| Popis: |
The strategy and chemistry employed to develop high resolution, high temperature positive resist systems (flow temperature >= 140 degree(s)C) based on novolak resin chemistry are reviewed and compared in this paper. Modest gains in resist thermal flow stability have been obtained using conventional cresol novolaks either by increasing molecular weight or decreasing the molecular weight dispersity by fractionation of the novolaks. Large gains in resist thermal flow stability have been obtained by adding a crosslinking agent to the resist. Similar gains have been obtained by redesigning the novolak structure by judicious choice of monomer to give high backbone rigidity. This rigidity imparts high thermal stability to the resists. Examples of the later two strategies are discussed in detail. The advantages and disadvantages of each approach, the trade-offs, and compromises in resist thermal flow stability, photospeed, and resolution are discussed in this review. |
