Optical system implemented in a system for high speed optical inspection of targets - Patents.com

Abstract

The system includes an optical device, a reflecting device, a movable reflecting device, and a detector. The optical devices are arranged about an axis of the system in a first plane and receive scattered radiation from the target. The reflecting devices are arranged about the axis in at least a second plane. Each of the reflecting devices receives scattered radiation from a corresponding one of the optical devices. The movable reflecting devices are arranged along the axis and receive scattered radiation from each of the reflecting devices. The detector receives scattered radiation from the movable reflecting devices.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 294,262, filed December 28, 2021, which is incorporated by reference in its entirety into this specification. [Background technology]

[0002]

[0002] The present disclosure relates to inspection devices and methods, for example scatterometers used for metrology in lithographic apparatus and systems.

[0003]

[0003] A lithographic apparatus is a machine that 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). Patterning devices, also referred to as masks or reticles, can then be used to generate a circuit pattern formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of a die, or one or more dies) on the substrate (e.g. a silicon wafer). Typically, the transfer of the pattern is by 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. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern with a radiation beam in a given direction (the "scan" direction) and simultaneously scanning the target portion parallel or anti-parallel to the scan direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004]

[0004] During a lithography operation, different processing steps may require different layers to be formed sequentially on a substrate. It may therefore be necessary to position the substrate with high accuracy with respect to a previous pattern formed thereon. Typically, an alignment mark is placed on the substrate to be aligned and positioned with reference to a second object. The lithography apparatus may use an alignment device to detect the position of the alignment mark and to use the alignment mark to align the substrate to ensure accurate exposure from the mask. The misalignment between the alignment marks in two different layers is measured as an overlay error.

[0005]

[0005] To monitor the lithographic process, parameters of the patterned substrate are measured. The parameters may include, for example, the overlay error between successive layers formed in or on the patterned substrate, and the critical line width of the developed photosensitive resist. The measurements may be performed on the product substrate and / or on a dedicated metrology target. Various techniques exist for making measurements of the microstructures formed in the lithographic process, including the use of scanning electron microscopes and various specialized inspection tools. A fast and non-invasive form of specialized inspection tool is a scatterometer, in which a beam of radiation is directed at a target on the surface of the substrate 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. This can be done, for example, by comparing the reflected beam to data stored in a library of known measurements associated with known substrate properties. A spectroscopic scatterometer directs a broadband beam of radiation onto the substrate and measures the spectrum (intensity as a function of wavelength) of the radiation scattered into a specific narrow angular range. In contrast, an angularly resolved scatterometer uses a monochromatic radiation beam and measures the intensity of the scattered radiation as a function of angle.

[0006]

[0006] Such optical scatterometers can be used to measure parameters such as the critical linewidth of a developed photosensitive resist, or the overlay error (OV) between two layers formed in or on a patterned substrate. By comparing the properties of the illumination beam before and after the beam has been reflected or scattered by the substrate, properties of the substrate can be determined.

[0007]

[0007] A lithography system can only output a finite number of manufactured devices in a given time frame. Summary of the Invention

[0008]

[0008] It is therefore desirable to improve the routines and processes used in lithography systems to increase manufacturing speed and throughput. For example, optical inspection processes can be performed faster based on the embodiments described herein.

[0009]

[0009] In some embodiments, the system includes an optical device, a reflecting device, a movable reflecting device, and a detector. The optical devices are arranged about an axis of the system in a first plane and are configured to receive scattered radiation from the target. The reflecting devices are arranged about the axis in at least a second plane. Each of the reflecting devices is configured to receive scattered radiation from a corresponding one of the optical devices. The movable reflecting devices are arranged along the axis and are configured to receive scattered radiation from each of the reflecting devices. The detector is configured to receive scattered radiation from the movable reflecting devices.

[0010] In some embodiments, the optical system includes an optical device, a reflecting device, and a movable reflecting device. The optical devices are arranged about an axis of the system in a first plane and are configured to receive scattered radiation from the target. The reflecting devices are arranged about the axis in at least a second plane. Each of the reflecting devices is configured to receive scattered radiation from a corresponding one of the optical devices. The movable reflecting device is arranged along the axis and is configured to receive scattered radiation from each of the reflecting devices.

[0011]

[0011] Further features of the present disclosure, together with the structure and operation of various embodiments, will be 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. Such embodiments are presented herein for illustrative purposes only. Based on the teachings contained herein, additional embodiments will be apparent to those skilled in the art. [Brief description of the drawings]

[0012]

[0012] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate the present disclosure and, together with the following description, further serve to explain the principles of the present disclosure and enable those skilled in the art to make and use the embodiments described in this specification. [Figure 1A]

[0013] 1 depicts a schematic diagram of a reflective lithographic apparatus according to some embodiments; [Figure 1B]

[0014] 1 depicts a schematic diagram of a transmission lithographic apparatus according to some embodiments; [Diagram 2]

[0015] 2 shows a more detailed schematic diagram of a reflective lithographic apparatus according to some embodiments; [Diagram 3]

[0016] 1 shows a schematic diagram of a lithographic cell according to some embodiments; [Figure 4A-4B]

[0017] 1 shows a schematic diagram of an inspection apparatus according to some embodiments. [Figure 5A]

[0018] 1 illustrates an optical system according to some embodiments. [Figure 5B-5C]

[0019] 5B illustrates an optical arrangement using the elements of FIG. 5A according to some embodiments. [Figure 6A]

[0020] 1 illustrates an optical system according to some embodiments. [Figure 6B]

[0021] 6B illustrates an optical arrangement using the elements of FIG. 6A according to some embodiments. [Figure 7A]

[0022] 1 illustrates an optical system according to some embodiments. [Figure 7B]

[0023] 7B illustrates an optical arrangement using the elements of FIG. 7A according to some embodiments. [Figure 8]

[0024] 1 illustrates an optical system according to some embodiments. [Figure 9]

[0025] 1 illustrates a movable reflective device according to some embodiments.

[0013]

[0026] Features of the present disclosure will become more apparent from the detailed description set forth below when considered in conjunction with the drawings, in which like reference numbers identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. Also, the leftmost digit(s) of a reference number generally identifies the figure in which that reference number first appears. The drawings provided throughout this disclosure should not be construed as drawings to scale unless otherwise indicated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014]

[0027] This specification discloses one or more embodiments incorporating features of the present disclosure. The disclosed embodiments are presented by way of example. The scope of the present disclosure is not limited to the disclosed embodiments. The claimed features are defined by the claims appended hereto.

[0015]

[0028] References to the described embodiments, and to "an embodiment," "one embodiment," "an example embodiment," and the like herein, indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments may necessarily include such a particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with one embodiment, it will be understood that it is within the knowledge of one of ordinary skill in the art to associate such feature, structure, or characteristic with other embodiments, whether or not expressly stated.

[0016]

[0029] Spatially relative terms such as "below," "below," "lower," "above," "on," "higher," and the like are used herein for ease of description and may describe the relationship of one element or feature to another element or feature as shown in the drawings. Spatially relative terms are intended to encompass various orientations of the device in use or operation in addition to the orientation shown in the drawings. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be similarly interpreted accordingly.

[0017]

[0030] The term "about" as used herein refers to a given quantity value that may vary based on the particular technique. Based on the particular technique, the term "about" can refer to a given quantity value that varies, for example, within 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0018]

[0031] The embodiments of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. The embodiments of the present disclosure may also be implemented as instructions stored on a machine-readable medium that may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, electrical, optical, acoustic or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Furthermore, firmware, software, routines and / or instructions may be described herein as performing certain operations. However, it should be understood that such description is merely for convenience and that such operations actually result from a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0019]

[0032] Before describing such embodiments in further detail, however, it is helpful to present an example environment in which embodiments of the present disclosure can be implemented.

[0020]

[0033] Exemplary Lithography System

[0034] 1A and 1B show schematic diagrams of lithographic apparatus 100 and lithographic apparatus 100', respectively, in which embodiments of the present disclosure can be implemented. Lithographic apparatus 100 and lithographic apparatus 100' each include the following: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. deep ultraviolet or extreme ultraviolet), a support structure (e.g. mask table) MT configured to support a patterning device (e.g. mask, reticle, or dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device MA, and a substrate table (e.g. wafer table) configured to hold a substrate (e.g. resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Lithographic apparatus 100 and 100' also include a projection system PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (e.g. comprising one or more dies). In lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In lithographic apparatus 100', the patterning device MA and the projection system PS are transmissive.

[0021]

[0035] The illumination system IL may include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping or controlling the radiation beam B.

[0022]

[0036] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA relative to a reference frame, the design of at least one of the lithographic apparatuses 100 and 100', and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device MA. The support structure MT may be, for example, a frame or a table, which may be fixed or movable as required. By using sensors, the support structure MT can ensure that the patterning device MA is at a desired position, for example with respect to the projection system PS.

[0023]

[0037] The term "patterning device" MA should be interpreted broadly as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section to create a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a particular functional layer in a device being created in the target portion C to form an integrated circuit.

[0024]

[0038] In this specification, the terms "inspection apparatus", "metrology system" and the like are used to refer to devices or systems (e.g. alignment apparatus) used, for example, to measure characteristics of structures (e.g. overlay error, critical dimension parameters) or used within a lithographic apparatus to inspect the alignment of a wafer.

[0025]

[0039] The patterning device MA may be transmissive (as in lithographic apparatus 100' of FIG. 1B) or reflective (as in lithographic apparatus 100 of FIG. 1A). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography and include mask types such as binary, alternating phase-shift, or attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern to a radiation beam B that is reflected by the matrix of small mirrors.

[0026]

[0040] The term "projection system" may encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optics, or any combination thereof, appropriate for the exposure radiation being used, or other factors such as the use of an immersion liquid or the use of a vacuum on the substrate W. For EUV or electron beam radiation, a vacuum environment may be used, as other gases may absorb too much radiation or electrons. Therefore, with the aid of a vacuum wall and vacuum pumps, a vacuum environment may be provided throughout the beam path.

[0027]

[0041] Lithographic apparatus 100 and / or lithographic apparatus 100' may be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such a "multi-stage" machine, the additional substrate tables WT may be used in parallel, or preliminary steps may be carried out on one or more tables whilst one or more other tables WT are used for exposure. In some circumstances the additional tables may not be substrate tables WT.

