Lithography apparatus, metrology system, digital holographic microscopy alignment sensor and method thereof

Abstract

A system includes an illumination system, an optical system, a detector system, and a processor. The illumination system directs a first illumination beam and a second illumination beam toward the target structure, and directs a first reference beam toward the detector system. The optical system directs the first scattered beam and the second scattered beam from the target structure to the detector system. A detector system captures the interference pattern and outputs a measurement signal. The first scattered beam, the second scattered beam, and the first reference beam generate an interference pattern. The processor analyzes the measurement signal to determine a characteristic of the target structure.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Application 63 / 585,762, filed on September 27, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This disclosure relates to a photolithography apparatus. For example, this disclosure relates to a measurement sensor based on digital holographic microscopy. Background Technology

[0003] A photolithography apparatus is a machine that applies a desired pattern onto a substrate (typically onto a target portion of the substrate). For example, a photolithography apparatus can be used to fabricate integrated circuits (ICs). In this instance, a patterning apparatus (alternatively referred to as a mask or photomask) can be used to generate circuit patterns to be formed on various layers of the IC. This pattern can be transferred onto target portions (e.g., including portions of a die, one or more dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is typically via imaging onto a radiation-sensitive material (resist) layer provided on the substrate. Typically, a single substrate will contain a network of adjacent target portions patterned sequentially. Known photolithography apparatuses include so-called steppers (where each target portion is irradiated by exposing the entire pattern onto the target portion at once) and so-called scanners (where each target portion is irradiated by scanning the pattern with a radiation beam in a given direction (“scanning” direction) while simultaneously scanning target portions parallel or antiparallel to that scanning direction). A pattern can also be transferred from a patterning apparatus to a substrate by imprinting the pattern onto the substrate.

[0004] During photolithography operations, different processing steps may require different layers to be formed sequentially on a substrate. Therefore, it may be necessary to position the substrate with high accuracy relative to the previously formed pattern. Typically, alignment marks are placed on the substrate to be aligned and positioned with reference to a second object. The photolithography apparatus can use alignment devices to detect the position of the alignment marks and use the alignment marks to align the substrate to ensure accurate exposure from the mask. Misalignment between alignment marks at two different layers is measured as overlay error.

[0005] To monitor the photolithography process, parameters of the patterned substrate are measured. These parameters may include, for example, overlay errors between successive layers formed in or on the patterned substrate and the critical linewidth of the developing photoresist. This measurement can be performed on product substrates and / or specialized measurement targets. Various techniques exist for measuring the microstructures formed in the photolithography process, including the use of scanning electron microscopy and various specialized tools. One rapid and non-invasive form of specialized inspection tool is a scatterometer, where a radiation beam is directed onto a target on the substrate surface, and the properties of the scattered or reflected beam are measured. By comparing the properties of the beam before and after reflection or scattering by the substrate, the properties of the substrate can be determined. For example, this can be done by comparing the reflected beam with data stored in a library of known measurements associated with known substrate properties. A spectroscopic scatterometer directs a broadband radiation beam onto the substrate and measures the spectrum (intensity as a function of wavelength) of the radiation scattered over a specific narrow angular range. In contrast, an angle-resolved scatterometer uses a monochromatic radiation beam and measures the intensity of the scattered radiation as a function of angle.

[0006] As discussed above, alignment devices or measurement systems can detect the position of alignment marks to align the substrate. However, optical aberrations in the alignment device or measurement system can cause errors in alignment measurements. Errors in wafer alignment in lithography apparatus lead to reduced fabrication equipment quality, unreliable performance, and lower yields, which in turn increase fabrication time and costs. Summary of the Invention

[0007] Therefore, it is desirable to improve the performance of measurement systems. For example, it is desirable to provide alignment measurements within the extended wavelength range discussed in the embodiments described herein.

[0008] In some embodiments, a system may include an illumination system, an optical system, a detector system, and a processor. The illumination system directs a first illumination beam and a second illumination beam toward a target structure, and directs a first reference beam toward the detector system. The optical system directs a first scattered beam and a second scattered beam from the target structure to the detector system. The detector system captures an interference pattern and outputs a measurement signal. The first scattered beam, the second scattered beam, and the first reference beam generate an interference pattern. The processor analyzes the measurement signal to determine the characteristics of the target structure.

[0009] In some embodiments, a method includes guiding a first illumination beam and a second illumination beam toward a target structure to generate a first scattered beam and a second scattered beam. The method may further include guiding a reference beam toward a detector system and detecting an interference pattern of the first scattered beam, the second scattered beam, and the reference beam. The method may also include using a processor to determine characteristics of the target structure based at least on the detected interference pattern.

[0010] In some embodiments, a photolithography apparatus may include an illumination system, a projection system, and an inspection system. The illumination system illuminates a pattern formed by a pattern forming apparatus. The projection system projects an image from the pattern forming apparatus onto a substrate. The inspection system includes an illumination system, an optical system, a detector system, and a processor. The illumination system guides a first illumination beam and a second illumination beam toward a target structure, and guides a first reference beam toward the detector system. The optical system guides a first scattered beam and a second scattered beam from the target structure to the detector system. The detector system captures an interference pattern and outputs a measurement signal. The first scattered beam, the second scattered beam, and the first reference beam generate an interference pattern. The processor analyzes the measurement signal to determine the characteristics of the target structure.

[0011] In some embodiments, a system may include an illumination system, an optical system, a detector system, and a processor. The illumination system directs a first illumination beam and a second illumination beam toward a target structure, and directs a first reference beam and a second reference beam toward the detector system. The first illumination beam and the first reference beam are coherent. The second illumination beam and the second reference beam are coherent, and the first illumination beam and the first reference beam are incoherent with the second illumination beam and the second reference beam. The optical system may be configured to direct a first scattered beam and a second scattered beam from the target structure to the detector system. The first scattered beam includes at least two positive diffraction orders, and the second scattered beam includes at least two negative diffraction orders. The detector system captures a first interference pattern and a second interference pattern, and at least generates a measurement signal. The processor analyzes the measurement signal to determine the alignment characteristics of the target structure.

[0012] Other features of this disclosure, as well as the structure and operation of the various embodiments, are described in detail below with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0013] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the disclosure and enable those skilled in the art to make and use the embodiments described herein.

[0014] Figure 1A A schematic diagram of a reflective lithography apparatus according to some embodiments is shown.

[0015] Figure 1B A schematic diagram of a transmission lithography apparatus according to some embodiments is shown.

[0016] Figure 2 A more detailed schematic diagram of a reflective lithography apparatus according to some embodiments is shown.

[0017] Figure 3 A schematic diagram of a photolithography unit according to some embodiments is shown.

[0018] Figure 4A and 4B A schematic diagram of an inspection apparatus according to some embodiments is shown.

[0019] Figure 5 A schematic diagram of an inspection system according to some embodiments is shown.

[0020] Figure 6A A schematic diagram of an inspection system according to some embodiments is shown.

[0021] Figure 6B A schematic diagram of the diffraction pattern at the pupil plane of an inspection system according to some embodiments is shown.

[0022] Figure 7A A schematic diagram of an inspection system according to some embodiments is shown.

[0023] Figure 7B A schematic diagram of an inspection system according to some embodiments is shown.

[0024] Figure 7C A schematic diagram of the diffraction pattern at the pupil plane of an inspection system according to some embodiments is shown.

[0025] Figure 8 A schematic diagram of an inspection system according to some embodiments is shown.

[0026] Figure 9A A schematic diagram of a process for determining target characteristics according to some embodiments is shown.

[0027] Figure 9B A schematic diagram of a process for determining target characteristics according to some embodiments is shown.

[0028] Figure 9C A schematic diagram of the diffraction pattern at the pupil plane of an inspection system according to some embodiments is shown.

[0029] Figure 10 This is a flowchart of a method for determining target characteristics according to some embodiments.

[0030] Figure 11 These are example computer systems for implementing various embodiments.

[0031] The features of this disclosure will become more apparent when viewed in conjunction with the accompanying drawings, through the detailed description of the embodiments described below, wherein similar reference numerals consistently identify corresponding elements. In the drawings, similar reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, typically, the leftmost numeral(s) of the reference numeral(s) identifies the drawing in which the reference numeral(s) first appear. Unless otherwise indicated, the drawings provided throughout this disclosure should not be construed as being drawn to scale. Detailed Implementation

[0032] This specification discloses one or more embodiments of the features incorporated herein. The disclosed embodiments are provided as examples. The scope of this disclosure is not limited to the disclosed embodiments. The claimed features are defined by the appended claims.

[0033] The described embodiments and references to "an embodiment," "embodiment," "example embodiment," etc., in the specification may include specific features, structures, or characteristics, but each embodiment may not necessarily include that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Further, when a specific feature, structure, or characteristic is described in conjunction with an embodiment, it is to be understood that, whether explicitly described or not, it is within the knowledge of those skilled in the art to implement such a feature, structure, or characteristic in conjunction with other embodiments.

[0034] Spatial terms (such as “below,” “under,” “lower,” “above,” “above,” “upper,” etc.) may be used herein for convenience of description to describe the relationship of an element or feature to another element or feature(s) illustrated in the accompanying drawings. In addition to the orientations depicted in the accompanying drawings, spatial relative terms are intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein may be interpreted accordingly.

[0035] As used herein, the term "approximately" indicates a given number of values ​​that may vary based on a particular technique. Based on a particular technique, the term "approximately" may indicate a given number of values ​​that vary within, for example, 10% to 30% of that value (e.g., ±10%, ±20%, or ±30% of the value).

[0036] Embodiments of this disclosure can be implemented in hardware, firmware, software, or any combination thereof. Embodiments of this disclosure can also be implemented as instructions stored on a machine-readable medium that can be read and executed by one or more processors. A machine-readable medium can include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium can include read-only memory (ROM); random access memory (RAM); disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.); and others. Further, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that this description is merely for convenience, and such actions are in fact caused by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0037] However, it is beneficial to present an example environment in which the embodiments of this disclosure can be implemented before describing such embodiments in more detail. Example lithography system

[0038] Figure 1A and 1B Schematic illustrations of lithography apparatus 100 and 100', respectively, for implementing embodiments of the present disclosure, are shown. Lithography apparatus 100 and 100' each include: an irradiation system (irradiator) IL configured to modulate a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., mask stage) MT configured to support a patterning apparatus (e.g., a mask, stencil, or dynamic patterning apparatus) MA and connected to a first positioner PM configured to accurately position the patterning apparatus MA; and a substrate stage (e.g., wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Lithography apparatuses 100 and 100' also have a projection system PS configured to project a pattern imparted by the radiation beam B by the patterning apparatus MA onto a target portion (e.g., comprising one or more dies) C of the substrate W. In the photolithography apparatus 100, the pattern forming device MA and the projection system PS are reflective. In the photolithography apparatus 100', the pattern forming device MA and the projection system PS are transmissive.

