Platinum Germanosilicide Contacts Formed on Strained and Relaxed Si1-xGex Layers

Contact resistivity is a key contributor to the parasitic series resistance of nanoscale MOSFETs. Since the contact resistivity is an exponential function of the Schottky barrier height, new contact materials that can provide smaller barrier heights to source-drain junctions are needed. Platinum germanosilicide (PtSi1-xGex) is of interest as a contact material to the recessed Si1-xGex junctions of p-channel MOSFETs due to the large work function of platinum silicide (PtSi). In this paper, we explore the impact of in-plane biaxial compressive strain in Si1-xGex layers on PtSi1-xGex formation and the impact of the PtSi1-xGex on the strain in Si1-xGex. The parameters considered in this paper include the Ge content, the thickness of the Si1-xGex epitaxial layer, and the PtSi1-xGex thickness. The results show that the resistance, surface morphology, and the crystalline structure of the PtSi1-xGex films are independent of the strain in the original Si1-xGex layer. The results also indicate that PtSi1-xGex does not influence the strain in the Si1-xGex layer. The barrier-height measurements suggest the presence of Fermi-level pinning, and the pinning position is independent of the strain in the alloy, and it is primarily determined by the Ge concentration. As a result of Fermi-level pinning, hole Schottky barrier height of PtSi1-xGex-Si1-xGex contacts is 0.1-0.2 eV higher than that of the PtSi-Si contacts.