Apparatus and method for combined display of optical measurement information

Abstract

Apparatus and methods are disclosed for simultaneously capturing and presenting multiple types of alignment information, in which the pupil is split and the radiation from the pupil is spatially separated. In some versions, the alignment information is first order diffraction information and polarization channel intensity information, which are presented simultaneously in an image-based system.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Application No. 63 / 428,762, filed November 30, 2022, which is incorporated herein by reference in its entirety.

[0002] The subject matter of this disclosure relates to apparatus and methods for acquiring and displaying metrology information in lithographic apparatus and processes. [Background technology]

[0003] A lithographic apparatus applies a desired pattern onto a substrate, usually onto a target portion of the substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A patterning device, also known as a mask or reticle, can be used to generate the circuit pattern formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., part of, one die, or several dies) on the substrate (e.g., a silicon wafer).

[0004] Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate: in general, a single substrate will contain a network of adjacent target portions that are successively patterned.

[0005]

[0005] ICs are built layer by layer, and modern ICs can have many layers. Successive layers, or multiple processes on the same layer, must be precisely aligned with the previous layer. Otherwise, poor electrical contact between structures will occur and the resulting device will not perform to specification. On Product Overlay (OPO) is a measure of a system's ability to print these layers precisely on top of one another. Good overlay increases device yield and allows for smaller product features to be printed.

[0006]

[0006] To control the lithography process and accurately place device features on the substrate, one or more patterns, such as overlay marks, are typically provided on the substrate. Different types of marks and different types of systems are known from different manufacturers at different times. Types of overlay marks include bidirectional fine (BF) wafer overlay marks and smaller format marks such as micro-diffraction-based overlay (μDBO) overlay marks (e.g., C16 or C10 marks). These marks are configured, for example, as patterns of lines.

[0007] Typically, these marks are printed in overlay registration with one another; that is, one mark is printed on one layer, and then a second mark is printed on another layer in a target position relative to the first mark, i.e., on top of the first mark. If the two marks are perfectly overlaid, the overlay error is zero, and the features on the second layer can be considered properly positioned. If the two marks are not perfectly overlaid, the overlay error is non-zero, indicating some degree of misalignment between the two layers. This misalignment is encoded in the intensities of the diffraction orders in the interference pattern of light scattered from the superimposed overlay marks.

[0008]

[0008] In particular, one type of alignment tool is a scatterometer, which directs a beam of radiation onto a target on the surface of the substrate and measures the properties of the scattered or reflected beam. By comparing the properties of the beam before and after interaction of the beam with the substrate, for example before and after the beam has been reflected or scattered by the substrate, the properties of the substrate can be determined. This can be achieved, for example, by comparing the reflected beam to data stored in a database of known measurements associated with known substrate properties. In a spectroscopic scatterometer, a broadband beam of radiation is directed onto the substrate and the spectrum (intensity as a function of wavelength) of the scattered radiation is measured 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.

[0009]

[0009] In angle-resolved scatterometry, an illumination branch illuminates an overlay target over a wide band in incident space. The diffracted orders of light from the grating are then captured. The zeroth-order intensity varies symmetrically as a function of overlay, while the + / - first-order intensities vary asymmetrically as a function of overlay. Overlay can be determined using the difference in first-order intensities.

[0010]

[0010] Properties measured by a scatterometer for different wavelengths and angles may include the relative intensities of radiation with different polarizations, which can be used to correct for deformations of the mark caused by asymmetries etc.

[0011]

[0011] Lithographic apparatuses are known to align substrates relative to the lithographic apparatus using a number of alignment systems. For example, data can be acquired by any type of alignment sensor, such as a SMASH (Smart Alignment Sensor Hybrid) sensor, which employs a self-referencing interferometer with a single detector and four different wavelengths and extracts alignment signals in software, as described in U.S. Patent No. 6,961,116, issued November 1, 2005, entitled "Lithographic Apparatus, Device Manufacturing Method, and Device Manufactured Thereby." Alternative systems include ATHENA (Advanced Technology using High order ENhancement of Alignment), which directs each of the seven diffraction orders to a dedicated detector, as described in U.S. Patent No. 6,297,876, issued October 2, 2001, entitled "Lithographic Projection Apparatus with an Alignment System for Aligning Substrate on Mask," or the ORION sensor, which uses multiple polarizations for each available signal (color).

[0012]

[0012] All patent applications, patents, and publications cited herein are incorporated by reference in their entirety, except for any definitions, subject matter disclaimers, or disclaimers, and except to the extent that the incorporated material contradicts the disclosure expressly set forth herein, in which case the language in the present disclosure shall control.

[0013] Another known alignment system is described in WO 2020 / 057900, entitled "Metrology Sensor for Position Metrology," published on March 26, 2020. One of the systems described therein uses multiple spatially incoherent illumination beams and multiple pupil points in the illumination pupil of a metrology device.

[0014]

[0014] To improve throughput, there is a need to make alignment information available in a way that facilitates and speeds up measurements. This need can be met, at least in part, by displaying multiple types of data in parallel, i.e., simultaneously. Thus, in a camera-based system, it would be beneficial in some applications to be able to simultaneously display, for example, polarization-resolved measurements and images conveying intensity information for each diffraction order. It is in this context that the need for the subject matter of the present disclosure arises. Summary of the Invention

[0015]

[0015] The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of the invention. This summary is not intended to be an exhaustive overview of all possible embodiments, nor is it intended to identify key or essential elements of all possible embodiments or to delineate the scope of all possible embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

[0016] According to one aspect of an embodiment, a metrology device configured to collect radiation that has interacted with a pattern on a substrate is disclosed, the metrology device including: an objective lens arranged to collect the radiation; and an optical module arranged to receive at least a portion of the radiation and adapted to split the radiation into first path radiation traveling in a first arm and second path radiation traveling in a second arm. One of the first arm and the second arm may include a polarization component adapted to rotate the polarization of a corresponding one of the first path radiation and the polarization intensity information, and the second arm may include a second arm component adapted to spatially separate the second path radiation.

[0017]

[0017] The optical module further includes a polarizing beam splitter arranged to receive the first path radiation from the first arm and the second path radiation from the second arm, split the first path radiation into first path radiation of the first channel and first path radiation of the second channel, and split the separated second path radiation into second path radiation of the first channel and second path radiation of the second channel, co-propagate the first path radiation of the first channel and the second path radiation of the first channel as combined first channel radiation, and co-propagate the first path radiation of the second channel and the second path radiation of the second channel as combined second channel radiation.

[0018] The metrology device may be an alignment sensor or part of an alignment sensing system. The metrology device may be an overlay sensor or part of an overlay sensing system. The second arm component adapted to spatially separate the second path radiation may be configurable. The second arm component adapted to spatially separate the second path radiation may include a rotatable wedge.

