Determining focus position based on field image position offset

Abstract

The metrology systems and methods described herein eliminate the need for separate focus branches (e.g., including illumination sources, several lenses, and many other optical components) commonly used in existing metrology systems to determine focus positions for imaging a substrate. Instead of using a separate focus branch, the present system and method uses the position of a field image acquired from the substrate during normal process of metrology measurements using existing sensing components to determine the focus position. An offset of the field image position relative to the expected field image position is determined, and a focus position for imaging the substrate is determined based on the offset.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to U.S. Application No. 63 / 429,666, filed on December 2, 2022, which is hereby incorporated by reference in its entirety. Technical field

[0003] This description relates to determining a focus position based on field image position offset. 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 comprise or provide a pattern corresponding to the various layers of the IC (“design layout”), and by methods such as irradiating a target portion through the pattern on the patterning device, the pattern can be transferred onto a target portion (e.g., including one or more dies) on a substrate (e.g., a silicon wafer), which has been coated with a layer of radiation - sensitive material (“resist”). Typically, a single substrate includes a plurality of adjacent target portions, and the pattern is transferred to the target portions by the lithographic projection apparatus continuously, one target portion at a time. In one type of lithographic projection apparatus, the pattern over the entire patterning device is transferred onto one target portion in one operation. Such a device is generally referred to as a stepper. In an alternative device, generally referred to as a stepper - scanner, the projection beam is scanned over the patterning device along a given reference direction (“scan” direction), while the substrate is moved synchronously parallel or anti - parallel to this reference direction. Different portions of the pattern on the patterning device are gradually transferred onto one target portion.

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

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

[0007] With the continuous progress of semiconductor manufacturing processes, the sizes of functional elements have been continuously decreasing, and the number of functional elements (such as transistors) per device has been steadily increasing for decades, following a trend commonly known as "Moore's Law". At the current state of the art, the layers of a device are manufactured using a lithographic projection apparatus that projects a design layout onto a substrate using irradiation from a deep ultraviolet light source, thereby creating individual functional elements with sizes far below 100 nm (i.e., less than half of the radiation wavelength from the light source (e.g., a 193 nm light source)).

[0008] According to the resolution formula CD = k1×λ / NA, the process of printing features smaller than the classical resolution limit of a lithographic projection apparatus is generally referred to as low k1 lithography, where λ is the wavelength of the radiation employed (currently mostly 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 is to reproduce a pattern on a substrate that is similar in shape and size to what the designer planned, in order to achieve 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 pattern forming device. For example, these include but are not limited to the optimization of NA and optical coherence settings, customized irradiation schemes, the use of phase shift pattern forming 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 metrology system and method described below eliminate the need for a separate focusing branch (e.g., including a light source, several lenses, and many other optical components) commonly used in existing metrology systems to determine the focusing position for imaging a substrate. Instead of using a separate focusing branch, the present system and method use the position of a field image obtained from the substrate during a metrology measurement using existing sensing components to determine the focusing position. The offset of the field image position relative to the expected field image position is determined, and the focusing position for imaging the substrate is determined based on the offset.

[0010] According to an embodiment, a metrology system is provided. The system includes a radiation sensor configured to receive radiation and generate a signal indicative of a field image position of the radiation. The system includes optical components configured to receive radiation reflected from a substrate, change an angle of the radiation, and direct the radiation to the sensor. The system includes one or more processors operatively connected to the radiation sensor and configured to: determine an offset of the field image position relative to an expected field image position based on the changed angle; and determine a focus position for imaging the substrate based on the offset.

[0011] In some embodiments, the focus position is determined based on a linear relationship between the offset and the defocus of the metrology system objective.

[0012] In some embodiments, the optical components include a wedge. In some embodiments, defocused radiation incident on a wedge pupil plane results in an offset. In some embodiments, the wedge includes quadrants, each quadrant configured to direct a portion of the radiation to a different region of interest of the sensor to form radiation spots on the sensor.

[0013] In some embodiments, the radiation spots include two radiation spots associated with 0th order diffracted radiation from the substrate and two radiation spots associated with 1st order diffracted radiation from the substrate. In some embodiments, the signal generated by the sensor indicates four separate field image positions of the radiation spots. One or more processors are configured to determine the offsets of the 0th order spots and the 1st order spots and determine the focus position based on the offsets of the 0th order spots and the 1st order spots.

[0014] In some embodiments, one or more processors are configured to automatically adjust the position of a stage of the metrology system holding the substrate based on the focus position such that subsequent images of the substrate are in focus.

[0015] In some embodiments, one or more processors are configured to determine an offset of the field image position of the field image based on the centroid of the radiation spots in the field image. In some embodiments, one or more processors are configured to determine an offset of the field image position of the field image based on the intensity of the field image. In some embodiments, the intensity is determined at one or more halves of one or more rings of the radiation spots in the field image.

[0016] In some embodiments, the substrate includes a semiconductor wafer having one or more overlapping targets configured to reflect radiation toward the optical components.

[0017] In some embodiments, the sensor includes a camera, a charge-coupled device (CCD) array, a complementary metal oxide semiconductor (CMOS), and / or a photodiode array.

[0018] In some embodiments, the sensor includes a micro-diffraction based overlay camera associated with overlay measurements. In some embodiments, the sensor includes a second camera, which is separated from the micro-diffraction based overlay camera associated with the overlay measurements in the metrology system.

[0019] In some embodiments, the optical component includes a micro-diffraction based overlay wedge with a high reflectivity beam splitter configured to simultaneously direct radiation from the substrate to both the micro-diffraction based overlay camera and the second camera.

[0020] In some embodiments, the system includes a radiation source and one or more lenses. The radiation source and the one or more lenses are configured to generate radiation and direct the radiation towards the substrate.

[0021] In embodiments, the optical component, the sensor, and one or more processors are configured for overlay detection. In some embodiments, the radiation received by the optical component is a micro-diffraction based overlay signal, and the overlay detection is micro-diffraction based overlay detection. In some embodiments, the metrology system is configured for semiconductor wafers and is used in semiconductor manufacturing processes.

[0022] According to another embodiment, a metrology method is provided. The method includes receiving, by an optical component, radiation reflected from a substrate, changing an angle of the radiation, and directing the radiation towards a sensor. The method includes receiving, by a radiation sensor, the radiation from the optical component and generating a signal indicative of a field image position of the radiation. The method includes determining, by one or more processors operatively connected to the radiation sensor, an offset of the field image position relative to an expected field image position based on the changed angle; and determining, by the one or more processors, a focus position for imaging the substrate based on the offset. Description of the Drawings

[0023] The above aspects, as well as other aspects and features, will become apparent to those of ordinary skill in the art when reviewing the following description of specific embodiments in conjunction with the accompanying drawings.

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

[0025] Figure 2 An embodiment of a lithography cell or cluster according to an embodiment is schematically depicted.

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

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

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

[0029] Figure 6 Illustrates a system configured to determine a focus position for imaging one or more measurement targets according to an embodiment.

[0030] Figure 7 Illustrates using an optical component to receive radiation reflected from a substrate, change the angle of the radiation, and direct the radiation to a sensor according to an embodiment; using a radiation sensor to receive the radiation from the optical component and generate a signal indicating the field image position of the radiation; and determining an offset of the field image position relative to an expected field image position based on the changed angle.

[0031] Figure 8 Illustrates how, depending on the target of the reflected radiation, four different offsets for eight different spots can be used to determine the offset of the field image position relative to the expected position according to an embodiment.

[0032] Figure 9 Illustrates determining an offset of the field image position of a field image based on the intensity of the field image (and / or an image indicating the intensity) and / or one or more semi-circular portions of the field image according to an embodiment.

[0033] Figure 10 Illustrates increasing the speed of focus position determination (compared to existing systems) by sending 0th order radiation to a fast camera or sensor array according to an embodiment.

[0034] Figure 11 Illustrates a measurement method according to an embodiment.

[0035] Figure 12 Is a block diagram of an example computer system according to an embodiment. Detailed Description

[0036] In semiconductor device manufacturing, measurement operations typically include determining the position of measurement marks (or a plurality of marks) and / or other targets in a semiconductor device structure layer. This position is determined by irradiating the measurement marks with radiation and comparing the characteristics of different diffraction order radiations reflected from the measurement marks. Such techniques are used to measure overlay, alignment, and / or other parameters.

