Determining focus positions for imaging a substrate with an integrated

Abstract

The metrology system (s) and method (s) described herein eliminate the need for separate focus branches commonly used in existing metrology systems to determine focus positions for imaging a substrate. The focus position is determined using an integrated photon sensor instead of using a separate focus branch. The integrated photon sensor is based on apodized grating couplers in which the amplitude and phase of the grating coupler mode are designed to have optimal coupling efficiency for a particular defocus (or initial / known focus position) by varying the grating period and / or duty cycle. A coupling efficiency between the emission grating and the reception grating is determined based on emitted radiation and reflected radiation received from the substrate, the emitted radiation having a particular amplitude and a particular phase configured for a known position relative to the substrate. A focus position is determined based on the coupling efficiency and the known position.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority of U.S. Application No. 63 / 431,429, filed on December 9, 2022, and the entire content of the U.S. application is incorporated herein by reference. Technical field

[0003] This specification relates to determining a focus position for imaging a substrate using an integrated photonic sensor. Background art

[0004] A lithographic projection apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A patterning device (e.g., a mask) can include or provide a pattern corresponding to an individual layer of the IC ("design layout"), and this pattern can be transferred onto a target portion (e.g., including one or more dies) on a substrate (e.g., a silicon wafer) that has been coated with a radiation - sensitive material ("resist") layer by irradiating the pattern on the patterning device onto the target portion. Typically, a single substrate includes a plurality of adjacent target portions, and the pattern is successively transferred onto the adjacent target portions one target portion at a time by the lithographic projection apparatus. In this type of lithographic projection apparatus, the pattern on the entire patterning device is transferred onto one target portion in one operation. Such a device is commonly referred to as a stepper. In an alternative device, commonly referred to as a step - scan device, the projection beam is scanned over the patterning device in a given reference direction ("scan" direction), while the substrate is moved synchronously parallel or antiparallel to this reference direction. Different portions of the pattern on the patterning device are transferred step - by - step onto one target portion.

[0005] Before transferring the pattern from the patterning device to the substrate, the substrate can undergo various processes, such as priming, resist coating, and soft baking. After exposure, the substrate can undergo other processes ("post - exposure processes"), such as post - exposure bake (PEB), development, hard baking, and measurement / inspection of the transferred pattern. Such an array of processes serves as a basis for manufacturing an individual layer of a device (e.g., an IC). The substrate can then undergo various processes, such as etching, ion implantation (doping), metallization, oxidation, deposition, chemical - mechanical polishing, etc., all of which are aimed at completing an individual layer of the device. If several layers are required in the device, the entire process or its variant is repeated for each layer. Eventually, there will be devices in each target portion on the substrate. These devices are then separated from each other by techniques such as dicing or sawing, so that individual devices can be mounted on a carrier, connected to pins, etc. Such a device manufacturing process can be regarded as a patterning process.

[0006] Lithography is a central step in the fabrication of devices such as ICs, where the pattern formed on a substrate defines the functional elements of the device, such as microprocessors, memory chips, etc. Similar lithography techniques are also used to form flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0007] As semiconductor manufacturing processes continue to advance, over the decades, the size of functional elements has been continuously decreasing, while the number of functional elements such as transistors per device has been steadily increasing, a situation that follows the trend commonly known as "Moore's Law". In the current state of the art, layers of a device are fabricated using a lithographic projection apparatus that projects a design layout onto a substrate using irradiation from a deep ultraviolet radiation source, thereby creating individual functional elements that have dimensions well below 100 nm, i.e., dimensions less than half the wavelength of the radiation from the radiation source (e.g., a 193 nm radiation source).

[0008] This process of printing features with dimensions smaller than the classical resolution limit of a lithographic projection apparatus is generally referred to as low k1 lithography according to the resolution formula CD = k1×λ / NA, where λ is the wavelength of the radiation used (currently in most cases 248 nm or 193 nm), NA is the numerical aperture of the projection optics in the lithographic projection apparatus, CD is the "critical dimension" - typically the smallest feature size printed - and k1 is an empirical resolution factor. Generally, the smaller k1 is, the more difficult it becomes to reproduce on the substrate a pattern similar in shape and dimensions to that planned by the designer in order to achieve a specific electrical functionality and performance. To overcome these difficulties, complex fine-tuning steps are applied to the lithographic projection apparatus, the design layout, or the patterning device. These steps include, for example but not limited to, optimization of the NA and optical coherence settings, custom illumination schemes, use of phase-shifting patterning devices, optical proximity correction (OPC, sometimes also referred to as "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement techniques" (RET). SUMMARY OF THE INVENTION

[0009] The (multiple) measurement systems and (multiple) methods described below eliminate the need for a separate focusing branch (e.g., including an illumination source, several lenses, and many other optical components) commonly used in existing measurement systems to determine the focusing position for imaging a substrate. The (multiple) systems and (multiple) methods of the present disclosure use an integrated photon sensor instead of a separate focusing branch to determine the focusing position. The integrated photon sensor is based on a tapered grating coupler. The integrated photon sensor uses a combination of grating couplers to illuminate (although illumination using a grating coupler may be optional) and detect changes in the distance to the substrate, thereby determining focusing and / or other uses. This method can provide continuous focusing measurements. This method is less expensive and uses less physical volume for components in the imaging system compared to current methods. This method also eliminates the potential problem of phase differences that exist in the case of using existing optical device designs.

[0010] By varying the grating period and / or duty cycle, the amplitude and phase of the grating coupler mode are designed to have an optimal coupling efficiency for a specific defocus (or initial / known focusing position). The coupling efficiency between the transmitting grating (e.g.) and the receiving grating is determined based on the emitted radiation having a specific amplitude and a specific phase and the reflected radiation received from the substrate, with the specific amplitude and specific phase configured for a known position relative to the substrate (e.g., the distance from the substrate). The focusing position is determined based on the coupling efficiency and the known position. It should be noted that the principles described herein can be used in applications beyond the above-described measurement focusing sensor applications.

[0011] According to an embodiment, a system configured to image a substrate is provided. The system includes a radiation emitter configured to emit radiation having an emission amplitude and an emission phase configured for a known position relative to the substrate. The system includes a radiation receiver configured to receive reflected radiation from the substrate. The reflected radiation has a reflection amplitude and a reflection phase. The system includes one or more processors operably connected to the emitter and the receiver. The one or more processors are configured to: determine the coupling efficiency between the emitter and the receiver based on the emitted radiation and the received reflected radiation; and determine the height for imaging the substrate based on the coupling efficiency and the known position.

[0012] In some embodiments, the system is a measurement system, the known position is a known focusing position, and the height is the measured focusing position.

[0013] In some embodiments, the height is determined based on a linear relationship between the coupling efficiency and the defocus of the system objective.

[0014] In some embodiments, the transmitter includes a transmitting grating, a transmitter in free space, or an optical fiber, and the receiver includes a receiving grating.

[0015] In some embodiments, the transmitter includes a transmitting grating, and the transmitting grating is configured to emit the radiation having the emission amplitude and emission phase by adjusting the grating period and / or duty cycle of the transmitting grating.

[0016] In some embodiments, the system further includes: a second transmitting grating configured to emit a second radiation having a second emission amplitude and a second emission phase configured for a second known position relative to the substrate; and a second receiving grating configured to capture the second reflected radiation from the substrate, the second reflected radiation having a second reflection amplitude and a second reflection phase.

[0017] In some embodiments, one or more processors are operably connected to the second transmitting grating and the second receiving grating. The one or more processors are further configured to: determine a second coupling efficiency between the second transmitting grating and the second receiving grating based on the emitted second radiation and the received second reflected radiation; and determine a height for imaging the substrate based on the coupling efficiency, the second coupling efficiency, the known position, and the second known position.

[0018] In some embodiments, the known position is associated with different defocuses (e.g., two different defocuses) (e.g., designed for different defocuses). For example, in some embodiments, the known position is associated with positive defocus, and the second known position is associated with negative defocus.

[0019] In some embodiments, the one or more processors are further configured to: determine a first capture power and a second capture power based on the phases and amplitudes of the reflected radiation and the second reflected radiation, and determine the height based on the ratio of the first capture power to the second capture power.

[0020] In some embodiments, the system is a metrology system, and the transmitter and the receiver are coupled to an objective of the metrology system.

[0021] In some embodiments, the transmitter and the receiver are tilted relative to the objective to increase the incident angle of the emitted radiation.

[0022] In some embodiments, the system is a metrology system, and the one or more processors are further configured to: automatically adjust a focus position of the metrology system based on the determined height such that subsequent images of the substrate are in focus.

[0023] In some embodiments, the substrate includes a semiconductor wafer having one or more overlapping targets configured to reflect the reflected radiation towards a receiver.

[0024] In some embodiments, the emitter and the receiver include gratings formed in a silicon-based substrate or any other type of substrate.

[0025] In some embodiments, the substrate includes a waveguide configured to direct the incident radiation to the emitter and / or direct the received radiation from the receiver.

[0026] In some embodiments, the emitter includes a transmitting grating, and the receiver includes a receiving grating, and the system further includes a tapered grating coupler.

[0027] In some embodiments, the height determination sensitivity is at least 120 nm.

[0028] In some embodiments, the emitter, the receiver, and one or more processors are configured to replace the focusing branch in a typical metrology system.

[0029] In some embodiments, the system further includes a radiation source and one or more lenses. The radiation source and one or more lenses are configured to generate incident radiation and direct the incident radiation towards the emitter.

[0030] In some embodiments, the system includes a metrology system configured for overlay detection of a semiconductor wafer and for use in a semiconductor manufacturing process.

[0031] According to another embodiment, a method for imaging a substrate is provided. The method includes: emitting radiation using a radiation emitter, the radiation having an emission amplitude and an emission phase configured for a known position relative to the substrate; receiving reflected radiation from the substrate using a radiation receiver, the reflected radiation having a reflection amplitude and a reflection phase; determining a coupling efficiency between the emitter and the receiver based on the emitted radiation and the received reflected radiation using one or more processors operatively connected to the emitter and the receiver; and determining a height for imaging the substrate based on the coupling efficiency and the known position using one or more processors. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] After reviewing the following description of specific embodiments in conjunction with the accompanying drawings, those of ordinary skill in the art will appreciate the above aspects and other aspects and features.

