Aberration Measurement in Electron Microscopes Using Virtual Ronchigrams
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Solution Overview
Problem
Conventional aberration measuring methods in electron microscopes, such as displacement-based and probe tableau methods, require extensive time and effort due to the need for repeated measurements, while methods using Ronchigrams are faster but require a detector for imaging, limiting their applicability.
Innovation Solution
A method for measuring lens aberration in charged particle optical devices that scans an electron beam with aberration correctors to generate a scanning Ronchigram equivalent image without the need for a detector, using a scanning coil upstream of the objective lens to detect secondary, reflected, or transmitted electrons, allowing for aberration calculation from a two-dimensional image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional aberration measuring methods (displacement-based or probe tableau) are used, then measurement accuracy can be achieved, but measurement time and operational complexity increase significantly
Solution Approach 1:
The patent creates a virtual Ronchigram by scanning the electron beam and synthesizing image data computationally, rather than directly capturing a physical Ronchigram. This copied approach allows aberration measurement with the speed of projected image methods while maintaining the accuracy needed for quantitative analysis
Solution Approach 2:
The patent replaces the mechanical/optical Ronchigram capture system with an electron beam scanning system that collects data point-by-point and reconstructs the Ronchigram computationally. This substitution enables the use of standard SEM detectors while achieving Ronchigram-based aberration measurement
2Measurement precision
If conventional aberration measuring methods are used, then measurement accuracy can be achieved, but operational complexity and effort increase
Solution Approach 1:
By computationally reconstructing a virtual Ronchigram from scanned image data, the patent simplifies the operational workflow. The system automatically processes the scanned data to generate aberration information, eliminating the need for manual Ronchigram capture and analysis while maintaining measurement accuracy
Solution Approach 2:
The patent enables the SEM system to automatically perform aberration measurement by integrating the scanning function and computational reconstruction. The system self-calibrates by processing its own scanned data to generate aberration coefficients, reducing operational complexity
3Productivity
If Ronchigram method is used for aberration measurement, then measurement speed improves, but device complexity increases due to requiring imaging detectors
Solution Approach 1:
The patent makes the electron beam scanning system perform multiple functions: it both scans the sample for imaging purposes and simultaneously collects data for aberration measurement. This multi-functionality eliminates the need for separate imaging detectors while maintaining measurement speed
Solution Approach 2:
The patent creates a virtual Ronchigram through computational reconstruction from scanned data, copying the essential information of a physical Ronchigram without requiring specialized imaging detectors. This approach enables Ronchigram-based measurement using standard SEM detectors
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 enables efficient aberration measurement applicable to SEMs without the need for imaging detectors, reducing measurement time and improving accuracy by generating aberration information patterns similar to Ronchigrams, thus facilitating quicker adjustments of aberration correctors.
Implementation Method 1
electron beam scanning means that is provided on the electron-optical upstream side of aberration measured lenses of the electromagnetic lenses, and scans and deflects the electron beam
Implementation Method 2
electromagnetic lenses disposed between the electron source and the sample mounting part
Implementation Method 3
detecting means that detects an electron signal induced from the sample by the electron beam impinging onto the sample; and the detecting means detects at least one of signals including a secondary electron, a reflected electron, a transmitted electron, and a scattered electron
Data Source
AI summary
Beam scanning for obtaining a scanned image is performed by an aberration corrector, which is an aberration measured lens, and a scanning coil disposed above an objective lens, instead of a scanning coil ordinarily placed on the objective lens. Thus, distortion with an aberration of an aberration measured lens is scanned on the surface of a sample, and then a scanned image is formed from a scattered electron beam, a transmission electron beam, or a reflected/secondary electron beam that is generated by the scan, achieving a scanning aberration information pattern equivalent to a conventional Ronchigram. Such means is a feature of the present invention.