Reflected Electron Detection with Secondary Electron Absorption
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Solution Overview
Problem
Existing charged particle beam devices suffer from decreased signal-to-noise ratio (SNR) of reflected electrons due to noise generated when secondary electrons collide with the diaphragm plate, which affects the detection of reflected electrons from the sample's bottom.
Innovation Solution
Incorporating an absorbing plate with a concave portion between the deflector and the reflected electron detector to absorb secondary electrons, and using a filter or second reflected electron detector to separate and block secondary electrons, along with controlling the deflector based on energy differences to improve SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diaphragm plate with pinhole is used to detect reflected electrons, then reflected electrons from deep holes or grooves can be detected, but secondary electrons colliding with the diaphragm plate generate noise that decreases the signal-to-noise ratio
Solution Approach 1:
The harmful secondary electrons are extracted and removed from the detection path by the absorbing plate before they can reach the detector. The absorbing plate selectively absorbs secondary electrons while allowing reflected electrons to pass through to the detector, thereby eliminating the noise source without affecting the useful signal.
Solution Approach 2:
The absorbing plate acts as an intermediary component between the diaphragm plate and the detector. It mediates the interaction between electrons and the detection system by selectively absorbing secondary electrons, thus preventing them from generating noise in the detector while maintaining the detection of reflected electrons.
2Object-affected harmful factors
If an absorbing plate is added to absorb secondary electrons, then the signal-to-noise ratio of reflected electrons is improved, but the device complexity increases
Solution Approach 1:
The absorbing plate is positioned at a specific location where secondary electrons pass through after being emitted from the sample but before reaching the detector. By placing the absorbing plate only in the path of secondary electrons and not reflected electrons, the solution addresses the noise problem locally without requiring a complete redesign of the entire detection system.
Solution Approach 2:
The absorbing plate changes the physical state or properties of secondary electrons by absorbing them, effectively removing them from the electron beam. This parameter change (from present to absorbed) selectively affects secondary electrons while allowing reflected electrons to maintain their trajectory to the detector.
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
Enhances the signal-to-noise ratio of reflected electrons by preventing secondary electrons from being detected, thereby improving the quality of observation images.
Implementation Method 1
an absorbing plate disposed between the deflector and the reflected electron detector and including a concave portion
Implementation Method 2
a deflector configured to deflect trajectories of a secondary electron and a reflected electron emitted from the sample
Data Source
AI summary
A charged particle beam device includes: a charged particle source configured to emit a charged particle beam to be emitted onto a sample; a deflector configured to deflect trajectories of a secondary electron and a reflected electron emitted from the sample; a reflected electron detector configured to detect the reflected electron; a control unit configured to acquire an observation image based on a detection signal output from the reflected electron detector and configured to control an operation of each unit; and an absorbing plate disposed between the deflector and the reflected electron detector and including a concave portion.