The calculation of the molecular flux of sputtered indium gallium zinc oxide (IGZO) and oxygen during IGZO growth is used to generalize the optimum synthesis conditions for thin film transistors (TFTs). TFTs fabricated with an O-2 and IGZO incorporation ratio approximate to 1 demonstrated the best transfer curve with the resistivity of similar to 5 x 10(3) Omega cm at similar to 1 mTorr of oxygen partial pressure. We demonstrate that the resistivity can be systematically varied almost 7 orders of magnitude by varying the oxygen partial pressure during sputtering. The relative Fermi level position was estimated as a function of the O-2/IGZO incorporation ratio. It is demonstrated that the resistivity curve with O-2/IGZO incorporation ratio can be used as a powerful tool to determine the IGZO sputtering conditions for optimum TFT fabrication. Furthermore, the proposed oxygen incorporation calculation method is applied to subsequent passivation layer sputtering; when the oxygen incorporation rate during SiO2 passivation sputtering is increased to a point that is higher than the amorphous IGZO incorporation rate during IGZO sputtering, the leakage current via the back channel is noticeably reduced. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3530779] All rights reserved.