Methods and systems for reticle conditioning and thermal modeling to improve reticle heating stability

Abstract

A method of reducing non-uniform thermomechanical effects of a reticle in a lithographic process includes conditioning the reticle on a reticle handler to adjust or maintain a temperature of the reticle, determining a temperature distribution of the reticle based on the conditioning, calibrating a reticle heating model based at least in part on the temperature distribution, and reducing a non-uniformity of the reticle based on the calibrated reticle heating model. Advantageously the method can reduce and / or compensate for non-uniform thermomechanical effects of the reticle, account for different reticle usage sequences, reduce conditioning times of the reticle, increase thermal stability of the reticle, increase calibration accuracy and speed of a reticle heating model, avoid rework of substrates, decrease overlay errors, increase throughput, and increase yield and accuracy of the lithographic process.

Description

METHODS AND SYSTEMS FOR RETICLE CONDITIONING AND THERMAL MODELING TO IMPROVE RETICLE HEATING STABILITYCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 565,911 which was filed on March 15, 2024 and which is incorporated herein in its entirety by reference.FIELD

[0002] The present disclosure relates to calibration apparatuses, systems, and methods, for example, reticle calibration apparatuses, systems, and methods to reduce non-uniform thermomechanical effects in a lithographic process.BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern of a patterning device (e.g., a mask, a reticle) onto a layer of radiation-sensitive material (resist) provided on a substrate.

[0004] To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which can be formed on the substrate. A lithographic apparatus, which uses extreme ultraviolet (EUV) radiation, having a wavelength within the range 4-20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, deep ultraviolet (DUV) radiation with a wavelength of 157 nm or 193 nm or 248 nm.

[0005] A lithographic apparatus can include a stage to hold a patterning device (e.g., a reticle) to transfer a pattern to a substrate. Reticle heating and / or cooling can cause changes in reticle 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 properties can be modeled and corrected with a reticle heating model. Current reticle heating models assume a uniform reticle heating, but this is generally not the case. Additionally, localized reticle cooling can create a non-uniform thermal environment, which can cause local hot spots on the reticle and lead to hysteretic reticle heating. In some examples, this approach can be inaccurate and inefficient, introduce errors and delays, and require rework of substrates.SUMMARY

[0006] Accordingly, there is a need to, e.g., reduce and / or compensate for non-uniform thermomechanical effects of a reticle, account for different reticle usage sequences (e.g., A-B-A lots), reduce conditioning times of the reticle, increase thermal stability of the reticle prior to and after exposure in a lithographic process, increase calibration accuracy and speed of a reticle heating model,avoid rework of substrates, decrease overlay errors, increase throughput, provide an option between decreasing overlay errors or increasing throughput, and increase yield and accuracy of the lithographic process.

[0007] In some aspects, a method of reducing non-uniform thermomechanical effects of a reticle in a lithographic process can include conditioning a reticle on a reticle handler to adjust or maintain a temperature of the reticle. In some aspects, the method can further include determining a temperature distribution of the reticle based on the conditioning. In some aspects, the method can further include calibrating a reticle heating model based at least in part on the temperature distribution. In some aspects, the method can further include reducing a non-uniformity of the reticle based on the calibrated reticle heating model.

[0008] In some aspects, conditioning the reticle can include cooling the reticle in a conditioning slot. In some aspects, cooling the reticle can include flowing gas uniformly over the reticle with a gas shower. In some aspects, flowing gas uniformly over the reticle can include flowing extreme clean dry air (XCDA).

[0009] In some aspects, the method can further include exchanging the reticle from the reticle handler to a reticle stage for a lithographic process.

[0010] In some aspects, the method can further include determining a thermal state of the reticle based on a previous location of the reticle. In some aspects, the method can further include calibrating the reticle heating model based on the thermal state. In some aspects, in a first configuration, the thermal state can include a cold state and the previous location can be the reticle handler. In some aspects, in a second configuration, the thermal state can include a hot state and the previous location can be a reticle stage.

[0011] In some aspects, the temperature distribution can include a two-dimensional (2D) thermal map of the reticle. In some aspects, the temperature distribution can include a three-dimensional (3D) temperature model of the reticle.

[0012] In some aspects, the method can further include exchanging a second reticle from a reticle stage to the reticle handler. In some aspects, the method can further include conditioning the second reticle on the reticle handler to adjust or maintain a temperature of the second reticle. In some aspects, the method can further include determining a second temperature distribution of the second reticle based on the conditioning. In some aspects, the method can further include calibrating the reticle heating model based on the second temperature distribution. In some aspects, the method can further include reducing a non-uniformity of the second reticle based on the calibrated reticle heating model.

[0013] In some aspects, calibrating the reticle heating model can include initializing the reticle heating model based on the temperature distribution. In some aspects, calibrating the reticle heating model can further include predicting modal deformation shapes of the reticle using a finite element model (FEM) based on the temperature distribution. In some aspects, calibrating the reticle heating model can further include measuring a reticle alignment (RA) between the reticle and a substrate. In some aspects,calibrating the reticle heating model can further include adjusting the modal deformation shapes of the reticle based on the measured reticle alignment (RA).

[0014] In some aspects, calibrating the reticle heating model can include providing an option between decreasing overlay errors in the lithographic process by calibrating the reticle heating model based on the temperature distribution or increasing throughput in the lithographic process by bypassing calibrating the reticle heating model based on the temperature distribution.

[0015] In some aspects, reducing the non-uniformity of the reticle can include reducing a spatially varying absorption distribution of the reticle. In some aspects, reducing the non-uniformity of the reticle can further include applying a correction to a substrate in the lithographic process.

[0016] In some aspects, a method of reducing non-uniform thermomechanical effects of an object in a lithographic process can include conditioning an object to adjust or maintain a temperature of the object. In some aspects, the method can further include determining a temperature distribution of the object based on the conditioning. In some aspects, the method can further include calibrating an object heating model based at least in part on the temperature distribution. In some aspects, the method can further include reducing a non-uniformity of the object based on the calibrated object heating model.

[0017] In some aspects, the object can include a reticle. In some aspects, the object can include a lens. In some aspects, the object can include a substrate.

[0018] In some aspects, a lithographic apparatus can include an illumination system, a projection system, and a controller. In some aspects, the illumination system can be configured to illuminate a reticle. In some aspects, the projection system can be configured to project an image of the reticle onto a substrate. In some aspects, the controller can be configured to reduce non-uniform thermomechanical effects of the reticle in a lithographic process. In some aspects, the controller can be configured to perform operations including conditioning the reticle on a reticle handler to adjust or maintain a temperature of the reticle, determining a temperature distribution of the reticle based on the conditioning, calibrating a reticle heating model based at least in part on the temperature distribution, and reducing a non-uniformity of the reticle based on the calibrated reticle heating model.

[0019] In some aspects, a non- transitory computer readable medium program can include computer readable instructions configured to cause a processor to perform operations including conditioning a reticle on a reticle handler to adjust or maintain a temperature of the reticle, determining a temperature distribution of the reticle based on the conditioning, calibrating a reticle heating model based at least in part on the temperature distribution, and reducing a non-uniformity of the reticle based on the calibrated reticle heating model.

[0020] Implementations of any of the techniques described above may include an EUV light source, a DUV light source, a system, an apparatus, a device, a method, a process, and / or a computer program product. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

[0021] Further features and exemplary aspects of the present disclosure, as well as the structure and operation of various aspects, are described in detail below with reference to the accompanying drawings. It is noted that the aspects are not limited to the specific aspects described herein. Such aspects are presented herein for illustrative purposes only. Additional aspects will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.BRIEF DESCRIPTION OF THE DRAWINGS / FIGURES

[0022] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the aspects and, together with the description, further serve to explain the principles of the aspects and to enable a person skilled in the relevant art(s) to make and use the aspects.

[0023] FIG. 1 is a schematic illustration of a lithographic apparatus, according to an exemplary aspect.

[0024] FIG. 2A is a schematic illustration of a lithographic cell, according to an exemplary aspect.

[0025] FIG. 2B is a schematic illustration of holistic lithography including a computer system to optimize a lithographic process, according to an exemplary aspect.

