Optics lifetime

Optics lifetime refers to the length of time a given optics can be used within the exposure environment before it has to be replaced or repaired so as to maintain a specified level of the element s reflectivity and, consequently, wafer throughput. 

Condenser optics have short lifetimes their optics specifications are less stringent than those for the projection optics. The condenser optical components are considered consumable and are replaced on a regular basis. In contrast, projection optics have extremely tight specifications and are difficult and time consuming to fabricate and to align. 

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The noble gases (Table 2.6) are uniform in their inability to bind a positron. The stability of the system of a positron and an excited helium atom in its metastable 23S state is interesting. This state has an optical lifetime of about 20 ns. The excited electron in a 2s-orbital is far enough from the nucleus to attract and bind a positron. Similar states of other atoms must be common. 

Under EUV photon irradiation in the presence of oxygen or oxidizing agents, the surfaces of EUV optics and reticles are easily oxidized, leading to reflectivity loss of such surfaces. Oxides strongly absorb EUV radiation, and a small increase in oxide film thickness ( 1.5 nm) can decrease EUV multilayer mirror reflectivity by up to 1.6% (absolute). Because oxidation is difficult to remove, even small amounts of oxidation can negatively affect the EUV optics lifetime. The oxidation of silicon-capped EUV multilayer reflectors has been reported to show similar trends as those observed for carbon deposition. In particular, the rate of reflectivity loss due to oxidation of EUV mirrors has been observed to increase with the partial pressure of water in the optics environment, as well as with the EUV radiation intensity (see Eig. 14.16). " ... 

Mertens B, Weiss M, Meiling H et al (2004) Progress in EUV optics lifetime expectations. Micromech Micromeng 73 16-22... 

In glass-ceramics, Ln " " ions are in a fluoride environment, with phonons of much lower energy than in an oxide or oxyfluoride environment. Table 9.1 summarizes the phonon energy cut-off for the different fluoride compounds. For comparison, the phonon energy cut-off in oxides is between 1100 and 1400cm [57]. In a low phonon energy environment, fast nonradiative de-excitations are less likely, inducing an increase of the optical lifetime. 

Especially with LTG GaAs, materials became available that were nearly ideal for time-resolved THz spectroscopy. Due to the low growth temperature and the slight As excess incorporated, clusters are fonned which act as recombination sites for the excited carriers, leading to lifetimes of <250 fs [45], With such recombination lifetunes, THz radiators such as dipole anteimae or log-periodic spirals placed onto optoelectronic substrates and pumped with ultrafast lasers can be used to generate sub-picosecond pulses with optical bandwidths of 2-4 THz. Moreover, coherent sub-picosecond detection is possible, which enables both... 

Many of the fiindamental physical and chemical processes at surfaces and interfaces occur on extremely fast time scales. For example, atomic and molecular motions take place on time scales as short as 100 fs, while surface electronic states may have lifetimes as short as 10 fs. With the dramatic recent advances in laser tecluiology, however, such time scales have become increasingly accessible. Surface nonlinear optics provides an attractive approach to capture such events directly in the time domain. Some examples of application of the method include probing the dynamics of melting on the time scale of phonon vibrations [82], photoisomerization of molecules [88], molecular dynamics of adsorbates [89, 90], interfacial solvent dynamics [91], transient band-flattening in semiconductors [92] and laser-induced desorption [93]. A review article discussing such time-resolved studies in metals can be found in... 

The vast majority of single-molecule optical experiments employ one-photon excited spontaneous fluorescence as the spectroscopic observable because of its relative simplicity and inlierently high sensitivity. Many molecules fluoresce with quantum yields near unity, and spontaneous fluorescence lifetimes for chromophores with large oscillator strengths are a few nanoseconds, implying that with a sufficiently intense excitation source a single... 

Chemical reactions can be studied at the single-molecule level by measuring the fluorescence lifetime of an excited state that can undergo reaction in competition with fluorescence. Reactions involving electron transfer (section C3.2) are among the most accessible via such teclmiques, and are particularly attractive candidates for study as a means of testing relationships between charge-transfer optical spectra and electron-transfer rates. If the physical parameters that detennine the reaction probability, such as overlap between the donor and acceptor orbitals. 

Ambrose W P, Goodwin P M, Martin J C and Keller R A 1994 Alterations of single-molecule fluorescence lifetimes in near-field optical microscopy Science 265 364-7... 

In additions to improvements in Si, a variety of devices based on compound semiconductors can be expected. Blue lasers witli high brightness and long operating lifetimes already exist in tlie laboratory. LEDs are likely to be used for all lighting purjDoses. The bandwidtli of optical communications will continue to increase witli ever faster semiconductor lasers. 

Wlrile tire Bms fonnula can be used to locate tire spectral position of tire excitonic state, tliere is no equivalent a priori description of the spectral widtli of tliis state. These bandwidtlis have been attributed to a combination of effects, including inlromogeneous broadening arising from size dispersion, optical dephasing from exciton-surface and exciton-phonon scattering, and fast lifetimes resulting from surface localization 1167, 168, 170, 1711. Due to tire complex nature of tliese line shapes, tliere have been few quantitative calculations of absorjDtion spectra. This situation is in contrast witli tliat of metal nanoparticles, where a more quantitative level of prediction is possible. 

Natural linewidths are broadened by several mechanisms. Those effective in the gas phase include collisional and Doppler broadening. Collisional broadening results when an optically active system experiences perturbations by other species. Collisions effectively reduce the natural lifetime, so the broadening depends on a characteristic impact time, that is typically 1 ps at atmospheric pressure ... 

The symptoms of vitamin E deficiency in animals are numerous and vary from species to species (13). Although the deficiency of the vitamin can affect different tissue types such as reproductive, gastrointestinal, vascular, neural, hepatic, and optic in a variety of species such as pigs, rats, mice, dogs, cats, chickens, turkeys, monkeys, and sheep, it is generally found that necrotizing myopathy is relatively common to most species. In humans, vitamin E deficiency can result from poor fat absorption in adults and children. Infants, especially those with low birth weights, typically have a vitamin E deficiency which can easily be corrected by supplements. This deficiency can lead to symptoms such as hemolytic anemia, reduction in red blood cell lifetimes, retinopathy, and neuromuscular disorders. 

In 1957, this team of brothers-in-law started working together on Townes s idea for an optical maser. They found atoms that they felt had the most potential, based on transitional probabilities and lifetimes. However, there was still one major problem In the visible light portion of the electromagnetic spectrum, atoms don t remain in an excited state as long as... 

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