Optical Sensor Head Cleaning via Polishing Pad Through-Hole
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Solution Overview
Problem
The optical film-thickness measuring system is hindered by clogged drain lines due to slurry and polishing debris, leading to inaccurate measurements and polishing failures, as the slurry dilutes and the debris adheres to the optical sensor head.
Innovation Solution
A method involving the use of a rinsing liquid to clean the optical sensor head and drain line by supplying it through a through-hole in the polishing pad, either before or after polishing, using a structural element to cover the hole and a drain pump to discharge the liquid, ensuring the system's proper operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pure water is supplied to the through-hole to ensure light path during polishing, then measurement accuracy is improved, but the drain line becomes clogged with slurry and polishing debris
Solution Approach 1:
The system performs preliminary cleaning action by supplying rinsing liquid through the through-hole before polishing begins or between polishing steps. This prevents slurry and debris from accumulating in the drain line during the measurement-critical polishing operation, maintaining both measurement accuracy and drain line functionality.
Solution Approach 2:
A rinsing liquid is introduced as an intermediary substance to clean the through-hole and drain line of slurry and polishing debris. This intermediary fluid facilitates the removal of harmful substances that would otherwise clog the drain line and interfere with the optical measurement system.
2Measurement precision
If pure water flows through the through-hole during polishing, then the light path is maintained, but slurry dilutes on the polishing pad causing polishing failure
Solution Approach 1:
The system performs preliminary cleaning with rinsing liquid before polishing to remove accumulated debris, then stops the rinsing liquid supply during the actual polishing operation. This ensures the polishing pad maintains proper slurry concentration for high-quality polishing while the through-hole remains clear for accurate optical measurements.
Solution Approach 2:
The system dynamically controls the supply and discharge of rinsing liquid based on the polishing cycle phase. Rinsing liquid is supplied during idle periods or before polishing to clean the through-hole, but stopped during active polishing to prevent slurry dilution, optimizing both measurement accuracy and polishing quality.
3Productivity
If the through-hole is left open during polishing, then debris can be discharged, but slurry and debris adhere to the optical sensor head reducing measurement accuracy
Solution Approach 1:
A rinsing liquid is used as an intermediary cleaning agent that flows through the through-hole and over the optical sensor head during idle periods or before measurement cycles. This rinsing fluid washes away adhered slurry and debris from the optical sensor head, restoring measurement accuracy without interfering with the polishing process.
Solution Approach 2:
The system performs preliminary cleaning of the optical sensor head with rinsing liquid before film thickness measurement begins. This preliminary action removes any slurry or debris that may have adhered during polishing, ensuring accurate measurements without requiring the through-hole to remain open during the actual measurement process.
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 method effectively cleans the optical sensor head and drain line, maintaining the accuracy of film thickness measurements and preventing polishing failures by ensuring a clear light path and removing debris.
Implementation Method 1
supplying a rinsing liquid into a through-hole (51) formed in a polishing pad (520) on a polishing table (515) before or after polishing of a substrate (W) with use of slurry is performed, and discharging the rinsing liquid from the through-hole (51) through a drain line (540)
Implementation Method 2
A light source 500 and a spectrometer 501 are coupled to an optical sensor head 510. The optical sensor head 510 is arranged in a polishing table 515. A through-hole 521 is formed in a polishing pad 520, and the optical sensor head 510 is located below the through-hole 521. The light emitted by the light source 500 is transmitted to the optical sensor head 510
Implementation Method 3
measure intensity of reflected light from the wafer with a spectrometer, and analyze a spectrum of the reflected light to determine the film thickness of the wafer
Data Source
AI summary
The present invention relates to a method of cleaning an optical film-thickness measuring system used for measuring a film thickness of a substrate, such as a wafer, while polishing the substrate. The method includes: cleaning an optical sensor head (7) by supplying a rinsing liquid into a through-hole (51) formed in a polishing pad (2) on a polishing table (3) before or after polishing of a substrate (W) with use of slurry, the optical sensor head (7) being located below the through-hole (51); and discharging the rinsing liquid from the through-hole (51) through a drain line (54).