Phase Mask and Spatial Filter for Excimer Lithography System

In response to AF95-135, we propose to determine the feasibility of enhancing the resolution of current excimer lithography systems by employing spatial filter and phase mask of novel designs. The spatial filter (which is a diffractive optical element) will be specially designed for edge enhancement to improve on the high frequency contents of the images illuminating the photoresist and the resolution performance of the excimer lithography system. The phase mask (which is another diffractive optical element) will be special designed for controlling the illumination direction of the mask (or reticle) in the excimer lithography system to achieve superresolution performance (or the performance of a larger effective aperture than the actual lens aperture). These two approaches will result in low cost add-on accessories (with mechanism similar to reticle or color filter changers) readily insertable to the production lithography system, one for each system model. They will overcome the disadvantage in the existing method of using phase shifting masks, which require custom design and fabrication specific to each integrated circuit; they will not require redesigning the lamp housing for illumination control. To demonstrate the feasibility of resolution enhancement, NIPT will work closely with ANVIK to ensure that the designs and the fabricated spatial filter and phase mask will function properly in their excimer lithography systems.