Nanoscale Dolan Bridges with Integrated Stress Relief for Self-Aligned Josephson Junctions

Josephson junctions are the operational backbone of many low-temperature metrology and detector technologies such as superconducting quantum interference devices (SQUIDs), superconducting tunnel junction (STJ) detectors, and qubits. These technologies find applications in diverse fields ranging from quantum computing to precision magnetometry. Josephson junctions are typically fabricated using a bi-layer resist stack whereupon a freestanding bridge structure, used for double angle evaporation, is created by the chemical development of the resist under layer. However, for applications that require sub-micron junction dimensions, this resist structure tends to collapse or fracture due to the intrinsic stresses that are exacerbated by overdevelopment or small feature dimensions. Here we demonstrate a new patterning design that incorporates stress-relief channels to overcome this issue, without the need to use orthogonal resists or perform cold development. In this talk, we will present the fabrication process used to develop these nanoscale junctions, modeling and stress analysis of the lithography resist stack, and low temperature measurements demonstrating junction performance.