Clamp and manufacturing method thereof

Abstract

The method includes joining the first and second layers of the clamp by heating the first and second layers to a holding temperature of at least 700°C, maintaining the first and second layers at the holding temperature during a holding period, and cooling the first and second layers at a cooling rate of up to 20°C / hour during a cooling period after the holding period.

Description

[Technical Field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Application No. 63 / 432,112, filed December 13, 2022, which is incorporated herein by reference in its entirety.

[0002] [Technical field] The present invention relates to a clamp for supporting an object such as a patterning device and / or a substrate in a lithographic apparatus, and to a method for manufacturing the same. [Background technology]

[0003] A lithographic apparatus is a machine that applies a desired pattern to a target portion of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In this case, a patterning device, also known as a mask or reticle, can be used to create a circuit pattern corresponding to an individual layer of the IC. This pattern can be imaged onto a target portion (e.g. comprising part of a die, or several dies) on a substrate (e.g. a silicon wafer) that has a layer of radiation-sensitive material (resist) on it. In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a beam in a given direction (the "scan" direction) while the substrate is synchronously scanned parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004] Lithography is widely recognized as one of the key steps in the manufacture of ICs and other devices and / or other structures. However, as the dimensions of features created using lithography decrease, lithography becomes an even more important factor in enabling the manufacture of miniaturized ICs and other devices and / or other structures.

[0005] A theoretical estimate of the limit of pattern printing can be given by the Rayleigh criterion for resolution, which is given by equation (1).

number

[0006] To shorten the exposure wavelength and thereby reduce the minimum printable size, the use of extreme ultraviolet (EUV) radiation sources has been proposed. EUV sources are electromagnetic waves with wavelengths in the 5-20 nm range, e.g., 13-14 nm range, e.g., 5-10 nm range, e.g., 6.7 nm or 6.8 nm. Possible radiation sources include, for example, laser-produced plasma sources, discharge plasma sources, or sources based on synchrotron radiation supplied by electron storage rings.

[0007] However, the radiation produced by such radiation sources is not limited to EUV radiation; they may also emit other wavelengths, including infrared (IR) and deep ultraviolet (DUV) radiation. DUV radiation can have adverse effects on lithography systems, potentially causing a reduction in contrast. Furthermore, unwanted IR radiation can cause thermal damage to components within the system. Therefore, it is known to use spectral purity filters to increase the proportion of EUV in the transmitted radiation and reduce or eliminate unwanted non-EUV radiation, such as DUV and IR radiation.

[0008] Lithographic apparatus using EUV radiation may require that the EUV radiation beam path, or at least a large portion thereof, be maintained in a vacuum during lithographic operations. In such vacuum regions of the lithographic apparatus, electrostatic clamps may be used to fix objects, such as a patterning device and / or a substrate, to structures of the lithographic apparatus, such as the patterning device table and / or substrate table, respectively.

[0009] Furthermore, lithographic apparatus using EUV radiation may require temperature conditioning of, for example, the patterning device and / or the substrate. Heat generated by EUV radiation or unwanted non-EUV radiation can cause deformation of the patterning device and / or the substrate, for example, due to heat absorbed by the patterning device and / or the substrate during lithographic operations. To mitigate this deformation, a coolant may be circulated through the electrostatic clamp. However, configuring the electrostatic clamp to circulate a coolant can cause stresses in the clamp structure. This stress can be transferred to an object (e.g., patterning device, substrate) clamped by the electrostatic clamp, causing deformation of the clamped object. Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, there is a need for an electrostatic clamp that can be configured to securely hold an object and prevent deformation caused by heat and stress in the clamped object. [Means for solving the problem]

[0011] According to one embodiment, a method is provided that includes bonding first and second layers of a clamp by heating the first and second layers to a hold temperature of at least 700°C, maintaining the first and second layers at the hold temperature during a hold period, and cooling the first and second layers at a cooling rate of up to 20°C / hr during a cooling period after the hold period.

[0012] In another embodiment, there is provided a lithographic apparatus including a chuck and an electrostatic clamp coupled to the chuck and configured to releasably hold a patterning device. The electrostatic clamp includes a first layer and a second layer. The first layer and the second layer are bonded to each other using a thermal treatment. The thermal treatment includes heating the first layer and the second layer to a hold temperature of at least 700°C, maintaining the first layer and the second layer at the hold temperature during a hold period, and cooling the first layer and the second layer at a cooling rate of up to 20°C / hr during a cooling period after the hold period.

[0013] According to yet another embodiment, a clamp is provided. The clamp may include a first layer and a second layer. The first layer and the second layer are bonded together using a heat treatment. The heat treatment includes heating the first layer and the second layer to a hold temperature of at least 700°C, maintaining the first layer and the second layer at the hold temperature during a hold period, and cooling the first layer and the second layer at a cooling rate of up to 20°C / hour during a cooling period after the hold period.

[0014] Further features of the present disclosure, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings. The present disclosure is not limited to the particular embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings contained herein. [Brief explanation of the drawings]

[0015] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate the present disclosure and, together with the description, further explain the principles of the present disclosure and enable one skilled in the relevant art to make and use the embodiments described herein.

[0016] [Figure 1A] 1 shows a schematic diagram of a reflective lithographic apparatus according to some aspects of the present disclosure.

[0017] [Figure 1B] 1 shows a schematic diagram of a transmissive lithographic apparatus according to some aspects of the present disclosure.

