Modeling of engineering objects with complex heterogeneous material structure at nanoscale level has emerged as an important research problem. In this research, we are interested in multiscale modeling and analysis of mechanical properties of the polymer structures created in the Step and Flash Imprint Lithography (SFIL) process. SFIL is a novel imprint lithography process designed to transfer circuit patterns for fabricating microchips in low-pressure and room-temperature environments. Since the smallest features in SFIL are only a few molecules across, approximating them as a continuum is not completely accurate. Previous research in this subject has dealt with coupling discrete models with continuum hyperelasticity models. The modeling of the post-polymerization step in SFIL involves computing solutions of large nonlinear energy minimization problems with fast spatial variation in material properties. An equilibrium configuration is found by minimizing the energy of this heterogeneous polymeric lattice. Numerical solution of such a molecular statics base model, which is assumed to describe the microstructure completely, is computationally very expensive. This is due to the problem size – on the order of millions of degrees of freedom (DOFs). Rapid variation in material properties, ill-conditioning, nonlinearity, and non-convexity make this problem even more challenging to solve. We devise a method for efficient approximation of the solution. Combining numerical homogenization, adaptive finite element meshes, and goaloriented error estimation, we develop a black-box method for efficient solution of problems with multiple spatial scales. The purpose of this homogenization method is to reduce the number of DOFs, find locally optimal effective material properties, and do goal-oriented mesh refinement. In addition, it smoothes the energy landscape. Traditionally, a finite element mesh is designed after obtaining material properties in different regions. The mesh has to resolve material discontinuities and rapid variations. In our approach, however, we generate a sequence of coarse meshes (possibly 1-irregular), and homogenize material properties on each coarse mesh element using a locally posed constrained convex quadratic optimization problem. This upscaling is done using Moore-Penrose pseudoinverse of the linearized fine-scale element stiffness matrices, and a material independent interpolation operator. This requires solution of a continuous-time Lyapunov equation on each element. Using the adjoint solution, we compute local error estimates in the quantity of interest. The error estimates also drive the automatic mesh adaptivity algorithm. The results show that this method uses orders of magnitude fewer degrees of freedom to give fast and approximate solutions of the original fine-scale problem. Critical to the computational speed of local homogenization is computing Moore-Penrose pseudoinverse of rank-deficient matrices without using Singular Value Decomposition. To this end, we use four algorithms, each having different desirable features. The algorithms are based on Tikhonov regularization, sparse QR factorization, a priori knowledge of the null-space of the matrix, and iterative methods based on proper splittings of matrices. These algorithms can exploit sparsity and thus are fast. Although the homogenization method is designed with a specific molecular statics problem in mind, it is a general method applicable for problems with a given fine mesh that sufficiently resolves the fine-scale material properties. We verify the method using a conductivity problem in 2-D, with chessboard like thermal conductivity pattern, which has a known homogenized conductivity. We analyze other aspects of the homogenization method, for example the choice of norm in which we measure local error, optimum coarse mesh element size for homogenizing SFIL lattices, and the effect of the method chosen for computing the pseudoinverse. / text

The semiconductor industry is continually challenged to maintain the trend identified in 1965 by Gordon Moore of increasing the density of transistors on an integrated circuit. These advances have been achieved by increasing the resolution that can be printed with photolithography, traditionally by decreasing the exposure wavelength. Decreasing the exposure wavelength from 193 nm, the current state of the art, presents significant technical challenges. To circumvent these challenges, resolution can be increased by enabling increases in numerical aperture (without changing the exposure wavelength), using immersion lithography. In immersion lithography, the air gap between the photoresist-coated wafer and lens is replaced with a high refractive index fluid. Immersion lithography has been demonstrated with water as the immersion fluid. With water immersion lithography at 193 nm, the maximum resolution that can be printed can be decreased from 65 nm to 45 nm. To enable further resolution increases, immersion fluids with a higher index than water are needed. The requirements for next generation high index fluids are: an index of refraction higher than water, high transparency, and physical properties similar to water. A variety of methods to identify a high index fluid were completed. First, the optical properties of aqueous solutions of metal cations with varying anions were tested. A series of linear, cyclic, and polycyclic alkanes were also studied, since saturated systems have electronic transitions at wavelengths less than 200 nm, to provide the necessary transparency at 193 nm. Large alkane groups were also incorporated into either the cation or anion of a salt to develop an aqueous solution with the optical properties of a saturated hydrocarbon. In addition to these empirical surveys, a modeling approach was used to develop “designer” absorbance spectra that would correspond to fluids with a high index and low absorbance at 193 nm. Additionally, in Appendix D, the results of an electrochemical study of the diffusion coefficient of ferrocene methanol in poly(ethylene glycol) diacrylate hydrogels of varying molecular weight and water content will be presented. The results of these mass transport studies can be used to qualitatively understand the mass transport characteristics of additional species in the hydrogel. / text

