• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:
    A lithographic apparatus includes an illumination system, a projection system, a stage, a motor, a thermal control system, and a controller. The illumination system illuminates a pattern of a patterning device. The projection system projects an image of the pattern onto a substrate. The 5 stage supports the patterning device or the substrate. The motor moves the stage. The thermal control system regulates a temperature of the motor. The controller controls the temperature of the motor during idling of the motor such that a difference between a maximum temperature and a minimum temperature of the motor during the idling is reduced.
    公开号:NL2025107A
    申请号:NL2025107
    申请日:2020-03-12
    公开日:2020-09-22
    发明作者:Chavez Isaac；Andrew Chieda Michael；Ian Mackenzie Ross
    申请人:Asml Holding Nv；
    IPC主号:
    专利说明:

    [0001] [0001] The present disclosure relates to motors and thermal control, for example, maintaining a temperature of a motor for actuating stages in a lithographic apparatus.BACKGROUND
    [0002] [0002] 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.
    [0003] [0003] 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.
    [0004] [0004] The advancement of lithography technologies has promoted improvement of lithographic tools in terms of efficiency. Some efficiency areas include time investment, volume production, and operational costs, among others. It is desirable to address issues or barriers that impede farther efficiency improvements of lithographic tools.
    [0005] [0005] During a reticle exchange process, a reticle handoff from a reticle handler to a clamp of a reticle stage can cause large changes in temperature (e.g., thermal cycling) of the motor that is responsible for moving the reticle stage. Thermal cycling can accelerate premature failure of the motor. There is a need to prevent premature failure of motors for preventing costly machine downtime and maintenance.SUMMARY
    [0006] [0006] In some embodiments, a lithographic apparatus comprises an illumination system, a projection system, a stage, a motor, a thermal control system and a controller. The illuminationsystem is configured to illuminate a pattern of a patterning device. The projection system is configured to project an image of the pattern onto a substrate. The stage is configured to support the patterning device or the substrate. The motor is configured to move the stage. The thermal control system is configured to regulate a temperature of the motor. The controller is configured to control the temperature of the motor during idling of the motor such that a difference between a maximum temperature and a minimum temperature of the motor during the idling is reduced.
    [0007] [0007] In some embodiments, method of regulating a temperature during idling of a motor of a stage in a lithographic apparatus comprises initiating the idling of the motor of the stage in the lithographic apparatus, sending motor temperature information to a controller during the idling, determining temperature regulation instructions based on the motor temperature information, sending the temperature regulation instructions to a heat regulating component of the lithographic apparatus, and adjusting the temperature of the motor during the idling using the heat regulating component such that a difference between a maximum temperature and a minimum temperature of the motor during the idling is reduced.
    [0008] [0008] In some embodiments, a non-transitory computer-readable medium having instructions stored thereon that, when executed by a controller, causes the controller to perform operations. The operations comprise initiating an idling of a motor of a stage in a lithographic apparatus, receiving motor temperature information, determining temperature regulation instructions based on the motor temperature information, sending the temperature regulation instructions to a heat regulating component of the lithographic apparatus, and adjusting the temperature of the motor during the idling using the heat regulating component such that a difference between a maximum temperature and a minimum temperature of the motor during the idling is reduced.
    [0009] [0009] Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. It is noted that the invention 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
    [0010] [0010] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:
    [0011] [0011] FIG. 1 shows a schematic illustration of a lithographic apparatus, according to some embodiments.
    [0012] [0012] FIG. 2 shows a perspective schematic illustration of part of a reticle stage, according to some embodiments.
    [0013] [0013] FIG. 3 shows a top plan view of the reticle stage of Figure 2.
    [0014] [0014] FIG. 4 shows a perspective schematic illustration of a reticle exchange apparatus, according to some embodiments.
    [0015] [0015] FIG. 5 shows a partial cross-sectional view of the reticle exchange apparatus of Figure 4.
