This report will introduce novel resist materials including specific photo acid generator (PAG) to improve flare
issue from the resist standpoint. We have developed a method to control the acid diffusion length from the PAG. It
previously reported that acid diffusion length can be altered by the PAG anion size. In this report, we focused on the
effect of the Tg of a resist film. The thermal flow rate of a resist film can suggest the approximate resist Tg.
Therefore, we measured the thermal flow rate of the resist. And we found out passivity of acid diffusion control by
changing PAG species and volume.
Moreover, newly designed PAG tested was confirmed to have uniform distribution in the resist film with no PAG
clustering at the resist surface at compared to our conventional PAG. This new positive tone resist formulation
shows good performance under flare condition.
In addition, we focused on the pattern density variation as one of the key parameters for flare value. Low
pattern density indicated less flare value. It is considered that negative tone resist to have advantage for isolated line
type features. Novel positive and negative tone type resists were compared side-by-side and discussed for its
advantages at varying pattern densities.
Changes in chemical nature of an ArF photoresist caused by various plasmas were analyzed, and it was found that the HBr plasma treatment induces a selective detachment of a heterocyclic unit of the photoresist, and the detached unit remains in the photoresist film. Thermomechanical analyses were performed, which showed that the softening temperature of the photoresist decreases by the HBr treatment, indicating that the detached heterocyclic unit acts as a plasticizer in the photoresist film. These results showed that the HBr treatment can be regarded as a softening process of the photoresist. This HBr treatment was applied to the fabrication of line patterns and it was shown that the treatment remarkably improves LWR (line width roughness) after etching. This improvement was more pronounced for the case of an isolated pattern than the case of a dense pattern. Further investigations on the HBr treatment were performed by changing the copolymerization ratio of a monomer containing the heterocyclic unit. It was shown that the reduction of LWR by the HBr treatment becomes more enhanced when the copolymerization ratio increases. However, an intensive HBr treatment was found to deteriorate LWR, showing that there is an optimum condition of the HBr treatment in terms of improving LWR.