Structural advantages of rectangular-like channel cross-section on electrical characteristics of silicon nanowire field-effect transistors

Abstract

We have experimentally demonstrated structural advantages due to rounded corners of rectangular-like cross-section of silicon nanowire (SiNW) field-effect transistors (FETs) on on-current ( I ON), inversion charge density normalized by a peripheral length of channel cross-section ( Q inv) and effective carrier mobility ( μ eff ). The I ON was evaluated at the overdrive voltage ( V OV) of 1.0 V, which is the difference between gate voltage ( V g) and the threshold voltage ( V th), and at the drain voltage of 1.0 V. The SiNW nFETs have revealed high I ON of 1600 μA/μm of the channel width ( w NW) of 19 nm and height ( h NW) of 12 nm with the gate length ( L g) of 65 nm. We have separated the amount of on-current per wire at V OV = 1.0 V to a corner component and a flat surface component, and the contribution of the corners was nearly 60% of the total I ON of the SiNW nFET with L g of 65 nm. Higher Q inv at V OV = 1.0 V evaluated by advanced split-CV method was obtained with narrower SiNW FET, and it has been revealed the amount of inversion charge near corners occupied 50% of all the amount of inversion charge of the SiNW FET ( w NW = 19 nm and h NW = 12 nm). We also obtained high μ eff of the SiNW FETs compared with that of SOI planar nFETs. The μ eff at the corners of SiNW FET has been calculated with the separated amount of inversion charge and drain conductance. Higher μ eff around corners is obtained than the original μ eff of the SiNW nFETs. The higher μ eff and the large fractions of I ON and Q inv around the corners indicate that the rounded corners of rectangular-like cross-sections play important roles on the enhancement of the electrical performance of the SiNW nFETs.