ESEM Gas Injection Anode Integrated with Concentrator
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Solution Overview
Problem
High vacuum scanning electron microscopes (SEM) face challenges in processing insulating samples due to charge accumulation, which deflects the electron beam and affects secondary electron detection, and existing solutions like High Pressure SEMs or environmental cells are not fully compatible with high vacuum systems.
Innovation Solution
A gas injection system (GIS) that concentrates gas locally near the sample surface, using a needle and shroud structure to direct gas flow and ionize it, with an electrically biased anode to neutralize charge and enhance secondary electron detection, allowing operation in a high vacuum environment while maintaining high resolution imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas is introduced into the chamber to neutralize charge on insulating samples, then charge neutralization is improved, but vacuum quality deteriorates due to gas molecules scattering the primary electron beam
Solution Approach 1:
The patent introduces gas locally at the sample surface through a needle positioned close to the sample, rather than flooding the entire chamber. This localized gas introduction zone creates a small region where charge neutralization can occur without significantly compromising the overall vacuum quality in the chamber, thereby reducing electron beam scattering while maintaining neutralization effectiveness.
2Reliability
If High Pressure SEM or environmental cell is used to process insulating samples, then charge neutralization is improved, but device complexity increases and compatibility with high vacuum systems is reduced
Solution Approach 1:
The patent extracts the gas introduction function from the complex environmental cell or High Pressure SEM system and implements it as a simple needle-based local gas introduction mechanism. This simplified approach achieves charge neutralization without requiring the complex pressure control systems, environmental cells, or high pressure chambers, thereby maintaining compatibility with high vacuum SEM systems while reducing overall device complexity.
3Reliability
If gas pressure is increased to enhance charge neutralization, then neutralization effectiveness is improved, but imaging resolution deteriorates due to increased beam scattering
Solution Approach 1:
The patent creates a localized gas environment only at the sample surface where charge neutralization is needed, while the rest of the chamber maintains high vacuum conditions. This spatial differentiation allows effective charge neutralization at the sample interface without significantly increasing the overall gas pressure in the chamber, thereby preserving imaging resolution by minimizing electron beam scattering across the entire optical path.
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
Effectively neutralizes charge on insulating samples, enables high-resolution imaging in high vacuum mode, and allows for processing of moist samples without flooding the chamber with gas, providing an ESEM environment within a high vacuum SEM system.
Implementation Method 1
Ionization of the gas by the sample surface provides charged particles
Implementation Method 2
The anode is electrically biased to repel positive ions and/or to attract negative electrons toward the sample
Implementation Method 3
A gas injection system (GIS) that concentrates gas locally near the sample surface, using a needle and shroud structure to direct gas flow
Data Source
AI summary
A gas injection system provides a local region at the sample surface that has sufficient gas concentration to be ionized by secondary electrons to neutralize charged on the sample surface. In some embodiments, a gas concentration structure concentrates the gas near the surface. An optional hole in the gas concentration structure allows the charged particle beam to impact the interior of a shrouded region. In some embodiments, an anode near the surface increases the number of ions that return to the work piece surface for charge neutralization, the anode in some embodiments being a part of the gas injection system and in some embodiments being a separate structure.