Overlay Metrology based on Fringe Patterns

Abstract

The measurement of overlay using a microscope-based sensor is described. This provides, among several advantages, the ability to measure alignment and overlay in a single system. The signal from the sensor is an intensity-modulated fringe pattern (e.g., an interference pattern). The sensor is configured to generate an intensity-modulated fringe pattern based on diffracted radiation received from a first metronome mark on a first layer of the pattern substrate and a second metronome mark on a second layer of the pattern substrate. The intensity-modulated fringe pattern is filtered for the expected fringe period. The overlay value is determined using the amplitude, phase, and / or other parameters of the fringe in the filtered fringe pattern.

Description

[Technical Field]

[0001]

[0001] This application claims priority to U.S. application US63 / 457,680 filed on April 6, 2023, and U.S. application US63 / 625,743 filed on January 26, 2024, both of which are incorporated herein by reference in their entirety.

[0002]

[0002] This description generally relates to overlay metrology based on fringe patterns. [Background technology]

[0003]

[0003] Lithography projection equipment can be used, for example, in the manufacture of integrated circuits (ICs). A patterning device (e.g., a mask) may include or provide patterns ("design layouts") corresponding to individual layers of the IC, and these patterns can be transferred to target portions (e.g., comprising one or more dies) on a substrate (e.g., a silicon wafer) coated with a layer of radiation-sensitive material ("resist") by methods such as irradiating the target portions through the patterns on the patterning device. Generally, a single substrate includes multiple adjacent target portions, and the pattern is transferred to these target portions continuously by the lithography projection equipment, one target portion at a time. In some types of lithography projection equipment, the pattern of the entire patterning device is transferred to one target portion in a single operation. Such equipment is generally referred to as a stepper. In alternative equipment, generally referred to as a step-and-scan device, the projection beam scans the patterning device in a given reference direction ("scan" direction), while simultaneously moving the substrate parallel or counterparallel to this reference direction. Different parts of the pattern of the patterning device are gradually transferred to a single target area.

[0004]

[0004] Before transferring the pattern from the patterning device to the substrate, the substrate may undergo various procedures such as priming, resist coating, and soft baking. After exposure, the substrate may undergo other procedures ("post-exposure procedures") such as post-exposure baking (PEB), development, hard baking, and measurement / inspection of the transferred pattern. This series of procedures is used as the basis for fabricating the individual layers of a device, such as an IC. The substrate may then undergo various processes such as etching, ion implantation (doping), metallization, oxidation, deposition, and chemical mechanical polishing, all of which are used to finish the individual layers of the device. If the device requires several layers, the entire procedure or a variation thereof is repeated for each layer. Ultimately, the device will be present in each target area on the substrate. These devices are then separated from each other by techniques such as dicing or sawing, so that the individual devices can be mounted on a carrier or connected to pins.

[0005]

[0005] Thus, manufacturing devices such as semiconductor devices typically involves processing a substrate (e.g., a semiconductor wafer) using several fabrication processes to form various features and multiple layers of the device. Such layers and features are typically manufactured and processed using, for example, deposition, lithography, etching, chemical mechanical polishing, and ion implantation. Multiple devices may be manufactured on multiple dies on a substrate and then separated into individual devices. This device manufacturing process can be considered a patterning process. A patterning process involves a patterning step such as photolithography and / or nanoimprint lithography, which uses a patterning device in a lithography apparatus to transfer a pattern on a patterning device to a substrate, and typically involves one or more related pattern processing steps, although optionally, such as resist development using a developer apparatus, baking of the substrate using a bake tool, etching using a pattern using an etching apparatus, and deposition.

[0006]

[0006] Lithography is a central step in the manufacturing of devices such as ICs, where patterns formed on a substrate define the functional elements of devices such as microprocessors and memory chips. Similar lithography techniques are also used in the formation of flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0007]

[0007] As semiconductor manufacturing processes continue to advance, the dimensions of functional elements have been continuously reduced, while the number of functional elements such as transistors per device has steadily increased over the decades, following a trend commonly known as "Moore's Law." At the current level of technology, layers of devices are manufactured using lithography projection equipment that projects a design layout onto a substrate using illumination from a deep ultraviolet or extreme ultraviolet illumination source, producing individual functional elements with dimensions far below 100 nm, i.e., less than half the wavelength of radiation from the illumination source (e.g., a 193 nm illumination source).

[0008]

[0008] This process, in which features having dimensions smaller than the classical resolution limit of a lithography projector are printed, is generally known as low-k1 lithography, by the resolution formula CD = k1 × λ / NA, where λ is the wavelength of radiation used, NA is the numerical aperture of the projection optical component in the lithography projector, CD is the "critical dimension" (generally the smallest feature size to be printed), and k1 is the empirical resolution coefficient. Generally, the smaller k1, the more difficult it becomes to reproduce a pattern on the substrate that resembles the shape and dimensions planned by the designer to achieve a particular electrical functionality and performance. To overcome these difficulties, elaborate fine-tuning steps are applied to the lithography projector, design layout, or patterning device. These steps include, but are not limited to, optimizing NA and optical coherence settings, customized lighting systems, using phase-shift patterning devices, optical proximity effect correction (OPC, sometimes referred to as "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement techniques" (RET). [Overview of the project]

[0009]

[0009] Measuring the overlay using a microscope-based sensor is described. This provides, among several advantages, the ability to measure the overlay with a single system. The signal from the sensor is an intensity-modulated fringe pattern (e.g., an interference pattern). The sensor is configured to generate an intensity-modulated fringe pattern based on diffracted radiation received from a first metronome mark on a first layer of the pattern substrate and a second metronome mark on a second layer of the pattern substrate. The intensity-modulated fringe pattern is filtered for the expected fringe period. The amplitude, phase, and / or other parameters of the fringe of the filtered fringe pattern are used to determine the overlay value.

[0010]

[0010] According to one embodiment, an overlay metrology system is provided. The overlay metrology system comprises a radiation sensor configured to generate a metrology signal based on diffracted radiation received from a first metrology mark on a first layer of a pattern substrate and a second metrology mark on a second layer of the pattern substrate. The metrology signal includes an intensity-modulated fringe pattern of diffracted radiation. The overlay metrology system comprises one or more processors operably coupled to the radiation sensor. The one or more processors are configured to filter the intensity-modulated fringe pattern for an expected fringe period, determine one or more parameters of the fringe of the intensity-modulated fringe pattern based on the filtered intensity-modulated fringe pattern, and determine an overlay value based on one or more parameters.

[0011]

[0011] In some embodiments, the second metronome mark is located above the first metronome mark.

[0012]

[0012] In some embodiments, the radiation sensor is configured such that the intensity-modulated fringe pattern of the diffracted radiation includes an interference pattern generated based on the diffracted radiation from a first metrology mark and a second metrology mark.

[0013]

[0013] In some embodiments, the first metronome mark of the first layer is shifted by a known bias amount relative to the second metronome mark.

[0014]

[0014] In some embodiments, the overlay metrology system comprises a radiation source operably coupled to one or more processors and radiation sensors. The radiation source is configured to irradiate first and second metrology marks with radiation.

[0015]

[0015] In some embodiments, the radiation from the radiation source is on-axis. In some embodiments, the radiation from the radiation source is off-axis. In some embodiments, the radiation from the radiation source is spatially incoherent. In some embodiments, the radiation from the radiation source is spatially coherent.

[0016]

[0016] In some embodiments, the first and second metronome marks include diffraction-based overlay metronome marks. In some embodiments, the first and second metronome marks include a grating. In some embodiments, the gratings have the same pitch. In some embodiments, the expected fringe period is determined based on the pitch. In some embodiments, the first and second metronome marks form a microdiffraction-based overlay (μDBO) target, and the first and second metronome marks include a grating in the first and second layers of the patterned substrate.

[0017]

[0017] In some embodiments, the intensity modulated fringe pattern includes one-dimensional or more interference patterns.

[0018]

[0018] In some embodiments, the radiation sensor is equipped with a camera.

[0019]

[0019] In some embodiments, one or more processors are configured such that determining one or more parameters of the fringe includes determining a first amplitude and a second amplitude of the fringe in the filtered intensity-modulated fringe pattern, and determining the overlay value is based on the difference in amplitudes, the sum of amplitudes, and a calibration coefficient.

[0020]

[0020] In some embodiments, the calibration coefficient is determined based on the radiation wavelength, the interlayer spacing between the first metronome mark and the second metronome mark, the ratio of diffraction efficiencies associated with the first metronome mark of the first layer and the second metronome mark of the second layer of the patterned substrate, the lattice pitch, and the lattice depth. In some embodiments, the calibration coefficient is determined by training a model associated with the overlay metronome system.

[0021]

[0021] In some embodiments, the first amplitude is associated with the positive bias of the first and second metrology marks relative to each other, and the second amplitude is associated with the negative bias of the first and second metrology marks relative to each other. In some embodiments, the first amplitude is associated with a segment of the metrology mark having a positive bias of the first and second metrology marks relative to each other, and the second amplitude is associated with a segment of the metrology mark having a negative bias of the first and second metrology marks relative to each other. In some embodiments, the first amplitude is associated with the positive bias of the entire first and second metrology marks relative to each other, and the second amplitude is associated with the negative bias of the entire first and second metrology marks relative to each other.

[0022]

[0022] In some embodiments, the determination of the overlay value is less affected by the surrounding structures of the first and second layers of the pattern substrate.

[0023]

[0023] In some embodiments, determining one or more parameters of the fringe includes determining the amplitude and average intensity of the fringes of the filtered intensity modulation fringe pattern, and determining the overlay value is configured to be based on the difference between the amplitude and the average intensity.

[0024]

[0024] In some embodiments, the overlay value is further determined based on the bias of the first and second metrology marks relative to each other.

[0025]

[0025] In some embodiments, the first amplitude is associated with segments of the metrologic mark having a positive bias of the first and second metrologic marks relative to each other, and the second amplitude is associated with segments of the metrologic mark having a negative bias of the first and second metrologic marks relative to each other. In some embodiments, the first amplitude is associated with the positive bias of the first and second metrologic marks as a whole relative to each other, and the second amplitude is associated with the negative bias of the first and second metrologic marks as a whole relative to each other.

[0026]

[0026] In some embodiments, the average strength of the fringe is susceptible to the surrounding structure of the first and second layers of the pattern substrate.

[0027]

[0027] In some embodiments, the first and second metronome marks are the same size as or larger than the C16 or C20μDBO marks.

[0028]

[0028] In some embodiments, determining the overlay value does not require a calibration coefficient.

[0029]

[0029] In some embodiments, the overlay metrology system is configured to first perform one or more of the above operations to determine a calibration coefficient, and then perform other operations using a metrology mark smaller than C16 or C20μDBO mark.

[0030]

[0030] In some embodiments, one or more processors are configured such that determining one or more parameters of the fringe includes determining the amplitude and phase of the fringe of the filtered intensity-modulated fringe pattern, and determining the overlay value is based on the amplitude and phase.

[0031]

[0031] In some embodiments, determining the phase includes determining the phase difference between (1) diffracted radiation received from the first corresponding upper and lower segments of the first and second metronome marks in the first and second layers of the pattern substrate and (2) diffracted radiation received from the second corresponding upper and lower segments of the first and second metronome marks. In some embodiments, the phase difference includes information indicating the mutual light intensity of the first and second metronome marks, and the overlay is determined at least partially based on the mutual light intensity.

[0032]

[0032] In some embodiments, the first and second corresponding upper and lower segments are spaced apart from each other by a known distance, and the overlay is determined at least partially based on the phase difference and the known distance.

[0033]

[0033] In some embodiments, the mutual light intensity is used by one or more processors to determine a calibration coefficient that associates the amplitude with the overlay value, and to determine the overlay based on the amplitude and the calibration coefficient. In some embodiments, determining the overlay value does not require a calibration coefficient.

[0034]

[0034] In some embodiments, determining the amplitude includes determining a first amplitude associated with segments of metrologic marks having a positive bias of the first and second metrologic marks relative to each other, and a second amplitude associated with segments of metrologic marks having a negative bias of the first and second metrologic marks relative to each other, and determining the phase includes determining a first phase associated with segments of metrologic marks having a positive bias, and a second phase associated with segments of metrologic marks having a negative bias.

[0035]

[0035] In some embodiments, one or more processors are configured to determine a complex amplitude based on first and second amplitudes and first and second phases, to determine the real part of the complex amplitude, and to determine an overlay based on the real part and positive and negative biases.

