Low temperature high k dielectric on poly-Si TFTs

Abstract In this work, it is demonstrated the application of a high k dielectric, as hafnium oxide (HfO 2 ), in poly-Si thin film transistors (TFTs) obtained by metal induced lateral crystallization (MILC). The dielectric layer was deposited at room temperature by sputtering, using argon and oxygen as process gases. As produced TFTs exhibit field effect mobility around 45 cm 2 V −1 s −1 and I on / I off ratio of about 2 × 10 5 . After annealing in a forming gas atmosphere for about 1 h at 200 °C, the threshold voltage and the sub-threshold slope are reduced, respectively from 4.8 to 2 V and from 1.6 to 1.4 V/dec. Nevertheless, by doing so, we notice a reduction on the field effect mobility of about 45% and a decrease of about 2.5 times on the I on / I off ratio. Longer annealing time will not improve the TFT’s performance.