Lithography Pre-Alignment Imaging Sensor with Integrated Coaxial Illumination

Abstract

A patterning device pre-alignment sensor system is disclosed. The system includes at least one illumination source configured to provide an incident beam along a normal direction toward the patterning device. The system further includes an objective lens group channel along the normal direction configured to receive a zero-order refracted beam from the patterning device. The system further includes a first optical reflector configured to redirect the zero-order refracted beam to form a first retro-reflected beam. The system further includes a first imaging lens group channel configured to transmit the first retro-reflected beam to a first optical sensor. The first optical sensor is configured to detect the first retro-reflected beam to determine a position characteristic of the patterning device.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS)

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 036,645, filed June 9, 2020, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to a pre-alignment imaging sensor with built-in coaxial illumination that can be used, for example, in a lithographic apparatus. [Background technology]

[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) or other devices designed to function. A patterning device, also called a mask or reticle, can then be used to generate a circuit pattern that is formed on an individual layer of the device designed to function. This pattern can be transferred onto a target portion (e.g. comprising part of one or several dies) on the substrate (e.g. a silicon wafer). The transfer of the pattern is typically 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. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion in one go, 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) while synchronously scanning the substrate parallel or anti-parallel to the given direction (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] The manufacture of devices, such as semiconductor devices, typically involves processing a substrate (e.g., a semiconductor wafer) using a number of manufacturing processes to form various features and often multiple layers of the device. Such layers and / or features are typically manufactured and processed using, for example, deposition, lithography, etching, chemical mechanical polishing, and ion implantation. Multiple devices can be manufactured into multiple dies on a substrate and then separated into individual devices. This device manufacturing process can be considered a patterning process. The patterning process includes a pattern transfer step, such as optical lithography and / or nanoimprint lithography using a lithography tool, to transfer a pattern to the substrate, and typically but optionally includes one or more associated pattern processing steps, such as developing a resist using a developer tool, baking the substrate using a bake tool, and etching the pattern using an etcher. Additionally, the patterning process includes one or more metrology processes.

[0005]

[0005] Metrology processes are used to monitor and / or control the process at various steps during a patterning process. For example, a metrology process may be used to measure one or more characteristics of a substrate, such as the relative position (e.g., registration, overlay, alignment, etc.) or dimensions (e.g., line width, critical dimension (CD), thickness, etc.) of features formed on a substrate during a patterning process, such that the performance of the patterning process can be determined from such one or more characteristics. If one or more characteristics are unacceptable (e.g., outside a predetermined range for such one or more characteristics), one or more variables of the patterning process can be designed or modified, for example, based on the measurements of the one or more characteristics, so that a substrate produced by the patterning process has an acceptable one or more characteristics.

[0006]

[0006] With the advancement of lithography and other patterning process technologies, the dimensions of functional elements have been shrinking over the past decades, while the amount of functional elements such as transistors per device is constantly increasing. Meanwhile, the requirements for accuracy in terms of overlay, critical dimension (CD), etc. are becoming more and more stringent. In the patterning process, errors such as overlay errors and CD errors inevitably occur. For example, imaging errors may arise from optical aberrations, heating of the patterning device, errors in the patterning device, and / or heating of the substrate, and may be characterized, for example, by overlay, CD, etc. Additionally or alternatively, errors may occur in other parts of the patterning process, such as etching, developing, baking, which may also be characterized, for example, by overlay, CD, etc. These errors may cause problems in the functioning of the device, including failure of the device to function or one or more electrical problems in a functioning device. It is therefore desirable to be able to characterize one or more of these errors and, further, to take steps to design, modify, control, etc., the patterning process to mitigate or minimize one or more of these errors.

[0007]

[0007] One such error that can occur involves the patterning device moving towards and with the corresponding patterning device electrostatic chuck. If the relative tilt of the patterning device and the patterning device electrostatic chuck is improper, such movement can potentially damage the patterning device or the chuck, or both. For example, variations in mechanical and positional tolerances of the patterning device can cause large corner impacts and unpredictable initial contact points with the electrostatic chuck, which can damage one or both of them.

[0008]

[0008] Furthermore, the relative tilt of the patterning device and / or damage caused as the tilted patterning device moves towards the electrostatic chuck can cause inaccuracies in the patterning process such that the circuits produced are damaged or may be malfunctioning. These errors can therefore contribute to additional costs due to equipment damage, inefficient processing, waste, and processing delays. Summary of the Invention

[0009]

[0009] Therefore, there is a need to provide a patterning device pre-alignment image sensor that protects the patterning device and electrostatic chuck during transfer operations and ensures patterning accuracy.

[0010] In some embodiments, a patterning device pre-alignment sensor system is disclosed that includes at least one illumination source configured to provide an incident beam along a normal direction toward a patterning device, an objective lens group channel along the normal direction configured to receive a zero order refracted beam from the patterning device, a first optical reflector configured to redirect the zero order refracted beam to form a first retro-reflected beam, and a first imaging lens group channel configured to transmit the first retro-reflected beam to a first optical sensor. The first optical sensor is configured to detect the first retro-reflected beam to determine a position characteristic of the patterning device.

[0011]

[0011] In some embodiments, the at least one illumination source includes a first illumination source disposed near the first reflector optical reflector and configured to emit an incident beam along the objective lens group channel.

[0012]

[0012] In some embodiments, the at least one illumination source includes a first illumination source positioned near the first imaging lens group channel, and the first imaging lens group channel includes a first source reflector configured to redirect incident light emitted from the first illumination source in a direction along the first imaging lens group channel.

[0013] In some embodiments, the first optical reflector includes a first beam splitter, and the system further includes a lower objective lens group channel configured to receive the zero order refracted beam from the first beam splitter, a second optical reflector configured to redirect the zero order refracted beam to form a second retro-reflected beam, and a second imaging lens group channel configured to transmit the second retro-reflected beam to a second optical sensor. The second optical sensor is configured to detect the second retro-reflected beam to determine another position feature of the patterning device.

[0014] In some embodiments, the first and second optical sensors are configured to detect the first and second retro-reflected beams to determine XY planar positional and rotational characteristics of the patterning device.

[0015]

[0015] In some embodiments, the at least one illumination source includes a first illumination source disposed near the second reflector optical reflector and configured to emit an incident beam along the lower objective lens group channel.

[0016] In some embodiments, the first illumination source simultaneously illuminates the first and second imaging lens group channels.

[0017]

[0017] In some embodiments, the at least one illumination source further includes a second illumination source positioned near the second reflector optical reflector and configured to emit an incident beam along the lower objective lens group channel, wherein the first illumination source and the second illumination source generate different wavelengths.

