Linear actuator with magnet bearings

Abstract

The present disclosure provides systems and methods for utilizing an actuator configured to contact an object. The actuator can include a coarse stage including a coarse stage actuator that is magnetically levitated by coarse stage repelling magnets. The actuator can also include a fine stage including a fine stage actuator coupled to the coarse stage actuator, the fine stage actuator having a range of travel less than the coarse stage actuator.

Description

LINEAR ACTUATOR WITH MAGNET BEARINGSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 746,080 which was filed on 16 January 2025, and which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] The description herein relates generally to actuators utilizing magnetically levitated bearings as used in the manufacturing of semiconductor devices. More particularly, the disclosure includes apparatuses for dual-stage magnetically levitated actuators for moving a reticle.BACKGROUND

[0003] A lithographic projection apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device (e.g., a mask) may contain or provide a pattern corresponding to an individual layer of the IC (“design layout”), and this pattern can be transferred onto a target portion (e.g. comprising one or more dies) on a substrate (e.g., silicon wafer) that has been coated with a layer of radiation-sensitive material (“resist”), by methods such as irradiating the target portion through the pattern on the patterning device. In general, a single substrate contains a plurality of adjacent target portions to which the pattern is transferred successively by the lithographic projection apparatus, one target portion at a time. In one type of lithographic projection apparatuses, the pattern on the entire patterning device is transferred onto one target portion in one go; such an apparatus may also be referred to as a stepper. In an alternative apparatus, a step-and-scan apparatus can cause a projection beam to scan over the patterning device in a given reference direction (the “scanning” direction) while synchronously moving the substrate parallel or anti-parallel to this reference direction. Different portions of the pattern on the patterning device are transferred to one target portion progressively. Since, in general, the lithographic projection apparatus will have a reduction ratio M (e.g., 4), the speed F at which the substrate is moved will be 1 / M times that at which the projection beam scans the patterning device. More information with regard to lithographic devices can be found in, for example, US 6,046,792, incorporated herein by reference.

[0004] Prior to transferring the pattern from the patterning device to the substrate, the substrate may undergo various procedures, such as priming, resist coating and a soft bake. After exposure, the substrate may be subjected to other procedures (“post-exposure procedures”), such as a post-exposure bake (PEB), development, a hard bake and measurement / inspection of the transferred pattern. This array of procedures is used as a basis to make an individual layer of a device, e.g., an IC. The substrate may then undergo various processes such as etching, ion-implantation (doping), metallization, oxidation, chemo-mechanical polishing, etc., all intended to finish off the individual layer of the device. If several layers are required in the device, then the whole procedure, or a variant thereof, is repeatedfor each layer. Eventually, a device will be present in each target portion on the substrate. These devices are then separated from one another by a technique such as dicing or sawing, whence the individual devices can be mounted on a carrier, connected to pins, etc.

[0005] Thus, manufacturing devices, such as semiconductor devices, typically involves processing a substrate (e.g., a semiconductor wafer) using a number of fabrication processes to form various features and multiple layers of the devices. Such layers and features are typically manufactured and processed using, e.g., deposition, lithography, etch, chemical-mechanical polishing, and ion implantation. Multiple devices may be fabricated on a plurality of dies on a substrate and then separated into individual devices. This device manufacturing process may be considered a patterning process. A patterning process involves a patterning step, such as optical and / or nanoimprint lithography using a patterning device in a lithographic apparatus, to transfer a pattern on the patterning device to a substrate and typically, but optionally, involves one or more related pattern processing steps, such as resist development by a development apparatus, baking of the substrate using a bake tool, etching using the pattern using an etch apparatus, etc.

[0006] As noted, lithography is a central step in the manufacturing of device such as ICs, where patterns formed on substrates define functional elements of the devices, such as microprocessors, memory chips, etc. Similar lithographic techniques are also used in the formation of flat panel displays, micro-electro mechanical systems (MEMS) and other devices.SUMMARY

[0007] In some aspects, the techniques described herein relate to an actuator configured to contact an object, the actuator including: a coarse stage including a coarse stage actuator that is magnetically levitated by coarse stage repelling magnets; and a fine stage including a fine stage actuator coupled to the coarse stage actuator, the fine stage actuator having a range of travel less than the coarse stage actuator.

[0008] In some aspects, the techniques described herein relate to an actuator, wherein the object is a reticle.

[0009] In some aspects, the techniques described herein relate to an actuator, wherein the object is a lens or mirror.

[0010] In some aspects, the techniques described herein relate to an actuator, wherein the coarse stage actuator includes a motorized threaded rod that translates a frame with a threaded hole and that is levitated by the coarse stage repelling magnets.

[0011] In some aspects, the techniques described herein relate to an actuator, wherein the coarse stage actuator has a range between 1mm and 20 mm.

[0012] In some aspects, the techniques described herein relate to an actuator, wherein the fine stage actuator includes a piezoelectric material that translates to facilitate the actuator contacting the object.

[0013] In some aspects, the techniques described herein relate to an actuator, wherein the fine stage actuator has a range between 1 micrometer and 100 micrometers.

[0014] In some aspects, the techniques described herein relate to an actuator, wherein the coarse stage repelling magnets are arranged in a polygonal configuration.

[0015] In some aspects, the techniques described herein relate to an actuator, wherein the polygonal configuration includes the coarse stage repelling magnets being arranged rectangularly in horizontal and / or vertical directions.

[0016] In some aspects, the techniques described herein relate to an actuator, wherein the coarse stage repelling magnets are arranged radially.

[0017] In some aspects, the techniques described herein relate to an actuator, wherein the coarse stage repelling magnets are in a Halbach configuration.

[0018] In some aspects, the techniques described herein relate to an actuator, wherein the fine stage actuator is magnetically levitated by fine stage repelling magnets.

[0019] In some aspects, the techniques described herein relate to an actuator, wherein the fine stage repelling magnets are arranged rectangularly in horizontal and / or vertical directions.

