Particle Detector Voltage Switching for Multi-Mode Ion and Electron Detection
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Solution Overview
Problem
Current detectors, such as the Everhardt Thornley Detector (ETD), are inefficient in collecting backscattered electrons and secondary ions due to their design, leading to low detection efficiency and the need for multiple detectors in electron- or ion-beam systems, which increases costs and occupies space in vacuum systems.
Innovation Solution
A particle detector with a sparse collecting electrode, Venetian Blind strips, a fine wire electrode, an extracting electrode, and a scintillating disc, which can switch voltages to selectively detect secondary electrons, secondary ions, or tertiary electrons by optimizing the placement and biasing of these components to enhance detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an ETD (Everhardt Thornley Detector) is used to detect secondary electrons, then detection efficiency for low energy secondary electrons is improved, but detection efficiency for backscattered electrons and secondary ions deteriorates
Solution Approach 1:
The patent implements dynamic voltage switching on the collecting electrode and converter plate to change the detector's function in real-time. By applying different voltages (+80 to +500V for electron mode, -3000 to -4000V for ion mode), the same physical detector can efficiently collect different types of particles, resolving the contradiction between optimized electron detection and versatility for multiple particle types.
Solution Approach 2:
The patent creates a universal detector that can detect secondary electrons, backscattered electrons, and secondary ions using the same physical components. The Venetian Blind strips and sparse collecting electrode serve multiple functions depending on voltage configuration, eliminating the need for separate detectors for different particle types and achieving both high efficiency and versatility.
2Adaptability or versatility
If multiple detectors are used to detect different particle types (secondary electrons, backscattered electrons, secondary ions), then detection coverage is improved, but system complexity and space requirements increase
Solution Approach 1:
The patent implements a single multi-functional detector that replaces multiple specialized detectors. By using voltage switching to change the collecting electrode's function, the system achieves comprehensive particle detection coverage while reducing the number of physical detector components, thereby decreasing system complexity and vacuum space requirements.
Solution Approach 2:
The patent merges the detection functions for secondary electrons, backscattered electrons, and secondary ions into a single integrated detector assembly. The sparse collecting electrode and Venetian Blind strips are shared components that serve different detection purposes based on voltage configuration, consolidating what would traditionally require separate detectors into one unified system.
3Productivity
If the collecting sparse grid voltage is optimized for secondary electron collection, then secondary electron collection efficiency is improved, but collection of backscattered electrons and tertiary electrons deteriorates
Solution Approach 1:
The patent uses dynamic voltage adjustment on the collecting sparse grid to optimize collection for different particle types. For secondary electrons, voltages of +80 to +500V create appropriate attraction fields, while for backscattered electrons and tertiary electrons, the voltage configuration is changed to create field-free or repelling regions, allowing efficient collection of each type without compromising the other.
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
The detector achieves high efficiency (>85%) in detecting secondary electrons, low energy positive ions, and tertiary electrons by selectively switching voltages, reducing the need for multiple detectors and improving the collection of backscattered electrons, thus reducing system costs and space requirements.
Implementation Method 1
An electron collecting sparse 1 at voltages +80 to +500 V attracts SE that are emitted from the sample
Implementation Method 2
The collected SE that pass the sparse grid are further accelerated to an aluminum coated scintillating plate 2 at +several kV to +15kV that produce several hundred photons for each impinging accelerated electron
Implementation Method 3
A light guide (LG) 3 attached to the back side of the scintillating plate guides tens % of the photons to a photomultiplier (PMT) 4. With a suitable design, the PMT of the ETD will start the signal multiplication with several photoelectrons (from the photocathode) for each electron accelerated to the scintillator
Data Source
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AI summary
A multi-purpose efficient charge particle detector that by switching bias voltages measures either secondary ions, or secondary electrons (SE) from a sample, or secondary electrons that originate from back scattered electrons (SE3), is described. The basic version of the detector structure and two stripped down versions enable its use for the following detection combinations: 1. The major version is for measuring secondary ions, or secondary electrons from the sample, or secondary electrons due to back-scattered electrons that hit parts other than the sample together or without secondary electrons from the sample. 2. Measuring secondary ions or secondary electrons from the sample (no SE3). 3. Measuring secondary electrons from the sample and/or secondary electrons resulting from back-scattered electrons hitting objects other than the sample (no ions).