Low-k SiO/AlO Nanolaminate Dielectric on Dielectric Achieved by Hybrid Pulsed Chemical Vapor Deposition

Selective and smooth low-k SiO/AlO nanolaminate dielectric on dielectric (DOD) was achieved by a hybrid water-free pulsed CVD process consisting of 50 pulses of ATSB (tris(2-butoxy)aluminum) at 330 °C and a 60 s TBS (tris(tert-butoxy)silanol) exposure at 200 °C. Aniline selective passivation was demonstrated on W surfaces in preference to Si₃N₄ and SiO₂ at 300 °C. At 200 °C, TBS pulsed CVD exhibited no growth on W or SiO₂, but its growth was catalyzed by AlO. Using a two-temperature pulsed CVD process, ∼2.7 nm selective SiO/AlO nanolaminate was deposited on Si₃N₄ in preference to aniline passivated W. Nanoselectivity was confirmed and demonstrated on nanoscale W/SiO₂ patterned samples by TEM analysis. For a 1:1 Si:Al ratio, a dielectric constant (k) value of 3.3 was measured. For a 2:1 Si:Al ratio, a dielectric constant (k) value of 2.5 was measured. The k value well below that of Al₂O₃ and SiO₂ is consistent with the formation of a low-density, low-k SiO₂/Al₂O₃ nanolaminate in a purely thermal process. This is the first report of a further thermal CVD process for deposition of a low-k dielectric and the first report for a selective low-k process on the nanoscale.