Abstract:
Metrology targets are formed by a lithographic process, each target comprising a bottom grating and a top grating. Overlay performance of the lithographic process can be measured by illuminating each target with radiation and observing asymmetry in diffracted radiation. Parameters of metrology recipe and target design are selected so as to maximize accuracy of measurement of overlay, rather than reproducibility. The method includes calculating at least one of a relative amplitude and a relative phase between (i) a first radiation component representing radiation diffracted by the top grating and (ii) a second radiation component representing radiation diffracted by the bottom grating after traveling through the top grating and intervening layers. The top grating design may be modified to bring the relative amplitude close to unity. The wavelength of illuminating radiation in the metrology recipe can be adjusted to bring the relative phase close to π/2 or 3π/2.
Abstract:
A method including: obtaining a measurement of a metrology target on a substrate processed using a patterning process, the measurement having been obtained using measurement radiation; and deriving a parameter of interest of the patterning process from the measurement, wherein the parameter of interest is corrected by a stack difference parameter, the stack difference parameter representing an un-designed difference in physical configuration between adjacent periodic structures of the target or between the metrology target and another adjacent target on the substrate.
Abstract:
A method to determine a metrology contribution from statistically independent sources, the method including providing a plurality of contributions from statistically independent sources obtained at a plurality of measurement settings, and determining a metrology contribution from the contributions wherein the metrology contribution is the contribution having least dependence as a function of the measurement settings.
Abstract:
A diffraction measurement target that has at least a first sub-target and at least a second sub-target, and wherein (1) the first and second sub-targets each include a pair of periodic structures and the first sub-target has a different design than the second sub-target, the different design including the first sub-target periodic structures having a different pitch, feature width, space width, and/or segmentation than the second sub-target periodic structure or (2) the first and second sub-targets respectively include a first and second periodic structure in a first layer, and a third periodic structure is located at least partly underneath the first periodic structure in a second layer under the first layer and there being no periodic structure underneath the second periodic structure in the second layer, and a fourth periodic structure is located at least partly underneath the second periodic structure in a third layer under the second layer.
Abstract:
A method of measuring overlay uses a plurality of asymmetry measurements from locations (LOI) on a pair of sub-targets (1032, 1034) formed on a substrate (W). For each sub-target, the plurality of asymmetry measurements are fitted to at least one expected relationship (1502, 1504) between asymmetry and overlay, based on a known bias variation deigned into the sub-targets. Continuous bias variation in one example is provided by varying the pitch of top and bottom gratings (P1/P2). Bias variations between the sub-targets of the pair are equal and opposite (P2/P1). Overlay (OV) is calculated based on a relative shifht (xs) between the fitted relationships for the two sub-targets. The step of fitting asymmetry measurements to at least one expected relationship includes wholly or partially discounting measurements (1506, 1508, 1510) that deviate from the expected relationship and/or fall outside a particular segment of the fitted relationship.
Abstract:
Corrections are calculated for use in controlling a lithographic apparatus. Using a metrology apparatus a performance parameter is measured at sampling locations across one or more substrates to which a lithographic process has previously been applied. A process model is fitted to the measured performance parameter, and an up-sampled estimate is provided for process-induced effects across the substrate. Corrections are calculated for use in controlling the lithographic apparatus, using an actuation model and based at least in part on the fitted process model. For locations where measurement data is available, this is added to the estimate to replace the process model values. Thus, calculation of actuation corrections is based on a modified estimate which is a combination of values estimated by the process model and partly on real measurement data.
Abstract:
A method including: determining recipe consistencies between one substrate measurement recipe of a plurality of substrate measurement recipes and each other substrate measurement recipe of the plurality of substrate measurement recipes; calculating a function of the recipe consistencies; eliminating the one substrate measurement recipe from the plurality of substrate measurement recipes if the function meets a criterion; and reiterating the determining, calculating and eliminating until a termination condition is met. Also disclosed herein is a substrate measurement apparatus, including a storage configured to store a plurality of substrate measurement recipes, and a processor configured to select one or more substrate measurement recipes from the plurality of substrate measurement recipes based on recipe consistencies among the plurality of substrate measurement recipes.
Abstract:
Disclosed is a device manufacturing method, and accompanying inspection and lithographic apparatuses. The method comprises measuring on the substrate a property such as asymmetry of a first overlay marker and measuring on the substrate a property such as asymmetry of an alignment marker. In both cases the asymmetry is determined. The position of the alignment marker on the substrate is then determined using an alignment system and the asymmetry information of the alignment marker and the substrate aligned using this measured position. A second overlay marker is then printed on the substrate; and a lateral overlay measured on the substrate of the second overlay marker with respect to the first overlay marker using the determined asymmetry information of the first overlay marker.
Abstract:
Disclosed is a method of metrology. The method comprises measuring at least one surrounding observable parameter relating to a surrounding signal contribution to a metrology signal which comprises a contribution to said metrology signal which is not attributable to at least one target being measured and determining a correction from said surrounding signal observable parameter. The correction is used to correct first measurement data relating to measurement of one or more targets using measurement radiation forming a measurement spot on one or more of said one or more targets which is larger than one of said targets.
Abstract:
Disclosed is a substrate and associated patterning device. The substrate comprises at least one target arrangement suitable for metrology of a lithographic process, the target arrangement comprising at least one pair of similar target regions which are arranged such that the target arrangement is, or at least the target regions for measurement in a single direction together are, centrosymmetric. A metrology method is also disclosed for measuring the substrate. A metrology method is also disclosed comprising which comprises measuring such a target arrangement and determining a value for a parameter of interest from the scattered radiation, while correcting for distortion of the metrology apparatus used.