[0028]

[0042] 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 a space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus (e.g. between the mask and the projection system). Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term "immersion" as used herein does not mean that a structure such as the substrate must be submerged in liquid, but simply that there is a liquid between the projection system and the substrate during exposure.

[0029]

[0043] 1A and 1B, the illuminator IL receives radiation from a radiation source SO. The source SO and the lithographic apparatus 100, 100' may be separate entities, for example if the source SO is an excimer laser. In such a case, the source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam B is delivered from the source SO to the illuminator IL using a beam delivery system BD (in FIG. 1B) that may include, for example, suitable directing mirrors and / or beam expanders. In other cases, the source SO may be an integral part of the lithographic apparatus 100, 100', for example if the source SO is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0030]

[0044] The illuminator IL may include an adjuster AD (in Figure 1B) for adjusting the angular intensity distribution of the radiation beam. Generally, 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 may 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 may be used to condition the radiation beam B so that it has a desired uniformity and intensity distribution in its cross-section.

[0031]

[0045] Referring to FIG. 1A, a radiation beam B is incident on a patterning device (e.g., mask) MA, which is held on a support structure (e.g., mask table) MT, and is patterned by the patterning device MA. In the lithographic apparatus 100, the radiation beam B is reflected from the patterning device (e.g., mask) MA. After being reflected from the patterning device (e.g., mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of a substrate W. The substrate table WT can be accurately moved (e.g. to position a different target portion C in the path of the radiation beam B) using a second positioner PW and a position sensor IF2 (e.g., an interferometer device, a linear encoder, or a capacitive sensor). Similarly, the patterning device (e.g., mask) MA can also be accurately positioned with respect to the path of the radiation beam B using a first positioner PM and another position sensor IF1. Patterning device (eg mask) MA and substrate W may be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2.

[0032]

[0046] 1B, 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 mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of a substrate W. The projection system has a pupil PPU that is conjugate with the illumination system pupil IPU. Portions of radiation originate from an intensity distribution in the illumination system pupil IPU and traverse the mask pattern without being subject to diffraction at the mask pattern to create an image of the intensity distribution in the illumination system pupil IPU.

[0033]

[0047] The projection system PS projects an image of the mask pattern MP, which is formed on a photoresist layer coated on the substrate W by diffracted beams generated from the mask pattern MP by radiation from the intensity distribution. For example, the mask pattern MP may include an array of lines and spaces. Radiation diffraction at the array but not zero-order diffraction produces stimulated diffracted beams redirected perpendicular to the lines. The non-diffracted beams (i.e. the so-called zero-order diffracted beams) traverse the pattern without changing their propagation direction. The zero-order diffracted beams traverse the upper lens or upper lens group of the projection system PS upstream of the conjugate pupil PPU of the projection system PS to reach the conjugate pupil PPU. The part of the intensity distribution in the plane of the conjugate pupil PPU associated with the zero-order diffracted beam is an image of the intensity distribution of the illumination system pupil IPU of the illumination system IL. The aperture device PD is for example arranged in a plane containing the conjugate pupil PPU of the projection system PS or is arranged substantially in said plane.

[0034]

[0048] The projection system PS is arranged to capture not only the zeroth order diffracted beam but also the first or higher order diffracted beams (not shown) by means of a lens or lens group L. In some embodiments, the resolution enhancing effect of dipole illumination can be exploited by using dipole illumination to image a line pattern extending in a direction perpendicular to the line. For example, a first order diffracted beam interferes with a corresponding zeroth order diffracted beam at the level of the wafer W to generate an image of the line pattern MP with the highest possible resolution and process window (i.e., a combination of the available depth of focus and the allowable exposure dose variation). In some embodiments, astigmatism can be reduced by providing poles (not shown) in opposing quadrants of the illumination system pupil IPU. Furthermore, in some embodiments, astigmatism can be reduced by blocking the zeroth order beam in a conjugate pupil PPU of the projection system associated with the poles in the opposing quadrants. This is explained in more detail in U.S. Pat. No. 7,511,799, issued Mar. 31, 2009, which is incorporated herein by reference in its entirety.

[0035]

[0049] The substrate table WT can be accurately moved (e.g. to position different target portions C in the path of the radiation beam B) using the second positioner PW and a position sensor IFD (e.g. an interferometer device, a linear encoder or a capacitive sensor). Similarly, the first positioner PM and a further position sensor (not shown in FIG. 1B) can be used to accurately position the mask MA with respect to the path of the radiation beam B (e.g. after mechanical retrieval from a mask library or during a scan).

[0036]

[0050] Typically, movement of the mask table MT may be achieved using a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be achieved 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 to a short-stroke actuator only, or may be fixed. The mask MA and substrate W may be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2. Although the (exemplary) substrate alignment marks occupy dedicated target portions, the substrate alignment marks may also be located in spaces between the target portions (known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

[0037]

[0051] The mask table MT and patterning device MA may be in a vacuum chamber V, and an in-vacuum robot IVR may be used to move the patterning device, such as a mask, in and out of the vacuum chamber. Alternatively, if the mask table MT and patterning device MA are outside the vacuum chamber, an ex-vacuum robot may be used for various transport operations, similar to the in-vacuum robot IVR. Both the in-vacuum and ex-vacuum robots need to be calibrated for smooth movement of any payload (e.g. a mask) to the fixed kinematic mount of the transfer station.

[0038]

[0052] Lithographic apparatus 100 and 100' can be used in at least one of the following modes:

[0039]

[0053] 1. In step mode, the support structure (e.g. mask table) MT and substrate table WT are kept essentially stationary, and the entire pattern imparted to the radiation beam B is projected onto a target portion C in one go (i.e. a single static exposure), while the substrate table WT is then shifted in the X and / or Y directions so that a different target portion C can be exposed.

[0040]

[0054] 2. In scan mode, the support structure (e.g. mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (i.e. a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure (e.g. mask table) MT can be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0041]

[0055] 3. In another mode, the support structure (e.g. mask table) MT is kept essentially stationary, holding a 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 used, 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 readily be applied to maskless lithography employing a programmable patterning device, such as a programmable mirror array.

[0042]

[0056] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be used.

[0043]

[0057] In a further embodiment, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate a beam of EUV radiation for EUV lithography. Typically, the EUV source is configured in a radiation system and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0044]

[0058] FIG. 2 shows the lithographic apparatus 100 in more detail, including a source collector apparatus SO, an illumination system IL, and a projection system PS. The source collector apparatus SO is constructed and arranged such that a vacuum environment can be maintained within an enclosure 220 of the source collector apparatus SO. The EUV radiation emitting plasma 210 can be formed by a discharge produced plasma source. The EUV radiation can be produced by a gas or vapor (such as, for example, Xe gas, Li vapor, or Sn vapor) in which a very hot plasma 210 is produced and emits radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is produced, for example, by creating an at least partially ionized plasma by an electric discharge. For efficient radiation generation, for example, a partial pressure of 10 Pa of Xe, Li, Sn vapor or any other suitable gas or vapor may be required. In some embodiments, a plasma of excited tin (Sn) is provided to produce the EUV radiation.

[0045]

[0059] Radiation emitted by the high temperature plasma 210 passes from the source chamber 211 into the collector chamber 212 via an optional gas barrier or contaminant trap 230 (sometimes also referred to as a contaminant barrier or foil trap) positioned in or behind an opening in the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further illustrated herein includes at least a channel structure.

[0046]

[0060] 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 traversing the collector CO may be reflected by a grating spectral filter 240 and focused into a virtual source point INTF. The virtual source point INTF is commonly called an intermediate focus, and the source collector arrangement is arranged such that the intermediate focus INTF is located at or near the opening 219 of the closure structure 220. The virtual source point INTF is an image of the radiation emitting plasma 210. The grating spectral filter 240 is used in particular to suppress infrared (IR) radiation.

[0047]

[0061] The radiation then traverses the illumination system IL, which may include a faceted field mirror device 222 and a faceted pupil mirror device 224 arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA, and to provide a desired radiation intensity uniformity at the patterning device MA. Upon reflection of the radiation beam 221 off the patterning device MA, held by the support structure MT, a patterned beam 226 is formed, which is imaged by the projection system PS via reflective elements 228, 229 onto the substrate W held by a wafer stage or substrate table WT.

[0048]

[0062] Generally, there may be more elements in the illumination optics unit IL and projection system PS than shown. A grating spectral filter 240 may be optionally present depending on the type of lithographic apparatus. Further, there may be more mirrors than shown in Figure 2, for example there may be 1-6 additional reflective elements in the projection system PS compared to those shown in Figure 2.

[0049]

[0063] 2 is shown as a nested collector with grazing incidence reflectors 253, 254 and 255 as just one example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are arranged axially symmetrically about the optical axis O, and this type of collector system CO is preferably used in combination with a discharge produced plasma source, often referred to as a DPP source.

[0050]

[0064] Exemplary Lithographic Cell

[0065] FIG. 3 shows a lithographic cell 300, sometimes also called a litho cell or lithocluster, according to some embodiments. The lithographic apparatus 100 or 100′ may form part of the lithographic cell 300. The lithographic cell 300 may also include one or more apparatuses for performing pre-exposure and post-exposure processes on a substrate. Conventionally, these include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chill 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 the different processing devices, and delivers them to a loading bay LB of the lithographic apparatus 100 or 100′. These devices, often collectively referred to as a track, are under the control of a track control unit TCU, which is itself controlled by a supervisory control system SCS, which also controls the lithographic apparatus via a lithography control unit LACU. In this manner, different devices can be operated to maximize throughput and processing efficiency.

[0051]

[0066] Exemplary Inspection Equipment

[0067] To control the lithographic process and accurately place device features on the substrate, alignment marks are typically provided on the substrate, and the lithographic apparatus includes one or more inspection devices for accurately positioning the marks on the substrate. These inspection devices are actually position measurement devices. Various types of marks and various types of alignment devices and / or systems are known from different times and different manufacturers. A type of system that is widely used in current lithographic apparatus is based on a self-referencing interferometer as described in US 6,961,116 (den Boef et al.). Typically, the marks are measured separately to obtain the position in the X and Y directions. However, combined measurements in the X and Y directions can be made using the technique described in US Publication No. US 2009 / 195768 A (Bijnen et al.). The entire contents of both of the above disclosures are incorporated herein by reference.

