Fabrication of a Cu/Ni stack in supercritical carbon dioxide at low-temperature

• Cu/Ni stack fabricated in supercritical CO2 at low temperature.
• A novel Cu(I) amidinate precursor was used to reduce the deposition temperature.
• Adhesion strength of Cu/Ni stack improved dramatically.
• Fabricated Cu/Ni stack is suitable for Cu interconnections in microelectronics.

We report the low-temperature deposition of Cu on a Ni-lined substrate in supercritical carbon dioxide. A novel Cu(I) amidinate precursor was used to reduce the deposition temperature. From the temperature dependence of the growth rate, the activation energy for Cu growth on the Ni film was determined to be 0.19 eV. The films and interfaces were characterized by Auger electron spectroscopy. At low temperature (140 °C), we successfully deposited a Cu/Ni stack with a sharp Cu/Ni interface. The stack had a high adhesion strength (> 1000 mN) according to microscratch testing. The high adhesion strength originated from strong interfacial bonding between the Cu and the Ni. However, at a higher temperature (240 °C), significant interdiffusion was observed and the adhesion became weak.