Electrical and dielectrical properties of tantalum oxide films grown by Nd:YAG laser assisted oxidation

摘要

Tantalum pentoxide (Ta2O5) thin films (20 to 44 nm) have been grown by 1064 nm Nd:YAG laser oxidation of Ta deposited films with various thickness on Si. Fourier Transform Infrared (FTIR) spectrum, thickness distribution, dielectric and electrical properties of laser grown oxide layers have been studied. The effect of the sputtered Ta film thickness, laser beam energy density and the substrate temperature on the final Ta2O5 film structure has been determined. It is shown that the oxide layers obtained for the laser beam energy density in the range from 3.26 to 3.31 J/cm2 and the substrate temperature around 350 °C have superior properties. FTIR measurement demonstrates that the Ta2O5 layers are obtained with the laser assisted oxidation technique. Metal Oxide Semiconductor capacitors fabricated on the grown oxide layers exhibits typical Capacitance-Voltage, Conductance-Voltage and Current-Voltage characteristics. However, the density of oxide charges is found to be slightly higher than the typical values of thermally grown oxides. The conduction mechanism studied by Current-Voltage measurements of the capacitors indicated that the current flow through the oxide layer is modified Poole-Frenkel type. It is concluded that the Ta2O5 films formed by the technique of Nd:YAG laser-enhanced oxidation at relatively low substrate temperatures are potentially useful for device applications and their properties can be further improved by post oxidation annealing processes. © 2008 Elsevier B.V