Through-membrane electron-beam lithography for ultrathin membrane applications

TL;DR

This paper introduces a novel through-membrane electron-beam lithography technique to create ultrathin, electron-transparent windows in SiN membranes, enabling advanced in situ transmission electron microscopy applications.

Contribution

The method allows precise fabrication of ultrathin windows in membranes without damaging the top surface, applicable to various chip designs and MEMS-based heating devices.

Findings

Successful fabrication of 20 nm ultrathin windows in SiN membranes.

Application demonstrated in nanogap electrode creation via electromigration.

Implementation of low-noise graphene nanopore devices.

Abstract

We present a technique to fabricate ultrathin (down to 20 nm) uniform electron transparent windows at dedicated locations in a SiN membrane for in situ transmission electron microscopy experiments. An electron-beam (e-beam) resist is spray-coated on the backside of the membrane in a KOH- etched cavity in silicon which is patterned using through-membrane electron-beam lithography. This is a controlled way to make transparent windows in membranes, whilst the topside of the membrane remains undamaged and retains its flatness. Our approach was optimized for MEMS-based heating chips but can be applied to any chip design. We show two different applications of this technique for (1) fabrication of a nanogap electrode by means of electromigration in thin free-standing metal films and (2) making low-noise graphene nanopore devices.