Second illumination mode selector (IMS) for YIELSTAR

Abstract

Embodiments disclosed herein relate to metrology devices and methods for measuring multiple indicia in parallel using a parallel sensor concept that geometrically arranges sensors in space to allow parallel acquisition. The selector may be configured to block a quadrant of the marker in order to generate an image. The intensity differences between the acquired images may be compared and balanced such that incoherent internal crosstalk is cancelled.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 482,959, filed on February 2, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a metrology device that measures multiple markers in parallel using a parallel sensor concept that geometrically arranges sensors in space to allow parallel acquisition. Background Art

[0004] A lithographic apparatus is a machine that applies a desired pattern to a substrate, typically to a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In this case, a patterning device (also referred to as a mask or reticle) can be used to generate a circuit pattern to be formed on a single layer of the IC. The pattern can be transferred to a target portion (e.g., a component comprising one or more dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is typically performed by imaging onto a radiation-sensitive material (resist) layer provided on the substrate. Generally speaking, a single substrate will contain a network of adjacent target portions that are continuously patterned. Known lithographic apparatuses include so-called steppers and so-called scanners. In a stepper, each target portion is irradiated by exposing the entire pattern to the target portion at once, and in a scanner, each target portion is irradiated by scanning the pattern in a given direction ("scanning" direction) with a radiation beam, while simultaneously scanning the target portion in parallel or antiparallel to the scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0005] During a photolithography operation, different processing steps may require sequentially forming different layers on a substrate. Therefore, it is necessary to position the substrate with high precision relative to the existing pattern formed on it. Generally, alignment marks are placed on the substrate to be aligned and positioned with reference to a second object. The photolithography apparatus may use an alignment device to detect the position of the alignment marks and use them to align the substrate to ensure accurate exposure of the mask. Misalignment between alignment marks on two different layers is measured as overlay error.

[0006] To monitor the lithographic process, parameters of the patterned substrate are measured. Parameters can include, for example, the overlay error between successive layers formed in or on the patterned substrate and the critical linewidth of the developed photoresist. Such measurements can be performed on production substrates and / or dedicated metrology targets. Various techniques are used to measure the microstructures formed during the lithographic process, including the use of scanning electron microscopes and various specialized tools. A rapid and non-invasive form of specialized inspection tool is a scatterometer, in which 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 it is reflected or scattered by the substrate, the properties of the substrate can be determined. For example, this can be achieved by comparing the reflected beam with data stored in a library of known measurements associated with known substrate properties. Spectral scatterometers direct a broadband radiation beam onto the substrate and measure the spectrum (intensity as a function of wavelength) of the radiation scattered into a specific narrow angular range. In contrast, angle-resolved scatterometers use a monochromatic radiation beam and measure the intensity of the scattered radiation as a function of angle.

[0007] This type of optical scatterometer can be used to measure parameters such as the critical dimension of developed photoresist or the overlay error (OV) between two layers formed in or on a patterned substrate. By comparing the properties of an irradiated beam before and after the beam is reflected or scattered by the substrate, the properties of the substrate can be determined.

[0008] Existing technology alignment sensors measure one alignment mark at a time. Summary of the Invention

[0009] Therefore, various embodiments are provided herein for measuring multiple markers in parallel using a parallel sensor concept that geometrically arranges sensors in space to allow for parallel acquisition.

[0010] Some embodiments are directed to a measurement system. In some embodiments, the first selector and the second selector are configured to pass light from two quadrants. In some embodiments, the first selector is configured to block a first pair of two quadrants and generate a first image. In some embodiments, the second selector is configured to block a different second pair of two quadrants and generate a second image. In some embodiments, the comparator is configured to compare an intensity difference between the first image and the second image. In some embodiments, the calibration device is configured to balance the intensity difference between the first image and the second image such that incoherent internal crosstalk is substantially eliminated.

[0011] In some embodiments, the first selector is located at a first pupil conjugate plane.

[0012] In some embodiments, the second selector is located at a second pupil conjugate plane.

[0013] In some embodiments, the first selector and the second selector each comprise an illumination mode selector.

[0014] In some embodiments, the first image and the second image are taken sequentially for each quadrant of the illumination mode selector.

[0015] In some embodiments, each illumination mode selector comprises an aperture.

[0016] In some embodiments, substantial elimination of incoherent internal crosstalk substantially eliminates its impact on overlay error.

[0017] In some embodiments, incoherent internal crosstalk does not affect overlay error.

[0018] Other features of the present disclosure and the structure and operation of various embodiments are described in detail below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the specific embodiments described herein. These embodiments are presented herein for illustrative purposes only. Based on the teachings contained herein, other embodiments will be apparent to those skilled in the relevant art(s). BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate the disclosure and, together with the description, further serve to explain the principles of the disclosure and to enable one skilled in the relevant art(s) to make and use the embodiments described herein.

[0020] Figure 1A A schematic diagram of a reflective lithography apparatus according to some embodiments is shown.

[0021] Figure 1B A schematic diagram of a transmissive lithography apparatus according to some embodiments is shown.

[0022] Figure 2 A more detailed schematic diagram of a reflective lithography apparatus according to some embodiments is shown.

[0023] Figure 3 A schematic diagram of a lithography cell is shown in accordance with some embodiments.

[0024] Figure 4A and Figure 4B A schematic diagram of a lithographic apparatus according to some embodiments is shown.

[0025] Figure 5A and Figure 5B Microdiffraction-based overlay imaging is shown in accordance with some embodiments.

[0026] Figure 6A and Figure 6BuDBO imaging associated with a first quadrant illumination pupil without incoherent internal crosstalk is shown in accordance with some embodiments.

[0027] Figure 7A and Figure 7B uDBO imaging associated with a third quadrant illumination pupil without incoherent internal crosstalk is shown in accordance with some embodiments.

[0028] Figure 8 is a flow chart illustrating a process of calibrating for homogeneity and incoherent internal crosstalk effects according to some embodiments.

[0029] Features of the present disclosure will become more apparent from the detailed description set forth below in conjunction with the accompanying drawings, in which like reference numerals identify corresponding elements throughout. In the accompanying drawings, like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost digit(s) of a reference numeral identifies the drawing in which the reference numeral first appears. Unless otherwise indicated, the drawings provided throughout the disclosure should not be construed as being drawn to scale. DETAILED DESCRIPTION

[0030] This specification discloses one or more embodiments incorporating features of the present disclosure. The disclosed embodiment(s) are provided as examples. The scope of the present disclosure is not limited to the disclosed embodiment(s). The required features are defined by the appended claims.

[0031] The described embodiment(s) and references in the specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment(s) may include certain features, structures, or characteristics, but not every embodiment must include certain features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it should be understood that it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0032] For ease of description, spatially relative terms, such as "beneath," "below," "lower," "above," "on," "upper," etc., may be used herein to describe the relationship of one element or feature to another (one or more) elements or features illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0033] As used herein, the term "about" indicates a value for a given quantity that may vary based on a particular technology. Based on a particular technology, the term "about" may indicate a value for a given quantity that varies, for example, within 10-30% of that value (e.g., ±10%, ±20%, or ±30% of that value).

