APPARATUS AND METHOD FOR DETECTING OVERLAY ERRORS USING SCATTEROMETRY

PROBLEM TO BE SOLVED: To provide improved scatterometry overlay (SCOL) target structures and methods.SOLUTION: The present invention includes a scatterometry target for use in determining the alignment between substrate layers. A target arrangement is formed on a substrate and includes a plurality of target cells. Each cell has two layers of periodic features constructed such that an upper layer is arranged above a lower layer and configured so that the periodic features of the upper layer have an offset to and/or different pitch from periodic features of the lower layer. The pitches are arranged to generate a periodic signal when the target is exposed to an illumination source. The target also includes disambiguation features arranged between the cells and configured to resolve ambiguities caused by the periodic signals generated by the cells when exposed to the illumination source.