Integrated optical system for scalable and accurate inspection systems

Abstract

An inspection system includes a radiation source, an integrated optical system, and first and second detectors. The radiation source generates radiation to irradiate a target. The integrated optical system includes: a substrate; first, second, third and fourth waveguides; first and second grating couplers; a first combiner coupled to the first and second waveguides; and a second combiner coupled to the third and fourth waveguides. The first grating coupler couples first and third portions of radiation scattered by the target into the first and third waveguides, respectively. The second grating coupler couples second and fourth portions of radiation scattered by the target into the second and fourth waveguides, respectively. The first combiner may combine a first portion and a second portion of radiation. The second combiner may combine a third portion and a fourth portion of the radiation. The first and second detectors generate measurement signals based on respective combined portions of radiation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application No. 63 / 352,037, filed on June 14, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to metrology apparatus, for example, an alignment sensor for measuring the position of a target in a lithographic apparatus. Background Art

[0004] A lithographic apparatus is a machine that applies a desired pattern to a substrate, usually on a target portion of the substrate. For example, a lithographic apparatus may be used in the manufacture of integrated circuits (ICs). In this case, a pattern forming device, which may be a mask or a reticle, may be used to produce a circuit pattern to be formed on a single layer of the IC. The pattern may be transferred to a target portion (e.g., including a portion of a die, one or several dies) on a substrate (e.g., a silicon wafer). Typically, the transfer of the pattern is performed by imaging the pattern onto a layer of radiation-sensitive material (photoresist or simply "resist") disposed on the substrate. Typically, a single substrate will contain a grid of adjacent target portions that are patterned successively. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern to the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the target portion synchronously parallel or antiparallel to this scanning direction while the radiation beam scans the pattern in a given direction (the "scanning" direction). The pattern may also be transferred from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0005] During a lithography operation, different processing steps may require the sequential formation of different layers on the substrate. Therefore, the substrate may need to be positioned with high accuracy relative to a previous pattern formed on the substrate. Typically, alignment marks are placed on the substrate to be aligned and positioned relative to a second object. A lithography apparatus may use an alignment device to detect the position of the alignment marks and to align the substrate using the alignment marks to ensure accurate exposure from a mask. The misalignment between alignment marks at two different layers is measured as an overlay error.

[0006] To monitor the lithography process, the alignment position of one or more alignment marks can be measured. Due to many limitations (e.g., the speed of alignment measurements), lithography systems can only output a limited number of fabricated devices within a given time frame. While multiple inspection sensors can be implemented in parallel within a lithography device to speed up the inspection of multiple targets, conventional sensors used in lithography metrology can be large and expensive due to their bulky optics, hindering their scalability. In addition, optical measurement results can be inaccurate due to the characteristics of the target being measured (e.g., tilt, height level, stack profile, etc.). Summary of the invention

[0007] Therefore, it is desirable to improve manufacturing throughput and accuracy.For example, aspects of the optical systems described herein can be used to construct scalable and accurate inspection systems.

[0008] In some aspects, the inspection system includes a radiation source, an integrated optical system, and a first detector and a second detector. The radiation source can generate radiation to irradiate a target. The integrated optical system can include: a substrate; a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide disposed on the substrate; a first and a second grating coupler disposed on the substrate; a first combiner coupled to the first waveguide and the second waveguide; and a second combiner coupled to the third waveguide and the fourth waveguide. The first combiner and the second combiner are disposed on the substrate. The first grating coupler can couple a first portion and a third portion of the radiation scattered by the target into the first waveguide and the third waveguide, respectively. The second grating coupler can couple a second portion and a fourth portion of the radiation scattered by the target into the second waveguide and the fourth waveguide, respectively. The first combiner can combine the first portion and the second portion of the radiation. The second combiner can combine the third portion and the fourth portion of the radiation. The first detector can receive the combined first portion and the second portion of the radiation from the first combiner, and can generate a first measurement signal based on the combined first portion and the second portion of the radiation. The second detector may receive the combined third and fourth portions of the radiation from the second combiner and may generate a second measurement signal based on the combined third and fourth portions of the radiation.

[0009] In some aspects, the lithographic apparatus includes an illumination system, a projection system, and an inspection system. The illumination system may illuminate a pattern of a pattern forming device. The projection system may project an image of the pattern onto a wafer. The inspection system includes a radiation source, an integrated optical system, and a first detector and a second detector. The radiation source may generate radiation to irradiate a target. The integrated optical system may include: a substrate; a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide disposed on the substrate; a first grating coupler and a second grating coupler disposed on the substrate; a first combiner coupled to the first waveguide and the second waveguide; and a second combiner coupled to the third waveguide and the fourth waveguide. The first combiner and the second combiner are disposed on the substrate. The first grating coupler may couple a first portion and a third portion of radiation scattered by the target into the first waveguide and the third waveguide, respectively. The second grating coupler may couple a second portion and a fourth portion of radiation scattered by the target into the second waveguide and the fourth waveguide, respectively. The first combiner may combine the first portion and the second portion of radiation. The second combiner may combine the third portion and the fourth portion of radiation. The first detector may receive the combined first and second portions of the radiation from the first combiner and may generate a first measurement signal based on the combined first and second portions of the radiation. The second detector may receive the combined third and fourth portions of the radiation from the second combiner and may generate a second measurement signal based on the combined third and fourth portions of the radiation.

[0010] In some aspects, a method includes generating radiation to irradiate a target. The method also includes receiving a first portion and a third portion of radiation scattered by the target at a first position and a third position of a first grating coupler, respectively. The phase delays of the first portion and the third portion of the radiation are based on the incidence at the first position and the third position, respectively. The method also includes receiving a second portion and a fourth portion of radiation scattered by the target at a second position and a fourth position of a second grating coupler, respectively. The phase delays of the second portion and the fourth portion of the radiation are based on the incidence at the second position and the fourth position, respectively. The method also includes: based on a combination of the first portion and the second portion of the radiation, generating a first measurement signal including information about the phase delay of the first portion and the second portion of the radiation. The method also includes combining the third portion and the fourth portion of the radiation. The method also includes: based on the combination of the third portion and the fourth portion of the radiation, generating a second measurement signal including information about the phase delay of the third portion and the fourth portion of the radiation. The method also includes determining a position of the target based on analyzing the information about the phase delay of the first portion and the second portion of the radiation. The method also includes determining a correction value for the position based on analyzing the information about the phase delay of the third portion and the fourth portion of the radiation.

[0011] In some aspects, the inspection system includes a radiation source, an integrated optical system, a first detector and a second detector, and a processor. The radiation source generates radiation to irradiate a target. The integrated optical system includes a substrate, a waveguide system, and a first grating coupler and a second grating coupler. The waveguide system and the first grating coupler and the second grating coupler are arranged on the substrate. The first grating coupler receives a first part and a third part of the radiation scattered by the target at a first position and a third position of the first grating coupler, respectively. The first grating coupler couples the first part and the third part of the radiation into the waveguide system. The phase delay of the first part and the third part of the radiation is based on the incidence at the first position and the third position, respectively. The second grating coupler receives a second part and a fourth part of the radiation scattered by the target at a second position and a fourth position of the second grating coupler, respectively. The second grating coupler couples the second part and the fourth part of the radiation into the waveguide system. The phase delay of the second part and the fourth part of the radiation is based on the incidence at the second position and the fourth position, respectively. The first detector receives a combination of the first part and the second part of the radiation. The first detector generates a first measurement signal including information of the phase delay of the first part and the second part of the radiation. The second detector receives a combination of the third and fourth portions of the radiation. The second detector generates a second measurement signal including information of the phase delays of the third and fourth portions of the radiation. The processor analyzes the first measurement signal and the second measurement signal. The processor determines the position of the target based on the information of the phase delays of the first and second portions of the radiation. The processor determines a correction value for the position based on the information of the phase delays of the third and fourth portions of the radiation.

[0012] The following detailed description of the additional features of various aspects of the present disclosure is made with reference to the accompanying drawings. Note that the present disclosure is not limited to the specific aspects described herein. These aspects are presented herein for illustrative purposes only. Based on the teachings contained herein, those skilled in the relevant art will understand additional aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and enable one skilled in the relevant art to make and use the various aspects described herein.

[0014] Figure 1A A reflective lithographic apparatus according to some aspects is shown.

[0015] Figure 1B A transmissive lithographic apparatus according to some aspects is shown.

[0016] Figure 2 More details of a reflective lithographic apparatus according to some aspects are shown.

[0017] Figure 3 A lithography cell according to some aspects is shown.

[0018] Figure 4A and Figure 4B An inspection apparatus according to some aspects is shown.

[0019] Figure 5 An integrated optical system according to some aspects is shown.

[0020] Fig. 6A , Figure 6B and Figure 6C An arrangement for collecting radiation scattered by a target is shown in accordance with some aspects.

[0021] Figure 7 and Figure 8 Shown is a graph corresponding to displacement of scattered radiation according to some aspects.

[0022] Fig. 9 , Fig.10 , Fig.11A and Fig. 11B An inspection device according to some aspects is shown.

[0023] Fig.12 An arrangement for collecting radiation scattered by a target is shown in accordance with some aspects.

[0024] Features of the present disclosure will become apparent from the detailed description produced below when combined with the accompanying drawings, in which the same reference numerals always identify corresponding elements. In the accompanying drawings, similar reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. In addition, generally, the leftmost digit of a reference numeral identifies the drawing in which the reference numeral first appears. Unless otherwise stated, the drawings provided throughout the present disclosure should not be construed as drawings drawn to scale. DETAILED DESCRIPTION

[0025] The embodiments described herein and the phrases "one aspect", "an aspect", "exemplary aspect" and the like mentioned in the specification indicate that the described aspects may include specific features, structures or characteristics, but each aspect may not necessarily include the specific features, structures or characteristics. In addition, such phrases do not necessarily refer to the same aspects. In addition, when specific features, structures or characteristics are described in conjunction with aspects, it should be understood that, whether or not explicitly described, it is within the knowledge of those skilled in the art to combine with other aspects to achieve such features, structures or characteristics.

