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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