[0026] FIG. 3A is a schematic bottom perspective illustration of a reticle stage and a reticle, according to an exemplary aspect.

[0027] FIG. 3B is a schematic bottom plan illustration of the reticle stage shown in FIG. 3A.

[0028] FIG. 4A is a schematic top perspective illustration of a reticle exchange apparatus with a reticle handler and gas showers, according to an exemplary aspect.

[0029] FIG. 4B is a schematic partial cross-sectional illustration of the reticle exchange apparatus shown in FIG. 4A.

[0030] FIG. 5 is a plot of a process flow for an A-B-A lot sequence, according to an exemplary aspect.

[0031] FIG. 6 is a plot of a reticle handler conditioning sensitivity for a reticle on a reticle handler, according to an exemplary aspect.

[0032] FIG. 7 is a schematic illustration of a reticle heating model with a reticle handler conditioning model, according to an exemplary aspect.

[0033] FIG. 8 is a flow diagram for reducing a non-uniformity of a reticle in a reticle heating model, according to an exemplary aspect.

[0034] FIG. 9 is a flow diagram for reducing a non-uniformity of an object in an object heating model, according to an exemplary aspect.

[0035] The features and exemplary aspects 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

[0036] Provided herein are system, apparatus, device, method, process, and / or computer program product aspects, and / or combinations and sub-combinations thereof, for reducing non-uniform thermomechanical effects of a reticle in a lithographic process.

[0037] A system as described below can utilize a uniformly cooled turret to condition a reticle, estimate a temperature distribution of the conditioned reticle, and calibrate a reticle heating model based on the estimated temperature distribution.

[0038] A method as described below can condition a reticle on a reticle handler, determine a temperature distribution of the reticle, calibrate a reticle heating model based on the temperature distribution, and reduce a non-uniformity of the reticle based on the calibrated reticle heating model.

[0039] This specification discloses one or more aspects that incorporate the features of this present disclosure.

[0040] The aspect(s) described, and references in the specification to “one aspect,” “an aspect,” “an example aspect,” “an exemplary aspect,” etc., indicate that the aspect(s) described may include a particular feature, structure, or characteristic, but every aspect may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same aspect. Further, when a particular feature, structure, or characteristic is described in connection with an aspect, 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 aspects whether or not explicitly described.

[0041] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, may 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 may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0042] The term “about” or “substantially” or “approximately” 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” or “substantially” or “approximately” can indicate a value of a given quantity that varies within, for example, 1-15% of the value (e.g., ±1%, ±2%, ±5%, ±10%, or ±15% of the value).

[0043] Numerical values, including endpoints of ranges, can be expressed herein as approximations preceded by the term “about,” “substantially,” “approximately,” or the like. In such cases, other aspects include the particular numerical values. Regardless of whether a numerical value is expressed as an approximation, two aspects are included in this disclosure: one expressed as an approximation, and another not expressed as an approximation. It will be further understood that an endpoint of each range is significant both in relation to another endpoint, and independently of another endpoint.

[0044] Aspects of the disclosure may be implemented in hardware, firmware, software, or any combination thereof. Aspects of the disclosure may also be implemented as instructions stored on a machine -readable medium (e.g., memory), which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); and others. Further, firmware, software, routines, and / or instructions may 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.

[0045] The term “reticle heating model” as used herein indicates a modal deformation approach (e.g., analysis of different reticle mode shapes) to determine reticle heating effects based on reticle alignment and / or reticle shape deformations and a finite element model (FEM) (e.g., COMSOL). For example, the reticle heating model can be deterministic (e.g., no random future states) or non-deterministic (e.g., including random future states) reticle heating effects. Further, the reticle heating model can be deemed a reticle heating execution algorithm (RHEA) that uses inline modal calibrations to determine the baseline reticle heating dynamics. The reticle heating model can be initialized (e.g., setting initial values) and / or calibrated by conditioning a reticle (e.g., uniform cooling) and measuring and / or estimating a temperature distribution of the reticle (e.g., thermal map (2D or 3D), 3D temperature model, temperature profile, thermal time constant, etc.) for inline real-time calibration of the reticle heating model. In some aspects, for example, the reticle heating model can be calibrated by exposing a reticle and a substrate to a dose of radiation for inline real-time calibration of the reticle heating model. Other reticle heating models utilize a sensor-based approach to calibrate the reticle heating model. This is described in further detail in U.S. Patent No. 10,429,749, U.S. Patent No. 10,281,825, and U.S. Patent No. 11,300,886, which are incorporated by reference herein in their entireties.

[0046] Reticle heating causes changes in reticle properties that can affect the radiation path and cause fabrication errors (e.g., overlay). Reticle mechanical deformations (e.g., based on reticle temperature) can be calculated and decomposed into k-parameters. Each thermo-mechanical mode (e.g., eigenvector) can be modeled in time using modal participation factor p and time constant r. Measured overlay and / or alignment can be used to model the related k-parameter drifts, which can be used to calculate adjustments to the feed-forward parameters p and r. The reticle heating model can also include adjusting feed-forward parameters p and r. This is described in further detail in U.S. Patent No. 10,429,749, U.S. Patent No. 11,300,886, and WIPO Publication No. 2021 / 043519, which are incorporated by reference herein in their entireties.

[0047] The term “non-uniformity” or “non-uniform” as used herein indicates a parameter or a property of an object (e.g., a reticle) in a lithographic process that is not uniform and varies spatially and / or over time. In some aspects, non-uniformity can include thermal effects, thermomechanical effects, temperature distribution, heating, absorption, transmission, transmittance, reflectance, reflectivity, emissivity, transparency, opacity, pattern density, design layout, or a combination thereof.

[0048] The term “object heating model” as used herein indicates a modal deformation approach (e.g., analysis of different object mode shapes) to determine object heating effects based on object shape deformations and a FEM (e.g., COMSOL). In some aspects, the object of the object heating model can include a reticle, a lens, a substrate, a mirror, a filter, a combination thereof, or any other component of a lithographic process that exhibits a non-uniformity. In some aspects, the object heating model can include a reticle heating model, a lens heating model, a substrate heating model, or a combination thereof. For example, the object heating model can be deterministic (e.g., no random future states) or non-deterministic (e.g., including random future states) object heating effects. Further, the object heating model can utilize inline modal calibrations to determine the baseline object heating dynamics. The object heating model can be initialized (e.g., setting initial values) and / or calibrated by conditioning a reticle (e.g. , uniform cooling) and measuring and / or estimating a temperature distribution of the reticle (e.g., thermal map (2D or 3D), 3D temperature model, temperature profile, thermal time constant, etc.) for inline real-time calibration of the object heating model. In some aspects, for example, the object heating model can be similar to the reticle heating model and the technique to reduce and / or compensate for non-uniformity (e.g., non-uniform heating) can be applied to other objects (e.g., a lens, a substrate, a mirror, a filter, etc.).

[0049] Object heating causes changes in object properties (e.g., reticle, lens, substrate, mirror, filter, etc.) that can affect the radiation path and cause fabrication errors (e.g., overlay). Object mechanical deformations (e.g., based on object temperature) can be calculated and decomposed into k-parameters. Each thermo-mechanical mode (e.g., eigenvector) can be modeled in time using modal participation factor p and time constant r. Measured overlay and / or alignment can be used to model the related k- parameter drifts, which can be used to calculate adjustments to the feed-forward parameters p and r. The object heating model can also include adjusting feed-forward parameters p and r.

[0050] The term “finite element model” or “FEM” as used herein indicates a method for numerically solving differential equations arising in the reticle heating model or object heating model (e.g., heat transfer equations, structural analysis equations, fluid flow equations, etc.). For example, baseline reticle heating dynamics or object 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. Patent No. 11,300,886, which are incorporated by reference herein in their entireties.

[0051] The term “key performance indicators” or “KPIs” or “k-parameters” as used herein indicates coefficients of polynomials that are fit to distortions of reticle alignment marks and / or edge alignmentmarks. The k-parameters parameterize the distortion of the imaging across the field of each substrate. For example, each k-parameter can describe a certain image distortion component (e.g., scaling error, barrel distortion, pincushion distortion, linear magnification distortion, curvature distortion, etc.). The k-parameters can be used as input to a lithographic process (e.g., lithographic apparatus LA, lithographic cell LC, control system CL) to correct the distortion. This is described in further detail in U.S. Patent No. 10,429,749, U.S. Patent No. 11,300,886, and WIPO Publication No. 2021 / 043519, which are incorporated by reference herein in their entireties.