[0037] Many metrology systems include a separate focusing branch (e.g., a part 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. A typical focusing branch is bulky and expensive. It requires an additional beam splitter to combine the focusing branch with the rest of the metrology system, which reduces the radiation throughput of the central sensor. Since it has its own radiation source, color defocus calibration is required due to the wavelength variation between the central sensor and the focusing branch. Further, in such a system, the focusing position determination is not continuous because the radiation used to determine the focusing position propagates along at least a part of the same optical path as the radiation ultimately used for metrology measurements. This means that the metrology system switches back and forth between a focusing position determination mode where the radiation source and optics in the focusing branch are "on" and a metrology image acquisition mode where the radiation source and optics in the focusing branch are "off". Due to defocus and / or other issues, the focusing gap between these modes may cause overlay errors. Additionally, different orders of diffracted light from metrology targets on the substrate have different focusing positions based on the objective wavefront error, and current metrology systems do not take this into account.

[0038] Advantageously, instead of using a separate focusing branch, the present system and method use the position of a field image acquired from a substrate during the course of metrology measurements using existing sensing components to determine the focusing position. The offset of the field image position relative to the expected field image position is determined, and the focusing position for imaging the substrate is determined based on the offset. For example, existing optical components in the sensing branch of the metrology system change the angle of the radiation received from a target on the substrate and direct the radiation to different regions of interest on a sensor (e.g., a camera). Defocused light has different angles of incidence on the pupil plane of the optical component, which results in the radiation incident on different regions of the sensor being offset. There are displacements of both the 0th and 1st order radiation spots on the sensor. The focusing position is determined based on the linear relationship between the offset and the metrology system objective defocus.

[0039] By way of brief introduction, the following description relates to semiconductor device fabrication and patterning processes. The following paragraphs also describe several components of systems and / or methods for semiconductor device metrology. For example, these systems and methods can be used to measure overlay, alignment, etc. during semiconductor device fabrication processes, or for other operations.

[0040] Although measurements of overlay, alignment or other parameters and the fabrication of integrated circuits (ICs) of semiconductor devices may be specifically mentioned herein, it should be understood that the description herein has many other possible applications. For example, it can be used in the fabrication of integrated optical systems, for guiding and detecting patterns for magnetic domain memories, liquid crystal display panels, thin film magnetic heads, etc. Those skilled in the art will appreciate that in the context of such alternative applications, any use of the terms "reticle", "wafer" or "die" herein should be considered interchangeable with the more general terms "mask", "substrate" and "target portion", respectively.

[0041] The term "projection optics" as used herein should be construed broadly to cover various types of optical systems, such as including refractive optics, reflective optics, apertures and catadioptric optics. The term "projection optics" may also include components operating according to any of these design types to jointly or individually direct, shape or control the projected beam of radiation. The term "projection optics" may include any optical component in a lithographic projection apparatus, regardless of where the optical component is located on the optical path of the lithographic projection apparatus. The projection optics may include optical components for shaping, conditioning and / or projecting radiation from a source before the radiation passes through the patterning device and / or for shaping, conditioning and / or projecting the radiation after the radiation passes through the patterning device. The projection optics generally do not include the source and the patterning device.

[0042] Figure 1 An 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 constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device 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 the 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 commonly referred to as a field) of the substrate W. The projection system is supported on a reference frame RF. As depicted, the apparatus is of the transmissive type (e.g., employing a transmissive mask). Alternatively, the apparatus may be of the reflective type (e.g., employing a programmable mirror array or employing a reflective mask).

[0043] The illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such a case, the source is not considered to form part of the lithographic apparatus, and the radiation beam is transferred from the source SO to the illuminator IL by means of a beam delivery system BD comprising, for example, suitable directing mirrors and / or beam expanders. In other cases, the source may be an integral part of the apparatus, for example when the source is a mercury lamp. The source SO, the illuminator IL and, if required, the beam delivery system BD may be referred to as the radiation system.

[0044] The illuminator IL may modify the intensity distribution of the beam. The illuminator may be arranged to limit the radial extent of the radiation beam such that the intensity distribution is non-zero within an annular region in the pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL may be operable to limit the distribution of the beam in the pupil plane such that the intensity distribution is non-zero in a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the radiation beam in the pupil plane of the illuminator IL may be referred to as the illumination mode.

[0045] The illuminator IL may include an adjuster AD configured to adjust the (angular / spatial) intensity distribution of the beam. In general, at least the outer and / or inner radial extent (commonly referred to as σ outer and σ inner respectively) of the intensity distribution in the pupil plane of the illuminator may be adjusted. The illuminator IL may be operable to change the angular distribution of the beam. For example, the illuminator may be operable to change the number and angular extent of the sectors 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 modes may be achieved. For example, by limiting the radial and angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution may have a multipole distribution, such as for example a dipole, quadrupole or hexapole distribution. For example, a desired illumination mode may be obtained by inserting the optics providing that illumination mode into the illuminator IL or using a spatial light modulator.

[0046] The illuminator IL can be operable to change the polarization of the beam and can be 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 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 be a linearly polarized radiation beam. The polarization direction of the radiation beam can vary across the pupil plane of the illuminator IL. In different regions in the pupil plane of the illuminator IL, the polarization direction of the radiation may be different. The polarization state of the radiation can be selected according to the illumination mode. For a multipole illumination mode, the polarization of each pole of the radiation beam can generally be perpendicular to the position vector of that pole in the pupil plane of the illuminator IL. For example, for a dipole illumination mode, the radiation can be linearly polarized in a direction substantially perpendicular to the line bisecting two opposite sectors of the dipole. The radiation beam can be polarized in one of two different orthogonal directions, which can be referred to as the X polarization state and the Y polarization state. For a quadrupole illumination mode, the radiation in the sector of each pole can be linearly polarized in a direction substantially perpendicular to the line bisecting that sector. This polarization pattern can be referred to as XY polarization. Similarly, for a hexapole illumination mode, the radiation in the sector of each pole can be linearly polarized in a direction substantially perpendicular to the line bisecting that sector. This polarization pattern can be referred to as TE polarization.

[0047] In addition, the illuminator IL typically includes various other components, such as the integrator IN and the condenser CO. The illumination system can include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components or any combination thereof, for directing, shaping, or controlling the radiation. Thus, the illuminator provides a conditioned radiation beam B having a desired uniformity and intensity distribution in its cross-section.

[0048] 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 for example whether the patterning device is held in a vacuum environment. The support structure can hold the patterning device using mechanical, vacuum, electrostatic, or other clamping techniques. The support structure can be a frame or a table, for example, which can be fixed or movable as required. The support structure can ensure that the patterning device is located at a desired position relative to the projection system, for example. Any use of the terms "reticle" or "mask" in this text can be considered synonymous with the more general term "patterning device".

[0049] The term "pattern forming device" as used herein should be construed broadly to mean any device that can be used to impart a pattern in a target portion of a substrate. In an embodiment, a pattern forming device is any device that can be used to impart a pattern to a radiation beam in its cross-section to create a pattern in a target portion of a substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase shift features or so-called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device (such as an integrated circuit) created in the target portion of the device.

[0050] The pattern forming device can be transmissive or reflective. Examples of pattern forming devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary mask types, alternating phase shift mask types, and attenuated phase shift mask types, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam reflected by the mirror matrix.

[0051] The term "projection system" should be construed broadly to cover any type of projection system, including refractive, reflective, refraction-reflective, magnetic, electromagnetic, and electrostatic optical systems or any combination thereof, as appropriate for the exposure radiation being used or other factors, such as the use of immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein can be considered synonymous with the more general term "projection system".

[0052] 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 to correct for aberrations (phase variations across the pupil plane over the entire field). To achieve this, the adjustment mechanism may be operable to manipulate one or more of the optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a coordinate system in which its optical axis extends in the z direction. The adjustment mechanism may be operable to perform any combination of the following: displacing one or more of the optical elements; tilting one or more of the optical elements; and / or deforming one or more of the optical elements. The displacement of the optical element may be in any direction (x, y, z, or combinations thereof). Although rotation about the z-axis may be used for aspherical optical elements that are not rotationally symmetric, the tilting of the optical element is generally out of the plane perpendicular to the optical axis by rotation about an axis in the x and / or y directions. The deformation of the optical element may include low-frequency shapes (e.g., astigmatism) and / or high-frequency shapes (e.g., freeform aspheres). The deformation of the optical element may be performed, for example, by applying forces on one or more sides of the optical element using one or more actuators and / or by heating one or more selected regions of the optical element using one or more heating elements. Generally, it may not be possible to adjust the projection system PS to correct for apodization (transmission variations across the pupil plane). When designing a patterning device (e.g., a mask) MA for a lithographic apparatus LA, the transmission profile of the projection system PS may be used. Using computational lithography techniques, the patterning device MA may be designed to at least partially correct for apodization.

