Polishing Unit Slip-Out Detection Using Color Difference Sensor
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Solution Overview
Problem
Current chemical mechanical polishing techniques face challenges in accurately detecting substrate slip-out due to variations in substrate thickness and material, leading to false detections caused by light reflectance differences and contamination from polishing slurry.
Innovation Solution
A polishing unit equipped with a light emitting member, a slip-out detector, and an elimination mechanism, where the slip-out detector uses both color and light amount changes to detect substrate slip-out and the elimination mechanism clears polishing liquid from the detection area to prevent false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a photoelectric sensor is used to detect substrate slip-out based on light-amount difference, then the detection method is simple, but false detections occur due to variations in substrate thickness and material affecting light reflectance
Solution Approach 1:
The patent employs a color difference sensor instead of a simple photoelectric sensor to detect substrate slip-out. The color difference sensor measures both light intensity and color information, allowing it to distinguish between variations caused by substrate properties and actual slip-out events. This resolves the contradiction by maintaining relatively simple detection hardware while significantly improving measurement precision through color-based differentiation.
2Measurement precision
If a color difference sensor is used to detect substrate slip-out, then detection accuracy improves, but false detections occur due to slurry flowing into the detection area
Solution Approach 1:
The patent divides the polishing pad surface into distinct functional zones: a detection area for the color difference sensor and a slurry discharge area positioned downstream. This spatial segmentation allows the detection area to remain relatively free of slurry contamination while the discharge area handles slurry removal. The segmentation resolves the contradiction by physically separating the detection function from the slurry-affected regions, maintaining detection accuracy while eliminating false positives from slurry interference.
3Ease of operation
If the detection area is positioned where slurry flows, then easy access for detection is achieved, but detection accuracy decreases due to slurry interference
Solution Approach 1:
The patent resolves this contradiction by utilizing the spatial dimension along the polishing pad's rotational direction. The detection area is positioned in a region that receives less slurry flow, while a separate discharge area handles slurry removal downstream. This dimensional arrangement allows both detection accessibility and detection accuracy to be maintained, as the sensor has clear access to the polishing interface without being contaminated by slurry that is directed away in another spatial direction.
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
Enhances the accuracy of substrate slip-out detection by mitigating the effects of substrate variations and slurry contamination, ensuring reliable operation of the polishing process.
Implementation Method 1
The light emitting member emits a light to a detection area on the polishing pad. The slip-out detector detects a slip out of the substrate from the top ring based on the light reflected from the detection area.
Implementation Method 2
The elimination mechanism eliminates a polishing liquid flowing into the detection area.
Data Source
AI summary
An accuracy of detecting a slip out of a substrate from a top ring is improved. A polishing unit 300 includes a polishing table 350, a top ring 302, a light emitting member 371, a slip-out detector 370, and an elimination mechanism 380. A polishing pad 352 that polishes a substrate WF is attached to the polishing table 350. The top ring 302 holds the substrate WF to press the substrate WF against the polishing pad 352. The light emitting member 371 emits a light to a detection area 372 on the polishing pad 352. The slip-out detector 370 detects a slip out of the substrate WF from the top ring 302 based on the light reflected from the detection area 372. The elimination mechanism 380 eliminates a polishing liquid flowing into the detection area 372.