Performance Analysis of High-kappa Material Gate Stack Based Nanoscale Junction Less Double Gate MOSFET

In the recent past, the channel lengths for conventional single gate MOSFETs have reduced below 45 nm and gate oxide thickness have also reduced below 2 nm. Due to these factors, there are considerable improvements in performance and packing density. But as channel node is scaled down, short channel effects like threshold voltage roll-off, drain induced barrier lowering and sub-threshold swing come into picture and they have significant role in deciding the performance of the devices. Furthermore with device scaling in sub-nanoscale, the fabrication of MOSFETs with junctions has become very difficult. Researcher's recently have focused on new devices such as the junction less double gate (JL-DG) MOSFETs which are electrostatically far better than the conventional single gate MOSFETs. There is no stringent requirement of high concentration gradients in the junction less devices compared with conventional devices. Scaling of gate oxide layers led to reduction in the thickness to around 1 nm which results in large leakage currents. So replacement of silicon dioxide (SiO2) with material having higher dielectric constant (kappa) or 'high-kappa' gate oxides such as hafnium oxide (HfO2) and hafnium silicate (HfO4Si) is necessary. With recent advancements in deposition processes, HfO2 can be used as the oxide layer for MOSFET. This paper compares the design of junction less double gate MOSFETs with silicon dioxide and hafnium oxide as gate oxide layers at 22 nm technology. The work carried out on both the devices gives the comparative study for drain current, on current to off current ratio (I-ON/I-OFF), drain induced barrier lowering (DIBL), sub-threshold swing and transconductance. The effect of variation of the workfunction of metal gate on the parameters of devices is also studied. It is observed that JL-DG MOSFET with HfO2 oxide layer has better I-ON/I-OFF ratio, better DIBL and sub-threshold swing (SS) parameter.