High-Performance Lateral-Actuating Magnetic MEMS Switch

Michael Glickman
Advisor: Jack Judy

Monday, May 24, 2010 at 2:30pm
Engr. IV Archives Room 53-135E

Abstract:
Traditional relays are used to switch electrical current in applications where outstanding off-isolation, linearity, and low on-resistance are important. Solid-state switches have much poorer off-isolation and linearity, but are smaller, faster, and use less power than traditional relays. In contrast, MEMS switches have the capability of attaining the high off-state isolation, linearity, and low on-state resistance of the bulky traditional relay, while being faster, smaller, lighter, and potentially less costly. A variety of MEMS switches using electrostatic forces, electrothermal expansion forces, and magnetic forces have been developed. Electrostatically actuated MEMS switches are easy to fabricate, and thus have been the most commonly demonstrated type of MEMS switch, but their utility has been limited by high actuation voltages, limited displacement (and thus limited off-isolation), and typically employ CMOS-incompatible fabrication processes, such as high-temperature (600 C) polysilicon deposition. Electrothermally actuated switches tend to be the slowest type of switches and use the most power, but provide the most contact force -- which is important for achieving a low contact resistance. Although magnetostatically actuated MEMS switches offer much larger displacements and have greater contact force than electrostatically actuated MEMS switches, they are slower, larger, consume much more power, and are often not produced with CMOS-compatible fabrication processes.

This work demonstrates a high-performance magnetostatic MEMS-switch that retains the high force (200 micro-Newtons) and long actuation distances (7.7 microns) of magnetostatic switches, while using less than 13 mW to actuate. We have a developed 3-D solenoidal coil patterning method over a ferromagnetic core to reduce the power loss and die-area cost of planar windings. We have also developed an electroplating process to deposit NiFe 80/20 with a permeability of approximately 8500, thus allowing for the very low power input requirements of the switch. The completed switch has been tested to over 3 million cycles while maintaining a contact resistance of 0.1 -- 0.4 ohms. We have combined Schwartz-Christoffel mapping with magnetic equivalent circuits to create highly accurate models 1000X faster than the finite element method. The process is the first published fully-integrated UV-MEMS magnetic-switch to use horizontal actuation, which allows for future use of wiping contacts that reduce contact resistance. The process does not etch into the bulk of wafer, which allows it to be easily integrated with any III-V or CMOS wafer.

Biography:
Michael Glickman received his B.S. Degree in Electrical Engineering from Yale University, New Haven, CT in 2004, and the M.S. Degree in Electrical Engineering (Physical & Wave Electronics) from University of California, Los Angeles (UCLA) in 2008. He is currently a Ph.D. candidate with Prof. Jack Judy in the Department of Electrical Engineering, University of California, Los Angeles.