Reticle adjustment for lithographic applications

Abstract

A method for conditioning a reticle includes determining a target operating temperature of the reticle during use. The method includes controlling a temperature of the reticle to approach the target operating temperature of the reticle during use. The method includes exposing the reticle to radiation to perform a manufacturing process.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Application No. 63 / 522,603, filed June 22, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the handling and adjustment of photomasks, for example, adjusting photomasks in lithography equipment and systems. Background Technology

[0004] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. Lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithography apparatus can project a pattern from a patterning apparatus (e.g., a mask, a photomask) onto a layer of radiation-sensitive material (resist, or simply "resist") disposed on a substrate.

[0005] To project a pattern onto a substrate, a photolithography apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Compared to a photolithography apparatus using radiation with a wavelength of, for example, 193 nm, a photolithography apparatus using extreme ultraviolet (EUV) radiation with wavelengths in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0006] Photolithography equipment may include patterning apparatus (e.g., a mask or photomask). Radiation that passes through or is reflected from the patterning apparatus can be provided to form an image on a substrate. A diaphragm assembly (also called a surface layer) may be configured to protect the patterning apparatus from airborne particles and other forms of contaminants. Contaminants on the surface of the patterning apparatus can cause manufacturing defects on the substrate.

[0007] During use, the photomask can be exposed to a radiation beam, causing it to heat up. To manage the mask's temperature, it can be cooled in the form of liquid cooling. The mask can be supported by a mask fixture that holds it in place. Even if the mask's temperature can be controlled, its shape changes when exposed to the radiation beam, which can cause mask deformation and lead to overlap problems. While some deformation can be corrected through alignment adjustments, some deformation cannot be corrected by existing methods and is therefore uncorrectable.

[0008] Reticles used in photolithographic wafer processing are subjected to conflicting heating and cooling during use. For example, a reticle can be subjected to local heating (e.g., from a portion of the reticle being heated by radiation used in wafer processing) and local cooling (e.g., from local cooling indirectly from contact with a chuck or clamp that is actively cooled to avoid overheating, or directly by local cooling with a blast of cold air on the reticle). In addition, a reticle can also be subjected to large temperature swings during use, from an initial temperature near room temperature to an operating temperature significantly above room temperature. Thus, during a reticle exposure used to perform wafer processing, a reticle can be subjected to large thermal strains, causing overlay errors.

[0009] As a specific example, during exposure of the first few wafers in a batch of wafers, the temperature of the reticle can change significantly. Thus, subsequent wafers in the batch will have a hotter reticle than the first wafer, causing "in- batch" overlay errors. A similar effect can also be seen for different fields within the same wafer, such that the last field of a wafer will have a hotter reticle than the first field, causing "in-wafer" overlay errors. This temperature change of the reticle during exposure causes thermal strains in the reticle, which can cause in-plane and out-of-plane distortion of the reticle and the potential for slip. These problems can be exacerbated when wafer processing requires more frequent switching of reticles.

[0010] Reticle alignment modeling provides only a limited correction for the above problems. Other methods are needed to reduce thermal-induced overlay errors. SUMMARY

[0011] Accordingly, it is desirable to reduce the thermal strains experienced by a reticle during use, to thereby reduce the resulting overlay errors. As discussed below, a reticle and a temperature of the reticle can be controlled to an approximate target operating temperature of the reticle prior to performing an exposure to begin wafer processing.

[0012] In some aspects, a reticle or a reticle blank can include a low-distortion material, where the reticle or reticle blank material has a zero-crossing temperature (ZCT) profile and a ZCT slope profile, where at least one of the ZCT profile and the ZCT slope profile is non-uniform.

[0013] Reticles and reticle blanks used in lithographic apparatuses and lithographic processes can comprise ultra-low expansion (ULE) glass. ULE can be used because the shape of ULE glass changes by only a small amount when the temperature of the ULE glass changes compared to other materials. In use, ULE glass can be heated by absorbing a large amount of energy from a radiation beam. Cooling can be used to control the temperature of the reticle, but some degree of heating can also occur. The reticle can be supported by a reticle clamp, and so the reticle can deform when constrained by the clamp. While some of these deformations can be corrected by aligning the reticle using fiducial marks on the reticle, high order deformations cannot be corrected by existing means.

[0014] Some aspects of the disclosure address this shortcoming by providing a reticle or reticle blank in which one or both of the zero-crossing temperature profile and the ZCT slope profile are non-uniform. The zero-crossing temperature is the temperature or temperature range at which the thermal expansion of the material making up the reticle crosses zero. Some materials, such as, for example, ULE glass, have a temperature or temperature range at which the thermal expansion coefficient crosses zero. Near the zero-crossing temperature, the material has dimensional stability to temperature fluctuations. The zero-crossing temperature slope is the rate at which the thermal expansion coefficient changes near the zero-crossing temperature. Existing reticles and reticle blanks are manufactured to have as uniform a ZCT profile as possible. The ZCT slope profile is based on the length of the annealing process used to form the reticle or reticle blank. This can cause in-use deformations that cannot be corrected. Some embodiments of the disclosure provide a reticle or reticle blank having a non-uniform ZCT profile and / or ZCT slope profile such that different portions of the reticle or reticle blank deform differently in use. This allows the reticle or reticle blank to be configured to have different deformation characteristics in use and limits the extent of uncorrectable deformations.

[0015] The reticle or reticle blank has x, y, and z directions. In some aspects, at least one of the ZCT profile and the ZCT slope profile can vary in the y direction. The ZCT profile and / or the ZCT slope profile in the y direction can be configured such that it is a lower order profile that can be easily corrected, such as a quadratic profile. Where the ZCT profile does not vary, the deformation is a higher order that cannot be easily corrected, such as higher than quadratic.

[0016] In some aspects, at least one of the ZCT profile and the ZCT slope profile varies in a region proximate to an edge of the reticle or reticle blank. It has been found that varying the ZCT profile and / or the ZCT slope profile proximate to an edge of the reticle or reticle blank is advantageous for reducing uncorrectable distortion. Without being bound by scientific theory, it is believed that distortion of an edge of a reticle or reticle blank can be altered in situ when supported by a reticle clamp. By varying the ZCT profile and / or the ZCT slope profile as described, distortion at an edge of a reticle or reticle blank can be controlled.

[0017] In some aspects, the ZCT of the reticle or reticle blank is higher at at least one boundary of the reticle or reticle blank. By having a higher ZCT at a boundary of the reticle, it has been found that there can be an overlay improvement of greater than 35%. According to some aspects, the ZCT of the reticle or reticle blank ranges from about ±1 °C, about ±2 °C, about ±3 °C, about ±4 °C, about ±5 °C, about ±6 °C, about ±7 °C, about ±8 °C, about ±9 °C, or about ±10 °C. By having a larger range of ZCT, the reticle or reticle blank has dimensional stability over a larger temperature range. In some aspects, the ZCT slope can be from about 0.5 ppb / K2to about 2.5 ppb / K2. The ZCT can be from about 1.0 ppb / K2to about 2.0 ppb / K2. In some aspects, the ZCT profile and / or the ZCT slope profile has at least one axis of symmetry. The axis of symmetry can be the y-axis, the x-axis, and / or the z-axis.

[0018] In some aspects, a reticle clamp can include a reticle as described herein.

[0019] In some aspects, a lithographic apparatus can include a reticle or reticle clamp according to the first or second aspects of the disclosure. The lithographic apparatus can be a deep ultraviolet (DUV) or extreme ultraviolet (EUV) lithographic apparatus.

[0020] In some aspects, a method of mitigating uncorrectable distortion in a reticle or reticle blank can include providing a reticle or reticle blank having at least one of a ZCT profile and a ZCT slope profile that is non-uniform across the reticle or reticle blank. With a non-uniform ZCT profile and / or ZCT slope profile, the amount of uncorrectable distortion in the reticle or reticle blank can be reduced, which can reduce overlay error. The method can include varying at least one of the ZCT profile and the ZCT slope profile in a region proximate to an edge of the reticle or reticle blank.

[0021] In some aspects, a method of generating a reticle or reticle blank for a lithographic process can include modeling deformation of a reticle or reticle blank in use, calculating a ZCT profile and / or a ZCT slope profile of the reticle or reticle blank for reducing any modeled uncorrectable deformation based on the deformation modeling, optionally repeating these steps until the modeled uncorrectable deformation has been reduced to a predetermined level, outputting the optimized ZCT profile and / or ZCT slope profile of the reticle or reticle blank, and generating the reticle or reticle blank with the optimized ZCT profile and / or ZCT slope profile.

