Improvement of physical properties of IGZO thin films prepared by excimer laser annealing of sol-gel derived precursor films

Indium gallium zinc oxide (IGZO) transparent semiconductor thin films were prepared by KrF excimer laser annealing of sol-gel derived precursor films. Each as-coated film was dried at 150 degrees C in air and then annealed using excimer laser irradiation. The influence of laser irradiation energy density on surface conditions, optical transmittances, and electrical properties of laser annealed IGZO thin films were investigated, and the physical properties of the excimer laser annealed (ELA) and the thermally annealed (TA) thin films were compared. Experimental results showed that two kinds of surface morphology resulted from excimer laser annealing. Irradiation with a lower energy density (<= 250 mJ cm(-2)) produced wavy and irregular surfaces, while irradiation with a higher energy density (>= 350 mJ cm(-2)) produced flat and dense surfaces consisting of uniform nano-sized amorphous particles. The explanation for the differences in surface features and film quality is that using laser irradiation energy to form IGZO thin films improves the film density and removes organic constituents. The dried IGZO sol-gel films irradiated with a laser energy density of 350 mJ/cm(2) had the best physical properties of all the ELA IGZO thin films. The mean resistivity of the ELA 350 thin films (4.48 x 10(3) Omega cm) was lower than that of TA thin films (1.39 x 10(4) Omega cm), and the average optical transmittance in the visible range (90.2%) of the ELA 350 thin films was slightly higher than that of TA thin films (89.7%). (C) 2013 Elsevier B.V. All rights reserved.