Research On The Effect Of Fin Variation On The Performance Of Negative Capacitance FinFET

Fin Field-Effect Transistor（FinFET）has become the mainstream device for sub-22-nm CMOS devices.The Negative Capacitance Field-Effect Transistor（NCFET）breaks through the Boltzmann limit by amplifying the internal gate voltage,which greatly reduces the power consumption.Therefore,by adding materials with negative capacitance effects to its gate-oxide layer of FinFET,negative capacitance FinFET（NC-FinFET）devices is expected to further improve device performance and reduce power consumption.However,the performance of FinFET depends largely on the geometry of fin,and the structural variation of fin caused by process limitations has an increasingly complexity on the performance of NC-FinFET.This thesis discusses the influence of different types of fin variation of NC-FinFET on its DC and analog/RF performance,and simulation study by Sentaurus technology computer-aided design（TCAD）.Firstly,the DC characteristics of NC-FinFET with different top fin width(W_Fin,Top)were compared and discussed.The results show that with the decrease of the width of top fin,the off-state current(I_OFF)of NC-FinFET can be effectively reduced,and its threshold voltage is increased with the suppressed short channel effect（SCE）,but the on-state current(I_ON)of NC-FinFET is also reduced.By increasing ferroelectric layer thickness(T_FE)of NC-FinFET,the negative effect caused by decreased top fin width can be effectively increased,and the DC characteristics of NC-FinFET can be further improved.Secondly,the parameter characterizations of analog/RF performance were extracted by AC small-signal analysis on NC-FinFET devices with different top fin widths.The results show that the change of top fin width affects ferroelectric polarization intensity of NC-FinFET,so that the change of the width of top fin does not have a linear relationship with the ferroelectric polarization.The variation of top fin width changes charge distribution of the channel,which affects the transconductance（g_m）and total gate capacitance(C_gg),and also makes voltage gain（A_V）and cutoff frequency（f _T）decrease at high frequency.With proper increase of T_FE,the analog/RF performance of NC-FinFET is improved and the adverse effects of reduced top fin width are alleviated.Finally,the variation types of other fin edge structures caused by manufacturing process limitation are summarized and analyzed by TCAD simulation.The results show that these types of fin edge variations have different influencing trends in DC and analog/RF performance of NC-FinFETs.The narrow-fin variation increases I_ON,gm and C_gg,and decreases I_OFFof NC-FinFET.The wide-fin variation increases I_OFF,while the channel surface roughness caused by the side-fin variation weakens control ability of gate to the channel.This work provides experimental data and theoretical analysis for the performance fluctuations of NC-FinFET caused by fin structure variations due to fabrication process limitation,and also provides a prediction for the fabrication performance of device with fin structure variation at early stage.