Metrological objectives and methods with inclined periodic structures

Abstract

The present invention discloses a metrology target, design method thereof, and measurement method thereof, wherein the target has a periodic structure tilted relative to the orthogonal generation axes X and Y of a lithography tool, thereby enabling more accurate overlay measurement of devices with diagonal (oblique / tilted) elements, such as DRAM devices. One or more tilted periodic structures can be used to provide one-dimensional or two-dimensional signals about one or more layers, thereby potentially providing overlay measurement for multiple steps applied to one layer. The tilted periodic structures can be used to modify current metrology target designs (e.g., imaging targets and / or scatterometry targets) or to design new targets, and measurement algorithms can be adjusted to derive signals from the tilted periodic structures and / or provide pre-processed images thereof, respectively. The disclosed targets are process-compatible and more accurately reflect device overlays with respect to various process steps.

Description

[0001] CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 617,086, filed on January 12, 2018, the entirety of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of metrology, and more particularly, to metrology target design. Background Art

[0004] U.S. Patent No. 6,921,916, which is incorporated herein by reference in its entirety, discloses overlay marks for determining relative positions between two or more consecutive layers of a substrate or between two or more separately generated patterns on a single layer of a substrate; and U.S. Patent Publication No. 2007 / 0008533, which is incorporated herein by reference in its entirety, discloses overlay targets with flexible symmetric properties and metrology techniques for measuring overlay errors between two or more consecutive layers of such targets. Summary of the invention

[0005] The following is a simplified summary to provide an initial understanding of the invention. The summary does not necessarily identify key elements, nor limit the scope of the invention, but merely serves as an introduction to the following description.

[0006] One aspect of the invention provides a metrology target comprising a plurality of periodic structures and produced by a lithography tool having orthogonal production axes X and Y, wherein at least one of the periodic structures is tilted relative to the X and Y axes.

[0007] These, additional and / or other aspects and / or advantages of the invention are set forth in the following detailed description; may be inferred from the detailed description; and / or may be learned by practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a better understanding of the embodiments of the invention and to show how the same may be carried out, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout.

[0009] In the attached picture:

[0010] Figure 1A to 1E is a layer of the device ( Figure 1A ) and a high-level schematic diagram of a prior art method ( FIGS. 1B to 1E ) for providing an overlay metrology target to measure overlays between different layers or features of a device 80.

[0011] Figure 2A , 2B3 to 5 are high-level schematic diagrams of metrology targets, periodic structures, and elements thereof, according to some embodiments of the present invention.

[0012] Figure 6B is a high level schematic diagram of a metrology target according to some embodiments of the present invention compared to the prior art target schematically illustrated in FIG. 6A .

[0013] Fig. 7A , 7B 7C is a high-level schematic diagram of a segmented edge configuration according to some embodiments of the present invention.

[0014] Figure 8 is a high-level flow chart illustrating methods according to some embodiments of the present invention. DETAILED DESCRIPTION

[0015] In the following description, various aspects of the present invention are described. For the purpose of explanation, specific configurations and details are stated in order to provide a thorough understanding of the present invention. However, it will also be understood by those skilled in the art that the present invention can be practiced without the specific details presented herein. In addition, well-known features may have been omitted or simplified so as not to obscure the present invention. With specific reference to the drawings, it is emphasized that the details shown are only by way of example and only for the purpose of illustrative discussion of the present invention, and are presented to provide the most useful and easily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show the structural details of the present invention in more detail than is required for a basic understanding of the present invention, and the description in conjunction with the drawings enables those skilled in the art to understand how several forms of the present invention can be embodied in practice.

[0016] Before explaining at least one embodiment of the present invention in detail, it should be understood that the present invention is not limited in its application to the construction details and component arrangements set forth in the following description or illustrated in the drawings. The present invention is applicable to other embodiments and combinations of disclosed embodiments that can be practiced or executed in various ways. Likewise, it should be understood that the phrases and terms used herein are for descriptive purposes and should not be considered limiting.

