Optical properties, including refractive index, photoabsorption coefficient, and film thickness, were derived with a
specular extreme ultraviolet reflectivity (SEUVR) method at 13.5 nm using a newly built ultrahigh-vacuum reflectometer.
Light at 13.5 nm was delivered from the 08A1BM-LSGM beamline at the National Synchrotron Radiation Research
Center in Taiwan. Samples of thin-film polymethylmethacrylate (PMMA), round-robin resist (RRR), and underlayer
materials were investigated. We observed an evolution in the reflectivity curve of most samples, which was ascribed
mainly to a loss of thickness in the film caused by photoabsorption followed by an ablation effect. The thickness-loss
rates of PMMA and RRR were (0.32±0.15) and (0.12±0.02) nm mJ-1 cm2, respectively, whereas the outgassing rate of
RRR, scaled to a 0.4 W cm-2 power density, was estimated as 1.3×1015 molecules cm-2 s-1. The loss of thickness was
further proven by examining the thickness profile of overexposed samples with a profilometer. From these results, we
have established a satisfactory correlation between the thin-film thickness losses with a structural metric, [σabs/doublebond
equivalent per carbon atom]. The reflectivity curve stopped changing when the sample was overexposed. EUV
photochemical reaction mechanisms were proposed, including outgassing by first-order exposure kinetics from the
surface, which corresponded approximately to the linear ablation rate, and a slower diffusion process for outgassing from
underneath the surface, which was observed for the overexposed sample as the stop of changes in the thickness.
The lens heating (LH) induced focus drift of the ASML i-line Step & Scan was measured at five NA/Sigma settings: three ASML default and two TSMC production settings. The new LH scaling constants at three ASML settings, when multiplied by a dose-matching factor for production, agreed well with the default constants. Experimental results at NAI11 of 0.21 - 0.228 indicate that the LH induced focus drift is NA dependent, and the extent is NA = 0.4A ~ 0.5B>0.63 - 0.65. At the TSMC production settings of NA = 0.4A and 0.5B, the focus drift is approximately 20% greater than those predicted by the ASML LH algorithm. This study applies the new set of scaling constants for the LH focus correction. Long-term focus stability can be maintained within three standard deviations of less than 70nm, for all i-line Step & Scans in the manufacturing environment of one TSMC Fab.
Element-specific magnetic hysteresis measurements on heteromagnetic materials have been achieved by using circularly polarized soft-x-rays. Dramatically different Fe and Co hysteresis curves of Fe/Cu/Co trilayers were obtained by recording the magnetic circular dichroism at their respective L3 white lines as a function of applied magnetic field. The data resolve the complicated hysteresis curves, observed by conventional magnetometry, and determine the individual magnetic moments for the Fe and Co layers. The data show a two-step-like hysteresis loop for all three elements, suggesting that the magnetic properties near the interfaces are very different from those away from the interfaces. The Mn layer was found to be ferromagnetic and aligned with the magnetic direction of Fe and Co. These measurements demonstrate a new application of circularly polarized soft-x-rays in the investigation of magnetic systems.
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