[0018] In some embodiments, the at least one illumination source includes a first illumination source disposed near the first imaging lens group channel and a second illumination source disposed near the second imaging lens group channel, the first imaging lens group channel includes a first light source reflector configured to redirect incident light emitted from the first illumination source in a first direction along the first imaging lens group channel, and the second imaging lens group channel includes a second light source reflector configured to redirect incident light emitted from the second illumination source in a second direction along the second imaging lens group channel.

[0019] In some embodiments, the first illumination source and the second illumination source produce different wavelengths.

[0020] In some embodiments, the system further comprises a third imaging lens group channel including a third optical reflector configured to redirect the zero order refracted beam to form a third retro-reflected beam and a collimator configured to focus the third retro-reflected beam onto a third optical sensor configured to detect the focused third retro-reflected beam to determine a relative tilt of the patterning device.

[0021]

[0021] In some embodiments, the at least one illumination source includes a first illumination source positioned near the second reflector optical reflector and configured to emit an incident beam along the lower objective lens group channel to simultaneously illuminate the first, second, and third image lens group channels.

[0022]

[0022] In some embodiments, the at least one illumination source further includes a second illumination source positioned near the second reflector optical reflector and configured to emit an incident beam along the lower objective lens group channel, wherein the first illumination source and the second illumination source generate different wavelengths.

[0023]

[0023] In some embodiments, the at least one illumination source includes a third light source generating a collimated beam, the collimated beam illuminating the patterning device, and the third optical sensor is configured to measure a relative tilt of the patterning device based on a displacement measurement between a focal point of the third optical sensor and a point generated by the focused third retro-reflected beam.

[0024] In some embodiments, the third optical sensor is a coaxial Kohler illumination source configured to provide uniform illumination of the patterning device.

[0025] In some embodiments, the third light source is disposed proximate to a third imaging lens group channel that includes a third light source reflector configured to redirect a collimated beam emitted from the third illumination source in a third direction along the third imaging lens group channel.

[0026] In some embodiments, the third light source is disposed in the objective lens group channel.

[0027] In some embodiments, the at least one illumination source includes a first illumination source disposed adjacent to the first imaging lens group channel, a second illumination source disposed adjacent to the second imaging lens group channel, and a third illumination source disposed adjacent to the third imaging lens group channel. In some embodiments, the first imaging lens group channel includes a first light source reflector configured to redirect incident light emitted from the first illumination source in a first direction along the first imaging lens group channel, the second imaging lens group channel includes a second light source reflector configured to redirect incident light emitted from the second illumination source in a second direction along the second imaging lens group channel, and the third imaging lens group channel includes a third light source reflector configured to redirect incident light emitted from the third illumination source in a third direction along the third imaging lens group channel.

[0028]

[0028] In some embodiments, the present disclosure also provides a lithographic apparatus comprising the disclosed patterning device pre-alignment sensor system.

[0029]

[0029] Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are described herein for illustrative purposes only. Based on the teachings contained herein, a person skilled in the art will be able to easily conceive further embodiments. [Brief description of the drawings]

[0030]

[0030] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate the invention and, together with the description, serve to further explain the principles of the invention and to enable those skilled in the art to make and use the invention.

[0031] [Figure 1]

[0031] FIG. 1 shows a schematic diagram of a reflective lithographic apparatus according to some embodiments. [Diagram 2]

[0032] 1 depicts a schematic diagram of a transmissive lithographic apparatus according to some embodiments; [Diagram 3]

[0033] 1 shows a detailed schematic diagram of a reflective lithographic apparatus according to some embodiments; [Figure 4]

[0034] 1 shows a schematic diagram of a lithographic cell according to some embodiments. [Diagram 5]

[0035] 1A-1D show schematic diagrams of various pre-alignment sensor systems according to various embodiments. [Figure 6] 1A-1C show schematic diagrams of various pre-alignment sensor systems according to various embodiments. [Figure 7] 1A-1C show schematic diagrams of various pre-alignment sensor systems according to various embodiments. [Figure 8] 1A-1C show schematic diagrams of various pre-alignment sensor systems according to various embodiments. [Figure 9] 1A-1C show schematic diagrams of various pre-alignment sensor systems according to various embodiments. [Figure 10] 1A-1C show schematic diagrams of various pre-alignment sensor systems according to various embodiments.

[0032]

[0036] The features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the drawings, in which like reference numerals identify corresponding elements throughout. In the drawings, like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Moreover, the leftmost digit(s) of a reference number generally identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout this disclosure should not be construed as drawings to scale. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033]

[0037] This specification discloses one or more embodiments incorporating the features of the present invention. The disclosed embodiment or embodiments are merely exemplary of the present invention. The scope of the present invention is not limited to the disclosed embodiment or embodiments. The present invention is defined by the claims appended hereto.

[0034]

[0038] References to the described embodiments, and to "one embodiment," "an embodiment," "exemplary embodiment," and the like, herein indicate that the described embodiment may include a particular feature, structure, or characteristic, but each embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that it is within the knowledge of one of ordinary skill in the art to implement such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0035]

[0039] Spatially relative terms such as "beneath," "below," "lower," "above," "on," "upper," and the like, may be used herein to facilitate describing the relationship of one element or feature to another element or features, as shown in the figures. The spatially relative terms are intended to encompass various orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.

[0036]

[0040] The term "about" as used herein refers to a given quantity value that may vary based on a particular technique. Based on a particular technique, the term "about" may refer to a given quantity value that may vary, for example, within 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0037]

[0041] 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 will be appreciated that such description is merely for convenience and that such operations may actually result from a computing device, processor, controller, or other device executing firmware, software, routines, non-transitory computer-readable instructions, etc.

[0038]

[0042] Before describing such embodiments in detail, it will be useful to provide an example environment in which embodiments of the invention may be implemented.

[0039]

[0043] Exemplary Lithography System

[0044] 1 and 2 show schematic diagrams of lithographic apparatus 100 and lithographic apparatus 200, respectively, according to some embodiments. In some embodiments, lithographic apparatus 100 and lithographic apparatus 200 each include an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. deep ultraviolet or extreme ultraviolet (EUV) radiation), 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) WT 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. As detailed herein, other configurations of the illuminator may be implemented for improved illumination and compactness of design.

[0040]

[0045] Lithographic apparatus 100 and 200 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 (e.g. comprising one or more dies) of a substrate W. In lithographic apparatus 100, the patterning device MA and projection system PS are reflective. In lithographic apparatus 200, the patterning device MA and projection system PS are transmissive.

[0041]

[0046] 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.

[0042]

[0047] 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 200, 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 and 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.

[0043]

[0048] The term "patterning device MA" as used herein 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 corresponds to a particular functional layer in a device being created in the target portion C, such as an integrated circuit.

