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Proceedings Paper

The effect of EUV molecular glass architecture on the bulk dispersion of a photo-acid generator
Author(s): David L. VanderHart; Anuja De Silva; Nelson Felix; Vivek M. Prabhu; Christopher K. Ober
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Paper Abstract

We have examined four molecular glasses (MGs) which are candidates for EUV photoresist formulations. These derivatized glasses, and their unprotected precursors, were investigated by both proton and 13C solid state NMR techniques in the bulk state as pure materials and as mixtures with 5 or 10 % by mass of the photoacid generator (PAG), triphenyl sulfonium perfluorobutanesulfonate. The 13C techniques gave information about crystallinity, purity, and the presence of the PAG. This paper characterizes the intimacy of mixing of the PAG and the MGs using proton spin diffusion methods. Phase separation of the PAG into PAG-rich larger domains was never seen; the PAG was always finely distributed. A maximum diameter for any PAG clustered into spherical domains was estimated to be 3.8 nm, which is too small to reflect thermodynamic incompatibility as the driving force during relatively slow removal of solvent. Hence, PAG blended samples are deduced to be thermodynamically compatible, with differential solubility in the preparation solvent the most likely candidate for producing the significant inhomogeneities in PAG concentration observed in a few samples. For one of the unprotected crystalline calix[4]resorcinarenes precursor materials, the solvent, N-methyl 2-pyrrolidinone (NMP) was used. The resulting solid was crystalline with a segregation of isomers, one of which formed a solid adduct with a 1:1 molecular ratio with NMP. Qualitatively, the strong NMP affinity for the calix[4]resorcinarenes is also evident in a) the immobility of the NMP, b) the fact that the 14N quadrupolar interaction changes when NMP goes from the crystalline, unprotected host to a glassy, protected host, and c) that NMP tends to remain as a significant residue. Only the underivatized materials display crystallinity implying that the mixing of the PAG with any derivatized MG is not restricted by crystallization, at least not before the post-exposure bake step. As a final note, very strong hydrogen bonds exist in three underivatized materials which is reduced or eliminated with partial protection with t-BOC.

Paper Details

Date Published: 15 April 2008
PDF: 15 pages
Proc. SPIE 6923, Advances in Resist Materials and Processing Technology XXV, 69231M (15 April 2008); doi: 10.1117/12.773048
Show Author Affiliations
David L. VanderHart, National Institute of Standards and Technology (United States)
Anuja De Silva, Cornell Univ. (United States)
Nelson Felix, Cornell Univ. (United States)
Vivek M. Prabhu, National Institute of Standards and Technology (United States)
Christopher K. Ober, Cornell Univ. (United States)

Published in SPIE Proceedings Vol. 6923:
Advances in Resist Materials and Processing Technology XXV
Clifford L. Henderson, Editor(s)

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