Environmental Cell for Charged Particle Beam Systems
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Solution Overview
Problem
Conventional High Pressure Scanning Electron Microscopes (HPSEMs) face challenges in beam chemistry due to impurities like H2O and O2, which interfere with processing, require lengthy gas introduction and evacuation times, and are not suitable for corrosive gases, limiting their use in beam chemistry and heat-induced processes.
Innovation Solution
A modular environmental cell that allows for controlled processing in a gaseous environment, enabling flexible and rapid processing and analysis without exposing samples to the atmosphere, with features like a sliding contact seal, retractable lid, and integrated gas injection capillary, facilitating multiple analysis techniques and reducing impurity concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional HPSEM is used for beam chemistry, then the sample can be processed in a gaseous environment, but impurities like H2O and O2 interfere with processing and require lengthy gas introduction and evacuation times
Solution Approach 1:
The system is divided into two differentially pumped chambers: a sample chamber that can be filled with process gases for beam chemistry, and a column chamber that maintains high vacuum for electron optics. A pressure-limiting aperture separates these chambers, allowing independent pressure control and reducing the time required for gas introduction and evacuation in the sample chamber without affecting the column vacuum.
Solution Approach 2:
The pressure-limiting aperture extracts and removes gas molecules from the column chamber by allowing them to pass through to the sample chamber, where they are pumped away. This prevents impurity accumulation in the column and enables rapid gas switching in the sample chamber without lengthy evacuation times.
2Adaptability or versatility
If a conventional HPSEM is used for beam chemistry, then the sample can be processed in a gaseous environment, but impurities like H2O and O2 interfere with processing
Solution Approach 1:
The system separates the sample processing environment from the electron optical environment using a pressure-limiting aperture. This allows the sample chamber to contain process gases necessary for beam chemistry while the column chamber maintains high vacuum, preventing impurity interference with the electron beam and processing reactions.
Solution Approach 2:
The pressure-limiting aperture acts as an intermediary element between the high-vacuum column and the gaseous sample chamber. It controls gas flow and pressure differential, allowing beam chemistry to proceed with process gases while preventing impurity accumulation that would interfere with processing.
3Object-affected harmful factors
If the pressure limiting aperture is positioned to minimize distance for reducing beam interference, then primary beam scattering is reduced, but the travel distance for secondary electron detection is insufficient for adequate gas cascade amplification
Solution Approach 1:
The pressure-limiting aperture is positioned at the interface between the column and sample chambers, creating distinct zones: the column chamber with high vacuum for minimal beam scattering, and the sample chamber with controlled pressure for adequate secondary electron travel distance and gas cascade amplification. This spatial segmentation resolves the conflicting requirements.
4Adaptability or versatility
If corrosive gases are used in beam chemistry, then more complex chemical processing is enabled, but the gases are incompatible with conventional HPSEM components
Solution Approach 1:
The system isolates corrosive process gases to the sample chamber, which is separated from the column chamber containing sensitive electron optical components. The pressure-limiting aperture and independent pumping system allow corrosive gases to be used for complex chemical processing without compromising the reliability of conventional HPSEM components in the column.
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
Enables efficient beam chemistry and heat-induced processes with improved control over the sample environment, reducing impurity interference and processing time, and allowing for various analysis techniques like cathodoluminescence and x-ray analysis without breaking vacuum.
Implementation Method 1
the lid including a pressure limiting aperture that restricts gas flow into the column, the cell interior being at a higher pressure than the charged particle beam column
Implementation Method 2
A sliding contact seal between the upper and lower parts of the cell allows relative movement between the lower and upper parts
Implementation Method 3
a secondary electron detector that uses gas ionization cascade amplification
Implementation Method 4
an electron beam source located within the vacuum envelope and capable of emitting electrons, one or more focusing lenses located within the vacuum envelope and capable of directing an electron beam
Data Source
AI summary
An environmental cell for a charged particle beam system allows relative motion between the cell mounted on an X-Y stage and the optical axis of the focusing column, thereby eliminating the need for a sub-stage within the cell. A flexible cell configuration, such as a retractable lid, permits a variety of processes, including beam-induced and thermally-induced processes. Photoelectron yield spectroscopy performed in a charged particle beam system and using gas cascade amplification of the photoelectrons allows analysis of material in the cell and monitoring of processing in the cell. Luminescence analysis can be also performed using a retractable mirror.