Measurement of manufacturing parameters based on moire interference pattern components

Abstract

A method for determining a parameter of interest in a manufacturing process is described. A sensitivity of a moire interference pattern component is determined for a measurement structure including a first grating having a first pitch and a second grating having a second pitch. The sensitivity is determined relative to a parameter of interest in the manufacturing process. The measurement structure for use in measuring the parameter of interest in the manufacturing process is evaluated based on the sensitivity. A method of measuring a parameter of interest based on a measurement structure is described. A method of generating a parameter of a measurement structure for measuring a parameter of interest based on an evaluation of the measurement structure is also described.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to PCT application PCT / CN2022 / 094137 filed on May 20, 2022, and the entire contents of that PCT application are incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to the measurement of parameters of interest in semiconductor manufacturing, and more particularly to measurements based on components of Moiré interference patterns. Background Art

[0004] The manufacture of devices such as semiconductor devices generally involves the use of multiple fabrication processes to process a substrate (e.g., a semiconductor wafer) to form various features and multiple layers of the device. These layers and features are generally manufactured and processed using, for example, deposition, lithography, etching, chemical mechanical polishing, and ion implantation. Multiple devices may be fabricated on multiple dies on a substrate, and then the devices may be separated into separate devices. Such a device fabrication process may be considered a patterning process. The patterning process involves a patterning step, such as optical and / or nanoimprint lithography using a pattern forming device in a lithographic apparatus to transfer a pattern on the pattern forming device to a substrate, and the patterning process generally but optionally involves one or more related pattern processing steps, such as resist development by a developing apparatus, baking the substrate using a baking tool, etching using a pattern using an etching apparatus, etc. Patterning may occur in multiple layers, so that a multilayer stack or device may be constructed from a set of patterned layers that are aligned with each other during patterning and other steps.

[0005] Photolithography is a central step in the manufacture of devices such as ICs, where patterns formed on a substrate define the functional elements of the device, such as microprocessors, memory chips, etc. Similar photolithography techniques are also used to form flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0006] As semiconductor manufacturing processes continue to advance, the size of functional elements has continued to decrease. At the same time, the number of functional elements (such as transistors) per device has steadily increased, following a trend commonly referred to as "Moore's Law." In the current state of the art, the layers of a device are manufactured using a lithographic projection apparatus that projects a design layout onto a substrate using illumination from a deep ultraviolet illumination source, thereby producing individual functional elements with sizes well below 100 nm (i.e., less than half the wavelength of the radiation from the illumination source (e.g., a 193 nm illumination source)).

[0007] This process for printing features with dimensions smaller than the classical resolution limit of a lithographic projection apparatus is often referred to as low-k1 lithography, based on the resolution formula CD=k1×λ / NA, where λ is the wavelength of the radiation used (currently 248 nm or 193 nm in most cases), NA is the numerical aperture of the projection optics in the lithographic projection apparatus, CD is the "critical dimension" (usually the smallest feature size printed), and k1 is an empirical resolution factor. In general, the smaller k1 is, the more difficult it becomes to reproduce a pattern on a substrate that resembles the shape and dimensions planned by the designer in order to achieve specific electrical functionality and performance. To overcome these difficulties, complex fine-tuning steps are applied to the lithographic projection apparatus, which may include alignment tools, design layouts, or patterning devices.

[0008] Monitoring device and material characteristics (including CD) and parameters of interest in the manufacturing process (e.g., manufacturing parameters such as overlay offset, dose, symmetry, etc.) allows process monitoring, control and correction, including control of lithography and other manufacturing steps. Metrology equipment can be used to determine the properties of a device and how the properties of different devices vary or how the properties associated with different layers of the same device vary from layer to layer. Metrology equipment, which can be a diffraction-based device, an optical device, an electron microscopy device, etc., is alternatively configured to identify defects on a device or align the device, and can, for example, be part of a lithography device or can be a separate device. Metrology equipment can measure properties on a latent image (an image in a resist layer after exposure), or properties on a semi-latent image (an image in a resist layer after a post-exposure bake step PEB), or properties on a developed resist image (where the exposed or unexposed portions of the resist have been removed), or even properties on an etched image (after a pattern transfer step such as etching). Summary of the invention

[0009] In one embodiment, a method includes: determining, for a measurement structure comprising a first grating having a first pitch and a second grating having a second pitch, a sensitivity of a moiré interference pattern component relative to a parameter of interest in a manufacturing process; and evaluating the measurement structure for use in measuring the parameter of interest in the manufacturing process based on the sensitivity.

[0010] In another embodiment, wherein determining the sensitivity includes determining a sensitivity that varies with at least one of the first pitch, the second pitch, or a combination thereof.

[0011] In another embodiment, wherein evaluating the measurement structure includes determining whether a phase of the moiré interference pattern component is substantially linear with respect to the parameter of interest in the manufacturing process.

[0012] In another embodiment, wherein evaluating the measurement structure includes determining whether a phase of the moiré interference pattern component is substantially constant over a wavelength range with respect to the parameter of interest in the manufacturing process.

[0013] In another embodiment, the moiré interference pattern component includes a moiré interference pattern component at a moiré pitch.

[0014] In another embodiment, the moiré interference pattern components include moiré interference pattern components at a pitch smaller than a moiré pitch.

[0015] In another embodiment, the moiré interference pattern components include moiré interference pattern components at a pitch greater than a moiré pitch.

[0016] In one embodiment, a method includes: obtaining a moiré interference pattern of a measurement structure, wherein the measurement structure includes a first grating at a first pitch in a first layer and a second grating at a second pitch in a second layer; identifying a moiré interference pattern component in the measured moiré interference pattern; and determining a measurement result of a parameter of interest in a manufacturing process based on the moiré interference pattern component.

[0017] In another embodiment, the method further includes: identifying a second moiré interference pattern component in the moiré interference pattern; and determining a measurement result of the parameter of interest in the manufacturing process based on the moiré interference pattern component and the second moiré interference pattern component.

[0018] In another embodiment, wherein the moiré interference pattern component comprises a component of the moiré interference pattern having a first frequency, and wherein the second moiré interference pattern component comprises a component of the moiré interference pattern having a second frequency.

[0019] In one embodiment, a method includes: determining a moiré interference pattern component of a measurement structure, wherein the measurement structure includes a first grating at a first pitch in a first layer and a second grating at a second pitch in a second layer; obtaining a moiré pattern of the measurement structure; removing the determined moiré interference pattern component from the moiré interference pattern; and determining a measure of a parameter of interest in a manufacturing process based on the moiré pattern with the moiré interference pattern component removed.

[0020] In one embodiment, a method includes: generating parameters for at least one measurement structure, wherein the at least one measurement structure includes a first grating at a first pitch in a first layer of a multilayer stack structure and a second grating at a second pitch in a second layer of the multilayer stack structure, wherein the first pitch and the second pitch are determined based on an evaluation of the at least one measurement structure for measuring a parameter of interest in a manufacturing process, wherein generating the parameters for the at least one measurement structure includes: determining, for the at least one measurement structure, a sensitivity of a moiré interference pattern component relative to a measurement of the parameter of interest in the manufacturing process; and evaluating the at least one measurement structure for use in measuring the parameter of interest in the manufacturing process based on the sensitivity.

[0021] In another embodiment, generating the parameters for the at least one measurement structure further comprises: determining whether the assessment of the at least one measurement structure used when measuring the parameter of interest in the manufacturing process is unfavorable; and based on determining that the assessment is unfavorable, adjusting at least one parameter of the at least one measurement structure to generate at least one adjusted measurement structure.

[0022] In another embodiment, it also includes: obtaining a moiré interference pattern of the at least one measurement structure; identifying a moiré interference pattern component in the moiré interference pattern; identifying a second moiré interference pattern component in the moiré interference pattern; and determining a measurement related to the at least one measurement structure of the parameter of interest in the manufacturing process based on the relationship between the moiré interference pattern component and the second moiré interference pattern component.

[0023] In one embodiment, a machine-readable medium has instructions thereon that, when executed by a processor, are configured to perform the method of another embodiment.

[0024] In another embodiment, a machine-readable medium and a processor as described in another embodiment are included. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments and together with the specification explain these embodiments. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which corresponding reference numerals indicate corresponding parts, and in which:

[0026] Figure 1 A schematic overview diagram of a lithographic apparatus according to an embodiment is depicted.

[0027] Figure 2Depicted is a schematic overview of a lithography cell according to an embodiment.

[0028] Figure 3 Depicted is a schematic representation of overall lithography showing the collaboration between three techniques for optimizing semiconductor manufacturing in accordance with an embodiment.

[0029] Figure 4 An example metrology apparatus according to an embodiment is illustrated.

[0030] Figure 5 Depicted is a schematic representation of a measurement structure comprising a first grating having a first pitch and a second grating having a second pitch according to an embodiment.

[0031] Fig. 6A A moiré interference pattern of an example measurement structure comprising a first grating having a first pitch and a second grating having a second pitch and having a zero overlap offset is illustrated according to an embodiment.

[0032] Figure 6B Describe the embodiment according to Fig. 6A Moiré interference pattern of an example measurement structure with non-zero overlap offset.

[0033] Figure 7 Depicting a diagram of the intensity of a moiré interference pattern measured in the xy plane of a measurement structure and with contributions from moiré interference pattern components at various frequencies according to an embodiment.

[0034] Figure 8 Describes the moiré interference pattern according to an embodiment along the Figure 7 A graph of the intensity of the cross section in the x-direction.

[0035] Fig. 9 Describe the embodiment according to Figure 8 A graph of the cross-sectional intensity components of a moiré interference pattern as a function of frequency.

[0036] Fig.10 A schematic illustration of scattering in a measurement structure comprising a grating having a first pitch and a second grating having a second pitch is depicted according to an embodiment.

[0037] Fig.11 An exemplary method for evaluating moiré interference pattern components for measurement of a parameter of interest in a manufacturing process according to an embodiment is illustrated.

[0038] Fig.12 Depicting a diagram of the intensity of a moiré interference pattern component of a measurement structure in the xy plane according to an embodiment.

[0039] Fig.13A and Fig. 13B Depicting a moiré interference pattern and extracted moiré interference pattern components according to an embodiment along the Fig.12 A graph of the intensity of the cross section in the x-direction.

[0040] Fig.14 An interference pattern of an example measurement structure including a first pitch, a second pitch, and a third pitch according to an embodiment is illustrated.

[0041] Fig.15 An exemplary method for generating a measurement structure for measuring a parameter of interest in a manufacturing process based on a plurality of moiré interference pattern components according to an embodiment is illustrated.

[0042] Fig.16 An exemplary method for determining a parameter of interest in a manufacturing process based on a plurality of moiré interference pattern components according to an embodiment is illustrated.

[0043] Fig.17A An example grating comprising an interlaced grating is illustrated according to an embodiment.

[0044] Fig. 17B An example grating comprising non-overlapping, staggered gratings is illustrated according to an embodiment.

[0045] Fig.18 An example grating comprising a vertically segmented staggered grating is illustrated according to an embodiment.

[0046] Fig.19 An example measurement structure comprising a grating with a varying pitch according to an embodiment is illustrated.

[0047] Fig. 20 An example measurement structure comprising a grating with interspersed regions of different pitches according to an embodiment is illustrated.

[0048] Fig.21 An example measurement structure comprising a grating with a resolvable pitch according to an embodiment is illustrated.

[0049] Fig. 22 An example measurement structure for measuring a parameter of interest in a manufacturing process based on components of a moiré interference pattern according to an embodiment is illustrated.

[0050] Fig.23A and Fig. 23B FIG. 1 is a diagram illustrating a method for Fig. 22 Moiré interference pattern of the measured structure.

[0051] Fig.24 An exemplary two-dimensional measurement structure according to an embodiment is shown.

[0052] Fig.25 FIG. 1 is a diagram illustrating a method for Fig.24 Moiré interference pattern of the measured structure.

[0053] Fig.26 FIG. 1 shows a schematic diagram of an embodiment of the present invention. Fig.25 Fourier transform of the moiré interference pattern.

[0054] Fig. 27 is a block diagram of an example computer system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0055] Embodiments of the present disclosure are described in detail with reference to the accompanying drawings, which are provided as illustrative examples of the present disclosure so that those skilled in the art can practice the present disclosure. It is worth noting that the following figures and examples are not intended to limit the scope of the present disclosure to a single embodiment, but other embodiments are possible by means of the interchange of some or all of the elements described or illustrated. In addition, in the case where some elements of the present disclosure can be implemented partially or completely using known elements, only those parts of such known elements necessary for understanding the present disclosure will be described, and detailed descriptions of other parts of such known elements will be omitted to avoid confusing the present disclosure. Unless otherwise specified herein, as will be understood by those skilled in the art, embodiments described as implemented in software should not be limited thereto, but may include embodiments implemented in hardware or a combination of software and hardware, and vice versa. In this specification, embodiments showing singular elements should not be considered restrictive; rather, unless otherwise explicitly stated herein, the present disclosure is intended to cover other embodiments including multiple identical elements, and vice versa. In addition, unless so explicitly stated, the applicant does not intend to attribute any term in this specification or claims to uncommon or special meanings. Further, the present disclosure encompasses present and future known equivalents to the known elements mentioned herein by way of illustration.

[0056] Although specific reference may be made herein to IC manufacturing, it should be clearly understood that the description of the present disclosure has many other possible applications. For example, the embodiments may be used to manufacture integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal display panels, thin film magnetic heads, etc. Those skilled in the art will appreciate that in the context of such alternative applications, any use of the terms "reticle", "wafer" or "die" herein should be considered interchangeable with the more general terms "mask", "substrate" and "target portion", respectively.

[0057] In this document, the terms "radiation" and "beam" are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm or 126 nm) and extreme ultraviolet radiation (EUV, e.g., having a wavelength in the range of about 5 nm to 100 nm).

[0058] (e.g., semiconductor) pattern forming device may include or may form one or more patterns. Patterns may be generated based on patterns or design layouts using a computer-aided design (CAD) process, which is often referred to as electronic design automation (EDA). Most CAD processes follow a predetermined set of design rules to generate a functional design layout / pattern forming device. These rules are set by process and design constraints. For example, design rules define the spatial tolerances between devices (such as gates, capacitors, etc.) or interconnects to ensure that devices or lines do not interact with each other in an undesirable manner. Design rules may include and / or specify specific parameters, restrictions on parameters and / or parameter ranges, and / or other information. One or more of the design rule restrictions and / or parameters may be referred to as "critical dimensions" (CD). The critical dimension of a device may be defined as the minimum width of a line or hole or the minimum space between two lines or two holes, or other features. Therefore, CD determines the overall size and density of the designed device. One of the goals in device manufacturing is to faithfully reproduce the original device intent (via a pattern forming device) on a substrate.

[0059] The term "mask" or "patterning device" as used herein may be broadly interpreted as referring to a general semiconductor patterning device that can be used to impart a patterned cross-section to an incident radiation beam that corresponds to the pattern to be produced in a target portion of the substrate; the term "light valve" may also be used in this context. In addition to classical masks (transmissive or reflective; binary, phase-shifting, hybrid, etc.), other examples of such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0060] As used herein, the term "patterning process" generally refers to a process that produces an etched substrate by applying a specified pattern of light as part of a photolithography process. However, a "patterning process" may also include (e.g., plasma) etching, as many of the features described herein may provide benefits to using an etching (e.g., plasma) process to form the printed pattern.

[0061] As used herein, the term "pattern" refers to an idealized pattern to be etched on a substrate (eg, a wafer), for example, based on the design layout described above. The pattern may include, for example, various shapes, arrangements of features, contours, etc.

[0062] As used herein, "printed pattern" refers to a physical pattern on a substrate that is etched based on a target pattern. The printed pattern may include, for example, grooves, channels, recesses, edges, or other two-dimensional and three-dimensional features produced by a photolithographic process.

[0063] As used herein, the terms "predictive model", "process model", "electronic model" and / or "simulation model" (which may be used interchangeably) refer to a model that includes one or more models that simulate a patterning process. For example, a model may include an optical model (e.g., modeling a lens system / projection system used to deliver light during a lithography process and may include modeling a final optical image of the light onto the resist), a resist model (e.g., modeling physical effects on the resist, such as chemical effects due to light), an OPC model (e.g., may be used to generate a target pattern and may include sub-resolution resist features (SRAFs), etc.), an etch (or etch bias) model (e.g., simulating the physical effects of an etch process on a printed wafer pattern), a source mask optimization (SMO) model, and / or other models.

[0064] As used herein, the term "calibration" refers to modifying (eg, improving or adjusting) and / or validating a model, algorithm, and / or other element of a current system and / or method.

[0065] The patterning system can be a system that includes any or all of the elements described above and is configured to perform any or all of the operations associated with these elements. For example, the patterning system can include a lithographic projection device, a scanner, a system configured to apply and / or remove resist, an etching system, and / or other systems.

[0066] As used herein, the term "diffraction" refers to the behavior of a beam of light or other electromagnetic radiation when encountering an aperture or series of apertures (including a periodic structure or grating). "Diffraction" can include both constructive and destructive interference, including scattering effects and interferometry. As used herein, a "grating" is a periodic structure that can be one-dimensional (i.e., composed of a column of dots), two-dimensional, or three-dimensional, and which causes optical interference, scattering, or diffraction. A "grating" can be a diffraction grating.

[0067] As a brief introduction, Figure 1A lithographic apparatus LA is schematically depicted. The lithographic apparatus LA comprises an illumination system (also referred to as an illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation), a mask support (e.g., a mask stage) T constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA according to certain parameters, a substrate support (e.g., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with resist) W and coupled to a second positioner PW configured to accurately position the substrate support according to certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0068] In operation, the illumination system IL receives a radiation beam from a radiation source SO, for example via a beam delivery system BD. The illumination system IL may include various types of optical elements for directing, shaping and / or controlling the radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic and / or other types of optical elements, or any combination thereof. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

[0069] The term "projection system" PS as used herein should be broadly interpreted as covering various types of projection systems suitable for the exposure radiation used and / or for other factors such as the use of immersion liquid or the use of a vacuum, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0070] The lithographic apparatus LA may be of a type in which at least a portion of the substrate may be covered by a liquid, such as water, having a relatively high refractive index so as to fill the space between the projection system PS and the substrate W - this is also known as immersion lithography. More information on immersion techniques is given in US6952253, incorporated herein by reference.

