Growth of IGZO Thin Films and Fabrication of Transparent Thin Film Transistor by RF Magnetron Sputtering

n-Type transparent conducting indiuim galium zinc oxide (IGZO) films were successfully grown on glass substrates at room temperature by rf magnetron sputtering. Structural, optical, morphological and electrical properties of IGZO films deposited at different rf power were investigated. Composition of the film was confirmed by EDAX measurement which shows that percentage of Zn increased with the rf power. Structural studies by X-ray diffraction showed that as deposited IGZO films were amorphous. The roughness of the film was increased with increase in rf power and smooth film of average roughness 0.75nm was obtained at 40W rf power. The average transmission in the visible range was greater than 80% and the transmission in the higher wavelength region decreased with increase in RF power. Refractive index of IGZO film calculated by Swanepoel technique was 1.92. The carrier concentration in IGZO films can be controlled by controlling rf which can vary Zn/(Ga+In+Zn) ratio. The bottom gate structured transparent TFTs fabricated using n-type IGZO active layers operated in enhancement mode with field effect mobility 2.5 cm(2)/Vs and threshold voltage 20V.