Area-selective plasma-enhanced atomic layer deposition of a silicon oxycarbide low-k dielectric via dynamic surface passivation

In advanced integrated circuit manufacturing, back-end-of-line patterning techniques such as fully self-aligned through-silicon vias required precise area-selective deposition (ASD) of low-dielectric-constant (low-k) materials to suppress parasitic capacitance and enable continued device scaling. However, conventional ASD approaches were often limited by the poor thermal and plasma stability of organic inhibitors, which restricted their reliability during extended deposition processes. Here, a plasma-enhanced atomic layer deposition strategy was developed for the selective growth of silicon oxycarbide (SiOC) thin films using octamethylcyclotetrasiloxane (OMCTS) as the precursor. Plasma-induced ring-opening of OMCTS enabled the formation of Si—O—Si networks on hydroxylated dielectric surfaces, while selective inhibition on Cu was achieved using n-dodecyl mercaptan self-assembled monolayers (SAMs). A cyclic surface passivation strategy was further introduced, where hydrogen plasma enabled in situ modulation of the SAM layer to maintain inhibition capability during repeated cycles. This approach achieved selective SiOC growth of at least 2 nm while effectively suppressing nucleation on Cu surfaces. The resulting SiOC films exhibited a dielectric constant of 3.2–3.4, confirming their suitability for advanced interconnect applications. The results highlighted the critical role of dynamic SAM stability in regulating selective deposition and suppressing parasitic growth on metal surfaces.