Here we examine a new methodology for spatially resolved molecular analysis to address an important area of need related to the performance of EUV resists, namely detection of molecular components at a scale below the current 20 nm critical dimension. Analysis consists of stochastically sampling the surface with a suite of nano projectiles each of which results in the emission of multiple secondary ions, SIs, from a volume 10-15 nm in diameter on the surface. The SI detector is a multi-anode detector allowing for the radial and translational energies of each SI to be examined. We tested this new methodology on model line patterned EUV resist materials and found the when bombarding the surface with the primary ion path perpendicular to the line pattern, impacts on top of the intact resist resulted in the emission of SI with high translational and axial energies in the forward direction. In contrast, impacts which occurred on the resist sidewalls results in emission in the backward direction. Thus, by examining the energies of emitted SIs molecular analysis can be undertaken on each part of the pattern (side wall, intact resist, substrate) with high resolution.
Characterizing chemical changes in photoresists during fabrication processes is critical to understanding how nanometric defects contribute to film stochastics. We used nanoprojectile secondary ion mass spectrometry (NP-SIMS) to evaluate the nanoscale homogeneity of components in positive-tone extreme ultraviolet resists. NP-SIMS was operated in the event-by-event bombardment/detection mode, where a suite of individual gold nanoprojectiles separated in time and space stochastically bombard the surface. Each impact ejects secondary ions from a volume 10 to 15 nm in diameter and up to 10 nm in depth allowing for analysis of colocalized moieties with high spatial resolution. Individual partially exposed extreme ultraviolet resists were analyzed after light exposure, postexposure bake, and development. Results showed an expected increase in protonated quencher versus exposure dose, while after development, we observed increased abundance in the remaining film. The latter, we attribute to poor solubility in the developing solvent. Examining the photoacid generator (PAG), we found decreased PAG cation abundance versus exposure dose in the exposed films, likely due to photodecomposition of the PAG cation. Moreover, after the development, we observed decreased homogeneity of PAG ions, which we attribute to preferential extraction caused by ion-exchange interactions with the developer. We found that the insoluble moieties persisting on the surface after the development were relatively rich in the protecting group, likely due to uneven deprotection of the polymer. Overall, NP-SIMS allows to characterize the resist at the nanoscale and identify conditions that lead to defect formation.
Characterizing chemical changes in photoresists during fabrication processes is critical to understanding how nanometric defects contribute to film stochastics. We used Nano-Projectile Secondary Ion Mass Spectrometry (NP-SIMS) to evaluate the nanoscale homogeneity of components in positive-tone extreme ultraviolet resists. NP-SIMS was operated in the event-by-event bombardment/detection mode, where a suite of individual gold nanoprojectiles separated in time and space stochastically bombard the surface. Each impact ejects secondary ions from a volume 10-15 nm in diameter and up to 10 nm in depth allowing for analysis of colocalized moieties with high spatial resolution. Individual partially exposed EUV resists were analyzed after light exposure, postexposure bake (PEB), and development. Results showed an expected increase in protonated quencher versus exposure dose, while after development we observed increased abundance in the remaining film. The latter we attribute to poor solubility in the developing solvent. Examining the photoacid generator, PAG, we found decreased PAG cation abundance versus exposure dose in the exposed films, likely due to photodecomposition of the PAG cation. Moreover, after development we observed decreased homogeneity of PAG ions, which we attribute to preferential extraction caused by ion-exchange interactions with the developer. We found that the insoluble moieties persisting on the surface after development were relatively rich in the protecting group, likely due to uneven deprotection of the polymer. Overall, NP-SIMS allows to characterize the resist at the nanoscale and identify conditions that lead to defect formation.
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