Reticle stage system, lithographic apparatus comprising reticle stage system, and method

Abstract

Embodiments herein describe methods, devices, and systems for an object stage system. The disclosure provides an object stage system, comprising: a body having a top surface, a bottom surface, and side surfaces; a clamp connected to the top surface of the body for clamping the object; and at least one actuator arranged in or on the body for changing a flatness of the clamp or the object.

Description

RETICLE STAGE SYSTEM, LITHOGRAPHIC APPARATUS COMPRISING RETICLE STAGE SYSTEM, AND METHODCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 720,001 which was filed on 13 November 2024 and which is incorporated herein in its entirety by referenceFIELD

[0002] The present disclosure relates to a reticle stage system, to a lithographic apparatus comprising a reticle stage system, and a method for clamping a reticle.BACKGROUND

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

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

[0005] Reticles are critical and sensitive components for imparting patterns on substrates. Reticles contain the chip pattern to be printed on the substrate. A reticle handler may be used to move and position multiple reticles for scanning and / or patterning operations in a lithographic apparatus. Input disturbances in the reticle handler may put the reticle at risk of slipping and generating particles, which may end up on the reticle front-side or back side, causing defects on every die. Furthermore, increased vibrations may lead to blurring and failure of imaging sensors, which are utilized for reticle prealignment and particle detection. In EUV lithography, reticles are multilayer reflectors that use interference to reflect light from the pattern.

[0006] EUV systems typically use a reticle handler provided with a robot gripper to transport reticles within a so-called “EUV inner pod” (EIP). For instance, one or more handlers may be provided to transport reticles between a storage container and a reticle stage inside the lithographic apparatus.

[0007] The reticle stage may be referred to as a chuck. The chuck may comprise an electrostatic clamp, which can electrostatically clamp the reticle. Typically, the reticle faces downward.

[0008] To ensure proper transfer of the pattern from the reticle to the imparting beam of radiation, it is relatively important that the reticle remains flat while it is being clamped. However, for instance thermalexpansion of components mounted to the top of the reticle chuck may affect the flatness of the clamp during operation.

[0009] Conventionally, this effect is minimized by mounting components to the reticle chuck using flexures, to isolate the chuck from the thermal expansion of these components. This method of controlling the flatness of the EUV Reticle Clamp is passive. The method may limit the flatness to a certain range, based on varying operational parameters such as dose, scan speed, etc. This range of flatness may change over time, as forces applied by chuck interfaces, such as epoxy, O-rings, and bolts, relax over time.

[0010] A second method may involve measuring the flatness of the clamp, and adjusting the shape of the clamp using, for instance, Ion Beam Flattening. The latter method thus mechanically and irreversibly changes the shape of the clamp. Consequently, clamp replacement is inevitable at some point, rendering this method relatively expansive.

[0011] Despite improvements sought by typical devices, the respective devices may still have limitations and disadvantages with respect to clamp deformation. Also, in particular wafer clamps at least in part support a substrate due to gravity, and as a result these devices are typically unsuitable to hold a relatively fragile reflective reticle facing downward.SUMMARY

[0012] The present disclosure aims to provide an improved reticle stage, obviating one or more of the disadvantages as outlined above.

[0013] Accordingly, the present disclosure provides an object stage system, comprising:a body having a top surface, a bottom surface, and side surfaces;a clamp connected to the top surface of the body for clamping an object; andat least one actuator arranged in or on the body for changing a flatness of the clamp or the object.

[0014] In an embodiment, the at least one actuator comprises a linear actuator.

[0015] In an embodiment, the at least one actuator comprises a block actuator.

[0016] In an embodiment, the at least one actuator is arranged on the bottom surface of the body.

[0017] In an embodiment, the at least one actuator is arranged on a side surface of the body.

[0018] In an embodiment, the at least one actuator is arranged inside the body.

[0019] In an embodiment, each at least one actuator comprises pairs of linear actuators, oriented in mutually perpendicular directions.

[0020] In an embodiment, the system comprises: at least one component connected to a side surface of the body, wherein the at least one actuator is adapted to counteract effects of thermal expansion of the at least one component on the body. Herein, the component may comprise equipment connected to the body for operation thereof. The component may include one or more motors. The component may include other equipment, such as sensors, electrical wiring, a processing unit, etcetera.

[0021] In an embodiment, the at least one motor is connected to the body via one or more flexures. The motor does not necessarily have to be connected to the chuck body via flexures. The actuators of the present disclosure may even replace the requirement for flexures.

[0022] In an embodiment, the object stage is a reticle stage or a wafer stage, the object being a reticle of a wafer respectively.

[0023] In an embodiment, the clamp is an electrostatic clamp or a vacuum clamp.In an embodiment, the system comprises a controller and a sensing system comprising one or more sensors for providing measurement data to the controller, wherein the controller is configured to: operate the object stage in a first manner, wherein the at least one actuator is not activated; monitor the measurement data and use the data to check a predetermined flatness map relating to the flatness of one or more of the clamp or the object; if any of the measurement data indicates that a flatness of the object or the clamp deviates from the predetermined flatness map beyond a set threshold, start to activate one or more of the at least one actuator to modify the flatness of the clamp and / or the object.

