Image-based metrology based on local signal strength of diffracted radiation based on deformation

Abstract

In semiconductor structures, metrology marks can be covered by non-planar layers, such as resist layers. Resist layers can have tilted or disc-shaped regions that distort radiation diffracted by metrology marks. This reduces the measurement accuracy of interferometer-based systems. Advantageously, the present systems and methods use imaging sensors, such as cameras (rather than interferometers) and local signal strength in distorted diffracted radiation to generate accurate alignment, overlay, and / or other measurement results. For example, a camera can generate a metrology signal in the form of an image based on diffracted radiation received from metrology marks in a layer of a patterned substrate. Local signal strength can be determined based on the image; and a position of the metrology marks can be determined based on the local signal strength. The local signal strength can be determined in various ways.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Application 63 / 570,748, filed March 27, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This specification generally relates to image-based measurements of local signal intensity based on deformation-based diffraction radiation. Background Technology

[0004] For example, photolithography projection equipment can be used in the fabrication of integrated circuits (ICs). A patterning apparatus (e.g., a mask) can contain or provide a pattern (“design layout”) corresponding to a single layer of the IC, and this pattern can be transferred onto a target portion (e.g., comprising one or more dies) on a substrate (e.g., a silicon wafer) that has already been coated with a layer of radiation-sensitive material (“resist”) by methods such as irradiating the target portion through the pattern on the patterning apparatus. Typically, a single substrate comprises multiple adjacent target portions, and the pattern is transferred sequentially, one target portion at a time, by the photolithography projection equipment onto these multiple adjacent target portions. In one type of photolithography projection equipment, the entire pattern on the patterning apparatus is transferred onto a single target portion in a single operation. This type of equipment is often referred to as a stepper. In an alternative equipment (often referred to as a step-scanning apparatus), a projection beam scans over the patterning apparatus along a given reference direction (“scanning” direction) while the substrate is moved synchronously parallel or antiparallel along the reference direction. Different portions of the pattern on the patterning apparatus are progressively transferred onto a single target portion.

[0005] Before the pattern is transferred from the patterning apparatus to the substrate, the substrate may undergo various processes, such as primer coating, resist coating, and soft baking. After exposure, the substrate may undergo other processes (“post-exposure processes”), such as post-exposure baking (PEB), development, hard baking, and measurement / inspection of the transferred pattern. This series of processes is used as the basis for fabricating a single layer of a device (e.g., an IC). The substrate may then undergo various processes, such as etching, ion implantation (doping), metallization, oxidation, deposition, chemical mechanical polishing, etc., all of which aim to ultimately complete a single layer of the device. If multiple layers are required in the device, all processes or variations thereof are repeated for each layer. Ultimately, the device will exist in each target portion of the substrate. These devices are then separated from each other using techniques such as sawing or cutting, allowing individual devices to be mounted onto carriers, connected to pins, etc.

[0006] Therefore, fabricating devices (such as semiconductor devices) typically involves processing a substrate (e.g., a semiconductor wafer) using multiple fabrication processes to form various features and multiple layers of the device. These layers and features are typically fabricated and processed using processes such as deposition, photolithography, etching, chemical mechanical polishing, and ion implantation. Multiple devices can be fabricated on multiple dies on a substrate and then separated into individual devices. This device fabrication process can be considered a patterning process. A patterning process involves patterning steps using patterning apparatus in a photolithography apparatus, such as optical and / or nanoimprint lithography, to transfer a pattern from the patterning apparatus onto the substrate, and the patterning process typically, but optionally, involves one or more associated patterning processing steps, such as resist development by a developing apparatus, baking the substrate using a baking tool, etching the pattern using an etching apparatus, deposition, etc.

[0007] Photolithography is a central step in the fabrication of devices such as integrated circuits (ICs), in which patterns formed on a substrate define the functional elements of the device, such as microprocessors and memory chips. Similar photolithography techniques are also used to form flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0008] As semiconductor manufacturing processes continue to advance, the size of functional elements has been shrinking for decades, while the number of functional elements, such as transistors, per device has been steadily increasing, following a trend commonly known as "Moore's Law." In the current state of technology, photolithography projection equipment is used to fabricate layers of devices. This equipment projects a design layout onto a substrate using irradiation from a deep ultraviolet or extreme ultraviolet source, resulting in individual functional elements with dimensions sufficiently below 100 nm, i.e., less than half the wavelength of the radiation from the irradiation source (e.g., a 193 nm irradiation source).

[0009] This process for printing features smaller than the classical resolution limit of photolithography projection equipment 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, NA is the numerical aperture of the projection optics in the photolithography projection equipment, CD is the "critical size" (typically the smallest feature size to be printed), and k1 is an empirical resolution factor. Generally, the smaller k1 is, the more difficult it becomes to reproduce patterns on a substrate that resemble the shape and size planned by the designer to achieve specific electrical functions and performance. To overcome these difficulties, complex fine-tuning steps are applied to the photolithography projection equipment, design layout, or patterning apparatus. These steps include, for example, but not limited to, optimization of NA and optical coherence settings, custom illumination schemes, the use of phase-shifting patterning apparatus, optical proximity correction (OPC, sometimes also called "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement techniques" (RET). For example, these resolution enhancement techniques often rely on accurate metrological measurements, such as the alignment and / or overlap of one layer relative to another. Summary of the Invention

[0010] In semiconductor structures, measurement marks may be covered by non-planar layers, such as resist layers. These resist layers may have tilted or disk-shaped regions that distort the radiation diffracted by the measurement marks. This reduces the measurement accuracy of interferometer-based systems. Advantageously, this system and method use imaging sensors, such as cameras (instead of interferometers), and local signal intensities in the distorted diffracted radiation to generate accurate alignment, overlap, and / or other measurement results. For example, a camera can generate a measurement signal in the form of an image based on diffracted radiation received from measurement marks in a layer of a patterned substrate. Local signal intensities can be determined based on the image; and the position of the measurement mark can be determined based on the local signal intensities. Local signal intensities can be determined in various ways.

[0011] According to an embodiment, a measurement system is provided. The measurement system includes a radiation sensor configured to generate a measurement signal based on diffracted radiation received from measurement marks in a layer of a patterned substrate. The measurement signal includes an image. The measurement system includes one or more processors operatively coupled to the radiation sensor. The one or more processors are configured to: determine local signal intensities of the diffracted signal based on the image; and determine the position of the measurement mark based on the local signal intensities.

[0012] In some embodiments, the radiation sensor includes an imaging sensor. In some embodiments, the imaging sensor includes a camera.

[0013] The measurement marks are covered by a non-planar layer on a patterned substrate that distorts diffraction radiation. In some embodiments, the non-planar layer includes a resist. The non-planar layer includes locally tilted or disc-shaped recesses. For example, the non-planar layer may include a top surface having one or more regions that are not parallel to the layer in the patterned substrate.

[0014] In some embodiments, determining the location of the measurement mark includes: determining the thickness profile of the non-planar layer covering the measurement mark based on the local signal intensity, and determining the location of the measurement mark based on the thickness profile.

[0015] In some embodiments, determining the local signal intensity of a measurement signal based on an image includes: determining the local intensity of one or more pixels in the image and comparing the local intensity with a nominal intensity; determining the signal intensity of one or more colors and / or polarizations to monitor resonances in the spectrum of the diffracted radiation; determining local contrast variations in the image to determine in-focus or out-of-focus portions of the image; determining the gradient of the local intensity and / or the gradient of the local resonances in the spectrum of the diffracted radiation, and / or determining the gradient of the local image contrast; and / or correlating the changes in local signal intensity, the changes in intensity, and / or the changes in contrast with the curvature of a non-planar layer covering the measurement mark.

[0016] In some embodiments, the one or more processors are configured to determine the alignment and / or overlap of the layers in the patterned substrate and / or the non-planar layers covering the measurement marks based on the local signal intensity and / or the position of the measurement marks. In some embodiments, the one or more processors are configured to facilitate the correction of the alignment and / or overlap of the layers in the patterned substrate and / or the non-planar layers covering the measurement marks based on the local signal intensity and / or the position of the measurement marks.

[0017] In some embodiments, the one or more processors are configured to: determine local phase changes in the diffracted radiation, and based on the local phase changes and: the local intensity of one or more pixels in the image compared to the nominal intensity; local contrast changes in the image; and / or gradients of local intensity and / or local resonances in the spectrum of the diffracted radiation, and / or gradients of local image contrast, to facilitate correction of overlap and / or alignment. Facilitating correction of overlap and / or alignment based on local phase changes may include correcting, for example, amplification errors caused by the curvature of a non-planar layer covering the markings.

[0018] In some embodiments, the image includes an intensity-modulated pattern. In some embodiments, the radiation sensor is configured such that the intensity-modulated pattern of the diffracted radiation includes a one-dimensional or multi-dimensional interference pattern.

[0019] The measurement system can be a dark field or a bright field measurement system.

[0020] The measurement markers can be, for example, periodic or non-periodic gratings.

[0021] In some embodiments, the measurement system includes a radiation source operatively coupled to one or more processors and radiation sensors. The radiation source is configured to irradiate the measurement markers.

[0022] According to another embodiment, a measurement method is provided that includes one or more of the operations described above. Attached Figure Description

[0023] The above and other aspects and features will become clear to those skilled in the art from the following description of the specific embodiments in conjunction with the accompanying drawings.

[0024] Figure 1 A lithography apparatus according to an embodiment is schematically depicted.

[0025] Figure 2 An embodiment of a photolithography element or photolithography cluster is schematically depicted according to the embodiments.

[0026] Figure 3 An example measurement system according to an embodiment is schematically depicted.

[0027] Figure 4 An example measurement technique according to an embodiment is schematically depicted.

