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SILICON AND QUARTZ MEMS INERTIAL SENSORS FOR AVIONICS AND SPACE APPLICATIONS

Santiram Kal
Dept. of Electronics & Elect. Commun. Engg.
Indian Institute of Technology A major attention of micromachining technology has recently been focused on miniature inertial sensors. Rapid advancement of micromachined accelerometer technology has enabled cost effective high performance micro accelerometers that revolutionizes the traditional accelerometer market. Apart from commercial and consumer applications, one major applications of miniature high precision accelerometer is in the field of avionics and space. This lecture deals with the development of both silicon and quartz micromachined MEMS accelerometers and gyros for avionics and space applications. An accelerometer of the range of „b 13 g with very low off-axis acceleration, a resolution of „b 2 mg and a linearity of less than 1% has been designed and fabricated. As the piezoresistive accelerometers are less susceptible to parasitic capacitance and electromagnetic interference, we opted for the same because of simple fabrication process and read out circuitry. The piezoresistive accelerometer consists of a silicon base, a proof mass supported by double cantilever beam and cap layers. Coventorware 2001.3 software package has been used to design the accelerometer. Simulation results indicate that the maximum output voltage under 13 g acceleration along z-axis is nearly 20 mV with 5 volts bridge supply whereas off-axis response is about 3-4 order less than z-axis response, which is one of the requirement of the navigational grade accelerometers. TMAH based five mask accelerometer technology has been indigenously developed at IIT Kharagpur and the MEMS accelerometers were fabricated, bonded and packaged. Interface electronics for the MEMS accelerometer has been designed and the chips were tested with available facilities. Characterization of the chip has been conducted up to „b 10 g and results are found to be highly encouraging. Plot of acceleration with output voltage is found to be highly linear (< 1 %) and with negligible offset value. The off-axis sensitivity was less than nearly two orders of magnitude than z-axis acceleration. IIT Kharagpur was the first in India to develop quartz micromachining technology. The indigenous development of the quartz technology is considered significant because quartz micromachining is protected technology with very little details are available in scientific literature. We have made use of this technology to fabricate tiny dual tuning fork structures with built-in electrodes via flexures, for sensing rotation (gyro), and double-ended tuning forks (DETF) used in MEMS accelerometers. This lecture also covers design and fabrication of quartz double-ended tuning fork accelerometer and dual tuning fork gyros.

Location: Olin Hall of Engineering (OHE) - 230

Audiences: Everyone Is Invited

Contact: Ericka Lieberknecht