JP6570018B2 - Overlay target, system and method for performing overlay measurement - Google Patents

Description

  The present disclosure relates generally to the field of overlay targets for overlay measurement, and more particularly to designing and using overlay targets with orthogonal lower layer dummy fills.

  Semiconductor devices are often manufactured by generating multiple layers disposed on a substrate such as a silicon wafer. The alignment between the various process layers is typically controlled to ensure proper function and performance of the resulting device. Misalignment between device features or structures formed in two or more successive layers is often referred to as overlay error. The ability to detect and correct overlay errors between patterned layers on a wafer is very important for the manufacture of integrated circuits and other semiconductor devices.

  Overlay metrology is typically done by analyzing an overlay “target” or “mask” that is placed in close proximity to one or more device layers of interest, thereby making mistakes between patterned device layers. A known technique for determining alignment or overlay errors. For example, overlay measurements can be performed by a test pattern (ie, one or more overlay target structures) printed with various patterned device layers on the wafer. The overlay metrology system can include an imaging tool configured to collect image frames, which are analyzed by the processing unit to detect relative displacements or errors of pattern elements that make up the device and target layer. The alignment is determined.

  Several techniques are currently applied to maintain or improve the process compatibility of the substrate that supports the overlay target. For example, one or more patterned layers of dummy fill (ie, non-functional structures or features) are disposed on the substrate and are required under certain semiconductor manufacturing equipment or semiconductor test equipment design rules. Spatial attributes or physical characteristics can be achieved. Further, the pattern elements that form the target structure or layer of the metrology target can be constructed from features that are nominally smaller than the selected segmentation or sub-pattern to improve process compatibility.

International Publication No. 2012/018673 US Application Publication No. 2007/0096094

  Although there are existing solutions, the shortcomings in the art continue to result in process damage to overlay metrology targets or lack of target conformance with respect to design rules in semiconductor manufacturing. Some disadvantages in the current state of the art are: dishing in or near the target by chemical mechanical polishing, etch bias in the vicinity of the target by non-conforming pattern density, and subsequent in the manufactured device due to design rule violations at the target. Includes parasitic capacitance, target lithographic incompatibility that results in metrology bias in overlay measurements, reticles for excessive target sizes, and increased metrology footprint on the wafer.

  The present disclosure is directed to an overlay target design that includes an orthogonal lower layer dummy fill to eliminate one or more deficiencies in the current state of the art.

  In one aspect, the present disclosure is directed to an overlay target that includes one or more segmented overlay pattern elements that form at least one overlay target structure. The overlay target further includes one or more inert pattern elements that form at least one dummy fill target structure. Each of the one or more inert pattern elements can include a dummy fill segmented along an axis orthogonal to the segmentation axis of at least one proximally disposed overlay pattern element. According to some embodiments, each of the target structures or layers can be formed from separate process layers disposed sequentially on a substrate such as a silicon wafer.

  In another aspect, the present disclosure is directed to an overlay metrology system for performing overlay measurements on a substrate. The system can include a sample stage configured to support a substrate, wherein the overlay target is disposed on the substrate, the overlay target forming at least one overlay target structure. One or more segmented overlay pattern elements, the overlay target further comprising one or more inert pattern elements forming at least one dummy fill target structure, the one or more inert pattern elements Each includes a dummy fill that is segmented along an axis that is orthogonal to the segmentation axis of at least one proximally disposed overlay pattern element. The system further comprises at least one illumination source configured to illuminate the overlay target and at least one detector configured to receive illumination reflected, scattered or emitted from the overlay target. Can be included. A computing system communicatively coupled to the at least one detector may receive information (eg, one or more image frames or contrast data) related to illumination reflected, scattered, or emitted from the overlay target. Utilizing can be configured to determine misalignment between at least two layers disposed on a substrate. In some implementation liquids, the overlay and dummy fill target structures can be two or four-fold symmetric to allow certain manufacturing or metrology advantages. However, 2 or 4 rotation symmetry is not required by all applications such as using scatterometry overlay (SCOL) or diffraction based overlay (DBO) measurement targets. Absent.

