System and methods for offline calibration of reticle, optical element and substrate thermal heating models

Abstract

A lithography system includes a reticle, an optical element, a substrate, a database, and a predictor. The database includes a plurality of heating models for the reticle, optical element, and / or substrate, which are generated offline using a combination of simulated and measured data. The predictor utilizes a heating model in the plurality of heating models to predict reticle, optical element, and / or substrate temperature and deformations before wafer production begins.

Description

SYSTEM AND METHODS FOR OFFLINE CALIBRATION OF RETICLE, OPTICAL ELEMENT AND SUBSTRATE THERMAL HEATING MODELSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 612,494 which was filed on 20 December 2023 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 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. Current heating models, such as reticle heating models, rely on inline calibrations (e.g., overlay measurements) to tune the models. Inline calibrations typically take anywhere between 4-25 minutes depending upon the layer. Furthermore, inline calibrations may take place inside a critical computational path of a lithography apparatus, which can lead to reduced throughput.SUMMARY

[0005] Accordingly, it desirable to calculate heating models offline, before wafer production begins.

[0006] In some aspects, a lithography system includes a reticle, a substrate, an optical element, a database containing a plurality of heating models, and a predictor. The plurality of heating models may be generated offline using measured data. The predictor may use a heating model in the plurality of reticle heating models to predict reticle temperature and deformations during wafer production.

[0007] In some aspects, a method includes receiving data, determining predefined datasets, selecting a thermal deformation model, and determining thermal deformation of a reticle, lens, and / or substrate. The data may comprise reticle transmission data, wafer manufacturing data, measured wafer resist data, and / or finite element method data. The predefined datasets may be a combination of finite element method data and measured resist data. The thermal deformation model may be selected from a database of thermal deformation models based on the reticle transmission data and wafer manufacturing data. The selected thermal deformation model may be used to determine thermal deformations of the reticle, lens, and / or substrate before wafer production begins.

[0008] In some aspects, the above method may be implemented by a computer-readable storage medium containing program instructions for a method that is executed by an application. The application may comprise code for one or more components that are called by the application during runtime.

[0009] 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

[0010] 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.

[0011] FIG. 1 A shows a schematic of a reflective lithographic apparatus, according to some aspects.

[0012] FIG. IB shows a schematic of a transmissive lithographic apparatus, according to some aspects.

[0013] FIG. 2 shows a more detailed schematic of the reflective lithographic apparatus, according to some aspects.

[0014] FIG. 3 shows a schematic of a lithographic cell, according to some aspects.

[0015] FIGS. 4 shows a schematic of an inspection apparatus, according to some aspects.

[0016] FIGS. 5A and 5B show schematics of reticle stage, according to some aspects.

[0017] FIG. 6 shows a method of calibrating a thermal heating model, according to some aspects.

[0018] FIG. 7 shows a schematic of a computer system, according to some aspects.

[0019] 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 leftmost 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

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 a given quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0024] 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 readonly 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.

[0025] The term “finite element model” or “FEM” as used herein indicates a method for numerically solving differential equations arising in a heating model (e.g., heat transfer equations, structural analysis equations, fluid flow equations, etc.). For example, baseline reticle heating dynamics can be analyzed with the FEM through finite element analysis. This is described in further detail in U.S. Patent No. 10,429,749, U.S. Patent No. 10,281,825, and U.S. Publication No. 2020 / 0166854, which are incorporated by reference herein in their entireties.

[0026] 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.

[0027] Example Lithographic Systems

[0028] FIGS. 1 A 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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).

[0033] 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.

[0034] 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 appropriate 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.

[0035] 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 carried out 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.

[0036] 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.g., 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 techniquesare 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.

[0037] Referring to FIGS. 1A 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 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.

[0038] 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 “o-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.

[0039] 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 radiation beam 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.

[0040] 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 withoutbeing affected by diffraction at the mask pattern and create an image of the intensity distribution at the illumination system pupil IPU.

[0041] 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.

[0042] 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 US 7,511,799 B2, issued Mar. 31, 2009, which is incorporated by reference herein in its entirety.

[0043] 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).

[0044] 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.

[0045] Mask table MT and patterning device MA may be in a vacuum chamber V, where an in-vacuum 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.

[0046] The lithographic apparatus 100 and 100’ may be used in at least one of the following modes:

[0047] 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.

