Translated Abstract
Today, the displayer developed in the direction of the larger area, higher-definition, the competitiveness of TFT-LCD and AMOLED seems prominently noticeable, it is hard to satisify the requirements for thin film transistors of futhure displayer just depending on the a-Si TFT and p-Si TFT which are widely used presently. What’s more, transparent and flexible display technologys have appeared on the market recently. IGZO thin film transistors attarted widely attention for its various of advantages such as transparent, high carrier mobility and low preparation temperature and so on. IGZO now is known as the most promising materials as the channel layer of thin film transistors in the application of diaplayers.The channel layer is the very important for the thin film transistors, and the property and performance of the IGZO thin films are of great concern for the final performance of the transistors. In this paper, we prepared the IGZO thin films on the substrate of microcrystal glass and single crystal silicon by refrequency sputerrings using the ceramic target of IGZO which was fabricated by the power of In2O3, Ga2O3 and ZnO as a ratio of 1:1:2. We changed the preparation conditions of the IGZO thin films and took the post-annealling treament trying to improve the performance of the IGZO thin films, and getting better thin films whose material character and electrical properties are greatly improved.In this paper, we do the reasearch about the influnce of the deposition condition. For the first, we studied the influnce of oxygen ratio on the optical and electrical properties of the a-IGZO thin films. The results showed that the microstructure of the films kept amorphouse which was almost irrelevant to the sputterring ambient, and the transmittance of the a-IGZO thin films were all above 80%. However, the a-IGZO thin films turned semi-conductive to semi-insulative. Besides, we studied the effect of the substrate temperature on the performance of the IGZO thin films, the results betrayed that the IGZO thin films kept being amorphous within the scope of our experiment, however, the electrical properties greatly improved. The a-IGZO thin films deposited in pure Ar abiment with the substrate temperature of 400℃ have a carrier concentration of 4.06*1019cm-3 and the carrier mobility is 10.42 cm-2/Vs which lead to a decreased sheet resistance of 2.95*103Ω/□.Then, we studied the influnce of annealing temperature on the properties of a-IGZO thin films, the results indicated that after the annealing treament the performance of the a-IGZO thin films improved greatly regardless of the deposition ambient. In addition, the a-IGZO thin films kept being amorphous even the annealing temperature reached to 500℃. We took the example of the a-IGZO thin films deposited in pure Ar ambient to deeply explore the effect of annealing temperature on the material characteristic of a-IGZO thin films. We found that the surface roughness decreased with the increase of annealing temperature suggestting a better surface morphology, however, the local atomic configuration did not change after annealing. The XPS anelysis results showed that the chemical bonding of the oxygen varied after annealing, and the oxygen vacancy increase which effectively lead to the augment of the carrier concentration. The a-IGZO thin films which is annealled at 300℃ have the best comprehensive properties, whose sheet resistance was 7.12*102Ω/□, the carrier concentration reached 6.28*1019cm-3 and the carrier mobility come to 12.4 cm-2/Vs, while its transmittance attain to above 90%.When we futhure increase the annealing temperature, we found that 600℃ and even higher annealing temperature led to the crystallization of the IGZO thin fims, what’ s worse the surface morphology were deteriorated for high temperature annealing treament. When the annealing temperature reached to 800℃, the distribution of the three elements were not so equal, and the Si of the substrate became to diffused into the IGZO thin films.We also detect the influnece of post-annealing on the IGZO thin films deposited at 300℃. The results showed that the performance of the IGZO thin films improved a little after annealing, however, the IGZO thin films started being deteriorated.Finnally, we compared the effect of post-annealing treament with the measurement of rising the substrate temeprature, the results betrayed that the two methods have different mechanisms of action the post-annealing treament changed the chemical bonding of oxygen increasing the carrier concentration, while increasing the susbstrate temperature effectively removed the number of structure defects which increased the carrier mobility with effect. As a whole, rising the substrate temeprature is a better way to get comprehensive performance of a-IGZO thin films.
Translated Keyword
[IGZO RF sputering annealing temperature substrate temperature eleatrical property]
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