Inspection system using metasurfaces and integrated optical systems for lithography

Abstract

The inspection system includes a substrate, a waveguide system, an integrated optical system including first and second grating couplers disposed on the substrate, first and second detectors, and a microstructure illumination adjuster. The integrated optical system receives first to fourth portions of illumination scattered from the target, each having a corresponding first to fourth wavelength. The first to fourth grating couplers input the first to fourth portions into the waveguide system. The first and second wavelengths are different from the third and fourth wavelengths. The first detector receives a combination of the first and second portions to generate a first measurement signal. The second detector receives a combination of the third and fourth portions to generate a second measurement signal. The microstructure illumination adjuster includes first to fourth microstructure regions for directing the first to fourth portions to corresponding ones of the first to fourth grating couplers.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Patent Application No. 63 / 415,246, filed October 11, 2022, which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE INVENTION The present disclosure relates to alignment sensors for wafer positioning in inspection systems, for example, lithography apparatus and systems. [Background technology]

[0003] A lithographic apparatus is a machine that transfers a desired pattern onto a substrate, usually onto a target portion of the substrate. Lithographic apparatus are used, for example, in the manufacture of integrated circuits (ICs). In such cases, patterning devices such as masks or reticles can be used to create a circuit pattern to be formed in an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of one or several dies) on the substrate (e.g. a silicon wafer). The pattern is typically imaged onto a layer of radiation-sensitive material (photoresist or simply "resist") provided on the substrate. Typically, a single substrate will contain a network of adjacent target portions that are successively patterned. Known types of lithographic apparatus are called steppers and scanners. In a stepper, each target portion is irradiated by exposing the entire pattern onto the target portion at once. In a scanner, the radiation beam scans the pattern in a given direction (scan direction) and irradiates each target portion by scanning the target portion parallel or anti-parallel to the scan direction. Transfer of the pattern from the patterning device to the substrate can also be done by imprinting the pattern onto the substrate.

[0004] In a lithography process, different layers may be formed sequentially on a substrate in different processing steps. Therefore, the substrate may need to be positioned with high precision relative to previous patterns formed on it. Typically, alignment marks are placed on the substrate to be aligned and are positioned relative to a second object. Lithography equipment can use an alignment device to detect the position of the alignment marks and use them to align the substrate to ensure accurate exposure from the mask. The deviation between the alignment marks on two different layers is measured as the overlay error.

[0005] To monitor the lithography process, the alignment position of one or more alignment marks can be measured. Lithography systems are limited in the number of devices manufactured within a given timeframe due to several constraints. One example of a constraint is the speed of alignment measurements. While it is possible to implement multiple inspection sensors in parallel within a lithography tool to speed up the inspection of multiple targets, traditional sensors used for lithography metrology can be large and expensive due to their bulk optics, making them unscalable. Furthermore, optical inspection using multiple photon wavelengths presents several design challenges. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, it is desirable to improve manufacturing throughput and accuracy. For example, aspects of the optical systems described herein can be used to build scalable and highly accurate inspection systems that can simultaneously use multiple photon wavelengths.

[0007] In some embodiments, the inspection system may include an integrated optical system, first and second detectors, and a microstructure illumination adjuster. The integrated optical system may include a substrate, a waveguide system, and first, second, third, and fourth grating couplers. The integrated optical system may be configured to receive, direct, and combine first, second, third, and fourth portions of illumination scattered by the target. The first, second, third, and fourth portions may have corresponding first, second, third, and fourth wavelengths. The waveguide system may be disposed on the substrate. The first grating coupler may be disposed on the substrate and configured to couple a first portion into the waveguide system based on a first wavelength. The second grating coupler may be disposed on the substrate and configured to couple a second portion into the waveguide system based on a second wavelength. The first wavelength and the second wavelength may be the same. The third grating coupler may be disposed on the substrate and configured to couple a third portion into the waveguide system based on a third wavelength. The first wavelength and the third wavelength may be different. The fourth grating coupler may be disposed on the substrate and configured to input the fourth portion into the waveguide system based on the fourth wavelength. The third wavelength and the fourth wavelength may be the same. The first detector may be configured to receive the combination of the first portion and the second portion through the waveguide system and generate a first measurement signal including information on the phase delay of the first portion and the second portion. The second detector may be configured to receive the combination of the third portion and the fourth portion through the waveguide system and generate a second measurement signal including information on the phase delay of the third portion and the fourth portion. The microstructure illumination adjuster may include first, second, third, and fourth microstructure regions configured to direct corresponding ones of the first, second, third, and fourth portions to corresponding ones of the first, second, third, and fourth grating couplers.

[0008] In some embodiments, the inspection system may include an integrated optical system, first and second detectors, and a microstructure illumination adjuster. The integrated optical system may include a substrate, a waveguide system, and first and second grating couplers. The integrated optical system may be configured to receive, direct, and combine first and second portions of illumination scattered by the target. The first and second portions may have corresponding first and second wavelengths. The waveguide system may be disposed on the substrate. The first grating coupler may be disposed on the substrate and configured to couple a first portion into the waveguide system based on the first wavelength. The second grating coupler may be disposed on the substrate and configured to couple a second portion into the waveguide system based on the second wavelength. The first and second wavelengths may be different. The first detector may be configured to receive the first portion through the waveguide system and generate a first measurement signal based on the intensity of the first portion. The second detector may be configured to receive the second portion through the waveguide system and generate a second measurement signal based on the intensity of the second portion. The microstructured illumination adjuster can include first and second microstructured regions configured to direct corresponding ones of the first and second portions to corresponding ones of the first and second grating couplers.

[0009] In some embodiments, the lithographic apparatus can include an illumination system, a projection system, and an inspection system. The illumination system can be configured to illuminate a pattern on a patterning device. The projection system can be configured to project an image of the pattern onto a substrate. The inspection system can include an integrated optical system, first and second detectors, and a microstructure illumination adjuster. The integrated optical system can include a substrate, a waveguide system, and first and second grating couplers. The integrated optical system can be configured to receive, direct, and combine first and second portions of illumination scattered by a target on the substrate. The first and second portions can have corresponding first and second wavelengths. The waveguide system can be disposed on the substrate. The first grating coupler can be disposed on the substrate and configured to couple a first portion into the waveguide system based on the first wavelength. The second grating coupler can be disposed on the substrate and configured to couple a second portion into the waveguide system based on the second wavelength. The first and second wavelengths can be different. The first detector can be configured to receive the first portion through the waveguide system and generate a first measurement signal based on the intensity of the first portion. The second detector can be configured to receive the second portion through the waveguide system and generate a second measurement signal based on the intensity of the second portion. The microstructure illumination adjuster can include first and second microstructure regions configured to direct corresponding ones of the first and second portions to corresponding ones of the first and second grating couplers.

[0010] Further features of various aspects of the present disclosure are described in detail below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the particular aspects described herein. Such aspects will be apparent to those skilled in the relevant art based on the teachings contained herein. [Brief explanation of the drawings]

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the present disclosure and, together with the detailed description, serve to explain the principles of the disclosure and to enable one skilled in the relevant art to make and use the aspects described herein.

[0012] [Figure 1A] FIG. 1 illustrates a reflective lithographic apparatus according to some embodiments.

[0013] [Figure 1B] FIG. 1 illustrates a transmissive lithographic apparatus according to some embodiments.

[0014] [Figure 2] FIG. 1 illustrates a reflective lithographic apparatus in accordance with some embodiments in further detail.

[0015] [Figure 3] FIG. 1 illustrates a lithography cell according to some embodiments.

[0016] [Figure 4A] FIG. 1 illustrates an inspection apparatus according to some embodiments. [Figure 4B] FIG. 1 illustrates an inspection apparatus according to some embodiments.

[0017] [Figure 5] 1A and 1B illustrate an integrated optical system according to some embodiments. [Figure 6] 1A and 1B illustrate an integrated optical system according to some embodiments. [Figure 7] 1A and 1B illustrate an integrated optical system according to some embodiments. [Figure 8] 1A and 1B illustrate an integrated optical system according to some embodiments. [Figure 9] 1A and 1B illustrate an integrated optical system according to some embodiments.

[0018] [Figure 10A]FIG. 1 illustrates a periodic structure of a grating coupler according to some embodiments. [Figure 10B] FIG. 1 illustrates a periodic structure of a grating coupler according to some embodiments. [Figure 10C] FIG. 1 illustrates a periodic structure of a grating coupler according to some embodiments. [Figure 10D] FIG. 1 illustrates a periodic structure of a grating coupler according to some embodiments.

[0019] [Figure 11A] FIG. 1 illustrates a unit cell of a metasurface according to some embodiments. [Figure 11B] FIG. 1 illustrates a unit cell of a metasurface according to some embodiments.

