Patent ID: 7528953
Filing Date: 2009-05-05
Classification: G03F

Abstract:
1. A system for imaging a plurality of targets in a semiconductor inspection or metrology tool, comprising: a beam generator for directing at least one incident beam having a wavelength λ towards a periodic target having structures with a specific pitch p, wherein a plurality of output beams are scattered from the periodic target in response to the at least one incident beam; an imaging lens system for passing only a first output beam and a second output beam from the target, wherein the imaging lens system is adapted such that an angular separation between the first and the second output beams, λ, and the pitch are selected to cause the first and second output beams to form a substantially pure sinusoidal image; a sensor for imaging the sinusoidal image; and a controller for causing the beam generator to direct the at least one incident beam towards a first and second periodic target, each having a specific pitch p, so that the sensor detects a first sinusoidal image of the first target and a second sinusoidal image of the second target and to analyze the first and second sinusoidal images to determine whether the first and second targets have an overlay error or an alignment error, wherein the first target is on a first layer and the second target is on a second layer, wherein the controller is arranged to determine an overlay error between the first and second targets by defining a misalignment between the first and second sinusoidal images as the overlay error.