Study of Acid-Base Equilibrium in Chemically Amplified Resist

Abstract

Protons generated in chemically amplified resists drive pattern formation reactions such as acid catalytic deprotection reactions. Proton dynamics is controlled by the addition of base quenchers so that ultrafine patterns are obtained. However, the details of interaction between protons and base quenchers are still unclear. In this study, we investigated the reactions of protons with base quenchers in a model system of chemically amplified resists with a typical backbone polymer, poly(4hydroxystyrene). We confirmed that an acid-base equilibrium was reached in the model system without elevating the temperature of the films. The proton affinities of resist ingredients give us a general estimation of protonation sites. When the proton affinities of resist ingredients are close to each other, we have to take into account acid-base equilibrium using pK a for the accurate prediction of protonation sites.

Radiation Chemistry in Chemically Amplified Resists

“…220) To clarify the proton migration and protonation sites in resist materials, the formation of C6 proton adducts in PHS films was investigated in the presence of quenchers with different proton affinities. 221,222) Figure 26 shows the relationship between the concentration of C6 proton adducts and the proton affinity of quenchers. 222) When the proton affinity of the quencher was increased, the formation of C6 proton adducts was not observed.…”

Relationship between Sensitization Distance and Photon Shot Noise in Line Edge Roughness Formation of Chemically Amplified Resists Used for Extreme Ultraviolet Lithography

“…The preneutralization of acids before PEB [17,18] was assumed because an annealingtype resist is generally used in EUV lithography. The proton migration range at room temperature was set to 2.4 nm [19].…”

Requirement for Suppression of Line Width Roughness in Fabrication of Line-and-Space Patterns with 7 nm Quarter-Pitch Using Electron Beam Lithography with Chemically Amplified Resist Process

“…The preneutralization of acids before PEB [16,17] was assumed because an annealing-type resist is generally used in EB lithography. Using the acid distribution after the preneutralization as the initial condition, the catalytic chain deprotection during PEB was calculated by solving the reaction-diffusion equations for acids and quenchers.…”