    [0016] [0016] FIG. 6A shows a partial schematic illustration of a reticle exchange apparatus in an approach configuration, according to some embodiments.
    [0017] [0017] FIG. 6B shows a partial schematic illustration of a reticle exchange apparatus in a first contact configuration, according to some embodiments.
    [0018] [0018] FIG. 6C shows a partial schematic illustration of a reticle exchange apparatus in a full contact configuration, according to some embodiments.
    [0019] [0019] FIG. 7 shows a schematic of a subsection of a lithographic apparatus, according to some embodiments.
    [0020] [0020] FIG. 8 shows a graph that illustrates thermal cycling during successive lithographic processes, according to some embodiments.
    [0021] [0021] FIG. 9 shows a schematic of a subsection of a lithographic apparatus, according to some embodiments.
    [0022] [0022] FIG. 10 shows method steps for regulating a temperature during idling of a motor of a stage in a lithographic apparatus, according to some embodiments.
    [0023] [0023] The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, inwhich 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 left-most 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
    [0024] [0024] This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodiment(s) merely exemplify the invention. The scope of the invention is not limited to the disclosed embodiment(s). The invention is defined by the clauses appended hereto.
    [0025] [0025] 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.
    [0026] [0026] 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.
    [0027] [0027] 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 a given quantity that varies within, for example, 10-30% of the value (e.g., £10%, 220%, or £30% of the value).
    [0028] [0028] 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 S 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. For non-transitory machine-readable media and the like, the term “non-transitory” can refer to all computer/machine readable media, with the sole exception being a transitory propagating signal.
    [0029] [0029] 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.
    [0030] [0030] Exemplary Lithographic System
    [0031] [0031] FIG. 1 shows a lithographic system comprising a radiation source SO and a lithographic apparatus LA. 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,
    [0032] [0032] 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.
    [0033] [0033] 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 forming an image with features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 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).
    [0034] [0034] 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.
    [0035] [0035] 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.
    [0036] [0036] The radiation source SO can be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL), or any other radiation source that is capable of generating EUV radiation.
    [0037] [0037] Exemplary Reticle Stage
    [0038] [0038] FIGS. 2 and 3 show schematic illustrations of an exemplary reticle stage 200, according to some embodiments. Reticle stage 200 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.
    [0039] [0039] 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 motions of 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.
    [0040] [0040] 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.
    [0041] [0041] 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 onthe 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, an 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.
    [0042] [0042] Exemplary Reticle Exchange Apparatus
    [0043] [0043] FIGS. 4 through 6 show schematic illustrations of an exemplary reticle exchange apparatus 100, according to some embodiments. 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.
    [0044] [0044] As shown in FIGS. 4 and 5, 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.
    [0045] [0045] In some embodiments, 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.
    [0046] [0046] In some embodiments, as shown in FIG. 4, reticle handler 402 can include one or more reticle handler arms 404. Reticle handler arm 404 can include reticle baseplate 406. Reticle baseplate 406 can be configured to hold an object, for example, reticle 408.
    [0047] [0047] In some embodiments, reticle baseplate 406 can be an extreme ultraviolet inner pod (EIP) for a reticle. In some embodiment, reticle baseplate 406 includes reticle baseplate frontside 407, and reticle 408 includes reticle backside 409.
    [0048] [0048] In some embodiments, as shown in FIGS. 4 and 5, 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
    [0050] [0050] In some embodiments, as shown in FIG. 4, 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. In some embodiments, reticle handler arms 404 can be arranged asymmetrically about reticle handler 402. For example, two reticlehandler 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.
    [0051] [0051] 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 408 can 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.
    [0052] [0052] 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.
    [0053] [0053] As shown in FIGS. 6A through 6C, reticle exchange apparatus 100 can include clamp 300, reticle 408, and reticle baseplate 406. The multi-stage movement can occur in four stages: (1) approach; (2) first contact; (3) full contact; and (4) voltage applied to clamp.
