In this paper, the rare earth element praseodymium-doped indium tin zinc oxide semiconductor is used as the channel layer of the thin film transistor, and the aluminum oxide-based wet back channel etched thin film transistor is successfully prepared. The effect of N ₂O plasma treatment on the back-channel interface of thin film transistor is studied, and the effect of treatment power and time on device performance are studied in detail. The results show that the good device performance can be obtained under certain power and time treatment, and the prepared device has good thermal stability of positive bias and negative bias under light conditions. The results from high-resolution transmission electron microscopy show that the amorphous structure of the metal oxide semiconductor material can effectively resist the wet etchant, and that no obvious component segregation phenomenon is found. Further, X-ray photoelectric spectroscopy tests show that N ₂O plasma treatment can form an oxygen-rich, low-carrier-concentration interface layer at the interface. On the one hand, it can effectively resist the damage of the back channel caused by the plasma of plasma enhanced chemical vapor deposition (PECVD), and on the other hand, it acts as a passivation body of hydrogen from PECVD plasma, suppressing the generation of low-level donor state of hydrogen. This study provides an important reference for low-cost, high-efficiency thin film transistor performance optimization methods.