Effects of post plasma treatment on material properties and device characteristics in indium zinc oxide thin film transistors

Presented in this study are the results of an experiment that was performed regarding the effects of plasma post-treatment on the material properties of amorphous indium zinc oxide (a-IZO) films, and on the device characteristics of the thin film transistor when an a-IZO film is used as the channel layer. Prior to the source/drain deposition, post-treatment was performed on the area that was not covered by photoresist (PR), using Ar and H2 plasma. The electrical resistivity of a-IZO films was dramatically reduced when they were plasma-treated. The creation of an oxygen vacancy and the formation of hydroxyls in the a-IZO film due to plasma treatment were identified via X-ray photoelectron spectroscopy (XPS) analysis. The change in the field effect mobility (μFE) due to the plasma post-treatment was inversely proportional to the change in the contact resistance (RC) of the plasma-treated a-IZO layer. The prolonged (> 1 min) treatment using H2 plasma caused deep electron traps and surface damages, resulting in the increased RC (or decreased μFE) of the a-IZO TFT. In addition, for the a-IZO TFT that underwent H2 plasma treatment, the VT monotonically decreased whereas the VT of the a-IZO TFT that was Ar-plasma-treated remained almost the same as that of the untreated a-IZO TFT.