Nickel silicide nanowires formed in pre-patternedSiO2 trenches and their electrical transport properties

Abstract

Nickel silicide (NiSi) nanowires with different linewidth (from 1000 to 32 nm) are formed in pre-patternedSiO2 trenches on asilicon substrate. SiO2 trenches are milled by focused ion beam (FIB) etching, and an electrical endpoint detectiontechnique is used to control the FIB milling depth to just reveal the silicon surface. Theformation is based on Ni thin film deposition and the subsequent annealing at550 °C. Compared with the previously reported self-aligned formation processof NiSi nanowires, the present technique can form NiSi nanowires withcontrolled length and linewidth because of the pre-patterning of theSiO2 trenches.The as-formed NiSi nanowires show metallic transport characteristics with a rather low resistivity ofabout 15 µΩ cm, which exhibits very weak dependence on linewidth above 50 nm. The lowest resistivity ofthe nanowire is observed at a linewidth of about 100 nm. The low resistivity is thought tobe due to the good crystalline structure of our as-formed NiSi nanowires. When thelinewidth of NiSi nanowires is decreased to 32 nm, the resistivity increased abruptly to22.7 µΩ cm, which can be explained by considering the short electron mean free path (about 5 nm), aswell as the obvious effect of grain boundary on electron transport properties ofNiSi.