Patent ID: 8502955
Filing Date: 2013-08-06
Classification: G03B,G03F

Abstract:
1. A method of determining a characteristic of features on a substrate, the method comprising: forming a first population of a first target and a first population of a second target on a single layer of the substrate, the first population of the first target being distinct from the first population of the second target; forming a second population of the first target and a second population of the second target on the single layer of the substrate, the second population of the first target being distinct from the second population of the second target; detecting radiation reflected from the first target; calculating a first characteristic of either the first population or the second population of the first target using radiation reflected from the first target; detecting radiation reflected from the second target; and calculating a second characteristic of either the first population or the second population of the second target using radiation reflected from the second target; wherein the first population of the first target has a first asymmetry with respect to the second population of the first target and the first population of the second target has a second asymmetry with respect to the second population of the second target, the first asymmetry comprising a difference in the spacing between the features of the first and second populations of the first target, and the second asymmetry comprising a difference in a critical dimension of the features of the first and second populations of the second target.