Selective Studies of Crystalline Ta205 Films

Tantalum pentoxide (Ta~Q) films were reactively sputter deposited from a tantalum target using Ar/O ~ sputtering gas mixtures and annealed to form crystalline beta Ta~O ~ films. The postannealed (1000 ~ films were characterized to evaluate the effects of deposition parameters and postdeposition processing on selected physical and electrical proper-ties: Variations in the microstructure, increasing dielectric onstant, and increasing dc leakage were observed as a func-tion of film thickness between 5 and 40 nm. RF-sputtered films exhibited micropores not observed with dc-sputtered films. Both RF- and dc-sputtered films exhibited microcracks whose density increased with film thickness. Samples having the greatest number of defects exhibited the highest dc leakage (10 nA/cm 2 at 1 MV/cm), which suggests that these defects provide dc leakage paths. The measured ielectric onstants varied from 10.4 to 38.9 within the film thick-ness range of 10-40 nm. There is significant current interest in the potential use of high dielectric constant insulators, such as Ta~Q, for various applications which include: silicon-integrated cir-cuits (SIC) memory storage (1), coupling capacitors (2), and gate insulators for metal-gated thin film transistor