[0024] According to another aspect, the disclosure provides a lithographic apparatus comprising: an illumination system configured to condition a radiation beam; a support structure constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a projection system configured to project the patterned radiation beam onto a target portion of an object, and an object stage system, comprising: a body having a top surface, a bottom surface, and side surfaces; a clamp connected to the top surface of the body for clamping the object; and at least one actuator arranged in or on the body for changing a flatness of the clamp or the object.

[0025] In an embodiment, the reticle stage system comprises at least one component connected to a side surface of the body, wherein the at least one actuator is adapted to counteract effects of thermal expansion of the at least one component on the body.

[0026] In an embodiment, the object stage is a reticle stage or a wafer stage, the object being a reticle of a wafer respectively.

[0027] In an embodiment, the clamp is an electrostatic clamp or a vacuum clamp.

[0028] According to another aspect, the disclosure provides a method of operating an object handler apparatus, the method comprising the steps of: providing an object stage system, comprising a body having a top surface, a bottom surface, and side surfaces, a clamp connected to the top surface of the body for clamping an object, and at least one actuator arranged in or on the body, and using the at least one actuator to modify a flatness of the clamp or the object.

[0029] In an embodiment, the method comprises the steps of: providing a predetermined flatness map of the clamp to a controller, using the controller to input the predetermined flatness map into an actuation model; using the actuation model to determine forces to achieve the predetermined flatness of the clamp; and providing the forces to the at least one actuator.

[0030] In an embodiment, the method comprises the steps of: operating at least one component connected to a side surface of the body, and counteracting effects of thermal expansion of the at least one component on the body using the at least one actuator.

[0031] In an embodiment, the method comprises the steps of: - operating the object stage system, wherein the at least one actuator is not activated; monitoring measurement data as provided by one or more sensors of a sensing system and use the measurement data to check a predetermined flatness map relating to a flatness of one or more of the clamp or the object; if any of the measurement data indicates that the flatness of the clamp or the object deviates from the predetermined flatness map beyond a set threshold, start to activate one or more of the at least one actuator to modify the flatness of the clamp and / or the object.

[0032] In an embodiment, the method comprises the steps of: comparing measurement data as provided by a sensor system to a flatness map; if the step of comparing indicates that the flatness of the clamp or the object deviates from the flatness map beyond a threshold at one or more points, a controller uses an actuation model to determine forces for the at least one actuator to achieve or maintain the predetermined flatness of the clamp or object.

[0033] In an embodiment, the method comprises the steps of: comparing measurement data as provided by a sensor system to a flatness map; if the step of comparing indicates that a temperature grade of equipment connected to the body has increased beyond a temperature threshold from a default value, a controller uses an actuation model to determine forces for the at least one actuator to achieve or maintain the predetermined flatness of the clamp or object.

[0034] In an embodiment, the object stage is a reticle stage or a wafer stage, the object being a reticle of a wafer respectively.

[0035] In an embodiment, the clamp is an electrostatic clamp or a vacuum clamp.

[0036] Further features of the disclosure, as well as the structure and operation of various embodiments of the disclosure, are described in detail below with reference to the accompanying drawings. It is noted that the disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.BRIEF DESCRIPTION OF THE DRAWINGS / FIGURES

[0037] The accompanying drawings, which are incorporated herein and form 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(s) to make and use the disclosure. Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0038] FIG. 1 shows a schematic illustration of a lithographic apparatus, according to some embodiments.

[0039] FIG. 2 shows a perspective schematic illustration of a reticle stage, according to some embodiments.

[0040] FIG. 3 shows a top plan view of the reticle stage of Figure 2, according to some embodiments.

[0041] FIG. 4 shows a perspective schematic illustration of a reticle stage and a reticle exchange apparatus, according to some embodiments.

[0042] FIGS. 5 A to 5F show perspective views of embodiments of a reticle, according to some embodiments.

[0043] FIG. 6 shows a diagram of an embodiment of a method, according to some embodiments.

[0044] The features of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout the disclosure should not be interpreted as to-scale drawings.DETAILED DESCRIPTION

[0045] This specification discloses one or more embodiments that incorporate the features of this disclosure. The disclosed embodiment(s) merely exemplify the disclosure. The scope of the disclosure is not limited to the disclosed embodiment(s). The disclosure is defined by the claims appended hereto.

[0046] The embodiment(s) described, and references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment! s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0047] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0048] The term “about” as used herein indicates the value of a given quantity that can vary based on a particular technology. Based on the particular technology, the term “about” can indicate a value of agiven quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0049] Embodiments of the disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine -readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc., and in doing that may cause actuators or other devices to interact with the physical world.

[0050] Before describing such embodiments in more detail, however, it is instructive to present an example environment in which embodiments of the present disclosure may be implemented.

[0051] Exemplary Lithographic System

[0052] FIG. 1 shows a lithographic system comprising a radiation source SO and a lithographic apparatus FA. The radiation source SO is configured to generate an EUV radiation beam B and to supply the EUV radiation beam B to the lithographic apparatus LA. 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.

