Optical Polishing Endpoint Detection Wavelength Selection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical polishing end point detection methods face challenges in accurately monitoring the thickness of transparent insulating films during polishing, particularly when the film thickness is small, and are prone to photocorrosion, leading to inconsistent results and reduced yield due to variations in initial film thickness and underlying layer convexities.
Innovation Solution
A method and apparatus for selecting optimal wavelengths of light for optical polishing end point detection by calculating relative reflectances, identifying local maximum and minimum points, and plotting coordinates to determine the most effective wavelengths for monitoring the polishing process, which helps in accurately detecting the polishing end point and preventing photocorrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical polishing end point detection is used to monitor film thickness during polishing, then polishing progress can be monitored, but photocorrosion occurs leading to inconsistent results and reduced yield
Solution Approach 1:
The patent changes the wavelength parameter of the light used in optical polishing end point detection. By selecting specific wavelengths from the reflected light spectrum, the method avoids wavelengths that cause photocorrosion while maintaining detection precision. The system calculates relative reflectances at multiple wavelengths and identifies optimal wavelengths for detection based on local maximum and minimum points in the spectral data.
2Measurement precision
If light is applied to detect polishing endpoint, then film thickness can be monitored, but variations in initial film thickness and underlying layer convexities cause inconsistent results
Solution Approach 1:
The patent performs preliminary analysis of the reflected light spectrum before the actual polishing endpoint detection. By calculating relative reflectances at multiple wavelengths and identifying local maximum and minimum points in advance, the system establishes a reference spectral pattern that accounts for variations in initial film thickness and underlying layer characteristics. This preliminary spectral analysis enables the system to adapt to different substrate conditions.
Solution Approach 2:
The system continuously monitors the reflected light spectrum during polishing and compares it against the preliminary spectral pattern. By tracking changes in relative reflectance at selected wavelengths and identifying when local maximum or minimum points occur, the system provides real-time feedback on polishing progress. This feedback mechanism compensates for initial variations in film thickness and underlying layer convexities.
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 precise monitoring of the polishing process, reduces photocorrosion risks, and improves the accuracy of polishing end point detection, leading to consistent film thickness and increased yield by selecting wavelengths that optimize the detection of local maximum and minimum points.
Implementation Method 1
apply light to a surface of a substrate having a film and receive reflected light from the substrate
Implementation Method 2
The spectroscope decomposes the reflected light from the substrate according to wavelength and measures reflection intensity at each wavelength
Data Source
AI summary
A method of polishing end point detection includes polishing a surface of a substrate; applying light to the surface of the substrate and receiving reflected light from the substrate during the polishing of the substrate; measuring reflection intensities of the reflected light at respective wavelengths; creating a spectral profile indicating a relationship between reflection intensity and wavelength from the reflection intensities measured; extracting at least one extremal point indicating extremum of the reflection intensities from the spectral profile; during polishing of the substrate, repeating the creating of the spectral profile and the extracting of the at least one extremal point to obtain plural spectral profiles and plural extremal points; and detecting the polishing end point based on an amount of relative change in the extremal point between the plural spectral profiles.