The Design,Fabrication And Performance Study Of Hafnium Oxide-Based Thin Film And Its Transistors

With the rapid development of the semiconductor industry and the demand for highly integrated modern chips,the process of device miniaturization is constantly accelerating.Hf O₂ based High-k materials have attracted widespread attention due to their large dielectric constant,bandgap width,simple preparation,and perfect integration with silicon based processes.Especially as the gate dielectric layer of transistors,Hf O₂ based materials have unparalleled advantages compared to other materials.Therefore,this article prepared HfAlO thin films doped with Al,as well as MIM structured capacitors used as dielectric materials,to regulate and study the structure,composition,and electrical properties of HfAlO thin films.In addition,this article selected the HfAlO thin film with the best performance as the gate dielectric layer material of the thin film transistor,and Zn O as the active layer material of the thin film transistor to study the effect of oxygen partial voltage prepared by different Zn O on the transistor performance.The main research work of this article is as follows:（1）The（-111）oriented single crystal HfAlO thin films were prepared on Si wafers by Magnetron sputtering.This article explored the effect of temperature on the microstructure of HfAlO thin films based on different preparation processes.Research has shown that the HfAlO thin film has the largest grain size at a preparation temperature of 550℃.In addition,based on the testing of sputtering duration and film thickness,the sputtering rate of HfAlO thin films was investigated.The results indicate that under certain process conditions,the film thickness with a 2-hour sputtering time was 700 nm.（2）After attempting to obtain HfAlO thin films with different concentrations using a"Target+Aluminum foil"stacking sputtering method,a dual target co sputtering method was used to prepare HfAlO thin films with 25%and 50%Al doping concentrations by adjusting the sputtering power of Al targets.（3）By adjusting the preparation temperature and doping concentration,the structure and composition of HfAlO thin films are changed to study their leakage current characteristics.The research results indicated that the minimum leakage current density was 7.90×10^-8 A/cm² at a film preparation temperature of 550℃and a field strength of 10 MV/cm.When the concentration of Al doping was increased to 50%,the leakage current density reduced to 5.58×10^-9 A/cm² at a field strength of 10 MV/cm.Further analysis of the leakage current mechanism shows that the leakage current of HfAlO thin films prepared at low field strengths of 250℃,400℃,550℃and 700℃is related to the Schottky emission mechanism.In high field strength environments,HfAlO thin films prepared at 250℃were broken down,and the leakage current mechanism at 400℃and 550℃was F-N emission mechanism,while the leakage current mechanism at 700℃was Ohmic conduction mechanism.On the other hand,when the concentration of Al doping was 25%and the field strength was low,the leakage current mechanism was Schottky emission,and the high field strength was F-N emission mechanism.When the concentration of Al doping was 50%,the leakage current mechanism was space charge limiting current.（4）Study the effects of preparation temperature and doping concentration on the dielectric properties of HfAlO thin films.The results shown that the HfAlO film has a high dielectric constant,and the film shows a negative capacitance effect due to the ferroelectricity produced by doping.As the preparation temperature increases,the dielectric constant of HfAlO thin films first increases and then decreases,reaching a maximum absolute value of 32.8 at 400℃.As the concentration of Al doping increased from 25%to 50%,the absolute value of the dielectric constant of HfAlO thin film decreased to 29.5.In addition,HfAlO films had good anti-aging properties.（5）Prepare ZnO thin films with different oxygen partial pressures as active layers for transistors,and study the effect of carrier concentration in the active layer on transistors.Research has shown that when the oxygen partial pressure of Zn O thin film was 20%,the carrier concentration in the active layer decreases,the transistor saturation mobility was 13.11 cm²/VS,the switching ratio reaches the order of 10⁶,the threshold voltage was 0.5 V,and the subthreshold swing was 141.08m V/dec.When the oxygen partial pressure of Zn O thin film was 5%,the active layer carrier concentration increases,the transistor saturation mobility was 21.76 cm²/VS,the threshold voltage was 0.1 V,the switching ratio was reduced to 340,and the sub threshold swing was as high as623.92 m V/dec.