[0053] The illumination system IL is configured to condition the EUV radiation beam B before the EUV radiation beam B is incident upon the patterning device MA. Thereto, the illumination system IL can include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and faceted pupil mirror device 11 together provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The illumination system IL can include other mirrors or devices in addition to, or instead of, the faceted field mirror device 10 and faceted pupil mirror device 11.

[0054] After being thus conditioned, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B’ is generated. The projection system PS is configured to project the patterned EUV radiation beam B’ onto the substrate W. For that purpose, the projection system PS can comprise a plurality of mirrors 13, 14 that are configured to project the patterned EUV radiation beam B’ onto the substrate W held by the substrate table WT. The projection system PS can apply a reduction factor to the patterned EUV radiation beam B ’ , thus formingan image with features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 can be applied. Although the projection system PS is illustrated as having only two mirrors 13, 14 in FIG. 1, the projection system PS can include a different number of mirrors (e.g. six or eight mirrors).

[0055] The substrate W can include previously formed patterns. Where this is the case, the lithographic apparatus LA aligns the image, formed by the patterned EUV radiation beam B’, with a pattern previously formed on the substrate W.

[0056] A relative vacuum, i.e. a small amount of gas (e.g. hydrogen) at a pressure well below atmospheric pressure, can be provided in the radiation source SO, in the illumination system IL, and / or in the projection system PS.

[0057] The radiation source SO can be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a hydrogen plasma source, a free electron laser (FEL), or any other radiation source that is capable of generating EUV radiation.

[0058] Exemplary Reticle Stage

[0059] Some reticle chucks are incorporated by reference herein in their entireties, including those found in U.S. Patent No. 8599360, U.S. Publication Nos. 2005093666 and 2006146313, and publication Steur, M.M.A. (2017), “Design of an active wafer clamp for wafer machines” [Phd Thesis 1 (Research TU / e / Graduation TU / e), Mechanical Engineering], Technische Universiteit Eindhoven.

[0060] For example, US8599360 provides a reflective reticle chuck, a reflective illumination system including the chuck, a method of controlling the flatness of a reflective reticle using the chuck, and a method of manufacturing a semiconductor device using the chuck. The reflective reticle chuck includes a fixed portion and a mobile portion that together provide a securing surface for the reflective reticle. The mobile portion may alter a height of the securing surface relative to the fixed portion.

[0061] For example, US2005093666 discloses a technology for holding a substrate and, specifically, an object holding apparatus including a chuck for holding an object, a holding unit for holding the chuck, a generating unit provided in the holding unit, for generating a field related to an attraction force, a member provided in the chuck and attracted by the generating unit in accordance with the field, and a supporting unit for supporting one of the generating unit and the member, for movement at least in a direction nearing the other and in a direction away from the other. By disposing a coil iron core and a ferromagnetic material member opposed to each other with a clearance, unwanted deformation of the mask chuck due to their mutual surface precision can be avoided. Furthermore, each coil iron core is provided with a piezoelectric actuator or, alternatively, a distance adjusting mechanism, such that the flatness of the mask chuck can be corrected thereby.

[0062] For example, US2006146313 discloses a method for adjusting the flatness of a lithographic mask includes determining an initial mask flatness of the mask, determining an applied stress for bringing the mask to a desired mask flatness, and determining a mounting temperature of a pellicleframe to be mounted to the mask, the mounting temperature corresponding to the applied stress. The actual temperature of the pellicle frame is adjusted to the determined mounting temperature.

[0063] For example, Steur, M.M.A. (2017), “Design of an active wafer clamp for wafer machines” [Phd Thesis 1 (Research TU / e / Graduation TU / e), Mechanical Engineering], Technische Universiteit Eindhoven, discloses a design of an active wafer clamp for wafer machines. The thesis investigates a feasible design of an active wafer clamp, proposed to mechanically deform the wafer in the edge region to counteract Edge Roll-Off (ERO). The concept consists of 1636 embedded piezoelectric actuators in the edge region of a wafer clamp which is designed to provide flatness throughout processing. With means of numerical modelling, an accurate description of wafer deformations throughout processing is created to depict the mechanical ERO issues.

[0064] FIGS. 2 and 3 show schematic illustrations of an exemplary reticle stage 200, according to some embodiments. Reticle stage 200 may have a body 201, which may generally be referred to as chuck or chuck body. The body 201 can include top stage surface 202, bottom stage surface 204, side stage surfaces 206, and clamp 300. In some embodiments, reticle stage 200 with clamp 300 can be implemented in lithographic apparatus LA. For example, reticle stage 200 can be support structure MT in lithographic apparatus LA. In some embodiments, clamp 300 can be disposed on top stage surface 202. For example, as shown in FIG. 2, clamp 300 can be disposed at a center of top stage surface 202 with clamp frontside 302 facing perpendicularly away from top stage surface 202.

[0065] In some embodiments, as shown in FIGS. 2 and 3, reticle stage 200 can include first encoder 212 and second encoder 214 for positioning operations. For example, first and second encoders 212, 214 can be interferometers. First encoder 212 can be attached along a first direction, for example, a transverse direction (i.e., X-direction) of reticle stage 200. And second encoder 214 can be attached along a second direction, for example, a longitudinal direction (i.e., Y-direction) of reticle stage 200. In some embodiments, as shown in FIGS. 2 and 3, first encoder 212 can be orthogonal to second encoder 214.