  In yet another aspect, the present disclosure is directed to a method for performing overlay measurements on a substrate, the method comprising at least the following steps: illuminating an overlay target disposed on the substrate, comprising: The overlay target includes one or more segmented overlay pattern elements that form at least one overlay target structure, and the overlay target includes one or more inert patterns that form at least one dummy fill target structure. Each of the one or more inert pattern elements includes a dummy fill segmented along an axis orthogonal to the segmentation axis of the at least one proximally disposed overlay pattern element; Illumination step and overlay Detecting mis-reflected, scattered or emitted illumination from the substrate, and utilizing information related to the detected illumination, misalignment between at least two layers disposed on the substrate Determining.

  It is understood that the foregoing general description and the following detailed description are exemplary and explanatory only and do not necessarily limit the disclosure. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the subject matter of this disclosure. Both the description and the drawings serve to explain the principles of the present disclosure.

  Some advantages of the present disclosure may be better understood by those of ordinary skill in the art with reference to the accompanying drawings.

FIG. 3 illustrates an overlay target according to an embodiment of the present disclosure. FIG. 4 illustrates a portion of an overlay target in which the segmentation axis of the dummy fill pattern is orthogonal to the segmentation axis of the overlay pattern element, according to an embodiment of the present disclosure. FIG. 4 illustrates a 2-fold / 4-fold symmetrical overlay target according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating a dummy fill target structure and an overlay target structure of a 2-fold / 4-fold symmetrical overlay target according to an embodiment of the present disclosure. FIG. 4 illustrates a 2-fold / 4-fold symmetrical overlay target according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating a dummy fill target structure and an overlay target structure of a 2-fold / 4-fold symmetrical overlay target according to an embodiment of the present disclosure. FIG. 4 illustrates a 2-fold / 4-fold symmetrical overlay target according to an embodiment of the present disclosure. FIG. 4 illustrates a dummy fill target structure and an overlay target structure of a 2-fold / 4-fold symmetrical overlay target, each of the target structures including a plurality of pattern elements, according to an embodiment of the present disclosure. FIG. 4 illustrates a two-fold symmetric overlay target in which a first portion of an overlay pattern element is printed over a dummy fill in response to a first exposure according to an embodiment of the present disclosure. FIG. 6 illustrates a two-fold symmetric overlay target in which a second portion of an overlay pattern element is printed over a dummy fill in response to a second exposure according to an embodiment of the present disclosure. FIG. 3 illustrates an overlay target according to an embodiment of the present disclosure. 1 is a block diagram illustrating an overlay measurement system according to an embodiment of the present disclosure. FIG. FIG. 5 is a flow diagram illustrating a method for performing overlay measurement according to an embodiment of the present disclosure.

  Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings.

  1A-8 generally illustrate the design and use of overlays with orthogonal lower layer dummy fills according to various embodiments of the present disclosure. US Patent Application Serial No. 13 / 186,144 describes, at least in part, an orthogonal alignment of a dummy fill and an overlay target structure disposed below or on the dummy fill. In addition, U.S. Patent Application Serial No. 12 / 455,640 describes a metrology target that at least partially includes a dummy fill (referred to in that application as a “dummy field”). US Patent Application Serial No. 13 / 186,144 and Serial No. 12 / 455,640 are incorporated by reference as if fully set forth herein. It should be understood that the following embodiments are provided for purposes of illustration, and that the features and arrangements described below can be combined to produce further embodiments. For example, those of ordinary skill in the art will be able to combine portions of the following embodiments to achieve an overlay target or overlay metrology system that meets a set of manufacturing design rules and meets a selected level of process suitability. Will recognize.

  FIG. 1A illustrates an overlay metrology target 100 according to an embodiment of the present disclosure. The overlay target 100 includes a plurality of target structures. In some embodiments, the target structure is manufactured from a separate process layer and disposed sequentially on a substrate such as a silicon wafer. Target 100 may include one or more of inert pattern elements 102a-102d consisting essentially of segmented dummy fill. Inactive pattern elements 102a-102d may form at least a first "dummyfill" target structure. Target 100 is derived from overlay features known in the art as described or referenced in US patent application serial number 13 / 186,144 and / or serial number 12 / 455,640. One or more overlay pattern elements 104a-104d may be further included.

