Patent ID: 8885150

Claim:
A scatterometer configured to measure a property of a substrate comprising: a radiation source configured to provide a radiation beam to produce a radiated spot on a target on a surface of the substrate, the radiated spot comprising: a dimension smaller than a dimension of the target in a direction along the target, the direction being a movement direction of the radiated spot on the target, the movement of the radiated spot being performed in a series of discrete steps, and a plurality of positions on the target, wherein each of the plurality of positions corresponds to a respective discrete step movement of the radiated spot; a detector configured to: detect a spectrum of the radiation beam reflected from each of the plurality of positions of the radiated spot on the target on the surface of the substrate, and produce a plurality of measurement signals, wherein: each of the plurality of measurement signals corresponds to a respective one of the plurality of positions of the radiated spot, and each of the plurality of measurement signals is a representative of the spectrum detected from the corresponding respective one of the plurality of positions of the radiated spot; and a processor configured to: process each of the plurality of measurement signals produced by the detector corresponding to the respective one of the plurality of positions of the radiated spot; and derive, using the plurality of measurement signals, a single value that is representative of the property of the substrate.