Method and system for determining reticle deformation

Abstract

Disclosed herein is a computer system configured to: model a deformation of a reticle during a first period of time using boundary conditions that are dependent on a first state of the reticle during the first period of time; modeling a deformation of the reticle during a second period using a boundary condition that depends on a second state of the reticle during the second period; and controlling the operation of the lithographic process according to the modeled deformation of the reticle; wherein the first state of the mask plate is different from the second state of the mask plate; and the modeled deformation of the reticle at the beginning of the second time period is based on the modeled deformation of the reticle at the end of the first time period.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application No. 63 / 435,500, filed on December 27, 2022, and the entire contents of that U.S. application are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to techniques for improving the accuracy of prediction of reticle deformation. Process corrections can be determined and applied based on the determined deformation to reduce reticle-induced errors in a lithography process. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern to a substrate. Lithographic apparatuses are used, for example, in integrated circuit (IC) manufacturing. They can project a pattern from a patterning device (e.g., a mask, reticle) onto a layer of radiation-sensitive material (resist) applied to the substrate.

[0005] To project patterns onto substrates, lithographic equipment uses electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. Compared to lithographic equipment using deep ultraviolet (DUV) radiation, for example, with wavelengths of 157 nm, 193 nm, or 248 nm, lithographic equipment using extreme ultraviolet (EUV) radiation with wavelengths in the 4 nm to 20 nm range (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on substrates.

[0006] A lithographic apparatus may include a reticle stage for holding a patterning device (e.g., a reticle) for transferring a pattern to a substrate. Heating and / or cooling of the reticle may cause changes in reticle properties that may affect the radiation beam path (e.g., focus) and cause deformations in the patterned substrate (e.g., overlay errors). Changes in reticle properties may be modeled and corrected by a reticle heating model. Known reticle heating models rely on a sensor-based approach to calibrate the reticle heating model using a reticle temperature sensor (RTS) and require calibration across a large number of production wafers. In some examples, this approach may be inaccurate and inefficient because the RTS may exhibit errors, introducing unnecessary delays and requiring rework of production wafers.

[0007] The shape of the reticle may also be deformed due to other influences, such as clamping forces applied to the reticle. If not compensated, all reticle shape deformations may increase deformations (eg, overlay errors) in the patterned substrate. Summary of the Invention

[0008] There is a general need to improve known techniques for determining the deformed shape of a reticle. Process corrections can be determined and applied based on the determined deformation to reduce reticle-induced errors in the lithography process. This can avoid rework of production substrates and / or increase manufacturing throughput and yield of the lithography process.

[0009] According to a first aspect of the present disclosure, a computer system is provided, which is configured to: model a deformation of the mask during a first time period using boundary conditions that depend on a first state of the mask during the first time period; model the deformation of the mask during a second time period using boundary conditions that depend on a second state of the mask during the second time period; and control the operation of a lithography process according to the modeled deformation of the mask; wherein: the first state of the mask is different from the second state of the mask; and the modeled deformation of the mask at the beginning of the second time period is based on the modeled deformation of the mask at the end of the first time period.

[0010] According to a second aspect of the present disclosure, a method is provided, comprising: modeling a deformation of the mask during a first period using boundary conditions that depend on a first state of the mask during the first period; modeling a deformation of the mask during a second period using boundary conditions that depend on a second state of the mask during the second period; and controlling the operation of a lithography process according to the modeled deformation of the mask; wherein: the first state of the mask is different from the second state of the mask; and the modeled deformation of the mask at the beginning of the second period is based on the modeled deformation of the mask at the end of the first period.

[0011] According to a third aspect of the present disclosure, there is provided a system comprising: a computer system according to the first aspect; and a lithographic apparatus; wherein the computer system is configured to control the operation of the lithographic apparatus.

[0012] According to a fourth aspect of the present disclosure, there is provided a device manufacturing method using a photolithography process, the device manufacturing method including the method according to the second aspect.

[0013] According to a fifth aspect of the present disclosure, there is provided a non-transitory computer-readable medium program comprising computer-readable instructions configured to cause a processor to control a lithographic apparatus according to the method of the second aspect.

[0014] Embodiments of any of the technologies described herein may include EUV light sources, DUV light sources, systems, methods, processes, devices, and / or apparatus. Details of one or more embodiments are set forth below in the accompanying drawings and description. Additional features will be apparent from the description and drawings, as well as from the claims.

[0015] Other features and exemplary aspects of the various aspects, as well as the structure and operation of various aspects, are described in detail below with reference to the accompanying drawings. It should be noted that the aspects are not limited to the specific aspects described herein. Such aspects are presented herein for illustrative purposes only. Based on the teachings included in this disclosure, those skilled in the relevant art will understand additional aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated herein and form a part of this specification, illustrate various aspects and, together with the embodiments, further serve to explain the principles of the aspects and to enable one skilled in the relevant art to make and use the aspects.

[0017] Figure 1 is a schematic diagram of a lithographic apparatus according to an exemplary aspect.

[0018] Figure 2A is a schematic diagram of a lithographic cell according to an exemplary aspect.

[0019] Figure 2B is a schematic diagram of an overall lithography process including a computer system for optimizing a lithography process according to an exemplary aspect.

[0020] Figure 3A is a schematic bottom perspective view of a reticle platform and a reticle according to an exemplary aspect.

[0021] Figure 3B yes Figure 3A A schematic bottom plan view of the reticle platform is shown in FIG.

[0022] Figure 4A is a schematic top perspective view of a reticle exchange apparatus according to an exemplary aspect.

[0023] Figure 4B yes Figure 4A Schematic partial cross-sectional view of a reticle exchange device shown in FIG.

[0024] Figure 5 Overlay errors that may be caused by the temperature of the reticle without performing a process for correcting this source of overlay error are schematically illustrated.

[0025] Figure 6 Schematically illustrating the magnitude of deformation modeled by the reticle deformation model according to an embodiment.

[0026] Figure 7 A flow chart illustrating a process according to an embodiment is shown.

