Methods for inferring and estimating reticle temperature based on reticle shape measurements

Abstract

Embodiments herein describe systems, methods, and devices for determining reticle temperature based on reticle shape measurements. The system can include an illumination path configured to direct radiation onto a patterning device and a detection path configured to direct a portion of the radiation after the portion interacts with the patterning device onto a detector configured to output a signal representative of the portion of the radiation beam. A controller can receive the signal and determine information about a physical characteristic or alignment of the patterning device and use this information to estimate a load temperature of the patterning device. The controller or another controller can use the estimated load temperature to compensate for temperature-induced magnification of the patterning device. The controller or another controller performs the compensation by adjusting the positioning of a stage or lens of the system.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS)

[0001] This application claims priority to U.S. Patent Application No. 63 / 433,709, filed December 19, 2022, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to systems, methods, and devices relating to reticle temperatures in lithographic apparatus. [Background technology]

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

[0004] To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. Lithographic apparatus may use extreme ultraviolet (EUV) radiation, which has a wavelength in the range of 4 nm to 20 nm, for example 6.7 nm or 13.5 nm, or deep ultraviolet (DUV) radiation, which has a wavelength in the range of about 120 to 400 nm, for example 193 or 248 nm.

[0005] In DUV lithography, the radiation beam can induce a thermal response in the reticle. Specifically, the reticle can absorb a large amount of thermal energy from the DUV radiation beam, causing the reticle to heat up and expand. Other sources, such as various mechatronic devices in the reticle handler and reticle stage module, can also contribute to reticle heating. Reticle heating, which creates a non-uniform reticle thermal profile, can be a major source of image distortion and overlay errors in lithography systems.

[0006] Currently, reticle temperatures are measured using reticle temperature sensors (RTS). However, this has drawbacks, such as sensor degradation over time, known as sensor end-of-life (EOL). Another drawback is that the sensor itself has a temperature gradient and may not be able to capture the fast exponential behavior of reticle temperature. Furthermore, each measurement can take approximately 5 seconds per wafer, which creates additional overhead. What is needed is a better way to determine reticle temperature. Summary of the Invention

[0007]

[0007] The present disclosure provides systems and methods for determining reticle temperature based on reticle shape measurements.

[0008] In some embodiments, the system includes an illumination path configured to direct radiation onto a patterning device, and a detection path configured to direct a portion of the radiation after the portion of the radiation interacts with the patterning device onto a detector configured to output a signal representative of the portion of the radiation beam. A controller is configured to receive the signal, determine information regarding a physical characteristic or alignment of the patterning device, and use this information to estimate a load temperature of the patterning device.

[0009] In some embodiments, the controller or another controller uses the estimated load temperature to compensate for temperature-induced expansion of the patterning device.

[0010] In some embodiments, the controller or another controller performs the compensation by adjusting the positioning of a stage or lens in the system.

[0011] In some embodiments, the controller or another controller alters a physical feature, another physical feature, or an alignment of the patterning device.

[0012] In some embodiments, the information includes magnification features of the patterning device.

[0013] In some embodiments, the information comprises a deformation of the patterning device.

[0014] In some embodiments, the controller is further configured to store a model of reticle shape metrology corresponding to the deformation data.

[0015] In some embodiments, the controller is configured to use the information and to use the model to output predicted deformation data.

[0016] In some embodiments, the controller is further configured to predict an absolute increase or decrease in temperature of the patterning device using the predicted deformation data.

[0017] In some embodiments, the patterning device is a reticle, and the controller uses the magnification features to predict the reticle heating profile.

[0018] In some embodiments, a method for estimating a patterning device load temperature includes receiving patterning device alignment data measured between a patterning device and a wafer and determining a patterning device heating profile based on a previous position of the patterning device. Based on the patterning device alignment data, the heating profile, and a thermal expansion coefficient, the patterning device load temperature can be determined. Future deformation of the patterning device can also be determined. Adjustments to the position of a stage or lens of the system that generated the alignment data can be made to compensate for the future deformation of the patterning device.

[0019] In some embodiments, the method may include directing radiation onto a patterning device, and directing a portion of the radiation onto a detector configured to output a signal representative of a portion of the radiation beam after the portion of the radiation has interacted with the patterning device. The method may determine information about a physical characteristic or alignment of the patterning device, and use this information to estimate a load temperature of the patterning device.

[0020] In some embodiments, using the information in the method can include estimating the load temperature using magnification features of the patterning device.

[0021] In some embodiments, using the information in the method can include estimating the load temperature using the patterning device deformation information.

[0022] In some embodiments, the method can store a model of the shape measurements of the patterning device corresponding to the deformation data.

[0023] In some embodiments, the method can use the information to output predicted deformation data using a model.

[0024] In some embodiments, the method may use the predicted deformation data to predict an absolute increase or decrease in temperature of the patterning device.

[0025]

[0025] In some embodiments, the patterning device is a reticle and the reticle temperature is estimated using a model based on reticle shape or reticle alignment data, a reticle heating profile based on the previous position of the reticle, and the thermal expansion coefficient of the reticle material.

[0026]

[0026] Further features of the present disclosure, as well as the structure and operation of various embodiments of the present disclosure, will be described in detail below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Based on the teachings contained herein, additional embodiments will be apparent to those skilled in the art. [Brief explanation of the drawings]

[0027]

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate the present disclosure and, together with the description, serve to explain the principles of the present disclosure and to enable those skilled in the art to make and use the present disclosure.

