Electron Beam Inspection Apparatus Using Adaptive Thresholds for Semiconductor Defect Detection
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Solution Overview
Problem
Current electron beam inspection methods detect subtle defects excessively in regions outside critical points due to the lack of specified critical point information, leading to false positives and difficulties in identifying true defects in semiconductor wafer inspections.
Innovation Solution
An electron beam inspection apparatus and method that stores design substrate pattern images, acquires secondary electron images, and uses analyzing and comparison circuits to specify feature points and adjust threshold values based on position information, allowing for precise comparison between design and actual patterns to inhibit false defect detection in non-critical regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a strict determine threshold value is used for die-to-database inspection across the entire inspection region, then critical points can be reliably detected, but subtle defects are excessively detected in non-critical regions leading to false positives
Solution Approach 1:
The patent applies local quality by setting different determine threshold values for different regions of the inspection target. Specifically, a first (stricter) threshold is applied to critical point regions and a second (looser) threshold to non-critical regions. This resolves the contradiction by allowing high detection accuracy in critical areas while reducing false positives in non-critical areas, as each region is evaluated with an appropriate threshold level.
Solution Approach 2:
The inspection region is segmented into multiple types based on criticality: critical point regions, non-critical regions, and intermediate regions. This segmentation allows the system to apply different determination strategies to different segments, thereby achieving both high precision in critical areas and low false positive rates in non-critical areas simultaneously.
2Ease of manufacture
If die-to-database inspection is performed across the entire inspection region with uniform threshold, then all regions are inspected consistently, but critical point information is lost and subtle defects are over-detected
Solution Approach 1:
The patent applies preliminary action by performing critical point extraction and region classification before the actual defect determination process. The system first identifies critical points from design data, classifies inspection regions based on these critical points, and then applies appropriate threshold values accordingly. This preliminary preparation preserves critical point information and enables differentiated inspection without complicating the overall manufacturing process.
3Reliability
If the determine threshold value is varied by region, then false defect detection is reduced in non-critical regions, but the inspection system becomes more complex
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the determine threshold value parameter based on the classified region type. The system automatically selects appropriate threshold values (first threshold for critical regions, second threshold for non-critical regions) based on the inspection target's region classification. This parameter adaptation reduces false defect detection while maintaining manageable system complexity through automated threshold selection.
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 effectively reduces false defect detection in non-critical regions while enabling accurate identification of critical points, improving the efficiency and accuracy of semiconductor wafer inspections by using design pattern information to set appropriate threshold values.
Implementation Method 1
a secondary electron image acquisition mechanism that acquires a secondary electron image by secondary electrons including a reflected electron generated by irradiating the semiconductor substrate with an electron beam
Data Source
AI summary
An electron beam inspection apparatus includes an analyzing circuit to input design pattern data of design pattern of a semiconductor element, and specify a position of a pattern portion including a feature point, which has previously been set, by analyzing the design pattern data; and a comparison circuit to input information on a specified position of the pattern portion including the feature point, and determine by comparing a secondary electron image and a design substrate pattern image of a region corresponding to the secondary electron image while varying a determine threshold value for the pattern portion including the feature point by using the information.