Chemical Mechanical Polishing of Superconducting Metals for Quantum Device Interconnections

Fabrication of more and more complex multi-chip assemblies with quantum devices and quantum bits is driving efforts toward superconducting interconnect developments. In this context, we investigate the damascene integration of Nb-based vias with a focus on the chemical mechanical polishing of Nb. Various slurries typically used for common metal or oxide polishing are evaluated using the following criteria: the removal rate of Nb, the selectivity on SiO2 dielectrics, the polishing within wafer non uniformity and the resulting Nb roughnesses. Damascene integration of the Nb-based vias is then presented using the selected slurries.