[0022] According to some aspects, uncorrectable deformation in a reticle or reticle blank can be reduced by adjusting a ZCT profile and / or a ZCT slope profile on the reticle or reticle blank. In other words, the ZCT and ZCT slope can be different in different portions of the reticle or reticle blank. By modeling deformation of the reticle or reticle blank, uncorrectable deformation can be reduced by adjusting the ZCT profile and / or ZCT slope profile, and subsequently a reticle or reticle blank with a desired ZCT profile and / or ZCT slope profile can be generated.

[0023] In some aspects, a method includes determining a target operating temperature of the reticle during use, controlling a temperature of the reticle to approach the target operating temperature of the reticle during use, and exposing the reticle to radiation to perform a manufacturing process.

[0024] In some aspects, the method includes directly measuring an operating temperature of a precursor reticle or a reticle used during a previous manufacturing process. In some aspects, the method includes modeling one or more target operating conditions of the reticle.

[0025] In some aspects, the temperature of the reticle can be controlled during writing of the reticle, before loading the reticle into a device for performing a manufacturing process, after loading the reticle into a device for a manufacturing process, and / or during the manufacturing process. In some aspects, the temperature of the reticle can be controlled while the reticle is stored in a reticle library, a reticle transport, or a turret, while the reticle is mounted on a stage or a clamp or chuck, during overhead time between exposures of two wafers, and / or while the reticle is being scanned or being exposed.

[0026] In some aspects, one or more regions of the reticle are actively heated during scanning and / or exposure of the wafer. In some aspects, the one or more regions of the reticle are actively heated using radiation used in the manufacturing process to heat the reticle or using heat supplied from a source other than the radiation used in the manufacturing process. In some aspects, the reticle can be heated using a gas jet or infrared light.

[0027] In some aspects, the method further includes measuring the temperature of the chuck or clamp, modeling a future temperature of the chuck or clamp based on a result of measuring the temperature of the chuck or clamp, and controlling the temperature of the chuck or clamp based on the modeling of the future temperature of the chuck or clamp. In another aspect, this includes modeling the operating temperature of the clamp and / or chuck.

[0028] In some aspects, a system for pre-conditioning a reticle includes a housing configured to hold one or more reticles, one or more heating elements configured to heat at least one of the one or more reticles, and a controller configured to control a temperature of the at least one reticle to a predetermined temperature using the one or more heating elements prior to the reticle being exposed to radiation to perform a manufacturing process. The predetermined temperature can be a predicted operating temperature of the reticle during exposure to the radiation to perform the manufacturing process. The predicted operating temperature of the reticle can be based on a predicted dose of the radiation on the reticle.

[0029] Further features of the aspects of the disclosure are described below in the detailed description of various aspects of the disclosure with reference to the accompanying drawings. It should be noted that the disclosure is not limited to the specific aspects described herein. These aspects are presented for illustrative purposes only. Additional aspects will be apparent to persons skilled in the relevant art based on the teachings contained herein. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the disclosure and to enable a person skilled in the relevant art to make and use aspects described herein.

[0031] Figure 1 A lithographic apparatus according to some aspects is shown.

[0032] Figure 2A A reflective lithographic apparatus according to some aspects is shown.

[0033] Figure 2B A transmissive lithographic apparatus according to some aspects is shown.

[0034] Figure 2C A lithography cell is shown in accordance with some aspects.

[0035] Figure 3 Distortion of a reticle in a reticle clamp in accordance with some aspects is shown.

[0036] Figure 4A and Figure 4B Distortion of a reticle with nominal uniform ZCT in the y direction and a reticle with a quadratic ZCT profile in the y direction in accordance with some aspects is shown.

[0037] Figure 5 An exemplary embodiment of a reticle or reticle blank in accordance with some aspects is shown.

[0038] Figure 6 and Figure 7 A reticle stage in accordance with some aspects is shown.

[0039] Figure 8 and Figure 9 A reticle exchange apparatus in accordance with some aspects is shown.

[0040] Figure 10 A flowchart of a method of conditioning a reticle in accordance with some aspects is shown.

[0041] Figure 11A , Figure 11B and Figure 11C A configuration for conditioning a reticle in accordance with some aspects is shown.

[0042] Figure 12A and Figure 12B Heating of a wafer during wafer processing without and with conditioning of a reticle in accordance with some aspects is shown.

[0043] Figure 13 A flowchart of a method of conditioning a reticle in accordance with some aspects is shown.

[0044] The features of the present disclosure will become more fully understood from the detailed description given hereinafter, taken in conjunction with the accompanying drawings, in which like reference signs designate identical or corresponding elements throughout. In the drawings, the same reference numerals are generally used to refer to identical, similar, or corresponding elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. The drawings provided throughout the disclosure should not be interpreted as being drawn to scale unless specifically indicated. DETAILED DESCRIPTION

[0045] In this document, references to“one aspect,”“an aspect,”“example aspect,”“exemplary aspect,” etc., mean that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect. The appearances of the phrase“in one or more aspects” in various places in the specification are not necessarily all referring to the same aspect, nor are separate or alternative aspects mutually exclusive of other aspects. Moreover, various features are described which can be exhibited in

[0046] For ease of description, spatially relative terms, such as“under,”“below,”“lower,”“on,”“above,”“upper,” and the like, can be used herein for describing the relationship of one element or feature to another element or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0047] The terms“about,”“approximately” and the like can be used herein to indicate that a value can have a value that varies from a given value by an amount that can vary based on specific technical requirements. Based on specific technical requirements, the terms“about,”“approximately” and the like can indicate a value of a given quantity that varies, for example, within ±10% to 30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0048] Aspects of the disclosure can be implemented in hardware, firmware, software, or any combination thereof. Aspects of the disclosure can also be implemented as instructions stored on a machine-readable medium, which can be read and executed by one or more processors. A machine-readable medium can 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 can include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc. Further, firmware, software, routines, and / or instructions can be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. The term“machine-readable medium” can be used herein interchangeably with the term“computer program medium,” for example. The term“machine-readable medium” can also be used herein interchangeably with the term“computer readable medium,” for example. The term“machine-readable medium” can be used herein interchangeably with the term“non-transitory computer readable medium,” for example. The term“non-transitory” can be used herein to refer to a form of the computer readable medium other than a transitory propagated signal.

[0049] However, before these aspects are described in further detail, it is instructive to present an example environment in which aspects of the present disclosure can be implemented.

[0050] Example lithographic system

[0051] Figure 1 A lithographic system according to the application is shown. The lithographic system comprises a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam B. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA, e.g. a mask, a projection system PS and a substrate table WT configured to support a substrate W. The illumination system IL is configured to condition the radiation beam B before it enters the patterning device MA. The projection system is configured to project the radiation beam B, now patterned by the mask MA, onto the substrate W. The substrate W can include previously formed patterns. In such cases, the lithographic apparatus will align the patterned radiation beam B with a pattern previously formed on the substrate W. In this embodiment, a pellicle 15 is depicted as being located in the radiation path and protecting the patterning device MA. It will be appreciated that the pellicle 15 can be located in any desired position and can be used to protect any of the mirrors in the lithographic apparatus. The patterning device MA can be referred to as a reticle. The support structure MT can be referred to as a reticle stage.

[0052] The radiation source SO, the illumination system IL and the projection system PS can all be constructed and arranged such that they can be isolated from the external environment. An atmosphere at a low pressure, e.g. a hydrogen atmosphere, can be provided in the radiation source SO. A vacuum can be provided in the illumination system IL and / or the projection system PS. A small amount of gas, e.g. hydrogen, at a pressure much lower than atmospheric pressure can be provided in the illumination system IL and / or the projection system PS.

[0053] Figure 1 The radiation source SO shown in Fig. 1 is of a type which can be referred to as a laser produced plasma (LPP) source. A laser, which can for example be a CO2laser, is arranged to deposit energy via a laser beam into a fuel provided by a fuel emitter, such as tin (Sn). Although tin is mentioned in the following description, any suitable fuel can be used. The fuel can for example be in liquid form and can for example be a metal or an alloy. The fuel emitter can comprise a nozzle configured to direct tin, for example in the form of droplets, along a trajectory towards a plasma formation region. The laser beam is incident on the tin at the plasma formation region. Deposition of laser energy into the tin at the plasma formation region generates a plasma. Radiation, including EUV radiation, is emitted from the plasma during de-excitation and recombination of ions of the plasma.