[0034] Embodiments of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present disclosure may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. In addition, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only, and that such actions are actually generated by a computing device, processor, controller, or other device that executes the firmware, software, routines, instructions, etc.

[0035] However, before describing such embodiments in greater detail, it is instructive to describe an example environment in which embodiments of the present disclosure may be implemented.

[0036] An example photolithography system will now be described.

[0037] Figure 1A and Figure 1B Schematic illustrations of a lithographic apparatus 100 and a lithographic apparatus 100', respectively, in which embodiments of the present disclosure may be implemented are shown. The lithographic apparatus 100 and the lithographic apparatus 100' each include an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., a mask table) MT configured to support a patterning device (e.g., a mask, a reticle, or a dynamic patterning device) MA and connected to a first positioner PM configured to precisely position the patterning device MA; and a substrate table (e.g., a wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to precisely position the substrate W. The lithographic apparatuses 100 and 100' also have a projection system PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion (e.g., comprising one or more dies) C of the substrate W. In the lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In the lithographic apparatus 100', the patterning device MA and the projection system PS are transmissive.

[0038] The illumination system IL may include various types of optical components for directing, shaping or controlling the radiation beam B, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof.

[0039] The manner in which the support structure MT holds the patterning device MA depends on the orientation of the patterning device MA relative to the reference frame, the design of at least one of the lithographic apparatuses 100 and 100', and other conditions, such as whether the patterning device MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT can be, for example, a frame or a stage, which can be fixed or movable as desired. By using sensors, the support structure MT can ensure that the patterning device MA is in a desired position, for example, relative to the projection system PS.

[0040] The term “patterning device” should be broadly interpreted as referring to any device that can be used to impart a pattern to a cross-section of a radiation beam B, such as to create a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in the device created in the target portion C to form an integrated circuit.

[0041] The terms "inspection apparatus," "metrology system," etc., may be used herein to refer to, for example, an apparatus or system for measuring properties of a structure (e.g., overlay error, critical dimension parameters) or for use in a lithography apparatus to check wafer alignment (e.g., an alignment apparatus).

[0042] The patterning device MA can be a transmissive device (e.g. Figure 1B lithographic apparatus 100 ') or reflective (as shown in FIG. Figure 1A lithographic apparatus 100 is shown. Examples of patterning devices may include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography and include types such as binary, alternating phase-shift, or attenuated phase-shift, as well as various hybrid mask types. One example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B, which is reflected by the matrix of small mirrors.

[0043] The term "projection system" PS may encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof, adapted to the exposure radiation used, or adapted to other factors such as the use of an immersion liquid or the use of a vacuum on the substrate W. A vacuum environment may be used for EUV or electron beam radiation, as other gases may absorb too much radiation or electrons. Therefore, with the aid of vacuum walls and a vacuum pump, a vacuum environment may be provided for the entire beam path.

[0044] The lithographic apparatus 100 and / or the lithographic apparatus 100' may be of a type having two (dual-stage) or more substrate tables WT (and / or two or more mask tables). In such "multi-stage" machines, additional substrate tables WT may be used in parallel, or preparatory steps may be performed on one or more tables while one or more other substrate tables WT are being used for exposure. In some cases, the additional tables may not be substrate tables WT.

[0045] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index (e.g., water) so as to fill the space between the projection system and the substrate. Immersion liquid may be applied to other spaces in the lithographic apparatus, such as between the mask and the projection system. Immersion techniques are well known in the art and are used to increase the numerical aperture of the projection system. The term "immersion" as used herein does not imply that structures such as the substrate must be immersed in the liquid, but only means that the liquid is located between the projection system and the substrate during exposure.

[0046] refer to Figure 1A and Figure 1B , the illuminator IL receives a radiation beam from a radiation source SO. For example, when the source SO is an excimer laser, the source SO and the lithographic apparatus 100, 100' may be separate physical entities. In such cases, the source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam B is delivered to the lithographic apparatus 100 or 100' by means of a beam delivery system BD (in Figure 1B The beam is delivered from the source SO to the illuminator IL (in the embodiment of FIG. 1 ), with the beam delivery system BD including, for example, suitable guide mirrors and / or a beam expander. In other cases, such as when the source SO is a mercury lamp, the source SO may be an integral component of the lithographic apparatus 100, 100′. If desired, the source SO and the illuminator IL, together with the beam delivery system BD, may be referred to as a radiation system.

[0047] The illuminator IL may comprise an adjuster AD ( Figure 1BIn general, at least the outer and / or inner radial extent (commonly referred to as "σ-outer" and "σ-inner", respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components (in Figure 1B ), such as an integrator In and a condenser CO. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

[0048] refer to Figure 1A , a radiation beam B is incident on a patterning device (e.g., a mask) MA, which is held on a support structure (e.g., a mask table) MT and is patterned by the patterning device MA. In the lithographic apparatus 100, the radiation beam B is reflected from the patterning device (e.g., a mask) MA. After reflecting from the patterning device (e.g., a mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of a substrate W. With the aid of a second positioner PW and a position sensor IF2 (e.g., an interferometric device, a linear encoder, or a capacitive sensor), the substrate table WT can be precisely moved (e.g., in order to position a different target portion C in the path of the radiation beam B). Similarly, a first positioner PM and a further position sensor IF1 can be used to precisely position the patterning device (e.g., a mask) MA relative to the path of the radiation beam B. The patterning device (e.g., a mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0049] refer to Figure 1B , radiation beam B is incident on a patterning device (e.g., mask MA), which is held on a support structure (e.g., mask table MT), and is patterned by the patterning device. After passing through mask MA, radiation beam B passes through a projection system PS, which focuses the radiation beam onto a target portion C of a substrate W. The projection system has a pupil conjugate PPU with respect to an illumination system pupil IPU. Part of the radiation is emitted from the intensity distribution at the illumination system pupil IPU and passes through 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.

[0050] The projection system PS projects an image of a mask pattern MP onto a photoresist layer coated on a substrate W, wherein the image is formed by a diffraction beam generated from the marking pattern MP by radiation from an intensity distribution. For example, the mask pattern MP may comprise an array of lines and spaces. Diffraction of the radiation on the array other than the zeroth order diffraction generates a diffraction beam which is turned and whose direction changes in a direction perpendicular to the lines. The undiffracted beam, the so-called zeroth order diffraction beam, passes through the pattern without any change in the direction of propagation. The zeroth order diffraction beam passes through an upper lens or upper lens group of the projection system PS and reaches the pupil conjugate PPU upstream of the pupil conjugate PPU of the projection system PS. The part of the intensity distribution in the plane of the pupil conjugate PPU associated with the zeroth order diffraction beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. For example, the aperture device PD is arranged or is substantially arranged on a plane including the pupil conjugate PPU of the projection system PS.

