Reticle design to minimize thermal distortion

Abstract

A method for reducing thermal strain in a reticle includes determining the target operating temperature of the reticle during use, adjusting the thermal expansion (TE) characteristics of the reticle based on the target operating temperature, and irradiating the reticle to perform a manufacturing process.

Description

[Technical Field]

[0001] Cross-reference of related applications

[0001] This application claims priority to U.S. Patent Application No. 63 / 522,581, filed on 22 June 2023, which is incorporated herein by reference in its entirety.

[0002]

[0002] This disclosure relates to the processing and adjustment of reticles, for example, to the control of the thermal expansion characteristics of reticles in lithography apparatus and systems. [Background technology]

[0003]

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

[0004]

[0004] To project a pattern onto a substrate, a lithography apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. A lithography apparatus using extreme ultraviolet (EUV) radiation with a wavelength in the range of 4 to 20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on the substrate compared to a lithography apparatus using radiation with a wavelength of, for example, 193 nm.

[0005]

[0005] A lithography apparatus may include a patterning device (e.g., a mask or reticle). Radiation can be provided through or reflected from the patterning device to form an image on the substrate. A film assembly, also called a pellicle, may be provided to protect the patterning device from airborne particles and other forms of contamination. Contamination on the surface of the patterning device can cause manufacturing defects on the substrate.

[0006]

[0006] During use, the reticle may be exposed to a radiation beam, which heats the reticle. To control the temperature of the reticle, the reticle may be cooled, and the cooling may take the form of liquid cooling. The reticle may be supported by a reticle clamp that holds the reticle in place. Although the temperature of the reticle can be controlled, the shape of the reticle changes when exposed to a radiation beam, which can cause deformation of the reticle and lead to overlay problems. Some deformation can be corrected by alignment adjustments, but some deformation remains uncorrectable by existing methods and is therefore uncorrectable.

[0007]

[0007] Reticles used in lithography wafer processing are subjected to conflicting heating and cooling during use. For example, a reticle can be subjected to localized heating (e.g., from radiation used in wafer processing that heats a portion of the reticle) and localized cooling (e.g., from contact with a chuck or clamp that is actively cooled to avoid overheating). In addition, reticles also experience large temperature swings during use, and can be heated from an initial temperature near room temperature to an operating temperature considerably higher than room temperature. As a result, during exposure of the reticle to perform wafer processing, the reticle is subjected to large thermal strain, which can lead to overlay errors.

[0008]

[0008] As a specific example, the temperature of the reticle can change dramatically during the exposure of the first few wafers in a wafer processing lot. Therefore, subsequent wafers in the lot will have a higher temperature reticle than the first wafer, resulting in an "intra-lot" overlay error. A similar effect can be observed in different fields within the same wafer, where the last field of the wafer will have a higher temperature reticle than the first field, resulting in an "intra-wafer" overlay error. Such temperature changes in the reticle during exposure cause thermal strain in the reticle, which can lead to in-plane and out-of-plane deformation of the reticle, as well as the possibility of slippage. These problems can be exacerbated when it is necessary to switch reticles more frequently in wafer processing.

[0009]

[0009] Reticle alignment modeling can only provide limited compensation for the above problems. Further methods are needed to reduce thermally induced overlay errors. [Overview of the Initiative]

[0010]

[0010] Therefore, it is desirable to reduce the thermal strain that the reticle experiences during use and thereby reduce the resulting overlay error. As will be discussed below, the reticle and one or more of its thermal expansion (TE) properties may be tuned based on the target operating temperature of the reticle.

[0011]

[0011] In some embodiments, the reticle or reticle blank may include a low-deformation material, the reticle or reticle blank material having a zero-crossing temperature (ZCT) profile and a ZCT gradient profile, and at least one of the ZCT profile and the ZCT gradient profile is non-uniform.

[0012]

[0012] Reticles and reticle blanks for use in lithography apparatus and processes may include ultra-low expansion (ULE) glass. ULE can be used because it changes shape less when its temperature changes compared to other materials. When in use, ULE glass can be heated by absorbing a large amount of energy from the radiation beam. Cooling can be used to control the temperature of the reticle, but some heating can still occur. The reticle can be supported by a reticle clamp, and therefore the reticle can be deformed when constrained by the clamp. Some of these deformations can be corrected by aligning the reticle using reference marks on the reticle, but higher-order deformations cannot be corrected by existing means.

[0013]

[0013] Some embodiments of the present disclosure address this drawback by providing a reticle or reticle blank in which one or both of the zero-crossing temperature profile and the ZCT gradient profile are non-uniform. The zero-crossing temperature is the temperature or temperature range in which the coefficient of thermal expansion of the material containing the reticle crosses zero. Some materials, such as ULE glass, have a temperature or temperature range in which the coefficient of thermal expansion crosses zero. Near the zero-crossing temperature, the material is dimensionally stable with respect to temperature fluctuations. The zero-crossing temperature gradient is the rate at which the coefficient of thermal expansion changes around the zero-crossing temperature. Existing reticles and reticle blanks are manufactured to have as uniform a ZCT profile as possible. The ZCT gradient profile is based on the length of the annealing process of the material used to form the reticle or reticle blank. This can lead to deformation in use that cannot be corrected. Some embodiments of the present disclosure provide a reticle or reticle blank having a non-uniform ZCT profile and / or ZCT gradient profile so that different parts of the reticle or reticle blank deform in different ways during use. This makes it possible to configure the reticle or reticle blank to have different deformation characteristics during use, thereby limiting the degree of deformation that cannot be corrected.

[0014]

[0014] The reticle or reticle blank has x, y, and z directions. In some embodiments, at least one of the ZCT profile and the ZCT gradient profile may vary in the y direction. The ZCT profile and / or ZCT gradient profile in the y direction may be configured to be a low-order profile (such as a second-order profile), which can be easily corrected. If there is no variation in the ZCT profile, the deformation is high-order (such as higher than second-order), which cannot be easily corrected.

[0015]

[0015] In some embodiments, at least one of the ZCT profile and the ZCT gradient profile is varied in the region adjacent to the edge of the reticle or reticle blank. Varying the ZCT profile and / or ZCT gradient profile adjacent to the edge of the reticle or reticle blank has been found to be advantageous in reducing uncorrectable deformation. While not bound by scientific theory, it is conceivable that deformation at the edge of the reticle or reticle blank can be altered in situ when supported by a reticle clamp. By varying the ZCT profile and / or ZCT gradient profile as described above, deformation at the edge of the reticle or reticle blank can be controlled.

[0016]

[0016] In some embodiments, the ZCT of the reticle or reticle blank is higher at at least one boundary of the reticle or reticle blank. It has been found that by increasing the ZCT at the boundary of the reticle, an overlay improvement of more than 35% can be achieved. According to some embodiments, the ZCT of the reticle or reticle blank has a range of 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 wider range of ZCT, the reticle or reticle blank is dimensionally stable over a wider temperature range. In some embodiments, the ZCT gradient can be from about 0.5 ppb / K2 to about 2.5 ppb / K2. The ZCT can be from about 1.0 ppb / K2 to about 2.0 ppb / K2. In some embodiments, the ZCT profile and / or the ZCT gradient 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.

[0017]

[0017] In some embodiments, the reticle blank can include a reticle as described herein.

[0018]

[0018] In some embodiments, the lithographic apparatus can include a reticle or reticle blank according to the first or second aspect of the present disclosure. The lithographic apparatus can be a deep ultraviolet (DUV) or extreme ultraviolet (EUV) lithographic apparatus.

[0019]

[0019] In some embodiments, a method of reducing non-correctable deformations in a reticle or reticle blank may include providing a reticle or reticle blank having at least one of a non-uniform ZCT profile and a ZCT gradient profile across the reticle or reticle blank. The non-uniform ZCT profile and / or ZCT gradient profile can reduce the amount of non-correctable deformation in the reticle or reticle blank, thereby reducing overlay errors. The method may include changing at least one of the ZCT profile and the ZCT gradient profile in a region adjacent to an edge of the reticle or reticle blank.

[0020]

[0020] In some embodiments, a method of manufacturing a reticle or reticle blank for a lithography process may include modeling the deformation of the reticle or reticle blank under use conditions, calculating the ZCT profile and / or ZCT gradient profile of the reticle or reticle blank to reduce any modeled non-correctable deformation based on the deformation modeling, and optionally repeating these steps until the modeled non-correctable deformation is reduced to a predetermined level, outputting the optimized ZCT profile and / or ZCT gradient profile of the reticle or reticle blank, and manufacturing a reticle or reticle blank having the optimized ZCT profile and / or ZCT gradient profile.

