Ultrathin, High-Lifetime Silicon Nitride Membranes for Nanopore Sensing

Abstract

Thin membranes are highly sought-after for nanopore-based single-molecule sensing, and fabrication of such membranes becomes challenging in the ≲10 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 (Si x N y ) 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 Si x N y for membrane fabrication (near-stoichiometric and silicon-rich Si x N y ) 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.

Nanopore Fabrication Made Easy: A Portable, Affordable Microcontroller-Assisted Approach for Tailored Pore Formation via Controlled Breakdown

“…Nanopores were fabricated through ∼10 ± 3 nm thick Si-rich silicon nitride (SiN x ) membranes with a SiO 2 underlayer by applying an electric field <1 V/nm across the SiN x membrane. Figure shows the flowchart outlining the pore fabrication and the subsequent biomolecule translocation phase.…”

“…42 While legacy issues associated with nanopores (not limited CBD) have precluded nanopore operations lasting several hours, more recently, Dutt et al achieved >1.5 million detection events, using CBD with BSA as the analyte. 34 Saharia et al pushed the boundary of sensing even further with ∼2 million DNA events using a well-optimized CT-CBD protocol yielding ultra-stable open-pore currents lasting over several hours. 32 While the primary custom circuitry used for the CBD process is affordable (<100 USD), they are often connected to a block connector and a data acquisition (DAQ) system, which cost several thousands of dollars and upward.…”

Array of Nanopore Sensors Detect Nanoscale Biomolecules by Nucleic Acid Analysis

“…Nanopores were fabricated using the CBD method with estimated pore diameters of ∼2 nm. The surface charge density was determined by surveying the open pore conductance with changing pH and salt concentrations [54] …”

Modulation mechanism of ionic transport through short nanopores by charged exterior surfaces

“…28 The default pore diameter and length were 10 and 50 nm, respectively. 14,30,33,34 The system temperature was maintained at 298 K, and the dielectric constant of water was set to 80. Because KCl solutions are commonly applied in biosensing based on nanopores, 35–37 KCl solutions varying from 10 to 500 mM in concentration were chosen in the simulations, of which 100 mM was the default concentration.…”