Ta is a common barrier component for Cu metallization because of their immiscibility resulting in lack of mutual chemical reactivity and solubility. Conventionally, Cu is pre-sputtered on Ta as a seed layer, followed by Cu electroplating. Electroless metallization of Cu on Ta through self-assembled monolayer (SAM) seeding is rarely studied. Herein, electrochemical anodization of Ta films in an ethanol-based solution is performed to achieve a functionalized surface for sequential silanization of (3aminopropyl)trimethoxysilane (APTMS), seeding, and electroless Cu plating. The SAM grown on hydrously (1% H 2 O) anodized Ta films is fully oriented, acting as an effective seed anchoring agent and adhesion promoter to yield high densities of Ni seeds (>5 × 10 15 m −2 ) and tight binding of a Cu film (25.6 MPa). However, the SAM grown on anhydrously anodized Ta films has a substantially deteriorated ordering, giving poor seeding (<8 × 10 14 m −2 ) and Cu-film adhesion (8.8 MPa). Similar deteriorations are observable from the pristine Ta film. The enhancements of SAM silanization and Ni seeding are caused by the improvement of chemical structure of anodization-induced surface tantalum oxide. The role of water in the anodization solution in enhancing anodization efficiency and SAM orientation is fully discussed.

TaN in conjunction with adhesive Ta is a key barrier component of Cu-Damascene structure. However, the limited scalability and stability of TaN pose a dire need of an alternative molecularly thick (⩽1 nm) barrier. To this end, the feasibility of anodizing 2-nmthick Ta films with a mild ethanol based solution, rather than the commonly used strongly acidic (aggressive) chemical electrolytes, to enhance the formation of (3-aminopropyl) trimethoxysilane (APTMS) monolayer barrier is studied. Performing the anodization in an H 2 O-containing (1%) ethanol solution results in a prompt oxidization of the Ta film surface into fully passive Ta 2 O 5 layer with extremely smooth topography, subsequently facilitating the growth of a fully oriented monolayer serving triply as a seed adsorber (for electroless Cu plating), barrier and adhesion promoter. Using Ta (pristine)/Cu [and Ta (pristine)/SAM/Cu] as a control, Ta (anodized)/SAM/Cu exhibits markedly higher adhesion strength (25.2 vs <1 MPa) and resistance against thermal failure (>500 vs 425 °C) of Cu. H 2 O is heavily involved in the anodization efficiency of the Ta films and is the key underlying factor deciding orientation ordering and barrier capacity of the monolayer fabricated. This is related to H 2 O-enhanced surface hydroxylation and Ta 2 O 5 passivation of Ta.