Substrate Polishing Thickness Sensing With Waveform Noise Correction
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Solution Overview
Problem
Eddy current sensors struggle to accurately measure film thickness during substrate polishing due to interference from locally arranged metal structures in the substrate, such as through-electrodes and metal wires, which generate noise in the output signal.
Innovation Solution
A substrate polishing apparatus and method that utilizes an eddy current sensor installed in a polishing table, with a controller to detect minimum and maximum points in waveform data, correct the data using interpolation and prominence analysis, and calculate film thickness by removing noise from the output signal to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an eddy current sensor is used to measure film thickness during polishing, then real-time thickness measurement is enabled, but measurement accuracy deteriorates due to interference from metal structures in the substrate
Solution Approach 1:
The patent extracts and removes the harmful interference components (metal structure signals) from the eddy current sensor output waveform. By detecting minimum or maximum points in the waveform that correspond to metal structure interference and eliminating these points, the system isolates the true film thickness measurement signal from the noisy background.
Solution Approach 2:
The patent introduces waveform analysis and correction algorithms as an intermediary processing step between the eddy current sensor and the film thickness calculation. This intermediary process identifies and corrects distorted waveform portions caused by metal structures, enabling accurate thickness measurement despite the presence of interfering metal elements in the substrate.
2Adaptability or versatility
If metal structures are present in the substrate, then functional elements (through-electrodes, metal wires) are enabled, but noise in the eddy current sensor output signal increases
Solution Approach 1:
The patent converts the harmful noise generated by metal structures into a detectable pattern. By analyzing the waveform for characteristic minimum or maximum points that indicate metal structure interference, the system identifies and corrects these distorted portions, transforming the previously harmful noise into a useful diagnostic feature that guides the correction process.
3Measurement precision
If waveform correction is performed to remove noise, then measurement accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent applies partial correction by targeting only the specific portions of the waveform that are distorted by metal structures (identified through minimum or maximum point detection), rather than attempting to process the entire waveform uniformly. This selective approach reduces unnecessary computational complexity while maintaining measurement accuracy in the affected regions.
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 accurate film thickness measurement by reducing noise from metal structures, allowing for precise control of the polishing process and uniform film thickness distribution across the substrate.
Implementation Method 1
an eddy current sensor which moves along a path on a surface of a substrate while a polishing table is being rotated, and measures film thickness at respective points on the path
Data Source
AI summary
An object is to accurately measure, during polishing of a substrate, thickness of a film which is an object of polishing.A substrate polishing apparatus comprises: a polishing table which is provided with an eddy current sensor and is constructed to be able to be rotated; a polishing head which is positioned to be opposite to the polishing table, is constructed to be able to be rotated, and allows a substrate to be attached to a surface which is positioned to be opposite to the plating table, and a controller. The controller is constructed to obtain waveform data of output signals of the eddy current sensor during polishing of the substrate; detect minimum points or maximum points in the waveform data; correct, based on the detected minimum points or the detected maximum points, the waveform data; and calculate, based on the corrected waveform data, thickness of a film on a surface of the substrate.