In-Chamber Electron Detector Vacuum Signal Loss
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Solution Overview
Problem
Existing charged particle beam systems face limitations in detector flexibility and longevity due to the inflexibility of scintillator positioning and significant signal loss through optical components in conventional detectors, leading to reduced efficiency and shorter detector lifetimes.
Innovation Solution
A secondary particle detector with a scintillator and transducer, such as a photomultiplier tube, photodiode, or phototransistor, positioned entirely within the sample vacuum chamber, eliminating the need for light pipes and allowing for improved positioning and increased signal collection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ET detector with light pipe is used to detect secondary electrons, then the detector can be positioned outside the vacuum chamber, but significant signal loss occurs through the optical components and the scintillator positioning is inflexible
Solution Approach 1:
The patent extracts the photomultiplier tube from the vacuum chamber environment and positions it outside, eliminating the need for a light pipe to conduct light through the chamber wall. The scintillator remains inside the chamber close to the sample, while the PMT detects light externally, removing the signal loss pathway through optical interfaces and vacuum seals.
Solution Approach 2:
The patent introduces a transparent window as an intermediary element that allows light to pass from the scintillator inside the vacuum chamber to the photomultiplier tube outside, while maintaining vacuum integrity. This window serves as a mediator that eliminates the need for complex light pipe assemblies and reduces signal loss.
2Productivity
If the scintillator is positioned close to the work piece to maximize signal collection, then signal collection efficiency improves, but the rigid light pipe structure limits positioning flexibility and system reconfiguration
Solution Approach 1:
The patent segments the detector system into two separate components: the scintillator positioned inside the vacuum chamber close to the work piece for optimal signal collection, and the photomultiplier tube positioned outside the chamber. This segmentation allows independent optimization of each component's position and eliminates the constraints of a rigid integrated light pipe structure.
Solution Approach 2:
The patent transitions from a single-dimension constrained system (light pipe length and routing) to a multi-dimensional configuration where the scintillator can be positioned optimally in three-dimensional space inside the chamber, while the PMT is freely positionable outside the chamber, adding spatial flexibility.
3Adaptability or versatility
If multiple accessories are positioned near the work piece to enhance functionality, then system capability improves, but space congestion increases and detector positioning becomes more difficult
Solution Approach 1:
The patent extracts the photomultiplier tube from the congested vacuum chamber environment and positions it outside, removing it from the space management problem. This allows multiple accessories to be positioned near the work piece inside the chamber without competing for space with the detector components.
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 configuration enhances signal collection efficiency, extends detector lifetime, and provides greater flexibility in system reconfiguration, enabling better image quality and reduced damage to the work piece during scanning.
Implementation Method 1
impact a scintillator 108, which is composed of a material, (such as a phosphor, a light-emitting plastic or a garnet oxide) that emits light (called cathodoluminescence) when impacted by charged particles such as electrons 142
Implementation Method 2
The light is typically conducted by a rigid light pipe 110, a solid plastic or glass rod passing through a sealed port in the specimen chamber, through a transparent window 112 in the vacuum chamber to a photomultiplier tube (PMT) 114 that is positioned outside the vacuum chamber. In PMT 114, the light causes the emission of electrons
Data Source
AI summary
A secondary particle detector 302 for a charged particle beam system 300 includes a scintillator 304 and a transducer 312, such as a photomultiplier tube, positioned within a vacuum chamber 107. Unlike prior art Everhart-Thornley detectors, the photomultiplier is positioned within the vacuum chamber, which improves detection by eliminating optical couplings and provides flexibility in positioning the detector.