Dual exposure glass layer suspended structures: A simplified fabrication process for suspended nanostructures on planar substrates

Abstract

We have developed and demonstrated here a simplified flexible fabrication process for glass nanomechanical systems. This process uses a single layer of spin on glass (SOG) material with two negative tone electron beam exposures at two different exposure energies to define the suspended and support structures, respectively. After development the SOG can be converted into glass. The process is additive and can be applied to any flat substrate. We have fabricated a variety of glass nanomechanical oscillators and measured their mechanical resonances using a mechanical piezoelectric driving force and optical interferometric detection. Suspended structures were fabricated with thickness of less than 50 nm and lateral dimensions of less than 100 nm supported anywhere from 150 to 800 nm above the substrate. Resonance frequencies for glass wires with both ends fixed (cross section 110 nm×180 nm) and lengths of 4–9 μm range from 7 to 30 MHz, with quality (Q) factors of over 1000. Annealing the structures in an oxygen ambient roughly doubles both the frequencies and the Q factors.

Nanomechanical resonant structures in nanocrystalline diamond

“…To date, NEMS have been fabricated and reported, in Si, 3 Si x N y , 4 SiC, 5 AlN, 6 and spin-on glass. 7 In this work, we report on nanomechanical resonant structures fabricated in nanocrystalline diamond. For technological purposes, diamond may be one of the most desirable materials for many NEMS applications because it is chemically very resistant, has a high hardness and thermal conductivity.…”

Three dimensional HSQ structures formed using multiple low energy electron beam lithography

“…Tanenbum et al demonstrated suspended HSQ structures using a dual exposure technique [6]. They used the shallow penetration of low energy electrons to define thin HSQ wires suspended between two large supports.…”

“…However, the standard development of 60 seconds in AZ300MIF (2.38% tetra-methyl ammonium hydroxide) originally used to produce less closely packed single layered structures lacked the contrast necessary for multilayered structures. A number of development strategies were tested to increase the contrast including increasing the strength of developer and the post development bake suggested by Tanenbum et al [6]. The post development bake worked the best for our structures.…”

Three-dimensional nanofabrication using hydrogen silsesquioxane/poly(methylmethacrylate) bilayer resists

“…Methods for fabricating such 3D nanostructures using electron-beam lithography (EBL) include consecutive overlay exposures 4,5 or low-and high-electron energy exposures. 6,7,8 However, these approaches require alignment markers and accurate alignment routines for each additional layer. 3D nanostructures have also been fabricated using grayscale lithography, 9 but in this approach, the feature size was limited to several hundred nanometers.…”