[0019] The metrology device may further include a first lens positioned to receive and focus the first channel radiation, a first array detector positioned at a focal plane of the first lens, a second lens positioned to receive and focus the second channel radiation, and a second array detector positioned at a focal plane of the second lens. The first array detector may include a first camera, and the second array detector may include a second camera. The first array detector may have a first optical axis, and may be rotatable about the first optical axis to improve loading of the first channel radiation on the first array detector. The polarizing component may include a half-wave plate. The first arm may be the arm including the polarizing component adapted to rotate the polarization of the image information radiation. The polarizing component may include a half-wave plate.

[0020] The second arm component may include a segmented optical wedge arranged to spatially separate the second path radiation. The segmented optical wedge may be transmissive. The segmented optical wedge may be reflective. The second arm component may include a partitioned aperture wavefront (PAW) imaging lens.

[0021]

[0021] According to another aspect of one embodiment, a metrology device configured to collect radiation that has interacted with a pattern on a substrate is disclosed, the metrology device including an objective lens arranged to collect the radiation and an optical module arranged to receive at least a portion of the radiation and adapted to split the radiation into image information radiation traveling in a first arm and second path radiation traveling in a second arm.

[0022]

[0022] The first arm includes a half-wave plate adapted to rotate the polarization of the image information radiation, and the second arm includes a segmented optical wedge arranged to spatially separate the second path radiation. The optical module further includes a polarizing beam splitter arranged to receive the image information from the first arm and the second path radiation from the second arm, split the image information radiation into image information radiation of the first channel and image information radiation of the second channel, and split the separated second path radiation into second path radiation of the first channel and second path radiation of the second channel, co-propagating the image information radiation of the first channel and the second path radiation of the first channel as combined first channel radiation, and co-propagating the image information radiation of the second channel and the second path radiation of the second channel as combined second channel radiation.

[0023]

[0023] The device also includes a first lens positioned to receive and focus the first channel radiation, a first array detector positioned in the focal plane of the first lens, a second lens positioned to receive and focus the second channel radiation, and a second array detector positioned in the focal plane of the second lens.

[0024]

[0024] The metrology device may be an alignment sensor or part of an alignment sensing system. The metrology device may be an overlay sensor or part of an overlay sensing system.

[0025] The first array detector may include a first camera, and the second array detector may include a second camera. The first array detector may have a first optical axis, and the first array detector may be rotatable relative to the first optical axis to improve loading of the first channel radiation on the first array detector. The segmented optical wedge may be rotatable.

[0026]

[0026] According to another aspect of one embodiment, an optical module is disclosed that includes a first arm including a half-wave plate, a second arm including a segmented optical wedge, a neutral beam splitter arranged to split an incident radiation beam into a first portion that travels through the first arm and a second portion that travels through the second arm, and a polarizing beam splitter arranged to receive the first portion after the first portion has traveled through the first arm and to receive the second portion after the second portion has traveled through the second arm.

[0027]

[0027] The half-wave plate may rotate the polarization of the first portion by 90 degrees. The segmented optical wedge may separate the second portion into a plurality of spatially separated components. The polarizing beam splitter may cause a first portion of the first portion to co-propagate with a first portion of the second portion. The polarizing beam splitter may cause a second portion of the first portion to co-propagate with a second portion of the second portion.

[0028]

[0028] The optical module may be an alignment sensor or part of an alignment sensing system. The optical module may be an overlay sensor or part of an overlay sensing system. The segmented optical wedge may be rotatable.

[0029]

[0029] According to another aspect of one embodiment, an optical module is disclosed that includes a first optical component including a neutral beam splitter arranged to split an incident radiation beam into a first portion traveling in a first arm and a second portion traveling in a second arm, the first arm including a second optical component including a half-wave plate, and the second arm including a third optical component including a segmented optical wedge; and a fourth optical component including a polarizing beam splitter arranged to receive the first portion after the first portion has traveled through the first arm and to receive the second portion after the second portion has traveled through the second arm. The optical module further includes a first transparent element attached to and connecting the first optical component and the second optical component, a second transparent element attached to and connecting the second optical component and the fourth optical component, a third transparent element attached to and connecting the first optical component and the third optical component, and a fourth transparent element attached to and connecting the third optical component and the fourth optical component, thereby allowing the optical module to be configured as an integral block.

[0030]

[0030] The half-wave plate may rotate the polarization of the first portion by 90 degrees. The segmented optical wedge may separate the second portion into a plurality of spatially separated components. The polarizing beam splitter may cause a first portion of the first portion to co-propagate with a first portion of the second portion. The polarizing beam splitter may cause a second portion of the first portion to co-propagate with a second portion of the second portion.

[0031]

[0031] The optical module may be an alignment sensor or part of an alignment sensing system. The optical module may be an overlay sensor or part of an overlay sensing system. The segmented optical wedge may be rotatable.

[0032]

[0032] According to another aspect of one embodiment, a metrology method is disclosed that includes collecting radiation that has interacted with a pattern on a substrate, splitting at least a portion of the radiation into image information radiation and second path radiation, rotating the polarization of one of the second path and the image information radiation, the second arm having a second arm component adapted to spatially separate the second path radiation, and splitting the image information radiation into image information radiation of a first channel and image information radiation of a second channel while simultaneously splitting the separated second path into second path radiation of the first channel and second path radiation of the second channel, so that the image information radiation of the first channel and the second path radiation of the first channel co-propagate as combined first channel radiation, and so that the image information radiation of the second channel and the second path radiation of the second channel co-propagate as combined second channel radiation.

[0033]

[0033] The metrology method may further include focusing the first channel radiation onto a first array detector and focusing the second channel radiation onto a second array detector.

[0034]

[0034] Further embodiments, features, and advantages of the subject matter of the present disclosure, as well as the structure and operation of the various embodiments, are described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0035] [Figure 1]

[0035] A schematic diagram (not to scale) showing the overall broad concept of a photolithography system is shown. [Figure 2A]

[0036] 1 is an example of an overlay mark that may be used in accordance with aspects of some embodiments. [Figure 2B]

[0037] 2B is an image of diffraction orders such as may be produced by the interaction of an incident beam with the overlay mark of FIG. 2A. [Figure 3A]

[0038] 1 is a representation of the pupil corresponding to the radiation that occurs following scattering of the off-axis illumination beam. [Figure 3B]

[0039] The resulting pupil (only captured orders) for the four off-axis beams is shown. [Figure 4]

[0040] FIG. 1 illustrates a system for simultaneously displaying diffraction patterns and polarization channel intensity information, according to an aspect of an embodiment. [Figure 5A]

[0041] 5 illustrates an example of a simultaneous display such as can be generated by the system of FIG. 4. [Figure 5B]

