Effect of HCl catalyst in the formation of flat structures of Ta2O5 thin films by sol-gel technique

Ta2O5 thin films have been prepared from tantalum ethoxide solutions [Ta(C2 H5O)(5)] by sol-gel spin coating technique on Si (100) substrates and annea led at different temperatures ranging from 500 to 800 degrees C for 1 h, Th e physical, chemical and morphological characteristics of both fine powders and thin films have been characterized by bulk techniques like N-2 adsorpt ion and He porosimetry, thermogravimetry, differential thermal analysis and surface techniques like x-ray diffraction (XRD), atomic force microscopy ( AFM) and scanning electron microscopy (SEM), and x-ray photoelectron spectr oscopy (XPS). Additions of acid catalyst (HCl) and proper thermal treatment enable the formation of highly dense flat like films of Ta2O5, as observed by AFM observations. Films prepared From neutral precursor solutions show a micrometer-range porous network and a strongly marked rough polycrystalli ne surface structure. HCl catalyst resulted in a decrease of the crystalliz ation temperature to 630 degrees C, with respect to a crystallization tempe rature of 732 degrees C found fur the neutral prepared films. The evolution of dense structures upon HCl treatment has been confirmed by surface area and density measurements on the fine powders. XPS measurements have confirm ed the formation of stoichiometric Ta2O5 for the HCl prepared films. The PW of the precursor solution as well as the annealing thermal treatment have resulted in the key process parameters for controlling the microstructural characteristics of the deposited films. (C) 2000 American Vacuum Society. [ S0734-2101(00)16304-3].