In-Zn-Sn-O thin film based transistor with high-k HfO2 dielectric

Abstract

Indium zinc tin oxide (IZTO) semiconducting thin films have been investigated as active channel layers for thin-film transistor (TFT) applications. The IZTO layer was deposited by radio frequency magnetron sputtering (RFMS) using a sintered IZTO ceramic target with an In:Zn:Sn metal atomic ratio of 40:50:10 on the HfO2 layer either deposited using an atomic layer deposition (ALD) or RF-MS. The annealing treatments after IZTO and HfO2 film depositions were performed in air using a tube furnace and in an oxygen atmosphere using rapid thermal annealing at 400 degrees C, respectively. Optical transparency measured by UV-Vis spectroscopy showed that the HfO2 films deposited by either RF-MS or ALD were transparent in the visible region and had a similar band gap energy of about 4.9 eV. Electrical characteristics of IZTO based TFT were comparatively evaluated for the samples with IZTO/ALD or RF-MS HfO2/n(++)-Si structure. The IZTO TFT sample with 60 nm-thick HfO2 deposited by ALD had an on/off current ratio value of 7.0 x 10(6) and a field-effect mobility value of 6.2 cm(2)/Vs, which was superior to that with RF-MS deposited HfO2.