[0027] Features and exemplary aspects of the aspects will become apparent from the detailed description set forth below in conjunction with the accompanying drawings, in which like reference numerals identify corresponding elements throughout. In the drawings, like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, typically, the left-most digit of a reference numeral identifies the drawing in which the reference numeral first appears. Unless otherwise indicated, the drawings provided throughout this disclosure should not be construed as being drawn to scale. DETAILED DESCRIPTION

[0028] This specification discloses one or more aspects that incorporate features of the present invention. The disclosed aspects are merely illustrative of the present invention. The scope of the present invention is not limited to the disclosed aspects. The present invention is defined by the appended claims.

[0029] The described aspects and references in this specification to "one aspect," "aspect," "example aspect," "exemplary aspect," etc. indicate that the described aspects may include particular features, structures, or characteristics, but each aspect may not necessarily include the particular features, structures, or characteristics. Furthermore, these phrases do not necessarily refer to the same aspect. Furthermore, when particular features, structures, or characteristics are described in conjunction with an aspect, it should be understood that it is within the knowledge of those skilled in the art to implement such features, structures, or characteristics in conjunction with other aspects, whether or not explicitly described.

[0030] For ease of description, spatially relative terms, such as "below," "lower," "above," "upper," and similar terms, may be used herein to describe the relationship of one element or feature relative to another element or feature illustrated in the drawings. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0031] As used herein, the term "about" or "substantially" or "approximately" indicates that a value of a given quantity can vary based on the particular technology. The term "about" or "substantially" or "approximately" can indicate that a value of a given quantity varies within, for example, 1% to 15% of a value (e.g., ±1%, ±2%, ±5%, ±10%, or ±15% of a value) based on the particular technology.

[0032] The term "parasitic thermal effects" as used herein refers to induced or internal stresses and / or deformations of a reticle, such as mechanical stresses and / or deformations due to heating and / or cooling the reticle (e.g., by resistive heating, air flow cooling, exposing the reticle to a dose of radiation, etc.) or clamping and / or holding the reticle on a reticle stage.

[0033] As used herein, the term "non-production substrate" refers to a substrate (e.g., a wafer) that is not part of a production batch and is not fabricated into a device (e.g., an IC chip) through a photolithography process. For example, the non-production substrate can be a chuck temperature conditioning (CTC) wafer or a calibration wafer used in a reticle calibration method, such as to calibrate a reticle thermal model and conform the reticle by exposing the reticle and the CTC wafer to a dose of radiation and measuring the reticle alignment and / or reticle temperature.

[0034] As used herein, the term "production substrate" refers to a substrate (e.g., a wafer) that is part of a production batch and is fabricated into a device (e.g., an IC chip) through a photolithography process. For example, the production substrate may be a wafer (e.g., silicon) that is used for fabrication and in-line real-time calibration of a reticle thermal model, such as by exposing the reticle and wafer to a dose of radiation and measuring reticle alignment and / or reticle temperature.

[0035] As used herein, the term "reticle heating model" refers to a modal deformation method (e.g., analysis of different reticle mode shapes) used to determine reticle heating effects based on reticle alignment and / or reticle shape deformation and a finite element model (FEM) (e.g., COMSOL). For example, the reticle heating model can be deterministic (e.g., without random future states) or non-deterministic (e.g., including random future states) reticle heating effects. Furthermore, the reticle heating model can be considered a reticle heating execution algorithm (RHEA) that uses online modal calibration to determine baseline reticle heating dynamics. The reticle heating model can be calibrated by exposing a reticle and a non-production substrate to a dose of radiation for online, 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 production substrate to a dose of radiation for online, real-time calibration of the reticle heating model. Other reticle thermal models utilize sensor-based methods (e.g., using RTS measurements) to calibrate the reticle thermal 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 Application Publication No. 2020 / 0166854, which are incorporated herein by reference in their entireties.

[0036] Reticle heating causes changes in reticle properties that can affect the radiation path and cause manufacturing errors (e.g., overlay). Reticle mechanical deformation can be calculated (e.g., based on reticle temperature) and decomposed into k-parameters. Each thermomechanical mode (e.g., eigenvector) can be modeled in real time using modal participation factors μ and time constants τ. The measured overlay and / or alignment can be used to model the associated k-parameter drift, which can be used to calculate adjustments to the feedforward parameters μ and τ. The reticle heating model can also include adjusting the feedforward parameters μ and τ. This is further described in detail in U.S. Patent No. 10,429,749, U.S. Patent Application Publication No. 2020 / 0166854, and PCT Patent Application Publication No. 2021 / 043519, which are incorporated herein by reference in their entirety.

[0037] As used herein, the term "finite element model" or "FEM" refers to a method for numerically solving differential equations (e.g., heat transfer equations, structural analysis equations, fluid flow equations, etc.) that arise in reticle thermal models. For example, baseline reticle thermal dynamics can be analyzed using FEM via finite element analysis. This is further described in detail in U.S. Patent No. 10,429,749, U.S. Patent No. 10,281,825, and U.S. Patent Application Publication No. 2020 / 0166854, each of which is incorporated herein by reference in its entirety.

[0038] As used herein, the term "key performance indicator" or "KPI" or "k-parameter" refers to the coefficients of a polynomial fitted to the deformation of the reticle alignment marks and / or edge alignment marks. The k-parameters parameterize the imaging deformation on each substrate field. For example, each k-parameter can describe a certain image deformation component (e.g., scaling error, barrel distortion, pincushion distortion, etc.). For example, two important k-parameters are k4 (e.g., k5) representing the Y-axis magnification distortion and k6 (e.g., k7) representing the Y-axis magnification distortion. Figure 7 The k parameter represents the Y-axis barrel deformation (e.g., k4 / my shown in FIG8 ) and k18 represents the Y-axis barrel deformation (e.g., k18 / cshpy shown in FIG8 ). The k parameter can be used as an input to the lithography process (e.g., the lithography apparatus LA, the lithocell LC, the control system CL) to correct for the deformation. This is further described in U.S. Patent No. 10,429,749, U.S. Patent Application Publication No. 2020 / 0166854, and PCT Patent Application Publication No. 2021 / 043519, which are incorporated herein by reference in their entireties.

