© 2010 Ravindra Mukhiya.
IIT Kharagpur
ABSTRACT
Micro electro mechanical system (MEMS) based accelerometers are vastly attractive due to their low cost, small size, low power consumption and robust performances. Acceleration sensors have wide varieties of applications in military, industry, medical, automotive and consumer electronics. In this context, the primary goal of the thesis is to design and implementation of a complementary metal oxide semiconductor (CMOS) compatible bulk micromachined silicon accelerometer. Bulk micromachining is the most popular micromachining technique to realize sensors microstructures, because it is relatively easy to fabricate at low cost. Nevertheless, it is always desirable to integrate electronics with the sensors microstructures on the same chip to develop smart sensors. This thesis work focuses on the development of low cost CMOS-MEMS wet bulk micromachining technique for fabrication of the accelerometer to facilitate the desired integration.
To begin with the dissertation presents the design, mathematical modeling and finite element method (FEM) based simulations of a piezoresistive micro accelerometer having single degree-of-freedom (1-DOF). Simple analytical expressions to define the function of the designed microstructure along with the considerations for its fabrication
© 2010 Ravindra Mukhiya.
IIT Kharagpur
imperfections have been discussed. Finally, the details of the electromechanical design and simulations of the accelerometer are presented.
Subsequently, the dissertation focuses on the development of the MEMS accelerometer. The detailed experimental study of the CMOS compatible bulk micromachining and corner compensation techniques using 25% TMAH for the realization of the accelerometer structure have been carried out and reported in the thesis.
Proposed corner compensation structures are analyzed and empirical design equations have been derived. Subsequently, fabrication process derived from standard CMOS process is implemented to fabricate the structure. Finally, the device characterization using simple, non-conventional and non-destructive techniques is presented.
Experimental results show that the accelerometer has wide dynamic range and can measure large range of g values. Experimental results are also in good agreement with the analytical and simulated results.
The fabrication of accelerometer is followed by a proposal of novel application, where the accelerometer can be used for a fuel control unit of automobile engine. Design and simulation of the fuel control unit incorporating the accelerometer has also been presented in the thesis.
Keywords: Accelerometer, Bulk Micromachining, CMOS-MEMS, Corner Compensation, Automobile Application.
