Simulation On Electrical Characteristics Of GaAs-OI MOSFET And Study On Interface Characteristics Of Stack High-k Gate Dielectric GaAs MOS

With the development of CMOS integrated circuit technology to 5nm technology node,the characteristic size and device structure of traditional Si based MOSFET have reached their theoretical and physical limits,which limits the development of CMOS IC towards high performance and high integration.In order to meet the requirement of reducing the characteristic size of MOSFET in equal proportion,and to overcome a series of obstacles that affect device performance caused by small size effect,it is necessary to break the bottleneck of traditional technology from three aspects:substrate materials,gate dielectric materials and device structure.Because of its high electron mobility,large band gap width,excellent radiation resistance and photoelectric conversion ability,the MOSFET with Ga As semiconductor as channel has a larger operating temperature range,higher speed characteristics and lower static power consumption.However,Ga As resources are scarce and mechanical strength is weak,it is also easy to produce small size effect with the further reduction of MOSFET size,which will reduce the performance of Ga As MOSFET.In order to overcome the defects of Ga As materials and retain the advantages of Ga As materials,Ga As-OI MOSFET can solve this problem well.Ga As-OI substrate combines the advantages of Ga As materials and the structural advantages of SOI(silicon on insulator)(fast working speed,low power consumption and high temperature resistance).But at the same time,the surface of Ga As is easy to form defects,which leads to poor interface characteristics.Therefore,it is necessary to passivate the Ga As surface to improve the interface characteristics.In addition,in order to further reduce the subthreshold slope of the device and reduce the power consumption of the device,ferroelectric materials with negative capacitance effect can be used as gate dielectric materials of Ga As-OI MOSFETs,so as to further improve the device performance and comply with the future development trend of CMOS.In this paper,the electrical characteristics of Ga As-OI MOSFET based on Ga As/Al₂O₃/Si O₂/Si substrate and the interface characteristics of high-k gate dielectric Ga As MOS devices are studied from two aspects of simulation and experiments.The theoretical simulation work includes:(1)The Ga As-OI MOSFET with Ga As/Al₂O₃/Si O₂/Si substrate is built by using SILVACO TCAD simulation software.The influence of quantum confinement effect and Al₂O₃ transition layer on the electrical characteristics of the device is investigated.The results show that the addition of quantum confinement effect model and the use of Al₂O₃ transition layer can reduce the subthreshold slope to 91,and the switching ratio to 10¹⁰;(2)Based on the structure of the former,,the influence of structure and physical parameters such as doping concentration,channel thickness,gate dielectric constant on the switching characteristics,threshold voltage and short channel effect of the device is explored.The results show that the threshold voltage,on state current,off state current and short channel effect increase with the increase of channel thickness,while the switching state current decreases and the threshold voltage increases with the increase of channel length;(3)Based on the conclusion and the device structure of(2),a negative capacitance field effect transistor with MFIS(metal/ferroelectric layer/insulating layer/semiconductor)structure is formed by adding a layer of ferroelectric material to the high-k material.The influence of the thickness of ferroelectric layer,insulating layer and Ga As channel on the subthreshold slope of the device is investigated.The results show that the subthreshold slope can be reduced to52.6m V/dec,and the subthreshold slope decreases with the increase of ferroelectric layer thickness,and increases with the increase of insulating layer and channel layer thickness.The experimental work includes:(1)Using Hf Al O as gate dielectric material,the influence of Al N passivation layer on the interface characteristics and electrical characteristics of Ga As MOS devices is investigated.The results show that Al N has a good passivation effect,the interface density of states is reduced to 7.2×10¹² cm^-2e V^-1 and the accumulated capacitance is increased to 130.9p F;(2)Based on the conclusion of(1),the influence of N element on the interface and electrical characteristics of Ga As MOS devices is investigated.The results show that Hf Al ON/Al N MOS devices have steeper depletion slope and larger accumulated capacitance,the interface density of states is reduced to 1.1×10¹² cm^-2e V^-1 and the accumulated capacitance is increased to 170.4p F.Moreover,when the ratio of HF/Al in Hf Al ON is 1:1,the accumulated capacitance is the largest,and the hysteresis of C-V curve is the smallest,which further reduces the density of interface states and increases the k value of dielectric layer.