Spectra Contour Plot Monitoring for CMP Endpoint Detection
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in determining the polishing endpoint due to variations in slurry distribution, polishing pad condition, relative speed, and load on the substrate, making it difficult to determine when a substrate layer has been planarized to a desired flatness or thickness.
Innovation Solution
A computer program product and method that measure sequences of spectra of light reflected from the substrate during polishing, identify specific spectral features, and fit functions to determine a polishing endpoint or adjust the polishing rate based on changes in these features, allowing for more precise control of the polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polishing time is used to determine endpoint, then the process is simple to control, but variations in polishing conditions cause inaccurate endpoint determination
Solution Approach 1:
The patent replaces the mechanical/time-based endpoint determination method with an optical measurement system. A spectrometer measures reflected light spectra from the substrate during polishing, and spectral features are analyzed to determine the polishing endpoint. This substitution of optical measurement for time-based control resolves the contradiction by providing accurate endpoint detection independent of polishing condition variations.
Solution Approach 2:
The patent implements real-time feedback by continuously monitoring spectral features during polishing. The system measures spectra at multiple wavelengths, tracks changes in spectral features (such as peak positions or intensities), and uses this feedback information to determine when the polishing endpoint is reached. This feedback mechanism enables accurate endpoint determination that adapts to actual polishing conditions rather than relying on predetermined time schedules.
2Measurement precision
If spectral analysis is used to determine polishing endpoint, then endpoint accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent employs a multi-wavelength light source and spectrometer system that can analyze multiple spectral features simultaneously. This multi-functional approach allows the same optical system to monitor various polishing parameters (film thickness, material composition, surface characteristics) through different spectral features, improving endpoint accuracy without requiring multiple separate measurement systems.
Solution Approach 2:
The patent extracts specific diagnostic information from the full spectrum by focusing on particular spectral features such as peak positions, intensities, or wavelengths characteristic of the being-polished material. By extracting and analyzing only the relevant spectral features rather than processing the entire spectrum, the system achieves accurate endpoint detection with reduced computational complexity and simpler data processing requirements.
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 enables more accurate determination of the polishing endpoint and adjustment of polishing rates, leading to greater uniformity and consistency in substrate planarization across batches, reducing variability and improving the reliability of the CMP process.
Implementation Method 1
measure a sequence of spectra of light reflected from a substrate while the substrate is being polished
Data Source
AI summary
A method to assist in identifying a spectral feature and a characteristic of the selected spectral feature to monitor during polishing includes polishing a test substrate and measuring a sequence of spectra of light reflected from a substrate while the substrate is being polished, where at least some of the spectra of the sequence differ due to material being removed during the polishing. The sequence of spectra are visually displayed as a contour plot.