Abstract: A lithographic apparatus according to one embodiment includes an alignment system for aligning a substrate. The alignment system comprises an illuminator system configured to illuminate an alignment mark on the substrate with an illumination spot, the alignment mark comprising a plurality of lines and spaces. The system also includes a combiner system configured to transfer two images of the illuminated alignment mark without spatial filtering of the images, rotate the images 180° relatively to each other, and combine the two images; and a detection system configured to detect an alignment signal from the combined images and to determine a unique alignment position by selecting a specific one of extreme values in the detected alignment signal.

Abstract: A lithographic apparatus arranged to transfer a pattern from a patterning device onto a substrate includes two reference gratings provided in the substrate and two measurement gratings on top of the reference gratings, the measurement gratings being similar to the reference gratings, and oppositely biased in a single direction relative to the respective reference gratings. An overlay measurement device with an image sensor is used for obtaining pixel data of a measurement spot in each of the two measurement gratings. Asymmetry for each pixel in the measurement spot is measured, and from the pixel asymmetry measurements in associated pixels of each of the two measurement gratings an overlay value and a process dependent value is determined, as well as a quality indicator for the overlay value and the process dependent value.

Abstract: An inspection system is arranged to measure an overlay error by projecting a plurality of radiation beams, differing in wavelength and/or polarization, onto two targets. A first radiation beam is projected onto a first target and the reflected radiation A1+ is detected. The first target comprises two gratings having a bias +d with respect to each other. The first radiation beam is also projected on to a second target, which comprises two gratings having a bias ?d with respect to each other, and the reflected radiation A1? is detected. A second radiation beam, having a different wavelength and/or polarization from the first radiation beam, is projected onto the first target and reflected radiation A2+ is detected and projected onto the second target and reflected radiation A2? is detected. Detected radiations A1+, A1?, A2+, and A2? is used to determine the overlay error.

Abstract: A combined alignment and overlay target to be applied to a substrate to enable measurement of the alignment of the substrate with respect to its surroundings, and measurement of the relative alignment of a series of layers on the substrate, is disclosed. In an embodiment, the target comprises an array of structures substantially equidistant apart except for a portion of the structures that are offset by a specific amount in a first direction, and a second portion of the structures that are offset by the same amount in the opposite direction. This target on the substrate may be used to measure its alignment and the same target applied to a second layer, superposed on a first layer, may be used to measure overlay.

Abstract: Simultaneous measurement of two orthogonally polarized beams upon diffraction from a substrate is done to determine properties of the substrate. Linearly polarized light sources with their radiation polarized in orthogonal directions are passed via two non-polarizing beamsplitters, one rotated by 90° with respect to the other. The combined beam is then diffracted off a substrate before being passed back through a non-polarizing beamsplitter and through a phase shifter and a Wollaston prism before being measured by a CCD camera. In this way, the phase and intensities for various phase steps of the two polarized beams may thereby be measured and the polarization state of the beams may be determined. If the phase shifter is turned to zero (i.e. with no phase shifting), the grating of the substrate has its parameters measured with TE and TM polarized light simultaneously with the same detector system.

Abstract: An overlay target on a substrate includes two sets of gratings; the first set having a pitch P1 and the second set having a pitch P2 and each set including a grating with an orientation substantially perpendicular to the first grating of each set. When a layer of resist is to be aligned with the layer below it, the same overlay marks are provided on the upper layer and the relative positions of the overlay targets on the upper layer and the lower layer are compared by shining an overlay beam on to the overlay targets and measuring the diffraction spectrum of the reflected beam. Having two sets of overlay targets with different pitches in gratings enables the measurement of overlay errors that are greater than the pitch of either one of the overlay gratings.