[0020] Features of the present disclosure will become more apparent from the detailed description set forth below in conjunction with the drawings, in which like reference numerals identify corresponding elements throughout. Generally, like reference numerals in the drawings represent identical, functionally similar, and / or structurally similar elements. Furthermore, the leftmost digit(s) of a reference number generally identifies the drawing in which the reference number first appears. Unless otherwise specified, the drawings provided throughout this disclosure should not be construed as drawings to scale. DETAILED DESCRIPTION OF THE INVENTION

[0021] References to the embodiments described herein, and to terms such as "one embodiment," "one embodiment," "exemplary embodiment," "example embodiment," and the like, indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments necessarily include the particular feature, structure, or characteristic. Moreover, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with one embodiment, it is understood that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0022] Spatially relative terms such as "beneath," "below," "lower," "above," "on," "upper," and the like may be used herein to describe the relationship of one element or feature shown in the figures to another element or feature for ease of description. The spatially relative terms are intended to encompass various orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0023] As used herein, terms such as "about" and "approximately" may be used to indicate a value of a given quantity that may vary based on a particular technique. Based on a particular technique, terms such as "about" and "approximately" may indicate that the value of a given quantity varies, for example, within 10 to 30% of that value (e.g., ±10%, ±20%, or ±30% of that value).

[0024] Aspects of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Aspects of the present disclosure may also be implemented as instructions stored on a computer-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Furthermore, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such description is for convenience only and that such actions result from a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc. The term “machine-readable medium” may be used interchangeably with similar terms, such as “computer program product,” “computer-readable medium,” “non-transitory computer-readable medium,” etc. The term "non-transitory" is used herein to characterize one or more forms of computer-readable media other than transitory, propagating signals.

[0025] Before describing such aspects in more detail, it is helpful to present an exemplary environment in which aspects of the present disclosure can be implemented.

[0026] Lithography System Example

[0027] 1A and 1B respectively show lithographic apparatus 100 and lithographic apparatus 100' capable of implementing aspects of the present disclosure. Lithographic apparatus 100 and lithographic apparatus 100' each comprise: an illumination system (illuminator) IL that conditions a radiation beam B (e.g., deep ultraviolet radiation or extreme ultraviolet (EUV) radiation); a support structure (e.g., a mask table) MT configured to support a patterning device (e.g., a mask, reticle, or dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device; and a substrate table (e.g., a wafer table) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate. Lithographic apparatus 100 and lithographic apparatus 100' also comprise a projection system PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W. In lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In lithographic apparatus 100', the patterning device MA and the projection system PS are transmissive.

[0028] The illumination system IL may include various optical elements, or combinations thereof, such as refractive optical elements, reflective optical elements, catadioptric optical elements, magnetic optical elements, electromagnetic optical elements, electrostatic optical elements or other types of optical elements, to direct, shape or otherwise steer the radiation beam B.

[0029] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA relative to a reference frame, the design of at least one of lithographic apparatuses 100 and 100′, and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device MA. The support structure MT may, for example, be a frame or a table, which may be fixed or movable. By using sensors, the support structure MT can ensure that the patterning device MA is positioned at a desired position, for example with respect to the projection system PS.

[0030] The term "patterning device" MA may be broadly interpreted to refer to any device that can be used to impart a radiation beam B with a pattern in its cross-section to create a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a particular functional layer in a device being created in the target portion C to form an integrated circuit.

[0031] The patterning device MA can be transmissive (such as lithographic apparatus 100' in FIG. 1B) or reflective (such as lithographic apparatus 100 in FIG. 1A). Patterning devices MA include, for example, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. A programmable mirror array, for example, comprises a matrix arrangement of small mirrors, each individually tiltable so as to reflect an incoming radiation beam in different directions. The radiation beam is reflected by the matrix of small mirrors, imparted with a pattern by the tilted mirrors.

[0032] The term "projection system" PS can encompass any projection system including refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic optical elements, or a combination thereof, appropriate to the exposure radiation being used, or other factors such as the use of an immersion liquid or a vacuum on the substrate W. A vacuum environment can be used for EUV or electron beam radiation, as other gases can absorb the excess radiation or electrons. Therefore, a vacuum environment can be provided along the entire beam path with the aid of a vacuum wall and vacuum pumps.

[0033] Lithographic apparatus 100 and / or lithographic apparatus 100' may be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such a "multi-stage" apparatus, the additional substrate tables WT may be used in parallel, or exposure may be taking place on one or more tables while preparation steps are being performed on one or more other substrate tables WT. In some circumstances, the additional tables need not be substrate tables WT.

[0034] The lithographic apparatus can be of a type wherein at least a portion of the substrate is covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system and the substrate. Immersion liquids may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term "immersion", as used herein, does not imply that a structure such as a substrate must be immersed in liquid. For example, a liquid may be located between the projection system and the substrate during exposure.

[0035] 1A and 1B, the illuminator IL receives a radiation beam from a radiation source SO. The source SO and the lithographic apparatus 100, 100' may be separate physical entities, for example if the source SO is an excimer laser. In this case, the source SO is not considered to be part of the lithographic apparatus 100, 100' and the radiation beam B reaches the illuminator IL from the source SO via a beam delivery system BD (FIG. 1B). The beam delivery system BD may, for example, include appropriate redirecting mirrors and / or beam expanders. Alternatively, the source SO may be an integral part of the lithographic apparatus 100, 100', for example if the source SO is a mercury lamp. The radiation system may include the radiation source SO, the illumination apparatus IL, and / or the beam delivery system BD.

[0036] The illuminator IL may comprise an adjuster AD (FIG. 1B) for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial values ​​(commonly referred to as "σouter" and "σinner", respectively) of the irradiance distribution in a pupil plane of the illuminator are adjusted. In addition, the illuminator IL may comprise other elements, such as an integrator IN and a condenser CO (FIG. 1B). The illuminator IL is used to adjust the radiation beam B to obtain a desired uniformity and intensity distribution in its cross-section.

[0037] Referring to Figure 1A, a radiation beam B is incident on a patterning device (e.g., mask) MA, which is held on a support structure (e.g., mask table) MT, and is patterned by the patterning device. In lithographic apparatus 100, the radiation beam B is reflected from the patterning device (e.g., mask) MA. After reflecting from the patterning device (e.g., mask) MA, the radiation beam B passes through a projection system PS, which focuses the beam B onto a target portion C of a substrate W. With the aid of a second positioner PW and a position sensor IF2 (e.g., an interferometer, a linear encoder, a capacitance sensor, etc.), the substrate table WT is precisely moved (e.g., to position each of different target portions C in the path of the radiation beam B). Similarly, a first positioner PM and a further position sensor IF1 can be used to precisely position the patterning device (e.g., mask) MA relative to the path of the radiation beam B. Mask alignment marks M1, M2 and substrate alignment marks P1, P2 may be used to align patterning device (eg mask) MA and substrate W.

[0038] Referring to Figure 1B, a radiation beam B is incident on a patterning device (e.g., mask MA), which is held on a support structure (e.g., mask table MT), and is patterned by the patterning device. After passing the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of a substrate W. The projection system has a pupil conjugate PPU to an illumination system pupil IPU. A portion of the radiation arises from the intensity distribution in the illumination system pupil IPU and traverses the mask pattern without being affected by diffraction at the mask pattern, producing an image of the intensity distribution at the illumination system pupil IPU.

[0039] The projection system PS projects an image of the mask pattern MP onto a photoresist layer coated on the substrate W. The image is formed by diffracted beams generated from the mark pattern MP by radiation from the intensity distribution. For example, the mask pattern MP can include an array of lines and spaces. Non-zero-order diffraction of radiation at the array produces redirected diffracted beams that are redirected perpendicular to the lines. Non-diffracted beams (i.e., so-called zero-order diffracted beams) traverse the pattern without changing their direction of propagation. The zero-order diffracted beams traverse the upper lens or upper lens group of the projection system PS, which is upstream of the pupil conjugate PPU of the projection system PS, and reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU associated with the zero-order diffracted beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. The aperture device PD is, for example, arranged in a plane or substantially in a plane containing the pupil conjugate PPU of the projection system PS.

[0040] The projection system PS is positioned (e.g., using a lens or lens group L) to capture zero-order, first-order, and / or higher-order diffracted beams (not shown). In some embodiments, the resolution-enhancing effect of dipole illumination can be exploited by using dipole illumination to image a line pattern extending in a direction perpendicular to the line. For example, a first-order diffracted beam interferes with a corresponding zero-order diffracted beam at the wafer W level to produce an image of the line pattern MP at the highest possible resolution and process window (i.e., the usable depth of focus combined with the allowable exposure dose deviation). In some embodiments, astigmatism may be reduced by providing a radial pole (not shown) in an opposing quadrant of the illumination system pupil IPU. Furthermore, in some embodiments, astigmatism can be reduced by blocking the zero-order beam at the projection system pupil conjugate PPU associated with the radial pole in the opposing quadrant. This is described in more detail in U.S. Patent No. 7,511,799 B2, issued March 31, 2009, which is incorporated herein by reference in its entirety.

[0041] With the aid of the second positioner PW and a position sensor IFD (e.g. an interferometer, linear encoder, capacitive sensor, etc.), the substrate table WT can be accurately moved (e.g. to position a different target portion C in the path of the radiation beam B). Similarly, the mask MA can be accurately positioned with respect to the path of the radiation beam B (e.g. after a mask change from a mask library or during a scan) by means of the first positioner PM and another position sensor (not shown in Figure 1B).