[0039] Aspects of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Aspects of the present disclosure may also be implemented as instructions stored on a machine-readable medium, 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 that can be read by a machine (e.g., a computing device). For example, machine-readable media 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.), etc. In addition, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only and that such actions are actually performed by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0040] Before describing these aspects in further detail, however, it is instructive to present an example environment in which aspects of the disclosure may be implemented.

[0041] Exemplary lithography systems

[0042] Figure 1 A lithographic system is shown comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV or 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., mask stage, reticle stage, reticle platform) configured to support a patterning device MA (e.g., mask, reticle), a projection system PS, and a substrate table WT configured to support a substrate W.

[0043] The illumination system IL is configured to condition the EUV or DUV radiation beam B before it is incident on the patterning device MA. In addition, the illumination system IL may include a faceted field mirror arrangement 10 and a faceted pupil mirror arrangement 11. The faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11 together provide a desired cross-sectional shape and a desired intensity distribution to the EUV and / or DUV radiation beam B. In addition to or as an alternative to the faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11, the illumination system IL may include other mirrors or arrangements.

[0044] After being adjusted thus, the EUV or DUV radiation beam B interacts with the patterning device MA. This interaction may be of the reflective type (as shown), which may be preferred for EUV radiation. This interaction may be of the transmissive type, which may be preferred for DUV radiation. As a result of this interaction, a patterned EUV or DUV radiation beam B' is generated. The projection system PS is configured to project the patterned EUV or DUV radiation beam B' onto the substrate W. For said purpose, the projection system PS may comprise a plurality of mirrors 13, 14 configured to project the patterned EUV or DUV radiation beam B' onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV or DUV radiation beam B', thereby 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 Figure 1 While illustrated in FIG. 1 as having only two mirrors 13 , 14 , the projection system PS may comprise a different number of mirrors (eg six or eight mirrors).

[0045] The substrate W may include a previously formed pattern. In such a case, the lithographic apparatus LA aligns an image formed by the patterned EUV and / or DUV radiation beam B′ with the pattern previously formed on the substrate W.

[0046] Exemplary Lithography Cell

[0047] Figure 2A A lithography cell LC is shown, which is sometimes also referred to as a lithocell or cluster. The lithography apparatus LA may form part of the lithography cell LC. The lithography cell LC may also include one or more devices for performing pre-exposure and post-exposure processes on the substrate. Conventionally, these devices include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chill plate CH, and a bake plate BK. A substrate transport device or robot RO picks up substrates from input / output ports I / O1, I / O2, moves the substrates between different process equipment, and transfers the substrates to a feed table LB of the lithography apparatus LA. These devices, often collectively referred to as coating and developing systems, are under the control of a coating and developing system control unit TCU, which is itself controlled by a management control system SCS, which also controls the lithography apparatus LA via the lithography control unit LACU. Thus, different devices can be operated to maximize throughput and processing efficiency.

[0048] In order to correctly and consistently expose substrates W exposed by the lithographic apparatus LA, it is desirable to inspect the substrates to measure properties of the patterned substrate, such as overlay errors between subsequent layers, line thickness, critical dimensions (CD), and the like. For this purpose, an inspection tool (e.g., a metrology tool MT) may be included in the lithocell LC and / or the lithographic apparatus LA. If errors are detected, adjustments may be made, for example, to the exposure of subsequent substrates or to other processing steps to be performed on the substrate W, particularly if the inspection is performed before other substrates W from the same batch or lot are yet to be exposed or processed.

[0049] The inspection apparatus, which may also be referred to as a metrology apparatus or metrology tool MT, is used to determine properties of a substrate W, and in particular to determine how properties vary between different substrates W or how properties associated with different layers of the same substrate W vary between different layers. The inspection apparatus is alternatively configured to identify defects on the substrate W and may, for example, be part of the lithography cell LC, integrated into the lithography apparatus LA, and / or be a separate device. The inspection apparatus may measure properties on a latent image (e.g., an image in a resist layer after exposure), a semi-latent image (e.g., an image in a resist layer after a post-exposure bake step), a developed resist image (e.g., an image in which the exposed or unexposed portions of the resist have been removed), or an etched image (e.g., an image after a pattern transfer step such as etching).

[0050] Exemplary Computer System

[0051] Figure 2B A computer system CL is shown, which is also called a controller or processor. The computer system CL can be part of the lithography cell LC, integrated into the lithography apparatus LA and / or a separate device. The computer system CL is configured to optimize the lithography process, for example, to calibrate the reticle thermal model. Typically, the patterning process in the lithography apparatus LA is one of the most critical steps in the process, which requires a high degree of accuracy in the dimensioning and placement of the structures on the substrate W. In order to ensure this high accuracy, the computer system CL can be configured to optimize the lithography process, for example, to calibrate the reticle thermal model. Figure 2B The three systems are combined in a so-called "holistic" control environment schematically depicted in FIG. Figure 2B As shown in , the “whole” environment may include a lithographic apparatus LA, a computer system CL and a metrology tool MT. For example, the lithographic apparatus LA (first system) may be connected to a computer system CL (second system) and a metrology tool MT (third system).

[0052] The key to this holistic lithography is optimizing the collaboration between these three systems to optimize the lithography process, for example, to enhance the overall process window and provide a tight control loop to ensure that the patterning performed by the lithography apparatus LA remains within the process window. The process window defines the range of process parameters (e.g., dose, focus, overlay, etc.) within which a particular manufacturing process produces a defined result, such as a functional semiconductor device. Typically, variations in process parameters within the lithography process or patterning process are tolerated within this range.

[0053] The computer system CL may, for example, use a design layout to be patterned (e.g., a portion of a design layout) to predict which resolution enhancement techniques to use, and perform computational lithography simulations and calculations, e.g., to determine which mask layouts and lithographic equipment settings achieve a maximum overall process window (in terms of resolution enhancement techniques) for the patterning process. Figure 2B Typically, the resolution enhancement technique is arranged to match the patterning possibilities of the lithographic apparatus LA. The computer system CL may also be used to detect where within the process window the lithographic apparatus LA is currently operating (e.g. using input from the metrology tool MT) to predict whether defects may be present, e.g. due to suboptimal processing (e.g. in the example of FIG. 1 ). Figure 2B is indicated by the arrow pointing to “0” in the second scale SC2).

