Offset D-Shaped Ion Beam Aperture for Sharp-Edge Milling
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Solution Overview
Problem
Existing multi-lens systems are unsuitable for producing highly focused charged particle beams with desirable beam characteristics, often resulting in low-density and broad area intensity distributions.
Innovation Solution
Utilizing an elongated aperture offset with respect to the beam axis to create an asymmetric intensity profile with a sharp edge, minimizing spherical aberration and beam tails, thereby optimizing current distribution and milling precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-lens systems are used to image system apertures to a sample, then the beam can be focused to the sample, but the intensity distribution becomes low-density and broad area
Solution Approach 1:
The patent employs an asymmetric aperture shape (e.g., D-shaped, elliptical, or rectangular) instead of a conventional circular aperture. This asymmetric geometry creates an asymmetric intensity distribution in the focused beam, concentrating current density in specific regions while maintaining focus precision. The asymmetric shape allows one dimension to be highly focused while the other dimension provides extended current, resolving the contradiction between focus precision and current density.
Solution Approach 2:
The asymmetric aperture design creates different beam characteristics in different spatial directions. In the dimension perpendicular to the aperture's elongated axis, the beam achieves high current density and sharp focus. In the parallel dimension, the beam maintains extended current distribution. This local differentiation of beam quality allows simultaneous achievement of high current density in critical regions while maintaining overall beam intensity.
2Shape
If conventional apertures are used to produce intensity distributions, then the beam can be shaped, but the edges are not sharp and the area is broad
Solution Approach 1:
The asymmetric aperture geometry (D-shaped, elliptical, or rectangular) creates asymmetric diffraction patterns that result in sharp intensity edges in the focused beam. The straight edges of the asymmetric aperture directly translate to sharp intensity transitions in the beam cross-section, particularly on one side of the focal spot. This provides the sharp edges needed for precise material processing while maintaining the desired beam shape.
Solution Approach 2:
The asymmetric aperture introduces dimensional asymmetry to the traditionally symmetric circular aperture. By elongating the aperture in one dimension and creating straight edges, the system achieves sharp intensity transitions in that dimension while maintaining focus in the perpendicular dimension. This dimensional transformation converts the broad, soft-edged intensity distribution into a sharp-edged, anisotropic distribution suitable for precision applications.
3Measurement precision
If highly focused beams are produced, then the beam intensity is concentrated, but spherical aberration and beam tails increase
Solution Approach 1:
The asymmetric aperture shape modifies the diffraction pattern and intensity distribution of the focused beam. By concentrating aperture area in specific angular directions, the asymmetric shape enhances current density in desired regions while suppressing spherical aberration effects and reducing beam tails in opposite directions. The asymmetric geometry acts as an angular filter, shaping the beam's angular distribution to minimize harmful aberrations while maintaining focus concentration.
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
Achieves precise material processing with increased current density and reduced unwanted energy deposition, enhancing milling performance and minimizing damage to the target.
Implementation Method 1
an objective lens configured to focus the beam to the target to produce an asymmetric intensity cross-section for the beam
Data Source
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AI summary
Methods and apparatus 600 for producing a charged particle beam 606 with a charged particle beam source 604 and directing the charged particle beam along a beam axis 608 of a charged particle beam column 602 to a target 610, directing the charged particle beam through an elongated aperture 618 that is situated by an offset with respect to the beam axis, and focusing the beam to the target to produce an asymmetric intensity cross-section for the beam, wherein the cross-section has a sharp intensity edge at the target based on the offset elongated aperture.