[0048] 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- jmagnification and image reversal characteristics of the projection system PS.

[0049] 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.

[0050] Combinations and / or variations on the described modes of use or entirely different modes of use may also be employed.

[0051] 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.

[0052] 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 apparatusSO 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.

[0053] 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 barrier 230 further indicated herein at least includes a channel structure.

[0054] 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 the intermediate 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.

[0055] 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.

[0056] 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.

[0057] 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 Oand a collector optic CO of this type is preferably used in combination with a discharge produced plasma source, often called a DPP source.

[0058] Exemplary Lithographic Cell

[0059] 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.

[0060] Exemplary Inspection Apparatus

[0061] FIG. 4 shows a schematic of a cross-sectional view of an inspection apparatus 400 that may be implemented as a part of lithographic apparatus 100 or 100’ , according to some aspects. In some aspects, inspection apparatus 400 may be configured to align a substrate (e.g., substrate W) with respect to a patterning device (e.g., patterning device MA). Inspection apparatus 400 may be further configured to detect positions of alignment marks on the substrate and to align the substrate with respect to the patterning device or other components of lithographic apparatus 100 or 100’ using the detected positions of the alignment marks. Such alignment of the substrate may ensure accurate exposure of one or more patterns on the substrate.

[0062] In some aspects, inspection apparatus 400 may include an illumination system 412, a beam splitter 414, an interferometer 426, a detector 428, a beam analyzer 430, and an overlay calculation processor 432. Illumination system 412 may be configured to provide an electromagnetic narrow band radiation beam 413 having one or more passbands.

[0063] In some aspects, beam splitter 414 may be configured to receive radiation beam 413 and split radiation beam 413 into at least two radiation sub-beams. For example, radiation beam 413 may be split into radiation sub-beams 415 and 417, as shown in FIG. 4A. Beam splitter 414 may be further configured to direct radiation sub-beam 415 onto a substrate 420 placed on a stage 422. In one example, the stage 422 is movable along direction 424. Radiation sub-beam 415 may be configured to illuminate an alignment mark or a target 418 located on substrate 420. Alignment mark or target 418 may be coated with a radiation sensitive film. In some aspects, alignment mark or target 418 may have one hundred and eighty degrees (i.e., 180°) symmetry. That is, when alignment mark or target 418 is rotated 180° about an axis of symmetry perpendicular to a plane of alignment mark or target 418, rotated alignment mark or target 418 may be substantially identical to an unrotated alignment mark or target 418. Thetarget 418 on substrate 420 may be (a) a resist layer grating comprising bars that are formed of solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlay target structure comprising a resist grating overlaid or interleaved on a product layer grating. The bars may alternatively be etched into the substrate. This pattern is sensitive to chromatic aberrations in the lithographic projection apparatus, particularly the projection system PL, and illumination symmetry and the presence of such aberrations will manifest themselves in a variation in the printed grating. One in-line method used in device manufacturing for measurements of line width, pitch, and critical dimension makes use of a technique known as “scatterometry”. Methods of scatterometry are described in Raymond et al., “Multiparameter Grating Metrology Using Optical Scatterometry”, J. Vac. Sci. Tech. B, Vol. 15, no. 2, pp. 361-368 (1997) and Niu et al., “Specular Spectroscopic Scatterometry in DUV Lithography”, SPIE, Vol. 3677 (1999), which are both incorporated by reference herein in their entireties. In scatterometry, light is reflected by periodic structures in the target, and the resulting reflection spectrum at a given angle is detected. The structure giving rise to the reflection spectrum is reconstructed, e.g. using Rigorous Coupled- Wave Analysis (RCWA) or by comparison to a library of patterns derived by simulation. Accordingly, the scatterometry data of the printed gratings is used to reconstruct the gratings. The parameters of the grating, such as line widths and shapes, may be input to the reconstruction process, performed by processing unit PU, from knowledge of the printing step and / or other scatterometry processes.

[0064] In some aspects, beam splitter 414 may be further configured to receive diffraction radiation beam 419 and split diffraction radiation beam 419 into at least two radiation sub-beams, according to an embodiment. Diffraction radiation beam 419 may be split into diffraction radiation sub-beams 429 and 439, as shown in FIG. 4A.