[0033] Figure 1 A lithographic apparatus is schematically depicted according to an embodiment.

[0034] Figure 2 Schematically depict an embodiment of a lithography element or lithography cluster according to an embodiment.

[0035] Figure 3 Schematically depict an exemplary inspection system according to an embodiment.

[0036] Figure 4 Schematically depict an exemplary metrology technique according to an embodiment.

[0037] Figure 5 Illustrate the relationship between the radiation illumination spot and the metrology target of an inspection system according to an embodiment.

[0038] Figure 6 Illustrate a system configured to image a substrate according to an embodiment. Such an operation can include, for example, determining a focus position for imaging one or more metrology targets.

[0039] Figure 7 Illustrate the Gaussian beam of radiation traveling through a uniform space (and reflecting off a target) and the curvature of the wavefront of the radiation according to an embodiment.

[0040] Figure 8 Provide a schematic representation of how defocus changes the lateral displacement and travel distance of radiation according to an embodiment.

[0041] Figure 9 Illustrate a side view ( Figure 9 upper portion) and a top view ( Figure 9 lower portion) of an embodiment of the system of the present disclosure according to an embodiment, the system being configured to irradiate the surface of a target and capture reflected light using two sets of grating couplers.

[0042] Figure 10 Illustrate the amplitude and phase of the grating coupler shown in the previous figure and the associated incident field according to an embodiment.

[0043] Figure 11 Illustrate the effect of target defocus according to an embodiment.

[0044] Figure 12 Illustrate the effect of the angle of incidence according to an embodiment.

[0045] Figure 13 Illustrate the effect of the beam waist at the focus on the grating coupler according to an embodiment.

[0046] Figure 14 Illustrate the scalability of the range of the linear portion of the coupling efficiency of the grating coupler according to an embodiment.

[0047] Figure 15Illustrated is an exemplary embodiment of a system of the present disclosure according to an embodiment, where several different groups of grating couplers (e.g., multiple groups of generally triangular transmitters and receivers in this example) are operating in parallel.

[0048] Figure 16 Illustrated is an exemplary grating coupler (e.g., transmitter and / or receiver) design according to an embodiment.

[0049] Figure 17 Illustrated is the integration of transmitters and receivers into the system of the present disclosure according to an embodiment.

[0050] Figure 18 Illustrated is a method for imaging a substrate according to an embodiment.

[0051] Figure 19 is a block diagram of an exemplary computer system according to an embodiment. Detailed Description

[0052] In semiconductor device manufacturing, metrology operations typically include determining the location of metrology marks (or multiple metrology marks) and / or other targets in a semiconductor device structure layer. Such locations are typically determined by irradiating the metrology marks with radiation and comparing the characteristics of different diffraction orders of the radiation reflected from the metrology marks. These techniques are used to measure overlay, alignment, and / or other parameters.

[0053] Many metrology systems include separate focusing branches (e.g., a portion of the metrology system that includes a radiation source, several lenses, and many other optical components) to determine the focusing position for imaging a substrate. Typical focusing branches are bulky and expensive. A typical focusing branch requires an additional beam splitter to combine the focusing branch with the remainder of the metrology system, which reduces the radiation flux to the central sensor.

[0054] As described above, the (multiple) systems and (multiple) methods of the present disclosure use an integrated photon sensor rather than a separate focusing branch to determine the focusing position. The integrated photon sensor is based on a tapered grating coupler in which, by varying the grating period and / or duty cycle, the amplitude and phase of the grating coupler mode are designed to have optimal coupling efficiency for a particular defocus (or an initial / known focusing position). The coupling efficiency between an emission grating (e.g.) and a receiving grating is determined based on the emitted radiation having a particular amplitude and a particular phase and the reflected radiation received from the substrate, and the particular amplitude and particular phase are configured for a known position relative to the substrate (e.g., the distance from the substrate). The focusing position is determined based on the coupling efficiency and the known position. It should be noted that the principles described herein can be used for applications beyond the above-described metrology focusing sensor applications.

[0055] By way of brief introduction, the description herein relates to semiconductor device fabrication and patterning processes. The following paragraphs also describe a number of components of systems and / or methods for semiconductor device metrology. These systems and methods can be used, for example, to measure overlay, alignment, etc. during semiconductor device fabrication, or for other operations.

[0056] Although the measurement of overlay, alignment or other parameters and the fabrication of integrated circuits (ICs) for semiconductor devices may be specifically referenced herein, it should be understood that the description herein has many other possible applications. For example, the description can be used for fabricating integrated optical systems, guiding and detecting patterns for magnetic domain memories, liquid crystal display (LCD) panels, thin film magnetic heads, etc. Those skilled in the art should appreciate that in the context of these alternative applications, any use herein of the terms "reticle", "wafer" or "die" should be recognized as being interchangeable with the more general terms "mask", "substrate" and "target portion", respectively.

[0057] As used herein, the term "projection optics" should be interpreted broadly to encompass various types of optical systems, including, for example, refractive optical devices, reflective optical devices, catadioptric optical devices. The term "projection optics" can also include components that operate according to any of these design types to jointly or individually direct, shape or control a projection radiation beam. The term "projection optics" can include any optical component in a lithographic projection apparatus, regardless of where the optical component is positioned in the optical path of the lithographic projection apparatus. Projection optics can include optical components for shaping, conditioning and / or projecting the radiation from a source before it passes through a patterning device, and / or for shaping, conditioning and / or projecting the radiation after it passes through the patterning device. Projection optics generally excludes the source and the patterning device.

[0058] Figure 1An embodiment of a lithographic apparatus LA is schematically depicted. The apparatus includes: 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., a mask table) MT configured to support a patterning device (e.g., a 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., a wafer table) WT (e.g., WTa, WTb, or both) configured to hold a substrate (e.g., a wafer coated with resist) W and coupled to a second positioner PW configured to accurately position the substrate 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., including one or more dies and often referred to as a field) of the substrate W. The projection system is supported on a reference frame RF. As depicted, the apparatus has a transmissive type (e.g., using a transmissive mask). Alternatively, the apparatus may belong to a reflective type (e.g., using a programmable mirror array or using a reflective mask).

[0059] The illuminator IL receives the radiation beam from a radiation source SO. For example, when the source is an excimer laser, the source and the lithographic apparatus may be separate entities. In these cases, the source is not considered to form part of the lithographic apparatus, and the radiation beam is transmitted from the source SO to the illuminator IL by a beam delivery system BD including, for example, suitable directing mirrors and / or beam expanders. 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, the illuminator IL, and the beam delivery system BD may be referred to as the radiation system when needed.

[0060] The illuminator IL may modify the intensity distribution of the beam. The illuminator may be configured to limit the radial extent of the radiation beam such that the intensity distribution within an annular region in the pupil plane of the illuminator IL is non-zero. Additionally or alternatively, the illuminator IL may be operable to limit the distribution of the beam in the pupil plane such that the intensity distribution within a plurality of equally spaced segments in the pupil plane is non-zero. The intensity distribution of the radiation beam in the pupil plane of the illuminator IL may be referred to as the illumination mode.

[0061] The illuminator IL may include an adjuster AD arranged to adjust the (angular / spatial) intensity distribution of the beam. Generally, at least the outer radial extent and / or the inner radial extent of the intensity distribution in the pupil plane of the illuminator (commonly referred to as σ - outer and σ - inner, respectively) may be adjusted. The illuminator IL is operable to vary the angular distribution of the beam. For example, the illuminator is operable to change the number and angular extent of the segments in the pupil plane in which the intensity distribution is non - zero. By adjusting the intensity distribution of the beam in the pupil plane of the illuminator, different illumination patterns can be achieved. For example, by restricting the radial extent and angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution can have a multipole distribution, such as a dipole, quadrupole, or hexapole distribution. The illumination pattern can be obtained, for example, by inserting optics that provide the desired illumination pattern into the illuminator IL or using a spatial light modulator.

[0062] The illuminator IL is operable to change the polarization of the radiation beam and is operable to adjust the polarization using the adjuster AD. The polarization state of the radiation beam across the pupil plane of the illuminator IL can be referred to as the polarization pattern. Using different polarization patterns can allow for a 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 vary across the pupil plane of the illuminator IL. The polarization direction of the radiation can be different in different regions of the pupil plane of the illuminator IL. The polarization state of the radiation can be selected according to the illumination pattern. For a multipole illumination pattern, the polarization of each pole of the radiation beam can be substantially perpendicular to the position vector of the pole in the pupil plane of the illuminator IL. For example, for a dipole illumination pattern, the radiation can be linearly polarized in a direction substantially perpendicular to the line bisecting the two opposing segments of the dipole. The radiation beam can be polarized in one of two different orthogonal directions that can be referred to as the X - polarization state and the Y - polarization state. For a quadrupole illumination pattern, the radiation in each segment of the pole can be linearly polarized in a direction substantially perpendicular to the line bisecting the segment. This polarization pattern can be referred to as XY polarization. Similarly, for a hexapole illumination pattern, the radiation in each segment of the pole can be linearly polarized in a direction substantially perpendicular to the line bisecting the segment. This polarization pattern can be referred to as TE polarization.

[0063] In addition, the illuminator IL generally includes various other components, such as an integrator IN and a condenser CO. The illumination system can include various types of optical components for guiding, shaping, or controlling the radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof. Thus, the illuminator provides a conditioned radiation beam B having a desired uniformity and intensity distribution in its cross - section.

[0064] 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 such as whether the patterning device is held 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, for example, a frame or a table, which can be fixed or movable as required. The support structure can ensure that the patterning device is, for example, in a desired position relative to the projection system. Any use of the terms "mask" or "reticle" in this document can be considered synonymous with the more general term "patterning device".

[0065] The term "patterning device" as used herein should be interpreted broadly as referring to any device that can be used to impart a pattern in a target portion of a substrate. In an embodiment, the patterning device is any device that can be used to impart a pattern in a cross-section of a radiation beam to form a pattern in a target portion of a substrate. It should be noted that, for example, if the pattern imparted to the radiation beam includes phase-shifting features or so-called assist features, the pattern may not exactly correspond to the desired pattern in the target portion of the substrate. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device (such as an integrated circuit) produced in the target portion of the device.

