Chromium aluminum oxide films for ArF line high transmittance attenuated phase shifting mask application

Abstract

Phase shifting masks (PSMs) provide us with a breakthrough in the future semiconductor industry by extending submicrometer lithography further. PSMs have been used for several years, and their requirements are changing due to the development of other technologies. first, it became possible to use a high transmittance attenuated PSM (HT-Att-PSM) because of improvement in the photoresist technology. Second, continuous improvement in the inspectional equipment technology lowered the inspection wavelength. Now, we are provisionally targeting to make HT-Att-PSM having 20+/-5% transmittance at the ArF line and to choose the KrF line as the inspection wavelength. We simulate the optimum conditions for HT-Att-PSM using the matrix method. The simulation is performed to find the optimum range of the variables that yield 180 deg phase shift and 20+/-5% transmittance at the exposure wavelength, and less than 40% transmittance at the inspection wavelength. Based on the simulation results, we find the optimum fabrication condition of HT-Att-PSM. Using measured optical constants as a function of film composition, we determine the optimum film composition yielding 20+/-5% transmittance and 180 deg phase shift at the exposure wavelength and below 40% transmittance at the inspection wavelength. As a result, Cr2Al8O15 film with thickness of 124 nm is found to be suitable for an ArF line HT-Att-PSM. (C) 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)00211-7].