[0036]

[0036] In some embodiments, one or more processors are configured to determine scaling coefficients based on first and second amplitudes, to determine phase coefficients based on first and second phases, and to determine an overlay based on the scaling coefficients and phase coefficients. In some embodiments, determining an overlay based on the scaling coefficients and phase coefficients involves solving a system of two nonlinear equations, where each nonlinear equation is associated with the scaling coefficients and phase coefficients, and the two nonlinear equations have a common variable between them, including the overlay.

[0037]

[0037] In some embodiments, the metrology signal is configured to be used by one or more processors to coordinate the semiconductor device manufacturing process.

[0038]

[0038] According to another embodiment, a metrology method is provided which includes one or more of the above operations. [Brief explanation of the drawing]

[0039]

[0039] The above embodiments and other embodiments and features will become clear to those skilled in the art by examining the following description of specific embodiments in conjunction with the attached drawings.

[0040] [Figure 1]

[0040] A lithography apparatus according to one embodiment is schematically shown. [Figure 2]

[0041] A schematic diagram illustrates one embodiment of a lithographic cell or cluster according to one embodiment. [Figure 3]

[0042] An exemplary metrology system according to one embodiment is schematically illustrated. [Figure 4]

[0043] An exemplary metrologic technology according to one embodiment is schematically illustrated. [Figure 5]

[0044] This shows the relationship between the radioactive illumination spot and the metrology target of an inspection system according to one embodiment. [Figure 6]

[0045] An overlay metrology method according to one embodiment is shown. [Figure 7]

[0046] Another exemplary metrology system according to one embodiment is schematically illustrated. [Figure 8]

[0047] An example of a fringe pattern that may be used to determine the overlay according to one embodiment is shown. [Figure 9]

[0048] The first and second amplitudes of the fringe in a filtered intensity-modulated fringe pattern according to one embodiment are shown. [Figure 10]

[0049] This describes the determination of an overlay (e.g., an overlay value) based on the amplitude of a fringe pattern, such as the fringe pattern shown in Figure 9, according to one embodiment. [Figure 11]

[0050] This describes the determination of an overlay (e.g., an overlay value) based on the amplitude and phase of a fringe pattern, such as the fringe pattern shown in Figure 9, according to one embodiment. [Figure 12]

[0051] Metrology systems with different configurations are shown along with fringe patterns and associated images of different diffraction orders. [Figure 13]

[0052] This is a block diagram of an exemplary computer system according to one embodiment. [Modes for carrying out the invention]

[0041]

[0053] In semiconductor device manufacturing, determining an overlay typically involves determining the (relative) positions of different metronome marks on a metronome target, such as a diffraction-based overlay target, in different layers of the semiconductor device structure. To accommodate increasingly smaller node sizes and / or to use limited substrate area more efficiently, there is a need for increasingly smaller metronome (overlay, etc.) targets, multi-purpose targets (e.g., a single metronome target that can be used for both overlay and alignment), and / or other space-saving techniques. Smaller targets and / or targets that can be used for multiple purposes facilitate the need to reduce the number of targets, to place targets in a limited area field, to place targets closer to the substrate edge, and / or other advantages.

[0042]

[0054] Existing metronome systems often utilize separate sensors and metronome targets for overlay and alignment operations. Therefore, even when measuring the same mark, discrepancies can occur between the alignment position and the overlay, potentially leading to degraded on-product overlay (OPO) and / or other adverse effects. Furthermore, current overlay measurement solutions are susceptible to surrounding structures, requiring more surface area on the substrate for specific overlay targets and / or being highly sensitive to scattering from surrounding structures, making it difficult to position overlay targets on substrates surrounded by other structures. For example, the overlay target might be enlarged to allow the use of the region of interest within the target (surrounded by a buffer portion of the target separating the region of interest from other structures outside the target). Another example is positioning the overlay target at a certain distance from other structures on the substrate.

[0043]

[0055] In contrast to conventional systems, this system and method are configured to determine the overlay using a microscope-based sensor, allowing alignment and overlay to be determined in a single system, and enabling the use of the same physical target for alignment, overlay, and / or other metrological operations. This system and method may also use smaller marks and / or marks located relatively close to other structures within the substrate to determine the overlay.

[0044]

[0056] The system and method have these and other advantages because the signal from the sensor is an intensity-modulated fringe pattern (e.g., an interference pattern). The sensor is configured to generate an intensity-modulated fringe pattern based on diffracted radiation received from a first metronome mark on a first layer of a pattern substrate and a second metronome mark on a second layer of the pattern substrate (the first and second marks together constitute an overlay target). In the system and method, the intensity-modulated fringe pattern is filtered for the expected fringe period, and the overlay value is determined using the amplitude, phase, and / or other parameters of the fringe of the filtered fringe pattern. The system and method, as described herein, is more robust to the presence of adjacent structures in the substrate when determining the overlay compared to conventional systems because it determines the overlay using the amplitude and / or phase (or phase difference) of the fringe (instead of images and / or other data used in conventional overlay determination techniques, for example).

[0045]

[0057] As a brief introduction, the following description generally pertains to the manufacturing and patterning processes of semiconductor devices. More specifically, the following paragraphs describe some components of the system and / or related systems. As mentioned above, these systems and methods may be used, for example, for measuring overlays in semiconductor device manufacturing processes, or for other operations.

[0046]

[0058] While this specification may specifically refer to the measurement of semiconductor device overlays and the manufacture of integrated circuits (ICs), it should be understood that there are many other possible applications. For example, it may be used for measuring other parameters. It may be used in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memory, liquid crystal display panels, thin-film magnetic heads, etc. Those skilled in the art will understand that in the context of such alternative applications, the terms “reticle,” “wafer,” or “die” as used herein should be considered interchangeable with the more general terms “mask,” “substrate,” and “target portion,” respectively.

[0047]

[0059] The term “projection optics” should be interpreted broadly to encompass various types of optical systems, including, for example, refractive optics, reflective optics, apertures, and reflective-refractory optics. The term “projection optics” may also include components that operate collectively or individually, according to any of these design types, to guide, shape, or control the radiated projection beam. The term “projection optics” may include any optical component of a lithography projection apparatus, regardless of where that optical component is located in the optical path of the lithography projection apparatus. Projection optics may include optical components for shaping, adjusting, and / or projecting radiation from a radiation source before the radiation passes through a patterning device, and / or optical components for shaping, adjusting, and / or projecting radiation after the radiation has passed through a patterning device. Projection optics generally do not include the radiation source and patterning device.

[0048]

[0060] Figure 1 schematically illustrates one embodiment of a lithography apparatus LA. This apparatus comprises an illumination system (illuminator) IL configured to adjust a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a support structure (e.g., mask table) MT connected to a first positioner PM constructed to support a patterning device (e.g., mask) MA and configured to precisely position the patterning device according to certain parameters; a substrate table (e.g., wafer table) WT (e.g., WTa, WTb, or both) configured to hold a substrate (e.g., resist-coated wafer) W and connected to a second positioner PW configured to precisely position the substrate according to certain parameters; and a projection system (e.g., refractive projection lens system) PS configured to project the pattern applied to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (e.g., comprising one or more dies, often referred to as a field). The projection system is supported on a reference frame RF. As shown, the apparatus is of the transmissive type (e.g., using a transmissive mask). Alternatively, the device may be of the reflective type (for example, using a programmable mirror array or a reflective mask).

[0049]

[0061] The illuminator IL receives the radiation beam from the radiation source SO. The radiation source and the lithography apparatus may be separate entities, for example, when the radiation source is an excimer laser. In such cases, the radiation source is not considered to form part of the lithography apparatus, and the radiation beam is transmitted from the radiation source SO to the illuminator IL with the help of a beam delivery system BD, for example, equipped with a suitable guide mirror and / or beam expander. In other cases, for example, when the radiation source is a mercury lamp, the radiation source may be an integral part of the apparatus. The radiation source SO and the illuminator IL, together with the beam delivery system BD as needed, may be referred to as a radiation system.

[0050]

[0062] The illuminator IL may modify the beam intensity distribution. The illuminator may be positioned to limit the radial range of the emitted beam so that the intensity distribution is non-zero within the annular region of the pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL may be operable to limit the beam distribution in the pupil plane so that the intensity distribution is non-zero within a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the emitted beam in the pupil plane of the illuminator IL may be referred to as the illumination mode.

[0051]

[0063] The illuminator IL may include an adjuster AD configured to adjust the (angle / spatial) intensity distribution of the beam. Generally, at least the outer and / or inner radial ranges of the intensity distribution at the pupil plane of the illuminator (generally referred to as σ-outer and σ-inner, respectively) can be adjusted. The illuminator IL may be operable to change the angular distribution of the beam. For example, the illuminator may be operable to change the number and angular range of sectors at the pupil plane, where the intensity distribution is non-zero. Different illumination modes can be achieved by adjusting the beam intensity distribution at the pupil plane of the illuminator. For example, by limiting the radial and angular ranges of the intensity distribution at the pupil plane of the illuminator IL, the intensity distribution may have a multipolar distribution, such as a bipolar, quadrupole, or hexapole distribution. The desired illumination mode can be obtained, for example, by inserting an optical element that provides that illumination mode into the illuminator IL or by using a spatial light modulator.

[0052]

[0064] The illuminator IL may be operable to change the polarization of the beam, and may be operable to adjust the polarization using an adjuster AD. The polarization state of the radiated beam across the pupil plane of the illuminator IL may be referred to as the polarization mode. The use of different polarization modes may allow greater contrast to be achieved in the image formed on the substrate W. The radiated beam may be unpolarized. Alternatively, the illuminator may be configured to linearly polarize the radiated beam. The polarization direction of the radiated beam may vary across the pupil plane of the illuminator IL. The polarization direction of the radiation may differ in different regions of the pupil plane of the illuminator IL. The polarization state of the radiation may be selected depending on the illumination mode. In the case of a multi-pole illumination mode, the polarization of each pole of the radiated beam may be approximately perpendicular to the position vector of that pole on the pupil plane of the illuminator IL. For example, in the case of a bi-pole illumination mode, the radiation may be linearly polarized in a direction substantially perpendicular to the line that bisects the two opposing sectors of the two poles. The radiated beam may be polarized in one of two different orthogonal directions, which may be referred to as the X-polarized state and the Y-polarized state. In the case of a quadrupole illumination mode, the radiation in the sector of each pole may be linearly polarized in a direction substantially perpendicular to the line bisecting the sector. This polarization mode may be referred to as XY polarization. Similarly, in the case of a hexapole illumination mode, the radiation in the sector of each pole may be linearly polarized in a direction substantially perpendicular to the line bisecting the sector. This polarization mode may be referred to as TE polarization.

[0053]

[0065] Furthermore, an illuminator IL generally includes various other components such as an integrator IN and a capacitor CO. The lighting system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for inducing, shaping, or controlling radiation.

[0054]

[0066] Therefore, the illuminator provides a regulated radiant beam B having the desired uniformity and intensity distribution in its cross-section.

[0055]

[0067] The support structure MT supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithography apparatus, and other conditions such as whether the patterning device is held in a vacuum environment. The support structure may hold the patterning device using mechanical, vacuum, electrostatic, or other clamping techniques. The support structure may be, for example, a frame or a table, which may be fixed or movable as needed. The support structure may ensure that the patterning device is in a desired position relative to, for example, the projection system. The use of the terms “reticle” or “mask” may be considered synonymous with the more general term “patterning device.”

[0056]

[0068] The term "patterning device" should be interpreted broadly as any device that can be used to impart a pattern to a target portion of a substrate. In one embodiment, a patterning device is any device that can be used to create a pattern on a target portion of a substrate by imparting a pattern to the cross-section of a radiation beam. It should be noted that the pattern imparted to the radiation beam may not precisely correspond to the desired pattern on the target portion of the substrate, for example, if the pattern includes phase-shift features or so-called assist features. Generally, the pattern imparted to the radiation beam corresponds to a specific functional layer of a device, such as an integrated circuit, that is created on the target portion of the device.

[0057]

[0069] Patterning devices can be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well-known in lithography and include mask types such as binary masks, Levenson (alternating) phase-shift masks, halftone (attenuated) phase-shift masks, and various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect the incident radiation beam in a different direction. The tilted mirrors impart a pattern to the radiation beam reflected by the mirror matrix.

[0058]

[0070] The term “projection system” should be interpreted broadly to encompass any type of projection system, including refractive optical systems, reflective optical systems, reflector-refractor optical systems, magneto-optical systems, electromagnetic optical systems, and electrostatic optical systems, or any combination thereof, as appropriate in accordance with the exposure radiation used or other factors such as the use of immersion liquid or vacuum. The use of the term “projection lens” may be considered synonymous with the more general term “projection system.”

