Preserving the structural and functional integrity of interfaces and inhibiting deleterious chemical interactions are critical for realizing devices with sub-50 nm thin films and nanoscale units. Here, we demonstrate that ∼0.7-nm-thick self-assembled monolayers (SAMs) comprising mercapto-propyl-tri-methoxy-silane (MPTMS) molecules enhance adhesion and inhibit Cu diffusion at Cu/SiO2 structures used in device metallization. Cu/SAM/SiO2/Si(001) structures show three times higher interface debond energy compared to Cu/SiO2 interfaces due to a strong chemical interaction between Cu and S termini of the MPTMS SAMs. This interaction immobilizes Cu at the Cu/SAM interface and results in a factor-of-4 increase in Cu-diffusion-induced failure times compared with that for structures without SAMs.

Articles you may be interested inEffect of surface hydrophilicity on the nanofretting behavior of Si(100) in atmosphere and vacuum Recent work has shown that molecular nanolayers ͑MNLs͒ are attractive candidates for isolating and enhancing adhesion of Cu/ SiO 2 interfaces for sub 100 nm integrated circuits. Here, we report the effects of solution concentration and SiO 2 surface treatment on the adhesion of Cu/ SiO 2 interfaces treated with organosilane MNLs with two different nitrogen-containing termini. MNLs from 5 mM concentration solution form monolayers and enhance adhesion, while 50 mM solutions form multilayers via unregulated self-polymerization, leading to inferior adhesion. Electron spectroscopy of fracture surfaces reveals that the Cu/MNL interface is the weakest link.

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As the critical feature size in microelectronic devices continues to decrease below 100 nm, new barrier materials of > 5 nm thickness are required. Recently we have shown that self-assembled monolayers (SAMs) are attractive candidates that inhibit Cu diffusion into SiO2. For SAMs to be used as barriers in real applications, however, they must also promote adhesion at the Cu/dielectric interfaces. Here, we report preliminary quantitative measurements of interfacial adhesion energy and chemical binding energy of Cu/SiO2 interfaces treated with nitrogen-terminated SAMs. Amine-containing SAMs show a ~10% higher adhesion energy with Cu, while interfaces with Cu-pyridine bonds actually show degraded adhesion, when compared with that of the reference Cu/SiN interface. However, X-ray photoelectron spectroscopy (XPS) measurements show that Cu-pyridine and Cu-amine interactions have a factor-of-four higher binding energy than that of Cu-N bonds at Cu/SiN interfaces. The lack of correlation between adhesion and chemical binding energies is most likely due to incomplete coverage of SAMs.