[0044]

[0049] Patterning device MA may be transmissive (as in lithographic apparatus 200 of FIG. 2) or reflective (as in lithographic apparatus 100 of FIG. 1). 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 masks, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted 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.

[0045]

[0050] The term "projection system" PS can encompass any type of projection system including refractive, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate to the exposure radiation used or other factors such as the use of an immersion liquid or a vacuum on the substrate W. A vacuum environment may be used for EUV or electron beam radiation, as other gases may absorb too much radiation or electrons. Thus, a vacuum environment may be provided throughout the beam path using a vacuum wall and vacuum pumps.

[0046]

[0051] Lithographic apparatus 100 and / or lithographic apparatus 200 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 preparation steps may be performed on one or more other tables while one or more substrate tables WT are being used for exposure. In some circumstances, the additional tables may not be substrate tables WT.

[0047]

[0052] 1A and 1B, the illuminator IL receives a radiation beam from a radiation source SO. The source SO and the lithographic apparatus 100, 200 may be separate physical 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 200, and the radiation beam B is passed from the source SO to the illuminator IL by means of a beam delivery system BD (FIG. 2), which 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, 200, 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.

[0048]

[0053] The illuminator IL may include an adjuster AD (Figure 2) for adjusting the angular intensity distribution of the radiation beam. Typically, 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. Furthermore, the illuminator IL may include various other components (Figure 2), such as an integrator IN and a condenser CO. The illuminator IL may be used to adjust the radiation beam B so that it has a desired uniformity and intensity distribution in its cross-section.

[0049]

[0054] Referring to FIG. 1, 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 reflecting 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 various target portions C in the path of the radiation beam B) using a second positioner PW and a position sensor IF2 (e.g. an interferometric device, a linear encoder, or a capacitive sensor). Similarly, the patterning device (e.g. mask) MA can be accurately positioned with respect to the path of the radiation beam B using a first positioner PM and another position sensor IF1. The patterning device (e.g. mask) MA and substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0050]

[0055] Referring to Figure 2, 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. Having traversed 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 to the illumination system pupil IPU. A portion of the radiation arises from the intensity distribution in the illumination system pupil IPU and traverses the mask pattern without being subjected to diffraction at the mask pattern to create an image of the intensity distribution in the illumination system pupil IPU.

[0051]

[0056] Using the second positioner PW and a position sensor IF (e.g. an interferometric device, a linear encoder or a capacitive sensor), the substrate table WT can be accurately moved (e.g. to position various target portions C in the path of the radiation beam B). Similarly, the mask MA can be accurately positioned with respect to the path of the radiation beam B using the first positioner PM and a further position sensor (not shown in FIG. 2) (e.g. after mechanical retrieval from a mask library or during a scan).

[0052]

[0057] In some embodiments, movement of the mask table MT can be realized 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 can be realized 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 can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. The substrate alignment marks (as shown) occupy dedicated target portions, but they 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.

[0053]

[0058] The mask table MT and patterning device MA may be located inside a vacuum chamber. In that case, an in-vacuum robot IVR can 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 can be used for various transport operations, similar to the in-vacuum robot IVR. Both in-vacuum and ex-vacuum robots need to be calibrated to smoothly move any payload (e.g. a mask) to the fixed kinematic mount of the transfer station.

[0054]

[0059] The lithographic apparatus 200 may include a patterning device transport system. An example of a patterning device transport system is a patterning device exchange apparatus (V) that includes, for example, an in-vacuum robot IVR, a mask table MT, a first positioner PM, and other similar components for transporting and positioning a patterning device. The patterning device exchange apparatus V may be configured to transfer a patterning device between a patterning device carrier container and a processing tool (e.g., the lithographic apparatus 200).

[0055]

[0060] Lithographic apparatus 100 and 200 can be used in at least one of the following modes:

[0056]

[0061] 1. In step mode, the support structure (e.g. mask table) MT and substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam B is projected onto a target portion C in one go (i.e. a single static exposure), and the substrate table WT is then moved in the X and / or Y direction so that a different target portion C can be exposed.

[0057]

[0062] 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 velocity and direction of the substrate table WT relative to the support structure (e.g. mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0058]

[0063] 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. 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 is readily applicable to maskless lithography using a programmable patterning device, such as a programmable mirror array.

[0059]

[0064] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be employed.

[0060]

[0065] In some embodiments, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) radiation source. The EUV radiation source is configured to generate a beam of EUV radiation for EUV lithography. Typically, the EUV radiation source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV radiation source.

[0061]

[0066] FIG. 3 shows a lithographic apparatus 300 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. To generate EUV radiation, a very hot plasma 210 can be generated by a gas or vapor, such as Xe gas, Li vapor, or Sn vapor, emitting radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 can be generated, for example, by creating an at least partially ionized plasma by an electric discharge. For efficient radiation generation, a partial pressure of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor may be required. In some embodiments, an excited tin (Sn) plasma is provided to generate the EUV radiation.

[0062]

[0067] Radiation emitted by the high temperature plasma 210 is delivered 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 also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 as further illustrated herein includes at least a channel structure as known in the art.

[0063]

[0068] 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 off a grating spectral filter 240 and focused into a virtual source point IF. The virtual source point IF is commonly referred to as an intermediate focus, and the source collector arrangement is positioned such that the intermediate focus IF is at or near the opening 219 of the closure structure 220. The virtual source point IF is an image of the radiation emitting plasma 210. The grating spectral filter 240 is used in particular to suppress infrared (IR) radiation.

[0064]

[0069] The radiation then traverses an 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, which is held by the support structure MT, a patterned beam 226 is formed which is imaged by the projection system PS via reflective elements 228, 230 onto a substrate W held by a wafer stage or substrate table WT.

[0065]

[0070] In general, there may be more elements in the illumination optics unit IL and projection system PS than are shown. A grating spectral filter 240 may optionally be present depending on the type of lithographic apparatus. Furthermore, there may be more mirrors than are shown in the drawings, for example there may be one to six additional reflective elements in the projection system PS compared to those shown in FIG. 2.

[0066]

[0071] 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). Grazing incidence reflectors 253, 254, and 255 are arranged axially symmetrically about optical axis O, and this type of collector optic CO is suitable for use in combination with a discharge produced plasma source, often referred to as a DPP source.

