Multipole Aberration Correction for Charged Particle Beam Image Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing aberration correction methods in charged particle beam devices are inaccurate due to the determination of correction amounts based on the intensity of the multipole field, which fails to account for aberration measurement errors, leading to decreased accuracy in aberration correction.
Innovation Solution
The proposed solution involves a charged particle beam device with an aberration corrector that directly suppresses parasitic fields caused by multipole distortion by adjusting the correction voltage or current applied to the poles, thereby eliminating observation image shifts and achieving accurate aberration correction without relying on multipole field intensity corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correction amounts are determined based on multipole field intensity, then aberration correction can be performed, but measurement errors cause deviation from required correction amounts, reducing accuracy
Solution Approach 1:
The patent implements feedback by measuring the actual observation image shift caused by multipole distortion and using this measurement to determine the correction amounts. The controller continuously monitors the image shift and adjusts the correction voltages/currents accordingly, creating a closed-loop system that compensates for measurement errors and achieves accurate aberration correction despite initial inaccuracies in the distortion characteristics.
Solution Approach 2:
The patent replaces the theoretical calculation-based correction system with an experimental measurement-based system. Instead of relying on predetermined distortion characteristics and field intensity calculations, the system directly measures the actual image shift using the detector and observer, then uses this empirical data to determine correction amounts, substituting theoretical mechanics with direct observation and measurement.
2Reliability
If parasitic fields are expanded to multiple parasitic multipole fields for correction, then correction can be applied, but the process becomes complex and requires storing correction values for each field
Solution Approach 1:
The patent merges the correction of multiple parasitic multipole fields into a unified correction approach. Instead of treating each parasitic field separately with individual correction values, the system measures the combined effect of all parasitic fields as a total observation image shift and applies a unified correction using the distortion correction table, which stores correction amounts based on actual measured shifts rather than theoretical field expansions.
Solution Approach 2:
The patent extracts the essential correction information by directly measuring the observation image shift caused by parasitic fields and storing only the necessary correction amounts in the distortion correction table. This eliminates the need to separately identify, expand, and correct each individual parasitic multipole field, extracting only the net effect that needs correction.
3Manufacturing precision
If aberration corrector is mounted to reduce aberration influence, then resolution improves, but manufacturing variations cause multipole field distortion that reduces correction accuracy
Solution Approach 1:
The patent applies preliminary action by pre-measuring and storing the distortion characteristics of the multipole fields in the distortion correction table before actual aberration correction is performed. The system characterizes the actual multipole field distribution and image shift effects in advance, creating a lookup table that guides subsequent correction operations, allowing the system to compensate for manufacturing variations without requiring real-time complex calculations.
Solution Approach 2:
The patent changes the correction approach from using theoretical field distribution parameters to using empirically measured image shift parameters. By storing correction amounts based on actual observed image shifts rather than theoretical multipole field characteristics, the system adapts to the actual manufactured state of the aberration corrector, compensating for deviations from ideal field distributions through parameter transformation.
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 highly accurate aberration correction by directly addressing multipole distortion, thereby improving the precision of charged particle beam devices used in semiconductor manufacturing and defect inspection.
Implementation Method 1
generates a predetermined multipole field by applying a predetermined correction voltage or correction current to the plurality of poles
Implementation Method 2
generates a plurality of multipole fields in a superimposed manner in the multipoles of the plurality of stages in order to correct the aberration of the charged particle beam
Implementation Method 3
detects electrons emitted by an interaction between the charged particle beam and the sample
Data Source
AI summary
A charged particle optical system includes an aberration corrector 209 that corrects aberration of a charged particle beam and has multipoles of a plurality of stages. The aberration corrector generates a plurality of multipole fields in a superimposed manner for each of the multipoles of the plurality of stages in order to correct the aberration of the charged particle beam. In order to reduce the influence of a parasitic field due to distortion of the multipole, for a first multipole field to be generated in a multipole of any stage among the plurality of stages, a value of a predetermined correction voltage or correction current to be applied to a plurality of poles for generating the first multipole field is corrected so as to eliminate movement of an observation image obtained based on electrons detected from a detector 215 by irradiating a sample with the charged particle beam before and after the first multipole field is generated.