Optical Surface Monitoring Light Passage Cleaning
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Solution Overview
Problem
The existing semiconductor device manufacturing process faces issues with abrasive grains from the slurry entering the light passage of the polishing apparatus, causing interference with light travel and requiring replacement of optical components due to adhesion, which affects accurate measurement by the optical surface-monitoring device.
Innovation Solution
A cleaning method involving the use of a chemical liquid to etch and remove abrasive grains from the light passage, followed by a drying gas to maintain the passage's condition, ensuring accurate light travel and measurement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure water is supplied continuously to the light passage to prevent slurry entry, then the light passage remains clean, but the system complexity and water consumption increase
Solution Approach 1:
The invention extracts the cleaning function from the continuous water supply system by introducing a separate chemical liquid supply system that operates independently. The chemical liquid is supplied only when needed (when abrasive grains are detected), rather than continuously, thereby simplifying the overall system while maintaining cleaning effectiveness.
Solution Approach 2:
The chemical liquid supply system enables the light passage to clean itself on-demand. When abrasive grains are detected in the light passage, the system automatically supplies chemical liquid to dissolve and remove them, eliminating the need for manual intervention or continuous water supply.
2Measurement precision
If the light passage is replaced when abrasive grains adhere firmly, then measurement accuracy is restored, but the cost and downtime increase
Solution Approach 1:
The system performs preliminary detection of abrasive grains in the light passage using the optical monitoring system. When grains are detected, chemical liquid is supplied proactively to dissolve them before they can firmly adhere and cause measurement errors, preventing the need for component replacement.
Solution Approach 2:
The invention changes the chemical state of the abrasive grains by supplying chemical liquid that dissolves the grains. This transforms the physical state of the contaminants from solid adhered particles to dissolved substances that can be easily flushed away, maintaining measurement precision without hardware replacement.
3Reliability
If chemical liquid is supplied to remove abrasive grains, then the light passage is cleaned, but the chemical liquid may damage the light passage surface
Solution Approach 1:
The invention carefully controls the parameters of the chemical liquid, including its composition, concentration, temperature, and supply duration. By optimizing these parameters, the chemical liquid effectively dissolves abrasive grains while minimizing damage to the light passage surface. The supply is also controlled to occur only when needed, reducing overall exposure.
4Productivity
If the polishing process continues without interruption, then productivity is maintained, but abrasive grains can enter the light passage and cause measurement errors
Solution Approach 1:
The invention introduces chemical liquid as an intermediary substance that mediates between the polishing process and the optical monitoring system. The chemical liquid is supplied into the light passage to dissolve and remove abrasive grains, allowing the polishing process to continue uninterrupted while maintaining measurement precision.
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
The method effectively removes abrasive grains, allowing the optical surface-monitoring device to accurately detect substrate conditions without the need for frequent component replacement, maintaining the light passage's integrity and operational efficiency.
Implementation Method 1
supplying a chemical liquid into the light passage when the substrate is not present on the polishing pad to remove the abrasive grains adhering to the light passage by the chemical liquid
Implementation Method 2
supplying a drying gas into the light passage to dry the light passage
Data Source
AI summary
A cleaning method capable of removing abrasive grains adhering to a light passage provided in a polishing table is disclosed. The cleaning method includes: while supplying slurry containing abrasive grains onto a polishing pad supported by a polishing table, placing a substrate in sliding contact with the polishing pad to polish the substrate; during polishing of the substrate, directing light to the substrate through a light passage provided in the polishing table, and causing reflected light from the substrate to pass through the light passage; removing the polished substrate from the polishing pad; and supplying a chemical liquid into the light passage when the substrate is not present on the polishing pad to remove the abrasive grains adhering to the light passage by the chemical liquid.