[0054] The metrology tool MT may provide input to the computer system CL, for example, to enable accurate simulations and predictions. For example, the metrology tool MT may provide alignment information. The metrology tool MT may provide feedback (e.g., via the computer system CL) to the lithographic apparatus LA to identify, for example, possible drift in the calibration state of the lithographic apparatus LA (e.g., in the calibration state of the lithographic apparatus LA). Figure 2B (Indicated by the multiple arrows in the third scale SC3 in the figure). During the lithographic process, it is desirable to frequently measure the resulting structures, for example, for process control and verification. For example, different types of metrology tools MT can be used to measure one or more properties related to the lithographic apparatus LA, the substrate to be patterned W, and / or the reticle alignment. This is further described in detail in U.S. Patent No. 11,099,319 and PCT Patent Application Publication No. 2021 / 043519, which are incorporated herein by reference in their entirety.

[0055] Exemplary Reticle Platforms and Reticles

[0056] Figure 3A and Figure 3B A schematic diagram of a reticle platform 200 is shown, according to an exemplary aspect. Figure 3A is a schematic bottom perspective view of reticle platform 200 and reticle 300 according to example aspects. Figure 3B yes Figure 3ASchematic bottom plan view of reticle platform 200 and reticle 300 is shown in FIG.

[0057] The 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). The reticle stage 200 can include a stage bottom surface 202, a stage top surface 204, a stage side surface 206, a clamp 250, a reticle holder 224, and / or a reticle 300. In some aspects, the reticle stage 200 can be implemented with or with the reticle 300 in the lithographic apparatus LA. For example, the reticle stage 200 can be the support structure MT in the lithographic apparatus LA. In some aspects, the reticle 300 can be disposed on the stage bottom surface 202 and held by the clamp 250. For example, as Figure 3A and Figure 3B As shown in FIG, the reticle 300 can be placed on a fixture 250 (e.g., an electrostatic fixture) at the center of the platform bottom surface 202, wherein the reticle front side 302 is vertically facing away from the platform bottom surface 202. In some aspects, the reticle holder 224 can be placed on the platform bottom surface 202. For example, as shown in FIG. Figure 3A and Figure 3B As shown in , reticle 300 can be disposed at the center of platform bottom surface 202 and secured by reticle holders 224 adjacent to each corner of reticle 300 .

[0058] In some lithographic apparatuses, such as lithographic apparatus LA, a reticle stage 200 having or with a clamp 250 can be used to hold and position a reticle 300 for scanning or patterning operations. Figure 3A and Figure 3B As shown in FIG, , the reticle stage 200 may include a first encoder 212 and a second encoder 214 for positioning operations. For example, the first encoder 212 and the second encoder 214 may be interferometers. The first encoder 212 may be attached along a first direction of the reticle stage 200, such as the transverse direction (i.e., the X direction). Furthermore, the second encoder 214 may be attached along a second direction of the reticle stage 200, such as the longitudinal direction (i.e., the Y direction).

[0059] like Figure 3A and Figure 3B As shown in FIG, the mask 300 may include a mask front side 302, an alignment mark 310, and / or an edge alignment mark 320. The alignment mark 310 is configured to measure the mask alignment between the mask 300 and a substrate (e.g., substrate W, non-production substrate, production substrate). In some aspects, as shown in FIG. Figure 3A and Figure 3BAs shown in FIG, one or more alignment marks 310 may be provided in the corners and / or center of the mask 300 for RA measurement. The edge alignment mark 320 is configured to measure the mask shape deformation of the mask 300 due to thermal expansion when the mask 300 is not within a predetermined temperature (e.g., within 22°C ± 0.2°C). In some aspects, as Figure 3A and Figure 3B As shown in FIG, one or more edge alignment marks 320 can be provided along the peripheral edges (e.g., horizontal and vertical edges) of the reticle 300 for reticle shape deformation (RSD) measurement. In some aspects, the results of the RA measurement and / or the RSD measurement can be converted to the reticle temperature, for example, by an FEM that solves for the temperature based on the reticle alignment and / or reticle deformation.

[0060] Exemplary Reticle Exchange Equipment

[0061] Figure 4A and Figure 4B A schematic diagram of a reticle exchange apparatus 100 is shown, according to an exemplary aspect. Figure 4A is a schematic top perspective view of a reticle exchange apparatus 100 according to an exemplary aspect. Figure 4B yes Figure 4A FIG. 1 is a schematic partial cross-sectional view of a reticle exchange device 100 shown in FIG.

[0062] The reticle exchange apparatus 100 can be configured to reduce reticle exchange time and thermal stress in the reticle 300 to increase overall throughput in, for example, the lithography apparatus LA. In some aspects, the reticle exchange apparatus 100 can reduce stress in the reticle 300 by removing the reticle 300 from the reticle stage 200 to the vacuum robot (IVR) 400. For example, the reticle exchange apparatus 100 can quickly release the reticle 300 from the reticle holder 224 and the clamp 250 and transfer the reticle 300 to the IVR 400 to relieve thermal stress in the reticle 300. In some aspects, the reticle exchange apparatus 100 can reduce stress in the reticle 300 and increase throughput by releasing the reticle 300 and transferring the reticle from the reticle stage 200 to the IVR 400 and quickly returning and clamping the reticle 300 back to the reticle stage 200. Figure 4A and Figure 4B As shown in FIG. , the reticle exchanging apparatus 100 may include a reticle stage 200 , a fixture 250 , and an IVR 400 .

[0063] IVR 400 can include a reticle transport 402 having one or more reticle transport arms 404. In some aspects, reticle transport 402 can be a rapid exchange device (RED) configured to efficiently rotate and minimize reticle exchange time. Reticle transport arm 404 can include a reticle baseplate 406 configured to hold an object (e.g., reticle 300). In some aspects, reticle baseplate 406 can be an extreme ultraviolet inner chamber (EIP) for reticle 300. Reticle baseplate 406 includes a reticle baseplate front side 407, and reticle 300 includes a reticle back side 304.