[0066] The patterning device can be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array uses a matrix arrangement of small mirrors, each of which can be tilted individually so as to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam reflected by the mirror matrix.

[0067] The term "projection system" should be interpreted broadly as encompassing any type of projection system suitable for the exposure radiation used or for other factors such as the use of an immersion liquid or the use of a vacuum, including refractive, reflective, catadioptric, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof. Any use of the term "projection lens" in this document can be considered synonymous with the more general term "projection system".

[0068] The projection system PS may include a plurality of optical (e.g., lens) elements and may also include an adjustment mechanism configured to adjust one or more of the optical elements so as to correct for aberrations (phase variations across the pupil plane over the entire field). To effect such correction, the adjustment mechanism is 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 with its optical axis extending in the z direction. The adjustment mechanism is operable to effect any combination of the following: displacing one or more optical elements; tilting one or more optical elements; and / or deforming one or more optical elements. The displacement of an optical element may be in any direction (x, y, z, or a combination thereof). The tilting of an optical element is typically effected by rotation about an axis in the x and / or y direction out of a plane perpendicular to the optical axis, but for an aspherical optical element that is not rotationally symmetric, rotation about the z axis may be used. The deformation of an optical element may include a low-frequency shape (e.g., astigmatism) and / or a high-frequency shape (e.g., freeform aspheric). The deformation of an optical element may be effected, for example, by using one or more actuators to apply a force to one or more sides of the optical element and / or by using one or more heating elements to heat one or more selected regions of the optical element. In general, it is not possible to adjust the projection system PS to correct for apodization (transmission variations across the pupil plane). The transmission mapping of the projection system PS may be used in the design of a patterning device (e.g., a mask) MA for a lithographic apparatus LA. Using computational lithography techniques, the patterning device MA may be designed to at least partially correct for apodization.

[0069] The lithographic apparatus may be of the type having two (dual-platform) or more platforms (e.g., two or more substrate tables WTa, WTb, two or more patterning device tables, a substrate table WTa and a table WTb under the projection system without a substrate dedicated, for example, to facilitating measurement and / or cleaning, etc.). In these “multi-platform” machines, additional platforms may be used in parallel, or preparatory steps may be carried out on one or more platforms while one or more other platforms are used for exposure. For example, alignment measurements using an alignment sensor AS and / or leveling (height, tilt, etc.) measurements using a leveling sensor LS may be carried out.

[0070] A lithographic apparatus may also have a type in which at least a portion of a substrate can 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. The immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, the space between the patterning device and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of the projection system. As used herein, the term "immersion" does not mean that a structure such as a substrate must be immersed in a liquid, but only that the liquid is located between the projection system and the substrate during exposure.

[0071] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by an illumination system IL. The radiation beam B is incident on a patterning device (e.g., a mask) MA which is held on a support structure (e.g., a mask table) MT and patterned by the patterning device. After having traversed the patterning device MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of a substrate W. By means of a second positioning device PW and a position sensor IF (e.g., an interferometric device, a linear encoder, a 2D encoder or a capacitive sensor), the substrate table WT can be accurately moved, for example, so as to position different target portions C in the path of the radiation beam B. Similarly, for example, after mechanical retrieval from a mask library or during scanning, a first positioning device PM and another position sensor (which is not explicitly depicted in Figure 1 ) can be used to accurately position the patterning device MA relative to the path of the radiation beam B. Generally, movement of the support structure MT can be realized by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming part of the first positioning device PM. Similarly, long-stroke and short-stroke modules forming part of the second positioning device PW can be used to realize movement of the substrate table WT. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected only to a short-stroke actuator or may be fixed. Patterning device alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning device MA and the substrate W. Although as illustrated the substrate alignment marks occupy dedicated target portions, the marks may be located in the spaces between the target portions (these marks are referred to as scribe alignment marks). Similarly, in the case where more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0072] The apparatus depicted can be used in at least one of the following modes. In the step mode, the support structure MT and the substrate table WT remain substantially stationary while the pattern imparted to the radiation beam is projected onto the target portion C in one go (i.e., a single static exposure). Subsequently, the substrate table WT is displaced in the X and / or Y direction so that different target portions C can be exposed. In the step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. In the scan mode, the support structure MT and the substrate table WT are scanned synchronously while the 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 can be determined by the (reduction) magnification and image inversion characteristics of the projection system PS. In the scan mode, the maximum size of the exposure field limits the width of the target portion (in the non-scanning direction) in a single dynamic exposure, while the length of the scanning movement determines the length of the target portion (in the scanning direction). In another mode, while the pattern to be imparted to the radiation beam is projected onto the target portion C, the support structure MT remains substantially stationary, thus holding the programmable patterning device, and the substrate table WT is moved or scanned. In this mode, a pulsed radiation source is typically used, and the programmable patterning device is updated as needed after each movement of the substrate table WT or between successive radiation pulses during scanning. This mode of operation can be readily applied to maskless lithography using a programmable patterning device such as a programmable mirror array of the type mentioned above.

[0073] Combinations and / or variations of the above-described usage modes or completely different usage modes can also be used.

[0074] The substrate can be processed before or after exposure in, for example, a track or a coat develop system (a tool that typically applies a resist layer to the substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosures herein can be applied to these and other substrate processing tools. Additionally, the substrate can be processed more than once, for example to produce a multi-layer IC, such that the term "substrate" as used herein can also refer to a substrate that already includes multiple processed layers.

[0075] As used herein, the terms "radiation" and "beam" in the context of lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation or deep ultraviolet (DUV) radiation (e.g., having wavelengths of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having wavelengths in the range of 5 nm to 20 nm), as well as particle beams such as ion beams or electron beams.

[0076] The various patterns on or provided by a patterning device can have different process windows, i.e., the space of process variables according to which a pattern will be generated within specifications. Examples of pattern specifications regarding potential systematic defects include checking for necking, line pullback, line thinning, CD, edge placement, overlay, resist top loss, resist undercut, and / or bridging. The process window of the pattern on the patterning device or its area can be obtained by merging (e.g., overlaying) the process windows of each individual pattern. The boundaries of the process window of a pattern group include the boundaries of the process windows of some of the individual patterns. In other words, these individual patterns limit the process window of the pattern group.

[0077] As Figure 2 shown, a lithographic apparatus LA can form part of a lithographic cell LC (sometimes also referred to as a litho cell or cluster), which also includes equipment for performing pre-exposure processes and post-exposure processes on a substrate. Conveniently, this equipment includes one or more spin coaters SC for depositing one or more resist layers, one or more developers for developing the exposed resist, one or more chill plates CH, and / or one or more bake plates BK. A substrate transfer device or robot RO picks up one or more substrates from input / output ports I / O1, I / O2, moves them between different process equipment, and transfers them to the feed table LB of the lithographic apparatus. These devices, often collectively referred to as a track or coat develop system, are controlled by a track or coat develop system control unit TCU, which is itself controlled by a management control system SCS, which also controls the lithographic apparatus via a lithographic control unit LACU. Thus, different devices can be operated to maximize throughput and process efficiency.

[0078] To correctly and consistently expose the substrates exposed by the lithographic apparatus, and / or to monitor part of a patterning process (e.g., a device manufacturing process) including 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 (which can be, for example, between structures in an overlay layer or between structures in the same layer that have been separately provided to the layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, material properties, etc. Thus, a manufacturing facility in which a lithographic cell LC is located typically also includes a metrology system that measures some or all of the substrates W ( Figure 1 ) that have been processed in the lithographic cell or other objects in the lithographic cell. The metrology system can be part of the lithographic cell LC. For example, the metrology system can be part of the lithographic apparatus LA (such as an alignment sensor AS ( Figure 1 )).

[0079] For example, one or more measured parameters can include: alignment, overlap between successive layers formed in or on a patterned substrate, critical dimension (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 aberrations of an optical lithography step, etc. Such measurements are often performed on one or more dedicated metrology targets disposed on the substrate. The measurements can be performed after resist development but before etching, after etching, after deposition, and / or at other times.

[0080] There are various techniques for measuring structures formed during a patterning process, including using a scanning electron microscope, image-based metrology tools, and / or various dedicated tools. A dedicated metrology tool in a fast and non-invasive form is a metrology tool in which a radiation beam is directed onto a target on the surface of a substrate and the properties of the scattered (diffracted / reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. Conventionally, this can be referred to as diffraction-based metrology. Applications of such diffraction-based metrology include measurements of overlap, alignment, etc. For example, overlap and / or alignment can be measured by comparing portions of diffraction spectra (e.g., comparing different diffraction orders in the diffraction spectrum of a periodic grating).

[0081] Thus, during a device manufacturing process (e.g., a patterning process or a lithography process), a substrate or other object can be subjected to various types of measurements during or after the process. The measurements can determine whether a particular substrate is defective, can establish adjustments to the process and the equipment used in the process (e.g., aligning two layers on a substrate or aligning a patterning device to a substrate), can measure the performance of the process and the equipment, or can 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 an ASML YieldStar metrology tool, an ASML SMASH metrology system), mechanical measurements (e.g., profilometry using a stylus, atomic force microscopy (AFM)), and / or non-optical imaging (e.g., scanning electron microscopy (SEM)).

[0082] The measurement results can be provided directly or indirectly to the management control system SCS. If an error is detected, the exposure of subsequent substrates (especially if the inspection can be completed quickly enough such that one or more other substrates of the batch are still to be exposed) and / or the subsequent exposure of the exposed substrates can be adjusted. Additionally, the exposed substrates can be stripped and reprocessed to improve the yield, or discarded, thereby avoiding further processing of substrates known to be defective. In cases where only some target portions of the substrate are defective, further exposure can be performed only on those target portions that meet the specifications. Other manufacturing process adjustments are anticipated.

[0083] A metrology system can be used to determine one or more properties of a substrate structure, and in particular how one or more properties of different substrate structures vary, or how different layers of the same substrate structure vary from layer to layer. The metrology system can be integrated into the lithography apparatus LA or the lithography cell LC, or can be a separate device.

[0084] To enable metrology, one or more targets are often specifically provided on the substrate. Typically, the targets are specifically designed and can include periodic structures. For example, the targets on the substrate can include one or more 1-D periodic structures (e.g., geometric features such as gratings) that are printed such that after development, the periodic structure features are formed by solid resist lines. As another example, the targets can include one or more 2-D periodic structures (e.g., gratings) that are printed such that after development, one or more periodic structures are formed by solid resist pillars or vias in the resist. The bars, pillars, or vias can alternatively be etched into the substrate (e.g., into one or more layers on the substrate).