[0052] The term “inline calibration” or “inline real-time calibration” as used herein indicates calibration of the reticle heating model or object heating model during actual fabrication of substrates. For example, a calibration lot of substrates can be avoided and rework of substrates for calibration purposes can be reduced or avoided. The calibration can be done inline by exposing a reticle, a substrate, and / or an object (e.g., a lens, a mirror, a filter, etc.) to a dose of radiation. Further, the calibration can be done in real-time (e.g., at a real-time frame rate or a computing rate of 2.56 seconds or less). In some aspects, inline calibration can include reticle alignment (RA) results.

[0053] Before describing such aspects in more detail, however, it is instructive to present example environments in which aspects of the present disclosure may be implemented.

[0054] Exemplary Lithographic System

[0055] FIG. 1 shows a lithographic system comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV and / or a DUV radiation beam B and to supply the EUV and / or DUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT (e.g., a mask table, a reticle table, a reticle stage) configured to support a patterning device MA (e.g., a mask, a reticle), a projection system PS, and a substrate table WT configured to support a substrate W.

[0056] The illumination system IL is configured to condition the EUV and / or DUV radiation beam B before the EUV and / or DUV radiation beam B is incident upon the patterning device MA. Thereto, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and faceted pupil mirror device 11 together provide the EUV and / or DUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The illumination system IL may include other mirrors or devices in addition to, or instead of, the faceted field mirror device 10 and faceted pupil mirror device 11.

[0057] After being thus conditioned, the EUV and / or DUV radiation beam B interacts with the patterning device MA. This interaction may be reflective (as shown), which may be preferred for EUV radiation. This interaction may be transmissive, which may be preferred for DUV radiation. As a result of this interaction, a patterned EUV and / or DUV radiation beam B’ is generated. The projection system PS is configured to project the patterned EUV and / or DUV radiation beam B’ onto the substrate W. For that purpose, the projection system PS may comprise a plurality of mirrors 13, 14 which are configured to project the patterned EUV and / or DUV radiation beam B’ onto the substrate W held by the substratetable WT. The projection system PS may apply a reduction factor to the patterned EUV and / or DUV radiation beam B ’ , thus forming an image with features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is illustrated as having only two mirrors 13, 14 in FIG. 1, the projection system PS may include a different number of mirrors (e.g. six or eight mirrors).

[0058] The substrate W may include previously formed patterns. Where this is the case, the lithographic apparatus LA aligns the image, formed by the patterned EUV and / or DUV radiation beam B’ , with a pattern previously formed on the substrate W.

[0059] Exemplary Lithographic Cell

[0060] FIG. 2A shows a lithographic cell LC, also sometimes referred to as a lithocell or cluster. Lithographic apparatus LA may form part of lithographic cell LC. Lithographic cell LC may also include one or more apparatuses to perform pre- and post-exposure processes on a substrate. Conventionally 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 LA. 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 LA via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0061] In order for the substrates W exposed by the lithographic apparatus LA to be exposed correctly and consistently, it is desirable to inspect substrates to measure properties of patterned substrates, for example, overlay errors between subsequent layers, line thicknesses, critical dimensions (CD), etc. For this purpose, inspection tools (e.g., metrology tool MT) may be included in lithographic cell LC and / or lithographic apparatus LA. If errors are detected, adjustments, for example, may be made to exposures of subsequent substrates or to other processing steps that are to be performed on the substrates W, especially if the inspection is done before other substrates W of the same batch or lot are still to be exposed or processed.

[0062] An inspection apparatus, which may also be referred to as a metrology apparatus or metrology tool MT, is used to determine properties of the substrates W, and in particular, how properties of different substrates W vary or how properties associated with different layers of the same substrate W vary from layer to layer. The inspection apparatus may alternatively be constructed to identify defects on the substrate W and may, for example, be part of lithographic cell LC, integrated into lithographic apparatus LA, and / or be a stand-alone device. The inspection apparatus may measure the properties on a latent image (e.g., image in a resist layer after the exposure), on a semi-latent image (e.g., image in a resist layer after a post-exposure bake step), on a developed resist image (e.g., image in which theexposed or unexposed parts of the resist have been removed), or on an etched image (e.g., image after a pattern transfer step, such as etching).

[0063] Exemplary Computer System

[0064] FIG. 2B shows a computer system CL, also referred to as a controller or processor. Computer system CL may be part of lithographic cell LC, integrated into lithographic apparatus LA, and / or be a stand-alone device. Computer system CL is configured to optimize a lithographic process, for example, calibrate a reticle heating model. Typically the patterning process in lithographic apparatus LA is one of the most critical steps in the processing, which requires high accuracy of dimensioning and placement of structures on the substrate W. To ensure this high accuracy, three systems can be combined in a so- called “holistic” control environment as schematically depicted in FIG. 2B. As shown in FIG. 2B, the “holistic” environment can include lithographic apparatus LA, computer system CL, and metrology tool MT. For example, lithographic apparatus LA (a first system) can be connected to computer system CL (a second system) and metrology tool MT (a third system).

[0065] The key of such holistic lithography is to optimize the cooperation between these three systems to optimize a lithographic process, for example, to enhance the overall process window and provide tight controls loops to ensure that the patterning performed by lithographic apparatus LA stays within a process window. The process window defines a range of process parameters, for example, dose, focus, overlay, etc., within which a specific manufacturing process yields a defined result, for example, a functional semiconductor device — typically within which the process parameters in the lithographic process or patterning process are allowed to vary.

[0066] Computer system CL may, for example, use (e.g., part of) the design layout to be patterned to predict which resolution enhancement techniques to use and to perform computational lithography simulations and calculations, for example, to determine which mask layout and lithographic apparatus settings achieve the largest overall process window of the patterning process (shown in FIG. 2B by the double arrow in the first scale SCI). Typically, the resolution enhancement techniques are arranged to match the patterning possibilities of lithographic apparatus LA. Computer system CL may also be used to detect where within the process window lithographic apparatus LA is currently operating (e.g., using input from metrology tool MT) to predict whether defects may be present, for example, due to sub- optimal processing (shown in FIG. 2B by the arrow pointing “0” in the second scale SC2).

[0067] Metrology tool MT may provide input to computer system CL, for example, to enable accurate simulations and predictions. For example, metrology tool MT may provide alignment information. Metrology tool MT may provide feedback (e.g., via computer system CL) to lithographic apparatus LA to identify possible drifts, for example, in a calibration status of lithographic apparatus LA (shown in FIG. 2B by the multiple arrows in the third scale SC3). In lithographic processes, it is desirable to make frequent measurements of the structures created, for example, for process control and verification. Different types of metrology tools MT can be used, for example, to measure one or more properties relating to lithographic apparatus LA, a substrate W to be patterned, and / or reticle alignment. This isdescribed in further details in U.S. Patent No. 11,099,319 and WIPO Publication No. 2021 / 043519, which are incorporated by reference herein in their entireties.

[0068] Exemplary Reticle Stage and Reticle

[0069] FIGS. 3 A and 3B show schematic illustrations of reticle stage 200, according to exemplary aspects. FIG. 3A is a schematic bottom perspective illustration of reticle stage 200 and reticle 300, according to an example aspect. FIG. 3B is a schematic bottom plan illustration of reticle stage 200 and reticle 300 shown in FIG. 3A.

[0070] Reticle stage 200 (e.g., support structure MT) can be used in a lithographic apparatus (e.g., lithographic apparatus LA) to hold a patterning device (e.g., patterning device MA). Reticle stage 200 can include bottom stage surface 202, top stage surface 204, side stage surfaces 206, clamp 250, reticle cage 224, and / or reticle 300. In some aspects, reticle stage 200 with reticle 300 can be implemented in lithographic apparatus LA. For example, reticle stage 200 can be support structure MT in lithographic apparatus LA. In some aspects, reticle 300 can be disposed on bottom stage surface 202 and held by clamp 250. For example, as shown in FIGS. 3A and 3B, reticle 300 can be disposed on clamp 250 (e.g., an electrostatic clamp) at a center of bottom stage surface 202 with reticle frontside 302 facing perpendicularly away from bottom stage surface 202. In some aspects, reticle cage 224 can be disposed on bottom stage surface 202. For example, as shown in FIGS. 3A and 3B, reticle 300 can be disposed at a center of bottom stage surface 202 and secured by reticle cages 224 adjacent to each corner of reticle 300.