[0052]

[0068]

[0069] 4A shows a schematic cross-sectional view of an inspection apparatus 400 that may be implemented as part of lithographic apparatus 100 or 100' according to some embodiments. In some embodiments, inspection apparatus 400 may be configured to align a substrate (e.g., substrate W) relative to a patterning device (e.g., patterning device MA). Inspection apparatus 400 may be further configured to detect positions of alignment marks on the substrate and to use the detected positions of the alignment marks to align the substrate relative to the patterning device or other components of lithographic apparatus 100 or 100'. Such alignment of the substrate may ensure accurate exposure of one or more patterns on the substrate.

[0053]

[0070] In some embodiments, the inspection apparatus 400 may include an illumination system 412, a beam splitter 414, an interferometer 426, a detector 428, a beam analyzer 430, and an overlay calculation processor 432. The illumination system 412 may be configured to provide an electromagnetic narrowband radiation beam 413 having one or more passbands. In one example, the one or more passbands may be within a spectrum of wavelengths between about 500 nm and about 900 nm. In another example, the one or more passbands may be discrete narrow passbands within a spectrum of wavelengths between about 500 nm and about 900 nm. The illumination system 412 may be further configured to provide one or more passbands having a substantially constant central wavelength (CWL) value over an extended period of time (e.g., over the lifetime of the illumination system 412). Such a configuration of the illumination system 412 may help prevent shifts in the actual CWL value from the desired CWL value in current alignment systems, as discussed above. And, as a result, the use of a constant CWL value improves the long-term stability and accuracy of the alignment system (eg, inspection apparatus 400) as compared to current alignment apparatus.

[0054]

[0071] In some embodiments, the beam splitter 414 may be configured to receive the radiation beam 413 and split the radiation beam 413 into at least two radiation sub-beams. For example, as shown in FIG. 4A, the radiation beam 413 may be split into radiation sub-beams 415 and 417. The beam splitter 414 may be further configured to direct the radiation sub-beam 415 onto a substrate 420 disposed on a stage 422. In one example, the stage 422 is movable along a direction 424. The radiation sub-beam 415 may be configured to illuminate an alignment mark or target 418 positioned on the substrate 420. The alignment mark or target 418 may be coated with a radiation sensitive film. In some embodiments, the alignment mark or target 418 may have one hundred eighty degree (i.e., 180°) symmetry. That is, when the alignment mark or target 418 is rotated 180° about an axis of symmetry perpendicular to the plane of the alignment mark or target 418, the rotated alignment mark or target 418 may be substantially identical to the non-rotated alignment mark or target 418. The target 418 on the substrate 420 may be (a) a resist layer grating including bars formed from solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlay target structure including a resist grating superimposed or interleaved on a product layer grating. Alternatively, the bars may be etched into the substrate. This pattern is sensitive to chromatic aberrations in the lithographic projection apparatus, particularly the projection system PL, and illumination symmetry and the presence of such aberrations manifest themselves in the printed grating. One in-line method used in device manufacturing for measuring line widths, pitches and critical dimensions uses a technique known as "scatterometry".Scatterometry methods are described in Raymond et al., "Multiparameter Grating Metrology Using Optical Scatterometry," J.Vac.Sci.Tech.B, Vol. 15, No. 2, pp. 361-368 (1997), and Niu et al., "Specular Spectroscopic Scatterometry in DUV Lithography," SPIE, Vol. 3677 (1999), both of which are incorporated herein by reference in their entirety. In scatterometry, light is reflected by periodic structures in a target, and the resulting reflection spectrum at a given angle is detected. The structures giving rise to the reflection spectrum are reconstructed, for example, using rigorous coupled wave analysis (RCWA) or by comparison to a library of patterns derived by simulation. Thus, the scatterometry data of printed gratings are used to reconstruct those gratings. Parameters of the grating, such as linewidth and shape, may be input to the reconstruction process performed by processing unit PU, derived from knowledge of the printing and / or other scatterometry processes.

[0055]

[0072] In some embodiments, the beam splitter 144 may be further configured to receive the diffracted radiation beam 419 and split the diffracted radiation beam 419 into at least two radiation sub-beams, according to one embodiment. The diffracted radiation beam 419 may be split into diffracted radiation sub-beams 429 and 439, as shown in Figure 4A.

[0056]

[0073] It should be noted that although beam splitter 414 is shown directing radiation sub-beam 415 towards alignment mark or target 418 and diffracted radiation sub-beam 429 towards interferometer 426, this disclosure is not so limited. It will be apparent to one skilled in the art that other optical arrangements may be used to achieve a similar result of illuminating alignment mark or target 418 on substrate 420 and detecting an image of alignment mark or target 418.

[0057]

[0074] As shown in Figure 4A, the interferometer 426 may be configured to receive the radiation sub-beam 417 and the diffracted radiation sub-beam 429 through the beam splitter 414. In one example embodiment, the diffracted radiation sub-beam 429 may be at least a portion of the radiation sub-beam 415 that may be reflected from the alignment mark or target 418. In one example of this embodiment, the interferometer 426 comprises any suitable set of optical elements, such as a combination of prisms that may be configured to form two images of the alignment mark or target 418 based on the received diffracted radiation sub-beam 429. It should be understood that it is not necessary to form images of good image quality, but that features of the alignment mark 418 should be resolved. The interferometer 426 may be further configured to rotate one of the two images by 180° relative to the other of the two images, and interferometrically recombine the rotated and non-rotated images.

[0058]

[0075] In some embodiments, the detector 428 may be configured to receive the recombined image via the interferometer signal 427 when the alignment axis 421 of the inspection apparatus 400 passes through the center of symmetry (not shown) of the alignment mark or target 418 and detect interference as a result of the recombined image. According to an example embodiment, such interference may be due to the alignment mark or target 418 being 180° symmetrical and the recombined image constructively or destructively interfering. Based on the detected interference, the detector 428 may be further configured to determine the position of the center of symmetry of the alignment mark or target 418 and thus detect the position of the substrate 420. According to an example, the alignment axis 421 may be aligned with a light beam perpendicular to the substrate 420 and passing through the center of the image rotation interferometer 426. The detector 428 may be further configured to estimate the position of the alignment mark or target 418 by implementing sensor features and interacting with wafer mark processing variations.

[0059]

[0076] In a further 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: 1. Measuring the change in position at different wavelengths (position shift between colors) 2. Measurement of the position change at various orders (position shift between diffraction orders) 3. Measuring the position change at different polarizations (position shift between polarizations)

[0060]

[0077] This data can be obtained using any type of alignment sensor, such as, for example, a SMASH (SMart Alignment Sensor Hybrid) sensor as described in U.S. Pat. No. 6,961,116, which uses a self-referencing interferometer with a single detector and four different wavelengths to derive an alignment signal in software, or Athena (Advanced Technology using High order ENhancement of Alignment), which directs each of seven different diffraction orders to a dedicated detector, as described in U.S. Pat. No. 6,297,876, both of which are incorporated by reference in their entireties herein.

[0061]

[0078] In some embodiments, the beam analyzer 430 may be configured to receive and determine an optical state of the diffracted radiation sub-beam 439. The optical state may be a measure of the beam wavelength, polarization, or beam profile. The beam analyzer 430 may be further configured to determine the position of the stage 422 and correlate the position of the stage 422 with the position of the center of symmetry of the alignment mark or target 418. Thus, the position of the alignment mark or target 418, and therefore the position of the substrate 420, may be precisely known relative to the stage 422. Alternatively, the beam analyzer 430 may be configured to determine the position of the inspection apparatus 400 or any other reference element, such that the center of symmetry of the alignment mark or target 418 may be known relative to the inspection apparatus 400 or any other reference element. The beam analyzer 430 may be a point or imaging polarimeter with some form of wavelength band selectivity. In some embodiments, the beam analyzer 430 may be directly integrated into the inspection apparatus 400, or according to other embodiments, may be connected via some type of optical fiber: polarization-preserving single mode, multimode, or imaging.

[0062]

[0079] In some embodiments, the beam analyzer 430 may be further configured to determine overlay data between two patterns on the substrate 420. One of these patterns may be a reference pattern on a reference layer. The other pattern may be an exposure pattern on an exposed layer. The reference layer may be an etched layer already present on the substrate 420. The reference layer may be generated by a reference pattern exposed on the substrate by the lithographic apparatus 100 and / or 100'. The exposed layer may be a resist layer exposed adjacent to the reference layer. The exposed layer may be generated by an exposure pattern exposed on the substrate 420 by the lithographic apparatus 100 or 100'. The exposure pattern on the substrate 420 may correspond to a movement of the substrate 420 by the stage 422. In some embodiments, the measured overlay data may also indicate an offset between the reference pattern and the exposure pattern. The measured overlay data can be used as calibration data to calibrate the exposure pattern exposed by lithographic apparatus 100 or 100', so that after calibration, the offset between the exposed layer and the reference layer can be minimized.

[0063]

[0080] In some embodiments, the beam analyzer 430 may be further 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 includes information of the stacked products, such as alignment marks, the target 418, or the substrate 420, and may also include optical signature metrology induced by mark processing variations that are a function of illumination variations. The product stack profile may also include product grating profile, mark stack profile, and mark asymmetry information. One example of the beam analyzer 430 is the Yieldstar™ manufactured by ASML of Veldhoven, The Netherlands, as described in U.S. Pat. No. 8,706,442, which is incorporated herein by reference in its entirety. The beam analyzer 430 may be further configured to process information related to a particular characteristic of the exposure pattern within the layer. For example, the beam analyzer 430 may process overlay parameters of the rendered image in that layer (an indication of the accuracy of positioning of the layer relative to the previous layer on the substrate, or the accuracy of positioning of the first layer relative to a mark on the substrate), focus parameters, and / or critical dimension parameters (e.g., line width and its variation). Other parameters include image parameters related to the quality of the rendered image of the exposure pattern.

[0064]

[0081] In some embodiments, an array of detectors (not shown) may be connected to the beam analyzer 430, allowing for accurate stack profile detection as discussed below. For example, the detector 428 may be an array of detectors. For the array of detectors, several options are possible: a bundle of multimode fibers, a discrete pin detector per channel, or a CCD or CMOS (linear) array. Using a bundle of multimode fibers allows for the discrete elements to be positioned far apart for stability reasons. Discrete PIN detectors offer a large dynamic range, but each requires a separate preamplifier. Therefore, the number of elements is limited. A CCD linear array offers a large number of elements that can be read out at high speed, and is of particular interest when phase stepping detection is used.

