Multiple Lens Assembly for Charged Particle Beam Devices
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Solution Overview
Problem
Conventional charged particle beam devices face challenges in three-dimensional analysis due to limitations in tilting methods, which result in mechanical complexities, aberrations, and the need for constant focal adjustments, especially when analyzing specimen surfaces at varying angles.
Innovation Solution
A multiple lens assembly with at least two sub-units, each having inclined optical axes, allows the beam to be directed along different angles without tilting the specimen or the device, reducing aberrations and enabling three-dimensional imaging by deflecting the beam between sub-units, thereby eliminating the need for constant focal adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a deflector is placed downstream of the objective lens to tilt the beam, then the angle between beam and specimen surface can be varied, but the resolution suffers from the larger distance necessary between the objective lens and the specimen
Solution Approach 1:
The patent divides the single lens system into multiple lens sub-units (first, second, and third sub-units), each with different optical axes. This segmentation allows the beam to be focused at different angles without requiring downstream deflection, thereby maintaining resolution while achieving beam tilting capability.
Solution Approach 2:
Instead of tilting the beam in the horizontal plane using a downstream deflector, the patent introduces a new dimension by using lens sub-units with different optical axis orientations. This allows angular adjustment through the optical path geometry rather than lateral deflection, preserving resolution.
2Adaptability or versatility
If a deflector is placed upstream of the objective lens to deflect the beam, then the beam can be tilted, but the deflected beam passes the objective lens off-axially resulting in aberration
Solution Approach 1:
The patent segments the lens into multiple sub-units, each optimized for specific optical axis orientations. This allows the beam to pass through the appropriate sub-unit on-axis for each desired angle, avoiding off-axis aberrations that would result from using a single lens with upstream deflection.
Solution Approach 2:
Each lens sub-unit is designed with specific local optical properties and orientations. The first sub-unit has an optical axis perpendicular to the specimen plane, the second at a first angle, and the third at a second angle. This local optimization ensures on-axis passage and minimal aberration for each beam direction.
3Adaptability or versatility
If the specimen table is tilted to analyze the surface at different angles, then the angle between beam and specimen surface can be varied, but the focus of the beam has to be adjusted constantly
Solution Approach 1:
Instead of tilting the specimen table to change the viewing angle, the patent inverts the approach by keeping the specimen table fixed and using multiple lens sub-units with different optical axes. This inversion eliminates the need for constant focus adjustment while achieving the same angular viewing capability.
Solution Approach 2:
The patent changes the dimension of adjustment from specimen table tilt to lens optical axis orientation. By varying which lens sub-unit is used (with different fixed optical axes), the beam can be focused at different angles without requiring focus adjustment, simplifying operation.
4Manufacturing precision
If multiple deflectors are placed upstream of the objective lens with opposite deflection orientations, then the beam can be made to pass through the middle of the objective lens, but the beam still does not travel along the optical axis resulting in aberration and the optics becomes difficult to adjust
Solution Approach 1:
The patent segments the lens into multiple sub-units, each with a predetermined optical axis orientation. This eliminates the need for complex multi-deflector arrangements and manual alignment, as each sub-unit is pre-configured to focus the beam along its specific optical axis, simplifying both alignment and adjustment.
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 efficient three-dimensional analysis of specimen surfaces without mechanical tilting, reduces aberrations, and allows for simultaneous inspection of multiple spots on a specimen using a single beam source, improving the overall analytical performance and flexibility in charged particle beam devices.
Implementation Method 1
a multiple lens assembly for charged particle beam devices is provided which comprises at least two lens sub units (2), each sub unit (2) having an optical axis (3), wherein at least two of the optical axes (3) of the lens sub units (2) are inclined
Implementation Method 2
a deflection system (5) is provided which is suitable for deflecting a charged particle beam (12) such that the charged particle beam (12) is directed along the optical axis (3) of at least one of the at least two lens sub units (2)
Data Source
AI summary
The invention provides a multiple-lens assembly 1 for a charged particle beam device which comprises at least two lens sub units 2, each sub unit having an optical axis 3, wherein at least two of the optical axes of the lens sub units are inclined to each other. Further, the invention provides a charged particle beam device which comprises at least one multiple-lens assembly and a method for operating a charged particle beam device.