[0018] [Figure 2] 1 shows a more detailed schematic diagram of a reflective lithographic apparatus according to some aspects of the present disclosure.

[0019] [Figure 3] 1 shows a schematic diagram of a lithographic cell according to some aspects of the present disclosure.

[0020] [Figure 4] 1 shows a schematic diagram of a cross section of an electrostatic clamp, according to some aspects of the present disclosure.

[0021] [Figure 5] 1 shows a schematic cross-sectional view of an electrostatic clamp and chuck according to some aspects of the present disclosure.

[0022] [Figure 6A]1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6B] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6C] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6D] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6E] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6F] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6G] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6H] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6I] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6J] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6K] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6L] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6M] 1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure. [Figure 6N]1A-1C show cross-sectional schematic views of an electrostatic clamp at certain stages in the manufacturing process, in accordance with some aspects of the present disclosure.

[0023] [Figure 7] 1 shows a schematic cross-sectional view of an electrostatic clamp during mating with a chuck, according to some aspects of the present disclosure.

[0024] [Figure 8] 1 illustrates a flowchart of a manufacturing process for an electrostatic clamp, according to some aspects of the present disclosure.

[0025] [Figure 9] 1 shows a flowchart of a bonding method according to some aspects of the present disclosure.

[0026] [Figure 10] 1 shows a schematic diagram of a computer system according to some aspects of the present disclosure.

[0027] Features of the present disclosure will become apparent from the detailed description set forth below when considered in conjunction with the drawings in which like reference numbers identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. Furthermore, the leftmost digit(s) of a reference number generally identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout this disclosure should not be construed as drawings to scale. DETAILED DESCRIPTION OF THE INVENTION

[0028] This specification discloses one or more embodiments incorporating features of the present disclosure. The disclosed embodiments are provided by way of example. The scope of the present disclosure is not limited to the disclosed embodiments. The claimed features are defined by the claims appended hereto.

[0029] References to the described embodiments, and to "one embodiment," "an embodiment," "an exemplary embodiment," and the like, herein indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments necessarily include the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with one embodiment, it will be understood that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0030] Spatially relative terms such as "bottom," "lower," "lower side," "top," "upper," and "upper" may be used herein to describe and facilitate the relationship of one element or feature to another element or feature as shown in the drawings. These spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the drawings. The device may be oriented differently (rotated 90 degrees or at other orientations) and thus the spatially relative descriptions used herein may be interpreted similarly.

[0031] As used herein, the term "about" refers to a quantity that can vary based on a particular technique. Depending on the technique, the term "about" may refer to a value that varies within 10 to 30% of the quantity (e.g., ±10%, ±20%, or ±30% of the value).

[0032] Embodiments of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present disclosure may also be implemented as instructions stored on a machine-readable medium that can be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, and electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.). Furthermore, firmware, software, routines, and / or instructions may be described herein as performing certain operations. However, it should be understood that such description is for convenience and that, in reality, such operations result from a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0033] However, before describing such embodiments in more detail, it is useful to provide an example environment in which embodiments of the present disclosure may be implemented.

[0034] Exemplary Lithography System

[0035] 1A and 1B show schematic diagrams of lithographic apparatus 100 and lithographic apparatus 100', respectively, in which embodiments of the present disclosure can be implemented. Lithographic apparatus 100 and lithographic apparatus 100' each include an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet); a support structure (e.g., a mask table) MT configured to support a patterning device (e.g., a mask, reticle, or dynamic patterning device) MA and connected to a first positioner PM configured to precisely position the patterning device MA; and a substrate table (e.g., a wafer table) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to precisely position the substrate W. Lithographic apparatus 100 and 100' also include a projection system PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W. In lithographic apparatus 100, patterning device MA and projection system PS are reflective. In lithographic apparatus 100', patterning device MA and projection system PS are transmissive.

[0036] The illumination system IL may include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping or controlling the radiation beam B.

[0037] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA relative to a reference frame, the design of at least one of lithographic apparatuses 100 and 100′, and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device MA. The support structure MT may be, for example, a frame or a table, and may be fixed or movable as required. The support structure MT may use sensors to ensure that the patterning device MA is at a desired position, for example with respect to the projection system PS.

[0038] The term "patterning device" MA should be interpreted broadly as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section, such as to create a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a particular functional layer in a device being created in the target portion C to form an integrated circuit.

[0039] Terms such as "inspection apparatus," "metrology system," etc. may be used herein to refer to a device or system (e.g., an alignment apparatus) used, for example, to measure characteristics of a structure (e.g., overlay error, critical dimension parameters) or to inspect the alignment of a wafer in a lithography apparatus.

[0040] Patterning device MA may be transmissive (such as lithographic apparatus 100′ in FIG. 1B) or reflective (such as lithographic apparatus 100 in FIG. 1A). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilting mirrors impart a pattern to a radiation beam B, which is reflected by the matrix of small mirrors.

[0041] The term "projection system" PS may encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, etc. optics, or any combination thereof, depending on the exposure radiation used and other factors such as the use of an immersion liquid for the substrate W or the use of a vacuum. A vacuum environment may be used for EUV radiation or electron beam radiation, as other gases may absorb too much radiation or electrons. Therefore, a vacuum environment may be provided throughout the beam path with the aid of a vacuum wall and vacuum pumps.

