Dual-tone Application of a Tin-Oxo Cage Photoresist Under E-beam and EUV Exposure

We report on the dual-tone property of the tin-oxo cage (BuSn)₁₂O₁₄(OH)₆](OH)₂ photoresist. After exposing the resist film to a low dose extreme ultraviolet radiation or electron beam, applying a post exposure bake step and development with isopropanol/H₂O (2:1), a positive tone image is observed. The previously observed negative tone is found at higher doses. Atomic force microscopy and scanning electron microscopy were used to characterize the topography of the patterns. X-ray photoelectron spectroscopy was used to elucidate the chemical changes of the tin-oxo cages under different conditions. The photoresist, which has dual-tone property, paves the way to fabricate sophisticated structures in a single photoresist layer or may lead to metal-containing resists with improved sensitivity.