Nickel, Platinum and Zirconium Germanosilicide Contacts to Heavily Phosphorous Doped Silicon-Germanium Alloys for Advanced CMOS Source/Drain Junctions

Abstract

ABSTRACTAs the MOSFET dimensions continue to shrink, source/drain contact resistance is emerging as the dominant component of the MOSFET parasitic series resistance. To meet the series resistance requirements of future MOSFETs, contact resistivity values near 10-8 ohm-cm2 are required. Selective Si1-xGex source/drain technology has been proposed as an alternative to ionimplantation to form the ultra-shallow junctions of future CMOS technology nodes. One of the key advantages of this technology is the smaller band gap of Si1-xGex, which provides a smaller contact barrier height, an essential requirement for reducing the contact resistivity. We have previously reported low-resistivity of Ni germanosilicide NiSi1-xGex and Pt germanosilicide PtSi1-xGex contacts to boron doped Si1-xGex alloys. In this work, Zr germanosilicide, Zr(Si1-xGex)2 was considered as an alternative material with a higher thermal stability than Ni and Pt germanosilicides. The contact resistivity values for different contact materials were measured using four-terminal Kelvin structures. The results from this work show that both Zr and Pt germanosilicides yield high contact resistivity values around 10-7 ohm-cm2. On the other hand Ni germanosilicide contacts can reach 10-8 ohm-cm2 with further improvements using a thin layer of Pt under Ni.