[0017] Unless specifically noted otherwise, as is apparent from the following discussion, it should be understood that throughout the specification, discussions utilizing terms such as "processing," "computing / calculating," "determining," "enhancing," "deriving," or similar terms refer to the actions and / or processes of a computer or computing system or similar electronic computing device that manipulate and / or transform data represented as physical (e.g., electronic) quantities within registers and / or memories of the computing system into other data similarly represented as physical quantities within memories, registers, or other such information storage, transmission, or display devices of the computing system. In particular embodiments, the illumination techniques may include electromagnetic radiation in a certain range, such as the infrared range, visible range, ultraviolet or even shorter wave radiation (e.g., x-rays), and possibly even particle beams.

[0018] Embodiments of the present invention provide an efficient and economical method and mechanism for measuring process compatible designs of tilted semiconductor devices and thereby provide improvements in the art of metrology and semiconductor production. A new overlay mark design and algorithmic approach for reducing overlay measurement inaccuracy is provided for process compatible designs.

[0019] In certain embodiments, metrology targets, design methods thereof, and measurement methods are provided with periodic structures that are tilted relative to orthogonal generation axes X and Y of a lithography tool, thereby enabling more accurate overlay measurements of devices with diagonal (oblique / tilted) elements, such as DRAM devices. One or more tilted periodic structures can be used to provide one-dimensional or two-dimensional signals about one or more layers, possibly providing overlay measurements for multiple steps applied to one layer. The tilted periodic structures can be used to modify current metrology target designs (e.g., imaging targets and / or scatterometry targets) or to design new targets, and measurement algorithms can be adjusted to derive signals from the tilted periodic structures and / or provide pre-processed images thereof, respectively. The disclosed targets are process-compatible and more accurately reflect device overlays with respect to various process steps.

[0020] Figure 1A to 1E is a layer of device 80 ( Figure 1A ) and a high-level schematic diagram of a prior art method ( FIGS. 1B to 1E ) for providing an overlay metrology target 90 to measure overlays between different layers or features of a device 80 .

[0021] Figure 1A Schematically illustrates a structural characteristic of many contemporary semiconductor devices (e.g., DRAM (Dynamic Random Access Memory) devices), namely, that they have at least one layer that is aligned at a specified tilt to the regular Cartesian coordinates of a lithography tool (e.g., a scanner having X and Y axes (e.g., with a tilt of 22° relative to X)).

[0022] On-device optical superposition (OVL) based metrology is not feasible at this time, as the design rule pitch cannot be resolved by contemporary optical techniques of both imaging and SCOL (scatterometry based) OVL tools. Instead, OVL measurements are performed on specially designed "proxy" metrology targets with typical dimensions (pitch) greater than one hundred nanometers, compared to typical device pitches of tens of nanometers or less. Furthermore, standard targets are aligned only by XY directions.

[0023] FIGS. 1B-1E demonstrate prior art methods to measure mismatch of a device layer having tilted structures using a standard XY alignment target, such as designing an XY alignment target with device-like segmentation as schematically illustrated in FIG. 1B (e.g., a periodic target with a periodic structure having tilted segmented elements, possibly at a minimum design rule pitch), or designing a segmented target that does not resemble a tilted device as schematically illustrated in FIGS. 1C-1E (possibly at a minimum design rule pitch), such as FIG. 1C schematically illustrating segmentation perpendicular to the elements of the periodic structure and along the measurement direction of the periodic structure, FIG. 1D schematically illustrating segmentation parallel to the elements of the periodic structure and perpendicular to the measurement direction of the periodic structure, and FIG. 1E schematically illustrating a segmented two-dimensional dual-layer imaging target. Note that prior art target 90, as well as the targets disclosed below, are schematically illustrated to show partial sections of otherwise adequately designed targets with respect to the size and extent of the periodic structure.

