Formation of Self-Aligned Sub-Lithographic Mask for Nanostructure Patterning

Nanotechnologies : Physical Science Apps

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  • Paul Ho, Ph.D. , Mechanical Engineering
  • Zhuojie Wu , Physics

Background/unmet need

The current method commonly used to pattern nanostructures is to use nanolithography to form first a mask with structural features of nano-dimensions, followed by etching for pattern transfer.

Although nanolithography can pattern nanostructures of dimensions of a few tens of nanometers, each nanolithography technique has its disadvantages. For example, the writing of e-beam lithography is serial, resulting in an inherently low-throughput process.

Although nanoimprint lithography is parallel, defects generated during the imprint process present serious challenges to fabricate ultra-small structures. Furthermore, the fabrication of imprint mold requires expensive high resolution nanolithography. The wearing of the imprint mold will degrade the resolution of the imprint process.

Thus, optical lithography remains the preferred technique as long as it can produce nanostructures to meet the dimensional requirements.

Invention Description

An innovative method has been developed for the formation of self-aligned sub-lithographic patterns for fabrication of high-quality nanostructures. It is based on the formation of a self-aligned mask using polymer residue formed during reactive ion etching (RIE) and followed by etching step(s). Fully compatible with most lithographic techniques, including standard optical lithography, this method produces high-resolution, high aspect ratio patterns with a far simpler process that is both cost-effective and high throughput. This process has been successfully demonstrated in the formation of 3D Si nanochannels with a single lithography step, producing highly uniform nanochannels with atomically smooth sidewalls and controllable aspect ratio.


  • High quality nanochannels with highly uniform width, atomically flat sidewalls and very high aspect ratios
  • Both planar nanochannels and vertical nanochannels can be fabricated in a single lithography step.
  • Simple low-cost, high-throughput process


  • Smaller feature size than that defined by current lithography techniques can be achieved with this method
  • Possible to make much denser and finer nanostructures for biomedical applications such as nanofluidic devices
  • 3D structures can be realized with a cost-effective, high-throughput single lithography step.
  • Compatible to most lithographic techniques, including standard optical lithography

Market potential/applications

Applications include sorting, monitoring, and analysis of chemical and biological molecules, drug delivery systems, nanofluidic technology, proton-exchange-membranes for fuel cells and nanochannel-based batteries, transmission electron microscopy (TEM) grids, plasmonic cavities, filters for nanoparticles and molecules, and templates for nanofabrications.

Development Stage

Lab/bench prototype

IP Status