Radiation-Induced Acid Generation Reactions in Chemically Amplified Resists for Electron Beam and X-Ray Lithography

Abstract

The radiation-induced reactions of onium salts in some kinds of solutions and model compound solutions of chemically amplified electron beam (EB) and X-ray resists have been studied by means of picosecond and nanosecond pulse radiolysis. The following reaction mechanisms of the chemically amplified EB and X-ray resists have been elucidated. The radiation-induced reaction mechanisms are complicated due to the presence of several proton donors. The onium salts directly produce small amounts of Brønsted acids by EB and X-ray exposure and most of the Brønsted acids are formed from proton adducts of the base polymer. The onium salts are strong electron scavengers and promote the generation of the proton adducts in the chemically amplified resists.

Estimation of resist sensitivity for extreme ultraviolet lithography using an electron beam

“…The difference between EB and EUV resists is the energy absorption processes. [7][8][9] The EB-and EUV-induced radiation chemistry in CARs has been discussed from the perspective of the configuration of spurs, acid yield, and acid distribution. 10 Recently our research group found that the resist sensitivity in the EUV/soft X-ray region can be estimated from the exposure results at any wavelength in this region 11,12 and also from the exposure results for EB.…”

Radiation Chemistry of Triphenylsulfonium Salts in EB and X-Ray Chemically Amplified Resists-Proton Generation Mechanisms.

“…From the results of our research, the reaction mechanisms of the acid generation have been proposed for EB and Xray CA resists [6]. It is proposed that the main reaction path of the acid generation is considered to be the path through the ionization of a matrix polymer because the energy of the ionizing radiation is absorbed mostly by the matrix polymer.…”

“…In the presence of sulfonium salt, the electrons and radical anions (CH3CN') are scavenged through the one-electron reduction of the onium salts [6,10,11 ], and the salts are decomposed (reaction (4) and (5)):…”

“…CH3CNH+ + e -3 neutral products (6) CH3CNH+ + CH3CN'--> neutral products (7) Thus, the yield and lifetime of H+ (existing as CH3CNH in acetonitrile) are increased by adding sulfonium salts. As the decomposition of onium salts is very fast, we observed transient intermediates by nanosecond EB pulse radiolysis.…”

Influence of Water on Time-Delay Problem in a Chemically Amplified Resist.

“…This is the key difference between conventional and chemically amplified resist systems and causes problems specific to chemically amplified resists. One aspect that has s storng influence on lithographic performance is the deactivation of catalytic acid by air-borne contaminants during exposure and PEB [4][5][6][7][8]. The influence of a small amount of Nmethylpyrollidone (NMP) on the formation of insoluble layers has already been reported.…”