| A review of photolithography and carbon dioxide-based processes will be presented. The major driving force for this research is the trend in the manufacture of microelectronics to move to smaller wavelengths of exposure to produce smaller features and thus faster and cheaper integrated circuits. To create sub 90 nm features, through the photolithographic process, the microelectronics industry is considering the use of a fluorine excimer laser which operates at 157 nm. The key properties of a photoresist should include low absorption at the exposing wavelength, high glass transition temperature (Tg), good etch resistance, solubility for deposition, and a solubility switch which provides good contrast during development. A 157 nm photoresist must meet all of these requirements, however, low absorbance is of paramount concern. Given the intrinsically low absorbance of fluoropolymers at 157 nm, these materials are prime candidates for the next generation of photoresists.; The use of supercritical carbon dioxide (CO2) as a polymerization solvent for the production of fluoropolymers is firmly established. The objective of the work presented herein, was to couple the use of CO2 as a polymerization medium for fluoropolymer synthesis with the need for fluoropolymer based 157 nm photoresists. Initially, supercritical CO2 was used as a solvent for the preparation of fluoroolefin/norbornene copolymers. Important structure-property relationships between fluoroolefin selection and key photolithographic properties, such as 157 ran absorbance, will be discussed. This work showed that tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE) are effective comonomers for polymerization with norbornene in CO2. Furthermore, for the poly(CTFE-co-norbornene) system, an interesting trend on glass transition and absorbance at 157 nm was established. This trend was rationalized in terms of end group effects.; A functionalized TFE/norbornene terpolymer was prepared and examined as it relates to both conventional and CO2 based lithographic applications. This material showed very interesting absorbance trends with carbonyl content.; Finally, a novel alpha-trifluoromethacrylate monomer was prepared and polymerized with various comonomers. The materials were investigated for physical properties which relate to conventional and CO2 based photolithography. Furthermore, the inherent problems with the monomer synthesis will be discussed. |
