HIGHLY RELIABLE ULTRA-THIN TANTALUM OXIDE CAPACITORS FOR ULSI DRAMS

This paper describes the formation of ultrathin tantalum oxide capacit ors, using rapid thermal nitridation (RTN) of the storage-node polycry stalline-silicon surface prior to low-pressure chemical vapor depositi on of tantalum oxide, using penta-ethoxy-tantalum [(Ta(OC2H5)5] and ox ygen gas mixture. The films are annealed at 600-900-degrees-C in dry O 2 atmosphere. Densification of the as-deposited film by annealing in d ry O2 is indispensable to the formation of highly reliable ultra-thin tantalum oxide capacitors. The RTN treatment reduces the SiO2 equivale nt thickness and leakage current of the tantalum oxide film, and impro ves the time dependent dielectric breakdown characteristics of the fil m.