Patent ID: 7808638

Claim:
A method of conducting scatterometry measurements using simultaneous target illumination with a plurality of illuminating light beams, the method comprising: providing a substrate with at least two scatterometry overlay, SCOL, target groups, wherein each target group has a long axis that extends along the length of the target group and wherein a first target group and a second target group are arranged such that a long axis of the target group is arranged perpendicular to a long axis of the second target group; simultaneously directing a set of three illumination beams onto the substrate to form an illumination dot pattern such that an arrangement of two perpendicular dot pairs are formed with each pair sharing a common dot and wherein a first dot pair defines an illumination axis that is perpendicular to an illumination axis of a second dot pair; directing the first dot pair onto the first target group such that the illumination axis of the first dot pair is perpendicular to the long axis of the first target group and each dot of the first dot pair illuminates a target of the first target group to produce at least two associated scattering signals associated with each illuminated target of the first target group, measuring the scattering signals associated with the first dot pair and the first target group; directing the second dot pair onto the second target group such that the illumination axis of the second dot pair is perpendicular to the long axis of the second target group and each dot of the second dot pair illuminates a target of the second target group to produce at least two associated scattering signals associated with each illuminated target of the second target group; measuring the scattering signals associated with the second dot pair and the second target group; and processing measurements of at least two associated scattering signals to obtain scatterometry metrology information.