Systems and methods for reticle transmission measurements in a lithographic system

Abstract

A system includes a light source, a sensor, and a controller. The light source illuminates a reticle. The controller controls scanning of the sensor across a surface of the reticle such that transmission data for multiple points on the reticle are captured by the sensor. All desired aspects of the transmission data for the multiple points on the reticle are captured in less than about 30 seconds.

Description

SYSTEMS AND METHODS FOR RETICLE TRANSMISSION MEASUREMENTS IN A LITHOGRAPHIC SYSTEMCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority of US application 63 / 667,013 which was filed on 02 July,2024 and which is incorporated herein in its entirety by reference..FIELD

[0002] The present disclosure relates to heating models, for example, calibration of reticle, lens and substrate heating models for lithographic apparatuses and systems.BACKGROUND

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, can be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the target portions parallel or anti-parallel to this scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004] Components of a lithographic apparatus, such as a reticle, optical element, and / or substrate, may increase in temperature when exposed to radiation. Reticle, optical element and / or substrate heating can cause changes m reticle, optical element, and / or substrate properties that can affect the radiation beam path (e.g., focus) and cause distortions in the patterned substrate (e.g., overlay errors). Changes m reticle, optical element, and / or substrate properties can be modeled and corrected with a heating model. Current heating models can utilize average reticle transmission values (e.g., the percentage of a reticle that is transmissive) as an input. Accuracy of the heating models may be improved by replacing the average reticle transmission values with two dimensional reticle transmission maps. However, generating a two-dimensional reticle transmission map requires measuring transmission of multiple points a reticle surface, which may be time consuming.SUMMARY

[0005] Accordingly, it desirable to speed up collection of reticle transmission measurements.

[0006] In some aspects, a system includes a light source, a sensor, and a controller. The light source can be configured to illuminate a reticle. The controller can control scanning of the sensor across a surface of the reticle such that transmission data for multiple points on the reticle are captured by the sensor. All desired aspects of the transmission data for the multiple points on the reticle can be captured in less than about 30 seconds.

[0007] In some aspects, a method comprises scanning a sensor across a surface of a reticle and measuring transmission data for a plurality of points on the surface of the reticle. The scanning and measuring can capture all the points on the surface of the reticle in less than about 30 seconds.

[0008] Further features of the present disclosure, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings. It is noted that the present disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.BRIEF DESCRIPTION OF THE DRAWINGS / FIGURES

[0009] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable a person skilled in the relevant art(s) to make and use embodiments described herein.

[0010] FIG. 1A shows a schematic of a reflective lithographic apparatus, according to some aspects.

[0011] FIG. IB shows a schematic of a transmissive lithographic apparatus, according to some aspects.

[0012] FIG. 2 shows a more detailed schematic of the reflective lithographic apparatus, according to some aspects.

[0013] FIG. 3 shows a schematic of a lithographic cell, according to some aspects.

[0014] FIGS. 4A and 4B show an example reticle stage, according to some aspects.

[0015] FIG. 5 shows a flowchart of a heating model, according to some aspects.

[0016] FIG. 6 shows a method of generating a reticle transmission map, according to some aspects .

[0017] FIG. 7 shows a schematic of components involved in reticle transmission measurements, according to some aspects.

[0018] FIG. 8 shows a reticle scanning pattern, according to some aspects.

[0019] FIG. 9 shows a reticle transmission map, according to some aspects.

[0020] FIG. 10 shows a computer system, according to some aspects.

[0021] The features of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the left -most digit(s) of a reference number identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout the disclosure should not be interpreted as to -scale drawings.DETAILED DESCRIPTION

[0022] This specification discloses one or more embodiments that incorporate the features of the present disclosure. The disclosed embodiment(s) are provided as examples. The scope of the present disclosure is not limited to the disclosed embodiment(s). Claimed features are defined by the claims appended hereto.

[0023] The embodiment(s) described, and references in the specification to “one embodiment,”“an embodiment,” “an example embodiment,” etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, 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 skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0024] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, can be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0025] The term “about” as used herein indicates the value of a given quantity that can vary based on a particular technology. Based on the particular technology, the term “about” can indicate a value of agiven quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0026] Embodiments of the disclosure can be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine -readable medium, which can be read and executed by one or more processors. A machine- readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine -readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, and / or instructions can be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.

[0027] Before describing such embodiments in more detail, however, it is instructive to present an example environment in which embodiments of the present disclosure can be implemented.

[0028] Example Lithographic Systems

[0029] FIGS. 1A and IB show schematic illustrations of a lithographic apparatus 100 and lithographic apparatus 100’, respectively, in which embodiments of the present disclosure may 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 (for example, deep ultra violet or extreme ultra violet radiation); a support structure (for example, a mask table) MT configured to support a patterning device (for example, a mask, a reticle, or a dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device MA; and, a substrate table (for example, a wafer table) WT configured to hold a substrate (for example, a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Lithographic apparatus 100 and 100’ also have a projection system PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion (for example, comprising one or more dies) C of the substrate W. 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.

[0030] 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.

[0031] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA with respect to a reference frame, the design of at least one of the lithographic apparatus 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 a frame or a table, for example, which may be fixed or movable, as required. By using sensors, the support structure MT may ensure that the patterning device MA is at a desired position, for example, with respect to the projection system PS.

[0032] The term “patterning device” MA should be broadly interpreted as referring to any device that may be used to impart a radiation beam B with a pattern in its cross-section, such as to create a pattern in the target portion C of the 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.

