Research on correlation between metal oxide semiconductor target and magnetron sputtered film based on TFT application

The research on the intrinsic relationship between target quality and TFT (thin film transistor) performance is not perfect for magnetron sputtering processes. The systematic analysis of target-film-device still needs to be improved. This paper studied the internal relationship between metal oxide semiconductor targets, thin films, and TFT devices for the deterioration problem of device performance caused by the failure of the aging target. The experimental results showed that the target surface with a long cumulative sputtering time had apparent macroscopic concave, related to the electromagnetic field distribution. The concave region was the primary source of thin film composition, so the research object of this work was mainly the concave region. A multi-oxide target was used in this work, and its selective sputtering phenomenon was serious, mainly reflected in the sputtering rate of In2O3 grains with higher electrical conductivity than other components. There were many failure sites on the surface of the target, including nodules, holes, coating layers, and cracks. The failure sites would hinder the normal sputtering process and eventually form a vicious circle, failing the target. Due to the decline of target quality, sputtering particles would be in a state of insufficient kinetic energy, resulting in particle agglomeration, element segregation, weak M-O (metal-oxide) bonds, loose accumulation, and surface or block defects. Ultimately, the TFT performance with the aging target showed lower mobility, larger subthreshold swing, increased off-state current, and poorer stability. Clarifying the relationship between target quality and device performance is beneficial for the development of electronic devices.