[0028] [Figure 1]

[0028] FIG. 1 is a schematic diagram of a lithographic apparatus according to an exemplary embodiment. [Figure 2A]

[0029] 1 is a schematic diagram of a lithographic cell according to an exemplary embodiment. [Figure 2B]

[0030] FIG. 1 is a schematic diagram of an integrated lithography system including a computer system for optimizing a lithography process, according to an exemplary embodiment. [Figure 3A]

[0031] 1 is a schematic bottom perspective view of a reticle stage and a reticle according to an exemplary embodiment. [Figure 3B]

[0032] FIG. 3B is a schematic bottom view of the reticle stage shown in FIG. 3A. [Figure 4A]

[0033] 1 is a schematic top perspective view of a reticle exchange apparatus according to an exemplary embodiment; [Figure 4B]

[0034] 4B is a schematic partial cross-sectional view of the reticle exchange apparatus shown in FIG. 4A. [Figures 5A-5C]

[0035] 10 shows experimental results of reticle thermo-mechanical key performance indicators over time in accordance with an embodiment of the present disclosure. [Figure 6-8]

[0036] 10 illustrates various exemplary methods for predicting a reticle temperature profile, according to embodiments of the present disclosure.

[0029]

[0037] Features of the present disclosure will become more apparent from the following detailed description when read in conjunction with the drawings. Like reference numerals identify corresponding elements throughout the drawings. In the drawings, like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Also, the left-most digit(s) of a reference number generally identifies the figure in which that reference number first appears. Unless otherwise indicated, the figures provided throughout this disclosure should not be construed as being to scale. DETAILED DESCRIPTION OF THE INVENTION

[0030]

[0038] This specification discloses one or more embodiments incorporating features of the present invention. The disclosed embodiment(s) merely represent examples of the present invention. The scope of the present invention is not limited to the disclosed embodiment(s). The present invention is defined by the appended claims.

[0031]

[0039] References herein to one or more described embodiments, as well as to "one embodiment," "an embodiment," "an example embodiment," "an exemplary embodiment," and the like, indicate that one or more described embodiments may include a particular feature, structure, or characteristic, but not all embodiments necessarily include that particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with one embodiment, it will be understood that it is within the knowledge of one of ordinary skill in the art to implement such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0032]

[0040] For ease of description, spatially relative terms such as "beneath," "below," "lower," "above," "on," and "upper" may be used herein to describe the relationship of one element or feature shown in the figures to another element or features. Spatially relative terms are intended to encompass various orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be in other orientations (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be similarly interpreted accordingly.

[0033]

[0041] As used herein, the terms "about" or "substantially" or "approximately" refer to the value of a given quantity that may vary based on a particular technique. Based on a particular technique, the terms "about" or "substantially" or "approximately" may refer to the value of a given quantity that varies, for example, within 1-15% of the value (e.g., ±1%, ±2%, ±5%, ±10%, or ±15% of the value).

[0034]

[0042] As used herein, the term "parasitic thermal effects" refers to stresses and / or deformations induced in or within a reticle due to, for example, heating and / or cooling of the reticle (e.g., due to resistive heating, gas flow cooling, exposure of the reticle to a radiation dose, etc.) or mechanical pressure and / or deformation due to clamping and / or holding the reticle on a reticle stage.

[0035]

[0043] As used herein, the term "non-production substrate" refers to a substrate (e.g., a wafer) that is not part of a production lot and is not fabricated into a device (e.g., an IC chip) by a lithography process. For example, a non-production substrate can be a chuck temperature control (CTC) wafer or a calibration wafer for a reticle calibration method, such as exposing a reticle and a CTC wafer to a radiation dose and measuring reticle alignment and / or reticle temperature to calibrate a reticle heating model and acclimate the reticle.

[0036]

[0044] As used herein, the term "production substrate" refers to a substrate (e.g., a wafer) that is part of a production lot and that is fabricated into a device (e.g., an IC chip) by a lithographic process. For example, a product substrate can be a wafer (e.g., silicon) for fabrication and in-line real-time calibration of a reticle heating model, for example, by exposing the reticle and wafer to a radiation dose and measuring reticle alignment and / or reticle temperature.

[0037]

[0045] As used herein, the term "reticle heating model" refers to a modal deformation approach (e.g., analysis of various reticle mode shapes) for determining 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., non-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 determines baseline reticle heating dynamics using in-line modal calibration. The reticle heating model can be calibrated by exposing a reticle and a non-product substrate to a radiation dose for in-line real-time calibration of the reticle heating model. For example, in some aspects, the reticle heating model can be calibrated by exposing a reticle and a product substrate to a radiation dose for in-line real-time calibration of the reticle heating model. Other reticle heating models utilize sensor-based approaches (e.g., using RTS measurements) to calibrate the reticle heating model, as described in more detail in U.S. Pat. No. 10,429,749, U.S. Pat. No. 10,281,825, and U.S. Patent Application Publication No. 2020 / 0166854, which are incorporated herein by reference in their entireties.

[0038]

[0046] Reticle heating changes reticle properties, which can affect radiation paths and cause manufacturing errors (e.g., overlay). Mechanical deformation of the reticle (e.g., based on reticle temperature) can be calculated and decomposed into k-parameters. Each thermomechanical mode (e.g., eigenvector) can be modeled in time using modal contributions μ and time constants τ. Measured overlay and / or alignment can be used to model the drift of the associated k-parameters, which can then 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 described in more detail in U.S. Pat. No. 10,429,749, U.S. Patent Application Publication No. 2020 / 0166854, and WIPO Publication No. 2021 / 043519, which are incorporated herein by reference in their entireties.

[0039]

[0047] As used herein, the terms "finite element model" or "FEM" refer to methods for numerically solving differential equations (e.g., heat transfer equations, structural analysis equations, fluid flow equations, etc.) that arise in reticle heating models. For example, FEM can be used to analyze baseline reticle heating dynamics through finite element analysis, as described in further detail in U.S. Pat. No. 10,429,749, U.S. Pat. No. 10,281,825, and U.S. Patent Application Publication No. 2020 / 0166854.

