Index-based approaches are a popular method for assessing societal vulnerability to flooding, many of which differ in terms of indicator selection, underlying social data, spatial scale and aggregation methods. They are typically assessed at geographically broad spatial scales to provide a spatial picture of vulnerability for policy and decision-makers. However, aggregation of vulnerability at broad scales also potentially masks the true vulnerability of an area as the underlying data is not spatially refined. This research expands on a previous indicator approach, the Social Flood Vulnerability Index by using geodemographics to facilitate household and postcode level vulnerability assessment to explore the impact of spatial aggregation on vulnerability at national and local levels in Scotland. The results suggest that applying geodemographics to an existing approach increases spatial heterogeneity and has the potential to be adopted as a new dataset to guide indicator selection in future.

Given a realistic set of sub-surface data, the number of plausible geological models that can be constructed can run into the millions or tens of millions. It is therefore impractical for a geologist to examine the entire space of possible models and thereby correctly characterize uncertainty. Commonly applied approaches to this problem use simplifications such as experimental design, parameter sensitivity analysis or Monte Carlo simulation to attempt to reasonably account for input uncertainty while balancing computational expenditure and time. Broadly, this is undertaken by assessing which model inputs (for example porosity or permeability) have the most significant impact on response variables of choice, typically volume based or commercial metrics such as net present value (NPV) or estimated ultimate recovery (EUR). Specific parameters are then perturbed to produce an assumed representative subset (in many cases a low, mid and high case) of the range of possible models (see for example Pyrcz and Deutsch, 2014).

Floods are a significant issue worldwide with over 1 billion people living in areas of potential flood risk. With climate change these risks are anticipated to increase, but there is great uncertainty associated with future projections, which poses challenges to those making decisions on flood management. Climate change projections which explicitly capture climate model parameters uncertainty are available in the United Kingdom; however, their use by practitioners, rather than researchers, has so far been limited. This paper takes an inclusive approach, working with end users, to answer practitioner relevant questions regarding future climate change influence for flood hazards. The method developed demonstrates the findings across Scotland, United Kingdom and investigates (i) the regional impacts to extreme flows and the associated uncertainty, (ii) the changes in extreme peak flows in terms of frequency, and (iii) the physical and hydroclimatic factors controlling these results. The method used industry standard statistical methods, driven by practitioner requirements, and explicitly includes the statistical uncertainty in the climate and extreme value distribution models in extreme flow estimates. Results are analyzed using hierarchical clustering and decision tree analysis, and the subsequent trends are shown to be constrained by different hydrological, climatic, and physical catchment characteristics. Results suggest that there is a high probability that low return period peak flow events would exceed the baseline extreme high return period event by the 2080s, which has significant implications for future‐proofing infrastructure design. This study provides a practical example and outputs resulting from collaboration between research and industry practices.

Nanoimprint lithography is a potentially low-cost, high-resolution patterning technique, but most of the surrounding development work has been directed toward tool designs and processing techniques. There remains a tremendous opportunity and need to develop new materials for specific nanoimprint applications. This article provides an overview of relevant materials-related development work for nanoimprint lithographic applications. Material requirements for nanoimprint patterning for the sub-45-nm integrated-circuit regime are discussed, along with proposed nanoimprint applications such as imprintable dielectrics, conducting polymers, biocompatible materials, and materials for microfluidic devices. Polymers available for thermal nanoimprint processing and photocurable precursors for ultraviolet-assisted nanoimprint lithography are discussed.

Step and flash imprint lithography (SFIL) is low cost, high resolution patterning process and has found its way into a multitude of front end of the line (FEOL) and back end of the line (BEOL) applications. SFIL-R, a reverse tone variant of SFIL, and imprintable dielectrics are examples of such applications, and both require the design of specialized, silicon-based materials. Polyhedral oligomeric silsesquioxane (POSS) liquids were modified through a dual functionalization strategy to introduce photosensitive acrylate and thermally curable benzocyclobutane (BCB) groups to the molecule. The optimal functional group ratio was observed to be 3:5 acrylate to BCB, and the result was an imprintable dielectric with good mechanical properties and minimal post-exposure shrinkage. Thermal gravimetric analysis (TGA) revealed good thermal stability with minimal mass loss under annealing conditions of 400°C for 2 hours. Si-14 was designed to be a non-volatile, etch-resistant planarization layer for SFIL-R application. A polydimethylsiloxane (PDMS) derivative was modified to introduce acrylate functional groups and side branching for photosensitivity and low viscosity, respectively. Characterization of the material showed ideal planarization characteristics - low volatility (0.77 Torr at 25°C), low viscosity (15.1 cP), and minimal post-exposure shrinkage (5.1%).

