MEMS: From Micro Devices to Wireless Systems

Vol. 7, Special Issue, October 2009, pp.25-33

Micro-fabricated Rotational Actuators for Electrical Voltage Measurements Employing the Principle of Electrostatic Force

^1,2 Jan Dittmer, ²Rolf Judaschke and ¹Stephanus Büttgenbach

¹ Institute for Microtechnology (IMT), Technische Universität Braunschweig,
Alte Salzdahlumer Str. 203, 38124 Braunschweig, Germany

Tel.: +49-531-391-9747

² Physikalisch-Technische Bundesanstalt (PTB),

Bundesallee 100, 38116 Braunschweig, Germany

E-mail: j.dittmer@tu-bs.de

Received: 28 August 2009   /Accepted: 28 September 2009   /Published: 12 October 2009

Abstract: In this paper, we present an advanced RMS voltage sensor based on rotating parallel-plate capacitors based on the principle of electrostatic force. The actuator is built using a micromechanical thin bulk silicon batch process yielding structures with a high sensitivity mainly due to a low mechanical spring constant, realized with thin and long beams. Metal layers provide separated excitation and sensing electrodes. The actuator is anodically bonded on a matching glass substrate with a shallow rectangular cavity in which the opposite electrodes are located and which defines the working distance to be as low as 2.5 μm. To avoid stiction, bumpers with a small contact area physically prevent short circuiting under pull-in conditions and thus improve the reliability. Finally design choices and the micromechanical fabrication process are explained. Moreover, DC and RF characterization results of the devices are presented showing successful operation from below 10 Hz up to more than 1 MHz.

Keywords: MEMS, Metrology, RMS voltage sensor, High-frequency Measurements, Bulk silicon, Anodic bonding, Batch process

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