    [0054] [0054] First, as shown in FIG. 6A, reticle exchange apparatus 100 can be in an approach configuration 20 and 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 of reticle handler arm 404 in reticle exchange area 410. The motors (i.e, Z, Rx, and Ry) brake and rotation about Z-direction (i.e, Rz) activates.
    [0055] [0055] Second, as shown in FIG. 6B, reticle exchange apparatus 100 can be in a first contact configuration 30 and 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.
    [0056] [0056] Third, as shown in FIG. 6C, reticle exchange apparatus 100 can be in a full contact configuration 40 and 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
    [0057] [0057] In some embodiments, in full contact configuration 40, clamp 300 makes contact with all four corners of reticle 408 and continues to move in a substantially vertical direction (i.e., Z-direction) until a mechanical force of at least 5 N is achieved.
    [0058] [0058] Fourth, with clamp frontside 302 and reticle backside 409 aligned and coplanar, clamp 300 is turned on (i.e., a voltage is applied to clamp 300) and reticle 408 is held in a fixed plane on clamp 300.
    [0059] [0059] In some embodiments, as shown in FIG. 5, reticle exchange apparatus 100 can include clamp controller 360. Clamp controller 360 can be coupled to clamp 300 and be configured to control a position of clamp 300. For example, clamp controller 360 can be configured to control reticle stage 200 to allow compliant movement of clamp 300. In some embodiments, clamp controller 360 can be coupled to servo motors or servo actuators (i.e., X-direction, Y-direction, Z- direction, Rx, Ry, Rz) of reticle stage 200 and/or clamp 300. For example, clamp controller 360 can control translations of reticle stage 200 with clamp 300 along an x-axis, y-axis, and z-axis (i.e., X-direction, Y-direction, Z-direction) and rotations about the x-axis, y-axis, and z-axis (i.e., Rx, Ry, Rz), where the x-axis, y-axis, and z-axis are orthogonal coordinates.
    [0060] [0060] Exemplary Thermal Control of Motors
    [0061] [0061] A lithographic apparatus may have numerous moving parts (e.g., stages, wafer stage, reticle stage), many of which can be actuated by motors. Thus, motors for moving tables and stages that support objects in a machine can be referred to as actuators. Motors used in lithographic apparatuses can have numerous components, for example, heat transfer components to carry away heat dissipated by the motor.
    [0062] [0062] FIG. 7 shows a schematic of a subsection 700 of a lithographic apparatus, according to some embodiments. In some embodiments, subsection 700 comprises a motor 702 and a thermalcontrol system 704. Subsection 700 further comprises heat transfer piece 708 (e.g., a cooling plate). Motor 702 comprises coils 712 (e.g., as in a Lorentz force motor). The number of coil elements shown are for illustration and not limiting. Thermal control system 704 comprises a conduit system
    [0063] [0063] In some embodiments, each of coils 712 is electrically independent from the others. Heat transfer piece 708 is adhered to motor 702 using a bonding agent (e.g., epoxy with high thermal conductivity) for thermal coupling. Some advantages of using a bonding agent are, for example, cost-effectiveness and lower footprint for volume reduction. Heat transfer piece 708 can be part of thermal control system 704 in a permanent arrangement (e.g., welded to conduit system 714).
    [0064] [0064] In some embodiments, motor 702 is configured to move a stage in the lithographic apparatus (e.g., reticle stage 200, FIG. 2). The thermal coupling through heat transfer piece 708 allows thermal communication between motor 702 and thermal control system 704. Conduit system 714 is configured to circulate heat transfer fluid (e.g., water) to and from heat transfer piece 708 and motor 702. Thermal control system 704 is configured to regulate (e.g., adjust or maintain) a temperature of motor 702. A simple and cost-effective method to cool the motor as it generates heat during lithographic processes is to provide continuous heat removal at the cooling plate (e.g., continuous circulation of water). This is a solution for maintaining the motor temperature below a threshold overheated temperature. In some embodiments, subsection 700 can comprise a temperature sensor (not shown) for monitoring a temperature of motor 702.