[0054] EUV radiation is collected and focused by a near-normal-incidence radiation collector (sometimes more generally referred to as a normal-incidence radiation collector). The collector can have a multilayer structure arranged to reflect EUV radiation (e.g. EUV radiation having a desired wavelength such as 13.5 nm). The collector can have an elliptical configuration with two elliptical focal points. The first focal point can be located at the plasma formation region and the second focal point can be located at an intermediate focus point, as discussed below.

[0055] The laser can be separate from the radiation source SO. In such cases, the laser beam can be delivered from the laser to the radiation source SO by means of a beam delivery system (not shown) comprising, for example, suitable directing mirrors and / or a beam expander and / or other optical devices. The laser and the radiation source SO can together be considered as a radiation system.

[0056] The radiation reflected by the collector forms a radiation beam B. The radiation beam B is focused at a point to form an image of the plasma formation region which acts as a virtual radiation source for the illumination system IL. The point at which the radiation beam B is focused can be referred to as the intermediate focus. The radiation source SO is arranged so that the intermediate focus is located at or near an opening in the enclosing structure of the radiation source.

[0057] The radiation beam B passes from the radiation source SO into an illumination system IL configured to condition the radiation beam. The illumination system IL can include a facetted field mirror device 10 and a facetted pupil mirror device 11. The facetted field mirror device 10 and facetted pupil mirror device 11 together provide the radiation beam B with a desired cross-sectional shape and a desired angular distribution. The radiation beam B passes from the illumination system IL and is incident upon the patterning device MA held by the support structure MT. The patterning device MA reflects and patterns the radiation beam B. The illumination system IL can also include other mirrors or devices in addition to or instead of the facetted field mirror device 10 and facetted pupil mirror device 11.

[0058] After being reflected from the patterning device MA, the patterned radiation beam B passes into a projection system PS. The projection system includes a plurality of mirrors 13, 14 configured to project the radiation beam B onto the substrate W held by the substrate table WT. The projection system PS can apply a reduction factor to the radiation beam, so as to form an image of a feature smaller than the corresponding feature on the patterning device MA. For example, a reduction factor of 4 can be applied. Although the projection system PS has two mirrors 13, 14 in Figure 1 the embodiment, the projection system can include any number of mirrors (e.g. six mirrors).

[0059] In Figure 1The radiation source SO shown may include components not illustrated. For example, a spectral filter may be disposed within the radiation source. The spectral filter may essentially transmit EUV radiation but essentially block radiation of other wavelengths, such as infrared radiation.

[0060] If the pattern forming apparatus MA is not protected, contamination may necessitate cleaning or disposal of the pattern forming apparatus MA. Cleaning the pattern forming apparatus MA will interrupt valuable manufacturing time, and disposing of the pattern forming apparatus MA is very costly. Replacing the pattern forming apparatus MA will also interrupt valuable manufacturing time.

[0061] Figure 2A and Figure 2B Photolithography apparatus 200 and photolithography apparatus 200', which can implement aspects of this disclosure, are shown respectively. Each of photolithography apparatus 200 and photolithography apparatus 200' includes the following: an irradiation system (irradiator) IL configured to modulate a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., a mask stage) MT configured to support a patterning apparatus (e.g., a mask, stencil, or dynamic patterning apparatus) MA and connected to a first positioner PM configured to accurately position the patterning apparatus MA; and a substrate stage (e.g., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with resist) W and connected to a second positioner PW configured to accurately position the substrate W. Photolithography apparatuses 200 and 200' also have a projection system PS configured to project a pattern imparted by the patterning apparatus MA to the radiation beam B onto a target portion (e.g., comprising one or more dies) C of the substrate W. In lithography equipment 200, the pattern forming apparatus MA and the projection system PS are reflective. In lithography equipment 200', the pattern forming apparatus MA and the projection system PS are transmissive.

[0062] The irradiation system IL may include various types of optical components for guiding, shaping, or controlling the radiation beam B, such as refractive, reflective, reflective-refractive, magnetic, electromagnetic, electrostatic, or other types of optical components or any combination thereof.

[0063] The support structure MT holds the patterning apparatus MA, and the method of holding it depends on the orientation of the patterning apparatus MA relative to a reference frame, the design of at least one of the lithography apparatuses 200 and 200', and other conditions such as whether the patterning apparatus MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning apparatus MA. The support structure MT can be, for example, a fixed or movable frame or stage. By using sensors, the support structure MT can ensure that the patterning apparatus MA is in the desired position, for example, relative to the projection system PS.

[0064] The term "patterning apparatus" MA should be interpreted broadly as any apparatus that can be used to impart a pattern to the radiation beam B in a cross section in order to generate a pattern in a target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in a device formed in the target portion C to form an integrated circuit.

[0065] The pattern forming apparatus MA can be transmissive (e.g., in...). Figure 2B In lithography equipment 200') or reflective type (such as in Figure 2A (In a photolithography apparatus 200). Examples of pattern forming apparatus MA include photomasks, masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in photolithography and include mask types such as binary, alternating phase-shift, or attenuation phase-shift masks, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect the incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B reflected by the matrix of small mirrors.

[0066] The term "projection system" PS can encompass any type of projection system suitable for the exposure radiation used or for other factors such as the use of an immersion liquid on a substrate W or the use of a vacuum, including refractive, reflective, reflective-refractive, magnetic, electromagnetic, and electrostatic optical systems or any combination thereof. A vacuum environment can be used for EUV or electron beam radiation because other gases may absorb excessive radiation or electrons. Therefore, a vacuum environment can be provided throughout the beam path by means of vacuum walls and vacuum pumps.

[0067] The lithography apparatus 200 and / or lithography apparatus 200' may be of the type having two (dual-platform) or more substrate stages WT (and / or two or more mask stages). In these "multi-platform" machines, additional substrate stages WT can be used in parallel, or preparatory steps can be performed on one or more stages while one or more other substrate stages WT are used for exposure. In some cases, the additional stage may not be a substrate stage WT.

[0068] Photolithography apparatuses can also fall into the category where at least a portion of the substrate can be covered by a liquid (e.g., water) with a relatively high refractive index to fill the space between the projection system and the substrate. Immersion liquids can also be applied to other spaces within the photolithography apparatus, such as the space between the mask and the projection system. Immersion techniques are well-known in the art for increasing the numerical aperture of a projection system. The term "immersion" as used herein does not mean that a structure such as a substrate must be immersed in a liquid. For example, the liquid may be located between the projection system and the substrate during exposure.

[0069] Reference is made to Figure 2A and Figure 2B The illuminator IL receives a radiation beam from a radiation source SO. The source SO and the lithographic apparatus 200, 200' can be separate physical entities, for example, when the source SO is an excimer laser. In such cases, beam delivery system BD (in Figure 2B ) can include suitable directing mirrors and / or a beam expander. In other cases, the source SO can be an integral part of the lithographic apparatus 200, 200', for example, when the source SO is a mercury lamp. The radiation system can include the source SO, the illuminator IL, and / or the beam delivery system BD.

[0070] The illuminator IL can include an adjuster AD (in Figure 2B ) for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as "sigma-outer" and "sigma-inner," respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL can include various other components (in Figure 2B ), such as an integrator IN and a condenser CO. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

[0071] Reference is made to Figure 2A The radiation beam B is incident on the patterning device (e.g., mask) MA held on the support structure (e.g., mask table) MT, and is patterned by the patterning device MA. In the lithographic apparatus 200, the radiation beam B is reflected from the patterning device (e.g., mask) MA. After being reflected from the patterning device (e.g., mask) MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. The substrate table WT is accurately movable using the second positioner PW and position sensor IF2 (e.g., an interferometer device, a linear encoder, or a capacitive sensor). Similarly, the first positioner PM and another position sensor IF1 can be used for accurately positioning the patterning device (e.g., mask) MA in relation to the path of the radiation beam B. Alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning device (e.g., mask) MA and the substrate W.

[0072] Reference is made to Figure 2BThe radiation beam B is incident, after having traversed the mask MA, on the substrate W in the target portion C, the beam having passed through the projection system PS which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil conjugate PPU with respect to the illumination system pupil IPU. Parts of the radiation coming from the mask pattern MP, which have not been diffracted by the mask pattern at the illumination system pupil IPU, diverge with an intensity distribution at the illumination system pupil IPU and cross the mask pattern without being influenced by diffraction at the mask pattern and produce an image of the intensity distribution at the illumination system pupil IPU.

