For the past four decades, Moore's law has been the most important benchmark in microelectronic circuits. Continuous improvement in lithographic technology has key enabler for growth in transistor density. In recent times, the wavelength of the light source has not kept its pace in scaling. Consequently, modern devices have feature sizes that are smaller than the wavelength of light source used currently in lithography. Printability in sub-wavelength lithography is one of the contemporary research issues. Some of the printability issues arise from optical defocus, lens aberration, wafer tilting, isotropic etching and resist thickness variation. Many of such sources lead to line width variation in today's layouts. In this work we propose to simulate such lithographic variation and estimate their impact on current devices and interconnects. We also propose to model such effects and aim to provide measures at the design level to mitigate these problems. Variations arising out of lithography process also impact yield and performance. We plan to study the impact of sub-wavelength lithography on yield and provide solutions for its measure, and directed pattern developement and testing.

Optical Proximity Correction (OPC) is a part of a family of techniques called Resolution Enhancement Techniques (RET). These techniques are employed to increase the resolution of a lithography system and improve the quality of the printed pattern. The fidelity of the pattern is degraded due to the disparity between the wavelength of light used in optical lithography, and the required size of printed features. In order to improve the aerial image, the mask is modified. This process is called OPC, OPC is an iterative process where a mask shape is modified to decrease the disparity between the required and printed shapes. After each modification the chip is simulated again to quantify the effect of the change in the mask. Thus, lithography simulation is an integral part of OPC and a fast lithography simulator will definitely decrease the time required to perform OPC on an entire chip. A lithography simulator which uses wavelets to compute the aerial image has previously been developed. In this thesis I extensively modify this simulator in order to execute it on a Graphics Processing Unit (GPU). This leads to a lithography simulator that is considerably faster than other lithography simulators and when used in OPC will lead to drastically decreased runtimes. The other work presented in the proposal is a fast OPC tool which allows us to perform OPC on circuits faster than other tools. We further focus our attention on metrics like runtime, edge placement error and shot size and present schemes to improve these metrics.

Optical lithography is an indispensible step in the process flow of Design for Manufacturability (DFM). Optical lithography simulation is a compute intensive task and simulation performance, or lack thereof can be a determining factor in time to market. Thus, the efficiency of lithography simulation is of paramount importance. Coherent decomposition is a popular simulation technique for aerial imaging simulation. In this thesis, we propose an approximate simulation technique based on the 2D wavelet transform and use a number of optimization methods to further improve polygon edge detection. Results show that the proposed method suffers from an average error of less than 6% when compared with the coherent decomposition method. The benefits of the proposed method are (i) > 20X increase in performance and more importantly (ii) it allows very large circuits to be simulated while some commercial tools are severely capacity limited and cannot even simulate a circuit as small as ISCAS-85 benchmark C17. Approximate simulation is quite attractive for layout optimization where it may be used in a loop and may even be acceptable for final layout verification.

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Bottom-up self-assembly can be used to create structures with sub-20 nm feature sizes or materials with advanced electrical properties. Here I demonstrate processes to enable such self-assembling systems including block copolymers and DNA origami, to be integrated into nanoelectronic devices. Additionally, I present a method which utilizes the high stability and electrical conductivity of graphene, which is a material formed using a bottom-up growth process, to create archival data storage devices. Specifically, I show a technique using block copolymer micelle lithography to fabricate arrays of 5 nm gold nanoparticles, which are chemically modified with a single-stranded DNA molecule and used to chemically attach DNA origami to a surface. Next, I demonstrate a method using electron beam lithography to control location of nanoparticles templated by block copolymer micelles, which can be used to enable precise position of DNA origami on a surface. To allow fabrication of conductive structures from a DNA origami template, I show a method using site-specific attachment of gold nanoparticles to and a subsequent metallization step to form continuous nanowires. Next, I demonstrate a long-term data storage method using nanoscale graphene fuses. Top-down electron beam lithography was used to pattern atomically thin sheets of graphene into nanofuses. To program the fuses, graphene is oxidized as the temperature of the fuse is raised via joule heating under a sufficiently high applied voltage. Finally, I investigate the effect of the fuse geometry and the electrical and thermal properties of the fuse material on the programming requirements of nanoscale fuses. Programming voltages and expected fuse temperatures obtained from finite element analysis simulations and a simple analytical model were compared with fuses fabricated from tellurium, a tellurium alloy, and tungsten.

