Wafer Defect Detection Dual-Path System for Repeater Sensitivity
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Solution Overview
Problem
Conventional wafer defect detection systems face challenges in detecting repeater defects with high sensitivity while maintaining throughput and distinguishing between true and false repeaters, especially in identifying haze defects associated with mask faults.
Innovation Solution
A dual-path defect detection system that performs a single scan using a first defect detection path for random defects and a second weaker path for repeater detection, generating separate maps and employing filter cascades with lower thresholds to enhance sensitivity and purify repeaters, while maintaining throughput and identifying repeaters with high resolution and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single scan is used for both random defect detection and repeater defect detection, then throughput is maintained, but detection sensitivity for repeater defects cannot be substantially increased
Solution Approach 1:
The defect detection system is divided into two separate detection paths: a first defect detection path for random defects and a second weaker defect detection path for repeater defects. This segmentation allows each path to be optimized independently - the first path maintains high sensitivity for random defects while the second path uses lower thresholds to detect subtle repeater defects, all within a single scan without compromising throughput.
2Measurement precision
If higher sensitivity detection is applied to identify repeater defects, then detection precision improves, but false alarm rate increases making it difficult to distinguish true repeaters from false repeaters
Solution Approach 1:
Different detection thresholds and filtering criteria are applied locally to different detection paths. The second defect detection path uses lower thresholds specifically optimized for repeater defects, while the first path uses higher thresholds for random defects. This local quality differentiation allows high sensitivity detection of repeaters while maintaining overall system reliability through path-specific optimization.
Solution Approach 2:
The system performs preliminary defect detection using the first detection path to identify candidate defects, then applies repeater analysis filters to these candidates. This preliminary action allows the system to focus subsequent high-sensitivity detection only on relevant candidates, reducing false alarms while maintaining high detection precision for true repeaters.
3Device complexity
If conventional repeater analysis is performed on the final defect map, then processing is simplified, but detection sensitivity for repeater defects remains limited by inspection sensitivity
Solution Approach 1:
The system dynamically adjusts detection thresholds and path selection based on the defect type being sought. The second defect detection path operates with lower thresholds specifically for repeater detection, and the system dynamically merges results from both paths. This dynamic approach enables high-sensitivity repeater detection without the complexity of completely redesigning the processing pipeline.
Data Source
AI summary
Random defects and repeaters accommodated on a wafer are detected using slice information obtained by scanning a plurality of wafer slices; analyzing defect information using a first set of filters selected to detect random defects, thereby generating a first set of defects per slice, analyzing the defect information using a second set of filters selected to detect repeaters, thereby providing a second set of defects per slice; analyzing a plurality of the second sets of defects per slice using a third set of filters selected to detect repeater families, thereby providing a set of repeaters per wafer; and optionally combining the set of repeaters per wafer with a plurality of the first sets of defects per slice, thereby generating one or more defect maps indicative of random defects and/or repeaters.