CMP Polishing End Point Detection via Film Thickness Adjustment
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Solution Overview
Problem
The challenge in accurately determining the polishing end point of a substrate with non-uniform film thickness during chemical mechanical polishing (CMP) due to the lack of significant change in torque reflecting frictional force changes between the substrate and polishing pad.
Innovation Solution
A method that involves a film-thickness profile adjustment process, where pressing forces on the substrate are adjusted based on measured film thicknesses to achieve a flat surface, followed by a polishing-end-point detection process using torque measurements to determine the optimal polishing end point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional torque-based polishing end point detection is used on substrates with non-uniform film thickness, then the detection method is simple, but the polishing end point cannot be accurately determined
Solution Approach 1:
The patent applies preliminary action by performing a film thickness profile adjustment process before the polishing end point detection. This preliminary step flattens the film thickness profile across the substrate surface, creating uniform contact conditions that enable accurate torque-based detection. The system measures film thickness at multiple points, calculates adjustment amounts, and executes pressing force adjustments before the main polishing detection phase.
Solution Approach 2:
The patent implements feedback control by continuously measuring film thickness at multiple measurement points during polishing, comparing these measurements against target values, and dynamically adjusting pressing forces based on the deviations. This closed-loop feedback system ensures the film thickness profile remains uniform, enabling accurate torque-based end point detection throughout the polishing process.
2Manufacturing precision
If uniform pressing force is applied during polishing, then the polishing process is simple, but substrates with non-uniform film thickness cannot be polished uniformly
Solution Approach 1:
The patent applies local quality by dividing the substrate surface into multiple measurement regions and applying different pressing forces to different local areas. The pressing force adjustment amount is calculated separately for each measurement point based on its specific film thickness deviation, allowing localized correction of thickness non-uniformities while maintaining overall surface planarization.
Solution Approach 2:
The patent implements dynamics by making the pressing force adjustable and variable during the polishing process. The pressing force adjustment amount is dynamically calculated based on real-time film thickness measurements and is updated throughout polishing to maintain uniform film thickness profile, transforming a static pressing force system into a dynamic adaptive system.
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 approach allows for accurate determination of the polishing end point by ensuring the substrate surface is uniformly polished, enhancing the precision of torque-based end point detection and improving surface planarization.
Implementation Method 1
The surface of the substrate is placed in sliding contact with the polishing surface in the presence of the polishing liquid, so that the surface of the substrate is planarized to a mirror finish by a chemical action of the polishing liquid
Implementation Method 2
The surface of the substrate is placed in sliding contact with the polishing surface in the presence of the polishing liquid, so that the surface of the substrate is planarized to a mirror finish by a chemical action of the polishing liquid and a mechanical action of abrasive grains contained in the polishing liquid
Implementation Method 3
A frictional force acting between the substrate and the polishing pad changes depending on a material of the surface, to be polished, of the substrate
Data Source
AI summary
The present invention relates to a polishing method and a polishing apparatus for polishing a substrate, such as a wafer. The present invention further relates to a computer-readable storage medium storing a program for causing the polishing apparatus to perform the polishing method. The polishing method includes: rotating a polishing table (3); and polishing a substrate (W) by pressing the substrate (W) against a polishing surface (2a). Polishing the substrate (W) includes a film-thickness profile adjustment process and a polishing-end-point detection process. The film-thickness profile adjustment process includes adjusting pressing forces on the substrate (W) against the polishing surface (2a) based on a plurality of film thicknesses, and determining a point in time at which a film-thickness index value has reached a film-thickness threshold value. The film-thickness index value is determined from at least one of the plurality of film thicknesses. The polishing-end-point detection process includes measuring a torque for rotating the polishing table (3) and determining a polishing end point based on the torque.