The aim of this project was to improve the imaging performance of planar superlenses for evanescent near-field lithography. An experimental investigation of the performance of superlenses with reduced surface roughness was proposed. Such an investigation poses significant requirements in regards to process control in thin film deposition of silver onto dielectric substrates. Thin film deposition of silver films, onto silicon dioxide substrates, achieved films with root mean square surface roughness as low as 0.8 nm. While these experiments provided good understanding of the deposition process, significant variability of the surface roughness parameter remained an issue. The diffculty of achieving consistent control of surface roughness led to a finite element method simulation study where this parameter could be readily controlled. An improved understanding of how surface roughness affects superlens imaging performance was obtained from the results of this investigation. Furthermore, it was shown that in order to conduct an experimental investigation to verify the simulation results, it would be necessary to improve the imaging capability of super-resolution lithography protocols to achieve 3σ line edge roughness (LER) of <20 nm. Resist-scheme optimisation was identied as an important factor in this regard. Thus, a novel calixarene-based photoresist was formulated and characterised. The resist demonstrated superior imaging capabilities through interference lithography and evanescent near-field optical lithography, capable of resolving 250-nm period half-pitch line gratings with 3σ LER below 10 nm. The development of this novel photoresist will enable future lithographical investigations to be conducted with improved resolution and imaging fidelity.

Non-mechanical variable lenses are important for creating compact imaging devices. Various methods employing dielectrically actuated lenses, membrane lenses, and liquid crystal lenses were previously proposed [1-4]. In This dissertation the design, fabrication, and characterization of innovative flat tunable-focus liquid crystal diffractive lenses (LCDL) are presented. LCDL employ binary Fresnel zone electrodes fabricated on Indium-Tin-Oxide using conventional micro-photolithography. The light phase can be adjusted by varying the effective refractive index of a nematic liquid crystal sandwiched between the electrodes and a reference substrate. Using a proper voltage distribution across various electrodes the focal length can be changed between several discrete values. Electrodes are shunted such that the correct phase retardation step sequence is achieved. If the number of 2πzone boundaries is increased by a factor of m the focal length is changed from f to f/m based on the digitized Fresnel zone equation: f = rm²/2mλ, where r(m) is mth zone radius, and λ is the wavelength. The chromatic aberration of the diffractive lens is addressed and corrected by adding a variable fluidic lens. These LCDL operate at very low voltage levels (±2.5V ac input), exhibit fast switching times (20-150 ms), can have large apertures (>10 mm), and small form factor, and are robust and insensitive to vibrations, gravity, and capillary effects that limit membrane and dielectrically actuated lenses. Several tests were performed on the LCDL including diffraction efficiency measurement, switching dynamics, and hybrid imaging with a refractive lens. Negative focal lengths are achieved by adjusting the voltages across electrodes. Using these lenses in combination, magnification can be changed and zoom lenses can be formed. These characteristics make LCDL a good candidate for a variety of applications including auto-focus and zoom lenses in compact imaging devices such as camera phones. A business plan centered on this technology was developed as part of the requirements for the minor in entrepreneurship from the Eller College of Management. An industrial analysis is presented in this study that involves product development, marketing, and financial analyses (Appendix I).

