Patent ID: 9631979
Date: 2017-04-25
CPC Classifications: G01J,G03F

Claim:
1. A photomask structure for characterizing a beam parameter of an electromagnetic beam, the electromagnetic beam characterized by a wavelength, the photomask structure comprising: a. a substrate, having a planar surface, substantially transparent to the electromagnetic beam, and having a characteristic optical depth at the wavelength of the electromagnetic beam; and b. a plurality of linear segments of material opaque to the electromagnetic beam formed into a plurality of polygons upon the planar surface of the substrate, wherein each of the plurality of polygons encloses an enclosed region having an enclosed optical depth, different from the characteristic optical depth of the substrate, by a fraction less than one wavelength of the electromagnetic beam; and wherein any intersection, between closed polygons enclosing two enclosed regions characterized by an identical enclosed optical depth, occurs at no more than two points.