Stoichiometry and thickness distribution of BaCuO2 and CaCuO2 thin films by off-axis RF sputtering

Abstract

We have systematically studied the stoichiometry and thickness distribution of BaCuO2 and CaCuO2 thin films deposited by off-axis RF magnetron sputtering. We found a strong dependence of the thickness and composition on axial distance from the target. A gradual and quasi-linear dependence was observed at an axial distance of 70 mm from the target. There is a minimum in the variation of both thickness and composition for all cases at axial distances of 75–95 mm from the target. In this region, the observed thickness drop-off and compositional uniformity over a distance of 20 mm were within 30 and 10%, respectively. Also the variation in the lateral direction was improved within 10% in thickness and 15% in composition, respectively, for a lateral move of 10 mm from the normal axis of the target. A stoichiometrically uniform region as large as 20×20 mm2 was achieved in the optimum region. By selecting a proper region from the target, and by adjusting the target composition according to the stoichiometric distribution, we were able to obtain ideal film growth with a controllable deposition rate, yielding a large area of homogeneous thickness and composition, with the required stoichiometry.