Tungsten nanostructure formation in a magnetron sputtering device

Fuzzy tungsten is a phenomena that could potentially occur in future fusion reactors. There are three conditions for fuzz to form, the existence of He ions impinging on a tungsten sample for a sufficient amount of time, that these ions be of sufficient energy, and that the surface temperature of the tungsten is hot enough. These conditions will likely be fulfilled in ITER, the future flagship fusion reactor. Therefore efforts to understand and characterise the fuzz formation are of importance. A thorough literature review has been provided, bringing together for the first time works from over 100 papers on the area. The history of its discovery is explained and the characteristics of the structure are detailed. The potential for fuzz to occur in ITER is shown, and positive and negative aspects of fuzz for fusion operation are discussed. The current accepted growth mechanisms are explained and a brief summary of the current work on simulating the phenomena is given. Fuzz appearing on other metals is introduced, and evidence of creating fuzz in a tokamak is shown. Methods for removing fuzz are presented should it be deemed necessary to do so in ITER. Results are compiled from many fuzz samples created in the literature spanning four orders of magnitude of fluence. This provided the foundation for a collaboration with the UC San Diego, and lab time at their facilities. Several samples were created to complement the dataset. The compilation provides new insights into the growth equation surrounding fuzz formation. A new addition to the equation is introduced in the form of an incubation fluence, a minimum fluence required before fuzz can develop. The growth model is expanded to fuzz grown in erosive regimes, and a new equation is proposed that encompasses the competition between growth and erosion, giving good predictions for the resulting equilibrium thickness. A new method for creating fuzz has been developed in a cheap and simple way. Conventional methods involve using large scale expensive devices, only available in a select few places worldwide. Magnetrons are apparent in many laboratories around the world and a technique for making fuzz in them has been developed. The three parameters controlling fuzz formation have been studied in the magnetron by making samples at many different conditions. The results provide new insight into early fuzz formation, providing results in a fluence range often over-looked. A cross-over fluence is noted from pre-fuzz to fully formed fuzz, overlapping with the predicted incubation fluence. The results differ slightly from fuzz created in other devices at similar fluence. The most probable cause is due to the unique existence of deposition of metallic particles in a magnetron incident on the samples during the growth of fuzz

Removal of tin from exterme ultraviolet collector optics by an in-situ hydrogen plasma

Throughout the 1980s and 1990s, as the semiconductor industry upheld Moore’s Law and continuously shrank device feature sizes, the wavelength of the lithography source remained at or below the resolution limit of the minimum feature size. Since 2001, however, the light source has been the 193nm ArF excimer laser. While the industry has managed to keep up with Moore’s Law, shrinking feature sizes without shrinking the lithographic wavelength has required extra innovations and steps that increase fabrication time, cost, and error. These innovations include immersion lithography and double patterning. Currently, the industry is at the 14 nm technology node. Thus, the minimum feature size is an order of magnitude below the exposure wavelength. For the 10 nm node, triple and quadruple patterning have been proposed, causing potentially even more cost, fabrication time, and error. Such a trend cannot continue indefinitely in an economic fashion, and it is desirable to decrease the wavelength of the lithography sources. Thus, much research has been invested in extreme ultraviolet lithography (EUVL), which uses 13.5 nm light. While much progress has been made in recent years, some challenges must still be solved in order to yield a throughput high enough for EUVL to be commercially viable for high-volume manufacturing (HVM). One of these problems is collector contamination. Due to the 92 eV energy of a 13.5 nm photon, EUV light must be made by a plasma, rather than by a laser. Specifically, the industrially-favored EUV source topology is to irradiate a droplet of molten Sn with a laser, creating a dense, hot laser-produced plasma (LPP) and ionizing the Sn to (on average) the +10 state. Additionally, no materials are known to easily transmit EUV. All EUV light must be collected by a collector optic mirror, which cannot be guarded by a window. The plasmas used in EUV lithography sources expel Sn ions and neutrals, which degrade the quality of collector optics. The mitigation of this debris is one of the main problems facing potential manufacturers of EUV sources. which can damage the collector optic in three ways: sputtering, implantation, and deposition. The first two damage processes are irreversible and are caused by the high energies (1-10 keV) of the ion debris. Debris mitigation methods have largely managed to reduce this problem by using collisions with H2 buffer gas to slow down the energetic ions. However, deposition can take place at all ion and neutral energies, and no mitigation method can deterministically deflect all neutrals away from the collector. Thus, deposition still takes place, lowering the collector reflectivity and increasing the time needed to deliver enough EUV power to pattern a wafer. Additionally, even once EUV reaches HVM insertion, source power will need to be continually increased as feature sizes continue to shrink; this increase in source power may potentially come at a cost of increased debris. Thus, debris mitigation solutions that work for the initial generation of commercial EUVL systems may not be adequate for future generations. An in-situ technology to clean collector optics without source downtime is required. which will require an in-situ technology to clean collector optics. The novel cleaning solution described in this work is to create the radicals directly on the collector surface by using the collector itself to drive a capacitively-coupled hydrogen plasma. This allows for radical creation at the desired location without requiring any delivery system and without requiring any source downtime. Additionally, the plasma provides energetic radicals that aid in the etching process. This work will focus on two areas. First, it will focus on experimental collector cleaning and EUV reflectivity restoration. Second, it will focus on developing an understanding of the fundamental processes governing Sn removal. It will be shown that this plasma technique can clean an entire collector optic and restore EUV reflectivity to MLMs without damaging them. Additionally, it will be shown that, within the parameter space explored, the limiting factor in Sn etching is not hydrogen radical flux or SnH4 decomposition but ion energy flux. This will be backed up by experimental measurements, as well as a plasma chemistry model of the radical density and a 3D model of SnH4 transport and redeposition