[0020] In some aspects, the techniques described herein relate to an actuator, wherein the fine stage repelling magnets are arranged radially.

[0021] In some aspects, the techniques described herein relate to an actuator, wherein the fine stage repelling magnets are in a Halbach configuration.

[0022] In some aspects, the techniques described herein relate to an actuator, wherein the coarse stage repelling magnets are configured to create a coarse stage preload force on the coarse stage actuator.

[0023] In some aspects, the techniques described herein relate to an actuator, wherein the coarse stage repelling magnets include an inner race and an outer race that are magnetically asymmetric or geometrically offset to create the coarse stage preload force.

[0024] In some aspects, the techniques described herein relate to an actuator, wherein the fine stage includes fine stage repelling magnets that are configured to create a fine stage preload force on the fine stage actuator.

[0025] In some aspects, the techniques described herein relate to an actuator, wherein the fine stage repelling magnets include an inner race and an outer race that are magnetically asymmetric or geometrically offset to create the fine stage preload force.

[0026] In some aspects, the techniques described herein relate to an actuator, wherein a coarse stage preload at the coarse stage actuator and a fine stage preload at the fine stage actuator combine to create a net preload.

[0027] In some aspects, the techniques described herein relate to an actuator, further including a tip attached to a distal end of the fine stage actuator, the tip configured to contact the object, the fine stage supporting the distal end to have substantively little cantilevering of the fine stage actuator.

[0028] In some aspects, the techniques described herein relate to an actuator, further including a fluid layer in a gap between the coarse stage repelling magnets.

[0029] In some aspects, the techniques described herein relate to a reticle stage system further including: a chuck configured to support a reticle; and the actuator configured to contact an object, the actuator including a coarse stage including a coarse stage actuator that is magnetically levitated by coarse stage repelling magnets and a fine stage including a fine stage actuator coupled to the coarse stage actuator, the fine stage actuator having a range of travel less than the coarse stage actuator. The coarse stage includes a first housing attached to the chuck, the first housing levitating the coarse stage actuator using the coarse stage repelling magnets; and the fine stage including a second housing attached to the chuck, the second housing levitating the fine stage actuator using fine stage repelling magnets.

[0030] In some aspects, the techniques described herein relate to a semiconductor device manufacturing method including: controlling an actuator to contact a reticle to secure the reticle and / or move the reticle to a desired position, the actuator including a coarse stage and a fine stage, where at least the coarse stage has at least one coarse stage actuator that is magnetically levitated by coarse stage repelling magnets; receiving a substrate on a support surface, the substrate having a photoresist layer; directing EUV or DUV radiation from a radiation source to transfer a pattern from the reticle onto the photoresist layer; and removing a portion of the photoresist layer to form the pattern over the substrate.BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, show certain aspects of the subject matter disclosed herein and, together with the description, help explain some of the principles associated with the disclosed implementations. In the drawings,

[0032] Figure 1 illustrates a block diagram of various subsystems of a lithographic projection apparatus, according to an embodiment.

[0033] Figure 2 illustrates an exemplary flow chart for simulating lithography in a lithographic projection apparatus, according to an embodiment.

[0034] Figure 3 illustrates an example of actuators that hold a reticle held in place and counteract chuck accelerations, according to an embodiment.

[0035] Figure 4A illustrates an example of a magnetic bearing, according to an embodiment.

[0036] Figure 4B illustrates a simplified sectional view through Figure 4A, according to an embodiment.

[0037] Figure 4C illustrates a simplified sectional view of an example of a magnet bearing with magnets arranged in the axial direction, according to an embodiment.

[0038] Figure 5A illustrates an example of a magnet bearing in an alternating magnet configuration with coarse stage repelling magnets arranged in the vertical direction, according to an embodiment.

[0039] Figure 5B illustrates an example of a magnet bearing in an alternating magnet configuration with coarse stage repelling magnets arranged in the axial direction, according to an embodiment.

[0040] Figure 6 illustrates an example of a magnet bearing with magnets in a Halbach configuration, according to an embodiment.

[0041] Figure 7 illustrates an example of separated magnet bearings to individually support a coarse stage actuator and a fine stage actuator, according to an embodiment.

[0042] Figure 8A illustrates an example of offset repelling magnets that results in a preload force on an actuator, according to an embodiment.

[0043] Figure 8B illustrates a preload band resulting from the combined effect of two opposing preload forces.

[0044] Figure 9A illustrates a perspective view of an example pusher having actuators levitated by magnetic bearings, according to an embodiment.

[0045] Figure 9B illustrates a top view of the apparatus of Figure 9A, according to an embodiment.

[0046] Figure 10 illustrates a perspective view and two sectional views of an example pusher with damping material between one or more inner and outer races, according to an embodiment.DETAILED DESCRIPTION

[0047] Although specific reference may be made in this text to the manufacture of ICs, it should be explicitly understood that the description herein has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display 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 interchangeable with the more general terms “mask”, “substrate” and “target portion”, respectively.

[0048] In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g. with a wavelength of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultra-violet radiation, e.g. having a wavelength in the range of about 5-100 nm).

[0049] The patterning device can comprise, or can form, one or more design layouts. The design layout can be generated utilizing CAD (computer-aided design) programs, this process often being referred to as EDA (electronic design automation). Most CAD programs follow a set of predetermined design rules in order to create functional design layouts / patterning devices. These rules are set by processing and design limitations. For example, design rules define the space tolerance between devices (such as gates, capacitors, etc.) or interconnect lines, so as to ensure that the devices or lines do not interact with one another in an undesirable way. One or more of the design rule limitations may be referred to as “critical dimension” (CD). A critical dimension of a device can be defined as the smallest width of a line or hole or the smallest space between two lines or two holes. Thus, the CD determines the overallsize and density of the designed device. Of course, one of the goals in device fabrication is to faithfully reproduce the original design intent on the substrate (via the patterning device).

[0050] The term “mask” or “patterning device” as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate; the term “light valve” can also be used in this context. Besides the classic mask (transmissive or reflective; binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable LCD array.

