Aspects of barium contamination in high dielectric dynamic random access memories

Barium diffusion properties in silicon at 800 degreesC were studied using total X-ray fluorescence (TXRF), vapor-phase decomposition TXRE and time-of-flight secondary ion mass spectroscopy. Most of the Ba concentration dissolves in the native or thermally gown oxide. At 800 degreesC during 60 min, Ba diffuses 60 nm into silicon. The effects of Ba diffusion on the minority carrier recombination lifetime were also studied. No drastic decrease in lifetime was observed in silicon wafers of n- and p-type up to concentrations of 10(14) atoms/cm(2), which means that Ba does not act as a deep-level recombination center. The leakage current of Ba-contaminated diodes was also evaluated. No increase in leakage current was observed in Ba-contaminated diodes up to concentration of 10(14) atoms/cm(2). Therefore, and under the tested conditions, no drastic risk on lifetime and leakage current is seen for the intxegration of Ba containing dielectrics in future Gbit-scale dynamic random access memories. (C) 2000 The Electrochemical Society. S0013-4651(00)03-099-8. All rights reserved.