[0040]

[0048] As used herein, the terms "key performance indicator" or "KPI" or "k-parameter" refer to the coefficients of a polynomial that fits the distortion of the reticle alignment marks and / or edge alignment marks. The k-parameters parameterize the distortion of the imaging in each substrate field. For example, each k-parameter can describe a specific image distortion component (e.g., scaling error, barrel distortion, pincushion distortion, etc.). For example, two important k-parameters are k4 (e.g., k4 / my shown in FIG. 7 ), which represents the Y-axis magnification distortion, and k18 (e.g., k18 / cshpy shown in FIG. 8 ), which represents the Y-axis barrel distortion. These k-parameters can be used as inputs to the lithography process (e.g., the lithography apparatus LA, the lithography cell LC, and the control (controller) system CL) to correct for the distortions. This is described in further detail in U.S. Patent No. 10,429,749, U.S. Patent Application Publication No. 2020 / 0166854, and WIPO Publication No. 2021 / 043519.

[0041]

[0049] As used herein, the term "in-line real-time calibration" refers to calibration of a reticle heating model during actual production of product substrates. For example, calibration lots of product substrates can be avoided, reducing or eliminating rework of product substrates for calibration purposes. Calibration can be performed in-line by exposing the reticle and product substrate to a radiation dose. Furthermore, calibration can be performed in real time (e.g., at a real-time frame rate or a computing rate of 2.56 seconds or less).

[0042]

[0050] Aspects of the present disclosure, such as a controller, 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 readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Furthermore, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, as will be apparent to those skilled in the art, such description is merely for convenience and it will be recognized that such actions may actually result from a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0043]

[0051] However, before describing such aspects in further detail, it is beneficial to present an exemplary environment in which aspects of the present disclosure can be implemented.

[0044] Exemplary Lithography System

[0052] 1 shows a lithography system comprising a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate a beam of EUV and / or DUV radiation B and to provide this beam of EUV and / or DUV radiation B to the lithography apparatus LA. The lithography apparatus LA includes an illumination system IL, a support structure MT (e.g. a mask table, reticle table, reticle stage) configured to support a patterning device MA (e.g. a mask, reticle), a projection system PS, and a substrate table WT configured to support a substrate W.

[0045]

[0053] The illumination system IL is configured to condition the EUV and / or DUV radiation beam B before it is incident on the patterning device MA. To that end, the illumination system IL may include a facetted field mirror device 10 and a facetted pupil mirror device 11. Together, the facetted field mirror device 10 and the facetted pupil mirror device 11 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 facetted field mirror device 10 and the facetted pupil mirror device 11.

[0046]

[0054] After being so conditioned, the EUV and / or DUV radiation beam B interacts with the patterning device MA. This interaction may be reflective (not shown), which is preferred for EUV radiation. This interaction may be transmissive, which is preferred for DUV radiation. This interaction results in a patterned EUV and / or DUV radiation beam B'. The projection system PS is configured to project the patterned EUV and / or DUV radiation beam B' onto the substrate W. To this end, 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, which is held by a substrate table WT. The projection system PS may apply a demagnification factor to the patterned EUV and / or DUV radiation beam B' to form images of features that are smaller than corresponding features on the patterning device MA. For example, a demagnification factor of 4 or 8 may be applied. Although in Figure 1 the projection system PS is illustrated as having only two mirrors 13, 14, the projection system PS may include a different number of mirrors, for example 6 or 8 mirrors.

[0047]

[0055] The substrate W may include a previously formed pattern, and if this is the case, the lithographic apparatus LA aligns the image formed by the patterned EUV and / or DUV radiation beam B' with the previously formed pattern on the substrate W.

[0048] Exemplary Lithography Cell

[0056] FIG. 2A shows a lithography cell LC, sometimes referred to as a lithocell or cluster. A lithography apparatus LA may form part of the lithography cell LC. The lithography cell LC may also include one or more devices that perform pre-exposure and post-exposure processes on a substrate. Conventionally, these may include a spin coater SC that deposits a resist layer, a developer DE that develops exposed resist, a chill plate CH, and a bake plate BK. A substrate handler or robot RO retrieves substrates from input / output ports I / O1 and I / O2, moves them between various process tools, and delivers them to the loading bay LB of the lithography apparatus LA. These devices, often collectively referred to as a track, are under the control of a track control unit TCU, which is itself controlled by a supervisory control system SCS. The SCS also controls the lithography apparatus LA via a lithography control unit LACU. Thus, these various tools can be operated to maximize throughput and processing efficiency.

[0049]

[0057] In order to accurately and consistently expose a substrate W to be exposed by the lithographic apparatus LA, it is desirable to inspect the substrate to measure properties of the patterned substrate, such as, for example, overlay error between subsequent layers, line thickness, critical dimension (CD), etc. For this purpose, an inspection tool (e.g., metrology tool MT) may be included in the lithocell LC and / or lithographic apparatus LA. If an error is detected, then, for example, the exposure of a subsequent substrate or other processing steps subsequently performed on the substrate W may be adjusted, particularly if the inspection is performed before exposing or processing other substrates W in the same batch or lot.

[0050]

[0058] An inspection apparatus, sometimes referred to as a metrology apparatus or metrology tool MT, can be used to determine characteristics of a substrate W. Specifically, it can determine how the characteristics of different substrates W vary, or how the characteristics associated with different layers of the same substrate W vary from layer to layer. Alternatively, the inspection apparatus can be configured to identify defects in the substrate W, and can be, for example, part of a lithography cell LC, integrated into a lithography apparatus LA, or a stand-alone device. The inspection apparatus can measure characteristics of 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 where exposed or unexposed portions of the resist have been removed), or a post-etch image (e.g., an image after a pattern transfer step such as etching).

