Multi-Particle Beam Optics for Variable NA at Fixed Beam Pitch
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Solution Overview
Problem
Conventional multi-beam particle microscopes face challenges in independently altering the numerical aperture (NA) without changing the beam pitch, which limits resolution and flexibility in imaging, especially when dealing with different samples requiring varying pitch and NA settings.
Innovation Solution
A method involving a multi-beam generator with a multi-aperture plate and additional particle-optical components, such as electrostatic or magnetic lenses, allows for independent adjustment of the numerical aperture and beam pitch in the object plane, enabling flexible optimization of imaging parameters without structural modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the numerical aperture is altered in conventional multi-beam particle microscopes, then the resolution is improved, but the beam pitch changes which limits flexibility in imaging
Solution Approach 1:
The patent introduces a multi-aperture plate with multiple openings that divides the single particle beam into multiple individual beams. Each opening can be independently controlled, allowing the numerical aperture to be adjusted by selectively opening or closing specific apertures without affecting the spatial arrangement (pitch) of the beams on the sample. This segmentation enables independent control of resolution (via NA) and beam distribution (via pitch).
Solution Approach 2:
The patent employs electrostatic or magnetic lenses with variable focal lengths that can be dynamically adjusted during operation. By changing the lens parameters, the numerical aperture can be modified without mechanically moving the multi-aperture plate or changing the beam geometry. This dynamic adjustment allows the system to adapt resolution settings while maintaining fixed beam pitch, resolving the contradiction between resolution improvement and imaging flexibility.
2Adaptability or versatility
If additional particle-optical components are added to enable independent NA and pitch adjustment, then the flexibility and resolution are improved, but the device complexity increases
Solution Approach 1:
The patent designs the multi-aperture plate to serve multiple functions: it acts as both a beam splitter (creating multiple beams from one source) and a numerical aperture control element (by selectively opening/closing apertures). The electrostatic/magnetic lenses also perform dual roles of focusing the beams and controlling the numerical aperture. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in device complexity while achieving independent control of NA and pitch.
3Measurement precision
If the numerical aperture is optimized for one working point, then the resolution is maximized at that point, but the system cannot be optimized for other working points
Solution Approach 1:
The patent implements dynamic control of the numerical aperture through electrostatic or magnetic lenses whose focal lengths can be varied. By adjusting the lens parameters, the system can optimize the numerical aperture for different working conditions (different sample distances, beam energies, or magnifications) without requiring physical reconfiguration. This dynamic adaptability allows the resolution to be maximized across multiple working points rather than being fixed for a single operating condition.
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 enhances the resolution and flexibility of multi-beam particle microscopes by allowing for adjustable NA and pitch settings, improving imaging quality across various samples without the need for mechanical adjustments or exchanging components.
Implementation Method 1
One portion of the electrons of the electron beam impinges the multi-aperture plate and is absorbed there
Implementation Method 2
suitably chosen electric fields provided in the beam path upstream and/or downstream of the multi-aperture plate have the effect that each opening in the multi-aperture plate acts as a lens on the electron beam passing through the opening
Implementation Method 3
additional particle-optical components, such as electrostatic or magnetic lenses
Implementation Method 4
They generate interaction products, such as backscattered electrons or secondary electrons, emanating from the object
Data Source
AI summary
A method includes operating a multiple particle beam system at different working points. The numerical aperture can be set for each of the working points in such a way that the resolution of the multiple particle beam system is optimal. In the process, the beam pitch between adjacent individual particle beams on the sample to be scanned is kept constant as a boundary condition. There are no mechanical reconfigurations of the system whatsoever for the purposes of varying the numerical aperture.