KLA Corporation
IMPROVED SELF-MOIRE GRATING DESIGN FOR USE IN METROLOGY

Abstract:

A grating for use in metrology including a periodic structure including a plurality of units having a pitch P, at least one unit of the plurality of units including at least a first periodic sub-structure having a first sub-pitch P1 smaller than the pitch P, and at least a second periodic sub-structure arranged along-side and separated from the first periodic sub-structure within the at least one unit and having a second sub-pitch P2 smaller than the pitch P and different from the first sub-pitch P1, P1 and P2 being selected to yield at least one Moir pitch P.sub.m=P1P2/(P2-P1), the pitch P being an integer multiple of the first sub-pitch P and of the second sub-pitch P2.