[0085] Figure 3 An exemplary metrology (inspection) system 10 that can be used to detect overlay, alignment, and / or perform other metrology operations is depicted. The exemplary metrology (inspection) system 10 includes a radiation or illumination source 2 that projects or otherwise irradiates radiation onto a substrate W (e.g., the substrate W typically can include metrology marks). The redirected radiation is transmitted to a sensor such as a spectrometer detector 4 and / or other sensors that measure the spectrum (intensity as a function of wavelength) of the specularly reflected and / or diffracted radiation, e.g., as shown in the Figure 4 left-hand graph. The sensor can generate a metrology signal that transmits metrology data indicative of the properties of the reflected radiation. Based on such data, the structure or profile of the detected spectrum can be reconstructed by one or more processors PRO, or by other operations, a general example of one or more processors PRO is shown in Figure 4 as shown.

[0086] As inFigure 1 as in the lithographic apparatus LA, one or more substrate tables ( Figure 4 not shown) may be provided to hold the substrate W during the measurement operation. The one or more substrate tables may be similar or identical in form to Figure 1 the substrate tables WT (WTa or WTb or both) of. In an example where the inspection system 10 is integrated with a lithographic apparatus, the one or more substrate tables may even be the same substrate table. A coarse locator and a fine locator may be provided and configured to accurately position the substrate relative to the measurement optical system. Various sensors and actuators are provided, for example, to obtain the position of a target portion of interest of the structure (e.g., a metrology mark), and to bring the target portion of interest into a position under the objective lens. Typically, many measurements will be made of the target portions of the structure at different positions across the substrate W. The substrate support may be moved in both the X and Y directions to acquire different targets, and in the Z direction to obtain a desired position of the target portion relative to the focus of the optical system. For example, when in practice the optical system can be held (usually in the X and Y directions, but possibly also in the Z direction) substantially stationary and the substrate is moved, it is convenient to consider and describe the operation as if the objective lens is being brought to different positions relative to the substrate. Assuming the relative position of the substrate and the optical system is correct, in principle it is unimportant which of the substrate and the optical system is moving, or whether both the substrate and the optical system are moving, or a combination where a part of the optical system is moving (e.g., in the Z direction and / or the tilt direction) while the remainder of the optical system is stationary and the substrate is moving (e.g., in the X and Y directions, but also optionally in the Z direction and / or the tilt direction).

[0087] For typical metrology measurements, the target 30 on the substrate W may be a 1-D grating, which is printed such that after development, the grating bars are formed by solid resist lines (e.g., the solid resist lines may be covered by a deposited layer) and / or other materials. Or the target 30 may be a 2-D grating, which is printed such that after development, the grating is formed by solid resist pillars and / or other features in the resist.

[0088] Ribs, guide posts, through-holes, and / or other features may be etched into the substrate or onto the substrate (e.g., into one or more layers on the substrate), deposited on the substrate, covered by a deposited layer, and / or have other properties. The target (portion) 30 (e.g., of ribs, guide posts, through-holes, etc.) is sensitive to changes in processing during the patterning process (e.g., optical aberrations, focus changes, dose changes, etc. in a lithographic projection apparatus such as a projection system), such that process variations manifest as changes in the target 30. Thus, the measured data from the target 30 can be used to determine adjustments to one or more manufacturing processes during the manufacturing process, and / or as a basis for making actual adjustments.

[0089] For example, the measured data from the target 30 may indicate an overlap of layers of a semiconductor device. The measured data from the target 30 can be used (e.g., by one or more processors PRO and / or other processors) to determine one or more semiconductor device manufacturing process parameters based on the overlap, and to determine adjustments to the semiconductor device manufacturing equipment based on the one or more determined semiconductor device manufacturing process parameters. In some embodiments, this may include, for example, platform position adjustment, or this may include determining adjustments to mask design, metrology target design, semiconductor device design, intensity of radiation, angle of incidence of radiation, wavelength of radiation, pupil size and / or shape, resist material, and / or other process parameters.

[0090] Figure 5 A plan view of a typical target (e.g., a metrology mark) 30, and Figure 4 the extent of a typical radiation illumination spot S in the system of. Generally, in order to obtain a diffraction spectrum free from interference from surrounding structures, in an embodiment, the target 30 is a periodic structure (e.g., a grating) larger than the width (e.g., diameter) of the illumination spot S. The width of the spot S may be less than the width and length of the target. In other words, the target is "underfilled" by the illumination, and the diffraction signal is substantially free of any signal from product features, etc. outside of the target itself. For example, the illumination device may be configured to provide illumination of uniform intensity across the rear focal plane of the objective. Alternatively, the illumination may be limited to an on-axis or off-axis direction, for example, by including an aperture in the illumination path.

[0091] Figure 6FIG. illustrates a system 600 configured to image a substrate according to an embodiment. Such operation may include, for example, determining a focus position for imaging one or more metrology targets 30. For example, the targets 30 may include one or more metrology marks formed in a substrate 602 such as a semiconductor wafer, collectively referred to as the targets 30, such as diffraction grating targets. The targets 30 may include one or more structures in the patterned substrate that can provide a diffraction signal. For example, one or more of the targets 30 may be included in a substrate layer in a semiconductor device structure. In some embodiments, the features include geometric features such as 1D or 2D features and / or other geometric features. By way of several non-limiting examples, the features may include gratings, lines, edges, a series of lines and / or edges with a detailed pitch, and / or other features.

[0092] The system 600 includes a radiation sensor 604 configured to receive radiation from the target 30 and generate a signal indicative of the field image position of the radiation. The radiation may be used to obtain an image of the metrology target 30 and / or for other purposes. The radiation may include illumination such as light and / or other radiation. The system 600 includes an optical component 606 configured to receive the radiation reflected from the target 30 and the substrate 602 and direct the radiation towards the sensor 604. The system 600 includes: a radiation emitter 625 configured to emit radiation having an emission amplitude and an emission phase configured for a known position relative to the substrate 602; and a radiation receiver 635 configured to receive the reflected radiation from the substrate 602. The reflected radiation has a reflection amplitude and a reflection phase. The system 600 has one or more processors PRO operably connected to the emitter 625 and the receiver 635. The one or more processors PRO are configured to: determine the coupling efficiency between the emitter 625 and the receiver 635 based on the emitted radiation and the received reflected radiation; and determine the height for imaging the substrate 602 based on the coupling efficiency and the known position. The emitter 625 and the receiver 635 may be coupled to other components of the system 600, and the emitter 625 and the receiver 635 may form their own separate structures. The emitter 625, the receiver 635, the coupling efficiency, and the height are all discussed in detail below with respect to Figures 7 to 17 Detailed discussion.

[0093] The system 600 may be similar to and / or identical to Figure 3 The system 10 shown in. In Figure 6 Compared with the system 10, additional details are illustrated for the system 600. In some embodiments, the system 600 may form the above with respect to Figure 3Portions of the described system 10. For example, system 600 can be a subsystem of system 10. In some embodiments, one or more components of system 600 can be similar and / or identical to one or more components of system 10. In some embodiments, one or more components of system 600 can replace, be used with, and / or otherwise augment one or more components of system 10.

[0094] System 600 includes a radiation source 612; an optical component 606; an overlap detection branch 660 having a sensor 604; a beam splitter 670; an alignment branch 680; various lenses, reflectors, and other optical components (with an exemplary objective lens 690 labeled in Figure 6 ); and / or other components. In some embodiments, the components of system 600 form part of an overlap and / or alignment sensor for a semiconductor manufacturing process. The radiation source 612 is configured to generate radiation along a first optical path 621. In some embodiments, radiation from the radiation source 612 and / or other radiation sources can be provided to a transmitter 625. The radiation can have a target wavelength and / or wavelength range, a target intensity, and / or other characteristics. The target wavelength and / or wavelength range, the target intensity, etc. can be typed in and / or selected by a user, determined by the system (e.g., Figure 3 the system 10 shown in), and / or otherwise determined. In some embodiments, the radiation includes light and / or other radiation. In some embodiments, the light includes visible light, infrared light, near-infrared light, and / or other light. In some embodiments, the radiation can be any radiation suitable for interference.

[0095] As described above, system 600 does not include a separate focusing branch 650 (illustrated as removed in Figure 6 ). Focusing measurements 675 performed by the focusing branch 650 require detection apertures 677 and 679 along with corresponding sensors 681 and 683 before the focus and additional sensors 681 and 683 after the focus. When the two sensors detect the same radiation 685 intensity, the defocused position is defined. The intensity is determined before and after the focusing position conjugate to the substrate, and the normalized difference is determined as the focusing position. In Figure 6 , FS represents the focus signal (e.g., a representation of the (optimal) focusing position), and the focus signal has been determined for an existing system by the equation for FS shown in Figure 6 , where S1 and S2 are the first and second intensities at the corresponding sensors, O represents an object that can be the substrate (e.g., a wafer) plane in this example, O1' / O2' represents the conjugate plane of O, and P is the pupil plane.

[0096] System 600 provides a new optical design architecture. Instead of using the focusing branch 650 and the above-described focusing measurement principle, System 600 uses the emitter 625 and the receiver 635 to determine the imaging height (e.g., the focusing position) as described below. This new architecture reduces cost and volume compared to existing systems because the components of the focusing branch 650 are not required and / or has other advantages.

[0097] The emitter 625 is configured to emit radiation having an emission amplitude and an emission phase configured for a known position relative to the substrate 602. For example, the known position may be a known or initial focusing position of System 600. In some embodiments, the emitter 625 includes an emission grating, an emitter in free space, an optical fiber, and / or other emitters. For example, the emitter 625 may include an emission grating. The emission grating may be configured to emit radiation having an emission amplitude and an emission phase by adjusting the grating period and / or duty cycle of the emission grating.

