Patent ID: 7271905

Claim:
A reticle used for determining inter-field overlay error of a stage on a projection imaging tool, the reticle comprising: a first set of alignment attributes disposed along a first column; a second set of alignment attributes that are complementary to the first set of alignment attributes, the second set of alignment attributes disposed along a second column distinct from the first column, wherein the alignment attributes in the first and second sets are aligned in corresponding rows; a third set of alignment attributes distributed along a first row between the first and second column; and a fourth set of alignment attributes complementary to the third set of attributes, the fourth set of alignment attributes disposed in a second row distinct from the first row, wherein the alignment attributes in the third and fourth sets are aligned in corresponding columns, wherein the second and fourth alignment attributes are complementary to the first and third alignment attributes, respectively, in that exposure of the second and fourth alignment attributes interlock with a previous exposure of the first and third alignment attributes after the stage has been shifted in a desired direction relative to the reticle, wherein offset measurements of the exposed alignment attributes are used to determine a self referenced wafer stage overlay error map.