[0028] Figure 5 The figure illustrates the relationship between the radiation spot and the measurement target of the inspection system according to an embodiment.

[0029] Figure 6 The figure illustrates a measurement method according to an embodiment.

[0030] Figure 7 The figure illustrates a non-planar (or inclined or disc-shaped) resist layer covering measurement marks according to an embodiment.

[0031] Figure 8 The figure illustrates the diffraction radiation (e.g., by) a variation of an embodiment. Figure 7 The non-planar layer shown in the figure can reduce the measurement accuracy of an interferometer-based measurement system and / or render such a system completely unusable for measurement.

[0032] Figure 9The figure illustrates an image-based measurement system configured to interfere with diffraction orders via projection, according to an embodiment.

[0033] Figure 10 The figure illustrates an example image that, according to an embodiment, can be used to determine the local signal strength of a measurement signal (so that the position of a measurement marker can be determined based on the local signal strength, and alignment and / or overlap can be determined and / or other operations can be performed based on that position).

[0034] Figure 11 This is a block diagram of an example computer system according to an embodiment. Detailed Implementation

[0035] In semiconductor structures, measurement markers are increasingly covered by non-planar layers, such as resist layers. These resist layers can have tilted, disk-shaped, and / or other regions that distort the radiation diffracted by the measurement markers. This reduces the measurement accuracy of interferometer-based measurement systems. For example, in interferometer-based alignment sensors, if the amount of non-planarity (e.g., tilt, curvature, etc.) in the resist layer becomes too large, the resist-covered measurement markers cannot be used for alignment. The diffraction order (of the radiation diffracted by the measurement markers) may propagate through the resist layer and into the alignment sensor, exceeding the pattern-matching capability of the interferometric diffraction order. The diffraction order is (typically asymmetrically) shifted from the center of the pupil plane in the sensor. Therefore, interferometer-based alignment sensors cannot form the interferogram required to determine alignment.

[0036] In contrast, this system and method utilize image-based measurement sensors. These sensors are inherently more robust for capturing signals on these types of “distorted” measurement markers (from the perspective of diffraction radiation that passes through a non-planar layer of a semiconductor structure and asymmetrically strikes an interferometer-based alignment sensor) because these sensors interfere with the diffraction order through projection. Therefore, it is irrelevant whether the diffraction order is shifted in the pupil plane, as long as it is re-imaged on the image-based measurement sensor. This is because an image of the diffraction pattern is still formed, from which alignment and / or other measurements can be determined. The pattern itself may be asymmetric, shifted by a non-planar layer, and / or may even include components related to amplification errors, but the image of the pattern can still be analyzed for measurement purposes (e.g., as described below).

[0037] Advantageously, this system and method use imaging sensors such as cameras (rather than interferometer-based systems) and local signal intensities in deformed diffracted radiation to generate accurate alignment, overlap, and / or other measurements. For example, the camera can generate a measurement signal in the form of an image based on diffracted radiation received from measurement marks in layers of a patterned substrate. Local signal intensities can be determined based on the image; and the position of the measurement marks can be determined based on the local signal intensities. Local signal intensities can be determined in various ways and then used to determine alignment, overlap, and / or other indicators, regardless of any non-planar layers that may cover the marks.

[0038] For the sake of brevity, the following description generally relates to semiconductor device fabrication and patterning processes. More specifically, the following paragraphs describe several components of the systems and / or related systems. As described above, these systems and methods can be used to measure, for example, alignment and / or overlap in semiconductor device fabrication processes, or for other operations.

[0039] While this specification is specifically referenced to alignment and / or overlap measurements and the fabrication of integrated circuits (ICs) for semiconductor devices, it should be understood that it has many other possible applications. For example, it can be used for the measurement of other parameters. It can be used to fabricate integrated optical systems, guide and detection patterns for magnetic domain memories, liquid crystal display panels, thin-film magnetic heads, etc. Those skilled in the art will understand that in the context of such alternative applications, any use of the terms "mask," "wafer," or "die" should be considered interchangeable with the more general terms "mask," "substrate," and "target portion," respectively.

[0040] The term "projection optics" should be interpreted broadly to encompass various types of optical systems, including, for example, refractive optics, reflective optics, aperture and reflective-refractive optics. The term "projection optics" may also include components operating according to any of these design types for jointly or individually guiding, shaping, or controlling a projected radiation beam. The term "projection optics" can include any optical component in a lithographic projection apparatus, regardless of where the optical component is positioned in the optical path of the lithographic projection apparatus. Projection optics can include optical components for shaping, adjusting, and / or projecting radiation from a source before it passes through a patterning apparatus, and / or for shaping, adjusting, and / or projecting radiation after it has passed through the patterning apparatus. Projection optics typically exclude the light source and the patterning apparatus.

[0041] Figure 1An embodiment of a photolithography apparatus LA is schematically depicted. The apparatus includes: an irradiation system (irradiator) IL configured to modulate a radiation beam B (e.g., UV, DUV, or EUV radiation); a support structure (e.g., a mask stage) MT configured to support a patterning apparatus (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning apparatus according to predetermined parameters; a substrate stage (e.g., a wafer platform) WT (e.g., WTa, WTb, or both), configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate according to predetermined parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted by the patterning apparatus MA to the radiation beam B onto a target portion C (e.g., comprising one or more dies and often referred to as a field) of the substrate W. The projection system is supported on a reference frame (RF). As depicted, the apparatus is of the transmission type (e.g., employing a transmission mask). Alternatively, the device can be of the reflective type (e.g., using a programmable array of mirrors or a reflective mask).

[0042] The irradiator IL receives a radiation beam from a radiation source SO. The source and the lithography apparatus can be separate entities, for example, when the source is an excimer laser. In these cases, the source is not considered a component of the lithography apparatus, and the radiation beam is delivered from the source SO to the irradiator IL by means of a beam delivery system BD that includes, for example, suitable directional mirrors and / or beam expanders. In other cases, for example, when the source is a mercury lamp, the source can be an integral part of the apparatus. The source SO and the irradiator IL, along with the beam delivery system BD (if necessary), can be collectively referred to as the radiation system.

[0043] The illuminator IL can modify the intensity distribution of the beam. The illuminator can be arranged to limit the radial range of the radiation beam such that the intensity distribution within an annular region in the pupil plane of the illuminator IL is non-zero. Alternatively, the illuminator IL can be operated to limit the beam distribution in the pupil plane such that the intensity distribution in multiple equally spaced segments within the pupil plane is non-zero. The intensity distribution of the radiation beam in the pupil plane of the illuminator IL can be referred to as the illumination mode.

[0044] An illuminator IL may include an adjuster AD configured to adjust the (angular / spatial) intensity distribution of a beam. Typically, at least the outer radial range and / or inner radial range (often referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the pupil plane of the illuminator can be adjusted. The illuminator IL is operable to change the angular distribution of the beam. For example, the illuminator may be operable to change the number and angular range of segments in the pupil plane where the intensity distribution is non-zero. Different illumination modes can be achieved by adjusting the intensity distribution of the beam in the pupil plane of the illuminator. For example, by limiting the radial and angular ranges of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution can have a multipole distribution, such as a dipole, tetrapole, or hexapole distribution. The illumination mode can be obtained, for example, by inserting an optics device providing the desired illumination mode into the illuminator IL or by using a spatial light modulator.

[0045] The illuminator IL can be operable to change the polarization of the beam and operable to adjust the polarization using an adjuster AD. The polarization state of the radiation beam across the pupil plane of the illuminator IL can be referred to as a polarization mode. Using different polarization modes can allow for greater contrast in the image formed on the substrate W. The radiation beam can be unpolarized. Alternatively, the illuminator can be arranged to linearly polarize the radiation beam. The polarization direction of the radiation beam can vary across the pupil plane of the illuminator IL. The polarization direction of the radiation can be different in different regions of the pupil plane of the illuminator IL. The polarization state of the radiation can be selected depending on the illuminator mode. For a multi-pole illuminator mode, the polarization of each pole of the radiation beam can be approximately perpendicular to the position vector of said pole in the pupil plane of the illuminator IL. For example, for a dipole illuminator mode, the radiation can be linearly polarized in a direction approximately perpendicular to the line bisecting the two opposing segments of the dipole. The radiation beam can be top-polarized in one of two different orthogonal directions, which can be referred to as the X-polarization state and the Y-polarization state. For a quadrupole illuminator mode, the radiation in each pole segment can be linearly polarized in a direction approximately perpendicular to the line bisecting said segment. This polarization mode can be called XY polarization. Similarly, for a hexapolar illumination mode, the radiation in each pole segment can be linearly polarized in a direction approximately perpendicular to the line bisecting the segment. This polarization mode can be called TE polarization.

[0046] In addition, the irradiator IL typically includes various other components, such as an integrator IN and a concentrator CO. The irradiation system may include various types of optical components for guiding, shaping, or controlling radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof.

[0047] Therefore, the irradiator provides a modulated radiation beam B with the desired uniformity and intensity distribution in its cross-section.

[0048] The support structure MT supports the patterning apparatus in a manner dependent on the orientation of the patterning apparatus, the design of the lithography equipment, and other conditions such as whether the patterning apparatus is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning apparatus. The support structure can be, for example, a frame or stage that can be fixed or moved as needed. The support structure ensures that the patterning apparatus is in a desired position, for example, relative to a projection system. Any use of the terms "mask" or "mask" may be considered synonymous with the more general term "patterning apparatus".

[0049] The term "patterning apparatus" should be interpreted broadly as any apparatus that can be used to impart a pattern to a target portion of a substrate. In embodiments, a patterning apparatus is any apparatus that can be used to impart a pattern to a radiation beam in the cross-section of the radiation beam to form a pattern in the target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not correspond precisely to the desired pattern in the target portion of the substrate (e.g., if the pattern includes phase-shifting features or so-called auxiliary features). Typically, the pattern imparted to the radiation beam will correspond to a specific functional layer in the device (such as an integrated circuit) produced in the target portion of the device.

