Ni/sub 2/Si and NiSi formation by low temperature soak and spike RTPs

Abstract

As the size of metal oxide semiconductor devices continues to be scaled down to sub-90 nm, novel materials must be integrated successfully in order to meet the technical demands. Nickel silicide (NiSi) is being considered as an alternative material to cobalt silicide (CoSi2) for the self-aligned silicide process, because it forms at lower temperatures with less silicon consumption and is compatible with SiGe. In order to prevent excessive silicidation in narrow gate lines and at the edges of source/drain regions, NiSi integration requires limiting silicidation kinetics via reduced thermal budgets followed by forming the low resistance phase. This paper focuses on the low temperature regime of the Ni-Si reaction through the use of soak RTP at 300degC and spike RTP at 300 ~ 400degC. In order to study the formation of Ni2Si and NiSi and the transformation from Ni2Si to NiSi, the silicide films are characterized by Rs sheet resistance measurements, XRD for phase identification, and TEM for microstructure. The intermediate phase of Ni2Si is formed at 270degC and its growth is observed with increasing anneal time. At temperatures above 300degC, the NiSi phase is found in addition to the Ni2Si phase, and the transformation from Ni2Si to NiSi is observed. The sequence of the Ni2Si-NiSi transformation involves the initial formation of NiSi and the change in the alignment of the crystal planes as the low resistance phase of NiSi forms. Two RTP schemes, soak RTP and spike RTP, follow parallel trends in the sequence of the Ni2Si-NiSi transformation with marked differences in the reaction kinetics