[0026] For ease of description, spatially relative terms, such as "below," "beneath," "lower," "above," "on," "higher," etc., may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the accompanying drawings. The spatially relative terms are intended to encompass different orientations of the device when in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0027] The terms "about," "approximately," "approximately," and the like may be used herein to indicate a value of a given quantity that may vary based on a particular technology. Based on the particular technology, the terms "about," "approximately," and the like may indicate a value of a given quantity that varies, for example, within 10% to 30% above or below the value (e.g., ±10%, ±20%, or ±30% of the value).

[0028] 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 that can 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 that can be read by a machine (e.g., a computing device). For example, a machine-readable magnetic storage medium may include a read-only memory (ROM); a random access memory (RAM); a disk storage medium; an optical storage medium; a flash memory device; an electrical, optical, acoustic, or other form of propagation signal (e.g., a carrier wave, an infrared signal, a digital signal, etc.), etc. In addition, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are merely for convenience, and that these actions are generated by a computing device, a processor, a controller, or other devices that execute firmware, software, routines, instructions, etc. The term "machine-readable medium" may be interchangeable with similar terms, such as "computer program product", "computer-readable medium", "non-transitory computer-readable medium", etc. The term "non-transitory" may be used herein to characterize one or more forms of computer-readable media other than transient propagation signals.

[0029] However, before describing these aspects in further detail, it is instructive to present an example environment in which aspects of the disclosure may be implemented.

[0030] Example Lithography System

[0031] Figure 1A and Figure 1BA lithographic apparatus 100 and a lithographic apparatus 100' are respectively shown in which aspects of the present disclosure may be implemented. The lithographic apparatus 100 and the lithographic apparatus 100' each include the following components: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., a mask stage) MT configured to support a pattern forming device (e.g., a mask, a reticle, or a dynamic pattern forming device) MA and connected to a first positioner PM configured to accurately position the pattern forming device MA; and a substrate stage (e.g., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with resist) W and connected to a second positioner PW configured to accurately position the substrate W. The lithographic apparatus 100 and 100' also have a projection system PS configured to project a pattern imparted to the radiation beam B by the pattern forming device MA onto a target portion (e.g., including one or more dies) C of the substrate W. In lithographic apparatus 100, patterning device MA and projection system PS are reflective. In lithographic apparatus 100', patterning device MA and projection system PS are transmissive.

[0032] The illumination system IL may include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for guiding, shaping or controlling the radiation beam B.

[0033] 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 the lithographic apparatuses 100 and 100', and other conditions, such as whether 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 be a frame or a stage, for example, which may be fixed or movable. By using sensors, the support structure MT may ensure that the patterning device MA is in a desired position, for example relative to the projection system PS.

[0034] The term “patterning device” MA is to be broadly interpreted as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section so as 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 specific functional layer of a device to be created in the target portion C to form an integrated circuit.

[0035] The pattern forming device MA may be a transmissive type (e.g. Figure 1B lithographic apparatus 100 ′) or a reflective type (such as Figure 1A100). Examples of pattern forming devices MA include reticles / masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography and include mask types such as binary masks, alternating phase shift masks, or attenuated phase shift masks, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam B reflected by the matrix of small mirrors.

[0036] The term "projection system" PS as used herein includes any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems or any combination thereof, as appropriate for the exposure radiation used or other factors such as the use of an immersion liquid or the use of a vacuum on the substrate W. A vacuum environment may be used for EUV or electron beam radiation, as other gases may absorb too much radiation or electrons. A vacuum environment may therefore be provided to the entire beam path by means of vacuum walls and a vacuum pump.

[0037] The 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 substrate table" machine, additional substrate tables WT may be used in parallel, or one or more other substrate tables WT may be used for exposure while preparatory steps are performed on one or more tables. In some cases, the additional tables may not be substrate tables WT.

[0038] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, such as water, so as to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, such as the space between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of a projection system. The term "immersion" as used herein does not mean that structures such as substrates must be immersed in liquid. For example, during exposure, the liquid may be located between the projection system and the substrate.

[0039] refer to Figure 1A and Figure 1B , the illuminator IL receives a radiation beam from a radiation source SO. When the source SO is an excimer laser, the source SO and the lithographic apparatus 100, 100' may be separate physical entities. In this case, the source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam is delivered to the lithographic apparatus 100 or 100' by means of a beam delivery system BD (in the case of a laser beam) comprising, for example, suitable directional mirrors and / or a beam expander. Figure 1BThe radiation system may include a source SO, an illuminator IL and / or a beam delivery system BD.

[0040] The illuminator IL may comprise an adjuster AD (at Figure 1B Typically, at least the outer radial extent and / or the inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. Furthermore, the illuminator IL may include various other components (in Figure 1B ), such as an integrator IN and a condenser CO. The radiation beam B can be adjusted using an illuminator IL so as to have a desired uniformity and intensity distribution in its cross-section.

[0041] refer to Figure 1A , the radiation beam B is incident on and patterned by the pattern forming device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT. In the lithographic apparatus 100, the radiation beam B is reflected from the pattern forming device (e.g., mask) MA. After having been reflected from the pattern forming device (e.g., mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation 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 device, a linear encoder, a 2D encoder, or a capacitive sensor), the substrate table WT can be accurately moved (e.g., to position different target portions C in the path of the radiation beam B). Similarly, a first positioner PM and a further position sensor IF1 can be used to accurately position the pattern forming device (e.g., mask) MA relative to the path of the radiation beam B. A patterning device (eg, mask) MA and a substrate W may be aligned using mask alignment marks M1 , M2 and substrate alignment marks P1 , P2 .

[0042] refer to Figure 1B, the radiation beam B is incident on and patterned by the patterning device (e.g. mask MA), which is held on the support structure (e.g. mask table MT). Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil PPU that is conjugate to the illumination system pupil IPU. Portions of the radiation originate from the intensity distribution at the illumination system pupil IPU and traverse the mask pattern without being affected by diffraction at the mask pattern, and produce an image of the intensity distribution at the illumination system pupil IPU.

[0043] The projection system PS projects an image of a marking pattern MP onto a photoresist layer coated on the substrate W, wherein the image is formed by a diffraction beam generated from the marking pattern MP by radiation of the intensity distribution. For example, the mask pattern MP may include an array of lines and spaces. Diffraction of radiation different from the zero-order diffraction at the array produces a diverted diffraction beam having a direction change in a direction perpendicular to the lines. The undiffracted beam (i.e., the so-called zero-order diffraction beam) traverses the pattern without any change in the propagation direction. The zero-order diffraction beam passes through an upper lens or upper lens group of the projection system PS (located upstream of the conjugate pupil PPU of the projection system PS) to reach the conjugate pupil PPU. A portion of the intensity distribution in the plane of the conjugate pupil PPU and associated with the zero-order diffraction beam is an image of the intensity distribution of the illumination system IL in the illumination system pupil IPU. The aperture device PD is, for example, arranged at or approximately located at a plane including the conjugate pupil PPU of the projection system PS.

[0044] The projection system PS is arranged to capture (e.g., using a lens or lens group L) a zero-order diffraction beam, a first-order diffraction beam, and / or higher-order diffraction beams (not shown). In some aspects, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to exploit the resolution enhancement effect of dipole illumination. For example, the first-order diffraction beam interferes with the corresponding zero-order diffraction beam at the level of the wafer W to produce an image of the line pattern MP with the highest possible resolution and process window (i.e., the available focal depth combined with the tolerable exposure dose deviation). In some aspects, astigmatic aberrations can be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. In addition, in some aspects, astigmatic aberrations can be reduced by blocking the zero-order beam associated with the radiation poles in the opposite quadrant in the conjugate pupil PPU of the projection system. This is described in more detail in US 7,511,799 B2, issued on March 31, 2009, the entire contents of which are incorporated herein by reference.

[0045] With the aid of a second positioner PW and a position sensor IFD (e.g. an interferometer arrangement, a linear encoder, a 2D encoder or a capacitive sensor), 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 substrate table WT can be accurately moved (e.g. to position a different target portion C in the path of the radiation beam B) using a first positioner PM and another position sensor (not shown) (e.g. after mechanical retrieval from a mask library or during scanning). Figure 1B ) to accurately position the mask MA relative to the path of the radiation beam B.

[0046] Typically, movement of the mask table MT may be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) which form part of the first positioner PM. Similarly, movement of the substrate table WT may be achieved with 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 a short-stroke actuator, or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the illustrated substrate alignment marks occupy dedicated target portions, they may be located in the spaces between multiple target portions (these are referred to as scribe alignment marks). Similarly, where more than one die is provided on the mask MA, the patterning device alignment marks may be located between these dies.

[0047] The mask table MT and the patterning device MA may be located in a vacuum chamber, wherein an in-vacuum robot IVR may be used to move the patterning device (such as a mask or reticle) into and out of the vacuum chamber. Alternatively, when the mask table MT and the patterning device MA are outside the vacuum chamber, an out-of-vacuum robot may be used for various transport operations similar to the in-vacuum robot IVR. Both the in-vacuum and out-of-vacuum robots should be calibrated to smoothly transfer any payload (e.g., a mask) to the fixed kinematic mount of the transfer station.

[0048] The lithographic apparatus 100 and 100' may be used in at least one of the following modes:

[0049] 1. In step mode, the support structure (e.g. mask table) MT and the substrate table WT remain substantially stationary while an entire pattern imparted to the radiation beam is projected at once onto a target portion C (i.e. a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed.

[0050] 2. In scan mode, the support structure (e.g. mask table) MT and substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure (e.g. mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0051] 3. In another mode, the support structure (e.g. mask table) MT holding the programmable patterning device is held substantially fixed and the substrate table WT is moved or scanned, while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO may be employed, and the programmable patterning device updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation may be readily applied in maskless lithography using a programmable patterning device, such as a programmable mirror array.

[0052] Combinations and / or variations of the described modes of use or entirely different modes of use may also be employed.