[0051] Exemplary Computer System

[0059] FIG. 2B illustrates a computer system CL, also referred to as a controller or processor. The computer system CL can be part of a lithography cell LC, integrated into a lithography apparatus LA, and / or a stand-alone device. The computer system CL is configured to optimize the lithography process, for example, to calibrate a reticle heating model. Typically, the patterning process in the lithography apparatus LA is a critical step in processing and requires highly accurate dimensional measurement and placement of structures on the substrate W. To ensure this high accuracy, three systems can be combined into a so-called “integrated” control environment, as schematically illustrated in FIG. 2B. As illustrated in FIG. 2B, the “integrated” environment can include a lithography apparatus LA, a computer system CL, and a metrology tool MT. For example, the lithography apparatus LA (first system) can be connected to the computer system CL (second system) and the metrology tool MT (third system).

[0052]

[0060] A key aspect of such integrated lithography is optimizing the interaction between these three systems to optimize the lithography process, for example, to improve 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, such as dose, focus, and overlay, within which a particular manufacturing process will produce a specified result, such as a functional semiconductor device. Typically, within this range, the process parameters of the lithography process or patterning process can vary.

[0053]

[0061] The computer system CL predicts which resolution enhancement techniques to use when performing computational lithography simulations and calculations using the design layout (e.g., a portion thereof) for patterning, for example, to determine which mask layout and lithography apparatus settings will achieve the largest overall process window for the patterning process (shown by the double-headed arrow at the first scale SC1 in FIG. 2B). Typically, the resolution enhancement techniques are configured to match the patterning capabilities of the lithography apparatus LA. The computer system CL can also be used to detect where within the process window the lithography apparatus LA is currently operating (e.g., using input from the metrology tool MT) to predict whether defects due to, for example, suboptimal processing may exist (shown by the arrow pointing to "0" at the second scale SC2 in FIG. 2B).

[0054]

[0062] The metrology tool MT can provide input to the computer system CL, for example, to enable accurate simulations and predictions. For example, the metrology tool MT can provide alignment information. The metrology tool MT can provide feedback to the lithography apparatus LA (e.g., via the computer system CL) to, for example, identify possible drift in the calibration status of the lithography apparatus LA (as indicated by the multiple arrows at the third scale SC3 in FIG. 2B). In lithography processes, it is desirable to frequently measure generated structures, for example, for process control and verification. Various types of metrology tools MT can be used to measure one or more characteristics related to, for example, the lithography apparatus LA, the substrate W being patterned, and / or reticle alignment. This is described in more detail in U.S. Pat. No. 11,099,319 and WIPO Publication No. 2021 / 043519, which are incorporated herein by reference in their entireties.

[0055] Exemplary Reticle Stage and Reticle

[0063] 3A and 3B show schematic views of reticle stage 200 according to an exemplary embodiment. Fig. 3A is a schematic bottom perspective view of reticle stage 200 and reticle 300 according to an exemplary embodiment. Fig. 3B is a schematic bottom view of reticle stage 200 and reticle 300 shown in Fig. 3A.

[0056]

[0064] Reticle stage 200 (e.g., support structure MT) can be used to hold a patterning device (e.g., patterning device MA) in a lithographic apparatus (e.g., lithographic apparatus LA). Reticle stage 200 can include a stage bottom surface 202, a stage top surface 204, stage sides 206, clamps 250, a reticle cage 224, and / or a reticle 300. In some embodiments, reticle 200 with reticle 300 can be implemented in lithographic apparatus LA. For example, reticle stage 200 can be a support structure MT of lithographic apparatus LA. In some embodiments, reticle 300 can be placed on stage bottom surface 202 and held by clamps 250. 3A and 3B, the reticle 300 can be placed on a clamp 250 (e.g., an electrostatic clamp) in the center of the stage bottom surface 202 with the reticle front side 302 facing vertically away from the stage bottom surface 202. In some embodiments, a reticle cage 224 can be placed on the stage bottom surface 202. For example, as shown in FIGS. 3A and 3B, the reticle 300 can be placed in the center of the stage bottom surface 202 and secured by a reticle cage 224 adjacent each corner of the reticle 300.

[0057]

[0065] In some lithography apparatuses, such as lithography apparatus LA, a reticle stage 200 with clamps 250 can be used to hold and position a reticle 300 for scanning or patterning operations. In some embodiments, as shown in FIGS. 3A and 3B , the reticle stage 200 can include a first encoder 212 and a second encoder 214 for positioning operations. For example, the first and second encoders 212, 214 can be interferometers. The first encoder 212 can be mounted along a first direction, such as the horizontal direction (i.e., X direction) of the reticle stage 200. The second encoder 214 can be mounted along a second direction, such as the vertical direction (i.e., Y direction) of the reticle stage 200.

[0058]

[0066] As shown in Figures 3A and 3B, reticle 300 can include a reticle front side 302, alignment marks 310, and / or edge alignment marks 320. Alignment marks 310 are configured to measure reticle alignment between reticle 300 and a substrate (e.g., substrate W, non-production substrate, product substrate). In some embodiments, as shown in Figures 3A and 3B, one or more alignment marks 310 can be located at the corners and / or the center of reticle 300 for RA measurement. Edge alignment marks 320 are configured to measure reticle shape deformation of reticle 300 due to thermal expansion when reticle 300 is not within a predetermined temperature range (e.g., 22°C ± 0.2°C). 3A and 3B, one or more edge alignment marks 320 can be placed along the perimeter (e.g., horizontal and vertical edges) of the reticle 300 for reticle shape deformation (RSD) measurements. In some embodiments, the results of the RA and / or RSD measurements can be converted to reticle temperature by FEM, which solves for temperature based on reticle alignment and / or reticle deformation.

