Measurement Method for Odd Component of Aberration Function Utilizing Alternating Phase Shift Mask

A novel measurement method for an odd component of an aberration function utilizing an alternating phase shift mask (PSM) is proposed based on optical image calculations. When high coherent illumination is applied, lateral fringe shift in the image, which is formed with lines and spaces(L/S) patterns of alternating PSM, is caused by the phase difference between two beams in interference. The shift distance is simply expressed by a quotient of the phase difference (measured in distance) and sine of the beam incident angle. Thus, by measuring the fringe shift distance by changing the pattern pitch, the odd component of the aberration function can be derived. To measure the fringe shift distance, a test device structure utilizing a modified MOS process is considered. By fabricating the test structure under the appropriate optical conditions and measuring the capacitances of the MOS structure, the fringe shift distance could be measured with high accuracy.