S. Kamiyama et al., ULTRATHIN TANTALUM OXIDE CAPACITOR DIELECTRIC LAYERS FABRICATED USINGRAPID THERMAL NITRIDATION PRIOR TO LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION, Journal of the Electrochemical Society, 140(6), 1993, pp. 1617-1625
We describe the formation of ultrathin tantalum oxide capacitors, usin
g rapid thermal nitridation of the storage-node polycrystalline-silico
n surface prior to low pressure chemical vapor deposition of tantalum
oxide. The amorphous tantalum oxide film is deposited on the nitride p
olysilicon surface using penta-ethoxy-tantalum [Ta(OC2H5)5] and oxygen
(O2) gas mixture at 470-degrees-C. The films are annealed ai 600-900-
degrees-C in dry O2. Densification of the as-deposited film by anneali
ng in dry O2 is indispensable to the formation of highly reliable ultr
athin tantalum oxide capacitors. During this densification, CH4 and H2
O desorb from the as-deposited film, and the film crystallizes into an
orthorhombic structure. The RTN treatment allows a reduction of the S
iO2 equivalent thickness (t(eq)) of the capacitor dielectric layer and
results in superior leakage and reliability characteristics.