[0065]

[0082] 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, as shown in FIG. 4B. The optical state may be a measure of the beam wavelength, polarization or beam profile. The second beam analyzer 430' may be identical to the beam analyzer 430. Alternatively, the second beam analyzer 430' may be configured to perform at least all 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. Thus, the position of the alignment mark or target 418, and thus the position of the substrate 420, may be precisely known with respect to the stage 422. The second beam analyzer 430' may also be configured to determine the position of the inspection apparatus 400 or any other reference element, so that the center of symmetry of the alignment mark or target 418 may be known with respect to the inspection apparatus 400 or any other reference element. The second beam analyzer 430' may be further configured to determine overlay data between the two patterns and a model of the product stack profile of the substrate 420. The second beam analyzer 430' may also be configured to measure the overlay, critical dimensions, and focus of the target 418 in a single measurement.

[0066]

[0083] In some embodiments, the second beam detector 430' may be directly integrated into the inspection apparatus 400 or, according to other embodiments, may be connected via some type of optical fiber: polarization-preserving single mode, multimode, or imaging. Alternatively, the second beam detector 430' and the beam detector 430 may be combined to form a single analyzer (not shown) configured to receive and determine the optical state of both diffracted radiation sub-beams 429 and 439.

[0067]

[0084] In some embodiments, the processor 432 receives information from the detector 428 and the beam analyzer 430. For example, the processor 432 may be an overlay calculation processor. The information may include a model of the product stack profile constructed by the beam analyzer 430. Alternatively, the processor 432 may use the information received about the product mark to construct a model of the product mark profile. In either case, the processor 432 uses or incorporates the model of the product mark profile to construct a model of the stacked product and overlay mark profile. The stack model is then used to determine the overlay offset and minimize the spectral effects on the overlay offset measurement. The processor 43 may generate a basic correction algorithm based on the information received from the detector 428 and the beam analyzer 430, including but not limited to the optical conditions of the illumination beam, the alignment signal and associated position estimates, the optical conditions at the pupil plane, the image plane, and additional planes. The pupil plane is the plane where the radial position of the radiation defines the angle of incidence and the angular position defines the azimuthal angle of the radiation. The processor 432 may utilize basic correction algorithms to characterize the inspection system 400 with respect to the wafer marks and / or alignment marks 418 .

[0068]

[0085] In some embodiments, the processor 432 may be further configured to determine the position offset error of the printed pattern relative to the sensor estimate for each mark based on information received from the detector 428 and the beam analyzer 430. This information may include, but is not limited to, the product stack profile, the overlay, critical dimension and focus measurements of each alignment mark or target 418 on the substrate 420. The processor 432 may utilize a clustering algorithm to group the marks into sets of similar constant offset errors and generate an alignment error offset correction table based on that information. The clustering algorithm may be based on the overlay measurements, the position estimates and additional optical stack process information associated with each set of offset errors. The overlay is calculated for several different marks (e.g., overlay targets with positive and negative biases around the programmed overlay offset). The target that measures the smallest overlay is used as a reference (since it is measured with the best accuracy). From this small measured overlay and the known programmed overlay of its corresponding target, the overlay error can be estimated. Table 1 shows how this can be done. The minimum overlay measured in the example shown is -1 nm. However, this relates to a target with a programmed overlay of -30 nm. The process must have introduced an overlay error of 29 nm. [Table 1] The minimum value can be used as a reference point, with which the offset between the measured overlay and the predicted overlay due to the programmed overlay can be calculated. This offset determines the overlay error for each mark or for a set of marks with similar offsets. Thus, in the example of Table 1, the minimum measured overlay was -1 nm at the target location where the programmed overlay was 30 nm. The difference between the predicted and measured overlays at other targets is compared to this reference. A table such as Table 1 can also be obtained from the marks and targets 418 under different illumination settings, and the illumination setting that results in the minimum overlay error, and its corresponding calibration factor, may be determined and selected. Following this, the processor 432 may group the marks into sets of similar overlay errors. The criteria for grouping the marks may be adjusted based on different process controls, for example, different error ranges for different processes.

[0069]

[0086] In some embodiments, processor 432 may determine that all or most members of a group have similar offset errors and may apply an individual offset correction from a clustering algorithm to each mark based on additional optical stack metrology. Processor 432 may determine correction values ​​for each mark and feed those correction values ​​back to lithographic apparatus 100 or 100' to correct errors in overlay, for example by providing the correction values ​​to inspection apparatus 400.

[0070]

[0087] Exemplary Optical System

[0088] In some embodiments, the term "throughput" may be used to describe the rate at which a wafer clears a particular manufacturing step and proceeds to the next step. Throughput may be a performance marker for marketability of a lithography system. It is desirable for a lithography system to output as much product as possible in as little time as possible. Lithography manufacturing may include several complex processes. Each process encompasses technology choices that balance the desired properties (e.g., sub-nanometer accuracy, high yield) and drawbacks (e.g., slower production, cost). Such processes may include inspection of printed marks on a substrate. Inspection equipment may be used in conjunction with lithography processes, for example, to verify the conformity of a printed pattern on a substrate or to align a substrate to properly receive a new pattern. It is understood that inspection processes may greatly improve mass production using lithography processes. It is also understood that inspection processes have an associated time cost, thereby reducing throughput.

[0071]

[0089] Some embodiments herein include devices and features for increasing the speed of the inspection process.

[0072]

[0090] 5A illustrates an optical system 500 according to some embodiments. In some embodiments, the optical system 500 may include an optical device 502, a reflecting device 504, and a movable reflecting device 506. The optical system 500 may also include a lens system 508 (e.g., one or more lenses, a 4f lens system, etc.).

[0073]

[0091] In some embodiments, the optical device 502 may comprise an objective. An objective is an optical device that collects radiation scattered from a target and / or focuses the radiation to generate an image of the target. The objective may include, for example, one or more lenses, one or more mirrors, or a combination of several optical elements. The optical device 502 may be disposed in a plane 510 (e.g., a first plane). The optical device 502 may be arranged around an axis 512 of the optical system 500. The axis 512 may be a central axis of the optical system 500. The reflecting device 504 may be disposed in a plane 514 (e.g., a second plane). The reflecting device may be arranged around the axis 512. The reflecting device 504 may have a one-to-one correspondence with the optical device 502. The movable reflecting device 506 may be disposed along the axis 512. The lens system 508 may be disposed along the axis 512.

[0074]

[0092] It should be understood that in some embodiments, the adjectives of enumeration (e.g., "first," "second," "third," etc.) may be used as identifiers of components rather than order of introduction (unless otherwise noted). For example, the terms "first plane" and "second plane" may distinguish two planes, but need not specify which plane precedes the other. Furthermore, objects in the drawings need not be limited to the adjectives of enumeration used in this detailed description (e.g., plane 510 may be referred to as the second plane when using the adjectives of enumeration that distinguish the other plane).

[0075]

[0093] In some embodiments, the optical device 502 can receive scattered radiation from multiple targets 418 (FIG. 4). Although FIG. 4 illustrates only one target (for clarity reasons), it should be understood that a substrate undergoing a lithography process may receive a pattern that includes multiple targets (e.g., tens or hundreds of diffraction gratings used for alignment and / or overlay inspection). The optical system 500 can be part of a system for performing an inspection (e.g., inspection apparatus 400 (FIGS. 4A and 4B)). As a non-limiting example, the optical system 500 can be disposed at a position 434 (FIG. 4). In such an implementation, the movable reflecting device 506 can direct scattered radiation from a given target to a detector 428 (FIG. 4). The detector can receive the scattered radiation. The detector can generate a measurement signal based on the scattered radiation.

[0076]

[0094] In some embodiments, instead of moving a single one of the optical devices 502 from a first target to a second target, the movable reflecting device 506 can be used to select the appropriate one of the optical devices 502 that is closest to the second target. In this way, the relative movement between the targets and the optical devices 502 can be significantly reduced. In conventional inspection apparatus that rely on a single objective, when the inspection apparatus inspects multiple targets, the single objective may be moved from one target to another (assuming a stationary reference frame of the target, i.e., moving the target or the substrate achieves the same effect). In this inspection method, the movement time of the single objective from target to target may cause delays in manufacturing. Such delays can be significant due to the amount of time it takes to accelerate and decelerate inertial components and precisely align the optics with the targets.

[0077]

[0095] In some embodiments, the cumulative delay of multiple motions can be significant. Therefore, the technical significance of the optical system 500 is that the relative motion between the target and the optical device 502 can be reduced when inspecting multiple targets, compared to the motion required by a tool with a single objective. Therefore, the duration of the inspection of the target using the optical system 500 can be significantly less than the duration of the inspection of the target using a single objective tool. Another technical significance of the optical system 500 is that the number of radiation sources and detectors can be less than the number of optical devices 502 (e.g., using a single radiation source and a single detector device shared (or common) by two or more of the optical paths). This can reduce the cost of construction and the overall weight, as well as improve the scalability of the optical system 500 through the use of fewer optical devices with a large footprint.

[0078]

[0096] In some embodiments, each of the reflecting devices 504 can receive scattered radiation from a corresponding one of the optical devices 502. The movable reflecting device 506 can receive scattered radiation from each of the reflecting devices 504. A detector (e.g., detector 428 (FIG. 4)) can receive scattered radiation from the movable reflecting device 506. The optical components in the optical system 500 can be arranged such that the source (or illumination) branch of the inspection system (e.g., radiation traveling toward a target) and the detection branch of the inspection system (e.g., radiation traveling from a target) have overlapping optical paths. For example, radiation from the radiation source can be directed along axis 512 and along optical path 516 (e.g., a first optical path) to one of the targets 418 (FIG. 8) (e.g., a first target). After the radiation scatters from the target, the scattered radiation can be directed to the detector 428 (FIG. 4) via the optical path 516 and axis 512. When a different target is to be inspected, the movable reflective device 506 can be actuated (eg, reoriented, redirected, etc.) to select a different optical path (eg, optical path 518).

[0079]

[0097] In some embodiments, the movable reflecting device 506 can receive a radiation beam from a radiation source (e.g., illumination system 412 (FIG. 4)). The movable reflecting device 506 can direct the radiation beam towards a target 418 (FIG. 4) and generate scattered radiation from the target. The movable reflecting device 506 can direct the radiation beam using, for example, optical path 516 or 518 based on a position state of the movable reflecting device 506. The movable reflecting device 506 can direct the radiation beam, for example, through reflecting device 504 and deflect the radiation beam towards the target. The radiation beam can also be transmitted through optical device 502.