[0053] In another aspect, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Typically, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0054] Figure 2The lithographic apparatus 100 is shown in more detail, including the source collector device SO, the illumination system IL and the projection system PS. The source collector device SO is constructed and arranged to maintain a vacuum environment in an enclosure 220 of the source collector device SO. The plasma 210 emitting EUV radiation can be formed by a discharge-generated plasma source. EUV radiation can be generated by a gas or vapor (e.g., Xe gas, Li vapor, or Sn vapor), in which the EUV radiation-emitting plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum. For example, the EUV radiation-emitting plasma 210 is generated by a discharge that causes an at least partially ionized plasma. In order to effectively generate radiation, Xe, Li, Sn vapor, or any other suitable gas or vapor, for example, with a partial pressure of 10 Pa, can be used. In some aspects, a plasma of excited tin (Sn) is provided (e.g., via laser excitation) to generate EUV radiation.

[0055] Radiation emitted by EUV radiation emitting plasma 210 is transferred from source chamber 211 to collector chamber 212 via a gas barrier or contaminant trap 230 (also referred to as a contaminant barrier or fin trap in some cases) optionally positioned in or behind an opening in source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier, or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230, as further noted herein, includes at least a channel structure.

[0056] The collector chamber 211 may include a radiation collector CO which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation traversing the collector CO may be reflected out to be focused at a virtual source point INIF. The virtual source point is usually referred to as an intermediate focus INTF, and the source collector device is arranged so that the intermediate focus INTF is located at or near an opening 219 in the enclosure structure 220. The virtual source point INTF is an image of the EUV radiation emitting plasma 210. The grating spectral filter 240 is particularly used to suppress infrared (IR) radiation.

[0057] The radiation then traverses the illumination system IL which may include a faceted field mirror arrangement 222 and a faceted pupil mirror arrangement 224 arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA, and a desired uniformity of radiation intensity at the patterning device MA. When the radiation beam 221 is reflected at the patterning device MA held by the support structure MT, a patterned beam 226 is formed, and the patterned beam 226 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.

[0058] There may typically be more elements than shown in the illumination optics unit IL and the projection system PS. Optionally, a grating spectral filter 240 may be present, depending on the type of lithographic apparatus. Furthermore, there may be more than Figure 2 More reflectors, such as those shown in Figure 2 Compared to the reflective elements shown, there may be 1 to 6 additional reflective elements present in projection system PS.

[0059] Collector optics CO (eg Figure 2 ) is depicted as a nested collector with grazing incidence reflectors 253, 254 and 255, which is only one example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are arranged axially symmetrically around the optical axis O, and this type of collector optics CO is preferably used in conjunction with a discharge produced plasma source (often referred to as a DPP source).

[0060] Example Lithography Cell

[0061] Figure 3A lithography unit 300 is shown, which is sometimes also referred to as a lithography cell or cluster, according to some aspects. The lithography apparatus 100 or 100' may form a part of the lithography unit 300. The lithography unit 300 may also include one or more devices for performing pre-exposure processes and post-exposure processes on a substrate. Conventionally, these devices include: a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chill plate CH, and a baking plate BK. A substrate conveyor or robot RO picks up a substrate from an input / output port I / O1, I / O2, moves the substrate between different process devices, and transfers the substrate to a feed station LB of the lithography apparatus 100 or 100'. These devices are generally collectively referred to as a coating and developing system, and are under the control of a coating and developing system control unit TCU, which is itself controlled by a management control system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Therefore, different devices can be operated to maximize production volume and processing efficiency.

[0062] Sample inspection equipment

[0063] In order to control the lithography process to accurately place the device features on the substrate, alignment marks are usually set on the substrate, and the lithography equipment includes one or more inspection devices to accurately position the marks on the substrate. These alignment devices are effectively position measurement devices. Different types of marks and different types of alignment devices and / or systems are known from different times and different manufacturers. One type of system widely used in current lithography equipment is based on a self-reference interferometer as described in U.S. Patent No. 6,961,116 (den Boef et al.). Typically, the marks are measured separately to obtain the X position and the Y position. However, the combined X and Y measurements can be performed using the technology described in U.S. Publication No. 2009 / 195768 A (Bijnen et al.). The entire contents of these two published patents are incorporated herein by reference.

[0064] Figure 4A A cross-sectional view of an inspection apparatus 400 is shown, according to some aspects, and the metrology system 400 can be implemented as part of a lithographic apparatus 100 or 100'. In some aspects, the inspection apparatus 400 can be configured to align a substrate (e.g., substrate W) relative to a patterning device (e.g., patterning device MA). The inspection apparatus 400 can also be configured to detect positions of alignment marks on the substrate, and use the detected positions of the alignment marks to align the substrate relative to the patterning device or other components of the lithographic apparatus 100 or 100'. Such alignment of the substrate can ensure that one or more patterns are accurately exposed on the substrate.

[0065] The terms "inspection equipment", "measurement system", etc. may be used herein to refer to, for example, a device for measuring properties of a structure (e.g., an overlay sensor, a critical dimension sensor, etc.), or to a device used in a lithography device to check the alignment of a wafer (alignment sensor), etc.

[0066] In some aspects, the inspection device 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 spectrum of wavelengths between about 500 nm and about 900 nm. In another example, the one or more passbands may be discrete narrow passbands within a spectrum of wavelengths between about 500 nm and about 900 nm. The illumination system 412 may also be configured to provide one or more passbands having a substantially constant center wavelength (CWL) value over a long period of time (e.g., over the useful life of the illumination system 412). As discussed above, in the current alignment system, such a configuration of the illumination system 412 may help prevent the actual CWL value from shifting from the desired CWL value. And, therefore, using a constant CWL value may improve the long-term stability and accuracy of an alignment system (eg, inspection apparatus 400 ) as compared to current alignment apparatuses.

[0067] In some aspects, beam splitter 414 can be configured to receive radiation beam 413 and split radiation beam 413 into at least two radiation sub-beams. For example, radiation beam 413 can be split into radiation sub-beams 415 and 417, as shown in FIG. Figure 4AAs shown. The beam splitter 414 can also be configured to direct the radiation sub-beam 415 onto a substrate 420 placed on a platform 422. In one example, the platform 422 can be moved along a direction 424. The radiation sub-beam 415 can be configured to illuminate an alignment mark or target 418 located on the substrate 420. The alignment mark or target 418 can be coated with a radiation-sensitive film. In some aspects, the alignment mark or target 418 can have a one hundred and eighty degree (i.e., 180°) symmetry. That is, when the alignment mark or target 418 is rotated 180° around an axis of symmetry perpendicular to the plane of the alignment mark or target 418, the rotated alignment mark or target 418 can be substantially the same as the unrotated alignment mark or target 418. The target 418 on the substrate 420 can be: (a) a resist layer grating comprising bars formed by solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlay target structure comprising a resist grating overlapped or staggered on a product layer grating. The bars may alternatively be etched into the substrate. Such patterns are sensitive to chromatic aberrations in the lithographic projection apparatus (particularly the projection system PL) and to illumination symmetry, and the presence of such aberrations will manifest themselves as variations in the printed grating. One in-line method for measuring line width, pitch and critical dimensions in device manufacturing utilizes a technique known as "scatterometry". Scatterometry methods are described in Raymond et al., "Multiparameter Grating Metrology Using SPIE 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 a periodic structure in the target and the resulting reflection spectrum at a given angle is detected. The structure that produces the reflection spectrum is reconstructed, for example, using rigorous coupled wave analysis (RCWA) or by comparison with a library of patterns derived from simulations. Therefore, the scatterometry data of the printed grating are used to reconstruct the grating. The parameters of the grating, such as line width and line shape, can be input into the reconstruction process, which is performed by the processing unit PU based on knowledge of the printing steps and / or other scatterometry processes.

[0068] In some aspects, according to one aspect, the beam splitter 414 can also be configured to receive the diffracted radiation beam 419 and split the diffracted radiation beam 419 into at least two radiation sub-beams. The radiation beam 419 can be split into radiation sub-beams 429 and 439, such as Figure 4Ashown.

[0069] It should be noted that even though beam splitter 414 is shown as directing radiation sub-beam 415 toward alignment mark or target 418 and directing diffracted radiation sub-beam 429 toward interferometer 426, the present disclosure is not limited thereto. Other optical arrangements may be used to obtain similar results of illuminating alignment mark or target 418 onto substrate 420 and detecting an image of alignment mark or target 418.

[0070] like Figure 4A As shown, the interferometer 426 can be configured to receive the radiation sub-beam 417 and the diffracted radiation sub-beam 429 through the beam splitter 414. In an exemplary aspect, the diffracted radiation sub-beam 429 can be at least a portion of the radiation sub-beam 415 that can be reflected from the alignment mark or target 418. In an example of this aspect, the interferometer 426 includes any suitable optical element group, for example, it can be configured as a prism combination that forms two images of the alignment mark or target 418 based on the received diffracted radiation sub-beam 429. It should be understood that it is not necessary to form an image of good quality. It may be sufficient to resolve or distinguish the features of the alignment mark 418. The interferometer 426 can also be configured to rotate one of the two images by 180° relative to the other of the two images, and to recombinate the rotated image and the unrotated image in an interferometric manner.

[0071] In some aspects, the detector 428 may be configured to receive the recombined image via the interferometer signal 427 and detect interference resulting from the recombined image when the alignment axis 421 of the inspection device 400 passes through the center of symmetry of the alignment mark or target 418 (not shown). According to example aspects, such interference may be due to the alignment mark or target 418 being 180° symmetrical, and according to example embodiments, the recombined images interfere constructively or destructively. Based on the detected interference, the detector 428 may also be configured to determine the location of the center of symmetry of the alignment mark or target 418 and thus detect the location of the substrate 420. According to an example, the alignment axis 421 may be aligned with an optical beam perpendicular to the substrate 420 and passing through the center of the image rotation interferometer 426. The detector 428 may also be configured to estimate the location of the alignment mark or target 418 by implementing sensor characteristics and interacting with wafer marking process variations.