  The overlay pattern elements 104a-104d may form at least a second "dummy fill" target structure disposed proximate to the dummy fill target structure. For example, an overlay target structure can be subsequently disposed on the substrate over the dummy fill target structure. Accordingly, the dummy fill target structure can be referred to as a “dummy fill underlayer”. The dummy fills 102a-102d and / or overlay pattern elements 104a-104d can be segmented according to manufacturing / test design rules or according to a selected range or selected deviation from the design tool. As shown by FIG. 1B, each dummy fill pattern element 102 has a second “overlay” corresponding to at least one segmented overlay pattern element 104 disposed above or below the dummy fill pattern element. Can be segmented along a first “dummy fill” segmentation axis 106 orthogonal to the segmentation axis 108. Further, in some embodiments, at least a first set of one or more dummy fill pattern elements 102a, 102c is in a segmentation direction of a second set of one or more dummy fill pattern elements 102b, 102d. Segmented in orthogonal directions.

  The segmented dummy fill pattern element 102 is on a free space reserved for a pattern element or overlay pattern element, such as a device, which is subsequently disposed in accordance with one or more successive process layers of the substrate. A dummy fill may be included. The dummy fill pattern element 102 may further include an inner edge (ie, one or more rectangular apertures) that allows for location estimation of at least one overlay or dummy fill pattern element that forms part of the overlay target 100. . 2A and 2B illustrate a dummy fill target structure 201 formed from a plurality of dummy fill pattern elements 202a-202d disposed proximate to an overlay target structure 203 formed from a plurality of overlay pattern elements 204a-204d. A two-fold symmetric / 4-fold symmetric overlay target 200 is shown. In some embodiments, each target structure 201 and 203 is two or four-fold symmetric, resulting from the formation of an overlay target structure 203 covering the dummy fill target structure 201. The target structure 200 is correspondingly two-fold symmetric or four-fold symmetric. In some embodiments, for example, the target 200 is four-fold symmetric. Further, each of the dummy fill pattern elements 202a-202d can include a single axis segmentation dummy fill that forms a two-fold symmetric sub-pattern.

  In some embodiments, the dummy fill subpatterns 202a-202d are segmented along a selected axis, and the size and spacing of the dummy fill segments along the segmentation axis covers the dummy fill pattern elements 202a-202d. It is selected according to the spatial or physical characteristics of the overlay pattern elements 204a-204d to be printed. For example, a dummy fill segmentation is selected depending on the size, spacing, and / or segmentation of the features of overlay pattern elements 204a-204d to be subsequently printed, and the overlay disposed on the substrate orthogonal to the dummy fill segment. Contamination of measurement signals associated with features can be avoided. In some embodiments, the pitch and / or feature size of the dummy fill segmentation is a lithographic exposure tool on which the dummy fill sub-pattern is exposed (ie, printed or disposed on the surface of the substrate), etc. It is substantially larger than the minimum design rule for the exposure tool. Excessive segmentation can advantageously reduce line end pullback (eg, asymmetric pullback).

  As shown in FIG. 3A, overlay metrology target 300 may include a single axis segmented dummy fill pattern element 302a-302d having overlay pattern elements 304a-304d disposed proximally. FIG. 3B further illustrates a dummy fill target structure 301 formed from dummy fill pattern elements 302a-302d and an overlay target structure 303 formed from overlay pattern elements 304a-304d. In some embodiments, the selected distance between the dummy fill subpattern boundary and the overlayed subpattern boundary is greater than the predetermined light exclusion zone. The distance between the boundaries is greater than a given light exclusion zone only along an axis parallel or perpendicular to the dummy fill segmentation, or in both parallel and vertical directions.

  As shown in FIGS. 4A and 4B, the 2-fold symmetric / 4-fold symmetric overlay target 400 can include multiple overlays and dummy fill subpatterns in each quadrant. For example, each quadrant of the overlay target 400 can include six dummy fill pattern elements 402a-402d that form a dummy fill target structure 401. Each quadrant can further include five overlay pattern elements 404 a-404 d that form an overlay target structure 403 disposed on top of the dummy fill target structure 401. A two-rotation symmetric overlay target can be similarly designed with multiple overlays and dummy fill sub-patterns in the upper and lower halves or the left and right halves, respectively.

