Optical determination of electrical contacts between metallic features in different layers of a structure

Abstract

Optically determining whether metallic features in different layers of a structure are in electrical contact with each other is described. When the metallic features comprise different metals and / or have different sizes, resulting in detection of one or more resonances in reflected radiation, the metallic features in different layers are determined to be in contact or not in contact with each other based on the spectral position of the one or more resonances. When the metallic features are formed of the same metal and have the same size, the metallic features in different layers are determined to be in contact with each other in response to detection of a single resonance associated with the metallic features, and are determined to be not in contact with each other in response to detection of more than two resonances associated with the metallic features.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 19218265.7 filed on December 19, 2019 and EP application 20200638.3 filed on October 7, 2020, both of which are incorporated herein by reference in their entirety. Technical Field

[0003] The description herein generally relates to optically determining electrical contact between (eg, first and second) metallic features in different (eg, first and second) layers in a structure. Background Art

[0004] A lithographic projection apparatus may be used, for example, in the manufacture of integrated circuits (ICs). A patterning device (e.g., a mask) may include or provide a pattern corresponding to a separate layer of the IC (a "design layout"), and the pattern may be transferred to a target portion (e.g., including one or more dies) on a substrate (e.g., a silicon wafer) that has been coated with a layer of radiation-sensitive material ("resist") by a method such as irradiating the target portion through the pattern on the patterning device. Typically, a single substrate includes multiple adjacent target portions, and the pattern is transferred to these target portions successively, one target portion at a time, by the lithographic projection apparatus. In one type of lithographic projection apparatus, the pattern on the entire patterning device is transferred to one target portion in one operation. Such an apparatus is generally referred to as a stepper. In another type of apparatus, generally referred to as a step-and-scan apparatus, a projection beam scans the patterning device in a given reference direction (the "scanning" direction) while synchronously moving the substrate parallel or antiparallel to the reference direction. Different portions of the pattern on the patterning device are gradually transferred to one target portion. Typically, since the lithographic projection apparatus will have a reduction ratio M (eg 4), the speed F of the substrate movement will be 1 / M times the speed at which the projection beam scans the patterning device. More information on lithographic apparatus as described herein can be gleaned from US 6,046,792 for example reference.

[0005] Before the pattern is transferred from the patterning device to the substrate, the substrate may undergo various processes such as priming, resist coating, and soft baking. After exposure, the substrate may undergo other processes ("post-exposure processes") such as post-exposure baking (PEB), development, hard baking, and measurement / inspection of the transferred pattern. This series of processes is used to form the basis for making a single layer of a device (e.g., an IC). The substrate may then undergo various processes such as etching, ion implantation (doping), metallization, oxidation, deposition, chemical mechanical polishing, etc., all of which are aimed at completing a single layer of the device. If multiple layers are required in the device, the entire process or a variation thereof is repeated for each layer. Ultimately, a device will be present in each target portion on the substrate. These devices are then separated from each other by techniques such as cutting or sawing so that the individual devices can be mounted on a carrier, connected to pins, etc.

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

[0007] As mentioned earlier, photolithography is a central step in the fabrication of devices such as ICs, where patterns formed on a substrate define the functional elements of devices such as microprocessors, memory chips, etc. Similar photolithography techniques are also used in the formation of flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0008] As semiconductor manufacturing processes continue to advance, the size of functional elements continues to decrease, while the number of functional elements (such as transistors) per device has steadily increased over the past few decades, following a trend generally referred to as "Moore's Law." In the current state of the art, device layers are manufactured using photolithography projection equipment that projects a design layout onto a substrate using illumination from a deep ultraviolet illumination source, producing individual functional elements with sizes well below 100 nanometers, i.e., less than half the wavelength of radiation from the illumination source (e.g., a 193 nanometer illumination source).

[0009] According to the resolution formula CD = k1 × λ / NA, where λ is the wavelength of the radiation used (currently 248nm or 193nm in most cases), NA is the numerical aperture of the projection optics in the lithographic projection device, CD is the "critical dimension" - usually the minimum feature size printed - and k1 is the empirical resolution factor, the process in which features with a size smaller than the classical resolution limit of the lithographic projection device are printed is generally known as low-k1 lithography. In general, the smaller the k1, the more difficult it is to reproduce on the substrate a pattern of a shape and size similar to that planned by the designer to achieve specific electrical functions and performance. In order to overcome these difficulties, complex fine-tuning steps are applied to the lithographic projection device, the design layout or the patterning device. For example, these include but are not limited to the optimization of NA and optical coherence settings, customized illumination schemes, the use of phase-shifted patterning devices, optical proximity correction (OPC, sometimes also called "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement technology" (RET). Summary of the invention

[0010] According to one embodiment, a system configured to determine whether metal features in different layers in a structure are in electrical contact with each other is provided. The system includes a radiation source configured to irradiate a target portion of the structure with radiation. The target portion includes a first metal feature in a first layer of the structure and a second metal feature in a second layer of the structure. The system includes one or more sensors configured to detect one or more resonances in reflected radiation from the first metal feature and the second metal feature. The system includes one or more processors operably coupled to the radiation source and the one or more sensors. The one or more processors are configured to determine whether a first metal feature in the first layer and a second metal feature in the second layer are in electrical contact with each other based on (i) the number of detected resonances or (ii) the spectral position of the detected resonances.

[0011] In one embodiment, a first metal feature in a first layer and a second metal feature in a second layer comprise different metals and / or have different sizes, which causes one or more resonances in the reflected radiation to be detected by one or more sensors, and the first metal feature in the first layer and the second metal feature in the second layer are determined by one or more processors to be in electrical contact or not in electrical contact with each other based on the spectral position of the one or more resonances. In one embodiment, a first metal feature in the first layer and a second metal feature in the second layer are formed of the same metal and have the same size, and the one or more processors are configured to determine that the first metal feature in the first layer and the second metal feature in the second layer are in electrical contact with each other in response to detecting a single resonance associated with the first metal feature and the second metal feature, and to determine that the first metal feature in the first layer and the second metal feature in the second layer are not in electrical contact with each other in response to detecting more than two resonances associated with the first metal feature and the second metal feature.

[0012] In one embodiment, the one or more resonances include plasmon resonances.

[0013] In one embodiment, the one or more resonances comprise primarily dipolar (but may also include quadrupolar and / or magnetic dipole) surface plasmon polariton resonances in the reflected radiation.

[0014] In one embodiment, the one or more sensors include one or more spectrometer detectors configured to detect intensity as a function of wavelength of the reflected radiation.

[0015] In one embodiment, the one or more sensors are configured as a normal incidence inspection device, wherein the one or more sensors are oriented at an angle perpendicular to the target portion, or as an oblique incidence inspection device, wherein the one or more sensors are oriented at an angle non-perpendicular to the target portion.

[0016] In one embodiment, the radiation source is configured such that the radiation comprises broadband white light collimated with a lens system and transmitted through an interference filter and a polarizer.

[0017] In one embodiment, the first metal feature and the second metal feature comprise different portions of a via extending through the first layer and the second layer.

[0018] In one embodiment, a single resonance comprises a maximum in the wavelength spectrum of the reflected radiation.

[0019] In one embodiment, a first metal feature in a first layer of the structure and a second metal feature in a second layer are arranged in an array. The array has a spacing. Detecting one or more resonances in reflected radiation from the first metal feature and the second metal feature includes detecting resonances associated with the spacing with one or more sensors.

[0020] In one embodiment, the resonance associated with the spacing is a Fano resonance.

[0021] In one embodiment, the resonance associated with the spacing has a resonance shape. The determination of whether the first metallic feature and the second metallic feature are in electrical contact is based on the resonance shape.

[0022] In one embodiment, the one or more processors are further configured to facilitate adjusting a pitch of the array based on a resonance associated with the pitch.

[0023] In one embodiment, the one or more processors are further configured to determine one or more of an overlay, a manufacturing process failure rate, a critical dimension, and a critical dimension variance associated with a target portion of the structure based on the detected one or more resonances.

[0024] According to another embodiment, a method for determining whether metal features in different layers of a structure are in electrical contact with each other is provided. The method includes irradiating a target portion of the structure with radiation using a radiation source. The target portion includes a first metal feature in a first layer of the structure and a second metal feature in a second layer of the structure. The method includes detecting one or more resonances in reflected radiation from the first metal feature and the second metal feature using one or more sensors. The method includes: using one or more processors, based on the detected one or more resonances, determining whether the first metal feature in the first layer and the second metal feature in the second layer are in electrical contact with each other. In one embodiment, the first metal feature in the first layer and the second metal feature in the second layer include different metals and / or have different sizes, so that at least two different resonances in the reflected radiation are detected by one or more sensors, and the first metal feature in the first layer and the second metal feature in the second layer are determined by one or more processors as being in electrical contact or not in electrical contact with each other based on the spectral position of the detected resonances. In one embodiment, a first metal feature in a first layer and a second metal feature in a second layer are formed of the same metal and have the same size, and one or more processors are configured to determine that the first metal feature in the first layer and the second metal feature are in electrical contact with each other in response to detecting a single resonance associated with the first metal feature and the second metal feature, and to determine that the first metal feature in the first layer and the second metal feature are not in electrical contact with each other in response to detecting more than two resonances associated with the first metal feature and the second metal feature.

[0025] According to another embodiment, a method for determining an adjustment of a semiconductor device manufacturing apparatus is provided. The method includes irradiating a target portion of a semiconductor device with radiation. The target portion includes a first metal feature in a first layer of the semiconductor device and a second metal feature in a second layer. The method includes detecting one or more resonances in reflected radiation from the first metal feature and the second metal feature. The method includes determining a relative position of the first layer and the second layer based on the detected one or more resonances. The method includes determining whether the first metal feature in the first layer and the second metal feature in the second layer are in electrical contact with each other based on the detected one or more resonances. In one embodiment, the first metal feature in the first layer and the second metal feature in the second layer include different metals and / or have different sizes, which causes the one or more resonances in the reflected radiation to be detected by one or more sensors, and the first metal feature in the first layer and the second metal feature in the second layer are determined by one or more processors to be in electrical contact or not in electrical contact with each other based on the spectral position of the one or more resonances. In one embodiment, a first metal feature in a first layer and a second metal feature in a second layer are formed of the same metal and have the same size, and the first metal feature in the first layer and the second metal feature in the second layer are determined to be in electrical contact with each other in response to detecting a single resonance associated with the first metal feature and the second metal feature, and are determined to be not in electrical contact with each other in response to detecting more than two resonances associated with the first metal feature and the second metal feature. The method includes determining one or more semiconductor device manufacturing process parameters based on the relative positions of different layers and / or the determination of whether the first metal feature and the second metal feature are in electrical contact with each other. The method includes determining adjustments to semiconductor device manufacturing equipment based on the determined one or more semiconductor device manufacturing process parameters.

[0026] According to another embodiment, a method for determining relative positions of different layers in a structure is described. The method includes irradiating a target portion of a structure with radiation. The target portion includes metallic features in different layers of the structure. The method includes detecting one or more resonances in reflected radiation from the metallic features; and determining the relative positions of the different layers based on the detected one or more resonances.

[0027] In one embodiment, the radiation comprises light.

[0028] In one embodiment, determining the relative positions of the different layers comprises determining a relative displacement between the different layers. In one embodiment, determining the relative positions of the different layers comprises determining an overlay associated with the different layers.

[0029] In one embodiment, the method further includes determining whether metallic features in different layers are in contact with each other based on the detected one or more resonances.

[0030] In one embodiment, the metallic features in different layers comprise different metals and / or have different sizes, which results in at least two different resonances being detected in the reflected radiation.

[0031] In one embodiment, based on the distance between at least two different resonances, it is determined that metallic features in different layers are in contact or not in contact with each other.

[0032] In one embodiment, the distance between at least two different resonances corresponds to an amount by which the different layers are displaced relative to each other.

[0033] In one embodiment, metal features in different layers are formed of the same metal and have the same dimensions and are determined to be in contact with each other in response to detecting a single resonance associated with the metal features.

[0034] In one embodiment, metal features in different layers are formed of the same metal and have the same size and are determined to be not in contact with each other in response to detecting two or more resonances associated with the metal features.

[0035] In one embodiment, the distance between the resonances corresponds to the amount that the different layers are displaced relative to each other.

[0036] In one embodiment, the different layers include two layers, each layer having at least one metallic feature.

[0037] In one embodiment, the metal features include different portions of a via extending through different layers.

[0038] In one embodiment, the one or more resonances include plasmon resonances.

[0039] In one embodiment, a single resonance comprises a maximum in the wavelength spectrum of the reflected radiation.

[0040] In one embodiment, the metal features in different layers of the structure are arranged in an array. The array may have a pitch. Detecting one or more resonances in the reflected radiation from the metal features includes detecting resonances associated with the pitch.

[0041] In one embodiment, the resonance associated with the spacing is a Fano resonance.

[0042] In one embodiment, the resonance associated with the spacing has a resonance shape. The relative positions of the different layers are determined based on the resonance shape. In other words, the resonance associated with the spacing results in an asymmetric line shape. The relative positions of the different layers are determined by characterizing the asymmetry of the line shape.

[0043] In one embodiment, determining the relative positions of the different layers includes determining overlays associated with the different layers based on resonances associated with the spacings.

[0044] In one embodiment, the method further comprises adjusting a pitch of the array based on a resonance associated with the pitch.

[0045] In one embodiment, the structure includes at least a portion of a semiconductor device.

[0046] In one embodiment, determining the relative positions of different layers based on the detected one or more resonances is performed as part of a semiconductor device manufacturing process.

[0047] In one embodiment, the method further includes adjusting a semiconductor device manufacturing process or a design of the semiconductor device based on the relative positions of the different layers.

[0048] According to another embodiment, a method for determining an adjustment of semiconductor device manufacturing equipment is provided. The method includes irradiating a target portion of a semiconductor device with radiation. The target portion includes metal features in different layers of the semiconductor device. The method includes detecting one or more resonances in reflected radiation from the metal features; determining relative positions of the different layers based on the detected one or more resonances; determining one or more semiconductor device manufacturing process parameters based on the relative positions of the different layers; and determining an adjustment to the semiconductor device manufacturing equipment based on the determined one or more semiconductor device manufacturing process parameters.

[0049] In one embodiment, the radiation comprises light.

[0050] In one embodiment, determining the relative positions of different layers includes determining overlay as part of a semiconductor device manufacturing process.

