Detectable overlay targets with strong definition of center locations

A semiconductor device, the semiconductor device including an overlay measurement target, the overlay measurement target comprising:

• a first ring target located on a first measured layer of the semiconductor device, the first ring target including a plurality of detectable features arranged in a circular manner having a first circumference;
• and
• a second ring target located on a second measured layer of the semiconductor device, the second ring target including a plurality of detectable features arranged in a circular manner having a second circumference different from the first circumference,
• wherein a center of the first ring target is detectable by:
• constructing a first mathematically constructed circle overlaid on a portion of an image of the semiconductor device including the first ring target, wherein a circumference of the first mathematically constructed circle is aligned along the plurality of detectable features associated with the first ring target, and
• determining the center of the first ring target as a center of the first mathematically constructed circle,
• wherein a center of the second ring target is detectable by:
• constructing a second mathematically constructed circle overlaid on a portion of an image of the semiconductor device including the second ring target, wherein a circumference of the second mathematically constructed circle is aligned along the plurality of detectable features associated with the second ring target, and
• determining the center of the second ring target as a center of the second mathematically constructed circle, and
• wherein a displacement between the center of the first ring target and the center of the second ring target indicates an overlay error between the first measured layer and the second measured layer.