Step-and-Flash Imprint Lithography (S-FIL) has been extended to provide the capability to pattern two or more levels-such as a metal line and a metal via-with a single template Sacrificial imprint material (SIM) formulations can be tuned to optimize the etch selectivity to specific low-k dielectrics, and thus control topography of dual-damascene interconnect structures. Materials engineering of a directly patternable dielectric (DPD) has created an imprintable polymer with thermal stabilty to 343 degrees C.

The dual damascene process used to generate copper interconnects requires many difficult processing steps. Back End Of Line (BEOL) processing using Step and Flash Imprint Lithography (SFIL) on a directly patternable dielectric material can dramatically reduce the number of processing steps. By using multi-level SFIL rather than photolithography, two levels of interconnect structure (trench and corresponding via) can be patterned simultaneously. In addition, the imprinted material can be a imprintable dielectric precursor rather than a resist, further reducing the total number of steps in the dual damascene process. This paper presents progress towards integrating multi-level SFIL into a copper CMP process flow at ATDF, Inc. in Austin, Texas. Until now, work has focused on multi-level imprint process development. This report focuses on the development of new imprintable dielectric precursors for use with the dual damascene imprint process. SFIL compatible dielectric precursors were synthesized and characterized for integration into the ATDF copper CMP process flow. SFIL requires properties not found in currently available semiconductor dielectrics such as low viscosity and rapid photo-induced polymerization. Inorganic/organic hybrid materials derived from sol-gel chemistry and polyhedral oligomeric silsesquioxane (POSS) structures show promise for this application. The properties of three different dielectric layers are compared. The viability of each material as an interlayer dielectric is discussed and the results of multi-level patterning, metal fill, and polish are shown.

Advanced integrated circuits require eight or more levels of wiring to transmit electrical signal and power among devices and to external circuitry. Each wiring level connects to the levels above and below it through via layers. The dual damascene approach to fabricating these interconnected structures creates a wiring level and a via level simultaneously, thereby reducing the total number of processing steps. However, the dual damascene strategy (of which there are several variations) still requires around 20 process steps per wiring layer. In this work, an approach to damascene processing that is based on step-and-flash imprint lithography (SFIL) is discussed. This imprint damascene process requires fewer than half as many steps as the standard photolithographic dual damascene approach. Through use of a template with two tiers of patterning, a single imprint lithography step can replace two photolithography steps. Further improvements in efficiency are possible if the imprint material is itself a functional dielectric material. This work is a demonstration of the compatibility of imprint lithography (specifically SFIL) with back-end-of-line processing using a dual damascene approach with functional materials.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn Automated Statistical Process Control Study of Inline Mixing Using Spectrophotometric DetectionDavid A. Dickey , Michael D. Dickey , Michael D. Stewart , and C. Grant Willson View Author Information Department of Statistics, North Carolina State University, Raleigh, NC 27695 Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712Cite this: J. Chem. Educ. 2006, 83, 1, 110Publication Date (Web):January 1, 2006Publication History Received3 August 2009Published online1 January 2006Published inissue 1 January 2006https://pubs.acs.org/doi/10.1021/ed083p110https://doi.org/10.1021/ed083p110research-articleACS PublicationsRequest reuse permissionsArticle Views188Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Chemical engineering and industrial chemistry,Mathematical methods,Process control,Quality management,Students Get e-Alerts

