Charged-particle beam signal detection eliminating ringing noise
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Solution Overview
Problem
In scanning electron microscopes, the use of semiconductor elements as detectors for reflected electrons leads to impedance matching issues due to long-distance wiring, causing signal reflection and ringing noise in the detection waveform, which complicates accurate imaging.
Innovation Solution
A charged-particle beam system with a signal detection unit that separates detection signals into rising and falling components, processes the falling signal to eliminate ringing, and combines these signals to produce a clean detection signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photoelectric conversion element is used as a detector for reflected electrons, then the detection capability is improved, but impedance matching becomes difficult due to long-distance wiring
Solution Approach 1:
A buffer circuit is introduced as an intermediary component between the photoelectric conversion element and the signal processing circuit. The buffer circuit includes a first capacitor connected to the photoelectric conversion element and a second capacitor connected to the signal processing circuit, serving as a mediator to isolate impedance mismatches and eliminate ringing in the detection signal.
2Ease of operation
If the photoelectric conversion element is connected to the signal processing circuit through long-distance wiring, then the detector can be disposed outside the vacuum column, but signal reflection and ringing noise are generated
Solution Approach 1:
The buffer circuit acts as an intermediary that isolates the photoelectric conversion element from the signal processing circuit, preventing signal reflection and ringing noise while allowing long-distance wiring configuration.
Solution Approach 2:
Capacitors are预先 (in advance) arranged in the circuit to cushion against signal reflection and ringing before they can propagate and cause harmful effects. The first and second capacitors are positioned to preemptively absorb and dampen oscillations.
3Adaptability or versatility
If the output impedance of the photoelectric conversion element changes with output current, then the detection signal varies, but impedance matching with the signal processing circuit becomes difficult
Solution Approach 1:
The buffer circuit serves as a stable intermediary that decouples the variable output impedance of the photoelectric conversion element from the fixed input impedance of the signal processing circuit, maintaining reliable impedance matching despite current variations.
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 enables accurate measurement and observation of inspection images by eliminating ringing noise and ensuring high-speed falling signals, improving image quality in charged-particle beam systems.
Implementation Method 1
as a detector that can be disposed in the vicinity of the sample, it is preferable to use a semiconductor element such as a photoelectric conversion element
Data Source
AI summary
A charged-particle beam system comprises: a charged-particle beam device containing a detection unit for detecting electrons generated by irradiating a sample with a charged-particle beam released from a charged particle source; and a signal detection unit in which a detection signal from the detection unit is input through a wiring. The signal detection unit comprises: a separation unit for separating into a rising signal and a falling signal the detection signal from the detection unit; a falling signal processing unit for at least eliminating ringing in the falling signal; and a combination unit generating and delivering a combined signal produced by combining the rising signal, which has been separated by the separation unit, with the falling signal wherefrom the ringing has been eliminated by the falling signal processing unit.