[0071] The lithographic apparatus LA may be of a type having two or more substrate supports WT (also referred to as a "dual stage"). In such a "multi-stage" machine, the substrate supports WT may be used in parallel, and / or a step of preparing a substrate W for subsequent exposure may be performed on a substrate W located on one of the substrate supports WT while another substrate W on another substrate support WT is being used to expose a pattern on the other substrate W.

[0072] In addition to the substrate support WT, the lithographic apparatus LA may also comprise a measurement platform. The measurement platform is arranged to hold sensors and / or cleaning means. The sensors may be arranged to measure properties of the projection system PS or properties of the radiation beam B. The measurement platform may hold a plurality of sensors. The cleaning means may be arranged to clean parts of the lithographic apparatus, e.g. a part of the projection system PS or a part of a system for providing immersion liquid. The measurement platform may be moved under the projection system PS when the substrate support WT is away from the projection system PS.

[0073] In operation, a radiation beam B is incident on a patterning device (e.g. a mask) MA held on a mask support MT and is patterned by a pattern (design layout) presented on the patterning device MA. Having traversed the mask MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and the position measurement system IF, the substrate support WT can be accurately moved, for example in order to position different target portions C at focus and alignment positions in the path of the radiation beam B. Similarly, the first positioner PM and possible further position sensors (which are not in the position measurement system IF) are also provided. Figure 1 The patterning device MA may be accurately positioned relative to the path of the radiation beam B using the mask alignment marks M1, M2 and the substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 occupy dedicated target portions as shown, they may be located in spaces between target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are referred to as scribe line alignment marks.

[0074] Figure 2 A schematic diagram of a lithography cell LC is depicted. Figure 2As shown in , the lithography apparatus LA may form part of a lithography cell LC (sometimes also referred to as a lithocell or lithography cluster), which typically also includes devices for performing pre-exposure and post-exposure processes on a substrate W. Conventionally, these devices include a spin coater SC configured to deposit a resist layer, a developer DE for developing the exposed resist, a chill plate CH and a bake plate BK, for example, for regulating the temperature of the substrate W (e.g., for regulating the solvent in the resist layer). A substrate transport device or robot RO picks up the substrate W from the input / output ports I / O1, I / O2, moves the substrate W between the different process devices and transfers the substrate W to a feed station LB of the lithography apparatus LA. The devices in the lithography cell, which are also generally referred to as coating and developing systems, are typically under the control of a coating and developing system control unit TCU, which itself may be controlled by a management control system SCS, which may also control the lithography apparatus LA, for example, via a lithography control unit LACU.

[0075] In order to correctly and consistently expose the substrate W exposed by the lithographic apparatus LA ( Figure 1 ), it is desirable to inspect the substrate to measure properties of the patterned structure, such as overlay errors between subsequent layers, line thickness, critical dimension (CD), etc. For this purpose, an inspection tool (not shown) may be included in the lithography cell LC. If errors are detected, adjustments may be made, for example, to the exposure of subsequent substrates or other processing steps to be performed on the substrate W, particularly if the inspection is performed before other substrates W of the same batch or lot are yet to be exposed or processed.

[0076] The inspection equipment, which may also be referred to as metrology equipment, is used to determine properties of the substrate W ( Figure 1 ), and in particular, determine how properties of different substrates W vary or how properties associated with different layers of the same substrate W vary between different layers. The inspection apparatus is alternatively configured to identify defects on the substrate W, and may for example be part of the lithography cell LC, or may be integrated into the lithography apparatus LA, or may even be a separate device. The inspection apparatus may measure properties on a latent image (the image in the resist layer after exposure), or on a semi-latent image (the image in the resist layer after a post-exposure bake step PEB), or on a developed resist image (where either exposed or unexposed parts of the resist have been removed), or even on an etched image (after a pattern transfer step such as etching).

[0077] Figure 3 A schematic representation of overall lithography is depicted, which shows the collaboration between the three technologies used to optimize semiconductor manufacturing. Typically, the patterning process in the lithography apparatus LA is one of the most critical steps in the process, which requires a substrate W ( Figure 1) with high accuracy in sizing and placement of structures on the ). To ensure this high accuracy, the three systems (in this example) can be combined in a so-called “holistic” control environment, such as Figure 3 Schematically depicted in . One of these systems is a lithographic apparatus LA, which is (virtually) connected to a metrology apparatus (e.g., a metrology tool) MT (a second system), and to a computer system CL (a third system). The "holistic" environment can be configured to optimize the cooperation between these three systems to enhance the overall process window and provide a tight control loop to ensure that the patterning performed by the lithographic apparatus LA remains within the process window. The process window defines the range of process parameters (e.g., dose, focus, overlay) within which a particular manufacturing process produces a defined result (e.g., a functional semiconductor device) - typically within which process parameters of the lithographic process or patterning process are allowed to vary.

[0078] The computer system CL can use (part of) the design layout to be patterned to predict which resolution enhancement technology to use and perform computational lithography simulations and calculations to determine which mask layout and lithography equipment settings achieve the maximum overall process window for the patterning process (in Figure 3 Typically, the resolution enhancement technique is arranged to match the patterning possibilities of the lithographic apparatus LA. The computer system CL may also be used to detect where within the process window the lithographic apparatus LA is currently operating (e.g. using input from a metrology tool MT) to predict whether defects may be present (e.g. attributable to suboptimal processing) e.g. Figure 3 ) as depicted by the “0” arrow pointing in the second scale SC2.

[0079] The metrology equipment (tool) MT may provide input to the computer system CL to enable accurate simulation and prediction, and may provide feedback to the lithographic apparatus LA to identify, for example, possible drift in the calibration state of the lithographic apparatus LA (in Figure 3 , as depicted by multiple arrows in the third scale SC3).

[0080] During the lithographic process, it is desirable to frequently measure the produced structures, for example for process control and verification. Different types of metrology tools MT for making such measurements are well known, including scanning electron microscopes or various forms of optical metrology tools, image-based or scatterometry-based metrology tools. Scatterometers are versatile instruments that allow measuring parameters of the lithographic process by having a sensor in a pupil or a plane conjugated to the pupil of the objective of the scatterometer, the measurement being generally referred to as pupil-based measurement, or by having a sensor in an image plane or a plane conjugated to the image plane, in which case the measurement is generally referred to as image-based or field-based measurement. Such scatterometers and related measurement techniques are further described in patent applications US20100328655, US2011102753A1, US20120044470A, US20110249244, US20110026032 or EP1,628,164A, which are incorporated herein by reference in their entirety. For example, the aforementioned scatterometers can use light from soft x-rays and visible to near IR wavelength ranges to measure features of a substrate, such as a grating.

[0081] In some embodiments, the scatterometer MT is an angle-resolved scatterometer. In these embodiments, a scatterometer reconstruction method may be applied to the measurement signal to reconstruct or calculate the properties of the grating and / or other features in the substrate. Such a reconstruction may, for example, result from simulating the interaction of the scattered radiation with a mathematical model of the target structure and comparing the simulation results with those of the measurement. The parameters of the mathematical model are adjusted until the simulated interaction produces a diffraction pattern similar to the diffraction pattern observed from a real target.

[0082] In some embodiments, the scatterometer MT is a spectroscopic scatterometer MT. In these embodiments, the spectroscopic scatterometer MT can be configured so that radiation emitted by the radiation source is directed onto a target feature of the substrate and reflected or scattered radiation from the target is directed to a spectrometer detector, which measures the spectrum of the radiation reflected by the reflector (i.e., measures the intensity as a function of wavelength). From this data, the structure or profile of the target that produced the detected spectrum can be reconstructed, for example, by rigorous coupled wave analysis and nonlinear regression or by comparison with a library of simulated spectra.

[0083] In some embodiments, the scatterometer MT is an ellipsometric scatterometer. An ellipsometric scatterometer allows the parameters of a lithography process to be determined by measuring the scattered radiation for each polarization state. Such a measurement device (MT) emits polarized light (such as linear, circular or elliptical) by using, for example, an appropriate polarization filter in the illumination section of the measurement device. A source suitable for the measurement device can also provide polarized radiation. Various embodiments of existing ellipsometric scatterometers are described in U.S. patent applications 11 / 451,599, 11 / 708,678, 12 / 256,780, 12 / 486,449, 12 / 920,968, 12 / 922,587, 13 / 000,229, 13 / 033,135, 13 / 533,110 and 13 / 891,410, which are incorporated herein by reference in their entirety.

[0084] In some embodiments, the scatterometer MT is adapted to measure the overlap of two misaligned gratings or periodic structures (and / or other target features of the substrate) by measuring a reflection spectrum and / or an asymmetry in the detection configuration, the asymmetry being related to the degree of overlap. The two (usually superimposed) grating structures may be applied in two different layers (not necessarily continuous layers), and the two grating structures may be formed to be in substantially the same position on the wafer. The scatterometer may have a symmetrical detection configuration as described, for example, in patent application EP1,628,164A, so that any asymmetry can be clearly distinguished. This provides a way to measure misalignment in the gratings. Further examples of measuring overlap may be found in PCT patent application publication number WO 2011 / 012624 or in U.S. patent application US 20160161863, which are incorporated herein by reference in their entirety.

[0085] The focus and dose used in the lithography process can be determined by scatterometry (or alternatively by scanning electron microscopy) as described in U.S. Patent Application US2011-0249244, which is incorporated herein by reference in its entirety. A single structure (e.g., a feature in a substrate) can be used that has a unique combination of critical dimension and sidewall angle measurements for each point in a focus energy matrix (FEM, also called a focus exposure matrix). If these unique combinations of critical dimension and sidewall angle are available, then focus and dose values ​​can be uniquely determined from these measurements.

[0086] The measurement target can be a collection of composite gratings and / or other features in a substrate, which is formed by a lithography process (usually in a resist, but also after, for example, an etching process). Typically, the pitch and line width of the structures in the grating rely on the measurement optics (especially the NA of the optics) to be able to capture the diffraction orders from the measurement target. The diffraction signal can be used to determine the shift between two layers (also called "overlap" or "overlay") or can be used to reconstruct at least a portion of the original grating as produced by the lithography process. This reconstruction can be used to provide guidance on the quality of the lithography process and can be used to control at least a portion of the lithography process. The target can have smaller sub-segments configured to mimic the size of a functional portion of the design layout in the target. Due to this sub-segmentation, the target will behave more similar to the functional portion of the design layout, so that the overall process parameter measurement is similar to the functional portion of the design layout. The target can be measured in an underfill mode or in an overfill mode. In the underfill mode, the measurement beam produces a spot that is smaller than the overall target. In the overfill mode, the measurement beam produces a spot that is larger than the overall target. In such an overfill mode, it is also possible to measure different targets simultaneously and thereby determine different process parameters simultaneously.

[0087] The overall measurement quality of a lithography parameter using a specific target is at least partially determined by the measurement options used to measure such lithography parameters. The term "substrate measurement options" may include one or more parameters of the measurement itself, one or more parameters of one or more patterns measured, or both. For example, if the measurement used in the substrate measurement options is a diffraction-based optical measurement, one or more of the measured parameters may include the wavelength of the radiation, the polarization of the radiation, the angle of incidence of the radiation relative to the substrate, the direction of the radiation relative to the pattern on the substrate, etc. One of the criteria for selecting a measurement option may, for example, be the sensitivity of one of the measurement parameters to process variations. More examples are described in U.S. patent application US2016-0161863, which is incorporated herein by reference in its entirety, and published U.S. patent application US 2016 / 0370717A1.

[0088] Figure 4 An example metrology device (tool) MT such as a scatterometer is shown. MT comprises a broadband (white light) radiation projector 40 which projects radiation onto a substrate 42. The reflected or scattered radiation is passed to a spectrometer detector 44 which measures a spectrum 46 of the specularly reflected radiation (i.e. measures the intensity as a function of wavelength). From this data, it can be processed by a processing unit PU, for example by rigorous coupled wave analysis and nonlinear regression, or by comparing with a spectrometer as in Figure 448 to reconstruct 48 the structure or profile that produced the detected spectrum by comparison with the library of simulated spectra shown at the bottom of . Typically, for the reconstruction, the general form of the structure is known and some parameters are assumed based on knowledge of the process by which the structure was made, leaving only a few parameters of the structure to be determined from the scatterometry data. For example, such a scatterometer may be configured as a normal incidence scatterometer or an oblique incidence scatterometer.

[0089] It is often desirable to be able to determine computationally how a patterning process will produce a desired pattern on a substrate. Computational determination may include, for example, simulation and / or modeling. Models and / or simulations may be provided for one or more parts of a manufacturing process. For example, it is desirable to be able to simulate the photolithography process of transferring a pattern forming device pattern to a resist layer of a substrate and the pattern produced in the resist layer after the development of the resist, simulate measurement operations (such as determination of overlap), and / or perform other simulations. The purpose of the simulation may be to accurately predict, for example, measurement indicators (such as overlap, critical dimensions, reconstruction of the three-dimensional profile of features of a substrate, dose or focal length of a lithography device when features of a substrate are printed with a lithography device, etc.), manufacturing process parameters (such as edge placement, spatial image intensity slope, sub-resolution auxiliary features (SRAF), etc.), and / or other information that may then be used to determine whether an expected or target design has been achieved. The expected design is typically defined as a pre-optical proximity correction design layout, which may be provided in a standardized digital file format such as GDSII, OASIS, or another file format.

[0090] Simulation and / or modeling can be used to determine one or more metrology metrics (e.g., perform overlay and / or other metrology measurements), configure one or more features of a pattern forming device pattern (e.g., perform optical proximity effect correction), configure one or more features of the illumination (e.g., change one or more characteristics of the spatial / angular intensity distribution of the illumination, such as changing the shape), configure one or more features of the projection optical device (e.g., numerical aperture, etc.), and / or for other purposes. Such determination and / or configuration can be generally referred to as, for example, mask optimization, source optimization, and / or projection optimization. Such optimizations can be performed independently or combined in different combinations. One such example is source-mask optimization (SMO), which involves configuring one or more features of the pattern forming device pattern together with one or more features of the illumination. Optimization can, for example, use the parameterized models described herein to predict the values ​​of various parameters (including images, etc.).

[0091] In some embodiments, the optimization process of the system can be represented as a cost function. The optimization process can include finding a set of parameters (design variables, process variables, etc.) that minimize the cost function of the system. The cost function can have any suitable form depending on the purpose of the optimization. For example, the cost function can be the weighted root mean square (RMS) of the deviation of certain characteristics (evaluation points) of the system relative to the expected values ​​(e.g., ideal values) of these characteristics. The cost function can also be the maximum value (i.e., the worst deviation) of these deviations. The term "evaluation point" should be broadly interpreted as including any characteristic of the system or manufacturing method. Due to the applicability of the implementation of the system and / or method, the design and / or process variables of the system can be limited to a limited range and / or can be interdependent. In the case of a lithographic projection device, constraints are often associated with the physical properties and characteristics of the hardware (such as, tunable range and / or pattern forming device manufacturability design rules). The evaluation point can include a physical point on the resist image on the substrate, as well as non-physical characteristics, such as (for example) dose and focal length.

[0092] Figure 5 A schematic representation of a measurement structure including a first grating having a first pitch and a diffraction grating having a second pitch is depicted. The measurement structure 500 can be a measurement structure used with a metrology device, which can be a dedicated metrology device such as a diffraction metrology device, or can be a general metrology device such as a camera or imager. The measurement structure 500 includes a substrate 502, a first grating 506, a stacked medium 504, and a second grating 510. The first grating 506 can be a diffraction grating and the second grating 510 can be a diffraction grating. The substrate 502 can be a semiconductor substrate, a conductive substrate, an insulating substrate, etc. The substrate 502 can be a solid substrate, such as a silicon wafer, on which one or more electronic devices are manufactured. Alternatively, the substrate 502 can be any layer on which the first grating 506 is manufactured, such as a previously manufactured part of an electronic device.

[0093] The laminated medium 504 may include one or more layers, including stacked layers, self-assembled layers, deposited layers, oxide layers, etc. The laminated medium 504 may have material properties and electronic properties, such as refractive index, density, lattice constant, resistivity, etc., which are constant, linearly changing, or discontinuous, etc. The material properties and electronic properties of the laminated medium 504 may depend on its laminated structure or manufacturing method. The laminated medium 504 may include a medium having a refractive index greater than 1.

[0094] The first grating 506 may include any periodic structure having a first pitch 520 (e.g., P1). The first pitch 520 may be measured in terms of period, frequency, etc. and may correspond to a wavelength. The first grating 506 may include a periodic arrangement of linear elements, triangular elements, rectangular prism elements, etc. The first grating 506 may include a periodic arrangement of elements having a size that is the same as the pitch between the elements or a size that is different from the pitch between the elements. The first grating 506 may be manufactured by one or more deposition processes, photolithography processes, etching processes, or a combination thereof. The first grating 506 may be composed of one or more materials. For example, the first grating may be a metal or include a metal layer, such as a titanium bonding layer and a gold layer. Alternatively or additionally, the first grating 506 includes a semiconductive material, an insulating material, a conductive material, etc.

[0095] The second grating 510 may include any periodic structure having a second pitch 522 (e.g., P2). The second pitch 522 may be measured in terms of period, frequency, etc., and may correspond to a wavelength. The second pitch 522 may be different from the first pitch 520. The second pitch 522 may be greater than or less than the first pitch 520. The second pitch 522 may be a fraction or multiple of the first pitch 520, such that the first pitch 520 and the second pitch 522 have a least common multiple. The first pitch 520 and the second pitch 522 may include a periodic unit or super unit, which may include an integer multiple of the first pitch 520 and the second pitch 522. The second grating 510 may include a periodic arrangement of linear elements, triangular elements, rectangular prism elements, etc., which may be the same or different from the periodic arrangement of elements of the first grating 506. The second grating 510 may include a periodic arrangement of elements having a size that is the same as the pitch between the elements or a size that is different from the pitch between the elements. The elements of the first grating 506 and the second grating 510 may be stacked in a direction perpendicular to the plane of the grating (i.e., the y direction 532). Alternatively, the elements of the first grating 506 and the second grating 510 may not be stacked in the y direction 532. The second grating 510 may be manufactured by one or more deposition processes, photolithography processes, etching processes, or a combination thereof. The manufacturing process for producing the second grating 510 may be the same or different from the manufacturing process for producing the first grating 506. The second grating 510 may be composed of one or more materials. Alternatively or additionally, the second grating 510 includes a semiconductive material, an insulating material, a conductive material, etc. The second grating 510 may be the same or different material as the first grating 506. The second grating 510 may be coated with or otherwise covered with one or more additional layers. The second grating 510 may also be exposed to air, an inert gas, covered in oil, or otherwise prepared for optical or other measurements.

