We have examined four model molecular glasses (MGs) which are candidates for extreme ultraviolet lithography. One rationale for employing MGs is that these materials, on the basis of being molecules smaller than the usual polymeric materials, might yield more well defined features in the push towards smaller lithographic feature dimensions. These glass-forming materials were investigated by proton and 13C solid state NMR techniques in the bulk state as pure materials and as mixtures with a photoacid generator (PAG). The 13C techniques gave information about crystallinity, purity, and the qualitative existence of multiple phases. Proton studies focused mainly on using spin diffusion to characterize the intimacy of mixing of the PAG in the MG matrix. The four MGs were largely aromatic materials, originally containing several hydroxyl groups were partially protected by t-butoxycarbonyl (t-BOC) groups.We found that PAG was always finely distributed, however, in some cases the average concentration appeared to vary. Also, in the preparations involving one of the MGs, the solvent, N-methyl 2-pyrrolidinone (NMP) exhibited a very strong affinity for one isomer. In fact, one of the crystalline species identified in the underivatized product has a 1:1 molecular ratio of the MG and NMP. Qualitatively, the strength of the NMP affinity for the glass was evident in a) the immobility of the NMP, b) the 14N quadrupolar interaction that changes when NMP goes from the crystalline-underivatized host to the glassy-derivatized host, and c) that NMP remains as a significant residue in derivatized samples. Crystallinity was only seen associated with the underivatized materials implying that mixing with any derivatized MG is not restricted by crystallization. It is also noted that very strong hydrogen bonds exist in three of the four underivatized materials and were eliminated or weakened upon partial t-BOC protection.
Citation: Journal of Materials Chemistry
Pub Type: Journals
chenically amplified photoresists, molecular glass, nuclear magnetic resonance, photolithography, spin diffusion