[0051] In one embodiment, the one or more semiconductor device manufacturing process parameters determined include one or more of mask design, metrology target design, semiconductor device design, radiation intensity, radiation incident angle, radiation wavelength, pupil size and / or shape, and resist material.

[0052] In one embodiment, the method further includes adjusting semiconductor device manufacturing equipment based on the determined adjustment.

[0053] According to another embodiment, a computer program product is provided, including a non-transitory computer-readable medium having instructions recorded thereon, and when the instructions are executed by a computer, any and / or all of the above methods are implemented.

[0054] According to another embodiment, a system configured to determine relative positions of different layers in a structure is provided. The system includes a radiation source configured to illuminate a target portion of the structure with radiation. The target portion includes metallic features in different layers of the structure. The system includes one or more sensors configured to detect one or more resonances in reflected radiation from the metallic features; and one or more processors configured to determine the relative positions of the different layers based on the detected one or more resonances.

[0055] In one embodiment, the radiation comprises light.

[0056] In one embodiment, determining the relative positions of the different layers comprises determining a relative displacement between the different layers.

[0057] In one embodiment, determining the relative positions of the different layers includes determining overlays associated with the different layers.

[0058] In one embodiment, the one or more processors are further configured to determine whether metallic features in different layers are in contact with each other based on the detected one or more resonances.

[0059] In one embodiment, the metallic features in different layers comprise different metals and / or have different sizes, which enables at least two different resonances in the reflected radiation to be detected by one or more sensors.

[0060] In one embodiment, the one or more processors determine whether the metallic features in the different layers are in contact or not in contact with each other based on a distance between at least two different resonances.

[0061] In one embodiment, the one or more processors are configured such that the distance between at least two different resonances corresponds to an amount by which the different layers are displaced relative to each other.

[0062] In one embodiment, the one or more processors are configured such that metal features in different layers are formed of the same metal and have the same size and are determined to be in contact with each other in response to detecting a single resonance associated with the metal features.

[0063] In one embodiment, the one or more processors are configured such that metal features in different layers are formed of the same metal and have the same size and are determined to be not in contact with each other in response to detecting two or more resonances associated with the metal features.

[0064] In one embodiment, the distance between the resonances corresponds to the amount that the different layers are displaced relative to each other.

[0065] In one embodiment, the different layers include two layers, each layer having at least one metallic feature.

[0066] In one embodiment, the metal features include different portions of a via extending through different layers.

[0067] In one embodiment, the one or more resonances include plasmon resonances.

[0068] In one embodiment, a single resonance comprises a maximum in the wavelength spectrum of the reflected radiation.

[0069] In one embodiment, the metal features in different layers of the structure are arranged in an array. The array may have a pitch. Detecting one or more resonances in the reflected radiation from the metal features includes detecting resonances associated with the pitch with one or more sensors.

[0070] In one embodiment, the resonance associated with the spacing is a Fano resonance.

[0071] In one embodiment, the resonance associated with the spacing has a resonance shape. The relative positions of the different layers are determined by one or more processors based on the resonance shape. In other words, the resonance associated with the spacing results in an asymmetric line shape. The relative positions of the different layers are determined by characterizing the asymmetry of the line shape.

[0072] In one embodiment, the one or more processors are configured such that determining the relative positions of the different layers comprises determining overlays associated with the different layers based on a resonance associated with the spacing.

[0073] In one embodiment, the one or more processors are further configured to facilitate adjusting a pitch of the array based on a resonance associated with the pitch.

[0074] In one embodiment, the structure includes at least a portion of a semiconductor device.

[0075] In one embodiment, the one or more processors are configured such that determining the relative positions of different layers based on the detected one or more resonances is performed as part of a semiconductor device manufacturing process. In one embodiment, the one or more processors are further configured to facilitate adjustment of the semiconductor device manufacturing process or design of a semiconductor device based on the relative positions of the different layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] The above-described aspects and other aspects and features will become apparent to those of ordinary skill in the art upon reviewing the following description of specific embodiments in conjunction with the accompanying drawings.

[0077] Figure 1 An example of a yield versus overlay curve is shown in accordance with an embodiment.

[0078] Figure 2A lithographic apparatus according to an embodiment is schematically depicted.

[0079] Figure 3 Embodiments of a lithocell or cluster according to embodiments are schematically depicted.

[0080] Figure 4 Example inspection systems and metrology techniques according to embodiments are schematically depicted.

[0081] Figure 5 An example inspection system according to an embodiment is schematically illustrated.

[0082] Figure 6 The relationship between the illumination points and the metrology targets of the inspection system according to the embodiment is shown.

[0083] Figure 7 A method for determining relative positions of different layers in a structure according to an embodiment is shown.

[0084] Fig. 8A Metallic features in different layers comprising different metals are shown, along with two corresponding resonances detected in the reflected radiation, according to an embodiment.

[0085] Figure 8B Metal features in different layers including the same metal and the same size are shown, along with corresponding example detected resonances showing contact and non-contact features, according to an embodiment.

[0086] Fig. 9 Detected resonances associated with spacing are shown according to an embodiment.

[0087] Fig.10 A process of deriving a plurality of variables of interest based on measurement data according to an embodiment is schematically depicted.

[0088] Fig.11 is a block diagram of an example computer system according to an embodiment.

[0089] Fig.12 is similar to Figure 2 Schematic diagram of a lithography projection apparatus.

[0090] Fig.13 According to the embodiment Fig.12 A more detailed view of the devices in the

[0091] Fig.14 According to the embodiment Fig.12 and Fig.13 A more detailed view of the source collector module of the device. DETAILED DESCRIPTION

[0092] Voltage contrast (VC) is a commonly used defect detection method. Its application in metrology may require dedicated monitoring marks and inspection using a scanning electron microscope. Voltage contrast monitoring marks are created by forming an overlaid metal pattern on two (or more) different layers of a semiconductor device in the process. The bottommost layer must have an electrical connection to the wafer substrate (e.g., a connection to ground) in order for the voltage contrast method to work properly. Depending on the semiconductor device manufacturing process, the metal pattern in the top or other upper layer above the bottommost layer may or may not have an electrical connection to the bottommost layer (e.g., a connection to ground), which appears as a bright (connected to ground) or dark (not connected to ground) voltage contrast point on the scanning electron microscope image. The bright and dark points provide an indication of whether one layer is electrically connected to another layer. When the set of marks is averaged, a yield curve can be constructed.

[0093] Voltage contrast is a scanning electron microscope-based technique that is typically much slower than optical measurements. While voltage contrast can be used to determine a variety of metrics, semiconductor device manufacturing operation process windows determined based on voltage contrast measurements are typically inaccurate because voltage contrast is only sensitive to the very high resistance of the ground path between layers where the voltage contrast overlay monitors the mark.

[0094] Defects can also be detected using optical inspection techniques. As an example in semiconductor device manufacturing, optical overlay detection (e.g., determining the relative positions of features in different layers of a semiconductor device) is currently performed using different optical methods. For example, for structures with a pitch larger than the wavelength of the radiation, this can be done by comparing the higher diffraction orders of the reflected radiation. Such diffraction-based optical detection of overlay is often limited in application to cases where the pitch of the structures is smaller than the wavelength of the radiation. Detecting higher diffraction orders presents technical challenges, which further restrict the allowable pitch-to-wavelength ratio. As another example, in oblique illumination, the asymmetry of the reflected light in different illumination directions is also used to infer potential overlay of dielectric (and possibly metallic) gratings, even at sub-wavelength spacings.

[0095] By way of non-limiting example, Figure 1 An example of a yield 5 versus overlay 7 curve 3 is shown. Yield 5 is an indication of process yield. For example, overlay 7 may have nanometer units. Mark 9 may be used to determine overlay margin 11 and / or overlay estimate 13, as shown. By way of non-limiting example, one may 1) fit the data with a logistic curve, 2) find a plateau yield value, 3) find the 99% (99% yield) value corresponding to the plateau value. Figure 1 The vertical lines in 4) are the programmed overlays of the platform endpoints, where 4) the overlay estimate (13) is the sum of these two programmed overlays and the overlay edge is the absolute value of the difference.

[0096] Advantageously, metallic features (e.g., first and second metallic features) in a layer (e.g., first and second layers) of a semiconductor device produce a resonance effect when illuminated with radiation from a normal radiation source used for optical inspection (which is a faster and easier to use method than voltage contrast and scanning electron microscopy), which can be used as an alternative to typical optical or voltage contrast methods. (For clarification, optical does not necessarily refer to the optical part of the electromagnetic spectrum. It may also include infrared and even terahertz. In this article, optical measurement can loosely refer to "electromagnetic wave" measurement, rather than measurement using electrons.) Existing methods (e.g., voltage contrast and current optical measurement methods) do not take advantage of the effects described above. The present system and method can also be used to detect structures with sub-wavelength spacing, which is not possible with diffraction-based optical methods. This means that the present system and method can be used to directly measure semiconductor device features without the need for special markings. In addition, the present system and method rely on linear optical effects, which are repeatable (e.g., unlike voltage contrast methods). For comparison, using voltage contrast, different measurements of the same feature sometimes show different results, complicating the interpretation of the measurement data. VC measurements of the same feature at different times can sometimes show different results due to unstable charging conditions, surface contamination, or other unknown reasons. VC measurements can also result in potential sample damage. Electrons tend to be destructive to samples, and maintaining a low enough dose to keep damage to an acceptable minimum while providing acceptable measurements is a concern. Optical measurement techniques do not have these and other disadvantages.

[0097] Metallic features exhibit plasmon resonances that are sensitive to the geometry and / or relative position of the metallic features. These resonances can be used to determine whether electrical contact exists between metallic features in different layers of a semiconductor device. The resonances can be detected in radiation reflected from a layer of a semiconductor device (e.g., a reflection signal or spectrum used for measurement) regardless of the diffraction order. Measuring at a specific diffraction order presents additional hardware challenges for the incident illumination direction (which determines the angle of the reflection order) and the detector assembly that must collect diffracted light belonging to a specific diffraction order. Methods that are independent of specific diffraction orders generally make it easier to position the detector equipment. The method is not dependent on diffraction orders because it senses the metrology parameter by observing the spectrum.

[0098] The resonances in the reflected radiation depend on the degree of contact due to the sensitivity of the surface plasmon resonances to geometry (e.g., relative displacement and contact between metallic features in different layers of a semiconductor device structure). For example, if two metallic features in different layers of a structure are in physical (e.g., electrical) contact, there may be one resonance in the reflected radiation, one for each of the two features (represented by two maxima in the wavelength spectrum). If the two metallic features lose contact, this will again affect the resonant wavelengths due to the fundamental change in geometry after the loss of contact. In the special case where two isolated layers have resonances at the same wavelength, the separation (maxima) between the two resonances, the location of the resonances (maxima) in the wavelength spectrum, the relative strengths of the resonances (e.g., the height of the peak indicating the maximum), and / or other information in the reflected signal can be used to determine various metrics.

[0099] For example, if the first metal feature and the second metal feature in the first layer and the second layer include different metals and / or have different sizes, at least two different resonances in the reflected radiation can be detected. (Whether two resonances are actually detected depends on the bandwidth of the detector and / or other factors. Similarly, sometimes the material has such high absorption that only the main dipole resonance remains visible). Based on (for example, one or more) resonance spectral positions, the distance between at least two different resonances, and other information, it is determined whether the metal features in different layers are in contact or not in contact with each other. If the first metal feature and the second metal feature in the first layer and the second layer are formed of the same metal and have the same size, if the metal features are in contact with each other, a single resonance associated with the metal features is detected, and if the metal features are not in contact with each other, two (or more) resonances can be detected. This is further described below.

[0100] In some embodiments, in conjunction with and / or in lieu of the plasmon resonance described above, a resonance associated with the pitch of an array of metallic features may be used to determine alignment, as described herein.

[0101] The description herein generally relates to mask manufacturing and patterning processes. More specifically, the following paragraphs describe various components of systems and / or related systems, and methods for determining relative positions of layers in a structure. As described above, these systems and methods can be used for overlay and / or other measurements in semiconductor device manufacturing processes, for example, or during other operations.

[0102] Although specific reference may be made herein to the manufacture of integrated circuits (ICs) for semiconductor devices, it should be understood that the description herein has many other possible applications. For example, it can be used to manufacture integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal display panels, thin film magnetic heads, etc. Those skilled in the art will understand that in the context of such alternative applications, any use of the terms "reticle", "wafer" or "die" herein should be considered interchangeable with the more general terms "mask", "substrate" and "target portion", respectively.

[0103] The term "projection optical system" as used herein should be broadly interpreted to include various types of optical systems, including, for example, refractive optical systems, reflective optical systems, apertures, and catadioptric optical systems. The term "projection optical system" may also include components operating according to any of these design types for collectively or individually directing, shaping, or controlling a projection radiation beam. The term "projection optical system" may include any optical component in a lithographic projection apparatus, regardless of where the optical component is located in the optical path of the lithographic projection apparatus. The projection optical system may include optical components for shaping, conditioning, and / or projecting radiation from a source before the radiation passes through a patterning device, and / or optical components for shaping, conditioning, and / or projecting radiation after the radiation passes through a patterning device. A projection optical system typically does not include a light source and a patterning device.

[0104] As an introduction, Figure 2 An embodiment of a lithographic apparatus LA is schematically depicted. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a support structure (e.g., mask table) MT configured to support a patterning device (e.g., mask) MA and connected to a first positioner PM configured to accurately position the patterning device according to certain parameters; a substrate table (e.g., wafer stage) WT (e.g., WTa, WTb, or both) configured to accommodate a substrate (e.g., a resistively coated wafer) W and coupled to a second positioner PW configured to accurately position the substrate according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies and often referred to as a field) of the substrate W. The projection system is supported on a reference frame (RF).

[0105] As shown, the device is of the transmissive type (eg, using a transmissive mask). Alternatively, the device may be of the reflective type (eg, using a programmable mirror array of the type described above, or using a reflective mask).

[0106] The illuminator IL receives a radiation beam from a radiation source SO. When the source is an excimer laser, for example, the source and the lithographic apparatus may be separate entities. In this case, the source is not considered to constitute part of the lithographic apparatus, and the radiation beam is delivered from the source SO to the illuminator IL by means of a beam delivery system BD comprising, for example, suitable directing mirrors and / or a beam expander. In other cases, for example when the source is a mercury lamp, the source may be an integral part of the apparatus. The source SO and the illuminator IL, together with the beam delivery system BD if desired, may be referred to as a radiation system.