[0051] An example of a programmable mirror array can be a matrix-addressable surface having a viscoelastic control layer and a reflective surface. The basic principle behind such an apparatus is that (for example) addressed areas of the reflective surface reflect incident radiation as diffracted radiation, whereas unaddressed areas reflect incident radiation as undiffracted radiation. Using an appropriate filter, the said undiffracted radiation can be filtered out of the reflected beam, leaving only the diffracted radiation behind; in this manner, the beam becomes patterned according to the addressing pattern of the matrix-addressable surface. The required matrix addressing can be performed using suitable electronic methods.

[0052] An example of a programmable LCD array is given in U.S. Patent No. 5,229,872, which is incorporated herein by reference.

[0053] Figure 1 illustrates a block diagram of various subsystems of a lithographic projection apparatus 10A, according to an embodiment. Major components are a radiation source 12A, which may be a deep-ultraviolet excimer laser source or other type of source including an extreme ultra violet (EUV) source (as discussed above, the lithographic projection apparatus itself need not have the radiation source), illumination optics which, e.g., define the partial coherence (denoted as sigma) and which may include optics 14A, 16Aa and 16Ab that shape radiation from the source 12A; a patterning device 18A; and transmission optics 16Ac that project an image of the patterning device pattern onto a substrate plane 22A. An adjustable filter or aperture 20A at the pupil plane of the projection optics may restrict the range of beam angles that impinge on the substrate plane 22A, where the largest possible angle defines the numerical aperture of the projection optics NA= n sin(0max), wherein n is the refractive index of the media between the substrate and the last element of the projection optics, and ©max is the largest angle of the beam exiting from the projection optics that can still impinge on the substrate plane 22A.

[0054] In a lithographic projection apparatus, a source provides illumination (i.e. radiation) to a patterning device and projection optics direct and shape the illumination, via the patterning device, onto a substrate. The projection optics may include at least some of the components 14A, 16Aa, 16Ab and 16Ac. An aerial image (Al) is the radiation intensity distribution at substrate level. A resist model can be used to calculate the resist image from the aerial image, an example of which can be found in U.S. Patent Application Publication No. US 2009-0157630, the disclosure of which is hereby incorporatedby reference in its entirety. The resist model is related only to properties of the resist layer (e.g., effects of chemical processes which occur during exposure, post-exposure bake (PEB) and development). Optical properties of the lithographic projection apparatus (e.g., properties of the illumination, the patterning device and the projection optics) dictate the aerial image and can be defined in an optical model. Since the patterning device used in the lithographic projection apparatus can be changed, it is desirable to separate the optical properties of the patterning device from the optical properties of the rest of the lithographic projection apparatus including at least the source and the projection optics. Details of techniques and models used to transform a design layout into various lithographic images (e.g., an aerial image, a resist image, etc.), apply OPC using those techniques and models and evaluate performance (e.g., in terms of process window) are described in U.S. Patent Application Publication Nos. US 2008-0301620, 2007-0050749, 2007-0031745, 2008-0309897, 2010-0162197, and 2010-0180251, the disclosure of each which is hereby incorporated by reference in its entirety.

[0055] One aspect of understanding a lithographic process is understanding the interaction of the radiation and the patterning device. The electromagnetic field of the radiation after the radiation passes the patterning device may be determined from the electromagnetic field of the radiation before the radiation reaches the patterning device and a function that characterizes the interaction. This function may be referred to as the mask transmission function (which can be used to describe the interaction by a transmissive patterning device and / or a reflective patterning device).

[0056] The mask transmission function may have a variety of different forms. One form is binary. A binary mask transmission function has either of two values (e.g., zero and a positive constant) at any given location on the patterning device. A mask transmission function in the binary form may be referred to as a binary mask. Another form is continuous. Namely, the modulus of the transmittance (or reflectance) of the patterning device is a continuous function of the location on the patterning device. The phase of the transmittance (or reflectance) may also be a continuous function of the location on the patterning device. A mask transmission function in the continuous form may be referred to as a continuous tone mask or a continuous transmission mask (CTM). For example, the CTM may be represented as a pixelated image, where each pixel may be assigned a value between 0 and 1 (e.g., 0.1, 0.2, 0.3, etc.) instead of binary value of either 0 or 1. In an embodiment, CTM may be a pixelated gray scale image, where each pixel having values (e.g., within a range [-255, 255], normalized values within a range [0, 1] or [-1, 1] or other appropriate ranges).

[0057] The thin-mask approximation, also called the Kirchhoff boundary condition, is widely used to simplify the determination of the interaction of the radiation and the patterning device. The thin-mask approximation assumes that the thickness of the structures on the patterning device is very small compared with the wavelength and that the widths of the structures on the mask are very large compared with the wavelength. Therefore, the thin-mask approximation assumes the electromagnetic field after the patterning device is the multiplication of the incident electromagnetic field with the mask transmission function. However, as lithographic processes use radiation of shorter and shorterwavelengths, and the structures on the patterning device become smaller and smaller, the assumption of the thin-mask approximation can break down. For example, interaction of the radiation with the structures (e.g., edges between the top surface and a sidewall) because of their finite thicknesses (“mask 3D effect” or “M3D”) may become significant. Encompassing this scattering in the mask transmission function may enable the mask transmission function to better capture the interaction of the radiation with the patterning device. A mask transmission function under the thin-mask approximation may be referred to as a thin-mask transmission function. A mask transmission function encompassing M3D may be referred to as a M3D mask transmission function.