[0042] FIG. 5 is a diagram illustrating the relative angular orientation of a spot mirror and a segmented optical wedge in a system such as that shown in FIG. 4. [Figure 6A]

[0043] FIG. 10 depicts another system for simultaneously displaying diffraction patterns and polarization channel intensity information according to another aspect of an embodiment. [Figure 6B]

[0044] FIG. 10 depicts another system for simultaneously displaying diffraction patterns and polarization channel intensity information according to another aspect of an embodiment. [Figure 6C]

[0045] FIG. 10 depicts another system for simultaneously displaying diffraction patterns and polarization channel intensity information according to another aspect of an embodiment. [Figure 7]

[0046] FIG. 10 depicts another system for simultaneously displaying diffraction patterns and polarization channel intensity information according to another aspect of an embodiment. [Figure 8A]

[0047] FIG. 1 is a perspective view of an example of a segmented optical wedge as may be used in various embodiments. [Figure 8B]

[0048] FIG. 1 is a perspective view of an example of a segmented lens array as may be used in various embodiments. [Figure 9]

[0049] 1 is a graphical representation illustrating the arrangement of fields in a composite display according to an aspect of an embodiment. [Figure 10]

[0050] 1 is a graphical representation illustrating the arrangement of fields in a composite display according to an aspect of an embodiment. [Figure 11]

[0051] 1 is a graphical representation illustrating the arrangement of fields in a composite display according to an aspect of an embodiment. [Figure 12]

[0052] FIG. 1 illustrates a system for simultaneously displaying diffraction patterns and polarization channel intensity information, according to an aspect of an embodiment. [Figure 13A]

[0053] FIG. 1 illustrates a portion of a system for simultaneously displaying diffraction patterns and polarization channel intensity information, according to an aspect of an embodiment. [Figure 13B]

[0053] A diagram illustrating a portion of a system for simultaneously displaying diffraction patterns and polarization channel intensity information according to one aspect of one embodiment. [Figure 13C]

[0053] A diagram illustrating a portion of a system for simultaneously displaying diffraction patterns and polarization channel intensity information according to one aspect of one embodiment. [Figure 14]

[0054] FIG. 1 illustrates a portion of a system for simultaneously displaying diffraction patterns and polarization channel intensity information, according to an aspect of an embodiment. [Figure 15]

[0055] FIG. 1 illustrates a portion of a system for simultaneously displaying diffraction patterns and polarization channel intensity information, according to an aspect of an embodiment.

[0036]

[0056] Further features and advantages of the disclosed subject matter, as well as the structure and operation of various embodiments of the disclosed subject matter, are described in detail below with reference to the accompanying drawings. It should be noted that the scope of the disclosed subject matter 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 relevant art based on the teachings contained herein. DETAILED DESCRIPTION OF THE INVENTION

[0037]

[0057] Various embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. However, it will be apparent that in some or all cases, any of the embodiments described below can be implemented or practiced without adopting the specific design details set forth below. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments.

[0038]

[0058] Embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may 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 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.), etc.

[0039]

[0059] To begin with, one embodiment of a lithographic apparatus LA that can be associated with the system of the present invention is shown schematically in Figure 1. The lithographic apparatus LA includes an illumination system (illuminator) IL that is configured to condition a radiation beam B. As used herein, the terms "radiation" and "beam" encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g., radiation having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm), and extreme ultraviolet (EUV) radiation (e.g., radiation having a wavelength in the range of 5-20 nm), as well as particulate beams such as ion beams and electron beams.

[0040]

[0060] The lithographic apparatus LA also includes a support structure (e.g., mask table) MT constructed to support a patterning device (e.g., mask) MA, the support structure MT being coupled to a first positioner PM configured to accurately position the patterning device according to certain parameters, and one or more substrate tables (e.g., wafer tables) WT (in this example, two wafer tables WTa and WTb) configured to hold a substrate (e.g., a resist-coated wafer) W. Each wafer table is mechanically coupled to a respective positioner PW configured to accurately position the substrate on a wafer support surface WSS according to certain parameters.

[0041]

[0061] The lithographic apparatus LA also includes a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies, often referred to as a field) of the substrate W. The projection system is supported on a reference frame RF.

[0042]

[0062] As depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask) or it may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

[0043]

[0063] The illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such a case, the radiation beam is delivered from the source SO to the illuminator IL using a beam delivery system BD, which may comprise, for example, suitable directing mirrors and / or beam expanders. In other cases the radiation source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system. If the radiation source is of a type that produces EUV radiation, then reflective optics will typically be used.

[0044]

[0064] The illuminator IL may include an adjuster AD configured to adjust the (angular / spatial) intensity distribution of the beam. In addition, the illuminator IL will typically include various other components, such as an integrator IN and a condenser CO. The illumination system may include various types of optical components for directing, shaping or controlling the radiation. In this way, the illuminator IL provides a conditioned radiation beam B having a desired uniformity and intensity distribution in its cross-section.

[0045]

[0065] The support structure MT supports the patterning device using mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The term "patterning device", as used herein, should be interpreted broadly to refer to any device that can be used to impart a pattern in a target portion of a substrate. Patterning devices may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels.

[0046]

[0066] The lithographic apparatus may be of a type having two (dual stage) or more tables (e.g. two or more substrate tables WTa, WTb; two or more patterning device tables, e.g. a substrate table WTa and a table WTb below the projection system that does not contain a substrate and is dedicated to, for example, facilitating measurement and / or cleaning, etc.). In such a "multi-stage" machine, the additional tables can be used in parallel, or preliminary steps can be carried out on one or more tables while another table or tables are used for exposure. For example, alignment measurements can be made using alignment sensors AS and / or level (height, tilt, etc.) measurements can be made using level sensors LS.

[0047]

[0067] Alternatively, the lithographic apparatus may be of a type wherein the substrate is at least partially covered by a liquid having a relatively high refractive index (eg, water), so as to fill a space between the projection system and the substrate.

[0048]

[0068] During operation of the lithographic apparatus LA, a radiation beam B is conditioned and provided by an illumination system IL. The 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 the patterning device MA, the patterned radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of a substrate W. The wafer tables WTa and WTb can be precisely moved using respective positioners PW and position sensors IF (e.g., interferometric devices, linear encoders, 2D encoders, or capacitive sensors), for example to position different target portions C in the path of the patterned radiation beam B. Similarly, other positioners and other position sensors (not explicitly shown in FIG. 1 ) may be used to accurately position the patterning device MA with respect to the path of the radiation beam B, for example after mechanical retrieval from a mask library or during a scan.

[0049]

[0069] The patterning device MA and substrate W may be aligned using patterning device marks M1, M2 and marks P1, P2. In the illustrations shown, the marks occupy dedicated target portions, but they may also be located in spaces between the target portions. Similarly, in situations in which more than one die is provided on the patterning device MA, the patterning device marks may be located between the dies.