[0096] The measurement structure 500 can be subjected to incident electromagnetic radiation 512 in order to measure one or more characteristics of the measurement structure 500. The incident electromagnetic radiation 512 can have a specific wavelength or phase, such as laser light, or can have a range of wavelengths or phases including collimated light, white light, UV light, EUV light, etc. The incident electromagnetic radiation 512 can approach the measurement structure 500 obliquely, as shown, at a large angle to the substrate, obliquely at a small angle to the substrate, or perpendicular to the substrate, etc. The incident electromagnetic radiation 512 can produce outgoing electromagnetic radiation 514a, 514b. The outgoing electromagnetic radiation 514a, 514b can include reflected electromagnetic radiation, diffracted electromagnetic radiation, emitted electromagnetic radiation, or a combination thereof. The outgoing electromagnetic radiation 514a, 514b can be scattered radiation, wherein the scattering mechanism can vary. The outgoing electromagnetic radiation 514a, 514b may include an electromagnetic signal that may vary in wavelength, phase, intensity, polarization, etc. depending on the angle of incidence, azimuth, distance, etc. from the measurement structure 500 or the source of the incident electromagnetic radiation 512. The outgoing electromagnetic radiation 514a, 514b may have the same or a different wavelength than the incident electromagnetic radiation 512. The outgoing electromagnetic radiation 514a, 514b may be measured at a detector.

[0097] The first grating 506 and the second grating 510 may be offset in a y-direction 532 (which may be a fabrication direction) by means of the stacked medium 504. The first grating 506 and the second grating 510 may also be offset in an xy plane, which may be substantially orthogonal to the fabrication direction, wherein the stack of layers of the measurement structure 500 are placed on top of each other. An overlay offset may be measured in the x-direction 530, wherein the overlay offset is a measure of the deviation of the overlay from an ideal overlay, as determined. The overlay offset may be determined based on a difference between the measurement structure 500 or an electromagnetic signal generated using the measurement structure 500 and an ideal measurement structure 500 or an electromagnetic signal corresponding to the ideal measurement structure 500.

[0098] Fig. 6AMoire interference patterns for an example measurement structure are illustrated, the measurement structure comprising a first grating having a first pitch and a second grating having a second pitch and having a zero overlap offset. A moire interference pattern, also referred to as moire fringes or moire patterns, is an interference pattern produced by the interaction of two or more patterns, which may be periodic or aperiodic in nature and have transparent or semi-transparent portions and are at least slightly deformed from one another. A measurement structure comprising a first grating having a first pitch and a second grating having a second pitch may produce a moire interference pattern, wherein the first pitch is different from the second pitch. The moire interference pattern between the two pitches (first pitch 606 and second pitch 608) is depicted in region 622 as varying depending on the x-direction 602 and the z-direction 604. The grating having the first pitch 606 and the grating having the second pitch 608 are depicted as offset in the z-direction 604 in order to show the two gratings and the first pitch 606 and the second pitch 608, however, such an offset in the z-direction 604 may not be present in the measurement structure. The interaction of the first pitch 606 and the second pitch 608 produces a moiré interference pattern having regions of greater intensity (local maxima of intensity as depicted in box 618) and regions of lesser intensity. The intensity of the moiré interference pattern is represented by a sinusoidal curve 620 having a moiré period 612. The locations of local maxima and minima in the moiré interference pattern (e.g., the phase of the moiré interference pattern) can be used to measure overlay offset or another parameter of interest in the manufacturing process. For a reference point (which can be a midpoint, an endpoint, a distance, etc.) about the first pitch 606 or the second pitch 608, a moiré phase shift 614 can be determined. Fig. 6A The diagram shows a measurement configuration where the overlay offset is zero (eg, an ideal measurement configuration).

[0099] A moiré interference pattern may also be depicted based on the sinusoidal representation of the first pitch 606 and the second pitch 608. The first pitch 606 may be represented as a first sinusoidal intensity 630 having the same frequency as the first pitch 606, and the second pitch 608 may be represented as a second sinusoidal intensity 632 having the same frequency as the second pitch 608. An overlap 634 of the first sinusoidal intensity 630 and the second sinusoidal intensity 632 shows a relationship to the moiré interference pattern, corresponding to regions of greater intensity and regions of lesser intensity in the combination of the first sinusoidal intensity 630 and the second sinusoidal intensity 632.

[0100] Figure 6B Depiction Fig. 6A Moiré interference pattern of an example measurement structure with non-zero overlap offset. Fig. 6A The first pitch 606 has the same periodicity as the first pitch 656 and has the same periodicity as the first pitch 606. Figure 6BThe moiré interference pattern between the grating having the first pitch 656 and the grating having the second pitch 658, which is the same periodicity as the second pitch 608, is depicted in region 672 as varying according to the x-direction 652 and the z-direction 654. Again, for illustrative purposes, the grating having the first pitch 656 and the grating having the second pitch 658 are depicted as being offset in the z-direction 654. Fig. 6A , the first pitch 656 is also offset relative to the second pitch 658 in the x-direction 652 by an overlap offset 668. Since the first pitch 656 is not equal to the second pitch 658, the individual elements that make up the pitch show an offset over a large portion of the region 672. Line 610 is used to mark a reference point that can be used to make overlap offset measurements. However, in Figure 6B The offset of the first pitch 656 relative to the second pitch 658 is different from that in Figure 6B The offset of the first pitch 606 and the second pitch 608 in FIG.

[0101] The intensity of the moiré interference pattern is represented by a sinusoidal curve 670 having a moiré period 662. Due to the overlap offset 668, the locations of the local maxima and minima in the moiré interference pattern (eg, the phase of the moiré interference pattern) are relative to Fig. 6A The moiré phase shift 664 is determined by shifting the phase of the moiré pattern in the first pitch 606. The overlap offset 668 is shown as a shift relative to line 610, but can be measured relative to any suitable reference point. The moiré phase shift 664 can be determined for a reference point (which can be a midpoint, an endpoint, a distance, etc.) about the first pitch 606 or the second pitch 608. Fig. 6A The moiré phase shift of 614 and Figure 6B The phase change of the moiré pattern can be determined based on the moiré phase shift 664. The overlap offset 668 can be determined based on the change of the moiré pattern.

[0102] The moiré interference pattern can again be depicted based on a sinusoidal representation of the first pitch 656 and the second pitch 658. The first pitch 656 can be represented as a frequency versus the first pitch 656 (and Fig. 6A The first pitch 606) has the same first sinusoidal intensity 680, while the second pitch 658 can be represented as a frequency with the second pitch 658 (and Fig. 6A The overlap 684 of the first sinusoidal intensity 680 and the second sinusoidal intensity 682 shows a relationship with a moiré interference pattern, which corresponds to areas with greater intensity and areas with less intensity in the combination of the first sinusoidal intensity 680 and the second sinusoidal intensity 682.

[0103] The moiré pitch, which is representative of the periodicity of the moiré interference pattern, may be determined by the relationship between the first pitch and the second pitch, such as by using the following Equation 1:

[0104] (1).

[0105] Where P1 is the first pitch and P2 is the second pitch. For at least semi-transparent measurements (to incident radiation), the first pitch may represent the buried pitch or the pitch after exposure, while the second pitch may be another pitch for a dual pitch measurement structure. For simplicity, the buried pitch is referred to herein as the first pitch because it is usually produced first, but either pitch may be the buried pitch and the pitches may be produced in either order. The moiré pitch may be the maximum pitch of the moiré interference pattern (e.g., the lowest frequency component of the moiré interference pattern).

[0106] The moiré phase shift, which is the relationship between the overlap offset and the phase shift in the moiré pattern, can also be given by the relationship between the first pitch and the second pitch using the following equation 2:

[0107] (2).

[0108] Wherein, OVL is the overlap offset caused by the shift of the first pitch, P1 is the first pitch and P2 is the second pitch. A similar relationship can be determined for the shift of the second pitch. For the first pitch and the second pitch that are close in size but different, the moiré phase shift can therefore be larger than the actual OVL by a multiplication factor. By selecting the first pitch and the second pitch, a moiré phase shift that is larger than the overlap offset can be selected, and which is correspondingly easier to measure for smaller components (e.g., for ICs, on the order of CD). The relationship between the overlap offset and the moiré phase shift can be linear, which allows the overlap offset to be directly determined based on the moiré phase shift relative to a reference (e.g., zero overlap offset) moiré phase shift.

[0109] Figure 7A diagram depicting the intensity of a moiré interference pattern measured in an xy plane of a measurement structure with contributions from moiré interference pattern components at multiple frequencies. Diagram 700 depicts example moiré interference patterns for two measurement structures, wherein a first measurement structure is indicated by bracket 750 and a second measurement structure is indicated by bracket 760. The measurement structure includes a first grating having a first pitch and a second grating having a second pitch. The intensity of the outgoing electromagnetic radiation (e.g., an electromagnetic signal measured at a detector) is plotted as a function of grayscale according to scale 706 in arbitrary units. The electromagnetic signal is plotted along an x-axis 702 (in arbitrary distance units) and a y-axis 704 (in arbitrary distance units) for a first measurement structure oriented with a periodic element perpendicular to line 710 and a second measurement structure with a periodic element perpendicular to line 740. Diagram 700 shows the periodicity of the two measurement structures along the x-axis 702, but not the periodicity in a simple sinusoid. For example, the first measurement structure displays a global maximum and two satellite local maxima within box 720 , and the second measurement structure displays a variable local maximum peak height in box 730 .

[0110] Figure 8 Describe along the Figure 7 Graph 800 depicts the intensity of the moiré interference pattern of a cross section in the x-direction. Figure 7 700. Line 810 represents the measured intensity in arbitrary intensity units along the y-axis 804 as a function of distance (in arbitrary units) along the x-axis 802. Line 810 shows periodicity at several frequencies (e.g., various pitches or wavelengths). A first period 812 is shown by a repeating pattern of local maxima and minima of intensity. A second period 814 occurs between local maxima with varying intensity.

[0111] Fig. 9 Describe the embodiment according to Figure 8 A graph of the frequency components of the moiré interference pattern of the cross-sectional intensity as a function of frequency. Graph 900 depicts Figure 8800 . Line 930 represents the amplitude (in arbitrary units along the y-axis 904) as a function of frequency (along the x-axis 902). The frequency may be determined by using a Fourier transform or other frequency transform. Line 930 shows peaks at values ​​marked by the following lines: line 910, which may correspond to a moiré interference pattern component at a first frequency, which may be a moiré pitch frequency; line 912, which may correspond to a second moiré interference pattern component; line 914, which may correspond to a third moiré interference pattern component; line 916, which may correspond to a fourth moiré interference pattern component; line 918, which may correspond to a fifth moiré interference pattern component; and line 920, which may correspond to a sixth moiré interference pattern component. The depicted moiré interference pattern components are representative examples, and alternatively, there may be more or fewer moiré interference pattern components at different frequencies, with different intensities. For example, in the graph 900 , the sixth moiré interference pattern component has a relatively small amplitude. Additionally, the peak width of individual moiré fringes may depend on or correspond to the amplitude for the individual components, or may vary depending on the symmetry or degree of scattering of the electromagnetic source or measurement structure.

[0112] The moiré interference pattern may be composed of multiple components of various frequencies or pitches. For example, the moiré interference pattern may include a moiré pitch or a component having a period of the moiré pitch, and may also include a component having a period or pitch of each of the constituent pitches (e.g., the pitch of a grating that produces the moiré interference pattern). Additional components may be due to interference between the moiré pitch and the constituent pitches and other effects having a period. Additional components having a pitch or period of the order of the least common multiple of the constituent pitches or the order of a super unit may also be generated.

[0113] The moiré interference pattern components may correspond to frequencies related to their period or pitch.The moiré interference pattern components may be determined based on multiples of the moiré pitch, for example, using the following relationship.

[0114] (3).

[0115] Where n can be an integer. In some cases, n can be a fraction or ratio, such as 2 / 3 or 3 / 2. For an example measurement structure with a grating pitch of 500 and 600 (in arbitrary units), the moiré interference pattern can have a strong component that occurs at a pitch of 3000 (also in arbitrary units), where 3000 is both the least common multiple and the moiré pitch (as given by Equation 1). The moiré interference pattern can further have strong components at constituent pitches, for example, at 500 and 600 (in arbitrary units). Additional components may occur at 1500, 1000, 750, etc. These pitches represent multiples of the moiré frequency, which is the frequency corresponding to the moiré pitch.

[0116] Moiré interference patterns can be generated by interference between semi-transparent patterns. However, for a measurement structure including a first grating and a diffraction grating, diffraction and reflectance can generate a moiré interference pattern. A diffracted, refracted, reflected or otherwise changed pattern (hereinafter "scattered") can be generated from an embedded diffraction grating or an exposed diffraction grating. The intensity of the outgoing electromagnetic radiation may be affected by the absorbance of the laminated medium and other physical and electronic properties of the measurement structure. By taking into account scattered radiation (e.g., by including a first-order diffraction wave path and a higher diffraction wave path), a weaker electromagnetic signal can be enhanced so that a moiré interference pattern component can be measured based on the electromagnetic signal. The moiré interference pattern can therefore be measured as an optical image (e.g., captured by a lens or camera) or as a diffraction-based signal (e.g., measured as a diffracted or otherwise scattered electromagnetic signal).

[0117] Fig.10 A schematic illustration of scattering in a measurement structure comprising a first grating having a first pitch and a second grating having a second pitch is depicted. The measurement structure 1000 comprises a substrate 1002, a first grating 1006, a stacked medium 1004, and a second grating 1010. The substrate 1002 may be any suitable substrate, as previously described with reference to Figure 5 The stacked medium 1004 may be any suitable stacked medium, as previously described. The first grating 1006 may be any suitable grating having a first pitch, and the second grating 1010 may be any suitable grating having a second pitch, as previously described. The measurement structure is depicted with reference to the x-axis 1050 and the y-axis 1052.

[0118] The measurement structure 1000 can be subjected to incident electromagnetic radiation 1040 in order to measure one or more characteristics of the measurement structure 500. The incident electromagnetic radiation 1040 can have a specific wavelength or phase, such as laser light, or can have a wavelength or phase range including collimated light, white light, UV light, EUV light, etc. The incident electromagnetic radiation 1040 can approach the measurement structure 1000 obliquely, as shown, at a large angle to the substrate, at a small angle to the substrate, perpendicular to the substrate, etc. The incident electromagnetic radiation 1040 can be reflected, transmitted, diffracted, or a combination thereof by the second grating 1010. For ease of description, photons (e.g., electromagnetic radiation quanta) that are diffracted, reflected, or otherwise transmitted back from the second grating 1010 without interacting with the stack medium 1004 or the first grating 1006 will be identified by a wave path with a j value. A j value of zero (0) corresponds to a zero-order diffraction path (e.g., a reflected photon), while a j value of ±n refers to a ±n-order diffraction path. Within ellipse 1020, a zeroth order diffraction path as well as positive and negative first order diffraction paths are shown for electromagnetic radiation that interacts only with the second grating.

[0119] Incident electromagnetic radiation 1040 entering the stacked medium 1004 may be refracted depending on the refractive index of the stacked medium 1004 and the refractive index of the layer above the second grating 1010. Incident electromagnetic radiation 1040 entering the stacked medium 1004 may also be absorbed or otherwise scattered.

[0120] Incident electromagnetic radiation 1040 reaching the first grating 1006 may be reflected, transmitted, diffracted, or a combination thereof (e.g., scattered) by the first grating 1006. For ease of description, photons diffracted, reflected, or otherwise returned (e.g., via the stacked medium 1004) from the first grating 1006 are identified by wave paths having vector values ​​(l, m, q), where l represents the diffraction order of the transmitted beam, refracted beam, or a combination thereof that passes through the second grating 1010, m represents the diffraction order of the reflected beam, diffracted beam, or a combination thereof that passes back from the first grating 1006, and q represents the diffraction order of the transmitted beam, refracted beam, or a combination thereof that passes through the second grating 1010. Such paths represent transmission, reflection, transmission paths between a surface (or other direction from which the incident electromagnetic radiation 1040 approaches) and a detector. These paths correspond to those paths depicted under bracket 1030. Wave paths involving more reflections, less reflections, and higher or lower order diffraction may also occur. The wave paths depicted in this manner are illustrative only and should not be considered to represent all possible wave paths. Moiré interference (e.g., interference that produces a moiré interference pattern) can occur between any two wave paths, since each wave path represents a photon of wavelength traveling a certain distance. The distance traveled depends on the geometry of the measurement structure 1000, the first grating 1006, the second grating 1010, the material properties and electrical properties of the stacked medium 1004, etc. Diffraction (or other scattering) from the grating may cause changes in the moiré interference pattern. The frequency and amplitude of the moiré interference pattern may depend on the first pitch of the measurement structure 1000, the second pitch, their separation, and the material properties (e.g., the material properties of the stack).

[0121] Moiré interference patterns can be generated between various wave paths, and between moiré interference patterns and additional physical patterns or patterns generated by physical elements. , the outgoing electromagnetic radiation can be measured in the x direction using the following equation 4 :

[0122] (4).

[0123] Where j represents the imaginary unit, j 2 = -1, k i is the ith wave number, and is the amplitude coefficient of the outgoing electromagnetic radiation. The wave number is the allowed state or quantum state of the measurement structure and can be described using the following equation 5:

[0124] (5).

[0125] Where k0 is the wave number of the incident electromagnetic radiation, i is an integer, and P is the least common multiple of the first pitch (e.g., P1) and the second pitch (e.g., P2). i The intensity of the electromagnetic signal (e.g., the outgoing electromagnetic radiation that varies with the x-direction) can be given by the superposition of a set of frequency components defined in the algebraic calculation between the values, which can be approximated as a superposition of cosine waves, which can have a frequency or periodicity that depends on one or more wave numbers. Alternatively, the superposition of sine waves, exponential functions (including imaginary exponential functions), etc. with appropriately selected frequencies and phase shifts can be used to estimate the intensity of the electromagnetic signal. In the following, the superposition of cosine waves is discussed, but other periodic functions can be used.

