Experimental characterization of model resist materials

Abstract

New resists are needed to advance EUV lithography. Tailored design of efficient photoresist is impossible without fundamental understanding of EUV induced chemistry. The absorption of an EUV photon by a thin film resist leads to emission of primary and secondary electrons. The electrons may travel up to tens of nanometers before losing their kinetic energy via collisions which initiate chemical reactions. The “blur” of an aerial image is directly related to the distance that electrons are able to travel and initiate chemistry in the resist. Thus, identifying how to measure and influence the absorption of EUV photons, emission of electrons, and distance traveled by the secondary electrons is extremely beneficial to the resist community. In this work, we present several experimental techniques to probe model polymer materials to investigate the impact of specific chemical groups on three critical resist properties: EUV absorption, electron emission, and the electron attenuation length (EAL). EUV absorption dictates the efficiency of the film to absorb photons. Total electron yield (TEY) provides information on the conversion of absorbed EUV photons to electrons, whereas photoelectron spectroscopy (PES) provides information on energies and abundance of generated electrons. The EAL corresponds to the thickness of a material required to reduce the number of emitted electrons to 1/e of the initial value. The EAL reveals the distance the electrons can travel in a resist film, which is directly related to the electron blur. Correlations between the obtained experimental values is discussed.