[0039] The irradiation system IL may include various types of optical components, such as refractive, reflective, reflective-refractive, magnetic, electromagnetic, electrostatic or other types of optical components or any combination thereof, for guiding, shaping or controlling the radiation beam B.

[0040] The support structure MT holds the patterning apparatus MA in a manner dependent on the orientation of the patterning apparatus MA relative to a reference frame, the design of at least one of the lithography apparatuses 100 and 100', and other conditions such as whether the patterning apparatus MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning apparatus MA. The support structure MT can be a frame or a stage, which may be fixed or movable as needed. For example, by using sensors, the support structure MT can ensure that the patterning apparatus MA is positioned relative to the projection system PS at a desired location.

[0041] The term "patterning apparatus" MA should be interpreted broadly to refer to any apparatus that can be used to impart a pattern to a radiation beam B in its cross-section, such as creating a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B can correspond to a specific functional layer in the apparatus created in the target portion C to form an integrated circuit.

[0042] The terms “detection device” and “measurement system” may be used in this document to refer to, for example, a device or system used to measure the properties of a structure (e.g., overlay sensor, critical size sensor, etc.) or to check wafer alignment in a lithography apparatus (e.g., alignment device).

[0043] The pattern forming device MA can be transmissive (e.g., in...) Figure 1B In the photolithography apparatus 100') or reflective (such as in Figure 1A (In the photolithography apparatus 100). Examples of pattern forming apparatus MA include photomasks, masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in photolithography and include mask types such as binary mask types, alternating phase-shift mask types, or attenuation phase-shift mask types, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect the incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B reflected by the array of small mirrors.

[0044] The term "projection system" PS can encompass any type of projection system, including refractive, reflective, reflective-refractive, magnetic, electromagnetic, and electrostatic optical systems or any combination thereof, as suitable for the exposure radiation used or for other factors such as immersion on a substrate W or the use of a vacuum. A vacuum environment can be used for EUV or electron beam radiation because other gases may absorb excessive radiation or electrons. Therefore, a vacuum environment can be provided throughout the optical path by means of vacuum walls and vacuum pumps.

[0045] The lithography apparatus 100 and / or lithography apparatus 100' can be of the type having two (dual-platform) or more substrate stages WT (and / or two or more mask stages). In such a "multi-platform" machine, the additional substrate stages WT can be used in parallel, or preparation steps can be performed on one or more stages while one or more other substrate stages WT are being used for exposure. In some cases, the additional stage may not be a substrate stage WT.

[0046] Photolithography apparatuses can also be of the type in which at least a portion of the substrate can be covered by a liquid with a relatively high refractive index (e.g., water) to fill the space between the projection system and the substrate. Immersion liquid can also be applied to other spaces in the photolithography apparatus, such as the space between the mask and the projection system. Immersion techniques are well known in the art to increase the numerical aperture of the projection system. The term “immersion” as used herein does not mean that structures such as the substrate must be submerged in the liquid; rather, immersion simply means that the liquid is located between the projection system and the substrate during exposure.

[0047] refer to Figure 1A and 1B The irradiator IL receives a radiation beam from the radiation source SO. The source SO and the lithography apparatus 100, 100' can be separate physical entities, for example, when the source SO is an excimer laser. In this case, the source SO is not considered part of forming the lithography apparatus 100 or 100', and is delivered by means of a beam delivery system BD (in [the context of the lithography apparatus 100 or 100') including, for example, suitable directional mirrors and / or beam expanders). Figure 1B In the lithography apparatus 100, 100', the radiation beam B is delivered from the source SO to the irradiator IL. In other cases, the source SO may be an integral part of the lithography apparatus 100, 100', for example, when the source SO is a mercury lamp. The source SO, the irradiator IL, and (if necessary) the beam delivery system BD may be referred to as the radiation system.

[0048] The irradiator IL may include an adjuster AD (in) Figure 1B The irradiator (IL) is used to adjust the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial ranges of the intensity distribution within the pupil plane of the irradiator (generally referred to as "σ outer" and "σ inner," respectively) can be adjusted. Additionally, the irradiator IL may include various other components (in... Figure 1B (In the middle), such as integrator IN and convergent CO. Irradiator IL can be used to adjust the radiation beam B so as to have the desired uniformity and intensity distribution in its cross-section.

[0049] refer to Figure 1AA radiation beam B is incident on a patterning apparatus (e.g., a mask) MA and patterned by the patterning apparatus MA, which is held on a support structure (e.g., a mask stage) MT. In the lithography apparatus 100, the radiation beam B is reflected from the patterning apparatus (e.g., the mask) MA. After reflection from the patterning apparatus (e.g., the mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. The substrate stage WT can be accurately moved (e.g., to position different target portions C in the path of the radiation beam B) by means of a second positioner PW and a position sensor IF2 (e.g., an interferometer, a linear encoder, or a capacitive sensor). Similarly, a first positioner PM and another position sensor IF1 can be used to accurately position the patterning apparatus (e.g., the mask) MA relative to the path of the radiation beam B. The patterning apparatus (e.g., the mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0050] refer to Figure 1B A radiation beam B is incident on a patterning apparatus (e.g., a mask MA) and patterned by the patterning apparatus, which is held on a support structure (e.g., a mask stage MT). After traversing the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto the target portion C of the substrate W. The projection system has a pupil conjugate PPU that is connected to the illumination system pupil IPU. Part of the radiation is emitted from the intensity distribution at the illumination system pupil IPU and traverses the mask pattern without being affected by diffraction at the mask pattern, creating an image of the intensity distribution at the illumination system pupil IPU.

[0051] The projection system PS projects an image of a mask pattern MP onto a photoresist layer coated on a substrate W, where the image is formed by diffracted beams generated from radiation from the mask pattern MP via an intensity distribution. For example, the mask pattern MP may comprise an array of lines and spaces. Radiation diffraction located at the array, distinct from zero-order diffraction, generates deflected diffracted beams whose direction changes perpendicular to the lines. Non-diffracted beams (i.e., the so-called zero-order diffracted beams) traverse the pattern without any change in their propagation direction. The zero-order diffracted beam traverses the upper lens or upper lens group of the projection system PS, reaching the pupil conjugate PPU upstream of the projection system PS. The intensity distribution portion in the plane of the pupil conjugate PPU and associated with the zero-order diffracted beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. For example, an aperture device PD is disposed or substantially disposed at the plane comprising the pupil conjugate PPU of the projection system PS.

[0052] The projection system PS is arranged to capture not only the zeroth-order diffraction beam, but also first-order or higher-order diffraction beams (not shown) by means of a lens or lens group L. In some embodiments, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to utilize the resolution enhancement effect of dipole illumination. For example, a first-order diffraction beam interferes with a corresponding zeroth-order diffraction beam at the level of the wafer W to create an image of the line pattern MP with the highest possible resolution and process window (i.e., a combination of available depth of focus and tolerable exposure dose deviation). In some embodiments, astigmatic aberration can be reduced by providing a radiating pole (not shown) in the opposite confinement of the illumination system pupil IPU. Further, in some embodiments, astigmatic aberration can be reduced by blocking the zeroth-order beam in the projection system pupil conjugate PPU associated with the radiating pole in the opposite confinement. This is described in more detail in US 7,511,799 B2, published March 31, 2009, which is incorporated herein by reference in its entirety.

[0053] With the aid of a second positioner PW and a position sensor IFD (e.g., an interferometric device, a linear encoder, or a capacitive sensor), the substrate stage WT can be accurately moved (e.g., to position different target portions C within the path of the radiation beam B). Similarly, the first positioner PM and another position sensor (not in...) Figure 1B (As shown in the figure) can be used to accurately position the mask MA relative to the path of the radiation beam B (e.g., after mechanical retrieval from the mask library, or during scanning).

[0054] Typically, movement of the mask stage MT can be achieved using a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) that form part of the first positioner PM. Similarly, movement of the substrate stage WT can be achieved using a long-stroke module and a short-stroke module that form part of the second positioner PW. In the case of a stepper (opposite to the scanner), the mask stage MT can be connected only to the short-stroke actuator, or it can be fixed. The mask MA and substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they can be located in the space between the target portions (called scribing alignment marks). Similarly, when more than one die is provided on the mask MA, the mask alignment marks can be located between the dies.

[0055] The mask stage MT and patterning equipment MA can be located within a vacuum chamber V, where an in-vacuum robot IVR can be used to move patterning equipment such as masks into and out of the vacuum chamber. Alternatively, when the mask stage MT and patterning equipment MA are outside the vacuum chamber, an out-of-vacuum robot can be used for various transport operations, similar to the in-vacuum robot IVR. Both the in-vacuum and out-of-vacuum robots need to be calibrated to smoothly transfer any payload (e.g., masks) to a stationary motion base at the transfer station.

[0056] Photolithography devices 100 and 100' can be used in at least one of the following modes: 1. In step mode, while the entire pattern imparted by the radiation beam B is projected onto the target portion C in one go (i.e., a single static exposure), the support structure (e.g., mask stage) MT and the substrate stage WT remain substantially stationary. The substrate stage WT is then displaced in the X and / or Y directions, allowing different target portions C to be exposed. 2. In scanning mode, as the pattern imparted by the radiation beam B is projected onto the target portion C (i.e., single dynamic exposure), the support structure (e.g., mask stage) MT and the substrate stage WT are scanned synchronously. The velocity and direction of the substrate stage WT relative to the support structure (e.g., mask stage) MT can be determined by the magnification (reduction) and image inversion characteristics of the projection system PS. 3. In another mode, the support structure (e.g., mask stage) MT remains essentially stationary, thus holding the programmable patterning apparatus in place, and the substrate stage WT is moved or scanned as the pattern imparted by the radiation beam B is projected onto the target portion C. A pulsed radiation source SO can be employed, and the programmable patterning apparatus is updated as needed after each movement of the substrate stage WT or between consecutive radiation pulses during scanning. This mode of operation can be readily applied to maskless lithography, which utilizes programmable patterning apparatus such as programmable mirror arrays.

[0057] Combinations and / or variations of the described usage patterns, or entirely different usage patterns, may also be adopted.

[0058] In yet another embodiment, the lithography 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 irradiation system is configured to modulate the EUV radiation beam from the EUV source.

[0059] Figure 2The lithography apparatus 100 is shown in more detail, including a source collector device SO, an irradiation system IL, and a projection system PS. The source collector device SO is constructed and arranged such that a vacuum environment can be maintained within a closed structure 220 of the source collector device SO. EUV radiation emitting plasma 210 can be formed by a plasma source generated by a discharge. EUV radiation can be generated by a gas or vapor, such as xenon, lithium vapor, or tin vapor, wherein a very hot plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is created, for example, by a discharge that results in at least partially ionized plasma. For efficient radiation generation, a partial pressure of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor may be required. In some embodiments, a plasma that excites tin (Sn) is provided to generate EUV radiation.

