Segmented Electron Detector for Large-Angle BSE Imaging
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Solution Overview
Problem
Existing electron beam apparatuses face challenges in detecting backscattered electrons with high efficiency, particularly for high-energy electrons emitted at large angles, which are crucial for inspecting 3D structures and buried layers with high resolution.
Innovation Solution
A detector device with a segmented electron detector is introduced, featuring radially inner and outer detector segments. This device amplifies signals from signal electrons impinging on the inner segments with a first amplification strength and those impinging on the outer segments with a second, higher amplification strength, enhancing the detection of large-angle backscattered electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single amplification strength is used for all detector segments, then the device complexity is reduced, but the detection precision for backscattered electrons at different angles deteriorates
Solution Approach 1:
The detector device is divided into multiple detector segments arranged at different radial distances from the optical axis. Each segment can be independently configured to detect backscattered electrons at different emission angles, allowing optimized detection precision for each angular range while maintaining manageable device complexity through modular architecture
Solution Approach 2:
Different detector segments are assigned different amplification strengths according to their specific detection requirements. Segments detecting large-angle backscattered electrons use higher amplification strengths to enhance weak signals, while segments detecting small-angle electrons use lower amplification strengths, optimizing overall detection precision without uniformly increasing device complexity
2Measurement precision
If high amplification strength is applied to all detector segments, then the signal-to-noise ratio for large-angle backscattered electrons is improved, but the detection speed for secondary electrons deteriorates
Solution Approach 1:
The detector is segmented into regions with different amplification characteristics. By separating the detection of backscattered electrons (requiring high amplification) from secondary electrons (requiring fast response), the system achieves high signal-to-noise ratio for BSEs without compromising detection speed for SEs
Solution Approach 2:
High amplification strength is applied locally only to detector segments that primarily detect backscattered electrons, while segments detecting secondary electrons use lower amplification strength to maintain fast response. This localized optimization resolves the contradiction between signal-to-noise ratio and detection speed
3Productivity
If a detector is positioned close to the sample for high BSE detection efficiency, then the detection efficiency for backscattered electrons is improved, but the detection capability for secondary electrons deteriorates
Solution Approach 1:
The detector device is segmented into multiple detector segments positioned at different radial distances from the optical axis. This segmentation enables the detector to simultaneously capture backscattered electrons (detected by inner segments) and secondary electrons (detected by outer segments) with high efficiency, providing versatile detection capability while maintaining close positioning to the sample
Solution Approach 2:
The multi-segment detector structure enables a single detector device to perform multiple detection functions: detecting backscattered electrons with high efficiency through inner segments while simultaneously detecting secondary electrons through outer segments. This multi-functionality resolves the contradiction between detection efficiency and detection capability
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 solution significantly improves the detection efficiency of backscattered electrons, particularly high-energy ones, allowing for accurate inspection of both surface and buried structures with enhanced resolution and signal-to-noise ratio.
Implementation Method 1
backscattered electrons (BSEs), i.e. high-energy electrons backscattered from the sample
Implementation Method 2
secondary electrons (SEs), i.e. low energy signal electrons generated at the sample surface
Data Source
AI summary
A detector device (10) for detecting signal electrons in an electron beam apparatus (100) is described. The detector device (10) includes an electron detector (120) with a central opening (23) for the passage of a primary electron beam (105) and with one or more radially inner detector segments (21) and one or more radially outer detector segments (22) that at least partially surrounds the central opening. The detector device is configured to amplify one or more first detector signals caused by a first group of signal electrons impinging on the one or more radially inner detector segments (21) with a first amplification strength while amplifying one or more second detector signals caused by a second group of signal electrons impinging on the one or more radially outer detector segments (22) with a second amplification strength higher than the first amplification strength. Further described is an electron beam apparatus with the detector device described herein, as well as a method of imaging and/or inspecting a sample with an electron beam apparatus as described herein.