Tatiana Burtseva

Radiation-induced synergistic effects of athermal and thermal mechanisms on erosion and surface evolution of advanced electrode and condenser optics materials

In extreme ultraviolet lithography (EUVL) environments transient plasma dynamics dictate conditions for particle/surface interactions. A critical challenge facing EUVL development is optic component lifetime both in gas-discharge produced plasmas (GDPP) and laser-produced plasmas (LPP) devices. Optic components are exposed to impingent species, impurities (H,C,O,N) and debris leading to their degradation and consequently limiting 13.5 nm light reflection intensity. Experiments in the PRIME (Particles and Radiation Interaction with Matter Experiments) facility at the Argonne National Laboratory study the synergy between radiation-induced athermal and thermal mechanisms that influence the behavior of EUVL materials (electrodes and condenser optics) under irradiation conditions including: incident particle energy (50 eV - 5 keV), angle-of-incidence (near-normal to oblique), incident flux (1011-1017 ions/cm2/s), surface coatings (impurity: C,O or capping layers: Ru, W), and surface temperature (100 - 1000 C). Results of electrode and optical component interaction with singly-charged inert gases (Xe) are presented. Critical issues under study include: radiation enhanced diffusion, radiation induced segregation, preferential sputtering, collisional mixing, surface segregation, surface amorphization, thermal diffusion and thermal spike evolution. Experiments in PRIME will be complemented with atomistic modeling to study how these mechanisms modify surfaces and how these mechanisms can work synergistically to introduce solutions to enhance component lifetime of electrode and condenser optic materials.

Study of brittle destruction and erosion mechanisms of carbon-based materials during plasma instabilities

Abstract Erosion damage due to plasma instabilities such as hard disruptions, edge-localized modes, and vertical displacement events remains a major obstacle to successful realization of the tokamak-reactor concept. As a result of these plasma instabilities, intense plasma energy that is deposited during short periods can cause severe erosion, structural damage, and surface modifications of the plasma-facing materials. Experimental work is being carried out at the high-power VIKA-93 plasma-gun facility in the Efremov Institute, Russia. Interesting results were obtained during preliminary heating of the samples (to 1200°C) and use of maximum plasma gun parameters, i.e., E in =30 MJ/m 2 , τ=360 μ s. In all samples, a large increase in weight loss (up to 80%) was observed during plasma bombardment when preheating was used. Scanning electron microscope investigations have demonstrated a considerable evolution of surface recrystallization processes, especially for preheated CFC materials. Significant differences among various carbon materials are found for specimens with and without preliminary heating.

Experimental investigation of materials damage induced by hot Xe plasma in EUV lithography devices

Small plasma-pinch devices operating at a gas mixture of Xe and He with a frequency of 5-10 kHz and pulsed energy of 1-100 J are very promising sources of EUV radiation for lithography. A key issue in design of EUV sources is erosion of the pinch facing material under the hot Xe plasma and electric currents. Material erosion limits the lifetime of device components and thereby reduces the economical feasibility of these devices. Selection of high-resistant materials is critically important for development of future commercial EUV sources. Experiments are being carried out at plasma gun facilities in well-diagnosed and controlled conditions. The plasma gun is applied as a source of pulsed energetic Xe plasma capable of generating Xe plasma streams with a velocity 4 106 - 4 107 cm/s and duration of the plasma pulse 10-40 microseconds. Xenon plasma stream velocity of 4-10 106 is sufficient to obtain plasma temperture of 30-50 eV, i.e., typical for pinch EUV devices. The formation of plasma could makes possible to study erosion and surface damage induced by particles and radiation of Xe plasma at these temperatures. Initial results of material testing by Xe plasma particles are presented. Samples of copper and tungsten, which are currently being used as electrode materials in pinch devices, were exposed to multiple irradiations by pulsed energetic Xe plasma. Material erosion and surface damages are analyzed. Future results will permit identification of the erosion mechanisms induced by Xe plasma particles, plasma radiation, and electric currents and their contributions to the net material erosion. The experimental data are being used for validation of numerical models developed in the HEIGHTS-EUV package for evaluation of material erosion in EUV sources.

