The Investigation Of Fabrication And Electrical Properties Of HfO₂-based Ferroelectric-gated ITO Transistors For Three-dimensional Integration

HfO₂-based ferroelectric field effect transistor（FeFET）is a new type of non-volatile semiconductor memory,which owns the characteristics of fast read,write speed,high storage density,fatigue resistance and low power consumption,etc.It has great compatibility with CMOS technology and great potential to become the next-generation of storage-class memory（Storage-Class Memory）to solve the bottleneck problem of the existing"storage gap"and other storage structures problems.However,the ferroelectricity mechanism of Hf O₂-based thin films are complex,and specific materials are required as electrodes to obtain strong polarization properties;in addition,the interface layer is easily generated under the existing 3D integration of FeFETs,resulting in electrical signal loss and ferroelectricity failure.And 3D integration technological requirements are complex and the cost is high,which improves the research threshold.In this thesis,an etching process and atomic layer deposition（ALD）were used to fabricate zirconium-doped hafnium oxide（HZO）thin films with indium tin oxide（ITO）as the top electrode and a large ferroelectric polarization.Based on this,the 3D Fe FET unit is expanded on a plane to obtain a planar Fe FET with equivalent electrical properties under the corresponding size.Furthermore,Fe FET with ITO channel HZO gate was fabricated and programmed to realize the function of storing information.The theoretical basis and experimental basis are provided for the study of high-mobility channel Fe FET with 3D structure on the plane.The main research contents and results are as follows:（1）Based on the transistor gate capacitance structure,TiN/HZO/TiN and ITO/HZO/Ti N structure samples were prepared.The ferroelectric remanent polarizations of Ti N and ITO electrode samples are 16μC/cm² and 4μC/cm²,respectively.The stress and interface composition of the surface top and bottom electrodes will greatly affect the ferroelectricity of HZO thin films.In addition,the migration of oxygen element changes the concentration difference of oxygen vacancies above and below the HZO film and increases the built-in electric field,thereby reducing the reliability indicators such as fatigue,retention,and imprinting of the ITO electrodes HZO thin film.The remanent polarizations of the Ti N/HZO/TiN and ITO/HZO/TiN structural samples after the etching process reached 14μC/cm² and 12μC/cm²,respectively,and correspondingly improved in reliability tests.It indicates that this etching process will not significantly affect the ferroelectricity of the HZO thin film,and can greatly improve the ferroelectricity of the ITO electrode HZO thin film.（2）Based on the transistor structure,it is discussed that the 3D FeFET unit has equivalent electrical properties to the planar Fe FET of corresponding size,and the Fe FET with ITO channel and HZO ferroelectric gate is fabricated.The transistor has good gating capability,with the subthreshold swing of about 271 m V/dec,carrier mobility of 8.2 cm²/V·s.It is programmed with pulses of±4 V/100 us and has a memory window of about 0.5 V,which realizes storing and reading information by ferroelectric polarization.The application of the etching process to Fe FET has a significant impact on the quality of the channel,which enhances the effect of charge injection,and makes the transistor controlled by both ferroelectric polarization and charge injection,making it difficult for pulse programming.