Rapid Thermal Annealing of Sputtered Ti-Ni-Si Films
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RAPID THERMAL ANNEALING OF SPUTTERED Ti-Ni-Si FILMS STO*,*
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,J.E. FISCHER , AND M. SIEGAL . Laboratory for Research on the Structure of Matter, *Department of Materials Science and Engineering, ** Moore School of Electrical Engineering, Center for Sensor Technologies, University of Pennsylvania, Philadelphia, Pa. 19104 M. SETTON
E.H. HORACHE
,
J. VAN DER SPIEGEL
,
J.J. SANTIAGO
ABSTRACT
A ternary compound results from the fast radiative processing of Ni/Ti bilayers on Si substrates. In the Ti-Ni-Si system, Ni is the dominant moving specie at low temperatures while Si starts to diffuse at 575 0 C. For bilayers with Ti in excess, the final product,above 7500C, is a mixture of ternary compound and TiSi, whereas excess Ni leads to a layer of NiSi between the substrate and the ternary layer, at temperatures below 7000 C.
INTRODUCTION The properties and thermal evolution of metallic alloys or multilayered structures are of great technological and scientific interest for shallow silicide contacts and multilevel metallization schemes. To produce reliable contacts, the amount of Si consumed to form the silicide layer has to be minimal. Stable ternary compounds with low Si content are therefore particularly attractive. Alloying of a near noble and a refractory metal provides good control of the silicide reaction and results in the formation of a protective diffusion barrier [1]. The study of solid state reactions involving two metals with Si is also valuable for a better understanding of compound formation and phase separation. As the number of species increases, more factors influencing the reaction have to be taken into account. For ternary systems, the behavior of the reaction products is influenced by the solid solubility
of both the mono and di silicides, the diffusivity of an element through
several layers (possibly a ternary compound) and the presence of two initial interfaces, as in the case of bilayers. When the difference between atomic sizes of the components is large enough to allow a denser packing than the one resulting from the close packing of spheres of equal radii, a ternary compound with a Laves type structure is favored [2]. Due to the atomic size difference between Ti and Ni the Ti-Ni-Si system belongs to that group. Therefore the possible formation of ternary compound is studied in this paper. One can also notice three interesting characteristics. First, Ni and Ti form stable phases at low temperatures (eutectic at 950 0 C, Ti.Ni at 980"C) [3]. Second, the formation of TiSi 2 is diffusion controlled for clean interfaces [4] whereas nucleation processes are the rate limiting step for the transformation NiSi+NiSi~above 800*C [5]. Finally, equilibrium ternaries have been reported and partial phase diagrams are available [6,7].
Mat. Res. Soc. Symp. Proc. Vol. 74. c1987 Materials Research Society
686
EXPERIMENTAL PROCEDURE
Si(p type Boron doped (2E15 atomes/cm ) wafers with (100) orientation and resistivities of 6.3 to 8.5 9-cm are cleaned using a standard procedure, etched in 5%HF, ri
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