[0073] The projection system PS projects an image of the mask pattern MP onto a resist layer coated on the substrate W, wherein the image is formed by the diffracted beam resulting from the radiation having the intensity distribution from the mask pattern MP. For example, the mask pattern MP can comprise an array of lines and spaces. Diffracting of radiation at the array and different from the zeroth order of diffraction results in turning diffracted beams which change direction in a direction perpendicular to the lines. The undiffracted beam, i.e. the so-called zeroth order diffracted beam, crosses the pattern without any change of the propagation direction. The zeroth order diffracted beam crosses an upper lens or an upper lens group of the projection system PS upstream of the pupil conjugate PPU of the projection system PS to reach the pupil conjugate PPU. The part of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zeroth order diffracted beam is the image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. The aperture device PD is for example arranged at or substantially at the plane comprising the pupil conjugate PPU of the projection system PS.

[0074] The projection system PS is arranged to capture (e.g. using a lens or lens group L) the zeroth order diffracted beam, the first order diffracted beam and / or higher order diffracted beams (not shown). In some aspects, a dipole illumination for imaging a line pattern extending in a direction perpendicular to the lines can be used to exploit resolution enhancement effects of the dipole illumination. For example, the first order diffracted beam interferes with the corresponding zeroth order diffracted beam at the level of the wafer W to produce an image of the line pattern MP with the highest possible resolution and process window (i.e. the available depth of focus in combination with tolerable exposure dose deviations). In some aspects, astigmatism aberrations can be reduced by providing a radiation pole (not shown) in the object plane of the illumination system pupil IPU. Further, in some aspects, stigmation aberrations can be reduced by blocking the zeroth order beam in the pupil conjugate PPU of the projection system associated with the radiation pole in the object plane. This is described in more detail in US 7,511,799 B2, published on March 31, 2009, which is incorporated herein by reference in its entirety.

[0075] By means of the second positioner PW and a position sensor IFD (e.g. an interferometer device, a linear encoder or a capacitive sensor), the substrate table WT can be accurately moved (e.g. in order to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor (not shown in B) can be used to accurately position the mask MA relative to the path of the radiation beam B (e.g. after being fetched from a mask library or during a scan). Figure 1 B) can be used to accurately position the mask MA relative to the path of the radiation beam B (e.g. after being fetched from a mask library or during a scan).

[0076] Generally, movement of the mask table MT can be realized by means of a long stroke module (coarse positioning) and a short stroke module (fine positioning) forming part of the first positioner PM. Similarly, movement of the substrate table WT can be realized using a long stroke module and a short stroke module forming part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT can be connected only to a short stroke actuator, or can be fixed. Mask alignment marks Ml, M2 and substrate alignment marks Pl, P2 can be used to align the mask MA and the substrate W. While the substrate alignment marks (as illustrated) occupy dedicated target portions, the marks can be located in spaces between target portions (these marks are referred to as scribe-lane alignment marks). Similarly, in the case of more than one die being provided on the mask MA, the mask alignment marks can be located between the dies.

[0077] The mask table MT and the patterning device MA can be in a vacuum chamber V, wherein an in-vacuum robot IVR can be used to move patterning devices such as masks into and out of the vacuum chamber. Alternatively, when the mask table MT and the patterning device MA are outside the vacuum chamber, an out-of-vacuum robot can be used for various transport operations, similar to the in-vacuum robot IVR. Both the in-vacuum robot and the out-of-vacuum robot can be calibrated for smooth transfer of any payload (e.g. a mask) to a fixed-motion mounting table of a transfer station.

[0078] The lithographic apparatuses 200 and 200' can be used in at least one of the following modes:

[0079] 1. In a step mode, the support structure (e.g. the mask table) MT and the substrate table WT remain substantially stationary while the entire pattern imparted to the radiation beam B is projected onto a target portion C (i.e. a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed.

[0080] 2. In scan mode, the support structure (e.g., the mask table) MT and the substrate table WT are scanned synchronously so that a pattern imparted to the radiation beam B is projected onto a target portion C (i.e., a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (e.g., the mask table) MT can be determined by the (de-) magnification and the image reversal characteristics of the projection system PS.

[0081] 3. In an alternative mode, the support structure (e.g., the mask table) MT is kept essentially stationary holding a programmable patterning device and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. This mode of operation can be referred to as "vector- scan" mode. This is typically an alternative to immobile support structures for which the substrate table is moved or scanned while a pattern is synchronously projected onto a target portion C.

[0082] Combinations and / or variations on the described modes of use or entirely different modes of use can also be employed.

[0083] In some aspects, the lithographic apparatus 200 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Typically, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0084] In some aspects, the lithographic apparatus 200’ includes a deep ultraviolet (DUV) source configured to generate a DUV radiation beam for DUV lithography. Typically, the DUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the DUV radiation beam of the DUV source.

[0085] Example lithographic cell

[0086] Figure 2CA lithography cell 202, sometimes also referred to as a lithocell or cluster, is shown according to some aspects. The lithographic apparatus 200 or 200' can form part of the lithography cell 200. The lithography cell 202 can also include one or more apparatuses for performing pre-exposure processes and post-exposure processes on the substrate. Conventionally, these apparatuses include a spinner 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 handling device or robot RO picks up substrates from input / output ports I / O1, I / O2, moves the substrates between the different process apparatuses, and delivers the substrates to a load bench LB of the lithographic apparatus 200 or 200'. These devices, often collectively referred to as a coat develop system, are controlled by a coat develop system control unit TCU, which is itself controlled by a management control system SCS that also controls the lithographic apparatus via a lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and process efficiency. Mask deformation.

[0087] Mask deformation

[0088] Figure 3 Deformation of a mask MA in a mask holder 36 is depicted. The minimum amount of deformation of the mask MA is at the center of the mask MA. At the edges of the mask in the y direction 37, the deformation is maximum. In some embodiments, the mask can be loaded at about ambient temperature and when imaging of the mask begins, the outer edges of the mask expand as the area cools to the operating temperature of the holder 38, while the imaged area of the mask expands as the radiation beam heats the imaged area to a steady state temperature. The outer edges remain in an expanded cold state. The further the mask edge is from the zero temperature, the greater the strain in this area of the mask. This differential strain causes uncorrectable deformation.

[0089] Figure 4A And Figure 4B Deformation of a mask with a nominally uniform ZCT in the y direction and a mask with a quadratic ZCT profile in the y direction are depicted. In Figure 4A In the case of a mask 400 with a uniform ZCT profile and / or ZT slope profile, there is a large degree of deformation at the y boundaries, i.e. at the top and bottom of the grid. This deformation cannot be corrected by general alignment techniques. In such a case, the overlay can be optimized to about 0.5 nm. Figure 4B A non-uniform mask 402 according to the present disclosure is depicted. The deformation is reduced at the y boundaries, which allows the overlay to be optimized to about 0.31 nm.

[0090] Figure 5 One exemplary embodiment of a mask 500 according to the present disclosure is depicted. The mask 500 can be a mask blank. In Figure 5In the schematic diagram shown in FIG. 1, the ZCT of a reticle is depicted, where the lowest ZCT is provided at the middle portion of the reticle and the ZCT increases at the -Y and +Y reticle boundaries. There can be a symmetry axis along both the y-axis and along the x-axis.

[0091] By providing a reticle or reticle blank having a non-uniform ZCT profile or ZCT slope profile, when in use, the amount of uncorrectable distortion can be reduced, thereby improving the overlay accuracy of the apparatus using the reticle or reticle blank. Previously, reticles and reticle blanks were manufactured with the purpose of providing a uniform ZCT profile and / or ZCT slope profile across the extent of the reticle or reticle blank.

[0092] Example reticle stage

[0093] Figure 6 and Figure 7 A reticle stage 600 according to some aspects is shown. The reticle stage 600 can include a stage top surface 602, a stage bottom surface 604, a stage side surface 606, and a clamp 700. In some aspects, the reticle stage 600 with the clamp 700 can be implemented in a lithography apparatus LA. For example, the reticle stage 600 can be a support structure MT in the lithography apparatus LA. In some aspects, the clamp 700 can be disposed on the stage top surface 602. As shown, the clamp 700 can be disposed at the center of the stage top surface 602, with a clamp front side 702 facing vertically or perpendicularly away from the stage top surface 602. Figure 6

[0094] In some lithography apparatuses (e.g., the lithography apparatus LA), the reticle stage 600 with the clamp 700 can be used to hold and position a reticle for a scanning or patterning operation. In one example, the reticle stage 600 can rely on a high-power driver, a large balance mass, and a heavy frame to support it. In one example, the reticle stage 600 can have a large inertia and its weight can exceed 500 kg to push and position a reticle having a weight of about 0.5 kg. To achieve the reciprocating motion of the reticle, which is typically found in lithography scanning or patterning operations, acceleration and deceleration forces can be provided by a linear motor that drives the reticle stage 600.