[0060] Radiation emitted by the thermal plasma 210 enters the collector chamber 212 from the source chamber 211 via an optional gas barrier or contaminant trap 230 (also referred to in some cases as a contaminant barrier or fin trap) located in or behind an opening in the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further indicated herein includes at least a channel structure.

[0061] Collector chamber 212 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 from a grating spectral filter 240 to be focused in a virtual source point INTF. The virtual source point INTF is generally referred to as the intermediate focus, and the source collector arrangement is such that the intermediate focus INTF is located at or near an opening 219 in the enclosed structure 220. The virtual source point INTF is an image of the radiative emission plasma 210. The grating spectral filter 240 is specifically used to suppress infrared (IR) radiation.

[0062] Subsequently, a radiation traversal illumination system IL, which may include a faceted field mirror device 222 and a faceted pupil mirror device 224, is 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. As the radiation beam 221 is reflected at the patterning device MA, held by a support structure MT, a patterned beam 226 is formed, and the patterned beam 226 is imaged by a projection system PS via reflective elements 228 and 229 onto a substrate W, which is held by a wafer platform or substrate stage WT.

[0063] More components than shown can typically be present in the illumination optical unit IL and the projection system PS. Depending on the type of photolithography apparatus, the grating spectral filter 240 may optionally be present. Furthermore, more than shown components may be present. Figure 2 More mirrors are shown, such as those with Figure 2 In contrast, the projection system PS may contain 1 to 6 additional reflective elements.

[0064] like Figure 2 The collector optics CO illustrated is depicted as a nested collector with grazing incidence reflectors 253, 254, and 255, as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 are arranged axially symmetrically about the optical axis O, and preferably, this type of collector optics CO is used in combination with a plasma source generated by a discharge, commonly referred to as a DPP source. Exemplary photolithography unit

[0065] Figure 3 A lithography unit 300, sometimes referred to as a lithography unit or cluster, is shown according to some embodiments. A lithography apparatus 100 or 100' may form part of the lithography unit 300. The lithography unit 300 may also include one or more devices for performing pre-exposure and post-exposure processes on a substrate. In some examples, these include a spin coater SC for depositing a resist layer, a developer DE for developing the post-exposure resist, a cooling plate CH, and a baking plate BK. A substrate handler or robot RO picks up substrates from input / output ports I / O1, I / O2, moves them between different process devices, and delivers them to the loader rack LB of the lithography apparatus 100 or 100'. These devices, generally collectively referred to as tracks, are controlled by a track control unit TCU, which in turn is controlled by a monitoring system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Thus, different devices can be operated to maximize throughput and processing efficiency. Exemplary inspection device

[0066] To control the photolithography process and accurately place device features on the substrate, alignment marks are typically provided on the substrate, and the photolithography apparatus includes one or more inspection devices for accurately positioning the marks on the substrate. These alignment devices are essentially position measurement devices. Different types of marks and different types of alignment devices and / or systems are known at different times and from different manufacturers. One system widely used in current photolithography apparatuses is based on a self-reference interferometer described in U.S. Patent No. 6,961,116 (denBoef et al.). Typically, the marks are measured individually to obtain the X and Y positions. Combined X and Y measurements can be performed using techniques described in U.S. Publication No. 2009 / 195768 A (Bijnen et al.) and U.S. Patent No. 11,360,399 B2 (Goorden et al.). However, the entire contents of these disclosures are incorporated herein by reference.

[0067] Figure 4A A schematic cross-sectional view of an inspection apparatus 400, which may be implemented as part of a photolithography apparatus 100 or 100' according to some embodiments, is shown. In some embodiments, the inspection apparatus 400 may be configured to align a substrate (e.g., substrate W) relative to a patterning apparatus (e.g., patterning apparatus MA). The inspection apparatus 400 may also be configured to detect the position of alignment marks on the substrate and use the detected alignment mark positions to align the substrate relative to the patterning apparatus or other components of the photolithography apparatus 100 or 100'. Such alignment of the substrate can ensure accurate exposure of one or more patterns on the substrate.

[0068] In some embodiments, the inspection apparatus 400 may include an illumination system 412, a beam splitter 414, an interferometer 426, a detector 428, a beam analyzer 430, and an overlay calculation processor 432. The illumination system 412 may be configured to provide a narrow-band electromagnetic radiation beam 413 having one or more passbands. In one example, the one or more passbands may be within a wavelength spectrum between about 500 nm and about 900 nm. In another example, the one or more passbands may be discrete narrow passbands within a wavelength spectrum between about 500 nm and about 900 nm. The illumination system 412 may also be configured to provide one or more passbands with a substantially constant center wavelength (CWL) value over a long period of time, e.g., throughout the lifetime of the illumination system 412. In current alignment systems, this configuration of the illumination system 412 helps prevent shifts between the actual CWL value and the desired CWL value, as discussed above. And, therefore, using a constant CWL value can improve the long-term stability and accuracy of the alignment system (e.g., the inspection apparatus 400) compared to current alignment apparatuses.

[0069] In some embodiments, beam splitter 414 may be configured to receive radiation beam 413 and split radiation beam 413 into at least two radiation sub-beams. For example, as Figure 4A As shown, the radiation beam 413 can be split into radiation sub-beams 415 and 417. The beam splitter 414 can also be configured to guide the radiation sub-beam 415 onto a substrate 420 placed on a platform 422. In one example, the platform 422 is movable along 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 embodiments, the alignment mark or target 418 can have 180° symmetry. That is, when the alignment mark or target 418 is rotated 180° about an axis of symmetry perpendicular to the plane of the alignment mark or target 418, the rotated alignment mark or target 418 can be substantially identical to the unrotated alignment mark or target 418. The target 418 on substrate 420 can be (a) a resist layer grating comprising gratings formed by solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlay target structure comprising resist gratings overlaid or interlaced on the product layer grating. Alternatively, the gratings can be etched into the substrate. This pattern is sensitive to chromatic aberration in the photolithography projection apparatus, particularly the projection system PL, and the presence of illumination symmetry and this aberration will manifest in variations in the printed grating. One in-line method used in device fabrication to measure linewidth, pitch, and critical dimensions employs a technique called “scattering measurement.” Methods for scattering measurements are described in “Multiparameter Grating Metrology Using Optical Scatterometry” by Raymond et al., published in Volume 15, Issue 2, Series B, Vacuum Science and Technology, 1997, pp. 361-368, and in “Specular Spectroscopic Scatterometry in DUV Lithography” by Niu et al., published in SPIE, Volume 3677, 1999, both of which are incorporated herein by reference in their entirety. In scattering measurements, light is reflected by a periodic structure in a 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 simulated pattern library. Therefore, scattering measurement data of printed gratings are used to reconstruct the grating. The parameters of the grating, such as linewidth and shape, can be input into the reconstruction process performed by the processing unit (PU) through knowledge of the printing steps and / or other scattering measurement processes.

[0070] In some embodiments, according to the example, beam splitter 414 may also be configured to receive diffracted radiation beam 419 and split diffracted radiation beam 419 into at least two radiation sub-beams. For example... Figure 4A As shown, the diffraction beam 419 can be split into diffraction sub-beams 429 and 439.

[0071] It should be noted that although beam splitter 414 is shown guiding radiant sub-beam 415 toward alignment mark or target 418 and diffracted radiant sub-beam 429 toward interferometer 426, this disclosure is not limited thereto. Those skilled in the art will appreciate that similar results can be obtained by using other optical arrangements to illuminate alignment mark or target 418 on substrate 420 and to detect an image of alignment mark or target 418.

[0072] like Figure 4A As illustrated, interferometer 426 can be configured to receive a radiating sub-beam 417 and a diffracted radiating sub-beam 429 via beam splitter 414. In an example embodiment, the diffracted radiating sub-beam 429 may be at least a portion of a radiating sub-beam 415 that can be reflected from the alignment mark or target 418. In this example embodiment, interferometer 426 includes any suitable set of optical elements, such as a combination of prisms, which can be configured to form two images of the alignment mark or target 418 based on the received diffracted radiating sub-beam 429. It should be understood that it is not necessary to form images of good quality, but the characteristics of the alignment mark 418 should be resolved. Interferometer 426 can also be configured to rotate one of the two images by 180° relative to the other of the two images, and interferometrically reconstruct the rotated and unrotated images.

[0073] In some embodiments, when the alignment axis 421 of the inspection device 400 passes through the center of symmetry (not shown) of the alignment mark or target 418, the detector 428 can be configured to receive the reconstructed image via interferometer signal 427 and detect interference as a result of the reconstructed image. According to an example embodiment, this interference may be due to the alignment mark or target 418 being 180° symmetrical, and the reconstructed image interfering constructively or destructively. Based on the detected interference, the detector 428 can also be configured to determine the position of the center of symmetry of the alignment mark or target 418, and thus detect the position of the substrate 420. According to an example, the alignment axis 421 can be aligned with a light beam perpendicular to the substrate 420 and passing through the center of the image rotation interferometer 426. The detector 428 can also be configured to estimate the position of the alignment mark or target 418 by implementing sensor characteristics and interacting with variations in the wafer marking process.

[0074] In another embodiment, detector 428 determines the position of the center of symmetry of alignment mark or target 418 by performing one or more of the following measurements: 1. Measure the positional changes at various wavelengths (positional shifts between colors); 2. Measure the positional changes of various orders (positional shifts between diffraction orders); and 3. Measure the positional changes of various polarizations (positional shifts between polarizations).

[0075] This data can be obtained, for example, using any type of alignment sensor, such as the SMASH (SMart alignment sensor hybrid) sensor, as described in U.S. Patent No. 6,961,116, which employs a self-reference interferometer with a single detector and four different wavelengths and extracts the alignment signal in software; or Athena (using advanced techniques to enhance higher-order alignment), as described in U.S. Patent 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.

[0076] In some embodiments, the beam analyzer 430 may be configured to receive and determine the optical state of the diffracted radiation sub-beam 439. The optical state may be a measure of beam wavelength, polarization, or beam profile. The beam analyzer 430 may also be configured to determine the position of the platform 422 and correlate the position of the platform 422 with the position of the center of symmetry of the alignment mark or target 418. Therefore, the position of the alignment mark or target 418 can be accurately known with reference to the platform 422, thereby accurately knowing the position of the substrate 420. Alternatively, the beam analyzer 430 may be configured to determine the position of the inspection device 400 or any other reference element, such that the center of symmetry of the alignment mark or target 418 can be known with reference to the inspection device 400 or any other reference element. The beam analyzer 430 may be a point or imaging polarimeter with some form of band selectivity. In some embodiments, according to other embodiments, the beam analyzer 430 may be directly integrated into the inspection device 400 or via several types of fiber connections: polarization-maintaining single-mode, multimode, or imaging.

