Si02 + 4 HF -+ SiF4 + 2H20S o m e of the fundamental steps of microlithography (coating, irradiation, development of the film with base, removal of the Si02 layer) and on the right the chemical processes involved. This year some twenty billion integrated circuits will be produced worldwide. Almost all (98%) of them will be made with a photosensitive varnish, the photo resist, that allows the transfer of a fine line-pattern from an original transparency onto a silicon wafer. This photoresist has two components: one is a novolak resin, a low molecular weight phenol-formaldehyde condensation polymer; the other is a diazonaphthoquinone derivative (DNQ), which is the photoactive part of the system. Novolak-diazoquinone resists have played a crucial role in the microminiaturization of electronics. They are photographic materials of extremely high resolution, able to define features as small as 0.25pm. Although they are now an indispensible ingredient of modern computer technology, until quite recently their molecular mechanism was not understood. We report here on work at Polytechnic University in New York aimed at solving the mystery of these important and intriguing systems. The solution, in so far as it has revealed itself to us, is rather unique and quite unexpected. Novolak-Diazoquinone Resists

No abstract

No abstract

The dissolution rate of novolak resins in aqueous bases is an important factor in their practical applications, and the cation of the base has a significant effect on that rate. To try and understand this effect, we have determined the activation energy and activation entropy of dissolution, and we find that both are affected by the size of the cation. The activation entropy becomes more negative for larger cations, and the activation energy decreases. The two effects oppose each other; their competition determines the dissolution behavior of the resin.

Dissolution inhibition produced by diazonaphthoquinones in novolak and in other phenolic resins is based on the formation of phenolic clusters. The principal result of the exposure of novolakdiazoquinone resist films to light is the dispersal of these clusters. It occurs through the thermal effect of the Wolff rearrangement that follows the photolysis of diazonaphthoquinone. Indenecarboxylic acid, which is the final product of irradiation, is converted to indenecarboxylate ion in the penetration zone of the dissolving films, where it adds to the concentration of hydrophilic percolation sites. This causes the dissolution rate of exposed resist films to be accelerated above that of pure novolak.