[0126] Thus, the total moiré interference pattern can be represented by a superposition of cosine waves having frequencies represented by different wave numbers. The amplitude of each cosine wave component depends largely on the stack properties (e.g., absorbance, thickness, band gap, etc.). However, the spectrum and phase shift associated with the overlap can be estimated based on its constituent frequency contributions. In addition, the effect of the overlap offset (or another parameter of interest in the manufacturing process) on the frequency and phase shift can also be determined before (or even without) determining the amplitude.

[0127] Each cosine wave component may be estimated for at least a plurality of wave paths. Because higher-order diffraction and multiple reflections produce wave paths of lesser intensity, these terms may be substantially equal to zero. However, a first type of wave path in which diffraction occurs at a top diffraction grating (e.g., a second diffraction grating) and a second type of wave path in which electromagnetic radiation is transmitted through a top diffraction grating, diffracted from a buried diffraction grating (e.g., a first diffraction grating), reflected, and transmitted through the top diffraction grating may produce a significant contribution to the moiré interference pattern. Various first type wave paths and second type wave paths, as well as combinations of second type wave paths with other second type wave paths, may be analyzed to determine spatial frequencies that contribute significantly to the moiré interference pattern.

[0128] For example, the frequency distribution can be determined based on an analysis of the wave paths contributing to the wave number. For the interaction between the first type of wave paths and the second type of wave paths, refer to Fig.10 The frequency of the cosine wave component generated by the interaction of the two wave paths can be expressed as follows in Equation 6:

[0129] (6).

[0130] where the frequency of the cosine wave component related to the total wave number kc can be determined from the wave numbers of the various segments and the diffraction of the two wavelength paths. Similarly, for the interaction between the two second type wave paths, the frequency of the cross term can be expressed as follows in Equation 7:

[0131] (7),

[0132] Wherein the subscript 2 represents the wave number and diffraction order of the second second type wave path, and the subscript 1 represents the wave number and diffraction order of the first second type wave path.

[0133] The frequencies of different cross terms can be determined by exploring the possible values ​​(j, l, m, q) of the two types of wave paths and the interaction between the two types of wave paths. The spatial frequencies with significant contributions can be determined based on known P1 and P2 or based on a variable representation of the first pitch and the second pitch (e.g., the relationship between the first pitch and the second pitch).

[0134] Based on the diffraction order, the relationship between overlap (or another parameter of interest in the manufacturing process) and the moiré phase shift can be determined for each cosine wave component. In some cases, the relationship varies with respect to the beam path, that is, different beam paths may have different moiré shifts (or overlap sensitivities) relative to the same overlap offset. Differences in overlap sensitivity of various wave paths and their interference patterns may cause overlap offset errors, errors in the measured overlap offset for a known overlap offset, or overlap setting-obtaining errors. Other parameters of interest may be measured for one or more cosine wave components based on the relationship with the moiré phase shift. For example, the thickness of one or more stacked materials may be determined based on the interaction between the wave paths, because the distance traveled between the first grating and the second grating depends on the thickness of the one or more stacked materials, and because the length of the wave path may affect the phase of the scattered photons of the wave path.

[0135] For stable overlay sensitivity, a measure of overlay shift or another parameter of interest may be extracted from the moiré interference pattern, or from a measured moiré interference pattern comprising multiple components, or by extracting one or more moiré interference pattern components and determining a measure of overlay shift or another parameter of interest based on the extracted components. For example, the intensity of a particular moiré pattern may be written as follows in Equations 8 and 9:

[0136] (8),

[0137] (9).

[0138] Among them I +1 (x) and I -1(x) represents the intensity of the positive diffraction branch and the negative diffraction branch as a function of x. C is a constant about the total electromagnetic intensity of the wave paths that have interfered to produce the moiré interference pattern component c, and may represent the electromagnetic intensity of one or more wave paths that produce the moiré interference pattern component c—for example, E C can be equal to (including approximately equal to or equal to within a constant factor of) E A ×E B And has units of intensity or electromagnetic field strength squared. k c is the total wave number about the wave path of component c, and and denote the phase shifts with respect to positive and negative image orders, respectively. and The phase shift may include contributions from optical elements, such as from an incident electromagnetic source, from optical elements (lenses, focus, collimators, etc.), from detectors, etc.

[0139] Due to the number of variables or unknowns and the number of equations, two sets of measurement structures with opposite pitches (i.e., the first pitch of the first structure is the second pitch of the second structure, and vice versa) are often used to identify the overlay offset. Traditionally, the two measurement structures or pads may be referred to as M pads (where the top pitch is greater than the buried pitch) and W pads (where the buried pitch is greater than the top pitch), which is the case when continuous diffraction based overlay (cDBO) marks may be used to measure overlay offset or another parameter of interest in the manufacturing process. Alternatively, the measurement structures have different pitches (e.g., non-inverted pitches). By using moiré interference pattern components at multiple pitches (or frequencies) for overlay offset extraction, a single measurement structure (e.g., pad) may be used instead of a conventional two-pad configuration, which may save area and therefore cost during the manufacture of electronic devices. In simulations of conventional cDBO measurements, M and W may be used to represent different moiré components obtained from a single pad, e.g., two sets of equations generated from the Mth moiré frequency (or M path) and the Wth moiré frequency (or W path), respectively. Based on the moiré frequency component, the overlap offset may be measured using the following equation 10.

[0140] (10).

[0141] Where S M , S W , K M and K W are coefficients based on the M and W paths. Based on Equation 10, the overlay offset and other overlay information can be explicitly extracted from two different moiré interference pattern components (or frequencies).

[0142] Using multiple components of the moiré interference pattern can provide improvements over current techniques. For example, some measurement structures including a first grating and a second grating are used for optical metrology to measure overlay offset or other parameters of interest. A multi-grating structure can include gratings with frequencies visible to optical metrology tools (such as cameras, optical microscopes, etc.). Therefore, for the most advanced devices, the grating size can be larger than the CD. In addition, given the number of variables and equations to be solved, extracting overlay offset or other parameters of interest from a multi-grating structure may require multiple multi-grating structures.

[0143] In another example, the measurement structure may include a first grating and a second grating having different pitches and acting as diffraction gratings. A diffraction-based measurement structure may be used to generate a diffraction pattern, which may be a type of interference pattern. Based on the relationship between the diffraction pattern corresponding to the first grating and the diffraction pattern corresponding to the second grating, overlap offset and other parameters of interest may be measured. A diffraction-based measurement structure typically has a grating periodicity that is of the order of the wavelength used to investigate the structure, which may be less than the optical wavelength. However, a diffraction-based measurement structure may suffer from harmful electromagnetic effects. As the wavelength becomes smaller (e.g., to be used to investigate a device with a smaller CD), the photon energy increases, which may cause destructive interactions with the stacked structure (e.g., resist breakdown, ionization damage, etc.). In addition, diffraction-based measurements are based on detecting diffracted photons from a buried layer. For highly absorptive stacked materials (i.e., thick stacked materials, narrow bandgap materials, etc.), very few photons are diffracted.

[0144] By using multiple components of the moiré interference pattern for a multi-grating structure, the number of measurement structures required to explicitly identify the overlap offset or another parameter of interest can be reduced. The total number of equations that can be solved for the multi-grating measurement structure can be increased by the number of components of the moiré interference pattern used (e.g., those components that have a linear relationship with the overlap offset or the parameter of interest over the wavelength range). In addition, multiple types of scattered photons can be collected by the detector. This allows the investigation of buried gratings for layers where pure diffraction measurements are not strong enough, and therefore allows the determination of overlap offset or other parameters of interest for absorptive laminated materials. By identifying multiple components of the moiré interference pattern, the accuracy of the measurement (and optionally, alignment) can be improved. A single pad (e.g., a single multi-grating measurement structure) that can be used to determine the overlap offset or another parameter of interest also represents a geometric space saving in the die, which can increase the area of ​​the die that can be used for IC device manufacturing and thus increase the device density of the die and improve profitability.

[0145] Fig.11An exemplary method 1100 for evaluating a moiré interference pattern for overlay offset measurement is illustrated. Each of these operations is described in detail below. The operations of method 1100 presented below are intended to be illustrative. In some embodiments, the method 1100 may be implemented with one or more additional operations not described and / or may be implemented without one or more of the operations discussed. Additionally, in Fig.11 The order in which the operations of method 1100 are illustrated in and described below is not intended to be limiting. In some embodiments, one or more portions of the method 1100 may be implemented in one or more processing devices (e.g., one or more processors) (e.g., by simulation, modeling, etc.). The one or more processing devices may include one or more devices that perform some or all of the operations of method 1100 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured via hardware, firmware, and / or software that are specifically designed to perform, for example, one or more of the operations of method 1100.

[0146] At operation 1102, stack information is obtained. The stack information may include information about the substrate, the first grating, the stack medium, the second grating, and any other material dimensions and properties (e.g., material properties or electrical properties). The stack information may also include information about the incident electromagnetic radiation, such as wavelength, wavelength range, spot size, etc. The stack information may also include information about properties for measuring the outgoing electromagnetic radiation (e.g., electromagnetic signal), including detectable wavelength, detectable intensity, detectable angle, etc. The stack information may include information about the first grating and the second grating, including information about pitch, shape, physical size, material. The stack information may include a range of values ​​for one or more parameters, such as a range of pitches of the first grating or the second grating. The information about the first grating and the second grating may include lithography, deposition, etchant, or other manufacturing information, including manufacturing limitations and manufacturing thresholds. The stack information may include critical dimensions or geometry or overlay offset resolution thresholds. The stack information may include design parameters that may be iteratively updated. The design parameters may include design parameters of the first diffraction grating and the second diffraction grating, including pitch.

[0147] At operation 1104, a moire interference pattern component is selected for evaluation. The selected moire interference pattern component may be a moire interference pattern component having a period corresponding to the moire pitch or a moire interference pattern component having a smaller or larger pitch. The moire interference pattern component may be selected from a range of moire interference pattern components or a series of moire interference pattern components in order of pitch size or frequency. Optionally, the moire interference pattern component at the moire pitch may be omitted from the moire interference pattern components selected for evaluation. The moire interference pattern component may be limited to a range of moire interference pattern components (e.g., a range of pitch sizes, frequencies, the number of multiples of the pitch, the number of multiples of the frequency, etc.). As an example, the moire interference pattern component may be limited to a component having a period between the moire pitch and the minimum value of the constituent pitches (e.g., the minimum value of the top pitch and the buried pitch).

[0148] At operation 1106, based on the stack information needle, a sensitivity is determined for the selected moiré interference pattern component. The sensitivity can be an overlap sensitivity and can be determined in the manner previously described. Alternatively, the sensitivity can be a sensitivity relative to another parameter of interest in the manufacturing process. The sensitivity can be determined based on the pitch (e.g., the first pitch of the first grating and the second pitch of the second grating). The sensitivity can be determined based on the pitch and one or more parameters of the stack information. The sensitivity can be determined based on an overlap offset of the first grating relative to the second grating or an overlap offset of the second grating relative to the first grating. The sensitivity can be determined based on one or more of the pitches. The sensitivity can be determined for a range or set of wave paths that contribute to the selected moiré interference pattern component, as previously described. The sensitivity can be determined for a wavelength or wavelength range of the incident electromagnetic radiation.

[0149] At operation 1106, it is determined whether the sensitivity of the selected moiré interference pattern component is linear with respect to the overlap offset or another parameter of interest. If linearity is found with respect to the sensitivity, the selected moiré interference pattern component is conditionally accepted for the overlap offset measurement or the measurement of another parameter of interest. The linearity may encompass or include perfect linearity with respect to the overlap offset or another parameter of interest for the wavelength or wavelength range of the incident electromagnetic radiation. The linearity may also encompass or include a constant linear relationship or a substantially constant fit factor between the sensitivity and the overlap offset or another parameter of interest over the wavelength range. The linearity may also encompass or include substantially linearity, linearity within a threshold, linearity within a sub-range of the wavelength range, etc. If the overlap sensitivity of the selected moiré interference pattern component is determined to be linear, the process proceeds to operation 1112. If the overlap sensitivity of the selected moiré interference pattern component is determined to be not linear, the process proceeds to operation 1108.

[0150] At operation 1108, it is determined whether the sensitivity of the selected moiré interference pattern component is sufficiently linear. In some embodiments, it can be determined whether the overlap meets a minimum linearity threshold or is otherwise sufficiently linear. For example, if one or more wave paths of the selected moiré interference pattern component produce nonlinear contributions, a linear percentage can be determined, for example, which percentage of wave paths produce linear sensitivity relative to which percentage of wave paths produce nonlinear overlap sensitivity, or another measure can be determined. In some embodiments, the sensitivities can be grouped by the number of wave paths that contribute to the determined sensitivity. If a sensitivity is produced by a majority or multiple wave paths, the sensitivity can be conditionally marked or selected as being linear for the selected moiré order that is conditionally accepted for measurement of overlap offset. In some embodiments, if multiple sensitivities are produced by various wave paths, or a considerable number of wave paths are found for two or more sensitivities, the selected moiré interference pattern component can be rejected. If it is determined that the sensitivity of the selected moiré interference pattern component is not sufficiently linear, the process continues to operation 1110. If it is determined that the sensitivity of the selected moiré interference pattern component is sufficiently linear, flow proceeds to operation 1112 .

[0151] At operation 1110, the selected moire interference pattern component can be rejected for measurement of overlap offset or another parameter of interest. The rejection can be conditional or final. Data from the analysis of the selected moire interference pattern component can be stored for evaluating the contribution of the selected moire interference pattern component to the measured moire interference pattern. In a list or other data structure that can include all or a subset of all moire interference pattern components of the measurement structure that have been or will be evaluated, the selected moire interference pattern component can be marked as rejected, including information about the reason for the rejection. After rejecting the selected moire interference pattern component, additional moire interference pattern components can be selected for evaluation at operation 1104.

[0152] At operation 1112, the intensity of the selected moiré interference pattern component is determined. The intensity of the selected moiré interference pattern component can be determined based on a complete or partial electromagnetic simulation of the measurement structure at a wavelength or wavelength range. The electromagnetic simulation can be based on a complete reconstruction of the stacked medium and other elements of the measurement structure. The electromagnetic simulation can be based on some parameters of the stack information, which can be less than all parameters of the stack information. Alternatively, the electromagnetic simulation can be based on all or substantially all available parameters of the stack information.

[0153] Subsequently, a transformation can be used to extract the frequency components of the complete or partial electromagnetic simulation. The intensity of the selected moiré interference pattern component can be determined from the electromagnetic simulation based on the absolute peak intensity or peak intensity value (which can be a pixel value). One or more constant terms can be removed from the complete or partial electromagnetic simulation. The intensity of the selected moiré interference pattern component can be determined based on peak intensity rather than contrast or threshold. The intensity of the selected moiré interference pattern component can be determined as intensity, intensity above background, intensity above a minimum value or threshold, intensity ratio, etc. The intensity of the selected moiré interference pattern component can be determined based on pixel values ​​(for example, for an image generated by or based on electromagnetic simulation). In some embodiments, the intensity of one or more moiré interference pattern components can be determined in one operation, and the one or more moiré interference pattern components can include the selected moiré interference pattern component. This can include generating a complete or partial electromagnetic simulation and extracting one or more moiré interference pattern components by frequency transformation, frequency reconstruction, etc. The intensity of one or more moiré interference pattern components can be evaluated as relative intensity, absolute intensity, intensity difference, etc. The intensities of one or more moiré interference pattern components may be compared to the intensities of moiré interference pattern components for the moiré pitch, the incident electromagnetic radiation intensity, the total electromagnetic signal intensity, etc. The intensities of one or more moiré interference pattern components may also be determined based on the resolution or estimated resolution capability of any detector used to measure the outgoing electromagnetic radiation. A full or partial electromagnetic simulation may be performed at a first operation (such as operation 1112), wherein a set of intensities of one or more moiré interference pattern components are stored. At a subsequent operation, the intensities of the selected moiré interference pattern components may be recalled from the storage for use in analyzing the selected moiré order.

[0154] At operation 1114, it is determined whether the intensity of the selected moiré interference pattern component is sufficiently strong. The intensity of the selected moiré interference pattern component can be compared to a threshold, to an intensity in one or more other moiré order intensities, including to a zero order or incident electromagnetic radiation intensity. The intensity of the selected moiré interference pattern component can be compared to a threshold in relative terms (e.g., as a percentage or ratio), or can be compared to a threshold in absolute terms (e.g., in pixel value or absolute intensity).

[0155] Optionally, for a selected moire interference pattern component having multiple overlap sensitivities (e.g., a moire interference pattern component that is conditionally accepted for overlap offset measurement based on operation 1108 or a similar operation), the moire interference pattern component intensity can be evaluated for different previously determined sensitivities (e.g., a first overlap sensitivity, a second overlap sensitivity, etc.). The relative intensity of the multiple sensitivities can be used to evaluate the linearity of the selected moire interference pattern component. For example, for a selected moire interference pattern component having a first sensitivity determined to correspond to a first intensity and a second sensitivity determined to correspond to a second intensity, if the intensities are not equal, the selected moire interference pattern component can be accepted for overlap offset measurement or measurement of another parameter of interest so that one intensity dominates in the selected moire interference pattern component. Alternatively, if the intensities are substantially similar, the selected moire interference pattern component can be rejected for overlap offset measurement.

[0156] Determining the intensity of a selected moiré interference pattern component (or multiple moiré interference pattern components) may include determining the intensity of the selected moiré interference pattern component for one or more values ​​of an overlap offset or another parameter of interest. Electromagnetic simulation may include electromagnetic simulation for multiple values ​​of an overlap offset (e.g., zero overlap offset, a small positive overlap offset, a small negative overlap offset, etc.) or another parameter of interest. Electromagnetic simulation may include determining the intensity of a selected moiré interference pattern component for several overlap offsets (or other parameters of interest), and optionally determining the response of the selected moiré interference pattern component. Electromagnetic simulation may include evaluating the frequency, intensity, relative intensity, etc. of a selected moiré interference pattern component for a wavelength or wavelength range.

[0157] If it is determined that the intensity of the selected moiré interference pattern component is strong enough, the flow proceeds to operation 1116. If it is determined that the intensity of the selected moiré interference pattern component is not strong enough, the flow proceeds to operation 1110.

