Reactive Diffusion for Contact Formation in Advanced MOS Devices

Metallic silicides are used as contact materials on source/drain and gate in MOS structure since the 1970's. From the 65 nm technology node, NiSi is the preferred material for contact in microelectronic due to low resistivity, low thermal budget and low Si consumption. Ni(Pt)Si with 10 at.% Pt is currently employed in recent technologies since Pt allows to stabilise NiSi at high temperature. The presence of Pt and the very low thickness (< 10 nm) needed for the contact in the devices bring new concerns for actual devices. Indeed, for such film thicknesses, phenomena like nucleation, lateral growth, interfacial reaction, stress, texture and transient phase formation can play an important role. The presence of alloy elements (Pt, Pd) as well as stress and defects induced by the confinement in devices have some effects on the silicide formation mechanism and on the alloying element redistribution. In this work, in situ techniques (XRD, sheet resistance, DSC) were combined with atom probe tomography (APT) and transmission electron microscopy (TEM) to study the formation mechanisms as well as the redistribution of dopants and alloy elements (Pt, Pd) during the silicide formation. In particular, APT has been used for the local analysis of MOSFET in 3D and at the atomic scale [3]. The advances in the understanding of the mechanisms of formation and redistribution will be discussed.