[0051] By means of a lens or lens group L, the projection system PS can capture not only the zeroth-order diffraction beam, but also the first-order or first-order and higher-order diffraction beams (not shown). In some embodiments, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to exploit the resolution enhancement effect of dipole illumination. For example, the first-order diffraction beam interferes with the corresponding zeroth-order diffraction beam at the level of the wafer W, thereby creating an image of the line pattern MP with the highest possible resolution and process window (i.e., the available focal depth combined with the tolerable exposure dose deviation). In some embodiments, astigmatic aberrations can be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. Furthermore, in some embodiments, astigmatic aberrations can be reduced by blocking the zeroth-order beam in the pupil conjugate PPU of the projection system associated with the radiation poles in the opposite quadrant. This is described in more detail in B2 patent US 7,511,799 B2, issued on March 31, 2009, the entire contents of which are incorporated herein by reference.

[0052] With the help of a second positioner PW and a position sensor IFD (e.g. an interferometric device, a linear encoder or a capacitive sensor), the substrate table WT can be precisely moved (e.g. to position a different target portion C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor ( Figure 1B ) can be used to accurately position the mask MA relative to the path of the radiation beam B (eg after mechanical retrieval from a mask library or during scanning).

[0053] In general, movement of the mask table MT can be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT can be achieved using a long-stroke module and a short-stroke module which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected only to a short-stroke actuator or may be fixed. The mask MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks (as shown) occupy dedicated target portions, they can be located in the space between the target portions (referred to as scribe alignment marks). Similarly, where more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

[0054] The mask table MT and patterning device MA can be located in a vacuum chamber V, where an in-vacuum robot (IVR) can be used to move patterning devices (such as masks) into and out of the vacuum chamber. Alternatively, when the mask table MT and patterning device 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., a mask) to the fixed kinematic support of the transfer station.

[0055] The lithographic apparatuses 100 and 100 ′ may be used in at least one of the following modes:

[0056] 1. In step mode, the support structure (e.g. mask table) MT and substrate table WT are kept essentially stationary while an entire pattern imparted to the radiation beam B is projected at once onto a target portion C (i.e. a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed.

[0057] 2. In scan mode, the support structure (e.g. mask table) MT and substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (i.e. single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (e.g. mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0058] 3. In another mode, the support structure (e.g., mask table) MT remains essentially stationary, holding the programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO can be employed, and the programmable patterning device is updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography utilizing a programmable patterning device, such as a programmable mirror array.

[0059] Combinations and / or variations on the described modes of use or entirely different modes of use may also be employed.

[0060] In another embodiment, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Generally speaking, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0061] Figure 2 The lithographic apparatus 100 is shown in more detail and comprises a source collector arrangement SO, an illumination system IL and a projection system PS. The source collector arrangement SO is constructed and arranged so that a vacuum environment can be maintained in an enclosed structure 220 of the source collector arrangement SO. The EUV radiation emitting plasma 210 can be formed by a plasma source produced by a discharge. EUV radiation can be generated by a gas or vapor, such as Xe gas, Li vapor or Sn 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 a plasma that is at least partially ionized. In order to effectively generate radiation, a partial pressure of Xe, Li, Sn vapor or any other suitable gas or vapor of, for example, 10 Pa may be required. In some embodiments, a plasma of excited tin (Sn) is provided to generate EUV radiation.

[0062] The radiation emitted by the hot plasma 210 passes from the source chamber 211 into the collector chamber 212 via an optional gas barrier or contaminant trap 230 (also referred to as a contaminant barrier or foil trap in some cases), which is positioned within or behind the opening of 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.

[0063] The 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 passing through the collector CO may be reflected by a grating spectral filter 240 to be focused into a virtual source point INTF. The virtual source point INTF is often referred to as an intermediate focus, and the source collector arrangement is arranged so that the intermediate focus INTF is located at or near an opening 219 in the enclosure 220. The virtual source point INTF is an image of the radiation emitting plasma 210. The grating spectral filter 240 is particularly useful for suppressing infrared (IR) radiation.

[0064] The radiation then passes through illumination system IL, which may include a polygonal field mirror device 222 and a polygonal pupil mirror device 224, which are arranged to provide a desired angular distribution of radiation beam 221 at patterning device MA, and a desired uniformity of radiation intensity at patterning device MA. When radiation beam 221 is reflected at patterning device MA, which is held by support structure MT, patterned beam 226 is formed, and patterned beam 226 is imaged by projection system PS via reflective elements 228, 229 onto a substrate W held by wafer stage or substrate table WT.

[0065] There may generally be more elements present in the illumination optics unit IL and the projection system PS than shown. Depending on the type of lithographic apparatus, a grating spectral filter 240 may optionally be present. In addition, there may be more than Figure 2 More mirrors than shown, for example, may be present in the projection system PS. Figure 2 One to six additional reflective elements are shown.

[0066] like Figure 2 As shown, the collector optics CO is depicted as a nested collector with grazing incidence reflectors 253, 254 and 255, merely as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are arranged axisymmetrically around the optical axis O, and this type of collector optics CO is preferably used in conjunction with a discharge produced plasma source (commonly referred to as a DPP source).

[0067] An exemplary lithography cell will now be described.

[0068] Figure 3A lithography unit 300, sometimes also referred to as a lithography cell or cluster, is shown according to some embodiments. The lithography apparatus 100 or 100' may form part of the lithography unit 300. The lithography unit 300 may also include one or more devices that perform pre-exposure and post-exposure processing on the substrate. In some examples, these include a spin coater SC that deposits a resist layer, a developer DE that develops the exposed resist, a cooling plate CH, and a bake plate BK. A substrate handler or robot RO picks up substrates from input / output ports I / O1, I / O2, moves them between different processing devices, and delivers them to the loading area LB of the lithography apparatus 100 or 100'. These devices, which are generally referred to as tracks, are under the control of a track control unit TCU, which is itself controlled by a monitoring system SCS, which also controls the lithography apparatus via the lithography control unit LACU. Thus, the different devices can be operated to maximize throughput and processing efficiency.

[0069] An exemplary inspection apparatus will now be described.

[0070] In order to control the lithography process, so that the device feature portion is accurately placed on the substrate, alignment marks are generally provided on the substrate, and the lithography apparatus includes one or more inspection devices for accurately locating the marks on the substrate. These alignment devices are effective position measurement devices. Different types of marks and different types of alignment devices and / or systems are known from different times and different manufacturers. A system widely used in current lithography apparatuses is based on the self-referencing interferometer described in U.S. Patent No. 6,961,116 (den Boef et al.). In general, the marks are measured separately to obtain the X and Y positions. However, the technology described in U.S. Publication No. 2009 / 195768A (Bijnen et al.) can be used to perform combined X and Y measurements. The entire contents of these two disclosures are incorporated herein by reference.

[0071] Figure 4A A schematic diagram illustrates a cross-sectional view of an inspection apparatus 400 that can be implemented as a component of a lithographic apparatus 100 or 100', according to some embodiments. In some embodiments, the inspection apparatus 400 can be configured to align a substrate (e.g., substrate W) relative to a patterning device (e.g., patterning device MA). The inspection apparatus 400 can also be configured to detect the positions of alignment marks on the substrate and use the detected positions of the alignment marks to align the substrate relative to the patterning device or other components of the lithographic apparatus 100 or 100'. Such alignment of the substrate can ensure accurate exposure of one or more patterns on the substrate.

