Substrate Activated Conformal Deposition Through Interfacial Control by a Soft Energy Intensification Process for...

We demonstrate a soft energy vapor deposition process that enables atomic level control of the interface between the substrate surface and the growing multilayer film, while ensuring enhanced environmental sustainability and reduced energy consumption. The process combines the use of a low substrate temperature designed to induce selective ligand removal upon precursor interaction with the substrate surface, which we refer to as the "substrate surface activated" process, with the subsequent application of a soft plasma (ion energies below 5 eV and plasma power density below 0.05 W/cm²) that reacts with the adsorbed partially converted precursor species to complete the formation of a monolayer of the desired film. The soft plasma serves the additional role of pretreating the substrate surface and the interface between the successive film monolayers to micromodulate the chemical reactivity and density of active surface atomic sites to maximize reaction efficiency, leading to elimination of any potential incubation period (nucleation delay). One advantage of this methodology is that the low temperature deposition enables the use of thermally or electrically fragile substrates. Other benefits include conformality in aggressive substrate surface topographies and significant decrease in energy consumption, leading to enhancement of growth rate per cycle. In this proof-of-concept study, cobalt tricarbonyl nitrosyl (Co-(CO)₃NO) and 1,3,5-tri-(isopropyl)-cyclotrisilazane (TICZ, C₉H₂₇N₃Si₃) were employed as the source precursors for cobalt (Co) and silicon nitride (SiN), respectively. Cobalt was selected due to its current role as a conductor, liner, and cap layer in integrated circuitry (IC) metallization applications, while SiN was chosen given its multiple usages in IC technologies. Si₃N₄ and Co thin films were grown from the reaction of Co-(CO)₃NO with an argon (Ar) + 5 atom % hydrogen (H₂) plasma. In situ ellipsometry analyses demonstrated the effectiveness of the interfacial treatment in ensuring immediate film nucleation and elucidated the mechanisms of precursor-substrate surface interactions, leading to functional control of precursor decomposition pathways at low processing temperatures. X-ray photoelectron spectroscopy (XPS) investigations yielded stoichiometric Si₃N₄ and contaminant-free Co, while atomic force microscopy (AFM) shed light on the effects of post-deposition annealing on film microstructure and surface morphology.