Polishing End Point Detection Using Brewster Angle Polarization
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Solution Overview
Problem
Current methods for detecting the polishing end point of a multilayer structure, such as spectroscopic and laser-based techniques, face challenges in accurately determining the end point due to similar interference colors and periodic changes in reflected light intensity, leading to potential over-polishing and complexity in ellipsometry analysis.
Innovation Solution
A method and apparatus utilizing dual lights incident at Brewster's angles specific to each layer, analyzing brightness and saturation changes through a polarizing filter to determine the polishing end point without complex thickness and refractive index analysis, and an ellipsometry approach monitoring phase difference and amplitude ratio changes to quickly detect the end point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectroscopic polishing end point detection is used to monitor interference color, then the polishing end point can be detected, but accurate detection is difficult when layers have similar refractive indices
Solution Approach 1:
The invention changes the detection parameters from monitoring interference color (spectroscopic method) to monitoring brightness and saturation at specific Brewster angles. This parameter change enables reliable detection even when layers have similar refractive indices, as the polarization-based method detects brightness changes rather than relying on interference color differences.
Solution Approach 2:
The invention applies local quality by using different detection angles (first Brewster angle for upper layer, second Brewster angle for lower layer) to detect different layers. Each angle is optimized for detecting the interface at a specific depth, allowing precise localization of the polishing end point even when material properties are similar.
2Ease of manufacture
If laser light is used to detect polishing end point, then the method is simple, but periodic intensity changes prevent accurate detection
Solution Approach 1:
The invention changes from using monochromatic laser light to using polarized light at Brewster angles. This parameter change eliminates the periodic intensity variation problem inherent in laser-based methods, as the polarization-based detection at Brewster angles produces monotonic brightness changes that accurately indicate the polishing end point.
Solution Approach 2:
The invention introduces polarization state as an intermediary parameter between the light source and the detection process. By using polarized light and detecting brightness changes through a polarizing filter at Brewster angles, the system converts the complex periodic interference pattern into a simple monotonic brightness change that is easy to detect and interpret.
3Measurement precision
If ellipsometry is used to determine film thickness and refractive index, then accurate film characterization is achieved, but the analysis process is complex and time-consuming
Solution Approach 1:
The invention extracts only the essential information needed for polishing end point detection (brightness and saturation changes at Brewster angles) rather than performing full ellipsometric analysis of film thickness and refractive index. This extraction approach maintains sufficient detection accuracy while dramatically simplifying the analysis process and enabling real-time monitoring.
Solution Approach 2:
The invention applies partial action by performing only the necessary measurements (brightness and saturation at specific angles) rather than complete ellipsometric characterization. This partial measurement approach provides sufficient information for polishing end point detection without the complexity of full film parameter analysis.
4Productivity
If conventional polishing end point detection is used, then the process can be monitored, but over-polishing occurs due to detection delays
Solution Approach 1:
The invention implements real-time feedback by continuously monitoring brightness and saturation changes during polishing and immediately detecting the end point when the upper layer is removed. This feedback mechanism allows for precise control of polishing depth and prevents over-polishing, while the simplified detection method enables rapid response.
Solution Approach 2:
The invention performs preliminary action by pre-calculating the Brewster angles for the specific material layers involved. This preliminary setup enables the detection system to immediately recognize the polishing end point without requiring complex real-time analysis, thus preventing detection delays and over-polishing.
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 accurate and rapid detection of the polishing end point, preventing over-polishing and simplifying the analysis process by focusing on relative changes in brightness and saturation, and eliminating the need for complex refractive index and thickness calculations.
Implementation Method 1
emitting a first light and a second light to a surface of the workpiece at a first angle of incidence and a second angle of incidence, respectively, receiving the first light and the second light reflected from the surface through a polarizing filter
Implementation Method 2
receiving the first light and the second light reflected from the surface through a polarizing filter
Implementation Method 3
receiving the first light and the second light reflected from the surface
Implementation Method 4
Ellipsometry (polarization analysis) is also known as a method of detecting a polishing end point of a film. This ellipsometry is a technique of determining an index of refraction and a thickness of a film. Ellipsometry applies a linearly-polarized light to a film on a substrate, and measures a phase difference Δ between p-polarized light and s-polarized light in the reflected light from the film and an amplitude ratio ψ of the p-polarized light to the s-polarized light
Data Source
AI summary
A polishing end point detection method is to detect a polishing end point of a workpiece having a multilayer structure. The method is performed by emitting a first light and a second light to a surface of the workpiece at a first angle of incidence and a second angle of incidence, respectively, receiving the first light and the second light reflected from the surface through a polarizing filter, performing a first analyzing process of analyzing a brightness and a saturation of the surface from the first light received, performing a second analyzing process of analyzing a brightness and a saturation of the surface from the second light received, and determining removal of the upper layer based on changes in the brightness and the saturation of the surface.