ICMCTF1999 Session H3: MEMS Coatings

Tuesday, April 13, 1999 1:30 PM in Sunrise Room

Tuesday Afternoon

Start	Invited?	Item
1:30 PM	Invited	H3-1 SiC MEMS: Opportunities and Challenges for Application in Harsh Environemnts M. Mehregany (Case Western University); C.A. Zorman (Case Western Reserve University) Many measurement and control applications requiring MEMS technology are in the presence of harsh environments, e.g., high temperatures, intense shock/vibrations, erosive flows, and corrosive media. For example, the sensing and actuation needed to maximize the efficiency of gas turbine, rocket, and internal combustion engines must be able to reliably operate around combustion environments characterized by the aforementioned phenomenon. SiC as a semiconductor material and technology is exceptionally well suited for addressing such application opprotunities. However, many challenges must be met in order to develop a SiC MEMS technology. These challenges are primarily technical in nature and relate to material and processing aspects. In effect, the same material properties that make SiC very attractive in the presence of harsh environments, also make SiC very difficult to process. However, once the SiC material/process technology matures to a level competitive with Si MEMS, there may be merit in replacing Si with SiC as a mechanical material all together!
2:10 PM	Invited	H3-3 Thin Film MEMS for Biomedical Applications D.L. Polla (University of Minnesota) Microectromechanical systems, or MEMS, represents an exciting new technology derived from the same manufacturing processes used to make integrated circuits. There are many diverse applications of MEMS for sensing and actuation, which are being aggressively pursued throughout the world. A MEMS approach based on the integration of piezoelectric materials with micromechanical structures is being pursued at the University of Minnesota for physical sensing, minimally invasive surgery, and bioanalytic medicine. This talk will describe MEMS materials, processing technologies, and device applications including 1) physical microsensors for detecting force, pressure, and acoustic energy; 2) microvalves, micropumps, and capillaries for microfluidic controls; 3) biosensors based on molecular recognition structures; 4) miniature linear micromotors for precision positioning and manipulation of cells; and 5) surgical and scientific microinstruments. Selected demonstration applications from the fields of ophthalmology, arthroscopic surgery, gynecology, and laboratory medicine will be presented. Design issues, technology limitations, systems integration approaches, and future opportunities of MEMS technologies will be discussed.
2:50 PM		H3-5 Some Issues Associated With The Use Of Aluminum-4%Copper Alloys As Interconnect Material In Micromachined Devices J. Castelli (Standard Microsystems Corporation); M. D'Aquila (Raytheon Advanced Device Center); N. de Lanerolle, G. Fricano (Standard Microsystems Corporation) Aluminum-4%Copper alloys have been used as interconnect material in micro machined devices where the surface roughness was also found to play an important role in device yield. The purpose was to reduce the magnitude and intensity of the hillocks that tend to form on Aluminum alloys in similar applications. In this paper we describe observations based on manufacturing conditions using above alloy as interconnect material. It was found that the hillocks that form with above material is usually associated with a second phase precipitation. The effect of an overlayed highly compressive film was studied by laying down a multilayer silicon nitride/silicon carbide film on top of the aluminum-copper film. A further observation with this alloy was its tendency to form notches during the patterning process. The hillocks were examined using a Dektak profilometer, and scanning electron microscopy. The Aluminum-Copper alloy films were deposited using a commercial Balzers LLS 801 sputter deposition system. The patterning was performed using a Perkin-Elmer commercial optical lithographic system followed by wet spray etching. In this paper we give an explanation to account for the above observations.
3:30 PM	Invited	H3-7 Ferroelectric Thin Films for MEMS Applications S. Trolier-McKinstry (Pennsylvania State University); J.-P. Maria, R. Polcawich, J.F. Shepard, W. Ren (Consultant); F. Xu (Pennsylvania State University) Ferroelectric thin films offer significant advantages over alternative piezoelectrics such as oriented ZnO in terms of both the magnitude of the piezoelectric coefficients and the energy densities which are available. Consequently, there are real advantages to using them in microelectromechanical systems (MEMS). This talk will focus on the factors which affect the piezoelectric properties of ferroelectric thin films, including clamping of the extrinsic contributions to the properties, preferred polarization directions, aging mechanisms, and preferred orientation. In particular, it was found that for undoped sol-gel lead zirconate titanate 40/60, 52/48, and 60/40 thin films under a micron in thickness, the extrinsic contributions to the dielectric and electromechanical properties make very modest contributions to the film response. Despite this, the aging rate for the piezoelectric coefficients can be quite rapid (exceeding 20%/decade), which is believed to be associated with depolarization of the films. The aging rate can be controlled (and reduced nearly to zero) by tailoring the preferred polarization direction in the films. Finally, the properties of epitaxial lead magnesium niobate - lead titanate thin films will be compared to those of oriented lead zirconate titanate. This work is supported by NSF, ONR, and DARPA.
4:10 PM	Invited	H3-9 Integrated Ferroelectric Thin Films for MEMS Microactuator and Thin Film IR Imaging Devices P.G. Clem, J.A. Ruffner, T.J. Garino, B.A. Tuttle, W.K. Schubert, M.-A. Mitchell, D.B. Dimos (Sandia National Laboratories) Ferroelectric thin films enable a variety of novel electronic devices, especially when integrated with bulk or surface micromachined silicon substrates. In particular, the large piezoelectric coefficients of materials such as Pb(Zr,Ti)O₃ [PZT] are ideal for micromachined silicon actuators and force sensors. Bulk micromachined MEMS devices produced by integration of PZT thin films will be presented, as well as integration and processing strategies for ferroelectric thin films on a variety of other substrates. Ferroelectric materials also possess high pyroelectric coefficients and are of interest for 8-14um infrared night vision applications. The development of such devices atop thermal isolation structures including aerogel films will be presented. High pyroelectric coefficents have been measured for such structures, and noise equivalent temperature difference values below 0.1 degrees C are calculated. Integration strategies, including adhesion, planarization, and stress control, will be discussed for unorthodox substrates. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy under contract DE-AC04-94A185000.