[0059]

[0071] The projection system PS may comprise multiple optical (e.g., lens) elements and may further comprise an adjustment mechanism configured to adjust one or more of these optical elements to correct aberrations (phase variations across the pupil plane of the entire field). To achieve this, the adjustment mechanism may be operable to manipulate one or more optical (e.g., lens) elements in the projection system PS in one or more different ways. The projection system may have a coordinate system, the optical axis of which extends in the z direction. The adjustment mechanism may be operable to perform any combination of the following: displacing one or more optical elements, tilting one or more optical elements, and / or deforming one or more optical elements. The displacement of an optical element may be in any direction (x, y, z, or a combination thereof). The tilt of an optical element typically moves it out of the plane perpendicular to the optical axis by rotating it about the x and / or y axes, but in the case of a non-rotationally symmetric aspherical optical element, rotation about the z axis may be used. The deformation of the optical element may include low-frequency shapes (e.g., astigmatism) and / or high-frequency shapes (e.g., free-form aspherical surfaces). The deformation of the optical element may 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. Generally, it would be impossible to adjust the projection system PS to correct apodization (transmission variation across the pupil plane). A transmission map of the projection system PS may be used when designing the patterning device (e.g., mask) MA of the lithography apparatus LA. Using computer lithography techniques, the patterning device MA may be designed to correct apodization at least partially.

[0060]

[0072] Lithography equipment may be of the type having two (dual stage) or more tables (e.g., two or more substrate tables WTa, WTb, two or more patterning device tables, e.g., substrate table WTa and table WTb under a projection system without a substrate, specialized for facilitating measurement and / or cleaning). In such a “multistage” machine, additional tables may be used in parallel, or preparation steps may be performed on one or more tables while one or more other tables are used for exposure at the same time. For example, alignment measurements may be performed using an alignment sensor AS, and / or level measurements (height, tilt, etc.) may be performed using a level sensor LS.

[0061]

[0073] During operation of the lithography apparatus, the radiant beam is regulated and supplied by the illumination system IL. The radiant beam B is incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a mask table) MT, and is patterned by the patterning device. After crossing the patterning device MA, the radiant beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. With the help of a second positioner PW and a position sensor IF (e.g., an interferometer device, a linear encoder, a 2D encoder, or a capacitive sensor), the substrate table WT can be precisely moved to position, for example, various target portions C within the path of the radiant beam B. Similarly, using a first positioner PM and another position sensor (not shown in Figure 1), the patterning device MA can be precisely positioned relative to the path of the radiant beam B, for example, after or during a machine search of a mask library. In general, the movement of the support structure MT can be achieved with the help of long-stroke modules (coarse positioning) and short-stroke modules (fine positioning) that form part of the first positioner PM. Similarly, the movement of the substrate table WT can be achieved using long-stroke modules and short-stroke modules 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 short-stroke actuators or may be fixed. The patterning device MA and the substrate W can be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2. The illustrated substrate alignment marks occupy dedicated target portions, but the substrate alignment marks may be located in the space between the target portions (these are known as scribe line alignment marks). Similarly, in situations where two or more dies are provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0062]

[0074] The illustrated apparatus can be used in at least one of the following modes: In step mode, the support structure MT and substrate table WT are kept essentially stationary, and simultaneously, the pattern applied to the projection beam is projected onto the target portion C in a single pass (i.e., single static exposure). Next, the substrate table WT is shifted in the X and / or Y directions to allow exposure of another target portion C. In step mode, the maximum size of the exposure field limits the size of the target portion C that is imaged during single static exposure. In scan mode, the support structure MT and substrate table WT are scanned synchronously, and simultaneously, the pattern applied to the radiation beam is projected onto the target portion C (i.e., single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure MT can be determined by the scaling (reduction) 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 (in the non-scanning direction) during single dynamic exposure, while the length of the scan operation determines the height of the target portion (in the scanning direction). In another mode, the support structure MT is kept essentially stationary, holding the programmable patterning device, and the pattern applied to the radiation beam is projected onto the target portion C simultaneously with the movement or scanning of the substrate table WT. In this mode, a pulsed radiation source is generally used, and the programmable patterning device is updated as needed after each movement of the substrate table WT or between consecutive radiation pulses during scanning. This operating mode can be readily applied to maskless lithography utilizing programmable patterning devices such as the type of programmable mirror array mentioned above.

[0063]

[0075] Combinations and / or variations of the above-mentioned usage modes, or entirely different usage modes, may also be used.

[0064]

[0076] The substrate may be processed before or after exposure with, for example, a track (typically a tool for coating a layer of resist onto the substrate and developing the exposed resist), a metronome tool, or an inspection tool. Where applicable, this disclosure may also apply to such and other substrate processing tools. Furthermore, the substrate may be processed multiple times, for example, to produce a multilayer IC, and therefore the term substrate may also refer to a substrate that already contains multiple processed layers.

[0065]

[0077] The terms “radiation” and “beam” as used in relation to lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation 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.

[0066]

[0078] The various patterns on or provided by a patterning device may have different process windows, i.e., spaces of processing variables under which the patterns are generated within the specifications. Examples of pattern specifications related to potential systematic defects include inspections for necking, line pullback, line thinning, CD, edge placement, overlap, resist top loss, resist undercut, and / or bridging. The process window of a pattern on a patterning device or in a particular area thereof may be obtained by merging (e.g., overlapping) the process windows of individual patterns. The boundary of a group of patterns' process windows comprises the boundaries of some of the individual patterns' process windows. In other words, these individual patterns limit the process window of that group of patterns.

[0067]

[0079] As shown in Figure 2, the lithography apparatus LA may form part of a lithographic cell LC, sometimes referred to as a lithocell or cluster, and the lithographic cell also includes equipment for performing pre-exposure and post-exposure processes on the substrate. Conventionally, this 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 cooling plates CH, and / or one or more bake plates BK. A substrate handler, i.e., a robot RO, takes one or more substrates from input / output ports I / O1 and I / O2, moves them between various process equipment, and delivers them to the loading bay LB of the lithography apparatus. These devices, often collectively referred to as tracks, are under the control of a track control unit TCU, the TCU itself is controlled by a monitoring and control system SCS, which in turn controls the lithography apparatus via a lithography control unit LACU. In this way, the various devices can be operated to maximize throughput and processing efficiency.

[0068]

[0080] To ensure that substrates exposed by a lithography apparatus are exposed accurately and consistently, and / or to monitor a patterning process (e.g., a device manufacturing process) that includes at least one pattern transfer step (e.g., a photolithography step), it is desirable to inspect the substrate or other objects to measure or determine one or more properties such as alignment, overlay (e.g., between structures in an overlying layer, or between structures within the same layer that are separately provided, e.g., by a double patterning process), line thickness, critical dimension (CD), focus offset, and material properties. Therefore, the manufacturing facility where the lithocell LC is located typically also includes a metrology system for measuring some or all of the substrates W (Figure 1) processed in the lithocell or other objects within the lithocell. The metrology system may be part of the lithocell LC, for example, part of the lithography apparatus LA (e.g., alignment sensor AS (Figure 1)).

[0069]

[0081] One or more measured parameters may include, for example, overlays between continuous layers formed in or on a patterned substrate, alignment, critical dimension (CD) (e.g., critical linewidth) of features formed in or on a patterned substrate, focus or focus error of a photolithography step, dose or dose error of a photolithography step, optical aberration of a photolithography step, etc. This measurement is often performed on a dedicated metronidatory target provided on the substrate. The measurement can be performed after resist development but before etching, after etching, after deposition, and / or at other points in time.

[0070]

[0082] Various techniques exist for measuring structures formed during a patterning process, including the use of scanning electron microscopes, image-based measurement tools, and / or various specialized tools. One form of specialized metrology tool is a high-speed, non-invasive method in which a radiation beam is directed onto a target on the substrate surface, and the properties of the scattered (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. This is sometimes referred to as diffraction-based metrology. One application of diffraction-based metrology is the measurement of overlays (as described below, for example).

[0071]

[0083] Thus, in device manufacturing processes (e.g., patterning or lithography processes), substrates or other objects may undergo various types of measurements during or after the process. Measurements may determine whether a particular substrate is defective, 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 device to the substrate), measure the performance of the process and equipment, or for other purposes. Examples of measurements include optical imaging (e.g., optical microscopy), non-imaging optical measurements (e.g., diffraction-based measurements such as the ASML YieldStar metrology tool and the ASML SMASH metrology system), mechanical measurements (e.g., stylus profiling, atomic force microscopy (AFM)), and / or non-optical imaging (e.g., scanning electron microscopy (SEM)).

[0072]

[0084] Metrology results may be provided directly or indirectly to the monitoring and control system (SCS). If an error is detected, adjustments may be made to the exposure of subsequent substrates and / or to the subsequent exposure of exposed substrates (especially if the inspection can be performed immediately and quickly enough to allow one or more other substrates in the same batch to still be exposed). Also, substrates that have already been exposed may be removed and reprocessed to improve yield or discarded, thereby avoiding further processing of substrates known to be defective. If defects are present only in certain target areas of a substrate, further exposure may be performed only on the target areas that meet the specifications. Other manufacturing process adjustments are also possible.

[0073]

[0085] A metronome system can be used to determine one or more properties of a substrate structure, and in particular, how one or more properties of different substrate structures change, or how different layers of the same substrate structure change layer by layer. The metronome system may be integrated into a lithography apparatus (LA) or lithocell (LC), or it may be a standalone device.

[0074]

[0086] To enable metrologic, one or more targets are often specially provided on the substrate. These targets may include overlay targets, such as alignment marks, and / or other targets. Typically, targets are specially designed and may include one or more periodic structures. For example, a target on a substrate may include one or more 1D periodic structures (e.g., geometric features such as grids) in one or more layers of the substrate, printed such that after development, the periodic structural features are formed by solid resist lines. Alternatively, a target may include one or more 2D periodic structures (e.g., grids) in one or more layers, printed such that after development, the periodic structures are formed by solid resist pillars or vias within the resist. Bars, pillars, or vias may be etched into the substrate (e.g., within one or more layers of the substrate).

[0075]

[0087] Figure 3 illustrates an exemplary inspection (metrology) system 10 that may be used to detect overlays, alignments, and / or other metrology operations. The inspection system 10 comprises a radiation source 2 that projects or irradiates radiation onto a substrate W. The substrate W may typically contain metrology targets 30, such as overlay targets, alignment marks, and / or other structures. The oriented radiation is passed to radiation sensors and / or other sensors, such as a spectrometer detector 4, which measure the spectrum (intensity as a function of wavelength) of specularly reflected and / or diffracted radiation, for example, as shown in the graph on the left side of Figure 4. The sensors may generate metrology signals that transmit overlay data, alignment data, and / or other data that characterize the reflected radiation. From this data, the structures or profiles that give rise to the detected spectrum may be reconstructed by one or more processors PRO (a generalized example of which is shown in Figure 4), or by other operations. Note that these are generalized examples. In many cases, the illumination of targets such as overlay targets and / or alignment marks is performed perpendicular to the target and / or mark, rather than at the angle shown in Figure 3.

[0076]

[0088] Similar to the lithography apparatus LA in Figure 1, one or more substrate tables (not shown in Figure 4) may be provided to hold the substrate W during metrologic operation. One or more substrate tables may be similar in form to or identical to the substrate table WT (WTa or WTb or both) in Figure 1. In examples where the inspection system 10 is integrated with the lithography apparatus, they may even be the same substrate table. Coarse and fine positioners may be provided and configured to precisely position the substrate relative to the measuring optical system. Various sensors and actuators are provided, for example, to acquire the position of a target portion of interest of the structure (e.g., an overlay target and / or alignment mark) and move it to a position below the objective lens. Typically, many measurements will be taken on the target portion of the structure at various locations across the substrate W. The substrate support may be moved in the X and Y directions to acquire various targets, and in the Z direction to obtain the desired position of the target portion relative to the focal point of the optical system. For example, when the optical system is actually substantially stationary (typically in the X and Y directions, but possibly also in the Z direction) and the substrate is moving, it is convenient to describe the operation by considering that the objective lens is brought to a different location relative to the substrate. In principle, if the relative positions of the substrate and the optical system are correct, it does not matter which of them is moving, or whether both are moving, or the combination of the rest of the optical system being stationary while part of the optical system is moving (e.g., in the Z direction and / or in the tilt direction) and the substrate is moving (e.g., in the X and Y directions, but optionally in the Z direction and / or in the tilt direction).