[0058] According to an embodiment of the present disclosure, one or more images may be generated. The images includes various types of signal that may be characterized by pixel values or intensity values of each pixel. Depending on the relative values of the pixel within the image, the signal may be referred as, for example, a weak signal or a strong signal, as may be understood by a person of ordinary skill in the art. The term “strong” and “weak” are relative terms based on intensity values of pixels within an image and specific values of intensity may not limit scope of the present disclosure. In an embodiment, the strong and weak signal may be identified based on a selected threshold value. In an embodiment, the threshold value may be fixed (e.g., a midpoint of a highest intensity and a lowest intensity of pixel within the image. In an embodiment, a strong signal may refer to a signal with values greater than or equal to an average signal value across the image and a weak signal may refer to signal with values less than the average signal value. In an embodiment, the relative intensity value may be based on percentage. For example, the weak signal may be signal having intensity less than 50% of the highest intensity of the pixel (e.g., pixels corresponding to target pattern may be considered pixels with highest intensity) within the image. Furthermore, each pixel within an image may considered as a variable. According to the present embodiment, derivatives or partial derivative may be determined with respect to each pixel within the image and the values of each pixel may be determined or modified according to a cost function based evaluation and / or gradient based computation of the cost function. For example, a CTM image may include pixels, where each pixel is a variable that can take any real value.

[0059] Figure 2 illustrates an exemplary flow chart for simulating lithography in a lithographic projection apparatus, according to an embodiment. Source model 31 represents optical characteristics (including radiation intensity distribution and / or phase distribution) of the source. Projection optics model 32 represents optical characteristics (including changes to the radiation intensity distribution and / or the phase distribution caused by the projection optics) of the projection optics. Design layout model 35 represents optical characteristics of a design layout (including changes to the radiation intensity distribution and / or the phase distribution caused by a design layout), which is the representation of an arrangement of features on or formed by a patterning device. Aerial image 36 can be simulated from design layout model 35, projection optics model 32, and design layout model 35. Resist image 38 can be simulated from aerial image 36 using resist model 37. Simulation of lithography can, for example, predict contours and CDs in the resist image.

[0060] More specifically, it is noted that source model 31 can represent the optical characteristics of the source that include, but not limited to, numerical aperture settings, illumination sigma (o) settings as well as any particular illumination shape (e.g. off-axis radiation sources such as annular, quadrupole, dipole, etc.). Projection optics model 32 can represent the optical characteristics of the projection optics, including aberration, distortion, one or more refractive indexes, one or more physical sizes, one or more physical dimensions, etc. Design layout model 35 can represent one or more physical properties of a physical patterning device, as described, for example, in U.S. Patent No. 7,587,704, which is incorporated by reference in its entirety. The objective of the simulation is to accurately predict, for example, edge placement, aerial image intensity slope and / or CD, which can then be compared against an intended design. The intended design is generally defined as a pre-OPC design layout which can be provided in a standardized digital file format such as GDSII or OASIS or other file format.

[0061] From this design layout, one or more portions may be identified, which are referred to as “clips.” In an embodiment, a set of clips is extracted, which represents the complicated patterns in the design layout (typically about 50 to 1000 clips, although any number of clips may be used). These patterns or clips represent small portions (i.e. circuits, cells or patterns) of the design and more specifically, the clips typically represent small portions for which particular attention and / or verification is needed. In other words, clips may be the portions of the design layout, or may be similar or have a similar behavior of portions of the design layout, where one or more critical features are identified either by experience (including clips provided by a customer), by trial and error, or by running a full-chip simulation. Clips may contain one or more test patterns or gauge patterns.

[0062] An initial larger set of clips may be provided a priori by a customer based on one or more known critical feature areas in a design layout which require particular image optimization. Alternatively, in another embodiment, an initial larger set of clips may be extracted from the entire design layout by using some kind of automated (such as machine vision) or manual algorithm that identifies the one or more critical feature areas.

[0063] In a lithographic projection apparatus, as an example, a cost function may be expressed aswhere (z1;z2, ••• , zN) are N design variables or values thereof. fp(z-[,z2, -" ,zN) can be a function of the design variables (z1;z2, • • • , zw) such as a difference between an actual value and an intended value of a characteristic for a set of values of the design variables of (z1;z2, ••• , zN). wpis a weight constant associated with / p(z1,z2, --- ,zN). For example, the characteristic may be a position of an edge of a pattern, measured at a given point on the edge. Different fp(z1;z2, • • • , zw) may have different weight wp. For example, if a particular edge has a narrow range of permitted positions, the weight wpfor the fp(z^, z2, ••• ,zN) representing the difference between the actual position and the intended position ofthe edge may be given a higher value. fp(z1,z2, ---,zN') can also be a function of an interlayer characteristic, which is in turn a function of the design variables (z1;z2, '" >ZN) ■ Of course, CF(z1,z2, --- ,zw) is not limited to the form in Eq. 1. CF(z1,z2, --- ,zw) can be in any other suitable form.

[0064] The cost function may represent any one or more suitable characteristics of the lithographic projection apparatus, lithographic process or the substrate, for instance, focus, CD, image shift, image distortion, image rotation, stochastic variation, throughput, local CD variation, process window, an interlayer characteristic, or a combination thereof. In one embodiment, the design variables (z1,z2, --- ,zw) comprise one or more selected from dose, global bias of the patterning device, and / or shape of illumination. Since it is the resist image that often dictates the pattern on a substrate, the cost function may include a function that represents one or more characteristics of the resist image. For example, fp(z1;z2, • • • , zw) can be simply a distance between a point in the resist image to an intended position of that point (i.e., edge placement error FPFp(z1,z2, ••• , zN). The design variables can include any adjustable parameter such as an adjustable parameter of the source, the patterning device, the projection optics, dose, focus, etc.

[0065] The lithographic apparatus may include components collectively called a “wavefront manipulator” that can be used to adjust the shape of a wavefront and intensity distribution and / or phase shift of a radiation beam. In an embodiment, the lithographic apparatus can adjust a wavefront and intensity distribution at any location along an optical path of the lithographic projection apparatus, such as before the patterning device, near a pupil plane, near an image plane, and / or near a focal plane. The wavefront manipulator can be used to correct or compensate for certain distortions of the wavefront and intensity distribution and / or phase shift caused by, for example, the source, the patterning device, temperature variation in the lithographic projection apparatus, thermal expansion of components of the lithographic projection apparatus, etc. Adjusting the wavefront and intensity distribution and / or phase shift can change values of the characteristics represented by the cost function. Such changes can be simulated from a model or actually measured. The design variables can include parameters of the wavefront manipulator.

