Study On Application Of Spacer To Multi-gate Negative Capacitor Field Effect Transistor

Fin field-effect transistors（Fin FETs）and Gate-All-Around（GAA）nanosheet field-effect transistors（NSFETs）often use spacer technology to enhance gate control ability and improve short-channel effects（SCE）.Meanwhile,negative capacitance field-effect transistors（NCFETs）can flexibly adjust the gate capacitance of the baseline device to better meet the special requirements of capacitance matching in NCFET by using spacer technology.Therefore,applying spacer technology in negative capacitance Fin FET（NC-Fin FET）and negative capacitance NSFET（NC-NSFET）is expected to be an effective approach to improve and optimize the performance of the aforementioned multi-gate NCFETs.This thesis explores the structure and type of spacers for these NCFET and verifies them through Technology Computer-Aided Design（TCAD）simulations.Firstly,the impact of spacer structures of materials with single-layer dielectric constant（single-κ）and double-layer dielectric constant（double-κ）on the switch performance of NC-Fin FET was analyzed.The results showed that NC-Fin FET exibited better gate control ability and capacitance matching characteristics with double-κspacer compared to single-κspacer,and double-κspacer was more advantageous in improving the inherent delay of the device.In addition,by adjusting the dielectric constant and structure of the spacer,NC-Fin FET was made to have a switching current ratio(I_ON/I_OFF)of up to 10⁸,a sub-threshold swing（SS）as low as 57 m V/decade,and a drain-induced barrier lowering（DIBL）effect of-47 m V/V.Secondly,the effects of three double-κspacer structures（dual/corner/selective）on the performance of NC-NSFET were discussed.The results showed that the NC-NSFET with selective spacer owned better characteristics in increasing the gate control ability of the device,and the I_ON/I_OFFis increased by about 189%,SS is reduced by about 3.0%,and the negative DIBL effect is also reduced by about 48%compared with that of the ordinary dual spacer.The asymmetric spacer with the source-side being selective spacer and the drain-side being corner spacer not only maked the NC-NSFETs had smaller gate-to-gate total capacitance(C_GG)and good capacitance matching performance,but also can effectively increased the gate control capability of the device.The results also showed that in the case of double-layer spacer,the horizontal extension of the high dielectric constant（high-κ）spacer was more beneficial for the device performance improvement,thereby provided conditions for improving the analog/RF characteristics of NC-NSFETs such as transconductance（g_m）and cutoff frequency（f _T）.Finally,the DC characteristics of NC-Fin FET with dielectric spacer,ferroelectric spacer and high-κspacer（Hf O₂）and NC-NSFET with three kinds of double-κspacers（i.e.dual/corner/selective）were discussed.The results showed that the switching characteristics of NC-Fin FET were better when using Hf O₂ spacer than that using ferroelectric spacer;while NC-NSFET had better DC characteristics when using ferroelectric spacer.Under the dual-κspacer structure,the NC-NSFET did not show significant differences in DC characteristics when using dielectric spacer as the high-κspacer,while it did when using ferroelectric spacer as the high-κspacer.This work provides a reference for selecting suitable spacer structures and materials for multi-gate NCFETs to improve device performance and achieve device performance tradeoff.