[0064] like Figure 4A and Figure 4B As shown in FIG, the reticle base plate 406 can hold the reticle 300 so that the reticle base plate front side 407 and the reticle back side 304 each face the platform bottom surface 202 and the fixture front side 252. For example, the reticle base plate front side 407 and the reticle back side 304 can be perpendicular or vertically facing away from the platform bottom surface 202 and the fixture front side 252. Figure 4B As shown in FIG, reticle exchange apparatus 100 may include a reticle exchange area 410, which is a cross-sectional area between clamp 250, reticle 300, reticle base plate 406, and reticle conveyor arm 404 during a reticle exchange process.

[0065] In one example, during a reticle exchange process, reticle transport arm 404 of reticle transport device 402 positions reticle 300 on reticle base plate 406 toward gripper 250 in reticle exchange area 410. As described above, the transfer of the reticle from reticle transport device 402 to gripper 250 and from gripper to reticle transport device can relieve thermal stress in reticle 300 and reduce parasitic thermal effects in reticle 300.

[0066] Determination of mask deformation

[0067] Operation conditions of reticle 300 may cause deformation of the shape of reticle 300. Specifically, since reticle 300 is heated by each exposure process performed using reticle 300 during a photolithography process, the shape of reticle 300 may be deformed.

[0068] References below Figure 5 The influence of temperature-induced deformation of the reticle 300 will be described.

[0069] Figure 5Schematically illustrates overlay errors that may result from temperature-induced deformation of the reticle 300 without performing a process for correcting sources of such overlay errors. The magnitude of the overlay errors shown on the y-axis is exemplary, and actual magnitudes of the overlay errors may be larger or smaller than shown.

[0070] Period A1 begins at t0 and ends at t1. At t0, the appropriately temperature-regulated reticle 300 is clamped to the reticle stage 200. Reticle 300 can be referred to as being in a cold state. During period A1, reticle 300 is illuminated during the exposure process and heated. The effect of heating is to increase the shape deformation of reticle 300, which increases the magnitude of the overlay error. At time t1, reticle 300 can be referred to as being in a hot state.

[0071] Period B begins at t1 and ends at t2. During period B, reticle 300 is not used and, therefore, cools down. The shape deformation of reticle 300 decreases as reticle 300 cools to ambient temperature and the cold state of reticle 300. The effect of cooling is to reduce the expected magnitude of the overlay error of reticle 300 to be used.

[0072] Period A2 begins at t2. During period A2, the mask 300 is reused and heated during the exposure process. The effect of heating is to increase the shape deformation of the mask 300 and thus increase the magnitude of the overlay error.

[0073] like Figure 5 As shown in FIG, period B may not be long enough to cool the mask 300 to the same cold state as at the beginning of period A1 (ie, at t0). Therefore, the temperature-induced shape deformation of the mask 300 is greater at t2 than at t0.

[0074] As described earlier, it is known to determine deformation of the reticle 300 based on one or more reticle alignment RA measurement results. The reticle 300 may include edge alignment marks 320 that can be measured in one or more RA measurements. The shape deformation of the reticle 300 due to thermal expansion can be determined based on the one or more RA measurement results.

[0075] It is also known to use a thermomechanical finite element model (FEM) for a reticle thermal controller to determine how the shape deformation of the reticle 300 changes during the period of use of the reticle. For example, the inputs to the model may include parameters related to the use and properties of the reticle 300, such as input energy, field size, the location of features on the reticle 300, and the initial condition of the reticle 300 in a cold state. The output of the model may be a determination of the current deformation of the reticle shape. If there is a temperature change of the reticle 300, the current deformation of the reticle shape may differ from the deformation measured by the most recent RA measurement.

[0076] Based on the determined current deformation of the reticle shape, the configuration and / or operation of a process performed by reticle 300 can be altered to at least partially compensate for overlay errors that would otherwise be caused by the current deformation of the reticle shape.

[0077] The problem with known mask deformation models is that they cannot Figure 5 The situation shown in FIG is accurately modeled, which may be referred to as the ABA batch sequence problem, the rapid wear-out transition problem, or the hot mask re-chucking problem. Known reticle deformation models only model the deformation of the reticle 300 while it is used in the lithography process. Therefore, the deformation of the reticle 300 is only Figure 5 The model assumes that the mask 300 is in a cold state each time the mask 300 is used. However, as described above, this may not be an accurate assumption because when the mask 300 is reused (such as in Figure 5 At t2 in FIG, reticle 300 may still be hot. The incorrect assumption that reticle 300 is cold at the beginning of each use is a source of error in known techniques for modeling the deformation of reticle 300. Consequently, the process corrections determined to compensate for the deformation of reticle 300 will also be inaccurate.

[0078] The embodiment provides a mask deformation model that improves upon the prior art.

[0079] The reticle deformation model according to an embodiment models the deformation of the reticle 300 during use of the reticle 300, and also models the deformation of the reticle 300 between uses of the reticle 300. For example, Figure 5 The deformation during period B in t2 can be modeled and used to improve the determination of the reticle deformation at the beginning of the next reuse of reticle 300 (ie, at time t2).

[0080] Whenever the mask 300 is used in a photolithography process, the mask 300 is clamped to the mask stage 200. Figure 5During periods A1 and A2 of FIG. 2 , clamp 250 applies a clamping force to reticle 300 to secure reticle 300 to reticle platform 200. The applied clamping force may generate thermomechanical stress within reticle 300. When reticle 300 is not used in a photolithography process (e.g., during Figure 5 During the period B in FIG1 , the same clamping force is not applied to the mask 300 and this can release the thermomechanical stress in the mask 300. Therefore, the application and release of the clamping force during different periods can also change the shape deformation of the mask 300.

[0081] Embodiments provide a new reticle thermal model for modeling deformation of reticle 300 while reticle 300 is in use, as well as deformation of reticle 300 between uses of reticle 300. The reticle thermal model according to embodiments uses boundary conditions that depend on whether a clamping force is applied to reticle 300. Advantageously, deformation of reticle 300 may be more accurately modeled, particularly when rapid batch changeovers occur.

