Investigation on plasma treatment for transparent Al–Zn–Sn–O thin film transistor application

• The physical characteristics and electrical performance of bottom gate a-AZTO TFTs were investigated.
• The device’s electrical performance was enhanced after thermal annealing.
• Reliability of the devices improved significantly after O2 (or N2O) plasma treatment.
• The electron mobility of a-AZTO TFTs increased around 130% after NH3 plasma post treatment.

This work reported the physical characteristics and electrical performance of amorphous Al–Zn–Sn–O thin film transistor (a-AZTO TFT) device under the temperature effects of thermal annealing process and various gas plasma post-treatments. The thermal annealing at 450 °C could strengthen the oxygen bonding of a-AZTO film, thereby improving the film quality and TFT device performance. In addition, the oxygen deficient can be reduced effectively by the O2 and N2O plasma treatments, respectively, leading to enhanced electrical reliability. Also, the optical energy gap of a-AZTO films with O2 or N2O plasma treatment was measured about 3.5 eV, which indicated that all of the a-AZTO films were insensitive to visible light. On the other hand, the electron mobility of a-AZTO TFT was observed to be promoted after NH3 plasma post-treatment. The improvement could be attributed to a slight doping effect of H+ ions. These results showed the potential of post-treatments for flat panel displays applications of transparent a-AZTO TFT technology.