[0042] In general, movement of the mask table MT may be realized by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized by means of a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected to the short-stroke module. Alternatively, the mask table MT may be fixed. The mask MA and substrate W may be aligned using mask alignment marks M1, M2 and / or substrate alignment marks P1, P2. Although the substrate alignment marks (as shown) occupy dedicated target portions, the substrate alignment marks may be located in the areas between the target portions (these are known as scribe-lane alignment marks). Similarly, in cases where the mask MA comprises more than one die, the mask alignment marks may be located between the dies.

[0043] The mask table MT and patterning device MA can be located within a vacuum chamber. An in-vacuum robot IVR can be used to move a patterning device, such as a mask, in and out of the vacuum chamber. Alternatively, the mask table MT and patterning device MA can be outside the vacuum chamber, and an ex-vacuum robot can be used for various transport tasks similar to the in-vacuum robot IVR. The in-vacuum and ex-vacuum robots can be calibrated for smooth transport of any payload (e.g., a mask) to a fixed kinematic mount in a transfer station.

[0044] Lithographic apparatus 100, 100' can be used in at least one of the following modes.

[0045] 1. In step mode, the support structure (e.g. mask table) MT and substrate table WT are kept substantially stationary while the entire pattern imparted to the radiation beam B is projected onto one target portion C in one go (i.e. a single static exposure), and the substrate table WT is then moved in the X and / or Y direction so that a different target portion C can be exposed.

[0046] 2. In scan mode, the support structure (e.g. mask table) MT and the substrate table WT are scanned synchronously (i.e. a single dynamic exposure) while a pattern imparted to the radiation beam is projected onto a target portion C. The velocity and direction of the substrate table WT relative to the support structure (e.g. mask table) MT is determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0047] 3. In another mode, the support structure (e.g. mask table) MT holds a programmable patterning device and is kept substantially stationary, while the substrate table WT is moved or scanned, while a pattern imparted to the radiation beam is projected onto a target portion C. A pulsed radiation source SO is used, and the programmable patterning device is updated as the substrate table WT moves during a scan, or as required between successive pulses. This mode of operation is applicable to maskless lithography using a programmable patterning device such as a programmable mirror array.

[0048] It is possible to operate in a combination of the above modes, to operate in a modified mode, or even to use a completely different mode.

[0049] In a further aspect, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) radiation source configured to generate a beam of EUV radiation for EUV lithography. Typically, the EUV radiation source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV radiation source.

[0050] Figure 2 shows lithographic apparatus 100 in more detail. EUV lithographic apparatus 100 includes a radiation collector apparatus SO, an illumination system IL, and a projection system PS. The radiation collector apparatus SO is constructed and arranged such that a vacuum environment can be maintained within an enclosure 220 of the radiation collector apparatus SO. An EUV radiation emitting plasma 210 is formed by a discharge plasma source. In some embodiments, a plasma of excited tin (Sn) (e.g. laser excited) is provided to generate EUV radiation.

[0051] Radiation emitted by the EUV radiation-emitting plasma 210 passes from the source chamber 211 through an optional gas barrier or contaminant trap 230 (sometimes referred to as a contaminant barrier or foil trap) to the collector chamber 212. The gas barrier or contaminant trap 230 is located at or behind the opening of the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant traps shown herein include at least a channel structure.

[0052] Collector chamber 212 includes a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation that passes through the radiation collector CO is reflected by a grating spectral filter 240 and focused onto a virtual point source INTF located at an opening in collector chamber 48. The virtual point source INTF is commonly referred to as an intermediate focus, and the source collector arrangement is positioned such that the intermediate focus INTF is located at or near opening 219 in enclosure 220. The virtual point source INTF is an image of the EUV radiation-emitting plasma 210. The grating spectral filter 240 is used to suppress, in particular, infrared (IR) radiation.

[0053] The radiation then traverses the illumination system IL, which may include a faceted field mirror device 222 and a faceted pupil mirror device 224 arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA, together with a desired radiation intensity uniformity at the patterning device MA. Reflection of the radiation beam 221 off the patterning device MA, which is held by the support structure MT, forms a patterned beam 226, which is imaged by the projection system PS via reflective elements 228, 229 onto a substrate W held by a wafer stage or substrate table WT.

[0054] Typically, more elements than shown may be present in the illumination optics unit IL and the projection system PS. A grating spectral filter 240 may optionally be present depending on the type of lithographic apparatus. Furthermore, more mirrors may be present than shown in Figure 2. For example, between one and six additional reflective elements may be present in the projection system PS than shown in Figure 2.

[0055] 2, the collector optical system CO is shown as a nested collector with grazing incidence reflectors 253, 254, and 255, just as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 are arranged axially symmetrically about the optical axis O, and this type of collector optical system CO is suitable for use in combination with a discharge plasma source, referred to as a DPP source.

[0056] Exemplary Lithography Cell

[0057] FIG. 3 illustrates a lithography cell 300, sometimes referred to as a lithocell or cluster, according to some embodiments. Lithography apparatus 100 or 100′ can form part of lithography cell 300. Lithography cell 300 may also include one or more apparatuses for performing pre-exposure and post-exposure processes on a substrate. Conventionally, these include a spin coater SC for depositing a resist layer, a developer DE for developing exposed resist, a chill plate CH, and a bake plate BK. A substrate handler or robot RO retrieves substrates from input / output ports I / O1 and I / O2, moves the substrates between different process tools, and delivers them to a loading bay LB of lithography apparatus 100 or 100′. These devices (often collectively referred to as a track) are under the control of a track control unit TCU, which is itself controlled by a supervisory control system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Thus, different equipment can be operated to maximize throughput and process efficiency.

[0058] Exemplary Inspection Equipment

[0059] To control the lithography process and accurately place device features on the substrate, alignment marks are typically provided on the substrate, and the lithography apparatus includes one or more inspection devices for accurately placing the marks on the substrate. These alignment devices are essentially position measurement devices. Different types of marks and different types of alignment devices and / or systems are known from different times and different manufacturers. A type of system widely used in current lithography apparatus is based on a self-referencing interferometer, as described in U.S. Pat. No. 6,961,116 (den Boef et al.). Typically, the marks are measured separately to obtain X and Y positions. However, combined X and Y measurements can be performed using techniques described in U.S. Publication No. 2009 / 195768 A (Bijnen et al.). The entire disclosures of both of these documents are incorporated herein by reference.

[0060] 4A shows a cross-sectional view of an inspection apparatus 400 that can be implemented as part of lithographic apparatus 100 or 100′ according to some embodiments. In some embodiments, inspection apparatus 400 may be configured to align a substrate (e.g., substrate W) with respect to a patterning device (e.g., patterning device MA). Inspection apparatus 400 may also be configured to detect the positions of alignment marks on the substrate and use the detected positions of the alignment marks to align the substrate with respect to the patterning device or other components of lithographic apparatus 100 or 100′. Such alignment of the substrate can ensure accurate exposure of one or more patterns on the substrate.

[0061] As used herein, terms such as "inspection apparatus," "metrology system," and the like may refer to, for example, devices used to measure characteristics of structures (e.g., overlay sensors, critical dimension sensors, etc.), devices or systems used to inspect the alignment of wafers in lithography apparatus (e.g., alignment sensors), and the like.

[0062] In some embodiments, the inspection apparatus 400 may include an illumination system 412, a beam splitter 414, an interferometer 426, a detector 428, a beam analyzer 430, and a processor 432. The illumination system 412 may be configured to provide an electromagnetic narrowband radiation beam 413 having one or more passbands. In one example, the one or more passbands may be within a wavelength spectrum between about 500 nm and about 900 nm. In another example, the one or more passbands may be discrete narrow passbands within a wavelength spectrum between about 500 nm and about 900 nm. The illumination system 412 may also be configured to provide one or more passbands with a substantially constant center wavelength (CWL) value over an extended period of time (e.g., over the lifetime of the illumination system 412). Such a configuration of the illumination system 412 may help prevent shifts in the actual CWL value from the desired CWL value in current alignment systems, as discussed above. Also, as a result, the use of a constant CWL value can improve the long-term stability and accuracy of the alignment system (eg, inspection tool 400) compared to current alignment tools.