[0059] Exemplary Reticle Exchange Apparatus

[0067] 4A and 4B show schematic diagrams of a reticle exchange apparatus 100 according to an exemplary embodiment. Figure 4A is a schematic top perspective view of the reticle exchange apparatus 100 according to an exemplary embodiment, and Figure 4B is a schematic partial cross-sectional view of the reticle exchange apparatus 100 shown in Figure 4A.

[0060]

[0068] The reticle exchange apparatus 100 can be configured to reduce reticle exchange time and reduce thermal stress in the reticle 300, for example, to increase overall throughput in the lithography apparatus LA. In some embodiments, the reticle exchange apparatus 100 can reduce stress in the reticle 300 by removing the reticle 300 from the reticle stage 200 and transferring it to an in-vacuum robot (IVR) 400. For example, the reticle exchange apparatus 100 can release thermal stress in the reticle 300 by quickly removing the reticle 300 from the reticle cage 224 and clamps 250 and transferring the reticle 300 to the IVR 400. In some embodiments, the reticle exchange apparatus 100 can reduce stress in the reticle 300 and increase throughput by removing the reticle 300 from the reticle stage 200, transferring it to the IVR 400, and quickly transferring the reticle 300 back to the reticle stage 200 for clamping. As shown in FIGS. 4A and 4B, the reticle exchange apparatus 100 may include a reticle stage 200, a clamp 250, and an IVR 400.

[0061]

[0069] The IVR 400 can include a reticle handler 402 with one or more reticle handler arms 404. In some embodiments, the reticle handler 402 can be a rapid exchange device (RED) configured to efficiently rotate and minimize reticle exchange time. The reticle handler arm 404 can include a reticle base plate 406 configured to hold an object, such as a reticle 300. In some embodiments, the reticle base plate 406 can be an extreme ultraviolet inner pod (EIP) for the reticle 300. The reticle base plate 406 includes a reticle base plate front side 407, and the reticle 300 includes a reticle back side 304.

[0062]

[0070] 4A and 4B, the reticle base plate 406 can hold the reticle 300 such that the reticle base plate front side 407 and the reticle back side 304 face the stage bottom surface 202 and the clamp front side 252, respectively. For example, the reticle base plate front side 407 and the reticle back side 304 can face vertically away from the stage bottom surface 202 and the clamp front side 252. As shown in FIG. 4B, the reticle exchange apparatus 100 can include a reticle exchange area 410, which is the cross-sectional area between the clamp 250, the reticle 300, the reticle base plate 406, and the reticle handler arm 404 during the reticle exchange process.

[0063]

[0071] In one example, during a reticle exchange process, reticle handler arm 404 of reticle handler 402 positions reticle 300 on reticle base plate 406 toward clamps 250 in reticle exchange area 410. As described above, the handoff of the reticle from reticle handler 402 to clamps 250 and vice versa can relieve thermal stresses in reticle 300 and reduce parasitic thermal effects in reticle 300.

[0064] Exemplary Reticle Calibration Method

[0072] As discussed above, a lithographic apparatus (e.g., lithographic apparatus LA) may include a reticle stage (e.g., support structure MT, reticle stage 200) that holds a patterning device (e.g., patterning device MA, reticle 300) to transfer a pattern onto a substrate (e.g., substrate W). Heating and / or cooling of the reticle may change the reticle properties, which may affect the radiation beam path (e.g., focus) and cause distortions (e.g., overlay errors) in the patterned substrate. Changes in the reticle properties can be modeled and corrected for by a reticle heating model. Current reticle heating models rely on sensor-based, application-specific approaches that use an RTS to calibrate the reticle heating model and require a calibration lot of production wafers.

[0065]

[0073] In some instances, this approach can be inaccurate and inefficient because the RTS can introduce errors, causing unnecessary delays and requiring rework of product wafers. In some embodiments, the RTS has a temperature gradient variation of approximately ±0.6°C, which can result in an overlay mismatch of approximately 1 nm / °C. Also, in some embodiments, each reticle temperature measurement using the RTS takes approximately 5 seconds per wafer, which can result in additional delays. Current reticle preconditioning techniques can slow wafer processing. Furthermore, variations in the thermomechanical properties of the reticle before calibration can amplify and worsen overlay mismatch (e.g., increasing from 1 nm / °C to over 2.1 nm / °C). Furthermore, product wafers used for calibration can be reworked over time, which can result in additional delays and reduce overall throughput.

[0066]

[0074] Aspects of the reticle calibration apparatus, systems, and methods discussed in PCT / EP2022 / 078447, the entire contents of which are incorporated herein by reference, can improve the accuracy and speed of calibration of reticle heating models, reduce reticle adjustment time, reduce stress in the reticle, avoid reworking of product substrates, and / or improve manufacturing throughput and yield of the lithography process.

[0067] Exemplary Method for Improving Reticle Calibration Methods by Deriving Reticle Temperature Information

[0075] As noted above, current reticle calibration and / or measurement systems and methods can utilize sensor-based direct measurement techniques. In some aspects, the present disclosure improves the performance of such current temperature sensors.

[0068]

[0076] In some embodiments, systems and methods are disclosed for determining reticle temperature by inferring the reticle temperature based on reticle shape measurements. For example, the systems and methods can determine the load temperature of a patterning device based on alignment data, a heating profile of the reticle, and a thermal expansion coefficient of the reticle.