[0095] In some aspects, as Figure 6 and Figure 7 ​As shown, the mask platform 600 may include a first encoder 612 and a second encoder 614 for performing positioning operations. For example, the first encoder 612 and the second encoder 614 may be interferometers. The first encoder 612 may be attached along a first direction, such as the lateral direction of the mask platform 600 (i.e., the X direction). The second encoder 614 may be attached along a second direction, such as the longitudinal direction of the mask platform 600 (i.e., the Y direction). In some aspects, such as Figure 6 and Figure 7 As shown, the first encoder 612 can be orthogonal to the second encoder 614.

[0096] like Figure 6 and Figure 7 The mask platform 600 may include a clamp 700. The clamp 700 is configured to hold a mask 808 in a fixed plane on the mask platform 600. The clamp 700 includes a clamp front side 702 and may be disposed on the top surface 602 of the platform. In some aspects, the clamp 700 may use mechanical, vacuum, electrostatic, or other suitable clamping techniques to hold and secure the object. In some aspects, the clamp 700 may be an electrostatic clamp, which may be configured to electrostatically clamp (i.e., hold) an object, such as a mask, in a vacuum environment. For EUV generation performed in a vacuum environment, it may be difficult to use a vacuum clamp to hold the mask or mask plate. Alternatively, one or more electrostatic clamps may be used. For example, the clamp 700 may include electrodes, a resistive layer on the electrodes, a dielectric layer on the resistive layer, and protrusions projecting from the dielectric layer. In use, a voltage of, for example, several kV may be applied to the clamp 700. Current can flow through the resistive layer, causing the voltage at the upper surface of the resistive layer to be substantially the same as the voltage of the electrodes and generating an electric field. Coulomb forces (attraction between particles with opposite charges) attract the object to the clamp 700 and hold it in place. In some aspects, the clamp 700 can be a rigid material, such as a metal, dielectric, ceramic, or a combination thereof.

[0097] Example mask switching device

[0098] Figure 8 and Figure 9 A mask exchange apparatus 801 is shown according to some aspects. The mask exchange apparatus 801 can be configured to minimize mask exchange time, particle generation, and contact forces or stresses from the jig 700 and / or the mask 808, in order to reduce damage to the jig 700 and the mask 808 and increase the overall throughput during the mask exchange process (e.g., in a lithography apparatus LA).

[0099] like Figure 8 and Figure 9As shown, the reticle exchange apparatus 801 can include the reticle stage 600, the gripper 700, and the in-vacuum robot 800. The in-vacuum robot 800 can include a reticle transport device 802.

[0100] In some aspects, the reticle transport device 802 can be a rapid exchange device (RED) configured to rotate efficiently and minimize reticle exchange time. For example, the reticle transport device 802 can save time by moving multiple reticles from one location to another substantially simultaneously, rather than consecutively.

[0101] In some aspects, as shown, Figure 8 The reticle transport device 802 can include one or more reticle transport device arms 804. The reticle transport device arms 804 can include a reticle baseplate 806. The reticle baseplate 806 can be configured to hold an object, such as a reticle 808.

[0102] In some aspects, the reticle baseplate 806 can be an extreme ultraviolet in-pod (EIP) of a reticle. In some aspects, the reticle baseplate 806 includes a reticle baseplate front side 807, and the reticle 808 includes a reticle back side 809.

[0103] In some aspects, as shown, Figure 8 and Figure 9 The reticle baseplate 806 can hold the reticle 808 such that the reticle baseplate front side 807 and the reticle back side 809 each face the stage top surface 602 and the gripper front side 702. For example, the reticle baseplate front side 807 and the reticle back side 809 can be vertically or perpendicularly facing away from the stage top surface 602 and the gripper front side 702.

[0104] As shown, Figure 9 The reticle exchange apparatus 801 can include a reticle exchange area 810, which is a cross-sectional area between the gripper 700, the reticle 808, the reticle baseplate 806, and the reticle transport device arms 804 during a reticle exchange process.

[0105] In some aspects, as shown, Figure 8 The reticle transport device arms 804 can be arranged symmetrically around the reticle transport device 802. For example, the reticle transport device arms 804 can be spaced apart from each other by about 90 degrees, 120 degrees, or 180 degrees. In some aspects, the reticle transport device arms 804 can be arranged asymmetrically around the reticle transport device 802. For example, two reticle transport device arms 804 can be spaced apart from each other by about 135 degrees, while the other two reticle transport device arms 804 can be spaced apart from each other by about 90 degrees.

[0106] In one example, during a reticle exchange process, the reticle transport device arm 804 of the reticle transport device 802 positions a reticle 808 on a reticle base plate 806 in a reticle exchange area 810 toward the gripper 700. As described above, the reticle handoff from the reticle transport device 802 to the gripper 700 includes an unknown reticle position offset that includes a reticle vertical distance offset (i.e., Z-direction offset) and a reticle tilt offset (i.e., R X offset and R Y offset). The tilt or excessive misalignment between the gripper 700 and the reticle 808 can be a source of particle generation and can damage the reticle 808 or the gripper 700 over time. The reticle backside 809 and the gripper frontside 702 can be co-planarly aligned for final delivery. Despite the calibration, there are still variations due to reticle mechanical tolerances and positioning tolerances that can cause high corner impact and unpredictable first point of contact between the gripper 700 and the reticle 808.

[0107] In one example, the reticle exchange process can involve lowering the reticle stage 600 with the gripper 700 (this operation starts away from the reticle transport device 802) to get as close as possible to the reticle 808 until the gripper 700 contacts the reticle 808 to account for all possible offsets and / or tilts. The reticle stage 600 with the gripper 700 can be adjusted in multiple stages of movement (e.g., long stroke stage (coarse motion), short stroke stage (fine motion)) during the reticle exchange process.

[0108] In some aspects, as Figure 9 shown, the reticle exchange apparatus 801 can include a gripper controller 760. The gripper controller 760 can be coupled to the gripper 700 and configured to control the position of the gripper 700. For example, the gripper controller 760 can be configured to control the reticle stage 600 to allow compliant movement of the gripper 700. In some aspects, the gripper controller 760 can be coupled to servo motors or servo actuators (i.e., X-direction, Y-direction, Z-direction, R X , R Y , R Z ) of the reticle stage 600 and / or the gripper 700. For example, the gripper controller 760 can control the translation of the reticle stage 600 with the gripper 700 along x-axis, y-axis, and z-axis (i.e., X-direction, Y-direction, Z-direction) and the rotation of the reticle stage 600 with the gripper 700 around x-axis, y-axis, and z-axis (i.e., R X , R Y , R Z ), where the x-axis, y-axis, and z-axis are orthogonal coordinates.

[0109] reticle thermal strain

[0110] The thermal strain in the reticle can be modeled as:

[0111] ,

[0112] where is the thermal strain of the reticle; T0and T f are the initial and final temperatures of the reticle during exposure or process, respectively; and CTE(T) is the coefficient of thermal expansion (CTE) of the reticle.

[0113] In some aspects, the reticle can be composed of a material with an appropriate ZCT. For example, the reticle is composed of ultra-low expansion (ULE) glass. In the case of these reticles, and for small temperature changes (denoted as T ZC in the following equation) originating from the ZCT, the CTE of the reticle can be approximated as a linear function of temperature:

[0114] ,

[0115] where c can be determined as a function (or value) through experimentation or through simulation. It will be understood by those skilled in the art that, without departing from the present invention, the CTE of the reticle can also be approximated as a non-linear function according to some aspects.

[0116] Combining the above equations together, the thermal strain of the reticle can be given as:

[0117] .

[0118] Integrating the above equation for T from T0to T f , the above equation yields:

[0119] ,

[0120] which can be rewritten as:

[0121] .

[0122] According to the above equation, the thermal strain of the reticle along any z-direction becomes zero under the following two possible conditions:

[0123] … (1),

[0124] or

[0125] … (2).

[0126] Condition (1) above implies that the final temperature of the reticle is equal to (or approximately equal to) the initial temperature of the reticle, such that the temperature of the reticle is approximately constant throughout the process. This condition can be applied to inter-wafer effects.

