Low-<i>k</i> SiO_<i>x</i>/AlO_<i>x</i> Nanolaminate Dielectric on Dielectric Achieved by Hybrid Pulsed Chemical Vapor Deposition

Abstract

Selective and smooth low-<i>k</i> SiO_<i>x</i>/AlO_<i>x</i> 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(<i>tert</i>-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_<i>x</i>. Using a two-temperature pulsed CVD process, ∼2.7 nm selective SiO_<i>x</i>/AlO_<i>x</i> 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 (<i>k</i>) value of 3.3 was measured. For a 2:1 Si:Al ratio, a dielectric constant (<i>k</i>) value of 2.5 was measured. The <i>k</i> value well below that of Al₂O₃ and SiO₂ is consistent with the formation of a low-density, low-<i>k</i> SiO₂/Al₂O₃ nanolaminate in a purely thermal process. This is the first report of a further thermal CVD process for deposition of a low-<i>k</i> dielectric and the first report for a selective low-<i>k</i> process on the nanoscale.