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1 June 1991 Dissolution inhibition mechanism of ANR photoresists: crosslinking vs. -OH site consumption
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This paper reports our recent studies of crosslinking of phenolic resins with melamines through 1H and 13C NMR, GPC, and dissolution rate changes. For the NMR studies, we used model phenolic compounds such as 4-ethylphenol, and the hexafunctional crosslinker, hexamethoxymethylmelamine (HMMM). The NMR clearly reveals that the crosslinking reaction occurs quantitatively at the hydroxyl site of the phenol. This result raises the question of whether the dissolution inhibition observed in the ANR resists is due to -OH site consumption or to the rapid rise in molecular weight of the phenolic polymer. Comparison of tetrahydrofuran (THF) extraction vs. aqueous tetramethylammonium hydroxide (TMAH) development shows that the dose required to insolubilize the resist is much higher for THF. Gel permeation chromatography on the soluble fraction extracted into THF showed a fraction with molecular weights up to 400,000 Daltons. We believe that crosslinking and -OH site protection provide synergistic dissolution selectivity in TMAH, leading to high contrast and high resolution. Finally, we present results on the effect of (chi) , which is proportional to the ratio of phenolic hydroxyl groups to melamine methoxy groups, on the lithographic performance of ANR photoresists. At low (chi) , the DUV resists can be used as increased absorption resists over topography, and development times can be shortened significantly. We have also found that increasing the melamine loading can lessen the degree of bridging residue observed between lines.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
James W. Thackeray, George W. Orsula, Martha M. Rajaratnam, Roger F. Sinta, Daniel J.C. Herr, and Edward K. Pavelchek "Dissolution inhibition mechanism of ANR photoresists: crosslinking vs. -OH site consumption", Proc. SPIE 1466, Advances in Resist Technology and Processing VIII, (1 June 1991);

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