Charged Particle Beam Drift Correction for Scan Position Accuracy
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Solution Overview
Problem
Charged particle beam apparatuses face challenges in maintaining high positional accuracy during scanning due to specimen and optical system drifts, making it difficult to set an appropriate frequency for correcting electron probe irradiation positions.
Innovation Solution
A control unit in the charged particle beam apparatus performs correction processing by comparing reference images to criterion images to determine drift amounts and adjusts the frequency of correction processing based on these drifts, allowing for precise alignment of the electron probe irradiation position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electron probe irradiation position is corrected frequently, then the positional accuracy is improved, but the analysis time increases
Solution Approach 1:
The patent implements dynamic adjustment of correction frequency based on real-time drift detection. The system initially performs corrections at a first frequency, then detects drift amounts between corrections, and switches to a second frequency based on whether the drift exceeds a threshold. This dynamic approach optimizes the balance between positional accuracy and analysis time.
Solution Approach 2:
The system uses feedback from drift detection to control correction frequency. By monitoring the drift amount between corrections and comparing it to a threshold value, the system adjusts the correction frequency accordingly. This feedback mechanism ensures corrections are performed appropriately based on actual drift conditions rather than using a fixed frequency.
2Ease of operation
If the electron probe irradiation position is corrected using a fixed frequency, then the operation is simple, but the positional accuracy deteriorates when drift is unpredictable
Solution Approach 1:
The system performs self-adjustment by automatically detecting drift amounts and determining appropriate correction frequencies without user intervention. The control unit autonomously monitors drift between corrections, compares it to thresholds, and switches frequencies as needed, eliminating the need for users to manually predict or set correction frequencies based on uncertain drift conditions.
Solution Approach 2:
The feedback mechanism enables the system to automatically adapt to unpredictable drift conditions. By continuously monitoring drift amounts and using this information to adjust correction frequency, the system maintains high positional accuracy without requiring complex user input or prediction of drift behavior.
3Productivity
If the correction frequency is set too low, then the analysis time is reduced, but the positional accuracy deteriorates
Solution Approach 1:
The system dynamically adjusts correction frequency based on actual drift conditions rather than using a fixed low frequency. By initially using a higher first frequency and then switching to a lower second frequency based on drift detection, the system maintains positional accuracy while optimizing analysis speed according to real-time conditions.
Solution Approach 2:
The system changes the correction frequency parameter based on drift amount detection. When drift exceeds a threshold, the system switches from a first frequency to a second frequency, effectively adapting the correction rate to match actual specimen and optical system stability conditions, thereby optimizing both accuracy and speed.
Data Source
AI summary
A charged particle beam apparatus that forms a probe with a charged particle beam and scans a specimen with the probe to acquire a scanning image. The charged particle beam apparatus includes an optical system for scanning the specimen with the probe; a detector that detects a signal generated from the specimen through the scanning of the specimen with the probe; and a control unit that controls the optical system. The control unit performs correction processing of acquiring a reference image obtained by the scanning of the specimen with the probe, comparing the reference image to a criterion image to determine a drift amount, and correcting a displacement of an irradiation position with the probe on the specimen based on the drift amount; and processing of setting a frequency with which the correction processing is to be performed based on the drift amount.