[0158] At operation 1116, the selected moiré interference pattern component may be approved for use in an overlay offset measurement or another parameter of interest during a manufacturing process. A tag may be added to the approved moiré interference pattern component so that one or more approved moiré interference pattern components may be sorted and compared. Alternatively, the approved moiré interference pattern component may be stored, including along with its electronic analog component and intensity analog component. The approved moiré interference pattern component may also be modeled or simulated.

[0159] At operation 1118, it is determined whether there are other moire interference pattern components to be evaluated or to be selected for evaluation. Moire interference pattern components that have been evaluated, accepted (including conditionally), rejected (including conditionally), etc. can be compared with a set of moire interference pattern components to be evaluated. If it is determined that there are other moire interference pattern components to be evaluated, the process continues to operation 1104, in which another moire interference pattern component is selected. If it is determined that there are no other moire interference pattern components to be evaluated, the process continues to operation 1120. In some embodiments, if a sufficient number of moire interference pattern components have been received for the measurement of the overlay offset or another parameter of interest, it can be determined that there are no other moire interference pattern components to be evaluated. The number of accepted moire interference pattern components that will terminate the evaluation of other moire interference pattern components can be set by a threshold. The threshold can be the number of moire interference pattern components that can produce an overlay offset error or an order of magnitude of an overlay offset error or produce another accuracy or error threshold. The threshold may be the number of moiré interference pattern components that allows a single measurement structure (e.g., rather than a dual M and W measurement structure) to be used for measurement of overlay offset or another parameter of interest. The threshold may be the threshold number of moiré interference pattern components at a moiré pitch that are accepted and additional moiré interference pattern components for use in measurement of overlay offset or another parameter of interest. The threshold may be the number of moiré interference pattern components that are not moiré interference pattern components at a moiré pitch.

[0160] At operation 1120, it is determined whether the accepted moire interference pattern components include moire interference pattern components that are not moire interference pattern components at the moire pitch. If the accepted moire interference pattern components do not include moire interference pattern components with a period less than or greater than the moire pitch (e.g., the accepted moire interference pattern components only include moire interference pattern components at the moire pitch), then at operation 1122, the moire interference pattern components at the moire pitch may be selected for overlay offset measurement (or measurement of another parameter of interest). If the accepted moire interference pattern components include multiple moire interference pattern components, then the moire interference pattern components may be accepted at operation 1124 for overlay offset measurement. Alternatively, if no moire interference pattern components are accepted, the stacking information may be adjusted and the adjusted moire interference pattern components of the measurement structure may be evaluated. For example, the pitch of the first grating may be adjusted, the pitch of the second grating may be adjusted, the wavelength of the incident electromagnetic radiation may be adjusted, etc.

[0161] As described above, the method 1100 (and / or other methods and systems described herein) is configured to evaluate moiré interference patterns and their components for overlay shift measurement or measurement of another parameter of interest.

[0162] Fig.12 Graph depicting the intensity of moiré interference pattern components in the xy plane of a measurement structure. Graph 1200 depicts an example moiré interference pattern of extracted moiré interference pattern components at one quarter of the moiré pitch of a measurement structure including a first grating having a first pitch and a second grating having a second pitch. The intensity of the outgoing electromagnetic radiation (e.g., electromagnetic signal) is plotted as a function of grayscale according to scale 1206 in arbitrary units. The electromagnetic signal is plotted along an x-axis 1202 (in arbitrary distance units) and a y-axis 1204 (in arbitrary distance units) for a first measurement structure having periodic elements oriented perpendicular to line 1210 and a second measurement structure having periodic elements oriented perpendicular to line 1220. Graph 1200 shows the periodicity of the two measurement structures along the x-axis 1202, wherein the periodicity is sinusoidal.

[0163] Fig.13A and Fig. 13B Describes the embodiment according to the Fig.12 A graph of the moiré interference pattern of a cross section in the x-direction and the intensities of the extracted moiré interference pattern components.

[0164] Fig.13A Describe along the Fig.12 Graph 1300 depicts a cross-sectional moiré interference pattern in the x-direction and an intensity of the extracted moiré interference pattern components. Fig.12 13. The intensity of line 1210 of graph 1200 of FIG. 13. Line 1310 represents the measured intensity (in arbitrary intensity units) along y-axis 1304 as a function of distance (in arbitrary units) along x-axis 1302. Line 1310 shows periodicity at several frequencies. Line 1320 represents the intensity in arbitrary units of the extracted moiré interference pattern component having the measured intensity. Line 1320 exhibits sinusoidal periodicity at a frequency equal to four times the moiré pitch frequency.

[0165] Fig. 13B Describe along the Fig.12 Graph 1350 depicts a cross-sectional moiré interference pattern in the x-direction and an intensity of the extracted moiré interference pattern components. Fig.1213. The intensity of line 1220 of graph 1200 of FIG. 13. Line 1360 represents the measured intensity along y-axis 1354 (in arbitrary intensity units) as a function of distance along x-axis 1352 (in arbitrary units). Line 1360 shows periodicity at several frequencies. Line 1370 represents the intensity in arbitrary units of the extracted moiré interference pattern component having the measured intensity. Line 1370 exhibits sinusoidal periodicity at a frequency equal to four times the moiré pitch frequency.

[0166] In addition to a measurement structure comprising a first grating at a first pitch and a second grating at a second pitch, a measurement structure comprising three of the more pitches may produce a moiré interference pattern and may be used to measure overlay offset and other parameters of interest in the manufacturing process.

[0167] Fig.14 Interference patterns of an example measurement structure including a first pitch, a second pitch, and a third pitch are illustrated. The measurement structure is depicted as a set of three pitches (e.g., first pitches 1410A-1410C, second pitches 1420A-1420C, and third pitches 1430A-1430C) with various offsets (e.g., zero offset of the first pitch 1410A, the second pitch 1420A, and the third pitch 1430A in the x-direction 1402; a negative offset 1460 of the second pitch 1420B relative to the first pitch 1410B and the third pitch 1430B in the x-direction 1402; and a positive offset 1470 of the second pitch 1420C relative to the first pitch 1410C and the third pitch 1430C in the x-direction 1402).

[0168] For illustrative purposes, the first pitch 1410A to 1410C, the second pitch 1420A to 1420C, and the third pitch 1430A to 1430C are depicted as separate gratings having overlapping regions in the z-direction 1404. Alternatively, the first pitch 1410A to 1410C, the second pitch 1420A to 14020C, and the third pitch 1430A to 1430C may be substantially overlapping or completely overlapping. In addition, multiple pitches may be combined in one or more gratings, wherein the measurement structure may include a first grating in a first layer and a second grating in a second layer. A grating including multiple pitches may be referred to as a composite grating because it is composed of two or more pitches. For example, the first pitch 1410A to 1410C and the third pitch 1430A to 1430C may together include a first grating (e.g., a composite grating), while the second pitch 1420A to 1420C may include a second grating. Likewise, the first grating may be composed of any two pitches, while the second grating is composed of the other of the pitches. The composite grating may be a buried grating or a top grating. In some examples, both the first grating and the second grating may be composite gratings. FIG. 17A to FIG. 17B , Fig.18 , Fig.19 , Fig. 20 , Fig.21 and Fig. 22 Various arrangements of the composite grating are further discussed. In the example as depicted, the first pitch 1410A to 1410C is smaller than the second pitch 1420A to 1420C, and the second pitch 1420A to 1420C is smaller than the third pitch 1430A to 1430C. The relationship between the pitches may actually be different. In addition, each of the pitches may vary or itself be a composite pitch.

[0169] Each pitch can produce an interference pattern when combined with another pitch. In an example, the first pitch 1410A-1410C and the third pitch 1430A-1430C can correspond to a first grating in the first layer, and the second pitch 1420A-1420C can correspond to a second grating in the second layer. In this example, the first pitch 1410A-1410C and the third pitch 1430A-1430C have a substantially fixed relationship to each other, while the relationship between the first pitch 1410A-1410C and the second pitch 1420A-1420C and the relationship between the third pitch 1430A-1430C and the second pitch 1420A-1420C change as the second grating in the second layer is shifted relative to the first grating in the first layer.

[0170] A representation of a moiré interference pattern (e.g., a total interference pattern) resulting from the superposition of the three pitches is depicted as pattern 1480A for zero offset, pattern 1480B for negative offset 1460, and pattern 1480C for positive offset 1470. As depicted, patterns 1480A-1480C are compressed in the z-direction 1404 relative to first pitch 1410A-1410C, second pitch 1420A-1420C, and third pitch 1430A-1430C. The sizes and spacings of the elements of the pitches are selected for ease of illustration, and the sizes and separations may be substituted with other sizes, spacings, orientations, etc.

[0171] For zero offset of the first pitch 1410A, the second pitch 1420A, and the third pitch 1430A in the x-direction 1402, a first moire interference pattern is generated between the first pitch 1410A and the second pitch 1420A, and a second moire interference pattern is generated between the third pitch 1430A and the second pitch 1420A. The local maximum of the first interference pattern is indicated by ellipse 1440A. The local maximum of the second interference pattern is indicated by ellipse 1450A.

[0172] For a negative offset 1460 of the second pitch 1420B relative to the first pitch 1410B and the third pitch 1430B in the x-direction 1402, a first moire interference pattern is generated between the first pitch 1410B and the second pitch 1420B, and a second moire interference pattern is generated between the third pitch 1430B and the second pitch 1420B. The local maxima of the first interference pattern are indicated by ellipse 1440B. The local maxima of the first interference pattern are separated by substantially the same distance as the local maxima of the first interference pattern for zero offset; however, the location of the local maxima of ellipse 1440B is shifted relative to the local maxima of ellipse 1440A in the positive x-direction 1402, as indicated by arrow 1442. The local maxima of the second interference pattern are indicated by ellipse 1450B. The local maxima of the second interference pattern are separated by substantially the same distance as the local maxima of the second interference pattern for zero offset; however, the location of the local maxima of ellipse 1450B is shifted relative to the local maxima of ellipse 1450A in the negative x-direction 1402, as indicated by arrow 1452. The shift between the local maxima of ellipses 1440A, 1450A for the zero offset example and the local maxima of ellipses 1440B, 1450B for the negative offset 1460 example can be viewed as a phase shift in the moiré interference pattern. In some cases, there can also be a shift in the local maxima of ellipses 1440B, 1450B relative to the spacing between the local maxima of ellipses 1440A, 1450A, e.g., a change in the frequency of the moiré interference pattern. For example, a change in the focus (e.g., caused by a change in the thickness of a layer of the measurement structure) may cause a change in the pitch or the size of the pitch elements, which may be reflected in a change in the frequency of the moiré interference pattern. Likewise, local minima and other features of the moiré interference pattern may exhibit similar shifts in phase and frequency.

[0173] Negative offset 1460 can be any offset and can include offsets in more than one direction (e.g., along more than one axis). The magnitude of the shift of the local maxima of the first interference pattern and the second interference pattern can depend on the magnitude and direction of the offset between the pitches. Negative offset 1460 also causes a change in pattern 1480B relative to pattern 1480A, wherein pattern 1480B is a composite of the first interference pattern and the second interference pattern. Pattern 1480B can be decomposed into multiple frequency components (e.g., via a frequency transform such as a fast Fourier transform (FFT), via superposition, etc.) to reconstruct the first interference pattern and the second interference pattern to determine the phase shift and frequency shift of each pattern.

[0174] For a positive offset 1470 of the second pitch 1420C relative to the first pitch 1410C and the third pitch 1430C in the x-direction 1402, a first moiré interference pattern is generated between the first pitch 1410C and the second pitch 1420C, and a second moiré interference pattern is generated between the third pitch 1430C and the second pitch 1420C. The local maxima of the first interference pattern are indicated by ellipse 1440C. The local maxima of the first interference pattern are separated by substantially the same distance as the local maxima of the first interference pattern for zero offset; however, the location of the local maxima of ellipse 1440C is shifted relative to the local maxima of ellipse 1440A in the negative x-direction 1402, as indicated by arrow 1444. The local maxima of the second interference pattern are indicated by ellipse 1450C. The local maxima of the second interference pattern are separated by substantially the same distance as the local maxima of the second interference pattern for zero offset; however, the location of the local maximum of ellipse 1450C is shifted relative to the local maximum of ellipse 1450A in the positive x-direction 1402, as indicated by arrow 1454. The shift between the local maxima of ellipses 1440A, 1450A of the zero offset example and the local maxima of ellipses 1440C, 1450C of the positive offset 1470 example can be viewed as a phase shift in the moiré interference pattern. As previously discussed, there can also be a change in the frequency of the moiré interference pattern. Local minima and other features of the moiré interference pattern can exhibit shifts in phase and frequency similar to the shifts in phase and frequency exhibited by the local maxima of ellipses 1440C, 1450C described above.

[0175] The positive offset 1470 can be any offset and can include offsets in more than one direction (e.g., along more than one axis). The magnitude of the shift of the local maxima of the first interference pattern and the second interference pattern can depend on the magnitude and direction of the offset between the pitches. For example, the direction of the shift of the local maximum of the ellipse 1440B, 1450B relative to the local maximum of the ellipse 1440A, 1450A of the zero offset example is opposite to the direction of the shift of the local maximum of the ellipse 1440C, 1450C relative to the local maximum of the ellipse 1440A, 1450A of the zero offset example. For an interference pattern consisting of three pitches, the shift can also be in the same direction, can have the same magnitude, or can have different magnitudes. The magnitude and direction of the shift of the interference pattern relative to the offset of at least one pitch can also vary depending on the wavelength, for example, can depend on the wavelength of the electromagnetic radiation used to investigate the measurement structure.

[0176] Positive shift 1470 also causes a change in pattern 1480C relative to pattern 1480A, where pattern 1480C is a composite of the first and second interference patterns. Pattern 1480C can be decomposed into multiple frequency components to reconstruct the first and second interference patterns or otherwise determine phase and frequency shifts.

[0177] The phase (and optionally frequency) shift of the first interference pattern and the second interference pattern relative to the zero offset pattern can be used to measure a parameter of interest in the manufacturing process. The first interference pattern and the second interference pattern can be used to measure the parameter of interest using a single pad geometry. The relative displacement of the first interference pattern and the second interference pattern can be used to determine the center or other zero point of the moiré interference pattern. In addition, the interference pattern can be centrally symmetric, thereby eliminating the need for multiple measurement pads to determine the symmetry and / or center of the measurement structure. A single pad may be more accurate because the multi-grating measurement structure undergoes less process variation than multiple multi-grating measurement structures. A single pad can also reduce the wafer space used for the measurement structure and thereby increase the yield and profit of the electronic device. The first interference pattern and the second interference pattern can be used to calculate the overlap as previously described for multiple moiré interference pattern components (e.g., by using Equation 10).

[0178] Fig.15 An exemplary method 1500 for generating a measurement structure for measuring a parameter of interest in a manufacturing process based on multiple moiré interference pattern components is illustrated. Each of these operations is described in detail below. The operations of method 1500 presented below are intended to be illustrative. In some embodiments, method 1500 may be implemented with one or more additional operations not described and / or implemented without one or more of the operations discussed. Additionally, in Fig.15 The order in which the operations of method 1500 are illustrated and described below is not intended to be limiting. In some embodiments, one or more portions of the method 1500 may be implemented in one or more processing devices (e.g., one or more processors) (e.g., by simulation, modeling, etc.). The one or more processing devices may include one or more devices that perform some or all of the operations of method 1500 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured via hardware, firmware, and / or software that are specifically designed to perform, for example, one or more of the operations of method 1500.

[0179] At operation 1502, stack information is obtained. The stack information may be obtained according to the method previously described with reference to operation 1102.

[0180] At operation 1504, a first grating having a first pitch and a second grating having a second pitch are selected for evaluation. The first grating may be a composite grating, wherein the first pitch includes a third pitch and a fourth pitch. The second grating may be a composite grating, wherein the second pitch includes a fifth pitch and a sixth pitch. The first grating may be a buried grating and the second grating may be a top grating. The second grating may be a buried grating and the first grating may be a top grating. The first pitch and the second pitch may be selected based on stack information (including thickness, absorbance, etc.). The first pitch and the second pitch may be selected based on design constraints from the stack information. The first pitch and the second pitch may be selected based on electromagnetic requirements (such as the wavelength range of the electromagnetic source and the detector). The first pitch and the second pitch may be selected based on the critical dimensions of one or more features of the stack information. In some cases, additional gratings having one or more additional pitches may also be selected.

[0181] At operation 1506, a first moiré interference pattern component is selected for evaluation. The first moiré interference pattern component may be a moiré interference pattern component for a first pitch of the first grating and a second pitch of the second grating. Additionally, for one or more composite gratings, the first moiré interference pattern component may be a moiré interference pattern component for a pitch constituting the first pitch of the first grating and a pitch constituting the second pitch of the second grating. For a specific example, the first moiré interference pattern component may be a moiré interference pattern component for a third pitch, wherein the first grating is a composite grating having a third pitch and a fourth pitch and a second pitch of the second grating, wherein the second grating is not a composite grating. The first moiré interference pattern component may be further selected as previously described with respect to operation 1104.

[0182] At operation 1508, it is determined whether the selected first moire interference pattern component is acceptable for measurement of the parameter of interest. The determination of whether the selected moire interference pattern component is acceptable for measurement of the parameter of interest may be performed as previously described with respect to operations 1106 to 1116 or any other suitable method. The first moire interference pattern may be evaluated based on linearity, wavelength range, intensity, etc. If the selected first moire interference pattern is acceptable for measurement of the parameter of interest, the process proceeds to operation 1520. If the selected first moire interference pattern is unacceptable for measurement of the parameter of interest, the process proceeds to operation 1510.

[0183] At operation 1510, it is determined whether another first moire interference pattern can be selected for a first grating having a first pitch and a second grating having a second pitch. For example, a component of the first moire interference pattern can be selected, wherein the component can be a component of the first moire interference pattern at another frequency. In a specific example, if the moire pitch of the first moire interference pattern is X, a component of the first moire interference pattern at a pitch of X×m / n can be selected for evaluation, wherein m and n are integers. If another first moire interference pattern can be selected or a component of the first moire interference pattern can be selected, the process proceeds to operation 1512. If another first moire interference pattern or a component of the first moire interference pattern cannot be selected, the process proceeds to operation 1514.

[0184] At operation 1512 , another first moiré interference pattern or component of the first moiré interference pattern is selected for evaluation.The selected first moiré interference pattern or component of the first moiré interference pattern is then evaluated at operation 1508 .

