MEMS fabrication using aluminum films

Micro Electro Mechanical Systems (MEMS) devices have rapidly become a hidden but integral part of daily life, starting from air bag deployment sensors in automobiles to biological sample analyzers in medical equipments. The ability to use silicon and silicon-like materials as structural elements to fabricate miniature devices has greatly impacted the rate of deployment of MEMS devices into everyday use. The research presented here explores techniques that can be used to shorten the product cycle time and to extend the applications for new devices.;Aluminum films have been an integral part of semiconductor devices for several decades. One of the challenges in integrating MEMS devices with integrated circuitry is the incompatibility of some processes used in MEMS processing with standard integrated circuit processing. The work presented here explores the use of Aluminum as sacrificial and structural layers for MEMS devices.;To validate the use of Aluminum as a sacrificial film, two devices, a MEMS switch and a stress gradient sensor are fabricated. The fabricated MEMS switch has a bistable design with two fixed electrodes and one movable electrode. The fabricated stress sensors are used to characterize stress gradient across the thickness of deposited silicon dioxide films.;In order to validate the use of Aluminum as a structural film, a blast dosimeter is fabricated. Blast dosimeters to detect the intensity of explosions experienced by soldiers in the field are fabricated using Aluminum films. The sensor is capacitive with two electrodes separated by an air gap, the top movable electrode is designed to collapse and make contact with the bottom fixed electrode. Resistance change between the two states is used to display the amount of shock experienced. A passive g-force sensor to monitor the shock experienced by cargo in transit is also fabricated to use Aluminum conduction lines. The latching design used in the sensor enables it to measure and record the shock experienced without consuming any power, which in turn lowers system power requirements.;These four MEMS devices were designed, simulated, and subsequently successfully fabricated, characterized and tested. Compressive stresses in the range of 80MPa/mu have been measured in silicon dioxide thin films. A contact resistance change from 10O to 500MO is observed for a sensor 200microns in radius while a resistance change from 25O to 60MO is observed in the 70micron radius sensor.