Polishing Apparatus Optical Sensor Gas-Liquid Cycling
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Solution Overview
Problem
Existing polishing processes for semiconductor wafers face challenges in accurately measuring film thickness without affecting the polishing rate, as the slurry can become diluted with pure water, leading to a local decrease in polishing efficiency.
Innovation Solution
A polishing apparatus and method that incorporates a light source, illuminating and light-receiving fibers, a spectrometer, and a processor to analyze reflected light for film thickness measurement, with a liquid and gas supply system to prevent slurry dilution by alternately bringing gas and liquid into contact with the fibers, ensuring accurate thickness measurement without impacting the polishing rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure water is supplied to the optical sensor during polishing, then the optical sensor is protected from slurry adhesion, but the slurry becomes diluted causing a local decrease in polishing rate
Solution Approach 1:
The system alternates between gas supply mode and liquid supply mode in periodic cycles. During gas supply, the optical sensor is protected from slurry adhesion. During liquid supply, the slurry is refreshed to maintain polishing rate. This periodic switching resolves the contradiction by providing protection when needed and polishing efficiency when needed.
Solution Approach 2:
The system dynamically switches the supply medium from gas to liquid and back based on the polishing process stage. The operation controller adjusts the supply mode in real-time, making the system adaptive to different operational requirements rather than using a static supply method.
2Productivity
If gas is supplied to prevent slurry dilution, then polishing rate is maintained, but optical measurement accuracy may be affected by gas interference
Solution Approach 1:
The system performs optical measurements during the liquid supply phase when the optical path is clear of gas interference. The periodic switching allows measurement at optimal conditions while maintaining gas supply during polishing phases to prevent slurry dilution.
Solution Approach 2:
The liquid medium acts as an intermediary that allows both optical transmission for measurement and prevents slurry adhesion to the optical sensor. During liquid supply phases, the liquid provides a clear optical path for accurate film thickness measurement while also protecting the sensor.
3Measurement precision
If liquid is continuously supplied to the optical sensor, then optical measurement is maintained, but slurry dilution occurs reducing polishing efficiency
Solution Approach 1:
Instead of continuous liquid supply, the system uses periodic liquid supply pulses synchronized with the polishing process. Liquid is supplied briefly for measurement and sensor protection, then gas takes over to prevent dilution during the polishing phase, optimizing both measurement and polishing efficiency.
Solution Approach 2:
The supply system dynamically adjusts between liquid and gas based on real-time process requirements. The operation controller monitors the polishing state and switches supply modes accordingly, making the system responsive to actual needs rather than using continuous supply.
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
Enables high-accuracy film thickness measurement during polishing without reducing the polishing rate, as the gas prevents slurry dilution and the liquid maintains cleanliness and prevents evaporation, ensuring precise control over the polishing process.
Implementation Method 1
directing light from an illuminating fiber to the wafer and receiving reflected light from the wafer with a light-receiving fiber
Implementation Method 2
an illuminating fiber coupled to the light source and having a distal end disposed in a flow passage formed in the polishing table; a light-receiving fiber coupled to the spectrometer and having a distal end disposed in the flow passage
Implementation Method 3
a spectrometer configured to resolve reflected light from the wafer in accordance with wavelength and measure an intensity of the reflected light at each of the wavelengths
Implementation Method 4
bringing a liquid and a gas alternately into contact with the distal end of the illuminating fiber and the distal end of the light-receiving fiber during polishing of the wafer
Data Source
AI summary
A polishing apparatus which can measure a film thickness with high accuracy without affecting a polishing rate of a wafer is disclosed. The polishing apparatus includes: a polishing head configured to press a wafer against a polishing pad; an illuminating fiber having a distal end disposed in a flow passage formed in the polishing table; a spectrometer configured to resolve reflected light from the wafer in accordance with wavelength and measure an intensity of the reflected light at each of the wavelengths; a light-receiving fiber having a distal end disposed in the flow passage; a liquid supply line communicating with the flow passage; a gas supply line communicating with the flow passage; a liquid supply valve attached to the liquid supply line; a gas supply valve attached to the gas supply line; and an operation controller configured to control operations of the liquid supply valve and the gas supply valve.