Acid generation mechanism in anion-bound chemically amplified resists used for extreme ultraviolet lithography

Abstract

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.

Resist material options for extreme ultraviolet lithography

“…A hexafluoroalcohol is also an effective proton source [41]. The acid generation mechanisms in the absence of an effective proton source such as the phenol units of PHS have been also investigated [42]. As an example of such case, the following mechanism has been reported for a triphenylsulfonium salt.…”

Acid Quantum Efficiency of Anion-bound Chemically Amplified Resists upon Exposure to Extreme Ultraviolet Radiation

“…are diphenylsulfide (DPS) and a phenyl radical, respectively. The subsequent reactions for the generation of the protons of acids are [23]:…”

“…We have investigated the acid generation mechanisms induced in ABP by secondary electrons, considering that the acid generation mechanism is a reason for low sensitivity [22,23]. On the basis of experimental results, we have modeled the proposed acid generation mechanisms of anion-bound resists and developed a simulation code for facilitating the development and improvement of resist materials and processes for EUV lithography [1].…”

Dynamics of radical cations of poly(4-hydroxystyrene) in the presence and absence of triphenylsulfonium triflate as determined by pulse radiolysis of its highly concentrated solution

“…Pulse radiolysis, a time-resolved spectroscopic method used for ionized resist polymers such as novolaks [6,7], acrylates [8][9][10], and polyoxystyrenes [11][12][13][14][15][16], has been used to model base polymers of CARs. Pulse radiolysis studies of resist polymers have been conducted mainly in dilute solution.…”