Substrate Thickness Measurement via Multi-Angle Color Metrology
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Solution Overview
Problem
Current optical metrology techniques for determining the thickness of layers on substrates during chemical mechanical polishing (CMP) face challenges such as variations in material removal rates and computational complexity, leading to inaccuracies in endpoint detection and thickness measurement.
Innovation Solution
A system utilizing a color imaging system with multiple cameras capturing images at different angles of incidence, processing the images in a higher-dimensional color space to enhance thickness measurement accuracy and reliability, and using a controller to calculate thickness values based on color data from the images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional spectrographic or ellipsometric optical metrology systems are used to measure layer thickness, then measurement capability is provided, but computational complexity increases and measurement precision decreases due to variations in material removal rates
Solution Approach 1:
The patent applies color imaging to detect thickness variations by capturing color changes in the substrate layer during CMP polishing. The system uses color cameras to capture images at different angles of incidence, and thickness is determined by analyzing color data in a coordinate space, converting complex optical measurements into simpler color-based measurements that reduce computational requirements while maintaining measurement precision
Solution Approach 2:
The patent introduces multiple angles of incidence for light illumination to create additional measurement dimensions. By capturing images at different angles and analyzing color data in a multi-dimensional coordinate space, the system enhances measurement accuracy and compensates for variations in material removal rates without significantly increasing computational complexity
2Manufacturing precision
If polishing endpoint is determined merely as a function of polishing time, then process control is simplified, but manufacturing precision deteriorates due to variations in material removal rates
Solution Approach 1:
The patent implements real-time feedback control by continuously monitoring color changes in the substrate layer during CMP polishing. The system captures color images at different angles, analyzes the color data to determine current thickness, and uses this feedback information to dynamically adjust polishing parameters, ensuring precise endpoint detection that compensates for variations in material removal rates
Solution Approach 2:
The patent replaces time-based mechanical control with optical-based color imaging and analysis. Instead of relying on predetermined polishing times, the system uses color cameras and coordinate space analysis to optically detect thickness variations, substituting mechanical process control with a more precise optical measurement and control mechanism
3Measurement precision
If color imaging at multiple angles of incidence is used to improve thickness measurement accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent makes the color imaging system multi-functional by using the same color cameras and optical assembly to perform both thickness measurement and uniformity assessment. The system captures color images at multiple angles of incidence and processes the data through coordinate space analysis, enabling a single optical system to handle multiple measurement functions without proportionally increasing complexity
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
Improves the accuracy and reliability of thickness measurements, allowing for better control of polishing parameters and uniformity, with reduced computational load compared to traditional spectrographic methods.
Implementation Method 1
an optical assembly to capture a first color image of at least a portion of the substrate held by the support with light impinging the substrate at a first angle of incidence and a second color image of the at least a portion of the substrate held by the support with light impinging the substrate at a different second angle of incidence
Data Source
AI summary
A system for obtaining a measurement representative of a thickness of a layer on a substrate includes a support to hold a substrate, an optical assembly to capture two color images with light impinging the substrate at different angles of incidence, and a controller. The controller is configured to store a function that provides a value representative of a thickness as a function of position along a predetermined path in a coordinate space of at least four dimensions. For a pixel in the two color images, the controller determines a coordinate in the coordinate space from the color data, determines a position of a point on the predetermined path that is closest to the coordinate, and calculates a value representative of a thickness from the function and the position of the point on the predetermined path.