Odo Wunnicke

Surface properties and topography of 193-nm resist after exposure and development

Surface properties of photo resist lines are of particular interest in future semiconductor applications. Current hot topics as pattern collapse (PC) and line edge roughness (LER) are closely related to surface properties of the resist. The surface origin on PC and LER based on the interaction of the rinse liquid with the resist and the interaction between the resist surface and the developer, respectively. In this paper we present a characterization of a reference surface prepared by an open frame exposure. Utilizing scanning force microscopy (SFM) the surface topography is analyzed. From the SFM images vertical structures (root mean square roughness) as well as lateral structures (most prominent in-plane lengths) are extracted. Advancing and receding contact angles were measured to characterize changes in hydrophilic/hydrophobic surface properties of the photo resist after development. With increasing thickness loss of the initial film the surface roughness and the most prominent in-plane length scales increase while the contact angle decreases. An analogy of the prepared surfaces with phase separated structures is presented.

On the effect of cationic surfactants in the rinse to reduce pattern collapse in high aspect ratio patterning of photoresists

This paper presents a novel concept based on the mechanism of cationic surfactant adsorption on the photoresist surface. The minimum capillary forces calculated from the study with model photoresist surfaces and surfactant solutions correlated with a maximum of pattern collapse reduction obtained in the photolithographic process.