[0033] The terms “inspection apparatus,” “metrology system,” or the like may be used herein to refer to, e.g., a device or system used for measuring a property of a structure (e.g., overlay error, critical dimension parameters) or used in a lithographic apparatus to inspect an alignment of a wafer (e.g., alignment apparatus).

[0034] The patterning device MA may be transmissive (as in lithographic apparatus 100’ of FIG.IB) 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 may be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B, which is reflected by a matrix of small mirrors.

[0035] The term “projection system” PS may encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropnate for the exposure radiation being used, or for other factors, such as the use of an immersion liquid on the substrate W or the use of a vacuum. A vacuum environment may be used for EUV or electron beam radiation since other gases may absorb too much radiation or electrons. A vacuum environment may therefore be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps.

[0036] 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 “multiple stage” machines, the additional substrate tables WT may be used in parallel, or preparatory steps may be carriedout on one or more tables while one or more other substrate tables WT are being used for exposure. In some situations, the additional table may not be a substrate table WT.

[0037] The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e . . , water, so as to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, 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 a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0038] Referring to FIGS. lA and IB, the illuminator IL receives a radiation beam from a radiation source SO. The source SO and the lithographic apparatus 100, 100’ may be separate physical entities, for example, when the source SO or SO is an excimer laser. In such cases, the source SO is not considered to form part of the lithographic apparatus 100 or 100’, and the radiation beam B passes from the source SO to the illuminator IL with the aid of a beam delivery system BD (in FIG. IB) including, for example, suitable directing mirrors and / or a beam expander. In other cases, the source SO may be an integral part of the lithographic apparatus 100, 100’, for example, when 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.

[0039] The illuminator IL may include an adjuster AD (in FIG. IB) for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as “a-outer” and “o-inner,” respectively) of the intensity distribution in a pupil plane of the illuminator may be adjusted. In addition, the illuminator IL may comprise various other components (in FIG. IB), such as an integrator IN and a condenser CO. The illuminator IL may be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross section.

[0040] Referring to FIG. 1A, the radiation beam B is incident on the patterning device (for example, mask) MA, which is held on the support structure (for example, mask table) MT, and is patterned by the patterning device MA. In lithographic apparatus 100, the radiation beam B is reflected from the patterning device (for example, mask) MA. After being reflected from the patterning device (for example, mask) MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF2 (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT may be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor IF1 may be used to accurately position the patterning device (for example, mask) MA with respect to the path of the radiationbeam B. Patterning device (for example, mask) MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2.

[0041] Referring to FIG. IB, the radiation beam B is incident on the patterning device (for example, mask MA), which is held on the support structure (for example, mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil conjugate PPU to an illumination system pupil IPU. Portions of radiation emanate from the intensity distribution at the illumination system pupil IPU and traverse a mask pattern without being affected by diffraction at the mask pattern and create an image of the intensity distribution at the illumination system pupil IPU.

[0042] The projection system PS projects an image of the mask pattern MP, where the image is formed by diffracted beams produced from the mark pattern MP by radiation from the intensity distribution, onto a photoresist layer coated on the substrate W. For example, the mask pattern MP may include an array of lines and spaces. A diffraction of radiation at the array and different from zeroth order diffraction generates diverted diffracted beams with a change of direction in a direction perpendicular to the lines. Undiffracted beams (i.e., so-called zeroth order diffracted beams) traverse the pattern without any change in propagation direction. The zeroth order diffracted beams traverse an upper lens or upper lens group of the projection system PS, upstream of the pupil conjugate PPU of the projection system PS, to reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zeroth order diffracted beams is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. The aperture device PD, for example, is disposed at or substantially at a plane that includes the pupil conjugate PPU of the projection system PS.

[0043] The projection system PS is arranged to capture, by means of a lens or lens group L, not only the zeroth order diffracted beams, but also first-order or first- and higher-order diffracted beams (not shown). In some aspects, dipole illumination for imaging line patterns extending in a direction perpendicular to a line may be used to utilize the resolution enhancement effect of dipole illumination. For example, first-order diffracted beams interfere with corresponding zeroth -order diffracted beams at the level of the wafer W to create an image of the line pattern MP at highest possible resolution and process window (i.e., usable depth of focus in combination with tolerable exposure dose deviations). In some aspects, astigmatism aberration may be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. Further, in some aspects, astigmatism aberration may be reduced by blocking the zeroth order beams in the pupil conjugate PPU of the projection system associated with radiation poles in opposite quadrants. This is described in more detail in U.S. Patent No. 7,511,799 B2, issued Mar. 31, 2009, which is incorporated by reference herein in its entirety.

[0044] With the aid of the second positioner PW and position sensor IFD (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT may be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor (not shown in FIG. IB) may be used to accurately position the mask MA with respect to the path of the radiation beam B (for example, after mechanical retrieval from a mask library or during a scan).

[0045] In general, movement of the mask table MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may 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. Mask MA and substrate W may be aligned using mask alignment marks Ml, M2, and substrate alignment marks Pl, P2. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they may be located in spaces between 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.

[0046] Mask table MT and patterning device MA may be in a vacuum chamber V, where an invacuum robot IVR may be used to move patterning devices such as a mask in and out of vacuum chamber. Alternatively, when mask table MT and patterning device MA are outside of the vacuum chamber, an out- of-vacuum robot may be used for various transportation operations, similar to the in-vacuum robot IVR. Both the in-vacuum and out-of-vacuum robots need to be calibrated for a smooth transfer of any payload (e.g., mask) to a fixed kinematic mount of a transfer station.