    [0065] [0065] During lithographic processes, a motor can experience idling periods where the motor dissipates reduced or no heat, for example, when a reticle stage idles during a reticle exchange process. A continuous circulation of cooling fluid, while being a simple and cost- effective, can cause a motor’s temperature to decrease significantly from a nominal operating temperature. Once the reticle exchange process ends, the motor moves the reticle stage for a subsequent lithographic process, bringing the temperature of the motor back to a nominal operating temperature. This thermal cycling places a significant amount of cyclic stress at interfaces where materials with different coefficients of thermal expansion (CTE) meet, e.g., an epoxy interface between a cooling plate and a motor.
    [0066] [0066] FIG. 8 shows a graph 800 that illustrates thermal cycling during successive lithographic processes, according to some embodiments. In graph 800, the vertical axis representsa temperature of a motor (e.g., a reticle stage motor) and the horizontal axis represents time. The time scale of events in graph 800 are given as an example for discussion and are not limiting. Plot line 802 represents a typical motor temperature during lithographic processes when using an “always cooling” thermal control system, for example, as described in reference to FIG. 7. The datain graph 800 can be generated by using the temperature sensor as described above in reference to FIG. 7. Time length 804 represents a length of time for a wafer expose process and time length 806 represents a length of time for a reticle exchange process. A wafer exposure and a reticle exchange processes can be repeated numerous time in succession depending on the number of layers to be patterned onto a substrate. Region 808 indicates a behavior of interest regarding the temperature of the motor (e.g., thermal cycling).
    [0067] [0067] As stated earlier, a motor in operation has a nominal operating temperature. In the case of the motor represented in graph 800, the nominal temperature is indicated by dashed line 810 and is slightly greater than 70 °C. The thermal fluctuations (e.g., small zig-zag patterns) shown in plot line 802 are shown for illustration purposes and are not limiting. For example, the thermal fluctuations may be present at the flat portion of plot line 802. During time length 804, plot line 802 shows that the motor temperature is maintained substantially at the nominal operating temperature. The elevated nominal operating temperature is due to the motor continuously providing acceleration and deceleration motion during wafer exposure with almost no idling periods. However, during time length 806, the motor enters into an idling period, causing the motor to be constantly cooled by the “always cooling” thermal control system. Time length 806 is long enough for the motor to approach a temperature of the cooling fluid in the thermal control system (e.g., room temperature or approximately 20-25 °C). The temperature change in the thermal cycle shown in region 808 is approximately 50 °C. When the reticle exchange process is completed, the motor begins operation, the motor temperature climbs up to the nominal operating temperature, and the processes repeat. The thermal cycle can cause stress at interfaces where materials with different CTE meet (e.g., the epoxy interface between heat transfer piece 708 and motor 702, FIG. 7). The exact temperature values represented by plot line 802 are given as examples and are not limiting as the performances can vary depending on, for example, types of lithographic apparatuses, motors, and processes.
    [0068] [0068] Though one thermal cycle may not immediately cause motor failure (e.g., detaching of the epoxy), the number of thermal cycles can approach the millions in a typical lifetime of alithographic apparatus. In a rough estimate, at 12 reticle exchanges per hour, approximately 735,000 thermal cycles can occur over 7 years of usage of a lithographic apparatus. Each thermal cycle can cause cumulative damage at interfaces of mismatched CTEs, accelerating premature failure of a motor. Embodiments of the present disclosure provide structures and methods for reducing or eliminating thermal cycling of motors in lithographic apparatuses.
