ArF exciplex lasers

E, F Sg) state of H2 following two-photon excitation with an ArF exciplex laser. 

The 1980s and 1990s saw the development of lithographic exposure sources such as KrF and ArF exciplex lasers. Today, the majority of advanced IC circuits are fabricated with these laser-based exposure tools. 

Examples of the application of exciplexes in hthography include KrF and ArF exciplex laser light sources for 248 nm and 193 nm hthographies, respectively. 

Reactions [13.1]-[13.11] illustrate the specific photochemical reactions involved in the lasing actions of KrF exciplex lasers. (Similar reactions are also involved in ArF exciplex lasers.)... 

Figure 13.6 Spectrum of a free-running ArF exciplex laser in 1-m air path and in N2.

Figure 13.7 Spectraof line-narrowed ArF exciplex laser. The line was narrowed with both a standard output coupler and an etalon output coupler (EOC). ...

Figure 13.12 shows the UV absorption profile of typical gases found (O2, H2O) and formed (O3) in the ambient environment of exposure tools. The Schumann-Runge band (180-210-nm) and continuum (<180-nm) regions dominate the photochemistry of molecular oxygen around 193 nm (of ArF exciplex laser) and 157 nm (of F2 excimer laser), respectively. 

Figure 13.14 Molecular oxygen absorption spectrum over the spectrum of a free-running ArF exciplex laser. The absorption peaks in the molecular oxygen spectrum are Schumann-Runge absorption bands. (Courtesy of R. Kunz and R. Dammel...

At the heart of dry ArF lithography lies an exposure tool equipped with ArF exciplex laser source (emitting 193-nm wavelength photons). The insertion of ArF (193-nm) lithography into production was originally expected to take place in... 

NH2 radicals, generated by photolysis of NH3 (0.5 mbar) with an ArF exciplex laser at 193 nm, were detected by time-resolved, coherent anti-Stokes Raman spectroscopy in the NH stretch regions at 3334 and 3220 cm [1]. Two Raman bands of NH2, V3 = 3276 2 and V2 = 1471 2 cm were observed in solid ammonia at 77 K after irradiation with an atomic aluminium beam [2]. 

Finally, electrons have been generated with nanosecond pulses from the KrF exciplex laser at 248 nm via photodetachment of OH and Cl in aqueous and methanol solutions, and could be via one-photon photoionization in liquids with the ArF laser at 193 nm, and via one and two-photon processes in aqueous naphthol and naphtholate with nanosecond pulsed nitrogen lasers at 337 nm. With the improved fluxes and short pulses now available from gain modulation techniques applied to the TEA exciplex lasers, semiconductor lasers and F-center lasers, they may prove to be convenient sources for future studies of electron relaxation and transfer processes from the ultraviolet to infrared region. 

The key operational parameters of exciplex and excimer lasers used in optical lithographic applications include exposure-dose-related parameters comprising average power, pulse energy, repetition rate, and pulse width temporal coherence spatial coherence including beam dimensions, beam divergence, and beam uniformity and maintenance and reliability. Table 13.2 lists some of the key operational parameters of KrF, ArF, and F2 laser systems used in optical lithography. 

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