Micro-electromechanical sensors have been developed for high-frequency voltage metrology applications. They should ultimately allow RF to DC voltage transfer. The conventional measurement principle is based on RF power dissipation by ohmic resistances allowing RMS voltage conversion by the square power law. The principle of electrostatic force, which has already been demonstrated to work from DC to gigahertz frequencies, is a completely novel principle for RMS voltage measurement. An elastically suspended plate is subjected to the electrostatic pressure of a voltage and the resulting deflection is measured using a capacitive feedback circuit. For calculability and reproducibility purposes, the geometry of the devices has to be known as exactly as possible. The sensitivity is maximized by a construction with relatively large plates divided by a small gap only and a suspension with a very low spring constant. A key factor for the use in metrology applications is the stability and reliability of the devices. Therefore, bulk-silicon is taken for the suspension of the movable plate. It is a readily available micro fabrication material with high grades of purity. Moreover, it has virtually no region of plastic deformation and is fatigue free. Devices have been manufactured using bulk-silicon with a thickness of 350 μm down to 20 μm for the suspension. In this contribution, we examine the stability and reliability of these sensors as well as the influence of other environmental factors on the performance of the devices.

Date Published: 9 February 2009
PDF: 6 pages
Proc. SPIE 7206, Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS and Nanodevices VIII, 72060C (9 February 2009); doi: 10.1117/12.809464

Published in SPIE Proceedings Vol. 7206:
Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS and Nanodevices VIII
Richard C. Kullberg; Rajeshuni Ramesham, Editor(s)