[0021]

[0021] According to some embodiments, uncorrectable deformation in the reticle or reticle blank can be reduced by adjusting the ZCT profile and / or ZCT gradient profile across the reticle or reticle blank. In other words, the ZCT and ZCT gradient may differ in different parts of the reticle or reticle blank. By modeling the deformation of the reticle or reticle blank, uncorrectable deformation can be reduced by adjusting the ZCT profile and / or ZCT gradient profile, and then a reticle or reticle blank having the desired ZCT profile and / or ZCT gradient profile can be manufactured.

[0022]

[0022] In some embodiments, the method includes determining the target operating temperature of the reticle in use, adjusting the thermal expansion (TE) characteristics of the reticle based on the target operating temperature of the reticle, and irradiating the reticle in order to carry out a manufacturing process.

[0023]

[0023] In some embodiments, the TE characteristic of the reticle may be the coefficient of thermal expansion (CTE) of the reticle, which may be adjusted to approximate the target operating temperature of the reticle in use. In some embodiments, the CTE may be an instantaneous CTE adjusted to be nearly zero near the target operating temperature of the reticle, or an average CTE that may be adjusted to be nearly zero between the initial temperature of the reticle and the target operating temperature of the reticle. In some embodiments, the CTE may be spatially adjusted to minimize short-time effects, in-wafer effects, and / or inter-field effects.

[0024]

[0024] In some embodiments, the TE characteristic of the reticle may be the ZCT of the reticle. In some embodiments, the reticle may be drawn at a temperature that approximates the ZCT of the reticle. In some embodiments, adjusting the TE characteristic of the reticle includes adjusting the TE characteristic of each of the multiple zones of the reticle, where each of the multiple zones of the reticle has a different ZCT.

[0025]

[0025] In some embodiments, a method for manufacturing a reticle includes determining the target operating temperature of the reticle in use, determining a desired thermal expansion (TE) characteristic of the reticle based on the target operating temperature of the reticle, and manufacturing the reticle to approximate the desired thermal expansion (TE) of the reticle.

[0026]

[0026] Further features of various aspects of this disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the specific aspects described herein. Such aspects are presented herein for illustrative purposes only. Additional aspects will become apparent to those skilled in the art based on the teachings contained herein.

[0027]

[0027] The accompanying drawings incorporated herein and forming part thereof are illustrative of the disclosure and, together with the description, will help to illustrate the principles of the disclosure and enable those skilled in the art to create and use the embodiments described herein. [Brief explanation of the drawing]

[0028] [Figure 1]

[0028] Several embodiments of lithography apparatus are shown. [Figure 2A]

[0029] Several embodiments of reflective lithography apparatus are shown. [Figure 2B]

[0030] Several embodiments of a transmissive lithography apparatus are shown. [Figure 2C]

[0031] Several embodiments of lithographic cells are shown. [Figure 3]

[0032] The deformation of the reticle in a reticle clamp is shown in several embodiments. [Figure 4A]

[0033] The deformation in the y-direction of a reticle having nominally uniform ZCT is shown in several embodiments. [Figure 4B]

[0033] The deformation in the y-direction of a reticle having a secondary ZCT profile is shown in several embodiments. [Figure 5]

[0034] An exemplary embodiment of a reticle or reticle blank in several aspects is shown. [Figure 6]

[0035] Several embodiments of the reticle stage are shown. [Figure 7]

[0035] Several embodiments of the reticle stage are shown. [Figure 8]

[0036] Several embodiments of reticle exchange devices are shown. [Figure 9]

[0036] Several embodiments of reticle exchange devices are shown. [Figure 10]

[0037] A flowchart illustrating a method for manufacturing a reticle in several embodiments is shown. [Figure 11]

[0038] Schematic diagrams of reticles in several configurations are shown. [Figure 12]

[0039] A flowchart illustrating a method for manufacturing a reticle in several embodiments is shown. [Modes for carrying out the invention]

[0029]

[0040] The features of this disclosure will become clearer when viewed in conjunction with the detailed description below. In the drawings, similar reference numerals indicate corresponding elements throughout. In the drawings, similar reference numbers generally refer to identical, functionally similar, and / or structurally similar elements. In addition, generally, the leftmost digit of a reference number indicates the drawing in which that reference number first appears. Unless otherwise indicated, the drawings provided throughout this disclosure should not be interpreted as being drawn to actual size.

[0030]

[0041] The embodiments described herein, and the references thereto to “one aspect,” “an aspect,” “an exemplary aspect,” and “an example aspect,” indicate that the embodiments described may include certain features, structures, or characteristics, but not all embodiments necessarily include those specific features, structures, or characteristics. Furthermore, such terms do not necessarily refer to the same embodiment. Moreover, if certain features, structures, or characteristics are described in relation to one embodiment, it should be understood that realizing such features, structures, or characteristics in relation to other embodiments, whether explicitly stated or not, is within the knowledge of those skilled in the art.

[0031]

[0042] In this specification, spatially relative terms such as “beneath,” “below,” “lower,” “above,” “on,” and “upper” may be used to facilitate the description of the relationship between one element or feature and another shown in the drawings. Spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation shown in the drawings. The device may be oriented in other directions (rotated 90 degrees or oriented in other directions), and the spatially relative descriptors used herein may be interpreted accordingly.

[0032]

[0043] In this specification, terms such as “about” and “approximately” may be used to indicate a value of a given quantity that may vary based on a particular technique. Based on a particular technique, terms such as “about” and “approximately” may 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).

[0033]

[0044] Aspects of this disclosure may be implemented in hardware, firmware, software, or any combination thereof. Aspects of this disclosure may also be implemented as instructions stored on a computer-readable medium that can be read and executed by one or more processors. The machine-readable medium may include any mechanism for storing or transmitting information in a format readable by a machine (e.g., a computing device). For example, the 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 propagating signals (e.g., carrier waves, infrared signals, digital signals, etc.). Furthermore, in this specification, firmware, software, routines, and / or instructions may be described as performing certain actions. However, such descriptions are for convenience only, and it should be understood that such actions are brought about by the execution of firmware, software, routines, instructions, etc. by a computing device, processor, controller, or other device. The term “machine-readable medium” may be synonymous with similar terms, such as “computer program product,” “computer-readable medium,” or “non-temporary computer-readable medium.” The term “non-transient” may be used herein to characterize one or more forms of computer-readable media other than transient propagating signals.

[0034]

[0045] However, before describing such embodiments in more detail, it is helpful to present exemplary environments in which embodiments of this disclosure may be implemented.

[0035]

[0046] Exemplary lithography system

[0047] Figure 1 shows a lithography system according to the present invention. The lithography system comprises a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam B. The lithography 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 adjust the radiation beam B before it is incident on the patterning device MA. The projection system is configured to project the radiation beam B (patterned in this case by the mask MA) onto the substrate W. The substrate W may contain a previously formed pattern. In this case, the lithography apparatus aligns the patterned radiation beam B with the previously formed pattern on the substrate W. In this embodiment, a pellicle 15 is drawn in the path of radiation to protect the patterning device MA. It will be understood that the pellicle 15 may be placed in any required position and may be used to protect any of the mirrors in the lithography apparatus. The patterning device MA is sometimes called a reticle. The support structure MT is sometimes called a reticle stage.

[0036]

[0048] The radiation source SO, illumination system IL, and projection system PS can all be constructed and positioned to be isolated from the external environment. The radiation source SO can be supplied with gas (e.g., hydrogen) at a pressure below atmospheric pressure. The illumination system IL and / or projection system PS can be provided with a vacuum space. The illumination system IL and / or projection system PS can be supplied with small amounts of gas (e.g., hydrogen) at a pressure far below atmospheric pressure.

[0037]

[0049] The radiation source SO shown in Figure 1 is of a type that may be called a laser-generated plasma (LPP) source. A laser (which may be, for example, a CO2 laser) is configured to impart energy to a fuel, such as tin (Sn), provided from a fuel ejector, via the laser beam. Although tin is mentioned in the following description, any suitable fuel can be used. The fuel may be, for example, in liquid form, or it may be, for example, a metal or alloy. The fuel ejector may comprise a nozzle configured to guide the tin (for example, in the form of droplets) along a trajectory toward the plasma-forming region. The laser beam is incident on the tin in the plasma-forming region. Plasma is generated in the plasma-forming region by imparting laser energy to the tin. Radiation, including EUV radiation, is emitted from the plasma during the de-excitation and recombination of ions in the plasma.

[0038]

[0050] EUV radiation is focused and concentrated by a per-normal incident radiation collector (sometimes more commonly called a normal incident radiation collector). The collector may have a multilayer structure arranged to reflect EUV radiation (e.g., EUV radiation with a desired wavelength such as 13.5 nm). The collector may have an elliptical configuration with two elliptical foci. As will be discussed below, the first focal point may be in the plasma-forming region and the second focal point may be an intermediate focal point.

