Investigation of plasma-deposited ITO films by GIXR and GIXRD

Thin indium tin oxide (ITO) films were deposited by reactive DC magnetron s puttering to study the influence of oxygen and low energy ion bombardment o n film growth and film properties. Films were deposited at various oxygen g as flows (0 to 2 seem) as well as negative substrate voltages (0 to -50 V). The film properties were investigated by grazing incidence X-ray reflectom etry (GIXR), X-ray diffractometry (GIXRD), AFM and XPS. With increasing oxy gen flow film structure and composition change from crystalline metallic In /Sn to Xray-amorphous ITO. Simultaneously the deposition rates decrease fro m 0.6 to 0.25 nm/s and the film densities increase from 4.3 to 7.1 g/cm(3). The metallic films consist of large grains forming a rough surface. The de position with higher oxygen flows causes smooth surfaces, grain sizes are n ot clearly observable. In principle an increasing negative substrate voltag e leads to the same film properties but it works like a diminished oxygen f low. Post deposition annealing causes the formation of crystalline ITO film s. GIXRD measurements were carried out in situ at 200 degrees C at 10(-5) m bar. Two processes determine the ITO crystallite growth, a fast crystalliza tion of the deposited amorphous indium tin oxide and the diffusion of oxyge n into the layer. The formation rate k of the diffusion limited reaction de pends on the oxygen flows. With increasing oxygen flow k approximates zero. (C) 1999 Elsevier Science S.A. All rights reserved.