Charged Particle Beam Image Distortion Correction
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Solution Overview
Problem
Charged particle beam scanning technologies face challenges with sample image distortion due to shrinkage, contamination, and charging phenomena, making it difficult to determine the reliability of the observed image, as these issues can occur simultaneously and are influenced by various unknown or combined factors.
Innovation Solution
An image forming apparatus and computer program that calculate and analyze changes in feature quantities over time and across different scan directions to identify distortion-causing factors, allowing for the detection and suppression of image distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the charged particle beam scans the sample at high magnification ratios, then the resolution is improved, but sample image distortion increases due to shrinkage, contamination, and charging phenomena
Solution Approach 1:
The patent segments the scanning process into multiple passes with different scan directions (e.g., horizontal scan, vertical scan, diagonal scan). By dividing the single high-magnification scan into multiple directional scans, the system reduces the harmful effects of localized charging and beam-induced shrinkage that occur in conventional single-direction scanning, thereby maintaining high resolution while improving image reliability.
Solution Approach 2:
The patent implements periodic reversal of the scan direction during the scanning process. The beam scans in one direction, then reverses and scans in the opposite direction, creating a periodic scanning pattern. This periodic action distributes the beam irradiation more evenly across the sample, preventing localized charging accumulation and reducing beam-induced shrinkage, thus maintaining image reliability at high magnification.
2Object-affected harmful factors
If the scan interval is increased to reduce electron beam irradiation per unit area, then contamination and shrinkage are suppressed, but the observation time increases
Solution Approach 1:
The patent introduces the dimension of scan direction variation by implementing multiple scanning patterns including horizontal scans, vertical scans, and diagonal scans. Instead of simply increasing the scan interval in a single direction (which increases observation time), the system varies the scanning dimension itself, allowing adequate beam spacing to reduce contamination and shrinkage while maintaining efficient coverage of the sample area, thus reducing total observation time.
3Reliability
If multiple scanning patterns are used to reduce image distortion, then the identification of distortion factors becomes possible, but the complexity of the scanning control increases
Solution Approach 1:
The patent implements a feedback mechanism where the system acquires images using multiple scanning patterns, compares the results to identify distortion factors, and then adjusts the scanning parameters accordingly. The control unit analyzes the images obtained from different scan directions and uses this feedback information to optimize the scanning strategy, automatically identifying distortion causes (such as charging or shrinkage) and adjusting parameters like scan interval or scan direction to compensate for identified distortions, thereby managing complexity through intelligent control.
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 the identification of distortion contributing factors and improves the reliability of sample images by quantifying and addressing distortion, enhancing work efficiency and image accuracy.
Implementation Method 1
scans a sample with a thinly converged charged particle beam, and forms a sample image on the basis of a signal emitted from the sample
Implementation Method 2
secondary electron/backscattered electron yield of the sample
Implementation Method 3
the sample may be shrunk or a carbon-based deposit may become attached to the surface of the sample (contamination) due to dissociation of hydrocarbon-based residual gas in the apparatus and the sample caused by the energy of the beam
Implementation Method 4
when the sample is scanned with the charged particle beam, a charging bias may be produced in the observed area
Data Source
AI summary
In an image forming apparatus and a computer program, extraction of information about distortion in a charged particle beam scan area can be implemented. An image forming apparatus integrates image data obtained by a charged particle beam apparatus and calculates, from a plurality of images with different scan directions of the charged particle beam apparatus, first information about the amount of change in a feature quantity in accordance with the time of irradiation of the charged particle beam, second information about the amount of change in the feature quantity before and after a change in beam scan direction, and/or third information about a position error of a pattern on the image before and after the change in beam scan direction.