  In some embodiments, portions of the dummy fill or overlay subpattern are printed separately on the substrate with two or more side-by-side exposures. For example, in the embodiment of the overlay target 500 shown in FIGS. 5A and 5B, the overlay pattern elements 504a and 504b are dummy fill lower layers in response to a first exposure (see FIG. 5A) and a second exposure (see FIG. 5B) Printed over 502a and 502b. The segmented dummy fill sub-pattern can be printed with a separate exposure with no exclusion zone between the overlay sub-patterns. Furthermore, the dummy fill segmentation is the same for each of the dummy fill subpatterns and can be aligned according to lithographic overlay tolerances. In some embodiments, the overlay target may further include a subsequently overlaid segmented dummy fill subpattern having the same segmentation and aligned within lithographic overlay tolerances.

  In some embodiments, such as the exemplary embodiment shown in FIGS. 2A and 2B, overlay target 200 measures to estimate the location of at least one pattern element that defines an overlay or dummy fill subpattern. It may further include overlay subpatterns 204a-204d and / or dummy fill subpatterns 202a-202d having internal edges that can be (ie, including rectangular openings or “windows”). Thus, the overlay target 200 can include an arrangement that allows sub-pattern location estimation in a direction parallel and / or perpendicular to the segmentation axis of each overlay or dummy fill pattern element. In some embodiments, sub-pattern location estimation can be performed only in the direction perpendicular to the dummy fill segmentation line to avoid increasing scanner aberration sensitivity, particularly at the edge location, as a function of scanner focus. Alternatively, sub-pattern location estimation can be performed only in the direction parallel to the dummy fill segmentation line to avoid design rule violations.

  Certain embodiments of overlay targets may be advantageous for specific metrology or process suitability requirements. In one embodiment, for example, a four-rotation symmetric overlay target can include multiple layers (eg, four layers). Each quadrant of the overlay target can include two segmented dummy fill sub-patterns that allow measurement of the overlay along a first axis perpendicular to the dummy fill segmentation. Each quadrant can further include two segmented overlay sub-patterns that are subsequently disposed over the dummy fill pattern elements. The overlaid subpattern can be arranged to allow measurement of overlay along a second axis that is orthogonal to the first axis (ie, the measurement axis for the dummy fill subpattern). Alternatively, the overlaid subpattern can be arranged to allow measurement of overlay along a second axis that is parallel to the first axis.

  In another exemplary embodiment, each quadrant of a (two-layer) 4 rotationally symmetric overlay target is a single axis segmented dummy fill that substantially fills each quadrant, except for an opening (or window) having an internal edge. Sub patterns can be included. The inner edge of the aperture can be measured for sub-pattern location estimation in a direction parallel to the dummy fill segmentation. The target may further include a segmented overlay sub-pattern that is subsequently disposed over the dummy fill sub-pattern. Overlay subpatterns can be segmented according to manufacturing design rules. Furthermore, the edges of the overlay subpattern can be measured for subpattern location estimation in a direction parallel to the dummy fill segmentation axis.

  In another exemplary embodiment, a two-rotation symmetric (four-layer) overlay target may include four segmented dummy fill subpatterns (two in the X direction and two in the Y direction). Each of the dummy fill subpatterns can be arranged to allow measurement of overlay along each measurement axis. The overlay target may further include 12 segmented overlay subpatterns (6 for the X direction and 6 for the Y direction). Each of the overlay subpatterns that are subsequently printed over the dummy fill subpattern can be arranged to further allow measurement of the overlay along each measurement axis.

  Those skilled in the art will appreciate the exemplary nature of the previous embodiments, and thus the embodiments described herein are illustrative and are not intended to limit the present disclosure in any way. It should be understood as being. In some embodiments, segmentation is based on device or overlay layer feature sizes that exceed minimum design rules, thereby increasing the sub-pattern process window to be larger than the resulting device process window. . Furthermore, the segmentation can be relatively small compared to the geometry of the subpattern itself. According to various embodiments, a segmented single axis dummy fill underlayer can cover at least 50% of the process layer to improve metrology performance and process suitability.