[0053] The lithographic apparatus may be of a type having two (dual stage) or more stages (e.g., two or more substrate stages WTa, WTb, two or more patterning device stages, a substrate stage WTa and a stage WTb located below the projection system without a substrate dedicated for, e.g., facilitating measurement and / or cleaning, etc.). In such a “multi-stage” machine, the additional stages may be used in parallel, or preparatory steps may be performed on one or more stages while one or more other stages are being 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 performed.

[0054] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be overlapped by a liquid having a relatively high refractive index (e.g., 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, such as 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. The term “immersion” as used herein does not mean that structures such as the substrate must be submerged in the liquid; rather, immersion only means that the liquid is located between the projection system and the substrate during exposure.

[0055] In the operation of a 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 patterned by the patterning device MA that is held on a support structure (e.g., a mask table) MT. After passing through the patterning device MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of a substrate W. By means of a second positioner 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, e.g., to position different target portions C in the path of the radiation beam B. Similarly, e.g., after mechanical retrieval from a mask library or during scanning, a first positioner PM and another position sensor (not explicitly depicted in Figure 1 the figure) can be used to accurately position the patterning device MA relative to the path of the radiation beam B. Generally, the 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) that form part of the first positioner PM. Similarly, the movement of the substrate table WT can be realized using a long-stroke module and a short-stroke module that form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT can be connected only to a short-stroke actuator or can be fixed. The patterning device MA and the substrate W can be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2. Although the illustrated substrate alignment marks occupy dedicated target portions, they can be located in the spaces between the target portions (these are called scribe alignment marks). Similarly, in the case where more than one die is provided on the patterning device MA, the patterning device alignment marks can be located between the dies.

[0056] The apparatus shown can be used in at least one of the following modes. In the step mode, when the pattern imparted to the radiation beam is projected onto the target portion C once (i.e., single static exposure), the support structure MT and the substrate table WT remain substantially stationary. Then, 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 is limited to the size of the target portion C imaged in a single static exposure. In the scan mode, when the pattern imparted to the radiation beam is projected onto the target portion C (i.e., single dynamic exposure), the support structure MT and the substrate table WT are scanned synchronously. 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 is limited to the width of the target portion (in the non-scanning direction) in a single dynamic exposure, while the length of the scanning motion determines the height of the target portion (in the scanning direction). In another mode, while the pattern 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, typically a pulsed radiation source is employed, 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 operating mode can be readily applied to maskless lithography, which utilizes a programmable patterning device (such as a programmable mirror array of the type mentioned above).

[0057] Combinations and / or variations of the above usage modes or completely different usage modes can also be employed.

[0058] The substrate can be processed before or after exposure, for example in a track (a tool typically for applying a resist layer to the substrate and developing the exposed resist) or a metrology or inspection tool. Where applicable, the present disclosure herein can be applied to such and other substrate processing tools. Further, the substrate can be processed more than once, for example to create a multi-layer IC, such that the term substrate as used herein can also refer to a substrate that already includes multiple processed layers.

[0059] The terms "radiation" and "beam" as used herein with respect to lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g., wavelengths of 365, 248, 193, 157, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., wavelengths in the range of 5 to 20 nm) as well as particle beams, such as ion beams or electron beams.

[0060] The various patterns on a patterning device or provided by a patterning device can have different process windows, i.e., the space of process variables for generating patterns within specifications. Examples of pattern specifications related to potential system defects include checking for necking, line pullback, line thinning, CD, edge placement, overlay, anti-top loss, anti-etch bias, and / or bridging. The process window of a pattern or region thereof on a patterning device can be obtained by combining (e.g., overlapping) the process windows of each individual pattern. The boundaries of the process window of a set of patterns include the boundaries of the process windows of some of the individual patterns. In other words, these individual patterns limit the process window of the set of patterns.

[0061] As Figure 2 shown, a lithographic apparatus LA can form part of a lithographic cell LC, sometimes also referred to as a lithographic cell or cluster, which also includes equipment for performing pre-exposure and post-exposure processes on a substrate. Conventionally, these include one or more spin coaters SC for depositing one or more resist layers, one or more developers DE for developing the exposed resist, one or more cooling plates CH, and / or one or more baking plates BK. A substrate handler or robot RO picks up one or more substrates from input / output ports I / O1, I / O2, moves them between different process equipment, and then delivers them to the feed table LB of the lithographic apparatus. These devices, commonly referred to collectively as the track, are controlled by a track control unit TCU, which itself is controlled by a monitoring system SCS that also controls the lithographic apparatus via a lithographic control unit LACU. Thus, the different devices can be operated to maximize throughput and processing efficiency.

[0062] In order for a substrate exposed by a lithographic apparatus to be correctly and consistently exposed and / or in order to monitor part of a patterning process (such as a device manufacturing process) that includes at least one pattern transfer step (such as an optical lithography step), it is desirable to inspect the substrate or other object to measure or determine one or more properties, such as alignment, overlay (e.g., between structures in an overlay layer or between structures in the same layer, which can be provided to the layer separately, for example, by a double patterning process), line thickness, critical dimension (CD), focus offset, material properties, etc. Therefore, a manufacturing facility in which the 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 )).

[0063] One or more measurement parameters can include, for example, 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 aberration of an optical lithography step, etc. The measurement is typically performed on one or more dedicated metrology targets provided on the substrate. The measurement can be performed after resist development but before etching, after etching, after deposition, and / or at other times.

[0064] There are a variety of techniques for measuring structures formed during a patterning process, including using a scanning electron microscope, image-based measurement tools, and / or various specialized tools. A fast and non-invasive form of specialized metrology tool is a metrology tool in which a radiation beam is directed onto a target on the substrate surface and the properties of the scattered (diffracted / reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. Conventionally, this can be referred to as diffraction-based metrology. Applications of this diffraction-based metrology include measurement 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).

[0065] Thus, during a device fabrication process (e.g., patterning process or lithography process), the substrate or other object can be subjected to various types of measurements during or after the process. The measurement 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 the substrate or aligning a patterning device with the substrate), can measure the performance of the process and the equipment, or may be used for other purposes. Examples of measurements include optical imaging (e.g., optical microscopy), non-imaging optical measurement (e.g., diffraction-based measurement, such as ASML YieldStar metrology tool, ASML SMASH metrology system), mechanical measurement (e.g., profiling using a stylus, atomic force microscope (AFM)), and / or non-optical imaging (e.g., scanning electron microscope (SEM)).

[0066] The metrology results can be provided directly or indirectly to the monitoring system SCS. If an error is detected, adjustments can be made to the exposure of subsequent substrates (especially if the inspection can be completed quickly enough so that one or more other substrates in the batch are still to be exposed) and / or to the subsequent exposure of the exposed substrate. Also, an exposed substrate can be stripped and reworked to improve yield, or discarded, thus avoiding further processing of a known faulty substrate. In cases where only some target portions of the substrate are faulty, further exposure can be performed only on those target portions that meet the specifications. Other manufacturing process adjustments are also under consideration.

[0067] A metrology system can be used to determine one or more properties of a substrate structure, 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 a lithographic apparatus LA or a lithographic cell LC, or can be a stand-alone device.

[0068] To enable metrology, one or more targets are typically provided specifically on the substrate. Typically, the targets are specially designed and can include periodic structures. For example, the targets on the substrate can include one or more 1D 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 2D 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. Alternatively, the bars, pillars, or vias can be etched into the substrate (e.g., into one or more layers on the substrate).

[0069] Figure 3 An example metrology (inspection) system 10 is depicted that can be used to detect overlay, alignment, and / or perform other metrology operations. The metrology system 10 includes a radiation or illumination source 2 that projects or otherwise irradiates radiation onto a substrate W (which can typically include metrology marks). The redirected radiation is transmitted to sensors 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, as for example Figure 4 shown in the graph on the left. The sensors can generate metrology signals that convey metrology data indicative of the properties of the reflected radiation. From this data, the structure or profile of the detected spectrum can be reconstructed by one or more processors PRO (a general example of which is Figure 4 shown), or can be reconstructed by other operations.

[0070] As with Figure 1 the lithographic apparatus LA in Figure 4 (not shown in Figure 1The substrate tables WT (WTa or WTb or both) are similar or identical. In an example where the inspection system 10 is integrated with a lithographic apparatus, the inspection system 10 and the lithographic apparatus can even be the same substrate table. A coarse locator and a fine locator can be provided and configured to accurately position the substrate with respect to the measurement optical system. Various sensors and actuators are provided, for example to obtain the position of an object part of interest of the structure (such as a metrology mark) and place it in a position under the objective lens. Typically, a number of measurements will be made of the object part of the structure at different positions on the substrate W. The substrate support can be moved in the X and Y directions to obtain different objects, and can be moved in the Z direction to obtain a desired position of the object part with respect to the focus of the optical system. When, for example, in practice the optical system may remain substantially stationary (usually in the X and Y directions, but also possibly in the Z direction) while the substrate moves, it is convenient to think and describe the operation as if the objective lens were placed at different positions with respect to the substrate. As long as the relative position of the substrate and the optical system is correct, in principle it does not matter which of them is moving, or both are moving, or a part of the optical system is moving (such as in the Z and / or tilt directions) while the rest of the optical system is stationary and the substrate is moving (such as in the X and Y directions, but also optionally in the Z and / or tilt directions).

