Achieving large stable vertical displacement in surface-micromachined microelectromechanical systems (MEMS)

This thesis describes electrostatic actuation techniques and mechanical design features for realizing large planar analog vertical travel in an electrostatically actuated diffractive mid-infrared optical device, which is robust, both to manufacture, and against pull-in during use. This device, called the Polychromator, is fabricated by polysilicon surface-micromachining and consists of many parallel elements, each 20 microns wide and a centimeter in length. Typically, achieving such a large travel would require prohibitively large gaps and actuation voltages. In order to reduce the actuation voltage and achieve greater travel before pull-in, thinner beams are used which exploit stress stiffening. This, in turn, creates a number of stress control hazards because tensile stress in one layer can induce buckling in a lower layer. These issues have been solved with detailed attention to supports and their compliance. A multi-layer nonlinear spring has been incorporated to make the device robust against pull-in. The electromechanical behavior of the device is simulated using Energy Methods, Finite Difference Methods, and the MEMCAD software. Excellent agreement between MEMCAD simulation and experimental measurements for this structure are reported. Each detail, stress control, support structure, and pull-in, must be addressed in order to achieve the combined effects of large travel, robustness against pull-in, and optically flat beams.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Deutsch, Erik R. (Erik Robertson), 1974-

Advisor dc:contributor.advisor

• Stephen D. Senturia and Rajeev Ram.

• Electrical Engineering and Computer Science.

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/1721.1/8118

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8118