Charged Particle Beam Device Parasitic Aberration Correction
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Solution Overview
Problem
Existing methods for correcting parasitic aberrations in charged particle beam devices, such as SEMs, face challenges when the relationship between field intensity and aberration correction amount changes nonlinearly or over time, leading to discrepancies that hinder effective aberration correction.
Innovation Solution
A process involving the measurement of aberration coefficients and power supply control values, along with the storage of measurement histories, allows for the computation of parasitic aberration adjustment amounts, enabling real-time correction of parasitic aberrations by considering changes in the field intensity of the aberration corrector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If automatic aberration correction is implemented using multiple poles, then aberration correction capability is improved, but parasitic aberrations occur due to field distribution deviations
Solution Approach 1:
The patent introduces a parasitic aberration adjustment amount computation unit that acts as an intermediary between the aberration correction process and the multiple pole fields. This unit computes the necessary adjustment to counteract parasitic aberrations generated by field distribution deviations, thereby resolving the contradiction between achieving aberration correction and avoiding parasitic effects
Solution Approach 2:
The system implements a feedback mechanism where the measured aberration coefficients and power supply control values are used to compute parasitic aberration adjustment amounts. This feedback loop continuously adjusts the multiple pole fields to compensate for parasitic aberrations, maintaining correction effectiveness while minimizing harmful side effects
2Measurement precision
If the relationship between field intensity and aberration correction amount changes nonlinearly or over time, then correction accuracy deteriorates, but increasing measurement and computation complexity is required
Solution Approach 1:
The patent implements a dynamic correction approach where the system performs multiple cycles of aberration measurement and parasitic aberration adjustment. The parasitic aberration adjustment amount computation unit dynamically adapts to changing relationships between field intensity and correction amount by continuously measuring current aberration coefficients and computing appropriate adjustments, thereby maintaining accuracy despite nonlinear or time-dependent changes
Solution Approach 2:
Before performing main aberration correction, the system pre-computes parasitic aberration adjustment amounts based on measured power supply control values and historical data. This preliminary action separates the parasitic correction step from the main correction process, making the overall system more manageable despite the complexity of handling nonlinear relationships
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 effectively suppresses the influence of changes in the relationship between field intensity and aberration correction, ensuring accurate and continuous aberration correction even when the relationship is nonlinear or time-dependent.
Implementation Method 1
multiple stages of multipole lenses having magnetic poles or electrodes are used. In each stage, a non-rotationally symmetrical electric field or magnetic field, such as a dipole field, a quadrupole field, a hexapole field, or an octupole field, is applied to a beam in a manner superimposed thereon
Implementation Method 2
a non-rotationally symmetrical electric field or magnetic field, such as a dipole field, a quadrupole field, a hexapole field, or an octupole field, is applied to a beam in a manner superimposed thereon, so as to provide an inverse aberration to the probe beam
Data Source
AI summary
It is possible to determine an optimal parasitic aberration adjustment amount even when the relationship of the parasitic aberration adjustment amount with respect to the field intensity of multiple poles changes nonlinearly. To this end, in the present invention, an aberration correction amount is computed by measuring an aberration coefficient of an optical unit of a charged particle beam device, and at the same time, the present value of a power supply control value applied to an aberration corrector is measured. Then, the parasitic aberration adjustment amount for suppressing the amount of a parasitic aberration generated in the aberration corrector is computed on the basis of the aberration correction amount and the present value of the power supply control value.