[0066] The design variables may have constraints, which can be expressed as (z1;z2, ■■■ ,zN') G Z, where Z is a set of possible values of the design variables. One possible constraint on the design variables may be imposed by a desired throughput of the lithographic projection apparatus. Without such a constraint imposed by the desired throughput, the optimization may yield a set of values of the design variables that are unrealistic. For example, if the dose is a design variable, without such a constraint, the optimization may yield a dose value that makes the throughput economically impossible. However, the usefulness of constraints should not be interpreted as a necessity. For example, the throughput may be affected by the pupil fill ratio. For some illumination designs, a low pupil fill ratio may discard radiation, leading to lower throughput. Throughput may also be affected by the resistchemistry. Slower resist (e.g., a resist that requires higher amount of radiation to be properly exposed) leads to lower throughput.

[0067] In some semiconductor manufacturing processes, a reticle or mask is used to deliver a particular pattern of light to a substrate. In use, the reticle is often shifted in position to deliver the light to different portions of the substrate. In applications where a high throughput is desired, the translation of the reticle can occur very quickly, and thus, impart large accelerations to the reticle. In some cases, the reticle is secured to a chuck via a vacuum force applied through the chuck to one face of the reticle. Well, the vacuum force may be quite strong, in view of the potential for large accelerations, the reticle may slip relative to the chuck and therefore be out of position. To compensate for these accelerations, one or more pushers can be utilized to provide opposing corresponding force to the reticle to cancel out the force due to the inertia of the reticle during chuck acceleration. The present disclosure provides embodiments of such pushers where some portions are supported via magnetically levitated bearings that replace, for example, a structural coupling. Such magnetic bearings can act to reduce friction, avoid lateral coupling (e.g., in a direction other than the direction of acceleration), reduce lateral vibrations, and have fewer mechanical parts. While the magnets used can be permanent magnets (e.g., rare-earth or other types of permanent magnets) in some embodiments some or all of the magnets can be electromagnets.

[0068] Figure 3 illustrates an example of actuators that hold a reticle held in place and counteract chuck accelerations. Reticle stage system 300 can include chuck 310 configured to support reticle 320 and one or more actuators 330 (or pushers) that secure and provide compensating forces to reticle 320. In some embodiments, actuator 330 can include stages with different amounts of range and / or resolution. For example, actuator 330 can include coarse stage 340 having first housing 342 attached to chuck 310. First housing 342 can levitate coarse stage actuator 344 using coarse stage repelling magnets (e.g., as shown in Figure 4A). Actuator can also include fine stage 350 having second housing 352 attached to chuck 310, with second housing 352 levitating fine stage actuator 354 using fine stage repelling magnets. Fine stage actuator 354 can be coupled to coarse stage actuator 344, with fine stage actuator 354 having a range of travel less than coarse stage actuator 344. Coarse stage actuator 344 can be utilized to release or secure reticle and have a range sufficient to do so (e.g., 1-20 mm). An example of a coarse stage actuator 344 can include a motorized threaded rod that translates a frame with a threaded hole and that is levitated by the coarse stage repelling magnets (see Fig. 4A).

[0069] Fine stage actuator 354 can be utilized primarily to provide fast responses to chuck acceleration and thus need only a more limited range (e.g., 1-100 micrometers). An example of fine stage actuator 354 can be one that includes a piezoelectric material that translates to facilitate tip 356 of actuator 330 contacting an object (e.g., reticle 320). While the present disclosure describes the manipulation of a reticle, is contemplated that the actuators described herein can contact and actuate other objects. For example, such objects can include a lens or a mirror that may need similar actuation with the attendant benefits of the disclosed embodiments.

[0070] Figure 4A illustrates an example of a magnetic bearing. Figure 4B illustrates a simplified sectional view through Figure 4A. The disclosed magnet bearings can be utilized to support any portion of actuator 330, for example, coarse stage actuator 344 or fine stage actuator 354. In the simplified diagrams of Figures 4A and 4B, a single actuator is shown in a generic manner as it can be any sort of actuator (e.g., coarse stage actuator 344 or fine stage actuator 354). While the following description refers to this as coarse stage actuator 344, it is not essential that all embodiments include both the coarse and fine stage actuators shown in Figure 3. As shown in magnet bearing 400 of Figure 4A, in some embodiments, coarse stage actuator 344 can be held by coarse stage frame 410 suspended in first housing 342 that includes several coarse stage repelling magnets 420. Coarse stage frame 410 can be levitated in first housing 342 to form gap 430 between coarse stage frame 410 and first housing 342 that includes corresponding coarse stage repelling magnets 420. As used herein, the innermost portion (e.g., coarse stage frame 410) that is levitated may be referred to as the “inner race.” Similarly, the outermost portion (e.g., first housing 342) that surrounds the inner race may be referred to as the outer race.

[0071] The polarity of the magnets depicted in the figures herein are typically indicated by arrows within the magnets. It should be understood that the magnet polarities and exact configurations are examples only, and in particular, that the polarities can generally be reversed, so long as opposing polarities are maintained to provide the repelling force needed for levitation. As shown in Figure 4A, coarse stage repelling magnets 420 can be arranged in a polygonal configuration to be generally disposed on the perimeter of the polygonal shape. While the present disclosure contemplates configurations such as octagonal, hexagonal, etc., the embodiment of Figure 4A depicts an example of repelling magnets (e.g., coarse stage or fine stage) arranged rectangularly in horizontal and / or vertical directions. As used herein, the direction of actuation is referred to as the axial direction as this direction is generally along a longitudinal axis of a corresponding actuation mechanism (e.g., a threaded rod and / or a cylindrical piezoelectric material). The horizontal direction, then, is a direction perpendicular to the axial direction (e.g., in the plane of the reticle). Similarly, the vertical direction is another direction perpendicular to the axial direction (e.g., normal to the plane of reticle 320). In various embodiments, the repelling magnets (e.g., coarse stage repelling magnets 420 and / or fine stage repelling magnets) can be arranged radially rather than rectangularly. Examples of radial arrangements of fine stage repelling magnets is shown in the example depicted in Figures 7 and 8A.