[0042] Lithographic apparatus 100 and / or lithographic apparatus 100' may be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such a "multi-stage" machine, the additional substrate tables WT may be used in parallel, or one or more other substrate tables WT may be used for exposure while preparation steps are performed on one or more tables. In some circumstances, the additional tables may not be substrate tables WT.

[0043] The lithographic apparatus may be of a type in which at least a portion of the substrate is covered by a liquid having a relatively high refractive index, e.g., water, filling a space between the projection system and the substrate. Immersion liquids may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term "immersion", as used herein, does not imply that a structure such as the substrate has to be submerged in liquid, but rather merely that a liquid is located between the projection system and the substrate during exposure.

[0044] 1A and 1B, the illuminator IL receives a radiation beam from a radiation source SO. The radiation source SO and the lithographic apparatus 100, 100' may be separate physical entities, for example if the radiation source SO is an excimer laser. In such cases, the radiation source SO is not considered to be part of the lithographic apparatus 100 or 100', and the radiation beam B passes from the radiation source SO to the illuminator IL with the aid of a beam delivery system BD (see FIG. 1B), which may include, for example, appropriate directing mirrors and / or beam expanders. In other cases, the radiation source SO may be an integral part of the lithographic apparatus 100, 100', for example if the radiation source SO is a mercury lamp. The radiation source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0045] The illuminator IL may include an adjuster AD (see FIG. 1B ) for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial extent (commonly referred to as "σ-outer" and "σ-inner", respectively) of the intensity distribution in a pupil plane of the illuminator may be adjusted. In addition, the illuminator IL may comprise various other components (see FIG. 1B ), such as an integrator IN and a condenser CO. The illuminator IL may be used to condition the radiation beam B so that it has a desired uniformity and intensity distribution in its cross-section.

[0046] Referring to FIG. 1A, a radiation beam B is incident on a patterning device (e.g., mask) MA, which is held on a support structure (e.g., mask table) MT, and is patterned by the patterning device MA. In lithographic apparatus 100, the radiation beam B is reflected from the patterning device (e.g., mask) MA. After being reflected from the patterning device (e.g., mask) MA, the radiation beam B passes through a projection system PS. The projection system PS focuses the radiation beam B onto a target portion C of a substrate W. With the aid of a second positioner PW and a position sensor IF2 (e.g., an interferometer, a linear encoder, or a capacitance sensor), the substrate table WT may be precisely moved (e.g., to position different target portions C in the path of the radiation beam B). Similarly, a first positioner PM and another position sensor IF1 may be used to precisely position the patterning device (e.g., mask) MA relative to the path of the radiation beam B. Patterning device (eg mask) MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0047] Referring to Figure 1B, a radiation beam B is incident on a patterning device (e.g., mask MA), which is held on a support structure (e.g., mask table MT), and is patterned by the patterning device. After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of a substrate W. The projection system has a pupil PPU that is conjugate with the illumination system pupil IPU. A portion of the radiation emanates from the intensity distribution in the illumination system pupil IPU and passes through the mask pattern without being affected by diffraction at the mask pattern, forming an image of the intensity distribution in the illumination system pupil IPU.

[0048] The projection system PS projects an image of the mask pattern MP, formed by diffracted beams generated from the mark pattern MP by radiation from the intensity distribution, onto a photoresist layer coated on the substrate W. For example, the mask pattern MP may include an array of lines and spaces. Diffraction of the radiation at the array produces deflected diffracted beams whose direction changes perpendicular to the lines, unlike zero-order diffraction. The undiffracted beams (so-called zero-order diffracted beams) pass through the pattern without changing their direction of propagation. The zero-order diffracted beams pass through the upper lens or upper lens group of the projection system PS, upstream of the pupil conjugate PPU of the projection system PS, and reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU associated with the zero-order diffracted beam forms an image of the intensity distribution at the illumination system pupil IPU of the illumination system IL. The aperture device PD is, for example, positioned in a plane containing the pupil conjugate PPU of the projection system PS or substantially in that plane.

[0049] The projection system PS is configured to capture not only the zeroth-order diffracted beam but also first-order or higher-order diffracted beams (not shown) by means of a lens or lens group L. In some embodiments, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line may be used to take advantage of the resolution-enhancing effect of dipole illumination. For example, a first-order diffracted beam interferes with a corresponding zeroth-order diffracted beam at the level of the wafer W to generate an image of the line pattern MP with the highest possible resolution and process window (i.e., usable depth of focus combined with an acceptable exposure dose deviation). In some embodiments, astigmatism may be reduced by providing a radiation pole (not shown) at the anti-symmetry limit of the illumination system pupil IPU. Furthermore, in some embodiments, astigmatism may be reduced by blocking the zeroth-order beam at the pupil conjugate PPU of the projection system associated with the anti-symmetry radiation pole. This is described in more detail in US Pat. No. 7,511,799 B2, issued March 31, 2009, the entire contents of which are incorporated herein by reference.

[0050] With the aid of the second positioner PW and a position sensor IFD (e.g. an interferometer device, a linear encoder or a capacitance sensor), the substrate table WT may be precisely moved (e.g. to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and a further position sensor (not shown in FIG. 1B) may be used to precisely position the mask MA with respect to the path of the radiation beam B (e.g. after mechanical retrieval from a mask library or during a scan).

