The effects of rapid thermal annealing on the performance of ZnO thin-film transistors

Abstract

We fabricated and characterized zinc oxide (ZnO)-based thin-film transistors (TFTs) on a glass substrate, which can also be applied to plastic substrates such as polyimide or polynorbornene, at a maximum process temperature of 300 ◦C. Most of the component layers in ZnO-TFTs with a bottom-gate configuration were deposited by using rf magnetron sputtering techniques, except for the SiO2 gate insulating layer, which was deposited by using inductively coupled plasma chemical vapor deposition (ICP-CVD). Silicon-dioxide (SiO2) and ZnO layers were separately heat-treated at 300 ◦C by rapid thermal annealing (RTA) to study its effect on the device performance. The RTAtreated film had a surface morphology similar to that of the as-deposited film, but demonstrated higher crystallinity and transmittance, in addition to enhanced electrical properties, such as carrier concentration and mobility. When the SiO2 layer was RTA-treated before the ZnO deposition, the ZnO TFTs showed high field effect mobility and high on/off current ratio. As a result of the lowtemperature RTA treatment, we successfully fabricated high-performance and highly-transparent ZnO-TFTs. This process should be promising for various displays, such as organic light emitting diode (OLED) and liquid crystal display (LCD) that require low-temperature processes.