[0072] Figure 4C illustrates a simplified sectional view of an example of a magnet bearing 450 with magnets arranged in the axial direction. As noted above, the present disclosure contemplates many variations of magnet arrangements so long as the needed opposing polarities are preserved to provide the levitated bearing. In this embodiment, repelling magnets 422 (which may be coarse stage or fine stage) are arranged to have their polarities in the axial direction.

[0073] Figure 5A illustrates an example of a magnet bearing in an alternating magnet configuration with coarse stage repelling magnets arranged in the vertical direction. Figure 5B illustrates an exampleof a magnet bearing in an alternating magnet configuration with coarse stage repelling magnets arranged in the axial direction. In some embodiments, magnet bearing 500 with coarse stage actuator 344 can be levitated by multiple magnet arrangements 520 which may have alternating polarities of coarse stage repelling magnets 420. Such alternating arrangements can have advantageous field canceling properties in certain locations while still providing the needed repelling support for coarse stage actuator 344. Figures 5A and 5B depict four bearings, which in various embodiments may or may not be directly adjacent or abutting each other, and can generally support one or more actuators (e.g., coarse stage actuator 444 and or fine stage actuator 354). Magnet bearing 550 in Figure 5B is similar to magnet bearing 500 but with the coarse stage repelling magnets 522 arranged axially.

[0074] Figure 6 illustrates an example of a magnet bearing with magnets in a Halbach configuration. In some embodiments, the magnets in magnet arrangement 620 can be arranged in a Halbach configuration. This configuration can advantageously concentrate the magnetic flux on one side while having substantially canceling magnetic flux on the other side. As depicted, magnet bearing 600 has the high flux side of magnet arrangement 620 directed towards gap 630 between the inner race and outer race. As with other embodiments herein, either or both of coarse stage repelling magnets and / or fine stage repelling magnets can be in a Halbach configuration.

[0075] Figure 7 illustrates an example of separated magnet bearings to individually support a coarse stage actuator and a fine stage actuator. In the depicted embodiment of magnet bearing 700, fine stage actuator 354 is supported by fine stage repelling magnets 720 and coarse stage actuator 344 is supported by coarse stage repelling magnets 420. In this example, the fine stage repelling magnets 720 can be oriented radially or vertically whereas coarse stage repelling magnets 420 are oriented axially, though, in other embodiments, they may be oriented similarly. Accordingly, the repelling magnets in either magnet bearing can have any of the disclosed configurations (e.g., alternating, horizontal / vertical, axial, Halbach, etc.). Accordingly, in various embodiments any given bearing can include an arbitrary number of magnets.

[0076] Another benefit of certain embodiments is that with additional magnet bearings non-axial forces (e.g., vertical) due to cantilevering of the actuator(s) can be reduced. As shown in the example of Figure 7 distal end 710 of the fine stage actuator can include tip 356 configured to contact the object, the fine stage actuator 354 can support distal end 710 to have substantively little cantilevering of fine stage actuator 354. As used herein, “substantively little cantilevering” means that a majority (e.g., 80%) of the fine stage actuator is behind the fine stage repelling magnets. Thus, a small amount of cantilevering can be allowed for (e.g., tip 356 and up to 20% of the length of fine stage actuator 354) but such embodiments generally describe where the combined actuators are supported near both ends to reduce vibrational motion in the radial or lateral directions.

[0077] Figure 8A illustrates an example of offset repelling magnets that results in a preload force on an actuator. In embodiments where actuator (e.g., coarse stage actuator) is a threaded rod mated with a corresponding nut in an inner race of coarse stage magnet bearing, there can be some gap between atooth of a thread and its corresponding groove. This gap can reduce the precision of actuation because the threaded rod may have to rotate an undetermined amount before engaging with the groove in inner race. To eliminate this effect, a preload force can be provided with a suitable arrangement of magnets. For example, in magnet bearing 800, coarse stage repelling magnets 420 can be configured to create a coarse stage preload force on coarse stage actuator 344. As shown in Figure 8A, coarse stage repelling magnets 420 are in an inner race and an outer race that are magnetically asymmetric or have a geometric offset 810 to create a coarse stage preload force. Figure 8B depicts preload forces created by geometric offset 810. To explain the preload force, first consider it configuration without an offset (i.e., the inner race magnets are aligned with the outer race magnets). Such a configuration would provide the needed levitation but its symmetry would result in no preferential force between the inner race and outer race. With a geometric offset as shown, the inner race for coarse stage actuator 344 is offset to the left. This directs a component of the repulsion force in the axial direction causing a preload force that pushes inner race to the left, resulting in engagement between the threads and grooves.

[0078] The present disclosure contemplates that there are numerous configurations that can generate a preload force. The embodiment in Figure 8A depicts separate magnet bearings for coarse stage actuator 344 and fine stage actuator 354. Accordingly, fine stage 350 can include fine stage repelling magnets 720 that can be configured to create a fine stage preload force on fine stage actuator 354 where fine stage repelling magnets 720 can include an inner race and an outer race that are also magnetically asymmetric or geometrically offset to create the fine stage preload force.

[0079] Figure 8B illustrates a preload band resulting from the combined effect of two opposing preload forces. Coarse stage preload at coarse stage actuator and fine stage preload at the fine stage actuator can combine to create a net preload. The plot shows the preload force for both the coarse stage actuator and fine stage actuator as a function of position. The coarse stage preload 860 (right curve) may be too strong and cause unacceptable frictional forces between the threads / grooves unless the coarse stage inner race has a large offset, but such a large offset may not be feasible for a given construction. To reduce the preload force, an opposing offset can be provided at the fine stage. The fine stage preload 870 is depicted and decreases as its inner race is offset to the right. At a particular offset 880 the forces cancel (making zero net preload) where the two curves cross. The net preload is the difference of the curves. Restricting the net preload (difference 882) to a given value (e.g., 20-30 N) provides a band 884 of allowable differences in the offsets.

