Turbo Molecular Pump Segmentation for Vacuum Contamination Control
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Solution Overview
Problem
Existing charged particle beam apparatuses face contamination issues during high-vacuum and low-vacuum exhaust due to oil evaporation from rotary pumps, which can lead to sample and chamber contamination, and the use of dry pumps is hindered by space and cost constraints.
Innovation Solution
The apparatus employs a composite turbo molecular pump with specific inlet ports and valves to manage vacuum levels, using the main inlet port for high-vacuum exhaust of the charged particle gun chamber and the sample chamber, and the intermediate inlet ports to maintain high vacuum in the gun chamber while allowing low-vacuum exhaust of the sample chamber, thereby preventing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an oil rotary pump is used for preliminary exhaust inside the vacuum chamber, then exhaust time is reduced and throughput is improved, but oil evaporates and contaminates the sample chamber and electron gun chamber
Solution Approach 1:
The exhaust system is segmented into two independent pathways: one for the sample chamber and one for the electron gun chamber. The turbo molecular pump has a first exhaust port connected to the sample chamber and a second exhaust port connected to the electron gun chamber, allowing separate exhaust control for each chamber.
Solution Approach 2:
A valve is introduced as an intermediary component to control the connection between the oil rotary pump and the electron gun chamber. The valve prevents direct connection during preliminary exhaust, blocking the contamination pathway while allowing the oil rotary pump to exhaust the sample chamber.
2Object-affected harmful factors
If a dry pump is used as the auxiliary vacuum pump to prevent contamination, then contamination is avoided, but installation space increases and cost increases
Solution Approach 1:
A valve is introduced as an intermediary component to control the connection between the oil rotary pump and the electron gun chamber. The valve prevents direct connection during preliminary exhaust, blocking the contamination pathway while allowing the oil rotary pump to exhaust the sample chamber.
Solution Approach 2:
The harmful function of the oil rotary pump (oil evaporation causing contamination) is separated from its useful function (providing vacuum exhaust). By controlling the valve to prevent connection between the oil rotary pump and the electron gun chamber during preliminary exhaust, only the beneficial exhaust function is utilized while the harmful evaporation function is isolated.
3Productivity
If the oil rotary pump exhausts the electron gun chamber, then low-vacuum exhaust is achieved, but the electron gun chamber cannot reach predetermined high vacuum and becomes contaminated
Solution Approach 1:
The exhaust system is segmented into two independent pathways: one for the sample chamber and one for the electron gun chamber. The turbo molecular pump has a first exhaust port connected to the sample chamber and a second exhaust port connected to the electron gun chamber, allowing separate exhaust control for each chamber.
Solution Approach 2:
The turbo molecular pump is designed with multi-functionality, serving both high-vacuum exhaust (through the second exhaust port for the electron gun chamber) and low-vacuum exhaust (through the first exhaust port for the sample chamber), eliminating the need for separate pumps for different vacuum levels.
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 prevents contamination within the apparatus, maintains high vacuum integrity, and reduces the risk of sample contamination, allowing for clearer and more efficient vacuum exhaust without the need for costly dry pumps.
Implementation Method 1
a composite turbo molecular pump 6 having a main inlet port 11 and first and second intermediate inlet ports 13, 12 in this order from a side of a charged particle gun chamber 1
Implementation Method 2
an oil rotary pump 7 performing preliminary exhaust of a vacuum chamber 7
Data Source
AI summary
In this charged particle beam device, when a sample chamber is to be placed in a high-vacuum state, a charged particle gun chamber and the sample chamber are evacuated via a main intake of a turbo molecular pump, and when the sample chamber is to be placed in a low-vacuum state, the sample chamber is evacuated via an intermediate intake of the turbo molecular pump while the charged particle gun chamber is evacuated via the main intake. An oil rotation pump for performing back pressure exhausting of the turbo molecular pump does not directly evacuate the charged particle gun chamber or the sample chamber. It is thereby possible to minimize contamination of the device interior in both high-vacuum and low-vacuum states, which makes it possible to prevent contamination of the observed sample and reduce deterioration over time in the ultimate vacuum.