[0071] In some lithographic apparatuses, for example, lithographic apparatus LA, reticle stage 200 with clamp 250 can be used to hold and position reticle 300 for scanning or patterning operations. In some aspects, as shown in FIGS. 3A and 3B, reticle stage 200 can include first encoder 212 and second encoder 214 for positioning operations. For example, first and second encoders 212, 214 can be interferometers. First encoder 212 can be attached along a first direction, for example, a transverse direction (i.e., X-direction) of reticle stage 200. And second encoder 214 can be attached along a second direction, for example, a longitudinal direction (i.e., Y-direction) of reticle stage 200.

[0072] As shown in FIGS. 3 A and 3B, reticle 300 can include reticle frontside 302, alignment mark 310, and / or edge alignment mark 320. Alignment mark 310 is configured to measure a reticle alignment between reticle 300 and a substrate (e.g., substrate W, non-production substrate, production substrate). In some aspects, as shown in FIGS. 3A and 3B, one or more alignment marks 310 can be disposed in the corners and / or the center of reticle 300 for an RA measurement. Edge alignment mark 320 is configured to measure a reticle shape deformation of reticle 300 due to thermal expansion when reticle 300 is not within a predetermined temperature (e.g., at 22 °C ± 0.2 °C). In some aspects, as shown in FIGS. 3 A and 3B, one or more edge alignment marks 320 can be disposed along the perimeter edges (e.g., horizontal and vertical edges) of reticle 300 for a reticle shape deformation (RSD) measurement. In some aspects, the results of the RA measurement and / or the RSD measurement can be converted toa reticle temperature, for example, by a FEM that solves for temperature based on reticle alignment and / or reticle deformation.

[0073] Exemplary Reticle Exchange Apparatus and Process Flows

[0074] FIGS. 4A and 4B show schematic illustrations of reticle exchange apparatus 100, according to exemplary aspects. FIG. 4A is a schematic top perspective illustration of reticle exchange apparatus 100 with reticle handler 402 and gas showers 420, according to an exemplary aspect. FIG. 4B is a schematic partial cross-sectional illustration of reticle exchange apparatus 100 shown in FIG. 4A.

[0075] Reticle exchange apparatus 100 can be configured to reduce reticle exchange time and nonuniformities (e.g., thermal non-uniformities) in reticle 300 to increase overall throughput and / or decrease overlay errors, for example, in lithographic apparatus FA. In some aspects, reticle exchange apparatus 100 can reduce non-uniformities in reticle 300 by removing reticle 300 from reticle stage 200 to in-vacuum robot (IVR) 400. For example, reticle exchange apparatus 100 can quickly unclamp reticle 300 from reticle cages 224 and clamp 250 and transfer reticle 300 to IVR 400 to condition reticle 300 (e.g., uniformly cool reticle 300). In some aspects, reticle exchange apparatus 100 can reduce non- uniformities in reticle 300 and increase throughput by unclamping and transferring reticle 300 from reticle stage 200 to IVR 400, conditioning reticle 300 (e.g., uniformly cool reticle 300) on a reticle hander arm 404 of IVR 400, and then returning and clamping reticle 300 back to reticle stage 200. As shown in FIGS. 4A and 4B, reticle exchange apparatus 100 can include reticle stage 200, clamp 250, and IVR 400.

[0076] IVR 400 can include reticle handler 402 with one or more reticle handler arms 404. In some aspects, reticle handler 402 can be a rapid exchange device (RED), which is configured to efficiently rotate and minimize reticle exchange time. Reticle handler arm 404 can include reticle baseplate 406 configured to hold an object, for example, reticle 300. In some aspects, reticle baseplate 406 can be an extreme ultraviolet inner pod (EIP) for reticle 300. Reticle baseplate 406 includes reticle baseplate frontside 407, and reticle 300 includes reticle backside 304. In some aspects, reticle baseplate 406 can include a conditioning slot configured to condition (e.g., cool) an object (e.g., reticle 300) on reticle handler arm 404. For example, reticle baseplate 406 can cool reticle 300 in the conditioning slot.

[0077] As shown in FIG. 4A, IVR 400 can include one or more gas showers 420 adjacent one or more reticle handler arms 404. Gas shower 420 can be configured to condition reticle 300 (e.g., uniformly cool reticle 300) on reticle handler arm 404. Gas shower 420 can be further configured to flow gas uniformly over reticle 300. Gas shower 420 can be further configured to adjust and / or maintain a temperature distribution of reticle handler arm 404. In some aspects, gas shower 420 can be in communication with a reticle handler conditioning model (e.g., reticle handler conditioning model 720 (FIG. 7)). As shown in FIG. 4A, gas shower 420 can include shower head 422, gas input 424, gas 426, temperature sensor 428, and temperature controller 430.

[0078] Shower head 422 can be coupled to gas input 424 and configured to flow gas 426 over reticle 300 and / or reticle handler arm 404. Shower head 422 can be further configured to reduce conditioningtimes of reticle 300. In some aspects, for example, as shown in FIG. 4A, shower head 422 can have a rectangular or square shape to provide a uniform gas flow to reticle 300. In some aspects, shower head 422 can have a surface area that is equal to or greater than a surface area of reticle 300 (e.g., reticle backside 304) to provide uniform coverage of gas flow to reticle 300. In some aspects, gas 426 can include extreme clean dry air (XCDA). In some aspects, gas 426 can include air, nitrogen (Nz), argon (Ar), some other inert gas, or a combination thereof.

[0079] Temperature sensor 428 can be configured to measure a temperature distribution (e.g., thermal map) of reticle 300 and / or reticle handler arm 404. In some aspects, temperature sensor 428 can include a contact temperature sensor (e.g., a thermostat, a thermocouple, a thermistor, a resistive temperature detector (RTD), etc.), a non-contact temperature sensor (e.g., an optical sensor, an IR sensor, an optical pyrometer, a radiation thermometer, a thermal imager, etc.), a combination thereof, or any other suitable temperature sensor.

[0080] Temperature controller 430 can be configured to adjust and / or maintain a temperature distribution of reticle 300 and / or reticle handler arm 404. Temperature controller 430 can be further configured to estimate and / or model a temperature distribution (e.g., thermal map) of reticle 300 and / or reticle handler arm 404. In some aspects, temperature controller 430 can be in communication with a reticle handler conditioning model (e.g., reticle handler conditioning model 720 (FIG. 7))

[0081] As shown in FIGS. 4A and 4B, reticle baseplate 406 can hold reticle 300 such that reticle baseplate frontside 407 and reticle backside 304 each face bottom stage surface 202 and clamp frontside 252. For example, reticle baseplate frontside 407 and reticle backside 304 can be facing perpendicularly away from bottom stage surface 202 and clamp frontside 252. As shown in FIG. 4B, reticle exchange apparatus 100 can include reticle exchange area 410, which is the cross-sectional area between clamp 250, reticle 300, reticle baseplate 406, and reticle handler arm 404 during a reticle exchange process. In some aspects, reticle stage 200 can include clamp controller 260 configured to control clamp 250 (e.g., secure and / or release reticle 300).

[0082] In one example, during a reticle exchange process, reticle handler arm 404 of reticle handler 402 can position reticle 300 on reticle baseplate 406 towards clamp 250 in reticle exchange area 410. As described above, a reticle handoff from reticle handler 402 to clamp 250 and vice-versa can reduce non-uniformities (e.g., thermal non-uniformities) in reticle 300 and reduce parasitic and / or hysteretic thermal effects in reticle 300.