[0024] However, a major difficulty is that none of the prior art target designs are process compatible (or even print well), are asymmetric, and do not have device-like behavior (especially with respect to tilted structures). For example, target 90 designed according to the principles illustrated in Figures 1B, 1C, and 1D typically produces overlay values ​​that do not reflect the overlay of the device well and has serious printability issues (target 90 illustrated in Figures 1B and 1C has worse printability than target 90 illustrated in Figure 1D). Similar difficulties arise using the extended design schematically illustrated in Figure 1E, which may be composed of the elements illustrated in Figures 1B to 1D. Segmented two-dimensional dual-layer imaging target 90 may include inner X periodic structure 95X and inner Y periodic structure 95Y, outer X periodic structure 95X' and outer Y periodic structure 95Y' (collectively represented as periodic structure 95). In particular, such structures are typically defined by the following constraints: (i) the outer X periodic structure 95X' is orthogonal to the outer Y periodic structure 95Y'; (ii) the inner X periodic structure 95X is orthogonal to the inner Y periodic structure 95Y; (iii) the outer X periodic structure 95X' is parallel to the inner X periodic structure 95X; and (i) the outer Y periodic structure 95Y' is parallel to the inner Y periodic structure 95Y.

[0025] In contrast to the prior art, a target 100 and method 200 are disclosed below that address the difficulties associated with the measurability and process compatibility of prior art targets and also reflect the misregistration encountered by devices with tilted structures. The following method provides modifications applicable to both imaging and scatterometry overlay target designs, and the examples presented are illustrative and non-limiting. In the disclosed target 100, at least one periodic structure and / or at least one layer is not aligned along the X and Y directions and can be applied to any of the following: (i) measuring only one direction (in Figure 4 and 5 ), which is independent of the scanner X or tool X direction and can reflect the inclination of the device structure, in which direction the outer structure and the inner structure are parallel (outer M is parallel to inner M); or a vector measuring the superposition between layers (possibly, the layers can be generated from two consecutive processes, such as a line in one direction and a cut in another direction), which requires Figure 2A and 2B In the figure, the two directions M and N are represented. Then it is only necessary that the corresponding outer periodic structures are not parallel to each other and the corresponding inner periodic structures are not parallel to each other ( Figure 2A Schematically represented as outer M (first pair of gratings) is not parallel to outer N (second pair of gratings), and inner M' (first pair of gratings) is not parallel to inner N' (second pair of gratings). Note that although some non-parallel associations are illustrated as being perpendicular, this angle selection is presented for explanation purposes only and is non-limiting. Note that the above description provides non-limiting examples and can be implemented along similar lines for different target types, such as multi-layer targets, targets with auxiliary features on the same and other layers, and targets that generate measurement signals using various methods (e.g., direct imaging, Moiré effect imaging, scatterometry, etc.).

[0026] Note that the disclosed target design principles can be applied to targets based on the moiré effect, for example, as disclosed in US Pat. No. 10,101,592, which is incorporated herein by reference in its entirety.

[0027] Figure 2A , 2B 3 to 5 are high-level schematic diagrams of a metrology target 100, a periodic structure 110, and its elements 120 according to some embodiments of the present invention. Figure 2A , 2B In Figures 3 to 5, some elements 120 of periodic structure 100 (and elements 97 of periodic structure 95) are illustrated as complete strips, but in various embodiments, elements 120 (and 97) may be segmented in various directions (e.g., along or across the corresponding measurement direction, or tilted, see, e.g., below). Figures 7A to 7C ). Although Figure 2A , 2B 3-5, some elements 120 of periodic structure 100 (and elements 97 of periodic structure 95) are illustrated as complete bars, but in various embodiments, elements 120 (and 97) may be unsegmented or segmented in different directions.

[0028] The metrology target 100 may include a plurality of periodic structures 110, each having a repeating element 120 (in Figure 2A ) and is produced by a lithography tool (e.g., a scanner, not shown) having orthogonal production axes X and Y. At least one of the periodic structures is tilted (diagonal) relative to the axes X and Y. For example, in Figure 2A 1E , periodic structures 95X, 95Y corresponding to the inner X periodic structure and the inner Y periodic structure of the imaging target 90 illustrated in FIG. 1E are also part of the metrology target 100, while the outer X periodic structure 95X' and the outer Y periodic structure 95Y' of the imaging target 90 illustrated in FIG. 1E are replaced by tilted periodic structures 110X, 110Y at angles α and β, respectively, relative to the X axis (which may correspond to the angles of the semiconductor device produced by the lithography tool). In a specific embodiment, the periodic structures 110X, 110Y may be orthogonal to each other (e.g., β=α-90°), for example, tilted relative to the axes X and Y and periodic along two non-parallel directions (e.g., orthogonal directions). The tilted periodic structures 110X, 110Y are collectively denoted as tilted periodic structures 110. Note that in various embodiments, at least two of the periodic structures may be placed side by side.

