| AVS 57th International Symposium & Exhibition | |
| Energy Frontiers Topical Conference | Thursday Sessions |
| Session EN+SS+TF-ThA |
| Session: | Transparent Conductors |
| Presenter: | Y. Hoshi, Tokyo Polytechnic University, Japan |
| Authors: | Y. Hoshi, Tokyo Polytechnic University, Japan Y. Yasuda, Tokyo Polytechnic University, Japan H. Shimizu, Niigata University, Japan |
| Correspondent: | Click to Email |
The ITO films deposited by magnetron sputtering and facing target sputtering at low substrate temperature have quite different distributions of film properties. However, their origin was still not clear. In this paper, we clarify the origin of the different distributions between the sputtering methods, and will propose a sputtering method to deposit the ITO films with good uniformity.
In the deposition of ITO films by a conventional planar magnetron sputtering, the films deposited at the center of the substrate have higher oxygen content than the films deposited at the end of the substrate. It should be noted that the film deposited by a facing target sputtering has much lower oxygen content than the films deposited by conventional planar magnetron sputtering. As a result, the ITO films with poor transparency were always obtained by the sputtering in pure Ar gas, when a Facing Target Sputtering system was used.
These phenomena can be explained by the following model; When sputter-deposition of ITO films was performed at a low temperature, only oxygen atoms produced by the sputter-emission from the target surface promote the oxidization of indium atoms on the film surface. In other words, oxygen molecules cannot oxidize the indium atoms at a low temperature.
In addition, oxygen atoms sputter-emitted from the target have different angular distributions than indium atoms have. That is, the emission ratio of oxygen atoms to indium atoms sputter-emitted from the target surface changes depending on the emission angle and gradually decreases with an increase of the emission angle. This phenomenon mainly causes the distribution of the properties of ITO films on the substrate, although bombardment of high energy negative oxygen ions also affects the distribution of film properties in planar magnetron sputtering.
In order to deposit uniform film on the substrate, compensation of the angular distribution in the emission ratio of oxygen atoms to indium atoms is necessary. Use of two sputtering sources arranged like a facing target sputtering system is one of the solutions to compensate the distribution and obtain the films with more excellent uniformity.