[0047] The lithographic apparatus 100 and 100’ may be used in at least one of the following modes:

[0048] 1. In step mode, the support structure (for example, mask table) MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam B is projected onto a target portion C at one time (i.e., a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C may be exposed.

[0049] 2. In scan mode, the support structure (for example, 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 (for example, mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0050] 3. In another mode, the support structure (for example, mask table) MT is kept substantially 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 may be employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation may be readily applied to maskless lithography that utilizes a programmable patterning device, such as a programmable mirror array.

[0051] Combinations and / or variations on the described modes of use or entirely different modes of use may also be employed.

[0052] In a further embodiment, lithographic apparatus 100 includes an extreme ultraviolet (EUV) source, which is configured to generate a beam of EUV radiation for EUV lithography. In general, 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.

[0053] FIG. 2 shows the lithographic apparatus 100 in more detail, including the source collector apparatus SO, the illumination system IL, and the projection system PS. The source collector apparatus SO is constructed and arranged such that a vacuum environment may be maintained in an enclosing structure 220 of the source collector apparatus SO. An EUV radiation emitting plasma 210 may be formed by a discharge produced plasma source. EUV radiation may be produced by a gas or vapor, for example Xe gas, Li vapor, or Sn vapor in which the very hot plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is created by, for example, an electrical discharge causing at least a partially ionized plasma. Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor may be required for efficient generation of the radiation. In some aspects, a plasma of excited tin (Sn) is provided to produce EUV radiation.

[0054] The radiation emitted by the hot plasma 210 is passed from a source chamber 211 into a collector chamber 212 via an optional gas barrier or contaminant trap 230 (in some cases also referred to as contaminant barrier or foil trap), which is positioned in or behind an opening in source chamber 211. The contaminant trap 230 may include a channel structure. Contamination trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barner 230 further indicated herein at least includes a channel structure.

[0055] The collector chamber 212 may include a radiation collector CO, which may be a so-called grazing incidence collector. Radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation that traverses collector CO may be reflected off a grating spectral filter 240 to be focused in a virtual source point INTF. The virtual source point INTF is commonly referred to as the intermediate focus, and the source collector apparatus is arranged such that theintermediate focus INTF is located at or near an opening 219 in the enclosing structure 220. The virtual source point INTF is an image of the radiation emitting plasma 210. Grating spectral filter 240 is used in particular for suppressing infra-red (IR) radiation.

[0056] Subsequently the radiation 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, as well as a desired uniformity of radiation intensity at the patterning device MA. Upon reflection of the beam of radiation 221 at the patterning device MA, held by the support structure MT, a patterned beam 226 is formed and the patterned beam 226 is imaged by the projection system PS via reflective elements 228, 229 onto a substrate W held by the wafer stage or substrate table WT.

[0057] More elements than shown may generally be present in illumination optics unit IL and projection system PS. The grating spectral filter 240 may optionally be present, depending upon the type of lithographic apparatus. Further, there may be more mirrors present than those shown in the FIG. 2, for example there may be one to six additional reflective elements present in the projection system PS than shown in FIG. 2.

[0058] Collector optic CO, as illustrated in FIG. 2, is depicted as a nested collector with grazing incidence reflectors 253, 254, and 255, just as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 are disposed axially symmetric around an optical axis O and a collector optic CO of this type is preferably used in combination with a discharge produced plasma source, often called a DPP source.

[0059] Example Lithographic Cell

[0060] FIG. 3 shows a lithographic cell 300, also sometimes referred to a lithocell or cluster, according to some aspects. Lithographic apparatus 100 or 100’ may form part of lithographic cell 300. Lithographic cell 300 may also include one or more apparatuses to perform pre- and post-exposure processes on a substrate. In some examples, these include spin coaters SC to deposit resist layers, developers DE to develop exposed resist, chill plates CH, and bake plates BK A substrate handler, or robot, RO picks up substrates from input / output ports I / Ol, I / O2, moves them between the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus 100 or 100’. These devices, which are often collectively referred to as the 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 lithography control unit LACU. Thus, the different apparatuses may be operated to maximize throughput and processing efficiency.

[0061] Example Reticle Stage

[0062] FIGS. 4A and 4B show schematic illustrations of reticle stage 400, according to some aspects. FIG. 4A is a schematic bottom perspective illustration of reticle stage 400 and reticle 402, according to some aspects. FIG. 4B is a schematic bottom plan illustration of reticle stage 400 and reticle 402 shown in FIG. 4A.

[0063] Reticle stage 400 (e.g., support structure MT) may be used in a lithographic apparatus (e.g., lithographic apparatus 100 and 100’) to hold a patterning device (e.g., patterning device MA). Reticle stage 400 may include bottom stage surface 504, top stage surface 406, side stage surfaces 408, clamp 410, reticle cage 412, and / or reticle 402. In some aspects, reticle stage 400 with reticle 402 may be implemented in lithographic apparatus 100 and 100’. For example, reticle stage 400 can be support structure MT in lithographic apparatus 100 and 100’. In some aspects, reticle 402 may be disposed on bottom stage surface 404 and held by clamp 410. For example, as shown in FIGS. 4A and 4B, reticle 402 can be disposed on clamp 410 (e.g., an electrostatic clamp) at a center of bottom stage surface 404 with reticle front side 414 facing perpendicularly away from bottom stage surface 404. In some aspects, reticle cage 412 may be disposed on bottom stage surface 404. For example, as shown in FIGS. 4A and 4B, reticle 402 may be disposed at a center of bottom stage surface 404 and secured by reticle cages 412 adjacent to each comer of reticle 402.