[0067]

[0072] Exemplary Lithography Cell

[0073] FIG. 4 shows a schematic diagram of a lithography cell 300, sometimes referred to as a lithocell or cluster. The lithography apparatus 100 or 200 may form part of the lithography cell 400. The lithography cell 300 may also include apparatus for performing pre-exposure and post-exposure processes on the 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 various process apparatus, and then delivers them to a loading bay LB of the lithography apparatus. These devices are often collectively referred to as a track, and are under the control of a track control unit TCU. The TCU is itself controlled by a supervisory control system SCS. The SCS also controls the lithography apparatus via a lithography control unit LACU. These various apparatus can thus be operated to maximize throughput and processing efficiency.

[0068]

[0074] Exemplary embodiments of a pre-alignment system

[0075] FIG. 5 shows a schematic diagram of a pre-alignment system 500 for measuring the X-position, Y-position and Rx-positioning of a patterning device with built-in coaxial illumination, according to some embodiments.

[0069]

[0076] In one embodiment, the pre-alignment system 500 can be a patterning device (e.g., reticle) pre-alignment system that includes a coaxial illumination source 518 and a single-path sensory system 502. In some embodiments, the coaxial illumination source 518 can be an LED or a laser-produced plasma and can be configured to provide an incident beam along a normal direction toward the patterning device 516. The single-path sensory system 502 can include an objective lens group 512 that forms an object light path (or objective lens group channel) and an imaging lens group 514 that forms an image light path (or imaging lens group channel). It will be understood that the terms optical system, lens system, lens group, light path, light path, and lens channel can be used interchangeably herein.

[0070]

[0077] In some embodiments, once the presence of the patterning device 516 is detected, the pre-alignment system 500 can illuminate the patterning device to perform the necessary inspection measurements. As shown in Figure 5, the pre-alignment system 500 can include a coaxial illumination source 518 that is coaxial with the objective lens group 512 and configured to provide illumination and an incident beam 520 to the patterning device 516. For example, the incident beam 520 from the coaxial illumination source 518 can pass through an optical reflector (e.g., a mirror, beam splitter, etc.) 510 and the object light path group 512 to illuminate the patterning device 516.

[0071]

[0078] Incident beam 520 may undergo reflection, diffraction, scattering, etc. from the patterning device to generate a zeroth diffraction order beam 522 and ±1st diffraction order beams 524. The generated zeroth diffraction order beam 522 may pass through objective lens group 512 and then be reflected by reflector 510 to form a retroreflected beam.

[0072]

[0079] The retro-reflected beam may pass through imaging lens group 514 and reach photodetector (or sensor) 508. Photodetector 508 and reflector 510 are positioned at opposite ends of imaging lens group 514, respectively. As shown in FIG. 5, optical reflector 510 is disposed between objective lens group 512 and imaging lens group 514 and reflects a zeroth order diffracted beam 522 from the illuminated patterning device to form a retro-reflected beam towards photodetector 508.

[0073]

[0080] The photodetectors 508 may be formed of a sensor or a sensor array, which may be capacitive or include one or more planar electrodes. Each sensor or array may be optical and may include a photodetector such as a photodiode (e.g., a quadrant avalanche photodiode, etc.). The photodetectors 508 may be configured to detect the retro-reflected beam to measure the XY position of the patterning device and the orientation of the patterning device (e.g., the Rz orientation).

[0074]

[0081] In some embodiments, the patterning device transport apparatus (e.g., patterning device exchange apparatus V in FIG. 2) may be configured to minimize patterning device / reticle exchange time and particle generation, and to reduce contact forces or stresses from a patterning device, such as a chuck and / or patterning device 516. The patterning device exchange apparatus V may also increase the overall throughput of a patterning device exchange process, for example in lithographic apparatus LA.

[0075]

[0082] In some existing pre-alignment systems, a set of illuminators are arranged in an oblique illumination scheme to project the incident beam onto the patterning device. In response to the illumination, the first order diffracted beam is collected by the objective lens group. That is, the set of illuminators are laid out at an angle equal to the diffraction angle 526 between the zeroth and first order diffracted beams. Most of the energy of the refracted light (e.g., more than about 99%) constitutes the zeroth order beam 522. Therefore, when using an oblique illumination scheme, multiple light sources are used to ensure that the intensity of the first order diffracted beam is large enough to be detected by a photodetector or sensor. For example, an existing EUV pre-alignment sensor utilizes four light emitting diodes (LEDs). By using the disclosed coaxial illumination, only one LED can be used to provide sufficient intensity to detect the zeroth order diffracted beam, since the zeroth order diffracted beam from the target is collected by the objective lens group for detection purposes.

[0076]

[0083] It should be noted that the coaxial illumination source may be mounted at different locations in the pre-alignment system depending on the desired size and performance considerations of the pre-alignment system. For example, FIG. 6 shows a schematic diagram of a pre-alignment sensor 600 that uses coaxial illumination to measure the X-position, Y-position, and Rx-position of a patterning device according to some other embodiments. The pre-alignment sensor 600 may be similar in configuration and components to the pre-alignment sensor 500, except that the coaxial illumination source 638 is located closer to the imaging lens group 514. The light source reflector 630 is configured to reflect the illumination beam generated from the coaxial illumination source 638 in the direction of the optical axis of the imaging lens group 514 (horizontal as shown in FIG. 6).

[0077]

[0084] In some embodiments, a coaxial illumination source can be used to simultaneously illuminate multiple optical channels / paths (e.g., an upper light path and one of multiple lower light paths) for imaging and / or other applications. Figure 7 shows a schematic diagram of a pre-alignment sensor 700 that uses built-in coaxial illumination to measure the X-position, Y-position, and Rx-positioning of a patterning device, according to some other embodiments.

[0078]

[0085] In one embodiment, the pre-alignment system 700 can be a patterning device (e.g., reticle) pre-alignment system that includes a coaxial illumination source 718 and a multi-path sensing array 702 that includes multiple lens groups. For example, in one embodiment, the multi-path sensing array 702 includes a common object light path 726, a lower object light path 728, an upper image light path 704, and a lower image light path 706.

[0079]

[0086] In some embodiments, once the presence of patterning device 516 is detected, pre-alignment system 700 can illuminate the patterning device to perform the necessary inspection measurements. As shown in FIG. 7, pre-alignment system 700 can include a coaxial illumination source 718 that is coaxial with a common object light path 726 and a lower object light path 728 and configured to provide an illumination and incident beam 520 to patterning device 516.

[0080]

[0087] For example, incident beam 520 from coaxial illumination source 518 can illuminate patterning device 516 through a lower object beam path 728 and a common object beam path 726 .

[0081]

[0088] Incident beam 520 may undergo reflection, diffraction, scattering, etc. from the patterning device to generate a zeroth diffraction order beam 522 and ±1st diffraction order beams 524. The generated zeroth diffraction order beam 522 may pass through a common object beam path 726 and a lower object beam path 728 and be reflected by upper reflector 710 and lower reflector 712 to form two retro-reflected beams.