[0066] As shown in FIGS. 2 and 3, reticle stage 200 can include clamp 300. Clamp 300 is configured to hold reticle 408 in a fixed plane on reticle stage 200. Clamp 300 includes clamp frontside 302 and can be disposed on top stage surface 202. In some embodiments, clamp 300 can use mechanical, vacuum, electrostatic, or other suitable clamping techniques to hold and secure an object. In some embodiments, clamp 300 can be an electrostatic clamp, which can be configured to electrostatically clamp (i.e., hold) an object, for example, reticle 408 in a vacuum environment. Due to the requirement for EUV radiation to perform in a vacuum environment, vacuum clamps cannot be used to clamp a mask or reticle and instead electrostatic clamps can be used. For example, clamp 300 can include an electrode, a resistive layer on the electrode, a dielectric layer on the resistive layer, and burls projecting from the dielectric layer. In use, a voltage can be applied to clamp 300, for example, several kV. And current can flow through the resistive layer, such that the voltage at an upper surface of the resistive layer will substantially be the same as the voltage of the electrode and generate an electric field. Also,a Coulomb force, attractive force between electrically opposite charged particles, will attract an object to clamp 300 and hold the object in place. In some embodiments, clamp 300 can be a rigid material, for example, a metal, a dielectric, a ceramic, or a combination thereof.

[0067] Exemplary Reticle Exchange Apparatus

[0068] FIG. 4 shows a schematic illustrations of the reticle stage 200 in conjunction with an exemplary reticle exchange apparatus 100, according to some embodiments. The reticle exchange apparatus 100 can be configured to minimize reticle exchange time, particle generation, and contact forces or stresses from clamp 300 and / or reticle 408 to reduce damage to clamp 300 and reticle 408 and increase overall throughput in a reticle exchange process, for example, in a lithographic apparatus LA.

[0069] As shown in FIG. 4, reticle exchange apparatus 100 can include reticle stage 200, clamp 300, and in-vacuum robot 400. In-vacuum robot 400 can include reticle handler 402.

[0070] The reticle handler 402 can be a rapid exchange device (RED), which is configured to efficiently rotate and minimize reticle exchange time. For example, reticle handler 402 can save time by moving multiple reticles from one position to another substantially simultaneously, instead of serially.

[0071] As shown in FIG. 4, the reticle handler 402 can include one or more reticle handler arms 404. In some embodiments, reticle handler arms 404 may be referred to herein as rapid exchange device (RED) grippers. Reticle handler arm 404 can include reticle baseplate 406. Reticle baseplate 406 can be configured to hold an object, for example, reticle 408. In some embodiments, reticle baseplate 406 may be referred to herein as a reticle base frame.

[0072] Reticle baseplate 406 can be an extreme ultraviolet inner pod (EIP) for a reticle. In some embodiments, reticle baseplate 406 includes reticle baseplate frontside 407, and reticle 408 includes reticle backside 409.

[0073] As shown in FIG. 4, reticle baseplate 406 can hold reticle 408 such that reticle baseplate frontside 407 and reticle backside 409 each face top stage surface 202 and clamp frontside 302. For example, reticle baseplate frontside 407 and reticle backside 409 can be facing perpendicularly away from top stage surface 202 and clamp frontside 302.

[0074] As shown in FIG. 4, the reticle handler arms 404 can be arranged symmetrically about reticle handler 402. For example, reticle handler arms 404 can be spaced from each other by about 90 degrees, 120 degrees, or 180 degrees. The reticle handler arms 404 can be arranged asymmetrically about reticle handler 402. For example, two reticle handler arms 404 can be spaced from each other by about 135 degrees, while another two reticle handler arms 404 can be spaced from each other by about 90 degrees.

[0075] In one example, during a reticle exchange process, reticle handler arm 404 of reticle handler 402 positions reticle 408 on reticle baseplate 406 towards clamp 300 in reticle exchange area 410. As described above, a reticle handoff from reticle handler 402 to clamp 300 includes an unknown reticle position offset, which includes a reticle vertical distance offset (i.e., Z-direction offset) and a reticle tilt offset (i.e., Rx offset and RY offset). Tilt or excessive non-alignment between clamp 300 and reticle 408can be a source of particle generation and can damage reticle 408 or clamp 300 over time. Reticle backside 409 and clamp frontside 302 should be in coplanar alignment for a final handoff. Despite calibration, variations still exist due to reticle mechanical and positioning tolerances, which can lead to high corner impacts and unpredictable first contact points between clamp 300 and reticle 408.

[0076] In one example, the reticle exchange process can involve lowering reticle stage 200 with clamp 300, which starts far away from reticle handler 402, as close to reticle 408 as possible until clamp 300 contacts reticle 408 to account for all possible offsets and / or tilts. During a reticle exchange process, reticle stage 200 with clamp 300 can be adjusted in a multi-stage movement.

