Solid State Detector Array for Secondary Electron Counting
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Solution Overview
Problem
Current secondary electron imaging in scanning electron microscopes is limited by noise, distortion, and non-linearity due to the use of scintillator-photomultiplier detectors, which restricts high-resolution quantitative measurements.
Innovation Solution
An array of solid state detectors, such as diodes or CMOS devices, is used to detect and count secondary electrons, employing Poisson statistics for error correction and time-to-digital converters to convert pulses into digital data, reducing noise and enhancing signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scintillator-photomultiplier detectors are used for secondary electron detection, then detection capability is achieved, but noise and distortion increase
Solution Approach 1:
The patent replaces the scintillator-photomultiplier detection system with a direct solid-state detector system. Solid state detectors directly convert incident secondary electrons into electrical signals without requiring scintillation conversion, thereby eliminating the associated noise and distortion while maintaining detection capability.
Solution Approach 2:
The patent extracts and removes the scintillator and photomultiplier components from the detection system. By taking out these problematic components that generate noise and distortion, the system achieves cleaner signals while retaining the essential electron detection function through solid state detectors alone.
2Reliability
If scintillator-photomultiplier detectors are used, then secondary electron detection is enabled, but measurement precision deteriorates
Solution Approach 1:
The patent substitutes the analog scintillator-photomultiplier system with a digital solid-state detector system that directly outputs digital counts. This substitution eliminates the analog-to-digital conversion process that introduces non-linearity and measurement errors, thereby improving quantitative measurement precision while maintaining detection functionality.
Solution Approach 2:
The patent uses solid state detectors that directly replicate the secondary electron signal in digital form without intermediate conversion steps. This direct digital copying of the electron signal preserves the original signal integrity and enables precise quantitative measurements.
3Power
If E-T detector with feedback loop is used, then signal amplification is achieved, but signal distortion increases
Solution Approach 1:
The patent replaces the feedback-based analog amplification system with a direct digital counting system using solid state detectors. Each detector independently counts incident electrons and outputs digital signals without requiring feedback loops, thereby achieving signal amplification through direct digital measurement while eliminating feedback-induced distortion.
Solution Approach 2:
The solid state detectors in the patent are self-sufficient units that independently detect and count electrons without requiring external feedback mechanisms. Each detector in the array operates autonomously, converting incident electrons directly into digital count signals, thereby eliminating the need for distortion-prone feedback loops.
4Ease of operation
If analog feedback loop is used in E-T detector, then system gain control is achieved, but non-linearity increases
Solution Approach 1:
The patent substitutes the analog feedback loop gain control system with a digital counting system using solid state detectors. The digital system inherently provides linear response because each detector independently counts electrons and outputs digital signals directly proportional to the number of incident electrons, eliminating the non-linearity introduced by analog feedback control mechanisms.
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 quantitative secondary electron detection with lower noise and improved signal-to-noise ratios, allowing for critical dimension metrology and enhanced imaging capabilities in materials science and nanotechnology.
Implementation Method 1
an array is comprised of multiple solid state detectors capable of detecting and counting single photons or particles as a digital counter
Implementation Method 2
The detector surface maintained at +10 kV further accelerates the SEs
Implementation Method 3
The scintillator layer emits photons upon being impinged upon by the SEs
Implementation Method 4
The photons travel down the light pipe, hit the photocathode, convert into electrical signal
Data Source
AI summary
Quantitative Secondary Electron Detection (QSED) using the array of solid state devices (SSD) based electron-counters enable critical dimension metrology measurements in materials such as semiconductors, nanomaterials, and biological samples (FIG. 3). Methods and devices effect a quantitative detection of secondary electrons with the array of solid state detectors comprising a number of solid state detectors. An array senses the number of secondary electrons with a plurality of solid state detectors, counting the number of secondary electrons with a time to digital converter circuit in counter mode.