[0051] In general, movement of the mask table MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected to a short-stroke actuator only, or may be fixed. The mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. The substrate alignment marks occupy dedicated target portions (as shown) but may be located in spaces between the target portions (known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

[0052] The mask table MT and patterning device MA may be within a vacuum chamber V, and an in-vacuum robot IVR may be used to move the patterning device, such as a mask, in and out of the vacuum chamber. Alternatively, if the mask table MT and patterning device MA are outside the vacuum chamber, an out-vacuum robot IVR may be used for various transfer operations, similar to the in-vacuum robot IVR. Both the in-vacuum robot and the out-vacuum robot need to be calibrated to smoothly transfer any payload (e.g., a mask) to the fixed kinematic mount of the transfer station.

[0053] Lithographic apparatus 100 and 100' may be used in at least one of the following modes:

[0054] 1. In step mode, the support structure (e.g. mask table) MT and substrate table WT are kept essentially stationary, while the entire pattern imparted to the radiation beam B is projected onto a target portion C at once (i.e. a single static exposure), where the substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed.

[0055] 2. In scan mode, the support structure (e.g. mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (e.g. mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0056] 3. In another mode, the support structure (e.g. mask table) MT is kept substantially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO may be used, with the programmable patterning device being updated after each movement of the substrate table WT or in between successive pulses of radiation during a scan as required. This mode of operation may readily be applied to maskless lithography employing a programmable patterning device such as a programmable mirror array.

[0057] Combinations and / or variations on the described modes of use may also be employed or entirely different modes of use may also be employed.

[0058] In yet another embodiment, lithographic apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Typically, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0059] FIG. 2 shows lithographic apparatus 100 in more detail, including a source collector apparatus SO, an illumination system IL, and a projection system PS. The source collector apparatus SO is constructed and arranged such that a vacuum environment can be maintained within an enclosure 220 of the source collector apparatus SO. The plasma 210 emitting EUV radiation may be formed by a discharge-produced plasma source. EUV radiation may be generated by a gas or vapor, such as Xe gas, Li vapor, or Sn vapor, in which a very hot plasma 210 is generated and emits radiation in the EUV region of the electromagnetic spectrum. The very hot plasma 210 may be generated, for example, by an electrical discharge that creates an at least partially ionized plasma. To efficiently generate radiation, a partial pressure of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor may be required. In some embodiments, an excited tin (Sn) plasma is provided to generate EUV radiation.

[0060] Radiation emitted by the high-temperature plasma 210 passes from the source chamber 211 to the collector chamber 212 through an optional gas barrier or contaminant trap 230 (sometimes also referred to as a contaminant barrier or foil trap). The contaminant trap 230 is located within or behind an opening in the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 includes at least a channel structure, as further described herein.

[0061] Collector chamber 212 may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation passing through the collector CO may be reflected by a grating spectral filter 240 and focused at a virtual source point INTF. The virtual source point INTF is commonly called the intermediate focus, and the source collector arrangement is positioned so that the intermediate focus INTF is located at or near an opening 219 in the enclosure structure 220. The virtual source point INTF is an image of the radiation-emitting plasma 210. The grating spectral filter 240 is used to suppress, in particular, infrared (IR) radiation.

[0062] The radiation then passes through an illumination system IL, which may include a faceted field mirror device 222 and a faceted pupil mirror device 224 arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA, and to provide a desired uniformity of the radiation intensity at the patterning device MA. When the beam of radiation 221 is reflected from the patterning device MA, which is held by the support structure MT, a patterned beam 226 is formed, which is imaged by the projection system PS via reflective elements 228, 229 onto a substrate W, which is held by a wafer stage or substrate table WT.

[0063] More elements than shown may typically be present in the illumination optics unit IL and projection system PS. Grating spectral filter 240 may optionally be present, depending on the type of lithographic apparatus. Furthermore, more mirrors may be present than shown in Figure 2, for example, there may be one to six additional reflective elements in the projection system PS than shown in Figure 2.

[0064] 2 is shown as a nested collector with grazing incidence reflectors 253, 254, and 255, an example of a collector (or collector mirror). Grazing incidence reflectors 253, 254, and 255 are arranged axially symmetrically about optical axis O, and this type of collector optic CO is preferably used in combination with a discharge produced plasma source, often referred to as a DPP source.

[0065] Exemplary Lithography Cell

[0066] FIG. 3 illustrates a lithography cell 300 (also called a lithocell or cluster) according to some embodiments. Lithography apparatus 100 or 100′ may form part of lithography cell 300. Lithography cell 300 may include one or more devices for performing pre-exposure and post-exposure processing on a substrate. Conventionally, these devices include a spin coater SC for depositing a resist layer, a developer DE for developing exposed resist, a chill plate CH, and a bake plate BK. A substrate handler (or robot RO) picks up substrates from input / output ports I / O1, I / O2, moves the substrates between different processing devices, and delivers the substrates to a loading bay LB of lithography apparatus 100 or 100′. These devices are often collectively referred to as a track and are controlled by a track control unit TCU. The track control unit TCU is itself controlled by a supervisory control system SCS, which also controls the lithography apparatus via a lithography control unit LACU. In this manner, the various devices may operate to maximize throughput and processing efficiency.

[0067] Electrostatic Clamp of an Exemplary Embodiment

[0068] 4 shows a schematic cross-sectional view of an electrostatic clamp 400 that may be implemented as part of lithographic apparatus 100 according to an embodiment. In one example of this embodiment, electrostatic clamp 400 may be used in lithographic apparatus 100 to hold a substrate W on a substrate table WT or a patterning device MA on a support structure MT.

