AVS 50th International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuA

Paper TF-TuA2
Reactive-Environment, Hollow Cathode Sputtering: Basic Characteristics and Application to Al@sub 2@O@sub 3@ and Doped ZnO

Tuesday, November 4, 2003, 2:20 pm, Room 329

Session: Transparent Conducting Oxides
Presenter: A.E. Delahoy, Energy Photovoltaics, Inc.
Authors: A.E. Delahoy, Energy Photovoltaics, Inc.
S.Y. Guo, Energy Photovoltaics, Inc.
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A novel method for thin film deposition by reactive sputtering has been studied. The method is based on metal sputtering in a hollow cathode configuration with supply of a reactive gas to the vicinity of the substrate. The working gas and entrained sputtered atoms exited the cathode through a slot having an aspect ratio of 8:1. The reactive gas is thereby largely prevented from reaching the target. The basic operation of the cathode was studied using a Cu target. These studies included lateral and longitudinal film thickness profiles, the dependence of deposition rate on power, pressure, and flow rate, and film resistivity as a function of substrate temperature and low energy ion bombardment. Al and Zn targets were used to prepare Al@sub 2@O@sub 3@ and ZnO films in a reactive environment of oxygen. Using quartz crystal rate monitoring it was demonstrated that only a very small amount of oxygen passing through the cathode will oxidize (poison) the target, whereas large quantities of oxygen supplied externally to the cathode need not affect the target at all. A very stable plasma discharge and ease of Al@sub 2@O@sub 3@ formation was realized in this latter mode. Using a Zn target, the method was then applied to the preparation of transparent, conductive films of ZnO doped with Al and B. The Al was introduced by co-sputtering, and the B from B@sub 2@H@sub 6@. The dopant concentrations were measured by ICP. The film resistivity was found to depend strongly on oxygen flow rate. Low film resistivities (0.49 x 10@super -3@ ohm-cm) and high deposition rates (a dynamic rate of 17 nm m/min) were achieved.