[0077] In some embodiments, the beam analyzer 430 may also be configured to determine overlay data between two patterns on the substrate 420. One of these patterns may be a reference pattern on a reference layer. The other pattern may be an exposure pattern on an exposure layer. The reference layer may be an etched layer already present on the substrate 420. The reference layer may be generated by exposing a reference pattern on the substrate using lithography apparatus 100 and / or 100'. The exposure layer may be a resist layer exposed adjacent to the reference layer. The exposure layer may be generated by exposing an exposure pattern on the substrate 420 using lithography apparatus 100 or 100'. The exposure pattern on the substrate 420 may correspond to movement of the platform 422 relative to the substrate 420. In some embodiments, the measured overlay data may also indicate an offset between the reference pattern and the exposure pattern. The measured overlay data may be used as calibration data to calibrate the exposure pattern exposed by lithography apparatus 100 or 100' such that, after calibration, the offset between the exposure layer and the reference layer can be minimized.

[0078] In some embodiments, the beam analyzer 430 may also be configured to model a product stack profile of the substrate 420 and may be configured to measure the overlay, critical dimensions, and focal length of the target 418 in a single measurement. The product stack profile contains information about the stacked product, such as alignment marks, target 418, or substrate 420, and may include optical signature measurements caused by variations in the marking process, which are functions of illumination variations. The product stack profile may also include product grating profiles, mark stack profiles, and mark asymmetry information. An example of the beam analyzer 430 is the Yieldstar™ manufactured by ASML in Feldhoven, Netherlands, as described in U.S. Patent No. 8,706,442, which is incorporated herein by reference in its entirety. The beam analyzer 430 may also be configured to process information relating to specific properties of the exposure pattern in the layer. For example, the beam analyzer 430 may process overlay parameters (an indication of the positioning accuracy of the layer relative to a previous layer on the substrate, or the positioning accuracy of the first layer relative to marks on the substrate), focus parameters, and / or critical dimension parameters (e.g., linewidth and its variations) of the image depicted in the layer. Other parameters are image parameters related to the quality of the image depicting the exposure pattern.

[0079] In some embodiments, a detector array (not shown) can be connected to the bundle analyzer 430, allowing for accurate stack profile detection as discussed below. For example, detector 428 can be a detector array. Several options are possible for the detector array: multimode fiber bundles, discrete pin detectors for each channel, or CCD or CMOS (linear) arrays. For stability reasons, using multimode fiber bundles allows for remote positioning of any dissipative element. Discrete pin detectors offer a large dynamic range, but each requires a separate preamplifier. Therefore, the number of elements is limited. CCD linear arrays offer many elements that can be read out at high speeds, and these elements are particularly interesting if phase-stepped detection is used.

[0080] In some embodiments, 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. Optical state can be a measure of beam wavelength, polarization, or beam profile. The second beam analyzer 430' can be the same as beam analyzer 430. Alternatively, the second beam analyzer 430' can be configured to perform at least all the functions of beam analyzer 430, such as determining the position of platform 422 and relating the position of platform 422 to the position of the alignment mark or target 418's center of symmetry. Therefore, the position of the alignment mark or target 418 can be accurately known by reference to platform 422, thereby accurately knowing the position of substrate 420. The second beam analyzer 430' can also be configured to determine the position of inspection device 400 or any other reference element, such that the center of symmetry of alignment mark or target 418 can be known by reference to inspection device 400 or any other reference element. The second beam analyzer 430' can also be configured to determine overlay data between two patterns and a model of the product stack profile of substrate 420. The second beam analyzer 430' can also be configured to measure the overlay, critical dimension, and focal length of target 418 in a single measurement.

[0081] In some embodiments, and according to other embodiments, the second beam analyzer 430' may be directly integrated into the inspection apparatus 400, or connected via several types of optical fibers: polarization-maintaining single-mode, multimode, or imaging. Alternatively, the second beam analyzer 430' and the beam analyzer 430 may be combined to form a single analyzer (not shown) configured to receive and determine the optical state of the diffracted radiation sub-beams 429 and 439.

[0082] In some embodiments, processor 432 receives information from detector 428 and beam analyzer 430. For example, processor 432 may be an overlay calculation processor. This information may include a model of the product stack profile constructed by beam analyzer 430. Alternatively, processor 432 may use received information about product markings to construct a model of the product marking profile. In either case, processor 432 uses or combines the product marking profile model to construct a model of the stacked product and overlay marking profiles. The stack model is then used to determine the overlay offset and minimize the spectral influence on the overlay offset measurement. Processor 432 may create a basic correction algorithm based on the information received from detector 428 and beam analyzer 430, including but not limited to the optical state of the illumination beam, alignment signals, associated position estimates, and optical states in the pupil, image, and additional plane. The pupil plane is a plane where the radial position of the radiation defines the angle of incidence and the angular position defines the azimuth angle of the radiation. Processor 432 may utilize the basic correction algorithm to characterize inspection apparatus 400 with reference to wafer markings and / or alignment marks 418.

[0083] In some embodiments, processor 432 may also be configured to determine a sensor-estimated printed pattern position offset error relative to each mark based on information received from detector 428 and beam analyzer 430. This information includes, but is not limited to, product stack profile, overlay measurements, critical dimensions, and the focus of each alignment mark or target 418 on substrate 420. Processor 432 may utilize a clustering algorithm to group marks into similar sets of constant offset errors and create an alignment error offset correction table based on this information. The clustering algorithm may be based on overlay measurements, position estimates, and additional optical stacking process information associated with each set of offset errors. Overlay is calculated for many different marks, for example, overlay targets with positive and negative deviations around a programmed overlay offset. The target with the smallest measured overlay is considered a reference (because it is measured with optimal accuracy). The overlay error can be inferred from this measured small overlay and the known programmed overlay of its corresponding target. Table 1 illustrates how this can be performed. The smallest measured overlay in the example shown is -1 nm. However, this is associated with a target with a programmed overlay of -30 nm. This process may introduce an overlay error of 29 nm. The minimum value can be considered a reference point, and relative to this, the offset between the measured overlay and the expected overlay due to the programmed overlay can be calculated. This offset determines the overlay error for each marker or a set of markers with a similar offset. Thus, in the example of Table 1, the minimum measured overlay is -1 nm, and at the target location, the programmed overlay is 30 nm. The difference between the expected and measured overlays at other targets is compared to this reference. Tables such as Table 1 can also be obtained from markers and targets 418 under different irradiation settings, allowing the determination and selection of the irradiation settings that result in the minimum overlay error and their corresponding calibration factors. After this, the processor 432 can group the markers into similar sets of overlay errors. The criteria for grouping the markers can be adjusted based on different process controls, such as different error tolerances for different processes.

[0084] In some embodiments, processor 432 may identify that all or most members of the group have similar offset errors and apply individual offset corrections from the clustering algorithm to each mark based on its additional optical stacking measurements. Processor 432 may determine the correction for each mark and feed the correction back to lithography apparatus 100 or 100' to correct for errors in overlay, for example by feeding the correction back to inspection apparatus 400. Additionally, a digital holographic microscope for overlay measurements is described in U.S. Patent Publication No. 2023 / 0044632 (Coene et al.), which is incorporated herein by reference in its entirety.

[0085] In some aspects, it is desirable to use an extended wavelength range (towards infrared (IR) wavelengths) for the illumination beam during alignment measurements to extend the measurement through the opaque layer. In some aspects, alignment sensors have stringent aberration requirements over a wide wavelength range, which leads to complex optics. Moreover, some alignment sensors use polarization optics that are difficult to manufacture in the extended wavelength range.

[0086] Embodiments of this disclosure provide apparatus and functionality for performing alignment measurements over an extended wavelength range. For example, measuring a complete complex field (phase and amplitude) enables the calculation and correction of hardware defects (e.g., optical aberrations) in the apparatus. Therefore, the apparatus can have an extended wavelength range. Furthermore, compared to other alignment sensors, the apparatus can be miniaturized because aberration correction is performed using a processor rather than additional optical elements. Example inspection system

[0087] Figure 5 A schematic diagram of an inspection system 500 according to some embodiments is shown. In some embodiments, the inspection system 500 may also represent a more detailed view of the beam analyzer 430. Note that for simplicity, Figure 5Only some components of the inspection system 500 are shown.

[0088] like Figure 5 As illustrated, a target 506 on substrate 508 can be irradiated by two radiation beams, namely, a first irradiation beam 502 and a second irradiation beam 504. In some aspects, the first irradiation beam 502 and the second irradiation beam can irradiate the target 506 simultaneously. The target 506 can be... Figure 4A and 4B Alignment mark or target 418. In some aspects, target 506 may be a micro-diffraction-based overlay (µDBO) grating or a bottom grating for overlay measurements.

[0089] In some respects, target 506 can be irradiated by a single irradiation beam. The irradiation beam (e.g., the first irradiation beam 502 and the second irradiation beam 504) can be an off-axis beam (e.g., Figure 5 (As shown). However, in other embodiments, the irradiation beam may be an on-axis beam.

[0090] A first irradiation beam 502 may be incident on the target 506 at a first incident angle in a first direction relative to the optical axis OA of the system 500. A second irradiation beam 504 may be incident on the target 506 at a second incident angle in a second direction relative to the optical axis OA. In some aspects, the incident angle of the second irradiation beam 504 may be the same as that of the first irradiation beam 502. In some aspects, the target 506 may be irradiated at a larger oblique incident angle (e.g., in the range between 70° and 90°, between 60° and 90°, or between 70° and 90°). The target 506 may scatter radiation. Depending on the structure of the target 506, the scattered radiation may include reflected radiation, diffracted radiation, and / or transmitted radiation.

[0091] In some embodiments, target 506 can diffract the first illumination beam 502 into multiple diffraction orders. In some aspects, target 506 may include a diffraction structure (e.g., multiple gratings). Target 506 can scatter multiple beams. Objective lens 514 (e.g., one or more lenses) can collect at least a first scattered beam 510 including at least one non-zero diffraction order (e.g., a negative first diffraction order). The first scattered beam 510 can be focused onto image sensor 518 (e.g., a capture device, camera).

[0092] In some embodiments, target 506 can diffract the second illumination beam 504 into multiple diffraction orders. A second scattered beam 512, including at least one non-zero diffraction order (e.g., a positive first diffraction order), can be collected by objective lens 514 and subsequently focused onto image sensor 518. In some aspects, objective lens 514 does not capture the 0th diffraction order (= specular reflection), so the +1 and -1 diffraction orders form a dark-field image of target 506 on image sensor 518. The zero diffraction order and other undesired orders can be blocked by a beam-blocking element (not shown) or configured to fall entirely outside the NA of objective lens 514. In some aspects, objective lens 514 can be used only in the detection path (as shown) and not for illumination (e.g., focusing illumination beams 502 and 504 onto target 506). Therefore, illumination does not necessarily have to pass through the same objective as the scattered light. In some embodiments, objective lens 514 can be used to collect scattered radiation and focus illumination beams 502 and 504 onto target 506. In some respects, the first scattered beam 510 and the second scattered beam 512 can be simultaneously incident on a common location of the image sensor 518.