[0050] Pattern forming apparatuses can be transmissive or reflective. Examples of pattern forming apparatuses include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in photolithography and include mask types such as binary masks, alternating phase-shift masks, and attenuation phase-shift masks, as well as various hybrid mask types. Examples of programmable mirror arrays employ a matrix arrangement of small mirrors, each of which can be individually tilted to reflect the incident radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam reflected by the mirror matrix.

[0051] A projection system PS may include multiple optical (e.g., lens) elements and may also include an adjustment mechanism configured to adjust one or more of the optical elements to correct for aberrations (phase changes across the pupil plane of the entire field). To achieve this correction, the adjustment mechanism may be operable to manipulate one or more optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a coordinate system in which its optical axis extends in the z-direction. The adjustment mechanism may be operable to perform any combination of: shifting one or more optical elements; tilting one or more optical elements; and / or deforming one or more optical elements. Shifting of optical elements can be performed in any direction (x, y, z, or a combination thereof). Tilting of optical elements typically involves rotating about an axis in the x and / or y directions away from a plane perpendicular to the optical axis, but rotation about the z-axis can be used for non-rotationally symmetric aspherical optical elements. Deformation of optical elements may include both low-frequency shapes (e.g., astigmatism) and / or high-frequency shapes (e.g., freeform aspherical surfaces). Deformation of an optical element can be performed, for example, by applying force to one or more sides of the optical element using one or more actuators and / or by heating one or more selected areas of the optical element using one or more heating elements. Typically, it is not possible to adjust the projection system PS to correct apodization (transmission variation across the pupil plane). Transmission mapping of the projection system PS can be used when designing a patterning apparatus (e.g., a mask) MA for a lithography device LA. Using computational lithography, the patterning apparatus MA can be designed to at least partially correct apodization.

[0052] Photolithography equipment can belong to the type having two (dual-stage) or more stages (e.g., two or more substrate stages WTa, WTb; two or more patterning apparatus stages; substrate stages WTa and WTb below the projection system in the absence of a substrate dedicated to, for example, facilitating measurement and / or cleaning). In these "multi-stage" machines, additional stages can be used in parallel, or preparatory steps can be performed on one or more stages while one or more other stages are used for exposure. For example, alignment measurements using an alignment sensor AS and / or level (height, tilt, etc.) measurements using a level sensor LS can be performed.

[0053] In the operation of a photolithography apparatus, a radiation beam is regulated and provided by an irradiation system IL. The radiation beam B is incident on a patterning apparatus (e.g., a mask) MA held on a support structure (e.g., a mask stage) MT and patterned by the patterning apparatus. After passing through the patterning apparatus MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. The substrate stage WT can be precisely moved, for example, to position different target portions C within the path of the radiation beam B, by means of a second positioner PW and a position sensor IF (e.g., an interferometer, a linear encoder, a 2-D encoder, or a capacitive sensor). Similarly, a first positioner PM and another position sensor (in…) Figure 1 (Not explicitly depicted) can be used to accurately position the patterning apparatus MA relative to the path of the radiation beam B, for example, after mechanical retrieval from a mask library or during scanning. Typically, the movement of the support structure MT can be achieved by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) that form part of the first positioner PM. Similarly, the movement of the substrate stage WT can be achieved using a long-stroke module and a short-stroke module that form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected only to the short-stroke actuator, or it may be fixed. The patterning apparatus MA and the substrate W can be aligned using patterning apparatus alignment marks M1, M2 and substrate alignment marks P1, P2. Although the illustrated substrate alignment marks occupy dedicated target portions, they can be located in the space between multiple target portions (these are called scribing alignment marks). Similarly, when more than one die is placed on the patterning apparatus MA, the patterning apparatus alignment marks can be located between these dies.

[0054] The depicted apparatus can be used in at least one of the following modes. In step mode, the support structure MT and substrate stage WT remain substantially stationary, and the pattern applied to the radiation beam is projected onto the target portion C in a single exposure (i.e., a single static exposure). The substrate stage WT then moves in the X and / or Y directions, allowing different target portions C to be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. In scan mode, the support structure MT and substrate stage WT are scanned simultaneously, while the pattern applied to the radiation beam is projected onto the target portion C (i.e., a single dynamic exposure). The speed and direction of the substrate stage WT relative to the mask support structure MT can be determined by the (reduced) magnification and image inversion characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width of the target portion (along the non-scanning direction) in a single dynamic exposure, while the length of the scan motion determines the height of the target portion C (along the scanning direction). In another mode, the support structure MT used to maintain the programmable patterning apparatus remains essentially stationary, and the pattern imparted by the radiation beam is projected onto the target portion C while the substrate stage WT is moved or scanned. In this mode, a pulsed radiation source is typically used, and the programmable patterning apparatus is updated as needed after each movement of the substrate stage WT or between consecutive radiation pulses during scanning. This mode of operation can be readily applied to maskless lithography utilizing programmable patterning apparatuses such as programmable mirror arrays of the type described above.

[0055] Alternatively, the above usage patterns or combinations and / or variations of completely different usage patterns may be adopted.

[0056] The substrate can be processed before or after exposure in, for example, in a coating and developing system (a tool that typically applies a resist layer to the substrate and develops the exposed resist) or in a measurement or inspection tool. Where applicable, this disclosure can be applied to these and other substrate processing tools. Additionally, the substrate can be processed more than once, for example to produce a multilayer IC, such that the term substrate can also refer to a substrate that includes multiple processed layers.

[0057] The terms “radiation” and “beam” used in lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g., with wavelengths of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., with wavelengths in the range of 5 nm to 20 nm), as well as particle beams, such as ion beams or electron beams.

[0058] Various patterns on or provided by a pattern forming apparatus can have different process windows, i.e., spaces within which the processing variables upon which the pattern is based will be generated within a specification. Examples of pattern specifications for potential systematic defects include checking for necking, line pullback, line thinning, CD, edge placement, overlay, resist top loss, resist undercut, and / or bridging. Process windows on the pattern forming apparatus or its area can be obtained by merging (e.g., overlaying) the process windows of each individual pattern. The boundaries of the process windows of a pattern group include the boundaries of the process windows of some of the individual patterns. In other words, these individual patterns limit the process windows of the pattern group.

[0059] like Figure 2 As shown, the lithography equipment LA can form part of a lithography unit LC (sometimes also referred to as a lithography cell or lithography cluster), which also includes equipment for performing pre-exposure and post-exposure processes on the substrate. Typically, this equipment includes one or more spin coaters SC for depositing one or more resist layers, one or more developers for developing the exposed resist, one or more chillers CH, and / or one or more bakers BK. A substrate transport device or robot RO picks up one or more substrates from input / output ports I / O1, I / O2, moves them between different process units, and delivers them to the lithography equipment's feed stage LB. These units, often collectively referred to as the coating and developing system, are controlled by a coating and developing system control unit TCU, which in turn is controlled by a management control system SCS, which in turn controls the lithography equipment via the lithography control unit LACU. Therefore, different units can be operated to maximize throughput and processing efficiency.

[0060] To ensure that the substrate exposed by the lithography equipment is correctly and consistently exposed, and / or to monitor a portion of a patterning process (e.g., a device fabrication process) including at least one pattern transfer step (e.g., an optical lithography step), it is desirable to examine the substrate or other object to measure or determine one or more properties, such as alignment, overlap (e.g., between structures in multiple overlapping layers, or between structures that have been separately set into the same layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, material properties, etc. Therefore, manufacturing facilities in which lithography units LC are positioned typically also include a measurement system that measures the substrate W (which has been processed in the lithography unit) Figure 1 Some or all of the objects in the lithography unit or other objects in the lithography unit. The measurement system may be part of the lithography unit LC, for example, it may be part of the lithography apparatus LA (such as the alignment sensor AS). Figure 1 )).

[0061] For example, one or more measured parameters may include, for example: overlap or alignment between successive layers formed in or on a patterned substrate; critical dimension (CD) (e.g., critical linewidth) of features formed in or on a patterned substrate; focal length or focus error of an optical lithography step; dose or dose error of an optical lithography step; optical aberration of an optical lithography step; etc. Such measurements are typically performed on a dedicated measurement target disposed on the substrate. Measurements may be performed after resist development but before etching, after etching, after deposition, and / or at other times.

[0062] Various techniques exist for measuring structures formed during the patterning process, including the use of scanning electron microscopy, image-based metrology tools, and / or various specialized instruments. A rapid and non-invasive form of specialized metrology tool is one in which a radiation beam is directed onto a target on the surface of a substrate and the properties of the scattered beam (diffracted / reflected beam) are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. Traditionally, this can be referred to as diffraction-based metrology. Such diffraction-based metrology is applied, for example, in alignment and / or overlap measurements.

[0063] Therefore, during or after a device manufacturing process (e.g., a patterning process or a photolithography process), a substrate or other object may be subjected to various types of measurements. Measurements may determine whether a particular substrate has defects, may establish adjustments to the process and the equipment used in the process (e.g., aligning two or more layers on the substrate or aligning a patterning apparatus to the substrate), may measure the performance of the process and the equipment, or may be used for other purposes.

[0064] Measurement results can be provided directly or indirectly to the management and control system (SCS). If an error is detected, adjustments can be made to the exposure of subsequent substrates (especially where inspection can be completed quickly enough that one or more other substrates in the batch remain to be exposed) and / or to the subsequent exposure of already exposed substrates. Additionally, exposed substrates can be stripped and reworked to improve yield, or discarded, thereby avoiding further processing of substrates known to be defective. In cases where only some target portions of the substrate are defective, further exposure can be performed only on those target portions that meet specifications. Other manufacturing process adjustments are anticipated.