[0082]

[0089] The upper beam splitter 710 can split the received zero-order diffracted beam into two beams, of which the first beam can be directed to the upper photodetector 708 and the second beam can be directed towards the lower image light path 706. The lower image light path 706 can include a lower beam splitter or a mirror 712 (depending on whether an additional lower channel is utilized). The two retro-reflected beams can travel through the upper image light path 704 and the lower image light path 706, respectively, to reach the upper photodetector 708 and the lower photodetector 714. The upper photodetector 708 and the upper reflector 710 are positioned at opposite ends of the upper image lens group 704, respectively. The lower photodetector 714 and the lower reflector 712 are positioned at opposite ends of the lower image lens group 706, respectively.

[0083]

[0090] Each of the upper photodetector 708 and the lower photodetector 714 may be formed of a sensor or sensor array that may be capacitive or include one or more planar electrodes. Each sensor or array may be optical and may include a photodetector such as a photodiode (e.g., a quadrant avalanche photodiode, etc.). As shown in FIG. 7, the upper reflector 710 is positioned between the common objective lens group 726 and the upper imaging lens group 704 and configured to redirect a portion of the zeroth order diffracted beam 522 toward the upper photodetector 708. Similarly, the lower reflector 712 is positioned between the lower objective lens group 728 and the lower imaging lens group 706 and configured to redirect a portion of the zeroth order diffracted beam 522 toward the lower photodetector 714.

[0084]

[0091] In some embodiments, the pre-alignment system 700 measures the patterning device position offset utilizing a two-channel configuration as illustrated in Figure 7. For example, the pre-alignment system 700 can utilize an upper image light path 704 and a lower image light path 706 to measure the XY position of the patterning device and the orientation (e.g., Rz orientation) of the patterning device.

[0085]

[0092] In some embodiments, the upper image light path 704 and the lower image light path 706 can be set up in different configurations to measure different properties of the reflected beam. For example, when the patterning device 516 is illuminated, the incident light can be reflected (or refracted in this example) and partially modified by the pattern seen on the patterning device. Upon receiving the refracted beam, the upper image light path 704 and the lower image light path 706 receive the same beam signal and can analyze and measure different optical properties of the patterning device 516 depending on their setup.

[0086]

[0093] In one example, the upper image light path 704 can receive a beam and project an image of the patterning device onto an upper photodetector 708 for processing the image of the patterning device and measuring the X and Y position of the patterning device by detecting device markers on the patterning device. Additionally, the upper photodetector 708 can be configured as a barcode reader and configured to read a barcode in the patterning device image to identify the patterning device. Similarly, the lower image light path 706 can receive a beam and project an image of the patterning device onto a lower photodetector 714 for inverting the image of the patterning device to measure different alignment and / or positioning attributes. It should be noted that the upper image light path 704 and the lower image light path 706 may be configured to perform other optical measurements of the patterning device image along with their sensors.

[0087]

[0094] As mentioned above, in existing oblique illumination schemes, multiple light sources are positioned at angles designed to meet the diffraction requirements imposed by the 2D diffraction grating formed on the elements of the alignment mark. In this regard, the illuminator tilt angle may be specific to the illumination wavelength used and the grating period of the alignment mark features in the patterning device. Because a two-channel or multi-channel configuration may require different wavelengths to measure different properties of the reflected beam, existing oblique illumination schemes require more light sources to be positioned at different angles designed to meet different diffraction requirements based on the different wavelengths of the reflected beam. For example, an existing EUV pre-alignment sensor may use eight light emitting diodes (LEDs) in a two-channel configuration.

[0088]

[0095] The use of the disclosed coaxial illumination can help reduce the complexity of the illumination source setup in oblique illumination. In some embodiments, the coaxial illumination source 718 can be used to simultaneously illuminate all optical channels / paths (e.g., the upper light path and one of the lower light paths) for imaging and / or other applications. For example, different light sources using different wavelengths can be mounted in the same location coaxial with a common objective lens group 726 and lower objective lens group 728. This can provide additional advantages to coaxial illumination, including ease of mounting and alignment of the illuminator, independence from illumination wavelength, ease of illuminator replacement, possibility of using a single illuminator for both channels, and uniformity of illumination.

[0089]

[0096] It should also be noted that coaxial illumination sources using different wavelengths may be mounted separately at different positions in the pre-alignment system depending on considerations regarding the desired size and performance of the pre-alignment system. For example, FIG. 8 shows a schematic diagram of a pre-alignment sensor 800 using coaxial illumination to measure the X-position, Y-position, and Rx-position of a patterning device according to some other embodiments. The pre-alignment sensor 800 may be similar in configuration and components to the pre-alignment sensor 700, except that two separate coaxial illumination sources 818 and 828 may be located near the upper imaging lens group 704 and the lower imaging lens group 706, respectively. The coaxial illumination sources 818 and 828 may have different wavelengths. The upper light source reflector 823 may be configured to reflect the illumination beam generated from the upper coaxial illumination source 828 toward the optical axis of the upper imaging lens group 704. The lower light source reflector 813 is configured to reflect the illumination beam generated from the lower coaxial illumination source 818 towards the optical axis of the lower imaging lens group 706 .

[0090]

[0097] In some embodiments, the multi-path sensing array may include even more optical paths that may be provided to measure various characteristics and / or attributes of the patterning device image. FIG. 9 shows a schematic diagram of a pre-alignment system 900 including a collimated optical branch as a level sensor, according to some embodiments. As mentioned above, patterning device level alignment (in X and Y directions) is important in the patterning device transfer stage of lithography. An unlevel or misaligned patterning device may be damaged, for example, during transfer to the electrostatic chuck. Such misalignment may also lead to damage to the electrostatic chuck itself, resulting in additional costs and processing delays. Furthermore, such damage may affect the accuracy of the lithography process. Thus, the pre-alignment system 700 shows a schematic diagram of a multi-channel (e.g., multi-branch, multi-optical path) system for measuring the position, orientation, and tilt of a patterning device in a compact and efficient design, as described further herein.

[0091]

[0098] In some embodiments, the pre-alignment system 900 includes a three-channel (branch) detector array incorporating an additional detector array channel 902 relative to the pre-alignment systems described in Figures 8 and 9. The detector array channel 902 can be configured as a collimated channel by including a collimator 904 within the channel. The detector array channel 902 can be interchangeably referred to as a collimated light path 902. In some embodiments, the collimated light path 902 can include a coaxial illumination source 906 coupled to a beam splitter 908. The coaxial illumination source 906 provides incident illumination to the patterning device 516. Once illuminated, the patterning device 516 can reflect and / or refract the beam, thereby providing a zero order refracted beam 910.