[0069] According to one embodiment, electrostatic clamp 400 may comprise a multi-layer structure including first layer 402 having opposing parallel surfaces 402a and 402b, second layer 404 having opposing parallel surfaces 404a and 404b, and third layer 406 having opposing parallel surfaces 406a and 406b. According to one example of this embodiment, first layer 402, second layer 404, and third layer 406 may have vertical dimensions within the ranges of approximately 1-4 mm, approximately 1-4 mm, and approximately 50-200 microns, respectively. First layer 402 may be bonded to second layer 404 such that surface 402a is in substantial contact with surface 404b, and third layer 406 may be bonded to second layer 404 such that surface 404a faces surface 406b. Surface 406a of third layer 406 may define clamping surface 406a of electrostatic clamp 400. The clamping surface 406a may be configured to receive an object 407 (e.g., a substrate W or a patterning device MA) to be clamped in the electrostatic clamp 400. The object 407 may be clamped such that it is in substantial contact with the clamping surface 406a. Optionally, the clamping surface 406a may include burls 405 configured to contact the object 407 during the clamping operation. The burls 405 may help provide a less contaminating contact between the object 407 and the clamping surface 406a because contaminants are less likely to adhere to the burls 405, which have a smaller surface area, than to the clamping surface 406a, which has a larger surface area.

[0070] In some embodiments, the first layer 402, the second layer 404, and the third layer 406 may comprise different materials. In other embodiments, the first layer 402, the second layer 404, and the third layer 406 may be fabricated from one or more dielectric materials configured to support the electrostatic field during operation of the electrostatic clamp 400, as described further below. The dielectric material may have an ultra-low coefficient of thermal expansion, which may be zero or substantially zero, such as, but not limited to, an ultra-low thermal expansion silicon-based material (e.g., ULE® from Corning Incorporated), a glass material, a ceramic material, a silicon-based glass-ceramic material (e.g., ZERODUR® from Schott Corporation), or a combination thereof. Any of these ultra-low thermal expansion materials may help reduce thermal stress in the structure of the electrostatic clamp 400 during fabrication. If not reduced, thermal stresses in the electrostatic clamp 400 can cause one or more undesirable deformations in the first layer 402, the second layer 404, and / or the third layer 406, which can be transferred to the object 407 during the clamping operation.

[0071] In another embodiment, first layer 402 and / or second layer 404 may be fabricated from one or more non-dielectric insulator materials having an ultra-low coefficient of thermal expansion.

[0072] In yet another embodiment, first layer 402, second layer 404, and third layer 406 may be fabricated from the same one or more ultra-low thermal expansion dielectric materials. Fabricating all three layers of electrostatic clamp 400 from similar materials may help further reduce thermal stresses caused by thermal expansion mismatches between dissimilar materials. In one example of this embodiment, first layer 402, second layer 404, and third layer 406 may be fabricated from a ULE® material, which offers greater electrical stability than ZERODUR® material.

[0073] As shown in FIG. 4 , electrostatic clamp 400, according to one embodiment, further comprises a composite layer 408 interposed between second layer 404 and third layer 406. In one example of this embodiment, composite layer 408 may have a vertical dimension in the range of approximately 50-400 nm. Composite layer 408 includes alternating conductive regions 410 and insulating regions 412 (also referred to herein as layers). One conductive region 410 is electrically isolated from another conductive region by one insulating region 412. While FIG. 4 shows only two conductive regions, it will be understood that in other variations of the present disclosure, composite layer 408 may include a single conductive layer or three or more conductive layers. In one embodiment, conductive region 410 and insulating region 412 are coplanar.

[0074] In various examples of this embodiment, conductive region 410 may be formed using any suitable conductive material, such as, but not limited to, aluminum, chromium, platinum, gold, or combinations thereof, and insulating region 412 may be formed using any suitable insulating material, such as, but not limited to, silicon oxide or other insulating metal oxides. In other examples, conductive region 410 may comprise a single layer of metal, multiple layers of the same metal, or multiple layers of different metals.

[0075] According to one exemplary embodiment, the conductive region 410 may be configured as an electrode 410 for generating an electrostatic field within the third layer 406 and clamping the object 407 to the clamping surface 406a. The electrostatic field may be generated by applying a clamping voltage to the electrode 410. The clamping voltage may induce a surface image charge on the conductive surface 407a of the object 407, electrostatically attracting and clamping the object 407 to the clamping surface 406a.

[0076] Electrostatic clamp 400, according to one embodiment, may optionally include an intermediate layer 414 interposed between composite layer 408 and second layer 404, as shown in FIG. 4. Intermediate layer 414 may comprise a silicon-based material, such as silicon oxide or aluminum oxide, and may be configured as a bonding medium for bonding composite layer 414 to second layer 404. In one example of this embodiment, intermediate layer 414 may have a vertical dimension of approximately 10-200 nm. Alternatively, intermediate layer 414 may be interposed between composite layer 408 and third layer 406, as described in further detail below with reference to FIGS. 6J-K.