[0050]

[0070] Substrates referred to herein may be processed, before or after exposure, in, for example, a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), or a metrology or inspection tool. Where appropriate, the disclosure herein may apply to such and other substrate processing tools. Furthermore, a substrate may be processed multiple times, for example, to create a multi-layer IC, and therefore the term "substrate," as used herein, may also refer to a substrate that already includes one or more processed layers.

[0051]

[0071] 2A and 2B illustrate some aspects of an example alignment mark for determining alignment parameters. FIG. 2A depicts target 310, which is an example of a μDBO overlay mark that can be used as an overlay mark in some embodiments. Target 310 includes four sub-targets, each containing two gratings (periodic structures) 315a extending in a first direction (x-direction) and two gratings 315b extending in a perpendicular second direction (y-direction). The pitch of these gratings can be, for example, in the range of 300 to 800 nm.

[0052]

[0072] As with other metrology devices that can be used for alignment sensing, shifts in the target grating position result in a phase shift between the diffraction orders, such as between the +1st and -1st diffraction orders, for each direction. These diffraction orders cause interference on the camera. If a phase shift occurs between the diffraction orders, the interference fringes on the camera will shift accordingly. Therefore, the alignment position can be determined from the position of the interference fringes on the camera.

[0053]

[0073] Specifically, in this example, the captured orders include a −1x diffraction order, a +1x diffraction order, a −1y diffraction order, and a +1y diffraction order. These diffraction orders are imaged onto a camera where they interfere to form a fringe pattern 350 having fields 316a and 316b corresponding to gratings 315a and 315b, respectively, as shown in FIG. 2B. In the illustrated example, the fringe pattern is oblique because the diffraction orders are arranged obliquely within the pupil, but other arrangements are possible, resulting in different orientations of the fringe pattern.

[0054]

[0074] 3A and 3B illustrate the operating principle of the metrology system. FIG. 3A is a representation of the pupil corresponding to the radiation generated following scattering of a single off-axis illumination beam 420. The zeroth-order diffracted beam is shown as 420′. The shaded areas 422 correspond to the blocking (i.e., reflective or absorbing) areas of a particular spot mirror design, while the white areas represent the transmissive areas that may be used in one embodiment. This spot mirror design is only one example of pupil blocking that ensures that unwanted light (e.g., zeroth-order and zeroth-order ambient light) is not detected. Other spot mirror profiles (or zeroth-order blocking in general) may also be used. As used herein, the term “spot mirror” refers to any optical element used for zeroth-order blocking.

[0055]

[0075] 3A, only one of the higher diffraction orders is captured, more specifically, the −1X diffraction order 425. The +1X diffraction order 430, the −1Y diffraction order 435, and the +1Y diffraction order 440 are outside the pupil (the detection NA represented by the extent of the spot mirror 422) and are not captured. Any higher orders (not shown) will also be outside the detection NA. The zeroth order 420 is shown for illustrative purposes but would actually be blocked by the spot mirror or the zeroth order blockage 422.

[0056]

[0076] FIG. 3B shows the resulting pupil (only the captured orders) of the four off-axis beams. The captured orders include a −1X diffraction order 425′, a +1X diffraction order 430′, a −1Y diffraction order 435′, and a +1Y diffraction order 440′. These diffraction orders are imaged on a camera, where they interfere to form the fringe pattern shown in FIG. 2B. Again, in the illustrated example, the fringe pattern is oblique because the diffraction orders are arranged obliquely within the pupil, but other arrangements are possible, resulting in different orientations of the resulting fringe pattern. The original off-axis illumination beam 420 is at least partially coherent for the X illumination order and at least partially coherent for the Y illumination order, allowing the corresponding diffraction orders to interfere.

[0057]

[0077] As mentioned above, in some applications it is desirable to be able to present multiple images, each conveying respective alignment data (e.g., images representing information related to the selection of diffraction orders for a particular polarization of radiation that has interacted with a pattern), in a coordinated and integrated format. According to an aspect of one embodiment, this is achieved using a system that can be implemented as a compact optical building block, without the need for switchable optical elements.

[0058]

[0078] According to one aspect of one embodiment, the optical arrangement includes at least two paths for radiation that has interacted with a pattern on the substrate. A first path transmits a first portion of the radiation (first path radiation) and a second path transmits a second portion of the radiation (second path radiation). The first path and second path include different optical elements such that the first path produces a first image containing first image information and the second path produces a second image containing second image information. These images may then be presented together for a simultaneous composite display of the first and second images.

[0059]

[0079] For example, the first image may be an interference image, and the second image may be an intensity image. As another example, if the second path includes optics that clip a portion of the pupil and image the clipped radiation, the first image may be characterized as a complete image, and the second image as a partial pupil image. As another example, the first path may create a conventional bright-field image, while the other path conveys a “dark-field imaging mode” image. In such an embodiment, a partial pupil block may be configured along with an image separation element (e.g., a wedge or tilted mirror, or a tilted beam splitter) to separate the images within the composite image. As another example, one of the paths may implement a “phase-contrast imaging mode.” In such an arrangement, a phase plate is used in a portion of the pupil, which shifts the phase of that portion of the pupil relative to the rest of the pupil. As yet another example, one path may provide a focused image, while the other path provides a defocused image. This can be achieved, for example, by adding a weak lens to the second path. Such an arrangement effectively makes it possible to obtain both the phase and amplitude of the light from a single image when spatially coherent light is used.

[0060]

[0080] 4, objective lens 500 receives radiation that has interacted with a pattern (e.g., an overlay mark, such as overlay mark 310 described above). The radiation from objective lens 500 passes through spot mirror 510, which partially blocks radiation that is not used for metrology, such as the zeroth order. The radiation then enters module 520 at the objective lens pupil plane.

[0061]

[0081] The entrance pupil is split into two arms, a first arm 535 and a second arm 537, by a non-polarizing beam splitter (NPBS) 530. This entrance pupil contains any polarization state information collected from the target 310. When this entrance pupil is projected based on orthogonal polarizations, for example, X and Y polarizations, the system presents information about the alignment response of the target 310. The first arm 535 transmits the first beam to an optical element 550 (e.g., a half-wave plate (HWP)) that rotates its polarization by 90 degrees. The second arm 537 uses a second-arm component 560 to achieve spatial separation of the images in the lower beam. The second-arm component 560 can be an optical wedge or a split-aperture wavefront (PAW) imaging lens, as described below. Spatial separation in this context means that the second arm component 560 imparts a controlled angle to each pupil segment so that each pupil segment is focused at a different location in the plane of the first array detector 610 and the second array detector 640. Each pupil segment can include an individual diffraction order or a selected number of diffraction orders. In some embodiments, the second arm component 560 is configurable. For example, if the second arm component 560 is implemented as an optical wedge, the optical wedge can be rotatable.

