Reticle OPC defect printability and detectability for 180-nm technology

An investigation was performed to determine the printability and defect detectability of reticle OPC defects for the 180 nm technology node. Two different OPC approaches were investigated, one based upon assist bar/serif features and the other based upon serif/jog features. Several critical defects were studied, including chrome extension defects on assist bars and pindots between assist bars and primary features. Wafers were printed using a 0.6 NA, DUV stepper and resulting wafer resist images measured by CD SEM. Edge defects as small as 200 nm cause greater than 10% change in local linewidth, 400 nm defects cause catastrophic wafer defects, and chrome spot with 260 nm diameter can shorten gap between two line ends by 10%. CD defects less than 75 nm on the reticle were found to have a significant impact on the process window. The programmed defect test reticles used to print the wafers were inspected on KLA-Tencor reticle inspection systems and the defect sensitivity capture curves plotted. Defect capture rates indicated that smaller than 200 nm edge defects and 125 nm CD defects are detected. Defect printability simulations were performed using database and aerial images gathered from an automated defect inspection system and compared to the experimental wafer results. The purpose of this test is to determine the feasibility of performing printability predictions in a mask production environment. A correlation between the simulations and the wafer results are shown.