The Study To The Effect Of Dielectric Layer And Space Charge On The Performance Of Ferroelectric Field Effect Transistor Based On Hafnium Oxide

In 2011,researchers unexpectedly found that silicon doped hafnium oxide(Hf O₂)thin films have ferroelectricity.Compared with traditional ferroelectric materials,hafnium oxide has the advantages of strong size miniaturization and compatibility with complementary metal oxide semiconductor(CMOS)process,which is expected to become a new generation of nonvolatile memory materials.The results show that ferroelectric thin films based on hafnium oxide are polycrystalline and multiphase,which is a great challenge to fabricate stable ferroelectric field effect transistor(Fe FET)based on hafnium oxide.The dielectric layer in the device can effectively reduce the leakage current,but the ferroelectric thin film structure will cause the polarization charge can not be fully compensated,thus forming a large depolarization field,which is not conducive to the information storage of ferroelectric field effect transistor based on hafnium oxide.In addition,the defects of ferroelectric thin films based on hafnium oxide are easy to cause charge trapping,which leads to the formation of built-in electric field and affects the performance of thin films and transistors.In this paper,the effects of dielectric layer and space charge on the performance of ferroelectric thin films and ferroelectric field effect transistor based on hafnium oxide are studied by phase field method,The specific research contents are as follows:(1)The effects of applied electric field frequency and resistivity on the properties of ferroelectric thin films based on hafnium oxide are studied.It is found that the higher the applied electric field frequency and resistivity are,the larger the coercive field is.(2)Considering the metal/ferroelectric/insulator/metal(MFIM)structure,the effects of thickness,resistivity and frequency of applied electric field on the overall performance of MFIM were studied.The results show that with the increase of the thickness of the ferroelectric layer,the overall dielectric properties change from paraelectric to like antiferroelectric,and then to ferroelectric.The higher the applied electric field frequency is,the larger the resistivity is,and the larger the remanent polarization and coercive field are.In addition,in the metal/ferroelectric/insulator/ferroelectric/metal(MFIFM)structure,the residual polarization and coercive field of the structure are reduced by the intervention of alumina.Considering the multiphase coexistence of ferroelectric films based on hafnium oxide,it is found that the experimental results are more consistent with the non ferroelectric phase penetrating the films.(3)The effect of space charge on the ferroelectric properties of metal/ferroelectric/metal(MFM)structure was studied.It was found that uniform space charge can reduce the remanent polarization and coercive field of ferroelectric thin films based on hafnium oxide,and non-uniform space charge can cause imprinting of ferroelectric thin films based on hafnium oxide.When MFIM structure is considered,uniform space charge not only reduces the remanent polarization and coercivity of ferroelectric thin films based on hafnium oxide,but also causes imprinting.On the contrary,the imprinting phenomenon can be weakened and the remanent polarization and coercive field can be increased by appropriate non-uniform space charge distribution.(4)The phase field model of hafnium oxide based ferroelectric field effect transistor is established,and the effects of the type and thickness of dielectric layer and space charge on the macro performance of hafnium oxide based ferroelectric field effect transistor are studied.The results show that the thicker the dielectric layer is,the smaller the relative permittivity of the dielectric layer is,the higher the space charge density of the ferroelectric layer and the dielectric layer is,and the smaller the storage window is.