Multi-beam SEM Gray Level Comparison for Beam Abnormality Detection
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Solution Overview
Problem
Multi-beam SEM devices face challenges in efficiently detecting and managing abnormalities in electron beams during inspection processes, leading to potential erroneous results due to increased complexity and the need for separate adjustment and management processes, which can compromise image acquisition speed and sensitivity.
Innovation Solution
A defect inspection method that compares the distribution of gray level values from SEM images acquired using multiple electron beams to identify abnormalities in real-time, allowing for simultaneous beam abnormality detection and correction during the inspection process, thereby improving image accuracy and measurement reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-beam SEM devices are used to simultaneously scan with multiple electron beams, then image acquisition speed is improved, but device complexity and difficulty in detecting beam abnormalities increase
Solution Approach 1:
The patent combines the beam abnormality detection function with the regular inspection process by using the same multiple electron beams for both purposes. The gray level comparison method integrates detection into the existing multi-beam scanning workflow, eliminating the need for separate detection procedures and reducing overall system complexity.
Solution Approach 2:
The system implements feedback by continuously comparing gray level values from multiple beams and automatically identifying abnormalities when differences exceed a threshold. This real-time feedback mechanism allows the system to self-diagnose beam issues without external intervention, simplifying the management of multi-beam operations.
2Reliability
If separate adjustment and management processes are implemented for electron beams, then beam abnormality detection capability is improved, but inspection speed and productivity deteriorate
Solution Approach 1:
The patent merges beam management and inspection functions into a single integrated process. By using the same electron beams to both inspect patterns and detect abnormalities through gray level comparison, the system eliminates separate management steps that would slow down production while maintaining reliable detection capability.
Solution Approach 2:
The system maintains continuous inspection speed by performing abnormality detection simultaneously with regular pattern scanning. The gray level comparison occurs in real-time during the inspection process, ensuring that beam management does not interrupt or slow down the productive inspection workflow.
3Measurement precision
If gray level comparison is performed across multiple beams, then measurement precision and image accuracy are improved, but processing time and complexity increase
Solution Approach 1:
The patent applies partial comparison by selecting specific gray level values (e.g., maximum, minimum, or specific percentile values) from the distribution for comparison rather than analyzing the entire gray level distribution. This selective approach maintains measurement precision while significantly reducing processing time and computational complexity.
Solution Approach 2:
The system performs preliminary sorting of gray level values to quickly identify representative values for comparison. By pre-organizing the data in sorted order, the system can rapidly extract comparison values without requiring complex real-time analysis, thus maintaining accuracy while minimizing processing time overhead.
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 method enables simultaneous beam abnormality detection and correction, enhancing the accuracy and speed of inspection images while maintaining the advantages of multi-beam SEM devices, such as high resolution and ability to detect electrical defects.
Implementation Method 1
scanning a plurality of patterns on a substrate with N charged particle beams and detecting secondary electrons respectively generated from each of the plurality of patterns to acquire N SEM images
Data Source
AI summary
A pattern inspection method includes scanning a plurality of patterns on a substrate with N charged particle beams and detecting secondary electrons respectively generated from each of the plurality of patterns to acquire N SEM images, determining a distribution of gray level values for each of the acquired N SEM images, selecting M gray levels from the distributions of the N gray levels, selecting a first gray level value from a first one of the M distributions, and comparing it to the corresponding first gray level value of the of the other M−1 distributions, and determining that an abnormality has occurred in the charged particle beam corresponding to the first one of the M distributions when the difference between the first value of the first one of the M distributions and the other M−1 distributions is greater than a predetermined threshold value.