[0098] The reflected radiation (e.g., a portion of the reflected radiation different from the portion used for the above overlap and / or alignment) from the substrate 602 is received by the radiation receiver 635. The reflected radiation has a reflection amplitude and a reflection phase. In some embodiments, the receiver 635 includes a receiving grating and / or other receivers. In some embodiments, the emitter 625 and the receiver 635 include gratings formed in a silicon-based substrate. In some embodiments, the silicon-based substrate includes waveguides configured to guide the incident radiation (e.g., from the source 612) to the emitter 625 and / or the received radiation from the receiver 635 (e.g., such that the corresponding signals can be processed by the processor PRO).

[0099] The coupling efficiency between the emitter 625 and the receiver 635 is determined based on the emitted radiation and the received reflected radiation. The coupling efficiency is determined using one or more processors (e.g., one or more processors PRO) operably connected to the emitter and the receiver. The height for imaging the substrate 602 is determined based on the coupling efficiency and the known (e.g., initial focusing) position. For example, the height may be the metrology focusing position of System 600. In some embodiments, the height is determined based on the linear relationship between the coupling efficiency and the defocus of the system objective. For example, the sensitivity of the height determination may be at least about 100 nm, 120 nm, or 140 nm.

[0100] In some embodiments, one or more processors PRO are configured to: automatically adjust the focus position of system 600 for imaging target 30 based on the determined height such that subsequent images of target 30 and / or substrate 602 are in focus. This can include generating incident radiation using radiation source 612 and one or more lenses and / or other components of system 600 and directing the radiation towards emitter 625 (e.g., via a waveguide in the substrate as described above).

[0101] Figures 7 to 17 And its corresponding description provides additional details regarding the various operations described above.

[0102] By varying the grating period and / or duty cycle of emitter 625 and / or receiver 635 ( Figure 6 ), the amplitude and phase of the grating coupler mode can be designed. The coupling efficiency (η) of the grating coupler is defined as:

[0103]

[0104] where H in (incident field) and P in are respectively the magnetic field and power distribution of the incident beam on the grating coupler, and E GC (graded mode) and P GC are respectively the electric field and power distribution of the grating coupler mode. To achieve optimal coupling, the amplitude and phase of the incident beam and the grating coupler mode should have maximum overlap. For a Gaussian incident beam, the phase wavefront is flat at the focus, but the phase wavefront has a paraboloidal shape that has opposite signs before and after the focus (e.g., see Figure 7 ). If the Gaussian beam has an oblique incidence at the surface, the lateral position and travel distance of the beam change in the presence of defocus ( Figure 7 ). In the systems and methods of the present disclosure, the grating coupler is designed to have an optimal coupling efficiency for different defocus. As the defocus changes, the coupling efficiency (S1 and S2) can have different functions for different grating couplers. In some embodiments, instead of designing two different grating couplers, the same coupler can be used but loaded with a metasurface having positive or negative focal power.

[0105] For example, Figure 7 illustrates a Gaussian beam of radiation 700 traveling through a uniform space 702 (and reflecting off target 30) and the curvature 704 of the wavefront of radiation 700. The curvature 704 of the wavefront of radiation 700 has opposite signs or polarities before and after focus 706. In some embodiments, capture grating couplers such as receivers 710 and / or 712 (e.g., receivers 635 having properties θ, d0, and α sin the form, where θ is the capture angle, and d0 and α s define the transition from a single-mode waveguide to a grating coupler, and θ, d0, and α s (configured to optimize the coupling efficiency of a desired incident beam) is configured to capture a Gaussian beam before (e.g., receiver 710) and / or after (receiver 712) the capture focus 706. Figure 7 Also illustrated is the coupling efficiency 720 of grating couplers such as receivers 710 (labeled GC1) and 712 (labeled GC2) as a function of defocus. The grating coupler is configured to have optimal coupling when the defocus (z) is z = z G = ±0.5 μm, where z G is the desired defocus. The equation for the coupling efficiency of the above grating coupler is included in Figure 7 where the grating mode and the incident field portions 750 and 752 are labeled respectively.

[0106] Figure 8 Provides a schematic representation of how defocus (z) changes the lateral displacement (Δx) and the travel distance (Δz) of the radiation 700. Increasing the incident angle (θ in ) enhances both Δx and Δz. For example, enhancing Δx and Δz enhances the deviation of the incident beam from the desired beam, such that, for example, the grating coupler becomes more sensitive to defocus. For example, the emitter 625 (a grating in this example) is configured for the radiation 700 emitted at a desired focal length. It should be noted that a hybrid or fully integrated approach can be used, in which a grating coupler (e.g., emitter 625) is used to emit radiation, such as light, and a second grating coupler (e.g., receiver 635) is used to capture the light. In this example, a change in the horizontal height of the platform holding the target 30 changes the propagation length Δz and the lateral position Δx of the beam. Increasing the incident angle or having a tighter focus increases the sensitivity of Δz and Δx to z.

[0107] In some embodiments, the system 600 ( Figure 6It includes two sets (or more sets) of grating couplers. The second emission grating can be configured to emit a second radiation having a second emission amplitude and a second emission phase configured for a second known position relative to the substrate. The system 600 is configured to capture, using the second receiving grating, the second reflected radiation from the substrate (e.g., the target 30). The second reflected radiation has a second reflection amplitude and a second reflection phase. One or more processors (e.g., as described above) are operably connected to the second emission grating and the second receiving grating. The one or more processors are configured to: determine a second coupling efficiency between the second emission grating and the second receiving grating based on the emitted second radiation and the received second reflected radiation; and determine a height for imaging the substrate based on the coupling efficiency, the second coupling efficiency, the known position, the second known position, and / or other information. In some embodiments, the known position is associated with positive defocus, and the second known position is associated with negative defocus. In some embodiments, the one or more processors are configured to: determine a first capture power and a second capture power based on the phases and amplitudes of the reflected radiation and the second reflected radiation, and determine the height based on the ratio of the first capture power to the second capture power.

[0108] As an example. Figure 9 Illustrated is a side view ( Figure 6 of the upper portion) and a top view ( Figure 9 of the lower portion) of an embodiment of the system 600 ( Figure 9 which is configured to illuminate the surface of the target 30 with two sets of grating couplers and capture the reflected light (compared to Figure 8 adding the emitter 925 and the receiver 935 along with the radiation 900). In this example, one set of grating couplers (e.g., the emitter 625 and the receiver 635) is designed to efficiently capture light when the defocus is z = z G and another set of grating couplers (e.g., the emitter 925 and the receiver 935) is configured to efficiently capture light when the defocus is z = -z G . Additional gratings can be used to add more functionality, such as functionality for different wavelengths, parallel sensing, etc.

[0109] Figure 10 Illustrated are the amplitude 1002 and phase 1004 of the grating coupler shown in the previous figure and the associated incident field. Figure 10The figure shows the amplitude and phase of the input beam ("Input" in the figure) at a defocus of z = 0.12 μm (for this example), as well as the amplitude and phase of the modes of the capture grating coupler. The overlap between the input mode and the mode of the grating coupler (e.g., GC1 and GC2 in the figure) defines the coupling efficiency of each grating coupler. In some embodiments, the mode of the grating coupler need not be exactly the same as the target mode at the desired defocus. The concepts described herein can be applied as long as the two grating couplers are designed such that their efficiencies are different at different defocuses.

[0110] Figure 11 The figure shows the effect of the targeted defocus z G (e.g., designing the grating coupler to have its highest efficiency at a specific defocus). Figure 11 The figure shows the coupling efficiency (S1 and S2) 1102 and the ratio (FS = (S1 - S2) / (S1 + S2)) 1104 as a function of defocus (z) 1103 when z G changes. There is a trade-off between the capture power on each channel and the slope of FS. The other parameters are the same as those Figure 10 mentioned in. Regarding the slope of the (multiple) curves, a linear range is preferred because the linear range defines the dynamic range of the focusing sensor (e.g., the grating coupler described above). The sharpness of the linear range defines the resolution of the sensor. The greater the sharpness of the linear range, the more sensitive to defocus, but there is a trade-off between the sharpness of the curve and the linear range. As will be described later with respect to Figure 14 and Figure 15 A series of sensors operating in different ranges can be used to obtain both a wider sensor range and a faster sensor response.

[0111] Figure 12 The figure shows the effect of the angle of incidence θ of the radiation on the grating coupler in . Figure 12 The figure shows the coupling efficiency (S1 and S2) 1202 and the ratio (FS = (S1 - S2) / (S1 + S2)) 1204 as a function of defocus (z) 1203 when θ in changes. There is a trade-off between the capture power on each channel and the slope of FS. The other parameters are the same as those Figure 10 mentioned in.

[0112] Figure 13 The figure shows the effect of the beam waist W0 at the focus on the grating coupler. Figure 13Illustrated is the coupling efficiency (S1 and S2) 1302 and the ratio (FS = (S1 - S2) / (S1 + S2)) 1304 as a function of defocus (z) 1303 when the waist (W0) at the focus changes. There is a trade-off between the capture power on each channel and the slope of FS. The other parameters are the same as those Figure 10 mentioned in

[0113] Figure 14 Illustrated is the scalability of the range of the linear portion of the coupling efficiency of the grating coupler. As described above, the linear range is preferred because the linear range defines the dynamic range of the focusing sensor (e.g., the grating coupler described above). The sharpness of the linear range defines the resolution of the sensor. The greater the sharpness of the linear range, the more sensitive it is to defocus. If the curve is flat, then FS (described above) is insensitive to changes in focus. The sensor operates optimally within the linear range. If this range is too narrow, the sensor cannot measure defocus when the defocus is far from the focus. By changing one or more of the parameters (e.g., with respect to Figures 11 to 13 ), the system 600 ( Figure 6 ) can be configured to scale the range of the linear portion of the coupling efficiency of the grating coupler at the expense of sensitivity. The system 600 can also be configured to have multiple sets of parallel grating couplers operating at different ranges. Figure 14 Illustrated is the coupling efficiency (S1 and S2) 1402 and the ratio (FS = (S1 - S2) / (S1 + S2)) 1404 as a function of defocus (z) 1403.

