AVS 49th International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeA

Paper TF-WeA5
Atomic Layer Deposition of Tribological Coatings for MEMS Devices

Wednesday, November 6, 2002, 3:20 pm, Room C-101

Session: Atomic Layer Deposition - Applications of ALD
Presenter: T.M. Mayer, Sandia National Laboratories
Authors: T.M. Mayer, Sandia National Laboratories
P.G. Kotula, Sandia National Laboratories
R.S. Goeke, Sandia National Laboratories
J.W. Elam, University of Colorado
S.M. George, University of Colorado
Correspondent: Click to Email
Friction and wear are major concerns in the performance and reliability of micromechanical (MEMS) devices. However, the severe geometric constraints of many micromechanical systems (high aspect ratios, shadowed surfaces) make most deposition methods for friction and wear-resistance coatings impossible. We have produced highly conformal coatings of Al@sub 2@O@sub 3@ and ZnO, deposited by atomic layer deposition (ALD), for use on surface micromachined (SMM) and LIGA structures. We demonstrate extremely uniform deposition of 10 nm films of amorphous Al@sub 2@O@sub 3@ on micromachine structures with aspect ratio up to 50 (feature depth vs. width). Friction coefficient of the Al@sub 2@O@sub 3@ on flat surfaces is measured to be approx. 0.3, while wear resistance of the films is improved over that of the SiO@sub 2@/Si substrate. ZnO is a potentially lubricious film, whose tribological properties depend on the crystallite structure in the film. Thin, nm-thick films are shown to be nanocrystalline with low friction coefficient, while thicker films with larger grain size exhibit high friction coefficient. We can control crystallite size through thickness and temperature control in the deposition process, or by laminating the ZnO film with nm-thick layers of Al@sub 2@O@sub 3@ in the ALD process. We will report the tribological properties of ZnO films and nanolaminates as a function of crystallite size and preparation methods.