Morphology of Ti 37 Al 63 Thin-Films Deposited by Magnetron Sputtering
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Morphology of Ti37Al63 Thin-Films Deposited by Magnetron Sputtering N. David Theodore1, Hyunchul C. Kim2, Kaustubh S. Gadre3, James W. Mayer2, and Terry L. Alford2 1
DigitalDNA™ Labs., Motorola Inc., 2100 E. Elliot Rd., MD-EL622, Tempe, AZ 85284, U.S.A. Department of Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287, U.S.A. 3 Intel Corp., RA3-402, 2501 NW 229th St., Hillsboro, OR 97124, U.S.A. 2
ABSTRACT TiAl based thin-films possess high oxidation-resistance and high melting points, making them possible candidates for application in electronics. The behavior of the films upon exposure to various temperatures is of interest for such application. In the present study, Ti37Al63 thin films were deposited onto SiO2 substrates using RF magnetron sputtering from a compound target. Anneals were performed in vacuum at temperatures ranging from 400 oC to 700 oC. The phases and microstructural behavior of the films were evaluated as a function of annealing. Microstructural behavior was correlated with resistivity changes in the films. The behavior of TiAl films as potential under-layers for silver metallization was also evaluated. The Ti-Al was observed to enhance the thermal stability of pure Al thin-films. The results are relevant for potential application of the films to electronics. INTRODUCTION Titanium aluminide thin films have high melting points, good high-temperature strengths, light weights, and good oxidation resistances [1,2] making them attractive for structural coatings. Some of these properties can make the layers relevant for electronics as well. Sputter-deposited titanium aluminide films have been studied for mechanical applications at high temperatures [36]. However, there have been very few studies for application in electronics. Silver has potential for application as an interconnect metal, due to its low resistivity. However Ag tends to agglomerate upon annealing. If Ag is to be used for interconnects, its thermal stability needs to be improved. In the present work, we study the structural, electrical, and Ag-underlayer properties of sputter-deposited Ti37Al63 thin films on SiO2/Si substrates, to evaluate the potential usefulness of the films for electronics applications. EXPERIMENTAL DETAILS RF magnetron sputtering was used to deposit titanium aluminide thin films onto SiO2 /Si substrates. A compound target was used, with a composition of 40 at. % Ti with 60 at. % Al. The depositions used 350 W power with 5 mTorr Ar gas at room temperature. The thin films were annealed in a vacuum furnace for 1 hour, at temperatures ranging from 400 oC to 700 oC. Base pressure was approximately 5 × 10-9 Torr. The resulting films had a composition of Ti37Al63 as measured by Rutherford backscattering spectrometry (RBS). Transmission electron microscopy (TEM) was performed using a JEOL 200 CX instrument, operating at a voltage of 200 KV. The microstructures of the as-deposited and annealed titanium aluminide films were characterized. Crystallinity and phase formation in the films were
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