Diffusion Instability and Tapering of Nickel Silicide Intrusions in Silicon Nanowires

Abstract

ABSTRACTThermally activated axial intrusion of nickel silicides into the silicon nanowire (NW) from pre-patterned Ni reservoirs is used in formation of nickel silicide/silicon contacts in SiNW field effect transistors. This intrusion consists usually of different nickel silicide phases which grow simultaneously during thermal annealing (TA). The growth is often accompanied by local thickening and tapering of the NW, up to full disintegration of segments adjacent to the silicon. In the present work this process was investigated in SiNWs of 30-60 nm in diameters with pre-patterned Ni electrodes after a TA at 420-440°C and times up to 15 s. The process was analyzed in the framework of a model taking into account simultaneous formation of two silicide phases in the NW. Additional flux of atoms caused by the NW curvature gradients due to different radii of different silicides was taken into account as well. For a certain set of parameters thickening of the nickel-rich silicide intrusion and tapering of the monosilicide part of intrusion were obtained.