THE EFFECTS OF FORMING GAS ANNEAL ON THE ELECTRICAL CHARACTERISTICS OF IR-ELECTRODED BST THIN-FILM CAPACITORS

The effect of various temperature nitrogen anneals prior to top electr ode deposition on the ability of Ba0.7Sr0.3TiO3 (BST) thin-film capaci tors with both Ir and Pt top electrodes to withstand hydrogen damage w as investigated. Experimental results show that samples that underwent a 750 degrees C N-2 pre-top electrode anneal exhibited the lowest lea kage current density at positive bias for both Ir- and Pt-electroded d evices after forming gas anneal. It was also found that DRAM polarizat ion values decreased slightly after forming gas anneal. Also, a post-t op electrode deposition 550 degrees C O-2 anneal improved both electri cal characteristics (lowered leakage and increased DRAM polarization) of these devices. Complete recovery of the leakage level prior to hydr ogen damage was obtained after a 550 degrees C N-2 recovery anneal for some devices independent of the pre-top electrode anneal. Ir- and Pt- electroded BST (40nm) capacitors have been shown to meet the 1 giga-bi t DRAM leakage current requirement of 10(-8) A/cm(2) at 1.7 V. These I r- and Pt-electroded BST devices achieved capacitance density levels o f approximately 50 fF/mu m(2).