[0064] In some lithographic apparatuses, for example, lithographic apparatus 100 and 100’, reticle stage 400 with clamp 410 may be used to hold and position reticle 402 for scanning or patterning operations . In some aspects, as shown in FIGS. 4A and 4B, reticle stage 400 may include first encoder 416 and second encoder 418 for positioning operations. For example, first and second encoders 416, 418 can be interferometers. First encoder 416 can be attached along a first direction, for example, a transverse direction (i.e., X-direction) of reticle stage 400. And second encoder 418 may be attached along a second direction, for example, a longitudinal direction (i.e., Y-direction) of reticle stage 400.

[0065] As shown in FIGS. 4A and 4B, reticle 400 can include reticle front side 414, alignment mark 420, and / or edge alignment mark 422. Alignment mark 420 is configured to measure a reticle alignment between reticle 400 and a substrate (e.g., substrate W). In some aspects, as shown in FIGS. 4A and 4B, one or more alignment marks 420 may be disposed in the comers and / or the center of reticle 400 for an RA measurement. Edge alignment mark 422 may be configured to measure a reticle shape deformation of reticle 400 due to thermal expansion. In some aspects, as shown m FIGS. 4A and 4B, one or more edge alignment marks 422 may be disposed along the perimeter edges (e.g., horizontal and vertical edges) of reticle 400 for a reticle shape deformation (RSD) measurement. In some aspects, the results of the RA measurement and / or the RSD measurement may be converted to a reticle temperature, for example, by a Finite element method analysis that solves for temperature based on reticle alignment and / or reticle deformation.

[0066] Example Process for Determining Thermal Models

[0067] Components of a lithographic apparatus, such as patterning device MA, substrate W, and lens L in projection system PS, may increase in temperature when exposed to radiation. Reticle, optical element and / or substrate heating can cause changes in reticle, optical element, and / or substrate properties that can affect the radiation beam path (e.g., focus) and cause distortions in the patterned substrate (e.g., overlay errors). Changes in reticle, optical element, and / or substrate properties can be modeled and corrected with a heating model.

[0068] FIG. 5 shows a flowchart of a method 500 for determining a reticle, optical element, and / or substrate heating model, according to some aspects.

[0069] In finite element method calculation step 502, reticle transmission data 504 and lithography recipe data 506 may be input into a finite element method calculation, according to some aspects. The finite element method calculation may generate thermo -mechanical deformation data 508. Thermo-mechanical deformation data 508 may include modal deformation shapes, modal deformation shape amplitudes, underlying physics, etc. of a reticle, lens, substrate, or the like. The simulated modal deformation shapes may be orthonormal. Mode shapes and amplitudes may be simulated for multiple field sizes and shifts.

[0070] In thermal model calculation step 510, thermo -mechanical deformation data 508 may be used to calculate a thermal model 512 of a reticle, optical element, substrate, or the like. Thermal model 512 may determine thermo-mechanical deformations for the duration of lot production. In some aspects, calculated thermo-mechanical deformations may be used to determine adjustments to a reticle, lens, substrate, etc. to account for deformations due to heating and / or cooling. In some aspects, thermal model 512 may determine changes in the temperature of the reticle during exposure.

[0071] In model calibration step 514, thermal model 512 can be calibrated using measured data516. Measured data 516 may include wafer resist data (e.g., overlay data). Measured data 516 may be measured inline (i.e., during wafer production) or before wafer production begins. In an alternative aspect (not shown), finite element method data 508 may be calibrated using measured data 516 before thermal model 512 is calculated. Calibrated thermal models may be stored in database 518.

[0072] The steps of process 500 in FIG. 5 merely reflect an example of operations and are nonlimiting.

[0073] The method steps of FIG. 5 may be performed in any conceivable order and it is not required that all operations be performed. Moreover, the method of FIG. 5 described above merely reflects an example of operations and are not limiting. That is, further method steps and functions are envisaged based aspects described in reference to FIGS. 6-9. More information on reticle heating models can be found in U.S. Patent No. 10,429,749, issued on Oct. 01, 2019, U.S. Patent No. 10,281,825, issued on May 07, 2019, and U.S. Patent No. 11,300,886 issued on Apr. 04, 2022, which are herein incorporated by reference.

[0074] Example Method of Determining Reticle Transmission

[0075] In current reticle heating models, reticle transmission data may comprise a single calculated value that estimates the percentage of light that is transmitted by a reticle (e.g., percent transmissivity). Replacing this percent transmissivity value with a two-dimensional (2D) reticle transmission map may increase accuracy of a reticle heating model. A two dimensional reticle transmission map can be implemented into existing reticle, optical element, and substrate heating models, as described in reference to FIG. 5.

[0076] To generate a two-dimensional reticle transmission map, transmission values for multiple points of a reticle may be measured. As described herein, reticle transmission measurements may refer to measurements of light transmitted through a transmissive reticle. Reticle transmission measurements may also refer to the measurement of light reflected from the surface of a reflective reticle.

