Charged Particle Beam Control System for Automatic Focus Adjustment
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Solution Overview
Problem
Current charged particle beam systems lack the capability for automatic focus measurement and adjustment, as well as three-dimensional shape measurement of samples, which limits their precision and efficiency in inspection and measurement processes.
Innovation Solution
A charged particle beam system equipped with a control system that performs multiple resolution analysis using wavelet transforms or discrete wavelet transforms to obtain coefficients, allowing for the calculation of adjustment parameters based on image analysis, enabling accurate focus adjustment and astigmatism correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If automatic focus measurement and adjustment capabilities are added to charged particle beam systems, then measurement precision and adjustment accuracy are improved, but device complexity increases
Solution Approach 1:
The patent introduces an image processing unit as an intermediary component that analyzes images captured by the charged particle beam apparatus. This unit performs wavelet transform and other image processing operations to automatically determine focus accuracy and astigmatism conditions, thereby improving measurement precision without requiring direct modification of the core beam generation system.
Solution Approach 2:
The patent replaces manual mechanical adjustment procedures with automated image processing and analysis. By using wavelet transform-based image analysis algorithms, the system automatically evaluates focus conditions and provides adjustment guidance, eliminating the need for operator intervention and reducing mechanical complexity while enhancing precision.
2Measurement precision
If three-dimensional shape measurement capability is implemented, then measurement precision is improved, but analysis complexity increases
Solution Approach 1:
The patent segments the three-dimensional shape measurement process into distinct computational stages: image acquisition, wavelet transform analysis, coefficient extraction, and 3D reconstruction. By dividing the complex analysis into modular processing steps, the system achieves high measurement precision while managing analysis complexity through structured computation.
Solution Approach 2:
The patent transitions from two-dimensional image data to three-dimensional shape information by analyzing focus variations across different depth planes. The image processing unit extracts depth information by examining how wavelet coefficients change with focal distance, effectively adding a third dimension to the measurement capability.
3Measurement precision
If multiple resolution analysis using wavelet transform is performed, then adjustment parameter evaluation accuracy is improved, but calculation time increases
Solution Approach 1:
The patent applies wavelet transform at multiple resolution levels, performing analysis only to the extent necessary for accurate parameter evaluation. By selectively processing images at different decomposition levels based on the specific measurement requirements, the system achieves high accuracy without unnecessarily increasing calculation time through excessive analysis depth.
Data Source
AI summary
A control system of a charged particle beam apparatus obtains a first coefficient by performing multiple resolution analysis based on wavelet transform or discrete wavelet transform on at least a part of an image or a signal acquired by the charged particle beam apparatus. The control system obtains a second coefficient by performing, on at least a part of the first coefficient or an absolute value of the first coefficient, any one of calculation of a maximum value, calculation of a numerical value corresponding to a specified order in an order related to a magnitude, fitting to a histogram, calculation of an average value, and calculation of a total sum.