In this thesis, we demonstrate in-situ scanning electron microscopy techniques for both electron beam lithography (EBL) and in-situ one dimensional nano materials electrical characterization. A precise voltage contrast image positioning for in-situ EBL to integrate nanowires into suspended structures for nanoswitch fabrication has been developed. The in-situ EBL eliminates the stage movement error and field stitching error by preventing any movements of the stage during the nanolithography process; hence, a high precision laser stage and alignment marks on the substrate are not needed, which simplifies the traditional EBL process. The ZnO piezoelectronics is also studied using nano-manipulators in scanning electron microscope. Methods to improve the contact have been demonstrated and the contacts between probe tips and the nanowires are found to have significant impact on the measurement results.

Arthur Ashkin's Nobel Prize-winning single-beam gradient force optical tweezers have revolutionized research in many fields of science. The invention has enabled various atomic and single molecular studies, proving to be an essential tool for observing and understanding nature at the nanoscale. This thesis showcases the uniqueness of single-beam gradient force traps and the advances necessary to overcome the limitations inherent in conventional techniques of optical trapping. With decreasing particle sizes, the power required for a stable trap increases and could potentially damage a particle. This is a significant limitation for studying biomolecules using conventional optical traps. Plasmonic nanoaperture optical trapping using double-nanohole apertures is introduced as a solution to overcoming these limitations. Achievements in double-nanohole optical trapping made possible by the pioneering work of Gordon et. al are highlighted as well. This thesis focuses on the advances in nanoaperture fabrication methods and improvements to experimental techniques adopted in single molecular optical trapping studies. The technique of colloidal lithography is discussed as a cost-effective high-throughput alternative method for nanofabrication. The limitation in using this technique for producing double-nanohole apertures with feature sizes essential for optical trapping is analyzed. Improvements to enable tuning of aperture diameter and cusp separation is one of the main achievements of the work detailed in this thesis. Furthermore, the thesis explains the modified fabrication process tailor-made for designing double-nanohole apertures optimized for optical trapping. Transmission characterization of various apertures fabricated using colloidal lithography is carried out experimentally and estimated by computational electrodynamics simulations using the finite-difference time-domain (FDTD) method. Optical trapping with double-nanohole apertures fabricated using colloidal lithography is demonstrated with distinct results revealing trapping of a single polystyrene molecule, a rubisco enzyme and a bovine serum albumin (BSA) protein. / Graduate

