摘要
This work aims to enhance the edge resistance and e-beam lithographic performance of two tin oxide clusters (vinylSn)6O4(sec-butylCO2)8Cl2 (1) and (vinylSn)3(i-PrSn)3O4(sec-butylCO2)8Cl2 (2) through chemical hydroxylation with aqueous LiOH, yielding two new hydroxylated tin oxide clusters, (vinylSn)6O4(sec-butylCO2)3(OH)7 (3) and (vinylSn)3(i-PrSn)3O4(sec-butylCO2)1.5(OH)8.5 (4) respectively. Clusters (3) and (4) each contain three functional groups: vinyltin moieties that serve as radical propagation units, sec-butylCO2 and i-Pr-Sn groups that act as radical sources, and additional Sn-OH groups serving as linkage units. Clusters (3) and (4) are better than initial carboxylate clusters (1) and (2), showing marked improvements in both edge resistance and e-beam lithographic performance, including pattern resolution and line edge roughness (LER), even at reduced energy doses. For cluster (4), a modest e-beam dose of J = 1280 μC/cm2 can resolve a small HP = 19 nm pattern with a low LER of 2.8 nm, corresponding to a small Z-factor of 6.88 × 10-7 nm3·μC. The etch selectivity, S = RateSiO2/RatePR, was calculated to be S = 5.7 for cluster (3) and S = 9.2 for cluster (4), much higher than the values S = 1.4 and 5.4, respectively, for clusters (1)-(2). Such a small Z-factor and a remarkable etch selectivity for cluster (4) highlight its commercial potential. Our mechanistic studies using FTIR and HRXPS reveal two aggregation processes that follow an initial light-induced decarboxylation step: (i) Sn-OH groups that promote molecular linkage, and (ii) a radical chain propagation process. The non-radical aggregation in step (i) contributes to high-quality EBL, while the high SnO2 content provides strong edge resistance.