[0114] Figure 15 Illustrated is an exemplary embodiment of the system 600 ( Figure 6 ), where several different sets of grating couplers (e.g., pairs of opposed, generally triangular-shaped transmitters and receivers) 1500 are operating in parallel. Figure 15 Only two examples of the emitted, reflected, and received radiation beams 1502 and 1504 are illustrated, but this is not intended to be limiting. Figure 15 Also illustrated are the grating couplers 1500 arranged in concentric circles, but the grating couplers 1500 can have any arrangement that allows the grating couplers 1500 to function as described herein. In Figure 15In this case, radiation beams (e.g., 1502, 1502) leave the emitter and are directed downward into the page such that the radiation beams can reflect off the substrate (e.g., the planar page in this example) to return to the receiver. The grating coupler 1500 can be arranged in different planes, at different angles, with different sizes, shapes, pitches, etc. For example, multiple sets of grating couplers can be configured (e.g., as described herein) to have different efficiencies at different defocuses. Multiple sets of grating couplers 1500 can be configured for the relationship between a larger dynamic range (linear range) and a sharper response (higher resolution) for different wavelengths of radiation, and / or multiple sets of grating couplers 1500 can be configured in other ways. Multiple sets of grating couplers 1500 can be configured.

[0115] Figure 16 FIG. illustrates an exemplary grating coupler (e.g., emitter and / or receiver) design 1600. In system 600 ( Figure 6 ), the mode of the grating coupler can be designed. The relatively large arrows indicate the direction of the incident beam and the direction of coupling into the waveguide. Such a design can include changing the fill factor (f Figure 16 ), period (Λ n ), and / or other parameters for each period of the transmitting grating and / or receiving grating (various exemplary grating designs 1602, 1604, 1606, and 1608 are shown as formed in n ). Different gratings can have different heights (h) and / or other characteristics. The structure of the grating can be optimized in this way to enhance the coupling efficiency of the radiation 1610, for example, using a larger angle of incidence and / or for other reasons. For example, the grating coupler can be made of 1D rods (see Figure 16 ), focusing gratings (see Figure 7 and Figure 9 ), a 2D collection of (extensively) scatterers, and / or other structures.

[0116] Returning to Figure 6 , in some embodiments, the emitter 625 and the receiver 635 are coupled to the objective 690 of the system 600. In some embodiments, the emitter 625 and the receiver 635 are tilted relative to the objective 690 to increase the angle of incidence of the emitted radiation. For example, Figure 17 FIG. illustrates the integration of the emitter 625 and the receiver 635 into the system 600. In this example, the emitter 625 and the receiver 635 are coupled to the objective 690 of the system 600. In some embodiments, this requires an increase in the angle of incidence of the radiation. This situation can be achieved by tilting and / or rotating the emitter 625 and the receiver 635 in other ways to maintain a high coupling efficiency. Figure 17It is also shown how the radiation 1700 emitted by the transmitter 625 and received by the receiver 635 and used for focus position determination is different from the radiation 1702 used for measurement.

[0117] Figure 18 A method 1800 for imaging a substrate is shown. In some embodiments, the method 1800 is performed as part of an overlay and / or alignment sensing operation, for example, in a semiconductor device manufacturing process. In some embodiments, for example, one or more operations of the method 1800 may be performed in Figure 6 The system 600 shown in FIG. Figure 3 The system 10 shown in FIG. 1 , a computer system (e.g., Figure 19 In some embodiments, the method 1800 includes: transmitting (operation 1802) radiation having a transmit amplitude and a transmit phase configured for a known position relative to a substrate; receiving (operation 1804) reflected radiation from the substrate; determining (operation 1806) a coupling efficiency between a transmitter and a receiver based on the transmitted radiation and the received reflected radiation; and determining (operation 1808) a height for imaging the substrate based on the coupling efficiency and the known position.

[0118] The operations of method 1800 are intended to be illustrative. In some embodiments, method 1800 may be implemented with one or more additional operations not described and / or without one or more operations discussed. For example, in some embodiments, method 1800 may include additional operations including determining adjustments to a semiconductor device manufacturing process. Additionally, the operations of method 1800 may be performed in a manner that is not described in detail. Figure 18 The order illustrated and described herein is not intended to be limiting.

[0119] In some embodiments, one or more portions of the method 1800 may be implemented in and / or controlled by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices that perform some or all of the operations of the method 1800 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include a processor that is specifically designed to perform one or more of the operations of the method 1800 (e.g., see below for instructions on performing the operations of the method 1800). Figure 19 One or more devices configured with hardware, firmware and / or software (discussed in ).

[0120] At operation 1802, radiation is emitted using a radiation emitter (e.g., similar and / or identical to the above-described (one or more) emitters) having an emission amplitude and an emission phase configured for a known position relative to the substrate. For example, the known position may be a known focus position of the metrology system. In some embodiments, the emitter includes an emission grating, an emitter in free space, an optical fiber, and / or other emitters. The emitter may include an emission grating. The emission grating may be configured to emit radiation having an emission amplitude and an emission phase by adjusting the grating period and / or duty cycle of the emission grating.

[0121] At operation 1804, reflected radiation from the substrate is received using a radiation receiver (e.g., similar or identical to the above-described (one or more) receivers). The reflected radiation has a reflection amplitude and a reflection phase. In some embodiments, the receiver includes a reception grating and / or other receivers.

[0122] In some embodiments, the emitter and the receiver are coupled to an objective lens of the metrology system. In some embodiments, the emitter and the receiver are tilted relative to the objective lens to increase the angle of incidence of the emitted radiation. In some embodiments, the substrate includes a semiconductor wafer having one or more overlapping targets configured to reflect the reflected radiation toward the receiver. In some embodiments, the emitter and the receiver include gratings formed in a silicon-based substrate. In some embodiments, the silicon-based substrate includes waveguides configured to direct incident radiation to the emitter and / or direct the received radiation from the receiver.

[0123] At operation 1806, the coupling efficiency between the emitter and the receiver is determined based on the emitted radiation and the received reflected radiation. The coupling efficiency is determined using one or more processors (e.g., one or more processors similar and / or identical to those described above) operably connected to the emitter and the receiver.

[0124] At operation 1808, the height for imaging the substrate is determined based on the coupling efficiency and the known position. The height is determined by one or more processors. For example, the height may be the metrology focus position of the metrology system. In some embodiments, the height is determined based on a linear relationship between the coupling efficiency and the defocus of the system objective lens. For example, the sensitivity of the height determination may be at least about 120 nm.

[0125] In some embodiments, operation 1808 includes automatically adjusting the focus position of the metrology system based on the determined height by using one or more processors such that subsequent images of the substrate are in focus. The method 1800 may include generating incident radiation using a radiation source and one or more lenses and directing the radiation toward a transmitter. For example, the method 1800 may be configured for overlap detection of a semiconductor wafer and may be used in a semiconductor manufacturing process.

[0126] In some embodiments, the method 1800 includes: emitting a second radiation using a second emission grating, the second radiation having a second emission amplitude and a second emission phase configured for a second known position relative to the substrate; and capturing second reflected radiation from the substrate using a second reception grating. The second reflected radiation has a second reflection amplitude and a second reflection phase. One or more processors are operably coupled to the second emission grating and the second reception grating. The one or more processors are configured to: determine a second coupling efficiency between the second emission grating and the second reception grating based on the emitted second radiation and the received second reflected radiation; and determine a height for imaging the substrate based on the coupling efficiency, the second coupling efficiency, the known position, and the second known position. In some embodiments, the known position is associated with positive defocus and the second known position is associated with negative defocus. In some embodiments, the one or more processors are configured to: determine a first capture power and a second capture power based on the phase and amplitude of the reflected radiation and the second reflected radiation, and determine the height based on a ratio of the first capture power to the second capture power.

[0127] In some embodiments, the method 1800 includes determining overlap and / or alignment. The overlap and / or alignment is determined based on the reflected diffracted radiation, the focus position, the shift, and / or other information from a diffractive grating target on the substrate.

[0128] In some embodiments, the method 1800 includes irradiating (and / or otherwise illuminating) one or more targets (e.g., Figure 3 the target 30 shown) in the patterned substrate. The radiation includes light and / or other radiation. The radiation may be from a radiation source (e.g., Figure 3Generated by the source 2) shown. In some embodiments, the radiation can be directed by the radiation source in other ways to multiple targets, a single target, a sub - part of a target (e.g., something less than the entire target), and / or onto a substrate. In some embodiments, the radiation can be directed by the radiation source to the target in a time - varying manner. For example, the radiation can be rasterized onto the target (e.g., by moving the target under the radiation) such that different parts of the target are irradiated at different times. As another example, the characteristics of the radiation (e.g., wavelength, intensity, etc.) can vary. This can produce a time - varying data envelope or window for analysis. The data envelope can facilitate the analysis of individual sub - parts of the target, the comparison of one part of the target with another part and / or other targets (e.g., in other layers), and / or other analyses.

[0129] In some embodiments, the method 1800 includes directly detecting (using the radiation sensors described above) the reflected radiation from one or more diffraction grating targets (e.g., the overlapping measurement part rather than the focused - determined part). Detecting the reflected radiation includes detecting one or more phase and / or amplitude (intensity) shifts of the reflected radiation from one or more geometric features of the target(s). The one or more phase and / or amplitude shifts correspond to one or more dimensions of the target. For example, the phase and / or amplitude of the reflected radiation from one side of the target is different from the phase and / or amplitude of the reflected radiation from the other side of the target.

[0130] Detecting one or more phase and / or amplitude (intensity) shifts of the reflected radiation from the target includes measuring the local phase shifts (e.g., local phase variables) and / or amplitude variations corresponding to different parts of the target. For example, the reflected radiation from a particular region of the target can include a sine wave with a particular phase and / or amplitude. The reflected radiation from different regions of the target (or targets in different layers) can also include sine waves, but the reflected radiation has different phases and / or amplitudes. The detected reflected radiation also includes measuring the phase and / or amplitude differences in the reflected radiation of different diffraction orders. Detecting one or more local phase and / or amplitude shifts can be performed using, for example, the Hilbert transform and / or other techniques. Interferometric techniques and / or other operations can be used to measure the phase and / or amplitude differences in the reflected radiation of different diffraction orders.

[0131] In some embodiments, the method 1800 includes generating a measurement signal based on the detected reflected radiation from the diffraction grating target(s), as described above. By a sensor such as Figure 3The detector 4, camera, and / or other sensors) in generate a measurement signal based on the radiation received by the sensor. The measurement signal includes measurement information regarding the target(s) on the substrate. For example, the measurement signal may be an overlap and / or alignment signal that includes overlap and / or alignment measurement information and / or other measurement signals. The principles of interferometry and / or other principles may be used to determine the measurement information (e.g., overlap values, alignment values, and / or other information).