[0065] Measurement systems can be used to determine one or more properties of a substrate structure, and specifically, how one or more properties vary between different substrate structures, or how different layers of the same substrate structure vary between different layers. Measurement systems can be integrated into lithography equipment (LA) or lithography units (LC), or they can be stand-alone devices.

[0066] To enable measurement, one or more measurement marks are typically provided specifically on the substrate. These measurement marks may include overlapping targets, such as alignment marks and / or other marks. Typically, the marks are specifically designed and may include one or more periodic structures. For example, a mark on the substrate may include one or more one-dimensional (1-D) periodic structures (e.g., geometric features, such as gratings) in one or more layers of the substrate, printed such that, after development, the periodic structure features are formed by solid resist lines. As another example, the mark may include one or more two-dimensional (2-D) periodic structures (e.g., gratings) in one or more layers, printed such that, after development, the one or more periodic structures are formed by solid resist pillars or vias in the resist. The gratings, pillars, or vias are alternatively etched into the substrate (e.g., etched into one or more layers on the substrate).

[0067] Figure 3 An example measurement system 10 is depicted that can be used to detect overlap, alignment, and / or perform other measurement operations. It includes a radiation source 2 that projects or otherwise irradiates radiation onto a substrate W. The substrate W typically includes measurement markers 30, such as overlap targets, alignment marks, and / or other structures. The redirected radiation is passed to a radiation sensor, such as a spectrometer detector 4—e.g., an imaging sensor, such as a camera as described below—and / or other sensors that measure the spectrum (intensity as a function of wavelength) of specularly reflected and / or diffracted radiation, for example, as... Figure 4 As shown in the graph on the left. The sensor can generate measurement signals that transmit overlap data, alignment data, and / or other data indicating the characteristics of reflected radiation. Based on this data, the structure or profile of the detected spectrum can be reconstructed by one or more processors (a generalized example is shown in...). Figure 4 (as shown in the diagram), or reconstructed through other operations. Note that these are generalized examples. Typically, illumination of targets such as overlapping markers and / or alignment markers is orthogonal to the target and / or markers rather than at an angle. Figure 3 It is performed from the angle shown in the image.

[0068] As in Figure 1 In a photolithography (LA) system, one or more substrate stages can be provided. Figure 4 (Not shown) to hold substrate W during measurement operations. One or more substrate stages may be formally connected to... Figure 1The substrate stages WT (WTa or WTb or both) are similar or identical. In an example where the measurement system 10 is integrated with a lithography apparatus, they can even be the same substrate stages. Coarse and fine positioners can be provided, and are configured to accurately position the substrate relative to the measurement optics. Various sensors and actuators are provided, for example, to obtain the position of the target portion of the structure (e.g., overlapping targets and / or alignment marks) and to position it below the objective lens. Typically, many measurements will be performed on the target portion of the structure at different locations across the substrate W. The substrate support can move in the X and Y directions to obtain different measurement targets and can move in the Z direction to obtain the desired location of the mark in focus relative to the optics. When, for example, in practice, the optics may remain substantially stationary (typically in the X and Y directions, but perhaps also in the Z direction) and the substrate moves, it is convenient to consider and describe the operation as if the objective lens is being moved to different positions relative to the substrate. Assuming the relative positions of the substrate and the optical system are correct, it is in principle irrelevant which of the substrate and the optical system is moving, or both are moving, or a part of the optical system is moving (e.g., in the Z and / or tilt directions) and the rest of the optical system is fixed in combination with the substrate being moving (e.g., in the X and Y directions, and optionally in the Z and / or tilt directions).

[0069] For typical metrological measurements, the metrological markers 30 on the substrate W can be one-dimensional (1-D) gratings printed such that, after development, the grating strips are formed from solid resist lines (e.g., which may be covered by a deposition layer) and / or other materials. Alternatively, the markers 30 can be two-dimensional (2-D) gratings printed such that, after development, the grating is formed from solid resist pillars and / or other features in the resist. The grating strips, pillars, vias, and / or other features can be etched into or on the substrate (e.g., etched into one or more layers on the substrate), deposited on the substrate, covered by a deposition layer, and / or have other properties. The markers 30 (e.g., stripes, pillars, vias, etc.) are sensitive to changes in the patterning process (e.g., optical aberrations, focus variations, dose variations, deformation caused by non-planar resist layers, etc. in a photolithographic projection apparatus), such that process variations manifest as changes in the markers 30. Therefore, the measurement data from mark 30 can be used to determine adjustments for one or more manufacturing processes, and / or as a basis for making actual adjustments. Note that in this example, mark 30 can represent one or more layers comprising one or more measurement marks.

[0070] For example, measurement data from marker 30 can indicate the alignment, overlap, and / or other information of layers in a semiconductor device. Measurement data from marker 30 can (e.g., by one or more processors) be used to determine one or more semiconductor device fabrication process parameters based on alignment, overlap, and / or other information, and / or to determine adjustments to semiconductor device fabrication equipment based on one or more determined semiconductor device fabrication process parameters. In some embodiments, this may include, for example, platform position adjustments, or it may include determining adjustments to mask design, measurement marker (e.g., overlap targets and / or alignment markers) design, semiconductor device design, radiation intensity, radiation incident angle, radiation wavelength, pupil size and / or shape, resist material, and / or other process parameters.

[0071] Figure 5 The illustration shows a typical marker 30 (e.g., overlapping targets, alignment markers, etc.) and Figure 4 A planar diagram of the extent of the radiation spot S in the system. Typically, to obtain a diffraction spectrum unaffected by interference from surrounding structures, in embodiments, the marker 30 includes one or more periodic structures (e.g., gratings) larger than the width (e.g., diameter) of the radiation spot S. The width of the spot S may be smaller than the width and length of the marker 30. In other words, the marker 30 is "underfilled" by illumination, and the diffraction signal is substantially unaffected by any signals from product features, etc., other than the target itself. For example, the illumination arrangement may be configured to provide illumination of uniform intensity throughout the back focal plane of the objective example. Alternatively, illumination may be restricted to an on-axis or off-axis direction, for example, by means of apertures included in the illumination path.

[0072] Figure 6 The figure illustrates a measurement method 600. In some embodiments, method 600 is performed as part of a semiconductor device manufacturing process. Method 600 is associated with an image-based measurement sensor, as described above, which is robust to capturing diffracted radiation that passes through non-planar layers of the semiconductor structure and asymmetrically impacts an interferometer-based alignment sensor. In some embodiments, for example, one or more operations of method 600 may be performed... Figure 3 System 10 shown in the diagram Figure 9 The system 900 shown in the figure (for example, as shown in the figure) Figure 11The method 600 is executed or performed by the computer system illustrated in the figure and described below, and / or executed or performed by other systems. System 10, System 900, System 1000, the computer system and / or other components may be or form a bright-field measurement system, a dark-field measurement system and / or other measurement systems (or form one or more of them). In some embodiments, method 600 includes: irradiating (operation 602) a measurement mark in a patterned substrate (such as a semiconductor wafer) with radiation, generating (operation 604) a measurement signal based on diffracted radiation received from the measurement mark, determining (operation 606) a local signal intensity of the measurement signal, and determining (operation 608) the position of the measurement mark based on the local signal intensity, determining and / or correcting (operation 610) alignment and / or overlap, and / or other operations. Method 600 is described below in the context of alignment and / or overlap, but this is not intended to be limiting. Method 600 can generally be applied to many different processes.

[0073] The operation of method 600 presented below is intended to be illustrative. In some embodiments, method 600 may be implemented with one or more additional operations not described and / or without one or more of the operations discussed. For example, in some embodiments, method 600 may include additional operations including determining adjustments for the semiconductor device manufacturing process. Additionally, in Figure 6 The order of operations of method 600, as illustrated in the diagrams and described below, is not intended to be restrictive.

[0074] In some embodiments, one or more portions of the method 600 may be integrated into one or more processing devices (e.g., digital processors, analog processors, digital circuits designed to process information, analog circuits designed to process information, state machines, and / or other mechanisms for electronically processing information—see also...) Figure 3 and Figure 11 The processor PRO (described in the text) is executed or controlled. One or more processing devices may include one or more means that perform some or all of the operations of method 600 in response to (machine-readable) instructions stored electronically on an electronic storage medium. One or more processing devices may include one or more means that are specifically designed to perform one or more of the operations of method 600 (e.g., see below regarding...). Figure 11 The hardware, firmware, and / or software (as discussed in the discussion) are used to configure the one or more devices.

[0075] Operation 602 includes irradiating measurement marks in a patterned substrate with radiation. In some embodiments, the measurement marks include measurement marks and / or other features in different layers of the patterned substrate. In some embodiments, the measurement marks are associated with alignment and / or overlap measurements of the patterned substrate. For example, the measurement marks may be or include dedicated alignment and / or overlap marks, which include one or more diffraction gratings in the same and / or different layers. The radiation may be diffracted by the diffraction gratings. In some embodiments, the measurement marks include one or more structures (e.g., gratings or some other structure) in the patterned substrate capable of providing a diffraction signal. In some embodiments, the measurement marks may be any structure in the patterned design layout capable of generating a wide-angle diffraction signal.

[0076] In some embodiments, measurement marks may be included in one or more layers of a substrate, such as in a semiconductor device structure. In some embodiments, measurement marks include one or more geometric features, such as one-dimensional (1D) or two-dimensional (2D) features, and / or other geometric features. As several non-limiting examples, measurement marks may include lines, edges, lines and / or edges of a series of fine pitches, lines and / or edges of multiple fine pitches, and / or other features.