[0082] When the mask 300 is clamped to the mask platform 200, the Figure 4B The coordinate system shown in FIG is such that the plane of reticle 300 lies in the xy plane. A clamping force can be applied along the z-axis to secure reticle 300 to reticle stage 200. In the model of reticle deformation, the z-axis thermomechanical and / or thermal boundary conditions depend on whether a clamping force is applied to reticle 300.

[0083] Embodiments provide a reticle deformation model that can be a FEM (such as a thermomechanical FEM). This model can be similar to known reticle deformation models in that it models the shape deformation of reticle 300 based on its modeled thermal properties. Embodiments differ from known techniques in that the reticle deformation model models the deformation of reticle 300 between uses. To model the deformation of reticle 300 between uses, the model according to embodiments can use different thermal and mechanical boundary conditions depending on whether reticle 300 is clamped to reticle stage 200. Advantageously, the effects of clamping forces on reticle deformation are included in the reticle deformation model.

[0084] When a clamping force is applied to the reticle 300, the reticle deformation model applied can be referred to as ,in, are the (x, y, z) coordinates of the point on the mask, and is the time base of the determined deformation.

[0085] When no clamping force is applied to the reticle 300, the applied reticle deformation model may be referred to as ,in, are the (x, y, z) coordinates of the point on the mask, and is the time base of the determined deformation.

[0086] Figure 6 Schematically illustrates the mask deformation model according to an embodiment when performing a mask 300. Figure 5 The modeled magnitude of the deformation during the rapid batch changeover is shown in . 、 or To determine the deformation, as shown below:

[0087] for , ,

[0088] for , ,

[0089] for , .

[0090] The time for clamping or unclamping the mask 300 to or from the mask stage 200 (ie, 、 、 ) is the time when the boundary condition of the mask 300 changes. The time can be determined from the data on the transport of the mask 300 and / or the operation data of the system. 、 、 .

[0091] The model determines the deformation of the reticle shape based on the current clamping state of the reticle 300 and the effect of the previous clamping state on the deformation. When the clamping state of the reticle 300 changes (i.e., from clamped to unclamped at t1, and from unclamped to clamped at t2), the boundary conditions of the reticle deformation model change. When the boundary conditions of the reticle deformation model change, the reticle deformation ultimately determined under the previously used boundary conditions serves as the starting deformation for the reticle thermal model under the new boundary conditions.

[0092] Therefore, as shown by the above equation, in period B, when no clamping force is applied to the mask 300, the mask deformation is According to the previously determined deformation of the mask 300 when it is clamped (which is ) and also modeling the time-dependence of the current deformation (which is ) to determine the overall mask deformation.

[0093] Similarly, as also shown by the above equation, in period A2, when the clamping force is applied to the mask 300, the mask deformation is According to the previously determined deformation of the mask 300 when it is not clamped (which is ) and also modeling the time-dependence of the current deformation (which is ) to determine the overall mask deformation.

[0094] A reticle deformation model according to embodiments can be used between measurements of the deformation of the reticle shape performed through RA measurements. Specifically, an initial deformation state of reticle 300 can be determined from a first set of one or more RA measurement results. The initial deformation state of reticle 300 can be used as an initial reticle shape by the reticle deformation model according to embodiments. The reticle deformation model according to embodiments can then be used to determine the current deformation of reticle 300 until a second set of one or more RA measurement results is used to determine the reticle deformation. The deformation determined by the second set of one or more RA measurement results can then be used as a new starting reticle shape by the reticle deformation model.

[0095] Embodiments improve upon known techniques by providing a reticle deformation model that relies on the effects of the current reticle clamping state and previous reticle clamping states on reticle deformation. Embodiments include determining process corrections that can be applied based on the determined shape deformation of reticle 300 to at least partially compensate for the effects of the deformation. For example, the applied process corrections can include one or more of changing the position of a stage lens, changing scan lens parameters, and moving the object stage. The improved accuracy of reticle deformation determination enables improved process corrections to be determined and applied. Embodiments thus provide improved overlay performance, i.e., lower overlay error, compared to known techniques.

[0096] Embodiments include controlling a reticle thermal controller based on deformation determined by a reticle deformation model according to embodiments.

[0097] Another advantage of the reticle deformation model according to embodiments is that when the model is a FEM, the model parameters are based on physical principles rather than the model being a “black box.” This allows the model to be adjusted given any hardware changes (such as changes in the type of reticle 300 and / or fixture 250).

[0098] Figure 7 A flow chart illustrating a process according to an embodiment is shown.

[0099] In step 701, the method starts.

[0100] In step 703 , the method models deformation of the reticle during the first time period using boundary conditions that depend on a first state of the reticle during the first time period.

[0101] In step 705, the method models deformation of the reticle during the second time period using boundary conditions that depend on a second state of the reticle during the second time period, wherein the first state of the reticle is different from the second state of the reticle, and the modeled deformation of the reticle at the beginning of the second time period is based on the modeled deformation of the reticle at the end of the first time period.

[0102] In step 707 , the method controls the operation of the lithography process based on the modeled deformation of the reticle.

[0103] In step 709, the method ends.

[0104] Embodiments include many modifications and variations of the above-described techniques.

[0105] The reticle deformation model according to embodiments is not limited to FEM. Embodiments include any type of reticle deformation model that models different conditions of the reticle 300 when the reticle 300 is clamped and unclamped.

[0106] A reticle deformation model according to embodiments may be used independently or in combination with any technique for measuring the deformation of a reticle.

[0107] exist Figure 6 In FIG, the y-axis shows the magnitude of the modeled deformation of the mask shape. Figure 5 The metric related to the modeled deformation of the reticle shape used in the y-axis is the expected magnitude of overlay error caused by deformation of the reticle 300 if no process for correcting this source of overlay error is performed. Such a related metric is used instead to demonstrate the impact of the improved modeling achieved by the embodiments.

[0108] Although the embodiments are described with reference to EUV systems, the embodiments may be applied to any type of lithography system. In particular, the embodiments may be applied to DUV systems.