[0062]

[0082] Both the first arm 535 and the second arm 537 are combined on a polarizing beam splitter (PBS) 570, or its optical equivalent, which allows polarization-resolved measurements. The PBS 570 projects the original object polarization in the second arm 537 onto a defined orthogonal polarization base, such as X or Y. That is, the radiation from the first arm and the radiation from the second arm combine at the PBS 570, which splits the incident radiation into two channels (in this example, two polarization-resolved channels), each containing radiation from the first arm and radiation from the second arm. Mirrors 540 and 580 are optional to enable a physically compact configuration by folding the beam path as needed. One of the projected polarization state channels propagates via lens 590 and optional folding optics 600 to the first array detector 610. The other orthogonal projected polarization state channel has its path folded by folding mirror 650 and propagates through lens 620 and optional folding optics 630 to second array detector 640. Here and elsewhere, the term "array detector" has its broadest meaning of any device or system capable of capturing a light distribution, including one-dimensional array detectors, two-dimensional array detectors (e.g., cameras), and CCD or CMOS sensors. In the illustrated example, array detectors 610 and 640 are cameras. Either first array detector 610 or second array detector 640, or both, can be rotated about their respective optical axes 612 and 642 to improve the degree to which the image fills the array detector sensor.

[0063]

[0083] The signals from array detectors 610, 640 are provided to processing unit 670, which processes the signals in a known manner to generate a composite display 700 that simultaneously displays fields 710, 720, 730, 740, and 750 that together contain information from both channels. As will be explained in more detail below, the placement and selection of optical components can be selected to achieve any one of several relative positionings of these fields in composite display 700.

[0064]

[0084] The resulting combined output results in a camera photograph containing multiple fields. An example of such a resulting composite display is shown in FIG. 5A as composite display 700. Center field 710 corresponds to the collection of fringe patterns 350 from FIG. 2B. Surrounding fields 720, 730, 740, and 750 contain photographs containing individual polarization intensity information. That is, diffraction and intensity patterns are imaged onto the same array detector for the same polarization projection state. Specifically, field 720 contains target field intensity information for one first diffraction order (e.g., the −1X order) of the displayed polarization channel. Field 730 contains target field intensity information for another diffraction order (e.g., the +1X order) of the displayed polarization channel. Field 740 contains target field intensity information for another first diffraction order (e.g., the −1Y order) of the displayed polarization channel. Field 750 contains target field intensity information for another diffraction order (e.g., the +1Y order) of the displayed polarization channel.

[0065]

[0085] The orientation, placement, and content of the field depend on the wedge orientation and design. Here, "content" refers to what diffraction orders are imaged at what locations in the displayed combined image. In the illustrated embodiment, second arm component 560 is a four-fold wedge oriented relative to spot mirror 510 as shown in FIG. 5B. However, it will be understood that other relative orientations and different numbers of wedge segments may be used. The concepts demonstrated herein may be extended to different numbers and / or orientations and / or shapes of segments, for example, to separate higher orders.

[0066]

[0086] In this embodiment, radiation forming the alignment pattern passes through a path defined by the following objects: NPBS 530-mirror 540-HWP 550-PBS 570. Radiation forming the surrounding field passes through a path defined by NPBS 530-wedge 560-mirror 580-PBS 570, each representing a selected diffraction order. Both image paths are recombined on PBS 570, so the transmitted output has orthogonal polarizations. The system is configured to analyze the polarization state of radiation reaching NPBS 530 by projecting radiation based on the desired polarization. This means that for a particular polarization state at NPBS 530, both resulting image paths corresponding to this particular polarization state are routed to the same focal plane. This is made possible by the introduction of HWP 550, which rotates the polarization state of the image by 90°.

[0067]

[0087] Instead of rotating the polarization state using an HWP 550 located in the image path NPBS 530-mirror 540-HWP 550-PBS 570, polarization rotation can also be achieved by placing the HWP in the path that forms an image of the surrounding structure: NPBS 530-wedge 560-mirror 580-PBS 570. This is shown in FIG. 6A, where the HWP 550 is located in the second arm 537. In another embodiment, the wedge is made of a material that rotates polarization in addition to a specific wedge shape adapted to redirect the beam in each pupil segment, thus eliminating the need for a separate element to perform this function. This is shown in FIG. 6B, where wedge 560′ functions both as an optical wedge and as a polarization rotation element.

[0068]

[0088] In embodiments where dispersion is utilized, the function of the wedge can be performed, for example, by a grating, resulting in a strong dependence of the deflection angle on wavelength. This is shown in Figure 6C, where the second arm component 560 of the embodiment of Figure 6A is realized as a deflecting element 565, which may be a grating or any other element that spatially separates the radiation passing through it.

[0069]

[0089] In accordance with another aspect of one embodiment, one potential advantage of the above-described embodiment is that the components may be fabricated as a monolithic block, for example, by fastening pieces of transparent material, such as glass, together using an adhesive. An example of such an arrangement is shown in FIG. 7. Module 522 consists of the optical components of the embodiment of FIG. 4 glued to transparent pieces 541, 551, 561, 571, and 581. Alternatively, air gaps may exist in at least a portion of the optical path between the individual optical components. The use of such air gaps can be utilized to minimize the optical path length.

[0070]

[0090] Simultaneous access to polarization channels and intensity information has the potential to enhance process robustness. In some applications, it is desirable to project diffraction order alignment information in field 710 (FIG. 5) and intensity information for the same polarization states of diffraction orders, as shown in fields 720, 730, 740, and 750, onto the same array detector. As previously mentioned, projecting information for the same polarization states can be achieved by placing HWP 550 or an equivalent within arm 535. If an element such as HWP 550 is not located within arm 535, the image in field 710 on array detectors 610 and 640 will be from a polarization state orthogonal to the polarization state of the intensity information being displayed. This may be appropriate for some applications. However, orthogonal polarization states may result in uncorrelated dynamic range differences between the two different types of patterns, making this undesirable in other deployments.

[0071]

[0091] All folding optics, including mirrors 540, 680, and 650 and folding optics 600 and 630, are optional to allow for a more compact arrangement. More or fewer such folding optics may be used depending on the design considerations of a particular implementation. Additionally, either or both of array detectors 610 and 640 may be rotated along the z-axis (with the plane of the figure being the xy plane) to provide better frame filling on the array detector.

