Phase formation and stability of Ni silicide contacts - scaling to ultra-thin films

We discuss the effect of scaling of the Ni thickness on the formation and stability of nickel silicide contacts. When scaling the Ni thickness from 15nm down to 5nm, the start of the agglomeration of the resulting NiSi layer is gradually shifted towards lower temperature. The influence of the microstructure of the polycrystalline NiSi layer on the agglomeration behavior, and methods to stabilize the NiSi film will be discussed. For an as deposited Ni film with a thickness less than 5nm, a completely different behavior is observed, where annealing results in the formation of a Ni silicide phase that exhibits an epitaxial orientation with respect to the Si substrate. Based on sheet resistance measurements and scanning electron microscopy, this ultra-thin film is surprisingly stable during post-annealing at high temperatures.