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

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.