[0029] In certain embodiments, the tilted periodic structure 110 may be formed relative to the corresponding axes X and Y (and / or in the target 110 such as Figure 2B The angle of the tilt axis X' and Y' in the case of tilt as in is between 20° and 70°.

[0030] The metrology target 100 may include two, three, or more layers, and the tilted periodic structure 110 may be designed in one or more layers. The metrology target 100 may include one, two, or possibly more measurement directions, and the tilted periodic structure 110 may be designed in one or more measurement directions. In a specific embodiment, different tilted periodic structures 110 may be of one, two, or more types, for example, different in pitch and / or CD (critical dimension). For example, Figure 2A and 2B Schematically illustrates a metrology target 100 having differently tilted periodic structures 110X, 110Y in one layer along two measuring directions, and Figure 4 and 5Schematically illustrates a metrology target 100 with different tilted periodic structures 110A, 110B in two layers along one measurement direction. Various embodiments include the same and / or different tilted periodic structures 110 in any combination of measurement directions and layers, for example, depending on the corresponding device design. The tilted periodic structures 110A, 110B are collectively denoted as tilted periodic structures 110.

[0031] about Figure 3 100, noting that such structures may be applied as any part of any fully designed target 100, emphasizing that any of the disclosed periodic structures may be printed in non-rectangular shapes (possibly with any number of sides), possibly in relation to available real estate. Two corresponding periodic structures may be rotationally symmetric (rotated 180°) relative to each other, for example, to allow TIS (tool induced offset) error measurement and reduction.

[0032] As in Figure 2A and 2B 1E , metrology target 100 may be tilted relative to the X and Y axes of the lithography tool, for example, to be designed along the X' and Y' axes. Note that while prior art 90 as illustrated in, for example, FIG. 1E may be tilted as a complete target, the disclosed metrology target 100 also includes tilted periodic structure 110 relative to the tilt axes X' and Y', and has a direction of the periodicity (along which the corresponding pitch is measured) that is also tilted relative to the tilt axes. In a particular embodiment, the disclosed metrology target 100 may have at least two non-orthogonal measurement directions (e.g., one corresponding to periodic structure 95 and another corresponding to periodic structure 110).

[0033] In a particular embodiment, with respect to any of the target types, the tilted periodic structure 110 may be arranged to fill a rectangle having sides along the X and Y axes, such as, for example, in Figure 2A and 4 In certain embodiments, the inclined periodic structure 110 may be configured to fill a rectangle having sides along inclined X' and Y' axes, such as, for example, in Figure 2B In the description.

[0034] In certain embodiments, with respect to any of the target types, the tilted periodic structure 110 may be arranged to fill a convex quadrilateral 115 (or possibly, a shape having more than four sides) designed according to the available wafer area, such as, for example, in Figure 3 and 5 In the description.

[0035] In a particular embodiment, with respect to any of the target types, the tilted periodic structure 110 can be arranged to fill any designated space designed according to the available wafer area.

[0036] In particular embodiments, target 100 may include a single periodic structure 110 per measurement direction and per layer rather than the pair of periodic structures 110 per measurement direction and per layer described above, for example if rotational symmetry is not desired.

[0037] In various embodiments, the target 100 may include at least one intermediate layer having assist features between two periodic structures. The assist features may be tilted relative to the X and Y axes.

[0038] Figure 6B 6A is a high-level schematic diagram of a metrology target 100 according to some embodiments of the present invention as compared to the prior art target 90 schematically illustrated in FIG6A. In a particular embodiment, the metrology target 100 may be configured as a SEM (scanning electron microscope) target (e.g., a CDSEM (critical dimension scanning electron microscope) target) and / or an imaging target having two partially overlapping, alternating periodic structures 110A, 110B (collectively indicated as tilted periodic structures 110), both of which are tilted relative to the X-axis (by an angle indicated as α).

