Program Organizers: Jagdish Narayan, Dept of Matls Sci & Engrg, Box 7916, NC State University, Raleigh, NC 27695; John Sanchez, Advanced Micro Devices, M3 160, PO Box 3453, Sunnyvale, CA 94088
Wednesday, PM Room: Orange County 5
February 7, 1996 Location: Anaheim Marriott Hotel
Session Chair: K.N. Tu, Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095
2:00 pm Invited
SCHOTTKY BARRIER HEIGHTS TO IV-IV SEMICONDUCTORS: F. Meyer, M. Mamor, V. Aubry-Fortuna, IEF CNRS URA 22, Bat. 220, Universite Paris Sud, 91405 Orsay Cedex, France; S. Bodnar, J.L. Regolini, France Telecom CNET BP98, 38243 Meylan Cedex, France
The variations of Schottky barrier heights to Si1-x-yGexCy films with composition and strain have been investigated and compared to those expected for the band gap energy. The results suggest that the Fermi level at the interface between tungsten and Si1-x-yGexCy alloys (x0) is pinned relative to the conduction-band. For Si1-xGex, the barrier on p-type follows the same trends than the band gap. For the ternary alloys, the variations of the barrier on p-type seems to be too large to be only due to a variation of the band-gap. In addition, we have investigated the role of the strain retained in the sputtered-W-gate on the barrier to silicon. Our results show that the barrier on n-type follows the same trends than the stress retained in the W-films as a function of the deposition pressure. The absence of change in the barrier height to p-type silicon suggests that the Fermi level at the interface with Si is pinned relative to the valence-band.
2:30 pm Invited
OHMIC CONTACTS IN Si-Ge ALLOYS: R. J. Nemanich, D. Aldrich, Z. Wang, D. Sayers, Department of Physics, North Carolina State University, Raleigh, NC 27695
This study addresses the interface stability and electrical properties of contacts on SiGe alloys. Reactive contact formation has been explored for a series of different metals (Ti, Co, and Zr) on MBE prepared SiGe epitaxial films grown on Si substrates. The results indicate that the reactions are significantly more complex than solid phase reactions of the same metals on Si (or Ge). Two different interface instabilities are identified in the Ti- SiGe and Co- SiGe materials systems, and these instabilities are modeled in terms of the thermodynamic properties and surface and interface energies of the materials. The intrinsic electrical property of the interface is the Schottky barrier, and we have measured the alloy dependence of the Schottky barrier of Co on both strained and unstrained SiGe alloys using angle resolved UV photoemission spectroscopy. The results indicate that the p- type Schottky barrier is the same for both strained and unstrained materials. Since the bandgap of the materials varies significantly with strain it is concluded that the n- type Schottky barrier shows significant strain dependence.
CONTACT FORMATION OF Cu3Ge ON Ge WAFERS: J.S. Huang, K.N. Tu, Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095-1595; F. Deng, S. S. Lau, Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, CA 92093-0407
We have carried out a study of formation of Cu3Ge by reacting Cu films with Ge wafers. Phase identification and reaction kinetics were performed by a combination of Read camera X- ray diffraction, Rutherford backscattering spectroscopy, and in- situ resistivity measurement. In the as- deposited samples, a trace of Cu3Ge phase was detected. The Cu3Ge grew rapidly at temperatures above 200deg.C. We have found that the Cu3Ge phase is very stable again oxidation in air, in contrast to the fast oxidation behavior of Cu and Cu3Si films. The oxidation behavior will be discussed.
Leaders: J.M. Woodall, Purdue University; J. Narayan, North Carolina State University; J.E. Sanchez, Jr., Advanced Micro Devices
Panel Members: D. Crawford, National Science Foundation; H. Morkoc,
University of Illinois at Urbana-Champaign; P.H. Holloway, University of
Florida; M. Murakami, Kyoto University; F. Meyer, University of Paris; K.N.
Tu, University of California at Los Angeles; T. Sands, University of California
at Berkeley; C.M. Osburn, North Carolina State University
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