[0072] In some embodiments, 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. Illumination system 412 may be configured to provide an electromagnetic narrowband radiation beam 413 having one or more passbands. In one example, the one or more passbands may be within a wavelength spectrum between approximately 500 nm and approximately 900 nm. In another example, the one or more passbands may be discrete narrow passbands within a wavelength spectrum between approximately 500 nm and approximately 900 nm. Illumination system 412 may also be configured to provide the one or more passbands with a substantially constant center wavelength (CWL) value over an extended period of time (e.g., over the lifetime of illumination system 412). As described above, in current alignment systems, such a configuration of illumination system 412 helps prevent drift of the actual CWL value from the desired CWL value. Thus, using a constant CWL value may improve the long-term stability and accuracy of an alignment system (e.g., inspection apparatus 400) compared to current alignment systems.

[0073] In some embodiments, beam splitter 414 can be configured to receive radiation beam 413 and split radiation beam 413 into at least two radiation sub-beams. For example, radiation beam 413 can be split into radiation sub-beams 415 and 417, as shown in FIG. Figure 4AAs shown. Beam splitter 414 can also be configured to direct radiation sub-beams 415 onto substrate 420 placed on stage 422. In one example, stage 422 can be moved along direction 424. Radiation sub-beams 415 can be configured to illuminate alignment marks or targets 418 located on substrate 420. Alignment marks or targets 418 can be coated with a radiation-sensitive film. In some embodiments, alignment marks or targets 418 can have one hundred and eighty degrees (i.e., 180°) symmetry. That is, when alignment marks or targets 418 are rotated 180° about an axis of symmetry perpendicular to the plane of alignment marks or targets 418, the rotated alignment marks or targets 418 can be substantially identical to the unrotated alignment marks or targets 418. Target 418 on substrate 420 can be (a) a resist layer grating comprising strips formed of solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlay target structure, comprising a resist grating overlaid or interleaved on a product layer grating. Alternatively, the stripes can be etched into the substrate. The pattern is sensitive to chromatic aberrations in the lithographic projection apparatus, particularly the projection system PL, and the illumination symmetry and the presence of such aberrations will manifest themselves in variations in the printed grating. One online method for measuring line width, spacing, and critical dimensions in device manufacturing utilizes a technique known as "scatterometry." Scatterometry methods are described in Raymond et al., "Multi-parameter grating metrology using optical scatterometry," Journal of Vacuum Science and Technology B (J. Vac. Sci. Tech. B), Vol. 15, No. 2, pp. 361-368 (1997) and Niu et al., "Spectral scatterometry in DUV lithography," SPIE, Vol. 3677 (1999), both of which are incorporated herein by reference in their entirety. In scatterometry, light is reflected by a periodic structure in the target, and the resulting reflection spectrum at a given angle is detected. The structure from which the reflection spectrum was derived is reconstructed, for example using rigorous coupled wave analysis (RCWA) or by comparison with a library of simulated patterns. Hence, the scatterometry data of the printed grating is used to reconstruct the grating.The parameters of the grating, such as line width and shape, may be input into a reconstruction process performed by the processing unit PU based on knowledge of the printing step and / or other scatterometry processes.

[0074] According to an embodiment, in some embodiments, the beam splitter 414 may further be configured to receive the diffracted radiation beam 419 and split the diffracted radiation beam 419 into at least two radiation sub-beams. The diffracted radiation beam 419 may be split into diffracted radiation sub-beams 429 and 439, as shown in FIG. Figure 4A shown.

[0075] It should be noted that although beam splitter 414 is shown as directing radiation sub-beam 415 to alignment mark or target 418 and directing diffracted radiation sub-beam 429 to interferometer 426, the present disclosure is not limited thereto. It will be apparent to those skilled in the relevant art that other optical arrangements may be used to achieve similar results of illuminating alignment mark or target 418 on substrate 420 and detecting an image of alignment mark or target 418.

[0076] like Figure 4A As shown, interferometer 426 can be configured to receive radiation sub-beam 417 and diffracted radiation sub-beam 429 via beam splitter 414. In an example embodiment, diffracted radiation sub-beam 429 can be at least a portion of radiation sub-beam 415 that can be reflected from alignment mark or target 418. In one example of this embodiment, interferometer 426 includes any suitable set of optical elements, such as a combination of prisms, that can be configured to form two images of alignment mark or target 418 based on the received diffracted radiation sub-beam 429. It should be understood that high-quality images need not be formed, but features of alignment mark 418 should be resolved. Interferometer 426 can also be configured to rotate one of the two images 180 relative to the other image and interferometrically recombine the rotated and unrotated images.

[0077] In some embodiments, detector 428 may be configured to receive the reconstructed image via interferometer signal 427 and detect interference resulting from the reconstructed image when alignment axis 421 of inspection apparatus 400 passes through a center of symmetry (not shown) of alignment mark or target 418. According to an example embodiment, such interference may be due to alignment mark or target 418 being 180° symmetrical and the reconstructed image interfering constructively or destructively. Based on the detected interference, detector 428 may also be configured to determine the location of the center of symmetry of alignment mark or target 418 and, therefore, detect the position of substrate 420. According to an example, alignment axis 421 may be aligned with a beam that is perpendicular to substrate 420 and passes through the center of image rotation interferometer 426. Detector 428 may also be configured to estimate the position of alignment mark or target 418 by implementing sensor characteristics and interacting with wafer marking process variations.

[0078] In another embodiment, the detector 428 determines the location of the center of symmetry of the alignment mark or target 418 by performing one or more of the following measurements:

[0079] 1. Measure the positional shift of various wavelengths (positional shift between colors);

[0080] 2. Measuring the positional shifts of different orders (positional shifts between diffraction orders); and

[0081] 3. Measure the positional changes of the various polarizations (positional shifts between polarizations).

[0082] This data can be obtained, for example, by any type of alignment sensor, such as a SMASH (SMart Alignment Sensor Hybrid) sensor, as described in U.S. Patent No. 6,961,116, which uses a self-referencing interferometer with a single detector and four different wavelengths and extracts the alignment signal in software, or an Athena (Advanced Technology using High-Order Alignment Enhancement) 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 in their entirety.

[0083] In some embodiments, beam analyzer 430 can be configured to receive and determine the optical state of diffracted radiation sub-beam 439. The optical state can be a measure of the beam wavelength, polarization, or beam profile. Beam analyzer 430 can also be configured to determine the position of stage 422 and correlate the position of stage 422 with the position of the center of symmetry of alignment mark or target 418. In this way, the position of alignment mark or target 418, and therefore the position of substrate 420, can be precisely known with reference to stage 422. Alternatively, beam analyzer 430 can 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 relative to inspection device 400 or any other reference element. Beam analyzer 430 can be a point polarimeter or an imaging polarimeter with some form of wavelength band selectivity. In some embodiments, beam analyzer 430 can be directly integrated into inspection device 400 or connected via several types of optical fiber: polarization-maintaining single-mode, multimode, or imaging, according to other embodiments.