[0092]

[0099] In some embodiments, the coaxial illumination may be a Kohler illumination, which acts to generate uniform illumination while ensuring that an image of the illumination source is not visible in the generated image. For example, Kohler illumination may act to generate uniform illumination of an object such as a patterning device or reticle while ensuring that an image of the illumination source is not visible in the generated image. Kohler coaxial illumination may provide the additional benefit of reducing glare and non-uniform illumination, which reduces interference with the generated patterning device image since the illumination source is not visible.

[0093]

[0100] In some embodiments, the zero order refracted beam 910 is split by a beam splitter 912 and projected to (a) the lower sensing array path 702 (for measuring patterning device positioning and Rx) and (b) a collimator 904 in the collimated light path 902. Upon receiving the retro-reflected beam reflected from the beam splitter 912, the collimator 904 provides a collimated beam 914 that is projected to a light sensor, such as detector 716.

[0094]

[0101] According to one embodiment, the multi-path sensing array may include a combination of a collimated light path 902 and a lower multi-path sensing array (e.g., sensing array 702 including upper light path 704 and lower light path 706). Such a combination provides performance and packaging advantages. For example, combining a collimated light path 902 designed to detect a level gauge of the patterning device and also measure the patterning device tilt with a multi-path sensing array 702 (which processes the patterning device image) provides simple packaging that separates the interferometric measurements. This implementation allows for the combination of measurements of the collimated light signal and the patterning device image data properties in a single pre-alignment sensor device that incorporates compact packaging and performing multiple measurements of the patterning device.

[0095]

[0102] In one example, the pre-alignment system 900 can be configured to use the collimated light path 902 simultaneously with either of the two lower light paths, which can reduce measurement time, processing power usage, processing capacity, etc. by extracting data only from sensors associated with the light path.

[0096]

[0103] FIG. 10 shows a schematic diagram of a pre-alignment system 1000 including a collimated light branch and an illuminator block below the level sensor, according to some embodiments. In some embodiments, the modular configuration of the pre-alignment system 1000 allows the coaxial illumination source 1006 to be placed in various positions based on the size requirements of the pre-alignment system itself and the multi-channel / multi-path configuration. For example, the illuminator can be placed in a common space belonging to two or more channels (light paths). This results in a minimum number of optical elements between the light source and the patterning device, thus reducing light loss. Furthermore, the illuminator can benefit from the additional space provided in the common space.

[0097]

[0104] In some embodiments, the coaxial illumination source 1006 can be implemented as the only illumination source for the entire pre-alignment system 1000. This configuration may provide additional benefits such as modular compactness and uniform illumination of the patterning device sample. Alternatively, the coaxial illumination source 1006 may be implemented as the illumination source for the collimated light path 902, and a different coaxial illumination source / mechanism (e.g., coaxial illumination sources 718, 818, 828 as shown in Figures 7 and 8) may be implemented for the lower branch (e.g., multi-path sensing array 702). In some embodiments, the patterning device can be positioned at various distances from the sensor without requiring assembly adjustments to the sensor. This provides an additional benefit with the coaxial illumination source 1006, as no additional illumination / sensor adjustments are required (as would typically be required with an external / oblique illumination source).

[0098]

[0105] In an exemplary embodiment, when the coaxial illumination source 1006 is activated, an incident beam is projected onto the beam splitter 1018. The beam splitter 1018 splits the incident light into an upward direction toward the collimated light path 902 and the patterning device 516 and a downward direction toward the multipath sensing array 702. The collimated light path 902 first receives the incident light and projects a collimated image of the light source as a reference point (first point) onto the detector 916. When the incident light is reflected from the patterning device 516, a zero order reflected beam is projected back onto the beam splitter 912 and then onto the collimated light path 902 and the multipath sensing array 702.

[0099]

[0106] As mentioned above, the combination of the multipath sensing array 702 and the collimated light path 902 allows the pre-alignment system 1000 to perform various measurements necessary for alignment and transfer of the patterning device. To this end, in one embodiment, the beam splitter 912 projects the received patterning device image onto the collimated light path 902 and the multipath sensing array 702. At this point, the collimated light path 902 collimates the received image and projects it as a collimated beam (e.g., a second point) onto the detector 916. In response, the sensor 916 then measures the relative tilt of the patterning device by measuring the difference (the offset distance) between the first point and the second point. A description of the operation of the sensor 916 is described further below in this specification. Because the collimated image is collimated to only one projected point, the content of the image is not relevant to the measurement made by the detector 916.

[0100]

[0107] As mentioned above, existing EUV reticle pre-alignment sensors use tilted illumination schemes that can have several drawbacks. For example, multiple LEDs tilted at an angle design are required to meet the diffraction requirements imposed by the 2D diffraction grating formed on the alignment mark elements. Multiple illumination LEDs are mounted with high precision, placing undue strain on mechanical design and alignment. Furthermore, since the illumination tilt angle is specific to the wavelength used and the grating period of the alignment mark features, changing the illumination wavelength may require mechanical redesign and / or changes to the feature's diffraction pattern. Further drawbacks include challenges associated with mounting additional illuminator sets for multi-channel systems and difficulties in maintaining illumination uniformity.

[0101]

[0108] The pre-alignment sensor described herein replaces oblique illumination with built-in coaxial illumination, resulting in a compact design and improved accuracy in patterning device measurements. Such built-in coaxial illumination configurations can be applied to single-branch, two-branch, or multi-branch pre-alignment sensor systems. As discussed above in connection with Figures 5 through 10, the placement of one or more coaxial illuminators can be selected depending on the mechanical layout of the available space.

[0102]

[0109] Advantages of the disclosed built-in coaxial illumination scheme include, but are not limited to, ease of mounting and alignment of the illuminator, independence from illumination wavelength, ease of illuminator replacement, use of a single illuminator in two or more branches of a multi-channel pre-alignment sensor, improved illumination uniformity, etc. Furthermore, the bright field illumination of the disclosed coaxial illumination configuration allows for more efficient utilization of the dynamic range of the sensor. Thus, erroneous features on the patterning device appear bright and blend with the background, and can be easily removed by image processing. Furthermore, replacing the oblique illumination with built-in coaxial illumination removes the oblique illuminator from the object space (near the reticle), making the space occupied by the oblique illuminator available for additional sensors, such as proximity sensors, tilt sensors, and other sensors, or combinations thereof.

[0103]

[0110] It should also be noted that in some embodiments of the present disclosure, different wavelength illuminators can be used in different branches of a multi-channel pre-alignment sensor system to measure different characteristics of the patterning device, and it is also possible to use different wavelength illuminators in a single branch of a multi-channel pre-alignment sensor system for improved reliability.

