Research On Key Technologies Of New Ge-based Tunneling Field Effect Transistor

As an indispensable component in semiconductor integrated circuits,MOSFET has made great contribution to the rapid development of integrated circuits.However,with the feature size of integrated circuit reaching nanometer level,MOSFET starts to have a series of problems,such as short channel effect,increased cost and decreased reliability.The TFET has become one of the most potential alternative devices of MOSFET.The subthreshold swing of TFET can reduce to below 60m V/dec.Meanwhile,the TFET will not cause short channel effect with the decrease of its feature size,so it can adapt to the higher and higher integration requirements.the threshold voltage of TFET is obviously lower,so its on-state voltage is smaller and its dynamic power consumption is lower.The main target of this paper is to obtain more ideal on-state current,off-state current,subthreshold swing and on/off current ratio of TFET device,so as to make the device integrity can get further promotion.This paper discusses the basic working mechanism of PIN type TFET,including the off-state working mechanism and the on-state working mechanism.Through device simulation,the influence factors of geometric and physical parameters on tunneling generation are studied,the results show that increasing source region doping concentration can increase the on-state current;small drain region doping concentration can reduce off-state current;thin gate oxide can reduce subthreshold swing;increasing channel length can reduce off-state current;and reducing device thickness can reduce off-state current.However,it is impossible to change only a single parameter to improve the overall performance of the device.On this basis,this paper compares and analyzes PIN type TFET and PN type TFET.It is proved that PN type TFET can increase the on-state current of the device.Due to the diffusion of the electric field by the oxide layer,the influence of the drain region and the source region with oxide layer on the TFET device is studied respectively.The Doxide-TFET structure is proposed to reduce the off-state current of the device and increase the on/off current ratio.On the basis of Doxide-TFET,the n-type FP-SGTFET structure with field plate structure in drain area is proposed.By introducing a drain field plate into the device,the electric field coupling effect formed by the field plate and the drain area is used to reduce the off-state electric field strength,and the performance of suppressing the off-state current of the device is obtained,and the oxide layer thickness,the length of different field plate,the oxide layer between field plate and gate different distances and the field plate metal with different metal semiconductor workfunction difference are respectively optimized are simulated to find the optimal geometric and physical parameters of the field plate structure.On this basis,the SD FP-SGTFET structure is formed by adding a field plate on the side of gate oxide near the source region,which can increase the electric field strength between the source and drain in the on-state without affecting the off-state current,thus increasing the on-state current;while the PR FP-SGTFET and CP FP-SGTFET structures do not change the on-state current,they further reduce the off-state current.The former reduces the electric field in the tunneling region by adding a protect ring between the gate and drain region,thus reducing the on/off current to 2.86×10^-13A/?m;the latter optimizes the oxide layer on the basis of the former,reducing the off-current to 2.03×10^-13A/?m,SS to 26.1m V/dec,and increasing the on/off current ratio to 1.8×10⁸.