[0185] At operation 1514, the first pitch, the second pitch, or both are adjusted. Adjusting the first pitch may include adjusting the third pitch, the fourth pitch, or both, wherein the first pitch is a composite pitch consisting of the third pitch and the fourth pitch. Similarly, adjusting the second pitch may include adjusting the fifth pitch, the sixth pitch, or both, wherein the second pitch is a composite pitch consisting of the fifth pitch and the sixth pitch. Adjusting at least one of the pitches may include adding an additional pitch. For example, adjusting the first pitch may include adding the third pitch to the first pitch so that the first grating becomes a composite pitch. At least one of the pitches may be adjusted based on the stacking information. The first pitch may be adjusted, the second pitch may be adjusted, or both pitches may be adjusted. At operation 1506, a first moiré interference pattern component for at least one adjusted pitch is selected for evaluation.

[0186] At operation 1520, a second moiré interference pattern is selected for evaluation. The second moiré interference pattern may be different from the first moiré interference pattern. The second moiré interference pattern component may be a moiré interference pattern component for a first pitch of the first grating and a second pitch of the second grating. In addition, for one or more composite gratings, the second moiré interference pattern component may be a moiré interference pattern component for a pitch constituting the first pitch of the first grating and a pitch constituting the second pitch of the second grating. For a specific example, the second moiré interference pattern component may be a moiré interference pattern component for a fourth pitch, wherein the first grating is a composite grating having a third pitch and a fourth pitch and a second pitch of the second grating, wherein the second grating is not a composite grating. The second moiré interference pattern component may be further selected as previously described with respect to operations 1104, 1506.

[0187] At operation 1522, it is determined whether the selected second moiré interference pattern component is acceptable for measurement of the parameter of interest. The determination of whether the selected moiré interference pattern component is acceptable for measurement of the parameter of interest may be performed as previously described with respect to operations 1106 to 1116 and 1508, or any other suitable method. The second moiré interference pattern may be evaluated based on linearity, wavelength range, intensity, etc. If the selected second moiré interference pattern is acceptable for measurement of the parameter of interest, the process proceeds to operation 1530. If the selected first moiré interference pattern is not acceptable for measurement of the parameter of interest, the process proceeds to operation 1524.

[0188] At operation 1524, it is determined whether another second moiré interference pattern can be selected for the first grating having the first pitch and the second grating having the second pitch. For example, a component of the second first moiré interference pattern can be selected, wherein the component can be a component of the second moiré interference pattern at another frequency. In a specific example, if the moiré pitch of the first moiré interference pattern is X, a component of the second moiré interference pattern at a pitch of X×n can be selected for evaluation. If another second moiré interference pattern can be selected or a component of the second moiré interference pattern can be selected, the process proceeds to operation 1526. If another second moiré interference pattern cannot be selected or a component of the second moiré interference pattern cannot be selected, the process proceeds to operation 1514.

[0189] At operation 1526, another second moiré interference pattern or component of a second moiré interference pattern is selected for evaluation.The selected second moiré interference pattern or component of a second moiré interference pattern is then evaluated at operation 1522.

[0190] At operation 1530, a measurement structure is generated based on the first moiré interference pattern and the second moiré interference pattern associated with the first pitch of the first grating and the second pitch of the second grating. Additional evaluations may be performed. The measurement structure may be generated on a fabricated device. Alternatively, one or more lithography steps, etching steps, deposition steps, etc. may be performed to generate the measurement structure. One or more lithography masks may be designed, generated, or designed and generated based on the measurement structure.

[0191] As described above, the method 1500 (and / or other methods and systems described herein) is configured to generate a measurement structure for a parameter of interest in a manufacturing process based on a plurality of moiré interference pattern components.

[0192] Fig.16 An exemplary method 1600 for determining a parameter of interest in a manufacturing process based on multiple moiré interference pattern components is illustrated. Each of these operations is described in detail below. The operations of method 1600 presented below are intended to be illustrative. In some embodiments, the method 1600 may be implemented with one or more additional operations not described and / or may be implemented without employing one or more of the operations discussed. Additionally, in Fig.16 The order in which the operations of method 1600 are illustrated and described below is not intended to be limiting. In some embodiments, one or more portions of the method 1600 may be implemented in one or more processing devices (e.g., one or more processors) (e.g., by simulation, modeling, etc.). The one or more processing devices may include one or more devices that perform some or all of the operations of method 1600 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured via hardware, firmware, and / or software that are specifically designed to perform, for example, one or more of the operations of method 1600.

[0193] At operation 1602, an interference pattern of a measurement structure is obtained. The interference pattern may be obtained by a detector. The interference pattern may be a moiré interference pattern or may be composed of one or more moiré interference patterns. The interference pattern may be generated by scattered radiation from the measurement structure. The interference pattern may be obtained from a data storage device. The interference pattern may be a synthetic interference pattern. The interference pattern may undergo image processing, including one or more frequency conversions, sharpening, filtering, etc. The interference pattern may be obtained for a range of wavelengths. The interference pattern may be obtained as a static image (e.g., a photograph or simulation of a photograph) or as a time series of images (e.g., a video or simulation of a video). The interference pattern may include one or more types of intensity information, phase information, etc.

[0194] At operation 1604, frequency components of the interference pattern are identified. The frequency components of the interference pattern may be determined by frequency transforms (such as FFT), by superposition, or by any other suitable method of frequency determination. The frequency components of the interference pattern may be identified in both the frequency domain and the spatial domain, where the interference pattern may be reconstructed or otherwise aligned with its frequency components. One or more components of the interference pattern are selected. The components of the interference pattern may themselves be moiré interference patterns or components of moiré interference patterns. The components may have a frequency and a phase.

[0195] At operation 1606, a phase shift is determined for a first component of the interference pattern. The phase shift may be determined based on a model of the measurement structure for a particular value of a parameter of interest (e.g., for a zero offset value). The phase shift may be determined based on an arbitrary zero point or center point of the interference pattern. The phase shift may be determined based on a phase, frequency, amplitude, or a combination thereof of the first component of the interference pattern. The phase shift of the first component may be determined as both a direction and a magnitude.

[0196] At operation 1608, a phase shift is determined for a second component of the interference pattern. The phase shift may be determined based on a model of the measurement structure for a particular value of a parameter of interest (e.g., for a zero offset value). The phase shift may be determined based on an arbitrary zero point or center point of the interference pattern. The phase shift may be determined based on a phase, frequency, amplitude, or a combination thereof of the second component of the interference pattern. The phase shift of the second component may be determined as both a direction and a magnitude. The phase shift of the second component may have the same or different direction and magnitude than the phase shift of the first component.

[0197] Alternatively or in addition, operation 1610 may be performed. At operation 1610, a relative phase shift between a first component of the interference pattern and a second component of the interference pattern is determined. The relative phase shift may be determined based on a model of the measurement structure for a particular value of a parameter of interest (e.g., for a zero offset value). The relative phase shift may be determined based on an arbitrary zero point or center point of the interference pattern. The phase shift may be determined based on a phase, frequency, amplitude, or a combination thereof of the first component of the interference pattern and the second component of the interference pattern. The relative phase shift may be determined as both a direction and a magnitude. The relative phase shift may have a zero or non-zero direction and magnitude. The relative phase shift may include information about the difference between the phase shift of the first component of the interference pattern and the phase shift of the second component of the interference pattern.

[0198] At operation 1612, a parameter of interest is determined based on a difference between a phase shift of a first component of the interference pattern and a phase shift of a second component of the interference pattern. The parameter of interest may be determined by comparing the interference pattern to one or more modeled interference patterns that vary with respect to the parameter of interest. The parameter of interest may be determined analytically, such as by using an equation as previously described.

[0199] As described above, the method 1600 (and / or other methods and systems described herein) is configured to determine a measurement of a parameter of interest in a manufacturing process based on a plurality of moiré interference pattern components.

[0200] Fig.17A An example grating including staggered gratings is illustrated. An example grating, which may include a buried grating or a top grating (e.g., a first grating or a second grating), is composed of two staggered gratings - a first staggered grating 1720 represented by a black rectangle and a second staggered grating 1730 represented by a gray rectangle. The first staggered grating 1720 and the second staggered grating 1730 are represented by different shading for illustration purposes only and may include the same or different materials. The first staggered grating 1720 and the second staggered grating 1730 are also depicted as including elements having the same width, but the elements of the first staggered grating 1720 and the second staggered grating 1730 may have different sizes. The first staggered grating 1720 and the second staggered grating 1730 are shown as offset in the z-direction 1704 (along the long axis of the grating elements) and dispersed with a pitch in the x-direction 1702. The first staggered grating 1720 has grating elements that appear at a first staggered pitch (P1A) 1722. The second interleaved grating 1730 has grating elements that occur at a second interleaving pitch (P1B) 1732. The first interleaving pitch 1722 and the second interleaving pitch 1732 may be different. For some x values ​​in the x direction 1702, the elements of the first interleaved grating 1720 and the second interleaved grating 1730 are superimposed. In some cases, depending on the resolution of the detector and the CD of the gratings, the grating elements of the first interleaved grating 1720 and the second interleaved grating 1730 may be physically superimposed or alternatively a single element. The representative schematic 1710 depicts elements of an example grating including the first interleaved grating 1720 and the second interleaved grating 1730. The example gratings may be combined with additional gratings in a measurement configuration to produce a moiré interference pattern.

[0201] Fig. 17BAn example grating including non-overlapping interlaced gratings is illustrated. An example grating, which may include a buried grating or a top grating (e.g., a first grating or a second grating), is composed of two interlaced gratings - a first interlaced grating 1770 represented by black lines and a second interlaced grating 1780 represented by gray lines. The first interlaced grating 1770 and the second interlaced grating 1780 are also represented by different shading for illustration purposes only and may include the same or different materials. The first interlaced grating 1770 and the second interlaced grating 1780 are also depicted as including elements having the same width, but may alternatively include elements having different sizes. The first interlaced grating 1770 and the second interlaced grating 1780 are shown as offset in the z-direction 1754 (along the long axis of the grating elements) and dispersed with a pitch in the x-direction 1752. The first interlaced grating 1770 has grating elements that appear at a first interlaced pitch (P1A) 1772. The second interleaved grating 1780 has grating elements that occur at a second interleaving pitch (P1B) 1782. The first interleaving pitch 1772 and the second interleaving pitch 1782 may be different. For some x values ​​in the x direction 1702, the elements of the first interleaved grating 1770 and the second interleaved grating 1780 are non-overlapping. In some cases, for a sufficiently high resolution or CD of the elements of the gratings, the elements of the first interleaved grating 1770 and the second interleaved grating 1780 are non-overlapping or substantially non-overlapping. Representative schematic 1760 depicts elements of an example grating including the first interleaved grating 1770 and the second interleaved grating 1780. The example gratings may be combined with additional gratings in a measurement configuration to produce a moiré interference pattern.

[0202] Fig.18The illustration includes an example grating of a vertically segmented staggered grating. The example grating, which may include a buried grating or a top grating (e.g., a first grating or a second grating), is composed of two staggered gratings - a first segmented grating 1820 represented by a black rectangle and a second segmented grating 1830 represented by a gray rectangle. The first segmented grating 1820 and the second segmented grating 1830 are represented by different shading for illustration purposes only and may include the same or different materials. The first segmented grating 1820 and the second segmented grating 1830 are also depicted as including elements having the same width and height, but the elements of the first segmented grating 1820 and the second segmented grating 1830 may have different sizes. The first segmented grating 1820 and the second segmented grating 1830 are shown as segmented into rectangular elements in the z-direction 1804 (along the segmentation axis of the grating elements) and dispersed with a pitch in the x-direction 1802. The first segmented grating 1820 has grating elements occurring at a first segment pitch (P1A) 1822. The second segmented grating 1830 has grating elements occurring at a second segment pitch (P1B) 1832. The first segment pitch 1822 and the second segment pitch 1832 may be different. The separation between the elements of the first segmented grating 1820 and the elements of the second segmented grating 1830 in the z-direction 1804 is depicted as being equal, but may alternatively be asymmetric or otherwise non-uniform. The elements of the first segmented grating 1820 and the second segmented grating 1830 are shown as being separated in the z-direction 1804, but may alternatively be at least partially overlapped in the z-direction 1804.

[0203] Elements of the first segmented grating 1820 and the second segmented grating 1830 are depicted as being different for x values ​​in the x-direction 1802. In some cases, depending on the resolution of the detector and the CD of the gratings, the grating elements of the first segmented grating 1820 and the second segmented grating 1830 may be physically superimposed in the x-direction 1802, or alternatively, may be a single element. A sinusoid 1824 representing the frequency and period of the first segmented grating 1820 is depicted. A sinusoid 1834 representing the frequency and period of the second segmented grating 1830 is depicted. The frequency and period of the gratings may be represented by the superposition or sum of the sinusoid 1824 at the first segmented grating 1820 and the sinusoid 1834 at the second segmented grating 1830. The example gratings may be combined with additional gratings in a measurement configuration to produce a moiré interference pattern.

[0204] Fig.19The illustration includes an example measurement structure with a grating having a varying pitch. The measurement structure includes a varying grating 1924 represented by a gray rectangle and a constant grating 1930 represented by a black rectangle. The varying grating 1924, which may include a buried grating or a top grating (e.g., a first grating or a second grating), is composed of a grating that varies at two frequencies or within two periods - a first pitch (P1A) 1622 represented by a rectangle 1920 outlined by a dotted line and an offset pitch 1926 represented by an offset between the rectangle 1920 and the elements of the varying grating 1924. That is, the placement of the elements of the varying grating 1924 is determined by the first pitch 1922 and the offset pitch 1926. The offset pitch 1926 (e.g., the second pitch) may have a smaller amplitude and a slower frequency than the first pitch 1922. The constant grating 1930 is depicted as a top grating, but may be a buried grating or a top grating. The constant grating 1930 is depicted as having a constant pitch 1932. In some embodiments, the constant grating 1930 alternatively has a variable pitch (e.g., may be a varying grating, may be an interlaced grating, etc.). The varying grating and the constant grating 1930 of the rectangle 1920 are represented by different shading for illustration purposes only and may include the same or different materials. The varying grating and the constant grating 1930 of the rectangle 1920 are also depicted as including elements having the same width, but the elements of the varying grating and the constant grating 1930 of the rectangle 1920 may be of different sizes. The varying grating and the constant grating 1930 of the rectangle 1920 are shown as offset in the z-direction 1904 (along the long axis of the grating elements) and dispersed with the pitch in the x-direction 1902. The offset is shown for illustration purposes, and alternatively, the grating elements may be aligned in the z-direction 1904. The first pitch 1922 may be different from the constant pitch 1932. Representative schematic 1910 depicts elements of an example measurement structure including a varying grating of rectangles 1920 and a constant grating 1930. The combination of gratings in the measurement structure produces a moiré interference pattern that can be used to determine overlay offset or other parameters of interest in the manufacturing process.

[0205] Fig. 20An example measurement structure is shown that includes a grating with interspersed regions of different pitches. The interspersed regions may include adjacent regions with different pitches. The measurement structure includes a dual pitch grating represented by a gray rectangle of a first grating 2020 and a black rectangle of a second grating 2030 and a constant grating 2040 represented by a hash rectangle. The dual pitch grating, which may include a buried grating or a top grating (e.g., a first grating or a second grating), is composed of segments or regions of a first grating 2020 at a first pitch (P1A) 2022 and segments or regions of a region of a second grating 2030 at a second pitch (P1B) 2032. The first pitch 2022 may be different from the second pitch 2032. The first pitch 2022 may be a pitch that is larger or smaller than the second pitch 2032. Regions of the first grating 2020 and regions of the second grating 2030 are interspersed to include a dual pitch grating. The regions of the first grating 2020 and the regions of the second grating 2030 are depicted as being different, but alternatively, the regions of the first grating 2020 and the second grating 2030 may be at least partially staggered or otherwise overlapped. The first grating 2020 and the second grating 2030 are depicted as being composed of elements of substantially the same size. Alternatively, the elements of the first grating 2020 and the second grating 2030 may be of different sizes or different dimensions. The first grating 2020 and the second grating 2030 are depicted as being aligned in the z-direction 2004, but alternatively, the first grating 2020 and the second grating 2030 may be offset in the z-direction 2004, and the first grating 2020 and the second grating 2030 are depicted as being dispersed in the x-direction 2002. Additionally, the dual pitch grating is depicted as including interspersed regions of two different pitches (e.g., first grating 2020 and second grating 2030), but alternatively, the dual pitch grating may include multiple different pitches (e.g., interspersed regions of three or more pitches). The dual pitch grating is depicted as a bottom grating, but may be a top grating or a bottom grating. The first grating 2020 and the second grating 2030 are represented by different shading for illustration purposes only, and may include the same or different materials.

[0206] The constant grating 2040 is depicted as having a constant pitch 2042. In some embodiments, the constant grating 2040 alternatively has a variable pitch (e.g., may be a varying grating, may be an interlaced grating, etc.). The dual pitch grating and the constant grating 2040 are represented by different shading for illustration purposes only, and may include the same or different materials. The dual pitch grating and the constant grating 2040 are also depicted as including elements having the same width, but the elements of the dual pitch grating and the constant grating 2040 may be of different sizes. The dual pitch grating and the constant grating 2040 are shown offset in the z direction 2004 (along the long axis of the grating elements) and dispersed with the pitch in the x direction 2002. The offset is shown for illustration purposes, and alternatively, the grating elements may be aligned in the z direction 2004. The first pitch 2022, the second pitch 2032, and the constant pitch 2042 may be different. The constant pitch 2042 may include a pitch sized between the first pitch 2022 and the second pitch 2032. Representative schematic diagram 2010 depicts elements of an example measurement structure including a dual pitch grating and a constant grating 2040. The combination of gratings in the measurement structure produces a moiré interference pattern that can be used to determine overlay offset or other parameters of interest in a manufacturing process.