[0104]

[0111] In particular, the coaxial Kohler illumination, combined with a collimated channel acting as a level detector, serves two main functions: improving the illumination technique and providing a measurement channel for detecting patterning device tilt. For a more compact and modular design, the coaxial Kohler illumination source may be integrated within the measurement channel. Furthermore, the illumination provided by the Kohler coaxial illumination source may be used as a common illumination source for a multi-channel system, which offers advantages such as modular compactness, uniform illumination of the sample patterning device, reduced image artifacts, and high contrast. Furthermore, the common illumination source approach simplifies the system design and allows for a modular design of the pre-alignment system. Such a modular design allows for the inclusion of additional modular channels to perform other measurements of the patterning device while maintaining compactness and accuracy.

[0105]

[0112] The embodiments may be further described using the following clauses. 1. At least one illumination source configured to provide an incident beam along a normal direction towards a patterning device; an objective lens group channel along a normal direction configured to receive a zeroth order refracted beam from the patterning device; a first optical reflector configured to redirect the zero-order refracted beam to form a first retro-reflected beam; a first imaging lens group channel configured to transmit the first retro-reflected beam to a first photosensor; a first optical sensor configured to detect the first retro-reflected beam to determine a position characteristic of the patterning device; Patterning device pre-alignment sensor system. 2. The system described in clause 1, wherein the at least one illumination source includes a first illumination source positioned near the first reflector optical reflector and configured to emit an incident beam along the objective lens group channel. 3. The at least one illumination source includes a first illumination source disposed near the first imaging lens group channel; The system of claim 1, wherein the first image lens group channel includes a first light source reflector configured to redirect incident light emitted from the first illumination source in a direction along the first image lens group channel. 4. The first optical reflector includes a first beam splitter; The system further comprises: a lower objective lens group channel configured to receive the zero order refracted beam from the first beam splitter; a second optical reflector configured to redirect the zero-order refracted beam to form a second retroreflected beam; a second imaging lens group channel configured to transmit the second retro-reflected beam to a second photosensor; The system of clause 1, wherein a second optical sensor is configured to detect the second retro-reflected beam to determine another position characteristic of the patterning device. 5. The system of claim 4, wherein the first and second optical sensors are configured to detect the first and second retro-reflected beams to determine XY planar positional and rotational characteristics of the patterning device. 6. The system described in clause 4, wherein the at least one illumination source includes a first illumination source positioned near the second reflector optical reflector and configured to emit an incident beam along the lower objective lens group channel. 7. The system of claim 6, wherein the first illumination source simultaneously illuminates the first and second imaging lens group channels. 8. The at least one illumination source further includes a second illumination source disposed near the second reflector optical reflector and configured to emit an incident beam along the lower objective lens group channel; 7. The system of claim 6, wherein the first illumination source and the second illumination source generate different wavelengths. 9. At least one illumination source is a first illumination source disposed proximate the first imaging lens group channel; a second illumination source disposed proximate the second imaging lens group channel; the first imaging lens group channel includes a first light source reflector configured to redirect incident light emitted from a first illumination source in a first direction along the first imaging lens group channel; The system described in clause 4, wherein the second image lens group channel includes a second light source reflector configured to redirect incident light emitted from the second illumination source in a second direction along the second image lens group channel. 10. The system of claim 9, wherein the first illumination source and the second illumination source generate different wavelengths. 11. A third optical reflector configured to redirect the zeroth order refracted beam to form a third retroreflected beam; a third imaging lens group channel including a collimator configured to focus the third retro-reflected beam onto a third photosensor; 5. The system of claim 4, wherein a third optical sensor is configured to detect the focused third retro-reflected beam to determine a relative tilt of the patterning device. 12. The system described in clause 11, wherein the at least one illumination source includes a first illumination source positioned near the second reflector optical reflector and configured to emit an incident beam along the lower objective lens group channel to simultaneously illuminate the first, second, and third image lens group channels. 13. At least one illumination source is a second illumination source disposed near the second reflector and configured to emit an incident beam along the lower objective lens group channel; 13. The system of claim 12, wherein the first illumination source and the second illumination source generate different wavelengths. 14. The at least one illumination source includes a third light source generating a collimated beam; The collimated beam illuminates a patterning device. The system of claim 12, wherein the third optical sensor is configured to measure a relative tilt of the patterning device based on a displacement measurement between a focal point of the third optical sensor and a point generated by the focused third retro-reflective beam. 15. The system of claim 14, wherein the third optical sensor is a coaxial Kohler illumination source configured to provide uniform illumination of the patterning device. 16. A third light source is disposed near the third imaging lens group channel; The system described in clause 14, wherein the third image lens group channel includes a third light source reflector configured to redirect a collimated beam emitted from the third illumination source in a third direction along the third image lens group channel. 17. The system of claim 14, wherein the third light source is disposed within the objective lens group channel. At least one illumination source is a first illumination source disposed adjacent to the first imaging lens group channel; a second illumination source disposed adjacent to the second imaging lens group channel; a third illumination source disposed adjacent to the third imaging lens group channel; the first imaging lens group channel includes a first light source reflector configured to redirect incident light emitted from a first illumination source in a first direction along the first imaging lens group channel; the second imaging lens group channel includes a second light source reflector configured to redirect incident light emitted from a second illumination source in a second direction along the second imaging lens group channel; The system described in clause 11, wherein the third image lens group channel includes a third light source reflector configured to redirect incident light emitted from a third illumination source in a third direction along the third image lens group channel. 19. At least one illumination source configured to provide an incident beam along a normal direction towards a patterning device; an objective lens group channel along a normal direction configured to receive a zeroth order refracted beam from the patterning device; a first optical reflector configured to redirect the zero order refracted beam to form a first retroreflected beam; a first imaging lens group channel configured to transmit the first retro-reflected beam to a first photosensor; a first optical sensor configured to detect the first retro-reflected beam to determine a position characteristic of the patterning device; Lithography equipment. 20. The patterning device pre-alignment sensor system further comprises: a lower objective lens group channel configured to receive the zero order refracted beam from the first optical reflector; a second optical reflector configured to redirect the zero-order refracted beam to form a second retroreflected beam; a second imaging lens group channel configured to transmit the second retro-reflected beam to a second photosensor; 20. A lithographic apparatus according to clause 19, wherein a second optical sensor is configured to detect the second retro-reflected beam to determine another position characteristic of the patterning device. 21. Patterning device pre-alignment sensor system a third optical reflector configured to redirect the zeroth order refracted beam to form a third retroreflected beam; a third imaging lens group channel including a collimator configured to focus the third retro-reflected beam onto a third photosensor; 21. The lithographic apparatus of clause 20, wherein the third optical sensor is configured to detect the focused third retro-reflected beam to determine a relative tilt of the patterning device.