[0132] The measurement signal includes an electrical signal that represents and / or otherwise corresponds to the radiation reflected from the target(s). The measurement signal may indicate measurement values and / or other information associated with, for example, a diffraction grating target. Generating the measurement signal includes sensing the reflected radiation and converting the sensed reflected radiation into an electrical signal. In some embodiments, generating the measurement signal includes sensing different portions of the reflected radiation from different regions and / or different geometries and / or multiple targets of the target, and combining the different portions of the reflected radiation to form the measurement signal. This may include using one or more of the radiation generation and / or analysis targets described herein to generate an image of the target. This sensing and conversion may be performed by components similar and / or identical to the detector 4 and / or the processor PRO shown in Figure 3 and / or other components.

[0133] In some embodiments, method 1100 includes determining an adjustment to a semiconductor device manufacturing process. For example, this may include automatically adjusting the position of the platform of the metrology system holding the substrate based on the determined focus position using one or more processors such that subsequent images of the substrate are in focus. In some embodiments, method 1800 includes determining one or more semiconductor device manufacturing process parameters. One or more semiconductor device manufacturing process parameters may be determined based on one or more detected phase and / or amplitude changes, overlap and / or alignment values indicated by the measurement signal, and / or other similar systems and / or other information. One or more parameters may include parameters of the radiation (radiation used for metrology), overlap values, alignment values, metrology inspection locations on the layers of the semiconductor device structure, radiation beam trajectories across the target, and / or other parameters. In some embodiments, the process parameters may be broadly interpreted to include platform position, mask design, metrology target design, semiconductor device design, intensity of the radiation (for exposing photoresist, etc.), angle of incidence of the radiation (for exposing photoresist, etc.), wavelength of the radiation (for exposing photoresist, etc.), pupil size and / or shape, photoresist material, and / or other parameters.

[0134] In some embodiments, the method 1800 includes determining a process adjustment based on one or more determined semiconductor device manufacturing process parameters, adjusting a semiconductor device manufacturing apparatus based on the determined adjustment, and / or other operations. This scenario may be performed by one or more processors, such as the PRO shown in Figure 3 , the processors that are described as being part of the computer system illustrated in Figure 19 and described below, and / or other processors. For example, if the determined metrology measurement is outside of the process tolerance, the measurement outside of the tolerance may be caused by one or more manufacturing processes whose process parameters have drifted and / or otherwise changed such that the one or more manufacturing processes no longer produce acceptable devices (e.g., the measurement may breach an acceptable threshold). One or more new or adjusted process parameters may be determined based on the measurement determination. The new or adjusted process parameters may be configured such that the manufacturing process again produces acceptable devices.

[0135] For example, the new or adjusted process parameters may cause a previously unacceptable measurement value to be adjusted back into the acceptable range. The new or adjusted process parameters may be compared to the existing parameters for a given process. For example, if there is a difference, the difference may be used to determine an adjustment to the apparatus for producing the device (e.g., parameter “x” should be increased / decreased / changed such that the apparatus matches the new or adjusted form of parameter “x” that is determined to be part of method 1800). In some embodiments, the method 1800 may include (e.g., based on the determined process parameters) electronically adjusting the apparatus. Electronically adjusting the apparatus may include sending, for example, an electronic signal and / or other communication that causes a change in the apparatus to the apparatus. The electronic adjustment may include, for example, changing settings on the apparatus, and / or other adjustments.

[0136] Figure 19 is an illustration of an exemplary computer system CS that may be used for one or more of the operations described herein. The computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or Figure 3The processor PRO shown is similar and / or identical to multiple processors). The computer system CS also includes a main memory MM coupled to the bus BS for storing information and instructions to be executed by the processor PRO, such as random access memory (RAM) or other dynamic storage. The main memory MM can also be used to store temporary variables or other intermediate information during the execution of instructions by the processor PRO. The computer system CS further includes a read-only memory (ROM) ROM or other static storage device coupled to the bus BS for storing static information and instructions for the processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to the bus BS for storing information and instructions.

[0137] The computer system CS can be coupled via the bus BS to a display DS for displaying information to a computer user, such as a flat panel or touch panel display or a cathode ray tube (CRT). An input device ID including alphanumeric and other keys is coupled to the bus BS for communicating information and command selections to the processor PRO. Another type of user input device is a cursor control CC for communicating direction information and command selections to the processor PRO and for controlling the movement of a cursor on the display DS, such as a mouse, trackball, or cursor direction keys. Such an input device typically has two degrees of freedom in two axes, namely 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 can also be used as an input device.

[0138] In some embodiments, all or some of one or more of the operations described herein can be performed by the computer system CS in response to one or more sequences of one or more instructions included in the main memory MM being executed by the processor PRO. These instructions can be read from another computer-readable medium, such as the storage device SD, into the main memory MM. Execution of the instruction sequence included in the main memory MM causes the processor PRO to perform the process steps (operations) described herein. One or more processors in a multiprocessing arrangement can also be used to execute the instruction sequence included in the main memory MM. In some embodiments, hardwired circuitry can be used in place of or in combination with software instructions. Thus, the description herein is not limited to any particular combination of hardware circuitry and software.

[0139] As used herein, the term "computer-readable medium" or "machine-readable medium" refers to any medium that participates in providing instructions to processor PRO for execution. Such a medium may take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as storage device SD. Volatile media includes volatile memory, such as main memory MM. Transmission media includes coaxial cables, copper wire, and fiber optics, including the wires that comprise bus BS. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. A computer-readable medium may be non-transitory, such as a floppy disk, flexible disk, hard disk, magnetic tape, any other magnetic medium, CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, RAM, PROM, and EPROM, FLASH-EPROM, any other memory chip or cartridge. The non-transitory computer-readable medium may have instructions recorded thereon. The instructions, when executed by a computer, may implement any of the operations described herein. For example, transitory computer-readable media may include a carrier wave or other propagated electromagnetic signal.

[0140] Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to processor PRO for execution. For example, the instructions may initially be carried on a magnetic disk of a remote computer. The remote computer may load the instructions into its volatile memory and send the instructions using a modem via a telephone line. A modem local to computer system CS may receive the data on the telephone line and convert the data to an infrared signal using an infrared transmitter. An infrared detector coupled to bus BS may receive the data carried in the infrared signal and place the data on bus BS. Bus BS carries the data to main memory MM, from which processor PRO retrieves and executes the instructions. The instructions received by main memory MM may optionally be stored on storage device SD before or after being executed by processor PRO.

[0141] Computer system CS may also include a communication interface CI coupled to bus BS. Communication interface CI provides a two-way data communication coupling to network link NDL, which is connected to local area network LAN. For example, communication interface CI 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, communication interface CI 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, communication interface CI sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information.

[0142] A network link NDL typically provides data communication with other data devices via one or more networks. For example, the network link NDL can provide a connection to a host computer HC via a local area network LAN. This can include data communication services provided via a global packet data communication network (now commonly referred to as the "Internet" INT). The local area network LAN (Internet) can use electrical, electromagnetic, or optical signals that carry digital data streams. Signals via various networks and signals on the network data link NDL and via the communication interface CI are exemplary forms of carriers for conveying information, which carry digital data to and from the computer system CS.

[0143] The computer system CS can send messages and receive data (including program code) via the (one or more) networks, the network data link NDL, and the communication interface CI. In the Internet example, the host computer HC can transmit the requested program code for an application via the Internet INT, the network data link NDL, the local area network LAN, and the communication interface CI. For example, one such downloaded application can provide all or part of the methods described herein. The received code can be executed by the processor PRO when it is received, and / or stored in the storage device SD or other non-volatile storage for later execution. In this way, the computer system CS can obtain application code in the form of a carrier wave.

[0144] Various embodiments of the present system and method are disclosed in the following list of numbered aspects. Hereinafter, other features, characteristics, and exemplary technical solutions of the present disclosure will be described in terms of aspects, which can optionally be claimed in any combination:

[0145] 1. A system configured to image a substrate, the system comprising: a radiation emitter configured to emit radiation having an emission amplitude and an emission phase configured for a known position relative to the substrate; a radiation receiver configured to receive reflected radiation from the substrate, the reflected radiation having a reflection amplitude and a reflection phase; and one or more processors operatively connected to the emitter and the receiver, the one or more processors being configured to: determine a coupling efficiency between the emitter and the receiver based on the emitted radiation and the received reflected radiation; and determine a height for imaging the substrate based on the coupling efficiency and the known position.

[0146] 2. The system according to aspect 1, wherein the system is a metrology system, the known position is a known focus position, and the height is a measured focus position.

[0147] 3. The system according to any one of the foregoing aspects, wherein the height is determined based on a linear relationship between the coupling efficiency and the defocus of the system objective lens.

[0148] 4. The system according to any one of the foregoing aspects, wherein the transmitter includes a transmitting grating, a transmitter located in free space, or an optical fiber, and the receiver includes a receiving grating.

[0149] 5. The system according to any one of the foregoing aspects, wherein the transmitter includes a transmitting grating, and the transmitting grating is configured to emit the radiation having the emission amplitude and emission phase by adjusting the grating period and / or duty cycle of the transmitting grating.

[0150] 6. The system according to any one of the foregoing aspects, further comprising: a second transmitting grating configured to emit a second radiation having a second emission amplitude and a second emission phase configured for a second known position relative to the substrate; and a second receiving grating configured to capture a second reflected radiation from the substrate, the second reflected radiation having a second reflected amplitude and a second reflected phase.

[0151] 7. The system according to any one of the foregoing aspects, wherein: the one or more processors are operably connected to the second transmitting grating and the second receiving grating, and the one or more processors are further configured to: determine a second coupling efficiency between the second transmitting grating and the second receiving grating based on the emitted second radiation and the received second reflected radiation; and determine the height for imaging the substrate based on the coupling efficiency, the second coupling efficiency, the known position, and the second known position.

[0152] 8. The system according to any one of the foregoing aspects, wherein the known position is associated with positive defocus, and the second known position is associated with negative defocus.

