Abstract

Lithography at 157nm using F₂ laser is currently thought of as one probable step after 193 nm for ULSI fabrication. One of the main challenges for the development of the 157 nm technology is the design of photoresists suitable for this spectral region. The high value of the absorption coefficient of the polymeric materials in the VUV, with typical values between 0 1 to 100 µm^–1, imposes severe restrictions on the selection of the photoresist material for 157 nm photolithography. On the other hand, at this wavelength there is high probability for breaking many chemical bonds commonly encountered in the organic molecules and causing outgasing and ablation. This is due to the fact that for almost all the organic molecules, the dissociative excited states of the small radicals usually occupy the energy range above 6.2 eV (200nm). These photodissociative ablative processes could impose serious contamination problems on the optics of the projection system. In this communication we are reporting results from the absorbance and the outgasing studies for photoresist candidates for 157nm lithography Figi. Several materials have been studied for their absorption below 200nm, and one typical epoxy novolac material, and one t-boc protected acrylate are studied for outgassing, as a first contribution on this subject.

© 2000 IEEE