O uso de magnetismo em sensores, transdutores e, principalmente, em mídias de gravação magnética, atinge uma escala de investimento no mercado global de bilhões de dólares anualmente. Essas aplicações tecnologicas, atualmente, apontam para usos do magnetismo na escala nanoscópica, por meio da miniaturização de dispositivos magnéticos sensores e transdutores; em gravação magnética através da nanoestruturação das unidades básicas de armazenamento; ou, ainda, na medicina pelo uso de nanopartículas magnéticas como carregadores de drogas medicinais ou como elementos aquecedores por meio da radiação em radiofrequência. Neste trabalho, adotamos uma abordagem top-down. Partimos de objetos magnéticos microscópicos e buscamos progressivamente reduzir a sua escala espacial visando atingir a escala nanoscópica. Produzindo objetos com formato regular e simples, como quadrados, discos e triângulos produzidos por litografia de feixe de elétrons e método lift-off, a partir de filmes finos produzidos por Magnetron Sputtering. Utilizando como elemento de estudo Metais de Transição (MT) e Terras Raras (TR). A estequiometria e espessura dos filmes finos de Tb-Fe foram obtidas com análise de RBS. Já a análise magnética dos filmes finos de Tb-Fe foram obtidas por técnicas de VSM e SQUID. O que possibilitou averiguar que as amostra com a proporção de Tb variando entre 22% e 36% possuem uma anisotropia magnética perpendicular bem definida e possuem um ordenamento sperimagnético. Através do microscópio de força magnética observamos a formação de domínios magnéticos do tipo bolha irregular nos filmes finos de Tb-Fe. Utilizando o microscópio eletrônico de varredura e o SNOM-MO foi possível analisar a morfologia dos micro-objetos produzidos. Os resultados mostram uma eficácia na preparação de estruturas com dimensões maiores que 2 µm, com altura de aproximadamente 50 nm. Fazendo-se necessário um estudo mais preciso para obtenção de amostra com dimensões abaixo desta dimensão. / The use of magnetism in sensors, transducers and, mainy, in magnetic recordable media reaches a total investment of billions of dollars annually in the markets worldwide. These applications in technology are currently being focused toward the uses of magnetism in the nanoscopic scale, by shrinking the magnetic sensor devices and transducers. Also, in magnetic recordings by the nanostructuration of basic storage units or - going even further - in the use of nanomagnetic particles in Medicine such as drug delivery or heating elements by radiofrequency radiation. In this paper, we take a \"top-down\" approach. We start with microscopic magnetic objects and seek progressively reduce its spatial scale in order to reach the nanoscale. Producing objects with regular and simple format, such as squares, triangles and discs produced by electron beam lithography and lift-off method, The thin films were based on transition metal and rare earth elements. The thickness and stoichiometry of thin films of Tb-Fe were meadured with RBS analysis. The analysis of the Tb-Fe magnetic thin films were obtained by techniques VSM and SQUID. The sample with the ratio of Tb ranging between 22% and 36% have a well-defined perpendicular magnetic anisotropy and have a sperimagnetic behavior. Through the magnetic force microscopy we observed the formation of magnetic domain structure of the \"irregular bubble\" type. Using scanning electron microscope and the SNOM-MO was possible to analyze the morphology of the produced micro-objects. The results show that efficiency in the preparation of structures with dimensions larger than 2 microns, and a height of approximately 50 nm. This result exposes the need for a more investigation in order to produce samples with smaller dimension.

Litografia óptica é o processo pelo qual os padrões desenhados pelos projetistas de circuitos integrados são transferidos para o wafer através de ondas de luz. Com a miniaturização dos componentes, aumenta cada vez mais a discrepância entre os padrões projetados e o que é realmente impresso. Tal fato ocorre porque as dimensões dos padrões são menores do que o comprimento de onda utilizado para imprimi-los. Desta forma, é imprescindível que se saiba ou se tenha uma aproximação do que será impresso antes da fabricação dos circuitos para eliminar possíveis defeitos, através da utilização de técnicas de melhoramento de resolução. Essa aproximação é obtida através de simuladores de litografia óptica, que possuem o grande desafio de obter uma aproximação em um tempo viável. Sendo assim, neste trabalho apresentamos o problema de litografia óptica e seu embasamento matemático, bem como técnicas para implementar um simulador litográfico de forma eficiente. Tais técnicas foram utilizadas para o desenvolvimento do simulador Lithux. E, também apresentamos brevemente, técnicas de melhoramento de resolução, onde muitas utilizam simuladores de litografia para reproduzir sua eficiência. / Optical Lithography is the process whereby the patterns designed by the integrated circuit designers are transferred to the wafer by light waves. With the miniaturization of components, the gap between the projected patterns and what is actually printed is steadily increasing as the pattern dimensions are now smaller than the wavelength used to print them. Therefore, in this work we present the problem of optical lithography and its mathematical foundations, as well as techniques to efficiently implement a lithographic simulator. These techniques were used to develop the Lithux simulator. We also briefly present techniques for resolution enhancement, where many of them use lithographic simulators to simulate their efficiency. Thus, it is essential to know or to have an approximation of what will be printed before the circuit manufacturing to eliminate potential defects through the use of resolution enhancement techniques. This approximation is obtained by optical lithography simulators that have the challenge of getting this approximation in a practicable time.

No description available.

This thesis describes two lithographic techniques that may be used to introduce black and white lithography to beginning art students. Aluminum plate and paper lithography are two relatively low cost and safe lithographic methods suitable for schools with limited budgets and limited space. It is recommended that the instructor interested in teaching the two processes described in this thesis have some previous experience in lithography.