Chemistry, microstructure, and electrical properties at interfaces between thin films of titanium and alpha (6H) silicon
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J.S. Bow, M. J. Kim, and R.W. Carpenter Center for Solid State Science, Arizona State University, Tempe, Arizona 85287-1704
R. C. Glass Westinghouse Science and Technology Center, Westinghouse Corporation, Pittsburgh, Pennsylvania 15235 (Received 25 January 1994; accepted 15 November 1994)
Epitaxial thin films (4-1000 A) of Ti contacts have been deposited via UHV electron beam evaporation at room temperature on monocrystalline, n-type, alpha (6H)-SiC(0001). The interfacial chemistry and microstructure, and the electrical properties, were investigated at room temperature and after annealing at 700 °C up to 60 min. High resolution TEM analyses revealed the formation during annealing of reaction zones consisting of Ti5Si3 and TiC. The corresponding electrical properties exhibited considerable stability except after an initial 20 min anneal. Current-voltage (I-V) measurements showed that the Ti contacts were rectifying with low ideality factors (n < 1.09) and typical leakage currents of 5 X 10"7 A/cm 2 at - 1 0 V. The Schottky barrier heights calculated from x-ray photoelectron spectroscopy and I-V and C-V measurements were between 0.79 and 0.88 eV for the as-deposited contacts and between 0.86 and 1.04 eV for the annealed contacts.
I. INTRODUCTION
The extreme thermal, mechanical, and electronic properties of SiC have allowed its use for both structural applications and high-power, high-temperature, highspeed, and high-frequency electronic and optoelectronic devices. The chemistry at annealed Ti/SiC interfaces has been investigated for structural applications by many groups, as discussed below. However, no integrated study has been found that has examined the Ti/SiC interface in terms of the chemistry, microstructure, and electrical properties for the purpose of contacts in semiconductor devices. The increased use of (6H)-SiC for many types of semiconductor devices is challenged by the difficulty of controlling the properties of the metal contact/SiC interface, including uniformity and thickness of the interfacial region, stability at high temperatures (~600 °C), and most importantly, the Schottky barrier height (SBH), or the energy barrier for electrons traversing the interface. It is important to understand the chemistry and microstructure at the interface between the metal contact and the SiC substrate before and after annealing at temperatures at or above which devices may be operated so that the resulting phases may be correlated with the electrical properties. In this study, analytical techniques have been employed to investigate the interfacial chemistry and 668
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J. Mater. Res., Vol. 10, No. 3, Mar 1995
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microstructure on both an atomic scale and a microscopic (
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