Platinum Germanosilicide Contacts Formed on Strained and Relaxed $\hbox{Si}_{1 - x}\hbox{Ge}_{x}$ 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 (PtSi
_1-x
Ge
_x
) is of interest as a contact material to the recessed Si
_1-x
Ge
_x
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 Si
_1-x
Ge
_x
layers on PtSi
_1-x
Ge
_x
formation and the impact of the PtSi
_1-x
Ge
_x
on the strain in Si
_1-x
Ge
_x
. The parameters considered in this paper include the Ge content, the thickness of the Si
_1-x
Ge
_x
epitaxial layer, and the PtSi
_1-x
Ge
_x
thickness. The results show that the resistance, surface morphology, and the crystalline structure of the PtSi
_1-x
Ge
_x
films are independent of the strain in the original Si
_1-x
Ge
_x
layer. The results also indicate that PtSi
_1-x
Ge
_x
does not influence the strain in the Si
_1-x
Ge
_x
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 PtSi
_1-x
Ge
_x
-Si
_1-x
Ge
_x
contacts is 0.1-0.2 eV higher than that of the PtSi-Si contacts.