Deprotonation mechanism of ionized poly(4-hydroxystyrene)

Poly(4-hydroxystyrene) (PHS), a backbone polymer in resist constituents is also a promising material for extreme ultraviolet (EUV) and electron beam (EB) lithography. Efficient deprotonation occurs from radical cations of irradiated PHS. A hydroxystyrene unit is incorporated in the chemically amplified resist structure as a proton source, in which reaction mechanism has not been well established. In this study, deprotonation mechanism of an ionized PHS was characterized by using pulse radiolysis techniques. The influence of several additives such as sulfoxides and amides with high acidity on the kinetics of the deprotonation was investigated to clarify the fundamentals of the enhancement of deprotonation efficiency from the PHS radical cation. Influence of the additives on the acid yield in thin film was also investigated.

[1]  Takahiro Kozawa,et al.  Acid Generation Mechanism of Poly(4-hydroxystyrene)-Based Chemically Amplified Resists for Post-Optical Lithography: Acid Yield and Deprotonation Behavior of Poly(4-hydroxystyrene) and Poly(4-methoxystyrene) , 2006 .

[2]  C. Willson,et al.  Chemical amplification in the design of dry developing resist materials , 1983 .

[3]  Takahiro Kozawa,et al.  Radiation-Induced Acid Generation Reactions in Chemically Amplified Resists for Electron Beam and X-Ray Lithography , 1992 .

[4]  Gerd Pohlers,et al.  Intrazeolite Photochemistry. 22. Acid−Base Properties of Coumarin 6. Characterization in Solution, the Solid State, and Incorporated into Supramolecular Systems , 1998 .

[5]  Takahiro Kozawa,et al.  Protonation Sites in Chemically Amplified Resists for Electron-Beam Lithography , 2006 .

[6]  S. Tagawa,et al.  Polymer screening method for chemically amplified electron beam and X-ray resists , 2003, Digest of Papers Microprocesses and Nanotechnology 2003. 2003 International Microprocesses and Nanotechnology Conference.

[7]  Hiroki Yamamoto,et al.  Deprotonation of Poly(4-hydroxystyrene) Intermediates: Pulse Radiolysis Study of Extreme Ultraviolet and Electron Beam Resist , 2013 .

[8]  Hiroki Yamamoto,et al.  Proton Dynamics in Chemically Amplified Electron Beam Resists , 2004 .

[9]  Hiroshi Ito,et al.  Microlithography・molecular imprinting , 2005 .

[10]  Takahiro Kozawa,et al.  Radiation and photochemistry of onium salt acid generators in chemically amplified resists , 2000, Advanced Lithography.

[11]  Takahiro Kozawa,et al.  Formation of intramolecular poly(4-hydroxystyrene) dimer radical cation. , 2008, The journal of physical chemistry. B.

[12]  Jin‐Pei Cheng,et al.  Substituent effects on the stabilities of phenoxyl radicals and the acidities of phenoxyl radical cations , 1991 .

[13]  S. Tagawa,et al.  Radiation Chemistry in Chemically Amplified Resists , 2010 .

[14]  Ralf Hermann,et al.  Free electron transfer from several phenols to radical cations of non-polar solvents , 2000 .