[0083] FIG. 5 illustrates process flow 500 for an A-B-A lot sequence, according to an exemplary aspect. Process flow 500 shows a plot of reticle temperature (°C) 502 as a function of time (s) 504 for a first sequence (A) 510 (e.g., exposure on reticle stage 200) at a first reticle temperature 512, a second sequence (B) 520 (e.g., cooling on reticle handler 402) at a second reticle temperature 522, and a third sequence (A) 530 (e.g., further exposure on reticle stage 200) at a third reticle temperature 532, forming an A-B-A lot sequence. An A-B-A lot is a fabrication sequence that uses a first reticle (A) for patterning a first lot of wafers (“A” lot), then a second reticle (B) for patterning a second lot of wafers (“B” lot),and then the first reticle (A) is again user for patterning a third lot of wafers (“A” lot), forming an ABA pattern). As shown in FIG. 5, third sequence (A) 530 can introduce one or more non-uniformities to the first reticle (A) (e.g., reticle 300) since the first reticle (A) is still in a hot state when exchanged back to reticle stage 200, and this residual heating can lead to overlay errors and / or decrease throughput. In some aspects, for example, as shown in FIG. 5, process flow 500 (e.g., A-B-A lot sequence) can be a fast wafer lot transition such that the exposure time for the second reticle (B) on reticle stage 200 (“B” lot) is much shorter than exposure time for the first reticle (A) on reticle stage 200 (“A” lot).

[0084] FIG. 6 illustrates reticle handler conditioning sensitivity 600 for reticle 300 on reticle handler 402, according to an exemplary aspect. Reticle handler conditioning sensitivity 600 shows a plot of reticle temperature (°C) 602 as a function of cooling time (s) 604 for a reticle (e.g., reticle 300) on reticle handler 402 exposed to gas shower 420. As shown in FIG. 6, a thermal time constant (T) 610 of conditioning reticle 300 (e.g., uniformly cooling with gas shower 420 (FIG. 4 A)) on reticle handler arm 404 can be determined. Thermal time constant (T) 610 can be used to estimate a temperature distribution of reticle 300 based on a cooling time of reticle 300 on reticle handler 402. In some aspects, thermal time constant (T) 610 can be in a range of about 100 s to about 400 s. For example, thermal time constant (T) 610 can be about 250 s. In some aspects, reticle handler conditioning sensitivity 600 can be part of a reticle handler conditioning model (e.g., reticle handler conditioning model 720 (FIG. 7)) to estimate and / or model a temperature distribution of reticle 300 based on the conditioning (e.g., cooling time of reticle 300 on reticle handler arm 404).

[0085] Exemplary Reticle Heating Models

[0086] As discussed above, a lithographic apparatus can include a reticle stage to hold a patterning device (e.g., a reticle) to transfer a pattern to a substrate. Reticle heating and / or cooling can cause changes in reticle 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 properties can be modeled and corrected with a reticle heating model. Current reticle heating models assume a uniform reticle heating, but this is generally not the case. In some examples, this approach can be inaccurate and inefficient, introduce errors and delays, and require rework of substrates.

[0087] Further, some reticle heating models are based only on reticle alignment (RA) measurements and do not account for other uncertainties during usage, for example, different reticle usage sequences (e.g., A-B-A lots). A-B-A lots can cause overlay errors and reduce throughput due to the non-uniform reticle heating of one or more reticles in the fabrication process. An A-B-A lot is a lot sequence that uses a first reticle (A) for patterning, then a second reticle (B) for patterning, and then the first reticle (A) again for patterning (e.g., ABA pattern). In some examples, the A-B-A lot is a fast wafer lot transition (e.g., exposure time for second reticle (B) is much shorter than exposure time for first reticle (A)). In this type of transition, the first reticle (A) is used to expose a first lot of wafers, the second reticle (B) in a cold state is used to expose a second lot of wafers, and the first reticle (A) in a hot stateis then quickly used again to expose a third lot of wafer. The residual heating of first reticle (A) may lead to overlay errors.

[0088] Additionally, localized reticle cooling (e.g., on a reticle handling turret) can create a non- uniform thermal environment, which can cause local hot spots on the reticle and lead to hysteretic reticle heating. The non-uniform reticle cooling of one or more reticles (e.g., first reticle (A) and / or second reticle (B)) in the fabrication process may lead to overlay errors and reduce throughput.

[0089] A temperature distribution of a reticle conditioned on a reticle handler (e.g., uniformly cooled) can be measured and / or estimated (e.g., via a reticle handler conditioning model) to initialize and calibrate the reticle heating model to account for reticle non-uniformities (e.g., non-uniform thermomechanical effects, non-uniform heating, non-uniform cooling, etc.) and provide a more accurate and efficient reticle heating model, decrease errors and delays (e.g., decrease overlay errors, increase throughput), and apply corrections to avoid rework of substrates.

[0090] Aspects of reticle calibration apparatuses, systems, and methods as discussed below can reduce and / or compensate for non-uniform thermomechanical effects of a reticle, account for different reticle usage sequences (e.g., A-B-A lots), reduce conditioning times of the reticle, increase thermal stability of the reticle prior to and after exposure in a lithographic process, increase calibration accuracy and speed of a reticle heating model, avoid rework of substrates, decrease overlay errors, increase throughput, provide an option between decreasing overlay errors or increasing throughput, and increase yield and accuracy of the lithographic process.

[0091] FIG. 7 is a schematic illustration of reticle heating model 700 with reticle handler conditioning model 720, according to an exemplary aspect. Reticle heating model 700 can be configured to reduce and / or compensate for non-uniform thermomechanical effects of reticle 300 in a lithographic process. Reticle heating model 700 can be further configured to reduce and / or compensate for non-uniformity (e.g., non-uniform thermomechanical effects) of an object (e.g., a reticle, a lens, a mirror, a filter, a substrate, etc.) in the lithographic process. Reticle heating model 700 can be further configured to account for different reticle usage sequences (e.g., A-B-A lots) and increase thermal stability of the reticle prior to and after exposure in the lithographic process. Reticle heating model 700 can be further configured to increase calibration accuracy and speed, avoid rework of substrates, decrease overlay errors, and increase throughput. Reticle heating model 700 can be further configured to provide an option between decreasing overlay errors or increasing throughput.

[0092] Although reticle heating model 700 is shown in FIG. 7 as a stand-alone system and / or method, the aspects of this disclosure can be used with other apparatuses, systems, and / or methods, such as, but not limited to, lithographic apparatus LA, lithographic cell LC, computer system CL, metrology tool MT, support structure MT, substrate table WT, reticle stage 200, reticle 300, IVR 400, gas shower 420, process flow 500, reticle handler conditioning sensitivity 600, flow diagram 800, and / or flow diagram 900.

[0093] As shown in FIG. 7, reticle heating model 700 can include reticle recipe database 710, reticle handler conditioning model 720 (e.g., conditioned reticle temperature distribution), finite element model (FEM) 730, principle component analysis (PCA) 740, inline calibration 750, and reticle heating feed-forward 760. In some aspects, reticle heating model 700 can reduce and / or compensate for non- uniform thermomechanical effects of reticle 300 in a lithographic process. In some aspects, reticle heating model 700 can be calibrated (e.g., initialized) with reticle handler conditioning model 720 (e.g., reticle handler conditioning sensitivity 600 shown in FIG. 6). In some aspects, reticle heating model 700 can decrease overlay errors in a lithographic process and avoid rework of substrates. In some aspects, reticle heating model 700 can be used for an object (e.g., a reticle, a lens, a mirror, a filter, a substrate, etc.) of a lithographic process in an object heating model.

[0094] Reticle recipe database 710 can be configured to provide reticle recipe data 712 (e.g., image size, position on reticle, lot sequence, etc.) to FEM 730. Reticle recipe database 710 can be further configured to provide reticle non-uniformity data 714 (e.g., reticle reference data, RA feedback, reticle temperature distribution, etc.) to FEM 730. As shown in FIG. 7, reticle recipe database 710 can send reticle recipe data 712 and reticle non-uniformity data 714 to FEM 730.

