Engineers at the Università di Pisa have developed a technique to build three-dimensional metal microinductors directly onto silicon contact pads using high-precision electrodeposition, according to a paper published in Nature Communications.
Traditional radio-frequency integrated circuits rely on planar inductors that occupy substantial surface area, limiting device miniaturization and raising manufacturing costs. The freestanding copper coils extend vertically above the chip surface. This design decouples component inductance from the planar silicon footprint beneath it.
The team fabricated copper microsolenoids in multiple geometries directly on test chips to evaluate high-frequency performance. During electrical characterization, the printed microinductors showed inductance values in the nanohenry range, achieved quality factors of up to 18, and maintained inductive behavior at frequencies up to 15 GHz. These experimental measurements matched the researchers' electromagnetic simulations.
Manufacturers can apply the maskless process after completing standard semiconductor fabrication runs. Because the additive step requires no adjustments to underlying circuit layouts, the method offers an avenue to shrink radio-frequency packages without overhauling existing silicon designs.
Alessandro Paghi and Farbod Abazar contributed equally as lead authors on the research, working alongside Giuseppe Barillaro and colleagues across the Università di Pisa and NEST. The European Commission funded the research through the ALERT project under its EIC Pathfinder Open programme, alongside backing from the Italian Ministry of Education, University and Research's FORELAB project. Exaddon AG provided technical support for the additive printing system.