[0063] In some embodiments, beam splitter 414 may be configured to receive radiation beam 413 and split radiation beam 413 into at least two radiation sub-beams. For example, as shown in FIG. 4A , radiation beam 413 may be split into radiation sub-beams 415 and 417. Beam splitter 414 may be further configured to direct radiation sub-beam 415 onto a substrate 420 disposed on a stage 422. In one example, stage 422 is movable along direction 424. Radiation sub-beam 415 may be configured to illuminate an alignment mark or target 418 located on substrate 420. Alignment mark or target 418 may be coated with a radiation-sensitive film. In some embodiments, alignment mark or target 418 may have 180-degree (i.e., 180°) symmetry. That is, if the alignment mark or target 418 is rotated 180° about an axis of symmetry perpendicular to the plane of the alignment mark or target 418, the rotated alignment mark or target 418 may be substantially identical to the non-rotated alignment mark or target 418. The target 418 on the substrate 420 may be (a) a resist layer grating including bars formed of solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlay target structure comprising a resist grating overlaid or interleaved on a product layer. Alternatively, the bars can be etched into the substrate. This pattern is susceptible to chromatic aberrations in the lithographic projection apparatus, particularly the projection system PL, and illumination symmetry and the presence of such aberrations will manifest themselves in variations in the printed grating. One in-line method used in device manufacturing for measuring linewidths, pitches, and critical dimensions utilizes a technique known as "scatterometry."Scatterometry methods are described in Raymond et al., "Multiparameter Grating Metrology Using Optical Scatterometry," J. Vac. Sci. Tech. B, Vol. 15, no. 2, pp. 361-368 (1997), and Niu et al., "Specular Spectroscopic Scatterometry in DUV Lithography," SPIE, Vol. 3677 (1999), both of which are incorporated herein by reference in their entirety. In scatterometry, light is reflected by periodic structures in a target, and the resulting reflectance spectrum at a given angle is detected. The structures giving rise to the reflectance spectrum are reconstructed, for example, using rigorous coupled wave analysis (RCWA) or by comparison with a library of patterns derived by simulation. Thus, scatterometry data of the printed grating is used to reconstruct the grating. Grating parameters, such as linewidth and shape, can be input to the reconstruction process, performed by the processing unit PU, from knowledge of the printing step and / or other scatterometry processes.

[0064] In some embodiments, beam splitter 414 may be further configured to receive diffracted radiation beam 419 and split diffracted radiation beam 419 into at least two radiation sub-beams according to an embodiment. As shown in Figure 4A, diffracted radiation beam 419 may be split into diffracted radiation sub-beams 429 and 439.

[0065] It should be noted that although beam splitter 414 is shown directing radiation sub-beam 415 towards alignment mark or target 418 and diffracted radiation sub-beam 429 towards interferometer 426, the disclosure is not limited in this respect. Other optical configurations can be used to achieve similar results in illuminating alignment mark or target 418 on substrate 420 and detecting an image of alignment mark or target 418.

[0066] 4A , interferometer 426 may be configured to receive radiation sub-beam 417 and diffracted radiation sub-beam 429 via beam splitter 414. In an exemplary embodiment, diffracted radiation sub-beam 429 may be at least a portion of radiation sub-beam 415 that may be reflected from alignment mark or target 418. In one example of this embodiment, interferometer 426 comprises any suitable set of optical elements, for example a combination of prisms, that may be configured to form two images of alignment mark or target 418 based on the received diffracted radiation sub-beam 429. It should be understood that good quality images need not be formed; it is sufficient that features of alignment mark 418 are resolved. Interferometer 426 may further be configured to rotate one of the two images by 180° relative to the other and interferometrically recombine the rotated and un-rotated images.

[0067] In some embodiments, detector 428 may be configured to receive the recombined image via interferometer signal 427 and detect interference resulting from the recombined image when alignment axis 421 of inspection apparatus 400 passes through a center of symmetry (not shown) of alignment mark or target 418. According to an exemplary embodiment, such interference may result from alignment mark or target 418 being 180° symmetric, causing the recombined images to constructively or destructively interfere. Based on the detected interference, detector 428 may be further configured to determine the position of the center of symmetry of alignment mark or target 418 and, consequently, detect the position of substrate 420. According to one example, alignment axis 421 may be aligned with a light beam that is perpendicular to substrate 420 and passes through the center of image rotation interferometer 426. Detector 428 may be further configured to estimate the position of alignment mark or target 418 by implementing sensor characteristics and interacting with wafer mark process variations.

[0068] In a further aspect, the detector 428 determines the location of the center of symmetry of the alignment mark or target 418 by performing one or more of the following measurements:

[0069] 1. Measuring the positional variation (positional shift between colors) for various wavelengths;

[0070] 2. Measuring the positional variation for the various orders (positional shift between diffraction orders), and

[0071] 3. Measuring the position variation (position shift between polarizations) for different polarizations.

[0072] This data can be obtained using any type of alignment sensor, such as a SMASH (Smart Alignment Sensor Hybrid) sensor, as described in U.S. Pat. No. 6,961,116, which employs a self-referencing interferometer with a single detector and four different wavelengths and extracts the alignment signal in software, or an Athena (Advanced Technology using High order ENhancement of Alignment) sensor, as described in U.S. Pat. No. 6,297,876, which directs each of the seven diffraction orders to a dedicated detector, both of which are incorporated herein by reference in their entirety.

[0073] In some aspects, the beam analyzer 430 may be configured to receive the diffracted radiation sub-beam 439 and determine its optical state. The optical state may be a measure of the beam wavelength, polarization, or beam profile. The beam analyzer 430 may also be configured to determine the position of the stage 422 and correlate the position of the stage 422 with the position of the center of symmetry of the alignment mark or target 418. Thus, the position of the alignment mark or target 418, and therefore the position of the substrate 420, may be precisely known relative to the stage 422. Alternatively, the beam analyzer 430 may be configured to determine the position of the inspection apparatus 400 or any other reference element such that the center of symmetry of the alignment mark or target 418 may be known relative to the inspection apparatus 400 or any other reference element. The beam analyzer 430 may be a point or imaging polarimeter with some form of wavelength band selectivity. In some embodiments, the beam analyzer 430 may be directly integrated into the inspection apparatus 400, or according to other embodiments, may be connected via some type of optical fiber, such as polarization-preserving single-mode, multimode, or imaging.

[0074] In some aspects, the beam analyzer 430 can be further configured to measure overlay data between two patterns on the substrate 420. One of these patterns can be a reference pattern on the reference layer. The other pattern can be an exposure pattern on the exposure layer. The reference layer can be an etched layer already present on the substrate 420. The reference layer can be generated by a reference pattern exposed on the substrate by the lithographic apparatus 100 and / or 100′. The exposure layer can be a resist layer exposed adjacent to the reference layer. The exposure layer can be generated by an exposure pattern exposed on the substrate 420 by the lithographic apparatus 100 or 100′. The exposure pattern on the substrate 420 can correspond to movement of the substrate 420 by the stage 422. In some aspects, the measured overlay data can also indicate an offset between the reference pattern and the exposure pattern. The measured overlay data can be used as calibration data to calibrate the exposure pattern exposed by lithography apparatus 100 or 100', so that after calibration, the offset between the exposure layer and the reference layer can be minimized.

[0075] In some embodiments, the beam analyzer 430 can be further configured to determine a model of the product stack profile of the substrate 420 and can be configured to measure the overlay, critical dimensions, and focus of the target 418 in a single measurement. The product stack profile contains information about the stacked products, such as the alignment marks, the target 418, or the substrate 420, and can also include optical signature measurements induced by mark processing variations, which are a function of illumination variations. The product stack profile can also include product grating profiles, mark stack profiles, and mark asymmetry information. One example of a beam analyzer 430 is the Yieldstar™ manufactured by ASML, Veldhoven, The Netherlands, as described in U.S. Patent No. 8,706,442, which is incorporated herein by reference in its entirety. The beam analyzer 430 can also be configured to process information related to specific characteristics of the exposure pattern within that layer. For example, the beam analyzer 430 may process overlay parameters of the image rendered within that layer (a measure of the accuracy of positioning of that layer relative to the previous layer on the substrate, or the accuracy of positioning of the first layer relative to a mark on the substrate), focus parameters, and / or critical dimension parameters (e.g., line width and its variation). Other parameters include image parameters related to the quality of the rendered image of the exposure pattern.

[0076] In some embodiments, a detector array (not shown) can be connected to the beam analyzer 430, allowing for accurate stack profile detection, as described below. For example, the detector 428 can be a detector array. Several options are possible for the detector array: a multimode fiber bundle, individual pin detectors per channel, or a CCD or CMOS (linear) array. Using a multimode fiber bundle allows for the placement of dissipating elements farther apart for stability reasons. Individual PIN detectors offer a large dynamic range, but each requires a separate preamplifier. Therefore, the number of elements is limited. A CCD linear array offers a large number of elements that can be read out at high speed and is particularly advantageous when phase-stepping detection is used.

[0077] In some embodiments, as shown in FIG. 4B , a second beam analyzer 430′ can be configured to receive the diffracted radiation sub-beam 429 and determine its optical state. The optical state can be a measure of the beam wavelength, polarization, or beam profile. The second beam analyzer 430′ can be identical to the beam analyzer 430. Alternatively, the second beam analyzer 430′ can be configured to perform one or more functions of the beam analyzer 430, such as determining the position of the stage 422 and correlating the position of the stage 422 with the position of the center of symmetry of the alignment mark or target 418. Thus, the position of the alignment mark or target 418, and therefore the position of the substrate 420, can be precisely known relative to the stage 422. The second beam analyzer 430′ can also be configured to determine the position of the inspection apparatus 400 or any other reference element, such that the center of symmetry of the alignment mark or target 418 can be known relative to the inspection apparatus 400 or any other reference element. The second beam analyzer 430′ can be further configured to determine overlay data between the two patterns and a model of the product stack profile of the substrate 420. The second beam analyzer 430′ can also be configured to measure the overlay, critical dimensions, and focus of the target 418 in a single measurement.

