Wafer Surface Feature Detection Using Local Phase Unwrapping
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Solution Overview
Problem
Existing wafer inspection tools cannot detect the height or depth of surface defects, limiting their ability to provide comprehensive defect information.
Innovation Solution
The method involves acquiring intensity frames of a wafer surface, extracting amplitude and phase maps, and using local one-dimensional or two-dimensional phase unwrapping techniques to detect and quantify defects, providing height and depth information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase unwrapping is used, then defect detection can be performed, but errors are introduced that reduce measurement precision
Solution Approach 1:
The patent extracts and analyzes phase information locally within small windows across the wafer surface, rather than performing global phase unwrapping. This local extraction approach isolates defect regions and allows accurate height/depth measurement without the errors introduced by conventional global phase unwrapping algorithms that struggle with discontinuities.
Solution Approach 2:
The wafer surface is divided into multiple small local windows or regions. Each window is processed independently to extract amplitude and phase information. This segmentation allows the system to handle phase discontinuities at defect boundaries without propagating errors across the entire surface, thereby improving measurement precision.
2Loss of information
If existing inspection tools are used, then surface defects can be detected, but height and depth information is not provided
Solution Approach 1:
The patent changes the measurement parameters by extracting both amplitude and phase information from interferometric data. By analyzing the phase component locally, the system derives height and depth information that complements the traditional amplitude-based defect detection, providing comprehensive three-dimensional defect characterization.
Solution Approach 2:
The inspection system transitions from two-dimensional surface mapping to three-dimensional defect characterization by incorporating phase information. The local phase analysis adds the height/depth dimension to defect measurement, enabling quantification of defect severity in addition to lateral positioning.
3Measurement precision
If conventional inspection methods are used, then defect areas can be classified, but comprehensive defect characterization is limited
Solution Approach 1:
The patent replaces complex mechanical measurement systems with optical interferometry and computational analysis. By using light interference patterns and mathematical phase extraction, the system achieves precise height and depth measurement without mechanical contact, simplifying the measurement process while improving accuracy.
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 enhances defect detection and quantification capabilities by avoiding errors associated with conventional phase unwrapping, allowing for accurate measurement of surface defects and their characteristics.
Implementation Method 1
acquiring a set of intensity frames of a surface of the wafer
Data Source
AI summary
Interferometer systems and methods for providing improved defect detection and quantification are disclosed. The systems and methods in accordance with the present disclosure may detect surface defects on patterned or bare wafer surfaces and subsequently quantify them. In certain embodiments in accordance with the present disclosure, amplitude maps of the wafer surfaces are obtained and are utilized in addition/alternative to phase maps for wafer surface feature detection. Furthermore, local one-dimensional and/or two-dimensional unwrapping techniques are also disclosed and are utilized in certain embodiments in accordance with the present disclosure to provide height and depth information of the detected defects, further improving the detection capabilities of the measurement systems.