[0107] The illuminator IL may vary the intensity distribution of the beam. The illuminator may be arranged to limit the radial extent of the radiation beam so that the intensity distribution is non-zero within an annular region in a pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL may be operable to limit the distribution of the beam in the pupil plane so that the intensity distribution is non-zero in a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the radiation beam in the pupil plane of the illuminator IL may be referred to as an illumination mode.

[0108] The illuminator IL may include an adjuster AD configured to adjust the (angular / spatial) intensity distribution of the light beam. Typically, at least the outer and / or inner radial range (typically referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the pupil plane of the illuminator can be adjusted. The illuminator IL is operable to change the angular distribution of the light beam. For example, the illuminator is operable to change the number and angular range of sectors in the pupil plane in which the intensity distribution is non-zero. By adjusting the intensity distribution of the light beam in the pupil plane of the illuminator, different illumination modes can be achieved. For example, by limiting the radial and angular range of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution can have a multipole distribution, for example, with a dipole, quadrupole or sextupole distribution. For example, by inserting an optical element providing the illumination mode into the illuminator IL or using a spatial light modulator, a desired illumination mode can be obtained.

[0109] The illuminator IL is operable to change the polarization of the beam, and is operable to adjust the polarization using an adjuster AD. The polarization state of the radiation beam passing through the pupil plane of the illuminator IL can be referred to as a polarization mode. Using different polarization modes can allow greater contrast to be achieved in the image formed on the substrate W. The radiation beam can be unpolarized. Alternatively, the illuminator can be arranged to linearly polarize the radiation beam. The polarization direction of the radiation beam can change in the pupil plane of the illuminator IL. In different areas within the pupil plane of the illuminator IL, the polarization direction of the radiation may be different. The polarization state of the radiation can be selected according to the illumination mode. For a multi-pole illumination mode, the polarization of each pole of the radiation beam can be generally perpendicular to the position vector of the pole in the pupil plane of the illuminator IL. For example, for a dipole illumination mode, the radiation can be linearly polarized in a direction substantially perpendicular to a line that divides two opposite sectors of the dipole into two. The radiation beam can be polarized in one of two different orthogonal directions, which can be referred to as an X polarization state and a Y polarization state. For a quadrupole illumination mode, the radiation in the sector of each pole can be linearly polarized in a direction substantially perpendicular to a line that divides the sector into two. This polarization mode can be referred to as XY polarization. Similarly, for a hexapole illumination mode, the radiation in a sector of each pole may be linearly polarized in a direction substantially perpendicular to a line bisecting the sector. This polarization mode may be referred to as TE polarization.

[0110] Furthermore, the illuminator IL typically includes various other components, such as an integrator IN and a condenser CO. The illumination 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 directing, shaping or controlling radiation.

[0111] The luminaire thus provides a conditioned radiation beam B having a desired uniformity and intensity distribution in its cross-section.

[0112] The support structure MT supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions (e.g., whether the patterning device is maintained in a vacuum environment). The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure can be a frame or a table, for example, which can be fixed or movable as required. The support structure can ensure that the patterning device is in a desired position, for example, relative to a projection system. Any use of the term "reticle" or "mask" herein can be considered to be synonymous with the broader term "patterning device".

[0113] The term "patterning device" as used herein should be broadly interpreted as referring to any device that can be used to impart a pattern in a target portion of a substrate. In one embodiment, the patterning device is any device that can be used to impart a radiation beam having a pattern in its cross-section to produce the pattern in the target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so-called assist features. Typically, the pattern imparted to the radiation beam will correspond to a specific functional layer in the device created in the target portion of the device (e.g. an integrated circuit).

[0114] The patterning device may 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, alternating phase shift, and attenuated phase shift, as well as 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 an incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam, which is reflected by the matrix of mirrors.

[0115] The term "projection system" as used herein should be broadly interpreted as including any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, appropriate to the exposure radiation used, or to other factors such as the use of immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the broader term "projection system".

[0116] The projection system PS has an optical transfer function that may be non-uniform, which may affect the pattern imaged on the substrate W. For unpolarized radiation, this effect can be fairly well described by two scalar mappings, which describe the transmission (apodization) and relative phase (aberration) of the radiation leaving the projection system PS as a function of its position in the pupil plane. These scalar mappings, which may be called transmission mappings and relative phase mappings, can be expressed as linear combinations of a complete set of basis functions. A convenient group is the Zernike polynomials, which form a set of orthogonal polynomials defined on the unit circle. The determination of each scalar mapping may include determining the coefficients in such an expansion. Since the Zernike polynomials are orthogonal on the unit circle, the Zernike coefficients can be determined by calculating the inner product of the measured scalar mapping with each Zernike polynomial in turn, and dividing by the square of the norm of the Zernike polynomial.

[0117] The transmission map and the relative phase map are field and system dependent. That is, in general, each projection system PS will have a different Zernike expansion for each field point (i.e. for each spatial position in its image plane). The relative phase of the projection system PS in its pupil plane can be determined by projecting radiation, for example from a point source in the object plane of the projection system PS (i.e. the plane of the patterning device MA) through the projection system PS and measuring the wavefront (i.e. the trajectory of points with the same phase) using a shearing interferometer. The shearing interferometer is a common path interferometer and therefore, advantageously, does not require a second reference beam to measure the wavefront. The shearing interferometer may comprise a diffraction grating, such as a two-dimensional grid in the image plane of the projection system (i.e. the substrate table WT), and a detector arranged to detect an interference pattern in a plane conjugate to the pupil plane of the projection system PS. The interference pattern is related to the derivative of the radiation phase in the shear direction with respect to the coordinates in the pupil plane. The detector may comprise an array of sensing elements, such as a charge coupled device (CCD).

[0118] The projection system PS of the lithographic apparatus may not produce visible fringes, so a phase stepping technique (e.g., moving a diffraction grating) can be used to improve the accuracy of determining the wavefront. The stepping can be performed in the plane of the diffraction grating and in a direction perpendicular to the scanning direction of the measurement. The stepping range can be one grating period, and at least three (evenly distributed) phase steps can be used. Thus, for example, three scanning measurements can be performed in the y direction, each for a different position in the x direction. This stepping of the diffraction grating effectively converts phase changes into intensity changes, allowing the phase information to be determined. The grating can be stepped in a direction perpendicular to the diffraction grating (z direction) to calibrate the detector.

[0119] The diffraction grating may be scanned sequentially in two perpendicular directions, which may coincide with the axes (x and y) of the coordinate system of the projection system PS, or may be at an angle of, for example, 45 degrees to these axes. The scan may be performed over an integer number of grating periods, for example one grating period. The scan averages the phase changes in one direction, allowing reconstruction of the phase changes in the other direction. This allows the wavefront to be determined as a function of the two directions.

[0120] The transmission (apodization) of the projection system PS in its pupil plane can be determined by projecting radiation, e.g. from a point source in the object plane of the projection system PS (i.e. the plane of the patterning device MA), through the projection system PS and measuring the intensity of the radiation in a plane conjugate to the pupil plane of the projection system PS using a detector. The same detectors as used for measuring the wavefront to determine aberrations can be used.

[0121] The projection system PS may include a plurality of optical (e.g., lens) elements, and may further include an adjustment mechanism AM configured to adjust one or more optical elements to correct for aberrations (phase variations across the pupil plane across the field). To achieve this, the adjustment mechanism may be operable to manipulate one or more optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a coordinate system in which its optical axis extends in the z-direction. The adjustment mechanism may be operable to perform any combination of: displacing one or more optical elements; tilting one or more optical elements; and / or deforming one or more optical elements. The displacement of the optical elements may be in any direction (x, y, z, or a combination thereof). The tilting of the optical element is typically deviated from a plane perpendicular to the optical axis by rotating about an axis in the x and / or y direction, although rotation about the z-axis may be used for non-rotationally symmetric aspheric optical elements. The deformation of the optical element may include low-frequency shapes (e.g., astigmatism) and / or high-frequency shapes (e.g., free-form aspheric surfaces). For example, deformation of the optical element may be performed by applying a force on one or more sides of the optical element using one or more actuators and / or by heating one or more selected areas of the optical element using one or more heating elements. Typically, it may not be possible to adjust the projection system PS to correct for apodization (transmission variations in the pupil plane). When designing a patterning device (e.g., mask) MA for the lithographic apparatus LA, a transmission map of the projection system PS may be used. Using computational lithography techniques, the patterning device MA may be designed to at least partially correct for apodization.

[0122] The lithographic apparatus may be of a type having two (dual-stage) or more tables (e.g., two or more substrate tables WTa, WTb, two or more patterning device tables, substrate tables WTa and tables WTb below the projection system without a dedicated substrate for, for example, facilitating measurement and / or cleaning, etc.). In such a "multi-stage" machine, additional tables may be used in parallel, or preparatory steps may be performed on one or more tables while one or more other tables are being used for exposure. For example, alignment measurements may be performed using an alignment sensor AS and / or level (height, tilt, etc.) measurements may be performed using a level sensor LS.

[0123] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, such as water, to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, such as between the patterning device and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of a projection system. The term "immersion" as used herein does not mean that structures such as substrates must be immersed in the liquid, but only means that the liquid is located between the projection system and the substrate during exposure.

[0124] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by the illumination system IL. The radiation 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 passing through the patterning device MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of a second positioner PW and a position sensor IF (interferometric device, linear encoder, 2-D encoder or capacitive sensor), the substrate table WT can be accurately moved, for example, to the position of different target portions C in the path of the radiation beam B. Similarly, a first positioner PM and a further positioning sensor MA ( Figure 2 The support structure MT may be used to accurately position the patterning device MA relative to the path of the radiation beam B (for example, after mechanical retrieval from a mask library, or during scanning). In general, movement of the support structure MT may be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) which form part of the first positioner PM. Similarly, movement of the substrate table WT may be achieved using a long-stroke module and a short-stroke module which 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 to the short-stroke actuator only, or may be fixed. The patterning device MA and the substrate W may be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks as shown occupy dedicated target portions, they may be located in the spaces between target portions (these are referred to as scribe lane alignment marks). Similarly, where more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0125] The described apparatus can be used in at least one of the following modes. In step mode, the support structure MT and the substrate table WT remain substantially stationary while a pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e., a static exposure). The substrate table WT is then moved in the X and / or Y direction so that different target portions C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. In scanning mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto the target portion C (i.e., a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure MT may be determined by the (zoom) magnification and image reversal characteristics of the projection system PS. In scanning mode, the maximum size of the exposure field limits the width of the target portion in a single dynamic exposure (in the non-scanning direction), while the length of the scanning movement determines the height of the target portion (in the scanning direction). In another mode, the support structure MT holding the programmable patterning device remains substantially stationary, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto the target portion C. In this mode, a pulsed radiation source is typically employed and the programmable patterning device is updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography utilizing a programmable patterning device, such as a programmable mirror array of the type described above.

[0126] Combinations and / or variations of the above-described modes of use or entirely different modes of use may also be employed.

[0127] Before or after exposure, the substrates referred to herein may be processed, for example, in a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, to produce multi-layer ICs, for example, a substrate may be processed more than once, so that the term substrate as used herein may also refer to a substrate that has included multiple processed layers.

[0128] As used herein, the terms "radiation" and "beam" include all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g., having a wavelength of 365, 248, 193, 157, or 126 nanometers) and extreme ultraviolet (EUV) radiation (e.g., having a wavelength in the range of 5-20 nanometers), as well as particle beams, such as ion beams or electron beams.

[0129] Various patterns on or provided by a patterning device may have different process windows, i.e., the space of process variables under which a pattern will be produced within specification. Examples of pattern specifications related to potential system defects include checking 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 an area thereof may be obtained by merging (e.g., overlapping) the process windows of each individual pattern. The boundaries of the process window of a set of patterns include the boundaries of the process windows of some individual patterns. In other words, these individual patterns limit the process window of a set of patterns. These patterns may be referred to as "hot spots" or "processing window limiting patterns (PWLP)", which are used interchangeably herein. It is possible and economical to focus on hot spots when controlling a portion of a patterning process. When there are no defects in the hot spots, it is most likely that there are no defects in other patterns.

[0130] like Figure 3 As shown, the lithography apparatus LA may form part of a lithography cell LC, which is sometimes also referred to as a lithography unit or cluster, and which also includes equipment for performing pre-exposure and post-exposure processing on a substrate. Typically, these include 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 cold plates CH and / or one or more bake plates BK. A substrate handler or robot RO picks up one or more substrates from input / output ports I / O1, I / O2, moves them between different processing equipment, and transfers them to a loading station LB of the lithography apparatus. These equipment are generally collectively referred to as tracks and are under the control of a track control unit TCU, which itself is controlled by a monitoring system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Thus, the different equipment may be operated to maximize throughput and processing efficiency.

[0131] In order to correctly and consistently expose a substrate exposed by a lithographic apparatus and / or to monitor a portion of a patterning process (device manufacturing process), which patterning process includes at least one pattern transfer step, (e.g., an optical lithography step), it is desirable to inspect the substrate or other object to measure or determine one or more properties, such as alignment, overlay (e.g., between structures in overlay layers or between structures in the same layer, e.g., a double patterning process has been provided to the layer alone), line thickness, critical dimension (CD), focus offset, material properties, etc. Therefore, the manufacturing facility in which the lithography cell LC is located also typically includes a measurement system that measures some or all of the substrates W or other objects in the lithography cell that have been processed in the lithography cell ( Figure 2), the metrology system may be part of the lithocell LC, for example, it may be part of the lithographic apparatus LA (e.g. an alignment sensor such as ( Figure 2 )).

[0132] The one or more measurement parameters may include, for example, alignment, overlay between successive layers formed in or on a patterned substrate, critical dimensions (CD) of features formed in or on a patterned substrate (e.g., critical line width), focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberration of an optical lithography step, etc. The measurement may be performed on a target on the product substrate itself and / or on a dedicated metrology target disposed on the substrate. The measurement may be performed after resist development but before etching, after etching, after deposition, and / or at other times.

[0133] There are various techniques for measuring structures formed in patterning processes, including the use of scanning electron microscopes, image-based measurement tools and / or various special tools. As described above, a fast and non-invasive special metrology tool is a tool that directs a radiation beam to a target on a substrate surface and measures the properties of a scattered (diffraction / reflection) beam. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. Traditionally, this can be referred to as diffraction-based metrology. One such application of this diffraction-based metrology is to measure the overlay between target layers. Other applications are also known. For example, asymmetry can be measured by comparing opposite parts of the diffraction spectrum (for example, comparing the -1st and +1st orders in the diffraction spectrum of a periodic grating). This can be performed as described above and in U.S. Patent Application Publication US 2006-066855, for example, the entire contents of which are incorporated herein by reference. The present system and method describe alternative overlay measurement techniques.

