Enhanced Edge Etching Resistance and EUV Lithographic Performance of a Tin-Oxide Photoresist via a Blend Strategy

Enhancing the edge resistance capability of extensively studied metal carboxylate clusters as extreme ultraviolet (EUV) photoresists is a formidable and unsolved task. This work reports the first blend strategy involving a tin oxide carboxylate cluster, (vinylSn)₆(sec-C₄H₉CO₂)₈Cl₂O₄ (3) and [(BuSn)₁₂O₁₄(OH)₆](BF₄)₂ (4) in a weight ratio (3)/(4) = 1:2. Although cluster (3) demonstrates excellent performance as a photoresist in both e-beam and EUV lithography, its lithographic nanopatterns exhibit limited thickness and poor etching resistance. After the blending with cluster (4), the resulting blend (5) exhibits increased thickness in EUV lithographic nanopatterns along with a significant improvement in etching resistance tests. Remarkably, this blend achieves very high EUV resolutions with half-pitch (HP) values of 13–16 nm at low exposure doses of J = 50–60 mJ/cm². One representative EUV pattern can reach an outstanding Z-factor with a very small value of 2.65 × 10^–8 mJ·nm³. In the operative mechanism, the high photosensitivity originates from cluster (3), whereas the EUV pattern resolutions, edge etching resistance, and nanopattern thickness are enhanced by the 12-oxide cluster (4). FTIR and high-resolution X-ray photoelectron spectroscopy (HRXPS) analyses suggest closely cooperative interactions between clusters (3) and (4), involving radical formation and molecular aggregation.