[0039]

[0051] The laser may be separated from the radiation source SO. If the laser is separated from the radiation source SO, the laser beam can be directed from the laser to the radiation source SO using a beam delivery system (not shown) that includes, for example, a suitable guide mirror and / or beam expander and / or other optical systems. The laser and the radiation source SO together can be considered as a radiation system.

[0040]

[0052] The radiation reflected by the collector forms radiation beam B. Radiation beam B is focused to a certain point, forming an image of the plasma-forming region, which acts as a virtual radiation source for the illumination system IL. The point where radiation beam B is focused can be called the intermediate focus. The radiation source SO is positioned such that the intermediate focus is located at or near an opening in the closed structure of the radiation source.

[0041]

[0053] The radiant beam B is sent from the radiation source SO to the illumination system IL, which is configured to adjust the radiant beam. The illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. Together, the faceted field mirror device 10 and the faceted pupil mirror device 11 provide a radiant beam B having a desired cross-sectional shape and a desired angular distribution. The radiant beam B is sent from the illumination system IL and incident on a patterning device MA held by a support structure MT. The patterning device MA reflects the radiant beam B to form a pattern. The illumination system IL may include other mirrors or devices in addition to, or instead of, the faceted field mirror device 10 and the faceted pupil mirror device 11.

[0042]

[0054] Following reflection from the patterning device MA, the patterned radiant beam B enters the projection system PS. The projection system comprises several mirrors 13, 14 configured to project the radiant beam B onto a substrate W held by a substrate table WT. The projection system PS can apply a reduction factor to the radiant beam to form an image with features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 can be applied. In Figure 1, the projection system PS has two mirrors 13, 14, but the projection system can include any number of mirrors (e.g., six mirrors).

[0043]

[0055] The radiation source SO shown in Figure 1 may include components not shown. For example, a spectral filter may be provided on the radiation source. The spectral filter may substantially transmit EUV radiation but substantially block radiation of other wavelengths, such as infrared radiation.

[0044]

[0056] If the patterning device (MA) is left unprotected, contamination may necessitate cleaning or disposal of the MA. Cleaning the MA interrupts valuable manufacturing time, and disposal is costly. Replacing the MA also interrupts valuable manufacturing time.

[0045]

[0057] Figures 2A and 2B show lithography apparatus 200 and lithography apparatus 200', respectively, in which embodiments of the present disclosure may be carried out. Lithography apparatus 200 and lithography apparatus 200' each include an illumination system (illuminator) IL configured to adjust a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet); a support structure (e.g., mask table) MT connected to a first positioner PM configured to support a patterning device (e.g., a mask, reticle, or dynamic patterning device) MA and to precisely position the patterning device MA; and a substrate table (e.g., wafer table) WT connected to a second positioner PW configured to hold a substrate (e.g., a resist-coated wafer) W and to precisely position the substrate W. Lithography apparatuses 200 and 200' also have a projection system PS configured to project the pattern applied to the radiation beam B by the patterning device MA onto a target portion (e.g., a portion containing one or more dies) C of the substrate W. In lithography apparatus 200, the patterning device MA and projection system PS are reflective. In lithography apparatus 200', the patterning device MA and projection system PS are transmissive.

[0046]

[0058] The illumination system IL may include various types of optical components, such as refractive, reflective, reflector-refracting, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, to guide, shape, or control the radiant beam B.

[0047]

[0059] The support structure MT holds the patterning device MA depending on the orientation of the patterning device MA relative to the reference coordinate system, the design of at least one of the lithography apparatus 200 and 200', and other conditions such as whether the patterning device MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT can be, for example, a frame or table that can be fixed or movable. By using sensors, the support structure MT can ensure that the patterning device MA is in a desired position, for example, with respect to the projection system PS.

[0048]

[0060] The term “patterning device” (MA) should be broadly interpreted to refer to any device that can be used to impart a pattern to a cross-section of a radiation beam B, such as forming a pattern on a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in a device formed on the target portion C to form an integrated circuit.

[0049]

[0061] The patterning device MA can be transmissive (as in the lithography apparatus 200' in Figure 2B) or reflective (as in the lithography apparatus 200 in Figure 2A). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, and programmable LCD panels. Masks are well-known in lithography and include various mask types such as binary, Levenson (alternating) phase shift, or halftone (attenuated) phase shift, as well as various hybrid mask types. In one example of a programmable mirror array, a matrix arrangement of small mirrors is used, each of which can be individually tilted to reflect the incident radiation beam in a different direction. The tilted mirrors impart a pattern to the radiation beam B reflected by the matrix of small mirrors.

[0050]

[0062] The term "projection system" PS can encompass any type of projection system. Such systems may include refractive, reflective, reflector-refracting, magnetic, electromagnetic, and electrostatic-optical systems, or any combination thereof, depending on the requirements of the exposure radiation being used or other factors (e.g., the use of immersion liquid or vacuum for the substrate W). A vacuum environment may be used for EUV or electron beam radiation because other gases may absorb excessive radiation or electrons. Therefore, a vacuum environment may be provided throughout the beam path using vacuum walls and vacuum pumps.

[0051]

[0063] The lithography apparatus 200 and / or lithography apparatus 200' may be of a type having two or more substrate tables WT (and / or two or more mask tables). In such a “multistage” machine, additional substrate tables WT can be used in parallel, or pre-steps can be performed on one or more tables while one or more other substrate tables WT are being used for exposure. Depending on the circumstances, the additional tables may not be substrate tables WT.

[0052]

[0064] Lithography apparatuses can also be of a type that can cover at least a portion of the substrate with a liquid having a relatively high refractive index (e.g., water) to fill the space between the projection system and the substrate. Additionally, immersion liquid can be applied to other spaces within the lithography apparatus, for example, between the mask and the projection system. Immersion techniques for increasing the numerical aperture of the projection system are well known in the art. As used herein, the term “immersion” does not mean that a structure such as a substrate must be submerged in a liquid. For example, a liquid may be placed between the projection system and the substrate during exposure.

[0053]

[0065] Referring to Figures 2A and 2B, the illuminator IL receives the radiation beam from the radiation source SO. For example, if the radiation source SO is an excimer laser, the radiation source SO and the lithography apparatus 200, 200' may be physically separate. In such a case, the radiation source SO is not considered to form part of the lithography apparatus 200 or 200', and the radiation beam B is delivered from the radiation source SO to the illuminator IL using a beam delivery system BD (Figure 2B), which includes, for example, a suitable guidance mirror and / or beam expander. In other cases, the radiation source SO can be an integral part of the lithography apparatus 200, 200', for example, if the radiation source SO is a mercury lamp. The radiation system may include the radiation source SO, the illuminator IL, and / or the beam delivery system BD.

[0054]

[0066] The illuminator IL may include an adjuster AD (Figure 2B) for adjusting the angular intensity distribution of the radiated beam. Generally, at least the outer and / or inner radial ranges of the intensity distribution at the pupil plane of the illuminator (generally referred to as "σ-outer" and "σ-inner," respectively) can be adjusted. In addition, the illuminator IL may include various other components (Figure 2B), such as an integrator IN and a capacitor CO. The illuminator IL may be used to adjust the radiated beam B to have desired uniformity and intensity distribution in the beam cross-section.

[0055]

[0067] Referring to Figure 2A, the radiant beam B is incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a mask table) MT, and a pattern is formed by the patterning device MA. In the lithography apparatus 200, the radiant beam B is reflected from the patterning device (e.g., a mask) MA. After being reflected from the patterning device (e.g., a mask) MA, the radiant beam B passes through a projection system PS, which focuses the radiant beam B onto a target portion C of the substrate W. A second positioner PW and a position sensor IF2 (e.g., an interference device, a linear encoder, or a capacitance sensor) can be used to precisely move the substrate table WT (e.g., to position different target portions C within the path of the radiant beam B). Similarly, a first positioner PM and another position sensor IF1 can be used to precisely position the patterning device (e.g., a mask) MA relative to the path of the radiant beam B. The patterning device (e.g., mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0056]

[0068] Referring to Figure 2B, the radiation beam B is incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a mask table MT), and a pattern is formed by the patterning device. After crossing the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil-conjugate PPU relative to the illumination pupil IPU. A portion of the radiation is emitted from the intensity distribution in the illumination pupil IPU, crosses the mask pattern without being affected by diffraction in the mask pattern, and forms an image of the intensity distribution in the illumination pupil IPU.

