Polishing Endpoint Detection via Torque Rate Change
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Solution Overview
Problem
Conventional polishing methods struggle to accurately determine the polishing end point when the polishing head oscillates along the polishing pad, leading to fluctuations in torque and inaccurate endpoint detection.
Innovation Solution
The method involves stopping the oscillation of the polishing head after reaching a preset torque threshold or time, and determining the polishing end point based on the rate of change of torque, using a predictive model to calculate the torque threshold value and ensuring accurate endpoint detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the polishing head oscillates along the polishing pad, then polishing performance and productivity are improved, but torque fluctuates and endpoint detection accuracy deteriorates
Solution Approach 1:
The polishing process is divided into two distinct phases: an oscillation polishing phase for material removal and a static polishing phase for endpoint detection. This segmentation allows each phase to optimize its function - oscillation during polishing improves productivity, while static positioning during detection ensures measurement accuracy.
Solution Approach 2:
The polishing head performs periodic oscillation during the polishing process, then stops oscillation periodically to allow for accurate torque-based endpoint detection. This periodic alternation between oscillating and static states enables both high polishing performance and accurate endpoint detection.
2Manufacturing precision
If the polishing head oscillates along the polishing pad, then surface planarization is improved, but torque measurement becomes inaccurate
Solution Approach 1:
The process segments polishing and measurement functions into separate time periods. During oscillation polishing, surface planarization is achieved through mechanical action. During static periods, accurate torque measurement is obtained without oscillation interference.
Solution Approach 2:
The system performs preliminary oscillation polishing to achieve the desired surface planarization, then transitions to a static state to perform accurate torque-based endpoint detection before final polishing completion.
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 precise determination of the polishing end point, reducing surface defects and maintaining polishing performance even with oscillating polishing heads.
Implementation Method 1
a chemical action of the polishing liquid and a mechanical action of abrasive grains contained in the polishing liquid
Implementation Method 2
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 that acts between the substrate and the polishing pad changes depending on a material of the surface, to be polished, of the substrate
Data Source
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AI summary
A polishing method capable of accurately determining a polishing end point of a substrate is disclosed. The method comprises: rotating a polishing table supporting a polishing pad; and polishing the substrate by pressing the substrate against a polishing surface of the polishing pad by a polishing head, wherein polishing the substrate includes: an oscillation polishing process of polishing the substrate while causing the polishing head to oscillate along the polishing surface; and a static polishing process of polishing the substrate with the oscillation of the polishing head stopped, the static polishing process is performed after the oscillation polishing process, and the static polishing process comprises determining a static polishing end point which is a point in time at which a rate of change of torque for rotating the polishing table has reached a change-rate threshold value.