Effect of PAG and matrix structure on PAG acid generation behavior under UV and high-energy radiation exposure

Chemically amplified resists (CAR) have successfully facilitated the development of deep ultra-violet (DUV) and 193 nm lithography techniques for more than two decades due to their acid-catalyzed deprotection scheme that enhances their photospeed. This acid-catalyzed mechanism provides a method for amplifying the initial chemical reactions caused by interaction of radiation with the resist film, thus making each interaction event between radiation and resist more productive. However, when switching from low energy photolysis to high energy radiolysis, changes in the manner in which the radiation interacts with the resist material can alter the acid generation efficiency and mechanism of PAG excitation. In high energy radiation cases where the radiation energy exceeds the ionization potential of the PAG and the polymer resin, the radiation absorption in the resist film becomes non-selective. The ratio of PAG excited by direct excitation as compared to polymer or matrix sensitization pathways can shift heavily in favor of matrix sensitization in such high energy exposure cases. Such sensitization pathways may become a potential method for enhancing resist sensitivity under high energy radiation through careful selection of matrix and PAG materials. A better understanding and study the efficiency of acid generation through direct and indirect PAG excitation pathways and the effect of PAG and matrix structure on these pathways would be extremely valuable for the design of future high sensitivity resist materials. In this work, the acid generation of typical ionic (onium salt) and non-ionic PAGs under DUV (248 nm) and electron-beam exposure in polymer film have been studied. The effect of PAG type and structure on its acid generation under photolysis and radiolysis has been determined. The effect of polymer resin structure on PAG photoacid generation under photolysis and radiolysis has also been investigated. Concepts for PAG and polymer design for producing enhanced sensitivity resists for excitational and ionizational exposure is discussed.

[1]  Hiroki Yamamoto,et al.  Relationship between Acid Generator Concentration and Acid Yield in Chemically Amplified Electron Beam Resist , 2006 .

[2]  Donald C. Hofer,et al.  PHOTOCHEMICAL AND PHOTOPHYSICAL STUDIES ON CHEMICALLY AMPLIFIED RESISTS , 1992 .

[3]  J. Crivello,et al.  Cationic polymerization — Iodonium and sulfonium salt photoinitiators , 1984 .

[4]  C. Willson,et al.  APPLICATIONS OF PHOTOINITIATORS TO THE DESIGN OF RESISTS FOR SEMICONDUCTOR MANUFACTURING. , 1983 .

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

[6]  Nigel P. Hacker,et al.  Cationic Photoinitiators: Solid State Photochemistry of Triphenylsulfonium Salts , 1990 .

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

[8]  Kevin M. Welsh,et al.  Mechanistic studies on the poly(4-tert-butoxycarbonyloxystyrene)/triphenylsulfonium salt photoinitiation process , 1991, Other Conferences.

[9]  Takahiro Kozawa,et al.  Pulse Radiolysis Study on Proton and Charge Transfer Reactions in Solid Poly(methyl methacrylate) , 2004 .

[10]  Todd R. Younkin,et al.  A new technique for studying photo-acid generator chemistry and physics in polymer films using on-wafer ellipsometry and acid-sensitive dyes , 2008, SPIE Advanced Lithography.

[11]  Nigel P. Hacker,et al.  Photochemistry of Triarylsulfonium Salts. , 1990 .

[12]  Masaru Yoshida,et al.  Novel electron-beam-induced reaction of a sulfonium salt in the solid state , 2006 .

[13]  Hiroki Yamamoto,et al.  Polymer-Structure Dependence of Acid Generation in Chemically Amplified Extreme Ultraviolet Resists , 2007 .