Effect of the deposition geometry on the electrical properties within Tin-doped indium oxide film deposited under a given RF magnetron sputtering condition

Abstract

Tin-doped indium oxide (ITO) film was deposited using RF-magnetron reactive sputtering and the electrical properties, such as resistivity, carrier concentration and mobility, were investigated as a function of the deposition position under a given magnetron sputtering condition. Non-homogeneity of the electrical properties was observed with the deposition position under a given magnetron sputtering condition. The resistivity of ITO thin film at the center of target had a minimum value, 2 similar to4 X 10(-4) Omega cm, which increased when the substrate deviated from the center. ITO thin film deposited at the center had a maximum density of 7.0 g/cm(3), which was a relative density of approximately 97% compared to the bulk. As the deposition position of ITO thin films deviated from the center, the density decreased. These experimental results clearly showed that non-homogeneity of the electrical properties with deposition position was due to the incidence angle, a, which had an atomic self-shadowing effect and also affected the film density. As the density of ITO thin film increased, both the mobility and conductivity increased with the same tendency. The mean free path increased with the density of ITO thin film and seemed to be saturated, while the grain size contracts with the variation of the mean free path. When the density of ITO thin films was close to the theoretical density, the mean free path was the same as the grain size (the distance between columns). However, in the other cases, the mean free path was smaller than the grain size. It is suggested that the scattering of free electrons at the grain boundary is the major factor for electrical conduction in ITO thin films having a high density, and other scattering sources, such as vacancies, holes, or pores, exist in ITO thin films having a low density. (C) 2001 Elsevier Science B.V. All rights reserved.