[0077] Clamp 300 can be adjusted in a substantially vertical direction (i.e., Z-direction) toward reticle backside 409. In approach configuration 20, clamp 300 is turned off (i.e., no applied voltage) and reticle handler 402 deactivates the vertical direction (i.e., Z-direction) and tilt (i.e., Rx and RY, rotation about X-direction and rotation about Y-direction, respectively) servo motors (not shown) of reticle handler arm 404 in reticle exchange area 410.

[0078] Clamp 300 can be adjusted in a substantially vertical direction (i.e., Z-direction) toward reticle backside 409 until clamp 300 makes contact with reticle backside 409. In first contact configuration 30, clamp 300 is turned off and clamp 300 makes contact with reticle backside 409, for example, a corner of reticle 408, and then rotates or tilts about the contact (i.e., Rx and RY).

[0079] Reticle exchange apparatus 100 can be in a full contact configuration. Herein, clamp 300 can be rotationally adjusted about the contact (i.e., Rx and RY) toward reticle backside 409 until clamp 300 makes full contact with reticle backside 409. In full contact configuration 40, clamp 300 is turned off and clamp 300 makes full contact with reticle backside 409, for example, all four corners of reticle 408, and is coplanar with reticle backside 409.

[0080] Embodiments

[0081] As described above, a lithographic apparatus, or other equipment used in a process to fabricate semiconductor based structures, may typically include one or more object stages for holding and positioning objects in preparation for and during certain steps of the production process. Herein, the object may include, but is not limited to, a wafer, a reticle, a mask, or a substrate in general. The object stage may include a clamp for clamping the object to the respective table. Herein, the clamp may include, but is not limited to, an electrostatic clamp or a vacuum clamp. While the specification herein below describes embodiments relevant to a reticle stage 300 and an electrostatic clamp 300, other embodiments can include any object stage (e.g., wafer stage or reticle stage) and any object clamp (e.g., wafer clamp, reticle clamp, electrostatic clamp, or vacuum clamp.

[0082] In some lithographic apparatuses, for example, lithographic apparatus LA, a reticle stage 200 with a clamp 300 can be used to hold and position a reticle 408 for scanning or patterning operations. In one example, the reticle stage 200 can require powerful drives, large balance masses, and heavy frames to support it. In one example, the reticle stage 200 can have a large inertia and can weigh over 500 kg to propel and position a reticle 408 weighing about 0.5 kg. To accomplish reciprocating motionsof the reticle 408, which are typically found in lithographic scanning or patterning operations, accelerating and decelerating forces can be provided by linear motors that drive the reticle stage 200. FIG. 2 exemplifies motors 218 and 220, provided on opposite sides of the body 201. More motors may be provided, on either side of the body 201.

[0083] Herein, the chuck body 201 is typically made of a thermally stable material to avoid thermal expansion upon heating. Thermally stable herein means that the body has a thermal expansion coefficient which is relatively low. For instance, the body 201 may be comprised of a material having a (very) low thermal expansion coefficient.

[0084] The material of the body 201 may include, but is not limited to, fused quartz, fused silica, quartz glass (a glass comprising almost pure silica, i.e. silicon dioxide or SiCF. in amorphous (non-crystalline) form, FeNise (Invar™, a nickel-iron alloy), or borosilicate glass (a type of glass with silica and boron trioxide as the main glass-forming constituents). For example, borosilicate glasses have very low coefficients of thermal expansion (~3 x 10“6K-1at 20 °C). Fused quartz has a coefficient of thermal expansion on the order of 0.6 x 10“6K-1at 20 °C. Invar™ has a coefficient of thermal expansion on the order of 1.2 x IO’6K-1at 20 °C.

[0085] However, the motors 218, 220 will typically have to comprise significant amounts of metallic parts, which inherently results in a relatively significant thermal expansion coefficient, in comparison to the low coefficient of thermal expansion of the body 201. Thus, in operation, the one or more motors 218, 220 may typically heat, and thereby also expand at least slightly. To avoid the thermal expansion of the motors 218, 220 affecting the size and shape of the chuck body 201, the motors, and other such parts, may be connected to the chuck body 201 using one or more flexures 222, 224. The flexures herein represent flexible couplings. The flexures may include, but are not limited to, spring elements, leaf springs, rubber, thermally stable high-performance elastomer elements, etc. The flexures 222, 224 significantly limit the impact of thermal expansion of the motors 218, 220 (or other equipment attached to the chuck body 201) from impacting the size and shape of the body 201. Nevertheless, in practice, up to about 10% of thermal expansion of equipment parts connected to respective sides of the body 201 may still impact the body 201, thereby also potentially impacting the shape and thus flatness of the clamp 300.

[0086] Conventional methods of controlling the flatness of the clamp 300 are passive. They control the flatness to a certain range that is based on the varying operational parameters (dose, scan speed, etc.). This range of flatness can also change over time as forces applied by interfaces to the reticle stage 200, such as epoxy, O-rings, and bolts, relax over time.

[0087] Generally referring to Figures 5A to 5F, in some embodiments of the present disclosure, the body 201 is provided with one or more actuators 500. The actuators may be linear actuators. The actuators may be piezo actuators. The actuators may be blocks made of piezo material, able to expand in one direction or in multiple directions.

