Theoretical study of interfacial effects on low-energy electron dynamics in chemically amplified resist processes of photomask fabrication

Abstract

The resist thickness has decreased with the miniaturization of transistors. In chemically amplified electron beam resists used for photomask fabrication, thermalized electrons play an important role in acid generation. The interfacial effects of low-energy electrons strongly affect the latent image formation in thin resist films. In this study, we investigated the relationships between the boundary conditions of low-energy electrons at interfaces and the protected unit distribution in terms of resist thickness, concentrations of photoacid generators and photodecomposable quenchers (PDQs), and sensitivity. The dependences of chemical gradient and optimum PDQ concentration on the boundary conditions at the interfaces for low-energy electrons were clarified. It was found that the PDQ concentration should be optimized, depending on not only the boundary conditions but also the resist film thickness. That is, the resist depth profile can be controlled by the boundary conditions at the interfaces for low-energy electrons.