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Solvent-Based Development Of Photoresists For Next-Generation Lithography
As feature sizes continue to shrink, the need for new materials and new processes for next-generation lithography becomes more urgent. Although aqueous base development has been the industry standard for over twenty years, there are still several issues that need to be overcome. First, the high surface tension of aqueous base developers can lead to pattern collapse of high aspect ratio patterns and limit resolution. The toxicity of aqueous base developers has also raised concerns about the environment. In order to reduce the problems related to aqueous development, solvents or materials with desirable properties must be used. Recently, there has also been growing interest in solvent-based negative-tone development (NTD) due to its better performance in printing certain feature types. Therefore, solvent-based development of photoresists was investigated in this study. One approach to reduce the pattern collapse problem and environmental issues of the lithographic process is through the use of environmentally friendly solvents with low surface tension. Supercritical carbon dioxide (scCO2) and linear methyl siloxanes (LMS) are green solvents that have low toxicity, low surface tension, low viscosity and can be recycled. Solvent-based development of both polymeric and molecular glass resists with positive- and negative-tone images have been successfully demonstrated in both solvents. High-resolution and high aspect ratio patterns were obtained with no pattern collapse observed using both solvents. As there is little iii understanding about the solvent power of linear methyl siloxanes, the dissolution behavior of polymers and molecular glasses in linear methyl siloxanes was also studied. Besides using low surface tension developers to mitigate pattern collapse problem, another approach is by using materials with high etch resistance that eliminates the use of thick films. Also, because of the low intensity of current EUV light source, the next-generation resists need to demonstrate high sensitivity and optimum absorbance. Inorganic metal oxide nanoparticles based on zirconium oxide (ZrO2) and hafnium oxide (HfO2) with organic ligands have been synthesized for EUV lithography. These nanoparticle resists can be developed as negative-tone patterns using an organic solvent and high-resolution patterns were achieved. The patterning performance of these nanoparticles in different organic solvents was also evaluated. iv
photoresists; Next-generation lithography; Environmentally friendly
Ober, Christopher Kemper
Giannelis, Emmanuel P; Jarrow, Robert A.
Materials Science and Engr
Ph.D. of Materials Science and Engr
Doctor of Philosophy
dissertation or thesis