[0080]

[0098] In some embodiments, the first optical path may be defined by a first reflective element of the reflective element 504, a first optical device of the optical device 502, and a first target of the target 418 (FIG. 4). In a non-limiting example, the first optical path may be an optical path 516 (or an optical path 518) defined by the optical device, the reflective element, and the corresponding optical device along the optical path, the reflective element, and the target. The second optical path may be defined by a second reflective element of the reflective element 504, a second optical device of the optical device 502, and a second target of the target 418 (FIG. 4). In a non-limiting example, the second optical path may be an optical path 518 (or an optical path 516) defined by the optical device, the reflective element, and the corresponding optical device along the optical path, the reflective element, and the target. The movable reflective device 506 may be actuated to shift the radiation beam between the first and second optical paths.

[0081]

[0099] In some embodiments, an inspection system implementing the optical system 500 can perform inspection measurements on multiple targets 418 (FIG. 4). For example, a relative movement between the target and the optical device 502 can occur to align a first target of the targets with a first optical device of the optical device 502. The relative movement can be achieved by moving the optical device 502 relative to the target, moving the target relative to the optical device 502, or both. The movable reflecting device 506 can be oriented (e.g., by actuation) such that an optical path of the first optical device of the optical device 502 is selected (e.g., optical path 516). A radiation beam can be directed to the first target and subsequent scattered rays can be detected at the detector 428 (FIG. 4), all using the first optical path. It should be understood that at this point, the first optical device of the optical device 502 may not be the one closest to the next target to be measured (e.g., the second target of the target). There may be another optical device of the optical device (e.g., the second optical device of the optical device) closest to the second target of the target.

[0082]

[0100] Thus, in some embodiments, the inspection system can generate a relative movement between the target and the optical device 502 to align the second target of the target with the second optical device of the optical device 502. The movable reflecting device 506 can be actuated such that an optical path of the second optical device of the optical device 502 is selected (e.g., optical path 518). This shifts the radiation beam from the first optical path to the second optical path. By measuring the second target using the second optical device of the optical device 502 (rather than measuring the second target using the first optical device of the optical device 502), the relative movement between the target and the optical device 502 can be limited to be less than the distance between the first and second targets of the target. In contrast, in a situation where a single objective (or optical device) is moved from target to target, the distance that the single objective moves is equal to the distance between the targets. In this manner, the use of multiple optical devices of the optical device 502 can reduce the distance that the optical device moves relative to the target, thereby reducing the time to perform measurements on multiple targets. It should be understood that measurements of the first and second targets can be performed sequentially. The inspection system can complete the measurement sequence faster than an alternative measurement sequence that includes aligning a single optical device to a first one of the targets and then aligning the single optical device to a second one of the targets.

[0083]

[0101] In some embodiments, the movable reflecting device 506 can be actuated to switch from one optical path to another at a given speed, i.e., a given rate or frequency. The frequency of actuating the movable reflecting device 506 can be based on the inverse of the duration for effecting the shifting of the radiation beam between the optical paths 516 and 518. The movable reflecting device 506 can be operated up to a frequency of about 500 Hz. The upper frequency limit can be higher based on the capabilities of a given actuator.

[0084]

[0102] 5A and 5B, FIG. 5 illustrates an arrangement of optical devices 502 in a plane 510 (FIG. 5A), according to some embodiments. In some embodiments, the optical devices 502 can be arranged in an array arrangement. The array arrangement can be symmetric about an axis 512. An example of axial symmetry can be 12-fold symmetry (e.g., an optical device 502 can be diametrically opposed to another optical device 502). Another example of axial symmetry can be 5-fold symmetry (e.g., an optical device 502 does not have a diametrically opposed optical device). The array arrangement can be annular. For example, the array arrangement can conform to the shape of a circle or an ellipse. In some embodiments, the array arrangement can be polygonal. For example, the array arrangement can be such that the optical devices 502 are arranged at the vertices of a polygonal shape.

[0085]

[0103] In some embodiments, the optical devices 502 can be disposed at equal optical distances relative to the axis 512. The optical devices 502 can be disposed at equal optical distances relative to the movable optical device 506. An optical magnification associated with a first optical device of the optical devices 502 can be the same as an optical magnification associated with a second optical device of the optical devices 502.

[0086]

[0104] In some embodiments, the optical devices may be arranged symmetrically, but are not limited to belonging to a particular n-fold symmetry, such as that shown in FIG. 5C.

[0087]

[0105] 5A and 5C, FIG. 5C shows an arrangement of optical devices 502 in a plane 510 (FIG. 5A), according to some embodiments. The array arrangement may have some symmetry about an axis 512 (e.g., one half is symmetrical with respect to the other half). In this arrangement, the optical devices 502 may be disposed at equal optical distances about the axis 512. The optical devices 502 may be disposed such that there is a gap 516 between a first and second optical device of the optical device 502. The gap 520 may enable additional capabilities to be implemented in the inspection system. For example, in addition to having a component or target for performing measurements, the measurement system may include one or more additional sensors for other purposes.

[0088]

[0106] In some embodiments, the measurement system may include, in addition to the inspection apparatus 400 (FIGS. 4A and 4B), the optical system 500, a second system (e.g., a height or level sensor) for making measurements of the substrate and / or target. The second system may send radiation to the substrate and / or target through the gap 520. The second system may determine the height position of the substrate (height measured along an axis approximately parallel to the axis 512). The gap 520 is particularly useful when the optical device 502 includes an objective with a short working distance (e.g., focused when the optical device 502 is disposed very close to the target). In this scenario, the optical device 502 may block measurement radiation intended to be incident on the substrate 420 (FIG. 4) at a position close to the axis 512. However, the gap 520 may provide a line-of-sight path to an area that would normally be blocked if the optical devices 502 were closely spaced without the gap. It is understood that the gap 520 may also be incorporated into other arrangements disclosed herein.

[0089]

[0107] In some embodiments, the movable reflecting device 506 may be used to scramble some property of the radiation (e.g., coherence scrambling, aberration scrambling, etc.). For example, the motion of the movable reflecting device 506 may be modulated and / or randomized.

[0090]

[0108] FIG. 6A illustrates an optical system 600 according to some embodiments. In some embodiments, the optical system 600 may have a similar structure and function as the optical system 500 described with reference to FIGS. 5A, 5B, and 5C. Thus, unless otherwise stated, the description of elements in FIGS. 5A, 5B, and 5C may also be applied to corresponding elements in FIG. 6A (e.g., reference numbers having the same two rightmost digits). Furthermore, for brevity, certain elements may not be numbered, but the structure and function of those elements should be clear based on the numbered similar elements.

[0091]

[0109] In some embodiments, Figure 6A shows an example arrangement of optical components that scales the concepts described with reference to Figures 5A, 5B and 5C. Optical system 600 may include optical device 602, reflecting device 604, and movable reflecting device 606. Optical system 600 may also include one or more lens systems 608. Planes 610 and 614, axis 612, and optical paths 616 and 618 may represent spatial relationships and functions as described with reference to Figure 5A above. Optical device 600 may be implemented within a system for inspecting a substrate (e.g., at position 434 (Figures 4A and 4B)).

[0092]

[0110] In some embodiments, the optical system may be scaled to the point where the optical devices 602 no longer fit into a single compact arrangement (e.g., no longer fit into an annular arrangement). It may therefore be desirable to place the extra optical devices 602 further away from the axis 612. In some embodiments, a first arrangement may be achieved using the optical devices 602 and a first portion of the reflecting device 604. In FIG. 6, the internal arrangement of the optical devices 602 and the reflecting device 604 (proximal to the axis 612) may be as described above with reference to FIGS. 5A, 5B and 5C. A second arrangement is also envisioned, in which the optical devices 602 and a second portion of the reflecting device 604 are placed further away from the axis 612. It should be understood that the scaling can continue to a third arrangement even further away from the axis 612, a further fourth arrangement, and so on. The arrangement may then be made to avoid blocking the optical path, as described with reference to FIG. 6B.

[0093]

[0111] In some embodiments, the lens system 608 can be disposed in a first arrangement corresponding to the first arrangement of the optical device 602. The lens system 608 can be disposed between the planes 610 and 614. It should be understood that disposing additional lens systems can be extrapolated to second, third and / or additional arrangements. The lens system 608 can be disposed in an optical path (e.g., optical path 616 and / or 618). That is, the lens system 608 can be disposed such that a first optical path is defined by a first lens system of the lens system 608 and a second optical path is defined by a second lens system of the lens system, in addition to a first optical path and a second optical path being defined by corresponding optical devices and reflecting devices of the optical device 602 and the reflecting device 604.

[0094]

[0112] Figure 6B illustrates an arrangement of optical devices 602 in a plane 610 (Figure 6A), according to some embodiments. Unless otherwise stated, the descriptions of elements in Figures 5A, 5B, and 5C may also apply to corresponding elements in Figure 6B (e.g., reference numbers having the same two rightmost digits). Furthermore, for simplicity, certain elements may not be numbered, but the structure and function of those elements should be clear based on similarly numbered elements.

[0095]

[0113] In some embodiments, the inner annular arrangement (e.g., a first arrangement) of the optical devices 602 can be implemented such that gaps exist between the optical devices 602. Gaps also exist in the corresponding arrangement of the reflecting device 604 (FIG. 6A). The gaps can provide a line of sight such that radiation travels unobstructed between the outer reflecting device (e.g., a second arrangement) and the axis 612 of the reflecting device 604 (FIG. 6A), as shown by optical path 616. Optical path 618 corresponds to the path of radiation traveling between the inner reflecting device of the reflecting device 604 (FIG. 6A) and the axis 612.

[0096]

[0114] 6A , in some embodiments, the first and second arrangements can both be disposed in a plane 614. Stated differently, the plane of the first arrangement (e.g., the second plane) can be coincident with the plane of the second arrangement (e.g., a third plane that is coincident with the second plane).

