Low-Temperature Self Aligned TiSi2'TiN Bilayer by Rapid Thermal Nitridation of Metastable Titanium Silicide in NH3 Ambient

Abstract

ABSTRACTRapid thermal nitridation (RTN) of metastable Ti silicide in pure ammonia ambient has been shown to result in the formation of a bilayer TiSi 2'TiN structure. This bilayer structure provides an effective self-aligned diffusion barrier against aluminum spiking. Further, the simultaneous formation of TiN on top of the TiSi2 preserves the low resistivity of the silicide layer upon subsequent high temperature process steps. Rutherford backscatttering spectroscopy, Auger electron spectroscopy and four point probe techniques were used to analyze the stoichiometry of the nitrided layer, and to study the kinetics of the nitridation reaction. The nitridation of the metastable silicide film is a substitutional eaction which begins at the surface of the silicide and progresses by substituting nitrogen atoms for silicon. The nitrogen atoms result from dissociation of ammonia The released silicon atoms then diffuse to the silicide'silicon interface and deposit in an epitaxial manner. The benefits of the proposed metallization scheme are substantiated by electrical characterization of the bilayer structure in comparison with a conventional process.