CMP Film Thickness Measurement Using 3D Reflectance Spectra
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) techniques face challenges in accurately determining film thickness due to variations in the spectrum of reflected light from substrates, caused by disturbances and differences in underlying structures, leading to inaccuracies in film thickness measurement.
Innovation Solution
A method and apparatus that utilize three-dimensional data containing time-series spectra to determine film thickness by comparing it with reference data, minimizing differences and using an artificial intelligence-based film-thickness calculation model to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical film-thickness measuring devices are used to determine film thickness from the spectrum of reflected light, then the measurement process is simple and quick, but the measurement precision deteriorates due to spectrum variations caused by disturbances and underlying structure differences
Solution Approach 1:
The patent transforms the conventional two-dimensional spectrum data (intensity vs. wavelength) into three-dimensional data by adding the time dimension. Multiple spectra are acquired during the polishing process and arranged along the polishing time axis, creating a 3D dataset that captures the evolution of spectral features. This dimensional expansion enables more robust film thickness determination by utilizing temporal information to distinguish signal variations from noise.
Solution Approach 2:
The patent performs preliminary acquisition and arrangement of multiple spectra during the polishing process before final film thickness determination. By collecting spectral data at multiple time points and organizing them into 3D data structures, the system prepares comprehensive input data that enhances the accuracy of subsequent film thickness calculations, rather than relying on a single instantaneous spectrum.
2Measurement precision
If multiple reference spectra are compared to determine film thickness, then the measurement process becomes more thorough, but the loss of time increases due to multiple calculations
Solution Approach 1:
The patent creates a reference 3D dataset by arranging multiple reference spectra (obtained at different film thicknesses) along the polishing time axis, mirroring the structure of the measurement 3D data. This reference copying approach enables direct comparison and pattern matching between measurement data and known reference states, streamlining the determination process while maintaining high accuracy through comprehensive spectral evolution analysis.
3Reliability
If the spectrum of reflected light is used to determine film thickness, then the measurement is non-contact and quick, but reliability deteriorates due to spectrum variations from slurry, electrical noise, and optical noise
Solution Approach 1:
The system performs preliminary acquisition of multiple spectra during the polishing process and arranges them into 3D data structures before final analysis. This preliminary data collection captures the temporal evolution of spectral features, enabling the system to distinguish between genuine film thickness changes and transient noise from slurry, electrical interference, or optical disturbances.
Solution Approach 2:
The patent implements a feedback mechanism where the 3D spectral data is continuously compared with reference 3D spectra corresponding to different film thicknesses. By monitoring the evolution of spectral patterns over time and comparing them against known reference evolution patterns, the system provides feedback that enables accurate film thickness determination while compensating for various sources of noise and disturbance.
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 reduces the influence of spectrum variations, enabling accurate film thickness determination by considering the evolution of spectra over time and underlying structures, thus enhancing the precision of CMP processes.
Implementation Method 1
analyze a spectrum of reflected light from the substrate to determine a film thickness of the substrate
Data Source
AI summary
A substrate polishing method capable of reducing an influence of variation in spectrum of reflected light from a substrate, such as a wafer, and determining an accurate film thickness is disclosed. The method includes: polishing a surface of a substrate by pressing the substrate against a polishing pad on a rotating polishing table; producing a spectrum of reflected light from the surface of the substrate each time the polishing table makes one rotation; creating a three-dimensional data containing a plurality of spectra arranged along polishing time; and determining a film thickness of the substrate based on the three-dimensional data.