| In the drive for smaller image sizes in microelectronic devices, the lithography industry has reached a point where the solvents traditionally used for development are potentially damaging to the images formed. The use of a more gentle solvent, such as supercritical carbon dioxide, has been shown to alleviate this problem. Furthermore, replacement of the solvents in spin-coating and stripping with condensed CO2 could streamline the lithography process as the "wet" solvents would be eliminated. Also, CO2 is an environmentally benign and easily recyclable alternative to the solvents currently used in microlithography for the solvent-intensive steps of processing a photoresist.; As next generations of lithographic techniques for imaging a photoresist approach, more stringent requirements are placed on the resist. For 193 nm and 193 nm immersion resists, alicyclic backbones have been shown to impart etch resistance and to elevate glass transition temperatures, while fluorination has been shown to decrease absorbance. As an additional advantage for processing in CO2, fluorination also increases CO2 solubility. Various norbornene-based monomers were synthesized to include fluorinated moieties. Resist materials were synthesized by addition polymerization using allylpalladium chloride dimer. Fluorinated copolymers containing a "chemical switch" have been found to have a significant CO2 solubility difference, as well as a difference in intrinsic viscosities. Dry plasma etching of these polymers has demonstrated moderate etch resistance compared to Novolac. Imaging with an ASML 193 nm scanner has resolved 1 mum semidense lines, using CO 2 as the developer. |