[0084] In some embodiments, the beam analyzer 430 may also be configured to determine overlay data between two patterns on the substrate 420. One of the 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 etching layer already present on the substrate 420. The reference layer may be generated by a reference pattern exposed on the substrate by the 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 an exposure pattern exposed on the substrate 420 by the lithography apparatus 100 or 100'. The exposure pattern on the substrate 420 may correspond to movement of the stage 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 the lithography apparatus 100 or 100' so that, after calibration, the offset between the exposure layer and the reference layer may be minimized.

[0085] In some embodiments, the beam analyzer 430 may also be configured to determine a model of the product stack profile of the substrate 420 and may be configured to measure the overlay, critical dimensions, and focus of the target 418 in a single measurement. The product stack profile contains information about the stacked product, such as alignment marks, the target 418, or the substrate 420, and may include optical signature measurements caused by variations in the marking process as a function of illumination variations. The product stack profile may also include product raster profiles, mark stack profiles, and mark asymmetry information. An example of a beam analyzer 430 is the Yieldstar manufactured by ASML of Veldhoven, The Netherlands. TM , as described in U.S. Patent No. 8,706,442, the entire contents of which are incorporated herein by reference. The beam analyzer 430 may also be configured to process information related to specific properties of the exposure pattern in the layer. For example, the beam analyzer 430 may process overlay parameters (an indication of the accuracy of positioning of the layer relative to the previous layer on the substrate, or an indication of the accuracy of positioning of the first layer relative to a mark on the substrate), focus parameters, and / or critical dimension parameters (e.g., line width and its variation) of the image depicted in the layer. Other parameters are image parameters related to the quality of the depicted image of the exposure pattern.

[0086] In some embodiments, a detector array (not shown) may be connected to the beam analyzer 430 and accurate stack profile detection may be performed, as described below. For example, the detector 428 may be a detector array. For the detector array, a variety of options are possible: a bundle of multimode optical fibers, a discrete PIN detector for each channel, a CCD or CMOS (linear) array. For stability reasons, the use of a bundle of multimode optical fibers enables any dissipative elements to be located remotely. Discrete PIN detectors offer a larger dynamic range, but each requires a separate preamplifier. Therefore, the number of elements is limited. A CCD linear array offers many elements that can be read out at high speed, which is particularly interesting if phase-stepped detection is used.

[0087] In some embodiments, the second beam analyzer 430' may be configured to receive and determine the optical state of the diffracted radiation sub-beam 429, such as Figure 4BAs shown. The optical state can be a measure of the beam wavelength, polarization, or beam profile. The second beam analyzer 430' can be identical to the beam analyzer 430. Alternatively, the second beam analyzer 430' can be configured to perform at least all of the functions of the beam analyzer 430, such as determining the position of the stage 422 and correlating the position of the stage 422 with the position of the center of symmetry of the alignment mark or target 418. In this way, the position of the alignment mark or target 418, and therefore the position of the substrate 420, can be precisely known with reference to the stage 422. The second beam analyzer 430' can also be configured to determine the position of the inspection device 400 or any other reference element, so that the center of symmetry of the alignment mark or target 418 can be known relative to the 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 stacking profile of the substrate 420. The second beam analyzer 430' can also be configured to measure the overlay, critical dimension, and focus of the target 418 in a single measurement.

[0088] In some embodiments, second beam analyzer 430' may be integrated directly into inspection apparatus 400, or, according to other embodiments, may be connected via several types of optical fibers: polarization-maintaining single-mode, multimode, or imaging. Alternatively, second beam analyzer 430' and beam analyzer 430 may be combined to form a single analyzer (not shown) configured to receive and determine the optical state of diffracted radiation sub-beams 429 and 439.

[0089] 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 the received information about product markings to construct a model of the product marking profile. In either case, processor 432 uses or combines the model of the product marking profile to construct a model of the stacked product and overlay marking profile. The stack model is then used to determine overlay offset and minimize spectral effects on the overlay offset measurement. Processor 432 may create a basic correction algorithm based on 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 pupil, image, and additional planes. The pupil plane is a plane in which the radial position of the radiation defines the angle of incidence, and the angular position defines the orientation angle of the radiation. Processor 432 may utilize the basic correction algorithm to characterize inspection apparatus 400 with reference to wafer marks and / or alignment marks 418.

[0090] In some embodiments, processor 432 can also be configured to determine, for each mark, the printed pattern position offset error relative to the sensor estimate based on information received from detector 428 and beam analyzer 430. This information includes, but is not limited to, the product stack profile, overlay measurements, critical dimensions, and the focal point of each alignment mark or target 418 on substrate 420. Processor 432 can utilize a clustering algorithm to group marks into groups with similar constant offset errors and, based on this information, create an alignment error offset correction table. The clustering algorithm can be based on overlay measurements, position estimates, and additional optical stack process information associated with each group of offset errors. Overlay is calculated for multiple different marks, for example, overlay targets with positive and negative offsets around a programmed overlay offset. The target with the smallest measured overlay is used as a reference (because it is measured with the best accuracy). From this measured small overlay, and the known programmed overlay of its corresponding target, the overlay error can be derived. Table 1 illustrates how this is performed. In the example shown, the smallest measured overlay is -1 nm. However, this is relative to a target with a programmed overlay of -30 nm. This process can introduce an overlay error of 29nm.

[0091]

[0092] The minimum value can be used as a reference point, relative to which the offset between the measured overlay and the expected overlay due to programmed overlay can be calculated. This offset determines the overlay error for each mark or group of marks with similar offsets. 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 overlay on other targets is compared with this reference. A table such as Table 1 can also be obtained from marks and targets 418 under different illumination settings, and the illumination setting and its corresponding calibration factor that results in the minimum overlay error can be determined and selected. Thereafter, the processor 432 can group the marks into sets of similar overlay errors. The criteria for grouping the marks can be adjusted based on different process controls, for example, different error tolerances for different processes.

[0093] In some embodiments, the processor 432 can determine that all or most members of the group have similar offset errors and apply a separate offset correction of the clustering algorithm to each mark based on its additional optical stack measurement. The processor 432 can determine the correction for each mark and feed the correction back to the lithography apparatus 100 or 100' for correcting errors in overlay, for example, by feeding the correction back to the inspection apparatus 400.

[0094] Irradiation mode selector

[0095] The present disclosure describes exemplary embodiments of a metrology apparatus and is used to measure alignment or overlay in multiple directions in parallel using a parallel sensor concept that geometrically arranges sensors in space to allow parallel acquisition.

[0096] The beam analyzer system may include a prism assembly, often referred to as an optical pupil symmetrizer (OPS). The OPS can remove all odd symmetries in the input beam. However, half of the light may be sacrificed in the process. The OPS can also override odd pupil homogeneity in a portion of the beam analyzer optics. Odd symmetry can be removed by splitting the input beam into two beams and rotating one beam about the optical axis relative to the other and finally recombining the two beams. The odd symmetry can be removed in this process, but the incoherent internal crosstalk is not eliminated, or the contribution of the incoherent internal crosstalk to the overlay (OVL) error is not eliminated due to the introduction of odd homogeneity after the OPS. The incoherent internal crosstalk can come from aberrations, coherence or diffraction.

