A fully customized hardware system for ultra-fast feedback-controlled electromigration using FPGA

Electromigration (EM) method for the fabrication of nanogaps is specifically simple as compared with other methods because it is achieved by only passing a current through a metal nanowire. However, typical EM procedure induces an abrupt break that yields a nanogap with high tunnel resistance. Hence, various approaches have been reported to address this problem, and feedback-controlled electromigration (FCE) scheme has been successfully employed to make nanogaps safely and reliably. On the other hand, the formation of nanogaps by FCE method using a microprocessor-based controller with a general purpose operating system is considerably slow process. In this study, we designed a new system using field programmable gate array (FPGA). Furthermore, we applied this system to Au μm-wires. Consequently, the FCE experiments using FPGA-based control system were performed at 20 μsec of deterministic loop time. In addition, conductance was precisely controlled and adjusted from 10 mS to less than 77.5 μS for within 1 sec, which is 10^2-3 times shorter than that of conventional FCE procedure using microprocessor-based control system.