[0127] As one non-limiting example, a relatively cold reticle can be loaded into the processing equipment. During wafer processing, the reticle gradually heats up due to exposure to radiation, such that the temperature of the reticle is higher for each subsequent wafer until the temperature of the reticle eventually stabilizes after several wafers. In this example, the thermal strain on the reticle resulting from inter-wafer effects can be minimized by conditioning the reticle such that the initial temperature and the final temperature of the reticle are approximately equal, as in condition (1) above.

[0128] In view of the above, the thermal strain on the reticle can be minimized by reducing the difference between the initial temperature and the final temperature of the reticle during processing referred to below as "conditioning" of the reticle. Those of ordinary skill in the art will appreciate that the temperature difference can be considered, for example, as a spatial average of the reticle temperature or as a local temperature profile of the reticle. The following description provides methods and configurations for minimizing the difference between the initial temperature and the final temperature of the reticle, for example, to reduce inter-wafer thermal strain effects.

[0129] Example reticle conditioning

[0130] As explained above, one method for minimizing the thermal strain on the reticle is to condition the reticle to minimize the difference between the initial temperature and the final temperature (i.e., the target operating temperature) of the reticle. Figure 10 A flowchart showing a method for conditioning a reticle according to some aspects is shown. At step 1002, a target operating temperature of the reticle during use can be determined. At step 1004, the temperature of the reticle can be controlled to approach the target operating temperature of the reticle, as determined in step 1002. At step 1006, the reticle can be exposed to radiation to perform a wafer fabrication process.

[0131] In particular, in step 1002, a target operating temperature of the reticle during use can be determined. The target operating temperature of the reticle can be determined using any convenient method. For example, in some aspects, the target operating temperature of the reticle can be determined by directly measuring the operating temperature of a precursor reticle or by directly measuring the operating temperature of a reticle used during a previous manufacturing process. In some aspects, the target operating temperature of the reticle can be determined by modeling one or more target operating conditions of the reticle, such as a predicted dose of radiation on the reticle, an approximate absorption pattern of the reticle, a method of holding the reticle, a cooling environment of the reticle, a percent transmission of the reticle, a field size of an exposed reticle, etc.

[0132] At step 1004, the temperature of the reticle can be controlled to approach the target operating temperature of the reticle, as determined in step 1002. In some embodiments, a model of the reticle using one or more of the above inputs can be used. In some embodiments, a temperature calibration of the reticle can be used. Those skilled in the art will appreciate that the temperature of the reticle can be controlled to approach the target operating temperature of the reticle at various points during wafer processing without departing from the present invention.

[0133] In one non-limiting example, according to some aspects, the temperature of the reticle can be controlled to approach the target operating temperature of the reticle during writing or manufacturing of the reticle. Thus, the resulting reticle will be more representative of the state of the reticle during use.

[0134] In another non-limiting example, according to some aspects, the temperature of the reticle can be controlled to approach the target operating temperature of the reticle prior to loading the reticle into a device for performing manufacturing. As a non-limiting example, the temperature of the reticle can be the temperature when the reticle is stored in an internal reticle library (IRL) or the temperature when the reticle is transported from the IRL to a reticle stage.

[0135] As another example, according to some aspects, the temperature of the reticle can be controlled to approach the target operating temperature of the reticle after loading the reticle into a device for performing manufacturing by controlling the temperature of the reticle while the reticle is held prior to performing manufacturing. For example, the temperature of the reticle can be controlled prior to using the reticle to batch manufacture a first wafer. In some aspects, the reticle can be held in a reticle transport device, a turret, a reticle library, etc.

[0136] According to some aspects, the temperature of the reticle can be controlled to approach a target operating temperature of the reticle after the reticle is loaded into the apparatus for performing manufacturing by controlling the temperature of the reticle while the reticle is held during performance of the manufacturing process. In some aspects, the reticle can be mounted on a stage or chuck, and the temperature of the stage or chuck can be controlled based on the target operating temperature of the reticle. In some aspects, the temperature of the reticle can be controlled during overhead time between exposures of two wafers or while scanning and / or exposing the reticle.

[0137] In some aspects, when the temperature of the reticle is controlled while the reticle is being scanned and / or exposed, one or more regions of the reticle are actively heated. According to some aspects, the heat used to actively heat the reticle can be supplied, for example, by the radiation used in the manufacturing process. Alternatively, the heat used to actively heat the reticle can be supplied by a source other than the radiation used in the manufacturing process, non-limiting examples of which include one or more gas jets, lights (e.g., lasers, light emitting diodes (LEDs), flood lamps, etc.), etc. In some embodiments, the light used to heat the reticle can be provided in the form of a plurality of light sources that are individually controllable. In one embodiment, the reticle can be heated by providing a plurality of lasers that scan over the reticle at the beginning and / or end of a scan process. In one embodiment, the plurality of lasers can constitute, for example, ten lasers, although the present invention is not limited to such a number, and any suitable number of lasers can be used. In one embodiment, each laser can have a power that is modulated based on the portion of the reticle being scanned by the laser.

[0138] In some embodiments, the heat can be provided by placing the reticle adjacent to a local heating surface. In some embodiments, the heat can also be provided adjacent to a local heating surface in addition to or instead of other sources of heat.

[0139] In some embodiments, the one or more sources of heat can be controlled spatially and / or temporally. In some embodiments, the one or more sources of heat can use feedforward control based on modeling and prediction or feedback control based on temperature measurements.

[0140] Those skilled in the art will appreciate that by measuring the temperature of a reticle, for example, in the IRL, and measuring the temperature of the same reticle after the reticle is loaded into a reticle transport device, the heat loss during loading of the reticle can be calibrated. In some aspects, this calibrated heat loss can be used to improve temperature control of the reticle prior to loading by using the calibrated heat loss as feedback, for example, in an iterative process of adjusting the temperature control of the reticle.

[0141] Figure 11A 、 Figure 11B andFigure 11C A non-limiting example of a configuration of a system for controlling the temperature of a reticle according to some aspects is shown. According to some aspects, a system for pre-conditioning a reticle can include a housing, one or more heating elements, and a controller that uses the one or more heating elements to control the temperature of the reticle to a predetermined temperature.

[0142] As shown in Figure 11A one non-limiting example, a reticle conditioning system includes a housing composed of an IRL 1110. The IRL 1110 can include a plurality of slots 1112 for holding reticles, a heating layer 1114 for heating the reticles, and a slot 1116 for holding a reticle that is being actively heated by the heating layer 1114.

[0143] As another non-limiting example shown in Figure 11B , a reticle conditioning system includes a housing composed of an IRL 1120. The IRL 1120 can include a plurality of slots 1122. Gas jets 1124 supplied from a side of the IRL can provide heat to one or more of the reticles in the slots 1122. One or more temperature sensors 1126 can be disposed in the IRL to measure one or more temperatures of one or more of the reticles in the slots 1122. A controller (not shown) can be connected to the temperature sensors 1126. The controller can control the temperature of the one or more reticles to a predetermined temperature before the reticle is exposed to radiation to perform a manufacturing process. In some embodiments, a temperature control element can be used to control the temperature of the reticle. For example, the temperature control element can include one or more gas jets or gas nozzles, light (e.g., a laser, a light emitting diode (LED), an illumination bulb, etc.), a hot plate or a hot mass on the image side of the reticle, a cold plate on the chuck side of the reticle, or any other suitable device. In some embodiments, the temperature control element can also be implemented with a chuck or a clamp to heat and / or cool the reticle while it is supported by the chuck or clamp. In some embodiments, the temperature profile of the temperature control element (e.g., such a hot plate and / or cold plate) can be spatially varied (by using, for example, a peltier array, a tuned laser, etc.) to provide finer tuning of the one or more temperature profiles. For example, the temperature control element can heat and / or cool the reticle outside of the area of the reticle where the reticle is exposed to radiation.

[0144] According to some aspects, the predetermined temperature is a predicted operating temperature of the reticle during radiation exposure based on measurements and / or modeling. In some aspects, the predicted operating temperature can be determined using any of the measurement or modeling methods described above. In some aspects, the predicted operating temperature of the reticle during exposure can be based on a predicted dose of radiation to the reticle.

[0145] Another non-limiting example is shown in Figure 11C , where the reticle conditioning system includes a housing composed of a reticle transport device 1130 including a turntable 1132 and a heating array 1134 that heats the reticle 1136. In one non-limiting example, the heating array 1134 can be composed of an array of infrared (IR) light emitting diodes (LEDs) that can provide heat to the reticle 1136.

