Graduation Year

2004

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Bhansali, Shekhar.

Keywords

dc-dc converter, porous silicon, MEMS, switched capacitors

Abstract

This thesis explores high voltage converter circuits for MEMS applications using micromachined devices. A novel MEMS based tunable DC-DC converter has been developed. Conventional high voltage converters based on charge pumps are unable to convert voltages to higher than few tens of volts due to power handling limitations of the CMOS components. In order to overcome this limitation a high voltage circuit has been proposed, which when integrated with micromachined switches will generate output voltages in the range of 100 Volts. The converter is based on a two phase switched capacitor circuit, and allows regulation of voltage conversion ratio. Three prototype circuits have been built for proof of concept. A test program has been written for synchronized CPLD based control of the switched capacitors. Individual capacitor fabrication technology is explored using two methods - Porous Silicon and DRIE processing.

A micromachined capacitor bank has also been fabricated in silicon using a novel process sequence which provides for critical real estate savings and integration benefits. It enables on-chip integration of numerous microcapacitors, without losing customized configurability of the capacitor bank. The technique utilizes polyimide to facilitate lithography on a highly contoured surface. Plain capacitors have been fabricated on silicon with oxide-nitride-oxide stack being used as the dielectric to provide a building block for further fabrication of a variety of capacitors.

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