[0072]

[0092] In the above embodiments, a segmented wedge is used to create spatial separation of images within the pupil. Using a segmented wedge is advantageous in this regard, since wedges typically introduce only a negligible amount of dispersion. One possible implementation of such a segmented wedge is shown in FIG. 8A . As shown, the segmented optical wedge 1100 is composed of four identical segments 1110 symmetrically arranged to separate the pupil into four distinct regions. Such a segmented optical wedge 1100 can be fabricated, for example, by gluing the four segments together. The application of the principles revealed herein is not limited to systems using four segments or four identical segments, but may equally be applied to systems using different numbers, orientations, and / or shapes of segments, for example, to capture distinct higher orders.

[0073]

[0093] In some embodiments, the segments are the same size and shape and are evenly distributed across the pupil, although it will be appreciated that this may not be necessary in some applications.

[0074]

[0094] In the above description, the optical wedges used in the exemplary embodiments are of the transmissive type. It will be appreciated that, with appropriate changes to the ray paths and placement of other components, a reflective optical wedge can be used instead.

[0075]

[0095] In the above example, polarization filtering is used to create the separate channels, but it will be appreciated that color filtering can also be used to create the channels.

[0076]

[0096] Another advantage of the above exemplary embodiment is that it can be implemented using a relatively small number of demultiplexer modules.

[0077]

[0097] It will be appreciated that a segmented lens array can be used as another alternative to the combined use of optical wedges and lenses. Figure 8B shows a segmented lens array 1150 implemented as a 2x2 lens array, such as can be used as a split aperture wavefront (PAW) imaging lens. In the illustrated example, the segmented lens array 1150 is a quad-leaf lens consisting of four lenses 1160 cut off-axis and glued together. For each quadrant, an image is acquired from a portion 1170 of the lens 1160 near its intersection with the other lenses.

[0078]

[0098] FIG. 5A shows one possible arrangement of the fields of a composite display 700. As previously mentioned, the composite display 700 includes a central field 710 containing a collection of fringe patterns 350 from FIG. 2B. Peripheral fields 720, 730, 740, and 750 contain individual polarization intensity information. FIG. 9 is a graphical representation of the arrangement of the five fields 710, 720, 730, 740, and 750 of FIG. 5. The central field 710 is located at or near the center of the composite display 700, while the intensity fields 720, 730, 740, and 750 are located at the corners of a square centered around the central field 710. This arrangement is created by the action of an optical wedge, such as optical wedge 560 in the arrangement of FIG. 4, that displaces the peripheral fields relative to the center 710 of the combined image. Thus, to displace field 750 from the center of combined image 700 in the direction of arrow A, the optical wedge has a wedge angle that is proportional to the required image shift by a proportionality constant k, which is at least twice the field radius r. The proportionality constant k generally depends in known manner on the focal length of the lens used and the optical properties of the wedge (e.g., its refractive index, etc.).

[0079]

[0099] The field arrangement of Figure 9 is one of many possible such arrangements. In some implementations, other arrangements may be advantageous. For example, the arrangement shown in Figure 10 may be more compact than the arrangement shown in Figure 9. In the arrangement shown in Figure 10, a first optical wedge with a wedge angle A that produces a first displacement A and a second optical wedge with a wedge angle E that produces a second displacement E may be used to produce a net displacement shown by the dashed arrow. The arrangement of Figure 10 generally requires an image shift greater than k*√2r, where k is the proportionality constant mentioned above and r is the field radius.

[0080]

[0100] 11 shows an alternative arrangement in which the centers of the peripheral fields 720, 730, 740, and 750 are located at the vertices of a rectangle rather than at the vertices of a square. This composite display 700 is therefore compressed in terms of its vertical dimension, again resulting in a more compact display and allowing for larger fields.

[0081]

[0101] There are several different arrangements of optical elements that can be used to obtain the field arrangements shown in Figures 9, 10, and 11. Figure 12 shows one such arrangement, in which an additional optical wedge 562 is placed in one of the arms of the arrangement to introduce the additional field image displacement described above. Figure 13A shows an enlarged view of a combination 563 of optical wedge 560 and additional optical wedge 562. As shown in Figure 13B, the same displacement can also be obtained using a single optical wedge 564 that combines 562 and 560. In the embodiment shown in Figure 13B, the angle θ that the face of the lower portion of optical wedge 564 makes with the waist of the combined optical wedge 564 is such that this face extends to the left in the figure, i.e., the angle θ has the opposite (reverse) sign to the angle δ. Also possible is an arrangement 565, as shown in FIG. 13C, in which the angle θ of the face of the lower portion of the optical wedge 566 is such that this face extends to the right in the figure, i.e., the angle θ has the same sign as the angle δ.

[0082]

[0102] Relative positioning of the fields for the combined image 700 can also be achieved by placing an optical wedge 562 in the other arm of the arrangement. This is shown in FIG. 14. This effect can also be achieved by placing a first optical wedge with a first wedge angle in one arm and a second optical wedge with a second wedge angle in the other arm. The angles are selected to displace the beams in each arm in opposite directions and whose magnitudes add up to the desired net displacement. An example of such an arrangement is shown in FIG. 15. Thus, in the embodiment of FIG. 15, each optical wedge 567 and 568 provides half of the total displacement, and the wedge angle of optical wedge 568 displaces each beam in an opposite direction by half of the total net displacement.

[0083]

[0103] According to another aspect of an embodiment, instead of using or adjusting one or more optical wedges to produce the desired image displacement, the desired field displacement can be achieved in composite display 700 by tilting one or more of mirrors 540 or 580 or beam splitters 530 or 570. Employing such means to achieve displacement has the advantage of requiring fewer optical elements. Also, tilting mirrors to displace images may have less of a dispersive (achromatic) effect than adding transmissive wedges.

[0084]

[0104] Also, according to another aspect of an embodiment, in some arrangements the wedge angles of the optical wedges A, B, C and D can be reduced by a factor of √2 relative to the arrangements of FIGS. 5A and 9.

[0085]

[0105] The above describes an exemplary embodiment having two optical paths, with one path providing a complete image and the other path providing one or more partial images, e.g., four partial images (corresponding to a quarter pupil). However, it will be apparent to those skilled in the art that, in principle, alternating configurations are also possible. For example, as noted above, in one embodiment, a first path, which may be configured as described above, can carry a conventional brightfield image, while the other path can carry a "darkfield imaging mode" image. In such an embodiment, a partial pupil shield can be arranged along with an image separation element (e.g., a wedge, tilted mirror, or tilted beam splitter) to separate the images on the camera.

[0086]

[0106] As another example, one of the paths could implement a "phase contrast imaging mode." In such an arrangement, a phase plate is used in a portion of the pupil to shift the phase of that portion of the pupil relative to the rest of the pupil.

[0087]

[0107] As yet another example, one path can provide a focused image while the other path provides a defocused image. This can be achieved, for example, by adding a weaker lens to the second path. Such an arrangement effectively makes it possible to obtain both the phase and amplitude of the light from a single image (at least if spatially coherent light is used).

