Patterning of crystalline organic materials by electro-hydrodynamic lithography.

The control of semi-crystalline polymers in thin films and in micrometer-sized patterns is attractive for (opto-)electronic applications. Electro-hydrodynamic lithography (EHL) enables the structure formation of organic crystalline materials on the micrometer length scale while at the same time exerting control over crystal orientation. This gives rise to well-defined micro-patterned arrays of uniaxially aligned polymer crystals. This study explores the interplay of EHL structure formation with crystal alignment and studies the mechanisms that give rise to crystal orientation in EHL-generated structures.

Microsized piston-cylinder pneumatic and hydraulic actuators fabricated by lithography

Future microrobotic applications require actuators that can generate a high actuation force in a limited volume. Up to now, little research has been performed on the development of pneumatic or hydraulic microactuators, although they offer great prospects in achieving high force densities. In addition, large actuation strokes and high actuation speeds can be achieved by these actuators. This paper describes a fabrication process for piston-cylinder pneumatic and hydraulic actuators based on etching techniques, UV-definable polymers, and low-temperature bonding. Prototype actuators with a piston area of 0.15 mm2 have been fabricated in order to validate the production process. These actuators achieve actuation forces of more than 0.1 N and strokes of 750 μm using pressurized air or water as driving fluid. © 2009 IEEE.

Design and characteristion of a hydraulic microactuator fabricated by lithography

To improve the force output of microactuators, this work focuses on actuators driven by pressurized gasses or liquids. Despite their well known ability to generate high actuation forces, hydraulic actuators remain uncommon in microsystems. This is both due to the difficulty of fabricating these microactuators with the existing micromachining processes and to the lack of adequate microseals. This paper describes how to overcome these limitations with a combination of anisotropic micromachining, UV definable polymers and low temperature bonding. The functionality of these actuators is proven by extensive measurements which showed that actuation forces of 0.1 N can be achieved for actuators with an active cross-section of 0.15 mm2. This is an order of magnitude higher than what is reported for classic MEMS actuators of similar size.

Design, fabrication, and characterization of circular Dammann gratings based on grayscale lithography.

We describe the design, fabrication, and experimental demonstration of a circular Dammann grating element generating a point-spread function of two concentric rings with equal intensity. The element was fabricated using grayscale lithography, providing a smooth and accurate phase profile. As a result, we obtained high diffraction efficiency and good uniformity between the two rings.

Fabrication of a Low-Loss SSC Using High-Dose Electron Beam Lithography Exposure With Negative PMMA Resist

A silicon-on-insulator optical fiber-to-waveguide spot-size converter (SSC) using Poly-MethylMethAcrylate (PMMA) is presented for integrated optical circuits. Unlike the conventional use of PMMA as a positive resist, it has been successfully used as a negative resist with high-dose electron exposure for the fabrication of ultrafine silicon wire waveguides. Additionally, this process is able to reduce the side-wall roughness, and substantially depresses the unwanted propagation loss. Exploiting this technology, the authors demonstrated that the SSC can improve coupling efficiency by as much as over 2.5 dB per coupling facet, compared with that of SSC fabricated with PMMA as a positive resist with the same dimension.

Systematic considerations for the patterning of photonic crystal devices by electron beam lithography

Photonic crystal devices with feature sizes of a few hundred nanometers are often fabricated by electron beam lithography. The proximity effect, stitching error and resist profiles have significant influence on the pattern quality, and therefore determine the optical properties of the devices. In this paper, detailed analyses and simple solutions to these problems are presented. The proximity effect is corrected by the introduction of a compensating dose. The influence of the stitching error is alleviated by replacing the original access waveguides with taper-added waveguides, and the taper parameters are also discussed to get the optimal choice. It is demonstrated experimentally that patterns exposed with different doses have almost the same edge-profiles in the resist for the same development time, and that optimized etching conditions can improve the wall angle of the holes in the substrate remarkably. (c) 2006 Elsevier B.V. All rights reserved.