[0071] For typical metrology measurements, the object 30 on the substrate W can be a 1D grating, which is printed such that after development, the grating bars are formed by solid resist lines (which can be overlapped by a deposited layer, for example) and / or other materials. Alternatively, the object 30 can be a 2D grating, which is printed such that after development, the grating is formed by solid resist pillars and / or other features in the resist.

[0072] The grating bars, pillars, vias and / or other features can be etched into or onto the substrate (such as into one or more layers on the substrate), deposited on the substrate, overlapped by a deposited layer and / or have other properties. The object (part) 30 (such as the grating bars, pillars, vias, etc.) is sensitive to process variations during the patterning process (such as optical aberrations, focus variations, dose variations, etc. in a lithographic projection apparatus such as a projection system), such that the process variations manifest as variations in the object 30. Therefore, the measurement data from the object 30 can be used to determine adjustments to one or more manufacturing processes and / or used as a basis for making actual adjustments.

[0073] For example, measurement data from target 30 can indicate an overlap of semiconductor device layers. The measurement data from 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 an adjustment of a semiconductor device manufacturing apparatus based on the one or more determined semiconductor device manufacturing process parameters. In some embodiments, this can include, for example, stage position adjustment, or this can include determining an adjustment of a mask design, a metrology target design, a semiconductor device design, a radiation intensity, a radiation incident angle, a radiation wavelength, a pupil size and / or shape, a resist material, and / or other process parameters.

[0074] Figure 5 FIG. illustrates a plan view of a typical target (e.g., metrology mark) 30 and Figure 4 the extent of a typical radiation illumination spot S in a system. Generally, in order to obtain a diffraction spectrum not interfered with by surrounding structures, in one embodiment, target 30 is a periodic structure (e.g., a grating) that is larger than the width (e.g., diameter) of illumination spot S. The width of spot S can be less than the width and length of the target. In other words, the target is 'underfilled' with illumination, and the diffraction signal is substantially not affected by any signals from product features, etc. outside the target itself. For example, the illumination arrangement can be configured to provide illumination of uniform intensity in the back focal plane of the objective lens. Alternatively, the illumination can be restricted to an on-axis or off-axis direction, for example, by including an aperture in the illumination path.

[0075] Figure 6 FIG. illustrates a system 600 configured to determine a focus position for imaging one or more metrology targets 30. For example, target 30 can include one or more metrology marks formed in a substrate 602 (such as a semiconductor wafer), such as a diffraction grating target, collectively referred to as target 30. Target 30 can include one or more structures in the patterned substrate that can provide a diffraction signal. One or more targets 30 can be included in a layer of the substrate in, for example, a semiconductor device structure. In some embodiments, the feature includes geometric features such as 1D or 2D features and / or other geometric features. By way of several non-limiting examples, the feature can include gratings, lines, edges, a series of closely spaced lines and / or edges, and / or other features.

[0076] System 600 includes a radiation sensor 604 configured to receive radiation from a target 30 and generate a signal indicative of the position of a field image of the radiation. The radiation can be used to obtain an image of the target 30 and / or for other purposes. The radiation can include illumination, such as light and / or other radiation. System 600 includes an optical component 606 configured to receive radiation reflected from the target 30 and the substrate 602, change the angle of the radiation, and direct the radiation to the sensor 604. System 600 includes one or more processors PRO operatively connected to the radiation sensor 604 and configured to: determine an offset of the field image position relative to an expected field image position based on the changed angle; and determine a focus position for imaging the substrate based on the offset and / or other information.

[0077] System 600 can be similar and / or identical to Figure 3 the system 10 shown. In Figure 6 this, additional details are illustrated for system 600 as compared to system 10. In some embodiments, system 600 can form part of the system 10 described above with respect to Figure 3 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 one or more components of system 10, be used with them, and / or otherwise enhance one or more components of system 10.

[0078] 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 ( Figure 6 an example objective lens 690 is marked in this); and / or other components. In some embodiments, the components of system 600 form part of an overlap and / or alignment sensor used in semiconductor manufacturing processes. The radiation source 612 is configured to generate radiation along a first optical path 621. 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 and / or selected by a user, determined by the system (such as Figure 3 the system 10 shown) based on previous measurements, 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 interferometry.

[0079] As described above, system 600 does not include a separate focus branch 650 (in Figure 6Shown in the figure (removed). The focusing measurement 675 performed by the focusing branch 650 requires the detection apertures 677 and 679 and the corresponding sensors 681 and 683 before and after focusing. 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 where FS represents the focusing signal (e.g., the representation of the (optimal) focusing position), which has been determined by the Figure 6 The FS equation shown is determined for the existing system. S1 and S2 are the first and second intensities at the corresponding sensors. O represents the object, which can be the substrate (e.g., wafer) plane in this example. O1’ / O2’ represents the conjugate plane of O, and P is the pupil plane.

[0080] System 600 provides a new optical design architecture. Instead of using the focusing branch 650 and the above-mentioned focusing measurement principle, system 600 uses the position of the field image obtained for the target 30 in the substrate during the metrology measurement using the existing sensing components (such as sensor 604, optical component 606, etc.) to determine the focusing position. Compared with the existing system, this new architecture reduces cost and volume because the components of the focusing branch 650 are not required. This new architecture increases the radiation throughput of the sensor 604 because no additional beam splitter is needed to combine the focusing branch 650 with the rest of the system 600. This new architecture does not require color focusing calibration because the radiation wavelength between the sensor 604 and the focusing branch 650 no longer changes (e.g., because the focusing branch 650 does not exist at all). This new architecture provides a continuous focusing determination because there is no longer a need to switch back and forth between the focusing mode and the measurement mode, takes into account the objective wavefront error, and / or has other advantages.

[0081] The radiation reflected from the target 30 in the substrate 602 (such as a wafer) is received by the optical component 606, which changes the angle of the radiation and directs the radiation to the radiation sensor 604. In some embodiments, the optical component 606 includes a wedge and / or other optical components. In some embodiments, the optical component 606 includes a micro-diffraction-based overlapping wedge. For example, the wedge can include quadrants. Each quadrant is configured to direct a portion of the radiation to different regions of interest of the sensor 604 to form radiation spots on the sensor 604. For example, the radiation spots can include two radiation spots associated with the 0th order diffracted radiation from the target 30 on the substrate and two illumination spots associated with the 1st order diffracted radiation from the target 30.

[0082] The radiation from the optical component 606 is received by the sensor 604, and a signal indicating the position of the field image of the radiation is generated. The radiation sensor 604 can be associated with Figure 3The detector 4 and / or the processor PRO and / or other components shown are similar and / or identical. In some embodiments, the sensor 604 includes a camera, a charge-coupled device (CCD) array, a complementary metal-oxide semiconductor (CMOS), a photodiode array, and / or other sensors. In some embodiments, the sensor 604 includes a micro-diffraction-based overlay camera associated with overlay measurements. In some embodiments, the sensor 604 includes a second camera that is separate from the micro-diffraction-based overlay camera associated with the overlay measurements in the metrology system 600. In some embodiments, the optical component 606 includes a micro-diffraction-based overlay wedge having a high-reflectivity beam splitter configured to direct radiation from the substrate simultaneously to the micro-diffraction-based overlay camera and the second camera (e.g., as further described below with respect to Figure 10 Further described).

[0083] The offset of the field image position relative to the expected field image position is determined by one or more processors PRO based on the changed angle and / or other information. Defocused radiation incident on the wedge pupil plane causes the offset. The signals generated by the sensor 604 indicate four separate field image positions of the radiation spot. One or more processors PRO (e.g., and / or Figure 3 The PRO shown, and / or the processor described below with respect to Figure 12 described) can determine the offset of the field image position of the field image based on the centroid of the radiation spot in the field image. In some embodiments, the offset of the field image position of the field image is determined based on the intensity of the field image. In some embodiments, for example, the intensity is determined at one or more halves of one or more rings of the radiation spot in the field image.

