Demonstration of a CMOS-Compatible Superconducting Cryogenic Interposer for Advanced Quantum Processors

An advanced quantum processor requires millions of qubits but is at present limited in scalability due to limitations in the wiring of qubits. A 2.5D silicon (Si) interposer provides an attractive solution in enabling the scalability of the qubit devices. However, some qubits, like the superconducting qubits and solid-state spin-orbit qubits, operate in cryogenic temperatures below 1K. Copper (Cu) interconnects in conventional Si interposers are not superconductive in nature. As such, these metals contribute to losses and result in resistive heating, which can undesirably increase the temperature of the qubits during operation. This paper reports the full demonstration and electrical characterization of a cryogenic interposer with superconducting interconnects and TSV, using CMOS compatible materials like Aluminium (Al), Titanium (Ti), Titanium Nitride (TiN) and Tantalum (Ta).