[0069]

[0077] Reticles are positioned on and off the reticle station using a reticle handler. Such systems are described, for example, in U.S. Pat. No. 10,284,830, the entire contents of which are incorporated herein by reference. Such systems can utilize reticle heating compensation (RHC). In some instances, even with temperature preconditioning, it may not be uncommon for a hot reticle to arrive. In some embodiments, the reticle is thermally conditioned before exposure in the scanner to achieve a well-defined reticle temperature. This is desirable for optimal performance of the RHC, especially in systems that do not rely on reticle temperature sensor (RTS) measurements to determine the initial reticle temperature. In some embodiments, the reticle can be rapidly conditioned to the desired temperature (e.g., a 22±2°C reticle can be conditioned to near 22.18°C within 5 minutes), or, in a typical slot, the reticle can be conditioned more slowly (to 22.3-22.8°C within 45 minutes).

[0070]

[0078] In embodiments where a reticle needs to be conditioned, the reticle may be delivered by a user's reticle delivery system from outside the system or from various locations within the lithography system (scanner). The actual arrival temperature of the reticle will vary depending on its history. For example, when arriving from outside the scanner, the reticle temperature may range from approximately 20-24°C; from a reticle station, the reticle temperature may range from approximately 22-24°C depending on the exposure dose and throughput of the lot on which the reticle was exposed; from an integrated reticle inspection system (IRIS), the reticle temperature may range from approximately 22.2-22.5°C depending on the dwell time within the IRIS; or from an internal reticle library (IRL) slot, the reticle temperature may range from approximately 22-24°C depending on the previous history and dwell time within the slot. In some embodiments, measuring such small temperature differences may utilize sophisticated sensors, which may have the drawbacks described above.

[0071]

[0079] Embodiments of the present disclosure use reticle shape / alignment (RA) measurements to determine reticle temperature. In some aspects, RA measurements can have significantly lower repeatability (K) than RTS. Current RTS repeatability is approximately 0.6 K, whereas the presently disclosed systems and methods achieve 0.05 K. In some aspects, RA measurements associated with the presently disclosed systems and methods take approximately 1 second, resulting in a smaller throughput impact compared to current use of RTS, which requires approximately 5 seconds or more per measurement, representing a 5x improvement in throughput impact. Additionally, the presently disclosed systems and methods may not require any hardware changes or the addition of new hardware to the reticle system.

[0072]

[0080] In some embodiments, the reticle magnification data, along with data regarding the physical and mechanical properties of the reticle, is used to determine how much the temperature of the reticle will change. For example, if the system is typically at 22°C and the deformation data is 2 nanometers per centimeter of magnification, then using the reticle's thermal expansion coefficient, it can be calculated that the reticle will heat up by 0.4°C. Such temperature information can be fed back to the controller to better predict the reticle heating profile.

[0073]

[0081] As described above, a method for reducing the effects of reticle heating and / or cooling in a lithography process can include calibrating a linear, time-invariant reticle heating model or reticle heating execution algorithm (RHEA). In some embodiments, the method can predict reticle distortion using the reticle heating model and lithography process inputs, and then calculate and apply a correction based on the predicted reticle distortion to the lithography process. In some embodiments, the reticle heating mode shape can be obtained based on sensor data and / or simulation data. The simulation data can be generated, for example, by a finite element model that describes the relationship between reticle heating input parameters and the reticle distortion due to reticle heating caused by these input parameters.

[0074]

[0082] In some embodiments, physical characteristics of the reticle can be used, such as the dimensions of known features on the reticle or the deformation of the reticle based on a magnification measurement. In some embodiments, a magnification measurement that is characteristic of the length of the reticle can be obtained and used to infer or otherwise estimate the temperature of the reticle. For example, a reticle comprising quartz has a fixed coefficient of thermal expansion (CTE) (approximately 5.5×10 cm / cm °C). A reticle may comprise other materials with known CTEs. Therefore, the CTE and magnification measurements of the reticle can be used to calculate the temperature profile of the reticle.

[0075]

[0083] In some embodiments, measurements using PARIS (Parallel Integrated Lens Interferometry in Scanner Sensors) can be used. Such sensors are known to those skilled in the art. However, other known measurement techniques can also be used.

[0076]

[0084] 5A, 5B, and 5C show experimental results of reticle thermo-mechanical key performance indicators (KPIs) over time, according to some embodiments. FIG. 5A shows an example reticle heating curve. In one aspect, as the reticle warms up, the relative peak power change (K4) 502 increases and the (in)spontaneous imbalance (K18) 504 decreases. In contrast, FIG. 5B shows an example reticle cooling curve. In one aspect, as the reticle cools, the relative peak power change (K4) 506 decreases and the (in)spontaneous imbalance (K18) 508 increases. FIG. 5C shows an example reticle hot-reticle curve. In one aspect, as the reticle cools, the relative peak power change (K4) 510 decreases, similar to 506, and the (in)spontaneous imbalance (K18) 512 indicates heating followed by cooling.

[0077]

[0085] In some embodiments, thermomechanical key performance indicators (KPIs) can determine the reticle load temperature using measurements of reticle features in combination with reticle physical properties, i.e., a physical property such as the thermal expansion coefficient of quartz, a combination of k4 and k18 measured by a reticle alignment sensor within the lithography tool, and then a scale with a k4 of 1 nm / cm and a ratio of 0.2°C can be used to infer the reticle temperature, thereby calculating the reticle load temperature.

[0078]

[0086] In some embodiments, the reticle heating controller can then use the reticle load temperature to zero out the reticle heating profile. In other words, the reticle heating controller can predict heating or cooling (e.g., caused by EUV imaging) and then compensate with additional heating or cooling by the system to maintain a desired target temperature of the reticle. Thus, any reticle thermal state desired by a user (e.g., the temperature at which the reticle was loaded into the system or some other target temperature state) can be more easily maintained.

[0079]

[0087] In some aspects, reticle testing time and / or throughput is increased without requiring additional hardware. In some aspects, existing information about the reticle can be used by the controller to generate reticle load temperature data.