[0088] Referring to FIG. 5A, the actuators may include, for instance, one or more first actuators 502 and / or one or more second actuators 504 arranged on the bottom surface 204 of the chuck body 201. The first and second actuators may be linear actuators. The first actuators may be aligned with one side of the body 201. The second actuators may be aligned with another side of the body 201. The second actuators may be arranged perpendicular to a direction of the first actuators.

[0089] Referring to FIG. 5B, the actuators may include, for instance, one or more third actuators 510 and / or one or more fourth actuators 512 arranged on a side surface 206, 207 of the chuck body 201. The third and fourth actuators may be linear actuators. The third actuators may be aligned with one side of the body 201. The second actuators may be aligned with another side of the body 201. The third actuators 510 may be arranged perpendicular to a direction of the fourth actuators 512.

[0090] Referring to FIG. 5C, the actuators may include, for instance, one or more fifth actuators 520 and / or one or more sixth actuators 522 arranged on a side surface 209, 211 of the chuck body 201. The fifth and sixth actuators may be linear actuators. The fifth actuators may be aligned with one side of the body 201. The sixth actuators may be aligned with another side of the body 201. The fifth actuators 520 may be arranged perpendicular to a direction of the sixth 522.

[0091] Referring to FIG. 5D, the actuators may include, for instance, one or more seventh actuators 530 arranged inside of the body 201. The seventh actuators may be linear actuators. Alternatively, the seventh actuators may be piezo elements. The seventh actuators may be block shaped elements able to expand or contract in all directions.

[0092] Referring to FIG. 5E, the actuators may include, for instance, one or more eighth actuators 540 and / or one or more ninth actuators 542 arranged on the top surface 202 of the chuck body 201. The eighth and ninth actuators may be linear actuators. The eighth actuators 540 may be aligned with one side of the body 201. The ninth actuators 542 may be aligned with another side of the body 201. The ninth actuators 542 may be arranged perpendicular to a direction of the eighth actuators 540.

[0093] Referring to FIG. 5F, the chuck body 201 may be provided with any combination of the first to ninth actuators as referenced above. A controller 550 may be provided electronically connected to the one or more actuators 500. A sensing system 552, comprising at least one sensor, may be connected to the controller to provide measurement input. The sensing system 552 may provide, for instance, measurement data relating to, but not limited to, reticle flatness, topography of the reticle (reticle surface measurement), chuck body 201 position, temperature of motors 218, 220, temperature of the chuck body 201, temperature of the reticle 408, image alignment, radiation dose errors, etc.

[0094] The controller can be adapted to receive a predetermined flatness map of the clamp 300. The controller may be adapted to input the predetermined flatness map into an actuation model. Said model may be incorporated in the controller. The controller can use the actuation model to determine forces to achieve the predetermined flatness of the clamp 300, or at least, to maintain the predetermined flatness to within a preset range. Herein, the controller is adapted to provide the forces as determined to the one or more actuators 500. The actuation forces exerted by the actuators are typically designedto counteract impact of thermal expansion of equipment, such as the motors 218, 220 (Fig. 2) connected to the chuck body 201.

[0095] Exemplary Method of Operation

[0096] FIG. 6 is a flowchart 600 of an embodiment of a method, according to some embodiments. Herein, FIG. 5F and the description above exemplify a layout of one or more actuators. Herein, each actuator can apply at least one lateral force to the chuck body 201. By applying multiple actuators, forces can be applied in various locations. These forces can each modify the flatness of the top surface 202 of the chuck body 201, which in turn affects the flatness of the electrostatic clamp 300 and the reticle 408 clamped to it.

[0097] Through analysis and testing, a model can be developed that defines how to adjust the forces to modify the flatness of the clamp 300 and / or the reticle 408. Test exposures can be measured to establish a baseline flatness map. Said map can be used as input to the model. Feedback can also be obtained through measurement systems and sensors that are part of the lithographic apparatus. The sensors may include, but are not limited to, the image alignment sensor, imaging sensor, etc. The one or more actuators 500 can subsequently be activated to maintain the flatness within a set range by counteracting thermal influence on the chuck body 201 by equipment such as the motors 218, 220. The flatness adjustment can be used to achieve a higher degree of reticle flatness, or to deliberately produce a non-flat reticle surface that compensates for other errors within the scanner or induced by effects from other parts of the semiconductor fabrication process. This same method may be applicable to chucks and clamps for EUV and DUV based lithographic apparatuses. These could use different layouts and analytical models.

[0098] In a first step 602, the stage 200 may be operated in a conventional manner. The latter means, at least, that the actuators 500 are not activated. During operation, however, one or more sensors of the sensing system 552 measure and monitor operational parameters relating to the reticle stage 200. Said measurement data may, in part, be provided to the controller 550.

[0099] The controller 550 monitors the measurement data and uses the data to check a predetermined map relating to the flatness of one or more of the clamp 300 or the reticle 408. If any of the measurement data indicates that the reticle flatness deviates from the predetermined flatness map beyond a set threshold, the controller may start to activate one or more of the actuators 500 to modify a flatness of the clamp 300 and / or the reticle 408.