[0095] Reticle handler conditioning model 720 can be configured to estimate a temperature distribution of reticle 300 on a conditioned reticle handler arm 404 (e.g., uniformly cooled with gas shower 420). Reticle handler conditioning model 720 can be further configured to calibrate reticle heating model 700 based at least in part on the temperature distribution. Reticle handler conditioning model 720 can be further configured to reduce and / or compensate for non-uniform thermomechanical effects of reticle 300. Reticle handler conditioning model 720 can be further configured to calibrate (e.g., initialize) FEM 730 and account for non-uniformities in reticle 300. In some aspects, Reticle handler conditioning model 720 can include one or more temperature distributions (e.g., thermal map (2D or 3D), 3D temperature model, temperature profile, thermal time constant(s), etc.) of reticle 300. As shown in FIG. 7, reticle handler conditioning model 720 can send temperature distribution data 722 (e.g., 2D thermal map of conditioned reticle 300) to FEM 730 and receive simulated conditioned reticle data 724 (e.g., 3D temperature model of conditioned reticle 300) from FEM 730.

[0096] In some aspects, reticle handler conditioning model 720 can include one or more non- uniformity distributions (e.g., temperature distribution, thermal map, etc.) of reticle 300 in a lithographic process. In some aspects, reticle handler conditioning model 720 can include one or more non-uniformity distributions (e.g., temperature distribution, thermal map, etc.) of an object in a lithographic process, for example, a reticle (e.g., reticle 300), a lens (e.g., lens in lithographic apparatus LA), a mirror (e.g., first mirror 13), or a substrate (e.g., substrate W).

[0097] In some aspects, temperature distribution data 722 can initialize FEM 730 and account for nonuniformities of reticle 300 during exposure. In some aspects, temperature distribution data 722 can be determined by temperature sensor 428 and / or temperature controller 430 of gas shower 420. In someaspects, temperature distribution data 722 can be determined by thermal time constant (T) 610 for a respective conditioned reticle.

[0098] In some aspects, reticle handler conditioning model 720 can determine a thermal state of reticle 300 based on a previous location of reticle 300. For example, in a first configuration, the thermal state can be a cold state (e.g., conditioned reticle) and the previous location can be reticle handler 402. For example, in a second configuration, the thermal state can be a hot state (e.g., residual heating) and the previous location can be reticle stage 200.

[0099] In some aspects, reticle heating model 700 can provide an option between decreasing overlay errors in a lithographic process or increasing throughput of the lithographic process (e.g., based on critical dimension need, etc.). For example, reticle heating model 700 can bypass reticle handler conditioning model 720 in order to increase throughput at the cost of slightly higher overlay errors. Conversely, for example, reticle heating model 700 can utilize reticle handler conditioning model 720 in order to decrease overlay errors at the cost of slightly lower throughput.

[0100] In some aspects, reticle handler conditioning model 720 can be synchronized with reticle heating model 700 (e.g., FEM 730) to provide an improvement in overlay sensitivity. For example, the addition of reticle handler conditioning model 720 into FEM 730 can improve an overlay sensitivity by about 3x (e.g., overlay sensitivity in a range of about 0.35 nm to about 0.05 nm). In some aspects, reticle handler conditioning model 720 can be synchronized with reticle heating model 700 (e.g., FEM 730) to provide an improvement in sensitivity of usage sequences (e.g., A-B-A lots). For example, the addition of reticle handler conditioning model 720 into FEM 730 can improve sensitivity of reticles in a hot thermal state (e.g., A-B-A lots) by about 3x (e.g., sensitivity in a range of about 1 nm / °C to about 0.1 nm / °C).

[0101] FEM 730 can be configured to model (e.g., simulate) non-uniform thermomechanical effects of reticle 300 for a selected recipe (e.g., selected reticle pattern area, lot sequence, etc.). As shown in FIG. 7, FEM 730 can receive reticle recipe data 712 (e.g., image size, position on reticle, lot sequence, etc.) and reticle non-uniformity data 714 (e.g., temperature distribution data 722), simulate corresponding non-uniform thermomechanical effects through finite element analysis (e.g., thermodynamic equations), and send simulated reticle heating data 732 to PCA 740. In some aspects, FEM 730 can send reticle handler conditioning model 720 simulated conditioned reticle data 724 (e.g., 3D temperature model of conditioned reticle 300), for example, to form a feedback loop between reticle handler conditioning model 720 and FEM 730 to model and update a temperature distribution of conditioned reticle 300 to reduce and / or compensate for non-uniform thermomechanical effects of reticle 300.

[0102] PCA 740 can be configured to determine (e.g., extract) modal deformation shapes and amplitudes of modal deformation shapes of simulated reticle heating data 732 from FEM 730. In some aspects, modal deformation shapes can include spatially varying absorption distributions of reticle 300.In some aspects, modal deformation shapes can include deflection patterns (e.g., thermal expansion patterns) associated with particular modal frequencies of reticle 300. As shown in FIG. 7, PCA 740 can send simulated amplitudes of modal deformation shapes 742 to inline calibration 750, and send modal deformation shapes 744 to reticle heating feed-forward 760.

[0103] Inline calibration 750 can be configured to compare simulated amplitudes of modal deformation shapes 742 with actual alignment results of reticle 300. Inline calibration 750 can be further configured to calibrate simulated amplitudes of modal deformation shapes 742. In some aspects, inline calibration 750 can include reticle alignment (RA) measurements between reticle 300 and a substrate (e.g., substrate W). In some aspects, inline calibration 750 can include adjusting simulated amplitudes of modal deformation shapes 742 based on measured reticle alignment (RA). As shown in FIG. 7, inline calibration 750 can send calibrated amplitudes of modal deformation shapes 752 to reticle heating feedforward 760.

[0104] Reticle heating feed-forward 760 can be configured to reduce and / or correct non-uniform thermomechanical effects of reticle 300. Reticle heating feed-forward 760 can be further configured to apply corrections to substrate W and / or subsequent substrates based on modal deformation shapes 744 and calibrated amplitudes of modal deformation shapes 752 of reticle 300 for the selected recipe. As shown in FIG. 7, reticle heating feed-forward 760 can receive modal deformation shapes 744 from PCA 740 and calibrated amplitudes of modal deformation shapes 752 from inline calibration 750. In some aspects, reticle heating feed-forward 760 can reduce and / or compensate for a non-uniformity of reticle 300 (e.g., non-uniform thermal heating). In some aspects, reticle heating feed-forward 760 can reduce a spatially varying absorption distribution of reticle 300. In some aspects, reticle heating feed-forward 760 can apply a correction to a substrate and / or a subsequent substrate in a lithographic process (e.g., interwafer correction). In some aspects, reticle heating feed-forward 760 can decrease overlay errors in a lithographic process. In some aspects, reticle heating feed-forward 760 can increase throughput of a lithographic process.

[0105] Exemplary Flow Diagrams

[0106] FIGS. 8 and 9 illustrate flow diagrams 800, 900 for reticle heating model 700, according to various exemplary aspects. FIG. 8 illustrates flow diagram 800 for reducing a non-uniformity of a reticle (e.g., reticle 300) in a reticle heating model (e.g., reticle heating model 700). It is to be appreciated that not all steps in FIG. 8 are needed to perform the disclosure provided herein. Further, some of the steps may be performed simultaneously, sequentially, and / or in a different order than shown in FIG. 8. Flow diagram 800 shall be described with reference to FIGS. 1-7. However, flow diagram 800 is not limited to those example aspects. Although flow diagram 800 is shown in FIG. 8 as a stand-alone method, aspects of this disclosure can be used with other apparatuses, systems, and / or methods, for example, lithographic apparatus LA, lithographic cell LC, computer system CL, metrology tool MT, support structure MT, substrate table WT, reticle stage 200, reticle 300, IVR 400, gas shower 420, process flow500, reticle handler conditioning sensitivity 600, reticle heating model 700, reticle handler conditioning model 720, and / or flow diagram 900.

[0107] In step 802, as shown in the example of FIGS. 1-7, a reticle (e.g., reticle 300) on a reticle handler (e.g., reticle handler 402) can be conditioned (e.g., uniformly cooled) to adjust or maintain a temperature of the reticle. In some aspects, conditioning the reticle can include cooling the reticle in a conditioning slot (e.g., reticle baseplate 406). In some aspects, cooling the reticle can include flowing gas (e.g., gas 426) uniformly over the reticle with a gas shower (e.g., gas shower 420). In some aspects, flowing gas uniformly over the reticle can include flowing XCDA.

