Abstract

The burgeoning field of MicroSystems Technology (MST) has a tremendous potential for sensing and actuation of industrial systems in almost every field of human interest. This thesis proposes a synthesis of microsystems in order to explore the advantage of miniaturization by developing a technology suitable for fabricating integrated systems that consist of sensing, actuating and computing elements at the. micro level. The synthesis involves development of fabrication strategies using industrial CMOS process and design strategies, in order to manipulate the effect of inherent limitations of fabrication and other limitations due to structural configuration and environment on dynamic behavior of microsystems. Towards the success of fabrication synthesis, micromechanical components are fabricated through an industrial CMOS process, namely, the Mitel 1.5 om Double-Poly-Double-Metal process, and by post-releasing with gas phase xenon difluoride etching. The etching is described along with the details of the setup, the etching procedure and the effect of etching on end conditions of the fabricated structure. The types of structures fabricated show that they can be adopted for both piezoresistive and capacitive devices. The different factors that influence the elastic properties of both macro and micro systems include variations in structural geometry, process parameters and operational environment. A concept of boundary conditioning is proposed in this thesis as a unified approach for the quantification of the influence of structural geometry, support conditions, fabrication process and environmental influence on the dynamic behavior of the system. The influence of all the above parameters is represented by replacing the elastic influence with the equivalent spring stiffnesses. The modeling of boundary conditioning is carried out using artificial springs and boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method. The eigenvalues are predicted for plate type structures with stiffeners and cutouts using this approach. The concept of boundary conditioning is applied to structural tuning and localization of vibrational response. The results obtained for manipulation of harmonic combinations and vibrational response using artificial springs are useful and interesting. The boundary conditioning conceptualizes micro or macro system into equivalent elastic system. The equivalent stiffnesses which can be estimated through experiment or other methods may include uncertainties and vagueness. The fuzzy system identification technique is applied for modeling such micro or macro systems with fuzziness on input and output parameters. Automatic fuzzy system identification is carried out using subtractive clustering method. A higher order fuzzy system identification technique is proposed for modeling complicated systems with fewer number of rules. The structural tuning of elastic systems is identified by expert modeling and subtractive clustering. The influence of structural variations of microsystems on dynamic behavior is modeled using the method of artificial springs. The static and dynamic behavior of free standing microsystems under the influence of electrostatic field and residual stress are also presented. The comparison between predicted and experimental values of snapping voltage for capacitive type systems shows a good agreement. The non-classical end conditions resulting from micromachining processes are modeled using boundary conditioning technique. The application of fuzzy system identification of the boundary conditioning of microsystems, shows a potential for direct and indirect design of microsytems for the required dynamic behavior.