[0207] Fig.21An example measurement structure including gratings with resolvable pitches is illustrated. The measurement structure includes a first grating 2120 represented by a grey rectangle and a second grating 2130 represented by a black rectangle. The first grating 2120, which may include a buried grating or a top grating, includes periodic elements at a first pitch (P1) 2122. The second grating 2130, which may include a buried grating or a top grating (e.g., a grating in an alternative position from the first grating 2120), is composed of periodic elements at a second pitch (P2) 2132. The first pitch 2122 and the second pitch 2132 may be different. The first pitch 2122 may be a pitch that is larger or smaller than the second pitch 2132. The elements of the grating may be smaller than the spaces between the elements (as depicted), or larger than the spaces, or have substantially the same size. The first grating 2120 and the second grating 2130 are depicted as being composed of elements of substantially the same size. Alternatively, the elements of the first grating 2120 and the second grating 2130 may have different sizes or different dimensions. The first grating 2120 and the second grating 2130 are depicted as being offset in the z-direction 2104, but alternatively, the first grating 2120 and the second grating 2130 may be aligned in the z-direction 2104. The first grating 2120 and the second grating 2130 are depicted as being symmetrical about a center point in the x-direction 2102. The first grating 2120 and the second grating 2130 may be asymmetrical and may or may not include elements that are superimposed in the z-direction 2104. The first grating 2120 and the second grating 2130 are depicted as having a constant pitch, but alternatively, the first grating 2120 and the second grating 2130 may have a variable pitch or multiple pitches as previously described with reference to other figures. The first grating 2120 and the second grating 2130 are represented by different shading for illustration purposes only, and may include the same or different materials.

[0208] The first grating 2120 and the second grating 2130 can have a size that allows the resolution of individual components of an interference pattern, which can be a moiré interference pattern or can be a semi-interference pattern or other interference pattern. In some embodiments, the first pitch 2122 of the first grating 2120 and the second pitch 2132 of the second grating 2130 can be sized so that individual elements of the measurement structure can be resolved. In some embodiments, such a measurement structure can be used for both alignment (e.g., coarse alignment, fine alignment, etc.) and for measurement of overlay offset or another parameter of interest in the manufacturing process. Representative schematic 2110 depicts elements of an example measurement structure including the first grating 2120 and the second grating 2130. The combination of gratings in the measurement structure produces an interference pattern, which may or may not constitute a moiré interference pattern, which can be used to determine overlay offset or other parameters of interest in the manufacturing process.

[0209] Fig. 22 An example measurement structure for measuring a parameter of interest in a manufacturing process based on components of a moiré interference pattern is illustrated. The measurement structure may include a first grating 2220 and a second grating 2230 (e.g., a buried grating and a top grating, either grating may be located in either position). The first grating 2220 is depicted as a constant pitch grating having a first pitch (P1) 2222. Alternatively, the first grating 2220 may be a variable pitch grating, as previously described. The second grating 2230 is composed of two interleaved gratings or two pitches—a first interleaved grating having a first interleaved pitch (P2A) 2232 and a second interleaved grating having a second interleaved pitch (P2B) 2234. The elements of the second grating 2230 are the first interleaved pitch 2232 and the second interleaved pitch 2234, which are depicted as being superimposed or merged—e.g., superimposed elements at different pitches may become a single element by superimposing. Alternatively, the elements of the first interleaving pitch 2232 and the second interleaving pitch 2234 may be distinct, which may occur for some range of electromagnetic signal resolution and CD, as previously described with reference to Fig. 17B As described. The first grating 2220 and the second grating 2230 are represented by different shading for illustration purposes only and may include the same or different materials. The first grating 2220 and the second grating 2230 are also depicted as including elements having different widths, but the elements of the first grating 2220 and the second grating 2230 may have substantially the same size. The elements appearing at the first staggered pitch 2232 and the elements appearing at the second staggered pitch 2234 are depicted as having substantially the same size, but may alternatively be elements of different or variable sizes. The superposition of elements appearing at the first staggered pitch 2232 and the second staggered pitch 2234 may contribute to the variation in element size. The first grating 2220 and the second grating 2230 are shown as offset in the z-direction 2204 (along the long axis of the grating elements) and dispersed with the pitch in the x-direction 2202, but alternatively, the first grating 2220 and the second grating 2230 may be aligned in the z-direction. Representative schematic 2210 depicts elements of an example measurement structure including first grating 2220 and second grating 2230 that can produce a moiré interference pattern. The combination of gratings in the measurement structure produces a moiré interference pattern that can be used to determine overlay offset or other parameters of interest in a manufacturing process.

[0210] Fig.23A and Fig. 23B Diagram Fig. 22 Moiré interference pattern of the measured structure. Fig.23A Display for the positive diffraction branch plot Fig. 222300 is a graphical representation of an example moiré interference pattern of a measurement structure of FIG. The intensity of the moiré interference pattern is depicted as varying as a function of grayscale according to scale bar 2306 . Fig. 23B Display depiction for negative diffraction branches Fig. 22 2350 is a diagram of an example moiré interference pattern of a measurement structure of FIG. The intensity of the moiré interference pattern is depicted as varying as a function of grayscale according to scale bar 2356. The intensity of the moiré interference is depicted as varying in the x-direction 2302 and the z-direction 2304 of the measurement structure. The scales of the diagrams 2300 and 2350 may be the same as those of FIG. Fig. 22 The scales of are different. Based on the moiré interference patterns of diagrams 2300 and 2350, a measure of the overlap offset or another parameter of interest can be determined. The moiré interference patterns of diagrams 2300 and 2350 show a plurality of moiré interference pattern components corresponding to the pitch of the measurement structure, and based on the moiré interference pattern components, the relationship between the first grating 2220 and the second grating 2230 can be determined.

[0211] The example measurement structures provided above are presented as one-dimensional measurement structures. That is, although the measurement structure itself may have dimensions or be projected into all three dimensions (e.g., along Figures 5 to 8 , Fig.10 , Figure 12 to Figure 14 , FIG. 17A to FIG. 17B and Figure 18 to Figure 2 3), but each of the previously described structures is directed in a direction parallel to the long axis of the grating element (i.e., in the direction of Figures 5 to 8 , Fig.10 , Figure 12 to Figure 14 , FIG. 17A to FIG. 17B and Figure 18 to Figure 2 3) is substantially constant. The choice of axis orientation is at least to some extent arbitrary, wherein, for consistency across the figures and description, the x-direction has been selected to correspond to the short axis of the grating element, the y-direction has been selected to correspond to the axis substantially perpendicular to at least one of the planes including the grating element, and the z-direction has been selected to correspond to the axis substantially parallel to the long axis of the grating element of each of the depicted measurement structures. Alternatively, other axis orientations may be selected or depicted. Since the grating elements of a one-dimensional measurement structure have substantially less variation along the z-direction, they are less useful for measuring a parameter of interest that varies in the z-direction than for measuring a parameter of interest that varies in the x-direction. However, measurement structures that vary in two dimensions parallel to the plane of the grating element (e.g., in both the x-direction and the z-direction) may be generated. It can be inferred from this that the embodiments discussed above may be applied to the combination of two or more one-dimensional measurement structures, the generation of a two-dimensional measurement structure, and the measurement of a parameter of interest based on the interference pattern of a two-dimensional measurement structure.

[0212] Fig.24 An example two-dimensional measurement structure is shown. The measurement structure may include a first two-dimensional grating 2420 and a second two-dimensional grating 2430 (e.g., a buried grating and a top grating, either grating may be located in either position). The first two-dimensional grating 2420 and the second two-dimensional grating 2430 are composed of grating elements that vary in both the x-direction 2402 and the z-direction 2404 (e.g., elements arranged in a two-dimensional plane in the x-direction 2402 and the z-direction 2404).

[0213] The first two-dimensional grating 2420 is depicted as a constant pitch grating having a first pitch (P1Z) 2422 in the z-direction 2404 and a second pitch (P1X) 2424 in the x-direction 2402. The first pitch 2422 and the second pitch 2424 are depicted as being substantially similar, but may in fact be different (including multiples or least common multiples of each other). Either or both of the first pitch 2422 and the second pitch 2424 of the first two-dimensional grating 2420 may also or alternatively be a variable pitch, including a pitch that varies in any of the above-described manners. The second two-dimensional grating 2430 is depicted as a constant pitch grating having a first pitch (P2Z) 2432 in the z-direction 2404 and a second pitch (P1X) 2434 in the x-direction 2402. The first pitch 2432 and the second pitch 2434 are depicted as being substantially similar, but may be different from one another and additionally may be variable pitches as previously described with reference to the first two-dimensional grating 2420 .

[0214] The first two-dimensional grating 2420 and the second two-dimensional grating 2430 are represented by different shading for illustration purposes only, and may include the same or different materials. The first two-dimensional grating 2420 and the second two-dimensional grating 2430 are also depicted as including elements having substantially the same size in both the x-direction 2402 and the z-direction 2404, but alternatively, the elements of the first two-dimensional grating 2420 and the second two-dimensional grating 2430 may have different sizes in one or more dimensions or even have variable sizes in one or more dimensions. The first two-dimensional grating 2420 and the second two-dimensional grating 2430 are shown as symmetrical about a center point (indicated by a dashed circle 2440) consisting of grating elements of the first two-dimensional grating 2420 and the second two-dimensional grating 2430, which are substantially superimposed in the y-direction perpendicular to the xz plane. The first two-dimensional grating 2420 and the second two-dimensional grating 2430 may actually be asymmetrical, of different symmetry, symmetrical about different points or about a non-center point, etc. The grating elements of the first two-dimensional grating 2420 and the second two-dimensional grating 2430 may or may not overlap.

[0215] The first two-dimensional grating 2420 and the second two-dimensional grating 2430 can produce a two-dimensional interference pattern, such as at a detector, when illuminated by incident radiation. The interference pattern can be or include a moiré interference pattern. The interference pattern can vary in a direction corresponding to the x-direction 2402 and in a direction corresponding to the z-direction 2404. The variation in the interference pattern can be used to determine an overlay offset or other parameters of interest in a manufacturing process for the x-direction 2402, the z-direction 2404, or both the x-direction 2402 and the z-direction 2404.

[0216] Fig.25 Diagram Fig.24 Moiré interference pattern of the measured structure. Fig.25 The figure shows the depiction Fig.24 2500 is a diagram of an example moiré interference pattern of a measurement structure of FIG. The intensity of the moiré interference pattern is depicted as varying according to grayscale according to scale bar 2510. The intensity of the moiré interference is depicted as varying according to an x-direction along an x-axis 2502 and a z-direction along a z-axis 2504. The scale of diagram 2500 may not be the same as Fig. 22 The intensity of the moiré interference pattern varies along both the x-axis 2502 and the z-axis 2504. The moiré interference pattern may be composed of one or more moiré interference pattern components occurring along the x-axis 2502 and one or more moiré interference pattern components occurring along the z-axis 2504. The moiré interference pattern operating along each of the axes may produce additional interference or additive (or subtractive) intensity effects.

[0217] Based on the moiré interference pattern of diagram 2500, a measure of overlap offset or another parameter of interest can be determined for each dimension. The moiré interference pattern of diagram 2500 shows a plurality of moiré interference pattern components corresponding to the pitch of the measurement structure in each direction, and based on the moiré interference pattern components, the relationship between the first two-dimensional grating 2420 and the second two-dimensional grating 2430 can be determined. A two-dimensional Fourier or other transform can be used to identify the components of the interference pattern along each dimension. Based on the identified components, the moiré interference pattern of each dimension can be deconvolved. Alternatively, the moiré interference pattern components can be extracted separately for each dimension or the components can be manipulated together in a two-dimensional frequency space.

[0218] Fig.26 Diagram Fig.25 Fourier transform of the moiré interference pattern. Fig.26 Display drawing Fig.252600 of a two-dimensional Fourier transform of an example moiré interference pattern. The x-axis 2602 corresponds to the values ​​of the Fourier transform of the moiré interference pattern in the x-direction frequency domain, while the z-axis 2604 corresponds to the values ​​of the Fourier transform of the moiré interference pattern in the z-direction frequency domain. The various components of the interference pattern are apparent in the Fourier transform, where they appear as squares 2620 (which roughly correspond to pixels or groups of pixels). The color of the squares corresponds to the order or component pitch (e.g., the value of m / n for the moiré interference pattern component X*m / n for moiré pitch X). The scale 2610 indicates the value of the order (e.g., m / n) to which the component corresponds, where the darker ones in the squares 2620 correspond to higher values ​​of m / n and the lighter ones in the squares correspond to lower values ​​of the order (e.g., m / n). The spectrum of the illustration 2600 is based on an ideal geometry that produces a clear, approximately single-pixel response in the Fourier transform. In the acquired image, geometrical imperfections may result in broadening of the Fourier transformed peaks and leakage of other signals into the image, which may change the shape of the spectrum in frequency space. Even for non-ideal examples, the location and relative position of the peaks can still be used to determine the measurement results of the parameter of interest (e.g., by using the centroid of the peaks, peak fitting, etc.).

[0219] The two-dimensional Fourier transform can separate the components of the interference pattern into components generated by interference along each direction, as seen in the distribution of squares 2620. The components of squares 2620 placed along the vertical line corresponding to the x value of zero are components due to interference in the z direction only. The components of squares 2620 placed along the horizontal line corresponding to the z value of zero correspond to components due to interference in the x direction only. Components having non-zero values ​​along both the x-axis 2602 and the z-axis 2604 correspond to components having contributions from both the x-direction and the z-direction interference. In order to determine the parameters of interest in the manufacturing process, two moiré components can be selected from the two-dimensional interference pattern. In illustration 2600, for example, the components surrounded by dashed circles 2630 and dashed circles 2632 can be compared relative to each other to determine the parameters of interest 2660 in the y direction, such as overlap. Similarly, the components surrounded by dashed circles 2640 and dashed circles 2642 can be compared relative to each other to determine the parameters of interest 2650 in the x direction, such as overlap. Prior to the comparison, the components may optionally be extracted from the interference pattern.

[0220] Fig. 27is a diagram of one or more example computer systems CS that can be used in the operations described herein. The computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or multiple processors) connected to the bus BS for processing information. The computer system CS also includes a main memory MM, such as a random access memory (RAM) or other dynamic storage device, connected to the bus BS for storing information and instructions to be executed by the processor PRO. The main memory MM can also be used to store temporary variables or other intermediate information during the execution of instructions by the processor PRO. The computer system CS also includes a read-only memory (ROM) ROM or other static storage device connected to the bus BS for storing static information and instructions for the processor PRO. A storage device SD such as a magnetic disk or optical disk is provided, and the storage device is connected to the bus BS for storing information and instructions.

[0221] The computer system CS can be connected by a bus BS to a display DS for displaying information to a computer user, such as a cathode ray tube (CRT), or a flat panel or touch panel display. An input device ID including alphanumeric and other keys is connected to the bus BS for communicating information and command selections to the processor PRO. Another type of user input device is a cursor control CC, such as a mouse, trackball or cursor direction keys, for communicating direction information and command selections to the processor PRO and for controlling cursor movement on the display DS. This input device typically has two degrees of freedom on two axes, a first axis (e.g., x) and a second axis (e.g., y), allowing the device to specify a position in a plane. A touch panel (screen) display can also be used as an input device.

[0222] In some embodiments, the computer system CS can be executed in response to one or more sequences of one or more instructions included in the processor PRO executing the main memory MM to perform part of one or more methods described herein. These instructions can be read into the main memory MM from another computer-readable medium such as a storage device SD. The execution of the instruction sequence included in the main memory MM causes the processor PRO to perform the process steps (operations) described herein. One or more processors in a multi-processing arrangement can also be used to execute the instruction sequence included in the main memory MM. In some embodiments, a hard-wired circuit system can be used instead of or in combination with software instructions. Therefore, the description of the present disclosure is not limited to any specific combination of hardware circuits and software.

[0223] As used herein, the term "computer-readable medium" and / or "machine-readable medium" refers to any medium that participates in providing instructions to the processor PRO for execution. Such a medium can be in many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical disks or disks, such as storage devices SD. Volatile media include volatile memories, such as main memory MM. Transmission media include coaxial cables, copper wires, and optical fibers, including wires containing bus BS. Transmission media can also take the form of sound waves or light waves, such as sound waves or light waves generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non-temporary, such as floppy disks, flexible disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, punch cards, paper tapes, any other physical media with hole patterns, RAMs, PROMs and EPROMs, FLASH-EPROMs, any other memory chips or cassettes. Non-temporary computer-readable media can have instructions recorded thereon. The instructions, when executed by a computer, may perform any of the operations described herein.Transitory computer-readable media may include, for example, a carrier wave or other propagated electromagnetic signal.

[0224] Various forms of computer-readable media can be involved when one or more sequences of one or more instructions are carried to the processor PRO for execution. For example, instructions can be initially carried on a disk of a remote computer. The remote computer can load instructions into its volatile memory and send instructions via a telephone line using a modem. The modem local to the computer system CS can receive data on the telephone line and use an infrared transmitter to convert the data into an infrared signal. An infrared detector connected to the bus BS can receive the data carried in the infrared signal and place the data on the bus BS. The bus BS carries the data to the main memory MM, from which the processor PRO obtains and executes the instruction. The instruction received by the main memory MM can optionally be stored on a storage device SD before or after being executed by the processor PRO.

[0225] The computer system CS may also include a communication interface CI connected to the bus BS. The communication interface CI provides a bidirectional data communication coupling with a network link NDL, which is connected to a local area network LAN. For example, the communication interface CI may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection with a corresponding type of telephone line. As another example, the communication interface CI may be a local area network (LAN) card that provides a data communication connection with a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface CI sends and receives electrical signals, electromagnetic signals, or optical signals that carry digital data streams representing various types of information.

[0226] The network link NDL usually provides data communication to other data devices via one or more networks. For example, the network link NDL can provide a connection to the host computer HC by a local area network LAN. This can include data communication services provided via the global packet data communication network (now generally referred to as the "Internet" INT). The local area network LAN (Internet) can use electrical signals, electromagnetic signals or optical signals that carry digital data streams. Signals via various networks and signals on the network data link NDL and via the communication interface CI are carrier waves that convey information in an exemplary form, and the signals carry digital data to and from the computer system CS.

[0227] The computer system CS can send messages and receive data (including program code) through the network, the network data link NDL and the communication interface CI. In the Internet example, the host computer HC can transmit the requested program code for the application program through the Internet INT, the network data link NDL, the local network LAN and the communication interface CI. For example, such a downloaded application program can provide all or part of the method described herein. The received code can be executed by the processor PRO when it is received, and / or stored in the storage device SD or other non-volatile storage for later execution. In this way, the computer system CS can obtain the application code in the form of a carrier wave.

[0228] Further embodiments according to the present invention are described in the following numbered aspects:

[0229] 1. A method comprising:

[0230] determining, for a measurement structure including a first grating having a first pitch and a second grating having a second pitch, a sensitivity of a moiré interference pattern component with respect to a parameter of interest in a manufacturing process; and

[0231] The measurement structure for use in measuring the parameter of interest in the manufacturing process is evaluated based on the sensitivity.

