AZO target – Hot pressing process

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Transparent Conductive Oxide (Transparent Conductive Oxide, TCO) is a visible light spectrum (380 nm lambda < 780 nm) high transmittance and low resistivity of thin film materials, because of its excellent photoelectric performance in energy saving, thermal, electromagnetic shielding window glass, touch screen, LCD panels, solar cells, light-emitting diodes, and other fields, was as intelligent window material, conductor of heat, electromagnetic shielding materials, plastic film material, Transparent Conductive electrode and widely used.

TCO thin film materials mainly include CDOS, In2O3, SnO2, ZnO and other oxides and their corresponding composite multi-compound semiconductor materials. With the rapid development of electronics industry, the comprehensive performance of transparent conductive films is increasingly required. Meanwhile, the huge amount of use makes the cost of ITO transparent conductive films, mainly composed of rare metal indium, greatly increase. Aluminum doped zinc oxide (ZnO: Al, AZO) has attracted wide attention due to its excellent photoelectric properties, abundant raw material reserves, good etching performance and stable existence in hydrogen plasma.

AZO target features
AZO transparent conductive film has a band gap width of 3.4eV and an intrinsic absorption limit of 360nm, which can reduce the absorption of light in P and N doped regions and improve the utilization rate of light energy, making it an appropriate window layer material. At the same time, AZO has good stability in plasma, simple preparation technology, cheap and easy to obtain raw materials, non-toxic, and comparable with ITO in performance. These characteristics make AZO a substitute for ITO. With the development of transparent conductive films, AZO sputtering target and thin film deposition technology have become research hotspots.

Magnetron sputtering principle
Magnetron sputtering coating technology refers to a coating technology in which the coating material is used as the target cathode, and argon ion bombards the target material to generate cathode sputtering, and target atoms are sputtered onto the workpiece to form a sedimentary layer.

Magnetron sputtering coating process has high requirements on sputtering target materials, such as size, flatness, purity, impurity content, density, N/O/C/S, grain size and defect control.

AZO target preparation process by hot pressing
AZO target performance indexes include density, grain size and uniformity, porosity size and distribution, resistivity, etc., which are closely related to the preparation process of the target material, especially the sintering densification process of the target material.
Compared with non-press sintering process, hot pressing sintering can reduce sintering temperature, shorten sintering time, inhibit grain growth, and obtain products with fine grain, high density and good electrical properties. The AZO target prepared by hot pressing sintering process has advantages of high purity, low impurity, high relative density, uniform grain and high consistency. Therefore, it is of great significance to study the hot pressing densification technology of AZO target for the industrialization development of AZO target and thin-film solar energy industry.

Preparation of AZO powder
Al uniformly doped AZO powders are generally prepared by chemical coprecipitation and mechanical alloying.

Chemical coprecipitation method: it refers to a method of dissolving the required metal salt in solvent, adding precipitant to form precursor, filtering and calcination to prepare the required powder.

Mechanical alloying method: after the ZnO and Al2O3 powder are fully mixed, the powder is repeatedly deformed, cold welded and broken during the operation of the ball mill, so as to realize the horizontal alloying of atoms between elements.

AZO target material hot pressing sintering
Specific preparation technology of high-density target material:
The raw material powder is packed into a mold, compacted and prepared by hot pressing sintering under the protection of vacuum state or inert gas.

Hot pressing process parameters: vacuum up to 1 ~ 100Pa, pressure 30MPa; Then slowly heat up, in 1000℃ ~ 1200℃ heat preservation for about 2 hours, and then slowly cool down.

Learn More : Vacuum Hot Pressing Furnace