Charged-particle beam device field-of-view movement control
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Solution Overview
Problem
Charged-particle beam devices, such as scanning electron microscopes, face challenges in accurately moving the field-of-view over actual samples due to fluctuations in the magnetic field and hysteresis changes, affecting deflection accuracy and image quality, especially when dealing with fine patterns and high magnification.
Innovation Solution
A charged-particle beam device incorporating an objective lens, a field-of-view moving deflector, and a control device that adjusts the lens conditions and deflector signals based on acquired images of reference patterns to maintain focus and correct for magnetic field fluctuations, ensuring precise field-of-view movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image shift is performed using a deflector to move the scanning position, then field-of-view movement speed and precision are improved, but magnetic field fluctuations and hysteresis changes cause deflection accuracy to deteriorate
Solution Approach 1:
The patent implements feedback control by detecting the actual position of reference patterns after field-of-view movement and comparing it with the expected position. The deviation information is fed back to adjust subsequent deflection signals, compensating for magnetic field fluctuations and hysteresis effects. This closed-loop control ensures that the field-of-view movement precision is maintained despite environmental changes.
Solution Approach 2:
The patent dynamically adjusts deflection parameters based on detected position deviations. By changing the deflection signal parameters (such as voltage or current applied to the deflector) in response to measured errors, the system compensates for magnetic field instability and hysteresis, maintaining reliable deflection accuracy over time.
2Measurement precision
If the scanning position is moved by moving the stage, then the system structure is simple, but the field-of-view movement precision is insufficient compared to using a deflector
Solution Approach 1:
The patent divides the field-of-view movement function into two independent parts: stage movement for coarse positioning and deflector-based image shift for fine positioning. This segmentation allows each component to perform its optimal function - the stage provides stable mechanical support while the deflector delivers high-precision angular adjustment, achieving superior overall precision without excessive complexity.
Solution Approach 2:
The patent introduces a control system as an intermediary that coordinates between the stage and deflector. The control system processes position information, determines the appropriate combination of stage movement and image shift, and generates corresponding control signals. This intermediary manages the complexity by providing a unified control interface while leveraging the advantages of both positioning methods.
3Measurement precision
If image shift correction is performed based on pattern deviation, then field-of-view movement accuracy is improved, but the field-of-view may not be positioned at the appropriate position on actual samples
Solution Approach 1:
The patent implements self-service by using the actual sample or workpiece features as the reference for position correction. Instead of relying on separately fabricated reference patterns that may not represent the actual sample characteristics, the system detects features directly from the sample and uses their deviation to correct the field-of-view position. This ensures that the correction is relevant to the actual measurement task.
Solution Approach 2:
The patent performs preliminary detection of reference pattern positions before executing the field-of-view movement. By acquiring images of reference patterns, calculating their center positions, and determining deviations in advance, the system prepares the necessary correction data before the actual positioning operation. This preliminary action enables accurate positioning by pre-computing the required adjustments based on detected feature positions.
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 configuration enables high-accuracy field-of-view movement even with magnetic field changes, improving image quality and maintaining precision during inspections of fine patterns and high-magnification imaging.
Implementation Method 1
an objective lens whereby a charged-particle beam emitted from a charged-particle source is focused and irradiated onto a sample
Implementation Method 2
a field-of-view moving deflector which deflects the charged-particle beam
Data Source
AI summary
The objective of the present invention is to provide a charged-particle beam device capable of moving a field-of-view to an exact position even when moving the field-of-view above an actual sample. In order to attain this objective, a charged-particle beam device is proposed comprising an objective lens whereby a charged-particle beam is focused and irradiated onto a sample; a field-of-view moving deflector for deflecting the charged-particle beam; and a stage onto which the sample is placed. The charged-particle beam device is equipped with a control device which controls the lens conditions for the objective lens in such a manner that the charged-particle been focuses on the sample which is to be measured; moves the field-of-view via the field-of-view moving deflector while maintaining the lens conditions; acquires a plurality of images at each position among a reference pattern extending in a specified direction; and uses the plurality of acquired images to adjust the signal supplied to the field-of-view moving deflector.