[0072] In further aspects, 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:

[0073] 1. Measure the position change for each wavelength (position shift between colors);

[0074] 2. Measure the position change for each order (position shift between diffraction orders); and

[0075] 3. The position change is measured for each polarization (position shift between the polarizations).

[0076] For example, this data may 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 ATHENA (Advanced Techniques Using High Order Alignment Enhancement), 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.

[0077] In some aspects, the beam analyzer 430 can be configured to receive and determine the optical state of the diffracted radiation sub-beam 439. The optical state can be a measure of the beam wavelength, polarization, or beam profile. The beam analyzer 430 can also be configured to determine the position of the platform 422 and correlate the position of the platform 422 with the position of the symmetry center of the alignment mark or target 418. In this way, the position of the alignment mark or target 418 relative to the alignment platform 422 can be accurately known, and therefore the position of the substrate 420 relative to the alignment platform 422 is known. Alternatively, the beam analyzer 430 can be configured to determine the position of the inspection device 400 or any other reference element, so that the symmetry center of the alignment mark or target 418 can be known relative to the inspection device 400 or any other reference element. The beam analyzer 430 can be a point or imaging polarimeter with some form of band selectivity. In some aspects, according to other aspects, the beam analyzer 430 can be directly integrated into the inspection device 400, or connected to the inspection device 400 via the following types of optical fibers: polarization-maintaining single mode, multimode, or imaging.

[0078] In some aspects, the beam analyzer 430 may also be configured to determine overlap data between two patterns on the substrate 420. One of the patterns may be a reference pattern on a reference layer. Another pattern may be an exposure pattern on an exposure layer. The reference layer may be an etch layer already present on the substrate 420. The reference layer may be generated by exposing a reference pattern on the substrate by the lithography apparatus 100 and / or 100'. The exposure layer may be an exposed resist layer adjacent to the reference layer. The exposure layer may be generated by exposing an exposure pattern on the substrate 420 by the lithography apparatus 100 or 100'. The exposure pattern on the substrate 420 may correspond to the movement of the substrate 420 by the platform 422. In some aspects, the measured overlap data may also indicate an offset between the reference pattern and the exposure pattern. The measured overlap data may be used as calibration data to calibrate the exposure pattern exposed by the lithography apparatus 100 or 100', so that after calibration, the offset between the exposure layer and the reference layer may be minimized.

[0079] In some aspects, the beam analyzer 430 may also be configured to determine a model of a product stack profile of the substrate 420 and may be configured to measure the overlap, critical dimensions, focal length, etc. of the target 418 in a single measurement. The product stack profile contains information about the stacked product, such as alignment marks, the target 418, or the substrate 420, and may include optical signature metrics caused by marking process variations, which are a function of illumination variations. The product stack profile may also include product grating profiles, mark stack profiles, and mark asymmetry information. An example of a beam analyzer 430 is the Yieldstar manufactured by ASML of Veldhoven, The Netherlands. TM , as described in U.S. Patent No. 8,706,442, the entire contents of which are incorporated herein by reference. The beam analyzer 430 may also be configured to process information related to specific properties of the exposure pattern in the layer. For example, the beam analyzer 430 may process: overlay parameters (indicating the accuracy of positioning of the 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 of the image depicted in the layer (e.g., line width and its variation). Other parameters are image parameters related to the quality of the image of the depicted exposure pattern.

[0080] In some aspects, a detector array (not shown) can be connected to the beam analyzer 430 and allow the possibility of accurate stack profile detection, as discussed below. For example, the detector 428 can be a detector array. There may be multiple options for the detector array: a multimode fiber bundle, a discrete pin detector per channel, or a CCD or CMOS (linear) array. For stability reasons, the use of a multimode fiber bundle allows any dissipative elements to be remotely located. Discrete pin detectors can provide a larger dynamic range, but each detector requires a separate preamplifier. Therefore, the number of elements is limited. CCD linear arrays provide many elements that can be read at high speed and are particularly noteworthy when using phase step detection.

[0081] In some aspects, the second beam analyzer 430' can be configured to receive and determine the optical state of the diffracted radiation sub-beam 429, such as Figure 4B As shown. The optical state may be a measure of the beam wavelength, polarization, or beam profile. The second beam analyzer 430' may be identical to the beam analyzer 430. Alternatively, the second beam analyzer 430' may be configured to perform one or more functions of the beam analyzer 430, such as determining the position of the platform 422, and associating the position of the platform 422 with the position of the center of symmetry of the alignment mark or target 418. In this way, the position of the alignment mark or target 418 relative to the alignment platform 422 may be accurately known, and therefore the position of the substrate 420 relative to the alignment platform 422 may be known. Alternatively, the beam analyzer 430 may be configured to determine the position of the inspection device 400 or any other reference element, so that the center of symmetry of the alignment mark or target 418 may be known relative to the inspection device 400 or any other reference element. The second beam analyzer 430' may also be configured to determine the overlap data between the two patterns and a model of the product stack profile of the substrate 420. The second beam analyzer 430 may also be configured to measure the overlap, critical dimensions, focal length, etc. of the target 418 in a single measurement.

[0082] In some aspects, second beam analyzer 430' may be directly integrated into inspection device 400, or it may be connected to inspection device 400 via several types of optical fibers: polarization-maintaining single-mode fiber, multimode fiber, or imaging fiber, in accordance with other aspects. Alternatively, second beam analyzer 430' and beam analyzer 430 may be combined to form a single analyzer (not shown) configured to receive and determine the optical state of diffracted radiation sub-beams 429 and 439.

[0083] In some aspects, processor 432 may determine a correction for each marker.

[0084] Exemplary Integrated Optical Systems

[0085] In some aspects, the term "throughput" can be used to characterize the rate of photolithography manufacturing. For example, throughput can refer to the rate at which photolithography manufacturing is completed on a wafer, the rate at which a wafer clears a specific preparation step and moves to the next step, etc. Throughput can be a performance indicator of a lithographic device. It is expected that the lithography system outputs as many products as possible in as little time as possible. Photolithography manufacturing can include several complex processes. Each process includes a technical choice that compromises between quality (e.g., sub-nanometer accuracy, high yield) and disadvantages (e.g., slower preparation, cost). An example process involving improved accuracy may include checking printed marks on a substrate. As described above, an inspection device can be used to determine the consistency of a printed pattern on a substrate or to align a substrate so as to properly receive a new pattern. However, the inspection process may greatly affect the throughput (e.g., seeking higher accuracy increases the inspection duration, resulting in reduced throughput). Other examples of integrated optical systems can be found in WO 2021 / 058571, published on April 1, 2021, which incorporates the entire contents of WO 2021 / 058571 herein by reference.

[0086] In some aspects, multiple targets can be measured in conjunction with the lithography process. The throughput can be increased by increasing the speed of inspecting multiple targets. Although multiple inspection sensors can be implemented in parallel within the lithography equipment to speed up the inspection of multiple targets, conventional sensors used in lithography measurement can be large and expensive due to their bulky optics, which hinders their scalability. A solution may be to implement sensors using different operating principles, such as integrated optics. Terms such as "integrated optics", "integrated optical systems", "integrated optical circuits", etc. can be used to refer to integrated devices that can propagate optical signals. For example, an integrated optics may include a waveguide disposed on a substrate. The waveguide can guide the optical signal to other areas of the substrate, where the optical signal can be received to be converted into measurement information. Compared with bulky free-space optics, integrated optics can be made very small and cost only a fraction of the cost. Therefore, sensors based on integrated optics can be a scalable solution to increase the speed of inspecting multiple marks.

[0087] Figure 5 An integrated optical system 500 according to some aspects is shown. In some aspects, the integrated optical system 500 can be used to replace at least a portion of the detection branch of the inspection device 400 ( Figure 4A and Figure 4B The term "irradiation branch" and the like may refer to a portion of an inspection device that includes emitting and / or directing radiation toward a target (eg, radiation sub-beam 415 ( ) toward target 418 ). Figure 4A and Figure 4BThe term "detection branch" or the like may refer to a portion of an inspection device that includes directing and / or receiving radiation scattered from a target (eg, diffracted radiation 419 ( Figure 4A and Figure 4B )) of the device. It should be understood that the illumination branch can also be implemented on an integrated optical device. In some aspects, multiple parts of the illumination branch and the detection branch can be implemented on the same substrate (e.g., a shared integrated optical system).

[0088] In some aspects, the integrated optical system 500 may include grating couplers 502 and 504 (e.g., a first grating coupler and a second grating coupler), waveguides 506 and 508 (e.g., a first waveguide or waveguide system and a second waveguide or waveguide system), and a combiner 522. The elements of the integrated optical system 500 may be disposed on a substrate (not shown). The integrated optical system 500 may also include a detector 530. Alternatively, the detector 530 may be a separate element (e.g., not integrated on a substrate).

[0089] In some aspects, enumerated adjectives (e.g., "first," "second," "third," etc.) can be used to distinguish similar elements without establishing an order, hierarchy, or numerical correspondence (unless otherwise specified). For example, the terms "first waveguide" and "second waveguide" can distinguish two waveguides without specifying a particular order or hierarchy. Furthermore, the elements in the figures are not limited to any particular enumerated adjectives. For example, waveguide 506 can be referred to as a first waveguide or a second waveguide, in which case the other waveguide can use an appropriately distinguishing enumerated adjective.

[0090] In some aspects, a radiation source can generate radiation for irradiating a target (e.g., as described in reference Figure 4A and Figure 4B 530 ). The target may scatter the radiation (e.g., as one or more diffraction orders, the 0th order, the ±1st order, etc.). The scattered radiation, illustrated as radiation 538 and 540 (e.g., +1 and -1 diffraction orders, +2 and -2 diffraction orders, etc.), may be received at the integrated optical system 500. The grating coupler 502 may couple the radiation 538 into the waveguide 506. The grating coupler 504 may couple the radiation 540 into the waveguide 508. The combiner 522 may combine the radiation 538 and 540 (e.g., to perform interferometry). The combined radiation may be received at the detector 530. The detector 530 may generate a measurement signal based on the combined radiation.