[0093] A first off-axis reference beam 516 is coherently added to a first scattered beam 510, and a second off-axis reference beam 520 is coherently added to a second scattered beam 512. For example, the first off-axis reference beam 516 may be incident on the image sensor 518 at the same location as the first scattered beam 510 and the second scattered beam 512.

[0094] The path difference between the -1st and +1st order beams is intentionally made greater than the coherence length of the beam (approximately 100 μm) so that the +1st and -1st order beams do not coherently interfere with the image sensor 518.

[0095] As previously described herein, target 506 may include a grating. In some aspects, the pitch of the grating is selected such that objective 514 captures only the +1 and -1 diffraction orders. In this way, two overlaid off-axis digital holograms are recorded on image sensor 518, and the complex -1 and +1 order images of the grating can be retrieved from image sensor 518 using a Fourier transform method.

[0096] To extract the alignment signal, the complex +1 order image 𝐸+1 and the -1 order image 𝐸-1 are summed to obtain a composite intensity image, from which the grating position 𝑋𝑔 can be inferred:

[0097] Here, K xis the spatial frequency of the interference pattern between the +1 and -1 order beams, and β is an (unknown) phase factor describing the phase difference between the two illumination beams and the reference beam. As can be seen from equation (1), any unknown drift in the phase difference β between the illumination beam and the reference beam can lead to uncorrectable alignment errors.

[0098] However, a grating with a sufficiently large pitch can be used to capture the second diffraction order as well. The grating is designed so that objective 514 generates and captures both diffraction orders. To capture the second diffraction order as well, the grating pitch *k* is chosen such that:

[0099] In system 500, sin( ) ≈0.95 and =0.8, where This corresponds to the incident angles of the first illumination beam 502 and the second illumination beam 504 relative to OA. For example, assuming the longest wavelength is 1600 nm, this produces a lower limit of approximately 2 μm in pitch. Under these conditions, the intensities of the two retrieved +1 and -1 images are given by:

[0100] Therefore, two calculated intensity images of target 506 were obtained. It should be noted that the position of the fringe pattern is also affected by the Z position (i.e., the grating height), but these two images allow us to correlate the Z-induced shift with the actual grating position X. g Separation.

[0101] In some embodiments, the third scattered beam 522 and the fourth scattered beam 524 may also be collected by the objective lens 514. In some aspects, the third scattered beam 522 may include a negative second diffraction order. The fourth scattered beam 524 may include a positive second diffraction order.

[0102] In order to generate an interference pattern between two or more beams, the two or more beams should be at least partially coherent with each other to a degree sufficient to form an interference pattern. Furthermore, the coherence between the two or more beams should be temporal and spatial coherence. Therefore, the first illumination beam 502 and the first off-axis reference beam 516 are coherent with each other, and the second illumination beam 504 and the second off-axis reference beam 520 are coherent with each other.

[0103] The characteristics of target 506 can be determined using a processing unit (not shown) of inspection system 500 (e.g., computer system 1100). The processing unit uses an interference pattern recorded by image sensor 518. The processing unit can be coupled to image sensor 518 to receive a signal including information about the interference pattern recorded by image sensor 518. The processing unit can correct aberrations in inspection system 500. In some aspects, the processing unit can correct aberrations of objective lens 514 of inspection system 500. The processing unit uses the interference pattern to calculate the complex radiation field at image sensor 518. A complex field refers to a situation where both amplitude and phase information are present. As will be understood by those skilled in the art, complex field calculations are known in the field of holography. Compared to techniques where neither phase nor amplitude information is available, knowledge of the complex field provides additional information about the characteristics of target 506.

[0104] However, in some respects, a large marker pitch may be undesirable because of poorer reproducibility test results, lower averaging of line edge roughness, and other advantages that could be obtained if alignment with a bottom grating (with a small pitch) is used.

[0105] Figure 6A A schematic diagram of an inspection system 600 according to some embodiments is shown. In some embodiments, the inspection system 600 may also represent a more detailed view of the beam analyzer 430. Note that for simplicity, Figure 6A Only some components of the inspection system 600 are shown to illustrate how the system works.

[0106] A first illumination beam 602 may be incident obliquely onto a target 606 on a substrate 608. In some aspects, a first scattered beam 610 is collected by a lens 614. The first scattered beam 610 may be focused onto a sensor 618 (e.g., an image sensor). Depending on the structure of the target 606, the scattered radiation may include reflected radiation, diffracted radiation, or transmitted radiation. The target 606 may diffract the first illumination beam 602 into multiple diffraction orders. For example, the first scattered beam 610 may include at least one non-zero diffraction order, such as a positive first diffraction order (+1 diffraction order). Similarly, a second illumination beam 604 may be incident obliquely onto the target 606. In some aspects, the incident angle of the second illumination beam 604 may be the same as that of the first illumination beam 602. In some aspects, the target 606 may be illuminated at a larger oblique incident angle (typically between 70° and 80°). In some aspects, the second illumination beam 604 is incident on the target 606 from an opposite side of the system 600. The second scattered beam 612 is collected by lens 614. The second scattered beam 612 may include at least one non-zero diffraction order, such as a negative first diffraction order (-1 diffraction order).

[0107] In some aspects, lens 614 may be used only for path detection (as shown) and not for illumination (e.g., focusing illumination beams 602 and 604 onto target 606). Therefore, illumination does not necessarily have to pass through the same objective lens as the scattered light. In some embodiments, lens 614 may be shared and used to collect scattered radiation and focus illumination beams 602 and 604 onto target 606.

[0108] The reference beam 616 can interfere with the first scattered beam 610 and the second scattered beam 612. Therefore, a two-dimensional (2D) interference pattern can be formed on the sensor 618. The 2D interference pattern can represent a digital hologram including information about the objective lens (e.g., lens 614) of the inspection system 600. This information can therefore be used to correct for wavefront aberrations of the beam. The reference beam 616 can be incident at the same location on the sensor 618 as the first scattered beam 610 and the second scattered beam 612. In some aspects, the first illumination beam 602, the second illumination beam 604, and the reference beam 616 are coherent relative to each other.

[0109] Hardware and optical defects (such as defocus) can be corrected for on the 2D interference pattern. The corrected 2D interference pattern can be used to obtain the position. In some aspects, the algorithm can be used to fit the aligned position in the first and second dimensions (e.g., in the x and y directions). Because aberrations are digitally corrected, some aberrations in one or more objectives 614 are tolerable, and alignment measurements can be performed over an extended wavelength range (e.g., 400 nm to 1600 nm) without reducing accuracy or the number of elements in one or more objectives 614. Due to the reduced number of elements, more alignment sensors can be used, which increases the throughput of the lithography apparatus.

[0110] In some embodiments, the first illumination beam 602 and the second illumination beam 604 are relatively stable (i.e., less than 0.1 nm). To maintain stability between the first illumination beam 602 and the second illumination beam 604, the illumination beams 602 and 604 may primarily have a common path from the light source (not shown) to the target 606. In some aspects, the reference beam 616 may have stability of 10 nm to 100 nm relative to the first illumination beam 602 and the second illumination beam 604. The global phase difference between the reference beam 616 and the illumination beams (e.g., the first illumination beam 602 and the second illumination beam 604) is not used. The phase gradient of the reference beam 616 on the sensor 618 is known and is used in digital holographic calculations to determine alignment, as understood by those skilled in the art.

[0111] Figure 6B A schematic diagram of the diffraction pattern at the pupil plane (PP) of a system 600 according to some embodiments is shown.

[0112] In some aspects, target 606 may be a microdiffraction-based overlay (µDBO) grating. Insert 620 illustrates an exemplary µDBO bottom grating. For example, target 606 may be an µDBO bottom grating. Target 606 may include one or more x-grating segments and one or more y-grating segments. Each segment may include a series of grating bars or grating lines. The x-grating segments may include grating bars parallel to the y-axis to provide periodicity in the x-direction. The y-segments may include grating bars parallel to the x-axis to provide periodicity in the y-direction. Figure 6B The -1 and +1 diffraction spots for x and y are shown. Typically, for the x-grating segment, interference occurs primarily between the x-diffraction order and the reference beam. Similarly, for the y-grating segment, interference occurs primarily between the y-diffraction order and the reference beam. However, crosstalk can be a problem when there is a large difference in wafer quality (WQ) between the x and y segments.

[0113] In some embodiments, the second reference beam (not shown) may interfere with the first scattered beam 610 and the second scattered beam 612. The incident angle of the second reference beam on the sensor 618 may differ from that of the reference beam 616. The second reference beam may be coherent relative to the first illumination beam 602, the second illumination beam 604, and the reference beam 616. In some aspects, the second reference beam may have orthogonal polarizations (e.g., p-polarized and s-polarized, respectively) compared to the reference beam 616. Both polarization components of the signal beam (or measurement signal) are obtained using a single image captured by the sensor 618.

[0114] In some embodiments, x-measurement and y-measurement are decoupled. In some aspects, decoupling between measurements (e.g., x-measurement and y-measurement) is achieved by making the bundles incoherent relative to each other in the x and y directions.

[0115] Figure 7A and 7B A schematic diagram of an inspection system 700 according to some embodiments is shown. Figure 7A A front view of the inspection system 700 is shown. Figure 7B A side view of the inspection system 700 is shown. In some embodiments, the inspection system 700 may also represent a more detailed view of the beam analyzer 430. Note that for simplicity, Figure 7A and 7B Only some components of the inspection system 700 are shown.

[0116] In some embodiments, a first beam is used to obtain the characteristics of a target in a first direction (e.g., the x-direction), and a second beam is used to obtain the characteristics of the target in a second direction (e.g., the y-direction) different from the first direction. The first beam is incoherent with respect to the second beam. The first beam may include a first illumination beam 702a, a second illumination beam 704a, and a first reference beam 716a. The second beam may include a third illumination beam 702b, a fourth illumination beam 704b, and a second reference beam 716b. The first illumination beam 702a, the second illumination beam 704a, and the first reference beam 716a are coherent with respect to each other, but incoherent with respect to the second beam (the third illumination beam 702b, the fourth illumination beam 704b, and the second reference beam 716b). The third illumination beam 702b, the fourth illumination beam 704b, and the second reference beam 716b are coherent with respect to each other, but incoherent with respect to the first illumination beam 702a, the second illumination beam 704a, and the first reference beam 716a.

[0117] Interference occurs between beams within the same group, while interference between different beam groups is suppressed. Therefore, only the desired interference pattern is formed on the image sensor 718.

