Preparation And Research Of High-k Metal Oxide Thin Films And Transistors

In 20 th century,the emergence of the flat panel display?FPD?technology has brought human being into the information society.Since then the human society jumped into a new era.The core component of FPD is the thin film transistor?TFT?,with the continuous development of semiconductor technology,substantial research efforts have been directed toward the development of large-area,high-resolution,low-cost displays.To increase the capacitance density,it is a traditional method to decrease the thickness of the dielectric thin film with the goal of increasing the field-effect mobility.However,when the thickness of Si O2 dielectric is reduced to several nanometers,the gate leakage current and static power consumption will increase dramatically due to the quantum tunneling effect.In the future,the high-k materials will take the place of the traditional materials and be used as dielectric thin film.The thickness of the high-k dielectric is much larger than the thickness of SiO2 when they have a same capacitance density and the larger thickness will decrease the quantum tunneling effect.Herein,the history,operating principle,and parameters of TFT were introduced in this dissertation..The experiments were carried out to investigate the high-k dielectric,e.g.magnesium oxide?MgO?,aluminum oxide?Al₂O₃?,and titanium oxide?TiO₂?.MgO dielectric films were fabricated using the spin-coating method and the effect of different annealing temperatures at 300,400,500,and 600 oC were investigated.The obtained films were characterized by thermogravimetric analysis,X-ray diffraction,and atomic-force microscopy.In order to clarify the potential application of MgO thin films as gate dielectrics in TFTs,solution-derived In₂O₃ channel layers were separately fabricated on various MgO dielectric layers.The results demonstrate that the MgO thin films annealed at 500 oC for 2.5h showed a low leakage current of 3.5×10-10 A/cm2 at 4V and a high capacitance density of 370 nF/cm2 at 100 Hz.On the basis of its implementation as the gate dielectric,the indium oxide TFT exhibited a high field mobility of 5.48 cm2/Vs,an on/off current?Ion/Ioff?of 107.Besides,prepared by electrospinning,the stack dielectric thin film combining the advantages of TiO₂ and Al₂O₃ were fabricated and studied.The as-prepared In₂O₃ TFT based on TiO₂/Al₂O₃ stack dielectric was proved to be excellent with an operating voltage of 4 V,on/off current ratio of 108.