  Various changes are contemplated in segmentation spacing / pitch, number of process layers, symmetry, and other attributes of the metrology target. The above-described embodiments exhibit various features, but are not intended to limit the present disclosure in any way. For example, various embodiments herein describe a two-turn symmetric or four-turn symmetric overlay metrology target, but two-fold / four-fold symmetry is not required for all applications. In some embodiments shown in FIG. 6, the overlay metrology target 600 is generally not two-turn symmetric or four-turn symmetric. However, various portions of the overlay target 600, such as individual subpatterns or groups of two or more subpatterns, can be at least twice symmetric.

  Some applications, such as SCOL or DBO metrology, do not require a 2-fold / 4-fold symmetric target. For example, overlay target 600 includes a first plurality of overlay pattern elements 602a-602d that form a first overlay target structure and a second plurality of overlay pattern elements 604a-604d that form a second overlay target structure. Both target structures may be formed continuously over a dummy fill underlayer that includes orthogonally aligned inert pattern elements 606a-606d. As further shown in FIG. 6, the dummy fill segmentation (ie, spacing and pitch) in the first (X) direction may be different from the dummy fill segmentation in the second (Y) direction.

  In some embodiments, the target 600 allows overlay measurements in a first direction depending on the first target structure or layer defined by the first plurality of overlay pattern elements 602a-602d. Further, the overlay can be measured in at least a second direction depending on a second target structure or layer defined by the second plurality of overlay pattern elements 604a-604d. Those skilled in the art will recognize that the number of layers and types (eg, device, dummy fill, or overlay layer) may vary without departing from the scope of the present disclosure.

  FIG. 7 is a block diagram illustrating an overlay measurement system 700 according to an embodiment of the present disclosure. Overlay metrology system 700 can include an optical metrology system, such as the system described or referenced in US patent application serial number 13 / 186,144. The system 700 can include at least one illumination source 702 configured to illuminate an overlay metrology target 704 disposed on a substrate 706, the overlay target 704 including a target according to previous embodiments. The substrate 706 can be supported by a sample stage 708, which can include at least one linear or rotational actuator for translating or rotating the substrate to a selected position.

  The system emits illumination from illumination source 702 along at least a first (object) path to overlay target 704 and along a second (reference) path depicted by reference optics 716 such as a reference mirror. At least one beam splitter 712 configured to direct may be included. Illumination reflected, scattered or emitted from the surface of the substrate 706 that includes the overlay target 704 can be collected by the objective lens 714 and directed to at least one detector 710 along the collection path. At least one computing system 718 in communication with the detector can be configured to collect imaging data associated with illumination received from the surface of the substrate 706. The computing system 718 utilizes overlay information or spatial errors between at least two layers formed on the substrate 706 utilizing information related to the imaging data collected for the overlay target 704 (eg, image frames or contrast data). It can be configured to determine misalignment.

  It should be appreciated that the various steps and functions described throughout this disclosure can be implemented by a single computing system or by multiple computing systems. For example, the computing system 718 may include a personal computing system, mainframe computing system, workstation, image computer, parallel processor, or any other device known in the art, such as It is not limited. In general, the computing system 718 may include at least one single core or multiple core processor configured to execute program instructions 722 from at least one carrier medium 720.

  FIG. 8 generally illustrates a method 800 for performing overlay measurements by the overlay measurement system 700. However, it will be appreciated that one or more steps of method 800 may be performed by a system or device that varies from previous embodiments of system 700 without departing from the essence of the present disclosure. In some embodiments, the method 800 can include at least the following steps. In step 802, the overlay measurement target 704 disposed on the substrate is illuminated. At step 804, illumination reflected, scattered or emitted by the target is collected by an optical component, such as objective lens 714, and directed to at least one imaging detector 710, such as a TDI camera. At step 806, the imaging data is processed to determine misalignment between at least two layers disposed on the substrate. It is noted herein that the imaging data can be processed according to any overlay measurement algorithm known in the art. For example, a spatial comparison between a target structure formed from device features and / or pattern elements forming a pattern can be performed to determine relative displacement (ie, overlay error).