[0065] It should be noted that even though beam splitter 414 is shown to direct radiation sub-beam 415 towards alignment mark or target 418 and to direct diffracted radiation sub-beam 429 towards interferometer 426, the disclosure is not so limiting. It would be apparent to a person skilled in the relevant art that other optical arrangements may be used to obtain the similar result of illuminating alignment mark or target 418 on substrate 420 and detecting an image of alignment mark or target 418.

[0066] As illustrated in FIG. 4A, interferometer 426 may be configured to receive radiation sub-beam 417 and diffracted radiation sub-beam 429 through beam splitter 414. In an example embodiment, diffracted radiation sub-beam 429 may be at least a portion of radiation sub-beam 415 that may be reflected from alignment mark or target 418. In an example of this embodiment, interferometer 426 comprises any appropriate set of optical-elements, for example, a combination of prisms that may be configured to form two images of alignment mark or target 418 based on the received diffracted radiation sub-beam 429. It should be appreciated that a good quality image need not be formed, but that the features of alignment mark 418 should be resolved. Interferometer 426 may be further configured to rotate one of the two images with respect to the other of the two images 180° and recombine the rotated and unrotated images interferometrically.

[0067] In some aspects, detector 428 may be configured to receive the recombined image via interferometer signal 427 and detect interference as a result of the recombined image when alignment axis 421 of inspection apparatus 400 passes through a center of symmetry (not shown) of alignment mark or target 418. Such interference may be due to alignment mark or target 418 being 180° symmetrical, and the recombined image interfering constructively or destructively, according to an example embodiment. Based on the detected interference, detector 428 may be further configured to determine a position of the center of symmetry of alignment mark or target 418 and consequently, detect a position of substrate 420. According to an example, alignment axis 421 may be aligned with an optical beam perpendicular to substrate 420 and passing through a center of image rotation interferometer 426. Detector 428 may be further configured to estimate the positions of alignment mark or target 418 by implementing sensor characteristics and interacting with wafer mark process variations.

[0068] In some aspects, beam analyzer 430 may be configured to determine the overlay data between two patterns on substrate 420. One of these patterns may be a reference pattern on a reference layer. The other pattern may be an exposed pattern on an exposed layer. The reference layer may be an etched layer already present on substrate 420. The reference layer may be generated by a reference pattern exposed on the substrate by lithographic apparatus 100 and / or 100’. The exposed layer may be a resist layer exposed adjacent to the reference layer. The exposed layer may be generated by an exposure pattern exposed on substrate 420 by lithographic apparatus 100 or 100’. The exposed pattern on substrate 420 may correspond to a movement of substrate 420 by stage 422. In some aspects, the measured overlay data may also indicate an offset between the reference pattern and the exposure pattern. The measured overlay data may be used as calibration data to calibrate the exposure pattern exposed by lithographic apparatus 100 or 100’, such that after the calibration, the offset between the exposed layer and the reference layer may be minimized.

[0069] In some aspects, beam analyzer 430 may be further configured to determine a model of the product stack profile of substrate 420, and may be configured to measure overlay, critical dimension, and focus of target 418 in a single measurement. The product stack profile contains information on the stacked product such as alignment mark, target 418, or substrate 420, and may include mark process variation-induced optical signature metrology that is a function of illumination variation. The product stack profile may also include product grating profile, mark stack profile, and mark asymmetry information. An example of beam analyzer 430 is Yieldstar™, manufactured by ASML, Veldhoven, The Netherlands, as described in U.S. Patent No. 8,706,442, which is incorporated by reference herein in its entirety. Beam analyzer 430 may be further configured to process information related to a particular property of an exposed pattern in that layer. For example, beam analyzer 430 may process an overlay parameter (an indication of the positioning accuracy of the layer with respect to a previous layer on the substrate or the positioning accuracy of the first layer with respective to marks on the substrate), a focus parameter, and / or a critical dimension parameter (e.g., line width and its variations) of thedepicted image in the layer. Other parameters are image parameters relating to the quality of the depicted image of the exposed pattern.

[0070] In some aspects, processor 432 receives information from detector 428 and beam analyzer 430. For example, processor 432 may be an overlay calculation processor. The information may comprise a model of the product stack profile constructed by beam analyzer 430. Alternatively, processor 432 may construct a model of the product mark profile using the received information about the product mark. In either case, processor 432 constructs a model of the stacked product and overlay mark profile using or incorporating a model of the product mark profile. The stack model is then used to determine the overlay offset and minimizes the spectral effect on the overlay offset measurement. Processor 432 may create a basic correction algorithm based on the information received from detector 428 and beam analyzer 430, including but not limited to the optical state of the illumination beam, the alignment signals, associated position estimates, and the optical state in the pupil, image, and additional planes. The pupil plane is the plane in which the radial position of radiation defines the angle of incidence and the angular position defines the azimuth angle of the radiation. Processor 432 may utilize the basic correction algorithm to characterize the inspection apparatus 400 with reference to wafer marks and / or alignment marks 418.

