Patent ID: 7317824

Claim:
A method for determining the relative shift between two or more successive layers of a substrate, the method comprising: capturing an image of an overlay mark formed on the substrate, the overlay mark having a plurality of working zones and comprising: at least one test pattern for determining the relative shift between a first and a second layer of the substrate in a first direction, the test pattern having a first set of working zones and a second set of working zones, the first set being disposed on a first layer of the substrate and having at least two working zones diagonally opposed and spatially offset relative to one another, the second set being disposed on a second layer of the substrate and having at least two working zones diagonally opposed and spatially offset relative to one another, each of the working zones having a periodic structure positioned therein, each of the periodic structures including a plurality of coarsely segmented elements that are each formed from a plurality of finely segmented elements, the plurality of finely segmented elements being evenly divided over the entire coarsely segmented elements; selecting a plurality of working zones from the captured image, wherein at least one working zone from each layer is selected; forming representative signals for each of the selected working zones, wherein at least one signal for each layer is formed; and comparing the signal from a first layer to a signal from a second layer to determine the relative shift between different layers.