[0077] In a further embodiment, the electrostatic clamp 400 includes a fluid channel 416, as shown in FIG. 4. The fluid channel 416 extends parallel to the surface 402a and is configured to carry a thermally conditioned fluid (e.g., liquid or gas), such as, but not limited to, water, air, alcohol, glycol, or a phase-change refrigerant (e.g., chlorofluorocarbon, carbon dioxide). A fluid conditioning system 418 coupled to the electrostatic clamp 400 may be configured to condition the thermally conditioned fluid to a desired temperature before entering the fluid channel 416 and circulate the thermally conditioned fluid through the electrostatic clamp 400. The circulating thermally conditioned fluid may help regulate the temperature of the electrostatic clamp 400 to the desired temperature. Temperature regulation of the electrostatic clamp 400 may include absorbing unwanted heat from the electrostatic clamp 400 with the thermally conditioned fluid. This unwanted heat may be transferred from the clamped object 407 to the electrostatic clamp 400 through the clamping surface 406a and / or the crowbar.

[0078] In one example of this embodiment, object 407 may be a patterning device, and unwanted heat may be transferred to the patterning device during operation, for example, from the illumination system and / or other systems of lithographic apparatus 100. The presence of unwanted heat in the patterning device may cause deformation of the patterning device, potentially resulting in errors in the pattern transferred from the patterning device to the substrate. To prevent this deformation, according to various embodiments, the temperature of the patterning device may be maintained at substantially room temperature (approximately 22°C) or any other specified operating temperature. This temperature regulation of the patterning device may include heat transfer from the patterning device to electrostatic clamp 400 (e.g., via clamping surface 406a, burl 416), as described above, thereby reducing or eliminating thermal deformation of the patterning device.

[0079] FIG. 5 shows a schematic cross-sectional view of an electrostatic clamp 500 coupled to a chuck 520 according to an embodiment. The electrostatic clamp 500 and chuck 520 may be implemented as part of the lithographic apparatus 100, according to an example embodiment. The chuck 520 may be configured to couple the electrostatic clamp 500 to the substrate table WT and / or the support structure MA in an exemplary embodiment. The electrostatic clamp 500 may be similar in structure and function to the electrostatic clamp 400, except for the differences described below. The fluid channel 522 may extend parallel to the surface 520a and be configured to carry a thermally conditioned fluid as the fluid channel 416. A fluid conditioning system 518 coupled to the chuck 520 may be configured to condition the thermally conditioned fluid to a desired temperature before entering the fluid channel 522 and circulate the thermally conditioned fluid within the electrostatic clamp 500 and the chuck 504. The circulating thermally conditioned fluid may help to condition the temperature of the electrostatic clamp 500 and the chuck 520 to a desired temperature. Temperature regulation of the electrostatic clamp 500 and the chuck 520 may include absorbing unwanted heat from the electrostatic clamp 500 and the chuck 520 with a thermally conditioned fluid. The unwanted heat of the electrostatic clamp 500 may be transferred from the object 407 as described above, and the unwanted heat of the chuck 520 may be transferred from other parts of the lithographic apparatus 100 that are coupled to the electrostatic clamp 500 and / or the chuck 520.

[0080] An example of a manufacturing method for an electrostatic clamp

[0081] 6A-N show cross-sectional views of electrostatic clamp 400 (shown in FIG. 4) at certain stages in the manufacturing process, according to one embodiment.

[0082] 6A-B show cross-sectional views of a partially formed electrostatic clamp 400 during the formation of a fluid channel 416 (described above with reference to FIGS. 4-5), according to one embodiment. Forming the fluid channel 416 may include forming a trench 630 in the surface 402a of the first layer 402 (see FIG. 6A) and forming a laminate structure 632 (see FIG. 6B).

[0083] According to one embodiment, forming trench 630 may include polishing, machining, and etching surface 402a. Polishing surface 402a may be performed using any suitable polishing process, such as, but not limited to, a cerium oxide slurry polishing process, to obtain a smooth surface having a root-mean-square (RMS) roughness of approximately 0.5 mm or less. After polishing, surface 402a may be machined using standard glass processing techniques and / or patterned and etched using standard photolithography and glass etching processes to form trench 630 (shown in FIG. 6A). Note that the rectangular cross-sectional shape of trench 630 shown in FIG. 6A is for illustrative purposes and not limiting. Trench 630 may have other cross-sectional shapes (e.g., conical, trapezoidal) according to various embodiments without departing from the spirit and scope of the present disclosure. After machining, acid etching may be performed on machined surface 402a using, for example, an acid mixture comprising hydrofluoric acid. The acid etch may etch a few microns (e.g., about 5 microns) of material of layer 402 from machined surface 402a. This material removal from machined surface 402a may help relieve stress that may be induced in layer 402 by the machining process. This stress may result from small deformations induced in surface 402a by the physical forces of machining.

[0084] According to one embodiment, as shown in FIG. 6B, following the acid etching process, layer 402 may be bonded to second layer 404 to form laminate structure 632. The bonding process may include polishing surface 404b, cleaning surfaces 402a and 404b, and then directly bonding first layer 402 to second layer 404. Surface 404b may be polished to a root-mean-square (RMS) roughness of about 0.5 mm or less using any suitable polishing process, such as, but not limited to, a cerium oxide slurry polishing process. Surface 402a may be ground and polished after machining trench 630. First layer 402 may then be directly bonded to second layer 404 by pressing surface 402a against surface 404b under pressure appropriate for the layer materials used to form laminate structure 632. Optionally, the laminate structure 632 may be annealed at a temperature in the range of about 350-900° C. to strengthen the direct bond interface between the first layer 402 and the second layer 404. In some embodiments, bonding methods described later in this document may be applied.