[0077] As described herein, one example of measurement of “all desired” reticle transmission values may refer to the number of reticle transmission measurements collected to ensure that a reticle transmission map has an accuracy within 5% of the accuracy obtained when a full field set of measurements is made. A full field set of measurements may be defined as measurements of at least 60,000 points on a reticle.

[0078] In current implementations, measuring all desired reticle transmission values may take about 3-4 minutes. Reducing this measuring time can improve throughput of a lithographic apparatus.

[0079] FIG. 6 shows of method 600, according to some aspects. Method 600 may be used to generate a reticle transmission map for use in a reticle heating model. Method 600 may include steps 602, 604, 606, and 608.

[0080] In step 602, a reticle may be illuminated, according to some aspects. The reticle may be transmissive or reflective. The reticle may be illuminated by pulses of radiation, for example, EUV or DUV radiation. During illumination, reticle masking blades may block a portion of the reticle.

[0081] In step 604, a sensor may be scanned across a surface of the reticle, according to some aspects. The sensor may comprise a spot sensor, or the like. The sensor may be scanned across the surface of the reticle in a senes of concatenated lines. More details of scanning patterns is given below in reference to FIG. 8.

[0082] In step 606, transmission data is measured for a plurality of points on a reticle, according to some aspects. The plurality of points may be evenly spaced. In some aspects, about 6,000 points may be measured. In other aspects about 60,000 points may be measured. In a further example, between 6,000 and 60,000 points may be measured. The number of points measured may depend on the reticle size and / or desired accuracy of a reticle transmission map.

[0083] In step 608, a two-dimensional transmission map of the reticle may be generated using the transmission data measured in step 606, according to some aspects. The transmission map may be generated by plotting a measured transmission value for each point of the reticle measured in step 606.

[0084] In some aspects, transmission values for non-measured points of the reticle may be generated via interpolation of the measured transmission data. For example, unmeasured points on a reticle surface may be interpolated by Bayseian filtering, or the like. Inputs to an interpolation algorithm may include measured transmission data. Outputs of an interpolation algorithm may include estimates of reticle transmission values for unmeasured points of a reticle.

[0085] In some aspects, the scanning of step 604 and the measuring of step 606 may be completed for a full reticle in less than about 30 seconds, less than about 10 seconds, or less than about 1 second. The amount of time it takes to scan and measure a reticle may depend on the number of measured points on a reticle.

[0086] Interpolation, as described in step 608, may allow for fewer points on a surface of a reticle to be measured. For example, without interpolation, around 50,000-60,000 points on a reticle surface may be measured. When interpolation methods are utilized, as few as 6,000-12,000 points may be measured for the same reticle while introducing an error of less than about 1%.

[0087] In some aspects, a reticle transmission map be generated once during the lifetime of the reticle.

[0088] The method of FIG. 6 can be performed in any conceivable order and it is not required that all operations be performed. Moreover, the method of FIG. 6 described above merely reflects an example of operations and are not limiting. That is, further method steps and functions are envisaged based aspects described in reference to FIGS. 7-9.

[0089] FIG. 7 shows a schematic of components of a lithography apparatus 700 that can be involved in reticle transmission measurements, according to some aspects. For example apparatus 700 can include a reticle 702 having surface 714, radiation 704, one or more reticle masking blades 706, a sensor 708, a stage 710, and a controller 712.

[0090] While FIG. 7 shows example components of a transmissive lithography apparatus, such as lithography apparatus 100’ in FIG. IB, it can understood by a person of ordinary skill m the art that a similar components with similar functions may be found m a reflective lithography apparatus.

[0091] In some aspects, during reticle transmission measurements, a reticle 702 can be illuminated with radiation 704. In some aspects, radiation 704 can comprise radiation in an EUV or DUV wavelength of the electromagnetic spectrum. In a transmissive lithography apparatus, radiation 704 may be either transmitted or absorbed by reticle 702. In a reflective lithography apparatus, radiation 704 may be either reflected or absorbed by the reticle.

[0092] In some aspects, reticle masking blades 706 may be positioned between a light source (e.g., light source SO in FIGS. 1A and IB) and reticle 702. Reticle masking blades 706 may control an amount and / or positioning of light incident on reticle 702. For example, reticle masking blades 706 may move rapidly to selectively block / unblock portions of a reticle 702 during transmission measurements.

[0093] In some aspects, controller 712 may control the movement of reticle masking blades 706.For a DUV light source, reticle masking blades 706 may be positioned in front of reticle 702 or at an image plane conjugate to reticle 702. For an EUV light source, reticle masking blades 706 may be positioned in front of reticle 702.

[0094] In some aspects, radiation 704 incident on reticle 702 may be transmitted and / or reflected towards sensor 708. Sensor 708 may be a spot sensor, or the like. In some aspects sensor 708 may have a pinhole size of about 120 pm.

[0095] In some aspects, sensor 708 may be located on stage 710. Sensor 708 and / or stage 710 may move across (e.g., parallel to) a surface of reticle 702. In some aspects, controller 712 may control the movement of stage 710. Stage 710 may be configured to move in the X and Y directions.

[0096] In some aspects, sensor 708 may capture transmission data for multiple points on surface714 of reticle 702, as sensor 708 is scanned across surface 714 of reticle 702. The transmission data captured by sensor 708 may be used to generate a two dimensional transmission map of surface 714.

[0097] In some aspects, controller 712 may be configured to scan sensor 708 across the surface714 of reticle 702 such that all desired points on surface 714 (e.g., all points needed to create a reticle transmission map) are scanned and measured in less than about 30 seconds. This can be accomplished by improving software that controls the scanning movements of stage 710 / sensor 708. For example, redundant preparation stages, such as setting laser wavelength, preparing a light source and adjusting a lens can be completed once per reticle scan instead of at the start of each line in a reticle scan.