[0057]

[0069] The projection system PS projects an image of the mask pattern MP, which is formed on a photoresist layer coated on the substrate W by a diffracted beam generated from the mask pattern MP by radiation from the intensity distribution. For example, the mask pattern MP may include a line-and-space array. Diffraction of radiation in the array, distinct from zero-order diffraction, generates an induced diffracted beam whose direction changes perpendicular to the lines. The undiffracted beam (i.e., the so-called zero-order diffracted beam) traverses the pattern without changing its propagation direction. The zero-order diffracted beam crosses the upper lens or upper lens group of the projection system PS upstream of the pupil-conjugate PPU of the projection system PS and reaches the pupil-conjugate PPU. Within the plane of the pupil-conjugate PPU, and a portion of the intensity distribution related to the zero-order diffracted beam, is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. The aperture device PD is positioned, for example, in or substantially in the plane containing the pupil-conjugate PPU of the projection system PS.

[0058]

[0070] The projection system PS is configured to capture a zero-order diffraction beam, a primary-order diffraction beam, and / or a higher-order diffraction beam (not shown) (for example, using a lens or lens group L). In some embodiments, dipole illumination for imaging a line pattern extending perpendicular to the line may be used to take advantage of the resolution-enhancing effect of dipole illumination. For example, the primary-order diffraction beam interferes with the corresponding zero-order diffraction beam at the wafer W level to form an image of the line pattern MP with the highest possible resolution and process window (i.e., usable depth of field in combination with an acceptable exposure dose deviation). In some embodiments, astigmatism can be reduced by providing a radiating pole (not shown) in the quadrant opposite the illumination system pupil IPU. Furthermore, in some embodiments, astigmatism can be reduced by blocking the zero-order beam in the projection system pupil-conjugate PPU related to the radiating pole in the opposite quadrant. This is described in detail in U.S. Patent No. 7,511,799B2, issued March 31, 2009, which is incorporated herein by reference in its entirety.

[0059]

[0071] A second positioner PW and position sensor IFD (e.g., an interference device, linear encoder, or capacitance sensor) can be used to precisely move the substrate table WT (e.g., to position different target portions C within the path of the radiation beam B). Similarly, a first positioner PM and another position sensor (not shown in Figure 2B) can be used to precisely position the mask MA relative to the path of the radiation beam B (e.g., after mechanically acquiring it from a mask library or during scanning).

[0060]

[0072] Generally, the movement of the mask table MT can be achieved using long-stroke modules (coarse positioning) and short-stroke modules (fine positioning) that form part of the first positioner PM. Similarly, the movement of the substrate table WT can be achieved using long-stroke modules and short-stroke modules that form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT can be connected to or fixed to a short-stroke actuator. The mask MA and substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. The substrate alignment marks (as shown in the figure) occupy dedicated target areas, but the substrate alignment marks may also be located in the space between the target areas (these are known as scribe line alignment marks). Similarly, in situations where two or more dies are provided on the mask MA, the mask alignment marks may be located between the dies.

[0061]

[0073] The mask table MT and patterning device MA may be located inside the vacuum chamber V, and an in-vacuum robot IVR can be used to move the patterning device, such as a mask, in and out of the vacuum chamber. Alternatively, if the mask table MT and patterning device MA are outside the vacuum chamber, an out-of-vacuum robot can be used for various transport tasks, similar to the in-vacuum robot IVR. Both in-vacuum and out-of-vacuum robots can be calibrated to smoothly transport any payload (e.g., a mask) to a fixed kinematic mount on a transport station.

[0062]

[0074] The lithography apparatus 200, 200' may be used in at least one of the following modes: 1. In step mode, the support structure (e.g., mask table) MT and substrate table WT are kept essentially stationary (i.e., single static exposure) while the entire pattern applied to the radiation beam B is projected onto the target portion C in a single pass. The substrate table WT is then shifted in the X and / or Y directions so that different target portions C can be exposed. 2. In scan mode, the support structure (e.g., mask table) MT and substrate table WT are scanned synchronously (i.e., single dynamic exposure) while the pattern applied to the radiation beam B is projected onto the target portion C. The speed and direction of the substrate table WT relative to the support structure (e.g., mask table) MT can be determined by the (reduction) magnification and image inversion characteristics of the projection system PS. 3. In another mode, the support structure (e.g., mask table) MT is kept essentially stationary, holding the programmable patterning device, while the substrate table WT is moved or scanned while the pattern applied to the radiation beam B is projected onto the target portion C. A pulsed radiation source SO is used, and the programmable patterning device is updated as needed after each movement of the substrate table WT or between consecutive radiation pulses during scanning. This operating mode can be readily applied to maskless lithography utilizing programmable patterning devices such as programmable mirror arrays.

[0063]

[0075] Combinations and / or variations of the described usage modes, or entirely different usage modes, can also be used.

[0064]

[0076] In some embodiments, the lithography apparatus 200 includes an extreme ultraviolet (EUV) source, which is configured to generate a beam of EUV radiation for EUV lithography. Generally, the EUV source is configured in a radiation system, and the corresponding illumination system is configured to adjust the EUV radiation beam of the EUV source.

[0065]

[0077] In some embodiments, the lithography apparatus 200' includes a deep ultraviolet (DUV) source, which is configured to generate a beam of DUV radiation for DUV lithography. Generally, the DUV source is configured in a radiation system, and a corresponding illumination system is configured to adjust the DUV radiation beam of the DUV source.

[0066]

[0078] Exemplary lithographic cell

[0079] Figure 2C shows a lithographic cell 202, sometimes called a lithocell or cluster, in several embodiments. A lithography apparatus 200 or 200' may form part of the lithographic cell 200. The lithographic cell 202 may also include one or more devices that perform pre-exposure and post-exposure processes on the substrate. Conventionally, these include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a cooling plate CH, and a bake plate BK. A substrate handler or robot RO picks up the substrates from input / output ports I / O1 and I / O2, moves the substrates between various process devices, and delivers them to the loading bay LB of the lithography apparatus 200 or 200'. These devices are often collectively referred to as tracks and are under the control of a track control unit TCU, which itself is controlled by a monitoring and control system SCS, which in turn controls the lithography apparatus via a lithography control unit LACU. Thus, different devices can be operated to maximize throughput and processing efficiency.

[0067]

[0080] Reticle deformation

[0081] Figure 3 shows the deformation of the reticle MA in the reticle clamp 36. The amount of deformation of the reticle MA is smallest at the center of the reticle MA. The deformation is largest at the edge of the reticle in the y direction 37. In some embodiments, the reticle may be loaded near ambient temperature, and when reticle imaging is started, the outer edge of the reticle expands as its region cools to the operating temperature of the clamp 38, while the imaging region of the reticle expands as the radiation beam heats its region to the steady-state temperature. The outer edge remains in an expanded, low-temperature state. The further the edge of the reticle is from the zero-crossing temperature, the greater the strain in this region of the reticle. This difference in strain causes deformation that cannot be corrected.

[0068]

[0082] Figures 4A and 4B show the deformation in the y-direction of reticle 400 having a nominally uniform ZCT and deformation in the y-direction of a reticle having a secondary ZCT profile. In Figure 4A, reticle 400 has a uniform ZCT profile and / or ZT gradient profile, with significant deformation at the y-boundary, i.e., the top and bottom of the grid. Such deformation cannot be corrected with conventional alignment techniques. In such cases, the overlay can be optimized to approximately 0.5 nm. Figure 4B shows a non-uniform reticle 402 according to this disclosure. The deformation is reduced at the y-boundary, which makes it possible to optimize the overlay to approximately 0.31 nm.

[0069]

[0083] Figure 5 shows one exemplary embodiment of the reticle 500 according to the present disclosure. The reticle 500 may be a reticle blank. In the diagram shown in Figure 5, the ZCT of the reticle is shown such that the lowest ZCT is provided in the middle portion of the reticle, and the ZCT increases at the -Y and +Y reticle boundaries. Axes of symmetry along both the y and x axes may be present.

[0070]

[0084] Providing non-uniform ZCT profiles or ZCT gradient profiles in the reticle or reticle blank can reduce the amount of deformation that cannot be corrected during use, thereby improving the overlay accuracy of the equipment in which the reticle or reticle blank is used. Previously, reticles and reticle blanks were manufactured with the intention of providing uniform ZCT profiles and / or ZCT gradient profiles across the entire range of the reticle or reticle blank.

[0071]

[0085] Exemplary reticle stage

[0086] Figures 6 and 7 show several embodiments of the reticle stage 600. The reticle stage 600 may comprise a stage top surface 602, a stage bottom surface 604, a stage side surface 606, and a clamp 700. In some embodiments, the reticle stage 600 with the clamp 700 may be implemented in a lithography apparatus LA. For example, the reticle stage 600 may be a support structure MT in the lithography apparatus LA. In some embodiments, the clamp 700 may be positioned on the stage top surface 602. For example, as shown in Figure 6, the clamp 700 may be positioned at the center of the stage top surface 602 with the clamp front surface 702 oriented perpendicularly away from the stage top surface 602.