[0071] Exemplary Reticle Stage

[0072] FIGS. 5 A and 5B show schematic illustrations of reticle stage 500, according to some aspects. FIG. 5A is a schematic bottom perspective illustration of reticle stage 500 and reticle 502, according to some aspects. FIG. 5B is a schematic bottom plan illustration of reticle stage 500 and reticle 502 shown in FIG. 5A.

[0073] Reticle stage 500 (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 500 may include bottom stage surface 504, top stage surface 506, side stage surfaces 508, clamp 510, reticle cage 512, and / or reticle 502. In some aspects, reticle stage 500 with reticle 502 may be implemented in lithographic apparatus 100 and 100’. For example, reticle stage 500 can be support structure MT in lithographic apparatus 100 and 100’. In some aspects, reticle 502 may be disposed on bottom stage surface 504 and held by clamp 510. For example, as shown in FIGS. 5 A and 5B, reticle 502 can be disposed on clamp 510 (e.g., an electrostatic clamp) at a center of bottom stage surface 504 with reticle front side 514 facing perpendicularly away from bottom stage surface 504. In some aspects, reticle cage 512 may be disposed on bottom stage surface 504. For example, as shown in FIGS. 5A and 5B, reticle 502 may be disposed at a center of bottom stage surface 504 and secured by reticle cages 512 adjacent to each corner of reticle 502.

[0074] In some lithographic apparatuses, for example, lithographic apparatus 100 and 100’, reticle stage 500 with clamp 510 may be used to hold and position reticle 502 for scanning or patterning operations. In some aspects, as shown in FIGS. 5A and 5B, reticle stage 500 may include first encoder 516 and second encoder 518 for positioning operations. For example, first and second encoders 516,518 can be interferometers. First encoder 516 can be attached along a first direction, for example, a transverse direction (i.e., X-direction) of reticle stage 500. And second encoder 518 may be attached along a second direction, for example, a longitudinal direction (i.e., Y-direction) of reticle stage 500.

[0075] As shown in FIGS. 5 A and 5B, reticle 500 can include reticle front side 514, alignment mark 520, and / or edge alignment mark 522. Alignment mark 520 is configured to measure a reticle alignment between reticle 500 and a substrate (e.g., substrate W). In some aspects, as shown in FIGS. 5A and 5B, one or more alignment marks 520 may be disposed in the corners and / or the center of reticle 500 for an RA measurement. Edge alignment mark 522 may be configured to measure a reticle shape deformation of reticle 500 due to thermal expansion. In some aspects, as shown in FIGS. 5A and 5B, one or more edge alignment marks 522 may be disposed along the perimeter edges (e.g., horizontal and vertical edges) of reticle 500 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.

[0076] Exemplary Method of Determining Thermal Models

[0077] Components of a lithographic apparatus, such as patterning device MA, substrate W, and lens L in projection system PS lens, 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. Current heating models rely on inline calibrations (e.g., overlay measurements) to tune the models. Inline calibrations typically take anywhere between 4-25 minutes depending upon the layer. Because inline calibrations take place inside a critical computational path of a lithography apparatus, they may lead to reduced throughput.

[0078] In some aspects, a heating model may be calibrated offline. Offline calibration may reduce computational time during wafer exposure while maintaining overlay performance (i.e., reduced overlay error).

[0079] FIG. 6 shows a method 600 according to some aspects. For example, method 600 may be for determining thermal deformations of a reticle, substrate, optical element, or the like. Method 600 may include operations including at least data receiving 602, dataset determination 604, model selection 606, deformation determination 608, and model tuning 610.

[0080] In 602, reticle transmission data, wafer manufacturing data, measured wafer resist data, and finite element analysis data may be collected.

[0081] Reticle transmission data may define the portion of illuminating radiation that passes through a reticle. Reticle transmission data for a plurality of reticles may be stored in a database.