[0100] For instance in a second step 604, a predetermined flatness map of the clamp or reticle is provided to the controller 550.

[0101] In a third step 606, the controller uses the flatness map to input the predetermined flatness map into an actuation model.

[0102] If the comparison of sensor input as provided by the sensor system 552 indicates that the flatness of the reticle or the clamp deviates from the flatness map beyond a threshold at one or more points, and / or that a temperature grade of equipment connected to the chuck body 201 has increasedbeyond a temperature threshold from a default value, the controller may use the actuation model to determine forces to achieve or maintain the predetermined flatness of the clamp or reticle. See the fourth step 608.

[0103] In a fifth step 610, the controller may provide the forces to the one or more actuators 500.

[0104] In operation of the lithographic apparatus, the one or more motors 218, 220 connected to the chuck body 201 are typically operated to move the reticle stage 200 along a predetermined pattern. According to the method of the present disclosure, effects of thermal expansion of the one or more motors 218, 220, or other equipment, on the chuck body 201 can be counteracted using the one or more actuators 500.

[0105] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses. In the following, further features, characteristics, and exemplary technical solutions of the present disclosure will be described in terms of clauses that may be optionally claimed in any combination:1. An object stage system, comprising:a body having a top surface, a bottom surface, and side surfaces;a clamp connected to the top surface of the body for clamping an object; andat least one actuator arranged in or on the body for changing a flatness of the clamp or the object. 2. The object stage system of clause 1, wherein the at least one actuator comprises a linear actuator.3. The object stage system of clause 1, wherein the at least one actuator comprises a block actuator.4. The object stage system of clause 1, wherein the at least one actuator is arranged on the bottom surface of the body.5. The object stage system of clause 1, wherein the at least one actuator is arranged on a side surface of the body.6. The object stage system of clause 1, wherein the at least one actuator is arranged inside the body.7. The object stage system of clause 1 , wherein each at least one actuator comprises pairs of linear actuators, oriented in mutually perpendicular directions.8. The object stage system of clause 1, comprising:at least one motor connected to a side surface of the body,wherein the at least one actuator is adapted to counteract effects of thermal expansion of the at least one motor on the body.9. The object stage system of clause 8, wherein the at least one motor is connected to the body via one or more flexures.10. The object stage system of clause 1, wherein the object stage is a reticle stage or a wafer stage, the object being a reticle of a wafer respectively.11. The object stage system of clause 1, wherein the clamp is an electrostatic clamp or a vacuum clamp.12. The object stage system of clause 1, the system comprising a controller and a sensing system comprising one or more sensors for providing measurement data to the controller,wherein the controller is configured to:operate the object stage in a first manner, wherein the at least one actuator is not activated; monitor the measurement data and use the data to check a predetermined flatness map relating to the flatness of one or more of the clamp or the object;if any of the measurement data indicates that a flatness of the object or the clamp deviates from the predetermined flatness map beyond a set threshold, start to activate one or more of the at least one actuator to modify the flatness of the clamp and / or the object.13. A lithographic apparatus comprising:an illumination system configured to condition a radiation beam;a support structure constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a projection system configured to project the patterned radiation beam onto a target portion of an object, andan object stage system, comprising:a body having a top surface, a bottom surface, and side surfaces;a clamp connected to the top surface of the body for clamping the object; andat least one actuator arranged in or on the body for changing a flatness of the clamp or the object. 14. The lithographic apparatus of clause 13, the object stage system comprising at least one component connected to a side surface of the body, wherein the at least one actuator is adapted to counteract effects of thermal expansion of the at least one component on the body.15. The lithographic apparatus of clause 13, wherein the object stage is a reticle stage or a wafer stage, the object being a reticle of a wafer respectively.16. The lithographic apparatus of clause 13, wherein the clamp is an electrostatic clamp or a vacuum clamp.17. A method of operating an object stage system, the method comprising the steps of: providing an object stage system, comprising a body having a top surface, a bottom surface, and side surfaces, a clamp connected to the top surface of the body for clamping an object, and at least one actuator arranged in or on the body, andusing the at least one actuator to modify a flatness of the clamp or the object.18. The method of clause 17, comprising the steps of:providing a predetermined flatness map of the clamp to a controller,using the controller to input the predetermined flatness map into an actuation model;using the actuation model to determine forces to achieve the predetermined flatness of the clamp; andproviding the forces to the at least one actuator.19. The method of clause 17, comprising the steps of:operating at least one component connected to a side surface of the body, andcounteracting effects of thermal expansion of the at least one component on the body using the at least one actuator.20. The method of clause 17, the method comprising the steps of:operating the object stage system, wherein the at least one actuator is not activated;monitoring measurement data as provided by one or more sensors of a sensing system and use the measurement data to check a predetermined flatness map relating to a flatness of one or more of the clamp or the object;if any of the measurement data indicates that the flatness of the clamp or the object deviates from the predetermined flatness map beyond a set threshold, start to activate one or more of the at least one actuator to modify the flatness of the clamp and / or the object.21. The method of clause 17, comprising the steps of:comparing measurement data as provided by a sensor system to a flatness map;if the step of comparing indicates that the flatness of the clamp or the object deviates from the flatness map beyond a threshold at one or more points, a controller uses an actuation model to determine forces for the at least one actuator to achieve or maintain the predetermined flatness of the clamp or object.22. The method of clause 17, comprising the steps of:comparing measurement data as provided by a sensor system to a flatness map;if the step of comparing indicates that a temperature grade of equipment connected to the body has increased beyond a temperature threshold from a default value, a controller uses an actuation model to determine forces for the at least one actuator to achieve or maintain the predetermined flatness of the clamp or object.23. The method of clause 17, wherein the object stage is a reticle stage or a wafer stage, the object being a reticle of a wafer respectively.24. The method of clause 17, wherein the clamp is an electrostatic clamp or a vacuum clamp.