[0080] In various embodiments, a similar effect can be obtained by having asymmetric magnet arrangements. For example, if the inner and outer races had four magnets (e.g., as shown in Fig. 5A) but the magnets were of increasing or decreasing strength in the axial direction, this also causes a preload force. The strength and arrangements of the asymmetric magnets can similarly be designed to provide a desirable net preload force.

[0081] Figure 9A illustrates a perspective view of an example pusher having actuators levitated by magnetic bearings. Figure 9B illustrates a top view of the apparatus of Figure 9A. In the exampleshown, pusher 900 is mounted the chuck and can include coarse stage actuator 344, which can be a threaded screw and also include fine stage actuator 354, which can be a piezoelectric material. Coarse stage actuator 344 can be within coarse stage frame 410 which may be magnetically levitated by coarse stage repelling magnets 420 within first housing 342. Coarse stage actuator 344 can be rotated by a motor within motor housing 610 that causes axial translation of coarse stage frame 410, which is coupled to fine stage actuator 354. Fine stage actuator 354 (when a piezoelectric) can be actuated via applied voltages utilizing power cables 910. Fine stage actuator 354 can be supported at its distal end by fine stage repelling magnets 720. Fine stage actuator 354 can include tip 356 making contact with the object to be actuated (e.g., a reticle). As shown in this example, fine stage repelling magnets 720 can be in a radial configuration.

[0082] Figure 10 illustrates a perspective view and two sectional views of an example pusher with damping material between one or more inner and outer races. In this example, the embodiment of Figure 9 A is reproduced as pusher 1000, though the describe use of damping material 1010 can be implemented in any of the disclosed embodiments. It can be beneficial to include a damping material 1010 in the previously-described gap between the outer race and the levitated inner race. Damping material can act to reduce vibrations (particularly non-axial vibrations) and may provide additional support for the inner race, as compared to an air gap. As one example, damping material 1010 can be a liquid, which can be sealed on either side of the corresponding magnet bearing with a sealing element such as a flexible sealing ring, bellows, or a fluid-tight membrane. The sealing element can be flexible to allow the actuation of the bearing while containing damping material 1010. Other liquids such as grease, oil, or other fluids of a desired viscosity can also be used. In some embodiments, damping material 1010 can be a flexible solid material, such as an elastomer like rubber or other such materials. Such flexible solid damping material can allow for shearing in response to actuator motion. While in the depicted example both bearings are shown having damping material 1010, in other embodiments only one bearing may have damping material 1010. Also, in other embodiments, the damping materials may differ between the bearings (or even within the bearings), to allow for use of different liquids, solids, and / or combinations thereof.

[0083] 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 actuator configured to contact an object, the actuator comprising:a coarse stage including a coarse stage actuator that is magnetically levitated by coarse stage repelling magnets; anda fine stage including a fine stage actuator coupled to the coarse stage actuator, the fine stage actuator having a range of travel less than the coarse stage actuator.2. The actuator of clause 1, wherein the object is a reticle.3. The actuator of clause 1, wherein the object is a lens or mirror.4. The actuator of clause 1 , wherein the coarse stage actuator comprises a motorized threaded rod that translates a frame with a threaded hole and that is levitated by the coarse stage repelling magnets.5. The actuator of clause 1, wherein the coarse stage actuator has a range between 1mm and 20 mm.6. The actuator of clause 1 , wherein the fine stage actuator comprises a piezoelectric material that translates to facilitate the actuator contacting the object.7. The actuator of clause 1, wherein the fine stage actuator has a range between 1 micrometer and 100 micrometers.8. The actuator of clause 1 , wherein the coarse stage repelling magnets are arranged in a polygonal configuration.9. The actuator of clause 5, wherein the polygonal configuration includes the coarse stage repelling magnets being arranged rectangularly in horizontal and / or vertical directions.10. The actuator of clause 1, wherein the coarse stage repelling magnets are arranged radially. 11. The actuator of clause 1, wherein the coarse stage repelling magnets are in a Halbach configuration.12. The actuator of clause 1, wherein the fine stage actuator is magnetically levitated by fine stage repelling magnets.13. The actuator of clause 7, wherein the fine stage repelling magnets are arranged rectangularly in horizontal and / or vertical directions.14. The actuator of clause 7, wherein the fine stage repelling magnets are arranged radially. 15. The actuator of clause 7, wherein the fine stage repelling magnets are in a Halbach configuration.16. The actuator of clause 1, wherein the coarse stage repelling magnets are configured to create a coarse stage preload force on the coarse stage actuator.17. The actuator of clause 8, wherein the coarse stage repelling magnets include an inner race and an outer race that are magnetically asymmetric or geometrically offset to create the coarse stage preload force.18. The actuator of clause 1, wherein the fine stage comprises fine stage repelling magnets that are configured to create a fine stage preload force on the fine stage actuator.19. The actuator of clause 9, wherein the fine stage repelling magnets include an inner race and an outer race that are magnetically asymmetric or geometrically offset to create the fine stage preload force.20. The actuator of clause 1 , wherein a coarse stage preload at the coarse stage actuator and a fine stage preload at the fine stage actuator combine to create a net preload.21. The actuator of clause 1, further comprising a tip attached to a distal end of the fine stage actuator, the tip configured to contact the object, the fine stage supporting the distal end to have substantively little cantilevering of the fine stage actuator.22. The actuator of clause 1, further comprising a fluid layer in a gap between the coarse stage repelling magnets.23. A reticle stage system further comprising:a chuck configured to support a reticle; andthe actuator of clause 1 ,the coarse stage comprising a first housing attached to the chuck, the first housing levitating the coarse stage actuator using the coarse stage repelling magnets; andthe fine stage comprising a second housing attached to the chuck, the second housing levitating the fine stage actuator using fine stage repelling magnets.24. A semiconductor device manufacturing method comprising:controlling an actuator to contact a reticle to secure the reticle and / or move the reticle to a desired position, the actuator comprising a coarse stage and a fine stage, where at least the coarse stage has at least one coarse stage actuator that is magnetically levitated by coarse stage repelling magnets;receiving a substrate on a support surface, the substrate having a photoresist layer; directing EUV or DUV radiation from a radiation source to transfer a pattern from the reticle onto the photoresist layer; andremoving a portion of the photoresist layer to form the pattern over the substrate.

