AVS 51st International Symposium
    Nanometer-scale Science and Technology Wednesday Sessions
       Session NS-WeA

Paper NS-WeA8
Gas Phase Lubrication of MEMS

Wednesday, November 17, 2004, 4:20 pm, Room 213D

Session: Nanotribology and Nanomechanics
Presenter: S.A. Smallwood, Universal Technology Corporation
Authors: S.A. Smallwood, Universal Technology Corporation
K.C. Eapen, University of Dayton Research Institute
J.S. Zabinski, Air Force Research Laboratory (AFRL/MLBT)
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A number of different MEMS systems have been designed, fabricated and a few have been marketed. Most commercial MEMS designs are void of parts that simultaneously move and undergo contact due to the problems of stiction, friction and wear. Candidate solutions to tribological problems include monolayers and self-lubricating hard materials. The problem with thin film lubricants is that the coating is fairly quickly worn away. Even though hard coatings such as diamond like carbon (DLC) are expected to have a longer life, improvements in durability are still required. A combination of bound and mobile phase lubricants has been used to extend life through flow of the mobile phase. This provides a protective bound coating and a fluid mobile constituent that offers replenishment. Another replenishment scheme is gas phase lubrication, which offers a way to continuously provide a protective coating by constantly replenishing the contact region. Gas phase lubrication results for MEMS are discussed in this talk. Accelerated screening tests have been performed in vacuum with a pin on disk tribometer tester using a range of Hertzian mean normal stress from 180 to 390 MPa. The tribometer includes a 0.25 inch dia. silicon nitride ball against a polysilicon sample. Protective gases were leaked into the vacuum system during friction tests. These gases include low boiling organic compounds with different functional groups. Surface tribochemistry in the wear track and wear debris were examined using x-ray photoelectron spectroscopy (XPS), microRaman spectroscopy, IR spectroscopy and scanning electron microscopy (SEM). In addition, performance tests were run on operational electrostatic MEMS motors. Surface chemical analyses on screening tests and operational devices are used to provide information on friction and wear mechanisms.