Low temperature photoformation of tantalum oxide

Recently, excimer lamps have opened up the field of intense vacuum ultraviolet (VUV) and ultraviolet (UV) light generation. A number of novel applications of these sources have been successfully demonstrated over the past few years. In this article, photo-induced deposition of tantalum pentoxide (Ta(2)O(5)) thin films by photo-CVD and sol-gel processing with the excimer lamps is presented, and the effect of low temperature UV annealing is discussed. Film properties determined using ellipsometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV spectrophotometry, scanning electron microscopy (SEM), capacitance-voltage (C-V) and current-voltage (I-V) techniques, shown that the high quality layers could be produced, rendering the photo-induced technique to be promising for low temperature microelectronic material processing. A significant reduction in the leakage current density of the films has been found after UV annealing using a 172 nm lamp. This is attributed to the reduction of suboxides, impurities, oxygen vacancies and defects in the films as well as the formation of SiO(2) on the surface of the Ta(2)O(5). A simple model explaining the observed reduction in the leakage current after UV annealing is proposed. The formation of active oxygen species by the 172 nm irradiation is considered to be the controlling influence that leads to the considerable improvement in the properties of the layer. (C) 2000 Elsevier Science Ltd. All rights reserved.