Microcoils for biosensors fabricated by focused ion beam (FIB)

Microcoils integrated with standard CMOS technology show an increasing interest in biosensor applications, as they allow very high sensitivity and selectivity. Simulations of the electromagnetic behaviour of the microcoils suggest the way for optimizing their properties. The sensitivity can be improved essentially by decreasing the external radius of the device, and the inductance variation increases with the number of rings, so the optimum configuration corresponds to a small coil with the highest number of rings. Focused ion beam (FIB) shows optimal capabilities to achieve these design rules, as it is a very versatile and precise direct-write technique. In this work, the fabrication process of reduced-size coils using FIB is described, as well as their preliminary characterization, showing the ability of this technique for achieving optimized sensing devices.