[0077]

[0089] In a typical metronidometry measurement, the target 30 on the substrate W may be a 1D diffraction grating, which is printed such that after development, the bars are formed of solid resist lines (which may be covered by a deposited layer) and / or other materials. Alternatively, the target 30 may be a 2D diffraction grating, which is printed such that after development, the grating is formed of solid resist pillars and / or other features within the resist. The bars, pillars, vias, and / or other features may be etched in or on the substrate (e.g., in one or more layers on the substrate), deposited on the substrate, covered by a deposited layer, and / or have other properties. The target 30 (e.g., bars, pillars, vias, etc.) may be sensitive to changes in processing during the patterning process (e.g., optical aberrations, focus changes, dose changes, etc. in a lithography projection device such as a projection system) so that process variations manifest as variations in the target 30. Therefore, measurement data from the target 30 may be used to determine and / or as a basis for making adjustments to one or more manufacturing processes. Note that in this example, target 30 may represent one or more layers containing one or more metronome targets.

[0078]

[0090] For example, measurement data from target 30 may indicate the overlay, alignment, and / or other information of the semiconductor device layers. Measurement data from target 30 may be used (e.g., by one or more processors) to determine one or more semiconductor device manufacturing process parameters based on the alignment, overlay, and / or other information, and / or to determine the adjustment of the semiconductor device manufacturing equipment based on the determined one or more semiconductor device manufacturing process parameters. In some embodiments, this may include, for example, stage position adjustment, or may include determining adjustments to mask design, metrology target (e.g., overlay target and / or alignment mark) design, semiconductor device design, radiation intensity, radiation incidence angle, radiation wavelength, pupil size and / or shape, resist material, and / or other process parameters.

[0079]

[0091] Figure 5 shows a plan view of the spread of the radiant illumination spot S in a typical target 30 (e.g., an overlay target, alignment mark, etc.) and the system in Figure 4. Typically, in one embodiment, to obtain a diffraction spectrum free from interference from surrounding structures, the target 30 includes one or more periodic structures (e.g., a grating) that are larger than the width (e.g., diameter) of the illumination spot S. The width of the spot S may be smaller than the width and length of the target 30. In other words, the target is "underfilled" by the illumination, and the diffraction signal essentially does not contain any signals from external product features, etc., outside the target itself. The illumination device may be configured, for example, to provide illumination of uniform intensity across the rear focal plane of the objective lens. Alternatively, illumination may be restricted in the on-axis or off-axis direction, for example, by including an aperture in the illumination path.

[0080]

[0092] Figure 6 shows the overlay metronome method 600. In some embodiments, the method 600 is performed as part of a semiconductor device manufacturing process. In some embodiments, one or more operations of the method 600 may be performed in or by a computer system (for example, shown in Figure 13 and described below) and / or by other systems, for example, as shown in Figures 3 and 4 (and Figure 7 described below). In some embodiments, the method 600 includes irradiating a metronome target in a pattern substrate (such as a semiconductor wafer) with radiation (operation 602), generating a metronome signal based on radiation received from a metronome mark (operation 604), filtering the metronome signal (operation 606), determining one or more parameters based on the filtered metronome signal (operation 608), determining an overlay value based on one or more parameters and / or other information (operation 610), and / or other operations. The method 600 is described below in the context of overlay, but is not limited thereto. Method 600 can generally be applied to a variety of processes.

[0081]

[0093] The operations of Method 600 described below are illustrative. In some embodiments, Method 600 may be performed with one or more additional operations not described and / or without one or more of the operations considered. For example, in some embodiments, Method 600 may include additional operations including determining adjustments to the semiconductor device manufacturing process. Also, the order of operations of Method 600 shown in Figure 6 and described below is not limiting.

[0082]

[0094] In some embodiments, one or more parts of Method 600 may be implemented and / or controlled by 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 the description of Processor PRO). One or more processing devices may include one or more devices that perform some or all of the operations of Method 600 in response to (machine-readable) instructions stored electronically in an electronic storage medium. One or more processing devices may include one or more devices configured through hardware, firmware, and / or software to be specifically designed to perform one or more operations of Method 600 (e.g., see the following discussion relating to Figure 13).

[0083]

[0095] Operation 602 includes irradiating a metronome target within the patterned substrate with radiation. In some embodiments, the metronome target includes metronome marks and / or other features in different layers of the patterned substrate. In some embodiments, the metronome target is associated with alignment and / or overlay measurements of the patterned substrate. For example, the metronome target is or may include a dedicated overlay target containing a diffraction grating in a different layer. The radiation may be diffracted by the diffraction grating. In some embodiments, the metronome target includes one or more structures within the patterned substrate (e.g., a metronome target or any other structure) capable of providing a diffraction signal. In some embodiments, this metronome target may be any structure in the pattern design layout capable of generating a wide-angle diffraction signal.

[0084]

[0096] In some embodiments, the metrology target may be included in one or more layers of a substrate of a semiconductor device structure, for example. In some embodiments, the metrology target includes one or more geometric features, such as 1D or 2D features, and / or other geometric features. In some non-limiting examples, the metrology target may include lines, edges, a series of fine-pitch lines and / or edges, a set of multiple series of fine-pitch lines and / or edges, and / or other features.

[0085]

[0097] In some embodiments, a radiation source (e.g., radiation source 2 shown in Figure 3) is configured to irradiate a metronome target including a first metronome mark on a first layer of a patterned substrate and a second metronome mark on a second layer of the patterned substrate. In some embodiments, the second metronome mark is directly above the first metronome mark on the patterned substrate in the second layer of the semiconductor structure, although the first metronome mark on the first layer may be shifted by a known bias amount relative to the second metronome mark.

[0086]

[0098] In some embodiments, the first and second metronome marks include diffraction-based overlay metronome marks such as gratings and / or other metronome marks. The gratings may have the same pitch, different pitches, and / or other characteristics. In some embodiments, the first and second metronome marks (or any two metronome marks in different layers) form a microdiffraction-based overlay (μDBO) target, and the first and second metronome marks include gratings in the first and second layers of the patterned substrate.

[0087]

[0099] The radiation may have a target wavelength and / or wavelength range, a 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, determined by the system based on previous metrologic measurements, and / or determined by other methods. In some embodiments, the radiation comprises light and / or other radiation. In some embodiments, the light comprises visible light, infrared light, near-infrared light, and / or other light. In some embodiments, the radiation may be any radiation suitable for interferometry.

[0088]

[0100] Radiation may be generated by a radiation source (e.g., radiation source 2 shown in Figures 3 and 4 and described above) and / or other components. In some embodiments, radiation may be directed by the radiation source (e.g., via one or more lenses, modulators, and / or other components) to a metronome target, a sub-part of a metronome target (e.g., a smaller part than the whole), multiple metronome targets, and / or other means to a substrate. In some embodiments, radiation from the radiation source is on-axis or off-axis. Off-axis may allow for greater wavelength pitch compatibility than on-axis. Conjugate diffraction orders that can interfere with each other are desirable. On-axis illumination (e.g., conventional dark-field microscopy) may have a wavelength pitch coverage range that is about 50% smaller than that of off-axis illumination. In some embodiments, radiation from the radiation source is spatially incoherent or spatially coherent. For example, assuming the target is illuminated by a spotlight in a single (stationary) state, microscopy using a spatially incoherent light source may be preferable to avoid crosstalk due to interference with the surroundings (e.g., speckles). Using spatially coherent light may require correcting this crosstalk using, for example, holographic methods and / or other methods. Spatially incoherent light may be preferred due to its robustness. However, spatially coherent light may be used after correcting for coherent artifacts.

[0089]

[0101] In some embodiments, the metrology target may remain substantially stationary while irradiation occurs, a radiation sensor generates a metrology signal, an image of the metrology target is generated based on the metrology signal and / or other information, and / or other operations are performed. In some embodiments, for example, radiation may be scanned over the metrology target. The scan may include rasterizing the radiation over the metrology target so that different parts of the metrology target are irradiated at different times. In some embodiments, the characteristics of the radiation (e.g., wavelength, intensity, etc.) may be varied over time by the radiation source (whether in stationary mode or scanning mode). This may generate and / or complement time-varying radiation for analysis. This may also facilitate analysis of individual parts of a feature, comparison of one part of a feature with another and / or other features, and / or other analyses.

[0090]

[0102] Operation 604 includes generating a metrology signal based on radiation received from a metrology target (e.g., from the first and second metrology marks described above) and / or other information. The metrology signal may be generated by a radiation sensor (e.g., sensor detector 4 shown in 3) and / or other components. The radiation sensor may include an interference microscope detector, such as an interference microscope-based alignment sensor. In some embodiments, the radiation sensor may include, for example, a camera and / or other components.

[0091]

[0103] Operation 604 includes detecting reflected and / or transmitted radiation from the metrology target. In some embodiments, the metrology signal includes overlay and / or alignment position information of the first and second layers, which is transmitted by reflected and / or transmitted radiation from the metrology target.

[0092]

[0104] Detecting such radiation involves detecting intensity shifts in radiation received (diffracted) from one or more geometric features. One or more phase and / or amplitude shifts correspond to one or more dimensions of the feature. For example, the phase and / or amplitude of reflected radiation from one side of a feature is different from the phase and / or amplitude of reflected radiation from the other side of the feature. Detecting one or more phase and / or amplitude (intensity) shifts in radiation from a metrology mark involves measuring local phase shifts (e.g., local phase deltas) and / or amplitude variations corresponding to different parts of the metrology mark. For example, radiation from a particular area of ​​a mark may contain sinusoidal waveforms with a particular phase and / or amplitude. Radiation from different areas of the mark may also contain sinusoidal waveforms with different phases and / or amplitudes. Detecting radiation also involves measuring the phase and / or amplitude differences of radiation of different diffraction orders. Detecting one or more local phase and / or amplitude shifts may be done using, for example, Fourier transforms, Hilbert transforms, and / or other techniques. Interferometry and / or other methods may be used to measure the phase and / or amplitude differences in reflected radiation of different diffraction orders.

[0093]

[0105] The metrology signal includes measurement information relating to the metrology target. For example, the metrology signal may be an alignment signal including alignment measurement information, an overlay signal including overlay measurement information, and / or other metrology signals. In some embodiments, operation 604 includes determining the overlay of one or more layers of the semiconductor layer structure based on the metrology signal. The measurement information may be determined using the principles of interferometry and / or other principles.

[0094]

[0106] A metrology signal includes an electronic signal representing and / or corresponding to radiation from a metrology target. The metrology signal may indicate overlay values ​​of one or more layers, e.g., alignment values, and / or other information. Generating a metrology signal involves detecting radiation and converting the detected radiation into an electronic signal. In some embodiments, generating a metrology signal involves detecting different portions of radiation from different parts of a metrology target and / or different geometries (e.g., different grids in different layers), and combining the detected portions of radiation to form a metrology signal. This detection and conversion may be performed by components similar to and / or identical to, and / or identical to, the radiation sensor detector 4 and / or processor PRO shown in Figures 3, 4, and 13, and / or other components.

[0095]

[0107] As described above, the metrology target is configured to diffract radiation from a radiation source. The radiation received by the radiation sensor includes diffracted radiation. The metrology signal includes an intensity-modulated fringe pattern of the diffracted radiation received from the metrology target. In some embodiments, the intensity-modulated fringe pattern includes one-dimensional or more interference patterns. In some embodiments, the radiation sensor is configured such that the intensity-modulated fringe pattern of the diffracted radiation includes an interference pattern generated based on the diffracted radiation from a first metrology mark and a second metrology mark.

[0096]

[0108] In operation 606, the metrology signal (e.g., the intensity-modulated fringe pattern described above) is filtered. In operation 608, one or more parameters are determined based on the filtered metrology signal and / or other information. In operation 610, an overlay value is determined based on one or more parameters and / or other information. Operations 606, 608, and / or 610 may be performed by one or more processor PROs (see Figures 3 and 13) and / or other components.

[0097]

[0109] One or more processor PROs are configured to filter intensity-modulated fringe patterns for the expected fringe period. The expected fringe period is determined based on the pitch of the first and / or second metrology marks (e.g., grids having the same pitch as described above) and / or other information. One or more processor PROs are configured to determine one or more parameters of the fringe of the intensity-modulated fringe pattern based on the filtered intensity-modulated fringe pattern and / or other information.