[0080]

[0088] Therefore, not only can the reticle temperature be estimated, but the absolute reticle temperature rise based on reticle shape measurements can be predicted (eg, using k4 and k18).

[0081]

[0089] In some embodiments, if the reticle heating is exponential, the controller is configured to heat or cool the reticle in an opposite manner to counteract that particular reticle heating behavior.

[0082]

[0090] 6-8 illustrate various exemplary methods for predicting a reticle temperature profile in accordance with the present disclosure. It will be appreciated that these operations may be performed in a different order, or that not all of the steps shown may be required.

[0083]

[0091] In some embodiments, such as shown in FIG. 6 , in step 610, a system controller receives patterning device alignment data measured between the patterning device and the wafer. In step 620, the controller may determine a patterning device heating profile, for example, based on a previous position of the patterning device. In step 630, the controller may determine a patterning device load temperature based on the patterning device alignment data, the heating profile, and a thermal expansion coefficient. In step 640, the controller may determine future deformation of the patterning device. In some embodiments, in step 650, the controller may adjust the positioning of a stage or lens of the system that generated the alignment data to compensate for future deformation of the patterning device.

[0084]

[0092] In some embodiments, such as that shown in Figure 7, in step 710, a projection system directs radiation onto a patterning device. Then, in step 720, a portion of the radiation is directed onto a detector configured to output a signal representative of this portion of the radiation beam after interaction with the patterning device. In step 730, a controller can determine information about a physical characteristic or alignment of the patterning device based on the signal. In step 740, the controller can use this information to estimate the load temperature of the patterning device.

[0085]

[0093] In another embodiment, as shown in Figure 8, in step 810, a projection system directs radiation onto a patterning device. Then, in step 820, a portion of the radiation is directed onto a detector configured to output a signal representative of this portion of the radiation beam after interaction with the patterning device. In step 830, a controller can determine information about a physical characteristic or alignment of the patterning device based on the signal. This information can be a magnified characteristic of the patterning device, and in step 840, the controller uses this information to estimate the load temperature. Alternatively, deformation information of the patterning device can be used to estimate the load temperature.

[0086]

[0094] Various embodiments of the present system and method are disclosed in the following numbered clause list: 1. An illumination path configured to direct radiation onto a patterning device; a detection path configured to direct a portion of the radiation after the portion of the radiation interacts with the patterning device onto a detector configured to output a signal representative of the portion of the radiation beam; a controller configured to receive the signal, determine information about physical characteristics or alignment data corresponding to the patterning device, and use this information to estimate a load temperature of the patterning device; A system comprising: 2. The system of clause 1, wherein the controller or another controller compensates for temperature-induced deformations of the patterning device using the estimated load temperature and / or relative temperature variation. 3. The system of clause 2, wherein the controller or another controller compensates by adjusting the positioning of a stage or lens of the system. 4. The system of clause 2, wherein the controller or another controller alters a physical feature, another physical feature, or alignment of the patterning device. 5. The system of clause 1, wherein the information includes magnified features of a patterning device. 6. The system of clause 1, wherein the information includes a deformation of the patterning device. 7. The system of clause 1, wherein the controller is further configured to store a model of reticle shape metrology corresponding to the deformation data. 8. The system of clause 7, wherein the controller is configured to use the information and to output predicted deformation data using the model. 9. The system of clause 8, wherein the controller is further configured to predict an absolute increase or decrease in temperature of the patterning device using the predicted deformation data. 10. The system of clause 1, wherein the patterning device is a reticle and the controller predicts a reticle heating profile using the magnification features. 11. A method for estimating a patterning device load temperature, comprising: receiving patterning device alignment data measured between the patterning device and the wafer; determining a patterning device heating profile based on a previous position of the patterning device; determining a load temperature of the patterning device based on the patterning device alignment data, the heating profile, and the thermal expansion coefficient; determining future deformations of the patterning device; adjusting the positioning of a stage or lens of the system that generated the alignment data to compensate for future deformations of the patterning device; A method comprising: 12. Directing radiation onto a patterning device; directing a portion of the radiation after the portion of the radiation has interacted with the patterning device onto a detector configured to output a signal representative of the portion of the radiation beam; determining information about physical characteristics or alignment of a patterning device; using the information to estimate a load temperature of the patterning device; and 12. The method of clause 11, further comprising: 13. The method of clause 12, wherein using the information includes using magnification features of the patterning device to estimate the load temperature. 14. The method of clause 12, wherein using the information includes using patterning device deformation information to estimate the load temperature. 15. The method of clause 11, further comprising storing a profilometric model of the patterning device corresponding to the deformation data. 16. The method of clause 15, further comprising using the information to output predicted deformation data using a model. 17. The method of clause 16, further comprising predicting an absolute increase or decrease in temperature of the patterning device using the predicted deformation data. 18. The method of clause 15, wherein the patterning device is a reticle and the model is used to estimate the reticle temperature based on reticle shape or reticle alignment data, a reticle heating profile based on a previous position of the reticle, and a thermal expansion coefficient of the material of the reticle. 19. A lithography tool comprising a system according to clause 1. 20. A lithography tool according to clause 19, wherein the controller or another controller compensates for temperature induced deformations of the patterning device using the estimated load temperature and / or relative temperature variation.

[0087]

[0095] Although specific reference may be made herein to a "reticle," it should be understood that this is merely one example of a patterning device and that the embodiments described herein may apply to any type of patterning device. Additionally, the embodiments described herein may be used to provide safety support for any object to ensure that if a clamp fails, the object does not fall and damage itself or other equipment.

