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We have finished the construction of an automated tool for step and flash imprint lithography. The tool was constructed to allow defect studies by making multiple imprints on a 200 mm wafer. The imprint templates for this study were treated with a low surface energy, self-assembled monolayer to ensure selective release at the template-etch barrier interface. This surface treatment is very durable and survives repeated imprints and multiple aggressive physical and chemical cleanings. The imprint and release forces were measured for a number of successive imprints, and did not change significantly. The process appears to be ''self-cleaning.'' Contamination on the template is entrained in the polymerizing liquid, and the number of defects is reduced with repeated imprints.

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Submicron patterning of 1 in. diameter curved surfaces with a 46 mm radius of curvature has been demonstrated with step and flash imprint lithography ͑SFIL͒ using templates patterned by ion beam proximity printing ͑IBP͒. Concave and convex spherical quartz templates were coated with 700-nm-thick poly͑methylmethacrylate͒ ͑PMMA͒ and patterned by step-and-repeat IBP. The developed resist features were etched into the quartz template and the remaining PMMA stripped. During SFIL, a low viscosity, photopolymerizable formulation containing organosilicon precursors was introduced into the gap between the etched template and a substrate coated with an organic transfer layer and exposed to ultraviolet illumination. The smallest features on the templates were faithfully replicated in the silylated layer.

This article addresses the issue of enhancing mobility of actively actuated vehicles by the use of optimal force distribution, and by actively controlling the location of the center of mass of the vehicle body. Force distribution in actively actuated vehicles is an underspecified problem, and optimal force distribution leads to improved contact conditions. Actively actuated vehicles also possess the ability to vary their configuration. This capability can be used to locate the center of mass of the system to further enhance mobility by providing sufficient traction, and ensuring vehicle stability, during difficult vehicle maneuvers. In this work, the general idea of control of the location of the center of mass, followed by optimal force distribution, is addressed first. This is followed by an application of these ideas to Gofor, a simple actively actuated wheeled micro‐rover system, that has been designed and fabricated at the Jet Propulsion Laboratory. An algorithm to achieve desired traction and stability has been developed. Simulation studies were performed to investigate negotiation of a vertical surface. It was found that one set of wheels readily climbed the vertical surface with the use of active mass and force distribution. This is a significant improvement over traditional wheeled vehicle systems. © 1994 John Wiley & Sons, Inc.

Step and flash imprint lithography ͑SFIL͒ is an alternative approach to high-resolution patterning based on a bilayer imprint scheme. SFIL utilizes the in situ photopolymerization of an oxygen etch resistant monomer solution in the topography of a template to replicate the template pattern on a substrate. The SFIL replication process can be affected significantly by the densification associated with polymerization and by the mechanical properties of the cured film. The densities of cured photopolymers were determined as a function of pendant group volume. The elastic moduli of several photopolymer samples were calculated based on a Hertzian fit to force-distance data generated by atomic force microscopy. The current SFIL photopolymer formulation undergoes a 9.3% ͑v/v͒ densification. The elastic modulus of the SFIL photopolymer is 4 MPa. The densification and the elastic modulus of the photopolymer layer can be tailored from 4% to 16%, and from 2 to 30 MPa, respectively, by changing the structure of the photopolymer precursors and their formulation. The complex interaction among densification, mechanical properties ͑elastic modulus and Poisson's ratio͒ and aspect ratio ͑height:width͒ was studied by finite element modeling. The effect of these parameters on linewidth, sidewall angle, and image placement was modeled. The results indicate that the majority of densification occurs by shrinkage in the direction normal to the substrate surface and that Poisson's ratio plays a critical role in defining the shape of the replicated features. Over the range of material properties that were determined experimentally, volumetric contraction of the photopolymer is not predicted to adversely affect either pattern placement or sidewall angle.

Step and flash imprint lithography (SFIL) is a technique that has the potential to replace photolithography for patterning resist with sub-100 nm features. SFIL is a low cost, high throughput alternative to conventional photolithography for high-resolution patterning. It is a molding process in which the topography of a template defines the patterns created on a substrate. The ultimate resolution of replication by imprint lithography is unknown but, to date, it has only been limited by the size of the structures that can be created on the template. It is entirely possible to faithfully replicate structures with minimum features of a few hundred angströms. SFIL utilizes a low-viscosity, photosensitive silylated solution that exhibits high etch contrast with respect to organic films in O2 reactive ion etching. In this article we describe the SFIL process, the development of a multilayer etch scheme that produces 6:1 aspect ratio features with 60 nm linewidths, a method for patterning high-aspect-ratio features over topography, and a metal lift-off process. A micropolarizer array consisting of orthogonal 100 nm titanium lines and spaces fabricated using this metal lift-off technique is reported.

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