[0084] The focus position for imaging the target 30 on the substrate is determined based on the offset and / or other information. The focus position is determined based on the relationship between the offset and the defocus of the metrology system objective. This relationship can be linear and / or have other corresponding relationships. For example, one or more processors (e.g., Figure 3 The PRO shown and / or the processor described below with respect to Figure 12 described) are configured to determine the offsets of the 0th and 1st order spots and determine the focus position based on the offsets of the 0th and 1st order spots. The linear relationship between the offset and the objective defocus means that as the defocus increases, the spot is farther from the expected position. This offset and this relationship can be used to determine the (optimal) focus position of the optical component (such as the objective 690) for imaging the target 30.

[0085] Figures 7 to 10 Illustrates the various operations described above. For example, Figure 7Illustrated is the reception of radiation 700 reflected from a target on a substrate by an optical component 606 including a wedge 702, changing the angle 704 of the radiation 700, and directing the radiation 700 to a sensor 604 (e.g., using a lens 706 of the optical component 606). Figure 7 Also illustrated is determining an offset “d” of the position of the field image 710 relative to the expected field image position “x” based on the changed angle 704 and / or other information. Defocused radiation 750 incident on the wedge pupil plane causes the offset “d”. The wedge 702 is configured to direct a portion of the radiation 700 to different regions of interest of the sensor 604 to form spots 720, 722, 724, and 726 of the radiation 700 on the sensor 604. For example, spots 720 to 726 of the radiation 700 include two radiation spots 720 and 724 associated with 0th order diffracted radiation from the target 30 on the substrate, and two illumination spots 722 and 726 associated with 1st order diffracted radiation from the target 30. As Figure 7 shown, the defocused rays of the radiation 750 have different angles of incidence on the pupil plane of the wedge 702, and then the field image 710 has the offset “d”. This offset exists in the 0th and 1st order spots 720 to 726.

[0086] The radiation 700 from the optical component 606 is received by the sensor 604, and a signal indicating the field image positions of the spots 720 to 726 is generated. The signal generated by the sensor 604 indicates four separate field image positions of the spots 720 to 726 of the radiation 700. One or more processors PRO (e.g., and / or Figure 3 、 Figure 6 the PRO shown, and / or the processor described below with respect to Figure 12 can determine the offset “d” (e.g., the offset “d” of each spot) of the field image position of the field image based on the centroid of the spots 720 to 726 in the field image 710, the intensity of the spots, and / or a portion of the spots 720 to 726 of the field image 710 and / or other information. For example, in some embodiments, one or more intensities can be determined at one or more halves of one or more annuli of the radiation spots in the field image (e.g., because this may be an appropriate region for the spots to be analyzed to determine if the spots have moved away from the expected position, as further described below). In some embodiments, the distance between the spots 720 and 724 and / or 722 and 726 can be determined, for example, by binarizing the image 710 with a grayscale threshold and / or using other methods. In Figure 7 the example shown, the spots 720 to 726 have moved from the expected position “x” to the position at “x + 2d”.

[0087] Figure 8 Illustrated is the target 30 depending on the reflected radiation 700 (Figure 7 ), how the four different offsets d1, d2, d3, and d4 of the eight different spots 802 to 816 in this example can be made available for determining the offset of the field image 800 position relative to the expected position. In some embodiments, d1 to d4 are used (more or fewer can be used as needed), because each rectangle (for example) defining the target area uses a different area of the pupil plane. For example, 816 uses the -1x and 808 uses the +1x area, 810 uses the -1y and 802 uses the +1y, where their wavefronts are all different on the pupil plane. Since typical metrology marks on the wafer have four small rectangles, each including a grating, there are four copies at the uDBO camera (or other sensor), thus providing the possibility of measuring multiple d's. The focus position can be determined to compensate for the aberration associated with a large NA (usually there are higher-order aberrations in the high-NA region of interest). Based on this idea, the focus of each spot can be compensated as continuous focusing.

[0088] Figure 9 Illustrated is determining the offset 900 of the field image position of the field image 902 based on the intensity 904 of the field image (and / or an image indicating the intensity) and / or one or more portions 910 of the field image 902. The system 600 ( Figure 6 ) can be configured for contrast detection or intensity 904 change detection as a function of defocus for the centroid, edges, and / or other regions of the spots 952, 954, 956, and / or 958 in the field image 902. Two semi-circular regions 920 and 922 of the edges of one or more of the spots 952 to 958 in the image 902 can be defined as regions of interest. In some embodiments, for example, the intensity 904 is determined at one or more semi-circular regions 920 and 922 of the radiation spots 950, 952, 954, 956 in the field image.

[0089] One or more intensities can be determined at the semi-circular regions 920 and / or 922 in the field image 902, because this may be a convenient region for the spots 952 to 958 to be analyzed to determine whether the spots 952 to 958 have moved away from the expected position. These regions of the image 902 exhibit the largest intensity changes with defocus. Additionally, each semi-circular region 920 or 922 sees an opposite change in intensity with defocus. For example, the expected intensity 904 at or near the edge of the spot can be a non-zero value. If the intensity 904 at the spot is zero or close to zero, then the spot may have shifted away from its expected position. Vice versa (whether on the opposite side of the same spot or on a different spot). The intensity at a position outside the expected position of the spot may be expected to be zero, and if not, the spot may have shifted away from its expected position. The processor PRO ( Figure 3 , Figure 6 ,Figure 12 This offset can be determined as described above and used to determine the (optimal) focus position for imaging a target (e.g., the target 30 as shown) in a substrate such as a semiconductor wafer using a (e.g., linear) relationship with defocus. The intensity in the semi-circular portion 920 becomes S1, and the intensity in the semi-circular portion 922 becomes S2. In this example, the focus signal FS is determined as FS = (S1 - S2) / (S1 + S2). Figure 6 This offset can be determined as described above and used to determine the (optimal) focus position for imaging a target (e.g., the target 30 as shown) in a substrate such as a semiconductor wafer using a (e.g., linear) relationship with defocus. The intensity in the semi-circular portion 920 becomes S1, and the intensity in the semi-circular portion 922 becomes S2. In this example, the focus signal FS is determined as FS = (S1 - S2) / (S1 + S2).

[0090] Figure 10 The figure illustrates an improvement in the speed of focus position determination (compared to existing systems) by sending 0th order radiation 1001 to a fast camera or sensor array 1002. In some embodiments, the focus position determination can be based on the output signal from the fast camera or sensor array 1002, while the overlap can be determined based on the output signal from the sensor 604. As described above, in some embodiments, the sensor 604 includes a micro-diffraction-based overlap camera associated with overlap measurement. In some embodiments, the sensor 604 includes a second camera, such as the fast camera or sensor array 1002, which is separated from the micro-diffraction-based overlap camera (sensor 604) associated with overlap measurement in the metrology system 600. In some embodiments, the optical component 606 includes a micro-diffraction-based overlap wedge (optical component 606) with a high-reflectivity beam splitter 1010 configured to direct the radiation 700 from the substrate simultaneously to the micro-diffraction-based overlap camera (sensor 604) and the second camera (e.g., 1002).

[0091] Returning to Figure 6 , various lenses ( Figure 6In the figure, an exemplary objective lens 690, reflectors, and other optical components (such as optical component 606, such as a wedge) are configured to receive, transmit, reflect, focus the illumination generated by source 612, split by beam splitter 670, transmitted or reflected by various optical elements, received by detection branch 660, received by alignment branch 680, and / or used by other parts of system 600, and / or perform other operations on the illumination. These various lenses, reflectors, and / or other optical components can include any type of lens, mirror, and / or other optical components configured to allow system 600 to operate as described. For example, objective lens 690 can be formed of any transparent material and have a curved surface configured to concentrate or otherwise focus one or more radiation spots on target 30. The various lenses, reflectors, optical elements, beam splitters, and other optical elements can be positioned at any location and / or at any angle relative to each other to allow system 600 to operate as described herein. This can include positioning at a specific relative distance between elements, a specific angle between elements, etc. In some embodiments, the various lenses, reflectors, optical elements, beam splitters, and other optical components are positioned relative to each other in system 600 via structural members, clips, fixtures, screws, nuts, bolts, adhesives, and / or other mechanical means. In some embodiments, various ones of the lenses, reflectors, optical elements, beam splitters, and other optical elements can be movable relative to each other. For example, the movement can be configured to adjust the position of the corresponding illumination spots on one or more targets 30. In some embodiments, the movement includes tilting, translating, or otherwise changing the distance between the various lenses, reflectors, and other optical components. Other examples of movement are also contemplated.

[0092] In some embodiments, the movement can be electronically controlled by a processor, such as processor PRO (also discussed below in Figure 3 and Figure 12 ). Processor PRO can be included in computing system CS ( Figure 12 ), and can operate based on computer or machine-readable instructions (such as as described below with respect to Figure 12 ). Electronic communication can be achieved by sending electronic signals between separate components, sending data between separate components of system 600, sending values and / or other communication between separate components. The components of system 600 can communicate via wires or wirelessly via a network, such as the Internet or the Internet combined with various other networks, such as a local area network, a cellular network, or a personal area network, an internal organizational network, and / or other networks.