[0078] In some embodiments, the second beam analyzer 430' may be directly integrated into the inspection apparatus 400, or according to other embodiments, it may be connected via some type of optical fiber, such as polarization-preserving single-mode, multimode, or imaging. Alternatively, the second beam analyzer 430' and the beam analyzer 430 may be combined to form a single analyzer (not shown) configured to receive both diffracted radiation sub-beams 429 and 439 and determine their optical states.

[0079] In some embodiments, the processor 432 can receive information from the detector 428 and the beam analyzer 430 .

[0080] Examples of integrated optical systems using metasurfaces

[0081] In some embodiments, the term "throughput" can be used to characterize the speed of lithographic manufacturing. For example, throughput can refer to the rate at which lithographic manufacturing is completed on a wafer, the rate at which a wafer moves through a particular manufacturing step, and so on. Throughput can be a performance indicator of a lithographic apparatus. It is desirable for a lithographic system to output as many products as possible in the shortest possible time. Lithographic manufacturing can consist of multiple complex processes. Each process involves selecting techniques that compromise quality (e.g., sub-nanometer accuracy, high yield) and drawbacks (e.g., reduced manufacturing speed, cost). An example of a process aimed at improving accuracy is the inspection of marks printed on a substrate. As mentioned above, inspection equipment can be used to verify the conformance of a pattern printed on a substrate or to align a substrate to properly accept a new pattern. However, the inspection process can have a significant impact on throughput (e.g., requiring greater accuracy can result in longer inspection times, resulting in lower throughput). Further examples of integrated optical systems are described in International Publication No. WO 2021 / 058571, published April 1, 2021, the contents of which are incorporated herein by reference.

[0082] In some embodiments, multiple targets can be measured in conjunction with a lithography process. Increasing the inspection speed of multiple targets can improve throughput. While it is possible to implement multiple inspection sensors in parallel within a lithography apparatus to speed up the inspection of multiple targets, traditional sensors used in lithography metrology can be large and expensive due to their bulk optics, hindering scalability. A potential solution is to implement sensors that use a different operating principle, such as an integrated optics system. Terms such as “integrated optics,” “integrated optics system,” “integrated optical circuit,” “integrated photonics system,” and “photonic integrated circuit” can be used to refer to integrated devices capable of propagating optical signals. For example, an integrated optics device can include a waveguide disposed on a substrate. The waveguide can direct the optical signal to another region of the substrate, where it can be received and converted into measurement information. Integrated optics systems are significantly smaller and significantly less expensive than bulky free-space optics. As such, sensors based on integrated optics systems offer a scalable solution for improving the inspection speed of multiple marks.

[0083] FIG. 5 illustrates an integrated optical system 500 according to some embodiments. In some embodiments, the integrated optical system 500 can be used to replace at least a portion of the detection branch of the inspection apparatus 400 ( FIGS. 4A and 4B ). Terms such as “detection branch” can refer to a portion of the inspection apparatus that includes devices that direct and / or receive illumination scattered from a target (e.g., diffracted radiation beam 419 from target 418 ( FIGS. 4A and 4B )). Similarly, terms such as “illumination branch” can refer to a portion of the inspection apparatus that includes devices that illuminate and / or direct illumination toward a target (e.g., radiation sub-beam 415 toward target 418 ( FIGS. 4A and 4B )). It should be understood that the illumination branch can be implemented as an integrated optical system. In some embodiments, portions of the illumination branch and the detection branch can be implemented on the same substrate (e.g., a shared integrated optical system).

[0084] In some embodiments, integrated optical system 500 may include grating couplers 506 and 508 (e.g., first and second grating couplers) and waveguide system 504. The elements of integrated optical system 500 may be disposed on a substrate (not shown). Integrated optical system 500 may also include detector 526. Detector 526 may be an integrated element or a separate element (e.g., an element not integrated on the substrate). Waveguide system 504 may include combiner 523.

[0085] In some embodiments, enumerative adjectives (e.g., “first,” “second,” “third,” etc.) may be used to distinguish between similar elements without establishing an order, hierarchy, or quantity (unless otherwise noted). For example, the terms “first grating coupler” and “second grating coupler” may distinguish between two grating couplers without specifying a particular order, hierarchy, or upper or lower limit on the total number of grating couplers. Furthermore, the elements in the figures are not limited to particular enumerative adjectives. For example, grating coupler 506 may be referred to as a first grating coupler in one embodiment and a second grating coupler in another embodiment.

[0086] In some embodiments, the illumination source can generate illumination for illuminating the target (e.g., as described with reference to FIGS. 4A and 4B ). The target can scatter the illumination (e.g., one or more diffraction orders, 0th order, ±1st order, etc.). The scattered illumination is received by integrated optical system 500 and is shown as scattered illumination 520 and 522 (e.g., +1st and −1st diffraction orders, +2nd and −2nd diffraction orders, etc.). Scattered illumination 520 can be referred to as a first portion of the scattered illumination. Scattered illumination 522 can be referred to as a second portion of the scattered illumination. Grating coupler 506 can couple scattered illumination 520 to waveguide system 504. Grating coupler 508 can couple scattered illumination 522 to waveguide system 504. Combiner 523 can combine the received scattered illumination 520 and 522 (e.g., to perform interferometric measurements). The combined illumination can be received by detector 526. The detector 526 can generate a measurement signal based on the combined illumination.

[0087] It is instructive to review an overview of a process for performing measurements that rely on changing illumination characteristics (e.g., interferometric measurements). As the illumination spot is moved / scanned over the target 418 (FIGS. 4A and 4B), the phase of the scattered illuminations 520 and 522 may change over time due to the scanning. Because the scattered illuminations 520 and 522 are interfered with (by the combiner 523), the illumination detected by the detector 526 may have AC modulation characteristics due to the scanning motion of the illumination spot. That is, the measurement signal generated by the detector 526 may be an AC signal. From the AC characteristics (e.g., intensity) of the measurement signal, characteristics (e.g., alignment position) of the target 418 (FIGS. 4A and 4B) can be determined. Characteristics include the phase and / or amplitude of the modulation of the signal intensity. For example, the measurement signal may contain information about the phase delay of the scattered illuminations 520 and 522. From there, characteristics of the inspection target (e.g., target position) can be determined.

[0088] In some embodiments, optical inspection of targets on a wafer can be performed using illumination of multiple colors (or wavelengths). Particular wavelengths can provide information about a target that is not readily apparent at other wavelengths. As used herein, concepts such as "multiple wavelengths," "multiple photon frequencies," and "multiple parameter values" can be used to characterize narrow band values ​​in a related property or parameter. As a non-limiting example of a wavelength parameter, a first wavelength can be characterized as including a narrow band having a first center wavelength. A second wavelength can similarly be characterized as including a narrow band having a second center wavelength. A characterization of a first wavelength as different from a second wavelength can be interpreted as the first center wavelength being different from the second center wavelength.

[0089] It will be appreciated that in some embodiments, the combiner and detector can be scaled to accommodate the number of grating couplers, and implementations with additional grating couplers are described with reference to Figures 6-9.

[0090] In some embodiments, illuminating a target with multiple wavelengths can impose constraints on the layout of the grating coupler, an example of which is described below with reference to FIG.

[0091] Figure 6 illustrates an integrated optical system 600 according to some embodiments. In some embodiments, the integrated optical system 600 can have a structure and function similar to that of the integrated optical system 500 described with reference to Figure 5. Therefore, unless otherwise noted, descriptions of elements in Figure 5 also apply to corresponding elements in Figure 6 (e.g., reference numbers sharing the rightmost two digits) and will not be exactly reintroduced. Examples of such elements in Figure 6 include grating couplers 606 and 608 and luminaires 620 and 622.

[0092] In some embodiments, the integrated optical system 600 can include a substrate 602 on which grating couplers 606 and 608 are disposed. Each of the grating couplers 606 and 608 is a plurality of grating couplers. For example, the grating coupler 606 is illustrated and labeled as 606-1 and 606-n (n=2 in the non-limiting example shown in FIG. 6 , i.e., n may be greater than or equal to 2). Similarly, the grating coupler 608 is illustrated and labeled as 608-1 and 608-2. The introduction of the additional grating coupler compared to FIG. 5 is to consider the sensitivity of the grating coupler structure to different wavelengths. That is, the grating coupler can be designed to have a predetermined structural size and a predetermined shape so that illumination of a specific wavelength can be injected into the waveguide. Different grating couplers with different structural parameters can be used for different wavelengths (e.g., a first grating coupler can inject illumination of a first wavelength into the waveguide system based on the first wavelength).

[0093] In some embodiments, illumination beam 616 is directed toward target 618 (e.g., a grating target, alignment mark, etc.). Interaction between illumination beam 616 and target 618 scatters the illumination along diffraction orders. The scattering angle depends on the wavelength of illumination beam 616. For example, at a first wavelength (denoted by the subscript n=1), the scattered illumination is divided into scattered illumination 620-1 and 622-1. This can be understood as +diffraction and -diffraction of the same order (e.g., +1 and -1, +2 and -2, etc.). The diffraction angle of scattered illumination 620-1 and 622-1 is denoted by α. At a second wavelength (denoted by the subscript n=2), the scattered illumination is divided into scattered illumination 620-2 and 622-2. The diffraction angle of scattered illumination 620-2 and 622-2 is denoted by β. Scattered illumination 620-1, 620-2, 622-1, and 622-2 (e.g., first, second, third, and fourth portions of the scattered illumination) are incident on a waveguide system (e.g., waveguide system 504 (FIG. 5)) for subsequent detection and analysis.