[0091] It is instructive to consider an overview of a process for performing measurements that rely on varying properties of radiation (e.g., interferometry). As the radiation spot moves / scans across the target 418 ( Figure 4A and Figure 4B), due to the scanning, the phase of radiation 538 and 540 (coherence) can evolve over time. When radiation 538 and 540 are interfered (due to combiner 522), the scanning motion of the radiation spot can cause the radiation detected at detector 530 to have AC modulation characteristics. That is, the measurement signal generated by detector 530 can be an AC signal. The target 418 ( Figure 4A and Figure 4B ) is a property of a (e.g., alignment position).

[0092] In some aspects, inconsistencies in the inspection process may result in uncertainty in the characteristics of the measurement signal. For example, substrate 420 ( Figure 4A and Figure 4B ) may cause the measured phase to shift. The height shift of substrate 420 may also be referred to as defocus. The shift in phase may be quantified as a phase shift value (eg, phase shift).

[0093] Fig. 6A , Figure 6B , Figure 6C , Figure 7 and Figure 8 1 shows how wafer tilt and wafer height can affect inspection of a target according to some aspects. In some aspects, Fig. 6A , Figure 6B and Figure 6C Can be shown with reference Figure 5 Unless otherwise specified, similar elements in the description correspond to the elements. Figure 5 The description of the elements can also be applied to Fig. 6A , Figure 6B and Figure 6C corresponding elements (eg, reference numerals share the two rightmost digits).

[0094] Fig. 6A An arrangement for collecting radiation scattered by a target 642 without tilt or defocus is shown in accordance with some aspects. In some aspects, radiation from a radiation source 644 can be incident on the target 642 coaxially (perpendicular to the plane of the substrate). Radiation scattered from the target 642 is shown as radiation 638 and 640. Radiation 638 and 640 can be received at grating couplers 602 and 604, respectively—specifically, at specific locations of the grating couplers 602 and 604.

[0095] In contrast, Figure 6BAn arrangement for collecting radiation scattered by a tilted target 642 is shown in accordance with some aspects. In some aspects, the tilt of target 642 can cause radiation 638 to change its path to the path of radiation 638'. Similarly, the path of radiation 640 can change to the path of radiation 640'. In this case, radiation 638' and 640' can be received at grating couplers 602 and 604, respectively, but at the same time as the grating couplers 602 and 604. Fig. 6A 638' and 640'.

[0096] Figure 6C An arrangement for collecting radiation scattered by a target 642 having a defocus is shown in accordance with some aspects. In another perspective, the grating couplers 602 and 604 are positioned further away (in the vertical direction of the drawing) from the target 642. In some aspects, the defocus can cause the radiation 638 and 640 to travel further before being received at the grating couplers 602 and 604. In this case, the radiation 638 and 640 can be received at the grating couplers 602 and 604, respectively, but at a time when the radiation is not received at the grating couplers 602 and 604. Fig. 6A 638 and 640. Defocus may have a reduced or negligible effect on the interference of radiation 638 and 640 because the two beams travel an additional but equal distance. This behavior can be relied upon when modifying integrated optical system 500 while retaining insensitivity to defocus.

[0097] Figure 7 Graph 700 corresponding to displacement of scattered radiation based on a tilted target is shown according to some aspects. In some aspects, the vertical axis represents the distance from the target (eg, target 642 ( Fig. 6A , Figure 6B and Figure 6C )). The values ​​of the displacements are not limiting (e.g., provided in arbitrary units (au)). The horizontal axis represents the diffraction order. The target tilt is set to 1 μrad. The data in graph 700 are similar to Figure 6B This is consistent with the behavior observed in Figure 6B In the graph 700, a pair of offset diffraction orders (e.g., +1 and -1) are represented by radiation 638' and 640'. The offset occurs to the right relative to radiation 638 and 640 (the direction to the right is considered the positive direction). In the graph 700, the diffraction orders are shifted to the right. Higher diffraction orders (e.g., 2nd order, 3rd order, etc.) have more pronounced positive shifts.

[0098] Figure 8800 is shown corresponding to the displacement of scattered radiation based on a defocused target according to some aspects. In some aspects, the vertical axis represents the distance from the incident position of different diffraction orders to the target (e.g., target 642 ( Fig. 6A , Figure 6B and Figure 6C ). The horizontal axis represents the diffraction orders. The target defocus (height variation) was set to 1 nm. The data in graph 700 are compared to Figure 6C This is consistent with the behavior observed in Figure 6C 800 , a pair of offset diffraction orders (e.g., +1 and -1) represented by radiation 638 and 640 are allowed to travel further (the direction to the right is considered the positive direction) before reaching grating couplers 602 and 604. Radiation 638 (e.g., a positive diffraction order) travels an additional distance to the left before being received by grating coupler 602. Radiation 640 (e.g., a negative diffraction order) travels an additional distance to the right before being received by grating coupler 604. In graph 800 , negative diffraction orders are shifted in the positive direction, and positive diffraction orders are shifted in the negative direction. Higher diffraction orders (e.g., 2nd order, 3rd order, etc.) have more pronounced displacements.

[0099] In some aspects, when the radiation beam received at the grating is offset, the phase of the scattered radiation may also be affected. Since interferometry relies on phase information, uncertainty in the tilt or defocus of the target may translate into phase uncertainty in the interferometry. This is highly undesirable because the lithography process is reluctant to perform partly with positioning accuracy of even a few picometers. For example, if tilt and / or height measurements are performed on the target 642, the phase uncertainty ( Fig. 6A , Figure 6B and Figure 6C ). In some aspects, a tilt and / or wafer level sensor can be implemented to quantify the effects of tilt and / or defocus. The quantified tilt and / or defocus effects can then be analyzed to calculate correction values ​​for the measured property involved (in this non-limiting example, the measured property involved is the alignment position of the target). However, conventional tilt and wafer level sensors have a large construction based on conventional bulky optics, thereby hindering scalability.

[0100] Thus, in some aspects, it is contemplated to modify the integrated optical system 500 to implement an inspection system capable of quantifying a primary measured property (e.g., alignment position) while also quantifying one or more correction values ​​for the measured property (e.g., tilt and / or defocus offset) (as opposed to independently measuring the property and the one or more correction values ​​using discrete sensors).

[0101] Fig. 9An integrated optical system 900 according to some aspects is shown. In some aspects, the integrated optical system 900 can be used to replace at least a portion of the detection branch of the inspection device 400 ( Figure 4A and Figure 4B ). In some aspects, Fig. 9 Can be shown with reference Figure 5 Unless otherwise specified, similar elements in the description correspond to the elements. Figure 5 The description of the elements can also be applied to Fig. 9 corresponding elements (eg, reference numerals share the two rightmost digits).

[0102] In some aspects, the integrated optical system 900 may include grating couplers 902 and 904 (e.g., a first grating coupler and a second grating coupler), waveguides 906, 908, 910, and 912 (e.g., a first, second, third, and fourth waveguide or waveguide system), and combiners 922 and 924 (e.g., a first combiner and a second combiner). The elements of the integrated optical system 900 may be disposed on a substrate (not shown). The integrated optical system 900 may also include detectors 930 and 932 (e.g., a first detector and a second detector). Alternatively, the detectors 930 and 932 may be elements that are not integrated on the substrate.

[0103] In some aspects, radiation scattered by the target - illustrated as radiation 938 and 940 (e.g., +1 and -1 diffraction orders, +2 and -2 diffraction orders, etc.) can be received at the integrated optical system 900. Grating coupler 902 can couple portions of radiation 938 into waveguides 906 and 910. Grating coupler 904 can couple radiation 940 into waveguides 908 and 912. The integrated optical system 900 is coupled to the optical system 500 ( Figure 5 ) is that each grating coupler of the optical system 900 is used to separate multiple portions of the received radiation along multiple waveguide paths. In a named non-limiting example, it can be described that a first grating coupler can couple a first portion and a third portion of the radiation scattered by the target into a first waveguide and a third waveguide, respectively. Similarly, a second grating coupler can couple a second portion and a fourth portion of the radiation scattered by the target into a second waveguide and a fourth waveguide, respectively.

[0104] In some aspects, combiner 922 can combine multiple portions of radiation 938 and 940 (e.g., to perform interferometry). Combiner 924 can combine other portions of radiation 938 and 940. As described in the previously proposed nomenclature, a first combiner connected to a first waveguide and a second waveguide can combine a first portion and a second portion of the radiation. A second combiner is connected to a third waveguide and a fourth waveguide and is configured to combine a third portion and a fourth portion of the radiation.

[0105] In some aspects, detector 930 may receive multiple portions of radiation combined by combiner 922. Detector 930 may generate a measurement signal based on the combined radiation from combiner 922. Detector 932 may receive multiple portions of radiation combined by combiner 924. Detector 932 may generate a measurement signal based on the combined radiation from combiner 924. Described in the previously suggested nomenclature, a first detector may receive a combined first portion and a second portion of radiation from a first combiner, and may generate a first measurement signal based on the combined first portion and the second portion of radiation. A second detector may receive a combined third portion and a fourth portion of radiation from a second combiner, and may generate a second measurement signal based on the combined third portion and the fourth portion of radiation.

[0106] In some aspects, the interference measured at detectors 930 and 932 can be expressed by Equations 1 and 2:

[0107] , (1)

[0108] . (2)

[0109] Here, the subscript of intensity I corresponds to Fig. 9 The waveguides and detectors in the 930 corresponds to the intensity of the radiation received by detector 930). Other quantities include Δx 938 (the displacement of the radiation beam 938 incident on the grating coupler 902), Δx 940 (the displacement of the radiation beam 940 incident on the grating coupler 904), k 938 (wave vector of radiation 938 in free space), k 940 (the wave vector of radiation 940 in free space), and the effective refractive index n of the grating coupler eff (For simplicity, it has been assumed that for two grating couplers, n eff is the same, but it is also assumed that each grating coupler is eff can have different values). Figure 7 and Figure 8 As shown, higher diffraction angles may correspond to larger displacements Δx. High diffraction angles may also be a result of a small pitch of the grating target. Thus, higher diffraction orders and / or high pitch grating targets may be more sensitive to the effects of target tilt and / or defocus.