[0088]

[0108] The above description includes examples of multiple embodiments. Of course, it is not possible to describe every conceivable combination of components or methodologies for describing the above-described embodiments, but those skilled in the art will recognize that many additional combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive, similar to the interpretation of "comprising" when used as a transitional term in the claims. Also, although elements of described aspects and / or embodiments may be described or claimed in the singular, the plural is contemplated unless expressly limited to the singular. Furthermore, unless stated otherwise, all or a portion of any aspect and / or embodiment may be utilized with all or a portion of any other aspect and / or embodiment.

[0089]

[0109] It is understood that the "Detailed Description" section, and not the "Summary" and "Abstract" sections, are intended to be used to interpret the claims. The "Summary" and "Abstract" sections may describe one or more (but not all) example embodiments of the invention as contemplated by the inventor(s), and therefore, are not intended to limit the scope of the invention and the appended claims in any way.

[0090]

[0110] The present invention has been described above using functional building blocks that show the implementation of specific functions and the relationships between those functions. The boundaries of these functional building blocks have been arbitrarily defined in this specification for the convenience of explanation. Other boundaries may be defined as long as the specific functions and the relationships between those functions are appropriately performed.

[0091]

[0111] The above embodiments can be further described using the following clauses. 1. A metrology device positioned to receive radiation that has interacted with a pattern on a substrate, the metrology device comprising: an optical module positioned to receive at least a portion of the radiation and adapted to split the radiation into first path radiation traveling in a first arm and second path radiation traveling in a second arm; one of the first arm and the second arm includes a polarizing component adapted to rotate the polarization of a corresponding one of the first path radiation and the second path radiation; and the second arm includes a second arm component adapted to spatially separate the second path radiation; the optical module further includes a polarizing beam splitter positioned to receive the first path radiation from the first arm and the second path radiation from the second arm, split the first path radiation into first path radiation of the first channel and first path radiation of the second channel, and split the separated second path radiation into second path radiation of the first channel and second path radiation of the second channel, causing the first path radiation of the first channel and the second path radiation of the first channel to co-propagate as combined first channel radiation, and causing the first path radiation of the second channel and the second path radiation of the second channel to co-propagate as combined second channel radiation. 2. The metrology device of clause 1, wherein the metrology device is an alignment sensor. 3. The metrology device of clause 1, wherein the metrology device is an overlay sensor. 4. The metrology device of clause 1, wherein the second arm component adapted to spatially separate the second path radiation is configurable. 5. The metrology device of clause 1, wherein the second arm component adapted to spatially separate the second path radiation includes a rotatable wedge. 6. A first lens positioned to focus the combined first channel radiation; a first array detector disposed in a focal plane of the first lens; a second lens positioned to focus the combined second channel radiation; and 10. The metrology device of claim 1, further comprising: a second array detector positioned in a focal plane of the second lens. 7. The metrology device of clause 6, wherein the first array detector includes a first camera and the second array detector includes a second camera. 8. A metrology device as described in clause 6, wherein the first array detector has a first optical axis, and the first array detector is rotatable relative to the first optical axis to improve filling of the first array detector with the first channel radiation. 9. The metrology device of clause 1, wherein the polarizing component includes a half-wave plate. 10. A metrology device as described in clause 1, wherein the first arm includes the polarizing component adapted to rotate the polarization of the first path radiation. 11. The metrology device of clause 10, wherein the polarizing component comprises a half-wave plate. 12. The metrology device of clause 1, wherein the second arm component includes a segmented optical wedge positioned to spatially separate the second path radiation. 13. The metrology device of clause 12, wherein the segmented optical wedge is transmissive. 14. The metrology device of clause 12, wherein the segmented optical wedge is reflective. 15. The metrology device of clause 1, wherein the second arm component includes a split aperture wavefront imaging lens. 16. At least one camera positioned to receive the combined first channel radiation; 10. The metrology device of claim 1, further comprising: a display arranged to display a first image based on the combined first channel radiation. 17. The metrology device of clause 16, wherein the second arm component is arranged such that the first image includes a central image and four displaced images arranged around the first image. 18. The metrology device of clause 16, wherein the first image includes a central image and four displaced images, and the second arm includes an additional second arm component positioned to laterally displace the four displaced images such that the four displaced images are displayed by the display laterally displaced from the central image. 19. The metrology device of clause 1, wherein the second arm component includes a tiltable beam splitter. 20. The metrology device of clause 1, wherein the second arm component includes a tiltable folding mirror. 21. A metrology device configured to collect radiation that has interacted with a pattern on a substrate, the metrology device comprising: an optical module arranged to receive at least a portion of the radiation and adapted to split the radiation into first path radiation traveling in a first arm and second path radiation traveling in a second arm, the first arm comprising a half-wave plate adapted to rotate the polarization of the first path radiation and the second arm comprising a segmented optical wedge arranged to spatially separate the second path radiation, the optical module further comprising a polarising beam splitter arranged to receive the first path radiation from the first arm and the second path radiation from the second arm, split the first path radiation into first path radiation of a first channel and first path radiation of a second channel, and split the separated second path radiation into second path radiation of the first channel and second path radiation of the second channel, causing the first path radiation of the first channel and the second path radiation of the first channel to co-propagate as combined first channel radiation, and causing the first path radiation of the second channel and the second path radiation of the second channel to co-propagate as combined second channel radiation; a first lens positioned to receive and focus the combined first channel radiation; a first array detector disposed in a focal plane of the first lens; a second lens positioned to receive and focus the combined second channel radiation; a second array detector disposed in the focal plane of the second lens; metrology devices, including: 22. A metrology device according to clause 21, wherein the metrology device is an alignment sensor. 23. The metrology device according to clause 21, wherein the metrology device is an overlay sensor. 24. The metrology device of clause 21, wherein the first array detector includes a first camera and the second array detector includes a second camera. 25. A metrology device as described in clause 21, wherein the first array detector has a first optical axis, and the first array detector is rotatable relative to the first optical axis to improve filling of the first channel radiation on the first array detector. 26. The metrology device of clause 21, wherein the segmented optical wedge is rotatable. 27. At least one camera positioned to receive the first path radiation and the spatially separated second path radiation; 22. The metrology device of clause 21, further comprising: a display arranged to simultaneously display a first image based on the first path radiation and at least one image based on the spatially separated second path radiation. 28. A metrology device as described in clause 27, wherein the second arm component is positioned so that said display simultaneously displays a first image in a central portion, and said at least one image includes four images arranged around the first image. 29. A metrology device as described in clause 27, wherein the at least one image comprises four images, and the second arm comprises an additional second arm component arranged to laterally shift the four images such that the four images are displayed by the display laterally displaced from the first image. 30. The metrology device of clause 21, wherein the second arm component includes a tiltable beam splitter. 31. The metrology device of clause 21, wherein the second arm component includes a tiltable folding mirror. 32. An optical module comprising: a first arm including a half-wave plate; a second arm including a segmented optical wedge; a neutral beam splitter positioned to split an incoming radiation beam into a first portion traveling in the first arm and a second portion traveling in the second arm; a polarizing beam splitter positioned to receive the first portion after it has traveled down the first arm and to receive the second portion after it has traveled down the second arm; an optical module including: 33. The optical module of clause 32, wherein the half-wave plate rotates the polarization of the first portion by 90 degrees. 34. The optical module of clause 32, wherein the segmented optical wedge separates the second portion into a plurality of spatially separated components. 35. The optical module of clause 32, wherein the polarizing beam splitter causes a first portion of the first portion to co-propagate with a first portion of the second portion. 36. The optical module of clause 35, wherein the polarizing beam splitter causes a second portion of the first portion to co-propagate with a second portion of the second portion. 37. The optical module according to clause 32, wherein the optical module is an alignment sensor. 38. The optical module according to clause 32, wherein the optical module is an overlay sensor. 39. The optical module according to clause 32, wherein the segmented optical wedge is rotatable. 40. An optical module, a first optical component including a neutral beam splitter arranged to split an incoming radiation beam into a first portion traveling in a first arm and a second portion traveling in a second arm, the first arm including a second optical component including a half wave plate, and the second arm including a third optical component including a segmented optical wedge; a fourth optical component including a polarizing beam splitter positioned to receive the first portion after it has traveled down the first arm and to receive the second portion after it has traveled down the second arm; and a first transparent element attached to and connecting the first optical component and the second optical component; a second transparent element attached to and connecting the second optical component and the fourth optical component; a third transparent element attached to and connecting the first optical component and the third optical component; a fourth transparent element attached to and connecting the third optical component and the fourth optical component; whereby the optical module is constructed as a monolithic block. Optical module. 41. The optical module of clause 40, wherein the half-wave plate rotates the polarization of the first portion by 90 degrees. 42. The optical module of clause 40, wherein the segmented optical wedge separates the second portion into a plurality of spatially separated components. 43. An optical module according to clause 40, wherein the polarising beam splitter causes a first portion of the first part to co-propagate with a first portion of the second part. 44. An optical module according to clause 43, wherein the polarising beam splitter causes a second part of the first part to co-propagate with a second part of the second part. 45. The optical module according to clause 40, wherein the optical module is an alignment sensor. 46. ​​The optical module according to clause 40, wherein the optical module is an overlay sensor. 47. The optical module according to clause 40, wherein the segmented optical wedge is rotatable. 48. A metrology method comprising: collecting radiation that has interacted with the pattern on the substrate; splitting at least a portion of the radiation into first path radiation and second path radiation; rotating the polarization of one of the first path radiation and the second path radiation; splitting the first path radiation into first path radiation of the first channel and first path radiation of the second channel, and splitting the separated second path radiation into second path radiation of the first channel and second path radiation of the second channel, so that the first path radiation of the first channel and the second path radiation of the first channel co-propagate as combined first channel radiation, and the first path radiation of the second channel and the second path radiation of the second channel co-propagate as combined second channel radiation; A metrology method, including: 49. The metrology method of clause 48, further comprising focusing the combined first channel radiation onto a first array detector and focusing the combined second channel radiation onto a second array detector. 50. A metrology device configured to collect radiation that has interacted with a pattern on a substrate, the metrology device comprising: an optical module arranged to receive at least a portion of the radiation and adapted to split the radiation into a first radiation portion propagating in a first arm having a first optical configuration and a second radiation portion propagating in a second arm having a second optical configuration different from the first optical configuration; an optical element positioned to receive the first radiation portion after the first radiation portion has passed through the first arm and to receive the second radiation portion after the second radiation portion has passed through the second arm, and to generate a composite image of the first radiation portion and the second radiation portion; metrology devices, including: 51. A metrology device as described in clause 50, wherein one of the first arm and the second arm includes a polarizing component adapted to rotate the polarization of the first path radiation, and the second arm includes a second arm module adapted to spatially separate the second radiation portion into spatially separated components.

