Acoustic Endpoint Detection in Substrate Polishing Control

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Solution Overview

Problem

Existing methods for detecting the end of substrate polishing in semiconductor manufacturing are unreliable due to variations in polishing conditions and inconsistencies in acoustic sensor readings, leading to inaccurate detection of the polishing endpoint.

Innovation Solution

A control method using acoustic sensors to generate power spectra and color maps of sound-pressure levels, with frequency bands tailored to substrate materials, and employing pressure feedback control to accurately detect the polishing endpoint.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the S/N ratio threshold method is used to detect polishing endpoint, then the detection process is simple, but the detection accuracy is low due to variations in polishing conditions

Engineering Contradiction:

Improvedetection process simplicityVSAvoidpolishing endpoint detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent transitions from one-dimensional S/N ratio analysis to two-dimensional spectral analysis by introducing frequency domain decomposition. The polishing sound spectrum is divided into multiple frequency bands, and the system monitors changes in sound pressure levels across different frequency ranges simultaneously, enabling more accurate endpoint detection despite variations in polishing conditions.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent changes the detection parameter from a single S/N ratio value to multiple frequency band sound pressure level parameters. By monitoring the temporal changes of sound pressure levels across different frequency bands (e.g., low-frequency band below 1kHz, mid-frequency band 1-10kHz, high-frequency band above 10kHz), the system can detect subtle changes in polishing state that are not reflected in overall S/N ratio.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the S/N ratio exceeds threshold method is used, then the detection calculation is fast, but the detection reliability is low when polishing conditions vary

Engineering Contradiction:

Improvedetection calculation speedVSAvoidpolishing endpoint detection reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent segments the polishing sound spectrum into multiple frequency bands and assigns different weights to each band based on its relevance to polishing state changes. This segmented approach allows the system to focus computational resources on critical frequency ranges while maintaining overall detection reliability, achieving a balance between calculation speed and accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements a feedback mechanism where the system continuously monitors sound pressure levels across frequency bands and adjusts detection thresholds dynamically based on observed polishing condition variations. This feedback loop enables the system to adapt to changing polishing conditions while maintaining reliable endpoint detection.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If full power spectrum analysis is performed, then the detection accuracy is high, but the processing time increases

Engineering Contradiction:

Improvepolishing endpoint detection accuracyVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent extracts only the relevant frequency components from the full power spectrum by dividing the spectrum into meaningful frequency bands and analyzing only those bands that contain information about polishing state changes. This extraction approach maintains detection accuracy while significantly reducing the amount of data that requires processing.

Inventive Principle:

Principle #2Taking out (Extraction)

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

Enables precise detection of the polishing endpoint by analyzing sound-pressure level changes, reducing processing time, and minimizing variations in film thickness distribution.

Implementation Method 1

detecting an acoustic event occurring with polishing of the substrate and outputting the acoustic event as acoustic signals

Methodology Applied

Scientific EffectAcoustic emission: Acoustic Emission

Implementation Method 2

generating power spectra from the acoustic signals, each of the power spectra indicating a spectrum of a sound-pressure level

Methodology Applied

Scientific EffectFourier transform:

Data Source

PatentUS12569956B2Control method for processing of a substrate

Publication Date: 2026.03.10 KIOXIA CORP

AI summary

A method of accurately detecting an end point of substrate polishing using an acoustic sensor is disclosed.The method includes: detecting an acoustic event occurring with polishing of a substrate and outputting the acoustic event as acoustic signals; generating power spectra from the acoustic signals, each of the power spectra indicating a spectrum of a sound-pressure level; generating a power spectrum map indicating a temporal change in power spectrum by arranging the power spectra in a time-series order; and detecting a polishing end point of the substrate based on a change in the sound-pressure level in the power spectrum map.