Study On Synthesis Mechanism Of IGZO Powder Solid State Reaction

Indium gallium zinc oxide (IGZO) material is a kind of typical transparent metal oxide semiconductor material. It is widely used in the preparation of thin film transistors (TFTs) because of its excellent conductivity, optical properties andstability. So it has been highly concerned by the photoelectric field research scholars and enterprises. The present research and the production of IGZO materials in China are still at the primary stage, in which the IGZO target and films contained multiple phase, that is difficult to meet the requirements of high-end IGZO products, which makes the process of establishing IGZO chain blocked and hinders the development of the information industry in China. So the preparation of IGZO sigle-phase powders is very crucial.This paper mainly studied the following aspects:First of all, this paper prepared IGZO powder with the method of solid-phase sintering reaction and with X-ray diffraction and scanning electron microscopy to characterize the phase composition and particle size of the powder to study the effects of process parameters during the preparation on the powder properties. During the preparation, the phase composition of the powder obtain was determined by sintering temperature directly, only when the sintering temperature was higher than 1200 ℃, that could get InGaZnO4 single-phase powder, but if it continues to increase in the sintering temperature whould make the powder particles increases. At the same time the powder particle size also would be affected by sintering time, the ratio of ball and feed and milling time. Within a certain range, the powder particle size would gradually thinning with the growth of the sintering time, the increase of ratio of ball and feed and the increase of milling time. When the sintering time was longer than 6h, the ratio of ball and feed greater than 10:1 or the milling time was longer than 18h, powders became agglomerated, so particle size increased. At the same time, the dispersant couldn’t introduce impurities, and reduced the powder agglomeration greatly.With the effects of the optimal process parameters on the powder properties, which were developed as follows:milling process of 18h with the ratio of ball and feed is 10:1, with adding dispersant to mill. Sintering process with the sintering temperature is 1200℃, sintering time is 6h. IGZO powder finally prepared contains only a single phase— InGaZnO4, has the small particle size, good dispersion and is irregular shaped relatively.On the basis of experiments, we used the first-principles calculation to study the stability InGaZnO4 and ZnGa2O4. After the calculations and analysis of binding energy and the enthalpy of formation, layout analysis, electronic structure of two structural models, a conclusion can be known was InGaZnO4 is more stable than ZnGa2O4 structure. On the basis of this conclusion to study the reaction mechanism of IGZO powder preparation,, By comparing the binding energy of the reaction product and the reactants, the absolute value of binding energy of the order from small to large is:ZnO<Ga2O3<ZnGa2O4<In2O3 <InGaZnO4, So the reaction mechanism is: ZnO and Ga2O3 react firstly, Ga2O3+ZnOâ†'较低温度ZnGa2O4; then In2O3 adds to the reaction, ZnGa2O4+ZnO+In2O3â†'较高温度2InGaZnO4.Finally, using CASTEP module to alculate and compare the electronic structures and optical properties of ITO material model, which is the structure of Sn-doped In2O3, with IGZO material model, which irepresented by InGaZnO4. The results show that the IGZO and ITO model builded all had excellent electrical and optical properties, can meet the requirements of the preparation of transparent conductive films. In contrast, the conductivity of ITO model is better than the IGZO, while the optical properties of the IGZO and ITO are same in the visible region and infrared region, but the absorption and the reflectivity of IGZO are lower than ITO in ultraviolet region.