Study And Design Of Tunnel Field Effect Transistor Inverters

With the gradual shrinking of integrated circuit feature sizes,the development of MOSFETs has been severely limited,and the contradiction between power consumption and performance of the chip has become increasingly prominent.In order to solve the contradiction between chip power consumption and performance,TFET has attracted the attention of a large number of scholars.Depending on the mechanism of BTBT,the subthreshold swing of TFET can break through 60 m V/dec at room temperature,enabling the device to operate normally at extremely low power supply voltages.At present,there have been many researches on TFET devices at home and abroad,but the researches on TFET inverters are relatively few,which are still in the initial stage.At the same time,the working mechanism of TFET and MOSFET is different,and the inverter design is also different.In TFET inverters,power consumption and frequency characteristics are easily affected by ambipolar effect,miller capacitance and other non-ideal factors,and device design and process parameters have an impact on the characteristics of the device itself,as well as the circuit,often the impact of various factors is complex.Therefore,the Design of TFET inverter is a process of multi-parameter optimization at material level,device level and circuit level.The Design of the inverter based on TFET should adopt the concept of Design Technology co-optimization(DTCO).Based on the above background,this paper first focuses on the design method of the All-Si TFET inverter with traditional structure,and proposes a new type of heterojunction TFET based on the problems existing in the All-Si TFET inverter.Finally,based on the new heterojunction TFET,a new heterojunction CTFET inverter is designed,which improves the power consumption and frequency characteristics of the inverter.the main results are summarized as follows:(1)Three important problems that have arisen during the design of All-Si TFET inverters are studied in this paper,so that the inverter characteristics are improved,such as:The ambipolar effect was solved by reducing the N_D of the TFET,thereby reducing the power consumption of the CTFET inverter;The Gate-Drain Underlap(GDU)structure was introduced into the device,which reduces the gate drain capacitance of the device,thereby reducing the Miller capacitance and improving the problem of excessive overshoot voltage of the CTFET inverter;By studying the effect of source doping concentration on TFETs,the performance of NTFET and PTFET devices can be matched,thus solving the problem of characteristic asymmetry in CTFET inverters.(2)In order to realize high performance inverter,a new Ge/Si heterojunction PTFET was designed from the device level.This device can operate at a lower operating voltage of 0.3v,and the minimum subthreshold swing of less than 3 m V/dec is beneficial to the reduction of energy consumption of the complementary inverters.The device adopts the heterojunction line tunneling structure to effectively improve the on-state current,making the capacitor charge and discharge more quickly,which is beneficial to the inverter's working frequency.After the design of the new device,the working mechanism of the device is deeply analyzed,and in order to match the characteristics of NTFET,the influence of physical parameters and structural parameters on the characteristics of the device is emphatically studied.(3)By using the novel heterojunction PTFET proposed in chapter 4,the main material structure and physical parameters of the novel heterojunction NTFET and PTFET were determined,so that their open-state characteristics and subthreshold characteristics could be matched.At the same time,The simulation software was used to simulate the new heterojunction CTFET inverter,and achieve the design goals of high speed and low power consumption,and compared with the work in other articles.The new heterojunction CTFET inverter designed in this paper can achieve a voltage gain of 35 at a working voltage of 0.2v,and the working frequency is close to GHz.Finally,for the smooth development of related experiments,the process design for the new heterojunction CTFET inverter was preliminary carried out.