  We present a fabrication process for fully superconducting interconnects
compatible with superconducting qubit technology. These interconnects allow for
the 3D integration of quantum circuits without introducing lossy amorphous
dielectrics. They are composed of indium bumps several microns tall separated
from an aluminum base layer by titanium nitride which serves as a diffusion
barrier. We measure the whole structure to be superconducting (transition
temperature of 1.1$\,$K), limited by the aluminum. These interconnects have an
average critical current of 26.8$\,$mA, and mechanical shear and thermal cycle
testing indicate that these devices are mechanically robust. Our process
provides a method that reliably yields superconducting interconnects suitable
for use with superconducting qubits.