[0118] In some embodiments, the first illumination beam 702a and the second illumination beam 704a may be obliquely incident on a target 706a (e.g., an x-grating segment of a µDBO bottom grating) on ​​a substrate 708. In some aspects, the first scattered beam 710a and the second scattered beam 712a may be collected by a lens 714. The first scattered beam 710a and the second scattered beam 712a may be focused onto a sensor 718 (e.g., an image sensor). Depending on the structure of the target 706a, the scattered radiation may include reflected radiation, diffracted radiation, or transmitted radiation. The target 706a may diffract the first illumination beam 702a and the second illumination beam 704a into multiple diffraction orders. For example, the first scattered beam 710a may include at least one non-zero diffraction order, such as a positive first diffraction order (+1 diffraction order). The second scattered beam 712a may include at least one non-zero diffraction order, such as a negative first diffraction order (-1 diffraction order).

[0119] In some embodiments, the third illumination beam 702b and the fourth illumination beam 704b may be obliquely incident on the target 706b (e.g., a y-grating segment of the µDBO bottom grating) on ​​the substrate 708. In some aspects, the third scattered beam 710b and the fourth scattered beam 712b may be collected by a lens 714. The third scattered beam 710b and the fourth scattered beam 712b may be focused onto a sensor 718. Depending on the structure of the target 706b, the scattered radiation may include reflected radiation, diffracted radiation, or transmitted radiation. The target 706b may diffract the third illumination beam 702b and the fourth illumination beam 704b into multiple diffraction orders. For example, the third scattered beam 710b may include at least one non-zero diffraction order, such as a positive first diffraction order (+1 diffraction order). The fourth scattered beam 712b may include at least one non-zero diffraction order, such as a negative first diffraction order (-1 diffraction order).

[0120] In some embodiments, the first interference pattern is formed by a scattered beam 710a, a scattered beam 712a, and a first reference beam 716a. The second interference pattern is formed by a scattered beam 710b, a scattered beam 712b, and a second reference beam 716b. The first interference pattern can be used to determine alignment in the x-direction. The second interference pattern can be used for alignment measurements in the y-direction.

[0121] Figure 7C A schematic diagram of the diffraction pattern at the pupil plane (PP) of a system 700 according to some embodiments is shown. The -1 and +1 diffraction spots measured in x and y are shown. The diffraction spots +1y, -1y, and Ref-y (shown as filled patterns) are coherent with each other. The diffraction spots +1x, -1x, and Ref-x (shown as solid patterns) are coherent with each other but not with other diffraction spots.

[0122] In some embodiments, the first beam may further include another reference beam (i.e., in addition to the first reference beam 716a). In some aspects, the other reference beam may have a polarization orthogonal to the first reference beam 716a. The other reference beam may be coherent with respect to the first illumination beam 702a, the second illumination beam 704a, and the first reference beam 716a, and incoherent with respect to the second beam. Additionally, the other reference beam may be incident at a different angle than the first reference beam 716a on the sensor 718. The second beam may further include another reference beam (i.e., in addition to the second reference beam 716b). In some aspects, the other reference beam in the second beam may have a polarization orthogonal to the second reference beam 716b. The other reference beam may be coherent with respect to the third illumination beam 702b, the fourth illumination beam 704b, and the first reference beam 716b, and incoherent with respect to the first beam. Additionally, the other reference beam may be incident at a different angle than the second reference beam 716b on the sensor 718.

[0123] Figure 8 A schematic diagram of an inspection system 800 according to some embodiments is shown. In some embodiments, the inspection system 800 may also represent a more detailed view of the beam analyzer 430. Note that for simplicity, Figure 8 Only some components of the inspection system 800 are shown.

[0124] In some embodiments, the inspection system 800 may include an illumination source 834, an image sensor 818, and an optical module 836. The light source 834 can generate a coherent radiation beam to illuminate a target 806 on a substrate 808. An optical element 822 (e.g., a beam splitter) receives the radiation beam from the illumination source 834 and splits it into a first radiation sub-beam 802 and a second radiation sub-beam 816. The first radiation sub-beam 802 can be guided toward a single-mode fiber using a reflective element 824 (e.g., a mirror). The second radiation sub-beam 816 is guided to a delay stage 820 and then coupled to the single-mode fiber.

[0125] In some embodiments, an illumination beam is generated near the target 806 to maintain stability between the two illumination beams. In some aspects, a first diffraction element 828 can be used to split the first radiation sub-beam 802 into multiple sub-beams. A second radiation sub-beam 816 can be split into multiple sub-beams using a diffraction element 826. Diffraction elements 826 and 828 may include a two-dimensional grating. Diffraction elements 826 and 828 can be used to generate off-axis illumination beams. Diffraction element 826 can generate two off-axis reference beams. The two off-axis reference beams can be guided toward the image sensor 818. Diffraction element 828 can generate two off-axis illumination beams used to illuminate the target 806. In other embodiments, a beam splitter can be used to split the second radiation sub-beam 816 and the first radiation sub-beam 802 into multiple beams.

[0126] In some embodiments, optical module 836 may include optical elements that apply incoherence between the illumination beam for x-measurement and the illumination beam for y-measurement. For example, optical module 836 may include a coherent delayer to make the x and y measurements incoherent relative to each other. A first radiant sub-beam 802 may be collimated using lens 812 and passes through delayer 832. Delayer 832 may be a coherent delayer configured to delay the x beam relative to the y beam. Similarly, a second radiant sub-beam 816 may be collimated using lens 810 and passes through delayer 830. In some aspects, delayer 830 may also block unwanted diffraction steps. In some aspects, delayers 830 and 832 are matched, such as a corresponding reference beam being coherent with the corresponding illumination beam. The second radiant sub-beam 816 may then be passed via beam splitter 838 and focused onto image sensor 818 using lens 804. The second radiant sub-beam 816 may include two beams incoherent relative to each other. As discussed further below, these two beams are used as reference beams for the X and Y measurements, respectively.

[0127] The first radiating sub-beam 802 is passed to the beam splitter 840 and focused onto the target 806 on the substrate 808 using the objective lens 814. The first radiating sub-beam 802 includes a first pair of beams (comprising two beams that are coherent with each other) and a second pair of beams (comprising two beams that remain coherent but are incoherent with the first pair of beams). The first pair of beams can be used for x-measurement. The second pair of beams can be used for y-measurement.

[0128] The scattered beam can be collected by objective lens 814 and focused onto image sensor 818 using lens 804. In some embodiments, optical module 836 may include optical element 842. Optical element 842 can block the zero-order diffraction of the scattered beam. Two interference patterns are formed on image sensor 818. The first interference pattern is formed by the scattered beams of a first pair of beams and a reference beam for x-measurement. The second interference pattern is formed by the scattered beams of a second pair of beams and a reference beam for y-measurement. As discussed earlier herein, the first and second interference beams can be used to determine the x and y alignment positions.

[0129] Figure 9A This is a flowchart of a method for analyzing interference patterns according to some embodiments. In 912, the interference pattern (holographic image) of the reference beam and the scattered beam is Fourier transformed into an image spectrum in the spatial frequency domain, as further described in WO 2022 / 200014 (Coene et al.), which is incorporated herein by reference in its entirety.

[0130] In 914, aberration correction is performed using the technique described in WO 2019197117A1 (De Boer et al.), to correct any aberrations in the optical system, which is incorporated herein by reference in its entirety. Note that when target 806 comprises a one-dimensional grating, the two-dimensional interference pattern captured on sensor 818 is transformed into a one-dimensional pattern. In some aspects, phase information may be discarded. In some aspects, both amplitude and phase information are used to determine the corrected image.

[0131] In 916, an inverse Fourier transform (IFT) is performed to obtain the corrected image. In 918, the alignment position is obtained from the one-dimensional interference pattern. The alignment position can be obtained from a complex-valued (aberration-corrected) image or the corresponding intensity image. When using an intensity image, methods described, for example, by reference in whole or in part in WO 2023126174A1 (Goorden et al.) and WO 2023030832A1 (Goorden et al.), which can be used to obtain the alignment position, including local fitting within the markings and corrections for finite sizes and other effects. These methods can also be applied to complex-valued images.

[0132] In some aspects, alternatively or additionally, the complex image can be digitally cropped to include only a portion of the markings. The complex field can be propagated to the Fourier plane. A first positive diffraction order and a first negative diffraction order can be selected. The corresponding stages of these orders can be determined. The alignment position can be determined by the phase difference.

[0133] In some embodiments, the reference beam illuminates the image sensor at a significantly larger angle compared to other beams (e.g., the scattered beam). However, in some cases, the angles of the reference beam and the other beams are comparable. Figure 9C The diffraction pattern at the pupil plane (PP) of an inspection system (e.g., inspection system 800, inspection system 700) is shown. Figure 9A As shown, the diffraction spots from the reference beam and the scattered beam are close to each other. Figure 9B As shown, the adjusted data analysis method can be used.

[0134] Figure 9B This is a flowchart for analyzing interference patterns according to some embodiments. In some aspects, a Fast Fourier Transform can be applied to the interference pattern 900. The interference pattern 900 can correspond to... Figure 9CThe diffraction pattern is shown. The Fourier representation 902 (Fourier spectrum) is obtained via a 2D Fourier transform. The Fourier representation is clipped along the first dimension (e.g., the x-direction) and moved to the origin, as shown in 904. Similarly, the edges of the Fourier representation are clipped along the second dimension (e.g., the y-direction) and moved to the origin, as shown in 906. In 908, an inverse fast Fourier transform is applied to 904 to obtain the x-position. In 910, an inverse fast Fourier transform is applied to the modified Fourier representation 906 to obtain the y-position.

[0135] Figure 10 Method steps (e.g., using one or more processors) for performing a method 1000 including the functions described herein, according to some embodiments, are shown. Figure 10 Method 1000 can be executed in any imaginable order, and it is not necessary to perform all the steps. Furthermore, the above... Figure 10 The method steps described are merely examples and not limitations.

[0136] In some embodiments, method 1000 illustrates a method for determining target characteristics.

[0137] In some embodiments, at 1002, a first and a second irradiation beam are directed toward the target structure to generate a first and a second scattered beam. In some aspects, a third and a fourth irradiation beam are directed toward the target structure.

[0138] In some embodiments, in 1004, the reference beam, the first scattered beam, and the second scattered beam are directed toward the detector system. In some aspects, another reference beam is directed toward the detector system. In some aspects, the third illumination beam, the fourth illumination beam, and the other reference beam are at least partially coherent, and wherein the first illumination beam, the second illumination beam, and the reference beam are at least partially coherent. In some aspects, incoherence between the first illumination beam and the third illumination beam is applied using optical elements (e.g., a coherent delayer).

[0139] In some embodiments, in 1006, the interference pattern (holographic image) of the first scattered beam, the second scattered beam, and the reference beam is detected.