[0077] In some embodiments, the measurement markers may be similar to Figure 3 and / or Figures 6 to 9 The markings shown are 30, and / or other measurement markings, or identical thereto. As described above, in some embodiments, the measurement markings may be gratings with specific pitch and / or other characteristics. For example, the grating may be periodic or aperiodic. The radiation may have a target wavelength and / or wavelength range, target intensity, and / or other characteristics. The target wavelength and / or wavelength range, target intensity, etc., may be input and / or selected by the user, or determined by the system (e.g., Figure 3 System 10 shown in the figure Figure 11 The computer system (CS) shown is determined based on previous measurement data and / or otherwise. In some embodiments, radiation includes light and / or other radiation. In some embodiments, light includes visible light, infrared light, near-infrared light, and / or other light. In some embodiments, radiation can be any radiation suitable for image-based measurements.

[0078] Radiation can be generated by a radiation source (e.g., in...) Figure 3The radiation is generated by source 2 (shown in the diagram and described above) and / or other components. In some embodiments, radiation may be directed by a radiation source (e.g., through one or more lenses, modulators, and / or other components) to a measurement mark, a sub-part of a measurement mark (e.g., a portion smaller than the whole), multiple measurement marks, and / or otherwise directed onto a substrate. In some embodiments, the measurement mark may be substantially stationary during irradiation, a radiation sensor generates a measurement signal, an image of the measurement mark is generated based on the measurement signal and / or other information, and / or other operations are performed. In some embodiments, for example, radiation may be scanned across the measurement mark. Scanning may include rasterizing the radiation on the measurement mark to irradiate different portions of the measurement mark at different times. In some embodiments, characteristics of the radiation (e.g., wavelength, intensity, etc.) may be varied by the radiation source over time (whether in stationary or scanned mode). This may generate and / or supplement time-varying radiation for analysis. This may also facilitate the analysis of individual portions of a feature, comparison of one portion of a feature with another portion and / or other features, and / or other analyses.

[0079] Operation 604 includes generating a measurement signal based on diffracted radiation and / or other information received from the measurement mark. The measurement mark may be covered by a non-planar layer of a patterned substrate that deforms the diffracted radiation. The non-planar layer includes a top surface having one or more regions that are not parallel to the layer in the patterned substrate. In some embodiments, the non-planar layer includes, for example, locally tilted or disc-shaped recesses. As a possible example, the non-planar layer may be a resist layer with a non-uniform or undulating top surface.

[0080] Operation 604 includes detecting reflected and / or transmitted diffracted radiation from the measurement mark via a non-planar layer. For example, some or all of the diffracted radiation from the measurement mark may be deformed by the non-planar layer. The deformed diffracted radiation includes radiation that has been moved from an expected location to an alternative location relative to one or more components of the radiation sensor (e.g., as described herein). In some embodiments, the measurement signal includes alignment and / or overlap position information for the layer, non-planar layer, and / or other layers in which the measurement mark is formed.

[0081] Measurement signals include measurement information related to measurement marks. For example, measurement signals may include alignment measurement information, overlap measurement information, and / or other measurement signals. Measurement signals may be generated by a radiation sensor (e.g., such as...). Figure 3 Sensor detector 4 shown in the figure Figure 9The radiation sensor (such as sensor 990 shown) and / or other components generate the signal. The radiation sensor can be operatively coupled to a radiation source and / or other components. In some embodiments, the radiation sensor includes an imaging sensor. In some embodiments, the imaging sensor may include, for example, a camera and / or other components. The measurement signal may include, for example, an image, and / or may take other imaging-related forms.

[0082] In operation 604, detecting such radiation includes detecting phase shifts and / or intensity (amplitude) in the (diffracted) radiation received from one or more geometric features of the measurement mark, and forming an image based on this information. One or more phase shifts and / or amplitudes correspond to one or more dimensions of the feature. For example, the phase shift and / or amplitude of diffracted radiation from one side of the feature differs from the phase shift and / or amplitude of diffracted radiation from the other side of the feature. Detecting one or more phase shifts and / or amplitudes (intensities) in the radiation from the measurement mark includes imaging local phase shifts (e.g., local phase increments) and / or amplitude variations corresponding to different portions of the measurement mark. For example, radiation from a specific region of the mark may include a sinusoidal waveform with a specific phase and / or amplitude. Radiation from different regions of the mark may also include sinusoidal waveforms, but with different phases and / or amplitudes. Detecting radiation also includes measuring phase differences and / or amplitude differences in radiation of different diffraction orders. Any and / or all of this information may be used to form one or more corresponding images.

[0083] The measurement signal includes an electronic signal representing and / or otherwise corresponding to diffracted radiation from the measurement mark, which can be used to form an image. The measurement signal may indicate overlap values ​​of one or more layers, such as alignment values ​​and / or other information. Generating the measurement signal includes sensing the diffracted radiation and converting the sensed radiation into an electronic signal and / or an image. In some embodiments, generating the measurement signal includes sensing different portions of radiation from different portions and / or different geometries (e.g., different portions of a grating, different gratings in different layers, etc.) of the measurement mark and combining the different portions of the sensed radiation to form the measurement signal and / or image. This sensing and conversion can be performed by a radiation sensor detector 4 ( Figure 3 ), Sensor 990 ( Figure 9 ) and / or Figure 3 and Figure 11 The processor PRO shown in the diagram performs the same and / or identical components and / or other components.

[0084] In some embodiments, the image includes an intensity-modulated pattern, such as a one-dimensional or multi-dimensional interference pattern. The intensity-modulated pattern can be used to determine alignment, overlap, and / or other parameters as described herein. The pattern can be generated based on radiation diffracted by measurement markers (e.g., marker 30 shown in the figures). For example, it can be generated by a radiation sensor (e.g., Figure 3 Sensor detector 4 shown in the figure Figure 9 The radiation received by the sensor 990 shown includes diffracted radiation. The radiation sensor (and / or one or more processors PRO of the radiation sensor — see [link]). Figure 3 and Figure 11 The sensor is configured to generate a measurement signal comprising an intensity-modulated pattern. In the intensity-modulated pattern, darker and brighter lines may extend across the image at an angle (including horizontally or vertically). Intensity modulation includes variations in the intensity of radiation reflected by marker 30 and received across the grating by sensor detector 4 and / or sensor 990. In the image, intensity modulation can be illustrated by variations in how dark or bright the darker and brighter lines are. The intensity-modulated pattern may comprise a one-dimensional, two-dimensional, or more-dimensional pattern. In some embodiments, the radiation sensor is configured such that the intensity-modulated pattern for diffracted radiation comprises an interference pattern generated based on diffracted radiation from different portions of a measurement marker, two separate measurement markers, and / or other measurement marker configurations.

[0085] At operation 606, an image, or one or more images, is used to determine the local signal intensity of the measurement signal. At operation 608, the position of the measurement marker is determined based on the local signal intensity and / or other information. At operation 610, alignment and / or overlap can be determined and / or corrected, and / or other operations can be performed. Operations 606, 608, and / or 610 can be performed by one or more processors PRO (see...). Figure 3 , Figure 11 The process is executed by one or more processors operatively coupled to a radiation sensor and / or radiation source and / or other components.

[0086] In some embodiments, one or more processors are configured such that determining the local signal intensity of a measurement signal based on an image includes determining the local intensity of one or more pixels in the image and comparing the local intensity with a nominal intensity. In some embodiments, determining the local signal intensity of a measurement signal based on an image includes determining the signal intensity of one or more colors and / or polarizations to monitor resonances in the spectrum of diffracted radiation. In some embodiments, one or more processors are configured such that determining the local signal intensity of a measurement signal based on an image includes determining local contrast variations in the image to determine in-focus or out-of-focus portions of the image. In some embodiments, one or more processors are configured such that determining the local signal intensity of a measurement signal based on an image includes determining the gradient of local intensity and / or the gradient of local resonances in the spectrum of diffracted radiation, and / or determining the gradient of local image contrast. In some embodiments, one or more processors are configured such that determining the local signal intensity of a measurement signal based on an image includes associating variations in local signal intensity, variations in intensity, and / or variations in contrast with the curvature of a non-planar layer covering the measurement mark, and / or other operations. In some embodiments, one or more processors PRO are configured such that determining the location of a measurement marker includes determining the thickness profile of a non-planar layer covering the measurement marker based on local signal strength (e.g., through one of the operations described above), and determining the location of the measurement marker based on the thickness profile.

[0087] For example, one or more processors may be configured to determine the alignment and / or overlap of layers in a patterned substrate and / or nonplanar layers covering the measurement marks based on local signal strength and / or the position of measurement marks. In some embodiments, one or more processors are configured to facilitate the correction of the alignment and / or overlap of layers in a patterned substrate and / or nonplanar layers covering the measurement marks based on local signal strength and / or the position of measurement marks. This may include making a determination about the position as described above, and then controlling... Figure 3 System 10 shown in the figure Figure 9 The system 900 shown herein includes one or more components to make changes to one or more semiconductor manufacturing process parameters, machine setpoints, design changes, etc., so as to align and / or overlap within a certain process specification.

[0088] In some embodiments, one or more processors are configured to determine local phase changes in the diffracted radiation and to facilitate correction of overlap and / or alignment based on these local phase changes. The correction may also be based on: the local intensity of one or more pixels in the image; local contrast changes in the image; local intensity gradients and / or local resonance gradients in the spectrum of the diffracted radiation, and / or gradients of local image contrast; and / or other information. In some embodiments, facilitating correction of overlap and / or alignment based on local phase changes includes correcting for magnification errors, for example, caused by the curvature of a non-planar layer (e.g., a resist layer) covering the mark.

[0089] Figures 7 to 11 Several examples of the various components and / or operations described above are provided.

