ITO thin films deposited at different oxygen flow rates on Si(100) using the PEMOCVD method

Abstract

Indium tin oxide (ITO) thin films were deposited on Si(100) substrates using plasma enhanced metallorganic chemical vapor deposition (PEMOCVD). Precursors used in this study were tris (2,2,6,6-tetramethyl-3,5-heptanedionato) indium(III) and tin(III) acetate of 99.9% purity, which are readily available. The precursors decompose at very low temperatures, giving flexibility to use low temperature substrates. The deposition of ITO films was carried out at different oxygen flow rates (5–20 sccm) and Argon flow rate of 200 sccm. R.F. power and reaction temperature was fixed at 150 W and 300 °C, respectively. The deposited films were analyzed using X-ray diffraction, scanning electron microscopy, α-step profilometer and X-ray photoelectronic spectroscopy (XPS). Sheet resistance of ITO film was measured using four-probe method. XRD analysis shows that grains are aligned in (222) and (400) direction and changes from (222) to (400) direction with the increasing oxygen flow rate. SEM results shows that the size of grains decreases as the oxygen flow rate increases with a slight increase in size at 20 sccm. The thickness of the films is ∼7500 Å in all the cases. Sheet resistance of ITO film decreases with increasing oxygen flow rate up to 15 sccm and a little increase in sheet resistance at 20 sccm. XPS results manifested that oxygen atoms are bonded to In and Sn atoms indicating the formation of ITO compound.