Solution-processed GaBo High-K Dielectric Films And Their Applications In Thin-Film Transistors

With the continuous progress of science and technology,electronic equipments are rapidly developing in the direction of intelligence,miniaturization and convenience.As device feature sizes continue to decrease,traditional Si O₂ dielectric layers gradually approach their tunneling thickness.In order to maintain the capacitance value of the dielectric layer,only using a high-K dielectric material instead of Si O₂ can avoid the huge leakage current caused by the reduction in thickness of the dielectric layer.The solution method is regarded as the next generation of promising production technology due to its advantages such as low cost,large area and high production capacity.The development of high-K gate dielectric materials by solution method is of great significance to promote the development of low-cost,large-area,low-power electronic devices in the future.In this paper,we prepared a Ga₂O₃-based high-K dielectric layer using a solution spin-coatingprocess and performed various characterization methods.The effects of annealing temperature on Ga Ox gate dielectric films and corresponding In₂O₃/Ga Ox TFT devices were systematically studied.After the process conditions were optimized,we performed a doping technigue to further improve Ga Ox gate dielectric films.After the process conditions were optimized,we performed a doping technique to improve the dielectric properties of Ga Ox film.The effects of bron doping on Ga₂O₃ gate dielectric films and corresponding In₂O₃/Ga BO TFT devices were systematically studied.The main contents are as follows:(1)A polymer-assisted method was used to realize one-step spin-on deposition of Ga Oxdielectric films to reduce defects caused by multiple spin-coating processe.We annealed Ga Ox over a wide temperature range of 200-800?to study the effects of annealing temperature on Ga Ox gate dielectric film and corresponding In₂O₃/Ga Ox TFT devices.The results indicate that with increasing annealing temperature,the solution-deposited Ga₂O₃ experiences the elimination of organic residuals as well as the transformation of amorphous Ga₂O₃ to crystalline Ga₂O₃.The 500?annealing temperature has the best film quality and dielectric properties.The surface is smooth and flat,the roughness is low,and the metal oxide frame is relatively complete.At the same time,it has best dielectric properties,including a capacitance value of178 n F cm^-2,dielectric constant of 10.8,and leakage current density of 5.6×10^-6 A cm^-2(@1.5MV cm^-1).Moreover,the corresponding In₂O₃/Ga Ox TFT device has the best performance,including a low operating voltage of 5 V,a mobility of 3.09 cm²V^-1s^-1,on/off current ratio of1.8×10⁵,and subthreshold swing of 0.18 V dec^-1,respectively.However,dielectric properties of the prepared Ga Ox films still have a large gap compared with Ga₂O₃ films prepared by atomic layer deposition,and corresponding TFT devices have lower performance and cannot meet the requirements of liquid crystal flat panel display.This is mainly because the polymer-assisted Ga Ox film annealed at 500?still contains a small amount of polymer residue.(2)On the basis of 500?annealing conditions,one step spin coating was achieved by increasing the precursor concentration instead of polymer-assist in this chapter.We prepared Ga₂O₃(Ga BO)dielectric films with different doped B contents of 0-20 at%to study the effects of B doping on Ga₂O₃ gate dielectric films and corresponding In₂O₃/Ga₂O₃(Ga BO)TFT devices.The results indicated that doping B can effectively suppress the generation of oxygen vacancies in the film,and promote the formation of a dense film,so that the prepared Ga BO films have a higher film quality.Among them,the Ga BO thin film with 10 at%doped B contents has the best dielectric properties,including a capacitance value of 140.7 n F cm^-2,dielectric constant of 11.71,and leakage current density of 8.1×10^-7 A cm^-2(@2.0 MV cm^-1)that comparable to that of the vacuum fabrication method.We then optimized the annealing temperature of the In₂O₃ active layer,the corresponding In₂O₃/Ga BO(10 at%B contents)TFT device has the best performance,including a low operating voltage of 5 V,a mobility of 17.01cm²V^-1s^-1,on/off current ratio of 1.3×10⁶,subthreshold swing of 0.16 V dec^-1,and excellent bias stability.Our prepared TFTs is qualified for the performance requirements of TFT devices for low-power liquid crystal flat panel displays.