Multi-Beam Raster Unit Alignment for Low-Aberration Electron Beams
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Solution Overview
Problem
Existing multi-beam charged particle microscopes suffer from aberrations and scattered particles due to manufacturing inaccuracies in multi-aperture plates, leading to image blurring and machine-to-machine deviations, which current fabrication processes fail to adequately address.
Innovation Solution
A multi-beam raster unit design with precise alignment and fabrication methods, including smooth conductive surfaces, controlled aperture shapes, and electrostatic elements, minimizes aberrations and scattering by ensuring high precision and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate control electrodes are provided for each deflection direction, then control precision is improved, but device complexity increases
Solution Approach 1:
The patent combines control electrodes for different deflection directions into a single shared electrode structure. This single control electrode can generate electric fields in multiple directions by varying the acceleration voltage, eliminating the need for separate control electrodes for each deflection direction while maintaining control precision.
Solution Approach 2:
The single control electrode is designed to perform multiple functions by controlling electron beams in different deflection directions through voltage variation. This multi-functional electrode replaces what would traditionally require multiple specialized electrodes, reducing device complexity while preserving control capabilities.
2Productivity
If multiple electron sources are used to generate multiple electron beams, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent segments a single electron source into multiple virtual electron sources through the use of a multi-layered condenser lens system. This creates multiple electron beams from one physical electron source, achieving the productivity benefits of multiple sources without the complexity of maintaining multiple actual electron sources.
Solution Approach 2:
The patent creates virtual copies of the electron source using the multi-layered condenser lens system. Each layer of the condenser lens generates a virtual image of the electron source at different positions and orientations, effectively copying the source functionality to produce multiple beams from a single physical source.
3Measurement precision
If a multi-layered condenser lens system is implemented, then beam focusing precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs a multi-layered condenser lens system where each layer can be independently adjusted and optimized. The dynamic capability to tune each lens layer allows for compensating manufacturing tolerances and achieving precise beam focusing despite the complexity of manufacturing multiple lens components.
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
The solution achieves well-defined beamlets with minimal aberrations and scattering, enhancing imaging performance and reducing machine-to-machine deviations, thereby improving the reliability and quality of multi-beam charged particle microscopes.
Implementation Method 1
an electrostatic deflecting unit having a plurality of control electrodes arranged in the first direction and extending in the second direction, and a plurality of electron beams corresponding to the control electrodes and extending in a direction intersecting the first direction and the second direction
Implementation Method 2
an electron source configured to generate a plurality of electron beams extending in a first direction
Data Source
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AI summary
Certain improvements of multi-beam raster units such as multi-beam generating units and multi-beam deflector units of a multi-beam charged particle microscopes are provided. The improvements include design, fabrication and adjustment of multi-beam raster units including apertures of specific shape and dimensions. The improvements enable multi-beam generation and multi-beam deflection or stigmation with higher precision. The improvements are relevant for routine applications of multi- beam charged particle microscopes, for example in semiconductor inspection and review, where high reliability and high reproducibility and low machine-to-machine deviations are required.