Academic Year 2019-2020 Faculty Excellence Showcase, AFIT Graduate School of Engineering & Management

An excerpt from the Dean\u27s Message: There is no place like the Air Force Institute of Technology (AFIT). There is no academic group like AFIT’s Graduate School of Engineering and Management. Although we run an educational institution similar to many other institutions of higher learning, we are different and unique because of our defense-focused graduate-research-based academic programs. Our programs are designed to be relevant and responsive to national defense needs. Our programs are aligned with the prevailing priorities of the US Air Force and the US Department of Defense. Our faculty team has the requisite critical mass of service-tested faculty members. The unique composition of pure civilian faculty, military faculty, and service-retired civilian faculty makes AFIT truly unique, unlike any other academic institution anywhere

Faculty Publications and Creative Works 1997

One of the ways we recognize our faculty at the University of New Mexico is through this annual publication which highlights our faculty\u27s scholarly and creative activities and achievements and serves as a compendium of UNM faculty efforts during the 1997 calendar year. Faculty Publications and Creative Works strives to illustrate the depth and breadth of research activities performed throughout our University\u27s laboratories, studios and classrooms. We believe that the communication of individual research is a significant method of sharing concepts and thoughts and ultimately inspiring the birth of new of ideas. In support of this, UNM faculty during 1997 produced over 2,770 works, including 2,398 scholarly papers and articles, 72 books, 63 book chapters, 82 reviews, 151 creative works and 4 patents. We are proud of the accomplishments of our faculty which are in part reflected in this book, which illustrates the diversity of intellectual pursuits in support of research and education at the University of New Mexico. Nasir Ahmed Interim Associate Provost for Research and Dean of Graduate Studie

Renewable Energy

Renewable Energy is energy generated from natural resources - such as sunlight, wind, rain, tides and geothermal heat - which are naturally replenished. In 2008, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood burning. Hydroelectricity was the next largest renewable source, providing 3% (15% of global electricity generation), followed by solar hot water/heating, which contributed with 1.3%. Modern technologies, such as geothermal energy, wind power, solar power, and ocean energy together provided some 0.8% of final energy consumption. The book provides a forum for dissemination and exchange of up - to - date scientific information on theoretical, generic and applied areas of knowledge. The topics deal with new devices and circuits for energy systems, photovoltaic and solar thermal, wind energy systems, tidal and wave energy, fuel cell systems, bio energy and geo-energy, sustainable energy resources and systems, energy storage systems, energy market management and economics, off-grid isolated energy systems, energy in transportation systems, energy resources for portable electronics, intelligent energy power transmission, distribution and inter - connectors, energy efficient utilization, environmental issues, energy harvesting, nanotechnology in energy, policy issues on renewable energy, building design, power electronics in energy conversion, new materials for energy resources, and RF and magnetic field energy devices