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

This paper reports the effects of post-deposition rapid thermal anneal ing 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 diff erent post-deposition annealing conditions are compared: a) 800-degree s-C rapid thermal O2 annealing (RTO) for 20 sec followed by rapid ther mal 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 capacit ance. However, over-reoxidation induces thicker oxynitride formation a t the Ta2O5/poly-Si interface, resulting in the worst time-dependent d ielectric breakdown (TDDB) characteristics.