[0094] To more clearly illustrate some of the problems and solutions, it is instructive to consider a non-limiting example in which the diffraction order is limited to one (i.e., +1 or -1). Variations with wavelength can be better understood by eliminating variations in the diffraction order (e.g., by eliminating the difference in diffraction angles associated with the first and second orders).

[0095] In some embodiments, the illumination beam 616 can include multiple wavelengths. Some commercially available alignment sensors can inspect alignment marks using 12 wavelengths covering a spectrum including infrared (IR), visible light, and ultraviolet (UV). When a broad wavelength spectrum is used, the target 618 can scatter illumination along a wide range of diffraction angles. Problems can arise at large diffraction angles, beyond the angle β shown in FIG. 6. The placement of the grating couplers depends on the diffraction angle. Depending on the location of the grating couplers, the footprint of the integrated optical system 600 can increase, which is counter to the goal of miniaturizing the inspection system. Another problem is that some grating couplers may need to be placed so close together that they collide (overlap). This can occur when the diffraction angles of the two wavelengths are close and the beam cross-sections of each wavelength at the target are large (e.g., α and β can be similar if the two wavelengths are similar and / or the grating pitch is large). This results in overlap between the beams of the two wavelengths. Aspects of the present disclosure address such problems arising from the use of multiple wavelengths.

[0096] FIG. 7 illustrates an integrated optical system 700 according to some embodiments. In some embodiments, the integrated optical system 700 can have a structure and function similar to the integrated optical systems 500 and 600 described with reference to FIGS. 5 and 6. Therefore, unless otherwise noted, descriptions of elements in FIGS. 5 and 6 are also applicable to corresponding elements in FIG. 7 (e.g., reference numbers sharing the rightmost two digits) and will not be precisely reintroduced. Examples of such elements in FIG. 7 can include a substrate 702, grating couplers 706-1, 706-2, 708-1, and 708-2, an illumination beam 716, a target 718, and scattered illumination 720-1, 720-2, 722-1, and 722-2.

[0097] In some embodiments, the integrated optical system 700 can include a microstructured illumination adjuster 710 including microstructured regions 712-1, 712-2, 714-1, and 714-2 (as mentioned above, the subscripts 1, 2, ..., n can indicate associations with different wavelengths). The microstructured illumination adjuster 710 can be disposed on the substrate 702. The microstructured illumination adjuster 710 can be disposed between the substrate 702 and the target 718. The microstructured region 712-1 can be disposed on the path of scattered illumination 720-1 having a diffraction angle α (e.g., a first portion of the scattered illumination from the target 718). The structure of the microstructured region 712-1 can be designed to direct the scattered illumination 720-1 toward the grating coupler 706-1. The structure of the microstructured region 712-2 can be designed to direct the scattered illumination 720-2 toward the grating coupler 706-2. The structure of microstructure region 714-1 can be designed so that scattered illumination 722-1 is directed toward grating coupler 708-1. The structure of microstructure region 714-2 can be designed so that scattered illumination 722-2 is directed toward grating coupler 708-2. In other words, the first, second, third, and fourth microstructure regions can direct corresponding ones of the first, second, third, and fourth portions of the scattered illumination toward corresponding ones of the first, second, third, and fourth grating couplers.

[0098] In some embodiments, the microstructured regions 712-1, 712-2, 714-1, and 714-2 can include diffraction gratings specifically designed for the individual wavelengths used in the illumination beam 716. For example, the microstructured regions can be diffraction gratings or metasurfaces. In the case of diffraction gratings, the linewidth and / or spacing of the diffraction grating can be on the order of the corresponding wavelength of the illumination beam 716.

[0099] FIG. 8 illustrates an integrated optical system 800 according to some embodiments. In some embodiments, the integrated optical system 800 may have a structure and function similar to the integrated optical systems 500, 600, and 700 described with reference to FIGS. 5-7. Therefore, unless otherwise noted, descriptions of elements in FIGS. 5-7 also apply to corresponding elements in FIG. 8 (e.g., reference numbers sharing the rightmost two digits) and will not be exactly reintroduced. Examples of such elements are illustrated in FIG. 8. FIG. 8 may include a substrate 802, grating couplers 806-1, 806-2, 808-1, and 808-2, a microstructure illumination adjuster 810, microstructure regions 812-1, 812-2, 814-1, and 814-2, an illumination beam 816, a target 818, and scattered illumination 820-1, 820-2, 822-1, and 822-2.

[0100] In some embodiments, the number of wavelengths n shown in Figure 8 is increased to three (non-limiting example, more wavelengths can be used) compared to the two wavelengths shown in Figure 7. Accordingly, additional grating couplers, such as grating couplers 806-3 and 808-3 (806-n and 808-n, where n=3), are disposed on substrate 802. The diffraction angle associated with the third wavelength is denoted γ.

[0101] In some embodiments, the microstructure illumination adjuster 810 is a metasurface array, and the microstructure region can be a metasurface region. The metasurface can include a spatially varying metasurface. A metasurface is a type of metamaterial. A metamaterial is a type of functional material designed with microscale and / or nanoscale patterns or structures. The structural patterns can affect illumination to interact with the metamaterial in a different way than traditional non-patterned materials (one example of an interaction with traditional non-patterned materials is refraction at a glass interface). Some examples of microscale and nanoscale patterns of metasurfaces are described with reference to FIG. 10.

[0102] In some embodiments, the structure of the metasurface can be designed to adjust the phase, amplitude, and / or polarization of the illumination received by the metasurface, which can control the direction of the radiation it receives based on adjusting the phase, amplitude, and / or polarization of the incident beam.

[0103] In some embodiments, the use of microstructured regions can avoid the use of large lenses to adjust illumination. In conventional optical sensors, large optics such as lenses tend to increase the size of the sensor, which is counter to the goal of miniaturization. Because metasurfaces can change the phase, amplitude, and / or polarization of illumination in a predictable manner, metasurfaces can adjust illumination (e.g., collimate, focus, phase correct, correct optical aberrations, etc.) without relying on large optics. That is, in some embodiments, no lenses are disposed between the microstructured illumination adjuster 810 and the target 818.

[0104] In some embodiments, the microstructured illumination adjuster 810 can be disposed on the substrate 802. The microstructured illumination adjuster 810 can include a transparent bulk material having a thickness such that a space for illumination propagation is formed between the microstructured illumination adjuster 810 and the substrate 802. The microstructured regions 812-1, 812-2, 812-3, 814-1, 814-2, and 814-3 can include metasurfaces that direct scattered radiation 820-1, 820-2, 820-3, 822-1, 822-2, and 822-3, respectively, toward corresponding grating couplers 806-1, 806-2, 806-3, 808-1, 808-2, and 808-3.

[0105] Figure 9 illustrates an integrated optical system 900 according to some embodiments. In some embodiments, the integrated optical system 900 may have a structure and function similar to the integrated optical systems 500, 600, 700, and 800 described with reference to Figures 5-8. Therefore, unless otherwise noted, the descriptions of elements in Figures 5-8 also apply to corresponding elements in Figure 9 (e.g., reference numbers sharing the rightmost two digits) and are not exactly reintroduced. Examples of such elements in FIG. 9 can include substrate 902, grating couplers 906-1, 906-2, 906-3, 908-1, 908-2, and 908-3, microstructure illumination adjuster 910, microstructure regions 912-1, 912-2, 912-3, 914-1, 914-2, and 914-3, illumination beam 916, target 918, scattered illumination 920-1, 920-2, 920-3, 922-1, 922-2, and 922-3.

[0106] In some embodiments, the microstructure illumination adjuster 910 can be designed to direct and / or split illumination based on the polarization of the illumination. The scattered illumination 920-1, 920-2, 920-3, 922-1, 922-2, and 922-3 can each be polarized in a predetermined direction. The interaction of the scattered illumination 920-1, 920-2, 920-3, 922-1, 922-2, and 922-3 with the microstructure regions 912-1, 912-2, 912-3, 914-1, 914-2, and 914-3 splits the scattered illumination 920-1, 920-2, 920-3, 922-1, 922-2, and 922-3 into two. The split scattered illumination can be separated into orthogonal polarization components.

[0107] In some embodiments, the number of grating couplers is doubled because the splitting of polarization components doubles the illumination paths (e.g., 12 as shown in FIG. 9 compared to 6 as shown in FIG. 8). The additional grating couplers are labeled with primes (e.g., grating couplers 906-1′, 906-2′, 906-3′, 908-1′, 908-2′, and 908-3′). In this way, the direction of scattered illumination can be engineered using metasurfaces. As a result, designers of integrated optical system 900 have more freedom regarding the optimal placement of grating couplers, allowing them to make integrated optical system 900 as compact as possible.

