Monolithic Fabrication of NPN/SiN_x Dual Membrane Cavity for Nanopore‐Based DNA Sensing

Abstract

Nanoscale preconfinement of DNA has been shown to reduce the variation of passage times through solid-state nanopores. Preconfinement has been previously achieved by forming a femtoliter-sized cavity capped with a highly porous layer of nanoporous silicon nitride (NPN). This cavity was formed by sealing a NPN nanofilter membrane against a substrate chip using water vapor delamination. Ultimately, this method of fabrication cannot keep a consistent spacing between the This article is protected by copyright. All rights reserved. 2 filter and solid-state nanopore due to thermal fluctuations and wrinkles in the membrane, nor can it be fabricated on thousands of individual devices reliably. To overcome these issues, we present a method to fabricate the femtoliter cavity monolithically, using a selective XeF 2 etch to hollow out a polysilicon spacer sandwiched between silicon nitride layers. These monolithically fabricated cavities behave identically to their counterparts formed by vapor delamination, exhibiting similar translocation passage time variation reduction and folding suppression of DNA without requiring extensive manual assembly. The ability to form nanocavity sensors with nanometer-scale precision and to reliably manufacture them at scale using batch wafer processing techniques will find numerous applications, including motion control of polymers for single-molecule detection applications, filtering of dirty samples prior to nanopore detection, and simple fabrication of singlemolecule nanobioreactors.

Screening for Group A Streptococcal Disease via Solid-State Nanopore Detection of PCR Amplicons

“…Figures 1a-c shows the results of a PCR mixture from a commercial kit sensed by a 6 ± 2 nm nanopore in 3.6M LiCl pH 8 at 200 mV (note the uncertainty in the pore size is due to the uncertainty in the effective membrane thickness, likely smaller than the nominal membrane thickness of 10 nm). 36,37 To perform this measurement, a commercial master mix (see Methods section) was added to a sensing salt to mimic the background signals expected of a PCR amplification reaction during nanopore sensing.…”

In situsolid-state nanopore fabrication

“…Utilising this advantage, nanopores were fabricated in a SiN x membrane which was separated from a nanoporous membrane by a sub-micron sized cavity. [135][136][137] Using this device structure, it was demonstrated that the conformation of DNA could be controlled by passing the molecules through the nanoporous membrane prior to translocation through the nanopore. This resulted in a narrower distribution of dwell times and in some cases a reduction in the number of folded translocation events, an important result for practical sensing applications.…”

Nanomembrane-assembled nanophotonics and optoelectronics: from materials to applications

“…Except for the wet methods of etching, dry etching such as vapor can also react with the selected sacrificial layer and release the nanomembrane. For example, HF vapor was used to remove the SiO 2 layer while Si and graphene layers were well protected [108], and XeF 2 vapor can etch semiconductor layer to release the SiN x and metal multilayer [109,110]. Generally, wet method is a cheap and easy method but easy to corrode the surface of the wanted nanomembrane, while dry method is expensive and complex but with better selectivity of sacrificial layer [111].…”