[0109] While specific reference may be made herein to the use of lithographic apparatus in IC manufacturing, it should be understood that the lithographic apparatus described herein may have other applications, such as in the manufacture of integrated optical systems, guide and detection patterns for magnetic domain memories, flat panel displays, LCDs, thin-film magnetic heads, and the like. Those skilled in the art will appreciate that, in the context of such alternative applications, any use of the terms "wafer" or "die" herein may be considered synonymous with the more general terms "substrate" or "target portion," respectively. The substrates referred to herein may be processed before or after exposure in, for example, automated resist coating and development system units (tools that typically apply a resist layer to a substrate and develop the exposed resist), metrology units, and / or inspection units. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Furthermore, a substrate may be processed more than once, for example to produce a multi-layer IC, such that the term substrate as used herein may also refer to a substrate that has already been processed with multiple layers.

[0110] While the above may have specifically referenced the use of the described aspects in the context of optical lithography, it should be understood that the described aspects can be used in other applications (e.g., imprint lithography) and are not limited to optical lithography where the context allows. In imprint lithography, a topography in a patterning device defines a pattern produced on a substrate. The topography of the patterning device can be pressed into a resist layer supplied to a substrate, where the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is removed from the resist, leaving a pattern therein.

[0111] It is to be understood that the phrases and terms herein are for the purpose of description and not limitation, so that the phrases and terms of this specification are to be interpreted by those skilled in the relevant art in light of the teachings herein.

[0112] As used herein, the term "substrate" describes a material that has a layer of material added thereon. In some aspects, the substrate itself can be patterned, and the material added on top of the substrate can also be patterned, or the material can remain unpatterned.

[0113] The following examples illustrate rather than limit aspects of the present disclosure. Other suitable modifications and adaptations of the various conditions and parameters normally encountered in the art and which should be apparent to those skilled in the relevant art are within the spirit and scope of the present disclosure.

[0114] While specific reference may be made herein to the use of the apparatus and / or system in the manufacture of ICs, it should be clearly understood that such apparatus and / or system has many other possible applications. For example, it may be used in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, LCD panels, thin film magnetic heads, etc. Those skilled in the art will appreciate that in the context of such alternative applications, any use of the terms "reticle," "wafer," or "die" herein should be considered to be replaced by the more general terms "mask," "substrate," and "target portion," respectively.

[0115] While certain 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.

[0116] It should be understood that the Detailed Description section, rather than 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 contemplated by the inventors, and thus, are not intended to limit the aspects and the appended claims in any way.

[0117] The above has been described with the aid of functional building blocks that illustrate the implementation of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries may be defined so long as the specified functions and their relationships are appropriately performed.

[0118] The foregoing description of specific aspects will thus fully reveal the general nature of the aspects: others may readily modify and / or adapt these specific aspects for various applications without undue experimentation by applying knowledge understood by those skilled in the relevant art 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.

[0119] Embodiments include the following numbered aspects:

[0120] 1. A computer system, the computer system being configured to:

[0121] modeling deformation of the reticle during the first time period using boundary conditions that depend on a first state of the reticle during the first time period;

[0122] modeling deformation of the reticle during the second time period using boundary conditions that depend on a second state of the reticle during the second time period; and

[0123] controlling the operation of a lithographic process according to the modeled deformation of the reticle,

[0124] in:

[0125] The first state of the reticle is different from the second state of the reticle; and

[0126] The modeled deformation of the reticle at the beginning of the second time period is based on the modeled deformation of the reticle at the end of the first time period.

[0127] 2. A computer system according to aspect 1, wherein the computer system is further configured to model the deformation of the mask during the third time period using boundary conditions that depend on the first state of the mask during the third time period, wherein the modeled deformation of the mask at the beginning of the third time period is based on the modeled deformation of the mask at the end of the second time period.

[0128] 3. The computer system of clause 2, wherein:

[0129] The second period begins approximately at the end of the first period; and

[0130] The third period begins approximately at the end of the second period.

[0131] 4. The computer system according to any preceding aspect, wherein the state of the mask during the first period is a clamped state; and the state of the mask during the second period is a released state.

[0132] 5. The computer system according to any preceding aspect, wherein the computer system is further configured to:

[0133] obtaining a measurement result of deformation of the mask before the first period of time;

[0134] determining an initial reticle deformation based on the measured deformation; and

[0135] Deformation of the reticle during the first period is modeled based on the initial reticle deformation.

[0136] 6. The computer system of clause 5, wherein the computer system is further configured to model deformation of the reticle during all time periods between the measurement of the deformation of the reticle and a later measurement of the deformation of the reticle.

[0137] 7. The computer system of clause 5 or 6, wherein each obtained measurement of deformation of the reticle is dependent upon one or more reticle alignment measurements of the reticle.

[0138] 8. The computer system of any preceding aspect, wherein controlling the operation of a lithography process based on the modeled deformation of the reticle comprises configuring the computer system to:

[0139] determining a change in an operating parameter of the lithography process based on the modeled deformation of the reticle to at least partially reduce an effect of the modeled deformation; and

[0140] The determined changes are applied to the operating parameters of the lithographic process.

[0141] 9. The computer system of any preceding aspect, wherein the computer system is configured to perform the modeling during each time period by means of a thermo-mechanical finite element model.

[0142] 10. A method comprising:

[0143] modeling deformation of the reticle during the first time period using boundary conditions that depend on a first state of the reticle during the first time period;

[0144] modeling deformation of the reticle during the second time period using boundary conditions that depend on a second state of the reticle during the second time period; and

[0145] controlling operation of a lithographic process based on the modeled deformation of the reticle;

[0146] in:

[0147] The first state of the reticle is different from the second state of the reticle; and

[0148] The modeled deformation of the reticle at the beginning of the second time period is based on the modeled deformation of the reticle at the end of the first time period.

[0149] 11. The method of clause 10, further comprising modeling deformation of the reticle during the third time period using boundary conditions that depend on the first state of the reticle during the third time period;

[0150] The modeled deformation of the mask at the beginning of the third time period is based on the modeled deformation of the mask at the end of the second time period.