[0082] Wafer manufacturing data may include data on the size and position of an image (e.g., a pattern) on a reticle. In some aspects, wafer manufacturing data may also include lot size (e.g., number of wafers exposed) and a dose of radiation supplied by SO.

[0083] Reticle transmission data and wafer manufacturing data may be input by a user before lot production.

[0084] Wafer resist data may comprise overlay data measured for a specific lithography apparatus. In some aspects, overlay data may be measured on a lot of non-production substrates (e.g., wafers that are not part of a production lot and are not fabricated by a lithographic process into a device) that have been exposed to a dose of radiation.

[0085] In some aspects, finite element method (FEM) data comprises thermo-mechanical deformation data of a reticle, a substrate, an optical element, or the like. Thermo-mechanical deformation data may include modal deformation shapes, modal deformation shape amplitudes, underlying physics, etc. of a reticle, lens, substrate, or the like. Simulated modal deformation shapes may be orthonormal. Mode shapes and amplitudes may be simulated for multiple field sizes and shifts.

[0086] In 604, pre-defined datasets are determined by combining FEM data and measured resist data, according to some aspects. FEM data may not capture the full dynamics of a reticle observed during customer use. For example, FEM data may not capture unique boundary conditions of a lithographic apparatus, or may be shifted in time compared to actual thermo-mechanical deformations. In some aspects, measured resist data may be used to calibrate the amplitudes of simulated modal deformation shapes generated by a FEM. The predefined datasets generated in 604 may be added to a database of reticle thermal models. In some aspects, 604 may be completed once during the lifetime of a lithographic apparatus.

[0087] In 606, a predictor may utilize customer input data to select an appropriate thermal model for a production lot from a database of thermal models. A database of thermal models may include the predefined datasets determined in 604. As described above, customer input data may include reticle transmission data and / or wafer manufacturing data. In some aspects, the predictor determines appropriate shapes and amplitudes of the predefined datasets based on the customer input data.

[0088] A predictor may comprise Bayesian optimization, free-energy minimization, Kalman-filtering, mixed-sensitivity synthesis, or the like.

[0089] In 608, calculated thermo-mechanical deformations of reticle, lens, substrate, etc. may be determined before lot production begins. The thermal model selected in 606 may be used to calculate thermo-mechanical deformations for the duration of lot production. In some aspects, calculated thermomechanical 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, the thermal model may determine changes in the temperature of the reticle during exposure.

[0090] In 610, the predefined datasets determined in 604 may be recalibrated. In some aspects, reticle alignment data may be measured by one or more alignment sensors (e.g., inspection apparatus 400)during or after lot production. Reticle alignment data may include measured distortions of reticle alignment marks and / or edge alignment marks. After lot production, the reticle alignment data may be integrated into the predefined datasets to further tune the heating model. For example, reticle alignment data may be used to calibrate amplitudes of modal deformation shapes.

[0091] In some aspects, the method 600 can be conducted outside of a critical computational path of a lithography apparatus. Operations 602-608 of method 600 may be performed before lot production begins.

[0092] 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. 1-5.

[0093] FIG. 7 illustrates an example computer system useful for implementing various embodiments in Figures 1-6.

[0094] Various embodiments may be implemented, for example, using one or more well-known computer systems, such as computer system 700 shown in FIG. 7. One or more computer systems 700 may be used, for example, to implement any of the embodiments discussed herein, as well as combinations and sub-combinations thereof.

[0095] Computer system 700 may include one or more processors (also called central processing units, or CPUs), such as a processor 704. Processor 704 may be connected to a communication infrastructure or bus 706.

[0096] Computer system 700 may also include user input / output device(s) 703, such as monitors, keyboards, pointing devices, cameras, other imaging devices etc., which may communicate with communication infrastructure 706 through user input / output interface(s) 702.

[0097] One or more of processors 704 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.

[0098] Computer system 700 may also include a main or primary memory 708, such as random access memory (RAM). Main memory 708 may include one or more levels of cache. Main memory 708 may have stored therein control logic (i.e., computer software) and / or data.

[0099] Computer system 700 may also include one or more secondary storage devices or memory 710. Secondary memory 710 may include, for example, a hard disk drive 712 and / or a removable storage device or drive 714. Removable storage drive 714 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.

