H2 annealing effect on the structural and electrical properties of amorphous InGaZnO films for thin film transistors

Abstract

Amorphous indium–gallium–zinc oxide (a-IGZO) thin films were deposited on quartz glass substrates via radio frequency magnetron sputtering. The effect of H2 annealing on the structural, electrical, and H-associated vibrational absorption properties of the a-IGZO films has been systematically studied. The temperature dependence of electrical conductivity of the as-grown and H2 annealed films showed n-type degenerated conduction behavior in the range of 10–300K. Transport properties of these a-IGZO films do not fit well with variable range hopping model. Carrier mobility exhibited increased thermally-exited behavior as H2 annealing temperature is higher than 300°C, suggesting existence of potential barriers above the mobility edge. Fourier Transform Infrared Spectroscopy illustrated OH vibrational mode absorption at around 3670cm−1, suggesting the formation of OH bonding by H2 annealing process which increased at 250°C then annealed away above 300°C along with electron carriers in the a-IGZO films. Comparatively, this OH ir line was greatly mitigated in the a-IGZO films annealed in air. Decrease in electron concentration results from reduced OH absorption in the H2 annealed a-IGZO films upon annealing above 300°C. Surface roughness of the a-IGZO films decreased with increasing H2 annealing temperature for the improvement of device interface uniformity.