[0098]

[0110] In some embodiments, one or more processors are configured to determine one or more parameters of the fringe, which includes determining a first amplitude and a second amplitude of the fringe in a filtered intensity-modulated fringe pattern. In some embodiments, the first amplitude is associated with the positive bias of the first and second metronome marks relative to each other, and the second amplitude is associated with the negative bias of the first and second metronome marks relative to each other. In some embodiments, the first amplitude is associated with a segment of the metronome mark having a positive bias of the first and second metronome marks relative to each other, and the second amplitude is associated with a segment of the metronome mark having a negative bias of the first and second metronome marks relative to each other. In some embodiments, the first amplitude is associated with the positive bias of the entire first and second metronome marks relative to each other, and the second amplitude is associated with the negative bias of the entire first and second metronome marks relative to each other.

[0099]

[0111] The overlay value is determined based on the difference in amplitude, the sum of amplitudes, and the calibration coefficient. Although the calibration coefficient is necessary, advantageously, because the overlay is determined in this way, the determination of the overlay value may be relatively unaffected by the surrounding structure of the first and second layers of the pattern substrate, for example. Scatter from the surroundings can have any type of period (device type, other marks, etc.). The mark signal has a specific period corresponding to the lattice pitch, illumination setting, and wavelength. In the signal processing for determining the amplitude, only scattering at this specific period is filtered out. Therefore, all ambient spatial frequencies that do not match this period are ignored. The calibration coefficient is determined based on the radiated wavelength, the interlayer spacing between the first and second metronome marks, the ratio of diffraction efficiencies related to the first metronome mark of the first layer and the second metronome mark of the second layer of the pattern substrate, the lattice pitch, the lattice depth, and / or other information.

[0100]

[0112] In some embodiments, the calibration coefficient is determined by training a model associated with the overlay metology system. In some embodiments, the model may include an algorithm configured to be trained using input-output training pairs and / or other training data. The input-output training pairs and / or training data may convey radiation wavelength, the interlayer spacing between a first metology mark and a second metology mark, the ratio of diffraction efficiencies associated with the first metology mark of the first layer of the pattern substrate and the second metology mark of the second layer, lattice pitch, lattice depth, etc., and the corresponding calibration coefficient. In some embodiments, the algorithm may be configured to learn to predict the calibration coefficient based on some or all of this information.

[0101]

[0113] In some embodiments, the model and / or algorithm may include one or more separate algorithms. In some embodiments, the algorithm may be a machine learning algorithm. In some embodiments, the machine learning algorithm may be a neural network, a classification tree, a decision tree, a support vector machine, or other model being trained, or may include them. For example, a neural network may be based on many neural units (or artificial neurons). A neural network may roughly mimic how a biological brain functions (for example, through a large cluster of biological neurons connected by axons). Each neural unit of the neural network may be simulated as being connected to many other neural units of the neural network. Such connections may be coercive or repressive in terms of their effect on the activation state of the connected neural units. In some embodiments, each separate neural unit may have an additive function that combines the values ​​of all its inputs. In some embodiments, each connection (or the neural unit itself) may have a threshold function that must exceed a threshold before a signal is allowed to propagate to other neural units. These neural network systems may be self-learning and trained rather than explicitly programmed, and can perform significantly better in specific areas of problem-solving compared to conventional computer programs. In some embodiments, the neural network may include multiple layers (e.g., signal paths traversing from one layer to the next). In some embodiments, backpropagation may be utilized by the neural network, in which case a forward stimulus is used to reset the weights for the "previous" neural unit. In some embodiments, stimuli and inhibitors to the neural network may flow more freely, and connections may interact in a more chaotic and complex manner.

[0102]

[0114] In some embodiments, one or more processor PROs (Figures 3 and 13) are configured to determine one or more parameters of the fringe, which includes determining the amplitude and average intensity of the fringe in the filtered intensity-modulated fringe pattern. In these embodiments, determining the overlay value is advantageous because it does not require a calibration coefficient. Instead, the overlay value is determined based on the difference between the amplitude and the average intensity.

[0103]

[0115] In some embodiments, the overlay value is also determined based on the biases of the first and second metrology marks relative to each other. The first amplitude may be associated with segments of the metrology marks that have a positive bias of the first and second metrology marks relative to each other, and the second amplitude may be associated with segments of the metrology marks that have a negative bias of the first and second metrology marks relative to each other. In some embodiments, the first amplitude is associated with the positive bias of the first and second metrology marks as a whole relative to each other, and the second amplitude is associated with the negative bias of the first and second metrology marks as a whole relative to each other.

[0104]

[0116] The average intensity of the fringe can be relatively susceptible to the influence of the surrounding structure of the first and second layers of the patterned substrate, for example. As a result, the first and second metronome marks may be the same size as, or larger than, the C16 (16 × 16 μm²) or C20 μDBO marks. This facilitates underfilling of the metronome marks by radiation, as explained above in relation to Figure 5, so that structures on the semiconductor substrate do not alter or interfere with the diffraction radiation from the metronome marks. In addition to underfilling, it is also possible to use ROIs in marks that are further away from the surroundings while maintaining a sufficient region of interest (ROI) area for signal analysis. (For larger marks, the last 2 μm of the mark edge is more easily ignored than for smaller marks from a performance standpoint.) When the mark is "far" from the surroundings, the influence from the surroundings (given by the system's resolution / point spread function) becomes smaller.

[0105]

[0117] In some embodiments, determining one or more parameters of the fringe by determining the amplitude and average intensity of the fringe of the filtered intensity-modulated fringe pattern and determining the difference between the amplitude and average intensity facilitates the determination of the calibration coefficient. Once the calibration coefficient is determined, the overlay value can be determined using the difference and sum of the first and second amplitudes (and the calibration coefficient just determined) using metronome marks smaller than the C16 or C20μDBO marks.

[0106]

[0118] In some embodiments, one or more processors PRO (Figures 3 and 13) are configured to determine one or more parameters of the fringe, which includes determining the amplitude and phase of the fringe of the filtered intensity-modulated fringe pattern. The overlay value is determined based on the amplitude and phase. Determining the phase includes determining the phase difference between (1) the diffracted radiation received from the first corresponding upper and lower segments of the first and second metronome marks in the first and second layers of the pattern substrate, and (2) the diffracted radiation received from the second corresponding upper and lower segments of the first and second metronome marks. In some embodiments, the phase difference includes information indicating the mutual light intensity of the first and second metronome marks, and the overlay is determined at least partially based on the mutual light intensity. For example, the first and second corresponding upper and lower segments may be separated from each other by a known distance, and the overlay may be determined at least partially based on the phase difference and the known distance.

[0107]

[0119] In some embodiments, the mutual light intensity is used by one or more processors to determine a calibration coefficient that associates the amplitude with the overlay value, and to determine the overlay based on the amplitude and the calibration coefficient. However, as described herein, in some embodiments, determining the overlay value does not require a calibration coefficient.

[0108]

[0120] In some embodiments, determining the amplitude includes determining a first amplitude related to the positively biased metronome mark segment and a second amplitude related to the negatively biased metronome mark segment relative to the first and second metronome marks. Determining the phase includes determining a first phase related to the positively biased metronome mark segment and a second phase related to the negatively biased metronome mark segment.

[0109]

[0121] In some embodiments, one or more processors are configured to determine a complex amplitude based on first and second amplitudes and first and second phases, to determine the real part of the complex amplitude, and to determine an overlay based on the real part and positive and negative biases.

[0110]

[0122] In some embodiments, one or more processors are configured to determine scaling coefficients based on first and second amplitudes, phase coefficients based on first and second phases, and an overlay based on the scaling coefficients and phase coefficients. In some embodiments, determining the overlay based on the scaling coefficients and phase coefficients involves solving a system of two nonlinear equations, each of which is associated with the scaling coefficients and phase coefficients, and which has a common variable between the two nonlinear equations including the overlay.

[0111]

[0123] Figures 7 through 12 show some examples of the various components and / or operations described above.

[0112]

[0124] Figure 7 shows an exemplary overlay (and alignment) metrology system 700. System 700 is identical or similar to system 10 described above with respect to Figure 3, and one or more components of system 700 are similar to and / or identical to one or more components of system 10 (Figure 7 shows possible additional components of the system). In some embodiments, one or more components of system 700 may replace, be used in conjunction with, and / or enhance one or more components of system 10. In Figure 7, radiation 702 may be generated by a radiation source (incoherent light source in this example), such as radiation source 2 (also shown in Figure 3), and directed towards a metrology target (e.g., target 30, a μDBO target in this example).

[0113]

[0125] In this example, the metronome target 30 on the substrate W has a grid in multiple layers of the substrate W (although only one layer is shown in Figure 7 for simplification). The grid may be formed by, for example, solid resist pillars, bars, vias, and / or other features. The metronome target 30 may be sensitive to changes in processing during the patterning process (e.g., optical aberrations, focus changes, dose changes, etc. in lithography projection equipment such as projection systems) so that process variations manifest as variations in the metronome target 30. Therefore, measurement data from the metronome target 30 may be used to determine the overlay value and / or adjustments based on the overlay value for one or more manufacturing processes, and / or as a basis for making actual adjustments. Again, note that in this example, the metronome target 30 may represent multiple layers containing multiple metronome marks.

[0114]

[0126] Figure 7 shows one or more lenses 704, 706, 708, 710, mirrors 703, 705, 707, detection pupil 712, image plane 714, illumination pupil 716, and / or other components configured to guide (and / or be associated with) radiation 702 from radiation source 2 to metrology target 30, and to guide diffracted radiation 702 from metrology target 30 toward radiation sensor 4. In this example, sensor 4 comprises a camera, one or more processors, and / or other components. The camera may be configured to generate a metrology signal as described above. One or more processors may also be configured to determine an overlay value based on the metrology signal, as described above.

[0115]

[0127] Figure 8 shows an example of a fringe pattern 800 that may be used to determine an overlay as described herein. The fringe pattern 800 may be generated based on radiation diffracted by a metrology target (e.g., target 30 shown in other figures). For example, radiation received by a radiation sensor (e.g., sensor 4 shown in Figures 3 and 7) includes diffracted radiation. The radiation sensor (and / or one or more processors PRO of the radiation sensor—see Figures 3 and 13) is configured to generate a metrology signal that includes an intensity-modulated fringe pattern such as the fringe pattern 800. The metrology signal also includes phase information of the radiation received by the radiation sensor. In Figure 8 and the fringe pattern 800, the dark and light lines diagonally across each rectangle are fringes. Intensity modulation includes changes in the intensity of radiation reflected by target 30 and received by sensor 4 from the entire grid. In Figure 8, intensity modulation is indicated by the varying shades of dark and light lines.

[0116]

[0128] The intensity-modulated fringe pattern 800 may include interference patterns of one, two, or more dimensions. In some embodiments, the radiation sensor is configured such that the intensity-modulated fringe pattern 800 of the diffracted radiation includes interference patterns generated based on the diffracted radiation from the first and second metrology marks of the μDBO target 30 as described above.

[0117]

[0129] One or more processor PROs (Figures 3 and 13) are configured to filter the intensity-modulated fringe pattern 800 for the expected fringe period. The expected fringe period is determined based on the pitch of the first and / or second metrology marks (e.g., grids having the same pitch as described above) and / or other information. One or more processor PROs are configured to determine one or more parameters (e.g., amplitude, phase, and / or other parameters) of the fringe (dark and light lines) in the intensity-modulated fringe pattern 800 based on the filtered intensity-modulated fringe pattern and / or other information.

[0118]

[0130] Figure 9 shows the first amplitude AC1 and the second amplitude AC2 of fringes 1 and 2 (dark and light lines) within segments or areas 910 and 912 (e.g., grids) in the filtered intensity-modulated fringe pattern 900, respectively. In this example, the first amplitude AC1 is associated with the positive bias 902 (x and / or y directions) of the first and second metronome marks 906 and 908 relative to each other (which may form a target 30 such as a μDBO target), and the second amplitude AC2 is associated with the negative bias 904 (x and / or y directions) of the first and second metronome marks 906 and 908 relative to each other. In some embodiments, as described above, the first amplitude AC1 is associated with a segment or area of ​​metrology mark 908 (see segment or area 910 marked in the fringe pattern 900) having a positive bias 902 between the first and second metrology marks 906 and 908 and the other, and the second amplitude AC2 is associated with a segment or area of ​​metrology mark 906 (see segment or area 912 (e.g., grid) marked in the fringe pattern 900) having a negative bias 904 between the first and second metrology marks 906 and 908 and the other. In some embodiments, the first amplitude AC1 is associated with the positive bias 902 between the entire first and second metrology marks 906 and 908 and the other, and the second amplitude AC2 is associated with the negative bias 904 between the entire first and second metrology marks 906 and 908 and the other. The overlay value may be determined based on one or both of these amplitudes and / or other information.