[0090] Figure 7 The figure illustrates a nonplanar layer 700 of a measurement mark 30 in layer 702 covering semiconductor structure 704. The nonplanar layer 700 may have a non-uniform or undulating top surface 720. Layer 700 may be, for example, a resist layer and / or other nonplanar layers. The nonplanar layer 700 includes a top surface 720 having one or more regions 710 that are not parallel to the patterned substrate of layer 702. In some embodiments, regions 710 include locally tilted (e.g., small segments tilted in one or another direction relative to layer 702 and / or mark 30) or disk-shaped recesses (e.g., shaped as a disk or cup, etc.), and / or other nonplanar features. As described herein, even though the nonplanar layer 700 distorts diffraction radiation, a measurement signal can be generated based on diffraction radiation received from the measurement mark 30.

[0091] Figure 8 The figure illustrates how deformed diffraction radiation 800 (in this example, 0th, +1st, and -1st order diffraction radiation) can reduce the measurement accuracy of an interferometer-based measurement system 802 and / or render such a system completely incapable of measurement. For example, as Figure 8 As shown in view 801, deformed diffracted radiation includes radiation that has been bent or moved from an expected position to an alternative position relative to one or more components of the radiation sensor. In this example, system 802 includes an interferometer with axis 803 and (positive) lens 860 and / or other components. System 802 includes a radiation source 810 configured to generate radiation 820, which is guided by point reflector 830 onto measurement marker 30 in layer 702. Other arrangements and / or components are contemplated. Figure 8 In (view 801), from Figure 7 The non-planar layer 700 is again covered on the semiconductor structure (e.g., Figure 7Measurement marks 30 in layer 702 of structure 704 shown in the diagram. Layer 700 may be, for example, a resist layer and / or other non-planar layers. Non-planar layer 700 includes a top surface having a tilted region 710 that is not parallel to the patterned substrate layer 702 (e.g., Figure 7 The top surface 720 is shown in the figure.

[0092] In the interferometer-based alignment system 802, if the amount of non-planarity (e.g., tilt in this example) in layer 700 becomes too large, the resist-covered measurement markers 30 cannot be used for alignment and / or other measurement operations. Diffraction orders (the 0th, +1st, and -1st orders of the radiation diffracted by the measurement markers 30 in this example) can propagate through layer 700 and to the alignment sensor 850, exceeding the pattern-matching capability of the interferometric diffraction orders. The diffraction orders are shifted from the center (e.g., axis 803) of the pupil plane in system 802 (typically asymmetrical, such as...). Figure 8 (See the diagram below) (see the different curvatures in the radiation lines between the resist layer 700 and the pupil plane 860). Therefore, an interferometer-based system cannot form the interferograms needed to determine alignment and / or other parameters. For example, a self-referenced interferometer may not be able to superimpose diffraction orders, and / or the diffraction orders may be shifted such that they cannot pass through the system's pupil filter. Figure 8 View 851 of system 802 (now shown with lens 861 and pupil 862) illustrates how the +1 and -1 diffraction orders of radiation would be blocked by pupil 862.

[0093] Figure 9 The figure illustrates an image-based measurement system 900 (such as one or more of those described herein) configured to interfere with diffraction orders via projection 902. Figure 8 In the middle, radiation 820 is guided onto the measurement mark 30 by the point reflector 830. The non-planar layer 700 again covers the semiconductor structure (e.g., Figure 7 Measurement mark 30 in structure 704 shown in the figure. Figure 9 The diagram also illustrates two example lenses 920 and 922, an object plane 950, a pupil plane 860, multiple focal lengths f, and an image-based measurement sensor 990 (e.g., a camera). System 900 interferes with the diffraction order through projection. Therefore, it is irrelevant whether the diffraction order is shifted 975 to different positions in the pupil plane 860, as long as the diffraction order is re-imaged on the image-based measurement sensor 990. As described above, this is because an image of the diffraction pattern is still formed, from which alignment and / or other measurements can be performed. The pattern itself may be asymmetric, or shifted by non-planar layers, and / or may even include components related to magnification errors, but the image of the pattern can still be analyzed for measurement purposes.

[0094] In this example, measurement mark 30 ( Figure 8 , Figure 7 (etc.) includes gratings in one or more layers of a patterned substrate. For example, the gratings may be formed from solid resist pillars, bars, vias, and / or other features. Measurement marks 30 may be sensitive to changes in processing during the patterning process (e.g., optical aberrations, focus variations, dose variations, etc. in a photolithography projection apparatus, such that process changes manifest as changes in measurement marks 30). Therefore, measurement data from measurement marks 30 can be used to determine alignment, overlap, and / or other values, and / or based on these alignment, overlap, and / or other values ​​to determine adjustments (e.g., corrections) for one or more manufacturing processes, and / or as a basis for making actual adjustments. Again, note that in this example, measurement marks 30 may represent multiple layers comprising multiple measurement marks.

[0095] In this example, system 900 includes an imaging sensor such as a camera, one or more processors PRO (see processors PRO illustrated in other figures) and / or other components. For example, the camera and / or some other imaging sensor can be configured to generate a measurement signal including image 951. One or more processors PRO can be configured to determine alignment and / or overlap values ​​based on image 951 and / or other information. In this example, image 951 includes an intensity-modulated pattern 952, such as a one-dimensional or multi-dimensional interference pattern. The intensity-modulated pattern 952 can be used to determine alignment, overlap, and / or other parameters. This can be based on diffraction by measurement marker 30 and by (tilted) region 710 (… Figure 9 , Figure 8 , Figure 7 The pattern 1052 is generated by deformed radiation. In the intensity-modulated pattern 952, darker and lighter lines extend vertically across image 951. Intensity modulation includes variations in the intensity of radiation reflected by marker 30 and received by sensor 990 across marker 30 (e.g., a grating). In image 951, intensity modulation is illustrated by variations in how dark or light the darker and lighter lines are. Image 951 and / or pattern 952 represent phase shifts and / or intensity (amplitude) in the (diffracted) radiation received from one or more geometric features of measuring marker 30. One or more phases and / or amplitudes correspond to one or more dimensions of the feature, but may or may not be symmetrical across pattern 952. For example, tilted region 710 ( Figure 9 , Figure 8 , Figure 7 It can cause different amounts of deformation in diffraction radiation.

[0096] The processor PRO uses image 951 and / or one or more other images to determine the local signal intensity of the measurement signal. The position of the measurement mark 30 is determined based on the local signal intensity and / or other information. Alignment and / or overlap can be determined and / or corrected based on this position, and / or other operations can be performed based on this position.

[0097] In some embodiments, one or more processors PRO are configured such that determining the local signal intensity of a measurement signal based on image 951 includes: determining the local intensity of one or more pixels in image 951 (defined in this example by a grid 980 spanning a portion of image 951), and comparing the local intensity with a nominal intensity. In some embodiments, determining the local signal intensity of a measurement signal based on an image includes: determining the signal intensity of one or more colors and / or polarizations to monitor resonances in the spectrum of diffracted radiation. In some embodiments, one or more processors PRO are configured such that determining the local signal intensity of a measurement signal based on an image includes: determining local contrast variations in image 951 to determine in-focus or out-of-focus portions of the image. In some embodiments, one or more processors PRO are configured such that determining the local signal intensity of a measurement signal based on image 951 includes: determining the gradient of local intensity and / or the gradient of local resonances in the spectrum of diffracted radiation, and / or determining the gradient of local image contrast. In some embodiments, one or more processors PRO are configured such that determining the local signal intensity of the measurement signal based on image 951 includes: associating changes in local signal intensity, changes in intensity, and / or changes in contrast with the curvature of the non-planar layer covering the measurement mark 30, and / or other operations. In some embodiments, one or more processors PRO are configured such that determining the position of the measurement mark 30 includes: determining the thickness profile of the non-planar layer covering the measurement mark 30 based on the local signal intensity (e.g., determined by one of the above operations), and determining the position of the measurement mark 30 based on the thickness profile.

[0098] In other words, when a nonplanar layer or surface is present in the semiconductor structure, system 900 is configured to use local signal intensity to determine and / or correct the alignment of measurement mark 30. Local signal intensity can be obtained in various ways (as described above), including monitoring the intensity of each (group of) pixels in image 951 and comparing that intensity to the nominal intensity of mark 30. Multiple colors / polarizations can be combined to monitor signal intensity resonance to make other underlying causes that may lead to intensity variations more robust. The measurement results can be combined with local contrast variations to identify in-focus / out-of-focus portions in image 951. The gradients in the above parameters are directly related to the curvature of the nonplanar surface. For example, local phase variations can be used to correct magnification errors, such as those caused by the curvature of the resist. This can be applied to bright-field or dark-field microscopy.

[0099] Figure 10 The figure illustrates an example image 1020 illustrating the local signal strength of a measurement signal that, according to an embodiment, can be used (e.g., by one or more processors PRO described herein) to determine the local signal strength of a measurement signal (such that the position of a measurement marker can be determined based on the local signal strength, and alignment and / or overlap can be determined and / or other operations can be performed based on that position). This image illustrates the local signal strength of various potential indicators that can be used (from...). Figure 10 The intensity of the shading / color in the image is shown as a systematic variation. Image 1020 illustrates the local signal intensity of the -1st order diffraction radiation from a measurement mark (e.g., mark 30 described above). In image 1020, higher local intensities (or signal intensities) are represented by darker (e.g., darker) colors. Analyzing these local signal intensities using one or more of the techniques described above helps determine the location of the measurement mark. For example, in image 1020, the local intensity tends to be higher on the left side of the image, which may indicate that a tilted resist covers the measurement mark in that area. The amount of tilt (or the thickness profile and / or other characteristics of the resist) can be determined based on differences in signal intensity (or color / intensity) and then used to analyze the diffraction radiation from the measurement mark, even if the diffraction radiation is deformed.