[0097] Most beam analyzers shine a beam onto a repeating alignment pattern or overlay mark on a substrate and can predict the resulting pattern. If a camera is used to collect the scattered light, the prediction can be compared with reality to see if the pattern matches. It can also be inferred how well the alignment pattern or overlay mark was printed. Most beam analyzers include an illumination mode selector (IMS). The IMS can have multiple apertures, each of which transmits light. The IMS can be arranged in such a way that there are multiple illumination modes.

[0098] For example, multiple images can be created simultaneously in the x or y direction for the normal channel and the complementary channel by micro-diffraction-based overlay (uDBO). In some embodiments, uDBO is a diffraction-based overlay that enables overlay measurements on smaller alignment marks, but may require very high contrast. In one example, since multiple images are taken at any given time, any intensity from x to y or from y to x is incoherent internal crosstalk. The intensity can be, for example, light projected in the wrong place or in the wrong direction. Incoherent internal crosstalk can directly affect OVL errors.

[0099] In order to eliminate or block incoherent internal crosstalk, a second IMS can be added to the beam analyzer so that there are at least two IMSs. The second IMS will be able to block light passing between quadrants.

[0100] Figure 5A and Figure 5B An illumination pupil and corresponding uDBO image are shown according to some embodiments.

[0101] In some embodiments, Figure 5A It is shown how the pupil can be illuminated using quadrants 510 and 520 configurations.

[0102] In some embodiments, Figure 5B It is shown how incoherent internal crosstalk occurs in the normal channel and the complementary channel.Incoherent internal crosstalk occurs between all uDBO images associated with the illumination pupils 510 and 520.

[0103] For example, the second IMS may perform two consecutive uDBO imaging operations for each quadrant 510 and 520, respectively. Each single quadrant measurement may be followed by an intensity calibration to predict the amount of incoherent crosstalk intensity that leaks into the image position assigned to the other quadrant for overlay calculation. Specifically, the intensity difference balance may be between quadrant A 510 and quadrant B 520, as shown in FIG. Figure 5A This intensity difference is a result of the uDBO camera's residual odd pupil homogeneity. Each single-quadrant measurement enables imaging exclusively in either the x or y direction, and sequentially. By measuring both separately but sequentially, the possibility of incoherent internal crosstalk is blocked, thus not contributing to the OVL error.

[0104] Furthermore, the amount of incoherent internal crosstalk can be better analyzed by sequential imaging, which contributes to the robustness of the beam analyzer.

[0105] In some embodiments, the IMS can support multiple modes. In some embodiments, matching the IMS from one beam analyzer machine to another can be difficult. Specifically, an image taken on one beam analyzer machine can occasionally give different results than the same image taken on another beam analyzer machine. This difference can be due to aberrations and / or any possible mismatch in the alignment mark configuration on the substrate, or calibration efficiency can vary between machines.

[0106] In some embodiments, calibration can be used to improve consistency between multiple machines. Calibration can include, but is not limited to, DC offset, camera gain, and / or temperature. Aberrations can also occur when light from one image intrudes into another component of the image.

[0107] The present disclosure includes methods of blocking aberrations, high coherence or diffraction and removing incoherent internal crosstalk.The second IMS does not remove aberrations or the like, but blocks or removes imaging channels so that only one imaging channel is active at a time.

[0108] In some embodiments, a second IMS can be added to remove incoherent internal crosstalk. For example, by adding a second IMS, any image blurring mechanisms caused by aberrations, high coherence, or diffraction can be blocked, which can result in a more stable calibration. In some examples, a second IMS can allow for better measurement accuracy and better correction factors, particularly with respect to incoherent internal crosstalk. In some embodiments, systematic errors introduced by the calibration can be difficult to characterize. These systematic errors include, but are not limited to, wavelength, target spacing, or the way light enters the optical system.

[0109] In some embodiments, a second IMS can be used to substantially eliminate incoherent internal crosstalk between captured images. For example, at an alignment or overlay mark on a substrate, target images for x and y alignment or overlay measurements are formed simultaneously during imaging. The alignment or overlay mark can be filled with excess light, and when imaged, light from adjacent features can be read out together, which is undesirable. Smaller alignment or overlay marks can save space required to measure alignment or overlay. However, alignment or overlay marks that are too small can make incoherent internal crosstalk more dominant.

[0110] Furthermore, the microchip may already be present on the substrate and surround alignment or overlay marks. When imaged, the microchip may also generate undesirable incoherent internal crosstalk. Since light rays may be on different parts of the image, aberrations in the optics may occur as the light rays pass through the optics.

[0111] Adding a second IMS allows the two quadrants to be illuminated at different times to eliminate incoherent internal crosstalk. The second IMS can be rotated so that only one quadrant, based on the pupil, is visible. Light can enter one optical path but not the other, resulting in a system free of incoherent internal crosstalk. One optical path can be probed, then the other, to gather information. This information can be used for calibration, resulting in a correction factor. This correction factor can be used to eliminate incoherent internal crosstalk when both quadrants are used simultaneously. Furthermore, the correction factor can be used across multiple machines to account for multiple machines.

[0112] In some embodiments, the correction factors may be present in a recipe that will be used across many systems. In some embodiments, the recipe is a measurement procedure that allows a beam analyzer machine to add calibrated correction factors to the software for that specific machine. The correction factors can be used to train for the systematic errors discussed previously. For example, by training the systematic errors into the recipe, it is possible to find that the systematic errors across multiple machines are similar and correct for them. However, this recipe should not be used to teach a machine incoherent internal crosstalk, as incoherent internal crosstalk should be captured via additional hardware measurements, for example, using a second IMS.

[0113] In some embodiments, the second IMS characterizes the optical hardware, which allows software corrections, in particular correction factors. Additionally, the energy can be measured in quadrants to assess the quality of the IMS.

[0114] In some embodiments, the following equations describe how the uDBO image calculates the overlay error of four different intensities. Specifically, A +d,-1x 、A -d,-1x 、B +d,+1x and B -d,+1x Used only for x-overlay measurements. A and B refer to the pupil quadrants, which are described later in Figures 6-7 and are responsible for the uDBO A- and B-images. +d and -d refer to the offsets programmed on the alignment or overlay target, and +1 / -1 refers to the first positive / negative diffraction from the target.

[0115] Specifically, the potential gain in OVL error along the x-measurement accuracy can be explained by the following formula:

[0116]

[0117] The formula can be applied similarly to y. Under the influence of incoherent internal crosstalk, for example, from the y image to the x image, the four x intensities are partially contaminated by the proximity of the adjacent y images, as Figure 5B As shown by the arrow in .

[0118] As a result of the incoherent crosstalk, the measured alignment or overlay information may be stretched and deviate from the ideal alignment or overlay information, which should be measured in the absence of crosstalk.

