Research And Design Of Key Technologies Of Novel Ge FET

In order to make integrated circuits continue to develop according to Moore's law,new technologies,new structures and new materials have been applied in semiconductor devices.High mobility devices are an exploration of new materials,which use materials with higher carrier mobility as channel of device to improve device performance.Compared with Si materials,the electron and hole mobility of Ge materials are 3 times and4 times higher than that,respectivily.The fabrication processes of Ge devices are compatible with the existing planar Si technology.In addition,compared with MOSFET,the TFET can achieve a steep sub threshold swing and a higher on/off ratio by"band tunneling"mechanism,which is an alternative logic device for ultra-low power integrated circuits.Moreover,the band gap of Ge material is much smaller than that of Si,which is beneficial for TFET devices to increase on state current.Thus,Ge is an ideal alternative material for TFET devices.In this paper,the novel device structures are proposed based on the difficulties and challenges of Ge MOSFET and TFET.Furthermore,the theoretical and experimental research of novel Ge MOSFET and TFET are studied.The main contributions of this thesis include:1.To suppress the DIBL effect of fully depleted Ge MOSFET,the structure of fully-depleted Ge NMOSFET with P-substrate is proposed in this paper.The results indicate that with the doping concentration of P-substrate increasing,the DIBL effect is lower and the leakage current decreases significantly.Therefore,the FDP-NMOS has excellent subthreshold characteristics,the subthreshold swing is 76.8 mV/dec and the on/off ratio is 1.65×10⁸,respectively;To suppress the GDIL effect of fully depleted Ge MOSFET,a novel structure of the Ge NMOSFET with field plate is proposed in this paper.The results indicate that the GIDL of the fully-depleted Ge NMOSFET is suppressed effectively by field plate.An on/off ratio I_on/I_off=2.57×10⁷,and a sub-threshold swing of76.8mV/dec are achieved.2.In this paper,Ge based MOSFET devices with field plate electrodes are fabricated,and the relevant simulation analysis and results are verified.Specifically,the process of the Ge MOSFET device is designed.The key parameters of ion implantation and high temperature annealing process are optimized.According to the results,the field plate structure can suppress the GIDL effect effectively,results in reducing the off state current by 60%and increasing on/off ratio.With the optimized parameter,the on/off ratio I_on/I_off=1.7×10⁴ is achieved.3.To increase the on state current of Ge TFET,a fully-depleted Ge double-gate nTFET structure is studied.the FD Ge DG-TFET increases about 1 order of magnitude comparing with the Conventional Ge DG-TFET.With optimized parameter,I_off is reduced about 2 orders of magnitude to 2.5×10^-13 A·?m^-1 and on-off ratio is increased to 1.58×10⁷;To suppress the GDIL effect of fully-depleted Ge NTFET,a novel fully-depleted Ge_1-xSn_x n-Tunneling FET(FD Ge_1-xSn_x NTFET)with field plate is investigated.By employing the field plate structure,the GIDL effect of FD-FP Ge_1-xSn_x NTFET is suppressed.With the optimized parameter,the on-state current I_on=4.6×10^-5 A/?m,the off-state current I_off=1.6×10^-13A·?m^-1 and the maximum on/off ration I_on/I_off=2.9×10⁸ are achieved.This thesis sufficiently proves the feasibility and effectiveness of Ge MOSFET and TFET,the research results in this paper provide a useful theoretical basis and reference for the research and application of the following high mobility devices.In this paper,the novel Ge MOSFET and TFET have been studied.The related results can provide a useful theoretical basis and reference for the research and application of the high mobility devices,which is of great significance for promoting the development of China's semiconductor industry.