[0100] return Figure 6 In some embodiments, operation 610 includes determining adjustments to the semiconductor device fabrication process. In some embodiments, operation 610 includes determining one or more semiconductor device fabrication process parameters. One or more semiconductor device fabrication process parameters may be determined based on one or more detected phase and / or amplitude changes, alignment values ​​indicated by measurement signals, overlap values ​​indicated by measurement signals, and / or other information. One or more parameters may include parameters of radiation (radiation used to determine alignment and / or overlap), alignment and / or overlap check locations on layers of the semiconductor device structure, alignment values, overlap values, and / or other parameters. In some embodiments, process parameters may be broadly interpreted to include stage position, mask design, measurement mark design, semiconductor device design, intensity of radiation (for exposing resist, etc.), angle of incidence of radiation (for exposing resist, etc.), wavelength of radiation (for exposing resist, etc.), pupil size and / or shape, resist material, and / or other parameters.

[0101] For example, parameters used to determine alignment and / or overlap of radiation may include the wavelength, intensity, angle of incidence, and / or other parameters of the radiation. These parameters can be adjusted to better measure features with a particular shape, enhance the intensity of reflected radiation, increase and / or otherwise enhance (e.g., maximize) the phase shift and / or amplitude of reflected radiation from one region of the feature to the next, and / or for other purposes. This can enable and / or enhance the detection of finer deviations, make phase shifts and / or amplitudes easier to detect, and / or have other advantages.

[0102] In some embodiments, operation 610 includes: determining process adjustments based on one or more determined semiconductor device manufacturing process parameters, and adjusting semiconductor device manufacturing equipment and / or other operations based on the determined adjustments. For example, photolithography exposure can be corrected based on measured alignment and / or overlap values. As another example, if the determined alignment and / or overlap values ​​are not within process tolerances, the misalignment may be caused by one or more manufacturing processes whose process parameters have drifted and / or otherwise changed, causing the processes to no longer produce acceptable devices (e.g., overlap measurements may violate an acceptability threshold). One or more new or adjusted process parameters can be determined based on overlap determination. The new or adjusted process parameters can be configured to cause the manufacturing process to produce acceptable devices again. For example, the new or adjusted process parameters can cause previously unacceptable alignment and / or overlap values ​​to be adjusted back to an acceptable range. The new or adjusted process parameters can be compared with existing parameters for a given process. If a discrepancy exists, it can be used to determine adjustments to the equipment used to produce the device (e.g., parameter "x" should be increased / decreased / changed to match a new or adjusted version of parameter "x" determined as part of operation 610). In some embodiments, operation 610 may include (e.g., based on the determined process parameters) electronically adjusting the equipment. Electronically adjusting the equipment may include, for example, sending electronic signals and / or other communications to the equipment that cause changes in the equipment. Electronic adjustment may include, for example, changing settings and / or other adjustments on the equipment.

[0103] Figure 11This is a diagram of an example computer system CS that can be used for one or more 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 main memory MM (such as random access memory (flush memory) or other dynamic memory), which is 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 further includes a read-only memory (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 disk or optical disk, is provided and connected to the bus BS for storing information and instructions.

[0104] The computer system CS can be connected via a bus BS to a display DS for displaying information to the computer user, such as a cathode ray tube (CRT), flat panel display, or touch panel display. Input devices ID, including alphanumeric keys and other keys, are connected to the bus BS for communicating information and command selections to the processor PRO. Another type of user input device is a cursor controller CC (such as a mouse, trackball, or arrow keys) for communicating directional 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. Touch panel (screen) displays can also be used as input devices.

[0105] In some embodiments, portions of one or more methods may be executed by a computer system CS in response to a processor PRO for executing one or more sequences of instructions contained in main memory MM. Such instructions may be read into main memory MM from another computer-readable medium, such as a storage device SD. Execution of the sequence of instructions contained in main memory MM causes the processor PRO to perform process steps (operations). In a multiprocessor arrangement, one or more processors may also be used to execute the sequence of instructions contained in main memory MM. In some embodiments, hardwired circuitry may be used in place of or in combination with software instructions. Therefore, this specification is not limited to any particular combination of hardware circuitry and software.

[0106] The terms "computer-readable medium" or "machine-readable medium" refer to any medium that participates in providing instructions to a processor (PRO) for execution. Such media can take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical discs or magnetic disks, such as storage devices (SDs). Volatile media include dynamic memory, such as main memory (MMs). Transmission media include coaxial cables, copper wires, and optical fibers, including wires containing a bus (BS). Transmission media can also take the form of sound waves or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non-transitory, such as floppy disks, floppy disks, hard disks, magnetic tapes, any other magnetic media (CD-ROM, DVD), any other optical media, punched cards, paper tape, any other physical media with a perforated pattern, RAM, PROM, and EPROM, FLASH-EPROM, any other memory chip, or cassette memory. Non-transitory computer-readable media can have instructions recorded thereon. These instructions, when executed by a computer, can perform any of the described operations. For example, a temporary computer-readable medium may include a carrier wave or other means of propagating electromagnetic signals.

[0107] Various forms of computer-readable media can be used to carry one or more sequences of instructions to the processor PRO for execution. For example, instructions may initially be carried on the disk of a remote computer. The remote computer may load the instructions into its dynamic memory and transmit them over a network. The computer system CS may receive data and place it on the bus BS. The bus BS carries the data to the main memory MM, and the processor PRO fetches and executes the instructions from the main memory 106. Instructions received by the main memory MM may optionally be stored on the storage device SD before or after execution by the processor PRO.

[0108] The computer system CS may also include a communication interface CI coupled to a bus BS. The communication interface CI provides bidirectional data communication to a network link NDL connected to a local network LAN. For example, the communication interface CI may be an Integrated Services Digital Network (ISDN) card or a modem to provide data communication connectivity. As another example, the communication interface CI may be a local area network (LAN) card for providing data communication connectivity to a compatible LAN. Wireless links may also be implemented. In any such implementation, the communication interface CI transmits and receives electrical, electromagnetic, or optical signals carrying digital data streams representing various types of information.

[0109] A network link (NDL) typically provides data communication to other data devices via one or more networks. For example, a network link (NDL) can provide a connection to a host computer (HC) via a local area network (LAN). This can include providing data communication services via the global packet data communication network commonly referred to as the "Internet." A LAN (Internet) can use electrical, electromagnetic, or optical signals to carry digital data streams. Signals through various networks and on the network data link (NDL) and through the communication interface (CI) (which transmits digital data to and from computer system CS and 1700) are exemplary forms of carriers for transporting information.

[0110] Computer system CS can send and receive messages, including program code, via a network, network data link (NDL), and communication interface (CI). In the Internet example, host HC can transmit request codes for an application via Internet (INT), network data link (NDL), local area network (LAN), and communication interface (CI). For example, such a downloaded application can provide all or part of the methods described herein. The received code can be executed by processor PRO upon receipt and / or stored in storage device SD or other non-volatile memory for later execution. In this way, computer system CS acquires application code in the form of a carrier wave.

[0111] Other embodiments of this system and method are disclosed in the following list of numbered entries:

[0112] 1. A measurement system comprising: a radiation sensor configured to generate a measurement signal based on diffracted radiation received from a measurement mark in a layer of a patterned substrate, the measurement signal including an image; and one or more processors operatively coupled to the radiation sensor, the processors being configured to: determine a local signal intensity of the diffracted signal based on the image; and determine the position of the measurement mark based on the local signal intensity.

[0113] 2. The system according to item 1, wherein the radiation sensor includes an imaging sensor.

[0114] 3. The system according to any one of the preceding clauses, wherein the imaging sensor includes a camera.

[0115] 4. The system according to any one of the preceding clauses, wherein the measurement mark is covered by a non-planar layer of the patterned substrate that deforms the diffraction radiation.

[0116] 5. The system according to any one of the preceding clauses, wherein the non-planar layer includes locally tilted or disc-shaped depressions.

[0117] 6. The system according to any one of the preceding clauses, wherein determining the position of the measurement mark comprises: determining the thickness profile of the non-planar layer covering the measurement mark based on the local signal intensity, and determining the position of the measurement mark based on the thickness profile.

[0118] 7. The system according to any one of the preceding clauses, wherein the non-planar layer comprises a resist.

[0119] 8. The system according to any one of the preceding clauses, wherein the non-planar layer includes a top surface having one or more regions that are not parallel to the layer in the patterned substrate.

[0120] 9. The system according to any one of the preceding claims, wherein determining the local signal intensity of the measurement signal based on the image comprises: determining the local intensity of one or more pixels in the image and comparing the local intensity with a nominal intensity; determining the signal intensity of one or more colors and / or polarizations to monitor resonances in the spectrum of the diffracted radiation; determining local contrast variations in the image to determine in-focus or out-of-focus portions of the image; determining the gradient of local intensity and / or the gradient of local resonances in the spectrum of the diffracted radiation, and / or determining the gradient of local image contrast; and / or relating the changes in local signal intensity, the changes in intensity, and / or the changes in contrast to the curvature of a non-planar layer covering the measurement mark.

[0121] 10. The system according to any one of the preceding clauses, wherein the one or more processors are further configured to: determine the alignment and / or overlap of the layers in the patterned substrate and / or the alignment and / or overlap of the nonplanar layers covering the measurement marks based on the local signal strength and / or the position of the measurement marks.

[0122] 11. The system according to any one of the preceding clauses, wherein the one or more processors are further configured to: facilitate the alignment and / or overlap correction of the layers in the patterned substrate and / or facilitate the alignment and / or overlap correction of nonplanar layers covering the measurement marks, based on the local signal strength and / or the position of the measurement marks.

