Wafer Repeater Defect Detection via Cell-to-Cell Image Comparison
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Solution Overview
Problem
Current wafer inspection methods face challenges in detecting repeater defects in array regions due to high noise interference, which reduces sensitivity and accuracy, especially when using standard die images that may not adequately represent wafer noise sources.
Innovation Solution
A computer-implemented method that generates test images and reference images from frame images scanned by an inspection system, using robust averaging and median image techniques to enhance the signal-to-noise ratio and suppress noise, allowing for cell-to-cell comparison to detect defects with higher sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If standard die images are used for inspection, then the inspection process is simple, but wafer-to-wafer noise and die-to-die noise interfere with defect detection and decrease sensitivity
Solution Approach 1:
The patent segments the array region into multiple individual cell images that can be independently analyzed. By dividing the wafer into discrete cells and comparing each cell against its own historical data rather than using a single standard die image, the method eliminates both wafer-to-wafer noise and die-to-die noise while maintaining operational simplicity.
Solution Approach 2:
The patent performs preliminary action by acquiring and storing historical cell image data before the actual defect detection process. This pre-acquired data serves as a noise-free reference that enables sensitive defect detection without requiring complex real-time noise filtering during inspection.
2Device complexity
If standard die images are used for inspection, then the process is straightforward, but noise interference decreases the sensitivity of defect detection
Solution Approach 1:
The patent segments the array region into multiple individual cell images that can be independently analyzed. By dividing the wafer into discrete cells and comparing each cell against its own historical data rather than using a single standard die image, the method eliminates both wafer-to-wafer noise and die-to-die noise while maintaining operational simplicity.
Solution Approach 2:
The patent creates copies of cell images from different wafers and time periods to build a historical database. These copied images serve as reference data for comparison, enabling sensitive defect detection through statistical analysis without requiring complex real-time processing during inspection.
3Ease of operation
If design data is used to generate standard die images, then the inspection process is simplified, but the standard die image may not adequately represent noise sources on the wafer
Solution Approach 1:
The patent enables each cell to serve itself by comparing its own historical data against itself. This self-service approach eliminates the need for external standard die images that may not represent actual wafer noise, while maintaining the simplicity of the inspection process through automated self-comparison algorithms.
Solution Approach 2:
The patent creates copies of cell images from different wafers and time periods to build a historical database. These copied images serve as reference data for comparison, enabling sensitive defect detection through statistical analysis without requiring complex real-time processing during inspection.
4Device complexity
If die-to-die comparison inspection is used, then the process is straightforward, but defects on all dies cancel each other resulting in weak or no signal from the defect
Solution Approach 1:
The patent segments the array region into multiple individual cell images that can be independently analyzed. By dividing the wafer into discrete cells and comparing each cell against its own historical data rather than using a single standard die image, the method eliminates both wafer-to-wafer noise and die-to-die noise while maintaining operational simplicity.
Solution Approach 2:
The patent performs preliminary action by acquiring and storing historical cell image data before the actual defect detection process. This pre-acquired data serves as a noise-free reference that enables sensitive defect detection without requiring complex real-time noise filtering during inspection.
Data Source
AI summary
Systems and methods for detecting defects on a wafer are provided. One method includes generating test image(s) for at least a portion of an array region in die(s) on a wafer from frame image(s) generated by scanning the wafer with an inspection system. The method also includes generating a reference image for cell(s) in the array region from frame images generated by the scanning of the wafer. In addition, the method includes determining difference image(s) for at least one cell in the at least the portion of the array region in the die(s) by subtracting the reference image from portion(s) of the test image(s) corresponding to the at least one cell. The method further includes detecting defects on the wafer in the at least one cell based on the difference image(s).