Charged Particle Beam Orbit Corrector for Aberration Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional aberration correction systems for charged particle beam optical systems, such as electron microscopes, face challenges in achieving high-precision and high-resolution convergence due to electro-optical aberrations, which limit the resolving power and accuracy of sample observation and microfabrication.
Innovation Solution
A combination of positive and negative lenses is used to cancel out chromatic and spherical aberrations by creating a diverging action with an electrode of the same sign as the charged particle beam, and a toroidal coil is employed to converge the magnetic flux density, allowing for a larger radiation angle and increased current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rotationally symmetrical electron lens is used to focus the charged particle beam, then the beam can be converged with good controllability, but electro-optical aberration occurs causing beam defocusing and deterioration in resolving power
Solution Approach 1:
The patent divides the optical system into multiple components: a rotationally symmetrical electron lens for basic focusing and an additional electrostatic lens with asymmetric electrodes for aberration correction. This segmentation allows each component to perform its specialized function without interfering with the other, resolving the contradiction between controllability and resolving power.
Solution Approach 2:
The patent introduces asymmetric electrodes (such as quadrupole or sextupole electrodes) that generate asymmetric electric fields to counteract the symmetric aberrations produced by the rotationally symmetrical lens. This asymmetry in the correction field specifically targets and cancels out the electro-optical aberrations while preserving the controllable focusing action of the original lens.
2Productivity
If the charged particle beam current is increased to enhance signal quantity and processing speed, then productivity improves, but the distribution of orbit widens causing increased aberration
Solution Approach 1:
The patent applies preliminary anti-action by introducing the electrostatic aberration correction system before the beam reaches the detection or processing stage. The correction fields are pre-configured to counteract the aberrations that will occur at high currents, allowing the system to operate at high productivity levels without suffering from increased aberration effects.
3Manufacturing precision
If a limiting aperture in ring zone form is disposed on the axis to inhibit aberration, then resolving power improves, but the space-charge effect and Coulomb repulsion increase
Solution Approach 1:
The patent replaces the mechanical limiting aperture approach with an electrostatic field-based correction system. Instead of physically blocking or limiting the beam through apertures, the system uses electric fields from asymmetric electrodes to correct aberrations, thereby avoiding the space-charge effects and Coulomb repulsion that would result from physical aperture limitations.
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 effectively reduces aberrations, enabling high-resolution and high-precision convergence of charged particle beams, improving the accuracy of sample observation and microfabrication while being cost-effective and compact.
Implementation Method 1
an electrode disposed on an axis of rotation symmetry of the off-axis electrode and configured to produce an electric field converging to the axis
Implementation Method 2
a toroidal coil radially distributed-wound and disposed close to the central axis, thereby enabling a magnetic flux density to converge toward the central axis
Implementation Method 3
a magnetic field type corrector formed of a toroidal coil radially distributed-wound and disposed close to the central axis, thereby enabling a magnetic flux density to converge toward the central axis under the influence of an angular divergence between the coils and a coil winding distribution
Data Source
AI summary
The present invention relates to an orbit correction method for a charged particle beam, and aims to solve problems inherent in conventional aberration correction systems and to provide a low-cost, high-precision, high-resolution optical converging system for a charged particle beam. To this end, employed is a configuration in which a beam orbit is limited in ring zone form to form a distribution of electromagnetic field converging toward the center of a beam orbit axis. Consequently, a nonlinear action outwardly augmented, typified by spherical aberration of an electron lens, can be cancelled out. Specifically, this effect can be achieved by an electron disposed on the axis and subjected to a voltage to facilitate the occurrence of electrostatic focusing. For a magnetic field, this effect can be achieved by forming a coil radially distributed-wound on a surface equiangularly divided in the direction of rotation to control convergence of a magnetic flux density.