[0092]

[0112] These and other embodiments are within the scope of the following claims.

Claims

1. a metrology device positioned to receive radiation that has interacted with a pattern on a substrate, the metrology device comprising: an optical module arranged to receive at least a portion of the radiation and adapted to split the radiation into first path radiation traveling in a first arm and second path radiation traveling in a second arm; one of the first arm and the second arm includes a polarizing component adapted to rotate the polarization of a corresponding one of the first path radiation and the second path radiation; and the second arm includes an optical module including a second arm component adapted to spatially separate the second path radiation; the optical module further includes a polarizing beam splitter positioned to receive the first path radiation from the first arm and the second path radiation from the second arm, split the first path radiation into first path radiation of a first channel and first path radiation of a second channel, and split the split second path radiation into second path radiation of a first channel and second path radiation of a second channel, cause the first path radiation of the first channel and the second path radiation of the first channel to co-propagate as combined first channel radiation, and cause the first path radiation of the second channel and the second path radiation of the second channel to co-propagate as combined second channel radiation.

2. The metrology device of claim 1 , wherein the metrology device is an alignment sensor.

3. The metrology device of claim 1 , wherein the metrology device is an overlay sensor.

4. The metrology device of claim 1 , wherein the second arm component adapted to spatially separate the second path radiation is configurable.

5. The metrology device of claim 1 , wherein the second arm component adapted to spatially separate the second path radiation comprises a rotatable wedge.

6. a first lens positioned to focus the combined first channel radiation; a first array detector disposed in a focal plane of the first lens; a second lens positioned to focus the combined second channel radiation; The metrology device of claim 1 further comprising: a second array detector disposed in a focal plane of the second lens.

7. The metrology device of claim 6 , wherein the first array detector comprises a first camera and the second array detector comprises a second camera.

8. 7. The metrology device of claim 6, wherein the first array detector has a first optical axis, and the first array detector is rotatable relative to the first optical axis to improve filling of the first array detector with the first channel radiation.

9. The metrology device of claim 1 , wherein the polarizing component comprises a half-wave plate.

10. The metrology device of claim 1 , wherein the first arm includes the polarizing component adapted to rotate the polarization of the first path radiation.

11. The metrology device of claim 10 , wherein the polarizing component comprises a half-wave plate.

12. The metrology device of claim 1 , wherein the second arm component includes a segmented optical wedge positioned to spatially separate the second path radiation.

13. The metrology device of claim 12 , wherein the segmented optical wedge is transmissive.

14. The metrology device of claim 12 , wherein the segmented optical wedge is reflective.

15. The metrology device of claim 1 , wherein the second arm component comprises a split aperture wavefront imaging lens.

Images