Graphene features a unique combination of exceptional properties and has emerged as one of the most promising nanomaterials for a variety of applications. The ability to structurally modify graphene with nanoscale precision enables the properties to be further extended. By introducing nanopores in the graphene lattice, nanoporous graphene can be used in high-performance electronic devices or as selective membranes for efficient molecular filtering. Although methods for deterministic nanopatterning already exists, key for the implementation of nanoporous graphene is the development of a scalable and customisable method of patterning graphene that does not require any lithographic mask that is introducing defects. In this project, a novel approach using a nanoporous mask and a broad beam of 20 keV Ar ions has been investigated. Masks with 60-600 nm circular pores have been fabricated, and by irradiating suspended graphene membranes grown by chemical vapor deposition (CVD) through the mask, nanoporous graphene has been deterministically generated. The masks are fabricated using electron beam lithography, and the pattern is highly customisable regarding pore size, pore distribution and areal coverage. In addition to perforating the graphene, the ion beam is also observed to significantly reduce the level of contamination on the graphene membrane. The proposed mechanism is the combination of electronic  sputtering of surface contaminants and the random diffusion that follows, with a low nuclear sputtering yield and to-site pinning of contaminants. An extension of this study could include a more comprehensive characterization of the nanoporous graphene obtained as well as further studies on the dependency of beam parameters.

Metasurfaces are arrays of subwavelength meta-atoms that shape waves in a compact and planar form factor. During recent years, metasurfaces have gained a lot of attention due to their compact form factor, easy integration with other devices, multi functionality and straightforward fabrication using conventional CMOS techniques. To provide and evaluate an efficient metasurface, an optimized design, high resolution fabrication and accurate measurement is required. Analysis and design of metasurfaces require accurate methods for modeling their interactions with waves. Conventional modeling techniques assume that metasurfaces are locally periodic structures excited by plane waves, restricting their applicability to gradually varying metasurfaces that are illuminated with plane waves. In this work, we will first provide a novel technique that enables the development of accurate and general models for 1D metasurfaces. This approach can be easily extended to 2D metasurfaces. Due to the remarkable importance of accurate characterization of metasurfaces, we will provide a rigorous method to characterize 1D metasurfaces. Finally, we will provide an accurate approach to fabricate and characterize 2D metasrufaces.

Extreme ultraviolet lithography(EUVL) is being developed worldwide as the next generation technology to be inserted in ~ 2009 for the mass production of IC chips with feature sizes <35 nm. One major challenge to its implementation is the development of a 13.5 nm EUV source of radiation that meets the requirements of current roadmap designs of the source of illumination in commercial EUVL scanners. The light source must be debris-free, in a free-space environment with the imaging EUV optics that must provide sufficient, narrow spectral band EUV power to print 100 wafers/hr. To meet this need, extensive studies on emission from a laser plasma source utilizing tin-doped droplet target was conducted. Presented in this work, are the many optical techniques such as spectroscopy, radiometry, and imaging, that were employed to characterize and optimize emission from the laser plasma source State of the art EUV spectrographs were employed to observe the source's spectrum under various laser irradiation conditions. Comparing the experimental spectra to those from theory, has allowed the determination of the Sn ion stages responsible for emitting into the useful EUV bandwidth. Experimental results were compared to spectral simulations obtained using Collisional-Radiative Equilibrium (CRE) model, as well. Moreover, extensive measurements surveying source emission from 2 nm to 30 nm, which is the region of the electromagnetic spectrum defined as EUV, was accomplished. Absolutely calibrated metrology was employed with the Flying Circus instrument from which the source's conversion efficiency (CE)--from laser to the useful EUV energy--was characterized under various laser irradiation conditions. Hydrodynamic simulations of the plasma expansion together with the CRE model predicted the condition at which optimum conversion could be attained. The condition was demonstrated experimentally, with the highest CE to be slightly above 2%, which is the highest value among all EUV source contenders. In addition to laser intensity, the CE was found to depend on the laser wavelength. For better understanding, this observation is compared to results from simulations. Through a novel approach in imaging, the size of the plasma was characterized by recording images of the plasma within a narrow band, around 13.5 nm. The size, approximately 100 ìm, is safely within the etendue limit set by the optical elements in the EUV scanner. Finally, the notion of irradiating the target with multiple laser beams was explored for the possibility of improving the source's conversion efficiency.

