Direct in- and out-of-plane writing of metals on insulators by electron-beam-enabled, confined electrodeposition with submicrometer feature size

TL;DR

This paper introduces a novel electron-beam-enabled method for direct, localized copper electrodeposition on insulators with submicrometer features, expanding additive microfabrication capabilities to non-conductive substrates.

Contribution

It demonstrates the first direct in- and out-of-plane metal deposition on insulators using confined electrolyte reservoirs created by electrohydrodynamic ejection.

Findings

Achieved ~200 nm feature size in copper deposition.

Enabled deposition on diverse insulating substrates.

Operando nanoscale observation of the process.

Abstract

Additive microfabrication processes based on localized electroplating enable the one-step deposition of micro-scale metal structures with outstanding performance, e.g. high electrical conductivity and mechanical strength. They are therefore evaluated as an exciting and enabling addition to the existing repertoire of microfabrication technologies. Yet, electrochemical processes are generally restricted to conductive or semiconductive substrates, precluding their application in the manufacturing of functional electric devices where direct deposition onto insulators is often required. Here, we demonstrate the direct, localized electrodeposition of copper on a variety of insulating substrates, namely Al2O3, glass and flexible polyethylene, enabled by electron-beam-induced reduction in a highly confined liquid electrolyte reservoir. The nanometer-size of the electrolyte reservoir, fed by electrohydrodynamic ejection, enables a minimal feature size on the order of 200 nm. The fact that the transient reservoir is established and stabilized by electrohydrodynamic ejection rather than specialized liquid cells could offer greater flexibility towards deposition on arbitrary substrate geometries and materials. Installed in a low-vacuum scanning electron microscope, the setup further allows for operando, nanoscale observation and analysis of the manufacturing process.