[0232] 2. The method of clause 1, wherein determining the sensitivity comprises determining a sensitivity that varies with at least one of the first pitch, the second pitch, or a combination thereof.

[0233] 3. The method of clause 1, wherein evaluating the measurement structure comprises determining whether a phase of the moiré interference pattern component is substantially linear with respect to the parameter of interest in the manufacturing process.

[0234] 4. The method of clause 1, wherein evaluating the measurement structure comprises determining whether a phase of the moiré interference pattern component is substantially constant over a wavelength range with respect to the parameter of interest in the manufacturing process.

[0235] 5. The method of clause 1, wherein evaluating the measurement structure comprises:

[0236] determining the intensity of the moiré interference pattern component; and

[0237] The measurement structure for measuring the parameter of interest in the manufacturing process is evaluated based on the intensity of the moiré interference pattern component.

[0238] 6. The method of clause 1, wherein evaluating the measurement structure comprises evaluating the sensitivity based on an absorbance of at least a first material of the measurement structure.

[0239] 7. The method of clause 1, wherein the moiré interference pattern components include moiré interference pattern components at a moiré pitch.

[0240] 8. The method of clause 1, wherein the moiré interference pattern components include moiré interference pattern components at a pitch that is less than a moiré pitch.

[0241] 9. The method of clause 1, wherein the moiré interference pattern components include moiré interference pattern components at a pitch greater than a moiré pitch.

[0242] 10. The method according to aspect 1, further comprising:

[0243] determining a sensitivity of a second moiré interference pattern component relative to the parameter of interest in the manufacturing process; and

[0244] The measurement structure for use in measuring the parameter of interest in the manufacturing process is evaluated based on the sensitivity of the second moiré interference pattern component.

[0245] 11. The method according to aspect 10, further comprising:

[0246] comparing the sensitivity of the moiré interference pattern component and the sensitivity of the second moiré interference pattern component; and

[0247] The measurement structure is evaluated for use in measuring the parameter of interest in the manufacturing process based on the comparison.

[0248] 12. The method according to aspect 10, further comprising:

[0249] For the measurement structure, determining at least one of phase sensitivity, phase shift sensitivity, frequency sensitivity, or a combination thereof of a relationship between the moiré interference pattern component and the second moiré interference pattern component relative to the parameter of interest in the manufacturing process; and

[0250] The measurement structure for measuring the parameter of interest in the manufacturing process is evaluated based on the relationship between the moiré interference pattern component and the second moiré interference pattern component relative to at least one of the phase sensitivity, the phase shift sensitivity, the frequency sensitivity, or a combination thereof of the parameter of interest in the manufacturing process.

[0251] 13. The method of clause 1, wherein the moiré interference pattern component comprises a moiré interference pattern component generated by at least one scattered wave path.

[0252] 14. The method of clause 1, wherein the first grating and the second grating are separated by at least a first material having a first refractive index.

[0253] 15. A method according to aspect 1, wherein the first grating is located in a first plane and the second grating is located in a second plane, and wherein the first plane is offset from the second plane by a distance in a direction substantially perpendicular to the first plane, the second plane, or a combination thereof.

[0254] 16. A method according to aspect 1, wherein the first grating is located in a first plane and the second grating is located in a second plane, and wherein the first plane is offset from the second plane by a distance that is substantially parallel to at least one of the first plane, the second plane, and a combination thereof.

[0255] 17. The method of clause 1, wherein determining the sensitivity of the moiré interference pattern component with respect to the parameter of interest in the manufacturing process comprises determining the sensitivity based on at least a first material property of the measurement structure.

[0256] 18. The method according to aspect 1, wherein the manufacturing process comprises at least one of a photolithography process, a deposition process, an etching process, an ion implantation process, or a combination thereof.

[0257] 19. A method according to aspect 1, wherein the parameters of interest in the manufacturing process include at least one of overlap offset, overlap offset error, a measure of focus, dose, a measure of geometric change, a measure of geometric size, a measure of symmetry, a measure of asymmetry, or a combination thereof.

[0258] 20. The method of clause 1, wherein scattered radiation from the measurement structure forms a moiré interference pattern at a detector when the measurement structure is illuminated by incident radiation.

[0259] 21. A method comprising:

[0260] Obtaining a moiré interference pattern of a measurement structure, wherein the measurement structure comprises a first grating at a first pitch in a first layer and a second grating at a second pitch in a second layer;

[0261] identifying a moiré interference pattern component in the measured moiré interference pattern; and

[0262] A measurement result of a parameter of interest in a manufacturing process is determined based on the moiré interference pattern component.

[0263] 22. The method according to aspect 21, further comprising:

[0264] identifying a second moiré interference pattern component in the moiré interference pattern; and

[0265] A measurement result of the parameter of interest in the manufacturing process is determined based on the moiré interference pattern component and the second moiré interference pattern component.

[0266] 23. A method according to aspect 22, wherein determining the measurement result of the parameter of interest in the manufacturing process includes: determining the parameter of interest in the manufacturing process based on at least one of the phase, phase shift or frequency between the moiré interference pattern component and the second moiré interference pattern component.

[0267] 24. The method of clause 22, wherein the sensitivity of the moiré interference pattern component to the parameter of interest in the manufacturing process is different from the sensitivity of the second moiré interference pattern component to the parameter of interest in the manufacturing process.

[0268] 25. The method of clause 22, wherein the moiré interference pattern component comprises a component of the moiré interference pattern having a first frequency, and wherein the second moiré interference pattern component comprises a component of the moiré interference pattern having a second frequency.

[0269] 26. The method of clause 21, wherein the moiré interference pattern is at least one of a measured moiré interference pattern, a simulated moiré interference pattern, or a combination thereof.

[0270] 27. A method comprising:

[0271] determining a moiré interference pattern component of a measurement structure, wherein the measurement structure comprises a first grating at a first pitch in a first layer and a second grating at a second pitch in a second layer;

[0272] obtaining a moiré pattern of the measurement structure;

[0273] removing the determined moiré interference pattern component from the moiré interference pattern; and

[0274] A measure of a parameter of interest in a manufacturing process is determined based on the moiré pattern with the moiré interference pattern component removed.

[0275] 28. The method according to aspect 27, further comprising:

[0276] determining a second moiré interference pattern component of the measurement structure;

[0277] removing the determined second moiré interference pattern component from the moiré pattern; and

[0278] A measure of the parameter of interest in the manufacturing process is determined based on the moiré pattern with the moiré interference pattern component and the second moiré interference pattern component removed.

[0279] 29. A method comprising:

[0280] generating parameters for at least one measurement structure, wherein the at least one measurement structure comprises a first grating at a first pitch in a first layer of a multilayer stack structure and a second grating at a second pitch in a second layer of the multilayer stack structure, wherein the first pitch and the second pitch are determined based on an evaluation of the at least one measurement structure for measuring a parameter of interest in a manufacturing process,

[0281] Wherein, generating the parameters for the at least one measurement structure comprises:

[0282] determining, for the at least one measurement structure, a sensitivity of a moiré interference pattern component relative to measuring the parameter of interest in the manufacturing process; and

[0283] The at least one measurement structure for use in measuring the parameter of interest in the manufacturing process is evaluated based on the sensitivity.

[0284] 30. The method of clause 29, wherein evaluating the at least one measurement structure comprises:

[0285] determining whether the sensitivity of the moiré interference pattern component is substantially linear with respect to the parameter of interest in the manufacturing process; and

[0286] Based on a determination that the sensitivity is substantially linear, the at least one measurement structure is conditionally accepted for use in measuring the parameter of interest in the manufacturing process.

[0287] 31. A method according to clause 30, wherein evaluating the at least one measurement structure comprises:

[0288] determining whether the sensitivity of the moiré interference pattern component is substantially constant over a range of wavelengths with respect to the parameter of interest in the manufacturing process; and

[0289] Based on a determination that the sensitivity is substantially constant over a range of wavelengths, the at least one measurement structure is conditionally accepted for use in measuring the parameter of interest in the manufacturing process.

[0290] 32. The method of clause 31, wherein evaluating the at least one measurement structure comprises conditionally rejecting the at least one measurement structure for use in measuring the parameter of interest in the manufacturing process based on a determination that the sensitivity is not substantially constant over a range of wavelengths.

[0291] 33. The method of clause 30, wherein the sensitivity of the moiré interference pattern component comprises at least one of phase sensitivity, phase shift sensitivity, frequency sensitivity, or a combination thereof.

[0292] 34. The method of clause 30, wherein evaluating the at least one measurement structure comprises conditionally rejecting use of the at least one measurement structure in measuring the parameter of interest in the manufacturing process based on a determination that the sensitivity is not substantially linear.

[0293] 35. The method of clause 30, wherein evaluating the at least one measurement structure further comprises:

[0294] determining the intensity of the moiré interference pattern component; and

[0295] The moiré interference pattern component is evaluated based on the intensity for use in measuring the parameter of interest in the manufacturing process.

[0296] 36. The method of clause 35, wherein evaluating the at least one measurement structure further comprises:

[0297] determining whether the intensity of the moiré interference pattern component is substantially less than intensities of other moiré interference pattern components; and

[0298] Based on a determination that the moiré interference pattern component is substantially less in intensity than the other moiré interference pattern components, the moiré interference pattern component is conditionally rejected for use in measuring the parameter of interest in the manufacturing process.

[0299] 37. The method of clause 35, wherein evaluating the at least one measurement structure further comprises:

[0300] determining whether the intensity of the moiré interference pattern component is substantially less than intensities of other moiré interference pattern components; and

[0301] The at least one measurement structure is conditionally rejected for overlay shift measurement based on a determination that the moiré interference pattern component is not substantially linear and a determination that the moiré interference pattern component is not substantially less than the other moiré interference pattern components in intensity.

[0302] 38. The method of clause 29, wherein generating the parameters for the at least one measurement structure further comprises:

[0303] determining whether the evaluation of at least one measurement structure for use in measuring the parameter of interest in the manufacturing process is unfavorable; and

[0304] Based on a determination that the assessment is unfavorable, at least one parameter of the at least one measurement structure is adjusted to generate at least one adjusted measurement structure.

[0305] 39. The method of clause 38, further comprising evaluating the at least one adjusted measurement structure,

[0306] Wherein, evaluating the at least one adjusted measurement structure comprises:

[0307] determining, for the at least one adjusted measurement structure, a sensitivity of the moiré interference pattern component relative to measuring the parameter of interest in the manufacturing process; and

[0308] The at least one adjusted measurement structure for use in measuring the parameter of interest in the manufacturing process is evaluated based on the sensitivity.

[0309] 40. The method of clause 38, wherein determining whether the evaluation of the at least one measurement structure for measuring the parameter of interest in the manufacturing process is unfavorable comprises:

[0310] For the moiré interference pattern component it is determined whether the evaluation of the at least one measurement structure for the parameter of interest in the manufacturing process is unfavorable.

[0311] 41. The method of clause 40, wherein determining whether the evaluation of the at least one measurement structure for measuring the parameter of interest in the manufacturing process is unfavorable comprises:

[0312] For a second moiré interference pattern component it is determined whether the evaluation of the at least one measurement structure for the parameter of interest in the manufacturing process is unfavorable.

[0313] 42. The method of clause 29, wherein evaluating the at least one measurement structure for measuring the parameter of interest in the manufacturing process further comprises:

[0314] determining, for the at least one measurement structure, a sensitivity of a second moiré interference pattern component relative to measuring the parameter of interest in the manufacturing process; and

[0315] The at least one measurement structure for measuring the parameter of interest in the manufacturing process is evaluated based on the sensitivity of the second moiré interference pattern component.

[0316] 43. The method of clause 42, wherein evaluating the at least one measurement structure further comprises:

[0317] determining whether a sensitivity of the second moiré interference pattern component is substantially linear with respect to the parameter of interest in the manufacturing process; and

[0318] The at least one measurement structure is conditionally accepted for use in measuring the parameter of interest in the manufacturing process based on a determination that the sensitivity of the second moiré interference pattern component is substantially linear.

[0319] 44. The method of clause 43, wherein evaluating the at least one measurement structure further comprises:

[0320] determining whether the sensitivity of the second moiré interference pattern component is substantially constant over a range of wavelengths with respect to the parameter of interest in the manufacturing process; and

[0321] The at least one measurement structure is conditionally accepted for use in measuring the parameter of interest in the manufacturing process based on a determination that the sensitivity of the second moiré interference pattern component is substantially constant over a range of wavelengths.

[0322] 45. The method according to aspect 42, further comprising:

[0323] obtaining a moiré interference pattern of the at least one measurement structure;

[0324] identifying the moiré interference pattern component in the moiré interference pattern;

[0325] identifying the second moiré interference pattern component in the moiré interference pattern; and

[0326] Based on a relationship between the moiré interference pattern component and the second moiré interference pattern component, a measure for the at least one measurement structure of the parameter of interest in the manufacturing process is determined.

[0327] 46. ​​A method according to clause 29, wherein generating the parameters for the at least one measurement structure comprises:

[0328] creating the first grating at the first pitch in the first layer of the multilayer stack; and

[0329] The second grating at the second pitch is created in the second layer of the multilayer stack.

[0330] 47. A method according to aspect 46, wherein:

[0331] Creating the first grating comprises: at least one of a first photolithography step, a first etching step, a first deposition step or a combination thereof, and

[0332] Wherein, creating the second grating comprises: at least one of a second photolithography step, a second etching step, a second deposition step or a combination thereof.

[0333] 48. The method of clause 46, wherein at least one of the first pitch, the second pitch, or a combination thereof is created by a photolithographic mask.

[0334] 49. The method of clause 46, wherein creating the first grating further comprises creating at least a first photolithography mask, and wherein creating the second grating comprises creating at least a second photolithography mask.

[0335] 50. The method of clause 29, wherein the at least one measurement structure is created in a measurement region on the die during a manufacturing process.

[0336] 51. The method of clause 29, wherein generating the parameters for the at least one measurement structure comprises generating at least one mask for generating the at least one measurement structure based on the parameters.

[0337] 52. One or more non-transitory machine-readable media having instructions thereon which, when executed by a processor, are configured to perform the method of any one of aspects 1 to 51.

[0338] 53. A system comprising:

[0339] Processor; and

[0340] One or more non-transitory machine-readable media having instructions thereon, the instructions being configured to perform the method of any one of aspects 1 to 51 when executed by the processor.

[0341] While the concepts disclosed herein may be used for wafer fabrication on substrates such as silicon wafers, it should be understood that the disclosed concepts may be used with any type of manufacturing system, such as a manufacturing system for fabrication on substrates other than silicon wafers.

[0342] Furthermore, combinations and sub-combinations of disclosed elements may include separate embodiments. For example, one or more operations described above may be included in separate embodiments, or they may be included together in the same embodiment.

[0343] The above description is intended to be illustrative rather than limiting. Accordingly, it will be appreciated by those skilled in the art that modifications may be made as described without departing from the scope of the claims set forth hereinafter.

Claims

1. A method comprising: determining, for a measurement structure including a first grating having a first pitch and a second grating having a second pitch, a sensitivity of a moiré interference pattern component with respect to a parameter of interest in a manufacturing process; as well as The measurement structure for use in measuring the parameter of interest in the manufacturing process is evaluated based on the sensitivity.

2. The method according to claim 1, wherein: Determining the sensitivity includes determining a sensitivity that varies with at least one of the first pitch, the second pitch, or a combination thereof.

3. The method according to claim 1, wherein: Evaluating the measurement structure includes: A determination is made as to whether a phase of the moiré interference pattern component is substantially linear with respect to the parameter of interest in the manufacturing process.

4. The method according to claim 1, wherein: Evaluating the measurement structure includes: A determination is made as to whether a phase of the moiré interference pattern component is substantially constant over a wavelength range with respect to the parameter of interest in the manufacturing process.

5. The method according to claim 1, wherein: Evaluating the measurement structure includes: determining the intensity of the moiré interference pattern component; and The measurement structure for measuring the parameter of interest in the manufacturing process is evaluated based on the intensity of the moiré interference pattern component.

6. The method according to claim 1, wherein: Evaluating the measurement structure includes: The sensitivity is evaluated based on the absorbance of at least a first material of the measurement structure.

7. The method according to claim 1, wherein: The moiré interference pattern components include moiré interference pattern components at a moiré pitch.

8. The method according to claim 1, wherein: The moiré interference pattern components include moiré interference pattern components at a pitch smaller than a moiré pitch.

9. The method according to claim 1, wherein: The moiré interference pattern components include moiré interference pattern components at a pitch greater than a moiré pitch.

10. The method according to claim 1, further comprising: determining a sensitivity of a second moiré interference pattern component relative to the parameter of interest in the manufacturing process; as well as The measurement structure for use in measuring the parameter of interest in the manufacturing process is evaluated based on the sensitivity of the second moiré interference pattern component.

11. The method according to claim 10, further comprising: comparing the sensitivity of the moiré interference pattern component and the sensitivity of the second moiré interference pattern component; as well as The measurement structure is evaluated for use in measuring the parameter of interest in the manufacturing process based on the comparison.

12. The method according to claim 10, further comprising: For the measurement structure, determining at least one of a phase sensitivity, a phase shift sensitivity, a frequency sensitivity, or a combination thereof of a relationship between the moiré interference pattern component and the second moiré interference pattern component relative to the parameter of interest in the manufacturing process; as well as The measurement structure for measuring the parameter of interest in the manufacturing process is evaluated based on the relationship between the moiré interference pattern component and the second moiré interference pattern component relative to at least one of the phase sensitivity, the phase shift sensitivity, the frequency sensitivity, or a combination thereof of the parameter of interest in the manufacturing process.

13. The method according to claim 1, wherein: Determining the sensitivity of the moiré interference pattern component with respect to the parameter of interest in the manufacturing process comprises determining the sensitivity based on at least a first material property of the measurement structure.

14. The method according to claim 1, wherein: The manufacturing process includes at least one of a photolithography process, a deposition process, an etching process, an ion implantation process or a combination thereof.

15. The method according to claim 1, wherein: The parameters of interest in the manufacturing process include at least one of overlay offset, overlay offset error, a measure of focus, dose, a measure of geometric variation, a measure of geometric size, a measure of symmetry, a measure of asymmetry, or a combination thereof.

Images