[0072]

[0087] In some lithography systems, such as the lithography system LA, a reticle stage 600 equipped with clamps 700 can be used to hold and position the reticle for scanning or patterning operations. In one example, the reticle stage 600 may rely on a powerful drive mechanism, a large balance mass, and a heavy frame to support itself. In one example, the reticle stage 600 may have high inertia and may weigh over 500 kg to propel and position a reticle weighing approximately 0.5 kg. To achieve the reciprocating motion of the reticle typically seen in lithography scanning or patterning operations, acceleration and deceleration forces can be provided by linear motors driving the reticle stage 600.

[0073]

[0088] In some embodiments, as shown in Figures 6 and 7, the reticle stage 600 may be equipped with a first encoder 612 and a second encoder 614 for positioning operations. For example, the first encoder 612 and the second encoder 614 may be interferometers. The first encoder 612 may be mounted along a first direction, for example, the lateral direction (i.e., the X direction) of the reticle stage 600. The second encoder 614 may be mounted along a second direction, for example, the longitudinal direction (i.e., the Y direction) of the reticle stage 600. In some embodiments, as shown in Figures 6 and 7, the first encoder 612 may be orthogonal to the second encoder 614.

[0074]

[0089] As shown in Figures 6 and 7, the reticle stage 600 may include a clamp 700. The clamp 700 is configured to hold a reticle 808 on a fixed plane on the reticle stage 600. The clamp 700 may include a clamp front 702 and be positioned on the stage top surface 602. In some embodiments, the clamp 700 can hold and secure an object using mechanical, vacuum, electrostatic, or other suitable clamping techniques. In some embodiments, the clamp 700 may be an electrostatic clamp configured to electrostatically clamp (i.e., hold) an object, such as a reticle, in a vacuum environment. In the case of EUV generation performed in a vacuum environment, it may be difficult to use a vacuum clamp to clamp a mask or reticle. Instead, an electrostatic clamp can be used. For example, the clamp 700 may include an electrode, a resistive layer on the electrode, a dielectric layer on the resistive layer, and a bar protruding from the dielectric layer. When in use, a voltage (e.g., several kV) can be applied to the clamp 700. This allows current to flow through the resistive layer, so that the voltage at the top surface of the resistive layer becomes substantially the same as the voltage at the electrodes, generating an electric field. Furthermore, the Coulomb force, i.e., the attractive force between electrically oppositely charged particles, attracts the object to the clamp 700, holding it in place. In some embodiments, the clamp 700 may be made of a rigid material, such as a metal, dielectric, ceramic, or a combination thereof.

[0075]

[0090] Exemplary reticle exchange device

[0091] Figures 8 and 9 show several embodiments of the reticle exchange device 801. The reticle exchange device 801 may be configured to reduce damage to the clamp 700 and reticle 808 by minimizing reticle exchange time, particle generation, and contact force or stress from the clamp 700 and / or reticle 808, thereby improving the overall throughput of the reticle exchange process, for example, in a lithography apparatus LA.

[0076]

[0092] As shown in Figures 8 and 9, the reticle exchange device 801 may include a reticle stage 600, a clamp 700, and a vacuum robot 800. The vacuum robot 800 may include a reticle handler 802.

[0077]

[0093] In some embodiments, the reticle handler 802 may be a high-speed exchange device (RED) configured to rotate efficiently and minimize reticle exchange time. For example, the reticle handler 802 can save time by moving multiple reticles from one position to another substantially simultaneously rather than sequentially.

[0078]

[0094] In some embodiments, as shown in Figure 8, the reticle handler 802 may comprise one or more reticle handler arms 804. The reticle handler arms 804 may comprise a reticle base plate 806. The reticle base plate 806 may be configured to hold an object, such as a reticle 808.

[0079]

[0095] In some embodiments, the reticle baseplate 806 may be an extreme ultraviolet inner pod (EIP) for the reticle. In some embodiments, the reticle baseplate 806 comprises a front surface 807 of the reticle baseplate, and the reticle 808 comprises a back surface 809 of the reticle.

[0080]

[0096] In some embodiments, as shown in Figures 8 and 9, the reticle base plate 806 may hold the reticle 808 such that the front surface 807 of the reticle base plate and the back surface 809 of the reticle base plate face the top surface 602 of the stage and the front surface 702 of the clamp, respectively. For example, the front surface 807 of the reticle base plate and the back surface 809 of the reticle base plate may be oriented perpendicularly away from the top surface 602 of the stage and the front surface 702 of the clamp.

[0081]

[0097] As shown in Figure 9, the reticle exchange device 801 may include a reticle exchange area 810, which is a cross-sectional area between the clamp 700, the reticle 808, the reticle base plate 806, and the reticle handler arm 804 during the reticle exchange process.

[0082]

[0098] In some embodiments, as shown in Figure 8, the reticle handler arms 804 may be arranged symmetrically around the reticle handler 802. For example, the reticle handler arms 804 may be spaced about 90 degrees, 120 degrees, or 180 degrees apart from each other. In some embodiments, the reticle handler arms 804 may be arranged asymmetrically around the reticle handler 802. For example, two reticle handler arms 804 may be spaced about 135 degrees apart from each other, or two other reticle handler arms 804 may be spaced about 90 degrees apart from each other.

[0083]

[0099] In one example, during the reticle exchange process, the reticle handler arm 804 of the reticle handler 802 positions the reticle 808 on the reticle base plate 806 near the clamp 700 in the reticle exchange area 810. As described above, the transfer of the reticle from the reticle handler 802 to the clamp 700 involves an unknown reticle position offset, which includes a reticle vertical distance offset (i.e., Z-direction offset) and a reticle tilt offset (i.e., R-direction offset). X Offset and R YThis includes offsets. An inclination between the clamp 700 and the reticle 808, or excessive misalignment, can cause particle generation and potentially damage the reticle 808 or clamp 700 over time. The reticle back surface 809 and the clamp front surface 702 may be aligned on the same plane for final transfer. Despite calibration, variations due to the mechanical and positional tolerances of the reticle may still exist, which can lead to increased angular impact between the clamp 700 and the reticle 808 and unpredictable initial contact points.

[0084]

[0100] In one example, the reticle replacement process may involve lowering the reticle stage 600 with clamp 700 as close as possible to the reticle 808 until clamp 700 contacts the reticle 808, taking into account all possible offsets and / or inclinations, with the lowering starting far from the reticle handler 802. During the reticle replacement process, the reticle stage 600 with clamp 700 may be adjusted in multi-stage movement (e.g., long-stroke stage (coarse), short-stroke stage (fine)).

[0085]

[0101] In some embodiments, as shown in Figure 9, the reticle changing device 801 may include a clamp controller 760. The clamp controller 760 may be coupled to the clamp 700 and configured to control the position of the clamp 700. For example, the clamp controller 760 may be configured to control the reticle stage 600 to allow compliant movement of the clamp 700. In some embodiments, the clamp controller 760 may control the reticle stage 600 and / or the clamp 700 with a servo motor or servo actuator (i.e., X, Y, Z, R) X , R Y , R Z) can be coupled to. For example, the clamp controller 760 controls the translation (i.e., in the X direction, Y direction, Z direction) of the reticle stage 600 with clamps 700 along the x-axis, y-axis, and z-axis, as well as the rotation (i.e., R X R Y R Z ) about the x-axis, y-axis, and z-axis. The x-axis, y-axis, and z-axis are Cartesian coordinates.

[0086]

[0102] Thermal distortion and thermal expansion characteristics of the reticle

[0103] The thermal distortion in the reticle can be modeled as follows.

Equation

[0087]

[0104] In some embodiments, the reticle can be composed of a material having appropriate ZCT and other TE characteristics. These TE characteristics can be selected to vary as a function of position so as to reduce the amount of thermal distortion. For example, the reticle can be composed of ultra-low expansion (ULE) glass having variable TE characteristics throughout its thickness (in the z direction). For such a reticle, and for a slight temperature variation from the ZCT (shown as T ZC in the following equation), the CTE of the reticle along any z direction of the reticle can be approximated as a linear function of temperature as follows. CTE(z)=α(z)*(T - T zc (z)), In the equation, α(z) can be determined experimentally or by simulation as a function (or value). Those skilled in the art will understand that, without departing from the present invention, this linear approximation of the CTE variation of the reticle can also be approximated as a nonlinear function according to several embodiments.

