Date of Award

Fall 1997

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Electrical Engineering - (Ph.D.)

Department

Electrical and Computer Engineering

First Advisor

William N. Carr

Second Advisor

Roy H. Cornely

Third Advisor

Durgamadhab Misra

Fourth Advisor

Robert Boris Marcus

Fifth Advisor

Yi-Yuan Yu

Abstract

A family of microrelay devices together with integrated inductor networks has been designed, simulated, fabricated and experimental characterized. These switched networks utilize microelectromechanical systems (MEMS) as a fabrication technology and take advantage of the economies of semiconductor cleanroom batch-processing.

A new type of microrelay has been developed using a suspended TaSi2/SiO2 bimorph cantilever beam, gold-to-gold electrical contact, aluminum as sacrificial layer, and a combined thermal and electrostatic means of actuation. For the first time a micro variable inductor network which is digitally controlled by microrelays has been demonstrated. A test structure for electrical micro contact characterization has been designed, built and characterized as a support task in this research. The microrelay design has utilized the Rayleigh-Ritz method to simulate the actuation and the electrical contact force.

The cantilever structure of the microrelay contains a specially-shaped area which provides a symmetric force to the electrical contact region and thus reduces the electrical contact resistance. The required thermal power and electrostatic voltage for the combined actuation of microrelays were measured typically as II mW and 30 - 40 volts, respectively. The electrical contact resistance was typically 0.6 to 0.8 Ohms. The maximum operation frequency was 10 KHz and the microrelay closure and opening time were typically 12 µS. A limited number of lifetime tests were performed indicating the device lifetime to be about 106 cycles.

A micro variable inductor network consisting of a 16-turn rectangular spiral coil and four controlling microrelays was designed and fabricated. A larger coil structure was divided into four segments. Each inductor segment had a microrelay connected with it in parallel. The network inductance values were determined by combinations of switching states of microrelays. Sixteen different inductance values ranging from 2.5 nH to 324.8 nH were obtained. The silicon substrate underneath the inductor region was etched out to reduce the substrate loss. The minimum self-resonant frequency was measured 1.9 GHz.

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