Abstract: Alignment of mask layers in semiconductor manufacturing is carried out by using alignment lines having at least one row of diffractively reflecting or scattering features on the lines. The features are made using a phase shift mask which, in combination with selected photoresist, suppresses second and higher order lobes, thereby allowing the features to be more closely spaced than by lithography. The features appear as light reflecting or scattering dots or spots in rows on ridges of standard or non-standard alignment lines. Laser light of only one color is used for mask alignment.