Charged Particle Microscope Image Shift Aberration Correction
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Solution Overview
Problem
Charged particle microscopes face challenges in maintaining high resolution during image shift due to off-axis aberrations and misalignment of electrostatic and electromagnetic lenses, which affects focus accuracy and throughput in process monitoring applications.
Innovation Solution
The solution involves dynamically controlling the focus of an electrostatic lens while using an electromagnetic lens, with feedback mechanisms to adjust coil currents and voltages to maintain image stability and prevent visual field shifts, utilizing multivariate data interpolation for precise alignment and correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If image shift is performed by deflecting the primary charged particle beam trajectory using a deflector lens, then the visual field can be moved in micrometer order, but the resolution is degraded due to increase of off-axis aberrations
Solution Approach 1:
The patent introduces a trajectory corrector as an intermediary device between the deflector lens and the objective lens. This corrector specifically compensates for off-axis aberrations introduced by the deflector, acting as a mediator that allows the deflector to move the visual field while simultaneously correcting the resulting image degradation, thus resolving the contradiction between visual field movement capability and image resolution
Solution Approach 2:
The patent dynamically adjusts the strength and configuration parameters of the trajectory corrector based on the deflection amount. By changing these parameters in real-time according to the visual field movement requirements, the system maintains optimal resolution across different visual field positions while preserving the image shift functionality
2Device complexity
If the upper and lower ratio of the deflector is fixed, then the device complexity is reduced, but the optimal resolution condition changes with deflection distance requiring frequent reset
Solution Approach 1:
The patent implements dynamic adjustment of the trajectory corrector parameters based on the deflection distance. The system automatically adapts the corrector strength and configuration in real-time according to the current visual field position, allowing the fixed upper and lower ratio deflector to maintain optimal resolution across different deflection distances without manual intervention
Solution Approach 2:
The patent incorporates feedback mechanisms that monitor the deflection distance and automatically adjust the trajectory corrector parameters accordingly. This closed-loop control ensures that the optimal resolution condition is maintained dynamically as the visual field moves, eliminating the need for frequent manual reset while keeping the deflector configuration simple
3Device complexity
If dynamic focus control is implemented using a single focus system, then the device complexity is reduced, but the upper and lower ratio of image shift can only be associated with image shift not with focus
Solution Approach 1:
The patent segments the focus control into multiple independent focus systems rather than using a single unified system. This segmentation allows different focus systems to be independently controlled and associated with different parameters such as image shift and focus, providing the necessary flexibility while keeping each individual focus system relatively simple
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 enhances the throughput and maintains image resolution during image shifts, ensuring accurate focus determination and reducing the impact of lens misalignment, thereby improving the overall performance of charged particle microscopes in process monitoring.
Implementation Method 1
an output value of an aligner coil is determined by a coil current and a voltage of an electromagnetic lens applied to an electrode, an acceleration voltage, and an input value of an image-shift coil
Implementation Method 2
a voltage of an electromagnetic lens applied to an electrode, an acceleration voltage
Implementation Method 3
a method that deviates the trajectory of the primary charged particle beam using a deflector lens to move the observation portion
Data Source
AI summary
A charged-particle-beam device is characterized in having a control value for an aligner coil (29) being determined by: a coil current and an electrode applied-voltage at a control value for objectives (30, 31), which is an electromagnetic-field superposition lens; a control value for image-shift coils (27, 28); and the acceleration voltage of the charged-particle-beam. By doing this, it has become possible to avoid image disturbances that occur on images to be displayed at boundaries between charged areas and non-charged areas, and provide a charged-particle-beam device that obtains clear images without any unevenness in brightness.