A Microdischarge-Based Monolithic Pressure Sensor

Abstract

This paper describes the investigation of a microdischarge-based approach for sensing the diaphragm deflection in a monolithically fabricated pressure sensor. This transduction approach is appealing from the viewpoint of miniaturization. The device consists of a deflecting Si diaphragm with a sensing cathode, and a glass substrate with an anode and a reference cathode. The total exterior volume of the device is 0.05 mm 3 ; typical electrode size and separations are 35 and 10 µm. Pulsed microdischarges are initiated in a sealed chamber formed between Si and glass chips, and are filled with Ar gas. External pressure deflects the Si diaphragm and changes the interelectrode spacing, thereby redistributing the current between the anode and two competing cathodes. The differential current is indicative of the diaphragm deflection which is determined by the external pressure. A 6-mask microfabrication process is investigated for device fabrication. Electrode connections to the interior of the chamber are provided by laser drilling and copper electroplating through high aspect ratio glass vias. The Si and glass substrates are bonded by Au-In eutectic. The redistribution of plasma current between competing cathodes, as a consequence of diaphragm deflection over a range of pressure, was experimentally demonstrated. First principles modeling of transient microdischarges have provided insights to the fundamental processes responsible for the differential current and guidance for scaling the device to smaller dimension.[2013-0200]

Recent Progress of Miniature MEMS Pressure Sensors

“…As the external pressure increased from 1 atm to 8 atm, the (I1 − I2)/(I1 + I2) monotonically increased from −0.7 to 0.2. Other micro-discharge based pressure sensors were fabricated [202,203]. A discharge based pressure sensor for high temperature applications was introduced.…”

A 100μm diameter capacitive pressure sensor with 50 MPa dynamic range

“…Amongst the large variety of micromachined pressure sensors that have been investigated [2], including piezoresistive [3], capacitive [4], optical [5], resonant-beam [6] and microplasma-based sensors [7], capacitive pressure sensors are known to provide high sensitivity, low temperature coefficients, low noise and low power consumption [8][9][10][11][12][13]. A number of challenges and considerations are encountered in the design of microfabricated capacitive pressure sensors, including the formation of a sealed cavity, lead transfer from within the cavity, device miniaturization, and system integration [11].…”