Deep UV lithography

Dumon, P. Bogaerts, W. Wiaux, V. Wouters, J. Beckx, S. van Campenhout, J. Taillaert, D. Luyssaert, B. Bienstman, P. van Thourhout, D. Baets, R. Low loss SOI photonic wires and ring resonators fabricated with deep UV lithography, IEEE Photonic Technol. Lett. 2004, 16, 1328 1330... 

The object of this study is to develop new photoresists for deep-UV lithography, by using the reversible photoreaction of pyrimidine bases (17-19). Applicability of pyrimidine containing polymers to both negative and positive type photoresists is due to this photoreversible reaction in which cyclobutane dimers are either formed or cleaved depending on the exposure wavelength (Scheme 2). 

P. Dumon, W. Bogaerts, V. Wiaux, J. Wouters, S. Beckx, J. van Campenhout, D. Taillaert, B. Luyssaert, P. Bientniau, D. van Thourhout, and R. Baets, "Low loss photonic wires and ring resonators fabricated with deep UV lithography," IEEE Phot. Technol. Lett. 16, 1328-1330 (2004). 

A major consequence of these considerations is that new exposure sources and/or very sensitive resist materials must be developed in order to realize the resolution enhancement offered by deep-UV lithography without the penalty of extremely long exposure times. Considerable advances have been made on both fronts. 

Deep-W Lithography. The important issues for deep-UV lithography (200-250 nm) are aligner optics and resist materials. Problems in aligner optics stem from the decreased transparency of standard lens materials in this frequency range, which necessitates the use of more-expensive construction materials such as quartz. Typical near-UV positive resists are not useful for deep-UV lithography because of unacceptable absorption at... 

Hind A (2001) Spectrophotometry Takes Measure of Deep-UV Lithography, Photonics Spectra, December 82-86. 

Novel terpolymer compositions containing 4-(di-trifluoromethyl-hydroxymethyl)-1-(di-trifluoromethy)methyl)cyclohexyl] vinylsulfonate have been prepared having excellent transparency, substrate adhesion, and plasma etching resistance. The introduction of perfluoronorbornene resulted polymers that were especially suitable for deep UV lithography. 

Combining the lithographic and etch mask functions into a single polymer can be a major challenge, especially for deep-UV lithography. The latitude in resist design is limited, because at least 10 and preferably 15 wt % of the polymer structure must be reserved for silicon. A few materials, like silicon-substituted poly(methyl methacrylates) (6) and polysilanes (7, 8), have been used as positive two-layer resists for deep-UV lithography, but these materials suffer from either poor to moderate sensitivities to deep-UV radiation or an excessive absorption in the UV that limits exposure depth in the resist layer. 

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