RF power dependence on structural and electrical properties of CU thin films on a glass substrate prepared using magnetron sputtering with multipolar magnetic plasma confinement

We fabricated copper (Cu) thin films on a glass substrate using magnetron sputtering with multipolar magnetic plasma confinement (MMPC) method. MMPC sputtering deposition technique is powerful method to be able to fabricate high quality thin film by the effect of ion irradiation so that plasma is transported to the substrate along magnetic lines of force formed by permanent magnets arranged on the sides of the target. In order to obtain the knowledge on the effects of ion irradiation, RF power (PT) dependence on structural and electrical properties of Cu thin films fabricated by MMPC method was investigated. For the deposition conditions, we changed PT in the range of 30-100 W under an Ar gas pressure (PAr) of 0.1 Pa. The film thickness was set to about 200 nm. From plasma emission spectroscopy, Ar ion density increased as PT increased. AFM image analysis revealed that the average surface grain size of the fabricated Cu thin films surface was almost constant as PT increased and was not significantly enhanced by ion irradiation. However, surface diffusion was promoted as PT increased and the film surface became smooth. From the XRD spectrum analysis, the crystallite size of fabricated Cu thin films changed as PT increased. From this result, we found that the effect of ion irradiation affect the film density. The resistivity of fabricated Cu thin films was dependent on the surface morphology and crystal structure affected by the change in the effect of ion irradiation. The minimum resistivity of the Cu thin film was 1.763 μΩcm at a PT = 100 W and PAr = 0.1 Pa. In this study, effective surface diffusion for high quality thin film formation was performed using only the effect of ion irradiation without heating substrate. We confirmed the possibility to fabricate Cu thin film with resistivity comparable to the bulk value. We concluded that this sputtering method was effective for high quality thin film formation. © 2020 The Institute of Electrical Engineers of Japan.