  In some embodiments, only the inner edge of the dummy fill pattern element is measured to avoid polishing damage. In some embodiments, the location of at least one dummy fill pattern element is determined by measurement in a first direction, and the location of at least one overlay pattern element subsequently disposed on the substrate 706 is a second Determined by measurement in a direction (eg, along an axis orthogonal to the first direction). In addition, the location of the edge of the segmented overlay or dummy fill sub-pattern that is parallel and perpendicular to the measurement direction can be measured to determine the measurement bias due to the direction of segmentation.

  There are various carriers (eg, hardware, software, and / or firmware) by which the processes and / or systems and / or other techniques described herein can be implemented, and / or processes and / or One skilled in the art will recognize that the preferred carrier will vary with the circumstances in which the system and / or other technology is deployed therein. Program instructions implementing the methods as described herein can be transmitted over or stored on a carrier medium. The carrier medium can include a transmission medium such as a wire, cable, or wireless transmission link. The carrier medium can also include read-only memory, random access memory, magnetic or optical disk, or magnetic tape.

  All of the methods described herein include storing the results of one or more steps of the method embodiments in a storage medium. The results can include any of the results described herein and can be stored in any manner known in the art. The storage medium can include any storage medium described herein or any other suitable storage medium known in the art. After the results are stored, the results are accessed and used in the storage medium by any of the method or system embodiments described herein, formatted for display to the user, and another software module. , Method, or system. Furthermore, the results can be stored “permanently”, “semi-permanently”, temporarily, or for a period of time. For example, the storage medium can be random access memory (RAM), and the results do not necessarily persist indefinitely in the storage medium.

  While specific embodiments of the invention have been shown, it will be apparent that various modifications and embodiments of the invention can be made by those skilled in the art without departing from the scope and spirit of the foregoing disclosure. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims (25)

