Aberration Correction in Charged Particle Beam Devices
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Solution Overview
Problem
The adjustment of aberration correctors in charged particle beam devices, such as SEMs, is inefficient due to the lack of a clear method to determine the influence of individual aberrations on image resolution, leading to prolonged correction times and suboptimal image resolution.
Innovation Solution
A charged particle beam device with an aberration correction optical system that includes a detection unit, image forming unit, aberration correction amount calculation unit, and control unit to separately measure and prioritize aberrations based on their influence on image resolution, allowing for targeted correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If aberration correction is performed using multiple multi-pole lenses with rotationally asymmetric fields, then various aberrations such as spherical aberration and chromatic aberration can be canceled, but the number of power supplies increases and adjustment work becomes complicated
Solution Approach 1:
The patent segments the aberration correction process by categorizing aberrations according to their rotational symmetry characteristics (n-fold symmetric astigmatism, coma aberration, star aberration, etc.). Each aberration type is corrected by dedicated correction values applied to specific multi-pole lenses, allowing systematic management of the complex correction process without requiring manual adjustment of each power supply individually.
Solution Approach 2:
The patent implements an automated feedback system that measures aberrations using SEM images, calculates appropriate correction values based on the measured aberration coefficients, and automatically applies these corrections. This feedback loop eliminates the need for manual adjustment of multiple power supplies while achieving precise aberration correction.
2Measurement precision
If all aberration components are corrected to maximize device performance, then image resolution is improved, but the adjustment process becomes time-consuming due to the large number of power supplies
Solution Approach 1:
The patent performs preliminary classification of aberrations by their rotational symmetry characteristics before correction. By measuring aberration coefficients and categorizing them into specific types (n-fold symmetric astigmatism, coma, star aberration, etc.), the system prepares correction values in advance for each aberration type, enabling efficient automated correction without time-consuming manual adjustment.
Solution Approach 2:
The system performs self-adjustment by automatically measuring aberrations from SEM images, calculating correction values based on the measured coefficients, and applying corrections without external intervention. This self-service capability significantly reduces adjustment time while achieving optimal image resolution.
3Ease of operation
If automated aberration measurement and feedback correction are implemented, then adjustment work is simplified, but the relationship between aberration coefficients and image resolution remains unclear
Solution Approach 1:
The patent introduces an intermediary classification system that connects aberration coefficients to image resolution through rotational symmetry characteristics. By measuring aberrations and categorizing them into specific types (n-fold symmetric astigmatism, coma, star aberration, etc.), the system establishes a clear relationship between aberration coefficients and their impact on image quality, enabling both automated correction and informative feedback.
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 improvement of image resolution by identifying and correcting aberrations with the greatest impact, thereby speeding up the adjustment process and enhancing image quality.
Implementation Method 1
a detection unit for detecting a secondary charged particle generated from a sample irradiated with the primary charged particle beam
Data Source
AI summary
A charged particle beam device using a multi-pole type aberration corrector includes: a charged particle source which generates a primary charged particle beam; an aberration correction optical system which corrects aberrations of the primary charged particle beam; a detection unit which detects a secondary charged particle generated from a sample irradiated with the primary charged particle beam whose aberrations have been corrected; an image forming unit which forms a charged particle image of the sample from a signal obtained by detecting the secondary charged particle; an aberration correction amount calculation unit which processes the charged particle image, separates aberrations having different symmetries, selects an aberration to be preferentially corrected from the separated aberrations, and calculates a correction amount of the aberration correction optical system; and an aberration correction optical system control unit which controls the aberration correction optical system based on the calculated correction amount.