Acoustic Bragg reflectors for Q-enhancement of unreleased MEMS resonators

In this thesis, the author introduces the first fully unreleased Micro-Electro-Mechanical (MEM) resonator, and the design of acoustic Bragg reflectors (ABRs) for energy localization and quality factor (Q)- enhancement for unreleased resonators. Two of the greatest challenges in MEMS are those of packaging and integration with CMOS technology. Development of unreleased MEMS resonators at the transistor level of the CMOS stack will enable direct integration into front-end-of-line (FEOL) processing, making these devices an attractive choice for onchip signal generation and signal processing. The demonstrated first fully unreleased resonator exhibits a resonance at 39 GHz with a Q of 129, corresponding to the 1st harmonic longitudinal resonance of the unreleased resonator, a silicon Resonant Body Transistor (RBT) fully clad in Si0 2. A spurious mode occurs at 41 GHz, which is in good correspondence with simulation results. The Q of 129 at 39 GHz is about 4 times lower than that of its released counterpart. Enhanced with the ABRs, the unreleased resonator is able to maintain high Q, and suppress spurious modes. Analysis on the ABR design for unreleased resonators covers design principles, fabrication variations, and comparison to released devices. In the end, it is demonstrated that the ABR is more favorable than the phononic crystal for acoustic energy localization for unreleased resonators, providing a 9 times higher Q.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2011

Author dc:creator

• Wang, Wentao, Ph.D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Dana Weinstein and Carol Livermore.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/67806

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/67806