[0098] In some aspects, concatenating line measurements may be used. For example, using concatenating line measurements during scanning may reduce the time required to measure and scan all desired points on reticle 702 to less than about 25 seconds. Scanning time may be further reduced by measuring fewer points on reticle 702 and using interpolation methods to estimate transmission values for unmeasured points. In this case, scanning and measuring can be completed in less than about 10 seconds, and m some instances, less than about 1 second.

[0099] In some aspects, when creating a reticle transmission map for a full reticle, transmission data may only be collected for a portion of the full reticle (i.e ., portions of the reticle may be skipped during a scanning and measuring process). Transmission data for unmeasured portions of the reticle may be estimated via interpolation, as described in reference to FIG. 6 above.

[0100] In some aspects, portions of a reticle which are scanned dunng a reticle transmission measurement may be determined by a scanning pattern chosen before reticle transmission measurements begin.

[0101] FIG. 8 shows an example scanning pattern 820 according to some aspects. Scanning pattern820 may be shown in reference to a surface (not shown, e.g., surface 714 in FIG. 7) of a reticle (not shown, e.g., reticle 702 in FIG. 7).

[0102] In some aspects, in scanning pattern 820 measurements may occur as a series of measurement lines 824. Regions of surface 814 that are not scanned are indicated by skipped portions 826. In FIG. 8, skipped portions 826 are shown as dashed lines. Scanning of measurement lines 824 may be concatenated.

[0103] In some aspects, scanning of measurement lines 824 may occur in one direction. For example, as shown in FIG. 8 scanning of measurement lines 824 may occur in the +X direction. In an alternative aspect, the scanning direction of measurement lines 824 may be alternated (e.g., a scan in the +X direction may be followed by a scan in the -X direction).

[0104] In some aspects, over 200 measurement lines 824 may be scanned. In some aspects, over100 measurement lines may be scanned. In some aspects, less than about 100 measurement lines may be scanned.

[0105] Transmission data can be collected at multiple points along each measurement line. In some aspects, about 200 points are measured per measurement line 824. In some aspects, between 100 and 200 points are measured per measurement line 824. In some aspects, less than about 100 points are measured per measurement line 824. Measured points may have even or uneven spacing.

[0106] Scanning patterns of a reticle may vary based on known characteristics of a reticle (e.g., symmetry) and / or the desired accuracy of a reticle transmission map. For example, if higher accuracy is desired, more transmission data may be measured and a scanning pattern may contain a larger number of measurement lines 824.

[0107] In FIG. 8, measurement lines 824 are shown as a series of evenly spaced lines. This measurement pattern is merely an example and is non -limiting. Other scanning patterns may be envisaged based on knowledge of a person of ordinary skill m the art.

[0108] FIG. 9 shows an example transmission map 930, according to some aspects. Transmission map 930 may plot transmission data 932 as a function of X position, indicated by axis 934, and Y position, indicated by axis 936, on a reticle. Values of transmission data 932 may be indicated by value bar 938. Transmission data 932 may refer to the amount of light that is transmitted by a point on a reticle .

[0109] In some aspects, regions of a reticle that that are relatively transmissive, for example 90% transmissive, may appear as light gray on transmission map 930. Regions of the reticle that are absorbing, for example less than 10% reflective, may appear black on transmission map 930.

[0110] In some aspects, transmission data 932 may comprise a combination of measured and interpolated transmission values. For example, parts of transmission data 932 may be interpolated as described in reference to FIG. 6 above.

[0111] In some aspects, reticle deformations are related the amount of radiation absorbed, transmitted, and / or reflected by a reticle. Regions of a reticle with lower transmissivity / reflectivity may heat faster, and deform differently, than regions of a reticle with higher transmissivity / reflectivity. Incorporating a reticle transmission map into a reticle heating model may account for uneven heating of the reticle, and thus improve accuracy of the model.

[0112] In some aspects, transmission map 930 is merely an example of a reticle transmission map and is non-limiting. Similar transmission maps may be measured for reflective reticles.

[0113] FIG. 10 illustrates an example computer system useful for implementing various embodiments in Figures 1-9.

[0114] Various embodiments may be implemented, for example, using one or more well-known computer systems, such as computer system 1000 shown in FIG. 10. One or more computer systems 1000 may be used, for example, to implement any of the embodiments discussed herein, as well as combinations and sub-combinations thereof.

[0115] Computer system 1000 may include one or more processors (also called central processing units, or CPUs), such as a processor 1004. Processor 1004 may be connected to a communication infrastructure or bus 1006.

[0116] Computer system 1000 may also include user input / output device(s) 1003, such as monitors, keyboards, pointing devices, cameras, other imaging devices etc., which may communicate with communication infrastructure 1006 through user input / output interface(s) 1002.

[0117] One or more of processors 1004 may be a graphics processing unit (GPU). In an embodiment, a GPU may be a processor that is a specialized electronic circuit designed to process mathematically intensive applications. The GPU may have a parallel structure that is efficient for parallel processing of large blocks of data, such as mathematically intensive data common to computer graphics applications, images, videos, etc.

[0118] Computer system 1000 may also include a main or primary memory 1008, such as random access memory (RAM). Main memory 1008 may include one or more levels of cache. Main memory 1008 may have stored therein control logic (i.e., computer software) and / or data.

