# Superconducting qubits free of fabrication residues

Nanofabrication techniques for superconducting qubits often suffer from residual contamination in the dielectric interfaces of these devices. This occurs because these techniques rely on resist-based electron-beam or optical lithography masks, which are placed and processed directly on the surface of the same wafer where the thin-film metallic qubit structures are deposited.

Researchers have developed a technique for making superconducting qubits that minimizes residual contamination and is compatible with high temperature processes. Their technique uses free-standing silicon shadow masks fabricated from silicon-on-insulator wafers, which are separate from the wafers that the qubit metallic layers are deposited on.

Their method involves a type of stencil lithography that naturally separates mask fabrication from device-wafer preparation. This not only minimizes cross-contamination between the mask and the device-wafer, but also makes it possible for researchers to optimize the surface of the device-wafer, without the limitations imposed by standard fabrication techniques.