Photolithographic system using modified illumination

A modified annular illumination method known as PHOENEX (Photolithography enhanced by modified exposure) is discussed. Compared with annular illumination, the modified illumination effectively cuts off the background element, which does not contribute to the imaging. In this study, the process latitudes of the modified illumination are evaluated using experiments and simulations. The DOF limit is doubled compared to the conventional method. The optical contrast is improved by the shifter-shade-type phase shift mask. The resolution limit is also improved by the modified illumination. >