A Surface-Silylated Single-Layer Resist Using Chemical Amplification for Deep Ultraviolet Lithography: II. Limited Permeation of Si Compounds from Liquid Phase*

Abstract

A single thick layer of poly(vinyl phenol) containing onium salt was surface-silylated uniformly through contact with hexamethyl-cyclotrisilazane or hexamethyl-disilazane in solution to obtain a bilevel structure, similarly to a previous silylation study in the vapor phase. Silicon atoms were effectively incorporated into the surface sublayer by limited permeation of the solute and reaction with –OH to form –O–SiR3. The O2 reactive ion etching (RIE) durability of the silylated sublayer of 170–220 nm thickness was 15–38 times as high as that of the unsilylated bulk layer. The resist layer was patterned by 5–10 mJ/cm2 deep ultraviolet exposure, chemically amplified desilylation during postexposure baking, and wet development with alkali to remove the surface sublayer in the exposed area, forming a shallow, recessed image. When the layer, particularly that silylated with hexamethyl-disilazane, was plasma-developed by O2 RIE, the bulk layer in the exposed area was clearly blanked to the substrate to give a positive-tone image with a high aspect ratio.