[0119] Computer system 1000 may also include one or more secondary storage devices or memory 1010. Secondary memory 1010 may include, for example, a hard disk drive 1012 and / or a removable storage device or drive 1014. Removable storage drive 1014 may be a floppy disk drive, a magnetic tape drive, a compact disk drive, an optical storage device, tape backup device, and / or any other storage device / drive.

[0120] Removable storage drive 1014 may interact with a removable storage unit 1018.Removable storage unit 1018 may include a computer usable or readable storage device having stored thereon computer software (control logic) and / or data. Removable storage unit 1018 may be a floppy disk, magnetic tape, compact disk, DVD, optical storage disk, and / any other computer data storage device. Removable storage drive 1014 may read from and / or write to removable storage unit 1018.

[0121] Secondary memory 1010 may include other means, devices, components, instrumentalities or other approaches for allowing computer programs and / or other instructions and / or data to be accessed by computer system 1000. Such means, devices, components, instrumentalities or other approaches may include, for example, a removable storage unit 1022 and an interface 1020.Examples of the removable storage unit 1022 and the interface 1020 may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and / or any other removable storage unit and associated interface.

[0122] Computer system 1000 may further include a communication or network interface 1024.Communication interface 1024 may enable computer system 1000 to communicate and interact with any combination of external devices, external networks, external entities, etc. (individually and collectively referenced by reference number 1028). For example, communication interface 1024 may allow computer system 1000 to communicate with external or remote devices 1028 over communications path 1026, which may be wired and / or wireless (or a combination thereof), and which may include any combination of LANs, WANs, the Internet, etc. Control logic and / or data may be transmitted to and from computer system 1000 via communication path 1026.

[0123] Computer system 1000 may also be any of a personal digital assistant (PDA), desktop workstation, laptop or notebook computer, netbook, tablet, smart phone, smart watch or other wearable, appliance, part of the Intemet-of-Things, and / or embedded system, to name a few non-limiting examples, or any combination thereof.

[0124] Computer system 1000 may be a client or server, accessing or hosting any applications and / or data through any delivery paradigm, including but not limited to remote or distributed cloud computing solutions; local or on-premises software (“on-premise” cloud-based solutions); “as a service” models (e.g., content as a service (CaaS), digital content as a service (DCaaS), software as a service(SaaS), managed software as a service (MSaaS), platform as a service (PaaS), desktop as a service (DaaS), framework as a service (FaaS), backend as a service (BaaS), mobile backend as a service (MBaaS), infrastructure as a service (TaaS), etc.); and / or a hybrid model including any combination of the foregoing examples or other services or delivery paradigms.

[0125] Any applicable data structures, file formats, and schemas in computer system 1000 may be derived from standards including but not limited to JavaScript Object Notation (JSON), Extensible Markup Language (XML), Yet Another Markup Language (YAML), Extensible Hypertext Markup Language (XHTML), Wireless Markup Language (WML), MessagePack, XML User Interface Language (XUL), or any other functionally similar representations alone or in combination. Alternatively, proprietary data structures, formats or schemas may be used, either exclusively or in combination with known or open standards.

[0126] In some embodiments, a tangible, non-transitory apparatus or article of manufacture comprising a tangible, non-transitory computer useable or readable medium having control logic (software) stored thereon may also be referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system 1000, main memory 1008, secondary memory 1010, and removable storage units 1018 and 1022, as well as tangible articles of manufacture embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices (such as computer system 1000), may cause such data processing devices to operate as described herein.

[0127] Based on the teachings contained in this disclosure, it will be apparent to persons skilled in the relevant art(s) how to make and use embodiments of this disclosure using data processing devices, computer systems and / or computer architectures other than that shown in FIG. 10. In particular, embodiments can operate with software, hardware, and / or operating system implementations other than those described herein.

[0128] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses:1. A system comprising: a light source configured to illuminate a reticle; a sensor; and a controller configured to control scanning of the sensor across a surface of the reticle such that transmission data for multiple points on the reticle are captured by the sensor, wherein all desired aspects of the transmission data for the multiple points on the reticle are captured in less than about 30 seconds.2. The system of clause 1, wherein the reticle is transmissive or reflective.3. The system of clause 1, wherein the sensor is a spot sensor.4. The system of clause 1, wherein the controller is further configured to generate a reticle transmission map from the transmission data.5. The system of clause 4, wherein to generate the reticle transmission map the controller is further configured to interpolate transmission values for points on the reticle that were not measured by the sensor.6. The system of clause 4, wherein the controller is further configured to estimate reticle, lens, and / or wafer deformations using the transmission map.7. The system of clause 1, wherein the controller is configured to continuously scan the sensor across the surface of the reticle in a series of concatenated lines.8. The system of clause 1 wherein, wherein all desired aspects of the transmission data for the multiple points on a reticle are captured in less than about 10 seconds.9. The system of clause 1, wherein all desired aspects of the transmission data for the multiple points on a reticle are captured in less than about 1 second.10. A lithography system comprising the system of clause 1.11. A method comprising: scanning a sensor across a surface of a reticle; and measuring transmission data for a plurality of points on the surface of the reticle; wherein the scanning and measuring capture all the points on the surface in less than about 30 seconds.12. The method of clause 11, further comprising generating a two-dimensional transmission map of the reticle using the transmission data.13. The method of clause 12, wherein the generating comprises interpolating transmission values for non-measured points on the reticle.14. The method of clause 11, wherein the scanning comprises scanning the sensor across the surface of the reticle in a continuous series of concatenated lines.15. The method of clause 11, wherein the scanning and measuring are completed in less than about 10 seconds.16. The method of clause 11, wherein the scanning and measuring are completed in about 1 second.17. The method of clause 11, wherein the measunng captures transmission data for more than or about 6,000 points on a reticle.18. The method of clause 11, wherein the measuring captures transmission data for less than or about 60,000 points on a reticle.19. The method of clause 11, further comprising using a transmissive or reflective type for the reticle.20. The method of clause 11, further comprising illuminating the reticle with pulses of radiation to measure the transmission of the reticle.

