inventive Principle:

Principle #30Flexible shells and thin films

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 configuration allows for accurate detection of the polishing end point by maintaining the visibility of the imaging element, thereby enhancing the precision of the polishing process.

Implementation Method 1

a light-transmissive liquid to fill a space between the periphery of the substrate and the terminal imaging element with the liquid

Methodology Applied

Scientific EffectLight transmission through liquid: Refraction

Data Source

PatentUS8771038B2Polishing apparatus

Publication Date: 2014.07.08 EBARA CORP

AI summary

A polishing apparatus includes a stage configured to hold a substrate, a stage-rotating mechanism configured to rotate the stage, and a polishing head configured to polish a periphery of the substrate held by the stage. The polishing apparatus also includes a controller configured to control operations of the stage, the stage-rotating mechanism, and the polishing head, an image-capturing device configured to capture an image of the periphery of the substrate through at least one terminal imaging element arranged so as to face the periphery of the substrate, an image processor configured to process the image captured by the image-capturing device, and a liquid ejector configured to eject a light-transmissive liquid toward the periphery of the substrate to fill a space between the periphery of the substrate and the terminal imaging element with the liquid.