Abstract:
Disclosed is a method of determining a characteristic of interest, in particular focus, relating to a structure on a substrate formed by a lithographic process, and an associated patterning device and lithographic system. The method comprises forming a modified substrate feature on the substrate using a corresponding modified reticle feature on a patterning device, the modified substrate feature being formed for a primary function other than metrology, more specifically for providing a support for a vertically integrated structure. The modified reticle feature is such that said modified substrate feature is formed with a geometry dependent on the characteristic of interest during formation. The modified substrate feature can be measured to determine said characteristic of interest.
Abstract:
A method including obtaining a measurement result from a target on a substrate, by using a substrate measurement recipe; determining, by a hardware computer system, a parameter from the measurement result, wherein the parameter characterizes dependence of the measurement result on an optical path length of the target for incident radiation used in the substrate measurement recipe and the determining the parameter includes determining dependence of the measurement result on a relative change of wavelength of the incident radiation; and if the parameter is not within a specified range, adjusting the substrate measurement recipe.
Abstract:
Disclosed is a method of measuring a focus parameter from a focus target. and associated substrate and associated patterning device. The focus target comprises at least a first sub-target and a second sub-target, each having at least a periodic main feature, wherein a respective pitch and/or dimensional parameter of at least some sub-elements of the main feature are configured such that said first sub-target and second sub-target have a respective different best focus value; and wherein each said main feature is formed with a focus dependent center-of-mass and/or pitch. The method comprises obtaining a first measurement signal from said first sub-target and a second measurement signal from said second sub-target; determining a difference signal of said first measurement signal and second measurement signal; and determining said focus parameter from said difference signal.
Abstract:
Focus performance of a lithographic apparatus is measured using pairs of targets that have been exposed (1110) with an aberration setting (e.g. astigmatism) that induces a relative best focus offset between them. A calibration curve (904) is obtained in advance by exposing similar targets on FEM wafers (1174, 1172). In a set-up phase, calibration curves are obtained using multiple aberration settings, and an anchor point (910) is recorded, where all the calibration curves intersect. When a new calibration curve is measured (1192), the anchor point is used to produce an adjusted updated calibration curve (1004′) to cancel focus drift and optionally to measure drift of astigmatism. Another aspect of the disclosure (FIG. 13-15) uses two aberration settings (+AST, −AST) in each measurement, reducing sensitivity to astigmatism drift. Another aspect (FIG. 16-17) uses pairs of targets printed with relative focus offsets, by double exposure in one resist layer.
Abstract:
Method for determining lithographic quality of a structure produced by a lithographic process using a periodic pattern, such as a grating, detects lithographic process window edges and optimum process conditions. Method steps are: 602: printing a structure using a lithographic process using a grating pattern; 604: selecting a first characteristic, such as a polarization direction, for the illumination; 606: illuminating the structure with incident radiation with first characteristic 608: detecting scattered radiation; 610: selecting a second characteristic, such as a different polarization direction, for the illumination; 612: illuminating the structure with incident radiation with the second characteristic; 614: detecting scattered radiation; 616: rotating one or more angularly resolved spectrum to line up the polarizations, thus correcting for different orientations of the polarizations; 618: determining a difference between the measured angularly resolved spectra; and 620: determining a value of lithographic quality of the structure using the determined difference.