Fabrication of metallic air bridges using multiple-dose electron beam lithography

The techniques of fabricating metallic air bridges using different resists in a one-step electron beam lithography are presented. The exposure process employed a single-layer polymethyl methacrylate (PMMA) or photoresists with either different doses in the span and feet areas or with varying acceleration voltage of the electron beam. The process using photoresists with different doses has produced air bridges more stable than what the PMMA method using various acceleration voltages would achieve. Using this method, air bridges up to 12 mu m long have been fabricated. The length and height of these metallic air bridges vary with the photoresist thickness. (c) 2006 American Institute of Physics.

Nanofabrication of grid-patterned substrate by holographic lithography

The two-dimensional grid patterns on Si(001) in nanometer scale have been fabricated by holographic lithography and reactive ion etching, which can be used as a substrate for positioning Ge islands during self-assembled epitaxy to obtain an ordered Ge quantum dots matrix. By changing the configuration of the holographic lithography and the etching rate and time, we can control the grid period, the shape of the pattern cell, and the orientation of those shapes, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.

Selective and lithography-independent fabrication of 20 nm nano-gap electrodes and nano-channels for nanoelectrofluidics applications

A new method has been developed to selectively fabricate nano-gap electrodes and nano-channels by conventional lithography. Based on a sacrificial spacer process, we have successfully obtained sub-100-nm nano-gap electrodes and nano-channels and further reduced the dimensions to 20 nm by shrinking the sacrificial spacer size. Our method shows good selectivity between nano-gap electrodes and nano-channels due to different sacrificial spacer etch conditions. There is no length limit for the nano-gap electrode and the nano-channel. The method reported in this paper also allows for wafer scale fabrication, high throughput, low cost, and good compatibility with modern semiconductor technology.

Fully lithography independent fabrication of nanogap electrodes for lateral phase-change random access memory application

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Lithography-independent and large scale fabrication of a metal electrode nanogap

A lithography-independent and wafer scale method to fabricate a metal nanogap structure is demon-strated. Polysilicon was first dry etched using photoresist (PR) as the etch mask patterned by photolithography.Then, by depositing conformal SiO_2 on the polysilicon pattern, etching back SiO_2 anisotropically in the perpendic-ular direction and removing the polysilicon with KOH, a sacrificial SiO_2 spacer was obtained. Finally, after metal evaporation and lifting-off of the SiO_2 spacer, an 82 nm metal-gap structure was achieved. The size of the nanogap is not determined by the photolithography, but by the thickness of the SiO_2. The method reported in this paper is compatible with modern semiconductor technology and can be used in mass production.

Fabrication of Silicon Crystal-Facet-Dependent Nanostructures by Electron-Beam Lithography

Silicon crystal-facet-dependent nanostructures have been successfully fabricated on a (100)-oriented silicon-on-insulator wafer using electron-beam lithography and the silicon anisotropic wet etching technique. This technique takes ad-vantage of the large difference in etching properties for different crystallographic planes in alkaline solution. The mini-mum size of the trapezoidal top for those Si nanostructures can be reduced to less than 10nm. Scanning electron microscopy(SEM) and atomic force microscopy (AFM) observations indicate that the etched nanostructures have controllable shapes and smooth surfaces.

An All-E-Beam Lithography Process for the Patterning of 2D Photonic Crystal Waveguide Devices

We present an all-e-beam lithography (EBL) process for the patterning of photonic crystal waveguides.The whole device structures are exposed in two steps. Holes constituting the photonic crystal lattice and defects are first exposed with a small exposure step size (less than 10nm). With the introduction of the additional proximity effect to compensate the original proximity effect, the shape, size, and position of the holes can be well controlled.The second step is the exposure of the access waveguides at a larger step size (about 30nm) to improve the scan speed of the EBL. The influence of write-field stitching error can be alleviated by replacing the original waveguides with tapered waveguides at the joint of adjacent write-fields. It is found experimentally that a higher exposure efficiency is achieved with a larger step size;however,a larger step size requires a higher dose.

Microlenses fabricated by discontinuous dewetting and soft lithography

This letter describes an approach to fabricating microlens arrays with low cost and large area through the combination of discontinuous dewetting and reversible water-ice transition via a soft lithography replica process. Microlenses with different curvature can be tuned by the modulation of the wettability of the substrates. The microlenses fabricated can project clear miniaturized images.