Effect of a Ti capping layer on thermal stability of NiSi formed from Ni thin films deposited by metal organic chemical vapor deposition using a Ni(Pr-i-DAD)(2) precursor

Abstract

Ni films were deposited by metal organic chemical vapor deposition (MOCVD) using a novel Ni precursor, bis(1,4-di-isopropyl-1,3-diazabutadienyl)nickel [Ni(Pr-i-DAD)(2)], and NH3 gas. To optimize process conditions, the deposition temperature and reactant partial pressure were varied from 200 to 350 degrees C and from 0.2 to 0.99 Torr, respectively. Ni films deposited at 300 degrees C with a reactant pressure of 0.8 Torr exhibited excellent quality, and had a low carbon impurity concentration of around 4%. In addition, a sacrificial Ti capping layer was deposited by an in situ e-beam evaporator on top of the Ni films to enhance the thermal stability of the subsequently formed NiSi films. Both the Ti-capped and uncapped Ni films were annealed by a two-step method, with a first annealing conducted at 500 degrees C, followed by wet etching and then a second annealing carried out from 500 to 900 degrees C. The Ti capping layer did not affect the silicidation kinetic process, but by acting-as an oxygen scavenger, it did enhance the morphological stability of the NiSi films and thus improve their electrical properties.