[0119]

[0131] For example, Figure 10 shows the determination of an overlay OV (e.g., overlay value) based on amplitude AC and / or other information from a filtered intensity-modulated fringe pattern, such as the fringe pattern 900 shown in Figure 9. Figure 10 shows a graph 1005 of radiant intensity 1001 versus position 1003 (e.g., across the grid and / or other parts of the metrologic mark) for radiation received by a sensor (e.g., sensor 4 shown in Figures 3 and 3) from a target 30 (Figures 3, 7, and 9). Graph 1005 shows exemplary amplitude AC along with exemplary average intensity DC of the fringe of the filtered intensity-modulated fringe pattern.

[0120]

[0132] In some embodiments, as shown in Equation 1000, the overlay value OV is determined based on the difference between amplitudes AC1 and AC2, the sum of amplitudes AC1 and AC2, and a calibration coefficient c. As described above, the calibration coefficient is determined based on the radiation wavelength, the interlayer spacing between the first and second metronome marks, the ratio of diffraction efficiencies associated with the first metronome mark of the first layer of the pattern substrate and the second metronome mark of the second layer, the lattice pitch, the lattice depth, and / or other information. The calibration coefficient may be determined by training a model associated with the overlay metronome system (e.g., system 700 shown in Figure 7) and / or by other means. This model may simulate, for example, the overlay response between sensors and / or other aspects of the overlay metronome system. When the overlay is determined in this way, the determination of the overlay value may be relatively less affected by, for example, the surrounding structure of the first and second layers of the pattern substrate. In the case of an asymmetric lattice, the AC (or AC / DC) component of the fringe changes as a function of asymmetry (maximum for symmetric marks). When a shifted upper grid is printed on a lower grid, an asymmetric grid is essentially created. Simply monitoring the AC component of the grid without bias does not allow us to determine whether the grid has shifted in the positive or negative direction. Introducing bias allows us to directly determine whether the grid has shifted in the positive or negative direction; that is, the asymmetry (overlay) is directly proportional to the change in AC.

[0121]

[0133] In some embodiments, one or more processors PRO (Figures 3 and 13) are configured to determine one or more parameters of the fringe, which includes determining the amplitude AC and mean intensity DC of the fringe in the filtered intensity-modulated fringe pattern. As described above, in these embodiments, determining the overlay value OV does not require a calibration coefficient. Instead, the overlay value OV is determined based on the difference between the amplitude AC and the mean intensity DC, as shown in equations 1050 and 1075. In equation 1050, O(x) represents an observable characteristic, where the observable characteristic O(x) is the difference between the amplitude AC of the fringe x and the mean intensity DC of the fringe x. As another example, AC / DC may be used. As shown in Equation 1075, the overlay value OV is also determined based on the biases of the first and second metrology marks relative to each other (see the bias / 2 term), the difference between the observable characteristics O(1) and O(2) associated with fringes 1 and 2, and the sum of the observable characteristics O(1) and O(2) associated with fringes 1 and 2 (e.g., from different segments or areas of the metrology target).

[0122]

[0134] In some embodiments, determining one or more parameters of the fringe by determining the amplitude and average intensity of the fringe of the filtered intensity-modulated fringe pattern and determining the difference between the amplitude and average intensity (for example, first determining OV using equations 1050 and 1075 shown in Figure 10) facilitates the determination of the calibration coefficient c. Once the calibration coefficient c is determined, the overlay value OV can be determined using the difference and sum of the first and second amplitudes (and the calibration coefficient just determined) as shown in equation 1000, using a metrology mark smaller than the C16 or C20μDBO mark.

[0123]

[0135] Determining the overlay OV according to equations 1000, 1050, and / or 1075 can lead to wafer area savings (e.g., by allowing the use of smaller marks and / or methods less affected by surrounding structures). Furthermore, because metrologic signals (e.g., grids from a μDBO overlay target) that can be used for alignment, overlay, and / or other metrologic operations can be acquired during a single sensing operation, measurement accuracy may be improved compared to conventional systems.

[0124]

[0136] Figure 11 shows the determination of an overlay OV (e.g., overlay value) based on amplitude and phase from a fringe pattern such as the fringe pattern 900 shown in Figure 9, according to one embodiment. For example, the amplitude of the fringe (A or AC, both representations are equivalent) contains information about the overlay. However, mapping the change in amplitude to the overlay (e.g., in nm units) requires an unknown proportionality constant or calibration coefficient. This constant or calibration coefficient depends on the stack configuration, color, target characteristics, and / or other variables. When measuring amplitude, phase is also obtained. Until now, phase has not been used to determine the overlay. The phase of the fringe pattern contains information about the position of the grid or segments of the metronome mark. This was thought to be relevant to alignment but not to the overlay. As described here, the phase difference can be used to measure the distance between grids. The phase difference provides information about the mutual light intensity of the upper and lower grids (or segments), which can be used to determine a constant or calibration coefficient. Thus, the embodiment shown in Figure 11 provides a self-consistent system that does not require a separate calibration step.

[0125]

[0137] In some embodiments, one or more processors PRO (Figures 3 and 13) are configured to determine one or more parameters of the fringe, which includes determining the amplitude (A or AC) and phase (Φ) of the fringe in the filtered intensity-modulated fringe pattern. The overlay value is determined based on the amplitude and phase, and / or other information. In this example, the first phase Φ + and amplitude A + These are associated with the positive biases (OV+ bias, see also 902 for x and / or y in Figure 9) of the first and second metrologic marks 906 and 908 (which may form a target 30 such as a μDBO target), respectively, and the second phase Φ - and amplitude A - These are associated with the negative biases (OV-bias, see also 904 for x and / or y in Figure 9) of the first and second metrologic marks 906 and 908 relative to each other (see, for example, the distance d between segments or areas 910 and 912 (e.g., grids), and the d-2 bias distance between segments or areas 1110 and 1112 (e.g., grids)).

[0126]

[0138] Determining the phase includes determining the phase difference between (1) diffracted radiation received from the first corresponding upper segment or area 910 (e.g., a grating) and lower segment or area 1110 (e.g., a grating) of the first and second metrology marks (906 and 908 respectively) in the first and second layers (1100 and 1150 respectively) of the pattern substrate (W), and (2) diffracted radiation received from the second corresponding upper segment or area 912 (e.g., a grating) and lower segment or area 1112 (e.g., a grating) of the first and second metrology marks (906 and 908). In some embodiments, the phase difference includes information indicating the mutual light intensity of the first and second metrology marks (906 and 908), and the overlay is determined at least partially based on the mutual light intensity. For example, the first and second corresponding upper (910 and 912) and lower (1110 and 1112) segments or areas (e.g., gratings) are separated from each other by a known distance (d), and the overlay may be determined at least partially based on the phase difference and the known distance.

[0127]

[0139] In some embodiments, one or more processors use the mutual light intensity to determine a calibration coefficient that associates the amplitude with the overlay value, and determine the overlay based on the amplitude and the calibration coefficient. However, as described herein, in some embodiments, determining the overlay value does not require a calibration coefficient.

[0128]

[0140] In some embodiments, determining the amplitude includes determining a first amplitude associated with a segment of a metrology mark having a positive bias (e.g., A + or AC + ) with respect to each other of the first and second metrology marks (906 and 908), and a second amplitude associated with a segment of a metrology mark having a negative bias (A - or AC - ) with respect to each other of the first and second metrology marks (906 and 908). Determining the phase includes a positive bias (Φ +A first phase related to the segment of the metrologic mark having ) and a negative bias (Φ - This includes determining a second phase related to a segment of a metrologic mark having ).

[0129]

[0141] In some embodiments, one or more processors have first and second amplitude (A + and A - ) and the first and second phases (Φ respectively) + and Φ - Complex amplitude based on )

[0130]

number

[0131] It is configured to determine the complex amplitude, determine the real part (Re) of the complex amplitude, and determine the overlay (OV) based on the real part and positive and negative biases (biases). For example, complex amplitude

[0132]

number

[0133] The overlay (OV) may be determined using equations 1160 and 1162 shown in Figure 11. The overlay (OV) may be determined based on the real part (Re) and positive and negative biases (bias) using, for example, equation 1165. The bias is a known variable (intentionally introduced) in equation 1165.

[0134]

[0142] In some embodiments, one or more processors have first and second amplitudes (A, respectively). + and A - The scaling coefficient (S) is determined based on the first and second phases (Φ, respectively). + and Φ -The system is configured to determine the phase coefficient (F) based on the scaling coefficient and the phase coefficient, and to determine the overlay based on the scaling coefficient and the phase coefficient. For example, the scaling coefficient S may be determined based on equation 1170 shown in Figure 11. The phase coefficient F may be determined based on equation 1175. In some embodiments, determining the overlay based on the scaling coefficient S and the phase coefficient F involves solving a system of two nonlinear equations 1180 and 1185, where one nonlinear equation is associated with the scaling coefficient S and the phase coefficient F, and the two nonlinear equations have a common variable between them, including the overlay. In equations 1180 and 1185, x is related to the overlay (OV in the previous equation in Figure 11) as shown in equation 1190, and y represents the target dependency term, which can also be determined as a second unknown variable in this system of two equations (where "b" in equation 1190 is the bias quantity, which is a known variable). With respect to Figure 11, it should be noted that there are other potential equations that may be used to make these same determinations. Generally, these equations are derived from the interference equations of diffracted light and by finding a way to separate the overlay (OV) variable from all other (stack and target) dependents. There may be other ways that make it possible to obtain OV from the equations. Generally, these equations are nonlinear.

[0135]

[0143] The principles described herein are not necessarily limited to use in metrology systems such as System 700, shown in Figure 7 and further described in Figures 8 to 11. These or similar principles may also work in other systems where interference between +1st-order diffraction radiation and -1st-order diffraction radiation is observed (and / or 0th-order radiation interferes with +1st-order and -1st-order diffraction to produce a fringe image). Furthermore, these principles are not limited to μDBO targets, and other DBO-like marks may also be used. These principles may also enable the use of hybrid metrology marks that can be used for both image-based and diffraction-based overlay determinations.

[0136]

[0144] Figure 12 shows, as a non-limiting example, a metrology system 1200 with a different configuration, along with a fringe pattern 1202 and associated images 1204, 1206, 1208, and 1210 of different diffraction orders. In the example shown in Figure 12, the metrology system 1200 comprises one or more lenses 1250, 1252, and 1254 (e.g., objective lenses), mirrors 1258, 1260, 1262, 1264, 1266, and 1268, beam splitters 1270 and 1272, a wedge 1280, and / or other components configured to guide (and / or be associated with) radiation 1290 from a radiation source 1295 to a metrology target (not shown in Figure 12), and to guide diffracted radiation 1290 from the metrology target toward radiation sensors 1297 and 1299. Figure 12 shows multiple intensity channels, multiple polarization channels, and / or other features. Similar to system 700 shown in Figure 7, system 1200 and / or other similar systems may also be used to determine the overlay based on the amplitude of the filtered intensity-modulated fringe, as described herein.

[0137]

[0145] Returning to Figure 6, in some embodiments, operation 610 includes determining adjustments to the semiconductor device manufacturing process. In some embodiments, operation 610 includes determining one or more semiconductor device manufacturing process parameters. One or more semiconductor device manufacturing process parameters may be determined based on one or more detected phase and / or amplitude variations, alignment values ​​indicated by the metrology signal, overlay values ​​indicated by the metrology signal, and / or other information. One or more parameters may include radiation parameters (radiation used to determine the overlay), overlay inspection locations on the layers of the semiconductor device structure, overlay values, and / or other parameters. In some embodiments, process parameters can be broadly interpreted to include stage position, mask design, metrology target design, semiconductor device design, radiation intensity (used for resist exposure, etc.), radiation incidence angle (used for resist exposure, etc.), radiation wavelength (used for resist exposure, etc.), pupil size and / or shape, resist material, and / or other parameters.

[0138]

[0146] The radiation parameters used to determine the overlay may include, for example, the wavelength, intensity, angle of incidence, and / or parameters of the radiation. These parameters may be adjusted to better measure features of a particular shape, to increase the intensity of reflected radiation, to increase and / or enhance (e.g., maximize) the phase and / or amplitude shift (if any) of reflected radiation from one area of ​​a feature to the next, and / or for other purposes. This may result in the detection of and / or enhancement of more subtle shifts, easier detection of phase and / or amplitude shifts, and / or other benefits.

