Relationships between the crystalline phase of an IGZO target and electrical properties of a-IGZO channel film

This study used powders containing different In2O3–Ga2O3–ZnO (IGZO) chemical compositions to manufacture targets using a metallurgical process. The resulting targets were used to deposit amorphous In–Ga–Zn–O (a-IGZO) channel films by a radio frequency magnetron sputtering process. This study examined the relationships between these target compositions and crystalline phases of the powders and the resulting material characterization, examining the impacts on electrical characteristics of a-IGZO films with varied O2 flow rates. The ternary compound phase of ZnGa2O4 became stable at 1000 °C according to XRD diagrams at different calcining temperatures. An analysis of the XRD diagrams of different compositions of IGZO powders showed that the atomic ratio of ZnO is larger than that of In2O3 and Ga2O3, and that the main peaks (1 0 1) and (0 0 15) intensity of the respective InGaZnO4 and InGaZnO6 phases intensity would increase. Ceramic targets with different compositions were used to deposit the a-IGZO films with varied O2 flow rates. When the O2 flow rate was zero, the results of a Hall measurement of a-IGZO films deposited from targets with higher Zn atomic ratio showed lower resistivity, higher carrier concentration, and lower mobility. Nevertheless, as the O2 flow rate was more than 5 sccm, increasing the atom ratio of Zn in the IGZO ceramic target obviously increased the capability of capturing O2 in the a-IGZO films, leading to higher resistivity, lower carrier concentration (<1018 cm−3), and higher mobility.