Magnetic Boosting Electrode in Object Lens to Prevent Beam Blur
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Solution Overview
Problem
Magnetic saturation in a magnetic field generation type object lens leads to leakage of unnecessary magnetic fields, causing electron beam blurring and reduced spatial resolution in charged particle beam devices, particularly at lower acceleration voltages.
Innovation Solution
Incorporating a boosting electrode made of magnetic material within the object lens to concentrate and manage the magnetic field, preventing leakage and enhancing beam focus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the acceleration voltage of the electron beam is reduced to 1 kV or less to prevent sample charging or damage, then the sample is protected from charging or damage, but chromatic aberration increases and spatial resolution of the observation image decreases
Solution Approach 1:
The patent changes the acceleration voltage parameter dynamically by introducing a boosting electrode that applies a positive voltage (e.g., +1 kV to +10 kV) to accelerate the electron beam through the object lens, while simultaneously applying a negative voltage to the sample to decelerate the beam before impact. This allows the beam to experience high acceleration voltage during lens passage (reducing chromatic aberration) while maintaining low impact voltage on the sample (preventing damage).
2Volume of moving object
If the size of the charged particle beam device is reduced, then the device becomes more compact, but the magnetic path thickness is reduced and magnetic field leakage occurs, causing electron beam blurring and reduced spatial resolution
Solution Approach 1:
The patent introduces a boosting electrode as an intermediary component within the object lens structure. This electrode, formed of magnetic material, serves as a mediator that both accelerates the electron beam and manages the magnetic field distribution. By positioning this magnetic material electrode inside the thin magnetic path, it acts as a local magnetic field manager that prevents leakage while enabling the compact device design.
Solution Approach 2:
The patent employs composite material construction by forming the boosting electrode from magnetic material (such as ferrite or permalloy) and integrating it within the object lens structure. This magnetic material electrode combines the functions of voltage application and magnetic field management, creating a composite structure that addresses both the compact size requirement and the magnetic field leakage problem simultaneously.
3Measurement precision
If a boosting electrode made of magnetic material is introduced to prevent magnetic field leakage, then spatial resolution is improved, but device complexity increases
Solution Approach 1:
The boosting electrode is designed as a multi-functional component that simultaneously performs three functions: (1) applying positive acceleration voltage to the electron beam, (2) managing and containing the magnetic field within the object lens, and (3) preventing magnetic field leakage to the electron beam trajectory. By consolidating these functions into a single component, the patent avoids adding separate elements that would increase device complexity.
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 configuration effectively prevents magnetic field leakage, maintaining beam clarity and improving spatial resolution by reducing chromatic aberration, even at lower acceleration voltages.
Implementation Method 1
a positive voltage for accelerating an electron beam is applied to a cylindrical electrode disposed in an electron beam passage of an object lens
Implementation Method 2
an object lens configured to generate a magnetic field for focusing the charged particle beam
Implementation Method 3
magnetic saturation in a magnetic field generation type object lens is not considered in PTL 1
Implementation Method 4
The boosting electrode is formed of a magnetic material
Data Source
AI summary
The invention provides a charged particle beam device that prevents a leakage of an unnecessary magnetic field to a trajectory of a charged particle beam with which a sample is irradiated in a sample observation according to a boosting method. The charged particle beam device includes: a charged particle source configured to generate the charged particle beam with which the sample is irradiated; an object lens configured to generate the magnetic field for focusing the charged particle beam; and a boosting electrode that is provided inside the object lens and to which a voltage for accelerating the charged particle beam is applied. The boosting electrode is formed of a magnetic material.