[0106]

[0113] 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 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 synonymous with the more general terms "substrate" or "target portion", respectively. The substrates described herein may be processed, before or after exposure, for example in a track (a tool that typically applies a layer of resist to the substrate and develops the exposed resist), a metrology tool, and / or an inspection tool. Where appropriate, the disclosure herein may be applied to these and other substrate processing tools. Furthermore, the 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.

[0107]

[0114] Although particular reference has been made to the use of embodiments of the invention in the field of optical lithography, it should be understood that the invention may also be used in other fields, 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.

[0108]

[0115] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, and thus, the terminology or terminology herein should be interpreted by one of skill in the art in light of the teachings herein.

[0109]

[0116] In the embodiments described herein, the terms "lens" and "lens element", where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

[0110]

[0117] Furthermore, the terms "radiation", "beam" and "light" as used herein include any type of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength λ of 365, 248, 193, 157 or 126 nm), extreme ultraviolet (EUV or soft x-ray) radiation (e.g., having a wavelength in the range of 5-20 nm, e.g., 13.5 nm), or hard x-ray operating below 5 nm, as well as ion beams or particulate beams such as electron beams. Generally, radiation having a wavelength between about 400 and about 700 nm is considered visible radiation. Radiation having a wavelength between about 780 and about 3000 nm (or greater) is considered IR radiation. UV refers to radiation having a wavelength between about 100 and 400 nm. In lithography, the term "UV" also commonly applies to wavelengths that can be produced by mercury discharge lamps, i.e., G-line at 436 nm, H-line at 405 nm, and / or I-line at 365 nm. Vacuum UV, or VUV (i.e., UV absorbed by gases), refers to radiation having a wavelength of approximately 100-200 nm. Deep UV (DUV) generally refers to radiation having a wavelength in the range of 126 nm to 428 nm, and in some embodiments, excimer laser devices can generate DUV for use in lithography tools. For example, it should be recognized that radiation having a wavelength in the range of 5-20 nm refers to radiation having at least a certain band of wavelengths in the range of 5-20 nm.

[0111]

[0118] The term "substrate" as used herein describes a material onto which a layer of material is added. In some aspects, the substrate itself may be patterned, and the material added onto it may also be patterned or may remain unpatterned.

[0112]

[0119] Although specific reference may be made herein to the use of the apparatus and / or system in the manufacture of ICs, it should be explicitly understood that such an apparatus and / or system has many other possible applications, such as in integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, LCD panels, thin film magnetic heads, etc. In light of these alternative applications, those skilled in the art will recognize that any use of the terms "patterning device," "reticle," "wafer" or "die" herein may be considered synonymous with (or interchangeable with) the more general terms "mask," "substrate," and "target portion," respectively.

[0113]

[0120] Although specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described and that these descriptions are not intended to limit the invention.

[0114]

[0121] 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 of the invention as envisioned by the inventors, but cannot describe all exemplary embodiments, and thus are not intended to limit the scope of the invention and the appended claims in any way.

[0115]

[0122] The present invention has been described above using functional components and their relationships that illustrate the implementation of specific functions. The boundaries of these functional components are arbitrarily defined in this specification for the convenience of description. Alternative boundaries can be defined as long as the specific functions and their relationships are appropriately performed.

[0116]

[0123] The foregoing description of specific embodiments fully discloses the overall nature of the present invention, such that those skilled in the art can, without undue experimentation, readily modify and / or adapt such specific embodiments to various applications without departing from the general concept of the present invention. Accordingly, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0117]

[0124] The breadth and scope of the present invention 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. at least one illumination source configured to provide an incident beam along a normal direction towards the patterning device; an objective lens group channel along the normal direction configured to receive a zero order refracted beam from the patterning device; a first optical reflector configured to redirect the zero-order refracted beam to form a first retroreflected beam, the first optical reflector including a first beam splitter; a first imaging lens group channel configured to transmit the first retro-reflected beam to a first photosensor; a lower objective lens group channel configured to receive the zero order refracted beam from the first beam splitter; a second optical reflector configured to redirect the zero-order refracted beam to form a second retroreflected beam; a second imaging lens group channel configured to transmit the second retro-reflected beam to a second photosensor; a third optical reflector configured to redirect the zeroth order refracted beam to form a third retroreflected beam; a third imaging lens group channel including a collimator configured to focus the third retro-reflected beam onto a third photosensor; the at least one illumination source includes a first illumination source generating a collimated beam; the collimated beam illuminates the patterning device; the first optical sensor is configured to detect the first retro-reflected beam to determine a position characteristic of the patterning device; the second optical sensor is configured to detect the second retro-reflected beam to determine another position characteristic of the patterning device; the third optical sensor is configured to measure a relative tilt of the patterning device based on a displacement measurement between a focal point of the third optical sensor and a point generated by the focused third retro-reflected beam. Patterning device pre-alignment sensor system.

2. 10. The system of claim 1, wherein the at least one illumination source includes a second illumination source disposed proximate the first optical reflector and configured to emit the incident beam along the objective lens group channel.

3. the at least one illumination source includes a third illumination source disposed proximate the first imaging lens group channel; 2. The system of claim 1, wherein the first imaging lens group channel includes a first light source reflector configured to redirect the incident beam emitted from the third illumination source in a direction along the first imaging lens group channel.

4. 2. The system of claim 1, wherein the first and second optical sensors are configured to detect the first and second retro-reflected beams to determine XY planar positional and rotational characteristics of the patterning device.

5. the at least one illumination source includes a fourth illumination source disposed proximate the second imaging lens group channel; 4. The system of claim 3, wherein the second imaging lens group channel includes a second source reflector configured to redirect the incident beam emitted from the fourth illumination source in a second direction along the second imaging lens group channel.

6. The system of claim 5 , wherein the third illumination source and the fourth illumination source produce different wavelengths.

7. 2. The system of claim 1, wherein the first illumination source is configured to emit the incident beam along the lower objective lens group channel to simultaneously illuminate the first, second, and third image lens group channels.

8. The system of claim 1 , wherein the first illumination source is a coaxial Kohler illumination source configured to provide uniform illumination of the patterning device.

9. the first illumination source is disposed proximate the third imaging lens group channel; 2. The system of claim 1, wherein the third imaging lens group channel includes a third source reflector configured to redirect the collimated beam emitted from the first illumination source in a third direction along the third imaging lens group channel.

10. The system of claim 1 , wherein the first illumination source is disposed within the objective lens group channel.

11. A lithography apparatus comprising a system according to any one of claims 1 to 10.

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