    [0069] [0069] FIG. 9 shows a schematic of a subsection 900 of a lithographic apparatus, according to some embodiments. In some embodiments, subsection 900 comprises a motor 902, a thermal control system 904, and a controller 906. Subsection 900 further comprises heat transfer piece 908 (e.g., a cooling plate). In some embodiments, subsection 900 further comprises a temperature sensor 910. Motor 902 comprises coils 912 (e.g., as in a Lorentz force motor). The number of coil elements shown are for illustration and not limiting. Thermal control system 904 comprises a conduit system 914. Conduit system 914 comprises a supply line 916 and a return line 918. In some embodiments. conduit system 914 further comprises a bypass line 920 and one or more valves 922. In some embodiments, subsection 900 further comprises a communication channel
    [0070] [0070] In some embodiments, a valve of the one or more valves 922 is disposed bisecting supply line 916. In some embodiments, another valve of the one or more valves 922 is disposed bisecting return line 918. One or more valves 922 can form a conduit arrangement using bypass line 920 to bypass motor 902—that is, one or more valves 922 connect with bypass line 920. Though controller 906 is shown as being external to thermal control system 904, in some embodiments, controller 906 can be disposed within thermal control system 904. Controller 906 can be in communication (e.g., electronic) with temperature sensor 910 and thermal control system
    [0071] [0071] In some embodiments, motor 902 is configured to move a stage in the lithographic apparatus (e.g., reticle stage 200, FIG. 2). The thermal coupling through heat transfer piece 908allows thermal communication between motor 902 and thermal control system 904. Conduit system 914 is configured to circulate heat transfer fluid (e.g., water) to and from heat transfer piece 908 and motor 902. Thermal control system 904 is configured to regulate (e.g., adjust or maintain) a temperature of motor 902. Controller 906 is configured to send the temperature regulation instructions to components in the lithographic apparatus, e.g., to thermal control system 904 or other components of the lithographic apparatus that lie outside of subsection 900.
    [0072] [0072] Shutting down and then restarting the thermal control system to work around the “always cooling” scenario is a coarse solution that may not be viable. Some reasons for this include, for example, insufficient timing accuracy to avoid thermal cycling, greater stress burden on other mechanical and electrical components, and power inefficiency, among others. Therefore, in some embodiments, controller 906 is configured to actuate one or more valves 922 to reduce or stop circulation of the heat transfer fluid during the time in which thermal cycling is expected to happen (e.g., reticle exchange, region 808, FIG. 8). This can be accomplished, for example, by controller 906 sending the temperature regulation instructions to thermal control system 904 to actuate one or more valves 922 for diverting the heat transfer fluid to bypass line 920. In this scenario, the temperature regulating instructions comprises instructions to actuate one or more valves 922. In some embodiments, one or more valves 922 can be used to stop the flow of heat transfer fluid through thermal control system 904. The use of valves is particularly useful in that many lithographic apparatuses in the field can be readily modified on their exterior without having to open the lithographic apparatus and compromise its clean environment. In some embodiments, one or more valves 922 and bypass line 920 can be implemented on the exterior of a lithographic apparatus where the supply and return lines are fed into the lithographic apparatus.
    [0073] [0073] Embodiments of the present disclosure also provide methods to regulate a temperature of a motor in a lithographic apparatus with minimal, or even without, structural alterations. In some embodiments, controller 906 is configured to supply AC current or voltage (e.g., at a high-frequency) to the motor (e.g., to coils 912). The high-frequency of the AC current or voltage continuously flips a direction of the force in the motor faster than it is capable of developing significant momentum in any particular direction (e.g., the motor is idle). Controller 906 can supply the AC current or voltage directly. In some embodiments, controller 906 can supply the AC current or voltage indirectly by using a device that is external to controller 906 or subsection 900. Controller 906 is configured to send the temperature regulation instructions toother components (not shown) outside of subsection 900 using communication channel 924. A component receiving temperature regulation instructions can be, for example, a power supply for coils 912 for driving motor 902. The power supply is configured to supply the coils an AC current or voltage. In this scenario, the temperature regulation instructions comprise instructions to cause the power supply to provide an AC current or voltage to the motor, causing the motor to generate Joule heating. The frequency of the AC current or voltage is such that the motor is idle, yet still generates Joule heating from the AC current or voltage running through coils 912. The phenomenon of Joule heating can be described as heat dissipated when an electrical current flows through a medium of finite impedance.
