Mechanisms of EUV Exposure: Photons, Electrons and Hole

The microelectronics industry's movement toward smaller and smaller feature sizes has necessitated a shift to Extreme Ultra-Violet (EUV) lithography to be able to pattern sub 20-nm features, much like earlier shifts from i-line to 248 nm. However, this shift from 193-nm lithography to EUV (13.5 nm) poses significant obstacles. EUV is the first optical lithography to operate in an energy range (92 eV per photon vs. 6.4 eV per photon for 193 nm lithography) above the electron binding energies of common resist atomic species. This significant energy increase complicates resist design. For exposures of equal dose, resists receive 14 times fewer photons in EUV relative to 193 nm. Thus, for EUV photoresists to be able to reap the benefits of smaller resolution they must also maximize absorption while still maintaining photo-reactivity. In order to design EUV resists for manufacturing, the first step is to understand the mechanisms of exposure involved in EUV photochemistry.;In this Thesis, we present three studies performed to understand the behavior and reactivity of electrons and holes in chemically amplified photoresists. These three studies can be characterized by their approaches---computational and experimental, and serve to develop better resist models for EUV reactions and mechanisms.;The first study discusses the adaptation and improvement of a Monte Carlo electron-resist simulation program to understand EUV photochemistry by modeling total electron yield, thickness loss, and sub-10 eV electron-resist interactions. The second study evaluates the mechanism of internal excitation as a possible pathway for acid generation in EUV resists by the investigation of electron-induced fluorescence. The third study aims to investigate the reactivity of electrons and holes in chemically amplified resists and determine their relative contributions to acid production.