Electron Beam Lithography on Irregular Surfaces Using an Evaporated Resist

Abstract

An electron beam resist is typically applied by spin-coating, which cannot be reliably applied on nonplanar, irregular, or fragile substrates. Here we demonstrate that the popular negative electron beam resist polystyrene can be coated by thermal evaporation. A high resolution of 30 nm half-pitch was achieved using the evaporated resist. As a proof of concept of patterning on irregular surfaces, we fabricated nanostructures on the AFM cantilever and the optical fiber. Although an ice (H2O) resist has also been recently demonstrated as being capable of nanopatterning on irregular and fragile substrates, it requires specially designed accessories mounted inside a SEM chamber, whereas our process works with any thermal evaporator and is thus simpler and much more accessible. Nanofabrication on nonplanar surfaces may find applications in fields such as (AFM) tip-enhanced Raman spectroscopy for chemical analysis and lab-on-fiber technology.

Demonstration of a 3D Radar‐Like SERS Sensor Micro‐ and Nanofabricated on an Optical Fiber

“…These approaches offer new exciting possibilities for advanced devices based on optical fi bers. [21][22][23][24] Optical-fi ber based SERS sensing [15][16][17][18][19][20] is one of the main branches in the fi eld of "Lab on Fiber" that attempts to combine the advantages of both SERS and optical fi bers to achieve powerful, fl exible, robust and miniaturized spectroscopic tools for remote and highly sensitive detection of low concentration molecular analytes in various, even harsh environments. Each of these fi elds of application is broad and requires in-depth investigations to tap the full potential of such devices.…”

“…Thus, the concept of "Lab on Fiber" is still in its infancy and the realization of more exquisite photonic structures on optical fi bers may be envisaged. [21][22][23][24] Optical-fi ber based SERS sensing [15][16][17][18][19][20] is one of the main branches in the fi eld of "Lab on Fiber" that attempts to combine the advantages of both SERS and optical fi bers to achieve powerful, fl exible, robust and miniaturized spectroscopic tools for remote and highly sensitive detection of low concentration molecular analytes in various, even harsh environments. As for planar SERS substrates for sensing applications, it is also desirable for optical-fi ber based SERS sensors to be of reliably high sensitivity and to be fabricated by a method offering high reproducibility.…”

Enhanced adhesion of electron beam resist by grafted monolayer poly(methylmethacrylate-co-methacrylic acid) brush

“…We have chosen PS because it is a very versatile and a popular negative resist, offering ultrahigh resolution for low molecular weight, 2 and ultrahigh sensitivity for high molecular weight. 11 As well, it can be thermally developed, 12 coated by thermal evaporation to allow nanofabrication on irregular surfaces such as AFM cantilever and optical fiber, 13 or doped with metal Cr to greatly enhance its etching resistance. 14 Yet its adhesion to the silicon substrate is weak, and a cross-linked polymer sublayer has been previously employed to promote its adhesion.…”

Ice lithography for 3D nanofabrication

“…For EBL on non-flat surfaces, polystyrene resists can be applied by thermal evaporation. For example, EBL has been implemented on an atomic force microscope (AFM) cantilever and optical fibers [9].…”