[0084] The lithographic apparatus and radiation source along with embodiments of the modular conditioning apparatus described herein can be used in a method for manufacturing a semiconductor device. A semiconductor device manufacturing method comprises controlling an actuator to contact the reticle to secure the reticle and / or move the reticle to a desired position. The actuator can include a coarse stage and a fine stage, where at least the coarse stage has at least one coarse stage actuator that is magnetically levitated by coarse stage repelling magnets. The method can also include receiving a substrate on a support surface with the substrate having a photoresist layer. The method further comprises directing a EUV or DUV radiation from a radiation source to transfer a pattern from a reticle onto the photoresist layer. This can be achieved by a patterning device which is configured to form a patterned radiation beam, imparting the patterned radiation beam onto the photoresist layer. The method for manufacturing a semiconductor device further comprises the step of removing a portion of the photoresist layer to form the pattern over the substrate.

[0085] The substrate may be made of silicon or other semiconductor materials. Alternatively or additionally, the substrate may include other semiconductor materials such as germanium (Ge) or carbon (C). In some embodiments, the semiconductor substrate is made of a compound semiconductor such as III-V compound semiconductors, II- V compound semiconductors, and / or any suitableintegration of Group IV materials. In some embodiments, the substrate may be a silicon-on-insulator (SOI) or a germanium-on-insulator (GOI) substrate.

[0086] The semiconductor device made from the substrate may have various device elements. Examples of semiconductor device elements that are formed over the substrate include transistors (e.g., planar or non-planar metal oxide semiconductor field effect transistors (MOSFET), bipolar junction transistors (BJT), high-voltage transistors, high-frequency transistors, etc.), diodes, CMOS image sensors, passive devices, and / or other applicable elements. Various processes may be performed to form the semiconductor device elements, such as deposition, etching, implantation, epitaxial growth, polishing, thermal treatment, and / or other suitable processes. In some embodiments, the substrate is coated with a photoresist layer sensitive to the EUV light.

[0087] The combinations and sub-combinations of the elements disclosed herein constitute separate embodiments and are provided as examples only. Also, 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 as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. An actuator configured to contact an object, the actuator comprising:a coarse stage including a coarse stage actuator that is magnetically levitated by coarse stage repelling magnets; anda fine stage including a fine stage actuator coupled to the coarse stage actuator, the fine stage actuator having a range of travel less than the coarse stage actuator.

2. The actuator of claim 1, wherein the object is a reticle, lens, or mirror.

3. The actuator of claim 1, wherein the coarse stage actuator comprises a motorized threaded rod that translates a frame with a threaded hole and that is levitated by the coarse stage repelling magnets.

4. The actuator of claim 1 , wherein the fine stage actuator comprises a piezoelectric material that translates to facilitate the actuator contacting the object.

5. The actuator of claim 1, wherein:the coarse stage repelling magnets are arranged in a polygonal configuration; andthe polygonal configuration includes the coarse stage repelling magnets being arranged rectangularly in horizontal and / or vertical directions.

6. The actuator of claim 1 , wherein the coarse stage repelling magnets are arranged radially or are arranged in a Halbach configuration.

7. The actuator of claim 1, wherein:the fine stage actuator is magnetically levitated by fine stage repelling magnets; and the fine stage repelling magnets are arranged rectangularly in horizontal and / or vertical directions, are arranged radially, or are in a Halbach configuration.

8. The actuator of claim 1, wherein:the coarse stage repelling magnets are configured to create a coarse stage preload force on the coarse stage actuator; andthe coarse stage repelling magnets include an inner race and an outer race that are magnetically asymmetric or geometrically offset to create the coarse stage preload force.

9. The actuator of claim 1, wherein:the fine stage comprises fine stage repelling magnets that are configured to create a fine stage preload force on the fine stage actuator; andthe fine stage repelling magnets include an inner race and an outer race that are magnetically asymmetric or geometrically offset to create the fine stage preload force.

10. The actuator of claim 1, wherein a coarse stage preload at the coarse stage actuator and a fine stage preload at the fine stage actuator combine to create a net preload.

11. The actuator of claim 1 , further comprising a tip attached to a distal end of the fine stage actuator, the tip configured to contact the object, the fine stage supporting the distal end to have substantively little cantilevering of the fine stage actuator.

12. The actuator of claim 1, further comprising a fluid layer in a gap between the coarse stage repelling magnets.

13. A reticle stage system further comprising:a chuck configured to support a reticle; andthe actuator of claim 1 ,the coarse stage comprising a first housing attached to the chuck, the first housing levitating the coarse stage actuator using the coarse stage repelling magnets; andthe fine stage comprising a second housing attached to the chuck, the second housing levitating the fine stage actuator using fine stage repelling magnets.

14. A semiconductor device manufacturing method comprising:controlling an actuator to contact a reticle to secure the reticle and / or move the reticle to a desired position, the actuator comprising a coarse stage and a fine stage, where at least the coarse stage has at least one coarse stage actuator that is magnetically levitated by coarse stage repelling magnets;receiving a substrate on a support surface, the substrate having a photoresist layer; directing EUV or DUV radiation from a radiation source to transfer a pattern from the reticle onto the photoresist layer; andremoving a portion of the photoresist layer to form the pattern over the substrate.

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