[0097]

[0115] Stated differently, in some embodiments, two or more of the optical devices 602 can be arranged around the axis 612 in a first arrangement. Another two or more of the optical devices 602 can be arranged in a second arrangement in the plane 610 (e.g., the first plane). The second arrangement can be geometrically similar to the first arrangement but larger than the first arrangement and surround the first arrangement. That is, the perimeter of the second arrangement of the optical devices 602 can be larger than the perimeter of the first arrangement of the optical devices 602. The first arrangement of the optical devices 602 can be arranged inside the second arrangement of the optical devices 602. Two or more of the reflecting devices 604 can be arranged in a first arrangement corresponding to the first arrangement of the optical devices 602. Another two or more of the reflecting devices 604 can be arranged in a second arrangement corresponding to the second arrangement of the optical devices 602.

[0098]

[0116] In some embodiments, the second arrangement of reflective devices 604 may be disposed in a plane 614 (e.g., a second plane). However, other planes may be used, as described with reference to Figures 7A and 7B.

[0099]

[0117] It should be understood that in some embodiments, the optical paths of the first arrangement may have the same optical distance. Similarly, the optical paths of the second arrangement may have the same optical distance. However, due to the second arrangement being positioned away from axis 612, the optical distance of the paths of the first arrangement may be different from the optical distance of the paths of the second arrangement. It should be understood that in some embodiments, additional optical components may be implemented to lengthen certain optical paths (e.g., introduce beam retarding material or deflect paths using reflectors to send radiation through longer paths) so that all optical paths have the same optical distance.

[0100]

[0118] In some embodiments, the concept of gap 520 (FIG. 5C) can be implemented in first, second and / or additional arrangements to enable a second inspection system to transmit radiation to the substrate through gap 520 (FIG. 5C).

[0101]

[0119] FIG. 7 illustrates an optical system 700 according to some embodiments. In some embodiments, the optical system 700 may have a similar structure and function as the optical systems 500 and / or 600 described with reference to FIGs. 5A, 5B, 5C, 6A, and / or 6B. Thus, unless otherwise stated, the description of elements in FIGs. 5A, 5B, 5C, 6A, and 6B may also be applied to corresponding elements in FIG. 7 (e.g., reference numbers having the same two rightmost digits). Moreover, for brevity, certain elements may not be numbered, but the structure and function of those elements should be clear based on the numbered similar elements.

[0102]

[0120] In some embodiments, Figure 7 illustrates an example arrangement of optical components that scales the concepts described with reference to Figures 5A, 5B, 5C, 6A, and / or 6B. Optical system 700 may include an optical device 702, a reflecting device 704, and a movable reflecting device 706. Optical system 700 may also include one or more lens systems 708. Planes 710 and 714, axis 712, and optical paths 716 and 718 may represent spatial relationships and functions as described with reference to Figure 5A above. Optical device 700 may be implemented within a system for inspecting a substrate (e.g., at position 434 (Figures 4A and 4B)).

[0103]

[0121] The difference between FIG. 6A and FIG. 7A is that in some embodiments, the second arrangement of the reflecting devices 704 can be disposed in a plane 722 (e.g., a third plane). This can be particularly useful for increasing the packing density of the optical objective 702, as shown in FIG. 7B. The gap that existed in FIG. 6B does not exist in the arrangement shown in FIG. 7B. That is, the optical devices 702 in the inner arrangement (e.g., a first arrangement) can be disposed close to each other such that there is a line of sight obstruction between the axis 712 and at least one of the optical devices 702 in the outer arrangement (e.g., a second arrangement). Accordingly, the reflecting device 704 in such an arrangement provides a line of sight obstruction between the movable reflecting device 706 and one of the reflecting devices in the second arrangement when the planes 714 and 722 coincide. Thus, the plane 722 can be offset from the plane 714 so that a line of sight can be established between the movable reflecting device 706 and the reflecting device 704 in the second arrangement.

[0104]

[0122] Before describing the movement of the movable reflecting device 706, it may be useful to first define a reference frame. Planes 710, 714, and / or 722 may define a horizontal direction, and axis 712 may define a zenith direction. An azimuth direction or rotation may be defined with respect to axis 712. It should be understood that the tilt angle may be defined as beginning at zero in the zenith direction, while the elevation angle may be the complement of the tilt angle (i.e., if the line of sight is pointing horizontally, it may have an elevation angle of zero, and the elevation angle may increase as the line of sight is made to point more vertically). The origin of the reference frame may be defined at the intersection of axis 712 with the surface of the movable reflecting device 706.

[0105]

[0123] In some embodiments, the optical path may have a portion of its path defined substantially parallel to the plane of the placement of the optical device 702. As shown as a non-limiting example in FIG. 7A, a horizontal portion of the optical path 718 is substantially parallel to the plane 714. Additionally, another optical path may have a portion of its path defined at a non-zero elevation angle relative to the plane of the placement of the optical device 702. As shown as a non-limiting example in FIG. 7A, there is a portion of the optical path 716 that is tilted at a non-zero angle relative to the plane 714. It should be understood that the drawings are non-limiting examples and other arrangements are envisioned. For example, the arrangement of the reflecting device 704 may be swapped, such that the reflecting device 704 at the plane 714 is now disposed at the plane 722, while the reflecting device 704 at the plane 722 is now disposed at the plane 714. Corresponding adjustments of other optical components (e.g., the lens system 708) are also envisioned.

[0106]

[0124] In some embodiments, the movable reflecting device 706 may be disposed in a plane 714 (e.g., a second plane). The movable reflecting device 706 may be adjusted to rotate its optical orientation about the axis 712 (e.g., to perform an azimuthal adjustment). As will be described later with reference to FIG. 9, rotation is not the only way to perform an azimuthal adjustment. The movable reflecting device 706 may be adjusted to adjust the elevation orientation of the surface of the movable reflecting device 706 (i.e., in a direction parallel to the axis 712). The elevation adjustment allows for obtaining line-of-sight access to the reflecting device 704 disposed in the plane 722 (e.g., the reflecting device in the second arrangement). In this way, it is possible to overcome line-of-sight problems due to the close packing of the optical objective 702 and the corresponding reflecting device 704 as shown in FIG. 7B.

[0107]

[0125] In some embodiments, the optical path length, arrangement of the lens system, and use of gap 520 (FIG. 5) may be implemented as described with reference to other figures.

[0108]

[0126] FIG. 8 illustrates an optical system 800 according to some embodiments. In some embodiments, the optical system 800 may have a similar structure and function to the optical systems 500, 600, and / or 700 described with reference to FIGs. 5A, 5B, 5C, 6A, 6B, 7A, and / or 7B. Thus, unless otherwise stated, the description of elements in FIGs. 5A, 5B, 5C, 6A, 6B, 7A, and 7B may also be applied to corresponding elements in FIG. 8 (e.g., reference numbers having the same rightmost two digits). Furthermore, for brevity, certain elements may not be numbered, but the structure and function of those elements should be clear based on the numbered similar elements.

[0109]

[0127] In some embodiments, optical system 800 may comprise an optical device 802, a reflecting device 804, a movable reflecting device 806, an additional reflecting device 803, and a refractive device 805 (e.g., a lens). Optical system 800 may also comprise one or more lens systems 808. Planes 810 and 814, axis 812, and optical paths 816 and 818 may represent spatial relationships and functions as described above with reference to corresponding elements in FIG. 5A. Optical system 800 may be implemented within a system for inspecting a substrate (e.g., at location 434 (FIGS. 4A and 4B)).

[0110]

[0128] In some embodiments, the reflecting device 804 and the additional reflecting device 803 may be arranged in a plane 814 (e.g., a second plane). The additional reflecting device 803 may be arranged in an arrangement corresponding to the arrangement of the reflecting device 804 (e.g., in a one-to-one correspondence). The additional reflecting device 803 may be arranged closer to the axis 812 than the optical device 804. In contrast to some of the previous figures, the movable reflecting device 806 may be arranged in or near the plane 810 (e.g., a first plane) rather than near the plane 814. The refractive device 805 may be arranged between the plane 814 and the movable reflecting device 806. And, although the movable reflecting device 806 may be shown as being in the foreground of FIG. 8, this is done for clarity, and it should be understood that the movable reflecting device 806 may be arranged inside the arrangement of the optical device 802 (e.g., arranged on the axis 802).

[0111]

[0129] In some embodiments, optical path 816 may be defined by one of the optical devices 802, one of the reflecting devices 804, and one of the additional reflecting devices 803 (e.g., a first optical path defined by a first of the optical elements mentioned above). Similar relationships may be defined for optical path 818 and corresponding optical elements.

[0112]

[0130] In some embodiments, the movable reflecting device 806 can be actuated to switch from one optical path to another. The movable reflecting device 806 can receive a radiation beam from a radiation source via an axis 812. The movable reflecting device 806 can direct the beam to one of the additional reflecting devices 803 corresponding to the optical path as defined by the movable reflecting device 806. The movable reflecting device 806 can receive scattered radiation from a target via an optical path as defined by the movable reflecting device 806. Each of the additional reflecting devices 803 can receive scattered radiation from a corresponding one of the reflecting devices 804. The refractive device 805 serves to deflect the radiation path to connect the optical path to the axis 812.

[0113]

[0131] In some embodiments (e.g., the embodiment relating to FIG. 6A ), the radiation relayed between the movable reflecting device 606 and the reflecting device 604 is oriented parallel to the plane 614, with no components moving parallel to the axis 612. However, in the embodiment relating to FIG. 8 , the positioning of the movable reflecting device 804, the radiation relayed between the movable reflecting device 806 and the reflecting device 804 has a portion of its path oriented parallel to the axis 812, which is achieved using an additional reflecting device 803 and a refractive device 805. Configurability of optical components is a desirable feature for the implementation of optical systems. The differences from one figure to the next go beyond a simple rearrangement of the optical path. As an example, the configuration in FIG. 8 may be more optimal for implementation depending on the capacity constraints imposed by a particular inspection tool or application.

[0114]

[0132] In some embodiments, the movable device 806 may be subject to excessive heating, for example due to actuation and due to being a common point for all radiation paths. Therefore, the movable reflective device 806 may be coupled to a heat exchange device 822 (e.g., a cooling plate). The heat exchange device 822 may exchange heat with a cooling system to regulate, maintain, or otherwise adjust the temperature of the movable reflective device 806. The use of the heat exchange device 822 may also be implemented in embodiments related to other figures.

