RMS voltage sensor based on a variable parallel-plate capacitor made of electroplated copper
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We present an advanced RMS voltage sensor based on a variable parallel-plate capacitor using the principle of electrostatic force. The device is fabricated in a micromechanical surface process with a high-aspect ratio actuator, reinforced by copper electroplating employing a sacrificial photo-resist layer. Another copper layer with a coplanar waveguide below the actuator provides separated excitation and sensing electrodes. Flip-chip technology is employed for low-loss electrical connectivity. The presented design has a plate area of up to 3 × 3 mm2 and an initial gap distance of only 1.5 μm. We present results achieving a pull-in voltage below 1 V at frequencies from DC up to 1 GHz and sensitivities up to 1 fF/mV.
KeywordsSacrificial Layer Coplanar Waveguide Stiff Actuator Surface Micromachining Process Copper Seed Layer
This research has been undertaken as a joined research project of the Institute of Microtechnology at the Technische-Universität Braunschweig and the High-Frequency Measuring Group of the Physikalisch-Technische Bundesanstalt (PTB).
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