Orientation dependence of nickel silicide formation in contacts to silicon nanowires

The orientation dependence of Ni silicide phase formation in the silicidation of silicon nanowires (SiNWs) by Ni has been studied. SiNWs with a [112] growth direction contacted by Ni pads form theta-Ni2Si for annealing conditions from 350 to 700 degrees C for 2 min. The theta-Ni2Si has an epitaxial orientation of theta-Ni2Si[001]parallel to Si[11 (1) over bar] and theta-Ni2Si(100)parallel to Si(112) with the SiNW. On the other hand, SiNWs with a [111] growth direction react with Ni pads to form NiSi2 with an epitaxial orientation of NiSi2[1 (1) over bar0]parallel to Si[1 (1) over bar0] and NiSi2[111]parallel to Si(111) after annealing at 450 degrees C for 2 min. The (111) SiNWs were also silicided at 700 degrees C for 2 min, forming the low-resistivity NiSi phase. The epitaxial phases identified in the reactions of Ni films with SiNWs suggest that lattice matching at both the silicide/Si growth front and the surface of the original SiNW may play a significant role in determining the first silicide segment to grow. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3115453]