[0115]

[0133] In some embodiments, the movable reflecting device 806 may comprise a galvanometer (or galvo), a beam steering mirror, a mirror on a rotation / translation actuator (e.g., a mirror on a hexapod stage), a digital micromirror device (DMD), a spatial light modulator, a single or multiple mirrors, a single or multiple prisms, a combination of one or more mirrors and one or more prisms, these are non-limiting examples. The movable reflecting device 806 may have multiple reflective surfaces (e.g., facets). Additionally, the movable reflecting device 806 may include a surface with a curvature to focus / defocus the radiation beam, a surface with a given texture and / or coating to control the properties of the radiation (e.g., polarization), etc. If a surface affects the properties of the radiation in an undesirable way, additional optical components may be implemented at some point in the radiation path (e.g., a waveplate in a detector) to provide correction.

[0116]

[0134] FIG. 9 illustrates a movable reflective device 906 according to some embodiments. In some embodiments, features illustrated in FIG. 9 may be similar to features described with reference to FIG. 5A, 5B, 5C, 6A, 6B, 7A, 7B, and / or 8. Thus, unless otherwise stated, the descriptions of elements in FIG. 5A, 5B, 5C, 6A, 6B, 7A, 7B, and 8 may also be applied to corresponding elements in FIG. 9 (e.g., reference numbers having the same rightmost two digits). Furthermore, it should be understood that the movable reflective device 906 may be used in place of the movable reflective devices 506 (FIG. 5A), 606 (FIG. 6A), 706 (FIG. 7A), or 806 (FIG. 8).

[0117]

[0135] In some embodiments, the movable reflecting device 906 may include facets 924. The movable reflecting device 906 may be disposed in the path of the axis 912. A particular one of the facets 924 may cause the optical path 916 to be selected. In some embodiments, the movable reflecting device 906 may be actuated (e.g., translated) such that a different one of the facets 924 is disposed in the path of the axis 912. A different one of the facets 924 may cause the optical path 918 to be selected. The movable reflecting device 906 may also be tilted and / or rotated to shift the radiation path between the different optical paths.

[0118]

[0136] In some embodiments, the reflective device may be more generally referred to as the "optical subsystem." The movable reflective device may be more generally referred to as the "central beam steering element." The terms "optical sub-elements" (and modifiers such as reflective or transmissive) may be used herein to refer to sub-elements of the central beam steering element.

[0119]

[0137] In some embodiments, a measurement system (e.g., inspection apparatus 400 (FIGS. 4A and 4B)) using an optical system described herein (e.g., optical system 900 (FIG. 9)) can perform measurements when the movement of the movable device is in a stationary phase of its movement (e.g., minimal acceleration and / or jitter). It will be appreciated that a movable device that starts and ends at rest can have at least two motion phases, e.g., an acceleration phase and a deceleration phase. There can also be a constant speed phase and a combination of phases. It will be appreciated that instabilities such as jitter and vibrations can also be present during the movement. For example, there may be some final jitter due to the transition from full speed to rest when the mover reaches a set point speed there. To address this issue, the measurement system may perform measurements during a settling period of the movement of the central beam steering device. Furthermore, predictable or measurable jitter can be applied as a correction to the measurement using, for example, a transfer function. In this way, the speed of the measurement can be increased and the throughput can be further improved.

[0120]

[0138] In some embodiments, the optical system (e.g., optical system 900 (FIG. 9)) may also include an actuation system. The actuation system may use an anti-rotational balance mass to actuate the central beam steering system. The actuation system may react to the anti-rotational balance mass.

[0121]

[0139] In some embodiments, the optical system (e.g., optical system 900 (FIG. 9)) may also include support structures that minimize the transfer of kinetic energy from moving components (e.g., central beam steering elements) to other light sensitive devices such as the objective and reflectors. The support structures can direct acceleration responses to a larger frame (e.g., the frame of a measurement system) that is different from the frame on which the optical components of the optical system are mounted. In this way, kinetic excitation of the optical components of the optical system can be minimized.

[0122]

[0140] The embodiments can be further described using the following clauses. 1. An optical device arranged about an axis of the system in a first plane and configured to receive scattered radiation from a target; reflecting devices disposed about the axis in at least a second plane, each of the reflecting devices configured to receive scattered radiation from a corresponding one of the optical devices; a movable reflecting device disposed along the axis and configured to receive scattered radiation from each of the reflecting devices; a detector configured to receive scattered radiation from the movable reflecting device; A system comprising: 2. The system of claim 1, wherein the optical devices are arranged in an array arrangement symmetrical about an axis. 3. The system of claim 1, wherein the array arrangement is circular or polygonal. 4. The system of claim 1, wherein the first and second optical devices are disposed at equal optical distances relative to the movable reflecting device. 5. The system of claim 1, wherein the movable reflecting device is further configured to direct the radiation beam towards a target and generate scattered radiation from the target. 6. The system of clause 1, wherein the optical device is an objective configured to collect scattered radiation for detection. 7. A first optical path is defined by a first target, an optical device, and a reflecting device of a target, an optical device, and a reflecting device; a second optical path is defined by a second target, an optical device and a reflecting device of the target, the optical device and the reflecting device; 13. The system of claim 1, wherein the movable reflecting device is further configured to operate to direct the beam through the reflecting device toward the target and to shift the beam between the first and second optical paths. 8. The system is Aligning a first target and optical device of the target and optical device; Thereafter, generating relative movement between the target and the optical device to align a second one of the target and the optical device; and measuring the target based on a movable reflecting device that shifts the beam between the first and second paths to limit relative movement to less than a distance between the first and second targets; 8. The system of claim 7, configured to: 9. The system of claim 8, wherein the system is further configured to sequence measurements of the target based on actuating the movable reflective device. 10. The measurement sequence includes aligning a first target and optical device of the target and optical device, and then aligning a second target and optical device of the target and optical device; The system of clause 7, wherein the system is further configured to complete the measurement sequence faster than an alternative measurement sequence that includes aligning a single optical device to a first target of the targets and then aligning the single optical device to a second target of the targets. 11. The system of clause 7, wherein the movable reflecting device comprises a rotatable reflector configured to rotate into engagement with the first or second optical path. 12. The system of clause 7, wherein the movable reflecting device comprises a multi-faceted reflector configured to translate and / or rotate to engage the first or second optical path. 13. The system of clause 7, wherein the movable reflecting device comprises a galvo configured to rotate into engagement with the first or second optical path. 14. The frequency of actuating the movable reflective device is based on the inverse of the duration for shifting the beam; 8. The system of claim 7, wherein the movable reflective device is further configured to operate at a frequency that is greater than or equal to about 500 Hz. 15. The system of clause 7, wherein based on a state of the movable reflecting device, the system is further configured to propagate the scattered radiation along a first optical path or a second optical path. 16. The system of clause 7, wherein the lengths of the first and second optical paths are approximately the same. 17. The system of claim 16, wherein an optical magnification associated with a first optical device of the optical device is the same as an optical magnification associated with a second optical device of the optical device. 18. The system described in clause 7, further comprising a radiation source configured to generate a beam for directing along the axis towards a movable reflecting device, the movable reflecting device further configured to direct the beam from the axis to the first optical path or from the axis to the second optical path. 19. The system described in clause 1, wherein the movable reflecting device is further configured to direct the scattered radiation toward the detector using the first optical path or using the second optical path. 20. The system of claim 7, further comprising a lens system. 21. The system of claim 20, wherein the lens system comprises a 4f lens system. 22. The first optical path is further defined by a first lens system of the lens systems; 21. The system of claim 20, wherein the lens systems are arranged such that the second optical path is further defined by a second of the lens systems. 23. The system of claim 1, wherein the arrangement of the optical devices includes a gap between the first and second optical devices. 24. The system of clause 23, further comprising another system configured to perform measurements on the substrate and / or target by sending radiation through the gap. 25. Another system includes a level sensor configured to determine a height position of a substrate; 25. The system of claim 24, wherein the axis of the elevation position is substantially parallel to an axis of the system. 26. Two or more of the optical devices are arranged in a first arrangement about an axis; 2. The system of claim 1, wherein two or more of the reflective devices are arranged in a first arrangement corresponding to a first arrangement of the optical devices. 27. The system of clause 26, further comprising a lens system disposed between the first and second planes in a first arrangement corresponding to the first arrangement of the optical device. 28. Another two or more of the optical devices are disposed in a second arrangement in the first plane; 27. The system of claim 26, wherein two or more other of the reflective devices are arranged in a second arrangement corresponding to the second arrangement of the optical devices. 29. The perimeter of the second arrangement of optical devices is greater than the perimeter of the first arrangement of optical devices; 29. The system of claim 28, wherein the first arrangement is disposed inside the second arrangement. 30. The system of claim 28, wherein the second arrangement of reflective devices is disposed in a second plane. 31. The two or more reflective devices in the first arrangement are arranged such that there is at least one gap between two or more of the reflective devices; 31. The system of claim 30, wherein the movable reflecting device is further configured to direct the radiation beam through the gap to the second location. 32. The system of claim 31, wherein the second arrangement of reflective devices is disposed in a third plane different from the second plane. 33. The system described in clause 32, wherein the movable reflective device is disposed in a second plane and is operable to orient a surface of the movable reflective device such that the surface of the movable reflective device is configured to optically interact with one of the reflective devices in the second plane or one of the reflective devices in the third plane. 34. Further comprising an additional reflecting device disposed about the axis in at least a second plane and closer to the axis than the reflecting device; each of the additional reflective devices is configured to receive the scattered radiation from a corresponding one of the reflective devices; The system described in clause 26, wherein the movable reflective device is disposed in a first plane and is operable to orient a surface of the movable reflective device such that the surface of the movable reflective device is configured to optically interact with an additional reflective device in a second plane. 35. A first optical path is defined by a first target, an optical device, a reflecting device, and an additional reflecting device; a second optical path is defined by a second target, an optical device, a reflecting device and an additional reflecting device of the target, the optical device, the reflecting device and the additional reflecting device; 35. The system of claim 34, wherein the movable reflecting device is further configured to direct the beam towards the target via the additional reflecting device and to operate to shift the beam between the first and second optical paths. 36. The system according to clause 35, wherein between the first additional reflective element of the additional reflective elements and the movable reflective device, the first optical path includes a portion oriented parallel to the axis. 37. The system of clause 1, wherein the movable reflective device comprises a galvanometer, a beam steering mirror, a faceted surface, and / or a digital micromirror device. 38. The system of clause 1, further comprising a heat exchange device thermally coupled to the movable reflecting device and configured to maintain and regulate a temperature of the movable reflecting device. 39. A system as described in clause 1, wherein the axis of the system is a central axis of the system. 40. An optical device disposed about the axis of the system in a first plane and configured to receive scattered radiation from the target; reflective devices arranged about the axis in at least the second plane, each of the reflective devices configured to receive scattered radiation from a corresponding one of the optical devices; a movable reflecting device positioned along the axis and configured to receive scattered radiation from each of the reflecting devices; An optical system comprising: 41. An optical device arranged about an axis of the system in a first plane and configured to irradiate and / or receive scattered radiation from the object; optical subsystems arranged about the axis in at least a second plane, each of the optical subsystems configured to irradiate and / or receive scattered radiation from a corresponding one of the objects; a central beam steering element configured to route radiation between the first plane and the optical subsystem to emit and / or receive scattered radiation from the object; A system comprising: 42. The system of claim 41, further comprising a detector configured to receive scattered radiation from the central beam steering element. 43. The system of claim 42, wherein the detector is disposed in a first plane. 44. The system of claim 42, wherein the detector is disposed in a third plane different from the first plane. 45. The system of claim 41, wherein the central beam steering element comprises one or more reflective and / or transmissive optical sub-elements. 46. ​​The central beam steering element is configured to translate and / or rotate to control the propagation direction of the radiation; one or more reflective optical sub-elements are configured to translate and / or rotate to control the propagation direction of the radiation; and / or 46. ​​The system of claim 45, wherein one or more transmissive optical sub-elements are configured to translate and / or rotate to control a propagation direction of the radiation. 47. The central beam steering element is an optical acoustic wafer for controlling the propagation direction of the radiation; and / or Electron photoinduced wafer for controlling the propagation direction of radiation 42. The system of claim 41, further comprising: 48. The system of claim 41, wherein the system is configured to take measurements of the object during a settling period of motion of the central beam steering element. 49. The system of clause 41, further comprising an actuation system configured to actuate the central beam steering element using an anti-rotational balance mass. 50. The system of clause 41, further comprising a support structure configured to support a central beam steering element and direct the acceleration response to a frame distinct from a frame of the optical device and the optical subsystem. 51. The central beam steering element comprises an actuation system having first and second actuators; the first actuator is configured to allow bulk adjustment of motion of the central beam steering element; 42. The system of claim 41, wherein the second actuator is configured to finely adjust the movement of the central beam steering element. 52. The system of claim 51, wherein the actuation system is configured to move the central beam steering element to correct a propagation direction of the radiation according to a given alignment. 53. The system of claim 41, wherein the central beam steering element comprises an optical surface configured to interact with the radiation beam. 54. The system of clause 41, wherein the optical surface is configured to focus and / or defocus a radiation beam incident on the optical surface. 55. The system of claim 54, wherein the optical surface is configured to adjust a characteristic of the radiation beam. 56. The system of claim 41, wherein the central beam steering element is further configured to move according to a modulation and / or randomization process. 57. The system of clause 56, wherein the central beam steering element is further configured to scramble characteristics of the radiation beam based on a modulation and / or randomization process.