[0110] In some aspects, a single detector system (e.g., Figure 5Measurements performed at detector 930 (e.g., detector 530) may have the disadvantage of having errors in the calculation of the measured property of the target due to phase shifts caused by target tilt or defocus. To correct for the effects of target tilt or defocus, additional measurements may be performed. Using additional tilt and / or wafer level sensors may have disadvantages as previously described. Therefore, integrated optical system 900 has additional measurement capabilities to allow additional measurements (e.g., more than one detector and corresponding optical circuit systems). As the displacement of radiation 938 and 940 across grating couplers 902 and 904 becomes larger (e.g., due to tilt and / or defocus), the phase of the combined radiation received at detector 930 may change independently (or semi-independently) from the phase of the combined radiation received at detector 932. If the alignment position of the mark is a first unknown to be solved for, and the error due to tilt is a second unknown to be solved for, the two different phases measured at detectors 930 and 932 may be used to extract the two unknowns. Furthermore, it is contemplated that the amount of tilt may also be extracted, effectively allowing an inspection apparatus including the integrated optical system 900 to function as a multi-purpose sensor for measuring both the alignment position and the tilt angle of the target / wafer.

[0111] In some aspects, additional measurement capabilities can be implemented for an increased number of unknowns. Furthermore, by using integrated optics, measurement capabilities can be increased with minimal impact on sensor size, allowing for a scalable system.

[0112] Fig.10 An integrated optical system 1000 according to some aspects is shown. In some aspects, the integrated optical system 1000 can be used to replace the inspection device 400 ( Figure 4A and Figure 4B ). In some aspects, Fig.10 Can be shown with reference Figure 5 and Fig. 9 Unless otherwise stated, similar elements in the description correspond to the elements. Figure 5 and Fig. 9 The description of the elements can also be applied to Fig.10 corresponding elements (eg, reference numerals share the two rightmost digits).

[0113] In some aspects, the integrated optical system 1000 may include grating couplers 1002 and 1004 (e.g., a first grating coupler and a second grating coupler), waveguides 1006, 1008, 1010, 1012, 1014, 1016, 1018, and 1020 (e.g., first to eighth waveguides), and combiners 1022, 1024, 1026, and 1028 (e.g., first to fourth combiners). Although not labeled, it is understood that the branch section of the waveguide may include a beam splitter for splitting light in one waveguide so that the light can travel in two or more waveguides. For example, waveguide 1006 has a branch that becomes waveguide 1014. It is understood that such a branch of the waveguide may include a beam splitter (e.g., an optical element that functions in the opposite manner of a combiner) or a similar optical component. The elements of the integrated optical system 1000 may be disposed on a substrate (not shown). The integrated optical system 1000 may further include detectors 1030, 1032, 1034, and 1036 (eg, first to fourth detectors). Alternatively, the detectors 1030, 1032, 1034, and 1036 may be elements that are not integrated on the substrate.

[0114] In some aspects, radiation scattered by a target - illustrated as radiation 1038 and 1040 (e.g., +1 and -1 diffraction orders, +2 and -2 diffraction orders, etc.) can be received at the integrated optical system 1000. The grating coupler 1002 can couple multiple portions (e.g., first through fourth portions) of the radiation 1038 into the waveguides 1006, 1010, 1014, and / or 1016. The grating coupler 1004 can couple multiple portions (e.g., fifth through eighth portions) of the radiation 1040 into the waveguides 1008, 1012, 1018, and / or 1020. In general, the grating coupler can be configured to separate and couple the radiation into different waveguide tracks based on one or more properties of the radiation (e.g., properties such as polarization, wavelength, etc.). Some examples of multi-directional grating coupler designs can be found in "Inverse design and implementation of a wavelength demultiplexing grating coupler" by Piggott et al. (Scientific reports, 4 (1), 1-5 (2014)) and "Focusing polarization diversity grating couplers in silicon-on-insulator" by Van Laere et al. (Journal of Lightwave Technology, 27 (5), 612-618 (2009)), which are incorporated herein by reference in their entirety. The grating couplers used in the aspects disclosed herein can be one-dimensional gratings, two-dimensional gratings, or other types of gratings. In some aspects, the grating couplers 1002 and 1004 can split multiple portions of the radiation so that the intensity is divided between two waveguides in a ratio of approximately 50 / 50 (e.g., or 80 / 20, 70 / 30, etc.), among three waveguides in a ratio of approximately 33 / 33 / 33, among four waveguides in a ratio of approximately 25 / 25 / 25 / 25, and so on. Other percentages (eg, unequal distributions of percentages) are also contemplated.

[0115] In some aspects, additional information may be extracted from the measurements of the target where more independent or semi-independent phases are measured. For example, it is contemplated that the amount of tilt and / or wafer level may also be extracted, effectively allowing an inspection device including the integrated optical system 1000 to function as a multi-purpose sensor for measuring the alignment position of the target / wafer, the tilt angle, and the height (defocus) of the target / wafer.

[0116] In some aspects, the integrated optical systems described herein can be adapted to have simplified optical circuits for isolated functions (eg, target / wafer height (defocus) measurement).

[0117] Fig.11A and Fig. 11B An integrated optical system 1100 for height level measurement (eg, height of a target or wafer) is shown in accordance with some aspects. Fig.11A An arrangement for collecting radiation scattered by a target 1142 having an adjusted height is shown. In some aspects, the target 1142 can be illuminated by radiation 1144 from a radiation source. Scattered radiation from the target 1142 can be represented by radiation 1140 for one height level of the target 1142. Scattered radiation from the target 1142 can be represented by radiation 1140' for another height level of the target 1142. Radiation 1140 and 1140' can be received at a grating coupler 1104.

[0118] Fig. 11B An integrated optical system 1100 is shown including a grating coupler 1104. In some aspects, Fig.11A and Fig. 11B Can be shown with reference Figure 5 , Fig. 9 and Fig.10 Unless otherwise specified, similar elements in the description correspond to the elements. Figure 5 , Fig. 9 and Fig.10 The description of the elements can also be applied to Fig.11A and Fig. 11B corresponding elements (eg, reference numerals share the two rightmost digits).

[0119] In some aspects, the integrated optical system 1100 may further include waveguides 1118 and 1120 (e.g., a first waveguide and a second waveguide) and a combiner 1128. The elements of the integrated optical system 1000 may be disposed on a substrate (not shown). The integrated optical system 1100 may further include a detector 1130. Alternatively, the detector 1130 may be an element that is not integrated on the substrate.

[0120] In some aspects, radiation 1144 is not on-axis (not perpendicular to the surface), but is incident at a non-zero angle of incidence. Due to the change in the height of target 1142, the receiving position on grating coupler 1104 changes, as shown by the difference between radiation 1140 and 1140'. As a result, the interference at detector 1136 can change accordingly, which can be used to estimate the height change. In this way, integrated optical system 1100 can allow for a very compact sensor for measuring height or distance changes. In some aspects, integrated optical system 1100 can be combined with integrated optical systems 900 and / or 1000 ( Fig. 9 and Fig.10 ) to produce a hybrid measurement system.

[0121] In some aspects, the inspection system disclosed herein may include an analyzer (e.g., processor 432) for analyzing measurement signals from detectors. For example, the processor may analyze first and second measurement signals from corresponding first and second detectors. The processor may determine a position of the target based on the analysis of the first measurement signal, and determine a correction value for the position based on the analysis of the second measurement signal. The correction value may correspond to one of the tilt, defocus, stack profile, etc. of the target. A second correction value may be determined, which may correspond to another one of the tilt, defocus, stack profile, etc. of the target.

[0122] In some aspects, tilt and defocus of the target are not the only mechanisms that can cause the radiation spot to shift on the grating coupler.For example, photolithographic preparation can include stacking multiple layers of patterns on a substrate.

[0123] Fig.12 An arrangement for collecting radiation scattered by a target 1242 having a lithographic stack (or stack) according to some aspects is shown. A radiation beam 1244 can be coaxially incident on the target 1242. The radiation 1244 can originate from a radiation source. An objective lens 1246 can be used to focus the radiation 1244. The objective lens 1246 can be disposed at a pupil plane. The target 1242 can scatter the radiation 1244 to produce scattered radiation 1238 and 1240 (e.g., +1 and -1 diffraction orders, +2 and -2 diffraction orders, etc.).

[0124] In some aspects, the angular spectrum of propagating radiation within the stack can vary. This can result in a shift in the perceived scattering point at target 1242. In addition, the stack spectral reflectivity can also cause a shift in the central wavelength. Thus, non-zero diffraction orders can be diffracted at angles different than expected (shown as radiation 1238' and 1240'), and the diffraction orders can be shifted at the pupil plane by an amount indicated by displacements 1248 and 1250 and corresponding phase shift 1252. Thus, if the total height map is known from another measurement, it can be used, for example Fig.10 , Fig.11A or Fig. 11B The setup shown in Figure 2 was used to measure the overlay variation.

[0125] In some aspects, the wavefront 1254 of the radiation at the objective lens 1246 may have aberrations (e.g., the wavefront is not a uniform wavefront). Even in systems that are sensitive to non-uniform wavefronts, pupil spot shifts, and / or wavelength shifts, aspects of the integrated optical systems described herein can be used to obtain accurate correction values.

[0126] The embodiments may be further described using the following aspects:

[0127] 1. An inspection system, comprising:

[0128] a radiation source configured to generate radiation to irradiate a target;

[0129] An integrated optical system, the optical integrated system comprising:

[0130] substrate;

[0131] a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide disposed on the substrate;

[0132] A first grating coupler and a second grating coupler are provided on the substrate, wherein

[0133] The first grating coupler is configured to couple a first portion and a third portion of radiation scattered by the target into the first waveguide and a third waveguide, respectively, and

[0134] the second grating coupler being configured to couple a second portion and a fourth portion of radiation scattered by the target into the second waveguide and the fourth waveguide, respectively;

[0135] a first combiner coupled to the first and second waveguides, disposed on the substrate, and configured to combine the first and second portions of radiation; and

[0136] a second combiner coupled to the third and fourth waveguides, disposed on the substrate, and configured to combine the third and fourth portions of radiation;

[0137] a first detector configured to receive the combined first and second parts of radiation from the first combiner and to generate a first measurement signal based on the combined first and second parts of radiation; and

[0138] A second detector is configured to receive the combined third and fourth portions of radiation from the second combiner and to generate a second measurement signal based on the combined third and fourth portions of radiation.