[0134] Thus, in a device manufacturing process (e.g., a patterning process or a lithography process), a substrate or other object may be subjected to various types of measurements during or after the process. The measurements may determine whether a particular substrate is defective, may establish adjustments to the process and equipment used in the process (e.g., aligning two layers on the substrate or aligning the patterning device to the substrate), may measure the performance of the process and equipment, or may be used 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, the ASML SMASH metrology system), mechanical measurements (e.g., profiling using a stylus, an atomic force microscope (AFM), and / or non-optical imaging (e.g., scanning electron microscope (SEM)). The SMASH (Smart Alignment Sensor Hybrid) system, as described in U.S. Pat. No. 6,961,116 (incorporated herein by reference in its entirety), employs a self-referencing interferometer that produces two overlapping and relatively rotated images of an alignment mark, detects intensities in a pupil plane that cause Fourier transform interference of the images, and extracts position information from the phase difference between the diffraction orders of the two images, which manifests itself as intensity variations in the interference orders.

[0135] The metrology results may be provided directly or indirectly to the monitoring system SCS. If an error is detected, the exposure of subsequent substrates may be adjusted (especially if the check can be done quickly and quickly enough so that one or more other substrates of the batch will still be exposed) and / or the subsequent exposure of already exposed substrates may be adjusted. In addition, already exposed substrates may be stripped and reworked to improve yield, or discarded to avoid further processing on substrates that are known to be defective. In the event that only some target portions of the substrate are defective, further exposure may be performed only on those target portions that meet the specification. Other manufacturing process adjustments are also under consideration.

[0136] The metrology system may be used to determine one or more properties of a substrate structure, specifically how one or more properties vary from one substrate structure to another, or how different layers of the same substrate structure vary from layer to layer. The metrology system may be integrated into the lithographic apparatus LA or the lithocell LC, or may be a standalone apparatus.

[0137] In order to achieve metrology, one or more targets are typically specifically set on the substrate. In one embodiment, the target is specially designed and can include a periodic structure. In one embodiment, the target is a part of a device pattern, for example, a periodic structure of a device pattern. In one embodiment, the target on the substrate may include one or more 1-D periodic structures (e.g., gratings) that are printed so that after development, the periodic structure features are formed by solid resist lines. In one embodiment, the target may include one or more 2-D periodic structures (e.g., gratings) that are printed so that after development, the one or more periodic structures are formed by solid resist posts or vias in the resist. Optionally, the rods, posts, or vias may be etched into the substrate (e.g., etched into one or more layers on the substrate).

[0138] However, in some embodiments, as described below, metrology does not require a specific target. Instead, metrology can be performed on the metal structures (e.g., as described) and / or other features of the actual device. For example, instead of including additional, separately designed metrology marks (or marks) in a given pattern, the present systems and methods can utilize the metal features of the actual device for overlay and / or other metrology. This can reduce and / or eliminate the time and effort spent on designing and manufacturing dedicated metrology marks, and / or have other advantages.

[0139] In some embodiments, one of the parameters of interest in the patterning process is overlay, as described herein. Conventional overlay can be measured using a dark field scattering method, in which the zeroth order diffraction (corresponding to specular reflection) is blocked and only higher order diffraction is processed. Examples of dark field metrology can be found in PCT patent application publications WO 2009 / 078708 and WO 2009 / 106279, which are incorporated herein by reference in their entirety. Further developments of the technology have been described in U.S. patent application publications US2011-0027704, US2011-0043791, and US2012-0242970, which are incorporated herein by reference in their entirety. Diffraction-based overlay uses diffraction orders detected by dark field, enabling overlay measurements of smaller targets. These targets can be smaller than the illumination point and can be surrounded by device product structures on the substrate. In one embodiment, multiple targets can be measured in one radiation capture.

[0140] As described above, compared to conventional overlay measurement techniques, the present system and method utilize how metal features in semiconductor device layers produce resonance effects when illuminated with radiation from common radiation sources used in optical overlay detection (a method that is faster and easier to use than voltage contrast and scanning electron microscopy), which can be used as an alternative to overlay detection. For overlay, these resonances can be used to determine whether there is contact between metal features in different layers of a semiconductor device. For example, if the metal features in different layers include different metals and / or have different sizes, at least two different resonances (indicated by maxima in the wavelength spectrum) in the reflected radiation can be detected. Based on the distance (maxima) between at least two different resonances, it is determined whether the metal features in different layers are in contact or not in contact with each other. If the metal features in different layers are formed of the same metal and have the same size, if the metal features are in contact with each other, a single resonance (maximum) associated with the metal features is detected, and if the metal features are not in contact with each other, two (or more) resonances (maxima) can be detected. The separation between the two resonances (maxima), the location of the resonances (maxima) in the wavelength spectrum, the relative strength of the resonances in the reflected signal (e.g., the height of the peak indicating the maximum) and / or other information can be used to determine the amount of overlay.

[0141] Figure 4 An example inspection system (e.g., scatterometer) 10 that can be used to detect overlay and / or perform other metrology operations is depicted. It includes a broadband (white light) radiation source projector 2 that projects or otherwise illuminates radiation onto a substrate W. The redirected radiation is passed to a sensor such as a spectrometer detector 4 and / or other sensor that measures the spectrum (intensity as a function of wavelength) of the specularly reflected radiation, such as Figure 4 The curve graph in the lower left corner is shown. Based on this data, one or more processors PU can be used, for example, by strictly coupling wave analysis and nonlinear regression, to Figure 4 By comparing with the simulated spectral library shown in the lower right corner, or through other operations, the structure or profile that produces the detected spectrum can be reconstructed. This inspection system can be configured as a normal incidence inspection device, an oblique incidence inspection device, and / or have other configurations.

[0142] Another example inspection system that can be used is Figure 5 For example, Figure 5 The system shown can be Figure 4A more detailed view of the system 10 is shown. In some embodiments, radiation emitted by the radiation source projector 2 is collimated using a lens system 12, transmitted through an interference filter 113 and a polarizer 17, reflected by a partially reflective surface 16, and focused to a spot S on a substrate W via an objective lens 15 having a high numerical aperture (NA) (e.g., at least 0.9). An immersion inspection version of the system 10 (using a relatively high refractive index fluid, such as water) may also be used, and may have a numerical aperture greater than 1.

[0143] As in Figure 2 In the lithographic apparatus LA in the embodiment of the present invention, one or more substrate tables ( Figure 5 The substrate table (not shown) is used to hold the substrate W during the measurement operation. The one or more substrate tables may be similar in form to Figure 2 The substrate table WT is similar or identical to the substrate table WT of the inspection system 10. In examples where the inspection system 10 is integrated with a lithographic apparatus, they may even be the same substrate table. Coarse and fine positioners may be provided and configured to accurately position the substrate relative to the measuring optical system. For example, various sensors and actuators are provided to obtain the position of a target portion of interest of the structure and place that position under the objective lens 15. Typically, many measurements will be made of the target portion of the structure at different locations on the substrate W. The substrate support may be moved in the X and Y directions to obtain different targets and in the Z direction to obtain the desired position of the target portion relative to the focus of the optical system. When, for example, the optical system can actually remain essentially stationary (usually in the X and Y directions, but possibly also in the Z direction) and the substrate moves, it may be convenient to think of and describe the operation as if the objective lens is brought to different positions relative to the substrate. If the relative position of substrate and optical system is correct, in principle it does not matter which of the two moves in the real world, or whether both move, or whether part of the optical system moves (e.g. in Z and / or tilt direction) and the rest of the optical system is stationary while the substrate moves (e.g. in X and Y direction, but optionally also in Z and / or tilt direction).

[0144] The radiation reflected and / or otherwise redirected by the substrate W then passes through the partially reflective surface 16 to a detector such as a detector 18 (similar to and / or similar to Figure 4 The detector 18 may be located at the back-projected focal plane 111 (i.e., at the focal length F of the objective lens 15), or the plane 111 may be re-imaged onto the detector 18 using auxiliary optics (not shown). The detector 18 may be a two-dimensional detector, so that a two-dimensional angular scattering spectrum of the substrate target 30 may be measured. For example, the detector 18 may be a CCD or CMOS sensor array, and, for example, an integration time of 40 milliseconds per frame may be used.

[0145] The reference beam can be used, for example, to measure the intensity of incident radiation. For example, when the radiation beam is incident on the partially reflective surface 16, a portion of it is transmitted through the partially reflective surface 16 toward the reference mirror 14 as a reference beam. The reference beam is then projected onto a different portion of the same detector 18, or alternatively onto a different detector (not shown).

[0146] One or more interference filters 113 may be used to select wavelengths of interest in, for example, 400-800 nm, 200-400 nm, 10-200 nm, and / or other ranges (e.g., depending on the metal used for the metallic feature and / or other factors). Interference filter 113 may be tunable, rather than comprising a set of different filters. In some embodiments, a grating may be used in place of an interference filter. In some embodiments, an aperture stop or spatial light modulator (not shown) may be provided in the illumination path to control the range of angles of incidence of the radiation on the target.

[0147] The detector 18 can measure the intensity of the redirected radiation at a single wavelength (or a narrow wavelength range), the individual intensities at multiple wavelengths, or the overall intensity over a wavelength range. In addition, the detector 18 can measure the intensities of the transverse magnetic polarized radiation and the transverse electric polarized radiation and / or the phase difference between the transverse magnetic polarized radiation and the transverse electric polarized radiation, respectively. The detector 18 can include a CCD device that records the spatially averaged incident intensity to obtain a scalar value for evaluation and / or for the reflected intensity of other components.

[0148] For typical overlay measurement, the target (portion) 30 on substrate W can be a 1-D grating, which is printed so that after development, the rods are formed by solid resist lines (for example, which can be covered by a deposited layer) and / or other materials. Alternatively, the target 30 can be a 2-D grating, which is printed so that after development, the grating is formed by solid resist columns and / or other features in the resist. However, advantageously, through the present system and method, the target (portion) 30 can include a target portion of a structure of substrate W, and different layers of the structure and / or other target portions include metal features. The target portion (for example, target 30) can be formed by any portion of a pattern including such layers and metal features. In other words, the target 30 does not have to be limited to a specific overlay target. In some embodiments, the different layers of the target (portion) 30 include two layers, each layer having at least one metal feature. In some embodiments, the metal features include different portions of vias extending through different layers. This example is not intended to be limiting.

[0149] The rods, posts, vias, and / or other features may be etched into or onto a substrate (e.g., etched into one or more layers on a substrate), deposited on a substrate, covered by a deposited layer, and / or have other properties. The target (portion) 30 (e.g., rods, posts, vias, etc.) is sensitive to process variations in the patterning process (e.g., in a lithographic projection apparatus, such as optical aberrations in the projection system, focus variations, dose variations, etc.), such that the process variations manifest themselves in variations in the target 30. Thus, measurement data from the target 30 may be used to determine adjustments to one or more manufacturing processes, and / or used as a basis for making actual adjustments.

[0150] For example, the measurement data from target 30 may indicate overlay of two layers of a semiconductor device. The 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 relative positions of different layers of the semiconductor device, and to determine adjustments to semiconductor device manufacturing equipment based on the determined one or more semiconductor device manufacturing process parameters. In some embodiments, the determined one or more semiconductor device manufacturing process parameters include mask design, metrology target design, semiconductor device design, radiation intensity, radiation incident angle, radiation wavelength, pupil size and / or shape, resist material, and / or other process parameters.

[0151] Angular resolved scattering is useful in measuring the asymmetry of features in products and / or resist patterns. One specific application of asymmetry measurement is the measurement of overlay. For example, using Figure 4 or Figure 5 The basic concept of measuring asymmetry in system 10 is described in U.S. Patent Application Publication US2006-066855, the entire contents of which are incorporated herein. In short, for such overlay measurements, while the positions of the diffraction orders in the diffraction spectrum of the target are determined solely by the periodicity of the target, the asymmetry in the diffraction spectrum represents the asymmetry in the individual features that make up the target. Figure 5 In a system where the detector 18 can be an image sensor, this asymmetry in the diffraction orders manifests itself directly as an asymmetry in the pupil image recorded by the detector 18. This asymmetry can be measured in PUs using digital image processing and calibrated based on known overlay values.

[0152] Figure 6 Shows Figure 5Plan view of a typical target 30 and the range of the illumination spot S in the system. In general, in order to obtain a diffraction spectrum that is not disturbed by surrounding structures, in one embodiment, the target 30 is a periodic structure (e.g., a grating) that is larger than the width (e.g., diameter) of the illumination spot S. The width of the spot S can be smaller than the width and length of the target. In other words, the target is "underfilled" by the illumination, and the diffraction signal is substantially unaffected by any signal from product features, etc., other than the target itself. Illumination devices 2, 12, 113, 17 ( Figure 5 ) can be configured to provide uniform intensity illumination at the rear focal plane of objective lens 15. Alternatively, illumination can be limited to an on-axis or off-axis direction, for example by including an aperture in the illumination path. Advantageously, the present system and method do not require these same characteristics. As described above, target 30 can include a target portion of a substrate structure including metal features in different layers of the structure and / or other target portions. The target portion (e.g., target 30) can be formed by any portion of a pattern including such layers and metal features. In other words, target 30 is not necessarily limited to a specific overlay target as described above. This is because the present system and method are configured to utilize the resonance of any metal feature in a layer of a semiconductor device structure to determine overlay. No periodic grating structure is required.

[0153] Figure 7 A method 700 is shown for determining whether (e.g., first and second) metal features in different (e.g., first and second) layers in a structure are in electrical contact with each other. In some embodiments, this may include determining the relative positions of different layers in the structure. In some embodiments, determining whether metal features in different layers in the structure are in electrical contact with each other and / or determining the relative positions of different layers in the structure is performed as part of a semiconductor device manufacturing process, wherein the structure forms at least a portion of the semiconductor device (e.g., as described herein). In some embodiments, for example, one or more operations of method 700 may be performed in Figure 4 and Figure 5 The system 10 shown or by Figure 4 and Figure 5 The method 700 may be implemented in or by the system 10 shown, and / or implemented in or by other systems. In some embodiments, the method 700 includes irradiating 702 a target portion of a structure with radiation, detecting 704 one or more resonances in reflected radiation from a metallic feature in the structure, determining 706 whether metallic features in different layers are in electrical contact with each other and / or determining relative positions of different layers of the structure, and / or other operations. Existing systems do not utilize resonances of metallic features using methods similar and / or the same as the method 700. The method 700 may be generally applicable to a number of different processes where detecting resonances in radiation reflected from metallic features is useful.

