The effect of triple capping layer (Ti/Ni/Tin) on the electrical and structural properties of nickel monosilicide

The effects of a triple capping layer (Ti/Ni/TiN) on the electrical and structural properties of nickel monosilicide (NiSi) have been investigated as a function of rapid thermal annealing temperature. It is shown that the samples with the triple capping layer produce lower sheet resistances than the samples with double (Ti/TiN) or single (TiN) capping layers across the whole annealing temperature range. Scanning transmission electron microscopy results show that, after annealing, interfacial layers consisting of Ni, Ti, and Si elements are formed in the samples with the triple and double capping layers. It is further shown that the triple-capped samples are more thermally stable than the double- and single-capped samples. This could be attributed to the segregation of Ti atoms in grain boundaries of NiSi film, which reduces grain boundary energy. The simple model is presented to explain the influence of Ti reaction flux on the surface morphology and the interface uniformity between the silicide and Si substrate.