Surface-silylated single-layer resist using chemical amplification for deep-ultraviolet lithography: I. Limited permeation of Si compounds from vapor phase

A single thick layer of poly(vinyl phenol) on a substrate was surface-silylated by exposure to hexamethyl-disilazane vapor to obtain a bilevel structure. Silicon atoms were effectively incorporated into the surface sublayer by limited vapor permeation and reaction with -OH to form -O-Si(CH3)3. The oxygen reactive-ion-etching (RIE) durability of the silylated sublayer of 50-150 nm thickness was 10-50 times as high as that of the unsilylated bulk layer. The surface-silylated single-layer (SSS) resist which contained a small amount of onium salt was patterned by 7-20 mJ/cm2 deep-ultraviolet (DUV) exposure, postexposure bake, wet development with aqueous tetramethyl-ammonium hydroxide, and dry development in an O2 RIE chamber. The surface sublayer in the exposed area was removed by wet development to form a shallow, recessed mesh pattern. When it was plasma-developed, the thick bulk layer in the exposed area was blanked to the substrate to form a positive-tone image with a high aspect ratio.