[0093] In some embodiments, one or more actuators ( Figure 6Actuators (not shown in FIG. 6) can be coupled to one or more components of system 600 and configured to move one or more components of system 600. The actuators can be coupled to one or more components of system 600 by adhesives, clips, fixtures, screws, collars, and / or other mechanisms. The actuators can be configured for electronic control. Each actuator can be configured to convert an electrical signal into mechanical displacement. The mechanical displacement is configured to move components of system 600. As an example, one or more actuators can be piezoelectric. One or more processors PRO can be configured to control the actuators. One or more processors PRO can be configured to control each of the one or more actuators individually.

[0094] Figure 6 The number of the various lenses, reflectors, and / or other optical components shown is not intended to be limiting. The principles described herein can be extended such that in some embodiments, system 600 includes additional or fewer lenses, reflectors, and / or other optical components.

[0095] Figure 11 Illustrated is a metrology method 1100 for determining a focus position for imaging a substrate. In some embodiments, for example, method 1100 is performed as part of an overlay and / or alignment sensing operation in a semiconductor device manufacturing process. In some embodiments, for example, one or more operations of method 1100 can be performed in Figure 6 the illustrated system 600, Figure 3 the illustrated system 10, a computer system (such as, for example, Figure 12 illustrated and described below), and / or other systems or implemented by them. In some embodiments, method 1100 includes: receiving (operation 1102) radiation reflected from a substrate using an optical component, changing the angle of the radiation, and directing the radiation to a radiation sensor; receiving (operation 1104) the radiation from the optical component using the radiation sensor and generating (operation 1104) a signal indicative of a field image position of the radiation; determining (operation 1106) an offset of the field image position relative to an expected field image position based on the changed angle; and determining (operation 1108) a focus position for imaging the substrate and / or other operations based on the offset.

[0096] The operations of method 1100 are illustrative. In some embodiments, method 1100 can be completed with one or more additional operations not described and / or without one or more of the operations discussed. For example, in some embodiments, method 1100 can include additional operations that include determining an adjustment of a semiconductor device manufacturing process. Additionally, the operations of method 1100 in Figure 11 the order illustrated and described herein is not intended to be limiting.

[0097] In some embodiments, one or more portions of method 1100 may be implemented and / or controlled in 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 that electronically process information). The one or more processing devices may include one or more devices that perform some or all of the operations of method 1100 in response to instructions electronically stored on an electronic storage medium. The one or more processing devices may include one or more devices that are configured by hardware, firmware, and / or software to be specifically designed to perform one or more operations of method 1100 (e.g., see the discussion related to Figure 12 below).

[0098] In operation 1102, radiation reflected from a substrate is received by an optical component that changes the angle of the radiation and directs the radiation to a radiation sensor. The radiation sensor may be similar and / or identical to detector 4 and / or processor PRO and / or other components shown Figure 3 below. In some embodiments, the optical component is similar and / or identical to the wedge described above. The wedge includes quadrants. Each quadrant is configured to direct a portion of the radiation to different regions of interest of the sensor to form a radiation spot on the sensor. The radiation spot includes two radiation spots associated with 0th order diffracted radiation from the substrate and two radiation spots associated with 1st order diffracted radiation from the substrate.

[0099] In operation 1104, the radiation from the optical component is received by the sensor, and a signal is generated that indicates the field image position of the radiation. In some embodiments, the sensor includes a camera, a charge-coupled device (CCD) array, a complementary metal oxide semiconductor (CMOS), a photodiode array, and / or other sensors. In some embodiments, the sensor includes a microdiffraction-based overlap camera associated with an overlap measurement. In some embodiments, the sensor includes a second camera that is separate from the microdiffraction-based overlap camera associated with the overlap measurement in the metrology system. In some embodiments, the optical component includes a microdiffraction-based overlap wedge having a high reflectivity beam splitter that is configured to direct radiation from the substrate simultaneously to the microdiffraction-based overlap camera and the second camera.

[0100] In operation 1106, an offset of the field image position relative to the expected field image position is determined based on the changed angle and / or other information. Defocused radiation incident on the wedge pupil plane causes the offset. The signal generated by the sensor indicates four separate field image positions of the radiation spot. One or more processors (e.g., Figure 3 PRO shown below and / or with respect to Figure 12The described processor) may determine an offset of the field image position of the field image based on the centroid of the radiation spot in the field image. In some embodiments, the offset of the field image position of the field image is determined based on the intensity of the field image. In some embodiments, the intensity is determined at one or more halves of one or more annuli of the radiation spot in the field image.

[0101] In operation 1108, a focus position for imaging the substrate is determined based on the offset and / or other information. For example, the focus position is determined based on a linear relationship between the offset and the defocus of the metrology system objective. For example, one or more processors (such as Figure 3 the PRO shown and / or the processor described below with respect to Figure 12 are configured to determine the offsets of the 0th and 1st order spots and determine the focus position based on the offsets of the 0th and 1st order spots.

[0102] In some embodiments, method 1100 includes determining overlap and / or alignment. The overlap and / or alignment is determined based on the reflected diffracted radiation from the diffraction grating target on the substrate, the focus position, the offset, and / or other information.

[0103] In some embodiments, method 1100 includes irradiating (and / or otherwise illuminating) one or more targets in the patterned substrate (such as Figure 3 the target 30 shown). The radiation includes light and / or other radiation. The radiation may be generated by a radiation source (such as Figure 3 the source 2 shown). In some embodiments, the radiation may be directed by the radiation source to multiple targets, a single target, a sub - portion of a target (such as something less than the whole) and / or otherwise directed onto the substrate. In some embodiments, the radiation may be directed by the radiation source to the target in a time - varying manner. For example, the radiation may be rasterized over the target (such as 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 (such as wavelength, intensity, etc.) may vary. This may create a time - varying data envelope or window for analysis. The data envelope may assist in analyzing individual sub - portions of the target, comparing one part of the target to another part and / or other targets (such as in other layers) and / or performing other analyses.

[0104] In some embodiments, method 1100 includes: detecting reflected radiation from one or more diffraction grating targets (using the radiation sensor described above). Detecting the reflected radiation includes: detecting one or more phase and / or amplitude (intensity) offsets in the reflected radiation from one or more geometric features of the target. The one or more phase and / or amplitude offsets 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.

[0105] Detecting one or more phase and / or amplitude (intensity) offsets in the reflected radiation from the target includes: measuring local phase shifts (such as local phase increments) and / or amplitude variations corresponding to different parts of the target. For example, the reflected radiation from a specific region of the target may include a sine wave with a specific phase and / or amplitude. The reflected radiation from different regions (or targets in different layers) of the target may also include sine waves, but with different phases and / or amplitudes. The detected reflected radiation also includes measuring the phase and / or amplitude differences of the reflected radiation of different diffraction orders. For example, detecting one or more local phase and / or amplitude offsets can be performed using the Hilbert transform and / or other techniques. Interferometric techniques and / or other operations can be used to measure the phase and / or amplitude differences of the reflected radiation of different diffraction orders.

[0106] In some embodiments, operation 1100 includes generating a measurement signal based on the detected reflected radiation from the diffraction grating target, as described above. The measurement signal is generated by a sensor (such as Figure 3 detector 4, camera, and / or other sensors in) based on the radiation received by the sensor. The measurement signal includes measurement information related to the target on the substrate. For example, the measurement signal can be an overlap and / or alignment signal and / or other measurement signals including overlap and / or alignment measurement information. The measurement information (such as overlap values, alignment values, and / or other information) can be determined using interferometric principles and / or other principles.

[0107] The measurement signal includes an electronic signal representing and / or otherwise corresponding to the radiation reflected from the target. For example, the measurement signal can indicate measurement values and / or other information associated with different grating targets. Generating the measurement signal includes: sensing the reflected radiation and converting the sensed reflected radiation into an electronic signal. In some embodiments, generating the measurement signal includes: sensing different parts of the reflected radiation from different regions and / or different geometries and / or multiple targets of the target, and combining the different parts of the reflected radiation to form the measurement signal. This can include generating and / or analyzing one or more images of the target using the radiation described herein. Such sensing and conversion can be performed by Figure 3The detector 4 and / or the processor PRO shown perform similar and / or identical components and / or other components.

