The ferroelectric field effect transistor?FeFET?is one of the most promising nonvolatile random access memories with the advantages of nonvolatileness,non-destructive readout and high-density integration.Hafnium oxide?HfO2?based ferroelectric film material is a new ferroelectric film material,which is compatible with advanced CMOS technology.Moreover,it exhibits good ferroelectric properties even with the film thickness scaled down to 3 nm.These advantages make the HfO2based ferroelectric film suitable for application to FeFET.Doping can enhance the ferroelectric performance of the HfO2 based ferroelectric film significantly.Chemical solution deposition?CSD?is a method with which is easy to dope,and its advantage is simple,economic and effective.In this thesis,the doped HfO2 ferroelectric film was choosen as the research object,and two elements of praseodymium?Pr?and cerium?Ce?were selected as dopants,and the films were prepared by CSD method.The main work is as follows:?1?Hafnium oxide films with different Pr doping contents?Pr:HfO2?were fabricated on?111?Pt/Ti/SiO2/?100?Si substrate.The ferroelectric orthorhombic phase in the film was confirmed by microstructural characterization,which indicated that the metastable ferroelectric orthorhombic phase could be induced by Pr doping in the HfO2 films.The P-E?polarization-electrical field?hysteresis loop measurement results demonstrated that the film with 5 mol%Pr exhibited a distinct ferroelectricity,with a maximum remanent polarization?Pr?of 6.9?C/cm2 and a coercive field?Ec?of1.2 MV/cm.The C-V?capacitance-voltage?measurements demonstrated that the curve of the 5 mol%Pr doped film exhibited an obvious butterfly shape,furtherly indicating the ferroelectricity in this sample.During endurance performance of the5 mol%Pr doped HfO2 ferroelectric film,the polarization degraded about 30%after1×108 switching cycles.The leakage current measurements demonstrated that the pure HfO2 film has the minimum leakage current.?2?Hafnium oxide films with different Ce doping contents?Ce:HfO2?were fabricated on n-type heavily doped Si.The surface morphology feature,crystal structural and electric properties of the films were characterized.The surfaces of these films were relatively flat,and their surface roughness root mean squares(RRMS)were all less than 1 nm,indicating the little fluctuations.Moreover,the ferroelectric orthorhombic phase in the film was confirmed by combining methods.The P-E hysteresis loop demonstrated that the ferroelectricity starts to emerge in the film with10 mol%Ce content.Furthermore,the film with 15 mol%Ce exhibited the best ferroelectricity,with a maximum Pr of 16?C/cm2 and a 2Ec of 2 MV/cm.The piezoelectricity results demonstrated that the amplitude-voltage curves of the films with 10 mol%and 15 mol%Ce were both with the butterfly shape.The phase-voltage curves demonstrated that the phase for the former could switch for 160owhile that for the later could switch for 180o. |