[0088]

[0096] Although specific reference may be made herein to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein has other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, LCDs, thin-film magnetic heads, and the like. In light of these alternative applications, those skilled in the art will recognize that when the terms "wafer" or "die" are used herein, they may be considered synonymous with the more general terms "substrate" or "target portion," respectively. The substrates described herein may be processed, before or after exposure, in, for example, a track unit (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 appropriate, the disclosure herein may be applied to these and other substrate processing tools. Furthermore, a substrate may be processed multiple times, for example to produce a multi-layer IC, and thus the term substrate, as used herein, may also refer to a substrate that already includes multiple processed layers.

[0089]

[0097] Although specific reference has been made to using embodiments of the present disclosure in the context of optical lithography, it will be appreciated that the present disclosure can be used in other applications, such as imprint lithography, and is not limited to optical lithography where the context allows. In imprint lithography, a topography in a patterning device defines the pattern to be created on a substrate. The topography of the patterning device is imprinted into a layer of resist supplied to the substrate and the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. The patterning device is then removed from the resist leaving a pattern in it after the resist is cured.

[0090]

[0098] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, and thus, the terminology or terminology of the present disclosure should be interpreted by one of ordinary skill in the art in light of the teachings herein.

[0091]

[0099] As used herein, the term "substrate" describes a material onto which a layer of material is added. In some embodiments, the substrate itself may be patterned, and the material added onto it may also be patterned or left unpatterned.

[0092]

[0100] Although specific reference may be made herein to the use of apparatus and / or systems according to the present disclosure in the manufacture of ICs, it should be expressly understood that such apparatus and / or systems have other possible applications. For example, they may be utilized in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, LCD panels, thin film magnetic heads, etc. In light of these alternative applications, those skilled in the art will recognize that any use of the terms "reticle," "wafer," or "die" herein may be considered interchangeable with the more general terms "mask," "substrate," or "target portion," respectively.

[0093]

[0101] While specific embodiments of the present disclosure have been described above, it will be appreciated that the present disclosure may be practiced otherwise than as described, and this description is not intended to limit the disclosure.

[0094]

[0102] It is recognized that the "Description of the Invention" section, rather than the "Summary" and "Abstract" sections, is intended to be used to interpret the claims. While the "Summary" and "Abstract" sections may describe one or more exemplary embodiments of the disclosure as envisioned by the inventors, they cannot describe every exemplary embodiment and are therefore not intended to limit the scope of the disclosure and the appended claims in any way.

[0095]

[0103] The present disclosure has been described above using functional components that illustrate the implementation of specific functions and relationships thereof. The boundaries of these functional components have been arbitrarily defined herein for the convenience of description. Alternative boundaries may be defined as long as the specific functions and relationships thereof are appropriately performed.

[0096]

[0104] The foregoing description of specific embodiments fully reveals the overall nature of the present disclosure, such that those skilled in the art can readily modify and / or adapt such specific embodiments for various applications without undue experimentation and without departing from the general concept of the present disclosure. Accordingly, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0097]

[0105] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. an illumination path configured to direct radiation onto a patterning device; a detection path configured to direct the portion of the radiation after it has interacted with the patterning device onto a detector configured to output a signal representative of the portion of the radiation beam; a controller configured to receive the signal, determine information about physical characteristics or alignment data corresponding to the patterning device, and use the information to estimate a load temperature of the patterning device; A system comprising:

2. the controller or another controller compensates for temperature-induced deformations of the patterning device using the estimated load temperature and / or relative temperature fluctuations; the controller or the other controller compensates by adjusting the positioning of a stage or lens of the system; The system of claim 1 , wherein the controller or the other controller alters the physical feature, another physical feature, or alignment of the patterning device.

3. The system of claim 1 , wherein the information comprises magnification features of the patterning device.

4. The system of claim 1 , wherein the information comprises a deformation of the patterning device.

5. the controller is further configured to store a model of reticle shape metrology corresponding to the deformation data; the controller is configured to use the information and to output predicted deformation data using the model; The system of claim 1 , wherein the controller is further configured to use the predicted deformation data to predict an absolute increase or decrease in temperature of the patterning device.

6. The system of claim 1 , wherein the patterning device is a reticle, and the controller uses the magnification features to predict a reticle heating profile.

7. 1. A method for estimating a patterning device load temperature, comprising: receiving alignment data of the patterning device measured between the patterning device and a wafer; determining a patterning device heating profile based on a previous position of the patterning device; determining a load temperature of the patterning device based on the alignment data, the heating profile, and a thermal expansion coefficient of the patterning device; determining future deformations of the patterning device; adjusting the positioning of a stage or lens of the system that generated the alignment data to compensate for the future deformation of the patterning device; A method comprising:

8. directing radiation onto the patterning device; directing the portion of the radiation after it has interacted with the patterning device onto a detector configured to output a signal representative of the portion of the radiation beam; determining information about physical characteristics or alignment of the patterning device; using the information to estimate the load temperature of the patterning device; and The method of claim 7 further comprising:

9. The method of claim 8 , wherein using the information comprises estimating the load temperature using magnification features of the patterning device.

10. The method of claim 8 , wherein using the information comprises using deformation information of the patterning device to estimate the load temperature.

11. storing a profilometric model of said patterning device corresponding to the deformation data; using said information to output predicted deformation data using said model; The method of claim 7 further comprising:

12. The method of claim 11 , further comprising predicting an absolute increase or decrease in temperature of the patterning device using the predicted deformation data.

13. 12. The method of claim 11, wherein the patterning device is a reticle, and the model is used to estimate a reticle temperature based on reticle shape or reticle alignment data, a reticle heating profile based on a previous position of the reticle, and a thermal expansion coefficient of a material of the reticle.

14. A lithography tool comprising the system of claim 1.

15. 15. A lithography tool according to claim 14, wherein the controller or another controller is configured to compensate for temperature induced deformations of the patterning device using the estimated load temperature and / or relative temperature variation.

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