Candidate plasma-facing materials for EUV lithography source components

Material selection and lifetime issues for extreme ultraviolet (EUV) lithography are of critical importance to the success of this technology for commercial applications. This paper reviews current trends in production and use of plasma-facing electrodes, insulators, and wall materials for EUV type sources. Ideal candidate materials should be able to: withstand high thermal shock from the short pulsed plasma; withstand high thermal loads without structural failure; reduce debris generation during discharge; and be machined accurately. We reviewed the literature on current and proposed fusion plasma-facing materials as well as current experience with plasma gun and other simulation devices. Both fusion and EUV source materials involve issues of surface erosion by particle sputtering and heat-induced evaporation/melting. These materials are either bare structural materials or surface coatings. EUV materials can be divided into four categories: wall, electrode, optical, and insulator materials. For electric discharge sources, all four types are required, whereas laser-produced plasma EUV sources do not require electrode and insulator materials. Several types of candidate alloy and other materials and methods of manufacture are recommended for each component of EUV lithography light sources.

Spent Fuel Sabotage Aerosol Test Program: FY 2005-06 Testing and Aerosol Data Summary

This multinational, multi-phase spent fuel sabotage test program is quantifying the aerosol particles produced when the products of a high energy density device (HEDD) interact with and explosively particulate test rodlets that contain pellets of either surrogate materials or actual spent fuel. This program has been underway for several years. This program provides source-term data that are relevant to some sabotage scenarios in relation to spent fuel transport and storage casks, and associated risk assessments. This document focuses on an updated description of the test program and test components for all work and plans made, or revised, primarily during FY 2005 and about the first two-thirds of FY 2006. It also serves as a program status report as of the end of May 2006. We provide details on the significant findings on aerosol results and observations from the recently completed Phase 2 surrogate material tests using cerium oxide ceramic pellets in test rodlets plus non-radioactive fission product dopants. Results include: respirable fractions produced; amounts, nuclide content, and produced particle size distributions and morphology; status on determination of the spent fuel ratio, SFR (the ratio of respirable particles from real spent fuel/respirables from surrogate spent fuel, measured under closely matched test conditions, in a contained test chamber); and, measurements of enhanced volatile fission product species sorption onto respirable particles. We discuss progress and results for the first three, recently performed Phase 3 tests using depleted uranium oxide, DUO{sub 2}, test rodlets. We will also review the status of preparations and the final Phase 4 tests in this program, using short rodlets containing actual spent fuel from U.S. PWR reactors, with both high- and lower-burnup fuel. These data plus testing results and design are tailored to support and guide, follow-on computer modeling of aerosol dispersal hazards and radiological consequence assessments. This spent fuel sabotage--aerosol test program, performed primarily at Sandia National Laboratories, with support provided by both the U.S. Department of Energy and the Nuclear Regulatory Commission, had significant inputs from, and is strongly supported and coordinated by both the U.S. and international program participants in Germany, France, and the U.K., as part of the international Working Group for Sabotage Concerns of Transport and Storage Casks, WGSTSC.

Candidate plasma-facing materials for extreme ultraviolet lithography source components

Material selection and lifetime issues for extreme ultraviolet (EUV) lithography are of critical importance to the success of this technology for commercial applications. This work reviews current trends in production and use of plasma-facing electrodes, insulators, and wall materials for EUV-type sources. Ideal candidate materials should be able to: withstand high thermal shock from the short pulsed plasma; withstand high thermal loads without structural failure; reduce debris generation during discharge; and be machined accurately. We reviewed the literature on current and proposed fusion plasma-facing materials as well as current experience with plasma gun and other simulation devices. Both fusion and EUV source materials involve issues of surface erosion by particle sputtering and heat-induced evaporation/melting. These materials are either bare structural materials or surface coatings. EUV materials can be divided into four categories: wall, electrode, optical, and insulator materials. For electric discharge sources, all four types are required, whereas laser-produced plasma EUV sources do not require electrode and insulator materials. Several types of candidate alloy and other materials and methods of manufacture are recommended for each component of EUV lithography light sources.