[0146] Figure 12A An example measurement of reticle temperature (T reticle ) as a function of the number of wafers in a process lot is shown according to some aspects. In such an example measurement, the temperature of the reticle can not be adequately controlled to approach a target operating temperature of the reticle during use. Thus, as shown in Figure 12A , the temperature of the reticle experiences a large change from the first wafer to the fifth wafer. On the other hand, as shown in Figure 12B , according to some aspects, the temperature of the reticle can be tightly controlled to approach a target operating temperature of the reticle during use. Thus, Figure 12B a much smaller change in temperature of the reticle from the first wafer to the fifth wafer is shown in Figure 12A . Thus, the thermal strain experienced by the reticle from the first wafer to the fifth wafer is also much smaller, and thus the resulting overlay error is minimized.

[0147] Figure 13 A flowchart of a method for conditioning a reticle according to some aspects is shown. In step 1302, the temperature of a chuck or clamp that can hold a reticle can be measured. In step 1304, a future temperature of the chuck or clamp can be modeled. As a non-limiting example, the future temperature of the chuck or clamp can be influenced by a number of factors, such as the temperature of the reticle during use, the dose of radiation on the reticle, the amount of cooling power supplied to the chuck or clamp, the material properties of the chuck or clamp and the reticle, etc. At step 1306, the temperature of the chuck or clamp can be controlled. As one non-limiting example, the amount of cooling power supplied to the chuck or clamp can be increased or decreased. As another non-limiting example, the temperature of the chuck or clamp can be controlled to vary spatially. For example, the temperature of the chuck or clamp can be controlled such that areas of the reticle outside of areas in which the reticle is exposed to radiation are heated and / or cooled. At step 1308, the reticle is exposed to radiation to perform a manufacturing process.

[0148] In some aspects, the method steps of Figure 10 may be performed together, in parallel, or simultaneously with the method steps of Figure 13 . In some aspects, the method steps of Figure 10 may be performed consecutively with the method steps ofFigure 13 method steps. As one example, according to some aspects, the temperature of the chuck or clamp can be controlled according to the method steps of Figure 13 while the temperature of the reticle can be controlled according to the method steps of Figure 10 As another example, according to some aspects, the temperature of the chuck or clamp can be controlled according to the method steps of Figure 13 while the temperature of the reticle can be controlled before or after performing the method steps of Figure 10

[0149] The method steps of Figure 10 and Figure 13 may be performed in any order that can be conceived and are not required to perform all steps. Moreover, the method steps described above are merely examples and are not limiting. That is, other method steps and functionality are contemplated based on the aspects described above.

[0150] Other aspects of the application

[0151] In some aspects, the reticle or reticle blank can comprise a low distortion material, wherein the reticle or reticle blank material has a ZCT profile and a ZCT slope profile, wherein at least one of the ZCT profile and the ZCT slope profile is non-uniform. The reticle or reticle blank can comprise an ultra-low expansion glass. The reticle or reticle blank can have x, y, and z directions, and at least one of the ZCT profile and the ZCT slope profile varies in the y direction. At least one of the ZCT profile and the ZCT slope profile can vary in a region proximate to an edge of the reticle or reticle blank. The ZCT of the reticle or reticle blank can be higher at at least one boundary of the reticle or reticle blank. The ZCT of the reticle or reticle blank can range from about ±1 °C, about ±2 °C, about ±3 °C, about ±4 °C, about ±5 °C, about ±6 °C, about ±7 °C, about ±8 °C, about ±9 °C, or about ±10 °C. The ZCT slope can be from about 0.5 ppb / K2to about 2.5 ppb / K2. The ZCT profile and / or the ZCT slope profile can have at least one axis of symmetry.

[0152] In some embodiments, a reticle clamp can comprise a reticle as described herein. In some embodiments, a lithographic apparatus can comprise a reticle or a reticle clamp as described herein.

[0153] ​In some embodiments, a method of mitigating uncorrectable distortion in a reticle or reticle blank can include providing a reticle or reticle blank having at least one of a ZCT profile and a ZCT slope profile that is non-uniform across the reticle or reticle blank. The method can include varying at least one of the ZCT profile and the ZCT slope profile in a region proximate to an edge of the reticle or reticle blank. The method can include modeling distortion of the reticle or reticle blank under use conditions, calculating a ZCT profile and / or a ZCT slope profile of the reticle or reticle blank for reducing any modeled uncorrectable distortion, optionally repeating these steps until the modeled uncorrectable distortion has been reduced to a predetermined level, outputting the optimized ZCT profile and / or ZCT slope profile of the reticle or reticle blank, and producing the reticle or reticle blank having the optimized ZCT profile and / or ZCT slope profile.

[0154] In some embodiments, a reticle, reticle blank, lithographic apparatus, or method as described above can be used.

[0155] Other embodiments of the present systems and methods are disclosed in the following numbered clauses:

[0156] 1. A method of conditioning a reticle, the method comprising:

[0157] determining a target operating temperature of the reticle during use; and

[0158] controlling a temperature of the reticle to approach the target operating temperature of the reticle during use.

[0159] 2. The method of clause 1, wherein determining the target operating temperature comprises directly measuring an operating temperature of a reticle or precursor reticle used during a previous manufacturing process.

[0160] 3. The method of clause 1, wherein determining the target operating temperature comprises modeling one or more target operating conditions of the reticle.

[0161] 4. The method of clause 1, wherein the temperature of the reticle is controlled to approach the target operating temperature of the reticle during writing of the reticle.

[0162] 5. The method of clause 1, wherein the temperature of the reticle is controlled prior to loading the reticle into an apparatus to perform a manufacturing process.

[0163] 6. The method of clause 5, wherein the temperature of the reticle is controlled while the reticle is stored in a reticle library.

[0164] 7. The method according to clause 6, wherein the temperature of the reticle is controlled using a temperature control element while the reticle is stored in the reticle library.

[0165] 8. The method according to clause 7, wherein the temperature control element comprises a gas jet or nozzle, a hot plate, a thermal mass, or a cold plate, and

[0166] wherein the temperature profile of the hot plate, thermal mass, or cold plate is varied spatially and / or temporally to control the temperature of the reticle while the reticle is stored in the reticle library.

[0167] 9. The method according to clause 1, wherein the temperature of the reticle is controlled after the reticle is loaded into a device for performing a manufacturing process.

[0168] 10. The method according to clause 9, wherein the temperature of the reticle is controlled while the reticle is held in a reticle handling device, a turntable, or a reticle library.

[0169] 11. The method according to claim 1, wherein the temperature of the reticle is controlled during a manufacturing process.

[0170] 12. The method according to clause 11, wherein the temperature of the reticle is controlled while the reticle is mounted on a stage or a chuck.

[0171] 13. The method according to clause 12, wherein the temperature of the reticle is controlled during an overhead time between exposures of two wafers.

[0172] 14. The method according to clause 12, wherein the temperature of the reticle is controlled while the reticle is being scanned and / or being exposed.

[0173] 15. The method according to clause 14, wherein one or more regions of the reticle are actively heated during scanning and / or exposure of a wafer.

[0174] 16. The method according to clause 15, wherein actively heating one or more regions of the reticle comprises heating the reticle using radiation used in the manufacturing process.

[0175] 17. The method according to clause 15, wherein actively heating one or more regions of the reticle comprises heating the reticle using heat supplied from a source other than radiation used in the manufacturing process.

[0176] 18. The method according to clause 17, wherein using heat supplied from a source other than radiation used in the manufacturing process comprises heating the reticle using a gas jet.

[0177] 19. The method of clause 17, wherein using heat supplied from a source other than radiation used in the manufacturing process comprises using light.

[0178] 20. The method of clause 19, wherein the light is provided by one or more of a laser, a light emitting diode (LED), or a light bulb.

[0179] 21. The method of clause 19, wherein the light is provided by a plurality of light sources that can be individually controlled.

[0180] 22. The method of clause 17, wherein using heat supplied from a source other than radiation used in the manufacturing process comprises using a feedforward or feedback controlled heat source.

[0181] 23. The method of clause 17, wherein using heat supplied from a source other than radiation used in the manufacturing process comprises placing a reticle proximate to a locally heated surface.

[0182] 24. The method of clause 1, wherein the temperature of a reticle is controlled prior to batch manufacturing of a first wafer using the reticle.

[0183] 25. The method of clause 1, further comprising controlling the temperature of a chuck or clamp used to hold a reticle based on a target operating temperature of the reticle.

[0184] 26. The method of clause 25, further comprising:

[0185] measuring the temperature of the chuck or clamp;

[0186] modeling future temperatures of the chuck or clamp based on results of measuring the temperature of the chuck or clamp; and

[0187] controlling the temperature of the chuck or clamp based on modeling future temperatures of the chuck or clamp.

