Two-step sintering of aluminum-doped zinc oxide sputtering target by using a submicrometer zinc oxide powder

Aluminum-doped zinc oxide (AZO) is a potential substitute for tin-doped indium oxide due to its versatility. The properties of AZO films are related to those of the AZO sputtering target. To improve the performances of AZO targets, two-step sintering was used to densify a submicrometer zinc oxide (ZnO) powder with a size of 0.4 μm to produce both AZO and ZnO targets. The results showed that the submicrometer ZnO powder cannot be densified by two-step sintering due to its coarse particle size and hexagonal structure. However, a 2 wt% additive of Al2O3 in ZnO can modify the kinetic window of two-step sintering and help in the densification. Using two-step sintering, the sintered density of the AZO target can be improved from 97.4% to 99.8%. The grain size is also reduced by 60%, from 9.1 μm to 3.6 μm.