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.
A novel scanning probe lithography scheme is introduced involving the field-induced deposition of etch resistant material generated from common organic solvents such as n-octane, toluene, ethyl alcohol, and dioxane in the tip/sample gap region of a liquid cell. An NH(4)F/H(2)O(2)/H(2)O etchant transfers these structures into 7 nm tall posts in a negative-tone fashion, indicating that an etch resistant, likely carbon-based material is produced by field-induced decomposition of the solvent. This is in sharp contrast to the positive tone images that result from a similar process involving water as the gap electrolyte followed by a similar fluorine-based etching.
An alpha,alpha-dimethyl-3,5-dimethoxybenzyloxycarbonyl (DDZ)-protected amine monolayer can be selectively deprotected by the application of a voltage bias from a conducting AFM tip to afford localized nanoscale patterns that can be visualized by self-assembly of dendritic molecular objects with terminal carboxylic acid groups and different aspect ratios.
A new scanning probe lithography scheme based on a self-assembled dendrimer monolayer on thin Ti films is presented. The method relies
on the versatility of the functionalized dendrimer molecules to effectively function as etch resists by forming a densely packed self-assembled
protective monolayer on a Ti film. Patterning of the Ti surface is accomplished using an AFM tip either as an ultra sharp scribe or as an
electrical field point source to modify the monolayer. This, coupled to carefully selected etching conditions, allows the use of the dendrimer
monolayers as both negative and positive tone resists. Facile formation of TiO2 features ca. 25 nm wide and 12 nm tall on silicon oxide and
ca. 50 nm wide gaps in a thin Ti film can easily be achieved. The dendrimer resist approach can be further developed in order to improve the
minimum feature size to the single dendrimer molecule level.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.