[0088]

[0105] Summarizing the above equations, according to some embodiments, the thermal strain of the reticle at any z position is given as follows:

number

[0089]

[0106] From T0(z) to T f Integrating with respect to T up to (z), we get the following equation from the above equation.

number

number

[0090]

[0107] According to the above equation, the thermal strain ε of the reticle at any z position is zero under the following two possible conditions:

number

[0091]

[0108] The above condition (2) is T (as a function of position along any z direction) zc However, this means that it is equal to the average of the initial and final temperatures of the reticle. In other words, in order to satisfy condition (2) or to minimize thermal distortion, T at a point in the reticle must zcThe temperature should be adjusted to be approximately equal to the average temperature of the reticle at that point during loading and use. This condition can be applied to inter-field and in-wafer processing, where short-time effects can significantly contribute to the thermal strain of the reticle. For example, during wafer processing, the reticle may be repeatedly exposed to different spots or "fields" on the same wafer, and this short-time heating of the reticle can cause thermal strain. Even if equation (2) above is not identically zero, thermal strain can be reduced (from its original value) by approximately matching the local zero-crossing temperature and / or matching the average TE characteristic in a finite region of the reticle to the average of the reticle's loading and use temperatures. Those skilled in the art will understand that this example can be extended to variations in the x and y directions.

[0092]

[0109] As an example, in a non-limiting example, the reticle may have an initial temperature of 22°C, and the front of the reticle may be heated to a final temperature of 50°C by exposure to radiation during the in-wafer lithography process, while the back of the reticle is maintained at 22°C by cooling from a chuck or clamp. In this example, condition (2) above is the back of T zc If the temperature is 22°C, it means that the thermal strain ε on the back of the reticle is zero, which is given by the following equation.

number

number

[0093]

[0110] Exemplary spatial variations in the thermal expansion properties of the reticle.

[0111] As explained above, one way to minimize the thermal strain ε of the reticle is to form a reticle with spatially varying thermal expansion (TE) properties across the reticle. Figure 10 shows flowcharts of methods for spatially varying the TE properties of a reticle in several embodiments. In step 1002, the target operating temperature of the reticle in use may be determined. In step 1004, the thermal expansion (TE) properties of the reticle may be adjusted. The TE properties of the reticle may be adjusted based on one or more of the following methods. In step 1006, the reticle may be exposed to radiation to carry out the manufacturing process.

[0094]

[0112] In particular, in step 1002, the target operating temperature of the reticle in use may be determined. The target operating temperature of the reticle may be determined using any convenient method. For example, in some embodiments, the target operating temperature of the reticle may be determined by directly measuring the operating temperature of a precursor reticle or by directly measuring the operating temperature of a reticle used in a previous manufacturing process. In some embodiments, the target operating temperature of the reticle may be determined by modeling one or more target operating conditions of the reticle, such as the expected radiation dose on the reticle, the approximate absorption pattern of the reticle, the method of holding the reticle, and the cooling environment of the reticle. In some embodiments, the target operating temperature may be determined by examining a stored target operating temperature corresponding to the target wafer manufacturing process. In some embodiments, the target operating temperature of the reticle may be based at least in part on the expected loading temperature of the reticle.

[0095]

[0113] In step 1004, one or more TE characteristics of the reticle may be adjusted based on the target operating temperature of the reticle determined in step 1002. In some embodiments, the TE characteristics of the reticle may be adjusted to approximate the target operating temperature of the reticle in use. In some embodiments, the TE characteristics of the reticle may be adjusted based on the average value between the initial temperature of the reticle into the processing apparatus and the target operating temperature of the reticle in use. As a non-limiting example, the initial temperature of the reticle may be the temperature of the reticle when it is loaded into the apparatus for the manufacturing process. According to some embodiments, the TE characteristics of the reticle may be spatially adjusted to minimize short-time effects. For example, the TE characteristics of the reticle may be adjusted so that the TE characteristics increase or decrease over one or more of the length, width, or height of the reticle, or the TE characteristics of the reticle may be adjusted so that there is a peak at a specific location on the reticle. In some embodiments, minimizing short-time effects may include minimizing one or both of the inter-field effects and the intra-wafer effects, as discussed above. In some embodiments, the TE characteristics to be adjusted are the coefficient of thermal expansion (CTE) and the zero crossing temperature (T) of the reticle. zc ), or other similar thermal properties.

[0096]

[0114] In some embodiments, the CTE characteristic can be the instantaneous CTE of the reticle, which is the derivative of the thermal strain ε at a particular temperature. In some embodiments, the instantaneous CTE can be adjusted to be approximately zero near the reticle's target operating temperature. In some embodiments, the CTE characteristic of the reticle can be the average CTE of the reticle over a particular temperature range. In some embodiments, the CTE can be adjusted to be between the reticle's initial temperature and its target operating temperature. As a non-limiting example, the CTE can be adjusted to be approximately midway between the reticle's initial temperature and its target operating temperature.

[0097]

[0115] Figure 11 shows non-limiting schematic examples of a reticle 1100 having spatially varying TE characteristics in several embodiments. As shown in Figure 11, each zone 1102, 1104, and 1106 of the reticle 1100 has different TE characteristics. According to some embodiments, the TE characteristics of each zone can be determined by determining the expected operating temperature or target operating temperature of the respective zone.

[0098]

[0116] For example, zone 1106 of reticle 1100 may correspond to an image field zone configured to be exposed to radiation during wafer processing. In some examples, zone 1106 may be directly exposed to the radiation used for wafer processing.

[0099]

[0117] In some embodiments, zone 1102 may correspond to an unheated zone configured not to be exposed to radiation during wafer processing. In some examples, zone 1102 may receive no radiation at all during wafer processing, or may receive a smaller dose of radiation than zone 1106. For this reason, the expected operating temperature of zone 1102 may be lower than the expected operating temperature of zone 1106 in some embodiments. Thus, according to some embodiments, the T of zone 1102 zc The T of each zone zc The T of zone 1106 is set so that it is approximately equal to the average temperature of each zone. zc It can be adjusted to be lower than each. zc Creating separate zones having T corresponds to imposing condition (2) in a spatially varying manner based on the expected operating temperature of each zone, as described above. In other words, since zones 1106 and 1102 may be expected to have different average operating temperatures, zc Each zone can be individually adjusted to minimize thermal distortion in that zone.

[0100]

[0118] Similarly, zone 1104 may, according to several embodiments, correspond to an actively cooled zone of the reticle. For example, zone 1104 may be actively cooled by contact with an actively cooled clamp or chuck. In this example, zone 1104 may be expected to have a lower operating temperature than the operating temperatures of the image zone 1106 and the unheated zone 1102. According to several embodiments, the average temperature of the actively cooled zone 1104 may be expected to be lower than the average temperatures of the image zone 1106 and the unheated zone 1102, respectively, thus the T of the actively cooled zone 1104 zc This refers to the T of the image zone 1106 and the unheated zone 1102, respectively. zc It can be adjusted to be lower than that. Therefore, according to some embodiments, the reticle 1100 each has a different T zc It may include three zones.

[0101]

[0119] Figure 11 shows a reticle 1100 having different zones 1102, 1104, and 1106, but it should be understood that the three different zones are shown for illustrative purposes only and the present invention is not limited to a reticle having three different zones. In practice, a reticle can have n zones, where n is any integer greater than or equal to 2. The number of zones n in a reticle can be determined by practical considerations such as the number of contact points between the reticle and the clamp, the amount of radiation dose applied to the reticle, and the pattern of radiation applied to the reticle.

[0102]

[0120] Zones 1102, 1104, and 1106 (and any other arbitrary zones) can have any shape corresponding to a desired profile of the TE characteristics. In some embodiments, the shape of one or more zones may be determined by the shape of the processing radiation, the clamp or chuck used to hold the reticle, etc. Figure 11 shows zones 1102, 1104, and 1106 having substantially rectangular cross-sections, but the present invention is not limited to such shapes. As a non-limiting example, zones 1102, 1104, and 1106 may have triangular, circular, or elliptical cross-sections. In some embodiments, zones 1102, 1104, and 1106 have shapes substantially corresponding to regular polygons, but zones 1102, 1104, and 1106 may also have shapes corresponding to non-regular polygons or any other two-dimensional shapes. Furthermore, as will be discussed later, zones 1102, 1104, and 1106 are not limited to one or two dimensions but can extend in all three spatial directions and thus may have shapes corresponding to any three-dimensional shape. In some embodiments, the length of the cross-section of a zone may vary along one or more directions of the reticle. As a particular non-limiting example, the cross-section of one or more zones may increase or decrease along the thickness direction of the reticle. This example is merely illustrative, and zones having cross-sections that vary along any direction can be created without departing from the present invention. In addition, such zone variations can be made in any way that optimizes the TE properties of the reticle, such as by varying them stepwise, linearly, or curvilinearly. Those skilled in the art will understand that the shape of each zone can be individually optimized based on the desired TE properties of the reticle.

[0103]

[0121] In addition, Figure 11 shows that the reticle 1100 has TE properties that vary over the length and width of the reticle 1100, but it should be understood that, in some embodiments, the TE properties of the reticle 1100 may also vary over the thickness of the reticle 1100. In some embodiments, the TE properties of the reticle can be varied over one, two, or all three spatial dimensions of the reticle.

