Photolithography using half-tone phase-shifting mask

A half-tone phase-shifting mask (HPM) is effective in improving resolution and focus latitude of an isolated hole pattern. HPM can be fabricated by the conventional method and a practical phase-shifting technique can be realized using HPM. The authors developed a mask-defect repair method and an opaque pattern formation technique which suppresses the peripheral exposure due to light leakage. The mask defect was repaired by blackening the defect. The formation of an opaque ring in the peripheral area of a main field was achieved by placing patterns with dimensions smaller than the resolution limit. In addition, it was found by both simulation and experiment that the focus latitude could be expanded by placing additional patterns at proper locations and by illumination of highly coherent light.