[0139]

[0147] In some embodiments, operation 610 includes determining process adjustments based on one or more determined semiconductor device manufacturing process parameters, adjusting the semiconductor device manufacturing equipment based on the determined adjustments, and / or other operations. For example, lithography exposure may be corrected based on measured overlay values. As another example, misalignment may be caused by one or more manufacturing processes in which process parameters have drifted and / or changed so that the process no longer produces an acceptable device (e.g., the overlay measurement may exceed an acceptable threshold) if the determined overlay value is not within process tolerance. One or more new or adjusted process parameters may be determined based on the determination of the measurement. The new or adjusted process parameters may be configured to cause the manufacturing process to produce an acceptable device again. For example, the new or adjusted process parameters may cause an overlay value that was previously unacceptable to be adjusted back to an acceptable range. The new or adjusted process parameters may be compared to existing parameters of a given process. If there is a difference, that difference may be used, for example, to determine adjustments to the apparatus used to produce the device (for example, 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 640 may include electronically adjusting the apparatus (for example, based on the determined process parameters). Electronically adjusting the apparatus may include, for example, sending electronic signals and / or other communications to the apparatus, which causes a change in the apparatus. Electronic adjustments may include, for example, changing settings to the apparatus and / or other adjustments.

[0140]

[0148] Figure 13 is a diagram of an exemplary computer system CS that may be used for one or more of the operations described herein. The computer system CS includes a bus BS or other communication mechanism for transmitting information and a processor PRO (or more processors) coupled to the bus BS for processing the information. The computer system CS also includes main memory MM, such as random access memory (RAM) or other dynamic storage device, coupled to the bus BS for storing information and instructions to be executed by the processor PRO. The main memory MM may 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 read-only memory (ROM) ROM or other static storage device, coupled to the bus BS for storing static information and instructions for the processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to the bus BS for storing information and instructions.

[0141]

[0149] The computer system CS may be connected via a bus BS to a display DS, such as a cathode ray tube (CRT), flat panel, or touch panel display, for displaying information to the computer user. An input device ID, including alphanumeric keys and other keys, is connected to the bus BS to transmit information and command selections to the processor PRO. Another type of user input device is a cursor control unit CC, such as a mouse, trackball, or cursor directional keys, for transmitting 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, a first axis (e.g., x) and a second axis (e.g., y), which allows the device to determine its position in a plane. A touch panel (screen) display may also be used as an input device.

[0142]

[0150] In some embodiments, some of the methods described may be implemented by a computer system CS in response to a processor PRO executing one or more sequences of one or more instructions stored 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 a processing step (operation). One or more processors in a multiplexing configuration may be employed to execute the sequence of instructions stored in main memory MM. In some embodiments, hardwired circuits may be used instead of or in combination with software instructions. Thus, this description is not limited to any particular combination of hardware circuits and software.

[0143]

[0151] The terms “computer-readable medium” or “machine-readable medium” refer to any medium involved in providing instructions to a processor PRO for execution. Such mediums can take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks such as storage devices SD. Volatile media include dynamic memory such as main memory MM. Transmission media include coaxial cables, copper wires, and optical fibers, including wires with buses 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-temporary and may include, for example, floppy disks, flexible disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, perforated cards, paper tapes, any other physical media having a pattern of holes, RAM, PROMs, and EPROMs, FLASH-EPROMs, any other memory chips or cartridges. Non-temporary computer-readable media may have recorded instructions. When an instruction is executed by a computer, it can implement any of the actions described. A temporary computer-readable medium may include, for example, a carrier wave or other propagating electromagnetic signal.

[0144]

[0152] Various forms of computer-readable media may be involved in transporting one or more sequences of one or more instructions to be executed to the processor PRO. For example, the instructions may initially reside on a magnetic disk of a remote computer. The remote computer may load the instructions into its dynamic memory and transmit them via a telephone line using a modem. A modem specific to the computer system CS may receive the data on the telephone line and convert it into an infrared signal using an infrared transmitter. An infrared detector connected to the bus BS may receive the data transported by the infrared signal and load it onto the bus BS. The bus BS transports the data to the main memory MM, from which the processor PRO retrieves and executes the instructions. Instructions received by the main memory MM may optionally be stored on a storage device SD before or after execution by the processor PRO.

[0145]

[0153] The computer system CS may also include a communication interface CI connected to the bus BS. The communication interface CI provides bidirectional data communication connected 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 modem for providing data communication connectivity to a corresponding type of telephone line. Another example is that the communication interface CI may be a LAN card for providing data communication connectivity to a compatible local area network (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.

[0146]

[0154] A network data link (NDL) typically provides data communication to other data devices over one or more networks. For example, a network data link (NDL) may provide a connection to a host computer (HC) over a local network (LAN). This may include data communication services provided over a global packet data communication network now commonly referred to as the "Internet" (INT). The local network (LAN) (Internet) may use electrical, electromagnetic, or optical signals to carry digital data streams. Signals that carry digital data to and from a computer system (CS) across various networks, as well as signals on a network data link (NDL) and through a communication interface (CI), are exemplary forms of information carriers.

[0147]

[0155] A computer system CS can send messages and receive data, including program code, through one or more networks, network data links (NDL), and communication interfaces (CI). In the case of the Internet, a host computer HC may transmit the code requested for an application program through the Internet (INT), network data link (NDL), local network (LAN), and communication interface (CI). One such downloaded application may provide, for example, all or part of the method described herein. The received code may be executed by a processor (PRO) at the time of reception and / or stored in a storage device (SD) or in other non-volatile storage devices for later execution. In this way, the computer system CS can acquire the application code in carrier form.

[0148]