[0119] In some embodiments, light can be simultaneously irradiated into both IMSs. To obtain a measurement, one or both IMSs can be shifted or moved. Incoherent internal crosstalk can be calculated by measuring intensity leakage from the X image to the Y image or vice versa. Crosstalk can then be corrected.

[0120] Figure 6A and Figure 6B FIG. 4 shows uDBO imaging associated with a first quadrant illumination pupil without incoherent internal crosstalk, according to some embodiments. For example, Figure 5A Depicts the pupil after the first IMS. Figure 6A A pupil that only allows quadrant 620 is depicted. Figure 6B Shown with Figure 6A The resulting uDBO image is an image made of the pupil in and associated with the illumination pupil 620. In this way, only quadrant 620 is visible, while the other quadrants are not. Figure 6A and Figure 6B Correction factors are calculated based on the images captured in the image.

[0121] Figure 7A and Figure 7B FIG. 4 shows uDBO imaging associated with a third quadrant illuminated pupil without incoherent internal crosstalk, according to some embodiments. Figure 7A and Figure 7B In one example, a different quadrant is imaged and a second IMS is selected. Figure 7A A second IMS image through quadrant 710 is shown, while Figure 7B Shown for Figure 7A The resulting uDBO image is an image taken in the image and associated with the illumination pupil 710. In some embodiments, it can also be seen that no incoherent internal crosstalk occurs. In some embodiments, only quadrant 710 is visible, while the other quadrants are not. Figure 7A and Figure 7B Correction factors are calculated based on the images captured in the image.

[0122] 6-7, when the first IMS images two quadrants, the second IMS is positioned at its pupil conjugate position so that the other quadrant is blocked. Specifically, the first IMS opens two quadrants, while the second IMS blocks one of the two quadrants at the rear pupil conjugate position.

[0123] In some embodiments, to improve accuracy, the correction factor should be calculated at least once per system and per recipe. The correction factor can be calculated multiple times using the first substrate. The correction factor can be recalculated whenever a different substrate is used. A correction factor can be calculated per recipe per transfer on the machine, per recipe per machine, per recipe per substrate, and so on. In some embodiments, the correction factor can be calculated daily or over a period of time based on external factors. However, the duration of this period can be based on machine usage.

[0124] Figure 8 8 is a flow chart illustrating a method 800 according to some embodiments. For example, the method 800 can be used to calibrate the effects of pupil odd homogeneity and incoherent internal crosstalk. It should be understood that these operations can be performed in other orders and that some operations are optional.

[0125] In one example, in step 802, the beam passes sequentially through a first selector and a second selector, each selector passing through a first quadrant and a second quadrant of the beam. Here, the first selector and the second selector may be IMSs. Furthermore, both selectors may be positioned at corresponding pupil conjugate planes. An aperture may also be used as an IMS or a mode selector, i.e., a single-quadrant filter selector. At least one IMS may include at least one illumination mode at another IMS.

[0126] In one example, a second selector is used to block the first quadrant and the second quadrant in step 804. By blocking the quadrants, a first image is generated.

[0127] In one example, in step 806 , the second selector is rotated about the optical axis.

[0128] In one example, in step 808, a second selector is used to block the third and fourth quadrants. By blocking different quadrants, a second image is generated. Furthermore, the images can be captured sequentially. The images can be generated based on the angular positions of the quadrants.

[0129] In one example, the intensity difference of the illumination is measured in step 810. The difference is the intensity difference between the first and second quadrants and the third and fourth quadrants. The comparison of the first image and the second image can be performed using an analyzer.

[0130] In one example, in step 810, intensity errors are compensated based on the measurements in step 810. A calibration device can be used to compensate for intensity differences, such that the intensity errors are derived from such calibration devices. Furthermore, this balancing can substantially eliminate any effects on overlay errors. This specifically refers to the overlay errors being eliminated, and then any incoherent internal crosstalk and pupil homogeneity being substantially eliminated based on the compensation.

[0131] The embodiments may be further described using the following terms:

[0132] 1. A measurement system comprising:

[0133] a first selector configured to pass light from the first quadrant or the second quadrant;

[0134] a second selector configured to block the first quadrant or the second quadrant to generate a first image and block the third quadrant or the fourth quadrant to generate a second image before rotating about the optical axis;

[0135] an analyzer configured to measure an intensity difference of illumination between the first quadrant or the second quadrant and the third quadrant or the fourth quadrant based on the first image and the second image; and

[0136] A calibration device is configured to compensate for intensity errors between the first image and the second image such that incoherent crosstalk is substantially eliminated.

[0137] 2. The metrology system according to clause 1, wherein the first selector is located at a first pupil conjugate plane.

[0138] 3. The metrology system according to clause 1, wherein the second selector is located at a second pupil conjugate plane.

[0139] 4. The metrology system of clause 1, wherein the first selector comprises a first illumination mode selector (IMS) and the second selector comprises a second IMS.

[0140] 5. The metrology system of clause 4, wherein the first IMS and the second IMS are mode selection selectors or single quadrant filter selectors.

[0141] 6. The metrology system of clause 4, wherein the first image and the second image are captured sequentially by the second IMS for each quadrant based on an angular position of one quadrant.

[0142] 7. The metrology system of clause 4, wherein the first IMS and the second IMS comprise apertures.

[0143] 8. The metrology system of clause 4, wherein the second IMS has at least one illumination mode at the first IMS.

[0144] 9. The metrology system of clause 1, wherein the substantial elimination of the incoherent crosstalk and pupil odd homogeneity substantially eliminates their effects on overlay error.

[0145] 10. A method comprising:

[0146] passing the beam sequentially through a first selector and a second selector, each selector passing a first quadrant or a second quadrant of the beam;

[0147] blocking the first quadrant or the second quadrant using the second selector to generate a first image;

[0148] Rotate the second selector around the optical axis,

[0149] blocking the third and fourth quadrants using the second selector to generate a second image;

[0150] measuring an intensity difference of illumination between the first and second quadrants and the third and fourth quadrants based on the first and second images; and

[0151] Intensity errors are compensated based on the measurements such that incoherent crosstalk is substantially eliminated.

[0152] 11. The method of clause 10, further comprising positioning the first selector at a first pupil conjugate plane.

[0153] 12. The method of clause 10, further comprising positioning the second selector at a second pupil conjugate plane.

[0154] 13. The method of clause 12, further comprising using an aperture as the first illumination mode selector (IMS) and the second illumination mode selector.

[0155] 14. The method of clause 10, further comprising using a first IMS as the first selector and using a second IMS as the second selector.

[0156] 15. The method of clause 14, further comprising using a mode selection selector or a single quadrant filter selector as the first IMS and the second IMS.

[0157] 16. The method of clause 14, further comprising capturing, by the second IMS, the first image and the second image in sequence for each quadrant based on an angular position of the quadrant.

[0158] 17. The method of clause 14, wherein the first IMS and the second IMS comprise apertures.

[0159] 18. The method of clause 16, wherein the second IMS has at least one illumination mode at the first IMS.

[0160] 19. The method of clause 9, further comprising: substantially eliminating incoherent crosstalk and pupil odd homogeneity based on the compensation.

