Pmma Dielectric Layer Of Indium Zinc Oxide Thin Film Transistor Preparation And Research

Indium zinc oxide based thin film transistors (IZO-TFTs) were fabricated at low temperature, where poly(methyl methacrylate) (PMMA) serves as the insulator. The inorganic channel layers were deposited by reactive de magnetron sputtering. The organic dielectric layers were prepared by dipping method and aluminum electrodes by thermal evaporation. The processing temperature all along is below 90℃, which is compatible with the fabrication of flexible electronics. The optical and electrical properties of channel layers and dielectric layers were characterized, respectively. The average transmittance in the visible region of PMMA layer together with IZO layer is more than 90%. The effects of experimental parameters including channel thickness, oxygen partial pressure, target composition and dielectric thickness on the electrical performances of IZO-TFTs were analyzed. Besides, electrical stability of the devices and transparent electrodes prepared at low temperature were investigated.Amorphous IZO channel layers were deposited from an alloy target by reactive dc magnetron sputtering at room temperature. The surfaces are smooth and the average transmittance in the visible region is over 85%. Channel thickness, oxygen partial pressure and target composition affect electrical performances of IZO-TFTs. IZO-TFTs exhibit optimum characteristics with channel thickness of 60～90 nm. The device prepared at oxygen partial pressure of 5.0×10-2 Pa reaches its highest saturation mobility of 7.67 cm2V-1s-1, with the threshold voltage of-14.59 V and on/off current ratio of 2.4×102. The increase of zinc content in the alloy target helps to enhance the mobility of TFT while off current increases simultaneously.The PMMA dielectric layers were prepared by dipping method. The average transmittance of PMMA thin film in the visible region is 92%. Its surface is rather smooth. The MIM capacitor with Al-PMMA-Al structure was fabricated. The dielectric property of PMMA is good and its relative dielectric constant is 3.49 measured at 1 kHz. With the enhancement of dielectric thickness from 150 to 580 nm, the saturation mobility and threshold voltage of devices both increase firstly and decrease afterward. The prepared IZO-TFT exhibits the optimum performance when dielectric thickness is around 360 nm. Its saturation mobility is 1.99 cm2V-1s-1and the threshold voltage is-2.77 V with on/off current ratio of 2.6×104.The electrical stability of IZO-TFT was tested by applying bias stress with gate voltage for some time. The variations of saturation mobility and threshold voltage of the device are studied. A prior aging process with a relatively small gate bias stress is conductive to device stability. Tungsten-doped indium oxide (IWO) films were investigated for the usage of transparent electrodes. The IWO films deposited at room temperature are amorphous and the ones prepared from 1 wt% tungsten-doped target reach a minimum resistivity of 5.75×10-4Ω·cm with the average transmittance of over 90% in the visible region.