[0108] In step 804, as shown in the example of FIGS. 1-7, a temperature distribution (e.g., 2D thermal map, etc.) of reticle 300 can be determined based on the conditioning. In some aspects, the temperature distribution can be based on a thermal time constant (e.g., thermal time constant (T) 610 shown in FIG. 6) of a reticle handler (e.g., gas shower 420) that is conditioning reticle 300 (e.g., uniformly cooling). In some aspects, determining the temperature distribution can include measuring a temperature distribution (e.g., 2D thermal map, etc.) of reticle 300 (e.g., via temperature sensor 428 shown in FIG. 4A). In some aspects, determining the temperature distribution can include estimating and / or modeling a temperature distribution (e.g., 3D temperature model, etc.) of reticle 300 (e.g., via reticle handler conditioning model 720 shown in FIG. 7).

[0109] In step 806, as shown in the example of FIGS. 1-7, a reticle heating model (e.g., reticle heating model 700) can be calibrated based at least in part on the temperature distribution. In some aspects, calibrating the reticle heating model can include initializing the reticle heating model based on the temperature distribution. In some aspects, calibrating the reticle heating model can further include predicting modal deformation shapes (e.g., modal deformation shapes 744) of reticle 300 using a finite element model (e.g., FEM 730) based on the temperature distribution. In some aspects, calibrating the reticle heating model can further include measuring a reticle alignment (RA) between reticle 300 and a substrate (e.g., substrate W) and adjusting the modal deformation shapes of reticle 300 based on the measured reticle alignment (RA) (e.g., inline calibration 750).

[0110] In some aspects, a thermal state (e.g., cold state, hot state) of reticle 300 can be determined based on a previous location of reticle 300 (e.g., on reticle stage 200, on reticle handler 402). For example, IVR 400 can monitor a position and exchange path of reticle 300, for example, from reticle handler 402 to reticle stage 200 and then back to reticle handler 402 (e.g., A-B-A lot sequence). In some aspects, calibrating the reticle heating model can be based at least in part on the thermal state of reticle 300. In some aspects, calibrating the reticle heating model can be based on the temperature distribution and the thermal state of reticle 300.

[0111] In step 808, as shown in the example of FIGS. 1-7, a non-uniformity (e.g., non-uniform reticle heating) of reticle 300 can be reduced and / or corrected based on the calibrated reticle heating model (e.g., reticle heating feed-forward 760). In some aspects, reducing the non-uniformity can include reducing and / or compensating for residual heating of reticle 300 (e.g., A-B-A lot sequence). In someaspects, reducing the non-uniformity can include reducing a spatially varying absorption distribution of reticle 300. In some aspects, correcting the non-uniformity can include correcting an overlay deformation distribution of reticle 300.

[0112] In step 810, optionally, as shown in the example of FIGS. 1-7, a correction can be applied to a substrate and / or a subsequent substrate in the lithographic process. In some aspects, the correction can decrease an overlay error of the lithographic process. In some aspects, the correction can increase throughput of the lithographic process.

[0113] FIG. 9 illustrates flow diagram 900 for reducing a non-uniformity of an object (e.g., a reticle, a lens, a mirror, a filter, a substrate, etc.) in an object heating model (e.g., similar to reticle heating model 700). It is to be appreciated that not all steps in FIG. 9 are needed to perform the disclosure provided herein. Further, some of the steps may be performed simultaneously, sequentially, and / or in a different order than shown in FIG. 9. Flow diagram 900 shall be described with reference to FIGS. 1-7. However, flow diagram 900 is not limited to those example aspects. Although flow diagram 900 is shown in FIG. 9 as a stand-alone method, aspects of this disclosure can be used with other apparatuses, systems, and / or methods, for example, lithographic apparatus LA, lithographic cell LC, computer system CL, metrology tool MT, support structure MT, substrate table WT, reticle stage 200, reticle 300, IVR 400, gas shower 420, process flow 500, reticle handler conditioning sensitivity 600, reticle heating model 700, reticle handler conditioning model 720, and / or flow diagram 800.

[0114] In step 902, as shown in the example of FIGS. 1-7, an object (e.g., a reticle, a lens, a mirror, a filter, a substrate, etc.) can be conditioned (e.g., uniformly cooled) to adjust or maintain a temperature of the object. In some aspects, conditioning the object can include cooling the object in a conditioning slot (e.g., similar to reticle baseplate 406). In some aspects, cooling the object can include flowing gas (e.g., similar to gas 426) uniformly over the object with a gas shower (e.g., similar to gas shower 420). In some aspects, flowing gas uniformly over the object can include flowing XCDA.

[0115] In step 904, as shown in the example of FIGS. 1-7, a temperature distribution (e.g., 2D thermal map, etc.) of the object can be determined based on the conditioning. In some aspects, the temperature distribution can be based on a thermal time constant (e.g., similar to thermal time constant (T) 610 shown in FIG. 6) of an object handler (e.g., similar to reticle handler 402 and gas shower 420) that is conditioning the object (e.g., uniformly cooling). In some aspects, determining the temperature distribution can include measuring a temperature distribution (e.g., 2D thermal map, etc.) of the object (e.g., via a temperature sensor, e.g., similar to temperature sensor 428 shown in FIG. 4A). In some aspects, determining the temperature distribution can include estimating and / or modeling a temperature distribution (e.g., 3D temperature model, etc.) of the object (e.g., via an object handler conditioning model, similar to reticle handler conditioning model 720 shown in FIG. 7).

[0116] In step 906, as shown in the example of FIGS. 1-7, an object heating model (e.g., similar to reticle heating model 700) can be calibrated based at least in part on the temperature distribution. In some aspects, calibrating the object heating model can include initializing the object heating modelbased on the temperature distribution. In some aspects, calibrating the object heating model can further include predicting modal deformation shapes (e.g., modal deformation shapes 744) of the object using a finite element model (e.g., FEM 730) based on the temperature distribution. In some aspects, calibrating the object heating model can further include measuring a reticle alignment (RA) between reticle 300 and a substrate (e.g., substrate W) and adjusting the modal deformation shapes of reticle 300 based on the measured reticle alignment (RA) (e.g., inline calibration 750).

[0117] In step 908, as shown in the example of FIGS. 1-7, a non-uniformity (e.g., non-uniform object heating) of the object can be reduced and / or corrected based on the calibrated object heating model (e.g., reticle heating feed-forward 760). In some aspects, reducing the non-uniformity can include reducing and / or compensating for residual heating of the object. In some aspects, reducing the non- uniformity can include reducing a spatially varying absorption distribution of the object. In some aspects, correcting the non-uniformity can include correcting an overlay deformation distribution of the object.

[0118] In step 910, optionally, as shown in the example of FIGS. 1-7, a correction can be applied to a substrate and / or a subsequent substrate in the lithographic process. In some aspects, the correction can decrease an overlay error of the lithographic process. In some aspects, the correction can increase throughput of the lithographic process.

