EFFECTS OF POST DEPOSITION ANNEALING ON THE ELECTRICAL-PROPERTIES AND RELIABILITY OF ULTRATHIN CHEMICAL-VAPOR-DEPOSITED TA2O5 FILMS

Abstract

This paper reports the effects of post-deposition rapid thermal annealing on the electrical characteristics of chemical vapor deposited (CVD) Ta2O5 (approximately 10 nm) on NH3-nitrided polycrystalline silicon (poly-Si) storage electrodes for stacked DRAM applications. Three different post-deposition annealing conditions are compared: a) 800-degrees-C rapid thermal O2 annealing (RTO) for 20 sec followed by rapid thermal N2 annealing (RTA) for 40 sec, b) 800-degrees-C RTO for 60 sec and c) 900-degrees-C RTO for 60 sec. Results show that an increase in RTO temperature and time decreases leakage current at the cost of capacitance. However, over-reoxidation induces thicker oxynitride formation at the Ta2O5/poly-Si interface, resulting in the worst time-dependent dielectric breakdown (TDDB) characteristics.