Oxide film deposition by radio frequency sputtering with electron cyclotron resonance plasma stimulation

Abstract

Various oxide films, including SiO2, ZnO, BaTiO3, SrTiO3, and BaFe12O19, are deposited by 13.56 MHz radio frequency mode (rf-mode) sputtering with 2.45 GHz electron cyclotron resonance (ECR) plasma stimulation. The rf plasma is effectively cooled by the ECR plasma as a result of the shielding effect on the rf electric field on the target surface. This causes the self-bias voltage of the target to decrease and the rf-mode sputtering is effectively performed as in a direct current mode (dc-mode) system. There are two stages in the deposition of the oxide films: an oxygen supply-determining stage controlled by the ECR plasma density, and a sputtered-particle supply-determining stage controlled by the rf sputtering power. In the former stage, the film deposition rate is dramatically enhanced by the ECR plasma irradiation onto the substrate surface (ten times higher than without ECR plasma). In the latter stage, the film deposition rate does not change with oxygen plasma density but with the sputtering power. In this stage, the film deposition uniformity depends only on the uniformity of the sputtered particles. Fully oxidized films can be easily deposited by this technique. Changes of film composition are mainly due to anisotropy of the angle at which sputtered atoms of each component are ejected from the target surface, and also to the sticking efficiency of each component on the film surface with ECR plasma irradiation.