A diffraction-based overlay target,
A first overlay target structure printed on a substrate and including a first plurality of segmented pattern elements;
Printed on the substrate and includes a second plurality of segmented pattern elements, wherein a portion of the second plurality of segmented pattern elements overlies a portion of the first plurality of segmented pattern elements. A second overlay target structure arranged to wrap;
And the arrangement of the first overlay target structure and the second overlay target structure is four-fold symmetric, and is at least part of the first plurality of segmented pattern elements or at least the second segmented pattern element. A part of the pattern element is formed on the substrate by two or more side-by-side exposures, the first plurality of segmented pattern elements are the same, and the second plurality of segmented pattern elements are the same der is,
The second overlay target structure is formed from a dummy fill;
A diffraction-based overlay target. The overlay target of claim 1,
The diffraction-based overlay target, wherein the two or more side-by-side exposures are exposures in which no light exclusion zone exists between successive exposures. The overlay target of claim 1,
The first plurality of segmented pattern elements of the first overlay target structure is along a first segmentation axis and the second plurality of segmented pattern elements of the second overlay target structure Is a diffraction-based overlay target along a second segmentation axis that is orthogonal to the first segmentation axis. The overlay target of claim 1,
The first overlay target structure is printed on a first layer of the substrate, and the second overlay target structure is printed on a second layer different from the first layer of the substrate. Overlay target. The overlay target of claim 1,
A diffraction-based overlay target, wherein the first overlay target structure is formed within a boundary defined by the second overlay target structure. The overlay target according to claim 5,
A diffraction-based overlay target, wherein the distance between the boundary defined by the second overlay target structure and the first overlay target structure is longer than the selected light exclusion zone. The overlay target according to claim 5,
A diffraction-based overlay target, wherein the first overlay target structure and the second overlay target structure share at least one common boundary. The overlay target of claim 1,
The first overlay target structure is segmented according to a selected pitch or feature size greater than a minimum design rule specified by an exposure tool configured to expose the first overlay target structure. Base overlay target. The overlay target of claim 1,
The second overlay target structure is a diffraction-based overlay target that covers most of the layers disposed on the substrate. The overlay target of claim 1,
At least one of the first overlay target structure and the second overlay target structure is a position of at least one of the first plurality of segmented pattern elements and the second segmented pattern element. A diffraction-based overlay target with an aperture having an internal edge that allows determination. The overlay target of claim 1,
A diffraction-based overlay target, wherein each of the first overlay target structure and the second overlay target structure is two-fold symmetric. The overlay target of claim 1,
A diffraction-based overlay target, wherein each of the first overlay target structure and the second overlay target structure is four-fold symmetric. A system that performs overlay measurement,
A sample stage configured to support a substrate comprising an overlay target, the overlay target comprising:
A first overlay target structure printed on a substrate and including a first plurality of segmented pattern elements;
Printed on the substrate and includes a second plurality of segmented pattern elements, wherein a portion of the second plurality of segmented pattern elements is a part of the first plurality of segmented pattern elements A second overlay target structure disposed to overlap, the arrangement of the first overlay target structure and the second overlay target structure being four-fold symmetric, and at least a first plurality of A part of the segmented pattern element or at least a part of the second segmented pattern element is formed on the substrate by two or more side-by-side exposures, and the first plurality of segmented pattern elements are the same, the second plurality of segmented pattern elements Ri identical der,
At least one illumination source configured to illuminate the overlay target;
At least one detector configured to detect illumination reflected, scattered, or emitted from the overlay target;
Connected to the detector and configured to determine misalignment between at least two layers disposed on the substrate using information related to illumination reflected, scattered or emitted from the overlay target. At least one computing system comprising one or more processors;
And the second overlay target structure is formed from a dummy fill . The system of claim 13, wherein
The two or more side-by-side exposures are exposures in which no light exclusion zone exists between successive exposures.   14. The system of claim 13, wherein the first plurality of segmented pattern elements of the first overlay target structure is along a first segmentation axis and the second of the second overlay target structure. A plurality of segmented pattern elements along a second segmentation axis perpendicular to the first segmentation axis. The system of claim 13, wherein
The system, wherein the first overlay target structure is printed on a first layer of the substrate and the second overlay target structure is printed on a second layer different from the first layer of the substrate. The system of claim 13, wherein
The system, wherein the first overlay target structure is formed within a boundary defined by the second overlay target structure. The system of claim 17, wherein
The system wherein the distance between the boundary defined by the second overlay target structure and the first overlay target structure is longer than the selected light exclusion zone. The system of claim 17, wherein
The system, wherein the first overlay target structure and the second overlay target structure share at least one common boundary. The system of claim 13, wherein
The first overlay target structure is segmented according to a selected pitch or feature size that is larger than a minimum design rule specified by an exposure tool configured to expose the first overlay target structure. . The system of claim 13, wherein
The system, wherein the second overlay target structure covers most of the layers disposed on the substrate. The system of claim 13, wherein
At least one of the first overlay target structure and the second overlay target structure is a position of at least one of the first plurality of segmented pattern elements and the second segmented pattern element. A system comprising an aperture having an internal edge that allows a decision. The system of claim 13, wherein
The system, wherein each of the first overlay target structure and the second overlay target structure is two-fold symmetric. The system of claim 13, wherein
The system, wherein each of the first overlay target structure and the second overlay target structure is four-fold symmetric. A method for performing overlay measurement,
Illuminating an overlay target disposed on a substrate, the overlay target comprising:
A first overlay target structure printed on a substrate and including a first plurality of segmented pattern elements;
Printed on the substrate and includes a second plurality of segmented pattern elements, wherein a portion of the second plurality of segmented pattern elements is a part of the first plurality of segmented pattern elements A second overlay target structure disposed to overlap, the arrangement of the first overlay target structure and the second overlay target structure being four-fold symmetric, and at least a first plurality of A part of the segmented pattern element or at least a part of the second segmented pattern element is formed on the substrate by two or more side-by-side exposures, and the first plurality of segmented pattern elements Illuminating, wherein the second plurality of segmented pattern elements are identical; and
Detecting illumination reflected, scattered or emitted from the overlay target;
Determining misalignment between at least two layers disposed on the substrate using information related to detected illumination;
Only including, the second overlay target structures are formed from dummy fill method.