Characterization of magnesium oxide gate insulators grown using RF sputtering for ZnO thin-film transistors

A ZnO thin-film transistor (TFT) with an MgO insulator was fabricated on a silicon (100) substrate using a radiofrequency magnetron sputtering system. The MgO insulator was deposited using the same deposition system; the total pressure during the deposition process was maintained at 5 mTorr, and the oxygen percentage of O₂/(Ar + O₂) was set at 30%, 50%, or 70%. The process temperature was maintained at below 300 °C. The dielectric constant of the MgO thin layer was approximately 11.35 with an oxygen percentage of 70%. This ZnO TFT displayed enhanced transistor properties, with a field-effect mobility of 0.0235 cm² V^?1 s^?1, an I_ON/I_OFF ratio of ～10⁵, and an SS value of 1.18 V decade^?1; these properties were superior to those measured for the MgO insulators synthesized using oxygen percentages of 30% and 50%.