The influence of the SiO2 deposition condition on the ZnO thin-film transistor performance

Thin-film transistors with bottom gate and staggered electrodes using radio frequency sputtering ZnO and SiO2 films as channel layer and gate insulator are fabricated in this work. The performance of ZnO-TFTs with different oxygen partial pressure (15%, 20% and 30%) SiO2 dielectrics are investigated and compared with each other. The experiment results show that the oxygen partial pressure plays an important role in enhancing both the field effect mobility and bias stability of the devices. The best performance device is obtained with 20% oxygen partial pressure SiO2 dielectric, which has the smallest leakage current compared with the other two types of insulators. The field effect mobility, on/off ratio and sub-threshold swing for the 20% oxygen partial pressure SiO2 dielectric based device are 8.1 cm2/V.s, 1.8×108 and 1.35 V/dec, respectively. The 20% oxygen partial pressure insulator based device also shows a much small threshold voltage shift of 2 V after a 20 V gate voltage stressed for 1 h, while these values for the 15% and 30% oxygen partial pressure insulator based devices are 7.3 V and 3 V, respectively.