Lateral shift measurement using an optical technique

摘要

Alignment of layers during manufacture of a multi-layer sample is controlled by applying optical measurements to a measurement site in the sample. The measurement site includes two diffractive structures located one above the other in two different layers, respectively. The optical measurements include at least two measurements with different polarization states of incident light, each measurement including illuminating the measurement site so as to illuminate one of the diffractive structures through the other. The diffraction properties of the measurement site are indicative of a lateral shift between the diffractive structures. The diffraction properties detected are analyzed for the different polarization states of the incident light to determine an existing lateral shift between the layers.

主权项

1. A structure configured for overlay measurement on a sample, said structure comprising a pair of diffractive structures having predetermined geometries and being arranged at locations relative to each other corresponding to alignment of layers in the sample, wherein
each of the diffractive structures of the pair comprises a diffractive pattern formed by features aligned along at least one axis, the diffractive structures of the pair are arranged such that the features of one of the diffractive structures of the pair are located either above or between the features of the other diffractive structure of said pair, with a predetermined lateral shift between the diffractive patterns in the diffractive structures in accordance with a predetermined model of simulated diffraction effects from incident electromagnetic radiation interaction with laterally shifted diffractive structures of a pair of such structures of said predetermined geometries, thereby enabling direct overlay measurement of a lateral shift between the layers in the sample from diffraction of incident electromagnetic radiation from said pair of diffractive structures.