Experiments are presented that investigate the mechanistic cause of multilayer erosion observed from condenser optics exposed to EUV laser-produced plasma (LPP) sources. Using a Xe filament jet source excited with Nd-YAG laser radiation (300 mJ/pulse), measurements were made of material erosion from Au, Mo, Si and C using coated quartz microbalances located 127 mm from the plasma. The observed erosion rates were as follows: Au=99nm/106 shots, Mo= 26nm/106 shots, Si=19nm/106 shots, and C=6nm/106 shots. The relative ratio Au:Mo:Si:C of erosion rates observed experimentally, 16:4:3:1 compares favorably with that predicted from an atomic sputtering model assuming 20 kV Xe ions, 16:6:4:1. The relative agreement indicates that Xe-substrate sputtering is largely responsible for the erosion of Mo/Si multilayers on condenser optics that directly face the plasma. Time-of-flight Faraday cup measurements reveal the emission of high energy Xe ions from the Xe-filament jet plasma. The erosion rate does not depend on the repetition rate of the laser, suggesting a thermal mechanism is not operative. The Xe-filament jet erosion is ~20x that observed from a Xe spray jet. Since the long-lived (millisecond time scale) plasma emanating from these two sources are the same to within ~30%, sputtering from this long-lived plasma can be ruled out as an erosion agent.
A critical issue in the realization of EUV lithography (EUVL) as a production technology is the lifetime of the condenser, the optic in closest proximity to any compact, high-power EUV source. During operation of the Engineering Test Stand (ETS), a full-field, high-power EUVL alpha tool, the silicon/molybdenum multilayer mirrors used as a condenser were eroded by extended exposure to the LPP source. The erosion rate varied considerably, and diagnostic instrumentation on the ETS was not intended to address this issue, so the cause of this erosion was not determined at the time. We present here the results of experiments in which samples of gold, molybdenum, and silicon were exposed to an LPP using a liquid xenon jet as the target. The measured erosion rates suggest a sputtering mechanism. Observations of the plasma environment at the condenser position show the presence of fast ions, which, if they are xenon, have kinetic energies of tens of keV. Such ions would contribute significantly to condenser erosion.
Full-field imaging with a developmental projection optic box (POB 1) was successfully demonstrated in the alpha tool Engineering Test Stand (ETS) last year. Since then, numerous improvements, including laser power for the laser-produced plasma (LPP) source, stages, sensors, and control system have been made. The LPP has been upgraded from the 40 W LPP cluster jet source used for initial demonstration of full-field imaging to a high-power (1500 W) LPP source with a liquid Xe spray jet. Scanned lithography at various laser drive powers of >500 W has been demonstrated with virtually identical lithographic performance.
The Engineering Test Stand (ETS) is an 'alpha-class' Extreme Ultraviolet (EUV) lithography tool designed to demonstrate full-field EUV imaging and provide data required to accelerate production-tool development. The illumination system of the ETS is based on a laser-produced plasma (LPP) source using a recirculating Xe target medium. A Nd:YAG laser focused onto a Xe-gas or liquid target creates a plasma producing 13.4 nm radiation, at the center of the Si/Mo multilayer mirror passband. A condenser system, comprised of multilayer-coated and grazing incidence mirrors, collects the EUV radiation and directs it onto a reflecting reticle. A 1500 W LPP source has been integrated with the ETS and used for lithography. Two Xe spray sources have been evaluated, a cluster jet and a liquid spray jet. The cluster jet Xe source output rapidly degraded from heating of the hardware by the plasma causing the Xe clusters to be too small for efficient conversion. The TRW-designed liquid spray jet operates stably for hours and with tripled conversion efficiency into the condenser optics, producing EUV in the ETS.
The Accident Response Mobile Manipulator System (ARMMS) is a teleoperated emergency response vehicle that deploys two hydraulic manipulators, five cameras, and an array of sensors to the scene of an incident. It is operated from a remote base station that can be situated up to four kilometers away from the site. Recently, a modular telerobot control architecture called SMART was applied to ARMMS to improve the precision, safety, and operability of the manipulators on board. Using SMART, a prototype manipulator control system was developed in a couple of days, and an integrated working system was demonstrated within a couple of months. New capabilities such as camera-frame teleoperation, autonomous tool changeout and dual manipulator control have been incorporated. The final system incorporates twenty-two separate modules and implements seven different behavior modes. This paper describes the integration of SMART into the ARMMS system.
Polarized transmission optical profiles were used to characterize the CdZnTe (CZT) room-temperature radiation detectors. The internal electric field distributions of the CZT detectors under bias were probed by a 952 nm illumination between two crossed Glan-Taylor polarizers. A 16-bit digital charge coupled device (CCD) was employed as an image sensor. The 2-dimensional (2D) images reflecting the internal electrical field intensity changes were obtained utilizing the Pockels electro-optic effect. CZT detectors of crystal sizes of 5 by 5 by 5 mm were investigated under different bias voltages. Uniform and nonuniform internal electric field distributions throughout the detector volumes, under different light illumination conditions, were observed and analyzed. A theoretical model of the semiconductor energy band structure under the bias was established and used to understand the measurement results.
Subpicosecond time-resolved transient grating and transient absorption experiments were
performed in mercuric iodide, a wide bandgap semiconductor. Sub-bandgap excitation in the Urbach tail
induces an index grating which forms in about 2 ps and which exhibits biexponential decay with time
constants 60 ps and 1 .5ns. We ascribe this change in the index of refraction to the formation of defect
states. In addition, coherent Raman excitation of the 1 14 cm1 Aig lattice mode was observed.