Plasma cathode—surface interaction in reactive magnetron sputtering for indium—tin-oxide thin film deposition

Abstract

The d.c. magnetron sputtering process of an indium-tin-oxide (ITO) target in Ar/O 2 is studied. Compared with the reactive sputtering of an aluminium target, which is very sensitive to the introduced O 2 pressure and which shows a clear transition between metal sputtering and oxide sputtering modes, the reactive sputtering of an ITO target is insensitive to the preset pressure of introduced O 2 in respect to the current-voltage characteristic. Experimental results of laser induced fluorescence measurement of sputtered indium atoms, optical emission measurement of neutral atoms in excited states, electrical measurement of discharge current-voltage characteristic, and measurement of deposited film properties (transmittance, resistivity and deposition rate) are presented. Effects of the preset pressure of introduced O 2 on these parameters are investigated under a wide variety of preset pressure ranges. The change of the sputtering process is mainly governed by a change in the surface condition of the target. An inherent supply of O 2 from the ITO target into the plasma during sputtering is an important key to understanding the reactive sputtering process of ITO target.