THERMAL DEGRADATION OF NiPt GERMANOSILICIDE FILMS FORMED ON UNDOPED AND DOPED SiGe SUBSTRATES

Abstract

With the continuous scaling down the VLSI technology, there is an escalating interest in SiGe alloys for performance enhancement of the MOSFETs transistors, since SiGe films can be present in the gate and source/drain areas of MOSFETs. In this work NiPt germanosilicides were fabricated with 20 nm thick Ni and different Pt layer (3, 6, 9, and 12 nm thick) by rapid thermal annealing (RTA) at 300 °C, and then the post-annealing effects on these samples were investigated in the temperature range between 400 oC to 750 oC. The obtained silicide samples were characterized by four point probe method, grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy with field emission gun (FESEM) and atomic force microscopy (AFM). Smooth and uniform Ni (Pt) monogermanosilicide films have been observed for all analyzed samples. For annealing temperatures lower than 500 °C the samples exhibited thermal stability with sheet resistances of 10 – 30 Ω/sq, and sheet resistance degradation for annealing temperatures of 500 °C and above. Structural transformation of the formed silicide to Ge rich Ni(Pt)Si 1-μ Ge μ films was found to occurs with increasing of the annealing temperature. Surface analysis revealed morphological instability of germanosilicides and strong tendency for agglomeration and mounds-like structure formation, which leads to an abrupt increase in the sheet resistance.