[0123]

[0141] Although particular reference is made herein to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein has other applications, such as, for example, 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. In light of these alternative applications, those skilled in the art will recognize that the use of the terms "wafer" or "die" herein may be considered as specific examples of the more general terms "substrate" or "target portion", respectively. The substrates referred to herein may be processed, before or after exposure, for example in a track unit (a tool that typically applies a layer of resist to the substrate and develops the exposed resist) and / or a metrology unit. Where appropriate, the disclosure herein may be applied to these and other substrate processing tools. Furthermore, a substrate may be processed multiple times, for example to produce a multi-layer IC, and thus the term substrate as used herein may also refer to a substrate that already includes multiple processed layers.

[0124]

[0142] Although particular reference has been made above to the use of embodiments of the present disclosure in the field of optical lithography, it should be understood that the present disclosure may also be used in other applications, for example imprint lithography, depending on the context, and is not limited to optical lithography. In imprint lithography, a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device is imprinted into a layer of resist supplied to the substrate and the resist is cured by application of electromagnetic radiation, heat, pressure, or a combination thereof. The patterning device is then removed from the resist leaving a pattern in it once the resist has hardened.

[0125]

[0143] It is to be understood that the language or terminology herein is for purposes of description and not of limitation, and thus the terms or language of the present disclosure should be interpreted by one of ordinary skill in the art in light of the teachings herein.

[0126]

[0144] As used herein, terms such as "radiation" and "beam of radiation" can encompass all types of electromagnetic radiation, including, for example, ultraviolet (UV) radiation (e.g., with wavelengths λ of 365, 248, 193, 157, or 126 nm), extreme ultraviolet (EUV or soft x-ray) radiation (with wavelengths in the range of 5-20 nm, e.g., 13.5 nm), or hard x-ray operating below 5 nm, as well as matter beams such as ion beams or electron beams. Terms such as "light" and "illumination" can refer to non-material radiation (e.g., photons, UV, x-rays, etc.). Generally, radiation with wavelengths between about 400 and about 700 nm is considered visible radiation. Generally, radiation with wavelengths between about 780 and 3000 nm (or greater) is considered to be IR radiation. UV refers to radiation with wavelengths between about 100 and 400 nm. In lithography, the term "UV" also applies to wavelengths that can be generated by mercury discharge lamps, G-line 436 nm, H-line 405 nm, and / or I-line 365 nm. Vacuum UV or VUV (i.e. UV absorbed by gases) refers to radiation with wavelengths of about 100-200 nm. Deep UV (DUV) generally refers to radiation with wavelengths in the range of 126 nm to 428 nm, and in some embodiments, excimer lasers can generate DUV radiation for use in lithography equipment. It is to be understood that radiation with wavelengths in the range of, for example, 5-20 nm, refers to radiation in a particular wavelength band, at least a portion of which is in the range of 5-20 nm.

[0127]

[0145] It is understood that the "Description of the Invention" section is intended to be used to interpret the claims, rather than the "Summary" and "Abstract" sections. The "Summary" and "Abstract" sections may describe one or more exemplary embodiments as envisioned by the inventors, but cannot describe all exemplary embodiments, and are therefore not intended to limit the scope of the disclosure and the appended claims in any way.

[0128]

[0146] The present disclosure has been described above using functional building blocks that show implementation forms of specific functions and their relationships. In this specification, the boundaries of these functional building blocks are arbitrarily defined for the convenience of description. Alternative boundaries may be defined as long as the specific functions and their relationships are appropriately implemented.

[0129]

[0147] Although specific embodiments of the disclosure have been described above, it will be understood that the embodiments of the disclosure may be practiced otherwise than as described. The description is intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the disclosure as described without departing from the scope of the claims set forth below.

[0130]

[0148] The above description of specific embodiments fully discloses the general nature of the present disclosure, such that those skilled in the art can readily modify and / or adapt such specific embodiments to various applications without undue experimentation and without departing from the general concept of the present disclosure. Such adaptations and modifications are therefore intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0131]

[0149] The breadth and scope of 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. an optical device disposed about an axis of the system in a first plane and configured to receive scattered radiation from the target; reflecting devices disposed about the axis in at least a second plane, each of the reflecting devices configured to receive the scattered radiation from a corresponding one of the optical devices; a movable reflecting device disposed along the axis and configured to receive the scattered radiation from each of the reflecting devices; a detector configured to receive the scattered radiation from the movable reflecting device; A system comprising:

2. The system of claim 1 , wherein the optical devices are arranged in an array configuration symmetrical about the axis.

3. The system of claim 2 , wherein the array configuration is a ring or a polygon.

4. The system of claim 1 , wherein the first and second ones of the optical devices are disposed at equal optical distances relative to the movable reflecting device.

5. The system of claim 1 , wherein the movable reflecting device is further configured to direct a beam of radiation towards the target to generate the scattered radiation from the target.

6. The system of claim 1 , wherein the optical device is an objective configured to collect the scattered radiation for detection.

7. a first optical path is defined by a first target, an optical device and a reflecting device of the target, the optical device and the reflecting device; a second optical path is defined by a second target, an optical device and a reflecting device of the target, the optical device and the reflecting device; The movable reflective device directing a beam through the reflecting device towards the target; and operative to shift the beam between the first and second optical paths; The system of claim 1 further configured to:

8. The system comprises: aligning the first target and the optical device of the target and optical device; thereafter, generating relative movement between the target and an optical device to align the second target and the optical device of the target and optical device; and performing a measurement of the target based on the movable reflecting device shifting the beam between the first and second paths to limit the relative movement to be less than a distance between the first and second targets of the target; The system of claim 7 configured to:

9. The system of claim 8 , wherein the system is further configured to sequence the measurements of the target based on the actuation of the movable reflective device.

10. the measurement sequence includes aligning the first target and optical device of the target and optical device, followed by aligning the second target and optical device of the target and optical device; 8. The system of claim 7, further configured to complete the measurement sequence faster than an alternative measurement sequence that includes aligning a single optical device to the first target of the targets and then aligning the single optical device to the second target of the targets.

11. The system of claim 7 , wherein the movable reflecting device comprises a rotatable reflector configured to rotate into engagement with the first or second optical path.

12. The system of claim 7 , wherein the movable reflective device comprises a multi-faceted reflector configured to translate and / or rotate to engage the first or second optical paths.

13. The system of claim 7 , wherein the movable reflective device comprises a galvo configured to rotate into engagement with the first or second optical path.

14. a frequency of the actuating the movable reflective device is based on an inverse of a duration for performing the shifting of the beam; The system of claim 7 , wherein the movable reflective device is further configured to operate at a frequency that is greater than or equal to about 500 Hz.

15. The system of claim 7 , wherein based on a state of the movable reflecting device, the system is further configured to propagate the scattered radiation along the first optical path or the second optical path.

16. The system of claim 7 , wherein the first and second optical paths have approximately the same length.

17. 17. The system of claim 16, wherein an optical magnification associated with the first optical device of the optical devices is the same as an optical magnification associated with the second optical device of the optical devices.

18. a radiation source configured to generate the beam for directing along the axis towards the movable reflecting device; The system of claim 7 , wherein the movable reflecting device is further configured to direct the beam from the axis to the first optical path or from the axis to the second optical path.

19. The system of claim 1 , wherein the movable reflecting device is further configured to direct the scattered radiation toward the detector using the first optical path or using the second optical path.

20. The system of claim 1 , wherein the arrangement of the optical devices includes a gap between a first and second one of the optical devices.

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