[0085] Direct bonding, as used herein, may refer to optical contact bonding, which, according to one embodiment, may be bonding between highly polished, substantially defect-free surfaces (e.g., surfaces 402a and 404b) without the use of bonding materials such as epoxy or any other adhesive material. Optical contact bonding may occur through intermolecular electrostatic interactions, such as van der Waals forces, between the bonding surfaces (e.g., surfaces 402a and 404b). Annealing the optical contact bond (as described above), for example, may convert the van der Waals bond between the bonding surfaces into a stronger covalent bond, thereby strengthening the optical contact bond structure.

[0086] According to one embodiment, after the formation of the fluid channels 416, the layer 404 may be thinned to about 2 mm. The surface 404b may be polished using any suitable polishing and / or grinding technique to thin the second layer 404. Alternatively, the thinning process of the second layer 404 may be performed by polishing the surface 404a and / or the surface 404b prior to the formation of the fluid channels 416.

[0087] 6C-D illustrate cross-sectional views of a partially formed electrostatic clamp 400 during the formation of a conductive region 410, according to one embodiment. Formation of the conductive region 410 may include, for example, depositing one or more metal layers 610 on the third layer 406, as shown in FIG. 6C. This metal deposition may be followed by a patterning and etching process to define the conductive region 410, as shown in FIG. 6D. Deposition of layer 610 may be performed using any conventional method suitable for metals, such as, but not limited to, sputtering, thermal evaporation, atomic layer deposition (ALD), or chemical vapor deposition (CVD). The patterning process may be performed by conventional photolithography processes, and the etching process may be performed by wet or dry etching methods, such as, but not limited to, reactive ion etching (RIE).

[0088] 6E-F show cross-sectional views of a partially formed electrostatic clamp 400 during the formation of insulating regions 412, according to one embodiment. The conductive regions 410 may be coated with photoresist, a dielectric may be deposited, and the insulating regions may be deposited flush with the top of the conductive regions 410. In some embodiments, the photoresist is then removed using a suitable organic solvent or dissolved using a strong oxidizing agent. In some embodiments, the insulating regions may be formed using other techniques known in the art.

[0089] 6G-H illustrate cross-sectional views of a partially formed electrostatic clamp 400 during bonding of a composite layer 408 to a laminate structure 632 (described with reference to FIG. 6B), according to one embodiment. The bonding process may include depositing an intermediate layer 414 on the composite layer 408, as shown in FIG. 6G. The intermediate layer 414 may help provide the composite layer 408 with a bonding surface 414a compatible with direct bonding with the surface 404a. The intermediate layer 414 may be deposited using any suitable method for depositing silicon oxide, such as a CVD process. The bonding process may further include pressing the composite structure of FIG. 6G against the laminate structure 632 to bond the surface 414a to the surface 404a, as shown in FIG. 6H. To strengthen the bonding interface between the surface 414a and the surface 404a, the bonded structure may be annealed at a temperature in the range of approximately 350-900°C.

[0090] Optionally, according to one embodiment, following the bonding process, third layer 406 may be thinned to a vertical dimension in the range of approximately 50-200 microns. Surface 406a may be polished using any suitable polishing and / or grinding technique to thin third layer 406. Alternatively, the thinning process of third layer 406 may be performed by polishing surface 406a and / or surface 406b prior to forming composite layer 408.

[0091] 6I-J illustrate cross-sectional views of electrostatic clamp 400 during the formation of burls 405 on clamping surface 406a, according to one embodiment. Burls 405 may be formed, for example, by depositing a polymer layer 605, as shown in FIG. 6I. Following this deposition, polymer layer 605 may be patterned and etched to define burls 405, as shown in FIG. 6J. The patterning and etching process may be performed by methods described above. Note that the rectangular cross-sectional shape of burls 405 is exemplary only and not limiting. Burls 405 may have other cross-sectional shapes (e.g., spherical, conical, trapezoidal) according to various embodiments.

[0092] In an alternative approach, according to one embodiment, as shown in Figure 6K, composite layer 408 and intermediate layer 414 may be formed on surface 404a of laminate structure 632. Third layer 406 may be directly bonded to intermediate layer 414 and thinned to a vertical dimension in the range of approximately 50-200 microns, as shown in Figure 6L. Direct bonding and thinning may be performed by methods previously described.

[0093] In another alternative approach, according to one embodiment, first and second portions 608a, 608b of composite layer 408 may be formed on surfaces 406b, 404a, respectively, as shown in Figure 6M. First and second portions 608a, 608b may be heat-sealed together to form composite layer 408, as shown in Figure 6N.

[0094] An example of how to couple an electrostatic clamp to a chuck

[0095] FIG. 7 shows a cross-sectional view of electrostatic clamp 400 during coupling to chuck 720. Chuck 720 may be similar in structure and function to chuck 520, as described above with reference to FIG. 5. In one embodiment, the bonding process may include polishing and cleaning surfaces 402b and 720a, followed by direct bonding of these surfaces. Surfaces 402b and 720a may be polished to a root-mean-square (RMS) roughness of approximately 0.5 mm or less using any suitable polishing process, such as, but not limited to, a cerium oxide slurry polishing process. Surfaces 402b and 720a may then be pressed together to form a direct bond between surfaces 402b and 720a. As will be appreciated by those skilled in the art, other types of bonding or joining may be used to couple electrostatic clamp 400 to chuck 720.