[0108] 5-9 illustrate interferometric inspection systems that analyze input from two opposite diffraction orders (e.g., +1 and −1 orders). However, the present disclosure is not limited to such paired detection. For example, unpaired grating coupler embodiments can also implement the microstructure illumination adjuster. As a non-limiting example, an embodiment can implement the right half of FIG. 8 without the left side (e.g., implementing grating couplers 806-1, 806-2, and / or 806-3 with microstructure regions 812-1, 812-2, and / or 812-3, and omitting the grating coupler and metasurface region on the left side of target 818).

[0109] In some embodiments, the ability to optically inspect a target using different illumination parameters (e.g., different wavelengths and / or polarizations) simultaneously allows for increased throughput by reducing inspection time. For example, a slower optical inspection method may involve using an illumination beam 916 that cycles through different wavelengths one at a time.

[0110] 10A, 10B, 10C, and 10D show periodic structures of grating couplers according to some embodiments. In some embodiments, the grating coupler can be composed of periodic blocks or lines ( FIG. 10A ). The grating coupler can be composed of a sawtooth-like periodic structure ( FIG. 10B ). The grating coupler can be composed of a unit cell and a compound periodic structure with additional structural features within the unit cell ( FIG. 10C ). FIG. 10D is similar to FIG. 10A but has a smaller periodicity. The pitch Λ of the periodic structure (or unit cell) can correspond to one wavelength λ (or more) of the wavelength used in the optical inspection operation.

[0111] 11A and 11B show a unit cell 1124 of a metasurface according to some embodiments. In some embodiments, the unit cell 1124 can include unit cell structures 1126 and 1128 (e.g., first and second unit cell structures). The unit cell structures 1126 and 1128 can each have a rectangular parallelepiped shape and volume. The unit cell structures 1126 and 1128 are not limited to a rectangular parallelepiped shape and volume. For example, they may be elliptical, asymmetric, etc. The unit cell 1124 is not limited to two substructures. For example, there can be one or more structures (e.g., three structures). The shape and number of structures can be designed to produce a desired interaction between the metasurface and incident light. The unit cell structure 1126 can have a height h, a length L1, and a width W1. The unit cell structure 1128 can have a height (e.g., equal to or unequal to h), a length L2, and a width W2. Unit cell structure 1126 can have a different size than unit cell structure 1128. Unit cell structures 1126 and 1128 can be separated by a gap g. One or both of unit cell structures 1126 and 1128 can be tilted at an angle θ with respect to the plane of the metasurface. Unit cell 1124 can be repeated throughout the metasurface to form a periodic structure.

[0112] The embodiments can be further described using the following clauses. 1. An inspection system comprising: an integrated optical system configured to receive, direct, and combine first, second, third, and fourth portions of illumination scattered by a target, the first, second, third, and fourth portions having corresponding first, second, third, and fourth wavelengths; A substrate; a waveguide system disposed on the substrate; a first grating coupler disposed on the substrate and configured to couple the first portion into the waveguide system based on the first wavelength; a second grating coupler disposed on the substrate and configured to couple the second portion into the waveguide system based on the second wavelength, the first wavelength and the second wavelength being the same; a third grating coupler disposed on the substrate and configured to couple the third portion into the waveguide system based on the third wavelength, the first wavelength and the third wavelength being different; a fourth grating coupler disposed on the substrate and configured to couple the fourth portion into the waveguide system based on the fourth wavelength, wherein the third wavelength and the fourth wavelength are the same; a first detector configured to receive the combination of the first portion and the second portion via the waveguide system and generate a first measurement signal containing information about the phase delay of the first portion and the second portion; a second detector configured to receive the combination of the third portion and the fourth portion via the waveguide system and generate a second measurement signal containing information about the phase delay of the third portion and the fourth portion; a microstructure illumination adjuster including first, second, third, and fourth microstructure regions configured to direct corresponding ones of the first, second, third, and fourth portions to corresponding ones of the first, second, third, and fourth grating couplers. 2. Analyzing the first and second measurement signals; determining a position of the target based on information of the phase delays of the first, second, third, and fourth portions; Item 1. The inspection system of item 1, further comprising a processor configured to: 3. The inspection system comprises: directing illumination toward the target to generate the first, second, third, and fourth portions; scanning the directed illumination across the target; Item 1. The inspection system according to item 1, wherein the optical system is configured as follows: 4. the integrated optical system is further configured to receive, direct, and combine fifth and sixth portions of illumination scattered by the target, the fifth and sixth portions having corresponding fifth and sixth wavelengths; The integrated optical system further comprises: a fifth grating coupler disposed on the substrate and configured to couple the fifth portion into the waveguide system based on the fifth wavelength, the fifth wavelength being different from the first and third wavelengths; a sixth grating coupler disposed on the substrate and configured to couple the sixth portion into the waveguide system based on the sixth wavelength, wherein the fifth wavelength and the sixth wavelength are the same; the inspection system further comprising a third detector configured to receive the combination of the fifth and sixth portions via the waveguide system and generate a third measurement signal containing information about the phase delay of the fifth and sixth portions; Item 1, an inspection system as described in Item 1, wherein the microstructure illumination adjuster further comprises fifth and sixth microstructure regions configured to direct corresponding ones of the fifth and sixth portions to corresponding ones of the fifth and sixth grating couplers. 5. The inspection system of item 1, wherein at least the first microstructured region of the microstructured illumination adjuster is polarization sensitive and configured to split and direct illumination based on polarization. 6. The inspection system of claim 1, wherein the first, second, third, and fourth microstructure regions are diffraction gratings. 7. The inspection system described in item 1, wherein the microstructure illumination adjuster is a metasurface array, and the first, second, third, and fourth microstructure regions are metasurface regions. 8. The inspection system of claim 7, wherein the metasurface region includes a periodic structure configured to adjust the phase, amplitude, and / or polarization of the first, second, third, and fourth portions. 9. The inspection system of claim 8, wherein the metasurface region is configured to control the orientation of the first, second, third, and fourth portions based on adjusting phase, amplitude, and / or polarization. 10. The inspection system described in paragraph 7, wherein the metasurface region is configured to control focus or optical aberrations of the first, second, third, and fourth portions and / or apply phase corrections to the first, second, third, and fourth portions. 11. The inspection system of claim 1, wherein no lens is disposed between the microstructure illumination adjuster and the target. 12. An inspection system comprising: an integrated optical system configured to receive, direct, and combine first and second portions of illumination scattered by a target, the first and second portions having corresponding first and second wavelengths; A substrate; a waveguide system disposed on the substrate; a first grating coupler disposed on the substrate and configured to couple the first portion into the waveguide system based on the first wavelength; a second grating coupler disposed on the substrate and configured to couple the second portion into the waveguide system based on the second wavelength, the first wavelength and the second wavelength being different; a first detector configured to receive the first portion through the waveguide system and generate a first measurement signal based on the intensity of the first portion; a second detector configured to receive the second portion through the waveguide system and generate a second measurement signal based on the intensity of the second portion; a microstructure illumination adjuster including first and second microstructure regions configured to direct corresponding ones of the first and second portions to corresponding ones of the first and second grating couplers. 13. Analyzing the first and second measurement signals; determining a characteristic of the target based on the intensities of the first and second portions; Item 13. The inspection system of item 12, further comprising a processor configured to: 14. The inspection system comprises: directing illumination toward the target to generate the first and second portions; scanning the directed illumination across the target; Item 13. The inspection system according to item 12, wherein the optical system is configured as follows. 15. The integrated optical system is further configured to receive, direct, and combine a third portion of the illumination scattered by the target, the third portion having a corresponding third wavelength; The integrated optical system further comprises a third grating coupler disposed on the substrate and configured to couple the third portion into the waveguide system based on the third wavelength, the third wavelength being different from the first and second wavelengths; the inspection system further comprising a third detector configured to receive the third portion through the waveguide system and generate a third measurement signal based on an intensity of the third portion; Item 13. The inspection system of item 12, wherein the microstructure illumination adjuster further comprises a third microstructure region configured to direct the third portion to the third grating coupler. 16. The inspection system described in paragraph 12, wherein the microstructure illumination adjuster is a metasurface array, and the first and second microstructure regions are metasurface regions including periodic structures configured to adjust the phase, amplitude, and / or polarization of the first and second portions. 17. The inspection system described in paragraph 16, wherein the metasurface region is configured to control the orientation of the first and second portions based on adjusting phase, amplitude, and / or polarization. 18. The inspection system described in paragraph 16, wherein the metasurface region is configured to control the focus of the first and second portions and / or apply phase correction. 19. The inspection system of claim 12, wherein no lens is disposed between the microstructure illumination adjuster and the target. 20. An illumination system configured to illuminate a pattern on a patterning device; a projection system configured to project an image of the pattern onto a substrate; an inspection system, wherein the inspection system comprises: an integrated optical system configured to receive, direct, and combine first and second portions of illumination scattered by a target on the substrate, the first and second portions having corresponding first and second wavelengths; A substrate; a waveguide system disposed on the substrate; a first grating coupler disposed on the substrate and configured to couple the first portion into the waveguide system based on the first wavelength; a second grating coupler disposed on the substrate and configured to couple the second portion into the waveguide system based on the second wavelength, the first wavelength and the second wavelength being different; a first detector configured to receive the first portion through the waveguide system and generate a first measurement signal based on the intensity of the first portion; a second detector configured to receive the second portion through the waveguide system and generate a second measurement signal based on the intensity of the second portion; a microstructure illumination adjuster including first and second microstructure regions configured to direct corresponding ones of the first and second portions to corresponding ones of the first and second grating couplers.