[0039] Figures 7A to 7C is a high-level schematic diagram of a segmented edge configuration according to some embodiments of the present invention. Note that Figure 7B The segmentation described in the example above may cause printability problems, which can be solved by Figure 7C and Fig. 7A The segmented solution described in .

[0040] In certain embodiments, the tilted periodic structure 110 may be segmented, such as in Figures 7A to 7C Schematically illustrated in FIG. 1 , in which the elements 120 of the periodic structure 110 are segmented into smaller pitches (in Figures 7A to 7C denoted as "segment pitch" in FIG. 1 ) (e.g., closer to or similar to the device pitch). For example, the pitch of the segment can be, for example, the pitch of the corresponding periodic structure 110 (in FIG. Figures 7A to 7C One-fifth or less of the pitch).

[0041] In particular embodiments, the segments may be two-dimensional.

[0042] Figures 7A to 7CSchematic illustration of an initial design of a segmented tilted element 120 in a tilted periodic structure 110 having a desired pitch, e.g., for imaging measurements, indicated using customer design rules and executed using, e.g., segmented customer design rules to ensure printability. Note that in any of the disclosed designs, the space on the mask can be filled with parallel SARFs (sub-resolution assist features), which are not shown herein to maintain simplicity, and which improve the printability of the target design 100.

[0043] Note that the terms "lines" and "spaces" (on a wafer or on a lithographic mask) are used for ease of explanation and do not limit the scope of the invention. In particular, the elements indicated herein as lines and spaces may be constructed from various types of structures that may fill the corresponding lines and / or spaces (similarly or differently across the object). For example, the spaces between different gratings that are periodic structures may be filled differently (using different types of elements) than the spaces within a grating.

[0044] In certain embodiments, sub-element 130 (segments of element 120) are optimized for a given illumination condition to avoid or minimize printability issues. For example, edges may be optimized by standard techniques such as OPC (optical proximity correction), CMP (chemical mechanical planarization) assistance, etc. Specifically, in the case of tilted dipole illumination, it is expected that the edges will be optimized according to the Fig. 7A and Figure 7C The principle design described in the section results in less than Figure 7B The printability problem of the segment described in .

[0045] Note that although the precise configuration of the edges of device structures is less critical in semiconductor device design, the metrology measurements of the disclosed metrology target 100 are sensitive to the details of the segment edges and may be degraded by the uneven generation of the segment edges. Therefore, the inventors suggest designing symmetric edges (as illustrated with respect to the major axis of ellipse 135) rather than asymmetric edges (as illustrated with respect to the major axis of ellipse 93).

[0046] In various embodiments, a series of measurement algorithms may be used to extract metrology measurements, such as those described in U.S. Patent No. 6,921,916 and U.S. Patent Publication No. 2007 / 0008533 and amendments thereto, incorporated herein by reference, and other algorithms (e.g., 2D fitting, correlation, etc.) to find the desired offset.

[0047] For example, the following non-limiting measurement algorithm may be used to measure a target 100 configured as an imaging target. First, image processing may be used to rotate a captured image of the target 100 (possibly with additional re-pixelation) so that each pair of periodic structures 110 (e.g., inner left and inner right) is parallel to the X or Y direction of the original target (e.g., corresponding to X and Y of a lithography tool or corresponding to tilted X' and Y', see respectively). Figure 2A and 2B ). The symmetry centers of each pair of periodic structures 110 can be derived from the image, from which the X and Y symmetry centers of the inner and outer structures can be calculated, and the vectors between the symmetry centers of the inner and outer structures provide a superposition. Obviously, any one-dimensional or two-dimensional measurement algorithm can be modified accordingly to provide metrological measurements of the disclosed target 100.

[0048] In various embodiments, other algorithms may be used (such as the following non-limiting examples). Figure 3 As an example, an image (or partial image) of each periodic structure 110 in the target 100 may be captured, and the periodic model (class of functions) in the corresponding direction M may be selected to be the sum of cosines and sines in the direction M with a period P, 2P, 3P, ..., nP (P is the pitch), and selected to be constant in the orthogonal direction N. The number of periods n may be selected so that the n+1th harmonic is either irrelevant to the optical system or is empirically known to be less than the noise level (including higher harmonics above n+1). A one-dimensional signal may be derived by projecting the selected periodic model into the M directions to produce a one-dimensional signal, which may then be processed in a canonical superposition algorithm using the one-dimensional signal per periodic structure (as described, for example, in U.S. Pat. No. 6,921,916 and U.S. Pat. Publication No. 2007 / 0008533, incorporated herein by reference, and other sources).

