Area-Selective Molecular Layer Deposition of a Silicon Oxycarbide Low-k Dielectric

Area-selective deposition (ASD) of low-k materials is desired in backend-of-line processes for fabricating nanopatterns such as fully self-aligned vias. However, the high temperature and/or aggressive coreactants used in conventional low-k material deposition have limited the application of the organic inhibitors used in ASD. Here, we report a strategy to selectively deposit low-k methylene-bridged silicon oxycarbide (SiOC) thin films on metal/dielectric patterns by combining growth using molecular layer deposition (MLD) and inhibition using self-assembled monolayers (SAMs). By using bis (trichlorosilyl)-methane and water as a precursor and coreactant, respectively, SiOC thin films with a dielectric constant of 3.6-3.8 are deposited at 40 degrees C and at a growth rate of 1.5 angstrom/cycle. We demonstrate area-selective MLD of this SiOC material for up to 30 cycles (equiv. 4.5 nm) on SiO2 vs Cu using a dodecanethiol SAM to block growth on Cu, and up to 70 cycles (equiv. 10 nm) on SiO2 vs Al using an octadecylphosphonic acid SAM to block growth on native oxide-covered Al. Positive and negative pattern transfer of SiOC films on a Cu/Al2O3 pattern is exhibited as a proof of concept. Moreover, because the Cu substrates are contaminated by HCl which is generated as a byproduct in the MLD process, we develop a mild post-treatment method using ethanol to remove chlorine residues.