Contrast Correction Lens for Uniform Multi-Beam Imaging
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Solution Overview
Problem
Existing multiple particle beam systems face issues with beam tilt and skew pencils of rays in the crossover plane, leading to non-uniform contrast and reduced imaging precision, particularly in multi-beam particle microscopes.
Innovation Solution
A multiple particle beam system with a contrast correction lens system that includes a magnetic contrast correction lens to adjust the beam tilts of secondary particle beams, ensuring they are superposed accurately in the crossover plane, and a controller to manage the lens's excitation, achieving telecentric illumination and uniform image contrast across all beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If magnetic immersion lenses are used as objective lenses to focus particle beams, then the particle beams can be effectively focused on the object surface, but beam tilts occur in the downstream beam path due to asymmetric magnetic fields
Solution Approach 1:
A contrast correction lens system is introduced as an intermediary component between the objective lens and the detector. This lens system generates a magnetic field that acts as a mediator to correct the beam tilts caused by the objective lens, allowing the beams to be properly aligned without modifying the objective lens itself
Solution Approach 2:
The beam tilt correction function is extracted from the objective lens system and implemented separately through the contrast correction lens system. This separation allows the objective lens to maintain its focusing function while the correction lens handles the alignment issue independently
2Productivity
If the number of particle beams is increased to scan larger areas, then productivity improves, but uniformity of contrast and resolution deteriorates due to varying beam tilts
Solution Approach 1:
The contrast correction lens system dynamically adjusts the magnetic field parameters (strength and distribution) to compensate for position-dependent beam tilts. By changing the field parameters across different radial positions, uniform contrast is maintained across all beams regardless of their position in the expanded scan area
Solution Approach 2:
The correction of beam tilts is segmented by position - different regions of the beam field receive tailored correction through the radial dependence of the magnetic field. Each beam's tilt is corrected according to its specific position, allowing uniform performance across multiple beams
3Manufacturing precision
If a contrast aperture is placed in the crossover region to improve image contrast, then edge contrast improves, but beam tilts cause skew pencils of rays that reduce filtering precision
Solution Approach 1:
The contrast correction lens system applies preliminary correction to prevent beam tilts before the beams reach the contrast aperture. By correcting the tilts in advance, the beams arrive at the aperture with proper alignment, ensuring both high contrast and precise filtering without the skew pencils of rays problem
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 system enhances imaging precision and uniformity of contrast by correcting beam tilts, allowing for high-resolution imaging even with a large number of particle beams, especially on planar samples like semiconductor wafers.
Implementation Method 1
a contrast correction lens system with a first magnetic contrast correction lens arranged in the second particle optical beam path between the objective lens and the contrast aperture, the first magnetic contrast correction lens being configured to generate a magnetic field with an adjustable strength
Implementation Method 2
the first magnetic contrast correction lens being configured to generate a magnetic field with an adjustable strength and correct beam tilts of the second individual particle beams
Data Source
AI summary
A multiple particle beam system comprises a magnetic immersion lens and a detection system. A cross-over of the second individual particle beams is provided in the secondary path between the beam switch and the detection system, and a contrast aperture with a central cutout for cutting out the secondary beams is arranged in the region of the cross-over. A contrast correction lens system with a first magnetic contrast correction lens is arranged between the objective lens and the contrast aperture. The contrast correction lens system is configured to generate a magnetic field with an adjustable strength and correct beam tilts of the secondary beams in the cross-over in relation to the optical axis of the multiple particle beam system. It is possible to obtain a more uniform contrast for different individual images and the contrast can be improved overall.