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POINT DEFECT INJECTION AND ENHANCED Sb DIFFUSION IN Si DURING Co-Si AND Ti-Si REACTIONS J.W. HONEYCUTr AND G.A. ROZGONYI North CarolinaState University, Department of Materials Science and Engineering, Raleigh, NC

ABSTRACT The effects of Co and Ti silicide film formation on diffusion of buried Sb-doped layers in Si have been investigated. Sb profile analysis by secondary ion mass spectrometry shows that greatly enhanced, non-uniform Sb diffusion occurs during reactions of various thicknesses (30300 nm) of Co and Ti by rapid thermal annealing. A simple non-equilibrium intrinsic diffusion model is invoked to estimate time-averaged excess vacancy concentrations. Vacancy concentrations of about 107 times equilibrium values are shown to exist during CoSi2 formation by reaction of a 30 nm Co film at 700'C for 5 min in Ar. Diffusion enhancements at large distances from silicide stripe edges are observed by bevel and etch techniques. These effects tend to decrease with increasing annealing time, indicating that film stresses may play an important role in the interfacial point defect injection process. INTRODUCTION Self-aligned silicidation has become an important process in silicon integrated circuit technology. In this process, the selective reaction of a thin metal film (e.g. Co, Ti, Pt, Ni, etc.) with exposed Si regions of a submicron device results in self-aligned formation of low resistance silicide contacts to shallow source/drain junctions, while also reducing the resistances of polysilicon gate and interconnect lines. The introduction of a self-aligned silicide process into a submicron device design usually demands a high degree of control over process integration, particularly with respect to interactions in the shallow junction regions of the device [1]. A major concern is the redistribution of dopants during the reaction of the deposited metal overlayer with the underlying ion-implanted silicon. Among the many dopant redistribution factors that need to be characterized is the generation of point defects at silicide-silicon interfaces. A research program has been undertaken to study this phenomenon, with the primary objectives of determining the identity of the injected point defects, their generation mechanisms, and the kinetics of their motion. Previous studies have shown that during thermal oxidation of silicon at temperatures in excess of 900'C, the diffusion of interstitialcy-type diffusers, such as B and P, is enhanced, while the diffusion of Sb, which is a vacancy diffuser, is retarded. These effects have been attributed to interfacial injection of self-interstitials into the silicon lattice. Thermal nitridation at temperatures over 1050'C causes opposite effects on diffusion of these dopants and therefore is believed to cause supersaturations of vacancies. (For a recent review of the effects of oxidation/nitridation on diffusion, see [2]). Such studies have provided much useful information at high temperatures. Silicidation, on the other hand, is a relatively low temperature process (usually _!_850'C) wh