Preparation Of Multi-ratio IGZO Films And Characterization Of Their Properties

Indium gallium zinc oxide(IGZO)thin film has many advantages,such as high transmittance,wide optical band gap,high electron mobility,etc.It is a transparent conductive oxide(TCO)thin film material with broad application prospects in flat panel displays(FPD).By modulating structure and composition of the film,the comprehensive performance of film can be improved to obtain properties that conventional films do not have and to meet some special applications.Some previous studies on IGZO thin films and TFT devices have been conducted by other scholars,but mainly on thin films prepared by specific IGZO sputtering targets or chemical vapor deposition methods.In this study,home-made IGZO targets with different compositions were used.Different series of thin films were prepared using magnetron sputtering technique.The material properties such as physical structure,surface morphology,chemical components and electrical and optical properties of the thin film samples were characterized separately,and the effects of target composition on the structure and properties of the films were investigated to provide guidance for the improvement of the target and film properties.On the other hand,different series of films were annealed to investigate the effect of annealing treatment process on the structure and optoelectronic properties of amorphous IGZO materials with different compositions to provide a reference for optimizing the film structure.The research of this topic has very important scientific and guiding significance for the composition regulation of IGZO thin films,and also for the research of other types of transparent conductive oxide thin films.It is believed that as the process research progresses,more potential of IGZO will be further developed and the performance will be further improved.The main research results are as follows:(1)To investigate the effect of magnetron sputtering process on the properties of IGZO thin films.IGZO films were prepared using different target-substrate distances based on certain previous studies.The experimental results show that the IGZO film have good uniformity and high deposition rate when the target-substrate distances is70 mm,and the film have uniform and dense organization with small grains,while the film obtains the best electrical properties.As the target-substrate distances increases,the transmittance of the film gradually increases and the optical band gap gradually increases.The IGZO films prepared at different target-substrate distances are amorphous phase,and the atomic ratios of In,Ga,and Zn in the films are close to those in the IGZO targets.(2)Based on the aforementioned process parameters,IGZO films with different compositions and structures were deposited by RF magnetron sputtering using different targets to investigate the effects of target composition differences on the structure and properties of the films.It is found that with the increase of Zn element content in the target,the film transformed from amorphous phase to nanocrystalline phase,the film thickness gradually increases,the deposition rate of the target gradually increases,and the average particle size and surface roughness of the film gradually increases.The atomic ratios of In,Ga,and Zn in the IGZO films deposited with different elemental ratios of targets are close to those in the IGZO targets.(3)The effect of target element ratio on the optoelectronic properties of the film is studied,and the results show that the average transmittance of the film gradually decreases and the optical band gap gradually decreases with the increase of Zn element content in the target.The resistivity of the film increases rapidly,the carrier concentration decreases gradually,and the mobility increases first and then decreases,which indicates that the increase of Zn element increases the film resistivity.And the XPS split-peak fitting results show that the oxygen vacancy variation is consistent with the carrier concentration results of Hall effect.(4)To investigate the effect of annealing process on the properties of IGZO films deposited on targets with different elemental ratios.It was found that the films transformed from amorphous to crystalline phase at 600～800°C.After annealing treatment,the short-range ordering of film atoms increases,the film crystallinity improves and the grain size increases.The average surface roughness of IGZO-111,IGZO-112,and IGZO-114 films are significantly reduced after annealing at 200°C,which indicates that a suitable annealing treatment is beneficial to improve the surface quality of the films.(5)The effect of annealing process on the optoelectronic properties of IGZO films deposited on targets with different element ratios was investigated.The results show that the transmittance of the films are the first to increase and then decrease with the increase of annealing temperature,and the average transmittance of films annealed below 800°C are greater than 87%.Hall effect results indicate that low temperature annealing(200～600°C)under vacuum conditions can cause significant changes in the electrical properties of the film.With the increase of annealing temperature,the mobility of the film increases first and then decreases,the carrier concentration gradually increases and the resistivity gradually decreases.The ordered crystal structure of the film under high temperature annealing(800°C)reduces the scattering of electrons within the film,so the mobility increases,the carrier concentration increases,and the film resistivity decreases.