In this study we examined a series of model EUV resists varying in photoacid generator, PAG, or photodecomposable quencher, PDQ loading and their effects on resist uniformity using Nano-Projectile Secondary Ion Mass Spectrometry, NP-SIMS. The EUV resists we examined consisted of a 40:60 random co-polymer of polytertbutylmethacrylate and polyhydroxylstyrene. NP-SIMS analysis revealed changes in the film composition evidenced by changes in both the abundance of characteristic secondary ions and homogeneity of analyte species. The resists were loaded with varying amounts of PAG – triphenylsulfonium and perfluorobutylsulfonium, and PDQ- triphenylsulfonium and p-cyanobenzoate. Examining different formulations before and after treatment revealed differences in homogeneity of the resist and differences in resist performance.
Here, we present a methodology for identifying and characterizing nanoscale sites in extreme ultraviolet (EUV) photoresists that deviate from the mean composition by 3σ. The methodology is based on nano-projectile secondary ion mass spectrometry (SIMS) operating in the event-by-event bombardment detection mode. Nanoscale analysis is achieved by probing the surface stochastically with a suite of individual nanoprojectile impacts in which each nano-projectile samples a volume that is 10 to 15 nm in diameter and up to 10 nm in depth. For each impact, the coemitted secondary ions are collected and mass-analyzed, allowing for the analysis of colocalized moieties. We applied this technique to study the fundamental processes occurring in partially developed positive-tone EUV resists, which simulate a critical problem in EUV resists, incomplete resist removal, and production of line edge features. Such features erode device yield and have been the focus of many previous studies. Using NP-SIMS, we examined the changing molecular composition in the partially developed resist and isolated measurements with a probability below 0.3%. Grouping measurements based on the number and type of detected molecular species allowed for the identification of rare sites on the surface that deviate from the mean composition. The mass spectrometry measurements showed that both the photoacid generator (PAG) cation and anion displayed decreased homogeneity on average with increasing exposure dose. The effect was more pronounced in the sites with probabilities below 0.3%, where the measured intensity of the PAG-related ions in these sites was more than twofold larger than the mean. Thus, we attribute these nanoscale sites to aggregations of PAG within the top 10 nm of the remaining film. These results suggest that identifying and characterizing the molecular composition of rare sites may be important in defect production and film stochastics.
In this study we examined a series of model EUV resists with varying concentration of photoacid generator, PAG, or photodecomposable quencher, PDQ and their effects on resist uniformity using Nano-Projectile Secondary Ion Mass Spectrometry, NP-SIMS. Nanoscale analysis with NP-SIMS is achieved due three innovative features of the technique (1) the mode of data acquisition (2) method of data analysis (3) the nature of the impacting projectile. The results showed that ionic interactions between PAG and PDQ are modified due to the relative/absolute loading of the two components. These results demonstrate the NP-SIMS is a useful tool for assessing the effect of additive loadings on EUV resist uniformity at the nanoscale.
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.
Here we present a methodology for identifying and characterizing nanoscale sites in EUV photoresists which deviate from the mean composition by 3σ. The methodology is based on Nano-Projectile Secondary Ion Mass Spectrometry (SIMS) operating in the in the event-by-event bombardment detection mode. Nanoscale analysis is achieved by probing the surface stochastically with a suite of individual nano-projectile impacts where each nano-projectile samples a volume 10-15 nm in diameter and up to 10 nm in depth. For each impact the coemitted secondary ions are collected, and mass analyzed, allowing for the analysis of co-localized moieties. We applied this method to study the changing film composition in an EUV resist and isolated measurements with a probability below 0.3%. By examining these measurements, we can identify rare sites on the surface that may correspond to molecular aggregations in the surface. In a developed film, the mass spectrometry measurements showed that the photoacid generator, PAG, cation displayed decreased homogeneity on average with increasing exposure dose. The effect was more pronounced in the sites with probabilities below 0.3%, where the measured intensity of the PAG cation in these sites was over 2-fold larger than the mean. Thus, we attribute these nanoscale sites to aggregations of PAG within the top 10 nm of the film. These rare sites may be important in defect production and film stochastics.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.