Cu wiring into nano-scale holes by electrodeposition in supercritical carbon dioxide emulsified electrolyte with a continuous-flow reaction system

•Cu electroplating in supercritical CO2 suspension with Cu particles.•The continuous flow reaction apparatus for Cu wiring by the plating method.•300 mm diameter round type substrate with holes of 60 nm diameter & 300 nm depth.•Filling of holes is completed with no void and pinhole.•Impurity is in the same level of conventional one.

In this paper, a continuous-flow reaction system was proposed and examined for filling of Cu into holes with 60 nm in diameter and aspect ratio of 2 and 5 by an electroplating method with supercritical carbon dioxide (sc-CO2) emulsified electrolyte on a round-type large-area hole test element group (TEG) with diameter of 300 mm, which has an integrated structure of Cu seed layer on TiN barrier layer sputtered on Si substrates. Copper-sulfate-based electrolyte was used and emulsified by sc-CO2 and a surfactant and Cu particles was added to create a suspension. 313 K and 12 MPa were used with various applied current density (1.41, 2.83 and 4.23 A/dm2). The TEG was found to be completely covered by electrodeposited Cu when 2.83 A/dm2 was used. All of the holes were filled by Cu without any voids at 2.83 A/dm2, while incomplete filling was observed at 1.41 and 4.23 A/dm2. Moreover, a contamination of carbon was not detected by glow discharge optical emission spectroscopy and the reaction was suggested to be feasible to apply into Cu wiring.

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