Extreme ultraviolet (EUV) lithography has gained momentum as the method of choice for <32-nm half-pitch device
fabrication. In this paper, we describe our initial attempts to increase an EUV resist's sensitivity without compromising
resolution and line roughness via introduction of a thermally crosslinkable underlayer. The main purpose is to test the
possibility of using a combination of photoacid generators (PAGs) and EUV sensitizers (phenol type) in the underlayer
designs to enhance the overall performance of EUV resists. We have demonstrated the possible benefits of adding an
EUV underlayer into the regular EUV litho stack and investigated the effect of PAG types and loadings on the
photospeed and litho performance of three different EUV resists.
A photosensitive developer-soluble bottom anti-reflective coating (DBARC) system is described for KrF and ArF lithographic applications. The system contains an acid-degradable branched polymer that is self-crosslinked into a polymeric film after spin coating and baking at high temperature, rendering a solvent-insoluble coating. The DBARC coating is tunable in terms having the appropriate light absorption (k value) and thickness for desirable reflection control. After the exposure of the resist, the DBARC layer decrosslinks into developer-soluble small molecules in the presence of photoacid generator (PAG). Thus the DBARC layer is removed simultaneously with the photoresist in the development process, instead of being etched away in a plasma-etching chamber in the case of traditional BARC layers. The etch budget is significantly improved so that a thin resist can be used for better resolution. Alternatively, the etch step can be omitted in the case of the formation of layers that may be damaged by exposure to plasma.