High mobility bottom gate InGaZnO thin film transistors with SiO_x etch stopper

The authors report on the fabrication of thin film transistors (TFTs), which use an amorphous indium gallium zinc oxide (a-IGZO) channel, by rf sputtering at room temperature and for which the channel length and width are patterned by photolithography and dry etching. To prevent plasma damage to the active channel, a 100-nm-thick SiO_x layer deposited by plasma enhanced chemical vapor deposition was adopted as an etch stopper structure. The a-IGZO TFT (W/L=10 μm/50 μm) fabricated on glass exhibited a high field-effect mobility of 35.8 cm²/V s, a subthreshold gate swing value of 0.59 V/decade, a thrseshold voltage of 5.9 V, and an I_on/off ratio of 4.9×10⁶, which is acceptable for use as the switching transistor of an active-matrix TFT backplane.