[0104]

[0122] In some embodiments, the TE properties of a reticle can be adjusted by spatially varying one or more properties of the reticle. For example, one way of spatially varying the TE properties of a reticle according to some embodiments may be to vary the thickness of the reticle material over one or more spatial dimensions of the reticle. In particular, by adjusting the thickness of one or more regions of the reticle, the temperature gradient across the reticle can be reduced, and therefore the thermal strain across the reticle can be reduced.

[0105]

[0123] In some embodiments, another way to spatially vary the TE properties of the reticle may be to vary the material composition across one or more spatial directions of the reticle. As a specific example, in some embodiments, the reticle may be composed of, for example, titanium oxide (TiO2)-doped silicon oxide (SiO2). The TE properties of the reticle may be adjusted up or down by increasing or decreasing the TiO2 doping concentration in a particular region of the reticle. As another example, in some embodiments, a similar effect can be achieved by laminating together layers having different TE properties, such as ZCT. In some embodiments, different TE properties can be obtained by changing the composition of the layers, for example, the ratio of SiO2 and TiO2. In some embodiments, thin layers of about 1 mm or less in thickness may be laminated together so that the TE properties through the laminated layers approximate a desired value, and / or so that the TE properties vary through the layers along the lamination direction. Depending on manufacturing and other considerations, thicker or thinner layers may be preferred. As another non-limiting example, according to some embodiments, the reticle may be composed primarily of ultra-low expansion (ULE) glass. In this example, the TE properties of the reticle can be altered by adjusting the TE properties along the lamination direction using another material, such as cordierite or other similar material. In some embodiments, different layers can be laminated together by using an adhesive (e.g., epoxy) between the layers or by using optical contact.

[0106]

[0124] The above examples are not limiting to the present invention, and it should be understood that the TE properties can be changed by alloying, mixing, doping, or laminating two or more materials having different values ​​for the same TE property. In this regard, it is not necessary for the materials to have different compositions, but it should be understood that the TE properties can also be spatially changed by processing a single material to have different TE properties in different regions, for example, through grain boundary engineering or heat treatment.

[0107]

[0125] Figure 12 shows a flowchart of a method for fabricating a reticle in several embodiments. In step 1202, the target operating temperature of the reticle in use may be determined, for example, by measurement and / or modeling. The target operating temperature of the reticle may be determined using any of the methods described above. In step 1204, the desired TE characteristics of the reticle may be determined based on the target operating temperature. The desired TE characteristics of the reticle may be determined using any of the methods described above. In step 1206, the reticle may be fabricated to approximate the desired TE characteristics. The reticle may be fabricated using any of the materials and / or methods described above, or any suitable method known in the art.

[0108]

[0126] In some embodiments, step 1206 may include drawing the reticle at a temperature based on a desired TE characteristic. For example, in some embodiments, the reticle may be drawn at a temperature approximating the ZCT of the reticle, which is determined based on the target operating temperature of the reticle in use. In some embodiments, the reticle may be drawn at a temperature approximating one of several ZCTs corresponding to different zones of the reticle. In some embodiments, the reticle may be drawn at a temperature approximating the average ZCT of the reticle.

[0109]

[0127] The method steps in Figures 10 and 12 can be performed in any possible order, and not all steps need to be performed. Furthermore, the method steps described above are merely examples and not limiting. In other words, further method steps and functions can be envisioned based on the above embodiments.

[0110]

[0128] Further aspects of the present invention

[0129] In some embodiments, the reticle or reticle blank may include a low-deformation material, and the reticle or reticle blank material has a ZCT profile and a ZCT gradient profile, where at least one of the ZCT profile and ZCT gradient profile is non-uniform. The reticle or reticle blank may include ultra-low expansion glass. The reticle or reticle blank may have x, y, and z directions, and at least one of the ZCT profile and ZCT gradient profile varies in the y direction. At least one of the ZCT profile and ZCT gradient profile may vary in a region adjacent to the edge of the reticle or reticle blank. The ZCT of the reticle or reticle blank may be higher at at least one boundary of the reticle or reticle blank. The ZCT of the reticle or reticle blank may have a range of 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 gradient can range from approximately 0.5 ppb / K² to approximately 2.5 ppb / K². The ZCT profile and / or ZCT gradient profile may have at least one axis of symmetry.

[0111]

[0130] In some embodiments, the reticle blank may include a reticle as described herein. In some embodiments, the lithography apparatus may include a reticle or reticle blank as described herein.

[0112]

[0131] In some embodiments, a method for mitigating uncorrectable deformation in a reticle or reticle blank may include providing a reticle or reticle blank having at least one of a ZCT profile and a ZCT gradient profile that is non-uniform across the reticle or reticle blank. This method may include varying at least one of the ZCT profile and the ZCT gradient profile in areas adjacent to the edges of the reticle or reticle blank. This method may include modeling the deformation of the reticle or reticle blank under operating conditions, calculating the ZCT profile and / or ZCT gradient profile of the reticle or reticle blank to reduce any modeled uncorrectable deformation based on the deformation modeling, optionally repeating these steps until the modeled uncorrectable deformation is reduced to a predetermined level, outputting an optimized ZCT profile and / or ZCT gradient profile of the reticle or reticle blank, and manufacturing a reticle or reticle blank having the optimized ZCT profile and / or ZCT gradient profile.

[0113]

[0132] In some embodiments, the reticle, reticle blank, lithography apparatus, or method described above may be used.

[0114]

[0133] Various embodiments of the System and Method are disclosed in the following numbered list of clauses. 1. Determine the target operating temperature of the reticle in use, Adjusting the thermal expansion (TE) characteristics of the reticle based on the target operating temperature of the reticle. Methods that include... 2. The method according to Clause 1, wherein adjusting the TE characteristics of the reticle includes adjusting the coefficient of thermal expansion (CTE) of the reticle. 3. Adjusting the TE characteristics includes adjusting the instantaneous CTE of the reticle. The method according to Clause 2, wherein the instantaneous CTE is adjusted to be nearly zero near the target operating temperature of the reticle. 4. Adjusting the TE characteristics includes adjusting the average CTE of the reticle. The method according to Clause 2, wherein the average CTE is adjusted to be approximately zero between the initial temperature of the reticle and the target operating temperature of the reticle. 5. The method according to Clause 2, wherein the CTE and other TE characteristics of the reticle are adjusted to approximate the target operating temperature of the reticle in use. 6. The method according to Clause 5, wherein adjusting the CTE and other TE characteristics of the reticle includes spatially adjusting the CTE and other TE characteristics of the reticle to minimize short-time effects. 7. The method according to Clause 6, wherein the CTE and other TE properties of the reticle are spatially adjusted to minimize short-time effects, thereby minimizing in-wafer effects. 8. The method according to Clause 6, wherein spatial adjustment of the reticle's CTE minimizes short-term effects, which in turn minimizes in-field effects. 9. The method according to Clause 1, wherein adjusting the TE characteristics of the reticle includes adjusting the zero crossing temperature (ZCT) of the reticle. 10. The method according to Clause 9, wherein adjusting the TE characteristics of the reticle includes adjusting the TE characteristics of each of the multiple zones of the reticle, each of the multiple zones of the reticle having a different ZCT. 11. Adjusting the TE characteristics of each of the multiple zones of the reticle, Adjusting the TE characteristics of at least one image field zone to have a first ZCT, Adjusting the TE characteristics of at least one unheated zone to have a second ZCT lower than the first ZCT, Adjust the TE characteristics of at least one cooling zone so that it has a third ZCT lower than the second ZCT. The method described in Clause 10, including the method described in Clause 10. 12. The method according to clause 9, further comprising drawing the reticle at a temperature approximating the ZCT of the reticle. 13. The method according to Clause 1, comprising adjusting the TE characteristics of the reticle to approximate the average temperature of the reticle loading into the apparatus for the manufacturing process and the target operating temperature of the reticle. 14. The method according to Clause 1, wherein adjusting the TE characteristics of the reticle includes adjusting the TE characteristics along the thickness direction of the reticle. 15. The method according to Clause 14, wherein adjusting the TE properties of the reticle involves changing the material composition of one or more materials forming the reticle throughout the thickness direction of the reticle. 16. The method according to Clause 14, wherein adjusting the TE properties of the reticle involves laminating together layers of materials having different thermal expansion properties to form a reticle. 17. The method according to Clause 14, wherein adjusting the TE characteristics of the reticle includes selecting the TE characteristics of the reticle such that they have a minimum value at the target operating temperature. 18. The method according to Clause 14, wherein the adjustment of the reticle's TE characteristics includes adjusting the reticle's TE characteristics to approximate the average of the TE characteristics between the reticle's initial temperature and the reticle's target operating temperature. 19. The method according to Clause 1, wherein the TE properties of the reticle are adjusted to form a cordierite or ultra-low expansion (ULE) glass reticle. 20. A method for manufacturing a reticle, wherein this method is Determining the target operating temperature of the reticle in use, Based on the target operating temperature of the reticle, the desired thermal expansion (TE) characteristics of the reticle are determined, To fabricate a reticle so as to approximate the desired thermal expansion (TE) characteristics of the reticle. Methods that include... 21. A reticle configured for use with a lithography apparatus, wherein the reticle comprises multiple zones, and each of the multiple zones of the reticle has a different ZCT. 22. Multiple zones of the reticle, An image field zone having a first ZCT, At least one unheated zone having a second ZCT lower than the first ZCT, At least one cooling zone having a third ZCT lower than the second ZCT and The reticle described in Clause 21, including the reticle described in Clause 21.