[0106] Although specific reference may be made in this text to a “reticle,” it should be understood that this is just one example of a patterning device and that the embodiments described herein may be applicable to any type of patterning device. Additionally, the embodiments described herein may be used to provide safety support for any object to ensure a clamping failure does not cause the object to fall and damage either itself or other equipment.

[0107] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, LCDs, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms“wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology unit and / or an inspection unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0108] Although specific reference may have been made above to the use of embodiments of the disclosure in the context of optical lithography, it will be appreciated that the disclosure can be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device can be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0109] 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 disclosure is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0110] The term “substrate” as used herein describes a material onto which material layers are added. In some embodiments, the substrate itself can be patterned and materials added on top of it may also be patterned, or may remain without patterning.

[0111] Although specific reference can be made in this text to the use of the apparatus and / or system according to the disclosure in the manufacture of ICs, it should be explicitly understood that such an apparatus and / or system has many other possible applications. For example, it can be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, LCD panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle,” “wafer,” or “die” in this text should be considered as being replaced by the more general terms “mask,” “substrate,” and “target portion,” respectively.

[0112] While specific embodiments of the disclosure have been described above, it will be appreciated that the disclosure can be practiced otherwise than as described. The description is not intended to limit the disclosure.

[0113] It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0114] The present disclosure has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0115] The foregoing description of the specific embodiments will so fully reveal the general nature of the disclosure that others can, by applying knowledge within the skill of the art, readily modify and / or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0116] The breadth and scope of the present disclosure should not be limited by any of the abovedescribed exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

CLAIMS1. An object stage system, comprising:a body having a top surface, a bottom surface, and side surfaces;a clamp connected to the top surface of the body for clamping an object; andat least one actuator arranged in or on the body for changing a flatness of the clamp or the object.

2. The object stage system of claim 1 , wherein the at least one actuator comprises a linear actuator.

3. The object stage system of claim 1 , wherein the at least one actuator comprises a block actuator.

4. The object stage system of claim 1 , wherein the at least one actuator is arranged on the bottom surface of the body.

5. The object stage system of claim 1, wherein the at least one actuator is arranged on a side surface of the body.

6. The object stage system of claim 1 , wherein the at least one actuator is arranged inside the body.

7. The object stage system of claim 1, wherein each at least one actuator comprises pairs of linear actuators, oriented in mutually perpendicular directions.

8. The object stage system of claim 1, comprising:at least one motor connected to a side surface of the body,wherein the at least one actuator is adapted to counteract effects of thermal expansion of the at least one motor on the body, and wherein the at least one motor is connected to the body via one or more flexures.

9. The object stage system of claim 1, wherein the object stage is a reticle stage or a wafer stage, the object being a reticle of a wafer respectively.

10. The object stage system of claim 1, wherein the clamp is an electrostatic clamp or a vacuum clamp.

11. The object stage system of claim 1, the system comprising a controller and a sensing system comprising one or more sensors for providing measurement data to the controller,wherein the controller is configured to:operate the object stage in a first manner, wherein the at least one actuator is not activated; monitor the measurement data and use the data to check a predetermined flatness map relating to the flatness of one or more of the clamp or the object;if any of the measurement data indicates that a flatness of the object or the clamp deviates from the predetermined flatness map beyond a set threshold, start to activate one or more of the at least one actuator to modify the flatness of the clamp and / or the object.

12. A lithographic apparatus comprising:an illumination system configured to condition a radiation beam;a support structure constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam;a projection system configured to project the patterned radiation beam onto a target portion of an object, andan object stage system, comprising:a body having a top surface, a bottom surface, and side surfaces;a clamp connected to the top surface of the body for clamping the object; andat least one actuator arranged in or on the body for changing a flatness of the clamp or the object.

13. The lithographic apparatus of claim 12, the object stage system comprising at least one component connected to a side surface of the body, wherein the at least one actuator is adapted to counteract effects of thermal expansion of the at least one component on the body.

14. The lithographic apparatus of claim 12, wherein:the object stage is a reticle stage or a wafer stage, the object being a reticle of a wafer respectively; andwherein the clamp is an electrostatic clamp or a vacuum clamp.

15. A method of operating an object stage system, the method comprising the steps of:providing an object stage system, comprising a body having a top surface, a bottom surface, and side surfaces, a clamp connected to the top surface of the body for clamping an object, and at least one actuator arranged in or on the body, andusing the at least one actuator to modify a flatness of the clamp or the object.

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