Fabrication and Electrical Characterization of a Suspended RF MEMS Sensor
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Radio frequency (RF) power measurement has an important part in radar and communication systems. Several approaches have been taken towards this measurement, including diode power sensors and thermal based sensors (thermistor and thermocouple based sensors), both with their own advantages and disadvantages. The diode sensors are widely used with fast response times with limitation in their power ratings. The thermal based sensors have higher power rating but suffer from slower response time. A MEMS based RF sensor could potentially overcome these limitations. These kind of sensors are also attractive because of the ease of fabrication, their small size, and further capability to be integrated in microelectronic ICs. This thesis work focuses on fabricating and characterizing such a novel MEMS based RF sensor.In a previous study in our group, it was demonstrated by COMSOL Multiphysics simulation that fast response time and power handling could be achieved in a MEMS sensor if the load is a suspended beam. A suspended beam structure was designed with the ability to measure high power (30 dBm) with a response time of 50 microsecond, and a VSWR less than 1.065:1 to ensure maximum power transfer. This thesis explored the fabrication of the suspended load in the UB cleanroom facilities. Several load materials and process were investigated. A NiCr load and SF6 based RIE process achieved a reliable and robust suspended beam. The DC and RF characterization of the supended load was carried out. A load value of ~ 50 Ohm was achieved on these loads.