Charged Particle Beam Aberration Retrieval From Defocus Images
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current charged particle beam systems, such as electron microscopes, face challenges in accurately determining and correcting beam aberrations, which limit the achievable resolution due to unknown aberration coefficients and the complexity of aberration correctors.
Innovation Solution
A method involving the iterative comparison of taken and simulated images or beam cross sections at varying defocus settings to determine and refine beam aberration coefficients, allowing for the precise correction of beam aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If aberration correctors are provided to compensate beam aberrations, then resolution is improved, but device complexity increases due to the large number of controls required for adjustment
Solution Approach 1:
The patent changes the approach from manually adjusting multiple aberration corrector controls to automatically determining aberration coefficients through image processing and simulation. By analyzing taken images at different defocus settings and comparing them with simulated images, the system automatically calculates the actual aberration coefficients, eliminating the need for complex manual adjustment of multiple controls while achieving the same resolution improvement
Solution Approach 2:
The system performs self-diagnosis and self-correction by automatically determining its own aberration coefficients through image analysis. The processing unit compares taken images with simulated images and iteratively adjusts the coefficients to minimize differences, allowing the system to self-correct without external intervention or complex control adjustments
2Manufacturing precision
If aberration correctors are provided to compensate beam aberrations, then resolution is improved, but ease of operation deteriorates because the beam aberration is generally unknown
Solution Approach 1:
The patent implements a feedback mechanism where the system takes images at different defocus settings, compares them with simulated images based on current aberration coefficients, and uses the difference (error signal) to iteratively update the coefficients. This closed-loop feedback approach automatically determines the actual aberration state and adjusts the coefficients accordingly, making the system easy to operate without requiring user knowledge of the aberration state
Solution Approach 2:
The system autonomously determines its own aberration coefficients through image analysis and simulation comparison. The processing unit performs iterative optimization to minimize the difference between taken and simulated images, allowing the system to self-diagnose and self-correct without external input or user expertise
3Measurement precision
If iterative simulation and comparison is performed to determine beam aberration coefficients, then measurement precision of aberration coefficients is improved, but loss of time increases due to multiple iterations
Solution Approach 1:
The patent performs preliminary actions by taking multiple images at different defocus settings before the iterative process begins. This preparatory data collection allows the iterative optimization to start with better initial conditions, reducing the number of iterations needed to achieve convergence and minimizing the time loss while maintaining high measurement precision
Data Source
AI summary
A method of determining aberrations of a charged particle beam (11) focused by a focusing lens (120) toward a sample (10) in a charged particle beam system is described. The method includes: (a) taking one or more images of the sample at one or more defocus settings to provide one or more taken images (h1...N); (b) simulating one or more images of the sample taken at the one or more defocus settings based on a set of beam aberration coefficients (iC) and a focus image of the sample to provide one or more simulated images; (c) comparing the one or more taken images and the one or more simulated images for determining a magnitude (Ri) of a difference therebetween; and (d) varying the set of beam aberration coefficients (iC) to provide an updated set of beam aberration coefficients (i+1C) and repeating (b) and (c) using the updated set of beam aberration coefficients (i+1C) in an iterative process for minimizing said magnitude (Ri). Alternatively, in (b), one or more beam cross sections may be simulated, and, in (c) the simulated beam cross sections may be compared with one or more retrieved beam cross sections retrieved from the one or more taken images for determining a magnitude (Ri) of a difference therebetween. Further, a charged particle beam system for imaging and/or inspecting a sample that is configured for any of such methods is provided.