[0156] Various embodiments of the system and method of the present invention are disclosed in the following numbered list of clauses. 1. A radiation sensor configured to generate a metrology signal including an intensity-modulated fringe pattern of diffracted radiation based on diffracted radiation received from a first metrology mark on a first layer of a pattern substrate and a second metrology mark on a second layer of a pattern substrate, One or more processors operably coupled to a radiation sensor, Filter the intensity-modulated fringe pattern for the expected fringe period. Based on the filtered intensity-modulated fringe pattern, one or more parameters of the fringe in the intensity-modulated fringe pattern are determined. An overlay metrology system comprising one or more processors configured to determine overlay values ​​based on one or more parameters. 2. The system of Clause 1, wherein the second metronome mark is above the first metronome mark. 3. A system according to any of the clauses 1 to 2, wherein the radiation sensor is configured such that the intensity-modulated fringe pattern of the diffracted radiation includes an interference pattern generated based on the diffracted radiation from a first metrology mark and a second metrology mark. 4. Any system of clauses 1 to 3, wherein the first metronome mark of the first layer is shifted relative to the second metronome mark by a known bias amount. 5. Any system according to any of the terms 1 to 4, further comprising a radiation source operably coupled to one or more processors and radiation sensors, the radiation source configured to irradiate first and second metrology marks. 6. A system that meets any of the conditions in clauses 1 through 5, in which the radiation from the radiation source is on-axis. 7. A system that meets any of the conditions in clauses 1 through 6, in which the radiation from the radiation source is off-axis. 8. A system that meets any of the conditions in clauses 1 through 7, in which the radiation from the radiation source is spatially incoherent. 9. A system that meets any of the conditions in clauses 1 through 8, in which the radiation from the radiation source is spatially coherent. 10. A system according to any of the clauses 1 to 9, wherein the first and second metronome marks include diffraction-based overlay metronome marks. 11. A system according to any of the clauses 1 to 10, wherein the first and second metrologic marks include a grid. 12. A system of any of the clauses 1 to 11, in which the grid has the same pitch. 13. A system of any of the clauses 1 to 12, in which the expected fringe period is determined based on the pitch. 14. A system according to any of the clauses 1 to 13, wherein the first and second metronome marks form a microdiffraction-based overlay (μDBO) target, and the first and second metronome marks include a grid in the first and second layers of the patterned substrate. 15. A system according to any of the clauses 1 to 14, wherein the intensity-modulated fringe pattern includes interference patterns of one or more dimensions. 16. A system of any of the provisions 1 through 15 in which the radiation sensor is equipped with a camera. 17. A system according to any of the clauses 1 to 16, wherein one or more processors are configured to determine one or more parameters of the fringe, which includes determining a first amplitude and a second amplitude of the fringe in a filtered intensity-modulated fringe pattern, and to determine an overlay value based on the difference in amplitudes, the sum of amplitudes, and a calibration coefficient. 18. A system according to any of the clauses 1 to 17, in which the calibration coefficient is determined based on the radiation wavelength, the interlayer spacing between the first metronome mark and the second metronome mark, the ratio of diffraction efficiencies related to the first metronome mark of the first layer and the second metronome mark of the second layer of the patterned substrate, the lattice pitch, and the lattice depth. 19. A system according to any of clauses 1 through 18, in which the calibration coefficient is determined by training a model associated with an overlay metrology system. 20. Any system according to clauses 1 to 19, wherein the first amplitude is associated with a positive bias of the first and second metronome marks relative to each other, and the second amplitude is associated with a negative bias of the first and second metronome marks relative to each other. 21. Any system of clauses 1 to 20, wherein a first amplitude is associated with segments of metrologic marks having a positive bias of the first and second metrologic marks relative to each other, and a second amplitude is associated with segments of metrologic marks having a negative bias of the first and second metrologic marks relative to each other. 22. Any system according to clauses 1 to 21, wherein the first amplitude is associated with a positive bias of the entire first and second metrologic marks relative to each other, and the second amplitude is associated with a negative bias of the entire first and second metrologic marks relative to each other. 23. A system according to any of clauses 1 to 22, wherein the determination of the overlay value is less affected by the surrounding structure of the first and second layers of the pattern substrate. 24. A system according to any of the clauses 1 to 23, wherein one or more processors are configured to determine one or more parameters of the fringe, which includes determining the amplitude and average intensity of the fringe of a filtered intensity-modulated fringe pattern, and to determine the overlay value, which is based on the difference between the amplitude and the average intensity. 25. Any system of clauses 1 to 24, in which the overlay value is further determined based on the bias of the first and second metrology marks toward each other. 26. Any system of clauses 1 to 25, wherein a first amplitude is associated with segments of metrologic marks having a positive bias of the first and second metrologic marks relative to each other, and a second amplitude is associated with segments of metrologic marks having a negative bias of the first and second metrologic marks relative to each other. 27. Any system according to clauses 1 to 26, wherein the first amplitude is associated with a positive bias toward each other for the entire first and second metrologic marks, and the second amplitude is associated with a negative bias toward each other for the entire first and second metrologic marks. 28. A system according to any of the clauses 1 to 27, wherein the average strength of the fringe is susceptible to the influence of the surrounding structure of the first and second layers of the pattern substrate. 29. Any system of Clauses 1 to 28, wherein the first and second metronome marks are the same size as or larger than the C16 or C20μDBO mark. 30. Any system from clauses 1 to 29 in which determining the overlay value does not require a calibration coefficient. 31. A system of any of the clauses 1 through 30, configured to first perform one of the actions of clauses 24 through 30, and then perform one of the actions of clauses 17 through 23. 32. A system according to any of the clauses 1 to 31, in which first, one of the operations in clauses 24 to 30 is performed to determine one of the calibration coefficients in clauses 17 to 23, and then a metronome mark smaller than C16 or C20μDBO mark can be used in one of the operations in clauses 17 to 23. 33. A system according to any of the clauses 1 to 32, wherein one or more processors are configured to determine one or more parameters of the fringe, which includes determining the amplitude and phase of the fringe in a filtered intensity-modulated fringe pattern, and to determine the overlay value, which is based on the amplitude and phase. 34. Any system of Clauses 1 to 33, wherein determining the phase includes determining the phase difference between (1) diffracted radiation received from the first corresponding upper and lower segments of the first and second metronome marks in the first and second layers of the pattern substrate and (2) diffracted radiation received from the second corresponding upper and lower segments of the first and second metronome marks. 35. A system according to any of the clauses 1 to 34, wherein the phase difference includes information indicating the mutual light intensity of the first and second metrology marks, and the overlay is determined at least partially based on the mutual light intensity. 36. A system according to any of the clauses 1 to 35, wherein the first and second corresponding upper and lower segments are separated from each other by a known distance, and the overlay is determined at least partially based on the phase difference and the known distance. 37. Any system of Clauses 1 to 36, wherein mutual light intensity is used by one or more processors to determine a calibration coefficient that relates amplitude to overlay value, and to determine the overlay based on amplitude and calibration coefficient. 38. Any system from clauses 1 to 37 in which determining the overlay value does not require a calibration coefficient. 39. Any system of Clauses 1 to 38, wherein determining amplitude includes determining a first amplitude relating to segments of metrologic marks having a positive bias of the first and second metrologic marks relative to each other, and a second amplitude relating to segments of metrologic marks having a negative bias of the first and second metrologic marks relative to each other, and determining phase includes determining a first phase relating to segments of metrologic marks having a positive bias, and a second phase relating to segments of metrologic marks having a negative bias. 40. One or more processors are further configured to determine a complex amplitude based on first and second amplitudes and first and second phases, to determine the real part of the complex amplitude, and to determine an overlay based on the real part and positive and negative biases, according to any of the systems in Clauses 1 to 39. 41. A system according to any of the clauses 1 to 40, wherein one or more processors are further configured to determine scaling coefficients based on first and second amplitudes, to determine phase coefficients based on first and second phases, and to determine an overlay based on the scaling coefficients and phase coefficients. 42. A system of any of the clauses 1 to 41, wherein determining the overlay based on scaling coefficients and phase coefficients involves solving a system of two nonlinear equations, each of which one nonlinear equation is associated with scaling coefficients and phase coefficients, and which has a common variable between the two nonlinear equations, including the overlay. 43. A system according to any of the clauses 1 to 42, wherein a metrologic signal is configured to be used by one or more processors to coordinate a semiconductor device manufacturing process. 44. An overlay metrology method comprising: generating a metrology signal including an intensity-modulated fringe pattern of diffracted radiation using a radiation sensor based on diffracted radiation received from a first metrology mark on a first layer of a pattern substrate and a second metrology mark on a second layer of a pattern substrate; filtering the intensity-modulated fringe pattern for an expected fringe period using one or more processors operably coupled to the radiation sensor; determining one or more parameters of the fringe of the intensity-modulated fringe pattern using one or more processors based on the filtered intensity-modulated fringe pattern; and determining an overlay value using one or more processors based on one or more parameters. 45. The method of Clause 34, wherein the second metronome mark is above the first metronome mark. 46. ​​The method of Clause 44 or 45, wherein the radiation sensor is configured such that the intensity-modulated fringe pattern of the diffracted radiation includes an interference pattern generated based on the diffracted radiation from a first metrology mark and a second metrology mark. 47. Any method of clauses 44 to 46, wherein the first metronome mark of the first layer is shifted relative to the second metronome mark by a known bias amount. 48. Any method of the provisions of 44 to 47, further comprising irradiating the first and second metrology marks with radiation using a radiation source operably coupled to one or more processors and radiation sensors. 49. The radiation from the radiation source is on-axis, in any manner described in clauses 44 to 48. 50. The radiation from the radiation source is off-axis, in any way described in clauses 44 to 49. 51. The radiation from the radiation source is spatially incoherent, in any way described in clauses 44 to 50. 52. The radiation from the radiation source is spatially coherent, in any way described in clauses 44 to 51. 53. The first and second metronome marks include diffraction-based overlay metronome marks, in any manner according to clauses 44 to 52. 54. Any method of the first and second metrologic marks including a grid, as described in clauses 44 to 53. 55. The grid has the same pitch, in any way described in clauses 44 to 54. 56. The expected fringe period is determined based on the pitch, in any way of clauses 44 to 55. 57. Any method according to clauses 44 to 56, wherein the first and second metronome marks form a microdiffraction-based overlay (μDBO) target, and the first and second metronome marks include a grid in the first and second layers of the patterned substrate. 58. Any method from clauses 44 to 57, wherein the intensity-modulated fringe pattern includes one-dimensional or greater interference patterns. 59. The radiation sensor is equipped with a camera, in any manner described in any of the provisions of 44 to 58. 60. Any method of Clauses 44 to 59, wherein determining one or more parameters of the fringe includes determining a first amplitude and a second amplitude of the fringe in a filtered intensity-modulated fringe pattern, and determining an overlay value is configured to be based on the difference in amplitudes, the sum of amplitudes, and a calibration coefficient. 61. Any method of clauses 44 to 60, wherein the calibration coefficient is determined based on the radiation wavelength, the interlayer spacing between the first metronome mark and the second metronome mark, the ratio of diffraction efficiencies related to the first metronome mark of the first layer and the second metronome mark of the second layer of the patterned substrate, the lattice pitch, and the lattice depth. 62. The calibration coefficient is determined by any method from clauses 44 to 61, wherein the calibration coefficient is determined by training a model associated with an overlay metrology system. 63. Any method of clauses 44 to 62, wherein the first amplitude is associated with a positive bias of the first and second metronome marks relative to each other, and the second amplitude is associated with a negative bias of the first and second metronome marks relative to each other. 64. Any method of clauses 44 to 63, wherein a first amplitude is associated with segments of metrologic marks having a positive bias of the first and second metrologic marks relative to each other, and a second amplitude is associated with segments of metrologic marks having a negative bias of the first and second metrologic marks relative to each other. 65. Any method of clauses 44 to 64, wherein the first amplitude is associated with a positive bias of the entire first and second metrologic marks toward each other, and the second amplitude is associated with a negative bias of the entire first and second metrologic marks toward each other. 66. Any method of clauses 44 to 65 wherein the determination of the overlay value is less affected by the surrounding structure of the first and second layers of the pattern substrate. 67. Any method of Clauses 44 to 66, wherein determining one or more parameters of the fringe includes determining the amplitude and average intensity of the fringe of a filtered intensity-modulated fringe pattern, and determining the overlay value is configured to be based on the difference between the amplitude and the average intensity. 68. The overlay value is further determined based on the bias of the first and second metrology marks relative to each other, in any way of clauses 44 to 67. 69. Any method of the provisions 44 to 68, wherein a first amplitude is associated with a segment of metrologic marks having a positive bias of the first and second metrologic marks relative to each other, and a second amplitude is associated with a segment of metrologic marks having a negative bias of the first and second metrologic marks relative to each other. 70. Any method of clauses 44 to 69, wherein the first amplitude is associated with a positive bias of the entire first and second metrologic marks toward each other, and the second amplitude is associated with a negative bias of the entire first and second metrologic marks toward each other. 71. Any method of clauses 44 to 70 wherein the average strength of the fringe is susceptible to the influence of the surrounding structure of the first and second layers of the pattern substrate. 72. The first and second metronome marks are the same size as or larger than the C16 or C20μDBO mark, in any manner according to clauses 44 to 71. 73. Any method from clauses 44 to 72 in which the overlay value is determined without requiring a calibration coefficient. 74. Any method of the provisions 44 to 73, further comprising first performing any method of the provisions 67 to 73, and then performing any method of the provisions 50 to 56. 75. First, determine the calibration coefficient of any of the clauses 60 to 66 by performing any of the methods of clauses 67 to 73, and then use any of the methods of clauses 60 to 66, wherein a metronome mark smaller than C16 or C20μDBO mark may be used in any of the methods of clauses 60 to 66. 76. Any method of the provisions of 44 to 75, wherein determining one or more parameters of the fringe includes determining the amplitude and phase of the fringe of a filtered intensity-modulated fringe pattern, and determining the overlay value is configured to be based on the amplitude and phase. 77. Any method of the provisions of 44 to 76, wherein determining the phase includes determining the phase difference between (1) diffracted radiation received from the first corresponding upper and lower segments of the first and second metronome marks of the first and second layers of the pattern substrate and (2) diffracted radiation received from the second corresponding upper and lower segments of the first and second metronome marks. 78. Any method of Clauses 44 to 77, wherein the phase difference includes information indicating the mutual light intensity of the first and second metrology marks, and the overlay is determined at least partially based on the mutual light intensity. 79. The first and second corresponding upper and lower segments are separated from each other by a known distance, and the overlay is determined at least partially on the basis of the phase difference and the known distance, in any way of the provisions of 44 to 78. 80. Any method of Clauses 44 to 79, wherein mutual light intensity is used by one or more processors to determine a calibration coefficient that relates amplitude to overlay value, and to determine the overlay based on amplitude and calibration coefficient. 81. Any method from clauses 44 to 80 that does not require a calibration coefficient to determine the overlay value. 82. Any method of the provisions of 44 to 81, wherein determining the amplitude includes determining a first amplitude relating to segments of metrologic marks having a positive bias of the first and second metrologic marks relative to each other, and a second amplitude relating to segments of metrologic marks having a negative bias of the first and second metrologic marks relative to each other, and determining the phase includes determining a first phase relating to segments of metrologic marks having a positive bias, and a second phase relating to segments of metrologic marks having a negative bias. 83. Any method of Clauses 44 to 82, wherein one or more processors are further configured to determine a complex amplitude based on first and second amplitudes and first and second phases, to determine the real part of the complex amplitude, and to determine an overlay based on the real part and positive and negative biases. 84. Any method of the provisions of 44 to 83, wherein one or more processors are further configured to determine scaling coefficients based on first and second amplitudes, to determine phase coefficients based on first and second phases, and to determine an overlay based on the scaling coefficients and phase coefficients. 85. Any method of Clauses 44 to 84, wherein determining the overlay based on scaling coefficients and phase coefficients involves solving a system of two nonlinear equations, each of which one nonlinear equation is associated with scaling coefficients and phase coefficients, and which has a common variable between the two nonlinear equations, including the overlay. 86. Any method of the provisions of 44 to 85, further comprising using metronome signals to coordinate a semiconductor device manufacturing process.

[0149]

[0157] The concepts disclosed herein may be associated with any general-purpose metronome and / or imaging system for imaging subwavelength features and may be particularly useful in emerging metronome and / or imaging technologies capable of generating increasingly shorter wavelengths.

[0150]

[0158] The concepts disclosed herein may be used for metronome and / or imaging on substrates such as silicon wafers, but it should be understood that these disclosed concepts may also be used in any type of metronome and / or imaging system, for example, for metronome and / or imaging on substrates other than silicon wafers. Furthermore, combinations and partial combinations of the disclosed elements may constitute separate embodiments.

[0151]

[0159] The above description is intended to be illustrative, not restrictive. Therefore, it will be apparent to those skilled in the art that modifications as described can be made without departing from the claims below.

Claims

1. A radiation sensor configured to generate a metrology signal including an intensity-modulated fringe pattern of diffracted radiation based on diffracted radiation received from a first metrology mark on a first layer of a pattern substrate and a second metrology mark on a second layer of the pattern substrate, One or more processors operably coupled to the radiation sensor, The intensity-modulated fringe pattern is filtered with respect to the expected fringe period. Based on the filtered intensity-modulated fringe pattern, one or more parameters of the fringe in the intensity-modulated fringe pattern are determined. An overlay metrology system comprising one or more processors configured to determine an overlay value based on one or more of the aforementioned parameters.

2. The system according to claim 1, wherein the second metrology mark is located above the first metrology mark.

3. The system according to claim 2, wherein the radiation sensor is configured such that the intensity modulation fringe pattern of the diffracted radiation includes an interference pattern generated based on the diffracted radiation from the first metrology mark and the second metrology mark.

4. The system according to claim 2 or 3, wherein the first metronome mark of the first layer is shifted with respect to the second metronome mark by a known bias amount.

5. A system according to any one of claims 1 to 4, further comprising a radiation source operably coupled to one or more processors and the radiation sensor, the radiation source configured to irradiate the first and second metrologic marks with radiation.

6. The system according to claim 5, wherein the radiation from the radiation source is on-axis.

7. The system according to claim 5, wherein the radiation from the radiation source is off-axis.

8. A system according to any one of claims 5 to 7, wherein the radiation from the radiation source is spatially incoherent.

9. A system according to any one of claims 5 to 7, wherein the radiation from the radiation source is spatially coherent.

10. The system according to any one of claims 1 to 9, wherein the first and second metronome marks include diffraction-based overlay metronome marks.

11. The system according to any one of claims 1 to 10, wherein the first and second metrologic marks include a grid.

12. The system of claim 11, wherein the grid has the same pitch.

13. The system according to claim 12, wherein the expected fringe period is determined based on the pitch.

14. The system according to any one of claims 1 to 13, wherein the first and second metronome marks form a microdiffraction-based overlay (μDBO) target, and the first and second metronome marks include a grid in the first and second layers of the patterned substrate.

15. The system according to any one of claims 1 to 14, wherein the intensity modulation fringe pattern includes one-dimensional or more interference patterns.

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