Photolithography System Using a Combination of Modified Illumination and Phase Shift Mask

Various methods have been developed to overcome the limitations in photolithography. Modified illumination and phase shift mask technologies have been developed in order to improve the depth of focus and resolution limit. We have combined these two methods and applied them to the step and repeat exposure system. Experiments using the modified illumination were carried out and subhalf-micron patterns were produced. The process latitude of 64M dynamic random access memory (DRAM) is doubled by this combination process.