Charged Particle Beam Drift Correction for Precise Probe Scanning
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Solution Overview
Problem
In charged particle beam apparatuses, such as scanning electron microscopes, specimen drift due to temperature unevenness and optical system fluctuations leads to inaccurate scanning images, making precise correction of the electron probe's irradiation position challenging, especially at high magnifications.
Innovation Solution
A control unit that acquires a reference image, compares it to a criterion image to determine the drift amount, and adjusts the electron probe's position accordingly, while dynamically setting the frequency of correction processing based on the drift amount to maintain positional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electron probe irradiation position is corrected frequently to maintain positional accuracy, then the scanning image quality is improved, but the analysis time is increased due to repeated correction processing
Solution Approach 1:
The patent applies dynamics by making the correction frequency adaptive rather than fixed. The control unit dynamically adjusts the correction interval based on the actual drift amount measured during analysis. When drift is large, correction frequency increases; when drift is small, correction frequency decreases. This dynamic adjustment resolves the contradiction by optimizing the balance between positional accuracy and analysis time in real-time.
Solution Approach 2:
The patent implements feedback by continuously monitoring the drift amount and using this information to adjust the correction frequency. The control unit measures the drift between the reference image and current image, then determines the appropriate correction frequency based on this feedback. This closed-loop control ensures that corrections are performed only when necessary, maintaining positional accuracy while minimizing analysis time.
2Measurement precision
If the correction frequency is set high to account for unpredictable drift, then positional accuracy is maintained, but the productivity is reduced due to frequent interruptions
Solution Approach 1:
The patent changes the parameter of correction frequency from a fixed user-defined value to a dynamically adjusted value based on actual drift conditions. The control unit modifies the correction frequency parameter in real-time according to the measured drift amount, allowing the system to adapt to varying stability conditions without requiring conservative high-frequency corrections, thus improving productivity while maintaining accuracy.
Solution Approach 2:
The system performs self-service by automatically determining the appropriate correction frequency based on its own measurements of drift. The control unit independently assesses the drift amount and adjusts the correction schedule without user intervention, enabling the system to optimize its own performance and avoid unnecessary corrections that would reduce productivity.
3Productivity
If the correction frequency is set low to maintain productivity, then analysis efficiency is improved, but the measurement precision deteriorates when drift occurs
Solution Approach 1:
The patent uses feedback to monitor drift and trigger corrections only when necessary. By continuously measuring the drift amount and comparing it against thresholds, the system determines when correction is needed, ensuring positional accuracy is maintained without performing unnecessary corrections that would reduce productivity. This feedback mechanism resolves the contradiction between efficiency and precision.
Solution Approach 2:
The system dynamically adjusts correction frequency based on actual drift conditions rather than using a fixed low frequency. When drift exceeds acceptable levels, the correction frequency increases automatically; when drift is minimal, the frequency remains low to maintain productivity. This dynamic behavior ensures both efficiency and precision are optimized according to real-time conditions.
Data Source
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AI summary
A charged particle beam apparatus (100) that forms a probe with a charged particle beam and scans a specimen (S) with the probe to acquire a scanning image, the charged particle beam apparatus (100) including: an optical system (20) for scanning the specimen (S) with the probe; a detector (70) that detects a signal generated from the specimen (S) through the scanning of the specimen (S) with the probe; and a control unit (80) that controls the optical system (20), the control unit (80) performing: correction processing of acquiring a reference image obtained by the scanning of the specimen (S) with the probe, comparing the reference image to a criterion image to determine a drift amount (D), and correcting a displacement of an irradiation position with the probe on the specimen (S) based on the drift amount (D); and processing of setting a frequency with which the correction processing is to be performed based on the drift amount (D).