[0153] 9. The system according to any one of the foregoing aspects, wherein the one or more processors are further configured to: determine a first capture power and a second capture power based on the phase and amplitude of the reflected radiation and the second reflected radiation, and determine the height based on a ratio of the first capture power to the second capture power.

[0154] 10. The system according to any one of the foregoing aspects, wherein the system is a metrology system, and the transmitter and the receiver are coupled to an objective lens of the metrology system.

[0155] 11. The system according to any one of the foregoing aspects, wherein the transmitter and the receiver are tilted with respect to the objective lens to increase the incident angle of the emitted radiation.

[0156] 12. The system according to any one of the foregoing aspects, wherein the system is a metrology system, and wherein the one or more processors are further configured to: automatically adjust the focus position of the metrology system based on the determined height such that subsequent images of the substrate are in focus.

[0157] 13. The system according to any one of the foregoing aspects, wherein the substrate comprises a semiconductor wafer having one or more overlapping targets configured to reflect the reflected radiation towards the receiver.

[0158] 14. The system according to any one of the foregoing aspects, wherein the transmitter and the receiver comprise gratings formed in a silicon-based substrate.

[0159] 15. The system according to any one of the foregoing aspects, wherein the silicon-based substrate comprises waveguides configured to direct incident radiation to the transmitter and / or direct received radiation from the receiver.

[0160] 16. The system according to any one of the foregoing aspects, wherein the transmitter comprises a transmitting grating, the receiver comprises a receiving grating, and the system further comprises a tapered grating coupler.

[0161] 17. The system according to any one of the foregoing aspects, wherein the sensitivity of the height determination is at least 120 nm.

[0162] 18. The system according to any one of the foregoing aspects, wherein the transmitter, the receiver, and the one or more processors are configured to replace the focusing branch in a typical metrology system.

[0163] 19. The system according to any one of the foregoing aspects, further comprising a radiation source and one or more lenses configured to generate incident radiation and direct the radiation towards the transmitter.

[0164] 20. The system according to any one of the foregoing aspects, wherein the system comprises a metrology system and is used in a semiconductor manufacturing process, and the metrology system is configured for overlay detection of semiconductor wafers.

[0165] 21. A method for imaging a substrate, the method comprising: emitting radiation using a radiation emitter, the radiation having an emission amplitude and an emission phase configured for a known position relative to the substrate; receiving reflected radiation from the substrate using a radiation receiver, the reflected radiation having a reflection amplitude and a reflection phase; determining, by one or more processors operably connected to the emitter and the receiver, a coupling efficiency between the emitter and the receiver based on the emitted radiation and the received reflected radiation; and determining, by one or more processors, a height for imaging the substrate based on the coupling efficiency and the known position.

[0166] 22. The method according to aspect 21, wherein the known position is a known focus position, and the height is a measured focus position.

[0167] 23. The method according to any one of the preceding aspects, wherein the height is determined based on a linear relationship between the coupling efficiency and system objective defocus.

[0168] 24. The method according to any one of the preceding aspects, wherein the emitter comprises an emission grating, an emitter located in free space, or an optical fiber, and the receiver comprises a receiving grating.

[0169] 25. The method according to any one of the preceding aspects, wherein the emitter comprises an emission grating, and the emission grating is configured to emit the radiation having the emission amplitude and the emission phase by adjusting a grating period and / or a duty cycle of the emission grating.

[0170] 26. The method according to any one of the preceding aspects, further comprising: emitting second radiation using a second emission grating, the second radiation having a second emission amplitude and a second emission phase configured for a second known position relative to the substrate; and capturing second reflected radiation from the substrate using a second receiving grating, the second reflected radiation having a second reflection amplitude and a second reflection phase.

[0171] 27. The method according to any one of the preceding aspects, wherein the one or more processors are operably connected to the second emission grating and the second receiving grating, and the method further comprises: determining, by the one or more processors, a second coupling efficiency between the second emission grating and the second receiving grating based on the emitted second radiation and the received second reflected radiation; and determining, by the one or more processors, the height for imaging the substrate based on the coupling efficiency, the second coupling efficiency, the known position, and the second known position.

[0172] 28. The method according to any one of the foregoing aspects, wherein the known position is associated with positive defocus, and the second known position is associated with negative defocus.

[0173] 29. The method according to any one of the foregoing aspects, further comprising using the one or more processors to determine a first capture power and a second capture power based on the phase and amplitude of the reflected radiation and the second reflected radiation, and determining the height based on a ratio of the first capture power to the second capture power.

[0174] 30. The method according to any one of the foregoing aspects, wherein the transmitter and the receiver are coupled to an objective lens of a metrology system.

[0175] 31. The method according to any one of the foregoing aspects, wherein the transmitter and the receiver are tilted with respect to the objective lens to increase an incident angle of the emitted radiation.

[0176] 32. The method according to any one of the foregoing aspects, further comprising using the one or more processors to automatically adjust a focus position of the metrology system based on the determined height such that a subsequent image of the substrate is in focus.

[0177] 33. The method according to any one of the foregoing aspects, wherein the substrate comprises a semiconductor wafer having one or more overlapping targets configured to reflect the reflected radiation toward the receiver.

[0178] 34. The method according to any one of the foregoing aspects, wherein the transmitter and the receiver comprise gratings formed in a silicon-based substrate.

[0179] 35. The method according to any one of the foregoing aspects, wherein the silicon-based substrate comprises waveguides configured to direct incident radiation to the transmitter and / or direct received radiation from the receiver.

[0180] 36. The method according to any one of the foregoing aspects, wherein the transmitter comprises a transmitting grating and the receiver comprises a receiving grating, and both the transmitting grating and the receiving grating are coupled to a tapered grating coupler.

[0181] 37. The method according to any one of the foregoing aspects, wherein a sensitivity of the height determination is at least 120 nm.

[0182] 38. The method according to any one of the foregoing aspects, wherein the transmitter, the receiver, and the one or more processors are configured to replace a focusing branch in a typical metrology system.

[0183] 39. The method according to any one of the foregoing aspects further comprises generating incident radiation using a radiation source and one or more lenses and directing the radiation towards the emitter.

[0184] 40. The method according to any one of the foregoing aspects, wherein the method is configured for detecting the overlay of semiconductor wafers and is used in a semiconductor manufacturing process.

[0185] The concepts disclosed herein can be associated with any general imaging system for imaging sub-wavelength features and, in particular, can be used with emerging imaging technologies that are capable of generating increasingly shorter wavelengths. Emerging technologies already in use include EUV (extreme ultraviolet), DUV lithography that are capable of generating a 193 nm wavelength by using an ArF laser and even capable of generating a 157 nm wavelength by using a fluorine laser. In addition, EUV lithography can generate wavelengths in the range of 5 nm to 20 nm by using a synchrotron or by impinging high-energy electrons on a material (either solid or plasma) to generate photons in this range.

[0186] Although the concepts disclosed herein can be used to image on a substrate such as a silicon wafer, it should be understood that the disclosed concepts can be used with any type of lithographic imaging system, e.g., a lithographic imaging system for imaging on a substrate other than a silicon wafer. In addition, combinations and sub-combinations of the disclosed elements can include separate embodiments.

[0187] The foregoing description is intended to be illustrative, not restrictive. Accordingly, those skilled in the art will appreciate that modifications can be made as described without departing from the scope of the claims set forth below.

Claims

1. A system configured to image a substrate, the system comprising: A radiation emitter configured to emit radiation having an emission amplitude and an emission phase configured for a known position relative to the substrate; A radiation receiver configured to receive reflected radiation from the substrate, the reflected radiation having a reflection amplitude and a reflection phase; And One or more processors operatively coupled to the emitter and the receiver, the one or more processors being configured to: Determine a coupling efficiency between the emitter and the receiver based on the emitted radiation and the received reflected radiation; And Determine a height for imaging the substrate based on the coupling efficiency and the known position.

2. The system according to claim 1, wherein, The system is a metrology system, the known position is a known focus position, and the height is a measured focus position.

3. The system according to claim 1 or 2, wherein Determine the height based on a linear relationship between the coupling efficiency and system objective defocus.

4. The system according to any one of claims 1 to 3, wherein, The emitter includes an emission grating, an emitter in free space, or an optical fiber, and the receiver includes a receiving grating.

5. The system according to claim 4, wherein The emitter includes an emission grating, and the emission grating is configured to emit the radiation having the emission amplitude and the emission phase by adjusting a grating period and / or a duty cycle of the emission grating.

6. The system according to claim 5, further comprising: A second emission grating configured to emit a second radiation having a second emission amplitude and a second emission phase configured for a second known position relative to the substrate; And A second receiving grating configured to capture a second reflected radiation from the substrate, the second reflected radiation having a second reflection amplitude and a second reflection phase.

7. The system according to claim 6, wherein: The one or more processors are operatively coupled to the second emission grating and the second receiving grating, and the one or more processors are further configured to: Determine a second coupling efficiency between the second emission grating and the second receiving grating based on the emitted second radiation and the received second reflected radiation; And Determine the height for imaging the substrate based on the coupling efficiency, the second coupling efficiency, the known position, and the second known position.

8. The system according to claim 7, wherein, The known position is associated with positive defocus, and the second known position is associated with negative defocus.

9. The system according to claim 7 or 8, wherein The one or more processors are further configured to: determine a first capture power and a second capture power based on the phases and amplitudes of the reflected radiation and the second reflected radiation, and determine the height based on a ratio of the first capture power to the second capture power.

10. The system according to any one of claims 1 to 9, wherein, The system is a metrology system, and the emitter and the receiver are coupled to an objective of the metrology system.

11. The system according to claim 10, wherein, The emitter and the receiver are tilted relative to the objective to increase an incident angle of the emitted radiation.

12. The system according to any one of claims 1 to 11, wherein, The system is a measurement system, and wherein, the one or more processors are further configured to: automatically adjust a focus position of the measurement system based on the determined height such that subsequent images of the substrate are in focus.

13. The system according to any one of claims 1 to 12, wherein The substrate includes a semiconductor wafer having one or more overlapping targets configured to reflect the reflected radiation toward the receiver.

14. The system according to any one of claims 1 to 13, wherein, The emitter and the receiver include gratings formed in a silicon-based substrate.

15. The system according to claim 14, wherein The silicon-based substrate includes waveguides configured to direct incident radiation to the emitter and / or direct received radiation from the receiver.

Images