[0049] In certain embodiments, several periodic structures 110 may be designed in one layer, for example, representing multiple process steps applied to the layer (e.g., a generation step and a cutting step, possibly one or both tilted relative to the axes (X, Y) of the lithography tool). For example, the generated layer may be regular (along the X or Y axis), while the cut layer may be diagonal, requiring tilted periodic structures 110 to provide metrology measurements thereof.

[0050] It is emphasized that the disclosed target 100 can be of any type and that the disclosed target design principles can be applied to a wide range of metrology targets 100. Further, it is noted that the present invention is not limited to a particular metrology tool, technique, or target type. For example, the target 100 can be any form or type of one-dimensional or two-dimensional target, an imaging target, any type of scatterometry target, or a target based on the moire effect, having a tilted periodic structure as part of its design.

[0051] Figure 8 is a high-level flow chart illustrating a method 200 according to some embodiments of the present invention. The method stages may be performed relative to the metrology target 100 described above, which may optionally be configured to implement the method 200. The method 200 may be implemented at least in part by, for example, at least one computer processor in a metrology module. Certain embodiments include a computer program product including a computer-readable storage medium having a computer-readable program embodied therewith and configured to implement the relevant stages of the method 200. Certain embodiments include a target design file for a corresponding target designed by an embodiment of the method 200. The method 200 may include the following stages, regardless of their order.

[0052] Particular embodiments include a target design method 200 that includes identifying tilted structures relative to axes X and Y in a device design (stage 205) and designing at least one tilted periodic structure of a metrology target at the same layer and at the same angle relative to axes X and Y as the identified tilted structure (stage 210).

[0053] Certain embodiments include a target design method 200 that includes configuring at least one periodic structure of a metrology target generated by a lithography tool having orthogonal generation axes X and Y to be tilted relative to axes X and Y (step 220).

[0054] In certain embodiments, method 200 may further include segmenting the elements of the periodic structure to approach or reach a minimum design rule pitch (stage 230 ) and possibly designing the segments to be rectangular, with vertical edges (stage 235 ).

[0055] In certain embodiments, the method 200 may further include designing any of the imaging, SEM (scanning electron microscope) and / or scatterometry targets accordingly (stage 240) and adjusting the corresponding measurement algorithms to exploit the tilted periodic structure (stage 250). For example, in certain embodiments, the method 200 may include applying image processing and possible re-pixelation to prepare an image of the target with the tilted periodic structure for analysis by a corresponding metrology algorithm (stage 255) and / or applying a corresponding model projected in the tilted measurement direction to derive a one-dimensional signal of the corresponding periodic structure and using it for overlay derivation (stage 257).

[0056] Note that the disclosed method can be applied to any type of metrology target and can be implemented using any metrology tool technology. For example, the method 200 can be applied to integrate tilted periodic structures as part of a design in any of the following: a one-dimensional or two-dimensional target, an imaging target, any type of scatterometry target, and / or a target based on the moire effect.

[0057] Advantageously, the disclosed target 100 and method 200 provide overlay measurements that accurately represent device overlay, e.g., pattern placement error (PPE) and etch placement error (EPE) of the target 100 that provide errors that are very close to minimum design rule dense device features. Furthermore, the disclosed target 100 and method 200 enable measurement of diagonal (tilted) periodic structures, such as one-dimensional or two-dimensional structures of target structures having non-orthogonal periodic structures in one or more layers, each of the previous layer and the current layer may include one or more tilted periodic structures 110. The disclosed target is process compatible and corresponds closely to device production performance. Adjustment of the segment edges of the segmented elements of the tilted periodic structure 110 may further enhance measurement accuracy (possibly with respect to the illumination used (e.g., dipole illumination, optionally rotated)).

