Low-k SiO_x/AlO_x Nanolaminate Dielectric on Dielectric Achieved by Hybrid Pulsed Chemical Vapor Deposition

Abstract

Selective and smooth low-k SiO x /AlO x 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 x . Using a two-temperature pulsed CVD process, ∼2.7 nm selective SiO x /AlO x 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.