Nanopatterning on Nonplanar and Fragile Substrates with Ice Resists

Abstract

Electron beam (e-beam) lithography using polymer resists is an important technology that provides the spatial resolution needed for nanodevice fabrication. But it is often desirable to pattern non-planar structures on which polymeric resists cannot be reliably applied. Furthermore, fragile substrates such as free-standing nanotubes or thin films cannot tolerate the vigorous mechanical scrubbing procedures required to remove all residual traces of the polymer resist. Here we demonstrate several examples where e-beam lithography using an amorphous ice resist eliminates both of these difficulties and enables the fabrication of unique nanoscale device structures in a process we call ice lithography1,2. We demonstrate the fabrication of micro and nanostructures on the tip of atomic force microscope probes, micro cantilevers, transmission electron microscopy grids, and suspended single-walled carbon nanotubes. Our results show that by using amorphous water ice as an e-beam resist, a new generation of nanodevice structures can be fabricated on non-planar or fragile substrates.

Facile electron-beam lithography technique for irregular and fragile substrates

“…8 The spray coating method is particularly suitable for sharp substrate features including deep trenches, but it requires special spray coating equipment and a complex optimized mixture of PMMA with acetate and ketone to facilitate vaporization during the coating process. 5 Thermal evaporation of polystyrene (PR) has been recently used in ebeam lithography to achieve 15 nm resolution, but generally, PR has poor exposure sensitivity compared to PMMA and thermal evaporation equipment adds complexity and cost to the process.…”

“…5 Thermal evaporation of polystyrene (PR) has been recently used in ebeam lithography to achieve 15 nm resolution, but generally, PR has poor exposure sensitivity compared to PMMA and thermal evaporation equipment adds complexity and cost to the process. Ice resist has been applied to fragile and nonplanar substrates such as carbon nanotubes, but this method requires specially designed e-beam lithography and e-beam evaporation systems to maintain the temperature < 120 K, 8 thereby increasing cost and limiting the selection of target substrates. Focused Ion Beam (FIB) can offer similar benefit, but the cost is very high and deposition materials are quite limited.…”

Study of Magnetic Micro-Ellipses by Cantilever Sensor

“…However, standard spin-coating technique fails to pattern non-planar surfaces and cannot cover pre-structured substrates with resist uniformly. A possible solution is offered by alternative methods of resist deposition, such as resist evaporation [4], spray coating [5] or ice (H 2 O) lithography [6]. Nevertheless, these are mostly laborious processes and require special equipment.…”

Electron Beam Lithography on Irregular Surfaces Using an Evaporated Resist

“…4 For example, nanopatterning on optical fibers allows the so-called lab-onfiber technology, 5 and that on an atomic force microscope (AFM) tip allows tipenhanced Raman spectroscopy, 6 near-field optical focusing, 7,8 and the study of fundamental quantum mechanical systems. 9,10 In addition, nanofabrication on a cylindrical roller may be needed as the mold for rollto-roll nanoimprint lithography (NIL).…”

“…This novel patterning process is named ice lithography. 6,23,24 However, for ice lithography the resist has to be kept at very low temperature before pattern transfer by liftoff or dry etching is completed, thus a specially designed tool or tool accessory is needed. In addition, the resist sensitivity is very low, three orders lower than PMMA, which is already considered an insensitive resist.…”