Structural investigation of zinc-based photoresists with different substituents for high-resolution lithography

Abstract

The fineness of the photolithographic pattern depends largely on the composition and structure of the photoresist, and different structures endow metal-based photoresists with different photon-absorbing capabilities. Here, we synthesized zinc-based photoresists with different electron-effect substituents (amine and bromine) in the ligands and investigated the influence of the ligand groups on the sensitivity and resolution at deep ultraviolet and electron beam. The developed resist patterns exhibit that the sensitivity of the Zn-based photoresists containing bromine groups (Zn-PBBA) is nearly seven times higher than the Zn-based photoresists containing amine groups (Zn-PABA) at the same resolution under ultraviolet irradiation, which is supported by the density functional theory (DFT) calculations where a smaller HOMO–LUMO gap for Zn-PBBA is obtained. Analogously, the Zn-PBBA also showed better sensitivity and resolution than Zn-PABA at EBL, with a resolution of 70 nm at a dose of 800 mJ cm−2 by characterization with AFM. This work provides an understanding of the efficient structural design of photoresists and future guidance for the development of better-performing materials.