Multi-Detector BSE Signal Discrimination Against Dark Pulses
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Solution Overview
Problem
Charged particle beam apparatuses face challenges in accurately measuring three-dimensional structures due to signal electrons being absorbed by the structure, leading to reduced signal-to-noise ratio and decreased measurement accuracy, particularly from dark pulses in back scattered electron detectors.
Innovation Solution
The system employs multiple back scattered electron detectors to differentiate between back scattered electron signals and dark pulses by analyzing the simultaneous occurrence of pulse signals across detectors, using a controller to determine time differences and thresholds to distinguish between BSE signals and dark pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single BSE detector is used to detect back scattered electrons, then the detection capability is simple and device complexity is low, but the ability to distinguish BSE signals from dark pulses is insufficient leading to poor measurement precision
Solution Approach 1:
The BSE detection system is divided into multiple independent detectors (at least two), each capable of detecting BSE signals separately. This segmentation allows the system to compare signals from different detectors to distinguish true BSE signals from dark pulses, thereby improving measurement precision while managing device complexity through modular architecture
Solution Approach 2:
Multiple BSE detectors are combined into a single integrated detection system with a unified controller that processes signals from all detectors. The controller merges the detection capabilities of individual detectors and applies signal comparison logic to differentiate BSE signals from dark pulses, achieving high measurement accuracy through collaborative detection
2Measurement precision
If multiple BSE detectors are used to improve signal discrimination, then measurement precision improves, but the device complexity and signal processing complexity increase
Solution Approach 1:
The controller implements a feedback mechanism where signals from multiple BSE detectors are continuously monitored and compared. When a dark pulse is detected in one detector, the system uses feedback from other detectors to identify and reject the false signal, maintaining high measurement precision through adaptive signal validation
Solution Approach 2:
The system uses a minimal number of detectors (at least two) to achieve the necessary signal discrimination capability without over-engineering the system. This partial action approach provides sufficient measurement precision improvement while avoiding excessive device complexity that would result from using many more detectors
3Reliability
If dark pulses are not distinguished from BSE signals, then the detection system is simple, but the signal-to-noise ratio deteriorates and measurement accuracy is reduced
Solution Approach 1:
The system extracts and removes dark pulse signals from the detection output by comparing signals from multiple BSE detectors. Since dark pulses occur randomly in individual detectors while true BSE signals appear simultaneously across multiple detectors, the system can extract and eliminate dark pulse noise, improving signal-to-noise ratio and measurement reliability
Solution Approach 2:
The detection system uses a composite approach combining multiple detector types or configurations to achieve both noise rejection and signal detection. By integrating multiple detection channels with different characteristics into a unified system, the apparatus achieves high signal-to-noise ratio while managing overall system complexity
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 approach enhances measurement accuracy by reducing the impact of dark pulses, allowing for precise detection and measurement of three-dimensional structures.
Implementation Method 1
The scintillator is a device that detects back scattered electrons and converts the back scattered electrons into photons
Implementation Method 2
The photomultiplier or the semiconductor photodetector is a device that converts the generated photons into a back scattered electron signal
Data Source
AI summary
There is provided a technique capable of reducing deterioration of a back scattered electron (BSE) detector caused by a dark pulse. Charged particle beam apparatus includes: a plurality of BSE detectors configured to detect a BSE from a sample; and a controller. The controller acquires, within a period, a first peak time of a first peak included in an output signal from a first BSE detector among the plurality of BSE detectors, and a second peak time of a second peak included in an output signal from a second BSE detector other than the first BSE detector among the plurality of BSE detectors, determines, when the second peak is present where a time difference between the first peak time and the second peak time is within a threshold value, that the first peak is caused by the BSE, and determines, when the second peak is not present where the time difference is within the threshold value, that the first peak is caused by the dark pulse.