[0154] As described herein, method 700 is optically based and does not require the same system components required by voltage contrast-based methods. For example, operation 702 includes irradiating a target portion of a structure with radiation. In some embodiments, the radiation includes visible light and / or other radiation. In some embodiments, the radiation includes broadband white light projected from a radiation source. The radiation is directed onto the target portion of the structure. In some embodiments, the radiation can be collimated using a lens system and transmitted through interference filters, polarizers, and / or other components.

[0155] In some embodiments, the structure includes at least a portion of a semiconductor device. The target portion includes metal features in different layers of the structure. The different layers may include two (or more) layers, each layer having at least one metal feature. The metal features may form some or all of the metrology marks of a particular design and / or be part of an actual semiconductor device. The metal features may have any size, shape, and / or arrangement that allows the present systems and methods to function as described herein. As a non-limiting example, the metal features may have a size of approximately 50 nm or less. The metal features may be part of a semiconductor device pattern, and / or arranged in other ways. By way of another non-limiting example, the metal features may include different portions of vias in a semiconductor device that pass through different layers. In some embodiments, operation 702 may be performed by Figure 4 and Figure 5 The invention may be performed using a radiation source similar or identical to source 2 shown and described above, and / or other sources, for example.

[0156] Operation 704 includes detecting one or more resonances in reflected radiation from metallic features in the structure. The radiation from operation 702 is reflected by metallic features in the structure. Since light can only be focused up to its diffraction limit, the reflected radiation is from the metallic features throughout the illumination point relative to the incident radiation. (Thus, this technique can help identify areas of semiconductor devices with defects. The present method and system can also be used to guide voltage contrast inspections.) The reflected radiation is passed to a sensor such as a spectrometer detector and / or other sensor that measures the spectrum (intensity as a function of wavelength) of the reflected radiation. Such a sensor can be configured as a normal incidence inspection device (e.g., where the sensor is oriented at an angle perpendicular to the structure), an oblique incidence inspection device, and / or have other configurations. Resonances can be detected in radiation reflected from metallic features in a layer of a structure such as a semiconductor device (e.g., a reflection signal or spectrum for optical measurement) regardless of the diffraction order of the radiation.

[0157] In some embodiments, one or more resonances include plasmon resonances. Plasmon resonances are coupled oscillations of free electrons in a metal with incident radiation, and are generated in the presence of a metal-dielectric interface. This appears in the far-field scattering / reflection spectrum in the form of a dipole resonance. For complex geometric configurations, there may also be additional smaller resonance peaks in the far-field spectrum that are only slightly visible above the background spectrum. The wavelength of the plasmon resonance is sensitive to both geometry and material. Therefore, when two particles (e.g., metal features) are in physical contact or close proximity to each other, the resonant wavelength shifts depending on the environment. When two particles (metal features) resonate individually at the same wavelength, they lose contact and their individual resonances couple, resulting in so-called spectral splitting, resulting in the appearance of two resonances. The physical separation between the two particles is inversely correlated with the spectral distance (and / or spectral position) between the two resonances produced.

[0158] A single resonance may include an intensity maximum in a wavelength spectrum of the reflected radiation. Detecting one or more resonances may include identifying a maximum value of the intensity of the reflected radiation in the entire wavelength spectrum. This may be performed by a processor (e.g., by electronically comparing the intensities of different wavelengths of the reflected radiation), and / or by other components. In some embodiments, if the (e.g., first and second) metal features in different (e.g., first and second) layers include different metals and / or have different sizes, this may cause one or more resonances in the reflected radiation to be detected by one or more sensors, and based on the spectral position of the one or more resonances (e.g., as shown in the figure), it is determined that the (first and second) metal features in the (first and second) layers are in electrical contact or non-electrical contact with each other. As an example, at least two different resonances may be detected in the reflected radiation. Based on the distance between at least two different resonances, it may be determined that the metal features in different layers are in electrical contact or non-electrical contact with each other.

[0159] However, in some cases only one resonance remains visible while the other is washed out due to high absorption. Also, there may be a situation where all resonances are washed out due to absorption losses. This may be the case, for example, when the two particles are in contact, no visible resonances are seen. But when they lose contact, one or more resonances shift to a frequency where material losses are minimal, allowing for observation. In this case, predictions can still be made by assuming that no resonant device features are in contact, and that non-contacting resonant device features are present.

[0160] In some embodiments, if metal features in different layers are formed of the same metal and have the same size, a single resonance associated with the metal features is detected if the metal features are in contact with each other, and two (or more) resonances may be detected if the metal features are not in contact with each other. By way of non-limiting examples of these different situations, Fig. 8AMetal features 801 (e.g., first metal feature), 803 (e.g., second metal feature) including different metals in different layers 805 (e.g., first layer), 807 (e.g., second layer) of a semiconductor device (different parts of a via, or any other geometric structure), and two corresponding detected resonances 809, 811 in reflected radiation are shown. In this example, the metal features 801 and 803 are formed of copper (Cu) and tungsten (W). In this example, the features 801 and 803 are surrounded by TaRu and TiN liners, respectively, and the layers 805 and 807 include various sub-layers (e.g., formed of SiO, low-k, SiN, Ni, Si, etc.).

[0161] Fig. 8A An example view 813 of wavelength 804 versus intensity 806 of reflected radiation is shown. Radiation may be reflected, for example, from metallic features 801, 803 in a structure (e.g., in layers 805, 807 of a semiconductor device). View 813 shows the spectral positions of two resonances (maxima) 809 and 811 across the wavelength 804 in the intensity 806. Metallic features 801, 803 in different layers 805, 807 are in electrical contact or not with each other based on the spectral position (e.g., the distance 815 therebetween) between the two different resonances 809, 811 (described below).

[0162] By way of a second non-limiting example, Figure 8B Metal features 814 (e.g., first metal features), 816 (e.g., second metal features) in different layers 818 (e.g., first layer), 820 (e.g., second layer) including the same metal and the same size are shown, as well as corresponding spectral positions of the resonances 808, 810, 812 detected by the example, and the corresponding spectral positions show the electrical contact (resonance 808) and non-electrical contact (resonances 810 and 812) features 814 and 816. In this example, the metal features 814 and 816 are both formed of copper (Cu) and have substantially the same size. In this example, the features 814 and 816 are surrounded by TaRu and TiN liners, respectively, and the layers 818 and 820 include various sublayers (e.g., formed of SiO, low-k, SiN, Ni, Si, etc.).

[0163] When two metal features 814, 816 (e.g., different portions of a via, or any other geometric shape) are in electrical contact with each other, they appear optically as one feature, exhibiting a dipole surface plasmon polariton resonance to radiation from a radiation source. The resonance in the reflected radiation depends on the degree of electrical contact between the metal features in different layers of the semiconductor device structure. For example, if two metal features in different layers of the structure are in electrical contact, then there is a dipole resonance in the reflected radiation. If the two metal features lose electrical contact, then they appear as two different features to the incident radiation, each with its own dipole resonance. These resonances hybridize or couple, resulting in two resonances in the reflected radiation.

[0164] Figure 8B Two example views 800, 802 of wavelength 804 versus intensity 806 of reflected radiation are shown. Radiation may, for example, be reflected from metal features 814, 816 in a structure (e.g., in layers 818, 820 of a semiconductor device). View 800 shows one resonance (maximum) 808 (e.g., at λ0), while view 802 shows two resonances (maxima) 810 and 812 in intensity 806 across wavelength 804. This means that the reflected radiation associated with view 800 is from metal features 814, 816 in different layers 818, 820 of a semiconductor device (e.g.), which are in electrical contact with each other and optically appear as a single object. The reflected radiation associated with view 802 is from metal features 814, 816 in different layers 818, 820 of a semiconductor device (e.g.), which are not in electrical contact with each other and optically appear as two separate objects.

[0165] Return to Figure 7 In some embodiments, operation 704 may be performed by Figure 4 and Figure 5 The process may be performed by a detector similar or identical to the detectors 4 and / or 18 shown in and described above, and / or one or more processors similar or identical to the processor PU.

[0166] Operation 706 includes determining whether (e.g., first and second) metal features in different (e.g., first and second) layers are in electrical contact with each other based on the detected one or more resonances and / or other information. Determining whether metal features in different layers are in electrical contact with each other can be based on the spectral position of one or more resonances. For example, if the metal features in different layers include different metals and / or have different sizes, at least two different resonances (maxima) in the reflected radiation can be detected. Based on the distance (maxima) between at least two different resonances, it is determined that the metal features in different layers are in electrical contact or not in electrical contact with each other. In some embodiments, if the metal features in different layers are formed of the same metal and have the same size, if the metal features are in contact with each other, a single resonance (maximum) associated with the metal features is detected, and if the metal features are not in contact with each other, two (or more) resonances (maxima) can be detected. In some embodiments, the distance between the resonances corresponds to the amount by which the different features are displaced (or not in electrical contact) relative to each other.

[0167] For example, operation 706 includes determining whether metal features in different layers are in electrical contact with each other based on the detected one or more resonances and / or other information. In some embodiments, as described above, the metal features in different layers include different metals and / or have different sizes, which causes at least two different resonances in the reflected radiation to be detected by one or more sensors, and the metal features in different layers are determined by one or more processors to be in contact or not in contact with each other based on the distance between the at least two different resonances. In some embodiments, as described above, the metal features in different layers are formed of the same metal and have the same size, and the one or more processors are configured to determine that the metal features in different layers are in contact with each other in response to detecting a single resonance associated with the metal features, and are determined to be not in contact with each other in response to detecting more than two resonances associated with the metal features.

[0168] In some embodiments, operation 706 includes determining the relative position of different layers of the structure. The relative position can be determined based on one or more detected resonances and / or other information. In some embodiments, determining the relative position of different layers includes determining the relative displacement between different layers. This can include determining the alignment and / or other indication of the relative displacement between layers. In some embodiments, determining the relative position of different layers includes determining the overlay associated with the different layers. For example (as described herein), the overlay can be determined as part of a semiconductor device manufacturing process.

[0169] By way of non-limiting example, returning Fig. 8A, the resonances indicated by resonances (maxima) 809 and 811 (and / or other maxima) can be used to determine the relative positions of different layers of a structure, the relative displacement between different layers, whether metal features in different layers are in electrical contact or not in electrical contact, overlay, and / or other information. The resonances indicated by (maxima) 809 and 811 can be used to determine the relative positions of different layers of a structure, the relative displacement between different layers, whether metal features in different layers are in electrical contact or not in electrical contact, overlay, and / or other information for, for example, semiconductor devices and / or semiconductor manufacturing processes. The separation distance 815 between the two resonances (e.g., maxima) 809 and 811; the relative strengths 831 and 835 of the resonances 809 and 811 in the reflected radiation (e.g., the heights of the peaks indicating the maxima); the positions 841 and 843 of the resonances (maxima); and / or other information can be used to determine the relative positions of different layers of a structure, the relative displacement between different layers, whether metal features in different layers are in electrical contact or not in electrical contact, the amount of overlay, and / or other information. For example, metal features 801 and 803 in different layers 805 and 807 may be determined to be in contact or not in electrical contact with each other based on a distance (e.g., 815) between (at least two) different resonances 809 and 811. The distance (e.g., 815) between the (at least two) different resonances corresponds to an amount by which the different layers 805 and 807 are displaced relative to each other.

[0170] For example, overlay can be determined based on detected resonances because the separation distance 815 (e.g., Δλ) between the locations (e.g., 841 and 843) of resonances (maxima) 809 and 811 is a function of overlay according to the equation Δλ=f(OVL), where Δλ represents the distance across the wavelength (λ) spectrum between individual resonances (e.g., 815 in this example) and OVL represents overlay. In some embodiments, one or more thresholds can be determined for one or more of the separation distance 815, relative intensities 831 and 835, locations 841 and 843, and / or other parameters, such that in response to a breach of one or more of these thresholds, it can be determined that features 801 and 803 are not in contact. These same relationships apply more generally to determining relative positions of different layers of a structure, relative displacements between different layers, whether metal features in different layers are in contact or not in contact, etc. (e.g., similar determinations that do not specifically determine overlay).

[0171] Figure 8B The structure shown in FIG. 1 , in which metal features 814 and 816 are both formed of copper and have substantially the same size, can be considered relative to Fig. 8A A special case of the structure shown in Figure 8B, the resonances indicated by (maxima) 808, 810, and / or 812 may again be used to determine the relative positions of different layers of the structure, the relative displacement between different layers, whether metal features in different layers are in electrical contact or not in electrical contact, overlay, and / or other information. The resonances indicated by (maxima) 808, 810, and / or 812 may be used, for example, to determine the relative positions of different layers of the structure, the relative displacement between different layers, whether metal features in different layers are in electrical contact or not in electrical contact, and / or overlay for semiconductor devices and / or semiconductor manufacturing processes. The separation distance 822 between two resonances (e.g., maxima 810 and 812); the relative intensities 830, 832, and 834 of the resonances 808, 810, and / or 812 in the reflected radiation (e.g., the height of the peak indicating the maximum); the locations 840, 842, and / or 844 of the resonances (maxima); and or other information can be used to determine the relative positions of different layers of the structure, the relative displacement between different layers, whether metal features in different layers are in electrical contact or not in electrical contact, the amount of overlay, and / or other information.

[0172] For example, overlay can be determined based on the detected resonances because the position of the resonance (maximum) (e.g., λ0) is a function of the overlay according to the equation λ0=f(OVL), where λ0 indicates the position of a single resonance (e.g., 808 in this example) and OVL again represents the overlay; and because the overlay is inversely proportional to the separation distance 822 between the resonances (e.g., 810 and 812) according to the equation OVLα1 / Δλ in this special case.

[0173] Figure 8B Views 800 and 802 of illustrative embodiments show exemplary spectra of reflected radiation from identical (e.g., identical metal, identical geometry) metallic features 814, 816 when in electrical contact (view 800) and identical metallic features 814, 816 when not in electrical contact (view 802) as typically found in subwavelength plasmonic structures. This means that view 800 showing a single resonance (maximum) 808 indicates that metallic features 814, 816 in different layers of the structure (in the target portion) are in electrical contact with each other, and that the relative displacement between the layers is small. In some embodiments, the intensity 830, position 840, shape, and / or other properties of the resonance (maximum) 808 may indicate whether the corresponding metallic features 814, 816 are (in electrical contact and) perfectly aligned, or whether they are displaced relative to each other but still in electrical contact.