ABSTRACT The Characterization and Analysis of In-vitro and Elevated Temperature Repassivation of Ti-6Al-4V via AFM Techniques Aaron J Guerrero Research in the corrosion of orthopaedic implants is a growing research field where implants have been known to show adverse effects in patients who have encountered the unfortunate dissolution of their implants due to corrosion. Once corrosion begins within the body, many adverse biological reactions can occur such as late on-set infections resulting in severe health complications. The focus of this research is specifically related to the problem of late on-set infections caused by localized corrosion of orthopaedic implants. In medical implants today the most common form of corrosion protection is the implant materials’ ability to impede corrosion through the formation of an oxide layer. This ability to passivate and quickly repassivate a uniform and stable oxide layer dictates how well an orthopaedic implant will survive in-vivo. To better understand the repassivation of orthopaedic implant materials, research was conducted at the nanoscale via atomic force microscopy (AFM) on anodized Ti-6Al-4V. Using an Asylum Research MFP-3DTM AFM and AFM lithography techniques, nano scratch test methods were created simulating in-vitro surface repassivation conditions. These nano-scratches were created and characterized in Hank’s balanced saline solution (HBSS) with the AFM in contact mode at 1 and 3 Hz scan rates. HBSS was used as it best simulates the pH, ionic compounds, and constituents that are commonly found in blood. It was discovered that the AFM was successful in creating in-vitro repassivation conditions. However, the ability of the AFM to successfully observe repassivation was limited by the speed of the AFM scanner. Using the same AFM scratch methods, experiments were performed in air and in-vitro and characterized with AFM conductance measurements at 20, 37, & 45 °C. The conductance measurements were taken using an AFM conductance module and allowed for observations of decreasing current measurements over time. The current data was then used to calculate current density, resistivity, conductance, and electron mobility and compared to similar experiments This study highlights the ability of the AFM to create and characterize repassivation and shows promise in developing further capability to use the AFM for characterization of repassivation on the nanoscale. Keywords: Orthopaedics, late on-set infections, repassivation, AFM, lithography, conductive measurements.

This thesis discusses the full scope of a project exploring the physics of hierarchical clusters of interacting nanomagnets. These clusters may be relevant for novel applications such as multilevel data storage devices. The work can be grouped into three main activities: micromagnetic simulation, fabrication and characterization of proof-ofconcept prototype devices, and efforts to scale down the structures by creating the hierarchical structures with the aid of diblock copolymer self assembly. Theoretical micromagnetic studies and simulations based on Landau-Lifshitz- Gilbert (LLG) equation were conducted on nanoscale single domain magnetic entities. For the simulated nanomagnet clusters with perpendicular uniaxial anisotropy, the simulation showed the switching field distributions, the stability of the magnetostatic states with distinctive total cluster perpendicular moments, and the stepwise magnetic switching curves. For simulated nanomagnet clusters with in-plane shape anisotropy, the simulation showed the stepwise switching behaviors governed by thermal agitation and cluster configurations. Proof-of-concept cluster devices with three interacting Co nanomagnets were fabricated by e-beam lithography (EBL) and pulse-reverse electrochemical deposition (PRECD). EBL patterning on a suspended 100 nm SiN membrane showed improved lateral lithography resolution to 30 nm. The Co nanomagnets deposited using the PRECD method showed perpendicular anisotropy. The switching experiments with external applied fields were able to switch the Co nanomagnets through the four magnetostatic states with distinctive total perpendicular cluster magnetization, and proved the feasibility of multilevel data storage devices based on the cluster concept. Shrinking the structures size was experimented by the aid of diblock copolymer. Thick poly(styrene)-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer templates aligned with external electrical field were used to fabricate long Ni/Fe magnetic nanowire array, dominant shape anisotropy was observed and compared to the result from previously reported Co nanowire array with strong crystalline anisotropy. Guided diblock copolymer poly(styrene)-b-poly(4-vinyl pyridine) (PS-b-P4VP) self assembly was performed to generate clustered microdomains. Direct e-beam patterning on PS-b-P4VP thin film showed precise and arbitrary patterning on the lateral ordering of the self assembly. Graphoepitaxy of self-assembled PS-b-P4VP copolymers on isolated SiN triangular plateaus successfully resulted in the exact clusters of three microdomains. Theoretical consideration and system modeling based on the micellar configuration of the microdomains were done, and the distribution of the cluster’s size and number of elements were explained qualitatively.