[0151] 12. The method of clause 11, wherein:

[0152] The second period begins approximately at the end of the first period; and

[0153] The third period begins approximately at the end of the second period.

[0154] 13. The method according to any one of clauses 10 to 12, wherein the state of the mask during the first period is a clamped state; and the state of the mask during the second period is a released state.

[0155] 14. The method according to any one of aspects 10 to 13, further comprising:

[0156] measuring deformation of the mask before the first period of time;

[0157] determining an initial reticle deformation based on the measured deformation; and

[0158] Deformation of the reticle during the first period is modeled based on the initial reticle deformation.

[0159] 15. The method of clause 14, further comprising modeling deformation of the reticle during all periods between the measurement of the deformation of the reticle and a later measurement of the deformation of the reticle.

[0160] 16. The method of any of clauses 14 or 15, wherein each measurement of deformation of the reticle is dependent upon one or more reticle alignment measurements of the reticle.

[0161] 17. The method of any one of clauses 10 to 16, wherein controlling a lithography process based on the modeled deformation of the reticle comprises:

[0162] determining a change in an operating parameter of the lithography process based on the modeled deformation of the reticle to at least partially reduce an effect of the modeled deformation; and

[0163] The determined changes are applied to the operating parameters of the lithographic process.

[0164] 18. The method of any one of aspects 10 to 17, wherein the modeling during each time period is performed by a thermo-mechanical finite element model.

[0165] 19. A system comprising:

[0166] A computer system according to any one of aspects 1 to 9; and

[0167] photolithography equipment;

[0168] The computer system is configured to control the operation of the lithographic apparatus.

[0169] 20. A device manufacturing method using a photolithography process, the device manufacturing method comprising the method according to any one of clauses 10 to 18.

[0170] 21. A non-transitory computer-readable medium program comprising computer-readable instructions configured to cause a processor to control a lithographic apparatus according to the method of any one of clauses 10 to 18.

[0171] 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

1. A computer system, the computer system being configured to: modeling deformation of the reticle during the first time period using boundary conditions that depend on a first state of the reticle during the first time period; modeling deformation of the reticle during the second time period using boundary conditions that depend on a second state of the reticle during the second time period; as well as controlling the operation of a lithographic process according to the modeled deformation of the reticle, in: The first state of the reticle is different from the second state of the reticle; and The modeled deformation of the reticle at the beginning of the second time period is based on the modeled deformation of the reticle at the end of the first time period.

2. The computer system according to claim 1, wherein: The computer system is further configured to model deformation of the reticle during a third time period using boundary conditions that depend on the first state of the reticle during the third time period, wherein the modeled deformation of the reticle at the beginning of the third time period is based on the modeled deformation of the reticle at the end of the second time period, and wherein: The second period begins approximately at the end of the first period; and The third period begins approximately at the end of the second period.

3. The computer system according to claim 1, wherein: The state of the mask during the first period is a clamped state; and The state of the mask during the second period is a released state.

4. The computer system of claim 1 , wherein: The computer system is further configured to: obtaining a measurement result of deformation of the mask before the first period of time; determining an initial reticle deformation based on the measured deformation; and modeling deformation of the reticle during the first period based on the initial reticle deformation; The computer system is further configured to model deformation of the reticle during all periods between the measurement of the deformation of the reticle and a later measurement of the deformation of the reticle; and Each obtained measurement of deformation of the reticle is dependent upon one or more reticle alignment measurements of the reticle.

5. The computer system according to claim 1, wherein: Controlling the operation of a lithography process based on the modeled deformation of the reticle includes configuring the computer system to: determining a change in an operating parameter of the lithography process based on the modeled deformation of the reticle to at least partially reduce an effect of the modeled deformation; and The determined changes are applied to the operating parameters of the lithographic process. The computer system according to claim 1 , wherein: The computer system is configured to perform the modeling during each time period using a thermo-mechanical finite element model.

7. A method comprising: modeling deformation of the reticle during the first time period using boundary conditions that depend on a first state of the reticle during the first time period; modeling deformation of the reticle during the second time period using boundary conditions that depend on a second state of the reticle during the second time period; as well as controlling the operation of a lithographic process according to the modeled deformation of the reticle, in: The first state of the reticle is different from the second state of the reticle; and The modeled deformation of the reticle at the beginning of the second time period is based on the modeled deformation of the reticle at the end of the first time period.

8. The method according to claim 7, further comprising: modeling deformation of the reticle during a third time period using boundary conditions that depend on the first state of the reticle during the third time period, wherein the modeled deformation of the reticle at the beginning of the third time period is based on the modeled deformation of the reticle at the end of the second time period, in: The second period begins approximately at the end of the first period; and The third period begins approximately at the end of the second period.

9. The method according to claim 7, wherein: The state of the mask during the first period is a clamped state; and The state of the mask during the second period is a released state.

10. The method according to claim 7, further comprising: measuring deformation of the mask before the first period of time; determining an initial reticle deformation based on the measured deformation; modeling deformation of the reticle during the first period based on the initial reticle deformation; as well as modeling deformation of the reticle during all periods between the measurement of the deformation of the reticle and a later measurement of the deformation of the reticle, Each measurement of the deformation of the reticle is dependent on one or more reticle alignment measurements of the reticle.

11. The method according to claim 7, wherein: The operation of controlling the lithography process according to the modeled deformation of the mask comprises: determining a change in an operating parameter of the lithography process based on the modeled deformation of the reticle to at least partially reduce an effect of the modeled deformation; and The determined changes are applied to the operating parameters of the lithographic process.

12. The method according to claim 7, wherein: The modeling during each period was performed using a thermomechanical finite element model.

13. A system comprising: The computer system according to claim 1; and Lithography equipment, Wherein, the computer system is configured to control the operation of the lithographic apparatus.

14. A device manufacturing method using a photolithography process, the device manufacturing method comprising the method according to claim 7.

15. A non-transitory computer-readable medium program comprising computer-readable instructions configured to cause a processor to control a lithographic apparatus according to the method of claim 7.

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