Tunneling Field Effect Transistor And Ingaas Field Effect Transistor Reliability Research

With the CMOS device scaling down, power dissipation and reliability become important issues which restrict the development of integrated circuits. In order to reduce power dissipation, TFETs and InGaAs MOSFETs have attracted much attention recently. Comparing with Si MOSFET, TFETs can break the physical limit of room temperature subthreshold swing of60mV/decade. The electron mobility of InGaAs is about one order of mangnitude larger than that of Si. Although TFET and InGaAs MOSFETs have obtained comprehensive investigations, there are only a few studies reporting their reliability issues.In this thesis, we have investigated the reliability performance of nTFETs and InGaAs nMOSFETs under PBTI stress or HCI stress.(1) This thesis discussed the degradation mechanisms of nTFETs under PBTI and HCI stresses by comparing with the degradation of conventional Si nMOSFETs.(2) This thesis proposed a trap model to interpret the PBTI degradation of InGaAs nMOSFETs, and discussed the origin of the off-current degradation.The main conclusions of the thesis are:(1) The degradation of nTFETs under PBTI stress or HCI stress is severe than that of conventional nMOSFETs. The stress induced interface traps and oxide charge reduce the tunneling electric field and the drain current.(2) If the gate overlaps with p+doping source in nTFET, there is a vertical electric-field peak close to the tunneling region which induces more interface traps and oxide charge and exacerbates the drain current degradation.(3) The degradation of the TFETs under HCI stress appears mainly close to the source.(4) For the InGaAs nMOSFETs under PBTI stress, at constant Is of Is Vg curves, there is negative△Vg in the sub-threshold regionand positive△Vg in the strong inversion region. The negative△Vg can recovery in the recovery phase and turns to positive at the end of recovery phase. However, the positive△Vg continuously degrades (increases) in the recovery phase until reaching a stable value.(5) The PBTI stress induces slow border traps near the△l2O3/InGaAs interface in InGaAs nMOSFETs which include recoverable donor traps and permanent acceptor traps. The recoverable donor traps have a large distribution of energy density in the InGaAs energy gap with a tail extending to the conduction band. The permanent acceptor traps distribute mainly in the conduction band of InGaAs with an energy density tail extending to the mid-gap.(6) The off-current degradation of In0.65Ga0.35As nMOSFET is severer than that of In0.53Ga0.47As nMOSFET.These studies are instructive for the technology development of TFETs and InGaAs nMOSFETs.