Spatial resistivity distribution of transparent conducting impurity-doped ZnO thin films deposited on substrates by dc magnetron sputtering

In transparent conducting impurity-doped ZnO thin films prepared by a conventional dc magnetron sputtering deposition (dc-MSD), the key factors in the deposition conditions that are necessary for practical use in transparent electrode applications were investigated. It was found that impurity-doped ZnO targets with a resistivity higher than approximately 3 m Omega cm are unsuitable for practical use in the preparation of transparent conducting Al-doped ZnO and Ga-doped ZnO thin films by conventional dc-MSD. Improvements of both the resulting resistivity distribution and resistivity can be sufficiently obtained only by using targets with a resistivity lower than about 0.5 m Omega cm. Using a low oxygen content target having a lower resistivity was found to reduce both the amount of oxygen in the chamber and the amount of oxygen reaching the substrate surface. As a result, it was demonstrated that sintered impurity-doped ZnO targets optimized for the preparation of thin films with lower resistivity as well as more uniform resistivity distribution on the substrate surface tended to exhibit a resistivity lower than about 0.5 m Omega cm. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3357284]