[0140] In some embodiments, at 1008, the characteristics of the target structure can be determined. In some aspects, a complex-valued image field can be extracted from the holographic image, and hardware defects can be computationally corrected.

[0141] The corrected complex field (amplitude and phase) can be used to fit the alignment position. In some embodiments, a Fourier transform is applied to the detected interference pattern to obtain a Fourier representation. The first diffraction order along the first dimension of the Fourier representation is clipped and shifted to the center of the Fourier representation. An inverse Fourier transform is applied to the clipped Fourier representation to obtain the properties of the target structure in the first dimension. The first diffraction order along the second dimension of the Fourier representation is clipped and shifted to the center of the Fourier representation. An inverse Fourier transform is applied to the clipped Fourier representation along the second dimension to obtain the properties of the target structure in the second dimension.

[0142] In some embodiments, the systems and methods described herein can be used for overlay measurements. In some aspects, a target including gratings is provided in two or more different layers adjacent to each other. Inspection system 500, inspection system 600, inspection system 700, or inspection system 800 can be used to capture an image of the target. In some aspects, as previously described herein, the alignment position of each grating in the grating is determined. Differences between grating positions correspond to overlay measurements.

[0143] In some embodiments, the systems and methods described herein can be used for focusing and dose measurement. A grating structure can be designed, exposed, and developed such that the measurement location of the grating structure is related to the defocus and / or dose used during exposure. Inspection system 500, inspection system 600, inspection system 700, or inspection system 800 can be used to determine defocus and / or dose.

[0144] For example, various embodiments can be implemented using one or more well-known computer systems, such as Figure 11 The computer system 1100 shown. For example, one or more computer systems 1100 can be used to implement any aspect of this disclosure and combinations and sub-combinations thereof discussed herein.

[0145] Computer system 1100 may include one or more processors (also known as central processing units or CPUs), such as processor 1104. Processor 1104 is connected to communication infrastructure or bus 1106.

[0146] The computer system 1100 may also include multiple client input / output devices 1103, such as monitors, keyboards, pointing devices, etc., which can communicate with the communication infrastructure 1106 through multiple client input / input interfaces 1102.

[0147] One or more processors 1104 may be graphics processing units (GPUs). In an embodiment, a GPU may be a processor, which is a specialized electronic circuit designed to process mathematically intensive applications. The GPU may have a parallel architecture that is highly efficient for parallel processing of large blocks of data, such as common mathematically intensive data in computer graphics applications, images, and videos.

[0148] Computer system 1100 may also include main memory or primary memory 1108, such as random access memory (RAM). Main memory 1108 may include one or more levels of cache. Main memory 1108 may store control logic (i.e., computer software) and / or data therein.

[0149] The computer system 1100 may also include one or more secondary storage devices or memories 1110. The secondary memory 1110 may include, for example, a hard disk drive 1112 and / or a removable storage device or drive 1114. The removable storage drive 1114 may be a floppy disk drive, a tape drive, a compact disk drive, an optical storage device, a tape backup device, and / or any other storage device / drive.

[0150] Removable storage drive 1114 can interact with removable storage unit 1118. Removable storage unit 1118 may include a computer-usable or readable storage device on which computer software (control logic) and / or data are stored. Removable storage unit 1118 may be a floppy disk, magnetic tape, compact disc, DVD, optical storage disc, and / or any other computer data storage device. Removable storage drive 1114 can read from and / or write to removable storage unit 1118.

[0151] Secondary memory 1110 may include other components, devices, parts, tools, or other methods that allow computer programs and / or other instructions and / or data to be accessed by computer system 1100. Such components, devices, parts, tools, or other methods may include, for example, removable storage unit 1122 and interface 1120. Examples of removable storage unit 1122 and interface 1120 may include a program box and box interface (such as those found in video game devices), a removable memory chip (such as EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and / or any other removable storage unit and associated interface.

[0152] Computer system 1100 may also include a communication or network interface 1124. Communication interface 1124 enables computer system 1100 to communicate and interact with any combination of external devices, external networks, remote entities, etc. (Referenced separately and collectively by reference numeral 1128). For example, communication interface 1124 may allow computer system 1100 to communicate with external or remote device 1128 via communication path 1126, which may be wired and / or wireless (or a combination thereof) and may include any combination of LAN, WAN, Internet, etc. Control logic and / or data may be sent to and from computer system 1100 via communication path 1126.

[0153] To give just a few non-limiting examples, computer system 1100 may also be any one or any combination thereof, a personal digital assistant (PDA), a desktop workstation, a laptop or notebook computer, a netbook, a tablet computer, a smartphone, a smartwatch or other wearable device, an appliance, part of the Internet of Things and / or an embedded system.

[0154] Computer system 1100 may be a client or server that accesses or hosts any application and / or data through any delivery paradigm, including but not limited to remote or distributed cloud computing solutions; on-premises or field software (“Field” cloud-based solutions); “as-a-service” models (such as Content as a Service (CaaS), Digital Content as a Service (DCaaS), Software as a Service (SaaS), Managed Software as a Service (MSaaS), Platform as a Service (PaaS), Desktop as a Service (DaaS), Framework as a Service (FaaS), Backend as a Service (BaaS), Mobile Backend as a Service (MBaaS), Infrastructure as a Service (IaaS), etc.); and / or hybrid models that include any combination of the foregoing examples or other services or delivery paradigms.

[0155] Any applicable data structures, file formats, and diagrams in computer system 1100 can be derived from standards, including but not limited to JavaScript Object Notation (JSON), Extensible Markup Language (XML), YAML, Extensible Hypertext Markup Language (XHTML), Wireless Markup Language (WML), MessagePack, XML User Interface Language (XUL), or any other functionally similar representation, alone or in combination. Alternatively, proprietary data structures, formats, or diagrams may be used alone or in combination with known or open standards.

[0156] In some embodiments, a tangible, non-transient, computer-usable or readable medium having control logic (software) stored thereon may also be referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system 1100, main memory 1108, secondary memory 1110, and removable storage units 1118 and 1122, and tangible articles implementing any combination thereof. When executed by one or more data processing devices, such as computer system 1100, this control logic can cause such data processing devices to operate as described herein.

[0157] Based on the teachings contained in this disclosure, it will be apparent to those skilled in the art (multiples) of the relevant fields how to use data processing devices, computer systems, and / or computer architectures (different from those used in this disclosure). Figure 11 The embodiments of this disclosure are carried out and used as shown. In particular, the embodiments may be implemented in a software, hardware and / or operating system manner (different from those described herein).

[0158] The embodiments may be further described using the following terms: 1. A system comprising: The irradiation system is configured to direct at least a first irradiation beam and a second irradiation beam toward a target structure and to direct a first reference beam toward a detector system; An optical system is configured to guide a first scattered beam and a second scattered beam from the target structure to a detector system; A detector system is configured to capture an interference pattern and output a measurement signal, wherein a first scattered beam, a second scattered beam, and a first reference beam generate the interference pattern; and The processor is configured to analyze measurement signals to determine the characteristics of the target structure. 2. The system according to Clause 1, wherein the first scattering beam is the first diffraction beam and the second scattering beam is the second diffraction beam. 3. The system according to Clause 1, wherein the first irradiation beam, the second irradiation beam, and the first reference beam are at least partially coherent. 4. The system according to Clause 1, wherein the irradiation system is further configured to direct a third irradiation beam and a fourth irradiation beam toward the target structure and to direct a second reference beam toward the detector system, the third irradiation beam, the fourth irradiation beam and the second reference beam being coherent; The optical system is further configured to guide the third and fourth scattered beams from the target structure to the detector system; the detector system is further configured to capture another interference pattern formed by the third scattered beam, the fourth scattered beam, and the second reference beam, the first and third illumination beams being incoherent with respect to each other, and to generate another measurement signal; and the processor is further configured to analyze the other measurement signal to determine another characteristic of the target structure. 5. The system according to Clause 4, wherein the target structure comprises a first periodic structure having a first pitch along a first direction and a second periodic structure having a second pitch along a second direction different from the first direction; and wherein a characteristic is associated with a first dimension and another characteristic is associated with a second dimension. 6. The system according to Clause 4 further includes: an optical element configured to apply incoherence between the first and third illumination beams. 7. The system according to Clause 1, wherein the processor is further configured to: clip along the first dimension and move a portion of the Fourier representation of the interference pattern to the center in the Fourier domain; and The properties of the target structure in the first dimension are obtained by performing at least an inverse Fourier transform operation. 8. In the system of Clause 1, the characteristics of the target structure include alignment characteristics. 9. The system according to Clause 1, wherein the first scattered beam includes positive diffraction orders in a first direction and a second direction, and the second scattered beam includes negative diffraction orders in both the first and second directions; and The target structure includes grating segments in the first and second directions. 10. The system according to Clause 1, wherein the irradiation system is further configured to guide a second reference beam toward the detector system; and wherein the polarization of the first reference beam is orthogonal to the polarization of the second reference beam. 11. A method comprising: directing a first illumination beam and a second illumination beam toward a target structure to generate a first scattered beam and a second scattered beam; directing a reference beam toward a detector system; using the detector system to detect an interference pattern of the first scattered beam, the second scattered beam, and the reference beam; and using a processor to determine characteristics of the target structure based at least on the detected interference pattern. 12. The method according to Clause 11 further includes: guiding a third and a fourth irradiation beam toward the target structure and guiding another reference beam toward the detector system, wherein the third, fourth, and other reference beams are at least partially coherent, and wherein the first, second, and other reference beams are at least partially coherent. 13. The method according to Clause 12 further includes: using optical elements to apply incoherence between the first and third irradiation beams. 14. The method according to Clause 11 further includes: applying a Fourier transform to the detected interference pattern to obtain a Fourier representation; cropping and shifting along a first dimension of the Fourier representation to a first diffraction order; applying an inverse Fourier transform to the cropped Fourier representation to obtain properties of the target structure in the first dimension; cropping along a second dimension of the Fourier representation and shifting the first diffraction order to the center; and applying an inverse Fourier transform along the second dimension to the cropped Fourier representation to obtain properties of the target structure in the second dimension. 15. A photolithography apparatus, comprising: an illumination system configured to illuminate a pattern forming apparatus; a projection system configured to project an image of the pattern onto a substrate; and an inspection system comprising: an optical system configured to: guide a first illumination beam and a second illumination beam toward a target structure and guide a first reference beam toward a detector system; and guide a first scattered beam and a second scattered beam from the target structure to the detector system; the detector system configured to capture an interference pattern and output a measurement signal, wherein the first scattered beam, the second scattered beam, and the first reference beam generate the interference pattern; and a processor configured to analyze the measurement signal to determine characteristics of the target structure. 16. A photolithography apparatus according to Clause 15, wherein the first scattering beam is a first diffraction beam and the second scattering beam is a second diffraction beam. 17. A lithography apparatus according to Clause 15, wherein the first irradiation beam, the second irradiation beam, and the first reference beam are at least partially coherent. 18. A lithography apparatus according to Clause 15, wherein the illumination system is further configured to guide a third illumination beam and a fourth illumination beam toward a target structure and to guide a second reference beam toward a detector system, the third illumination beam, the fourth illumination beam, and the second reference beam being at least partially coherent; wherein the optical system is further configured to guide the third scattering beam and the fourth scattering beam from the target structure to the detector system; wherein the detector is further configured to capture another 2D interference pattern formed by the third scattering beam, the fourth scattering beam, and the second reference beam, the first illumination beam and the third illumination beam being incoherent with respect to each other, and to generate another measurement signal; and wherein the processor is further configured to analyze the other measurement signal to determine another characteristic of the target structure. 19. A photolithography apparatus according to Clause 18, wherein the target structure includes a first periodic structure having a first pitch along a first direction and a second periodic structure having a second pitch along a second direction different from the first direction; and One characteristic is associated with the first direction, and the other characteristic is associated with the second direction. 20. A lithography apparatus according to Clause 18, wherein the inspection system further comprises: an optical element configured to apply incoherence between a first irradiation beam and a third irradiation beam. 21. A lithography apparatus according to Clause 15, wherein the characteristics of the target structure include alignment characteristics. 22. A system comprising: an illumination system configured to guide a first illumination beam and a second illumination beam toward a target structure and to guide a second reference beam toward a detector system, wherein the first illumination beam and the first reference beam are coherent, the second illumination beam and the second reference beam are coherent, and the first illumination beam and the first reference beam are incoherent with the second illumination beam and the second reference beam; an optical system configured to guide a first scattering beam and a second scattering beam from the target structure to the detector system, wherein the first scattering beam includes at least two positive diffraction orders, and the second scattering beam includes at least two negative diffraction orders; a detector system configured to capture a first interference pattern and a second interference pattern and to output at least a measurement signal; and a processor configured to analyze the measurement signal to determine alignment characteristics of the target structure. 23. A system comprising: an illumination system configured to guide an illumination beam toward a target structure and a reference beam toward a detector system; an optical system configured to guide at least a first scattered beam and a second scattered beam from the target structure to the detector system, wherein the first scattered beam and the second scattered beam include two or more diffraction orders; a detector system configured to capture an interference pattern and output a measurement signal, wherein the first scattered beam, the second scattered beam, and the reference beam generate the interference pattern; and a processor configured to analyze the measurement signal to determine characteristics of the target structure.