[0174] View 802 shows how a single resonance 808 (metal features when in contact) for identical metal features 814, 816 that are not in electrical contact splits into two resonances 810 and 812 when two metal features 814, 816 (e.g., in different layers) are in close proximity but no longer in electrical contact. As described above, overlay (as just one example of a method of optical determination that may benefit from the techniques described herein) is inversely proportional to the separation distance 822 between the resonances 810 and 812. Thus, by determining the distance between the resonances 810 and 812, the overlay between layers including the identical metal features 814, 816 that cause the resonances 810 and 812 can be determined. Since the overlay is inversely proportional to the separation distance 822 in this example, the closer the resonances 810 and 812 are to each other, the greater the corresponding overlay. Conversely, the farther the resonances 810 and 812 are from each other, the smaller the corresponding overlay (up to the point of resonance maxima associated with the different metal features).

[0175] As a non-limiting example, consider square metal blocks (metal features) with sides of 40 nm in both the upper and lower (or buried) layers. Both layers can have a spacing of 100 nm. From the calculated solution to Maxwell's equations, a spatial separation of 5 nm between the edges of the blocks in the top and buried layers (25 nm of overlay) results in a resonant splitting of 100 nm, while a spatial separation of 25 nm (45 nm of overlay) results in a resonant splitting of 10 nm in the reflection spectrum. Intermediate separation values ​​will result in intermediate separations in wavelength between the two reflection peaks, which may be nonlinear with overlay. The peak separation observed in the measurement is then compared with the calculated results to determine the potential gap between the blocks in the upper and lower layers.

[0176] In some embodiments, different layers of the structure (e.g., Fig. 8A and Figure 8B 805, 807, 818, 820) in the metal features (e.g., Fig. 8A and Figure 8B 801, 803, 814, 816) are arranged in an array. The array can be a patterned periodic arrangement of features. The patterned periodic arrangement of features can have rows, columns, and / or other periodic arrangements of features. The array may have a spacing. For example, the spacing can be the distance between rows and / or columns of the array. In these embodiments, one or more resonances in the reflected radiation from the metal feature are detected (e.g., as described above and described in Figure 7 Operation 704) shown in FIG. 1 includes detecting a resonance associated with the spacing. For example, the resonance associated with the spacing may be a Fano resonance and / or other resonances.

[0177] In some embodiments, the resonance associated with the spacing has a resonance shape. Electrical contact between features and / or relative positions of different layers can be determined based on the resonance shape and / or other information (e.g., as described above and in Figure 7 Operation 706 shown in FIG.

[0178] By way of non-limiting example, Fig. 9 A detected resonance 900 associated with a spacing is shown. The resonance 900 is shown in a plot 906 of wavelength 902 versus intensity 904. The resonance has a resonance shape 908. In this example, the shape 908 includes a double peak shape with one peak 910 being shorter and rounder than a second peak 912. Fig. 9 Also shown is an example resonance 914 (e.g., a plasmon resonance) from a single metallic feature (e.g., a resonance similar to or identical to the resonance shown in FIG. 8a or 8B). When a resonance associated with an array (e.g., a Fano resonance 900) overlaps with a resonance of a metallic feature (e.g., a plasmon resonance 914), the resonances interfere and the shape 908 of the resonance 900 forms a noticeable feature indicative of interference (e.g., the two peak shapes in this example). The noticeable feature is related to whether the features are in electrical contact and / or the relative position of different layers associated with the features in the structure. Determining whether a feature is in electrical contact and / or the relative position of different layers can be based on a resonance associated with spacing (e.g., the noticeable feature shown by shape 908). For clarity, in these cases, the spacing or plasmon resonance of the metallic feature is generally not visible (e.g., the line shown 914 is generally not visible). What is observed, i.e. Fig. 9 The 900 is a common response known as the Fano resonance.

[0179] For example, the interference between resonances 900 (Fano) and 914 (plasmons) depends on whether the corresponding metal features are in electrical contact and / or the alignment of the single metal object associated with resonance 914 with the rest of the array. It should be noted that the Fano shape is the name for the entire asymmetric spectrum, not the clean Lorentzian lineshape associated with a single plasmon and / or spacing resonance. The shape 908 of resonance 900 changes as the alignment of a single metal object changes. For example, a metal object that is perfectly aligned (with the rest of the array) will cause one shape 908 of resonance 900 (in electrical contact with another metal object), while a metal object that is not aligned (or not in electrical contact) will cause a different shape 908. Furthermore, shape 908 changes gradually as metal objects become more or less aligned (or not aligned - not in electrical contact) in one direction or another. This is shown in FIG. Fig. 9 This is shown in the illustrated insert 950. As the alignment 956 of a single metal feature changes relative to the rest of the array, the shape 952 of the resonance 954 associated with the spacing gradually changes.

[0180] In some embodiments, shape 908 of resonance 900 may be compared to a database of various shapes of spacing-related Fano resonances and corresponding overlay values ​​to determine overlay associated with shape 908 and / or resonance 900. In some embodiments, characteristics of shape 908 of resonance 900 may be compared to a database of various characteristics of spacing-related Fano resonances and corresponding overlay values ​​to determine overlay associated with shape 908 and / or resonance 900. For example, the location, height, width, slope, and / or other features of peaks 912 and / or 910 may be compared to database values ​​for such features and corresponding overlay (and / or other indication of alignment) values.

[0181] In some embodiments, the spacing of the array can be adjusted based on a resonance associated with the spacing. For example, for a given material geometry of a metallic feature, the spacing can be selected so that the array resonance coincides with one of the plasmon resonances. This can include adjusting the spacing until the Fano resonance associated with the spacing (and resulting from the tonal resonance) has a shape that substantially matches a database shape indicating alignment, for example and / or other operations. In some embodiments, one reason that Fano resonances are promising for this work is that their spectral signatures are typically much more sensitive to geometry than ordinary plasmon resonances, which themselves are thought to be very sensitive to their environment. This is why it may be advantageous to design the marker and / or other structure in a way that incorporates the spacing resonance so that a Fano lineshape is obtained in the measured spectrum. This is only true for marker designs in optical inspections. If the marker is designed for VC inspection, then the spacing is irrelevant.

[0182] Return to Figure 7 In some embodiments, operation 706 may include outputting an indication of whether metal features in different layers are in contact or not in contact with each other, an amount of relative displacement between layers, an indication of overlay, a manufacturing process failure rate, a critical dimension, a critical dimension variance, and / or other information associated with a target portion of a structure (e.g., a target portion of a semiconductor device). These metrics may be determined based on detected resonances (e.g., as described above) and / or based on other information. The indication may be displayed on a display associated with system 10 ( Figure 4 and Figure 5 ), for example, and / or other displays. In some embodiments, the indication may include Fig. 8A and / or Figure 8B , a graphical representation similar or identical to one of the graphics shown in , a number indicating relative displacement between layers, a number indicating overlay, an overlay and / or other operational process pass / failure indication (e.g., a color indicating pass / failure, etc.), and / or other information. In some embodiments, operation 706 may be performed by Figure 4 and Figure 5The illustrated processor PU (and / or processors 104 and 105 described below) is similar or identical to and executes one or more processors described herein.

[0183] In some embodiments, method 700 includes determining one or more semiconductor device manufacturing process parameters based on whether metal features are in electrical contact or not and / or relative positions of different layers, and determining a semiconductor device manufacturing equipment (e.g., Figure 2 LA) shown in , adjusting the semiconductor device manufacturing equipment based on the determined adjustment, and / or other operations 708.

[0184] For example, if two metal features in two layers of a semiconductor device are not in electrical contact with each other (e.g., the layers are not aligned), the non-contact (e.g., the misalignment) may be caused by one or more manufacturing processes whose process parameters have drifted and / or otherwise changed such that the process no longer produces acceptable devices (e.g., the overlay measurement may have breached an acceptable threshold). One or more new or adjusted process parameters may be determined based on the relative positions of the different layers (e.g., determining whether the metal features are in electrical contact with each other or are not in electrical contact with each other). The new or adjusted process parameters may be configured to cause the manufacturing process to once again produce acceptable devices. For example, the new or adjusted process parameters may cause a previously unacceptable amount of overlay to be reduced to an acceptable range. The new or adjusted process parameters may be compared to existing parameters for a given process. If there is a difference, the difference may be used to determine adjustments to equipment used to produce the device (e.g., parameter "x" should be increased / decreased / changed, e.g., so that it matches a new or adjusted version of parameter "x" determined as part of operation 708). In some embodiments, operation 708 may include electronically adjusting the equipment (e.g., based on the determined process parameters). Electronically adjusting a device may include sending an electronic signal and / or other communication to the device that causes, for example, a change in the device. Electronic adjustments may include changing settings on the device, for example, and / or other adjustments. It should be noted that process parameters may be broadly interpreted to include mask design, metrology target design, semiconductor device design, radiation intensity (for exposing resist, etc.), radiation incident angle, radiation wavelength, pupil size and / or shape, resist material, and / or other parameters.

[0185] Fig.10An example process for determining values ​​of one or more variables of interest for a target (pattern) 1030 based on measurement data obtained using metrology (e.g., overlay determined using the present systems and methods) is schematically depicted. Radiation detected by detector 1018 provides a measured radiation distribution 1008 for target 1030, which can be used to determine overlay, etc., as described herein. For a given target 1030, the radiation distribution 1014, overlay, etc. can be calculated / simulated from a parameterized model 1006 using, for example, a numerical Maxwell solver 1010. The parameterized model 1006 shows example layers of various materials that make up and are associated with the target. The parameterized model 1006 can include one or more variables for features and layers of the portion of the target under consideration, which variables can be varied and derived. As shown in FIG. Fig.10 As shown, the one or more variables may include the thickness t of one or more layers, the width w (e.g., CD) of one or more features, the height h of one or more features, and / or the sidewall angle α of one or more features. Although not shown, the one or more variables may further include, but are not limited to, the refractive index (e.g., real or complex refractive index, refractive index tensor, etc.) of one or more layers, the extinction coefficient of one or more layers, the absorption of one or more layers, the resist loss during development, the footing of one or more features, and / or the line edge roughness of one or more features. The initial values ​​of the variables may be the values ​​expected for the target being measured. The measured radiation distribution 1008, overlay, etc. are then compared to the calculated radiation distribution 1012, overlay, etc. to determine the difference between the two. If there is a difference, the values ​​of one or more variables of the parameterized model 1006 can be changed, and a new calculated radiation distribution 1012, overlay, etc. can be calculated and compared to the measured radiation distribution 1008, overlay, etc. until there is a sufficient match between the measured radiation distribution 1008, overlay, etc. and the calculated radiation distribution 1012, overlay, etc. At this point, the values ​​of the variables of the parameterized model 1006 provide a good or optimal match to the geometry of the actual target 1030. In one embodiment, a sufficient match exists when the difference between the measured radiation distribution 1008, overlay, etc. and the calculated radiation distribution 1012, overlay, etc. is within a tolerance threshold.

[0186] Fig.111 is a block diagram illustrating a computer system 100 that may assist in implementing the methods, processes, or systems disclosed herein. The computer system 100 includes a bus 102 or other communication mechanism for communicating information, and a processor 104 (or multiple processors 104 and 105) coupled to the bus 102 for processing information. The computer system 100 also includes a main memory 106, such as a random access memory (RAM) or other dynamic storage device, coupled to the bus 102 for storing information and instructions to be executed by the processor 104. The main memory 106 may also be used to store temporary variables or other intermediate information during the execution of instructions to be executed by the processor 104. The computer system 100 also includes a read-only memory (ROM) 108 or other static storage device coupled to the bus 102 for storing static information and instructions for the processor 104. A storage device 110, such as a magnetic disk or optical disk, is provided and coupled to the bus 102 for storing information and instructions.

[0187] The computer system 100 may be coupled to a display 112, such as a cathode ray tube (CRT) or a flat panel or touch panel display for displaying information to a computer user, via the bus 102. An input device 114 including alphanumeric and other keys is coupled to the bus 102 for communicating information and command selections to the processor 104. Another type of user input device is a cursor controller 116, such as a mouse, trackball, or cursor direction keys, for communicating direction information and command selections to the processor 104 and for controlling cursor movement on the display 112. The input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), which allows the device to specify a position in a plane. A touch panel (screen) display may also be used as an input device.

[0188] According to one embodiment, in response to processor 104 executing one or more sequences of one or more instructions contained in main memory 106, computer system 100 may perform portions of one or more methods described herein. Such instructions may be read into main memory 106 from another computer-readable medium, such as storage device 110. Execution of the sequences of instructions contained in main memory 106 causes processor 104 to perform the processing steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory 106. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions. Therefore, the description herein is not limited to any specific combination of hardware circuitry and software.

[0189] The term "computer-readable medium" as used herein refers to any medium that participates in providing instructions to processor 104 for execution. Such media can take a variety of forms, including, but not limited to, non-volatile media, volatile media, and transmission media. For example, non-volatile media include optical or magnetic disks such as storage device 110. Volatile media include dynamic memory, such as main memory 106. Transmission media include coaxial cables, copper wire, and optical fiber, including the wires that make up bus 102. 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. For example, common forms of computer-readable media include floppy disks, flexible disks, hard disks, magnetic tape, any other magnetic media, CD-ROMs, DVDs, any other optical media, punch cards, paper tape, any other physical media with a pattern of holes, RAM, PROMs and EPROMs, FLASH-EPROMs, any other memory chips or storage cartridges, carrier waves described below, or any other medium from which a computer can read.

[0190] Various forms of computer readable media may be used to transmit one or more sequences of one or more instructions to processor 104 for execution. For example, the instructions may initially be stored on a disk of a remote computer. The remote computer may load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system 100 may receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus 102 may receive the data carried in the infrared signal and place the data on bus 102. Bus 102 carries the data to main memory 106, from which processor 104 retrieves and executes the instructions. The instructions received by main memory 106 may optionally be stored on storage device 110 before or after execution by processor 104.

[0191] The computer system 100 may also include a communication interface 118 coupled to the bus 102. The communication interface 118 provides a bidirectional data communication coupling to a network link 120 connected to a local network 122. For example, the communication interface 118 may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, the communication interface 118 may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface 118 sends and receives electrical, electromagnetic, or optical signals carrying digital data streams representing various types of information.

