Characteristics of standing-wave effect of off-axis illumination depending on two different resist systems and the polarization effect of ste

摘要

Abstract: The off-axis illumination technique either using a quadrupole aperture or diffracting grating was known as a good method to enhance both resolution and depth of focus. Severe variations of critical dimension over topography area were observed in our initial experiments using advanced tilted illumination on mask (ATOM) on our actual device. In this paper, the difference of standing wave effect between ATOM and conventional illumination is analyzed and compared in view of two different resist systems, bleachable and non-bleachable resists, and the polarization affect of the stepper. As a result, bleachable resists show worse standing wave effect in ATOM than in conventional illumination. Non-bleaching resists, however, show no difference in standing wave effect for both ATOM and conventional illumination. This is in good agreement with simulation results. In conclusion, because standing wave effect is not only a function of resist thickness but also a function of bleaching rate, Dill's parameters A, B, and C should be controlled as well as resist thickness especially for off axis illumination. !7