Nanofabrication of Silicon Gratings Enabled by Vapor-Phase, Highly Uniform Self-Assembled Monolayer Resists

The emerging dry resists enable new avenues for advanced photoresist systems, which are pivotal to microelectronic fabrication technology. Herein, a highly uniform self-assembled monolayer (SAM) of octadecyltrichlorosilane (C₁₈H₃₇SiCl₃, OTS) is deposited from the vapor phase and employed as the dry resist material. The SAM resists are exposed to helium ion (He⁺) beams with a processing window of 60-200 μC cm^-2, identified by the outcomes of exposure and etching characterization. Following ultraviolet/ozone (UVO) development, the patterned SAM resists are employed as a mask to etch oxide in hydrofluoric acid (HF). X-ray photoelectron spectroscopy (XPS) reveals significant chemical compositional distinction on the He⁺/UVO-treated areas with oxygenated groups. The formation of hydrogen bonds between these hydrophilic functional groups and HF facilitates wet etching of the oxide. Finally, the patterns are transferred to the underlying silicon substrate by using the etched oxide as a hard mask, creating a grating structure with a uniform depth of 21 nm. The investigation of pattern transfer with highly uniform OTS facilitates the SAM resist and sheds light on the industrialization of dry resist technology.