Structural and Electrical Properties of Ta2O5 Grown by the Plasma-Enhanced Liquid Source CVD Using Penta Ethoxy Tantalum Source

We report on structural and electrical properties of tantalum penta oxide (Ta₂O₅) material with a high dielectric constant grown from a penta ethoxy tantalum [Ta(OC₂H₅)₅] liquid source by the plasma-enhanced liquid source chemical vapor deposition (PE-LS-CVD) technique. We have investigated several basic plasma deposition conditions. Structural properties investigated by θ-2θ X-ray measurements showed the amorphous nature of the films, and Auger electron spectrosopy (AES) and secondary ion mass spectroscopy (SIMS) indicated growth of Ta₂O₅ films having proper stoichiometry (Ta/O=0.4). Optical transmission spectroscopy showed that the band gap (E_g) of Ta₂O₅ is 5.28 eV. Electrical measurements performed on Au/Ta₂O₅/n, p-Si metal oxide semiconductor (MOS) structure exhibited very well defined capacitance-voltage (C-V) characteristics with flat band voltage as low as -0.1 eV, low leakage current, high breakdown voltage and high dielectric constant (25-38). As a hitherto unreported step in Ta₂O₅ processing we also performed rapid thermal (RTA) annealing at 700°C and 900°C for 5 min which resulted in much improved electrical properties. All results suggest growth of high-quality Ta₂O₅ films from a carbon-based Ta liquid source, due to an effect of plasma-enhanced deposition process.