Charged Particle Beam Detection Circuit for High-Speed SEM Imaging
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Solution Overview
Problem
In scanning electron microscopes, the pulse counting system faces issues with erroneous detection and omission of secondary electrons and reflection electrons due to their decreased occurrence frequency during high-speed scanning, leading to deteriorated image visibility, especially in deep grooves and deep holes.
Innovation Solution
Incorporating a pulse time detecting circuit using differential circuits to separate signals from plural continued secondary electrons and a pulse height value detecting circuit to detect overlapping signals, enhancing the detection accuracy and visibility of measurement inspection images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed scanning is used to increase productivity, then scanning speed is improved, but secondary electrons and reflection electrons are omitted or erroneously detected due to decreased occurrence frequency
Solution Approach 1:
The patent segments the detection process into two independent circuits: a pulse time detecting circuit that processes signals sequentially in time, and a pulse height value detecting circuit that processes signals simultaneously. This segmentation allows the system to maintain high scanning speed while accurately detecting all secondary electrons and reflection electrons without omission or erroneous detection.
2Measurement precision
If pulse counting system is used to improve measurement precision, then detection accuracy is improved, but image visibility deteriorates due to erroneous detection and omission at high scanning speeds
Solution Approach 1:
The patent merges the advantages of two different detection approaches by combining the pulse time detecting circuit (which processes signals sequentially with high precision) and the pulse height value detecting circuit (which processes signals simultaneously to capture all electrons). This combination resolves the contradiction between measurement precision and image visibility by eliminating both erroneous detection and omission that plague single-system approaches at high scanning speeds.
3Loss of time
If scanning speed is increased to reduce inspection time, then inspection time is reduced, but signal occurrence frequency decreases leading to detection errors
Solution Approach 1:
The patent addresses the contradiction by operating in two dimensional domains simultaneously: the pulse time detecting circuit operates in the time domain to process signals sequentially as they arrive, while the pulse height value detecting circuit operates in the amplitude domain to process all signals simultaneously regardless of timing. This dimensional approach allows high-speed scanning to proceed without losing detection accuracy despite reduced signal occurrence frequency.
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 effectively enhances the visibility of measurement inspection images by accurately detecting plural secondary electrons and reflection electrons, reducing erroneous detection and omission, and optimizing brightness histograms to improve image contrast and clarity.
Implementation Method 1
energy of secondary electrons, reflection, and the like generated from the radiation is detected
Implementation Method 2
energy of secondary electrons, reflection, and the like generated from the radiation is detected
Data Source
AI summary
There is provided a charged particle beam apparatus radiating a charged particle beam to a specimen so as to acquire an image of the specimen, the charged particle beam apparatus including: a charged particle gun that generates the charged particle beam; an electron optical system that radiates the charged particle beam emitted from the charged particle gun onto a surface of the specimen so as to scan the surface of the specimen; a detecting unit that detects secondary electrons or reflection electrons emitted from the specimen, and converts the electrons into pulse signals; a pulse signal detecting circuit that detects time detecting information regarding time of the pulse signals converted by the detecting unit, and peak value detecting information regarding each peak value of the pulse signals; and an image processing unit that generates luminance gradation of the acquired image based on a time detecting signal and a peak value detecting signal of the pulse signals detected by the pulse signal detecting circuit.