Improving the thermal stability of nickel monosilicide thin films by combining annealing with the use of an interlayer and a capping layer

Abstract

The authors investigated the effects of preannealing a 2-nm-thick Pd interlayer and a 20-nm-thick TiN capping layer on the electrical and thermal stability of nickel silicides as a function of the annealing temperature. The preannealed samples (prepoly-Si) produce lower sheet resistances compared to the samples without preannealing. For the preannealed samples, NiSi remains stable up to 600 degrees C. Transmission electron microscopy results show that the preannealed samples have a higher resistance against layer inversion. The addition of a Pd interlayer at the Ni film/prepoly-Si interface increases the formation temperature of NiSi(2) to 900 degrees C. The use of the capping layer on the Pd-interlayered prepoly-Si samples improves the electrical and morphological stabilities of NiSi. The possible mechanisms for the preannealing and interlayer-induced improvement of the thermal stabilities of the Ni-silicide samples are discussed in terms of grain growth and simple thermodynamic relations. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3565468]