Sensitizer for EUV Chemically Amplified Resist: Metal versus Halogen

Abstract

Extreme Ultraviolet (EUV) lithography utilizes photons of 91.6 eV energy to ionize resists, generating secondary electrons, thus enabling electron-driven reactions. Unlike photolithography, where photons below 7 eV selectively activate photoactive compounds, photons at 91.6 eV ionize all materials, subsequently generating secondary electrons. The energy and the numbers of secondary electrons generated after ionization are determined by the material chemistry. Several metals are reported to have high secondary electron generation capability and high EUV absorption, therefore metals can be one of the solution to deal with the insufficient photon density in resist. Halogen atoms like iodine and fluorine also provide high absorption which would be suitable alternative sensitizer to the metal salts sensitizer. In this work, we study metal salt sensitizers with different cations and anions as well as halogenated sensitizer in both polymer and PAG. Total electron yields are increased with increased resist absorption for both metal and halogen sensitizer. Sensitivity of resists with metal salt sensitizers increase, resulting in increased LCDU. However, halogenated sensitizers do not show positive correlation between sensitivity and electron yield as metal sensitizer. Through this study, we expect to explore materials that enable both high absorption and high photoelectron generation efficiency at 91.6 eV.

Effects of substituents in triphenylsulfonium cation on its radiation-induced decomposition and dissolution kinetics of chemically amplified resists

“…After exposure, the QCM substrates were baked at 90 °C for 60 s and cooled at 18 °C for 120 s. After being left overnight to discharge the QCM substrates, the samples were analyzed by QCM. The prepared PHS films were developed in a 2.38-wt% TMAH aqueous solution for 60 s or in water for 180 s at 23 °C. After the development, the samples were rinsed with pure water.…”

“…20,21) Tin (Sn) and iodine (I) are known to exhibit high absorption against EUV. 22,23) How such elements affect the dissolution of PHS films is still unknown. In this study, the substituent effects in acid generators were investigated using a typical acid generator, TPS-TF.…”

High Sensitivity Resists for EUV Lithography: A Review of Material Design Strategies and Performance Results

“…Metal sensitizers improve both EUV photon absorption and electron yield resulting in higher sensitivity. Fluorine and iodine sensitizers also improved electron generation with their higher absorption but the chemical environment where these halogens are bonded influences heavily the sensitivity [66]. Nagahara et al introduced Flood exposure Assisted Chemical gradient Enhancement Technology (FACET) to improve the resolution, process control, roughness, patterning failure, and sensitivity in EUV resist.…”

Application of higher absorption materials to the underlayer of EUV lithography

“…In recent years, metal oxide resists and other metal containing resists has been proposed as an alternative approach for the stochastic issue and the issue of sensitivity. These methods have been shown an improved resolution [3,4], and chemically amplified resists with higher absorption units have also been proposed [5,6,7,8].…”