Direct, sequential growth of copper film on TaN/Ta barrier substrates by alternation of Pb-UPD and Cu-SLRR

Abstract This study uses an electrochemical form of layer-by-layer deposition to grow Cu films on TaN/Ta barriers without the need for a copper seed layer. The process involves sequential underpotential deposition (UPD) of Pb and surface-limited redox replacement (SLRR) of Cu. Additionally, this work elucidates the influence of pH and Pb deposition potential on the growth mechanism and electrical properties of the resulting Cu films on TaN/Ta barriers. The results demonstrate that during Cu-SLRR, the onset of Cu 2+ substitution of Pb 2+ is delayed when Pb coverage is increased via deposition at a higher Pb-UPD. This is because perchlorate anions are adsorbed on the underlying UPD-deposited Pb adatoms. Cu films formed at a Pb-UPD of −1150 mV exhibit the lowest resistivity of 7.6 μΩcm in the as-deposited state because these films are formed with the Cu(111) texture. Additionally, the Cu layer remains thermally stable after annealing at 700 °C. The results of this study may be of interest for the fabrication of microelectronics, particularly for forming Cu-interconnections.