[0129] Although specific reference can be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have 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, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein can be considered as specific examples of the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein can be processed, before or after exposure, in for example a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) and / or a metrology unit. Where applicable, the disclosure herein can be applied to such and other substrate processing tools. Further, the substrate can be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0130] Although specific reference may have been made above to the use of embodiments of the present disclosure in the context of optical lithography, it will be appreciated that the present disclosure can be used in other applications, for example imprint lithography, and where the context allows, 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 can be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0131] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present disclosure is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0132] The terms “radiation,” “beam of radiation” or the like as used herein can encompass all types of electromagnetic radiation, for example, ultraviolet (UV) radiation (for example, having a wavelength X of 365, 248, 193, 157 or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (for example, having a wavelength in the range of 5-20 nm such as, for example, 13.5 nm), or hard X-ray working at less than 5 nm, as well as matter beams, such as ion beams or electron beams. The terms “light,” “illumination,” or the like can refer to non-matter radiation (e.g., photons, UV, X-ray, or the like). Generally, radiation having wavelengths between about 400 to about 700 nm is considered visible radiation; radiation having wavelengths between about 780-3000 nm (or larger) is considered IR radiation. UV refers to radiation with wavelengths of approximately 100-400 nm. Within lithography, the term “UV” alsoapplies to the wavelengths that can be produced by a mercury discharge lamp: G-line 436 nm; H-line 405 nm; and / or, I-line 365 nm. Vacuum UV, or VUV (i.e., UV absorbed by gas), refers to radiation having a wavelength of approximately 100-200 nm. Deep UV (DUV) generally refers to radiation having wavelengths ranging from 126 nm to 428 nm, and in some embodiments, an excimer laser can generate DUV radiation used within a lithographic apparatus. It should be appreciated that radiation having a wavelength in the range of, for example, 5-20 nm relates to radiation with a certain wavelength band, of which at least part is in the range of 5-20 nm.

[0133] It is to be appreciated that the Detailed Description section, and not the Summary andAbstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present disclosure as contemplated by the inventors), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0134] The present disclosure has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0135] While specific embodiments of the disclosure have been described above, it will be appreciated that embodiments of the present disclosure may be practiced otherwise than as described. The descriptions are 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 out below.

[0136] The foregoing description of the specific embodiments will so folly reveal the general nature of the present disclosure that others can, by applying knowledge within the skill of the art, readily modify and / or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0137] The breadth and scope of the protected subject matter should not be limited by any of the above-described exemplary embodiments, but should be defined only m accordance with the following claims and their equivalents.

Claims

1. CLAIMS1. A system comprising: a light source configured to illuminate a reticle; a sensor; and a controller configured to control scanning of the sensor across a surface of the reticle such that transmission data for multiple points on the reticle are captured by the sensor, wherein all desired aspects of the transmission data for the multiple points on the reticle are captured in less than about 30 seconds.

2. The system of claim 1, wherein the reticle is transmissive or reflective and the sensor is a spot sensor.

3. The system of claim 1, wherein: the controller is further configured to generate a reticle transmission map from the transmission data; to generate the reticle transmission map the controller is further configured to interpolate transmission values for points on the reticle that were not measured by the sensor; and the controller is further configured to estimate reticle, lens, and / or wafer deformations using the transmission map.

4. The system of claim 1, wherein the controller is configured to continuously scan the sensor across the surface of the reticle in a series of concatenated lines.

5. The system of claim 1 wherein, wherein all desired aspects of the transmission data for the multiple points on a reticle are captured in less than about 10 seconds.

6. The system of claim 1, wherein all desired aspects of the transmission data for the multiple points on a reticle are captured in less than about 1 second.

7. A lithography system comprising the system of claim 1.

8. A method comprising: scanning a sensor across a surface of a reticle; andmeasuring transmission data for a plurality of points on the surface of the reticle; wherein the scanning and measuring capture all the points on the surface in less than about 30 seconds.

9. The method of claim 8, further comprising generating a two-dimensional transmission map of the reticle using the transmission data, wherein the generating comprises interpolating transmission values for non-measured points on the reticle.

10. The method of claim 8, wherein the scanning comprises scanning the sensor across the surface of the reticle in a continuous series of concatenated lines.

11. The method of claim 8, wherein the scanning and measuring are completed in less than about 10 seconds.

12. The method of claim 8, wherein the scanning and measuring are completed in about 1 second.

13. The method of claim 8, wherein the measuring captures transmission data for more than or about 6,000 points on a reticle.

14. The method of claim 8, wherein the measuring captures transmission data for less than or about 60,000 points on a reticle.

15. The method of claim 8, further comprising: using a transmissive or reflective type for the reticle; and illuminating the reticle with pulses of radiation to measure the transmission of the reticle.

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