[0188] 27. The method of clause 25, further comprising:

[0189] modeling the temperature of the chuck or clamp;

[0190] modeling future temperatures of the chuck or clamp based on results of measuring the temperature of the chuck or clamp; and

[0191] controlling the temperature of the chuck or clamp based on modeling future temperatures of the chuck or clamp.

[0192] 28. The method of clause 25, further comprising:

[0193] measuring the temperature of the chuck or clamp and modeling the temperature of the chuck or clamp;

[0194] modeling future temperatures of the chuck or clamp based on results of measuring temperatures of the chuck or clamp and modeling the temperatures of the chuck or clamp;

[0195] controlling temperatures of the chuck or clamp based on the modeling future temperatures of the chuck or clamp.

[0196] 29. A system for pre-conditioning a reticle, the system comprising:

[0197] a housing configured to hold one or more reticles;

[0198] one or more heating elements configured to heat at least one of the one or more reticles; and

[0199] a controller configured to control a temperature of the at least one reticle to a predetermined temperature using the one or more heating elements prior to the reticle being exposed to radiation to perform a manufacturing process, wherein:

[0200] the predetermined temperature is a predicted operating temperature of the reticle during exposure to radiation to perform the manufacturing process; and

[0201] the predicted operating temperature of the reticle is based on a predicted dose of radiation on the reticle.

[0202] The terms "radiation," "beam," "light," "illumination," and the like can be used interchangeably within this document to refer to electromagnetic radiation of any type, e.g., ultraviolet (UV) radiation (e.g., having a wavelength lambda of 365, 248, 193, 157 or 126 nm), EUV (or soft X-ray) radiation (e.g., having a wavelength in a range of 5-100 nm, such as 13.5 nm), or hard X-rays working at less than 5 nm, as well as particle beams, such as ion beams or electron beams. In general, radiation having a wavelength between about 400 nm and about 700 nm is considered visible radiation; radiation having a wavelength between about 780 nm and 3000 nm (or more) is considered IR radiation. UV refers to radiation having a wavelength of about 100 nm to 400 nm. Within lithography, the term "UV" also applies to wavelengths that can be produced by mercury discharge lamps: G-line 436 nm; H-line 405 nm; and / or I-line 365 nm. Vacuum UV or VUV (i.e., UV absorbed by gases) refers to radiation having a wavelength of about 100 nm to 200 nm. DUV generally refers to radiation having a wavelength in a range of 126 nm to 428 nm, and in some aspects, excimer lasers can produce DUV radiation used within lithography apparatuses. It will be appreciated that radiation having a wavelength in a range of, for example, 5 nm to 20 nm refers to radiation having a band of wavelengths at least a portion of which is in the range of 5 nm to 20 nm.

[0203] While some aspects of the disclosure are described in the context of IC fabrication using a lithography apparatus, it is understood that the lithography apparatus described herein can be used in other applications, such as the fabrication of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. It will be appreciated that, in the context of such alternative applications, any use of the terms "wafer" or "die" herein can be considered as being specific examples of the more general terms "substrate" or "target portion," respectively. The substrates can be processed, before or after exposure, in, for example, one or more of the steps of a track (a tool that typically applies a resist layer to a substrate and develops the exposed resist), and / or a metrology

[0204] Furthermore, while some aspects of the present disclosure are described in the context of optical lithography, it is to be understood that aspects of the present disclosure are not limited to optical lithography. For example, in imprint lithography, the topography of the patterning device defines the pattern created on the substrate. The topography of the patterning device can be pressed into a layer of resist supplied to the substrate, which is then solidified by the application of electromagnetic radiation, heat, pressure, or a combination thereof. The patterning device is moved out of the resist after the resist is solidified, leaving the pattern therein.

[0205] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in the art in light of the teachings and

[0206] The foregoing has described the disclosure in terms of functional block components thereof. The boundaries of these functional blocks can be arbitrarily defined, in part based on the functionality of the particular aspect, in part based on the manner in which the aspect is implemented, and in part based on the manner in which the aspect is implemented. The foregoing description is thus made for the purpose of illustrating the general principles of the disclosure, and is not to be taken in a limiting sense. Other aspects of the disclosure will be apparent to one of ordinary skill in the art from the teachings and guidance presented herein.

[0207] It is to be understood that the specific implementation described in the detailed description section and illustrated in the accompanying drawings is intended to explain, and not to limit, the scope of the disclosure. The scope of the disclosure is to be limited only by the appended claims and their equivalents.

Claims

1. A method for adjusting a photomask, the method comprising: Determine the target operating temperature of the mask during its use; and The temperature of the mask is controlled to approach the target operating temperature of the mask during use.

2. The method according to claim 1, wherein, Determining the target operating temperature includes: Directly measure the operating temperature of the precursor mask or the mask used during the previous manufacturing process; or Model one or more target operating conditions for the mask.

3. The method according to claim 1, wherein: The temperature of the mask is controlled during writing to approximate the target operating temperature of the mask during use. or The temperature of the mask is controlled before it is loaded into the equipment used to perform the manufacturing process.

4. The method according to claim 3, wherein: The temperature of the mask is controlled while the mask is stored in the mask library; Temperature control elements are used to control the temperature of the mask while it is stored in the mask library; and The temperature control element includes a gas nozzle, a hot plate, a hot mass, or a cold plate, and wherein, when the mask is stored in the mask library, the temperature profile of the hot plate, the hot mass, or the cold plate is varied spatially and / or temporally to control the temperature of the mask.

5. The method according to claim 1, wherein, The temperature of the mask is controlled after it is loaded into the equipment for performing the manufacturing process, and wherein the temperature of the mask is controlled while the mask is held in a mask conveyor, turntable or mask library.

6. The method according to claim 1, wherein, The temperature of the mask is controlled during the manufacturing process, and wherein: The temperature of the mask is controlled when the mask is mounted on a platform or fixture; The temperature of the mask is controlled during the overhead time between exposures of the two wafers; or The temperature of the mask is controlled while the mask is being described or / or exposed.

7. The method according to claim 6, wherein, One or more areas of the mask are actively heated during wafer scanning and / or exposure.

8. The method according to claim 7, wherein, Actively heating one or more areas of the mask includes heating the mask using radiation used in the manufacturing process.

9. The method according to claim 7, wherein, Actively heating the one or more regions of the mask includes heating the mask using heat supplied from a source other than the radiation used in the manufacturing process; and The use of heat supplied from sources other than the radiation used in the manufacturing process includes: The mask is heated using a gas jet; The use of light, wherein the light is provided by one or more of a laser, a light-emitting diode (LED), a light bulb, or by multiple light sources that can be individually controlled; Use a feedforward controlled heat source or a feedback controlled heat source; or The mask is placed adjacent to the locally heated surface.

10. The method according to claim 1, wherein, The temperature of the mask is controlled before the first wafer is mass-produced using the mask.

11. The method of claim 1, further comprising controlling the temperature of a chuck or fixture used to maintain the mask based on the target operating temperature of the mask.

12. The method of claim 10, further comprising: Measure the temperature of the chuck or clamp; Based on the measured temperature of the chuck or clamp, a model is created for the future temperature of the chuck or clamp. as well as The temperature of the chuck or clamp is controlled based on modeling of the future temperature of the chuck or clamp.

13. The method of claim 10, further comprising: Model the temperature of the chuck or clamp; Based on the measured temperature of the chuck or clamp, a model is created for the future temperature of the chuck or clamp. as well as The temperature of the chuck or clamp is controlled based on modeling of the future temperature of the chuck or clamp.

14. The method of claim 10, further comprising: Measure the temperature of the chuck or clamp and model the temperature of the chuck or clamp; Based on the results of measuring the temperature of the chuck or clamp and modeling the temperature of the chuck or clamp, the future temperature of the chuck or clamp is modeled. as well as The temperature of the chuck or clamp is controlled based on modeling of the future temperature of the chuck or clamp.

15. A system for pre-adjusting a mask, the system comprising: A housing configured to hold one or more photomasks; One or more heating elements, said one or more heating elements being configured to heat at least one of said one or more masks; as well as A controller, configured to use one or more heating elements to control the temperature of the mask to a predetermined temperature prior to the exposure of at least one mask to radiation for the manufacturing process, wherein: The predetermined temperature is the predicted operating temperature of the mask during exposure to the radiation to perform the manufacturing process; and The predicted operating temperature of the mask is based on the predicted dose of radiation on the mask.

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