A poly(4-hydroxystyrene) (PHS) backbone polymer and a tetramethylammoniumhydroxide (TMAH) aqueous developer are typically combined to form a positive chemically amplified resist. We investigated the dissolution kinetics of PHS with different molecular weights and molecular weight dispersions and different concentrations of TMAH by quartz crystal microbalance (QCM) measurement. QCM graphs showed different dissolution rates and forms for different concentrations. We attempted to explain the dissolution kinetics by introducing a dissolution index calculated from swelling and dissolving factors. These factors were calculated using a penetrating factor (water or TMAH molecules) and a disentanglement factor. It is considered that the dissolution index depends on the molecular weight distribution because polymers with different molecular weight distributions have different voids in their bulk and different tendencies of disentanglement. Our results suggest that dissolution can be controlled by adjusting the molecular weight distribution, which will lead to reduced defect generation during the fabrication of fine structures.

In current optical lithography, resolution is required to reach for 45 nm half-pitch and a chemically amplified resist (CAR) is used for a wide variety of applications. For ArF lithography beyond the 45 nm half-pitch, it is important to control pattern quality. The molecular design of a photo acid generator (PAG) is very important in the study to control not only acid strength but also acid diffusion length. Various novel PAGs that have different characteristics were synthesized for resist performance improvement. Acid molecular size was determined by molecular orbital (MO) calculation, and the acid diffusion coefficients (D) of these PAGs were evaluated by a bilayer method. As a result, it was found that acid diffusion coefficient (D) could not be controlled simply by adjusting anion molecular size. It may be presumed that the molecular interaction between acid generated by the exposure and polymer matrix areas is one of the most important key factors for controlling acid diffusion.

Extreme ultraviolet (EUV) lithography is the most promising candidate for the high-volume production of semiconductor devices with half-pitches of sub-10 nm. An anion-bound polymer (ABP), in which the anion part of onium salts is polymerized, has attracted much attention from the viewpoint of the control of acid diffusion. In this study, the acid generation mechanism in ABP films was investigated using electron (pulse), γ, and EUV radiolyses. On the basis of experimental results, the acid generation mechanism in anion-bound chemically amplified resists was proposed. The major path for proton generation in the absence of effective proton sources is considered to be the reaction of phenyl radicals with diphenylsulfide radical cations that are produced through hole transfer to the decomposition products of onium salts.

The radiation-induced reactions of ligands play an important role in the sensitization of metal oxide nanocluster resists. However, the details in the radiation chemistry of ligands for metal oxide nanocluster resists are still unknown. In this study, the radiation-induced reactions of carboxylic acid ligands were investigated using a pulse radiolysis method. The rate constants for the reactions of molecular and ionic forms of tiglic, angelic, otoluic, and p-toluic acids with hydrated electrons were determined. The rate constants for the reactions of tiglic, angelic, benzoic, o-toluic, and ptoluic acids with dodecane radical cations were also determined. The radical ions of tiglic and angelic acids were more unstable than those of benzoic, o-toluic, and p-toluic acids. The results obtained in this study indicate that the molecular structures of ligands affect their reactivity to cationic and anion species and the stability of their radical cations and anions.