Thickness scaling issues of Ni silicide

Abstract

Ni silicidation processes without a capping layer and with a TiN capping layer are studied from the point of view of process window, morphology of the resulting silicide, and mechanisms of degradation at higher temperatures. The thermal stability of NiSi films on As- and on B-doped (100) Si substrates was investigated for Ni film thicknesses ranging from 5 to 30 nm. While agglomeration was the mechanism of degradation for the thin films, both morphological changes and transformation to NiSi 2 were possible for thicker films depending on anneal temperature and time. Activation energy of ∼2.5 eV for NiSi on n+ (100) Si and p+ (100) Si was determined for the process of morphological degradation. The measured temperature and time dependences for the thermal degradation of NiSi films suggest that the activation energy for transformation to NiSi 2 is higher than for morphological degradation.