A new fabrication method for ZnO:Al thin films using modified DC magnetron sputtering

Abstract

ZnO:Al thin film was deposited on glass substrates at room temperature. We used a ceramic ZnO:Al target. Since the oxygen vacancies were artificially introduced into the target, thin film could be deposited by DC magnetron sputtering. When ceramic targets are used, fabrication of transparent conductive ZnO:Al thin film in the facing-target is impossible, due to direct resputtering by oxygen anions. The substrate was colored yellow, and the conductivity was also lost. In this state, the thin film was considered to be “ZnO_1−x:Al”. In order to avoid the damage, we used a shield consisting of an upper plate, side plates, back plate and base plate. The substrate encapsulated in the assembled shield was placed on the anode in the magnetron sputter we used, the target was installed in the upper side of the chamber and the anode was installed in the under side. We also described the method of deciding the size of the shield. “Thermalized” sputter particles entered the channel consisting of upper plate, side plates and base plate, and are deposited on the substrate. The oxygen anions were blocked by the shield plates. The values of the resultant thin films were enumerated. Carrier concentration was 1.25 × 10²¹ cm⁻³, a rather high value. Resistivity was 1.13 × 10⁻³ Ω cm and Hall mobility was 4.43 cm²/Vs. Also in the area of high temperature superconductive oxides, thin films were damaged by resputtering by oxygen anions. A shield was also tried in this area. In such cases, simple metal plates were installed beneath the substrates in an off-axis position. Side shields were not installed beside the substrates. This confirmed the necessity of side shield plates. We removed the side shield plates and conducted sputtering. The carrier concentration was 6.92 × 10¹⁹ cm⁻³, resistivity was 1.15 × 10⁻² Ω cm and Hall mobility was 7.86 cm²/Vs. Based on these values, the effectiveness of the side plates was confirmed.