Development and characterization of nitride and oxide based composite materials for sub 0.18 μm attenuated phase shift masking

Abstract

Results are presented from investigations into the UV properties of various oxide, nitride, and intermetallic materials for application as attenuated phase shift masking films for 248 and 193 nm wavelengths. There are several materials which are potential candidates as attenuating phase shifting films at short UV wavelengths. None of these, however, are elemental films or stoichiometric compounds. Non-stoichiometric alloys, cermets, and composite materials do though allow for phase shift mask solutions. Through modeling of free electron and bound electron behavior of metals, dielectrics, and semiconductors, predications can be made about the optical properties of their combinations. By adjusting the material stoichiometry through control of sputter deposition parameters, films can be tailored for specific optical applications. Through use of extinction coefficient/refractive index plots (k-n plots), evaluation of phase shifting films is made possible. Details on four classes of materials are presented: a tantalum silicon oxide (TaSiO), an aluminum rich aluminum nitride (Al/AlN), a molybdenum silicon oxide (MoSiO), and non-stoichiometric silicon nitride (SixNy). Attenuated phase shifting films have been produced based on all four classes. Optical properties and RIE etch processes for materials are compared.