Energy-Discriminating Electron Detector for Scanning Electron Microscopes
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Solution Overview
Problem
Out-lens detectors in scanning electron microscopes lack energy discrimination functionality, leading to reduced signal intensity and noise in images, especially when observing insulator samples, due to the capture of high-energy electrons and SE3 electrons, which lose original information and contribute to image noise.
Innovation Solution
An energy discriminating electron detector system is introduced, featuring a main electrode with a negative voltage and a shield electrode, such as a grid electrode, to selectively detect low-energy electrons and control electron trajectories, preventing SE3 electron generation and guiding secondary electrons to the detector effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an out-lens detector is used to capture secondary electrons, then the detector can be installed on the wall of the sample chamber, but high energy electrons impinge on the wall surface and generate SE3 electrons that reach the detector as noise
Solution Approach 1:
An electrostatic lens is introduced as an intermediary component between the sample chamber wall and the out-lens detector. This electrostatic lens creates an electric field that selectively guides low energy secondary electrons to the detector while repelling high energy electrons, thereby preventing SE3 electron generation and eliminating the harmful noise effect.
Solution Approach 2:
The patent applies energy discrimination by controlling the electrostatic potential parameters of the electrostatic lens. By adjusting the voltage parameters of the electrostatic lens, the system selectively transmits electrons within a specific energy range (low energy secondary electrons) while blocking high energy electrons, thus changing the energy parameter distribution reaching the detector.
2Measurement precision
If energy discrimination is implemented to filter electrons, then low energy secondary electrons can be selectively detected, but the device complexity increases with additional electrodes and control mechanisms
Solution Approach 1:
The electrostatic lens serves multiple functions simultaneously: it acts as both an electron guiding element and an energy filtering mechanism. By integrating these functions into a single component rather than adding separate filtering devices, the patent achieves energy discrimination while minimizing the increase in device complexity.
Solution Approach 2:
Energy discrimination is achieved by controlling the electrostatic potential parameters of the lens rather than through mechanical or physical barriers. This parameter-based control allows for adjustable energy filtering without requiring complex mechanical structures, thus maintaining relative simplicity while achieving precise electron energy discrimination.
3Quantity of substance
If the out-lens detector captures all electrons, then signal intensity is high, but SE3 electrons contribute to noise and reduce image quality
Solution Approach 1:
The electrostatic lens creates an energy-selective electric field that changes the transmission parameter based on electron energy. Low energy secondary electrons are guided to the detector maintaining signal intensity, while high energy electrons are repelled, preventing SE3 electron generation and eliminating noise in the captured signal.
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 solution enables the detection of low-energy electrons, enhancing image clarity and contrast, and allows for more accurate observation of insulator samples by suppressing noise and improving signal intensity, thereby expanding the application range of scanning electron microscopy.
Implementation Method 1
a main electrode disposed between an energy beam radiating device radiating an electron or ion beam through an objective lens and an object emitting electrons in response to the irradiation of the ion or electron beam, the main electrode being applied with an negative voltage
Implementation Method 2
a shield electrode is provided that is disposed at least between the main electrode and the object, and shields an electric field caused by the negative voltage applied to the main electrode
Data Source
Figure 1(a)~1(b)
Figure 2~3(b)
Figure 4
AI summary
When an electrode (29) such as a grid applied with a negative voltage is installed in front of an objective lens (23), low energy electrons among secondary electrons (25) generated from a sample (24) by an electron beam or the like is reflected by the electrode to come into a detector (22) installed in the sample (24) side, while electrons of higher energy are not detected, since they are not reflected by the electrode. Accordingly, since only the electrons of lower energy of the secondary electrons can be detected by discriminating the secondary electrons by the energy, it is possible to obtain a detection signal, e.g., rich in the information on the surface state of the sample.