[0192] The network link 120 typically provides data communication through one or more networks to other data devices. For example, the network link 120 may provide a connection to a host computer 124 or to data equipment operated by an Internet Service Provider (ISP) 126 through a local network 122. The ISP 126, in turn, provides data communication services through the global packet data communication network now commonly referred to as the "Internet" 128. Both the local network 122 and the Internet 128 use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks, as well as the signals through the network link 120 and through the communication interface 118, that carry the digital data to and from the computer system 100, are exemplary forms of carrier waves that transport the information.

[0193] The computer system 100 can send messages and receive data, including program code, through the network, network link 120, and communication interface 118. In the Internet example, server 130 can send the requested code for an application program through Internet 128, ISP 126, local network 122, and communication interface 118. One such downloaded application program can, for example, provide all or part of the methods described herein. The received code can be executed by processor 104 as it is received, and / or stored in storage device 110 or other non-volatile storage for later execution. In this way, computer system 100 can obtain application code in the form of a carrier wave.

[0194] Fig.12 Schematically depicts the Figure 2 , which can be used in conjunction with the techniques described herein. The apparatus 1000 includes an illumination system IL for conditioning a radiation beam B. In this particular case, the illumination system also includes a radiation source SO; a first object table (e.g., patterning device table) MT provided with a patterning device holder to hold a patterning device MA (e.g., a mask) and connected to a first positioner PM (operating in association with a first position sensor PS1) to accurately position the patterning device; a second object table (substrate table) WT provided with a substrate holder to hold a substrate W (e.g., a resistor-coated silicon wafer) and connected to a second positioner PW (operating in association with a second position sensor PS2) to accurately position the substrate; and a projection system ("lens") PS (e.g., a refractive, reflective, or catadioptric optical system) for imaging an illuminated portion of the patterning device MA onto a target portion C (e.g., including one or more dies) of the substrate W.

[0195] As described here, the device is transmissive (i.e., has a transmissive patterning device). However, in general, it can also be reflective, for example (with a reflective patterning device). The device can use different kinds of patterning devices to classical masks; examples include programmable mirror arrays or LCD matrices.

[0196] A source SO (e.g. a mercury lamp or an excimer laser, an LPP (laser produced plasma) EUV source) generates a radiation beam. This beam is fed into an illumination system (illuminator) IL directly or after passing through an adjustment device such as, for example, a beam expander Ex. The illuminator IL may include adjustment means for setting the outer and / or inner radial extent (usually referred to as σ outer and σ inner, respectively) of the intensity distribution in the beam. In addition, it typically includes various other components, such as an integrator and a condenser. In this way, the beam B incident on the patterning device MA has a desired uniformity and intensity distribution in its cross section.

[0197] about Fig.12 It should be noted that the source SO can be within the housing of the lithographic projection device (for example, this is usually the case when the source SO is a mercury lamp), but it can also be remote from the lithographic projection device, the radiation beam it generates being introduced into the device (for example, with the aid of appropriate directing mirrors); the latter case usually occurs when the source SO is an excimer laser (for example based on KrF, ArF or F2 lasers).

[0198] The light beam B then intercepts the patterning device MA, which is held on the patterning device table MT. Having passed the patterning device MA, the light beam B passes through a lens, which focuses the light beam B onto a target portion C of the substrate W. With the aid of the second positioning device (and the interferometric measurement device), the substrate table WT can be precisely moved, for example, to position different target portions C in the path of the light beam B. Similarly, the first positioning device can be used to precisely position the patterning device MA relative to the path of the light beam B, for example, after mechanically retrieving the patterning device MA from a patterning device library, or during scanning. Typically, the movement of the object table MT, WT will be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) that are not explicitly described. However, in the case of a stepper (as opposed to a step-and-scan tool), the patterning device table MT may simply be connected to a short-stroke actuator, or may be fixed.

[0199] The tools depicted (with Figure 2The tool shown is similar or identical to that shown in Figure 1 and can be used in two different modes. In step mode, the patterning device table MT is kept essentially stationary and the entire patterning device image is projected onto a target portion C in one operation (i.e. a single "flash"). The substrate table WT is then shifted in the x and / or y direction so that different target portions C can be irradiated by the beam B. In scan mode, essentially the same situation applies, except that a given target portion C is not exposed in a single "flash". Instead, the patterning device table MT is moved in a given direction (the so-called "scanning direction", e.g. the y direction) at a speed v so that the projection beam B is scanned over the patterning device image; at the same time, the substrate table WT is moved simultaneously in the same or opposite direction at a speed V=Mv, where M is the magnification of the lens PL (typically M=1 / 4 or 1 / 5). In this way, relatively large target portions C can be exposed without having to compromise on resolution.

[0200] Fig.13 The apparatus 1000 is shown in more detail, including a source collector module SO, an illumination system IL, and a projection system PS. The source collector module SO is constructed and arranged so that a vacuum environment can be maintained in a closed structure 220 of the source collector module SO. The EUV radiation emitting plasma 210 can be formed by a plasma source generated by a discharge. EUV radiation can be generated by a gas or vapor, such as Xe gas, Li vapor, or Sn vapor, wherein a hot plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum. For example, the plasma 210 is generated by a discharge that causes a plasma that is at least partially ionized. For example, the partial pressure of Xe, Li, Sn vapor, or any other suitable gas or vapor may require 10 Pa to effectively generate radiation. In one embodiment, a plasma of excited state tin (Sn) is provided to generate EUV radiation.

[0201] The radiation emitted by the plasma 210 enters the collector chamber 212 from the source chamber 211 via an optional gas barrier or contaminant trap 230 (also referred to as a contaminant barrier or foil trap in some cases), which is located in or behind the opening of the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap 230 further shown here includes at least a channel structure.

[0202] The source chamber 211 may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation passing through the collector CO may be reflected from the grating spectral filter 240 to be focused in a virtual source point IF along the optical axis indicated by the line 'O'. The virtual source point IF is often referred to as an intermediate focus, and the source collector module is arranged so that the intermediate focus IF is located at or near an opening 221 in the enclosure 220. The virtual source point IF is an image of the radiation emitting plasma 210.

[0203] The radiation then passes through the illumination system IL, which may include a faceted field mirror arrangement 22 and a faceted pupil mirror arrangement 24 arranged to provide a desired angular distribution of the radiation beam 21 at the patterning device MA and a desired uniformity of radiation intensity at the patterning device MA. When the radiation beam 21 is reflected at the patterning device MA held by the support structure MT, a patterned beam 26 is formed, and the patterned beam 26 is imaged by the projection system PS via reflective elements 28, 30 onto a substrate W held by a substrate table WT.

[0204] There are typically more elements than shown in the illumination optics unit IL and the projection system PS. Depending on the type of lithographic apparatus, a grating spectral filter 240 may optionally be present. Furthermore, there may be more mirrors than shown in the figure, for example, there may be more than one mirror in the projection system PS. Fig.12 1-6 additional reflective elements as shown.

[0205] like Fig.13 As shown, the collector optics CO is depicted as a nested collector with grazing incidence reflectors 253, 254 and 255, just like the example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are arranged axially symmetrically around the optical axis O, and this type of collector optics CO can be used in combination with a discharge produced plasma source (commonly referred to as a DPP source).

[0206] Alternatively, the source collector module SO can be as follows Fig.14 A portion of the LPP radiation system shown. The laser LA is arranged to deposit laser energy into a fuel, such as xenon (Xe), tin (Sn) or lithium (Li), producing a highly ionized plasma 210 with an electron temperature of several 10 eV. The high-energy radiation produced during the deexcitation and recombination of these ions is emitted from the plasma, collected by the near normal incidence collector optics CO and focused onto an opening 221 in the closed structure 220.

[0207] The embodiments may be further described using the following terms:

[0208] 1. A method for determining an adjustment of a semiconductor device manufacturing equipment, the method comprising:

[0209] irradiating a target portion of a semiconductor device with radiation, the target portion comprising metal features in different layers of the semiconductor device;

[0210] detecting one or more resonances in reflected radiation from the metallic feature;

[0211] determining relative positions of different layers based on the detected one or more resonances;

[0212] determining one or more semiconductor device manufacturing process parameters based on the relative positions of the different layers; and

[0213] Based on the determined one or more semiconductor device manufacturing process parameters, adjustments of the semiconductor device manufacturing equipment are determined.

[0214] 2. A method according to item 1, wherein the radiation comprises light.

[0215] 3. A method according to clause 1 or 2, wherein determining the relative positions of different layers comprises determining overlay as part of a semiconductor device manufacturing process.

[0216] 4. A method according to any one of items 1 to 3, wherein one or more determined semiconductor device manufacturing process parameters include one or more of mask design, metrology target design, semiconductor device design, radiation intensity, radiation incident angle, radiation wavelength, pupil size and / or shape, and resist material.

[0217] 5. The method according to any one of items 1 to 4, further comprising adjusting the semiconductor device manufacturing equipment based on the determined adjustment.

[0218] 6. A method for determining the relative positions of different layers in a structure, the method comprising:

[0219] irradiating a target portion of the structure with radiation, the target portion comprising metallic features in a different layer of the structure;

[0220] detecting one or more resonances in reflected radiation from the metallic feature; and

[0221] The relative positions of the different layers are determined based on the detected one or more resonances.

[0222] 7. A method according to item 6, wherein the radiation comprises light.

[0223] 8. A method according to item 6 or 7, wherein determining the relative positions of different layers comprises determining the relative displacement between the different layers.

[0224] 9. A method according to any one of clauses 6 to 8, wherein determining the relative positions of different layers comprises determining overlays associated with the different layers.

[0225] 10. The method of any one of items 6 to 9, further comprising determining whether metallic features in different layers are in contact with each other based on the detected one or more resonances.

[0226] 11. A method according to item 10, wherein the metallic features in different layers comprise different metals and / or have different sizes, which results in at least two different resonances being detected in the reflected radiation.

[0227] 12. The method of item 11, wherein the metal features in different layers are determined to be in contact or not in contact with each other based on the distance between at least two different resonances.

[0228] 13. The method according to item 12, wherein the distance between at least two different resonances corresponds to the amount by which the different layers are displaced relative to each other.

[0229] 14. The method of item 10, wherein the metal features in different layers are formed of the same metal and have the same size, and are determined to be in contact with each other in response to detecting a single resonance associated with the metal features.

[0230] 15. A method according to item 10 or 14, wherein the metal features in different layers are formed of the same metal and have the same size, and are determined not to be in contact with each other in response to detecting more than two resonances associated with the metal features.

[0231] 16. A method according to item 15, wherein the distance between the resonances corresponds to the amount by which the different layers are displaced relative to each other.

[0232] 17. A method according to any one of items 6 to 16, wherein the different layers comprise two layers, each layer having at least one metallic feature.

[0233] 18. A method according to any one of clauses 6 to 17, wherein the metal features comprise different portions of vias extending through the different layers.

[0234] 19. A method according to any one of items 6 to 18, wherein the one or more resonances comprise plasmon resonances.

[0235] 20. A method according to any one of items 6 to 19, wherein a single resonance comprises a maximum in the wavelength spectrum of the reflected radiation.

[0236] 21. A method according to item 6, wherein the metal features in different layers of the structure are arranged in an array having a spacing; and wherein detecting the one or more resonances in the reflected radiation from the metal features includes detecting resonances associated with the spacing.

[0237] 22. The method according to item 21, wherein the spacing-related resonance is a Fano resonance.

[0238] 23. The method according to item 21 or 22, wherein the resonance associated with the spacing has a resonance shape, and wherein the relative positions of the different layers are determined based on the resonance shape.

[0239] 24. The method according to any one of items 21 to 23, wherein determining the relative positions of the different layers comprises determining the overlay associated with the different layers based on the resonance associated with the spacing.

[0240] 25. The method of any one of items 21 to 24, further comprising adjusting the spacing of the array based on a resonance associated with the spacing.

[0241] 26. A method according to any one of items 6 to 25, wherein the structure comprises at least a portion of a semiconductor device.

[0242] 27. A method according to any one of clauses 6 to 26, wherein determining the relative positions of different layers based on the detected one or more resonances is performed as part of a semiconductor device manufacturing process.

[0243] 28. The method according to item 27 further includes adjusting the semiconductor device manufacturing process or the design of the semiconductor device based on the relative positions of different layers.

[0244] 29. A computer program product, comprising a non-transitory computer-readable medium having instructions recorded thereon, which, when executed by a computer, implement the method of any one of items 1 to 28.

[0245] 30. A system configured to determine relative positions of different layers in a structure, the system comprising:

[0246] a radiation source configured to irradiate a target portion of the structure with radiation, the target portion comprising metallic features in a different layer of the structure;

[0247] one or more sensors configured to detect one or more resonances in reflected radiation from the metallic feature; and

[0248] One or more processors are configured to determine relative positions of different layers based on the detected one or more resonances.

[0249] 31. A system according to item 30, wherein the radiation comprises light.

[0250] 32. A system according to item 30 or 31, wherein determining the relative positions of different layers comprises determining the relative displacement between the different layers.

[0251] 33. A system according to any one of items 30 to 32, wherein determining the relative positions of different layers comprises determining overlays associated with the different layers.

[0252] 34. The system of any one of clauses 30 to 33, wherein the one or more processors are further configured to determine whether the metal features in the different layers are in contact with each other based on the detected one or more resonances.

[0253] 35. A system according to item 34, wherein the metallic features in different layers comprise different metals and / or have different sizes, which enables at least two different resonances in the reflected radiation to be detected by one or more sensors.

[0254] 36. A system according to item 35, wherein the one or more processors determine whether metal features in different layers are in contact or not in contact with each other based on the distance between at least two different resonances.

[0255] 37. A system according to item 36, wherein the one or more processors are configured such that the distance between the at least two different resonances corresponds to an amount by which the different layers are displaced relative to each other.

[0256] 38. A system according to item 34, wherein the metal features in different layers are formed of the same metal and have the same size, and the one or more processors are configured to determine that the metal features in different layers are in contact with each other in response to detecting a single resonance associated with the metal features.

[0257] 39. A system according to item 34 or 38, wherein the metal features in different layers are formed of the same metal and the same size, and one or more processors are configured to determine that the metal features in different layers are not in contact with each other in response to detecting more than two resonances associated with the metal features.

[0258] 40. A system according to item 39, wherein the distance between the resonances corresponds to the amount by which the different layers are displaced relative to each other.

[0259] 41. The system of any one of items 30 to 40, wherein the different layers comprise two layers, each layer having at least one metallic feature.

