A Study on Solid Phase Reactions of Ni and Pt on Si-Ge Alloys as Contacts to Ultra-Shallow P⁺N Junctions for CMOS Technology Nodes Beyond 70nm

Abstract

Recently, selectively deposited SiGeB alloys have been proposed to form ultra-shallow source/drain junctions for 35-70 nm CMOS. The technology provides super-abrupt junctions with above equilibrium dopant activation at temperatures lower than 800°C. In addition to their low resistivities, the lower bandgap of SiGeB provides the potential advantage of reducing the Schottky barrier height and therefore, the junction contact resistance. This is a critical concern for future CMOS technology nodes since the contact resistance will dominate the MOSFET series resistance unless new technologies yielding contact resistivities near 10⁻⁸ ω−cm² are developed. This paper examines the solid phase reactions of Ni and Pt with SiGeB alloys in order to form self-aligned low resistivity contacts. The results show that both Ni and Pt can form germanosilicides with low sheet resistances. Furthermore, both metals can form self-aligned contacts with a contact resistivity near 10⁻⁸ ω−cm².