[0159] While specific references may be made herein to the use of lithography apparatuses in IC manufacturing, it should be understood that the lithography apparatuses described herein can have other applications, such as the fabrication of integrated optical systems, the guiding and detection of patterns in magnetic domain memory, flat panel displays, LCDs, thin-film magnetic heads, etc. Those skilled in the art will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein can be considered as specific examples of the more general terms “substrate” or “target portion,” respectively. The substrate referred to herein may be processed before or after exposure in, for example, a track cell (a tool typically used to apply a resist layer to a substrate and develop the exposed resist) and / or a measurement cell. Where applicable, this disclosure may be applied to such and other substrate processing tools. Furthermore, the substrate may be processed more than once, for example to create a multilayer IC, such that the term “substrate” as used herein may also refer to a substrate that already contains multiple processed layers.

[0160] While the use of embodiments of this disclosure may have been specifically referenced above in the context of optical lithography, it is to be understood that this disclosure can be used in other applications, such as imprint lithography, and is not limited to optical lithography where the context permits. In imprint lithography, the morphology in a patterning apparatus defines a pattern created on a substrate. The morphology of the patterning apparatus can be pressed into a resist layer supplied to the substrate, whereby the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist has cured, the patterning apparatus is removed from the resist, thereby leaving a pattern therein.

[0161] It should be understood that the wording or terminology used herein is for descriptive purposes and not for limitation, and that the wording or terminology of this disclosure is to be interpreted by those skilled in the art in light of the teachings herein.

[0162] The terms “radiation,” “radiation beam,” etc., used herein can encompass all types of electromagnetic radiation, such as ultraviolet (UV) radiation (e.g., wavelengths λ of 365, 248, 193, 157, or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (e.g., wavelengths in the range of 5 to 20 nm, such as, for example, 13.5 nm), or hard X-rays operating at less than 5 nm, as well as matter beams (such as ion beams or electron beams). The terms “light,” “irradiation,” etc., can refer to non-material radiation (e.g., photons, UV, X-rays, etc.). Generally, radiation with wavelengths between about 400 and about 700 nm is considered visible radiation; radiation with wavelengths between about 780 and 3000 nm (or greater) is considered IR radiation. UV refers to radiation with wavelengths approximately 100 to 400 nm. In photolithography, the term “UV” also applies to wavelengths that can be produced by a mercury discharge lamp: G line 436 nm; H line 405 nm; and / or I line 365 nm. Vacuum UV or VUV (i.e., UV absorbed by a gas) refers to radiation with wavelengths approximately 100 to 200 nm. Deep UV (DUV) typically refers to radiation with wavelengths ranging from 126 nm to 428 nm, and in some embodiments, excimer lasers can generate DUV radiation for use within a photolithography apparatus. It should be understood that radiation with wavelengths in, for example, the range of 5 to 20 nm involves radiation having a desired wavelength band, with at least a portion falling within the 5 to 20 nm range.

[0163] It should be understood that the Detailed Description section, rather than the Summary and Abstract section, is intended to be used to interpret the claims. The Summary and Abstract section may state one or more, but not all, exemplary embodiments of this disclosure as conceived by the inventors, and is therefore not intended to limit this disclosure and the appended claims in any way.

[0164] The present disclosure has been described above using functional building blocks that illustrate the implementation of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks are arbitrarily defined herein. Alternating boundaries can be defined as long as the specified functions and their relationships are performed appropriately.

[0165] Although specific embodiments of this disclosure have been described above, it is to be understood that embodiments of this disclosure may be practiced in ways other than those described. The description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications may be made to the described disclosure without departing from the scope of the claims set forth below.

[0166] The foregoing description of the specific embodiments will fully demonstrate the generality of this disclosure. By applying knowledge in the art, others can readily modify and / or adapt such specific embodiments to various applications without excessive experimentation or departing from the general conception of this disclosure. Therefore, based on the teachings and guidance presented herein, such adaptations and modifications are intended to be within the meaning and scope equivalent to the disclosed embodiments.

[0167] The breadth and scope of the protected subject matter should not be limited by any of the exemplary embodiments described above, but should be defined only by the following claims and their equivalents.

Claims

1. A system comprising: The irradiation system is configured to direct at least a first irradiation beam and a second irradiation beam toward the target structure, and to direct a first reference beam toward the detector system; An optical system is configured to guide a first scattered beam and a second scattered beam from the target structure to the detector system; The detector system is configured to capture an interference pattern and output a measurement signal, wherein the first scattered beam, the second scattered beam, and the first reference beam generate the interference pattern; as well as The processor is configured to analyze the measurement signal to determine the characteristics of the target structure.

2. The system according to claim 1, wherein the first scattering beam is a first diffraction beam and the second scattering beam is a second diffraction beam.

3. The system of claim 1, wherein the first irradiation beam, the second irradiation beam, and the first reference beam are at least partially coherent.

4. The system of claim 1, wherein the irradiation system is further configured to direct a third irradiation beam and a fourth irradiation beam toward the target structure and to direct a second reference beam toward the detector system, the third irradiation beam, the fourth irradiation beam and the second reference beam being coherent; The optical system is further configured to guide a third and a fourth scattered beam from the target structure to the detector system; The detector system is further configured to capture another interference pattern formed by the third scattered beam, the fourth scattered beam, and the second reference beam and generate another measurement signal, wherein the first illumination beam and the third illumination beam are incoherent with respect to each other; and The processor is also configured to analyze the other measurement signal to determine another characteristic of the target structure.

5. The system of claim 4, wherein the target structure comprises a first periodic structure and a second periodic structure, the first periodic structure having a first pitch along a first direction, and the second periodic structure having a second pitch along a second direction different from the first direction; and The characteristic is associated with the first direction, and the other characteristic is associated with the second direction.

6. The system according to claim 4, further comprising: An optical element is configured to apply incoherence between the first irradiation beam and the third irradiation beam.

7. The system of claim 1, wherein the processor is further configured to: A portion of the Fourier representation of the interference pattern is clipped along the first dimension, and that portion of the Fourier representation of the interference pattern is moved to the center of the Fourier domain; and The properties of the target structure in the first dimension are obtained by performing at least an inverse Fourier transform operation.

8. The system of claim 1, wherein the characteristic of the target structure includes alignment characteristics.

9. The system of claim 1, wherein the first scattered beam includes positive diffraction orders in a first direction and a second direction, and the second scattered beam includes negative diffraction orders in the first direction and the second direction; and The target structure includes grating segments in the first direction and the second direction.

10. The system of claim 1, wherein the irradiation system is further configured to direct a second reference beam toward the detector system; and The polarization of the first reference beam is orthogonal to the polarization of the second reference beam.

11. A method comprising: The first and second irradiation beams are directed toward the target structure to generate a first and a second scattered beam; Orient the reference beam toward the detector system; The detector system is used to detect the interference pattern of the first scattered beam, the second scattered beam, and the reference beam; as well as Using a processor, the characteristics of the target structure are determined, at least based on the detected interference pattern.

12. The method of claim 11, further comprising: A third and a fourth irradiation beam are directed toward the target structure, and another reference beam is directed toward the detector system, wherein the third, the fourth, and the other reference beams are at least partially coherent, and wherein the first, the second, and the reference beams are at least partially coherent.

13. The method of claim 12, further comprising: Using optical elements, incoherence is applied between the first irradiation beam and the third irradiation beam.

14. The method of claim 11, further comprising: Fourier transform is applied to the detected interference pattern to obtain its Fourier representation; The first diffraction order is clipped along the first dimension of the Fourier representation and shifted to the center; Apply an inverse Fourier transform to the clipped Fourier representation to obtain the properties of the target structure in the first dimension; The first diffraction order is clipped along the second dimension of the Fourier representation and shifted to the center; and Apply an inverse Fourier transform along the second dimension to the clipped Fourier representation to obtain the properties of the target structure along the second dimension.

15. A photolithography apparatus, comprising: The irradiation system is configured to irradiate the pattern of the pattern forming device; A projection system is configured to project an image of the pattern onto a substrate; as well as Inspection system, including: The optical system is configured as follows: The first and second illumination beams are guided toward the target structure, and the first reference beam is guided toward the detector system; and The first and second scattered beams are guided from the target structure to the detector system; The detector system is configured to capture an interference pattern and output a measurement signal, wherein the first scattered beam, the second scattered beam, and the first reference beam generate the interference pattern; and The processor is configured to analyze the measurement signal to determine the characteristics of the target structure.

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