[0115]

[0134] Terms such as “radiation,” “beam,” “light,” and “illumination” may be used herein to refer to one or more types of electromagnetic radiation, e.g., ultraviolet (UV) radiation (e.g., having wavelengths λ of 365, 248, 193, 157, or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (e.g., having wavelengths in the range of 5–100 nm (e.g., 13.5 nm, etc.)), or hard X-rays operating at less than 5 nm, and particle beams such as ion beams or electron beams. Generally, radiation with wavelengths of about 400–700 nm is considered visible radiation, and radiation with wavelengths of about 780–3000 nm (or above) is considered infrared radiation. UV refers to radiation with wavelengths of about 100–400 nm. In lithography, the term “UV” also applies to wavelengths that can be produced by mercury discharge lamps, namely G-line 436 nm, H-line 405 nm, and / or i-line 365 nm. Vacuum UV, or VUV (i.e., UV absorbed by gas), refers to radiation with wavelengths of approximately 100–200 nm. Deep ultraviolet (DUV) generally refers to radiation with wavelengths in the range of 126 nm to 428 nm, and in some embodiments, excimer lasers can generate DUV radiation used in lithography equipment. For example, radiation with wavelengths in the range of 5–20 nm should be understood as relating at least part to radiation having a specific wavelength band in the range of 5–20 nm.

[0116]

[0135] While some aspects of this disclosure are described in relation to lithography equipment in the manufacture of ICs, it should be understood that the lithography equipment described herein may also be used in other applications, such as in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memory, flat panel displays, LCDs, and thin-film magnetic heads. Those skilled in the art will recognize that, in relation to such alternative applications, where the terms “wafer” or “die” are used herein, they may be considered specific examples of the more general terms “substrate” or “target portion,” respectively. Substrates may be processed before or after exposure, for example, with a track unit (typically a tool for coating a resist layer onto a substrate and developing the exposed resist) and / or a metrology unit. Where applicable, the aspects disclosed herein may be applied to such substrate processing tools and other substrate processing tools. Furthermore, since substrates may be processed two or more times, for example to create a multilayer IC, the term “substrate” as used herein may also refer to a substrate that already contains multiple processed layers.

[0117]

[0136] Furthermore, while some aspects of this disclosure are described in relation to photolithography, it should be understood that the aspects of this disclosure are not limited to photolithography. For example, in imprint lithography, topography in a patterning device defines the pattern to be created on a substrate. The topography of the patterning device is pressed into a resist layer supplied to the substrate, and the resist can then be cured by electromagnetic radiation, heat, pressure, or a combination thereof. After the resist has cured, the patterning device is pulled away from the resist, leaving the pattern in the resist.

[0118]

[0137] The use of terms and technical terms in this specification is for illustrative purposes only, not limitation, and should be understood as to be interpreted by a person skilled in the art in light of the teachings herein.

[0119]

[0138] The disclosure has been described above using functional building blocks that illustrate embodiments of specific functions and their relationships. The boundaries of these functional building blocks are arbitrarily defined herein for the sake of clarity. Different boundaries may also be defined, as long as the specific function and its relationship are adequately performed. The above descriptions of specific embodiments should adequately illustrate the general nature of the disclosure, so that others can easily modify and / or adapt such specific embodiments for various uses by applying their knowledge within the scope of their skill, without unnecessary experimentation and without departing from the general concepts of the disclosure. Accordingly, such adapted and modified forms are intended to be within the spirit and scope of equivalents of the disclosed embodiments, based on the teachings and guidance presented herein.

[0120]

[0139] It should be understood that the section "Modes for Carrying Out the Invention," rather than the sections "Summary of the Invention" and "Abstract," is intended to be used to interpret the claims. The sections "Summary of the Invention" and "Abstract" may indicate one or more, but not necessarily all, of the embodiments of this disclosure as contemplated by the inventors, and are therefore not intended in any way to limit the scope of this disclosure and the attached claims. The breadth and scope of the subject matter protected should not be limited by any of the above embodiments, but should be defined in accordance with the following claims and their equivalents.

Claims

1. Determining the target operating temperature of the reticle in use, The thermal expansion (TE) characteristics of the reticle are adjusted based on the target operating temperature of the reticle. Methods that include...

2. The method according to claim 1, wherein adjusting the TE characteristics of the reticle includes adjusting the coefficient of thermal expansion (CTE) of the reticle.

3. Adjusting the TE characteristics includes adjusting the instantaneous CTE of the reticle. The method according to claim 2, wherein the instantaneous CTE is adjusted to be approximately zero near the target operating temperature of the reticle.

4. Adjusting the TE characteristics includes adjusting the average CTE of the reticle. The method according to claim 2, wherein the average CTE is adjusted to be approximately zero between the initial temperature of the reticle and the target operating temperature of the reticle.

5. The CTE and other TE characteristics of the reticle are adjusted to approximate the target operating temperature of the reticle during use. The method according to claim 2, wherein adjusting the CTE and other TE characteristics of the reticle includes spatially adjusting the CTE and other TE characteristics of the reticle to minimize short-time effects.

6. The method according to claim 5, wherein spatially adjusting the CTE and other TE characteristics of the reticle to minimize short-time effects includes minimizing in-wafer effects, or spatially adjusting the CTE of the reticle to minimize short-time effects includes minimizing inter-field effects.

7. Adjusting the TE characteristics of the reticle includes adjusting the zero crossing temperature (ZCT) of the reticle. Adjusting the TE characteristics of the reticle includes adjusting the TE characteristics of each of the multiple zones of the reticle, wherein each of the multiple zones of the reticle has a different ZCT. Adjusting the TE characteristics of each of the multiple zones of the reticle Adjusting the TE characteristics of at least one image field zone to have a first ZCT, The TE characteristics of at least one unheated zone are adjusted so that it has a second ZCT that is lower than the first ZCT, Adjusting the TE characteristics of at least one cooling zone to have a third ZCT lower than the second ZCT, Includes, The method according to claim 1, further comprising drawing the reticle at a temperature that approximates the ZCT of the reticle.

8. The method according to claim 1, wherein the adjustment of the TE characteristics of the reticle includes adjusting the TE characteristics of the reticle to approximate the average temperature of the loading temperature of the reticle into the apparatus for the manufacturing process and the target operating temperature of the reticle.

9. The method according to claim 1, wherein adjusting the TE characteristics of the reticle includes adjusting the TE characteristics along the thickness direction of the reticle.

10. Adjusting the TE characteristics of the reticle is Varying the material composition of one or more materials forming the reticle through the thickness direction of the reticle, or Laminating layers of materials having different thermal expansion properties together to form the reticle. The method according to claim 9, including the method described in claim 9.

11. Adjusting the TE characteristics of the reticle is Selecting the TE characteristics of the reticle to have a minimum value at the target operating temperature, or Adjusting the TE characteristics of the reticle to approximate the average of the TE characteristics between the initial temperature of the reticle and the target operating temperature of the reticle. The method according to claim 9, including the method described in claim 9.

12. The method according to claim 1, wherein adjusting the TE properties of the reticle includes forming the reticle of cordierite or ultra-low expansion (ULE) glass.

13. A method for manufacturing a reticle, wherein the method is Determining the target operating temperature of the reticle in use, Based on the target operating temperature of the reticle, the desired thermal expansion (TE) characteristics of the reticle are determined. The reticle is manufactured to approximate the desired thermal expansion (TE) characteristics of the reticle. Methods that include...

14. A reticle configured for use with a lithography apparatus, wherein the reticle comprises a plurality of zones, and each of the plurality of zones of the reticle has a different zone-to-center (ZCT).

15. The plurality of zones of the reticle are An image field zone having a first ZCT, At least one unheated zone having a second ZCT lower than the first ZCT, A cooling zone having a third ZCT lower than the second ZCT, and The reticle according to claim 14, including the reticle.

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