Electron Microscope Compensation Electrode for Low-Angle Backscattered Electron Detection
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Solution Overview
Problem
Electron microscopes with semi-in-lens objective lenses struggle to detect low-angle backscattered electrons effectively due to the magnetic field interference, which affects image quality by returning these electrons to the sample rather than allowing their detection.
Innovation Solution
Incorporating a compensation electrode or magnetic pole between the sample and detector to control the trajectory of low-angle backscattered electrons, allowing for their detection without interfering with the electron beam's narrowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a semi-in-lens objective lens is used to narrow the electron beam, then the resolution of the observation image is improved, but low angle backscattered electrons are returned to the sample and cannot be detected
Solution Approach 1:
The objective lens is divided into two functional parts: an inner magnetic pole for focusing the electron beam and an outer magnetic pole for controlling backscattered electrons. This segmentation allows each part to perform its specific function without interfering with the other, resolving the contradiction between beam narrowing and electron detection.
Solution Approach 2:
A compensation electrode is introduced as an intermediary component between the sample and detector. This electrode generates an electric field that compensates for the magnetic field's harmful effect of returning low angle backscattered electrons to the sample, enabling their detection while maintaining beam focus.
2Measurement precision
If a detector is positioned close to the electron beam irradiation position to detect low angle backscattered electrons, then detection capability is improved, but the electron beam narrowing is adversely affected
Solution Approach 1:
The magnetic pole structure is segmented into inner and outer poles with distinct functions. The inner pole maintains beam focus while the outer pole, in conjunction with the compensation electrode, enables detection of low angle backscattered electrons without requiring the detector to be positioned close to the beam path.
Solution Approach 2:
The compensation electrode acts as a mediator that enables detection capability without requiring close detector positioning. By generating a compensating electric field, it allows low angle backscattered electrons to be detected while the detector can be positioned at an optimal distance that does not interfere with beam narrowing.
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
Enables the detection of low-angle backscattered electrons, improving the quality of scanning electron microscope images by preventing magnetic field interference and maintaining beam focus.
Implementation Method 1
an objective lens configured to focus the electron beam by a leakage magnetic field which is a magnetic field leaked toward the sample
Implementation Method 2
a compensation electrode or a compensation magnetic pole provided between the sample and the detector and configured to control a trajectory of the third electron
Data Source
AI summary
Provided is an electron microscope for generating an observation image of a sample by using an electron beam in order to obtain a scanning electron microscope image by low angle backscattered electrons, which are backscattered electrons emitted at a low angle with respect to a sample surface, even for an electron microscope including an objective lens that leaks a magnetic field to a sample. The electron microscope includes: an electron source configured to irradiate the sample with the electron beam; an objective lens configured to focus the electron beam by a leakage magnetic field which is a magnetic field leaked toward the sample; a detector configured to detect a third electron which is an electron emitted when a low angle backscattered electron is caused to collide with the sample by the leakage magnetic field, the low angle backscattered electron being a backscattered electron emitted at a low angle with respect to a surface of the sample; and a compensation electrode or a compensation magnetic pole provided between the sample and the detector and configured to control a trajectory of the third electron.