[0100] Removable storage drive 714 may interact with a removable storage unit 718. Removable storage unit 718 may include a computer usable or readable storage device having stored thereoncomputer software (control logic) and / or data. Removable storage unit 718 may be a floppy disk, magnetic tape, compact disk, DVD, optical storage disk, and / any other computer data storage device. Removable storage drive 714 may read from and / or write to removable storage unit 718.

[0101] Secondary memory 710 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 700. Such means, devices, components, instrumentalities or other approaches may include, for example, a removable storage unit 722 and an interface 720. Examples of the removable storage unit 722 and the interface 720 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.

[0102] Computer system 700 may further include a communication or network interface 724. Communication interface 724 may enable computer system 700 to communicate and interact with any combination of external devices, external networks, external entities, etc. (individually and collectively referenced by reference number 728). For example, communication interface 724 may allow computer system 700 to communicate with external or remote devices 728 over communications path 726, 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 700 via communication path 726.

[0103] Computer system 700 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 Internet-of-Things, and / or embedded system, to name a few non-limiting examples, or any combination thereof.

[0104] Computer system 700 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 (laaS), etc.); and / or a hybrid model including any combination of the foregoing examples or other services or delivery paradigms.

[0105] Any applicable data structures, file formats, and schemas in computer system 700 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.

[0106] 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 700, main memory 708, secondary memory 710, and removable storage units 718 and 722, 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 700), may cause such data processing devices to operate as described herein.

[0107] 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. 7. In particular, embodiments can operate with software, hardware, and / or operating system implementations other than those described herein.

[0108] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses:1. A lithography system comprising: a reticle; an optical element; a substrate; a database comprising a plurality of heating models for a reticle, optical element and / or substrate that are configured to be generated offline using measured data; and a predictor configured to utilize a heating model in the plurality of heating models to predict reticle, optical element, and / or substrate temperature and deformations during wafer production.2. The lithography system of clause 1 , wherein the plurality of heating models are generated using predefined datasets, reticle transmission data, and / or wafer manufacturing data.3. The lithography system of clause 2, wherein the predefined datasets combine finite element method simulations with measured resist data.4. The lithography system of clause 3, wherein the finite element method simulations provide simulated mode shapes for the reticle, the optical element, and / or the substrate.5. The lithography system of clause 2, further comprising: a user input device, such that the wafer manufacturing data and reticle transmission data are input by the user input device.6. The lithography system of clause 2, further comprising: an alignment sensor, wherein modal amplitudes of the pre-defined datasets are updated after wafer production using data from the alignment sensor.7. The lithography system of clause 1, wherein the predictor determines which heating model in the plurality of heating models to utilize based on input wafer manufacturing data and reticle transmission data.8. The lithography system of clause 2, wherein the predefined data sets are created once during a lifetime of the lithography system.9. A method comprising: receiving reticle transmission data; receiving wafer manufacturing data; receiving measured wafer resist data; receiving finite element analysis data; determining predefined datasets of a reticle, optical element, and or substrate based on the measured wafer resist data and the finite element analysis data; selecting thermal deformation model from a database of thermal deformation models based on the reticle transmission data, the wafer manufacturing data, and the predefined datasets; and determining thermal deformation of the reticle, optical element, and / or substrate based on the selected thermal deformation model before wafer production begins.10. The method of clause 9, wherein the finite element analysis data comprises mode shapes and amplitudes of deformations of the reticle, optical element, and / or substrate.11. The method of clause 9, wherein the pre-defined datasets are updated after lot production to account for systematic changes and drifts of a lithography system.12. The method of clause 11, wherein the pre-defined datasets are updated based on measurements from alignment sensors.13. The method of clause 9, wherein the wafer resist data comprises overlay data.14. The method of clause 9, wherein the wafer manufacturing data comprises an image size and an image position on the reticle.15. The method of clause 9, wherein the pre-defined datasets comprise orthonormal mode shapes for both full-field and small field calculations.16. The method of clause 9, wherein the reticle transmission data and wafer manufacturing data are provided by a user.17. The method of clause 9, wherein determined thermal deformations of the reticle, lens, and / or substrate are used to update operating parameters of a lithography system.18. The method of clause 9, wherein the selecting comprises using a predictor to select a thermal deformation model from the database of thermal deformation models.19. The method of clause 9, wherein the pre-defined datasets are determined once during the lifetime of a lithography system.20. A computer-readable storage medium containing program instructions for a method being executed by an application, the application comprising code for one or more components that are called by theapplication during runtime, wherein execution of the program instructions by one or more processors of a computer system causes the one or more processors to perform operations comprising: receiving reticle transmission data; receiving wafer manufacturing data; receiving measured wafer resist data; generating reticle finite element analysis data; determining predefined datasets of a reticle, optical element, and / or substrate based on the measured wafer resist data and the finite element analysis data; selecting a thermal deformation model from a database of thermal deformation models based on the reticle transmission data, the wafer manufacturing data, and the predefined datasets; determining thermal deformation of a reticle, optical element, and / or substrate based on the selected thermal deformation model before wafer production begins; and recalibrating the predefined datasets after lot production based on data measured during lot production.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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 I 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” also applies 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.

