AVS 52nd International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeM

Paper VT-WeM11
A Micromachined Vapor-Jet Vacuum Pump with an Integrated Pirani Pressure Sensor

Wednesday, November 2, 2005, 11:40 am, Room 201

Session: Gas Flow and Pump Technology
Presenter: M. Doms, Hamburg University of Technology, Germany
Authors: M. Doms, Hamburg University of Technology, Germany
J. Müller, Hamburg University of Technology, Germany
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A MEMS vapor-jet pump is presented which is based on the well-known principle of vapor-jet and diffusion pumps. A high velocity gas- or vapor-jet is used for vacuum generation. The microfabricated pump consists of two planar Laval nozzles (20-40 µm nozzle width) and water cooled sidewalls. Presently an external supply of the working fluid is used (nitrogen gas, water vapor). As no mechanically moving parts are required, the pump system offers an advanced long-term stability. A detailed mathematical and physical description of the micro vapor-jet pump has been described elsewhere.@footnote 1@ Based on simulation results, various systems with different geometries have been designed, fabricated and characterized. Starting from atmospheric pressure, a high pumping speed of more than 2.8 ml/min and an absolute pressure of 495 mbar were generated with this new type of micropump. Lower pressure regimes will be accessible with a full integration of all components (internal working fluid evaporation, condensation and recirculation) and by the use of more appropriate working fluids and multiple nozzle stages. Different concepts for the working fluid recirculation based on porous silicon and active or passive pump mechanisms which are currently investigated will be presented. The size of the complete pump system will not exceed 15 x 15 x 2 mm. Microfabricated pressure sensors based on the Pirani principle have been integrated into the micropump to monitor and control its function. Due to its novel geometry and fabrication process the operating range of the sensors can easily be adapted to different pressure ranges without any change of the layout. An integrated full bride layout is used for temperature compensation. The characteristics of the sensors correspond well with theory and fully satisfy the specifications. @FootnoteText@ @footnote 1@M. Doms, J. Müller, A Micromachined Vapor-Jet Pump, Sens. Act. A, Vol. 119 No 2, Mai 2005, p. 462-467.