Phase shift masks (PSMs) have been investigated to improve resolution and depth of focus in optical lithography process and phase shift masks using 157nm plused fluorine laser has emerged as the leading candidate at the next generation lithography for the post-193nm generation and its target application is for the 100 to 70 nm generation.
In this study, high-transmittance attenuated Phase Shift Masks (HT-Att-PSMs) have been investigated to satisfy the requirements of 20±5% transmittance and 180°phase shift at the exposure wavelength of 157 nm and less than 40% transmittance at the inspection wavelength of 193 nm.
Silicon oxynitrofluoride has been studied as a new candidate material for HT-Att-PSM. At first, optimum conditions of composition and thickness were shown by n(refractive index)-k(extinction coefficient)-d(thickness) charts developed to simulate the optimum range of optical constant for HT-Att-PSM using the matrix method. Silicon oxynitrofluoride films were deposited by changing of variables such as gas flow rate, deposition power and deposition time to find optimum conditions to meet the simulated range. This study examined effects of processing variables on the optical properties of silicon oxynitrofluoride films and established optimum conditions of silicon oxynitrofluoride films for HT-Att-PSM.
