Focused Ion Beam Processing of Superconducting Junctions and SQUID Based Devices

Focused ion beam (FIB) has found a steady and growing use as a tool for fabrication, particularly in the length-scale of micrometres down to nanometres. Traditionally more commonly used for materials characterisation, FIB is continually finding new research areas in a growing number of laboratories. For example, over the last ten years the number of FIB instruments in the U.K. alone has gone from single figures, largely supplied by a single manufacturer, to many tens of instruments supplied by several competing manufacturers. Although the smaller of the two research areas, FIB fabrication has found itself to be incredibly powerful in the modification and fabrication of devices for all kinds of experimentation. Here we report our use of FIB in the production of Superconducting QUantum Interference Devices (SQUIDs) and other closely related devices for metrological applications. This is an area ideally suited to FIB fabrication as the required precision is very high, the number of required devices is relatively low, but the flexibility of using FIB means that a large range of small-batch, and often unique, devices can be constructed quickly and with very short lead times.