[0260] 42. A system according to any one of clauses 30 to 41, wherein the metal features comprise different portions of vias extending through the different layers.

[0261] 43. A system according to any one of items 30 to 42, wherein the one or more resonances comprise plasmon resonances.

[0262] 44. A system according to any one of items 30 to 43, wherein a single resonance comprises a maximum in the wavelength spectrum of the reflected radiation.

[0263] 45. A system according to item 30, wherein the metal features in different layers of the structure are arranged in an array having a spacing; and wherein detecting the one or more resonances in the reflected radiation from the metal features includes detecting resonances associated with the spacing with the one or more sensors.

[0264] 46. ​​A system according to item 45, wherein the resonance associated with the spacing is a Fano resonance.

[0265] 47. A system according to item 45 or 46, wherein the resonance associated with the spacing has a resonance shape, and wherein the one or more processors determine the relative positions of the different layers based on the resonance shape.

[0266] 48. The system of any one of clauses 45 to 47, wherein the one or more processors are configured such that determining the relative positions of the different layers comprises determining an overlay associated with the different layers based on a resonance associated with the spacing.

[0267] 49. A system according to any of items 45 to 48, wherein the one or more processors are further configured to facilitate adjusting the spacing of the array based on a resonance associated with the spacing.

[0268] 50. The system of any one of items 30 to 49, wherein the structure comprises at least a portion of a semiconductor device.

[0269] 51. A system according to any one of clauses 30 to 50, wherein the one or more processors are configured such that determining the relative positions of different layers based on the detected one or more resonances is performed as part of a semiconductor device manufacturing process.

[0270] 52. A system according to item 51, wherein the one or more processors are further configured to facilitate adjustment of the semiconductor device manufacturing process or design of the semiconductor device based on the relative positions of the different layers.

[0271] 53. A system configured to determine whether metal features in different layers of a structure are in electrical contact with each other, the system comprising: a radiation source configured to irradiate a target portion of the structure with radiation, the target portion comprising a first metal feature in a first layer of the structure and a second metal feature in a second layer; one or more sensors configured to detect one or more resonances in reflected radiation from the first metal feature and the second metal feature; and one or more processors operably coupled to the radiation source and the one or more sensors, the one or more processors configured to determine whether the first metal feature in the first layer is in electrical contact with the second metal feature in the second layer based on (i) the number of detected resonances or (ii) the spectral position of the one or more resonances.

[0272] 54. A system according to item 53, wherein: (1) a first metal feature in the first layer and a second metal feature in the second layer comprise different metals and / or have different sizes, so that one or more resonances in the reflected radiation are detected by one or more sensors, and the first metal feature in the first layer and the second metal feature in the second layer are determined by one or more processors to be in electrical contact or not in electrical contact with each other based on the spectral position of the one or more resonances; or (2) the first metal feature in the first layer and the second metal feature in the second layer are formed of the same metal and have the same size, and the one or more processors are configured to determine that the first metal feature in the first layer and the second metal feature in the second layer are in electrical contact with each other in response to detecting a single resonance associated with the first metal feature and the second metal feature, and to determine that the first metal feature in the first layer and the second metal feature are not in electrical contact with each other in response to detecting more than two resonances associated with the first metal feature and the second metal feature.

[0273] 55. A system according to item 53 or 54, wherein the one or more resonances include plasmon resonances.

[0274] 56. A system according to any one of items 53 to 55, wherein the one or more resonances primarily comprise dipolar surface plasmon polariton resonances in the reflected radiation.

[0275] 57. A system according to any one of items 53 to 56, wherein the one or more sensors include one or more spectrometer detectors configured to detect intensity as a function of wavelength of reflected radiation.

[0276] 58. A system according to any one of items 53 to 57, wherein the one or more sensors are configured as a normal incidence inspection device, wherein the one or more sensors are oriented at an angle perpendicular to the target portion, or are configured as an oblique incidence inspection device, wherein the one or more sensors are oriented at an angle non-perpendicular to the target portion.

[0277] 59. A system according to any one of items 53 to 58, wherein the radiation source is configured such that the radiation comprises broadband white light collimated by a lens system and transmitted through an interference filter and a polarizer.

[0278] 60. The system of any one of items 53 to 59, wherein the first metal feature and the second metal feature comprise different portions of a via extending through the first layer and the second layer.

[0279] 61. A system according to any one of items 53 to 60, wherein a single resonance comprises a maximum in the wavelength spectrum of the reflected radiation.

[0280] 62. A system according to any one of items 53 to 61, wherein the first metal feature in the first layer of the structure and the second metal feature in the second layer are arranged in an array having a spacing; and wherein detecting one or more resonances in reflected radiation from the first metal feature and the second metal feature includes detecting resonances associated with the spacing with one or more sensors.

[0281] 63. A system according to item 62, wherein the spacing-dependent resonance is a Fano resonance.

[0282] 64. A system according to item 62, wherein the resonance associated with the spacing has a resonance shape, and wherein determining whether the first metal feature and the second metal feature are in electrical contact is based on the resonance shape.

[0283] 65. A system according to item 62, wherein the one or more processors are further configured to facilitate adjusting the spacing of the array based on a resonance associated with the spacing.

[0284] 66. A system according to any of items 53 to 65, wherein the one or more processors are further configured to determine one or more of overlay, manufacturing process failure rate, critical dimension, or critical dimension variance associated with a target portion of the structure based on the detected one or more resonances.

[0285] 67. A method for determining whether metallic features in different layers of a structure are in electrical contact with each other, the method comprising: irradiating a target portion of the structure with radiation from a radiation source, the target portion comprising a first metallic feature in a first layer of the structure and a second metallic feature in a second layer; detecting, by one or more sensors, one or more resonances in reflected radiation from the first metallic feature and the second metallic feature; and determining, using one or more processors, whether the first metallic feature in the first layer and the second metallic feature in the second layer are in electrical contact with each other based on the detected one or more resonances, wherein: (1) the first metallic feature in the first layer and the second metallic feature in the second layer comprise different metals and / or have different sizes, such that the first metallic feature in the first layer and the second metallic feature in the second layer are in electrical contact with each other. The method further comprises the steps of: (1) detecting at least two different resonances in the reflected radiation by a sensor, and determining by one or more processors whether a first metal feature in a first layer and a second metal feature in a second layer are electrically contacted or not electrically contacted with each other based on a distance between the at least two different resonances; or (2) the first metal feature in the first layer and the second metal feature in the second layer are formed of the same metal and have the same size, and the one or more processors are configured to determine that the first metal feature and the second metal feature in different layers are electrically contacted with each other in response to detecting a single resonance associated with the first metal feature and the second metal feature, and to determine that they are not electrically contacted with each other in response to detecting more than two resonances associated with the first metal feature and the second metal feature.

[0286] 68. A method for determining an adjustment of a semiconductor device manufacturing apparatus, the method comprising: irradiating a target portion of a semiconductor device with radiation, the target portion comprising a first metal feature in a first layer of the semiconductor device and a second metal feature in a second layer; detecting one or more resonances in reflected radiation from the first metal feature and the second metal feature; determining a relative position of different layers based on the detected one or more resonances; determining whether the first metal feature in the first layer and the second metal feature in the second layer are in electrical contact with each other based on the detected one or more resonances, wherein: (1) the first metal feature in the first layer and the second metal feature in the second layer comprise different metals and / or have different sizes, which causes one or more sensors to detect the one or more resonances in the reflected radiation, and the first metal feature in the first layer and the second metal feature in the second layer are electrically contacted by One or more processors determine that a first metal feature in a first layer and a second metal feature in a second layer are in electrical contact or not in electrical contact with each other based on the spectral position of one or more resonances; or (2) a first metal feature in a first layer and a second metal feature in a second layer are formed of the same metal and have the same size, and the first metal feature in the first layer and the second metal feature in the second layer are determined to be in electrical contact with each other in response to detecting a single resonance associated with the first metal feature and the second metal feature, and are determined to be not in electrical contact with each other in response to detecting more than two resonances associated with the first metal feature and the second metal feature; determine one or more semiconductor device manufacturing process parameters based on the relative positions of the different layers and / or determine whether the first metal feature and the second metal feature are in electrical contact with each other; and determine adjustments to semiconductor device manufacturing equipment based on the determined one or more semiconductor device manufacturing process parameters.

[0287] 69. A computer program product, comprising a non-transitory computer-readable medium having instructions recorded thereon, which, when executed by a computer, implement the method of any one of items 67 or 68.

[0288] The concepts disclosed herein can simulate or mathematically model any general imaging system for imaging sub-wavelength features and are particularly useful for emerging imaging technologies that are capable of producing shorter and shorter wavelengths. Emerging technologies already in use include EUV (extreme ultraviolet), DUV lithography, which can produce 193nm wavelengths using ArF lasers, and even 157nm wavelengths using fluorine lasers. In addition, EUV lithography is able to produce wavelengths in the 20-5nm range by using a synchrotron or by bombarding materials (solid or plasma) with high-energy electrons to generate photons in this range.

[0289] Although the concepts disclosed herein may be used for imaging on substrates such as silicon wafers, it should be understood that the disclosed concepts may be used in any type of lithography imaging system, for example, a lithography imaging system for imaging on substrates other than silicon wafers. In addition, combinations and subcombinations of the disclosed elements may include separate embodiments. For example, Figure 4 and Figure 5 The system 10 shown in FIG. 1 can be used to perform Figure 7 Some or all of the operations of method 700 shown in and / or system 10 may be used separately from the method 700 embodiment.

[0290] The above description is intended to be illustrative rather than restrictive. It will therefore be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the appended claims.

Claims

1. A system configured to determine whether metallic features in different layers of a structure are in electrical contact with each other, the system comprising: a radiation source configured to irradiate a target portion of the structure with radiation, the target portion comprising a first metallic feature in a first layer and a second metallic feature in a second layer of the structure; one or more sensors configured to detect one or more resonances in reflected radiation from the first metal feature and the second metal feature; as well as One or more processors are operatively coupled to the radiation source and the one or more sensors, the one or more processors being configured to determine whether the first metal feature in the first layer is in electrical contact with the second metal feature in the second layer based on (i) the number of the detected resonances or (ii) the spectral position of the detected resonances.

2. A system according to claim 1, wherein (1) the first metal feature in the first layer and the second metal feature in the second layer include different metals and / or have different sizes, so that the one or more resonances in the reflected radiation are detected by the one or more sensors, and the first metal feature in the first layer and the second metal feature in the second layer are determined by the one or more processors to be in electrical contact or not in electrical contact with each other based on the spectral positions of the one or more resonances; or (2) the first metal feature in the first layer and the second metal feature in the second layer are formed of the same metal and have the same size, and the one or more processors are configured such that the first metal feature in the first layer and the second metal feature in the second layer are determined to be in electrical contact with each other in response to detecting a single resonance associated with the first metal feature and the second metal feature, and are determined to be not in electrical contact with each other in response to detecting two or more resonances associated with the first metal feature and the second metal feature.

3. The system of claim 1, wherein the one or more resonances comprise plasmon resonances. 4 . The system of claim 3 , wherein the one or more resonances primarily comprise dipolar surface plasmon polariton resonances in the reflected radiation.

5. The system of claim 1, wherein the one or more sensors include one or more spectrometer detectors configured to detect intensity as a function of wavelength of the reflected radiation.

6. The system of claim 5, wherein the one or more sensors are configured as a normal incidence inspection device, wherein the one or more sensors are oriented at an angle perpendicular to the target portion, or the one or more sensors are configured as an oblique incidence inspection device, wherein the one or more sensors are oriented at an angle non-perpendicular to the target portion.

7. The system of claim 1, wherein the radiation source is configured such that the radiation comprises broadband white light that is collimated with a lens system and transmitted through an interference filter and a polarizer.

8. The system of claim 1, wherein the first metal feature and the second metal feature comprise different portions of a via extending through the first layer and the second layer.

9. The system of claim 1, wherein a single resonance comprises a maximum in the wavelength spectrum of the reflected radiation.

10. The system of claim 1, wherein the first metal features in the first layer of the structure and the second metal features in the second layer are arranged in an array, the array having a pitch; and wherein detecting the one or more resonances in the reflected radiation from the first metal features and the second metal features comprises: A resonance associated with the spacing is detected with the one or more sensors.

11. The system of claim 10, wherein the resonance associated with the spacing is a Fano resonance.

12. The system of claim 10, wherein the resonance associated with the spacing has a resonance shape, and wherein the determination of whether the first metallic feature and the second metallic feature are in electrical contact is based on the resonance shape.

13. The system of claim 1, wherein the one or more processors are further configured to determine one or more of an overlay, a manufacturing process failure rate, a critical dimension, or a critical dimension variance associated with a target portion of the structure based on the detected one or more resonances.

14. A method for determining an adjustment of a semiconductor device manufacturing equipment, the method comprising: irradiating a target portion of a semiconductor device with radiation, the target portion comprising a first metallic feature in a first layer and a second metallic feature in a second layer of the semiconductor device; detecting one or more resonances in reflected radiation from the first metallic feature and the second metallic feature; determining a relative position of the first layer and the second layer based on the detected one or more resonances; determining whether the first metallic feature in the first layer and the second metallic feature in the second layer are in electrical contact with each other based on (i) the number of detected resonances or (ii) the spectral positions of the detected resonances, wherein: (1) the first metal feature in the first layer and the second metal feature in the second layer comprise different metals and / or have different sizes, such that the one or more resonances in the reflected radiation are detected by one or more sensors, and the first metal feature in the first layer and the second metal feature in the second layer are determined by one or more processors to be in electrical contact or not in electrical contact with each other based on the spectral positions of the one or more resonances; or (2) the first metal feature in the first layer and the second metal feature in the second layer are formed of the same metal and have the same size, and the first metal feature in the first layer and the second metal feature in the second layer are determined to be in electrical contact with each other in response to detecting a single resonance associated with the first metal feature and the second metal feature, and are determined to be not in electrical contact with each other in response to detecting two or more resonances associated with the first metal feature and the second metal feature; determining one or more semiconductor device manufacturing process parameters based on the relative positions of the first layer and the second layer and / or the determination of whether the first metal feature and the second metal feature are in electrical contact with each other; and The adjustment of the semiconductor device manufacturing equipment is determined based on the determined one or more semiconductor device manufacturing process parameters. 15 . A computer program product, comprising a non-transitory computer-readable medium having instructions recorded thereon, the instructions implementing the method of claim 14 when executed by a computer.

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