[0161] 20. A lithographic apparatus comprising:

[0162] an illumination system configured to illuminate the pattern of the patterning device;

[0163] a support configured to support the patterning device;

[0164] substrate;

[0165] a projection system configured to project an image of the pattern onto a substrate; and

[0166] Measurement system, including:

[0167] a first selector configured to pass light from the first quadrant and the second quadrant;

[0168] a second selector configured to block the first quadrant and the second quadrant to generate a first image before rotating about the optical axis to block the third quadrant and the fourth quadrant to generate a second image;

[0169] an analyzer configured to measure an intensity difference of illumination between the first and second quadrants and the third and fourth quadrants based on the first and second images; and

[0170] A calibration device is configured to compensate for intensity errors between the first image and the second image such that incoherent crosstalk is substantially eliminated.

[0171] 21. The lithographic apparatus of clause 19, wherein:

[0172] The first selector comprises a first illumination mode selector (IMS),

[0173] The second selector includes a second IMS, and

[0174] For each quadrant of the second IMS, the first image and the second image are captured in sequence.

[0175] Although specific reference may be made herein to the use of lithographic apparatus in the manufacture of integrated circuits, it will be understood that the lithographic apparatus described herein may have other applications, such as in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, LCDs, thin film magnetic heads, and the like. The skilled person will understand that in the context of such alternative applications, any use of the terms "wafer" or "die" herein may be considered as a specific example of the more general terms "substrate" or "target portion", respectively. Before or after exposure, the substrates referred to herein may be processed in, for example, a tracking unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) and / or a metrology unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, a substrate may be processed more than once, such as to create a multi-layer IC, so the term substrate as used herein may also refer to a substrate that already contains multiple processed layers.

[0176] Although specific reference may have been made above to the use of embodiments of the present disclosure in the context of optical lithography, it should be understood that the present disclosure may be used in other applications, such as imprint lithography, and is not limited to optical lithography, where circumstances permit. In imprint lithography, the topography of a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a resist layer provided to the substrate, whereupon the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. The patterning device is removed from the resist, leaving a pattern therein after the resist has cured.

[0177] It should be understood that the phraseology or terminology herein is for the purpose of description rather than limitation, and thus persons skilled in the relevant art(s) may interpret the phraseology or terminology of the present disclosure based on the teachings herein.

[0178] As used herein, the terms "radiation," "beam of radiation," and the like may encompass various types of electromagnetic radiation, such as ultraviolet (UV) radiation (e.g., having a wavelength λ of 365, 248, 193, 157, or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (e.g., having a wavelength in the range of 5 nm to 20 nm, e.g., 13.5 nm), or hard X-rays operating at less than 5 nm, as well as beams of matter. Terms such as "light," "irradiation," and the like may refer to non-material radiation (e.g., photons, UV, X-rays, etc.). Generally, radiation with wavelengths between about 400 nm and about 700 nm is considered visible radiation; radiation with wavelengths between about 780 nm and 3000 nm (or greater) is considered IR radiation. Ultraviolet radiation refers to radiation with wavelengths of approximately 100-400 nm. In photolithography, the term "UV" also applies to wavelengths generated by mercury discharge lamps: G-line 436 nm; H-line 405 nm; and / or I-line 365 nm. Vacuum ultraviolet or VUV (i.e., ultraviolet absorbed by gases) refers to radiation with a wavelength of approximately 100 nm to 200 nm. Deep ultraviolet (DUV) generally refers to radiation with a wavelength ranging from 126 nm to 428 nm, and in some embodiments, excimer lasers can generate DUV radiation for use in lithographic apparatus. It should be understood that radiation with a wavelength in the range of, for example, 5 nm to 20 nm refers to radiation having a specific wavelength band, at least a portion of which is within the range of 5 nm to 20 nm.

[0179] It should be understood that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more, but not all, exemplary embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0180] The present disclosure has been described above by means of functional building blocks illustrating the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks are arbitrarily defined in this article. As long as the specified functions and their relationships are properly performed, alternative boundaries can be defined.

[0181] Although specific embodiments of the present disclosure have been described above, it should be understood that embodiments of the present disclosure may be practiced in ways other than those described above. These descriptions are intended to be illustrative rather than restrictive. Therefore, it will be apparent to those skilled in the art that modifications may be made to the disclosed content without departing from the scope of the claims set forth below.

[0182] The foregoing description of specific embodiments will fully reveal the general nature of the present disclosure, and others may, by applying knowledge within the art, readily modify and / or adapt these specific embodiments for various applications without departing from the general concepts of the present disclosure and without undue experimentation. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0183] The breadth and scope of the protected subject matter should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A measurement system comprising: a first selector configured to pass light from the first quadrant or the second quadrant; a second selector configured to block the first quadrant or the second quadrant to generate a first image and block the third quadrant or the fourth quadrant to generate a second image before rotating about the optical axis; an analyzer configured to measure an intensity difference of illumination between the first quadrant or the second quadrant and the third quadrant or the fourth quadrant based on the first image and the second image; as well as A calibration device is configured to compensate for intensity errors between the first image and the second image such that incoherent crosstalk is substantially eliminated. 2 . The measurement system according to claim 1 , wherein the first selector is located at a first pupil conjugate plane. The measurement system according to claim 1 , wherein the second selector is located at a second pupil conjugate plane. 4 . The metrology system of claim 1 , wherein the first selector comprises a first illumination mode selector (IMS), and the second selector comprises a second IMS. 5 . The measurement system according to claim 4 , wherein the first IMS and the second IMS are mode selection selectors or single-quadrant filter selectors. 6 . The metrology system according to claim 4 , wherein the first image and the second image are sequentially captured by the second IMS for each quadrant based on an angular position of one quadrant. The metrology system of claim 4 , wherein the first IMS and the second IMS comprise apertures. The metrology system of claim 4 , wherein the second IMS has at least one illumination mode at the first IMS.

9. The metrology system of claim 1, wherein substantially eliminating the incoherent crosstalk and pupil odd homogeneity substantially eliminates their effects on overlay error.

10. A method comprising: passing the beam sequentially through a first selector and a second selector, each selector passing a first quadrant or a second quadrant of the beam; blocking the first quadrant or the second quadrant using the second selector to generate a first image; Rotate the second selector around the optical axis, blocking the third and fourth quadrants using the second selector to generate a second image; measuring an intensity difference of illumination between the first and second quadrants and the third and fourth quadrants based on the first and second images; as well as Intensity errors are compensated based on the measurements such that incoherent crosstalk is substantially eliminated.

11. The method according to claim 10, further comprising: Positioning the first selector at a first pupil conjugate plane.

12. The method according to claim 10, further comprising: The second selector is positioned at a second pupil conjugate plane.

13. The method according to claim 12, further comprising: An aperture is used as the first illumination mode selector (IMS) and the second illumination mode selector.

14. The method according to claim 10, further comprising: A first IMS is used as the first selector, and a second IMS is used as the second selector.

15. The method according to claim 14, further comprising: A mode selection selector or a single-quadrant filter selector is used as the first IMS and the second IMS.

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