Laser plasma source for extreme ultraviolet lithography using a water droplet target

A laser produced extreme ultraviolet (EUV) source based on a water droplet target has been implemented an auxiliary electrode system between the source and the first collector mirror. The auxiliary electrode system creates a repeller electric field, possibly a dc voltage imposed on the mirror that slows down and reverses the trajectories of ions from the source before they impact the collection mirror. The source modified according to the invention was evaluated with respect to the demands of EUV lithography and found to have much extended operational lifetimes. The spectral distribution of the generated radiation as well as the conversion efficiency into line radiation at 13 nm was determined. Long time measurements of the reflectivity of silicon/molybdenum multilayer mirrors for up to from 10.sup.7 to 10.sup.9 shots show the useful influence of the treatment of ions emitted from the source. Several methods of debris reduction were tested and discussed. Surface analysis of the treate

The Potential for Augmented Reality to Bring Balance betweenthe Ease of Pedestrian Navigation and the Acquisition of Spatial Knowledge

Being completely lost in an unfamiliar environment can be inconvenient, stressful and, at times, even dangerous. Maps are the traditional tools used for guidance but many people find maps difficult to use. In recent years, new tools like outdoor Augmented Reality (AR) have become available which allow virtual navigation cues to be directly overlaid on the real world, potentially overcoming the limitations of maps. However, it has been hypothesized that lower effort invested in processing navigation guidance may lead to diminished spatial knowledge (SK) thereby making users of such navigation tools far more vulnerable to getting lost should the tools fail for any reason. This thesis explores the research question of how AR and maps compare as tools for pedestrian navigation guidance as well as for SK acquisition and if there is a potential for AR tools be developed that would balance the two. We present a series of studies to better understand the consequences of using AR in a pedestrian navigation tool. The first two studies compared time-on-task performance and user preferences for AR and Map navigation interfaces on an outdoor navigation task. The results were not aligned with expectations, which led us to build a controlled testing environment for comparing AR and map navigation. Using this simulated setting, our third study verified the assumption that AR can indeed result in more efficient navigation performance and it supported the hypothesis that this would come at the cost of weaker SK. In our fourth study, we used a dual task design to compare the relative cognitive resources required by map and AR interfaces. The quantitative data collected indicated that users could potentially accept additional workload designed to improve SK without incurring significantly more effort. Our fifth and final study explored an interface with additional AR cues that could potentially balance navigation guidance with SK acquisition. The contributions of this thesis include insights into performance issues relating to AR, a classification of user types based on navigation tool usage behavior, a testbed for simulating perfect AR tracking in a virtual setting, objective measures for determining route knowledge, the capacity that pedestrian navigation tool users may have for performing additional tasks, and guidelines that would be helpful in the design of pedestrian navigation tools

Debris-Free, Droplet Laser Plasma Sources In The Euv And Soft X-Ray Ranges

Previous work with a 100-kHz water droplet system generated 13-nm and 116-nm line emissions from a Li-like O2 plasma produced by 10-ns duration, 10-Hz Nd:YAG laser pulses at approximately 1012 W/cm2. A detailed quantitative study of this source was performed with a 100-Hz laser. The radiation efficiency and the long-term operation were characterized, and results show that the droplet laser plasma source comes close to satisfying all the near-term needs of extreme ultraviolet lithography (EUVL). In particular, an overall conversion efficiency of laser light to 13-nm emission within the required spectral bandwidth in excess of 0.6%, comparable to any other existing source at this wavelength

Narrowband laser produced extreme ultraviolet sources adapted to silicon/molybdenum multilayer optics

The extreme ultraviolet radiation emitted from a plasma generated by a pulsed Nd:yttrium aluminum garnet laser is investigated around 13 nm wavelength for several low Z elements (lithium, nitrogen, oxygen, fluorine). A narrowband EUV source can be designed by using the narrowband line emission of low Z elements in combination with the broadband reflection characteristic of silicon/molybdenum (Si/Mo) multilayer mirrors.Experimental results are discussed within a theoretical modell which allows a deduction of an optimization criterion for a maximum conversion efficiency.The Lyman-alpha line of hydrogenlike lithium ions fulfills the demands for high intense, free-standing narrowband emission, at the long wavelength side of the silicon absorption L edge

Laser-produced lithium plasma as a narrow-band extended ultraviolet radiation source for photoelectron spectroscopy

Extended ultraviolet (EUV) emission characteristics of a laser-produced lithium plasma are determined with regard to the requirements of x-ray photoelectron spectroscopy. The main features of interest are spectral distribution, photon flux, bandwidth, source size, and emission duration. Laser-produced lithium plasmas are characterized as emitters of intense narrow-band EUV radiation. It can be estimated that the lithium Lyman-alpha line emission in combination with an ellipsoidal silicon/molybdenum multilayer mirror is a suitable EUV source for an x-ray photoelectron spectroscopy microscope with a 50-meV energy resolution and a 10-mu m lateral resolution