[0058] Aspects of the present invention are described above with reference to flowchart illustrations and / or partial diagrams of methods, devices (systems) and computer program products according to embodiments of the present invention. It will be understood that each part of the flowchart illustrations and / or partial diagrams and the combination of parts in the flowchart illustrations and / or partial diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer or other programmable data processing device to produce a machine, so that instructions executed by the processor of the computer or other programmable data processing device produce components for implementing the functions / actions specified in the flowchart and / or partial diagram or parts thereof.

[0059] These computer program instructions may also be stored in a computer-readable medium, which may instruct a computer, other programmable data processing equipment or other devices to act in a specific manner so that the instructions stored in the computer-readable medium produce a product containing instructions for implementing the functions / actions specified in the flowchart and / or partial diagram or parts thereof.

[0060] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus or other devices to cause a series of operating steps to be performed on the computer, other programmable apparatus or other devices to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide a process for implementing the functions / actions specified in the flowchart and / or partial diagram or portions thereof.

[0061] The foregoing flowcharts and formulas illustrate the architecture, functionality and operation of possible implementation schemes of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each part in a flowchart or partial diagram may represent a module, segment or portion of a code, which includes one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative embodiments, the functions mentioned in the part may not occur in the order mentioned in the figure. For example, in fact, depending on the functionality involved, the two parts shown in succession may be executed substantially simultaneously or the parts may sometimes be executed in reverse order. It will also be noted that each part of the partial diagram and / or flowchart illustration and the combination of parts in the partial diagram and / or flowchart illustration can be implemented by a combination of a dedicated hardware-based system or dedicated hardware and computer instructions that perform a specified function or action.

[0062] In the above description, an embodiment is an example or implementation of the present invention. The various occurrences of "one embodiment", "embodiment", "specific embodiment" or "some embodiments" do not necessarily all refer to the same embodiment. Although the various features of the present invention can be described in the context of a single embodiment, the features can also be provided separately or in any suitable combination. On the contrary, although the present invention is described in the context of a single embodiment herein for the sake of simplicity, the present invention can also be implemented in a single embodiment. A specific embodiment of the present invention can include features from the different embodiments disclosed above, and a specific embodiment can incorporate elements from other embodiments disclosed above. The disclosure of the elements of the present invention in the context of a specific embodiment is not considered to limit its use alone in a specific embodiment. In addition, it should be understood that the present invention can be implemented or put into practice in various ways and can be implemented in the specific embodiments except for the embodiments outlined in the above description.

[0063] The present invention is not limited to the figures or corresponding descriptions. For example, the process does not have to move through each illustrated frame or state, or does not have to move in the same order as illustrated and described. Unless otherwise defined, the meaning of the technical and scientific terms used herein will be generally understood by those of ordinary skill in the art to which the present invention belongs. Although the present invention has been described with respect to a limited number of embodiments, these embodiments should not be interpreted as limitations on the scope of the present invention, but should be interpreted as examples of some preferred embodiments. Other possible changes, modifications and applications are also within the scope of the present invention. Therefore, the scope of the present invention should not be limited by what has been described so far, but should be limited by the attached claims and their legal equivalents.

Claims

1. A metrology target, comprising a plurality of periodic structures, wherein each of the plurality of periodic structures comprises a repetitive element having a long dimension and a short dimension, one of a first of the periodic structures and a second of the periodic structures is arranged as an inner periodic structure of the metrology target, and the other of the first of the periodic structures and the second of the periodic structures is arranged as an outer periodic structure of the metrology target, wherein the outer periodic structure is inclined relative to the inner periodic structure; wherein the external periodic structure in a first direction is not parallel to the external periodic structure in a second direction, the internal periodic structure in the first direction is orthogonal to the internal periodic structure in the second direction, and the first direction is not parallel to the second direction; wherein the outer periodic structure is inclined relative to axes X and Y and is periodic along the first direction and the second direction, and at least two of the plurality of periodic structures are placed side by side; and Different external periodic structures are arranged on the same layer.

