Patent ID: 11137692

Abstract:
Metrology targets, design methods and measurement methods thereof are provided with periodic structure(s) which are oblique with respect to orthogonal production axes X and Y of the lithography tool—enabling more accurate overlay measurements of devices having diagonal (oblique, tilted) elements such as DRAM devices. One or more oblique periodic structure(s) may be used to provide one- or two-dimensional signals, with respect to one or more layers, possibly providing overlay measurements for multiple steps applied to one layer. The oblique periodic structure(s) may be used to modify current metrology target designs (e.g., imaging targets and/or scatterometry targets) or to design new targets, and measurement algorithms may be adjusted respectively to derive signals from the oblique periodic structure(s) and/or to provide pre-processed images thereof. The disclosed targets are process compatible and reflect more accurately the device overlays with respect to various process steps.