    [0074] [0074] In some embodiments, each of coils 912 is electrically independent from the other coils. In some embodiments, controller 906 is configured to supply a current to a first coil of coils 912 and a second current to a second coil of coils 912. Controller 906 can supply the first and second currents directly. In some embodiments. controller 906 can supply the first and second currents indirectly by using a device that is external to controller 906 or subsection 900. A device receiving temperature regulation instructions can be, for example, a power supply for coils 912 for driving motor 902. The power supply is configured to supply the first and second currents. In this scenario, the temperature regulation instructions comprise instructions to cause the power supply to provide the first current to the first coil and the second current to the second coil such that the motor generates Joule heating during an idling period. The first current and the second current are selected such that a motor force produced by the first coil is opposite to the motor force produced by the second coil—a so-called null solution. Therefore, the motor is idle while the currents running through coils 912 generate Joule heating.
    [0075] [0075] Embodiments involving AC currents (or voltages) or null-solutions are advantageous in that they can be implemented with minimal to no structural changes. However, if structural changes within the lithographic apparatus are allowed, then heating elements can be introduced. In embodiments comprising heating element 926, controller 906 is configured to adjust a- heat output of heating element 926 so as to maintain a temperature of the motor while the motor is idle. In this scenario, the temperature regulation instructions comprise instructions to cause the heating element to heat the motor during an idling period.
    [0076] [0076] Any of the embodiments involving valves and bypass, AC currents (or voltages), null-solutions, or heating elements can be implemented in any combination (e.g., valves andbypass with null-solution, or AC currents by itself, and the like). Therefore, in some embodiments, one or more valves 922, bypass line 920, and/or heating element 926 can be omitted. Furthermore, any component described herein that can participate in the supplying or removal of heat from the motor (e.g., thermal control system 904, one or more valves 922, or the power supplies that provide S the currents for the null-solution or AC current solution, among others), can be referred to herein as a “heat regulating component” of the lithographic apparatus.
    [0077] [0077] In some embodiments, temperature sensor 910 is configured to generate motor temperature information. Controller 906 is configured to receive the motor temperature information and determine temperature regulation instructions based on the motor temperature information.
    [0078] [0078] Though some embodiments referencing FIGS. 7-10 may depict or describe a single motor, a skilled artisan will appreciate that the structures and methods described herein can be applied to a system with a plurality of motors (e.g., a lithographic apparatus). For example, two motors can implement thermal-cycling-avoidance solutions described herein with simple or no modifications to pertinent embodiments (e.g., two pair of supply/return lines in series can have two bypass lines or a single bypass line before a split of the supply/return lines).
    [0079] [0079] In some embodiments, in the event that a thermal cycle is not fully prevented, then at least a temperature difference between a maximum and a minimum temperature of the motor during an idling period (e.g., reticle exchange, region 808, FIG. 8) is reduced as compared to an “always cooling” setup. In some embodiments, the difference between a maximum and a minimum temperature of the motor during an idling period is reduced by more than approximately 20% as compared to an “always cooling” setup. In some embodiments, the difference between a maximum and a minimum temperature of the motor during an idling period is reduced by more than approximately 40% as compared to an “always cooling” setup. In some embodiments, the difference between a maximum and a minimum temperature of the motor during an idling period is reduced by more than approximately 60% as compared to an “always cooling” setup. In some embodiments, the difference between a maximum and a minimum temperature of the motor during an idling period is reduced by more than approximately 80% as compared to an “always cooling” setup. In other words, a substantial temperature drop of a motor is reduced by the relative amounts described above.