[0113] It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0114] 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.

[0115] 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.

[0116] The foregoing description of the specific embodiments will so fully 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.

[0117] The breadth and scope of the protected subject matter should not be limited by any of the abovedescribed exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

CLAIMS1. A lithography system comprising: a reticle; an optical element; a substrate; a database comprising a plurality of heating models for a reticle, optical element and / or substrate that are configured to be generated offline using measured data; and a predictor configured to utilize a heating model in the plurality of heating models to predict reticle, optical element, and / or substrate temperature and deformations during wafer production.

2. The lithography system of claim 1, wherein: the plurality of heating models are generated using predefined datasets, reticle transmission data, and / or wafer manufacturing data; the predefined datasets combine finite element method simulations with measured resist data; and the finite element method simulations provide simulated mode shapes for the reticle, the optical element, and / or the substrate.

3. The lithography system of claim 2, further comprising: a user input device, such that the wafer manufacturing data and reticle transmission data are input by the user input device; and an alignment sensor, wherein modal amplitudes of the pre-defined datasets are updated after wafer production using data from the alignment sensor.

4. The lithography system of claim 1 , wherein the predictor determines which heating model in the plurality of heating models to utilize based on input wafer manufacturing data and reticle transmission data.

5. The lithography system of claim 2, wherein the predefined data sets are created once during a lifetime of the lithography system.

6. A method comprising: receiving reticle transmission data; receiving wafer manufacturing data; receiving measured wafer resist data; receiving finite element analysis data;determining predefined datasets of a reticle, optical element, and or substrate based on the measured wafer resist data and the finite element analysis data; selecting thermal deformation model from a database of thermal deformation models based on the reticle transmission data, the wafer manufacturing data, and the predefined datasets; and determining thermal deformation of the reticle, optical element, and / or substrate based on the selected thermal deformation model before wafer production begins.

7. The method of claim 6, wherein: the finite element analysis data comprises mode shapes and amplitudes of deformations of the reticle, optical element, and / or substrate.

8. The method of claim 6, wherein: the pre-defined datasets are updated after lot production to account for systematic changes and drifts of a lithography system; and the pre-defined datasets are updated based on measurements from alignment sensors.

9. The method of claim 6, wherein: the wafer resist data comprises overlay data; and the wafer manufacturing data comprises an image size and an image position on the reticle.

10. The method of claim 6, wherein the pre-defined datasets comprise orthonormal mode shapes for both full-field and small field calculations.

11. The method of claim 6, wherein the reticle transmission data and wafer manufacturing data are provided by a user.

12. The method of claim 6, wherein determined thermal deformations of the reticle, lens, and / or substrate are used to update operating parameters of a lithography system.

13. The method of claim 6, wherein the selecting comprises using a predictor to select a thermal deformation model from the database of thermal deformation models.

14. The method of claim 6, wherein the pre-defined datasets are determined once during the lifetime of a lithography system.

15. A computer-readable storage medium containing program instructions for a method being executed by an application, the application comprising code for one or more components that are calledby the application during runtime, wherein execution of the program instructions by one or more processors of a computer system causes the one or more processors to perform operations comprising: receiving reticle transmission data; receiving wafer manufacturing data; receiving measured wafer resist data; generating reticle finite element analysis data; determining predefined datasets of a reticle, optical element, and / or substrate based on the measured wafer resist data and the finite element analysis data; selecting a thermal deformation model from a database of thermal deformation models based on the reticle transmission data, the wafer manufacturing data, and the predefined datasets; determining thermal deformation of a reticle, optical element, and / or substrate based on the selected thermal deformation model before wafer production begins; and recalibrating the predefined datasets after lot production based on data measured during lot production.

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