Step and flash imprint lithography (SFIL) has made tremendous progress since its initial development at The University of Texas at Austin in the late 1990s. The SFIL process went from laboratory to commercialization in under five years, and the number of technical hurdles that must be cleared before it is recognized as fully competitive with optical or EUV lithography for sub-50-nm patterning is dwindling. Patterning resolution has been demonstrated down to 20 nm, with the limit so far being only the template fabrication process. The SFIL method was developed from the beginning with the precision overlay/alignment requirements of multilevel device fabrication in mind. It was recognized that it would be inherently easier to achieve overlay and alignment accuracy with a constant temperature and low pressure imprinting process, and already tool designers have built on SFIL's advantages to produce tools that are viable for multilayer device fabrication. Early tools have demonstrated better than, 10-nm alignment resolution, and no insurmountable fundamental issues have been identified that would prevent alignment resolution from reaching the tight tolerances required for integrated circuit manufacturing. With any contact printing method, process-generated defects are a concern, but the SFIL process has proven to be surprisingly robust with an inherent self-cleaning mechanism for removing particle contamination. Furthermore, new template surface treatments have been developed that improve mold lifetime and minimize defect generation. SFIL shows promise as a low cost manufacturing tool for a wide variety of semiconductor, microelectromechanical, optoelectronic, microfluidic, and other devices. This work summarizes the state of development of step and flash imprint lithography and discusses its potential as a general nanofabrication tool. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Advanced microprocessors require several (eight or more) levels of wiring to carry signal and power from transistor to transistor and to the outside world. Each wiring level must make connection to the levels above and below it through via/contact layers. The dual damascene approach to fabricating these interconnected structures creates a wiring level and a via level simultaneously, thereby reducing the total number of processing steps. However, the dual damascene strategy (of which there are several variations) still requires around twenty process steps per wiring layer. In this work, an approach to damascene processing that is based on step-and-flash imprint lithography (SFIL) is discussed. This imprint damascene process requires fewer than half as many steps as the standard photolithographic dual damascene approach. By using an imprint template with two levels of patterning, a single imprint lithography step can replace two photolithography steps. Further efficiencies are possible if the imprint resist material is itself a functional dielectric material. This work is a demonstration of the compatibility of imprint lithography (specifically SFIL) with back-end-of-line processing using a dual damascene approach with functional materials.

Computer simulations and direct measurements were carried out to explore the effect of adding base quencher on the line edge roughness (LER) of photoresist images. The effect of variation of the polymer sequence distribution and hydrophilic units was also studied. The variation of surface roughness at different developed film thicknesses was measured by atomic force microscopy (AFM) for each polymer. It was concluded that the variation of dissolution rate (DR) and the distribution of acid and base are important parameters that must be considered in order to solve the LER problem for future lithography generation.

A direct analytical technique for measuring the solution quantum efficiencies of photoacid generators (PAGs) is presented. The technique is based on the nonaqueous potentiometric titration of the photogenerated acid and does not require separate calibrations, or the addition of sensing materials such as dyes or bases. Solutions of PAGs in acetonitrile were irradiated at 248 nm and subsequently titrated with known concentrations of triethanolamine base. The only quantities required for an accurate determination of the quantum efficiency are the incident radiation energy and the titration equivalence point. A mathematical analysis that enables this calculation is derived, and a table with calculated quantum efficiency values for three classes of PAGs having a variety of counterions is presented. The method is simple, accurate, and applicable to any class of PAG molecules.

Acrylates have been used as patterning monomers in step and flash imprint lithography. Vinyl ether formulations have a lower viscosity, faster curing rate, and higher tensile strength than acrylate formulations. However, the lack of commercially available, silicon-containing vinyl ether monomers has required the synthesis of several new vinyl ethers. An ideal monomer has low viscosity and low vapor pressure. The vapor pressure of silicon-containing vinyl ethers was predicted using the Joback-Reid, Lyderson, and Lee-Kesler methods. BVMDSO (1,1,3,3-tetramethyl-1,3-bis(vinyloxymethyl)-disiloxane) has the lowest viscosity of the synthesized silicon-containing vinyl ethers that meet the volatility requirement for a 80 pl dispense volume. The formulation of BVMDSO, CHDVE (cyclohexanedimethanol divinyl ether), and TEGDVE (triethylene glycol divinyl ether) shows good tensile strength and modulus. The formulation of BVMDSO, CHDVE, TEGDVE, and fluorinated acetate can print a 30 nm line because it has a low separation force and high tensile modulus.

