The Application of Silicon Rich Nitride Films for Use as Deep-Ultraviolet Lithography Phase-Shifting Masks

Abstract

Silicon rich nitride (SiRN) film prepared by plasma enhanced chemical vapor deposition (PECVD) for use as the phase-shifting mask for Deep-ultraviolet (UV) lithography has been developed. Optical properties and compositional characterizations of the SiRN films using Auger electron spectroscopy (AES) and spectroscopic ellipsometry (SE) combined with an empirical dielectric function (EDF), as well as phase-shifting mask simulation show that the SiRN is feasible for use in the application of single layer halftone phase-shifting mask (SLHTPSM) in the Deep-UV range. Optical constants of n ≈ 2.5 and k < 0.6 at 193 nm were realized by approaching the N/Si composition to the stoichiometric ratio of Si3N4. The deposition conditions for the films having the transmittance of 5 - 10% with a 180° phase shift at 193 nm (ArF) have been determined. Short wavelength extrapolation by EDF best-fit parameters based on a proper film-stack model provides a potential method to characterize the optical properties of amorphous SiRN down to about 190 nm, which is outside the range of most commercial SE's.