[0108] 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 stage of a metrology system holding a substrate based on a determined focus position by one or more processors such that subsequent images of the substrate are in focus. In some embodiments, method 1100 includes determining one or more semiconductor device manufacturing process parameters. The one or more semiconductor device manufacturing process parameters may be determined based on one or more detected phase and / or amplitude changes, overlay and / or alignment values indicated by measurement signals, and / or other similar systems and / or other information. The one or more parameters may include parameters of radiation (radiation for metrology), overlay values, alignment values, metrology inspection locations on semiconductor device structure layers, radiation beam trajectories on targets, and / or other parameters. In some embodiments, process parameters may be broadly interpreted to include stage position, mask design, metrology target design, semiconductor device design, radiation intensity (for exposing resist, etc.), radiation incident angle (for exposing resist, etc.), radiation wavelength (for exposing resist, etc.), pupil size and / or shape, resist material, and / or other parameters.

[0109] In some embodiments, method 1100 includes: determining a process adjustment based on one or more determined semiconductor device manufacturing process parameters, and adjusting semiconductor device manufacturing equipment and / or other operations based on the determined adjustment. This may be performed by one or more processors, such as Figure 3 the PRO shown, the processor described as Figure 12 a part of the computer system illustrated and described below, and / or other processors. For example, if a determined metrology measurement is outside of process tolerances, the measurement outside of tolerance may be caused by one or more manufacturing processes whose process parameters have shifted and / or other changes have occurred such that the process no longer produces acceptable devices (e.g., the measurement may violate an acceptability 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 to cause the manufacturing process to produce acceptable devices again.

[0110] For example, new or adjusted process parameters may cause previously unacceptable measurement values to be adjusted back into an acceptable range. The new or adjusted process parameters can be compared to the existing parameters of a given process. For example, if there is a difference, that difference can be used to determine an adjustment to the equipment used to produce the device (e.g., the parameter "x" should be increased / decreased / changed such that the parameter "x" matches the new or adjusted version of the parameter "x" determined as part of method 1100). In some embodiments, method 1100 can include electronically adjusting the equipment (e.g., based on the determined process parameters). Electronically adjusting the equipment can include sending an electronic signal and / or other communication to the equipment, such as which causes a change in the equipment. Electronic adjustment can include, for example, changing settings on the equipment and / or other adjustments.

[0111] Figure 12 is a diagram of an example computer system CS that can be used for one or more of the operations described herein. Computer system CS includes a bus BS or other communication mechanism for passing information, and a processor PRO (or multiple processors, similar and / or identical to the Figure 3 illustrated processor PRO) coupled to the bus BS for processing information. Computer system CS also includes a main memory MM, such as a random access memory (RAM) or other dynamic storage device, coupled to the bus BS for storing information and instructions to be executed by the processor PRO. The main memory MM can also be used to store temporary variables or other intermediate information during the execution of instructions by the processor PRO. Computer system CS also 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.

[0112] Computer system CS can be coupled via the bus BS to a display DS, such as a flat panel or touchpad display or a cathode ray tube (CRT), for displaying information to a computer user. An input device ID, including alphanumeric keys and other keys, is coupled to the bus BS for passing information and command selections to the processor PRO. Another type of user input device is a cursor control CC, such as a mouse, trackball, or cursor direction keys, for passing direction information and command selections to the processor PRO and controlling the movement of a cursor on the display DS. The input device typically has two degrees of freedom in two axes (a first axis (e.g., x) and a second axis (e.g., y)), allowing the device to specify a position in a plane. A touchpad (screen) display can also be used as an input device.

[0113] In some embodiments, all or some of the one or more operations described herein can be performed by a computer system CS in response to one or more sequences of one or more instructions included in a main memory MM executed by a processor PRO. Such instructions can be read into the main memory MM from another computer-readable medium, such as a storage device SD. 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 employed 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. Accordingly, the description herein is not limited to any specific combination of hardware circuitry and software.

[0114] As used herein, the term “computer-readable medium” or “machine-readable medium” refers to any medium that participates in providing instructions to a processor PRO for execution. Such a medium can 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 a storage device SD. Volatile media includes dynamic memory, such as a main memory MM. Transmission media includes coaxial cables, copper wire, and fiber optics, including the wires that make up a 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 can be non-transitory, such as a floppy disk, a flexible disk, a hard disk, a magnetic tape, any other magnetic medium, a CD-ROM, a DVD, any other optical medium, punch cards, paper tape, any other physical medium with hole patterns, RAM, PROM, and EPROM, flash EPROM, any other memory chip or cartridge. Instructions can be recorded on a non-transitory computer-readable medium. When executed by a computer, the instructions can implement any of the operations described herein. For example, a transitory computer-readable medium can include a carrier wave or other propagating electromagnetic signal.

[0115] Various forms of computer-readable media can be involved in carrying one or more sequences of one or more instructions to a processor PRO for execution. For example, the instructions may initially be carried on a disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to the computer system CS can receive the data on the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector coupled to the bus BS can receive the data carried in the infrared signal and place the data on the bus BS. The bus BS carries the data to the main memory MM, from which the processor PRO retrieves and executes the instructions. Before or after execution by the processor PRO, the instructions received by the main memory MM can optionally be stored on the storage device SD.

[0116] The computer system CS may also include a communication interface CI coupled to the bus BS. The communication interface CI provides a two-way data communication coupling with a network link NDL connected to a local network LAN. For example, the communication interface CI may be an Integrated Services Digital Network (ISDN) card or a modem to provide a data communication connection with a corresponding type of telephone line. As another example, the communication interface CI may be a local area network (LAN) card to provide a data communication connection with a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface CI transmits and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information.

[0117] The network link NDL typically provides data communication to other data devices through one or more networks. For example, the network link NDL may provide a connection to a host computer HC through a local network LAN. This may include data communication services provided through the global packet data communication network (now commonly referred to as the “Internet” INT). The local network LAN (Internet) may use electrical, electromagnetic, or optical signals that carry digital data streams. Signals through various networks and signals on the network data link NDL and through the communication interface CI (which carry digital data to and from the computer system CS) are exemplary forms of carriers that convey information.

[0118] The computer system CS may send messages and receive data, including program code, through the network, the network data link NDL, and the communication interface CI. In the Internet example, the host computer HC may send request code for an application through the Internet INT, the network data link NDL, the local network LAN, and the communication interface CI. For example, one such downloaded application may provide all or part of the methods described herein. The received code may be executed by the processor PRO when received, and / or stored in the storage device SD or other non-volatile storage device for later execution. In this way, the computer system CS may obtain application code in the form of a carrier.

[0119] Various embodiments of the system and method are disclosed in the list of numbered items that follow. In the following, further features, characteristics, and exemplary technical solutions of the present disclosure will be described in terms of items that may optionally be claimed in any combination:

[0120] 1. A measurement system, comprising: a radiation sensor configured to receive radiation and generate a signal indicative of a position of a field image of the radiation; an optical component configured to receive radiation reflected from a substrate, change an angle of the radiation, and direct the radiation to the sensor; and one or more processors operatively connected to the radiation sensor and configured to: determine an offset of the field image position relative to an expected field image position based on the changed angle; and determine a focus position for imaging the substrate based on the offset.

[0121] 2. The system of item 1, wherein the focus position is determined based on a linear relationship between the offset and defocus of an objective of the measurement system.

[0122] 3. The system according to any one of the preceding items, wherein the optical component includes a wedge.

[0123] 4. The system according to any one of the preceding items, wherein defocused radiation incident on a pupil plane of the wedge causes the offset.

[0124] 5. The system according to any one of the preceding items, wherein the wedge includes quadrants, each quadrant being configured to direct a portion of the radiation to a different region of interest of the sensor to form radiation spots on the sensor.

[0125] 6. The system according to any one of the preceding items, wherein the radiation spots include: two radiation spots associated with 0th order diffracted radiation from the substrate, and two radiation spots associated with 1st order diffracted radiation from the substrate.

[0126] 7. The system according to any one of the preceding items, wherein the signal generated by the sensor indicates four separate field image positions of the radiation spots, and wherein the one or more processors are configured to determine the offsets of the 0th order spots and the 1st order spots, and determine the focus position based on the offsets of the 0th order spots and the 1st order spots.

[0127] 8. The system according to any one of the preceding items, wherein the one or more processors are further configured to automatically adjust a position of a stage of the measurement system holding the substrate based on the focus position such that the substrate is subsequent in focus.

[0128] 9. The system according to any one of the preceding items, wherein the one or more processors are configured to determine an offset of the field image position of the field image based on a centroid of the radiation spots in the field image.

[0129] 10. The system according to any one of the preceding items, wherein the one or more processors are configured to determine an offset of the field image position of the field image based on an intensity of the field image.

[0130] 11. The system according to any one of the preceding clauses, wherein the intensity is determined at one or more halves of one or more rings of radiation spots in the in-field image.

[0131] 12. The system according to any one of the preceding clauses, wherein the substrate comprises a semiconductor wafer having one or more overlapping targets configured to reflect radiation towards the optical component.

