The joint specification projected in-band EUV power requirements at the intermediate focus will rise beyond 185W 2%-
bw to maintain the necessary 80-100WPH throughput for economic viability. New improvements in photon efficiency
and mask illumination are needed to reduce reflections and power demand, as well as improving source spatial
In 2006, Starfire presented a novel approach to the EUV source-optic architecture using a high-brightness light source
array for direct integration within the illumination optical system. Spatial uniformity and Kohler illumination across the
entrance pupil is achieved by dividing the incident light into discrete bundles on a fly's eye mirror. These light bundles
form a secondary source image plane that is projected onto the pupil of the projection optics. This configuration allows
electronic adjustment of partial coherence and depth of focus for improved lithographic contrast and resolving
capability. By distributing total EUV power across discrete units, thermal and particle loadings become manageable
without the need for exotic materials or cooling schemes and sources of contaminating debris are reduced.
Experimental data from a 5×5 xenon-fed microdischarge source array is presented, demonstrating repetition rate and
source addressability for illumination patterning and grayscaling capability. In addition, experimental data from xenon-based
sources will be presented with a suite of plasma and optical diagnostic instruments, including conversion
efficiency, spectral purity and debris generation. Projections for scaling to HVM conditions will also be presented.
The University of Illinois at Urbana-Champaign (UIUC) and several national laboratories are collaborating on an SEMATECH effort to characterize xenon plasma exposure effects on EUV condenser optics. A series of mirror samples provided by SEMATECH were exposed for 10M shots in an Xtreme Technologies XTS 13-35 commercial EUV discharge plasma source at UIUC and 5M at the high-power TRW laser plasma source at Sandia National Laboratories. Results for both pre and post-exposure material characterization are presented, for samples exposed in both facilities. Surface analysis performed by the Center for Microanalysis of Materials at UIUC investigates mirror degradation mechanisms by measuring changes in surface roughness, texture, and grain sizes as well as analysis of implantation of energetic Xe ions, Xe diffusion, and mixing of multilayers. Materials characterization on samples removed after varying exposure times in the XTS source, together with in-situ EUV reflectivity measurements, identify the onset of different degradation mechanisms within each sample over 1M-100M shots. Results for DPP-exposed samples for 10 million shots in our XCEED (Xtreme Commercial EUV Exposure Device) experiment showed, in general, that samples were eroded and the surfaces were roughened with little change to the texture. AFM results showed an increase in roughness by a factor of 2-5 times, with two exceptions. This was confirmed by x-ray reflectivity (XRR) data, which showed similar roughening characteristics and also confirmed the smoothening of two samples. SEM pictures showed that erosion was from 4-47 nm, depending on the sample material and angle of incidence for debris ions. Finally, microanalysis of the exposed samples indicated that electrode material was implanted at varying depths in the samples. The erosion mechanism is explored using a spherical sector energy analyzer (ESA) to measure ion species and their energy spectra. Energy spectra for ions derived from various chamber sources are measured as a function of the Argon flow rate and angle from the centerline of the pinch. Results show creation of high energy ions (up to E = 13 keV). Species noted include ions of Xe, the buffer gas, and various electrode materials. The bulk of fast ion ejection from the pinch includes Xe+ which maximizes at ~8 keV followed by Xe2+ which maximizes at ~5 keV. Data from samples analysis and ESA measurements combined indicate mechanism and effect for debris-optic interactions and detail the effectiveness of the current debris mitigation schemes.