Focused Ion Beam Induced Surface Damage Effect on the Mechanical Properties of Silicon Nanowires

Abstract

In this paper, the effect of surface damage induced by focused ion beam (FIB) fabrication on the mechanical properties of silicon (Si) nanowires (NWs) was investigated. Uniaxial tensile testing of the NWs was performed using a reusable onchip tensile test device with 1000 pairs of comb structures working as an electrostatic force actuator, a capacitive displacement sensor, and a force sensor. Si NWs were made from silicononnothing (SON) membranes that were produced by deep reactive ion etching hole fabrication and ultrahigh vacuum annealing. Micro probe manipulation and film deposition functions in a FIB system were used to bond SON membranes to the device's sample stage and then to directly fabricate Si NWs on the device. All the NWs showed brittle fracture in ambient air. The Young's modulus of 57 nmwide NW was 107.4 GPa, which was increased to 144.2 GPa with increasing the width to 221 nm. The fracture strength ranged from 3.9 GPa to 7.3 GPa. By assuming the thickness of FIBinduced damage layer, the Young's modulus of the layer was estimated to be 96.2 GPa, which was in good agreement with the literature value for amorphous Si.