[0139] 2. The inspection system according to aspect 1, further comprising a processor, wherein the processor is configured to:

[0140] analyzing the first and second measurement signals; and

[0141] The position of the target is determined based on the evaluation of the first measurement signal, and a correction value for the position is determined based on the evaluation of the second measurement signal.

[0142] 3. An inspection system according to aspect 2, wherein the correction value corresponds to a tilt, defocus or overlay profile of the target.

[0143] 4. The inspection system according to aspect 1, wherein the first detector and the second detector are arranged on the substrate.

[0144] 5. The inspection system according to aspect 1, wherein:

[0145] The integrated optical system further includes a fifth waveguide and a sixth waveguide disposed on the substrate;

[0146] the first grating coupler being configured to couple a fifth portion and a sixth portion of radiation scattered by the target into the fifth and sixth waveguides, respectively;

[0147] The integrated optical system further includes a third combiner coupled to the fifth and sixth waveguides, disposed on the substrate, and configured to combine the fifth and sixth portions of radiation; and

[0148] The inspection system further includes a third detector configured to receive the combined fifth and sixth portions of radiation from the third combiner and to generate a third measurement signal based on the combined first and second portions of radiation.

[0149] 6. The inspection system according to aspect 5, further comprising a processor, wherein the processor is configured to:

[0150] analyzing the first measurement signal, the second measurement signal and the third measurement signal; and

[0151] The position of the target is determined based on the evaluation of the first measurement signal, a first correction value for the position is determined based on the evaluation of the second measurement signal, and a second correction value for the position is determined based on the evaluation of the third measurement signal.

[0152] 7. The inspection system according to aspect 6, wherein:

[0153] The first correction value corresponds to one of a tilt, a defocus, or a stack profile of the target; and

[0154] The second correction value corresponds to a different one of a tilt, a defocus, or an overlay profile of the target.

[0155] 8. The inspection system according to aspect 1, wherein:

[0156] The integrated optical system further comprises:

[0157] a fifth waveguide and a sixth waveguide, wherein the fifth waveguide and the sixth waveguide are disposed on the substrate;

[0158] a third grating coupler disposed on the substrate and configured to couple fifth and sixth portions of radiation scattered by the target into the fifth and sixth waveguides, respectively; and

[0159] a third combiner coupled to the fifth and sixth waveguides, disposed on the substrate, and configured to combine the fifth and sixth portions of radiation; and

[0160] The inspection system further includes a third detector configured to receive the combined fifth and sixth portions of radiation from the third combiner and to generate a third measurement signal based on the combined first and second portions of radiation.

[0161] 9. The inspection system according to aspect 8, further comprising a processor, wherein the processor is configured to:

[0162] analyzing at least the third measurement signal; and

[0163] A defocus of the target is determined based on an analysis of the third measurement signal.

[0164] 10. The inspection system according to aspect 1, wherein:

[0165] The first grating coupler is further configured to perform coupling of the first and third portions of radiation such that the first and third portions of radiation have approximately equal intensities; and

[0166] The second grating coupler is further configured to perform coupling of the second and fourth portions of radiation such that the second and fourth portions of radiation have approximately equal intensities.

[0167] 11. A lithographic apparatus comprising:

[0168] an illumination system configured to illuminate a pattern forming device;

[0169] a projection system configured to project an image of the pattern onto a wafer; and

[0170] An inspection system, the inspection system comprising:

[0171] a radiation source configured to generate radiation to irradiate a target;

[0172] An integrated optical system, the optical integrated system comprising:

[0173] substrate;

[0174] a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide disposed on the substrate;

[0175] A first grating coupler and a second grating coupler are provided on the substrate, wherein

[0176] The first grating coupler is configured to couple a first portion and a third portion of radiation scattered by the target into the first waveguide and a third waveguide, respectively, and

[0177] the second grating coupler being configured to couple a second portion and a fourth portion of radiation scattered by the target into the second waveguide and the fourth waveguide, respectively;

[0178] a first combiner coupled to the first and second waveguides, disposed on the substrate, and configured to combine the first and second portions of radiation; and

[0179] a second combiner coupled to the third and fourth waveguides, disposed on the substrate, and configured to combine the third and fourth portions of radiation;

[0180] a first detector configured to receive the combined first and second parts of radiation from the first combiner and to generate a first measurement signal based on the combined first and second parts of radiation; and

[0181] A second detector is configured to receive the combined third and fourth portions of radiation from the second combiner and to generate a second measurement signal based on the combined third and fourth portions of radiation.

[0182] 12. The lithographic apparatus according to clause 11, further comprising a processor configured to:

[0183] analyzing the first and second measurement signals; and

[0184] The position of the target is determined based on the evaluation of the first measurement signal, and a correction value for the position is determined based on the evaluation of the second measurement signal.

[0185] 13. The lithographic apparatus of clause 12, wherein the correction value corresponds to a tilt, defocus or overlay profile of the target.

[0186] 14. The lithographic apparatus of clause 11, wherein the first detector and the second detector are disposed on the substrate.

[0187] 15. The lithographic apparatus of clause 11, wherein:

[0188] The integrated optical system further includes a fifth waveguide and a sixth waveguide disposed on the substrate;

[0189] the first grating coupler being configured to couple a fifth portion and a sixth portion of radiation scattered by the target into the fifth and sixth waveguides, respectively;

[0190] The integrated optical system further includes a third combiner coupled to the fifth and sixth waveguides, disposed on the substrate, and configured to combine the fifth and sixth portions of radiation; and

[0191] The inspection system further includes a third detector configured to receive the combined fifth and sixth portions of radiation from the third combiner and to generate a third measurement signal based on the combined first and second portions of radiation.

[0192] 16. The lithographic apparatus of clause 15, further comprising a processor configured to:

[0193] analyzing the first measurement signal, the second measurement signal and the third measurement signal; and

[0194] The position of the target is determined based on the evaluation of the first measurement signal, a first correction value for the position is determined based on the evaluation of the second measurement signal, and a second correction value for the position is determined based on the evaluation of the third measurement signal.

[0195] 17. The lithographic apparatus of clause 16, wherein:

[0196] The first correction value corresponds to one of a tilt, a defocus, or a stack profile of the target; and

[0197] The second correction value corresponds to a different one of a tilt, a defocus, or an overlay profile of the target.

[0198] 18. The inspection system according to aspect 11, wherein:

[0199] The integrated optical system further comprises:

[0200] a fifth waveguide and a sixth waveguide, wherein the fifth waveguide and the sixth waveguide are disposed on the substrate;

[0201] a third grating coupler disposed on the substrate and configured to couple fifth and sixth portions of radiation scattered by the target into the fifth and sixth waveguides, respectively; and

[0202] a third combiner coupled to the fifth and sixth waveguides, disposed on the substrate, and configured to combine the fifth and sixth portions of radiation; and

[0203] The inspection system further includes a third detector configured to receive the combined fifth and sixth portions of radiation from the third combiner and to generate a third measurement signal based on the combined first and second portions of radiation.

[0204] 19. The inspection system according to aspect 18, further comprising a processor configured to:

[0205] analyzing at least the third measurement signal; and

[0206] A defocus of the target is determined based on an analysis of the third measurement signal.

[0207] 20. The inspection system according to aspect 11, wherein:

[0208] The first grating coupler is further configured to perform coupling of the first and third portions of radiation such that the first and third portions of radiation have approximately equal intensities; and

[0209] The second grating coupler is further configured to perform coupling of the second and fourth portions of radiation such that the second and fourth portions of radiation have approximately equal intensities.

[0210] 21. A method comprising:

[0211] generating radiation to irradiate a target;

[0212] receiving first and third portions of radiation scattered by the object at first and third positions, respectively, of a first grating coupler, wherein phase delays of the first and third portions of radiation are based on incidence at the first and third positions, respectively;

[0213] receiving a second portion and a fourth portion of radiation scattered by the target at a second position and a fourth position, respectively, of a second grating coupler, wherein a phase delay of the second portion and the fourth portion of radiation is based on incidence at the second position and the fourth position, respectively;

[0214] combining the first and second portions of radiation;

[0215] generating, based on the combination of the first and second parts of radiation, a first measurement signal comprising information of a phase delay of the first and second parts of radiation;

[0216] combining the third and fourth portions of radiation;

[0217] generating, based on the combination of the third and fourth parts of the radiation, a second measurement signal comprising information of a phase delay of the third and fourth parts of the radiation;

[0218] determining the position of the target based on analyzing information of the phase delay of the first and second portions of radiation; and

[0219] A correction value for the position is determined based on information analyzing the phase delays of the third and fourth parts of the radiation.

[0220] 22. An inspection system comprising:

[0221] a radiation source configured to generate radiation to irradiate a target;

[0222] An integrated optical system, the optical integrated system comprising:

[0223] substrate;

[0224] A waveguide system disposed on the substrate; and

[0225] A first grating coupler and a second grating coupler are provided on the substrate, wherein

[0226] a first grating coupler configured to receive a first portion and a third portion of radiation scattered by the target at a first position and a third position of the first grating coupler, respectively, and to couple the first portion and the third portion of radiation into the waveguide system,

[0227] the phase delays of the first and third portions of radiation are based on incidence at the first and third positions, respectively,

[0228] a second grating coupler configured to receive a second portion and a fourth portion of radiation scattered by the target at a second position and a fourth position of the second grating coupler, respectively, and to couple the second portion and the fourth portion of radiation into the waveguide system, and

[0229] the phase delays of the second and fourth portions of radiation being based on incidence at the second and fourth locations, respectively;

[0230] a first detector configured to receive a combination of the first and second parts of radiation to generate a first measurement signal comprising information of a phase delay of the first and second parts of radiation;

[0231] a second detector configured to receive a combination of the third and fourth portions of radiation to generate a second measurement signal comprising information of a phase delay of the third and fourth portions of radiation; and

[0232] A processor configured to:

[0233] analyzing the first measurement signal and the second measurement signal;

[0234] determining the position of the target based on information about the phase delay of the first and second parts of radiation; and

[0235] A correction value for the position is determined based on information of the phase delays of the third and fourth parts of the radiation.

