Integrated Charged Particle Lens for Low-Energy SEM Aberration Control
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Solution Overview
Problem
Existing scanning electron microscopes (SEMs) face challenges with misalignment of electrostatic and magnetic lenses, leading to increased aberrations and deteriorated image resolution, particularly at low electron energies.
Innovation Solution
A charged particle lens is designed with a unified electrostatic and magnetic lens, integrated into a single physical element, eliminating the need for alignment and minimizing parasitic aberrations by generating both fields simultaneously within a single pole piece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate electrostatic and magnetic lenses are used in series, then each lens can provide its focusing effect, but misalignment between the lenses occurs leading to increased aberrations
Solution Approach 1:
The patent combines separate electrostatic and magnetic lenses into a single integrated lens assembly. The electrostatic lens and magnetic lens are merged into one physical unit with shared components, eliminating the alignment issues between separate lenses while maintaining both focusing effects simultaneously.
2Measurement precision
If the electrostatic lens is positioned closer to the sample, then optical properties are improved, but the lens creates a convergent effect that changes electron energy
Solution Approach 1:
The integrated lens combines the electrostatic and magnetic focusing functions into a single unit positioned close to the sample. This allows the electrostatic field to provide strong focusing (improving optical properties) while the magnetic field simultaneously acts to minimize energy changes and optical aberrations, resolving the contradiction between positioning and energy conservation.
3Measurement precision
If a compound lens with both electrostatic and magnetic components is used, then image resolution is improved, but the device complexity increases
Solution Approach 1:
The patent merges the electrostatic lens and magnetic lens into a single integrated assembly sharing common components such as the first pole piece, second pole piece, and lens coil. This unified structure provides compound lens functionality (improved image resolution) while reducing overall device complexity compared to having separate electrostatic and magnetic lens assemblies.
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 integrated lens provides improved image resolution and reduced aberrations by positioning the magnetic and electrostatic fields closer to the sample, enhancing the focusing capabilities of the SEM.
Implementation Method 1
a lens coil arranged to generate a magnetic field at the first pole piece and at the second pole piece
Implementation Method 2
at least one voltage supply, arranged to apply a potential difference between the second pole piece and the sample mounted at the sample position to generate an electric field
Implementation Method 3
the generated magnetic field and generated electric field for focusing a beam of charged particles passing through the central apertures of the first and second pole piece
Data Source
AI summary
A charged particle lens for focusing a beam of charged particles towards a sample mounted at a sample position. The charged particle lens comprises a first pole piece, a second pole piece, a lens coil and at least one voltage supply. The second pole piece is electrically insulated from the first pole piece and has a central aperture, wherein the second pole piece is arranged to be aligned with the first pole piece, which also has a central aperture, such that a central axis of the charged particle lens extends through the central aperture of the first pole piece and the second pole piece. The lens coil is arranged to generate a magnetic field at the first and second pole pieces, and the at least one voltage supply is arranged to apply a potential difference between the second pole piece and the sample to generate an electric field.