Optimization of n-channel silicon nanowire field effect transistor using Taguchi method

Abstract

In the last few decades, the performance of electronics devices, especially the transistors have made tremendous progress thanks to the novel metal-oxidesemiconductor field-effect-transistor (MOSFET) devices structure like Silicon Nanowire FET (SNWFET). As the device is scaled down into nanometer regime, SNWFET is believed could overcome the short channel effects (SCEs). The complexity of SNWFET is influenced by its device geometry such as gate and width size, nanowire shape, nanowire radius, channel orientation, etc. Therefore, the thesis describes the optimization of n-channel SNWFET by using Taguchi method. Taguchi method is straightforward, easy to apply and has fast simulation run time. The dimension of the SNWFET device i.e. gate length (Lg ) , silicon nanowire radius (Rnw) and gate oxide thickness (Tax) are altered for a range of sizes and dimensions by using Taguchi approach to get the most optimum dimensions of the device. The electrical properties of the SNWFET device which are threshold voltage (Vth), on/off current ratio (Ion/Iott ratio), Subthreshold Swing (55), and Drain-Induced Barrier Lowering (DIBL) are extracted and analyzed based on the I-V characteristics. The general idea of the Taguchi technique is the set of electrical properties are statistically distributed into standard normal distribution and the mean and the standard deviation are determined. From the results obtained, with fixed thin Tax, as the Rnw is reduces and Lg is increases, the electrical performance of the SNWFET device is better in terms of its subthreshold swing, switching speed and DIBL. Better threshold is observed in nSNWFET device with smaller Rnw. The Ion/Iott ratio also shows better result with longer Lg . Lastly, from the statistical analytic of the device's electrical characteristics, the most optimum device dimensions of n-channel SNWFET device structure has been successfully identified which are Rnw at 3nm, Tax at 3nm, and Lg at 40nm with their electrical characteristics of Vt h , Ion/Iott ratio, 55 and DIBL are O.22V, I.06xI05 , 64.69mVIdee and = 80.27mV/V respectively.