Deposition And Interfacial Modulation Of Hf-based Gate Dielectric Film By PEALD

Metal-oxide-semiconductor field-effect transistor?MOSFET?is the basic unit of complementary metal oxide semiconductor?CMOS?integrated circuit?IC?,and its geometric dimension is continually scaling down with the rapid development of CMOS IC.With its scaling down,there are some serious challenges about the transistor's properties,such as gate dielectric's performance,channel mobility,short channel controllability and reliability.Especially,when the technology node comes to 16 nm and beyond,transistor needs higher permittivity gate dielectric film,high mobility channel materials and new transistor structure.Therefore,this thesis focused on Hf-based oxide gate dielectric material to explore the influence of plasma enhanced atomic layer deposition?PEALD?process and doping elements on the properties of the Hf-based films,and to investigate the feasibility of Hf-based gate dielectric in ETSOI MOSFET devices.The main works and results are as follows:?1?The influence of PEALD process on the properties of HfO₂ films was studied.Compared with N₂ carrier gas,Ar carrier gas is more appropriate for the preparation of HfO₂ films with O₂ plasma precursor.The main reason is that N₂ carrier gas would involve into the deposition reaction of HfO₂ films under the plasma condition.And the forming of Hf-N-O and Hf-N bonds in HfO₂ film increases the oxide trapped charge density and deteriorates electrical performance of HfO₂ films.Additionally,the influence of oxygen precursors?O₂ plasma,H2O and O3?on the properties of HfO₂ films with Ar carrier gas was investigated.At the same physical thickness,the saturation density of capacitance for the HfO₂ films with different oxygen precursors is equivalent.And the HfO₂ film with utilizing O3 as oxygen precursor has the lowest of the oxide trapped charge density.?2?The effects of Ti,Zr and Gd doping on the chemical composition and electrical properties of Hf-based films were investigated.The results show that Ti,Zr,Gd doping can significantly increase the permittivity of HfO₂ films,which can reach 39,20.4 and 22.4,respectively.Among them,the effect of Ti doping on the permittivity is the most significant.Although the Zr doping decreases the conduction band offset of Hf-based film with Si substrates,the ZrO₂-HfO₂?ZHO?amorphous films with 10 at%Zr content have good electrical properties.Gd doping can effectively suppress the formation of the Gd2O3-HfO₂?GHO?/Si interfacial layer,which leads to a significant decrease of the oxide trapped charge density and leakage current density.?3?The HfO₂/SiO₂ interface and HfO₂/SiGe interface were treated by PEALD plasma,and the effect of plasma on the interfacial passivation was studied.After N₂ plasma processing HfO₂/SiO₂ interface,N atoms occupy the oxygen vacancy and O atom gap of SiO₂ intcrfacial layer to reduce the oxygen vacancy and to passivate O atom.At the same time,forming Si-N bond on the SiO₂ surface effectively suppress atom diffusion between HfO₂ and SiO₂ to reduce the O atom loss of HfO₂ film,thus improving Hf-based film performances,such as 3.2×1012 cm^-2 down to 2.5×1012 cm^-2 for oxide trapped charge density decreased,from 1.1×10-3 A/cm² down to 3.2×10-6 A/cm² for leakage current density,1.36?F/cm² up to 1.49 ?F/cm² for saturation capacitance density,and good electrical stability.After applying N₂/H2 plasma treatment on the surface of SiGe before the deposition of HfO₂ film,N atom remain on SiGe surface by Ge-N and Si-N bonds,reducing the generation of SiGe interface oxide and oxide trapped charge density of HfO₂/SiGe stack structure,to improve the electrical properties,such as 2.4×10-4 A/cm² down to 4.6×10-6 A/cm² for leakage current density,1.53 ?F/cm² up to 1.73 ?F/cm² for saturation capacitance density,1.82 nm down to 1.64 nm for the value of EOT.Additionally,frequency dispersion of C-V curves from 0.3 MHz to 1 MHz decreases from 9.7%to 8.7%,implying the reduction of the interface state density of HfO₂/SiGe stack.?4?GHO thin films were deposited on SiGe/Si substrate by PEALD.The effects of GHO film with N₂ cyclic plasma annealing on the chemical composition and electrical properties of GHO/SiGe stack were investigated.The results show that Gd doping can suppress the generation of oxygen vacancies of Hf-based film and reduce the formation of GHO/SiGe interfacial oxide.And Gd doping makes the film composition more consistent with the stoichiometry,improves saturation capacitance density and decreases leakage current density of Hf-based film.Additionally,the results show that after N₂ cyclic plasma annealing,N atoms occupy the oxygen vacancy position of the GHO film to reduce the oxide trapped charge density,while N atoms passivate interface by Ge-N and Si-N bonds to reduce the interface oxide and interface state density,result in the film leakage current density decrease from 1.9×10-5 A/cm² to 2×10-8 A/cm².?5?TiO₂-HfO₂?THO?high k gate dielectric was applied to the device prepared by 16/14 nm ETSOI CMOS process,to explore the feasibility of THO films in small size?Lg=25nm?and new structure devices.Compared with HfO₂ ETSOI MOSFET,THO ETSOI MOSFET has better properties,such as switching performance,short channel controllability and channel mobility.The main characteristics of THO ETSOI pMOSFETs are as follows:on state current density of 4.63 ×10-4 A/?m,off state current density of 1.5 ×10-8 A/?m,switch ratio of 3.1×104,transconductance of 2.67 mA/V,DIBL of 53 mV/V,SS of 65 mV/dec,the hole mobility of 28 cm²V-1s-1.Therefore,replacing HfO₂ by THO used as gate dielectric film can improve the overall performance of the device to meet the needs further scaling down of the device.