Synthesis, Characterization, and Electron-Beam Lithography of Tetakis(Triphenylstannyl) Orthosilicate and Tetrakis(Triacetoxystannyl) Orthosilicate for the Development of Inorganic Molecular EUV Resists.

As the continued miniaturization of semiconductor devices drives the adoption of extreme ultraviolet (EUV) lithography, inorganic molecular photoresists have attracted attention because of their small molecular size and high etch resistance. Among them, tin-oxo clusters are especially promising because of their high EUV absorption cross sections. Herein, we report the synthesis of tetrakis(triphenylstannyl) orthosilicate as an inorganic molecular photoresist candidate. Its structure was determined by single-crystal X-ray diffraction (SC-XRD) and supported by 1H, 13C, 119Sn, and 29Si NMR spectroscopy and field-desorption mass spectrometry (FD-MS). However, the compound exhibited extremely poor solubility in common organic solvents, limiting its applicability in lithography. To overcome this limitation, the phenyl ligands were replaced with acetoxy groups, yielding tetrakis(triacetoxystannyl) orthosilicate. Its structure was confirmed by 1H, 13C, 119Sn, and 29Si NMR spectroscopy, and the solubility was improved, enabling uniform thin-film formation. Electron-beam lithography evaluation demonstrated high sensitivity, producing 30 and 20 nm half-pitch line/space patterns at doses of 700 and 1500 μC/cm2, respectively. These results indicate that tetrakis(triacetoxystannyl) orthosilicate is a promising inorganic molecular photoresist candidate for EUV lithography.