[0123] 12. The system according to any one of the preceding clauses, wherein the one or more processors are further configured to determine local phase changes in the diffracted radiation and to facilitate correction of overlap and / or alignment based on the local phase changes and: the local intensity of one or more pixels in the image compared to the nominal intensity; the local contrast change in the image; and / or the gradient of the local intensity and / or the gradient of the local resonance in the spectrum of the diffracted radiation, and / or the gradient of the local image contrast.

[0124] 13. The system according to any one of the preceding clauses, wherein facilitating the correction of overlap and / or alignment based on local phase changes includes correcting for amplification errors caused by the curvature of the non-planar layer covering the measurement marks.

[0125] 14. The system according to any one of the preceding clauses, wherein the image comprises an intensity-modulated pattern.

[0126] 15. The system according to any one of the preceding clauses, wherein the radiation sensor is configured such that the intensity of the diffracted radiation is modulated in a pattern comprising a one-dimensional or multi-dimensional interference pattern.

[0127] 16. The system according to any one of the preceding clauses, wherein the measurement system is a dark field measurement system.

[0128] 17. The system according to any one of the preceding clauses, wherein the measurement system is a bright-field measurement system.

[0129] 18. The system according to any one of the preceding clauses, wherein the measurement mark is an aperiodic grating.

[0130] 19. The system according to any one of the preceding clauses, wherein the measurement mark is a periodic grating.

[0131] 20. The system according to any one of the preceding clauses further includes a radiation source operatively coupled to the one or more processors and the radiation sensor, the radiation source being configured to irradiate the measurement mark with radiation.

[0132] 21. A measurement method comprising: generating a measurement signal based on diffracted radiation received from a measurement mark in a layer of a patterned substrate using a radiation sensor, the measurement signal including an image; determining a local signal intensity of the measurement signal based on the image using one or more processors operatively coupled to the radiation sensor; and determining the position of the measurement mark based on the local signal intensity using the one or more processors.

[0133] 22. The method according to item 21, wherein the radiation sensor includes an imaging sensor.

[0134] 23. The method according to any one of the preceding clauses, wherein the imaging sensor includes a camera.

[0135] 24. The method according to any one of the preceding clauses, wherein the measurement mark is covered by a non-planar layer of the patterned substrate that deforms the diffraction radiation.

[0136] 25. The method according to any one of the preceding clauses, wherein the non-planar layer includes locally tilted or disc-shaped depressions.

[0137] 26. The method according to any one of the preceding clauses, wherein determining the position of the measurement mark comprises: determining the thickness profile of the non-planar layer covering the measurement mark based on the local signal intensity, and determining the position of the measurement mark based on the thickness profile.

[0138] 27. The method according to any one of the preceding clauses, wherein the non-planar layer comprises a resist.

[0139] 28. The method according to any one of the preceding clauses, wherein the non-planar layer includes a top surface having one or more regions that are not parallel to the layer in the patterned substrate.

[0140] 29. The method according to any one of the preceding clauses, wherein determining the local signal intensity of the measurement signal based on the image comprises: determining the local intensity of one or more pixels in the image and comparing the local intensity with a nominal intensity; determining the signal intensity of one or more colors and / or polarizations to monitor resonances in the spectrum of the diffracted radiation; determining local contrast variations in the image to determine in-focus or out-of-focus portions of the image; determining the gradient of local resonances and / or the gradient of local intensity in the spectrum of the diffracted radiation, and / or determining the gradient of local image contrast; and / or relating the changes in local signal intensity, the changes in intensity, and / or the changes in contrast to the curvature of a nonplanar layer covering the measurement mark.

[0141] 30. The method according to any one of the preceding clauses further comprises: using the one or more processors to determine the alignment and / or overlap of the layers in the patterned substrate and / or the alignment and / or overlap of the nonplanar layers covering the measurement marks, based on the local signal intensity and / or the position of the measurement marks.

[0142] 31. The method according to any one of the preceding clauses further comprises: using the one or more processors, based on the local signal strength and / or the position of the measurement mark, facilitating the correction of alignment and / or overlap of the layers in the patterned substrate and / or facilitating the correction of alignment and / or overlap of nonplanar layers covering the measurement mark.

[0143] 32. The method according to any one of the preceding clauses further comprises: determining local phase changes in the diffracted radiation using the one or more processors, and facilitating correction of overlap and / or alignment based on the local phase changes and: the local intensity of one or more pixels in the image compared to the nominal intensity; the local contrast change in the image; and / or the gradient of local resonances and / or the gradient of local intensity in the spectrum of the diffracted radiation, and / or the gradient of local image contrast.

[0144] 33. The method according to any one of the preceding clauses, wherein facilitating the correction of alignment and / or overlap based on local phase changes includes correcting for amplification errors caused by the curvature of the non-planar layer covering the mark.

[0145] 34. The method according to any one of the preceding clauses, wherein the image comprises an intensity-modulated pattern.

[0146] 35. The method according to any one of the preceding clauses, wherein the radiation sensor is configured such that the intensity of the diffracted radiation is modulated in a pattern comprising a one-dimensional or multi-dimensional interference pattern.

[0147] 36. The method according to any one of the preceding clauses, wherein the radiation sensor and the one or more processors are part of a dark field measurement system.

[0148] 37. The method according to any one of the preceding clauses, wherein the radiation sensor and the one or more processors are part of a bright-field measurement system.

[0149] 38. The method according to any one of the preceding clauses, wherein the measurement mark is an aperiodic grating.

[0150] 39. The method according to any one of the preceding clauses, wherein the measurement mark is a periodic grating.

[0151] 40. The method according to any one of the preceding clauses further comprises: irradiating the measurement mark with radiation using a radiation source operatively coupled to the one or more processors and the radiation sensor.

[0152] process.

[0153] The concepts disclosed herein can be associated with any general measurement and / or imaging system used for measuring and / or imaging subwavelength characteristics, and can be particularly useful for emerging imaging techniques capable of producing increasingly shorter wavelengths.

[0154] While the concepts disclosed herein can be used for measurement and / or imaging on substrates such as silicon wafers, it should be understood that the disclosed concepts can be used with any type of measurement and / or imaging system, such as a measurement and / or imaging system for measuring and / or imaging on substrates other than silicon wafers. Furthermore, combinations and sub-combinations of the disclosed elements may include individual embodiments.

[0155] The foregoing description is intended to be exemplary and not restrictive. Therefore, those skilled in the art will understand that modifications can be made as described without departing from the scope of the appended claims.

Claims

1. A measurement system, comprising: A radiation sensor configured to generate a measurement signal based on diffracted radiation received from measurement marks in a layer of a patterned substrate, the measurement signal including an image; and One or more processors, operatively coupled to the radiation sensor, wherein the one or more processors are configured to: The local signal intensity of the measurement signal is determined based on the image; and The position of the measurement mark is determined based on the local signal strength.

2. The measurement system according to claim 1, wherein, The radiation sensor includes an imaging sensor.

3. The measurement system according to claim 2, wherein, The imaging sensor includes a camera.

4. The measurement system according to any one of claims 1 to 3, wherein, The measurement marks are covered by a non-planar layer of the patterned substrate that deforms the diffraction radiation.

5. The measurement system according to claim 4, wherein, The non-planar layer includes locally tilted or disc-shaped depressions.

6. The measurement system according to claim 4 or 5, wherein, Determining the location of the measurement mark includes: determining the thickness profile of the non-planar layer covering the measurement mark based on the local signal intensity, and determining the location of the measurement mark based on the thickness profile.

7. The measurement system according to any one of claims 4 to 6, wherein, The non-planar layer includes a photoresist.

8. The measurement system according to any one of claims 4 to 7, wherein, The non-planar layer includes a top surface having one or more regions that are not parallel to the layer in the patterned substrate.

9. The measurement system according to any one of claims 1 to 8, wherein, Determining the local signal intensity of the measurement signal based on the image includes: Determine the local intensity of one or more pixels in the image, and compare the local intensity with the nominal intensity; Determine the signal intensity of one or more colors and / or polarizations to monitor resonances in the spectrum of the diffracted radiation; Determine local contrast changes in the image to identify in-focus or out-of-focus portions of the image; Determine the gradient of local resonances and / or local intensity in the spectrum of the diffracted radiation, and / or determine the gradient of local image contrast; and / or The changes in local signal intensity, intensity, and / or contrast are correlated with the curvature of the non-planar layer covering the measurement markers.

10. The measurement system according to any one of claims 1 to 9, wherein, The one or more processors are further configured to: determine the alignment and / or overlap of the layers in the patterned substrate and / or the alignment and / or overlap of the nonplanar layers covering the measurement marks based on the local signal strength and / or the position of the measurement marks.

11. The measurement system according to any one of claims 1 to 10, wherein, The one or more processors are further configured to: facilitate the alignment and / or overlap correction of the layers in the patterned substrate and / or facilitate the alignment and / or overlap correction of nonplanar layers covering the measurement marks, based on the local signal strength and / or the position of the measurement marks.

12. The measurement system according to any one of claims 1 to 11, wherein, The one or more processors are further configured to: determine local phase changes in the diffraction radiation, and facilitate corrections for overlap and / or alignment based on the local phase changes and the following: The local intensity of one or more pixels in the image compared to the nominal intensity; Local contrast changes in the image; and / or The gradient of local resonances and / or the gradient of local intensity in the spectrum of the diffraction radiation, and / or the gradient of local image contrast.

13. The measurement system according to claim 12, wherein, Facilitating alignment and / or overlap correction based on local phase changes includes correcting amplification errors caused by the curvature of the non-planar layer covering the mark.

14. The measurement system according to any one of claims 1 to 13, wherein, The image includes a pattern whose intensity is modulated.

15. The measurement system according to claim 14, wherein, The radiation sensor is configured such that the intensity of the diffracted radiation is modulated in a pattern comprising a one-dimensional or multi-dimensional interference pattern.

Images