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Fused silica for 157-nm transmittance

1999; SPIE; Volume: 3676; Linguagem: Inglês

10.1117/12.351163

1996-756X

Charlene M. Smith, Lisa A. Moore,

Advanced Measurement and Metrology Techniques

The use of silica glass for the photomask material in 157-nm lithography tools is proposed. While fused silica enjoys widespread application for 248 and 193-nm optics, its use for 157-nm applications has been largely discounted, in part because of low transmittance at this wavelength. It is demonstrated here that silica glass can be made to have high transmittance at 157-nm. This is accomplished by minimizing the OH content of the glass. It is also noted that the thermal and mechanical properties of so-called dry silica are very close to higher OH silicas that are commonly used for lithography applications.