Magnetically Levitated Drag Pump for Semiconductor Vacuum
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Solution Overview
Problem
Existing vacuum pumps are ineffective across a wide pressure range, particularly in semiconductor processing chambers that require pressures between 0.05 mbar and 0.2 mbar, where turbo pumps overheat and roots blowers are not effective due to conduit conductance limitations.
Innovation Solution
A vacuum pump design featuring a rotor with angled blades on a magnetically levitated bearing, combined with a stator comprising perforated elements with varying transparency along the helical path, allowing for effective pumping across the transitional flow regime and enabling the use of a backing pump for higher pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a turbo pump is used to evacuate the chamber, then high vacuum can be achieved, but the pump overheats at pressures above 0.05 mbar
Solution Approach 1:
The pumping system is segmented into multiple stages with different pump types operating in different pressure ranges. The drag pump handles the transitional flow regime (0.05-0.2 mbar), while the turbo pump handles high vacuum, preventing the turbo pump from overheating by limiting its operation to appropriate pressure ranges.
Solution Approach 2:
The drag pump acts as an intermediary device between the chamber and the turbo pump, conditioning the pressure range to protect the turbo pump from operating in its overheating zone. This intermediary pump ensures the turbo pump receives gas at acceptable temperatures and pressures.
2Stress or pressure
If a roots blower is used as a backing pump, then it can handle high pressures, but it is not effective at pressures below 0.2 mbar due to conduit conductance limitations
Solution Approach 1:
The drag pump is positioned locally close to the chamber with a short conduit, optimizing its performance in the transitional flow regime where it operates most effectively. This local placement maximizes pumping speed at pressures below 0.2 mbar by minimizing conduit conductance limitations.
3Power
If the rotor rotates close to the stator to optimize compression ratio, then compression is improved, but the stator channel depth is limited which reduces pumping capacity
Solution Approach 1:
The patent introduces transparency as a new dimension for optimizing drag pump performance. By controlling the transparency of the stator (through perforations or mesh structures), the pump achieves effective compression without requiring the rotor to rotate extremely close to the stator, thereby maintaining adequate stator channel depth for sufficient pumping capacity.
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
The pump achieves high pumping speed at low pressures and effective operation at higher pressures when backed by another pump, providing a reasonable capacity and efficient evacuation of semiconductor processing chambers across a wide pressure range.
Implementation Method 1
a rotor with angled blades on a magnetically levitated bearing
Implementation Method 2
As the gas flows through the pump it is compressed and this compression means that the open or transparent area can be reduced towards the outlet
Data Source
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AI summary
A vacuum pump, vacuum pump set and method for evacuating a semiconductor processing chamber is disclosed. The vacuum pump is configured for mounting to a semiconductor processing chamber to evacuate the chamber to pressures between 1 mbar and 5 X10-2 mbar. The vacuum pump comprises: a rotor rotatably mounted within a stator. The rotor comprises a plurality of angled blades arranged along a helical path from an inlet to an outlet. The stator comprises a plurality of perforated elements arranged to intersect the helical path, the perforations allowing gas molecules travelling along the helical path to pass through the perforated elements. The rotor mounted on a magnetically levitated bearing; and the perforated elements located towards an inlet of the vacuum pump comprise a transparency of more than 40% and the perforated elements located towards an outlet of the vacuum pump comprise a transparency of more than 30%.