[0132] 13. The system according to any one of the preceding clauses, wherein the sensor comprises a camera, a charge-coupled device (CCD) array, a complementary metal-oxide semiconductor (CMOS), and / or a photodiode array.

[0133] 14. The system according to any one of the preceding clauses, wherein the sensor comprises a micro-diffraction-based overlay camera associated with overlay measurement.

[0134] 15. The system according to any one of the preceding clauses, wherein the sensor comprises a second camera separated from the micro-diffraction-based overlay camera associated with overlay measurement in the metrology system.

[0135] 16. The system according to any one of the preceding clauses, wherein the optical component comprises a micro-diffraction-based overlay wedge having a high-reflectivity beam splitter configured to direct radiation from the substrate simultaneously to the micro-diffraction-based overlay camera and the second camera.

[0136] 17. The system according to any one of the preceding clauses, further comprising a radiation source and one or more lenses configured to generate radiation and direct the radiation towards the substrate.

[0137] 18. The system according to any one of the preceding clauses, wherein the optical component, the sensor, and one or more processors are configured for overlay detection.

[0138] 19. The system according to any one of the preceding clauses, wherein the radiation received by the optical component is a micro-diffraction-based overlay signal, and the overlay detection is micro-diffraction-based overlay detection.

[0139] 20. The system according to any one of the preceding clauses, wherein the metrology system is configured for a semiconductor wafer and is used in a semiconductor manufacturing process.

[0140] 21. A measurement method, comprising: receiving radiation reflected from a substrate using an optical component, changing the angle of the radiation, and directing the radiation to a sensor; receiving the radiation from the optical component using a radiation sensor and generating a signal indicating the position of the field image of the radiation; using one or more processors operatively connected to the radiation sensor to determine an offset of the field image position relative to an expected field image position based on the changed angle; and using one or more processors to determine a focus position for imaging the substrate based on the offset.

[0141] 22. The method according to item 21, wherein the focus position is determined based on a linear relationship between the offset and the defocus of the measurement system objective.

[0142] 23. The method according to any one of the preceding items, wherein the optical component includes a wedge.

[0143] 24. The method according to any one of the preceding items, wherein the defocused radiation incident on the pupil plane of the wedge causes an offset.

[0144] 25. The method according to any one of the preceding items, wherein the wedge includes a plurality of quadrants, each quadrant being configured to direct a portion of the radiation to a different region of interest of the sensor to form radiation spots on the sensor.

[0145] 26. The method according to any one of the preceding items, wherein the radiation spots include: two radiation spots associated with the 0th order diffracted radiation from the substrate, and two radiation spots associated with the 1st order diffracted radiation from the substrate.

[0146] 27. The method according to any one of the preceding items, wherein the signal generated by the sensor indicates four separate field image positions of the radiation spots, and wherein one or more processors are configured to determine the offsets of the 0th order spots and the 1st order spots and to determine the focus position based on the offsets of the 0th order spots and the 1st order spots.

[0147] 28. The method according to any one of the preceding items, further comprising: using one or more processors to automatically adjust the position of the stage of the measurement system holding the substrate based on the focus position such that subsequent images of the substrate are in focus.

[0148] 29. The method according to any one of the preceding items, further comprising: using one or more processors to determine an offset of the field image position of the field image based on the centroid of the radiation spots in the field image.

[0149] 30. The method according to any one of the preceding items, further comprising: using one or more processors to determine an offset of the field image position of the field image based on the intensity of the field image.

[0150] 31. The method according to any one of the preceding clauses, wherein the intensity is determined at one or more halves of one or more rings of radiation spots in the in-field image.

[0151] 32. The method according to any one of the preceding clauses, wherein the substrate comprises a semiconductor wafer having one or more overlapping targets configured to reflect radiation towards an optical component.

[0152] 33. The method according to any one of the preceding clauses, wherein the sensor comprises a camera, a charge-coupled device (CCD) array, a complementary metal-oxide semiconductor (CMOS), and / or a photodiode array.

[0153] 34. The method according to any one of the preceding clauses, wherein the sensor comprises a micro-diffraction-based overlay camera associated with overlay measurement.

[0154] 35. The method according to any one of the preceding clauses, wherein the sensor comprises a second camera separated from the micro-diffraction-based overlay camera associated with overlay measurement in the metrology system.

[0155] 36. The method according to any one of the preceding clauses, wherein the optical component comprises a micro-diffraction-based overlay wedge having a high-reflectivity beam splitter configured to direct radiation from the substrate simultaneously to the micro-diffraction-based overlay camera and the second camera.

[0156] 37. The method according to any one of the preceding clauses, further comprising: generating radiation using a radiation source and one or more lenses, the radiation source and one or more lenses being configured to generate radiation and direct the radiation towards the substrate.

[0157] 38. The method according to any one of the preceding clauses, wherein the optical component, the sensor, and one or more processors are configured for overlay detection.

[0158] 39. The method according to any one of the preceding clauses, wherein the radiation received by the optical component is a micro-diffraction-based overlay signal, and the overlay detection is micro-diffraction-based overlay detection.

[0159] 40. The method according to any one of the preceding clauses, wherein the method is configured for a semiconductor wafer and is used in a semiconductor manufacturing process.

[0160] The concepts disclosed herein can be associated with any general imaging system for imaging sub-wavelength features and may be particularly useful for emerging imaging technologies capable of generating increasingly shorter wavelengths. Emerging technologies that have been used include EUV (extreme ultraviolet), DUV lithography, which is capable of generating a wavelength of 193 nm using an ArF laser, and even 157 nm using a fluorine laser. Moreover, EUV lithography is capable of generating wavelengths in the range of 20 to 5 nm by using a synchrotron or by colliding high-energy electrons with a material (solid or plasma) to generate photons in that range.

[0161] 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, such as those for imaging on substrates other than silicon wafers. Additionally, combinations and sub-combinations of the disclosed elements can include separate embodiments.

[0162] The above description is intended to be illustrative and not restrictive. Thus, it will be apparent to those skilled in the art that modifications can be made as described without departing from the scope of the claims set forth below.

Claims

1. A measurement system, comprising: A radiation sensor configured to receive radiation and generate a signal indicative of the position of the field image of the radiation; An optical component configured to receive the radiation reflected from the substrate, change the angle of the radiation, and direct the radiation to the sensor; And One or more processors operatively connected to the radiation sensor and configured to: Determine an offset of the field image position relative to the expected field image position based on the changed angle; And Determine a focus position for imaging the substrate based on the offset.

2. The system according to claim 1, wherein the focus position is determined based on a linear relationship between the offset and the defocus of the measurement system objective.

3. The system according to claim 1 or 2, wherein the optical component includes a wedge.

4. The system according to claim 3, wherein the defocused radiation incident on the pupil plane of the wedge causes the offset.

5. The system according to claim 3 or 4, wherein the wedge includes quadrants, each quadrant being configured to direct a portion of the radiation to different regions of interest of the sensor to form radiation spots on the sensor.

6. The system according to claim 5, wherein the radiation spot comprises: Two radiation spots associated with the 0th order diffracted radiation from the substrate, and two radiation spots associated with the 1st order diffracted radiation from the substrate.

7. The system according to claim 6, wherein the signal generated by the sensor indicates four separate field image positions of the radiation spots, and Wherein the one or more processors are configured to determine the offsets of the 0th order spots and the 1st order spots, and determine the focus position based on the offsets of the 0th order spots and the 1st order spots.

8. The system according to any one of claims 1 to 7, wherein the one or more processors are further configured to automatically adjust the position of the stage of the measurement system holding the substrate based on the focus position such that subsequent images of the substrate are in focus.

9. The system according to any one of claims 1 to 8, wherein the one or more processors are configured to determine the offset of the field image position of the field image based on the centroid of the radiation spots in the field image.

10. The system according to any one of claims 1 to 9, wherein the one or more processors are configured to determine the offset of the field image position of the field image based on the intensity of the field image.

11. The system according to claim 10, wherein the intensity is determined at one or more halves of one or more rings of the radiation spots in the field image.

12. The system according to any one of claims 1 to 11, wherein the substrate includes a semiconductor wafer having one or more overlapping targets configured to reflect the radiation towards the optical component.

13. The system according to any one of claims 1 to 12, wherein the sensor includes a camera, a charge-coupled device (CCD) array, a complementary metal-oxide-semiconductor (CMOS), and / or a photodiode array.

14. The system according to claim 13, wherein the sensor includes a micro-diffraction based overlay camera associated with overlay measurements.

15. The system according to claim 13, wherein the sensor includes a second camera, which is separate from the micro-diffraction based overlay camera associated with overlay measurements in the metrology system.

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