  We report on the fabrication and metrology of superconducting caps for qubit
circuits. As part of a 3D quantum integrated circuit architecture, a cap chip
forms the upper half of an enclosure that provides isolation, increases vacuum
participation ratio, and improves performance of individual resonant elements.
Here, we demonstrate that such caps can be reliably fabricated, placed on a
circuit chip, and form superconducting connections to the circuit.
