| Transparent conductive film with high visible light transmittance and low resistivity can be used as flat panel displays and solar plane electrode materials. It can also be used in energy efficiency such as construction glass and automotive glass surfaces. The band gap of AZO transparent conductive film is 3.4 ev and its intrinsic absorption limit is 360 nm. It can reduce the absorption of light at P, N-type doping and improve the utilization of light energy. Therefore, AZO transparent conductive film is the appropriate window layer material. At the same time, AZO has lots of advantages such as good stability in plasma, simple preparation technology, easy to get, cheap raw materials, non-toxic which can be compared with ITO and make it a substitute for ITO.With the development of transparent conductive thin film, AZO sputtering target and the deposition technology of AZO film become a research hotspot. The main factors of film properties are target performance and film deposition process. Currently, AZO film deposition technology is more mature, but the porosity, pore evolution and microstructure in the hot pressing densification process and the impact on the film properties are rarely studied. Therefore, for the AZO target industrial development and thin-film solar industry, the study of hot pressing densification process of AZO target has an important significance.Firstly, AZO targets were prepared by hot-pressing using ZnO and Al2O3 mixture powder as raw materials with heating-rate of 20℃/min. Study about the influence of hot pressing process on target properties was carried on by method listed below:Archimedes method; Mercury intrusion porosimeter; SEM; XRD; Four-point probe meter. Results are as follows:Hot-pressing densification process of AZO target can be divided into two main stages with the rising of temperature.850℃-1100℃, with the rise of temperature, the distribution of pore size become concentrated as a result of merger and shrinkage of the channel pore volume and the content of the isolate volume has the lowest value at 1050℃-1100℃. The feature of this stage is that densification rate is fast and most holes are connected. When the temperature rise to 1100℃, with the continued mass transfer, pore volume is reduced and deformed gradually until all the pores become into isolation. The feature of this stage is that the content of isolate volume increased rapidly and densification rate is slower. According to the study about the influence of preserving time on hot pressing densification, we found that when the temperature is 1150℃, anti-densification phenomenon happens with extension of preserving time due to the increase of content of the isolate volume and the growth of the channel pore. According to the study about the influence of pressure on hot pressing densification, we found that larger pressure will promote the densification process at the same time lead to the increasing of content of the isolate volume.The densification process can be promoted by adding pressure in the heating process which can reduce the content volume of channel pore and isolate pore. According to the results of densification, AZO high-density target was prepared by process like this:1050℃, 60min and 1150℃,60min and its relative density is greater than 98%.Secondly, According to the study about composition of raw material, composition and structure of target, we found that some of Al element diffuses into the ZnO lattice, and the other part reacts to form ZnAl2O4 spinel because of limited solubility. During the hot pressing process, ZnAl2O4 compounds distributes at the ZnO grain boundary resulting in uneven distribution of composition effect of target due to the uneven distribution of Al elements.Finally, The RF magnetron coating test was carried on using the prepared targets as sputtering source. The thickness of the film was measured by Profiler. The transmittance was measured by UV spectrophotometer. The film resistivity was measured by Four-point probe meter and the phase structure was measured by X-ray diffraction. Coating test results are listed below:Under the same sputtering conditions, when the target porosity is lower, deposition rate can be faster and resistivity of film also is lower but the film transmittance was significantly reduced when the sputtering power is higher. The film has lower resistance when the target has smaller average pore size and concentrated pore size. When the power density is 3.9 W/cm2, the target life is less than 150 W·h when the relative density is lower than 80%.The film deposited for 20min under sputtering power 30W by the target which relative density is 94.79%has lower resistivity (3.14×10-4Ω·cm),greater transmittance (85%) and(002) preferred orientation,both which meets needs of transparent conductive oxide film for solar cell application.
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