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VA: Fachverband Vakuumphysik und Vakuumtechnik
VA 2: Vacuum Gauges and Instrumentation
VA 2.1: Hauptvortrag
Montag, 31. März 2014, 14:00–14:40, HSZ 105
Pirani type microsensors for pressure measurements from 103 mbar to 10−6 mbar — •Mario Grau1,2, Friedemann Völklein1, Andreas Meier1, Christina Kunz1, Lars Breuer1, and Peter Woias2 — 1RheinMain University of Applied Sciences, Wiesbaden — 2University of Freiburg, Dept. of Microsystems Engineering
Conventional thermal conductivity vacuum gauges cover a measurement range from typically 100 mbar to 10−3 mbar. By miniaturization of such sensors it is possible to significantly expand the sensitivity range. Heat flux to the surrounding gas depends on pressure and should be maximized to achieve high sensitivity, whereas the heat losses by radiation and solid thermal conduction have to be minimized. Design optimization leads to sensors with large area suspended membranes with reduced emissivity for the high vacuum range. In contradiction to this approach, we use small area suspended membranes for the rough vacuum range in order to minimize the required heating power. Furthermore small gaps in the order of 10 micrometers are necessary for the improvement of sensitivity in the rough vacuum range. Therefore,we have developed two specific microchips. The first one (VAC_03) is designed for the pressure range from 10−6 mbar to 1 mbar and the second one (VAC_04) for the range from 10−3 mbar to 103 mbar. The chip size of the VAC_04 is very small (1x1 mm) and can be integrated into the housing of the VAC_03 sensor. We present FEM Simulations of the various heat flux mechanisms, chip design and signal voltage versus pressure for the optimized microchips.