The requirement of nanometer dimensional control in photolithographic patterning underlies the future of emerging technologies, including next-generation semiconductors, nanofluids, photonics, and microelectromechanical systems. For chemically amplified resists, dimensional control is mediated by the diffusion and reaction of photogenerated acids within a polymer-based photoresist matrix. The complex nature of the combined processes of reaction and diffusion prohibit the routine measurement of this phenomenon. Using small-angle neutron scattering, we have measured the form of the diffusion–reaction path of a photogenerated acid within a model photoresist matrix with a labeled protection group on the polymer side group. During the deprotection reaction, changes in the scattering form factor result from the shape and form of the deprotected regions. The individual volumes or blobs of reacted material are diffuse, with a fuzzy boundary between the reacted and unreacted regions. The impact of these results on the pattern quality is also discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3063–3069, 2004

A variety of experimental evidence suggests that positive-tone chemically amplified photoresists have an intrinsic bias that might limit resolution during high-volume lithographic processing. If this is true, the implications for the semiconductor industry require careful consideration. The design concept of chemical amplification is based on generation of a chemically stable catalytic species in exposed regions of the photoresist film. The catalytic action of the photoproducts on the photoresist polymer causes a change in the dissolution rate in the irradiated regions of the film. Formation of a stable catalyst species is required for chemical amplification, but it has long been recognized that catalyst migration can produce a difference between the initial distribution of exposure energy and the final distribution of photoproducts. This difference, known as diffusion bias, depends on the photoresist chemistry and processing conditions. Diffusion bias is insensitive to exposure conditions, but it is possible to reduce catalyst migration through changes to resist formulation such as increasing the size of the catalyst molecule or processing conditions such as reducing the post exposure bake temperature. Another common approach to limiting diffusion bias is to incorporate base additives into the photoresist formulation to scavenge diffusing acid catalyst. All of these approaches to reducing catalyst migration generally reduce the catalytic efficiency of each photoproduct and therefore increase the total exposure dose required to pattern the film. Increases in required exposure dosage reduce the throughput of the exposure tools and can reduce the profitability of the manufacturing process. In. this paper we present experimental results that are suggestive of an intrinsic photoresist bias. This diffusion bias sets a minimum resolution limit for chemically amplified resist systems that can be improved at the cost of reduced throughput and productivity.

Progress toward a comprehensive, chemically detailed, mesoscale photoresist simulation with predictive capability is reported. The semiconductor industry has developed a need for mechanistically detailed simulations capable of studying photoresist performance at nanometer dimensions. The nanometer-scale dimensional tolerances on photoresist features are becoming increasingly difficult to meet and expensive to produce in high-volume manufacturing processes. A mesoscale Monte Carlo simulation for processing of positive tone, chemically amplified photoresists has been developed to enable detailed study of photoresist performance as a function of formulation and processing variables. In this model, the molecular components of the photoresist material are included explicitly within a three-dimensional lattice framework. Molecular level models for each processing step have been derived from experimental studies and are implemented in the simulation modules for the several photoresist processing steps. Simulation input variables are fundamental and measurable material properties and processing parameters. Empirical calibrations to expensive lithography experiments are not used. The mesoscale nature of the simulation offers the ability to study the stochastic processes that contribute to resist feature roughness, while the chemical detail included in the models enables investigation of the wide photoresist formulation variable space. This suite of programs provides a unique tool to guide the rational design of new photoresist materials. (C) 2004 The Electrochemical Society.

A mesoscale computer simulation for positive tone chemically amplified resists is reported. The simulation is based upon detailed models of resist function, and the required simulation inputs are fundamental quantities that can be measured independently of lithographic performance. These input parameters include resist formulation variables such as polymer molecular weight, blocking fraction, photoacid generator loading, and activation energy of the deprotection reaction, as well as processing variables such as temperature and duration of bake steps and developer concentration. The simulation can model all major resist processing steps, namely: spincoat and post apply bake, exposure, post exposure bake, aqueous base dissolution, and drying. The general approach involves representing the photoresist film on a three dimensional lattice. Some lattice sites represent acid or solvent molecules and other lattice sites are strung together to form polymer chains. Each lattice cell is considered individually during the simulation, and each behaves in a manner consistent with its chemical identity. The mesoscale nature of the model allows investigation of stochastic effects that lead to line edge roughness, such as shot noise during exposure and the finite size of resist molecules. The model is based upon extensive experimental studies, and has now yielded results that are qualitatively correct for all major lithographic processing steps.