[0236] The terms "radiation" and "beam", "light", "irradiation", etc. may be used herein to refer to one or more types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength λ of 365 nm, 355 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and extreme ultraviolet (EUV or soft X-ray) radiation (e.g., having a wavelength in the range of 5 nm to 100 nm, such as, for example, a wavelength of 13.5 nm), or hard X-rays operating at less than 5 nm, and particle beams (such as ion beams or electron beams). Generally, radiation having a wavelength between about 400 nm and about 700 nm is considered visible radiation; radiation having a wavelength between about 780 nm and 3000 nm (or greater) is considered IR radiation. UV refers to radiation having a wavelength of about 100 nm to 400 nm. In lithography, the term "UV" also applies to wavelengths that can be produced by mercury discharge lamps: G line 436 nm; H line 405 nm; and / or I line 365 nm. Vacuum UV or VUV (i.e., UV absorbed by gases) refers to radiation having a wavelength of about 100 nm to 200 nm. Deep UV (DUV) generally refers to radiation having a wavelength range from 126 nm to 428 nm, and in some aspects, an excimer laser can produce DUV radiation for use within a lithographic apparatus. It should be understood that radiation having a wavelength in the range of, for example, 5 nm to 20 nm refers to radiation having a wavelength band, at least a portion of which is in the range of 5 nm to 20 nm.

[0237] Although some aspects of the present disclosure are described in the context of a lithographic apparatus in the manufacture of an IC, it should be understood that the lithographic apparatus described herein may be used in other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal displays (LCDs), thin film magnetic heads, and the like. Those skilled in the art will appreciate that in the context of such alternative applications, any term "wafer" or "die" used herein may be considered to be a specific example of the more general term "substrate" or "target portion", respectively. The substrate may be processed before or after exposure, for example in a coating and developing system unit (a tool that typically applies a resist layer to a substrate and develops the exposed resist) and / or a metrology unit. Where applicable, the aspects disclosed herein may be applied to such and other substrate processing tools. In addition, the substrate may be processed more than once, for example to produce a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0238] In addition, although 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, the topography in the patterning device defines the pattern produced on the substrate. The topography of the patterning device can be imprinted into a resist layer supplied to the substrate, thereby curing the resist by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is removed from the resist, leaving a pattern in the resist.

[0239] It should be understood that the phraseology or terminology herein is for the purpose of description rather than limitation, so that the phraseology or terminology in this specification will be interpreted by those skilled in the relevant art in accordance with the teachings herein.

[0240] The present disclosure has been described above with the aid of functional building blocks illustrating the implementation methods of the specified functions and their interrelationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined in this article. As long as the specified functions and their relationships are properly performed, the boundaries of replacement can be defined. The foregoing description of specific aspects will fully reveal the general nature of the present disclosure so that others can easily modify and / or adapt to various applications of these specific aspects by applying knowledge within the technical scope of the art without departing from the overall concept of the present disclosure and without excessive experimentation. Therefore, based on the teachings and guidance proposed herein, such adaptations and modifications are intended to fall within the meaning and scope of equivalents of the disclosed aspects.

[0241] It will be understood that the Detailed Description section, rather than the Summary section and the Abstract section, is intended to be used to interpret the claims. As contemplated by the inventors, the Summary section and the Abstract section may illustrate one or more, but not necessarily all, aspects of the present disclosure, and therefore are not intended to limit the present disclosure and the appended claims in any way. The breadth and scope of the protected subject matter should not be limited by any of the aspects described above, but rather by the appended claims and their equivalents.

Claims

1. An inspection system, comprising: a radiation source configured to generate radiation to irradiate a target; An integrated optical system, the optical integrated system comprising: substrate; a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide disposed on the substrate; A first grating coupler and a second grating coupler are provided on the substrate, wherein The first grating coupler is configured to couple a first portion and a third portion of radiation scattered by the target into the first waveguide and a third waveguide, respectively, and the second grating coupler being configured to couple a second portion and a fourth portion of radiation scattered by the target into the second waveguide and the fourth waveguide, respectively; a first combiner coupled to the first and second waveguides, disposed on the substrate, and configured to combine the first and second portions of radiation; and a second combiner coupled to the third and fourth waveguides, disposed on the substrate, and configured to combine the third and fourth portions of radiation; a first detector configured to receive the combined first and second parts of radiation from the first combiner and to generate a first measurement signal based on the combined first and second parts of radiation; and A second detector is configured to receive the combined third and fourth portions of radiation from the second combiner and to generate a second measurement signal based on the combined third and fourth portions of radiation.

2. The inspection system of claim 1 , further comprising a processor configured to: analyzing the first and second measurement signals; and The position of the target is determined based on the evaluation of the first measurement signal, and a correction value for the position is determined based on the evaluation of the second measurement signal.

3. The inspection system according to claim 2, wherein: The correction value corresponds to the tilt, defocus or overlay profile of the target.

4. The inspection system according to claim 1, wherein: The first detector and the second detector are disposed on the substrate.

5. The inspection system according to claim 1, wherein: The integrated optical system further includes a fifth waveguide and a sixth waveguide disposed on the substrate; the first grating coupler being configured to couple a fifth portion and a sixth portion of radiation scattered by the target into the fifth and sixth waveguides, respectively; The integrated optical system further includes a third combiner coupled to the fifth and sixth waveguides, disposed on the substrate, and configured to combine the fifth and sixth portions of radiation; and The inspection system further includes a third detector configured to receive the combined fifth and sixth portions of radiation from the third combiner and to generate a third measurement signal based on the combined first and second portions of radiation.

6. The inspection system of claim 5, further comprising a processor configured to: analyzing the first measurement signal, the second measurement signal and the third measurement signal; and The position of the target is determined based on the evaluation of the first measurement signal, a first correction value for the position is determined based on the evaluation of the second measurement signal, and a second correction value for the position is determined based on the evaluation of the third measurement signal.

7. The inspection system according to claim 6, wherein: The first correction value corresponds to one of a tilt, a defocus, or a stack profile of the target; and The second correction value corresponds to a different one of a tilt, a defocus, or an overlay profile of the target.

8. The inspection system of claim 1, wherein: The integrated optical system further comprises: a fifth waveguide and a sixth waveguide, wherein the fifth waveguide and the sixth waveguide are disposed on the substrate; a third grating coupler disposed on the substrate and configured to couple fifth and sixth portions of radiation scattered by the target into the fifth and sixth waveguides, respectively; and a third combiner coupled to the fifth and sixth waveguides, disposed on the substrate, and configured to combine the fifth and sixth portions of radiation; and The inspection system further includes a third detector configured to receive the combined fifth and sixth portions of radiation from the third combiner and to generate a third measurement signal based on the combined first and second portions of radiation.

9. The inspection system of claim 8, further comprising a processor configured to: analyzing at least the third measurement signal; and A defocus of the target is determined based on an analysis of the third measurement signal.

10. The inspection system of claim 1, wherein: The first grating coupler is further configured to perform coupling of the first and third portions of radiation such that the first and third portions of radiation have approximately equal intensities; and The second grating coupler is further configured to perform coupling of the second and fourth portions of radiation such that the second and fourth portions of radiation have approximately equal intensities.

11. A lithographic apparatus comprising: an illumination system configured to illuminate a pattern forming device; a projection system configured to project an image of the pattern onto a wafer; as well as An inspection system, the inspection system comprising: a radiation source configured to generate radiation to irradiate a target; An integrated optical system, the optical integrated system comprising: substrate; a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide disposed on the substrate; A first grating coupler and a second grating coupler are provided on the substrate, wherein The first grating coupler is configured to couple a first portion and a third portion of radiation scattered by the target into the first waveguide and a third waveguide, respectively, and the second grating coupler being configured to couple a second portion and a fourth portion of radiation scattered by the target into the second waveguide and the fourth waveguide, respectively; a first combiner coupled to the first and second waveguides, disposed on the substrate, and configured to combine the first and second portions of radiation; and a second combiner coupled to the third and fourth waveguides, disposed on the substrate, and configured to combine the third and fourth portions of radiation; a first detector configured to receive the combined first and second parts of radiation from the first combiner and to generate a first measurement signal based on the combined first and second parts of radiation; and A second detector is configured to receive the combined third and fourth portions of radiation from the second combiner and to generate a second measurement signal based on the combined third and fourth portions of radiation.

12. The lithographic apparatus according to claim 11, further comprising a processor configured to: analyzing the first and second measurement signals; and The position of the target is determined based on the evaluation of the first measurement signal, and a correction value for the position is determined based on the evaluation of the second measurement signal.

13. The lithographic apparatus according to claim 12, wherein: The correction value corresponds to the tilt, defocus or overlay profile of the target.

14. The lithographic apparatus according to claim 11, wherein: The first detector and the second detector are disposed on the substrate.

15. The lithographic apparatus of claim 11, wherein: The integrated optical system further includes a fifth waveguide and a sixth waveguide disposed on the substrate; the first grating coupler being configured to couple a fifth portion and a sixth portion of radiation scattered by the target into the fifth and sixth waveguides, respectively; The integrated optical system further includes a third combiner coupled to the fifth and sixth waveguides, disposed on the substrate, and configured to combine the fifth and sixth portions of radiation; and The inspection system further includes a third detector configured to receive the combined fifth and sixth portions of radiation from the third combiner and to generate a third measurement signal based on the combined first and second portions of radiation.

Images