  Superconducting qubits based on Al/AlOx/Al Josephson junction are one of the
most promising candidates for the physical implementation of universal quantum
computers. Due to scalability and compatibility with the state-of-the-art
nanoelectronic processes one can fabricate hundreds of qubits on a single
silicon chip. However, decoherence in these systems caused by two-level-systems
in amorphous dielectrics, including a tunneling barrier AlOx, is one of the
major problems. We report on a Josephson junction thermal annealing process
development to crystallize an amorphous barrier oxide (AlOx). The dependences
of the thermal annealing parameters on the room temperature resistance are
obtained. The developed method allows not only to increase the Josephson
junction resistance by 175%, but also to decrease by 60% with precisions of 10%
in Rn. Finally, theoretical assumptions about the structure modification in
tunnel barrier are proposed. The suggested thermal annealing approach can be
used to form a stable and reproducible tunneling barriers and scalable
frequency trimming for a widely used fixed-frequency transmon qubits.