2. The metrology target according to claim 1, wherein the metrology target is configured as an imaging target, wherein the imaging target comprises at least one target layer having the plurality of periodic structures, wherein the internal periodic structure is not parallel to the external periodic structure. 3 . The metrology target of claim 2 , further comprising at least three target layers, wherein each of the periodic structures is disposed within one of the target layers. The metrology target of claim 1 , wherein the metrology target is configured as a moire effect based target. 5 . The metrology target of claim 4 , wherein the moire effect-based target comprises at least one target layer having the plurality of periodic structures, wherein the inner periodic structure is not parallel to the outer periodic structure. 6 . The metrology target of claim 1 , wherein the metrology target has a measurement direction tilted relative to the second one of the periodic structures, wherein the plurality of periodic structures have two types that are different in pitch and / or critical dimension.

7. The metrology target of claim 1, wherein each of the periodic structures is configured to fill a rectangle having sides along the X-axis and the Y-axis of the metrology target.

8. The metrology target of claim 1, wherein each of the periodic structures is configured to fill a designated space, wherein the designated space is designed according to available wafer area.

9. The metrology target of claim 1, wherein each of the periodic structures is configured to fill a convex quadrilateral, wherein the convex quadrilateral is designed according to available wafer area.

10. The metrology target of claim 1, wherein the metrology target is configured as a scanning electron microscope target having two partially overlapping, alternating periodic structures, wherein the two partially overlapping, alternating periodic structures are tilted relative to an X-axis.

11. The metrology target of claim 1, wherein each of the periodic structures comprises one or more elements, wherein each of the elements has segments.

12. The metrology target of claim 11, wherein the segmentation of each of the elements is two-dimensional.

13. The metrology target of claim 11, wherein a pitch of the segments of each of the elements is one-fifth or less of a pitch of its corresponding periodic structure.

14. The metrology target of claim 11, wherein the segments of each of the elements are rectangular.

15. The metrology target of claim 1, wherein the outer periodic structure forms an angle between 20° and 70° with respect to respective axes X and Y.

16. The metrology target of claim 1, wherein the metrology target further comprises at least one intermediate layer having assist features therebetween.

17. The metrology target of claim 16, wherein the assist features are inclined relative to the internal periodic structure.

18. A target design method comprising configuring an outer periodic structure of a metrology target to be tilted relative to an inner periodic structure of the metrology target; wherein the metrology target comprises a plurality of periodic structures, the plurality of periodic structures comprising a first periodic structure and a second periodic structure, wherein the first periodic structure and the second periodic structure each comprise a repetitive element having a long dimension and a short dimension, wherein one of the first periodic structure and the second periodic structure is arranged as the inner periodic structure of the metrology target, and the other of the first periodic structure and the second periodic structure is arranged as the outer periodic structure of the metrology target; wherein the external periodic structure in a first direction is not parallel to the external periodic structure in a second direction, the internal periodic structure in the first direction is orthogonal to the internal periodic structure in the second direction, and the first direction is not parallel to the second direction; wherein the outer periodic structure is inclined relative to axes X and Y and is periodic along the first direction and the second direction, and at least two of the plurality of periodic structures are placed side by side; and Different external periodic structures are arranged on the same layer.

19. The target design method according to claim 18, further comprising: Identify tilted structures relative to axes X and Y in device design; as well as At least one tilted periodic structure of the metrology target at the same layer and at the same angle with respect to the axes X and Y is designed as an identified tilted structure.

20. A method for measuring a metrology target, comprising: executing a metrology measurement algorithm using image processing and / or signal modeling to derive a corresponding signal from the tilted periodic structure; wherein the metrology target comprises a plurality of periodic structures, wherein each of the plurality of periodic structures comprises a repetitive element having a long dimension and a short dimension, one of a first of the periodic structures and a second of the periodic structures is arranged as an inner periodic structure of the metrology target, and the other of the first of the periodic structures and the second of the periodic structures is arranged as an outer periodic structure of the metrology target, wherein the outer periodic structure is inclined relative to the inner periodic structure; wherein the external periodic structure in a first direction is not parallel to the external periodic structure in a second direction, the internal periodic structure in the first direction is orthogonal to the internal periodic structure in the second direction, and the first direction is not parallel to the second direction; wherein the outer periodic structure is inclined relative to axes X and Y and is periodic along the first direction and the second direction, and at least two of the plurality of periodic structures are placed side by side; and Different external periodic structures are arranged on the same layer.

Images