Electrostatic Mirror Aberration Corrector for Multi-Beam Inspection
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Solution Overview
Problem
Charged particle beam apparatuses face a trade-off between inspection rate and resolution due to off-axial aberrations, which are challenging to correct with existing methods that require multiple high-precision power supply sources and precise alignment of multipoles, making them difficult to adjust and practical.
Innovation Solution
The introduction of an electrostatic mirror in the electron optical system reduces the number of required multipoles by half, allowing for automatic creation of a multipole field that maintains symmetry, simplifying the adjustment process and improving aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple multipoles are used to correct off-axial aberrations, then resolution is improved, but device complexity increases and adjustment becomes difficult
Solution Approach 1:
The patent combines multiple multipole fields (quadrupole and octupole fields) into a single integrated aberration corrector system. This merging approach maintains the capability to correct both two-fold and four-fold off-axial aberrations while reducing the number of separate components and power supply sources required, thereby simplifying the overall device structure and making adjustment more practical.
2Measurement precision
If multiple high-precision power supply sources are used for multipole alignment, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The aberration corrector is designed to perform multiple functions using a unified power supply system. The same power supply sources that control the quadrupole fields also control the octupole fields, allowing the system to correct both two-fold and four-fold off-axial aberrations simultaneously. This multi-functionality eliminates the need for separate high-precision power supply sources for each multipole type, significantly improving ease of operation while maintaining alignment precision.
3Productivity
If the number of multiple beams is increased to improve inspection rate, then productivity is improved, but off-axial aberration effects worsen
Solution Approach 1:
The patent converts the harmful effect of off-axial aberrations into a beneficial outcome by designing an aberration corrector that specifically targets and corrects these aberrations. The corrector uses quadrupole fields to correct two-fold aberrations and octupole fields to correct four-fold aberrations, thereby enabling the system to maintain high resolution even when using multiple beams for high-speed inspection. This approach allows the system to benefit from increased productivity while eliminating the detrimental resolution degradation that would normally accompany multi-beam operation.
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 solution enables high defect-detection sensitivity and high inspection rates while making the apparatus more adjustable and practical by reducing the complexity of aberration correction, thus overcoming the limitations of previous methods.
Implementation Method 1
an electrostatic mirror disposed in a path of charged particles emitted from the charged particle source between the charged particle source and the stage
Data Source
AI summary
With a multi-beam type charged particle beam apparatus, and a projection charged particle beam apparatus, in the case of off-axial aberration corrector, there is the need for preparing a multitude of multipoles, and power supply sources in numbers corresponding to the number of the multipoles need be prepared. In order to solve this problem as described, a charged particle beam apparatus is provided with at least one aberration corrector wherein the number of the multipoles required in the past is decreased by about a half by disposing an electrostatic mirror in an electron optical system.