[0119] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses:1. A method of reducing non-uniform thermomechanical effects of a reticle in a lithographic process, the method comprising: conditioning a reticle on a reticle handler to adjust or maintain a temperature of the reticle; determining a temperature distribution of the reticle based on the conditioning; calibrating a reticle heating model based at least in part on the temperature distribution; and reducing a non-uniformity of the reticle based on the calibrated reticle heating model.2. The method of clause 1, wherein conditioning the reticle comprises cooling the reticle in a conditioning slot.3. The method of clause 2, wherein cooling the reticle comprises flowing gas uniformly over the reticle with a gas shower.4. The method of clause 3, wherein flowing gas uniformly over the reticle comprises flowing extreme clean dry air (XCDA).5. The method of clause 1, further comprising exchanging the reticle from the reticle handler to a reticle stage for a lithographic process.6. The method of clause 1, further comprising determining a thermal state of the reticle based on a previous location of the reticle.7. The method of clause 6, further comprising calibrating the reticle heating model based on the thermal state.8. The method of clause 7, wherein: in a first configuration, the thermal state comprises a cold state and the previous location is the reticle handler, and in a second configuration, the thermal state comprises a hot state and the previous location is a reticle stage.9. The method of clause 1, wherein the temperature distribution comprises a two-dimensional (2D) thermal map of the reticle.10. The method of clause 1, further comprising: exchanging a second reticle from a reticle stage to the reticle handler; conditioning the second reticle on the reticle handler to adjust or maintain a temperature of the second reticle; determining a second temperature distribution of the second reticle based on the conditioning; calibrating the reticle heating model based on the second temperature distribution; and reducing a non-uniformity of the second reticle based on the calibrated reticle heating model.11. The method of clause 1, wherein calibrating the reticle heating model comprises initializing the reticle heating model based on the temperature distribution.12. The method of clause 11, wherein calibrating the reticle heating model further comprises predicting modal deformation shapes of the reticle using a finite element model (FEM) based on the temperature distribution.13. The method of clause 12, wherein calibrating the reticle heating model further comprises: measuring a reticle alignment (RA) between the reticle and a substrate; and adjusting the modal deformation shapes of the reticle based on the measured reticle alignment (RA).14. The method of clause 1, wherein calibrating the reticle heating model comprising providing an option between decreasing overlay errors in the lithographic process by calibrating the reticle heating model based on the temperature distribution or increasing throughput in the lithographic process by bypassing calibrating the reticle heating model based on the temperature distribution.15. The method of clause 1, wherein reducing the non-uniformity of the reticle comprises reducing a spatially varying absorption distribution of the reticle.16. The method of clause 15, wherein reducing the non-uniformity of the reticle further comprises applying a correction to a substrate in the lithographic process.17. A method of reducing non-uniform thermomechanical effects of an object in a lithographic process, the method comprising: conditioning an object to adjust or maintain a temperature of the object; determining a temperature distribution of the object based on the conditioning; calibrating an object heating model based at least in part on the temperature distribution; and reducing a non-uniformity of the object based on the calibrated object heating model.18. The method of clause 17, wherein the object comprises a reticle, a lens, or a substrate.19. A lithographic apparatus comprising: an illumination system configured to illuminate a reticle; a projection system configured to project an image of the reticle onto a substrate; and a controller configured to reduce non-uniform thermomechanical effects of the reticle in a lithographic process, the controller configured to perform operations comprising: conditioning the reticle on a reticle handler to adjust or maintain a temperature of the reticle; determining a temperature distribution of the reticle based on the conditioning; calibrating a reticle heating model based at least in part on the temperature distribution; and reducing a non-uniformity of the reticle based on the calibrated reticle heating model.20. A non-transitory computer readable medium program comprising computer readable instructions configured to cause a processor to perform operations comprising: conditioning a reticle on a reticle handler to adjust or maintain a temperature of the reticle; determining a temperature distribution of the reticle based on the conditioning; calibrating a reticle heating model based at least in part on the temperature distribution; and reducing a non-uniformity of the reticle based on the calibrated reticle heating model.

[0120] Although specific reference may be made in this text to the use of the apparatus, system, and / or lithographic apparatus in the manufacture of ICs, it should be understood that such an apparatus, system, and / or lithographic apparatus described herein may have other possible applications, for example, such as in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, LCD panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle,” “wafer,” or “die” herein may be considered as synonymous with the more general terms “mask,” “substrate,” or “target portion”, respectively.

[0121] Although specific reference may have been made above to the use of aspects in the context of optical lithography, it will be appreciated that aspects may 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 may 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 removed from the resist leaving a pattern in it after the resist is cured.

[0122] 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 specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0123] The term “substrate” as used herein describes a material onto which material layers are added. In some aspects, the substrate itself may be patterned and materials added on top of it may also be patterned, or may remain without patterning. The substrate referred to herein may be processed, before or after exposure, for example, in a track unit (e.g., a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology unit, and / or an inspection unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example, 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.

[0124] The above examples are illustrative, but not limiting, of the aspects of this disclosure. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the field, and which would be apparent to those skilled in the relevant art(s), are within the spirit and scope of the disclosure.

[0125] While specific aspects have been described above, it will be appreciated that the aspects may be practiced otherwise than as described. The description is not intended to limit the scope of the claims.

[0126] 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 aspects as contemplated by the inventor(s), and thus, are not intended to limit the aspects and the appended claims in any way.

[0127] The aspects have 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.

[0128] The foregoing description of the specific aspects will so fully reveal the general nature of the aspects that others can, by applying knowledge within the skill of the art, readily modify and / or adapt for various applications such specific aspects, without undue experimentation, without departing from the general concept of the aspects. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed aspects, based on the teaching and guidance presented herein.

[0129] The breadth and scope of the aspects should not be limited by any of the above-described exemplary aspects, but should be defined only in accordance with the following claims and their equivalents.

Claims

CLAIMS1. A method of reducing non-uniform thermomechanical effects of a reticle in a lithographic process, the method comprising: conditioning a reticle on a reticle handler to adjust or maintain a temperature of the reticle; determining a temperature distribution of the reticle based on the conditioning; calibrating a reticle heating model based at least in part on the temperature distribution; and reducing a non-uniformity of the reticle based on the calibrated reticle heating model.

2. The method of claim 1 , wherein: conditioning the reticle comprises cooling the reticle in a conditioning slot; cooling the reticle comprises flowing gas uniformly over the reticle with a gas shower; and flowing gas uniformly over the reticle comprises flowing extreme clean dry air (XCDA).

3. The method of claim 1 , further comprising exchanging the reticle from the reticle handler to a reticle stage for a lithographic process.

4. The method of claim 1, further comprising: determining a thermal state of the reticle based on a previous location of the reticle; and calibrating the reticle heating model based on the thermal state, wherein: in a first configuration, the thermal state comprises a cold state and the previous location is the reticle handler, and in a second configuration, the thermal state comprises a hot state and the previous location is a reticle stage.

5. The method of claim 1, wherein the temperature distribution comprises a two-dimensional (2D) thermal map of the reticle.

6. The method of claim 1, further comprising: exchanging a second reticle from a reticle stage to the reticle handler; conditioning the second reticle on the reticle handler to adjust or maintain a temperature of the second reticle; determining a second temperature distribution of the second reticle based on the conditioning; calibrating the reticle heating model based on the second temperature distribution; and reducing a non-uniformity of the second reticle based on the calibrated reticle heating model.

7. The method of claim 1, wherein calibrating the reticle heating model comprises initializing the reticle heating model based on the temperature distribution.

8. The method of claim 7, wherein calibrating the reticle heating model further comprises predicting modal deformation shapes of the reticle using a finite element model (FEM) based on the temperature distribution.

9. The method of claim 8, wherein calibrating the reticle heating model further comprises: measuring a reticle alignment (RA) between the reticle and a substrate; and adjusting the modal deformation shapes of the reticle based on the measured reticle alignment (RA).

10. The method of claim 1, wherein calibrating the reticle heating model comprising providing an option between decreasing overlay errors in the lithographic process by calibrating the reticle heating model based on the temperature distribution or increasing throughput in the lithographic process by bypassing calibrating the reticle heating model based on the temperature distribution.

11. The method of claim 1 , wherein reducing the non-uniformity of the reticle comprises reducing a spatially varying absorption distribution of the reticle and12. The method of claim 11, wherein reducing the non-uniformity of the reticle further comprises applying a correction to a substrate in the lithographic process.

13. A method of reducing non-uniform thermomechanical effects of an object in a lithographic process, the method comprising: conditioning an object to adjust or maintain a temperature of the object; determining a temperature distribution of the object based on the conditioning; calibrating an object heating model based at least in part on the temperature distribution; and reducing a non-uniformity of the object based on the calibrated object heating model.

14. The method of claim 13, wherein the object comprises a reticle, a lens, or a substrate.

15. A lithographic apparatus comprising: an illumination system configured to illuminate a reticle; a projection system configured to project an image of the reticle onto a substrate; and a controller configured to reduce non-uniform thermomechanical effects of the reticle in a lithographic process, the controller configured to perform operations comprising:conditioning the reticle on a reticle handler to adjust or maintain a temperature of the reticle; determining a temperature distribution of the reticle based on the conditioning; calibrating a reticle heating model based at least in part on the temperature distribution; and reducing a non-uniformity of the reticle based on the calibrated reticle heating model.

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