A microfabricated Pirani pressure sensor operating near atmospheric pressure

A micromachined pressure sensor based on the measurement of the pressure-dependent thermal conductivity of gaseous media (Pirani principle) is presented. The sensor consists of a freestanding microbridge with a defined distance to the substrate which acts as a heat sink. The theory to compute the necessary geometrical dimensions of the sensor element is presented. Due to a novel fabrication process, based on a sacrificial layer of ZnO, the sensor can readily be adapted to operate in different pressure ranges, even exceeding atmospheric pressure. A fully integrated bridge arrangement was used to compensate for ambient temperature changes. Experimental results for different sensor geometries are presented which correspond well with the theory. Basic design rules for micromachined Pirani pressure sensors are derived from the measurements.

[1]  Chr Edelmann,et al.  Miniaturized vacuum gauges , 2004 .

[2]  A. Herwaarden,et al.  Small-size vacuum sensors based on silicon thermopiles , 1991 .

[3]  Physikalische Grundlagen des Wärmeleitungs‐Vakuummeters , 1993 .

[4]  J. Müller,et al.  A Micro Mass Spectrometer , 2001 .

[5]  Joerg Mueller,et al.  Processing of complex microsystems: a micro mass spectrometer , 1999, Design, Test, Integration, and Packaging of MEMS/MOEMS.

[6]  Joseph T. Boyd,et al.  MOEMS pressure sensors for propulsion applications , 2000, SPIE MOEMS-MEMS.

[7]  James H. Smith,et al.  Micromachined pressure sensors: review and recent developments , 1997 .

[8]  Robert Puers,et al.  The NanoPirani—an extremely miniaturized pressure sensor fabricated by focused ion beam rapid prototyping , 2002 .

[9]  Carlos H. Mastrangelo,et al.  Microfabricated thermal absolute-pressure sensor with on-chip digital front-end processor , 1991 .

[10]  Oliver Paul,et al.  Novel integrated thermal pressure gauge and read-out circuit by CMOS IC technology , 1994, Proceedings of 1994 IEEE International Electron Devices Meeting.

[11]  J. Mueller,et al.  A micromachined vapor jet pump , 2005 .

[12]  Werner Kraus,et al.  Comparison of different micromechanical vacuum sensors , 2000 .

[13]  Jin-Shown Shie,et al.  High performance Pirani vacuum gauge , 1995 .

[14]  Franco Maloberti,et al.  CMOS integration of a thermal pressure sensor system , 1996, 1996 IEEE International Symposium on Circuits and Systems. Circuits and Systems Connecting the World. ISCAS 96.

[15]  Oliver Paul,et al.  Novel fully CMOS-compatible vacuum sensor , 1995 .