    [0080] [0080] FIG. 10 shows method steps for regulating a temperature during idling of a motor of a stage in a lithographic apparatus, according to some embodiments. In step 1002, the idling of the motor of the stage in the lithographic apparatus is initiated. In step 1004, motor temperature information is sent to a controller during the idling. In step 1006, temperature regulation instructions are determined based on the motor temperature information. In step 1008, the temperature regulating instructions are sent to a heat regulating component of the lithographic apparatus. In step 1010, the temperature of the motor during the idling is adjusted using the heat regulating component such that a difference between a maximum temperature and a minimum temperature of the motor during the idling is reduced. In some embodiments, the motor temperature information is generated by a temperature sensor disposed on or near the motor. A skilled artisan will appreciate that step(s) may be omitted or rearranged. For example, in embodiments lacking motor temperature information (e.g., lack of temperature sensor), steps 1002 and 1004 can be omitted.
    [0081] [0081] 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. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat- panel displays, liquid-crystal displays (LCDs), thin film magnetic heads, etc.
    [0082] [0082] Although specific reference may be made in this text to embodiments of the disclosure in the context of a lithographic apparatus, embodiments of the disclosure may be used 1n other apparatuses. Embodiments of the disclosure may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatuses may be generally referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non- vacuum) conditions.
    [0083] [0083] 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, where the context allows, is not limited to optical lithography and may be used in other applications, for example imprint lithography. In another example, embodiments described herein can be applied to actuators in other machines and systems that have movable tables and stages for supporting objects.
    [0084] [0084] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.
    [0085] [0085] The above examples are illustrative, but not limiting, of the embodiments of this disclosure. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the field, and which would be apparent to those skilled in the relevant art(s), are within the spirit and scope of the disclosure.
    [0086] [0086] While specific embodiments of the disclosure have been described above, it will be appreciated that the disclosure may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the disclosure as described without departing from the scope of the clauses set out below.
    [0087] [0087] 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 clauses. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended clauses in any way.
    [0088] [0088] The present invention 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.
    [0089] [0089] The foregoing description of the specific embodiments will so fully reveal the general nature of the invention 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 invention. 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.
    [0090] [0090] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with thefollowing clauses and their equivalents. Other aspects of the invention are set out as in the following numbered clauses. I. A lithographic apparatus comprising: an illumination system configured to illuminate a pattern of a patterning device; a projection system configured to project an image of the pattern onto a substrate; a stage configured to support the patterning device or the substrate; a motor configured to move the stage; a thermal control system configured to regulate a temperature of the motor; and a controller configured to control the temperature of the motor during idling of the motor such that a difference between a maximum temperature and a minimum temperature of the motor during the idling is reduced.
    2. The lithographic apparatus of clause 1, further comprising a temperature sensor, disposed on or near the motor, configured to generate motor temperature information, wherein the controller is further configured to: receive the motor temperature information; determine temperature regulation instructions based on the motor temperature information; and send the temperature regulation instructions to the thermal control system to maintain the temperature of the motor during the idling.
    3. The lithographic apparatus of clause 1, wherein the thermal control system comprises a conduit system that is thermally coupled to the motor and the conduit system is configured to circulate heat transfer fluid to and from the motor.
    4. The lithographic apparatus of clause 3, wherein the heat transfer fluid comprises water.
    5. The lithographic apparatus of clause 3, wherein: the conduit system comprises one or more valves; and the controller is further configured to actuate the one or more valves to reduce or stop circulation of the heat transfer fluid to maintain the temperature of the motor during the idling.
    6. The lithographic apparatus of clause 1, wherein: the controller is farther configured to supply AC current to the motor to maintain the temperature of the motor during the idling; and the AC current has a frequency such that the motor is idle.
