Ultra-Thin, High-Lifetime Silicon Nitride Membranes for Nanopore Sensing

TL;DR

This paper introduces a scalable method to fabricate ultra-thin silicon nitride membranes (~1.5 nm) for nanopore sensing, demonstrating high performance and extended pore lifetime with applications in single-molecule detection.

Contribution

The authors developed a controllable fabrication process for ultra-thin silicon nitride membranes using standard silicon processing and HF etching, enabling high-performance nanopores with extended lifetimes.

Findings

Membranes with ~1.5 nm thickness were successfully fabricated.

Nanopores with diameters down to ~1.8 nm were created, showing high event counts.

Membranes outperformed commercial options in durability and sensing performance.

Abstract

Thin membranes are highly sought-after for nanopore-based single-molecule sensing and fabrication of such membranes becomes challenging in the \lesssim10 nm thickness regime where a plethora of useful molecule information can be acquired by nanopore sensing. In this work, we present a scalable and controllable method to fabricate silicon nitride (SixNy) membranes with effective thickness down to ~1.5 nm using standard silicon processing and chemical etching using hydrofluoric acid (HF). Nanopores were fabricated using the controlled breakdown method with estimated pore diameters down to ~1.8 nm yielding events >500,000 and >1,800,000 from dsDNA and bovine serum albumin (BSA) protein, respectively, demonstrating the high-performance and extended lifetime of the pores fabricated through our membranes. We used two different compositions of SixNy for membrane fabrication (near stoichiometric and silicon-rich SixNy) and compared them against commercial membranes. The final thicknesses of the membranes were measured using ellipsometry and were in good agreement with the values calculated from the bulk etch rates and DNA translocation characteristics. The stoichiometry and the density of the membrane layers were characterized with Rutherford backscattering spectrometry while the nanopores were characterized using pH-conductance, conductivity-conductance and power spectral density (PSD) graphs.