ELSEVIER TIlin Solid Films 281-282 (1996) 209-212 Ozone in reactive gas for producing tin-doped indium oxide films by DC reactive magnetron sputtering A.H.M. Zahirul Alam *, Kimihiro Sasaki, Tomonobu Hata Facuuy of Technology, Kanazawu University, 2·40·20 Kodutsuno, Kanazawa 920. Japan Abstract We propose ozone (03) asa reactive gas for producing tin-doped indium oxide (ITO) films by DC reactive magnetron sputtering using 3 metallic alloy target for the first time. We show that incorporation of0 3 enhanced the reaction with the sputtered metal atoms on the substrate surface at room temperature due to its powerful oxidizing nature. The effect of0 3 in oxygen (02) gas on the properties of the ITO films was investigated. It is found that high transparency and low resistivity film can befabricated at high deposition rates and low substrate temperatures by using ozone in oxygen gas. Keywords: Sputtering; Oxygen; Ozone 1. Introduction Indium tinoxide (ITO) thin films have found a wide range of applications in various optoelectronic devices, such as liquid crystal displays, solar cells and electroluminescence displays, due to their high transparency and high electrical conductivity [1,2]. ITO films can be prepared by various methods. Among these, DC magnetron sputtering is widely used since it is superior in controllability and it provides good uniformity in film properties over a wide area of the substrate. In this method ; there are 2 different choices of targets: a sintered oxide target (ln203-8n02, ITO target) and an alloy target (In-Sn, IT target). In past years, the IT target was extensively used but it was found that it is difficult to control the deposition process because of the hysteresis nature of the discharge characteristics and it was difficult to obtain repro- ducibility of the film properties. The film resistivity is exces- sively sensitive to the fluctuation of the oxygen partial pressure [3] and the film must be post-annealed to obtain good quality [4,5]. Therefore, at present, the ITO ceramic target is being widely used for mass production. However, the disadvantages of using the ITO target are: (i) there is a low deposition rate, (ii) there is physical cracking during sputtering, (iii) there is a severe arc on the target surface, (iv) there is rapid formation of nodules on the target surface and these further reduce the deposition rate, and (v) it is II< Corresponding author. Present address : Dept. ofE.E.E., BUET. Dhaka 1000, Tel: (880-2) 504021; fax : (880-2) 863026. difficult to recycle the materials. However, many of these disadvantages are solved by using the IT target and it might be possible to overcome the unstable process control (hys- teresis nature) of the reactive sputtering. Therefore, we proposed ozone (0 3 ) as a reactive gas for producing films due to its powerful oxidizing agent. There is the possibility of activating the reaction of the metal atoms on the substrate surface and producing oxidized transparent films at low substrate temperatures. In this paper, we clarify the effects of using ozone in oxy- gen gas for producing transparent tin-doped indium oxide films (ITO) by reactive DC magnetron sputtering employing a metal alloy target. The effects of0 3 on the films areclarified through observation of the transparent region on the substrate near the inlet of the reactive gas and we describe how the 0 3 affects the properties of the ITO films compared to using oxygen only as the reactive gas. 2. Experimental details ITO films were deposited onto a microscope-slide glass substrate using DC reactive magnetron sputtering of a com- posite 90%ln + 10%Sn alloy target ( 198 X 108 mm") firmly clamped toa water -cooled backing plate. The deposition chamber was first evacuated toa base pres- sure around 2 X 10- 6 Torr using a conventional diffusion pump with a liquid nitrogen trap and then back-filled with Ar gas at a constant flow; it was then maintained at the desired 0040·6:" :'·, PlIS(,:. 00 @ 1996 Elsevier Science SA All rights reserved 196)08615-4