In-Column Back-Scattered Electron Detector for SEM
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Solution Overview
Problem
Existing electron-optical columns have low efficiency in detecting back-scattered electrons due to complex designs and additional control electrodes required for tuning the crossover position, resulting in inefficient detection of back-scattered electrons.
Innovation Solution
An in-column back-scattered electron detector is integrated into a combined electrostatic/magnetic objective lens, where the detector forms a charged particle-sensitive surface as part of the second electrode, eliminating the need for a third electrode and its power supply, and uses a scintillator disk with a photon detector to enhance detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a combined electrostatic/magnetic objective lens is used with a detector formed as part of the second electrode, then the detection efficiency for back-scattered electrons is improved to 85%, but the device complexity is reduced by eliminating the need for a third electrode and its power supply
Solution Approach 1:
The detector is merged with the second electrode of the objective lens, forming a unified structure where the detector surface is part of the electrode. This integration eliminates the need for a separate third electrode and its associated power supply, reducing device complexity while maintaining high detection efficiency for back-scattered electrons
Solution Approach 2:
The second electrode serves dual functions: it provides the electrostatic field necessary for lens operation and simultaneously acts as the detection surface for back-scattered electrons. This multi-functionality reduces the total number of components needed in the system
2Ease of manufacture
If the detector is placed in the objective lens as part of the second electrode, then the design is simplified and detection capabilities are improved, but additional electrodes or power supplies are eliminated
Solution Approach 1:
The detector is merged with the second electrode of the objective lens, forming a unified structure where the detector surface is part of the electrode. This integration eliminates the need for a separate third electrode and its associated power supply, reducing device complexity while maintaining high detection efficiency for back-scattered electrons
3Measurement precision
If a scintillator disk with photon detector is used, then the detection efficiency for back-scattered electrons is enhanced to 85%, but the device complexity increases due to the additional detection components
Solution Approach 1:
The scintillator disk and photon detector are integrated into the second electrode structure, combining the detection functions within the existing electrode framework. This approach enhances detection efficiency while minimizing the increase in overall device complexity by utilizing the available space within the lens structure
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 achieves an 85% detection efficiency for back-scattered electrons while maintaining lens performance, simplifying the design and improving detection capabilities without additional electrodes or power supplies.
Implementation Method 1
The detector is formed as a charged particle sensitive surface, preferably a scintillator disk that acts as one of the electrode faces forming the electrostatic focusing field. The photons generated in the scintillator are detected by a photon detector
Implementation Method 2
The photons generated in the scintillator are detected by a photon detector, such as a photo-diode or a multi-pixel photon detector
Implementation Method 3
The SEs are kept close to the axis of the objective lens due to the combined effect of the electrostatic and the magnetic field breaking out of the lens
Data Source
AI summary
The invention relates to an in-column back-scattered electron detector, the detector placed in a combined electrostatic/magnetic objective lens for a SEM. The detector is formed as a charged particle sensitive surface, preferably a scintillator disk that acts as one of the electrode faces forming the electrostatic focusing field. The photons generated in the scintillator are detected by a photon detector, such as a photo-diode or a multi-pixel photon detector. The objective lens may be equipped with another electron detector for detecting secondary electrons that are kept closer to the axis. A light guide may be used to offer electrical insulation between the photon detector and the scintillator.