Gas phase silylation in the diffusion enhanced silylated resist process for application to sub-0.5 μm optical lithography

Abstract

The diffusion enhanced silylated resist (DESIRE) process has been presented as one of the most attractive surface imaging technologies for advanced optical lithography. It has been shown that the silylation step, usually carried out in a hexamethyldisilazane (HMDS) ambient, is one of the more critical steps in the process. In this paper an in-depth study of the silylation is presented. Several alternative mono- and polyfunctional silylating agents are evaluated for application in the DESIRE process. DMSDMA, TMSDMA, and TMDS are promising candidates, showing several advantages over HMDS. For the case of HMDS and TMDS, the kinetics of the silylation are additionally studied using Rutherford backscattering spectroscopy, Auger electron spectroscopy, and infrared measurements for various process conditions. In an earlier study we have reported lateral swelling for silylation with HMDS resulting from volume expansion of the silylated resist. Because of the reduced volume expansion and/or the lower silylation temperature, these alternative silylating agents reduce the swelling and surface roughness. It has been observed that the silylation process window can be greatly increased by optimizing the presilylation bake.