Growth of ultrathin barrier layers with sub-5-nm metallic seeds fabricated by sequential treatments of vacuum plasma and electrochemical solution

This study describes the process of growing densely distributed metallic seeds of sizes ∼4 nm on SiO₂ dielectric layers by sequential treatment in N₂-H₂ vacuum plasma (to activate the surfaces) and an aqueous solution of metallic salt (to adsorb metallic seeds). After the plasma treatment, the metallic seeds can be densely adsorbed onto the SiO₂ dielectric layers, thus facilitating Co-P barrier layers of thickness only ∼10 nm to be grown using electroless plating. Conversely, for the SiO₂ dielectric layers without the plasma pre-treatment, the population density of the metallic seeds is significantly reduced by one order and thus can only initiate the growth of a relatively thick (∼40 nm) barrier layer by the identical seeding and electroless plating conditions. Improvement in seeding by the plasma pre-treatment is discussed based on surface bonding modification.