Higher order aberration measurement with printed patterns under extremely reduced σ illumination

Measurement techniques for higher order aberrations of a projection optical system in photolithographic exposure tools have been established. Even-type and odd-type aberrations are independently obtained from printed grouped lines on a wafer by three-beam interference under highly coherent illumination. Even-type aberrations, i.e. spherical aberration and astigmatism, are derived from the best focus position of vertical, horizontal and orthogonal grouped lines by an optical microscope. Odd-type aberrations, i.e. coma and trefoil, are obtained by detecting relative shifts of fine grouped lines to a large pattern by an overlay inspection tool. The quantitative diagnosis for lens aberrations was demonstrated to a krypton fluoride excimer laser scanner.