Quantum computers perform calculations using quantum bits, or qubits, which can be made from superconducting circuits. These superconducting qubits allow direct control over device parameters while leveraging conventional Si-based fabrication techniques. MIT Lincoln Laboratory is designing and building high performance superconducting qubit devices with increased connectivity and addressability by utilizing advanced process techniques and 3D integration. Our three-tier stack architecture combines separately fabricated qubit, interposer, and routing chips with indium bump bonding. This stack contains high performance qubits, resonators, and couplers, superconducting air bridge crossovers, hard-stop spacing control, superconducting high aspect-ratio through-Si vias, and planarized superconducting routing layers. I will discuss our most recent accomplishments in the fabrication of three-tier stack devices and the effects of additional processing on the uniformity and integrity of their individual components.
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