Method for forming superconducting structures

A method of forming a superconducting structure, the method comprising:

• performing a first cleaning process on a top surface of a plurality of first superconducting contact pads disposed on a top side of a first superconducting device, the first cleaning process comprising an oxygen based plasma process to remove contamination, a hydrofluoric (HF) acid etch to remove oxides, and an argon based sputter process to clean the top surfaces of the plurality of first superconducting contact pads;
• depositing a first under bump metallization (UBM) layer of gold having a thickness between 10 Å to 1000 Å, to provide similar properties as a superconductor, on the top surface of each of the plurality of first superconducting contact pads;
• depositing a superconducting metal layer on each of the first UBM layers;
• performing a second cleaning process on a top surface of each of the superconducting metal layers, the third cleaning process comprising another oxygen based plasma process to remove contamination, another hydrofluoric (HF) acid etch to remove oxides, and another argon based sputter process to clean the top surfaces of the plurality of second superconducting contact pads;
• performing a third cleaning process on a top surface of a plurality of second superconducting contact pads disposed on a bottom side of a second superconducting device;
• depositing a second UBM layer of gold having a thickness between 10 Å to 1000 Å, to provide similar properties as a superconductor, on the top surface of each of the plurality of second superconducting contact pads;
• performing a fourth cleaning process on a top surface of each of the second UBM layers;
• and
• performing a bonding process to connect the first superconducting device and the second superconducting device by coupling the superconducting metal layers of the first superconducting device to respective second UBM layers of the second superconducting device.