Charge Detector Layout for Cleaner Electron-Beam Signal Separation
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Solution Overview
Problem
Existing electron-beam imaging systems face challenges in accurately distinguishing between backscattered electrons and secondary electrons due to the generation of second-generation interaction products, which reduces the net current measured by the detector.
Innovation Solution
The electron-beam imaging system incorporates a charge detector with a low atomic mass region closer to the sample than a high atomic mass region, reducing the yield of second-generation interaction products and enhancing the distinction between backscattered and secondary electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If methods are used to repel secondary electrons at the detector, then secondary electrons can be distinguished from backscattered electrons, but second-generation interaction products are generated which reduce the net current measured by the detector
Solution Approach 1:
The detector is designed with spatially varying atomic mass properties: a low atomic mass region (first region) positioned closer to the sample and a high atomic mass region (second region) positioned farther from the sample. This local differentiation in material composition allows the detector to optimize electron interaction characteristics at different depths, reducing second-generation interaction products while maintaining detection precision.
Solution Approach 2:
The detector employs a composite structure combining materials with different atomic masses in specific spatial arrangements. The low atomic mass material (e.g., aluminum, carbon) and high atomic mass material (e.g., tungsten, lead) are integrated into a single detector assembly, leveraging the complementary properties of each material to achieve both secondary electron repulsion and minimized interaction product generation.
2Quantity of substance
If a charge detector is used to collect interaction products, then both backscattered electrons and secondary electrons can be detected, but it becomes difficult to distinguish between the two types of electrons
Solution Approach 1:
The detector utilizes spatially differentiated regions with distinct atomic mass characteristics. The low atomic mass region preferentially interacts with and repels secondary electrons, while the high atomic mass region is more effective for backscattered electron detection. This local quality variation enables the detector to distinguish between electron types based on their different interaction behaviors with materials of varying atomic masses.
Solution Approach 2:
The detector is segmented into functionally distinct regions: a first region with low atomic mass material and a second region with high atomic mass material. Each segment performs a specialized function in the electron detection process, with the segmentation allowing independent optimization of detection characteristics for different electron types without compromising overall signal collection.
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 effectively reduces the yield of second-generation interaction products, leading to more accurate detection of backscattered electrons and improved measurement precision in electron-beam imaging systems.
Implementation Method 1
The low atomic mass region is closer to the sample compared to the high atomic mass region for reducing a second-generation interaction products yield at the charge detector
Implementation Method 2
The interactions between the material structure at the probing spot and the landing electrons from the beam of electrons cause electrons to be emitted from the surface, such as secondary electrons, backscattered electrons or Auger electrons
Data Source
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AI summary
The present invention provides an electron-beam imaging system comprising an electron-beam source for generating a primary beam, an optical system for directing and focusing the primary beam onto a sample, and a charge detector for collecting interaction products. The charge detector comprises: a current detection electrode configured to connect to current measurement circuitry, a low atomic mass region comprising a low atomic mass material, and a high atomic mass region comprising a high atomic mass material. The high atomic mass material has a higher atomic mass than the low atomic mass material. The electron-beam imaging system is configured such that during use the low atomic mass region is closer to the sample compared to the high atomic mass region for reducing a second-generation interaction products yield at the charge detector.