[0113] As used herein, terms such as "radiation," "beam," "light," and "illumination" may refer to one or more types of electromagnetic radiation, such as ultraviolet (UV) radiation (e.g., with a wavelength λ of 365, 248, 193, 157, or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (e.g., with a wavelength in the 5-100 nm range, e.g., 13.5 nm), or hard X-rays operating at less than 5 nm, as well as particle radiation such as ion beams and electron beams. Generally, radiation having a wavelength of about 400 to about 700 nm is considered visible radiation, while radiation having a wavelength of about 780 to 3000 nm (or longer) is considered infrared. UV refers to radiation having a wavelength of about 100 to 400 nm. In lithography, the term "UV" also applies to wavelengths that can be produced by mercury discharge lamps, i.e., G-line at 436 nm, H-line at 405 nm, and / or I-line at 365 nm. Vacuum UV (VUV), or gas-absorbed UV, refers to radiation having a wavelength of approximately 100-200 nm. Deep UV (DUV) generally refers to radiation having a wavelength of 126 nm to 428 nm, and in some embodiments, excimer lasers can generate DUV radiation for use in lithography equipment. For example, radiation having a wavelength in the 5-20 nm range should be understood to refer to radiation having a specific wavelength band, at least a portion of which is in the 5-20 nm range. Some alignment sensors can use wavelengths in the 500-900 nm range.

[0114] While some aspects of the present disclosure are described in the context of a lithography apparatus in ICE manufacturing, it should be understood that the lithography apparatus described herein can also be used in other applications, such as the manufacture of integrated optical systems, magnetic domain memory guidance and detection patterns, flat panel displays, LCDs, thin-film magnetic heads, and the like. Those skilled in the art will appreciate that, in the context of such alternative applications, the use of the terms “wafer” or “die” herein can be considered specific examples of the more general terms “substrate” or “target portion,” respectively. The substrate can be processed before or after exposure, for example, in a track unit (a tool that typically applies a resist layer to the substrate and develops the exposed resist) and / or a metrology unit. Where applicable, aspects disclosed herein can be applied to such and other substrate processing tools. Furthermore, a substrate can also be processed multiple times, for example, to form a multi-layer IC; thus, the term “substrate” as used herein can also refer to a substrate that already includes multiple processed layers.

[0115] Additionally, while some aspects of the present disclosure are described in the context of optical lithography, it should be understood that aspects of the present disclosure are not limited to optical lithography. For example, in imprint lithography, a topography in a patterning device defines a pattern formed on a substrate. The topography of the patterning device is pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is moved from the resist leaving a pattern behind.

[0116] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, and therefore should be interpreted by one skilled in the relevant art in light of the teachings herein.

[0117] The present disclosure has been described above in terms of functional elements illustrating the performance of certain functions and their relationships. The boundaries of these functional elements have been arbitrarily defined herein for convenience of description. Alternate boundaries may be defined so long as the specified functions and their relationships are appropriately performed. The above description of specific embodiments sufficiently reveals the general nature of the present disclosure, such that those skilled in the art can readily modify and / or adapt such specific embodiments for various uses by applying their own knowledge without undue experimentation and without departing from the general concept of the disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0118] It is understood that the Detailed Description section, and not the Abstract and Summary sections, is intended to be used to interpret the claims. The Summary and Summary sections describe one or more aspects of the disclosure as contemplated by the inventors, but do not necessarily describe every aspect. As such, they are not intended to limit the scope of the disclosure and the appended claims in any way. The scope of protection should not be limited by any of the above aspects, but should instead be defined according to the following claims and their equivalents.

Claims

1. 1. An inspection system comprising: an integrated optical system configured to receive, direct, and combine first, second, third, and fourth portions of illumination scattered by a target, the first, second, third, and fourth portions having corresponding first, second, third, and fourth wavelengths; A substrate; a waveguide system disposed on the substrate; a first grating coupler disposed on the substrate and configured to couple the first portion into the waveguide system based on the first wavelength; a second grating coupler disposed on the substrate and configured to couple the second portion into the waveguide system based on the second wavelength, the first wavelength and the second wavelength being the same; a third grating coupler disposed on the substrate and configured to couple the third portion into the waveguide system based on the third wavelength, the first wavelength and the third wavelength being different; a fourth grating coupler disposed on the substrate and configured to couple the fourth portion into the waveguide system based on the fourth wavelength, wherein the third wavelength and the fourth wavelength are the same; a first detector configured to receive the combination of the first portion and the second portion via the waveguide system and generate a first measurement signal containing information about the phase delay of the first portion and the second portion; a second detector configured to receive the combination of the third portion and the fourth portion via the waveguide system and generate a second measurement signal containing information about the phase delay of the third portion and the fourth portion; a microstructure illumination adjuster including first, second, third, and fourth microstructure regions configured to direct corresponding ones of the first, second, third, and fourth portions to corresponding ones of the first, second, third, and fourth grating couplers.

2. analyzing the first and second measurement signals; determining a position of the target based on information of the phase delays of the first, second, third, and fourth portions; The inspection system of claim 1 , further comprising a processor configured to:

3. The inspection system includes: directing illumination toward the target to generate the first, second, third, and fourth portions; scanning the directed illumination across the target; 10. The inspection system of claim 1, wherein the optical system is configured as follows:

4. the integrated optical system is further configured to receive, direct, and combine fifth and sixth portions of illumination scattered by the target, the fifth and sixth portions having corresponding fifth and sixth wavelengths; The integrated optical system further comprises: a fifth grating coupler disposed on the substrate and configured to launch the fifth portion into the waveguide system based on the fifth wavelength, the fifth wavelength being different from the first and third wavelengths; a sixth grating coupler disposed on the substrate and configured to couple the sixth portion into the waveguide system based on the sixth wavelength, wherein the fifth wavelength and the sixth wavelength are the same; the inspection system further comprising a third detector configured to receive the combination of the fifth and sixth portions via the waveguide system and generate a third measurement signal containing information about the phase delay of the fifth and sixth portions; 2. The inspection system of claim 1, wherein the microstructure illumination adjuster further comprises fifth and sixth microstructure regions configured to direct corresponding ones of the fifth and sixth portions to corresponding ones of the fifth and sixth grating couplers.

5. The inspection system of claim 1 , wherein at least the first microstructured region of the microstructured illumination adjuster is polarization sensitive and configured to split and direct illumination based on polarization.

6. The inspection system of claim 1 , wherein the first, second, third, and fourth microstructured regions are diffraction gratings.

7. 10. The inspection system of claim 1, wherein the microstructure illumination adjuster is a metasurface array, and the first, second, third, and fourth microstructure regions are metasurface regions.

8. 8. The inspection system of claim 7, wherein the metasurface region includes a periodic structure configured to adjust the phase, amplitude, and / or polarization of the first, second, third, and fourth portions.

9. 10. The inspection system of claim 8, wherein the metasurface region is configured to control orientation of the first, second, third, and fourth portions based on tuning of phase, amplitude, and / or polarization.

10. 8. The inspection system of claim 7, wherein the metasurface region is configured to control focus or optical aberrations of the first, second, third, and fourth portions and / or apply phase corrections to the first, second, third, and fourth portions.

11. The inspection system of claim 1 , wherein no lens is disposed between the microstructure illumination adjuster and the target.

12. 1. An inspection system comprising: an integrated optical system configured to receive, direct, and combine first and second portions of illumination scattered by a target, the first and second portions having corresponding first and second wavelengths; A substrate; a waveguide system disposed on the substrate; a first grating coupler disposed on the substrate and configured to couple the first portion into the waveguide system based on the first wavelength; a second grating coupler disposed on the substrate and configured to couple the second portion into the waveguide system based on the second wavelength, the first wavelength and the second wavelength being different; a first detector configured to receive the first portion through the waveguide system and generate a first measurement signal based on the intensity of the first portion; a second detector configured to receive the second portion through the waveguide system and generate a second measurement signal based on the intensity of the second portion; a microstructured illumination adjuster including first and second microstructured regions configured to direct corresponding ones of the first and second portions to corresponding ones of the first and second grating couplers.

13. analyzing the first and second measurement signals; determining a characteristic of the target based on the intensities of the first and second portions; The inspection system of claim 12 , further comprising a processor configured to:

14. The inspection system includes: directing illumination toward the target to generate the first and second portions; scanning the directed illumination across the target; 13. The inspection system of claim 12, wherein the optical system is configured as follows:

15. the integrated optical system is further configured to receive, direct, and combine a third portion of the illumination scattered by the target, the third portion having a corresponding third wavelength; The integrated optical system further comprises a third grating coupler disposed on the substrate and configured to couple the third portion into the waveguide system based on the third wavelength, the third wavelength being different from the first and second wavelengths; the inspection system further comprising a third detector configured to receive the third portion through the waveguide system and generate a third measurement signal based on an intensity of the third portion; The inspection system of claim 12 , wherein the microstructured illumination adjuster further comprises a third microstructured region configured to direct the third portion to the third grating coupler.

Images