    7. The lithographic apparatus of clause 1, wherein: the motor comprises a first coil and a second coil that is electrically independent from the first coil; the controller is further configured to supply a first current to the first coil and second current to the second coil to maintain the temperature of the motor during the idling; and the first current and the second current generate opposing forces such that the motor is idle.
    8. The lithographic apparatus of clause 1, further comprising a heating element disposed on or near the motor, wherein the controller is further configured to allow the heating element to heat the motor to maintain the temperature of the motor during the idling.
    9. A non-transitory computer-readable medium having instructions stored thereon that, when executed by a controller, causes the controller to perform operations comprising: initiating an idling of a motor of a stage in a lithographic apparatus; sending the temperature regulation instructions to a heat regulating component of the lithographic apparatus; and adjusting the temperature of the motor during the idling using the heat regulating component such that a difference between a maximum temperature and a minimum temperature of the motor during the idling is reduced.
    10. The non-transitory computer-readable medium of clause 9, wherein the operations further comprise: receiving motor temperature information generated by a temperature sensor disposed on or near the motor; and determining the temperature regulation instructions based on the motor temperature information.
    11. The non-transitory computer-readable medium of clause 9, wherein: the lithographic apparatus comprises a thermal control system comprising a conduit system configured to circulate heat transfer fluid to and from the motor, the conduit system comprising one or more valves, and the adjusting comprises actuating the one or more valves to reduce or stop circulation of the heat transfer fluid to maintain the temperature of the motor during the idling; and/or the lithographic apparatus comprises a heating element disposed on or near the motor and the adjusting comprises heating the motor using the heating element to maintain the temperature of the motor during the idling.
    12. The non-transitory computer-readable medium of clause 9, wherein: the adjusting comprises supplying AC current to the motor to maintain the temperature of the motor during the idling, the AC current having a frequency such that the motor is idle; and/or the motor comprises first and second coils and the adjusting comprises supplying a first current to the first coil and a second current to the second coil to maintain the temperature of the motor during the idling, the first current and the second current generating opposing forces such that the motor is idle.
    13. A system for maintaining a temperature of an actuator during idling of the actuator, the system comprising: a table configured to support an object; an actuator configured to move the table; a thermal control system configured to regulate a temperature of the actuator; and a controller configured to control the temperature of the actuator during the idling such that a difference between a maximum temperature and a minimum temperature of the actuator during the idling is reduced.
    14. The system of clause 13, further comprising a temperature sensor, disposed on or near the actuator, configured to generate actuator temperature information, wherein the controller is further configured to: receive the actuator temperature information;
    determine temperature regulation instructions based on the actuator temperature information; and send the temperature regulation instructions to the thermal control system to maintain the temperature of the actuator during the idling.
    15. The system of clause 13, wherein: the thermal control system comprises a conduit system thermally coupled to the actuator and is configured to circulate heat transfer fluid to and from the actuator, the conduit system comprising one or more valves, and the controller is further configured to actuate the one or more valves to reduce or stop circulation of the heat transfer fluid to maintain the temperature of the actuator during the idling; and/or the system comprises a heating element disposed on or near the actuator and the controller is further configured to allow the heating element to heat the actuator to maintain the temperature of actuator during the idling.
    16. The system of clause 13, wherein: the controller is further configured to supply AC current to the actuator to maintain the temperature of the actuator during the idling, the AC current having a frequency such that the actuator 1s idle; and/or the actuator comprises a first coil and a second coil that is electrically independent from the first coil and the controller is further configured to supply a first current to the first coil and a second current to the second coil to maintain the temperature of the actuator during the idling, the first current and the second current generating opposing forces such that the actuator is idle.
    权利要求:
    Claims (1)
    [1]
    1. An apparatus adapted to expose a substrate.
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    US5998889A|1996-12-10|1999-12-07|Nikon Corporation|Electro-magnetic motor cooling system|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    US201962819866P| true| 2019-03-18|2019-03-18|
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