[0096] Joint Profile

[0097] With reference to Figures 4, 6H, and 6M, one or more layers described herein may be treated by heat treatment. This heat treatment may be used to form a durable connection between layers of a laminate structure and may be referred to as bonding. In some embodiments, first layer 402 and second layer 404 may be heat treated to bond surface 402a and surface 404b of Figure 4. In additional embodiments, heat treatment may be applied to structure 632 to bond surface 414a to surface 404a of Figure 6H, heat treatment may be applied to third layer 406 to bond with middle layer 414, or heat treatment may be applied to first portion 608a and second portion 608b of Figure 6M.

[0098] The structure (i.e., one or more layers) may be heated in a bonding oven. The structure may be heated to a holding temperature. In some embodiments, the structure may be heated to the holding temperature at a predetermined heating rate. In some embodiments, the holding temperature may be greater than about 350°C. In some embodiments, the holding temperature may be from about 350°C to about 900°C, from about 700°C to about 900°C, from about 750°C to about 850°C, from about 780°C to about 820°C, from about 805°C to about 810°C, or about 815°C. In some embodiments, the heating rate may be from about 2°C / hour to about 60°C / hour, from about 10°C / hour to about 55°C / hour, or may be less than 60°C / hour, or less than 55°C / hour.

[0099] In some embodiments, the structure may be heated to an intermediate temperature (below the hold temperature) at a first heating rate and then heated to the hold temperature at a second heating rate, hi some embodiments, the first heating rate is greater than the second heating rate.

[0100] In some embodiments, the first heating rate can be from about 20°C / hour to about 80°C / hour, from about 30°C / hour to about 70°C / hour, from about 40°C / hour to about 60°C / hour, or from about 45°C / hour to about 55°C / hour. In some embodiments, the second heating rate can be from about 1°C / hour to about 5°C / hour, or from about 2°C / hour to about 4°C / hour. In some embodiments, the intermediate temperature can be from about 5°C to about 20°C lower than the hold temperature. For example, the hold temperature can be from about 805°C to about 815°C, and the intermediate temperature can be from about 795°C to about 805°C.

[0101] In some embodiments, the structure may be maintained at the hold temperature for a hold period. In some embodiments, the hold period may be at least 5 hours, at least 10 hours, at least 15 hours, or at least 20 hours. In some embodiments, the hold period may be from about 5 hours to about 30 hours, from about 10 hours to about 25 hours, from about 15 hours to about 20 hours, from about 20 hours to about 30 hours, or from about 22 hours to about 26 hours.

[0102] The structure may be cooled after the holding period. The temperature may be reduced from the holding temperature to room temperature. In some embodiments, the structure may be cooled at different cooling rates until the desired temperature or room temperature is reached. That is, the temperature of the structure may be reduced at different cooling rates. For example, more than one cooling rate may be used. In some embodiments, the structure may be cooled at a first cooling rate until the desired temperature is reached. Thereafter, cooling can be performed (i.e., uncontrolled) at any cooling rate until room temperature is reached.

[0103] In some embodiments, the first cooling rate can be from about 5°C / hour to about 20°C / hour, from about 7°C / hour to about 15°C / hour, or about 10°C / hour. In some embodiments, the desired temperature can be about 100°C lower than the hold temperature. For example, if the hold temperature is about 810°C, the desired temperature can be about 700°C. In some embodiments, the desired temperature can be about 700°C, about 600°C, about 500°C, about 400°C, or about 300°C.

[0104] In some embodiments, the structure may be cooled at a first cooling rate until a first desired temperature is reached, and then at a second cooling rate until a second desired temperature is reached. In some embodiments, the second cooling rate may be greater than the first cooling rate. For example, the first cooling rate may be from about 5°C / hour to about 15°C / hour, and the second cooling rate may be from about 40°C / hour to about 60°C / hour. In some embodiments, the first desired temperature may be from about 650°C to about 750°C, and the second desired temperature may be from about 550°C to about 450°C. After the second desired temperature is reached, cooling may continue at an uncontrolled rate until room temperature is reached.

[0105] In some embodiments, the structure may be cooled at a first cooling rate until a first desired temperature is reached, and then at a second cooling rate until a second desired temperature is reached. The structure may then be cooled at a third cooling rate until a third desired temperature is reached. After reaching the third desired temperature, the structure may be cooled at an unconstrained cooling rate until room temperature is reached. In some embodiments, the second cooling rate may be greater than the first cooling rate, and the third cooling rate may be greater than the second cooling rate. For example, the first cooling rate may be from about 5°C / hour to about 15°C / hour, and the second cooling rate may be from about 40°C / hour to about 60°C / hour. In some embodiments, the third cooling rate may be from about 80°C / hour to about 120°C / hour. In some embodiments, the first desired temperature may be from about 650°C to about 750°C, and the second desired temperature may be from about 550°C to about 450°C. In some embodiments, the third desired temperature may be from about 350°C to about 250°C.

[0106] In some embodiments, the structure may be cooled at a controlled rate over a first period of time, which in some embodiments may be at least about 10 hours, at least about 15 hours, or at least about 20 hours.

[0107] In some embodiments, the cooling rate, hold temperature, and hold time may be selected based on the material properties of the layers of the structure. For example, measurements may be performed to determine one or more properties of the material, and the cooling rate may be selected based on the measured properties. As previously described herein, the layers of the structure (clamp) may be fabricated from one or more dielectric materials configured to support an electrostatic field during operation of the clamp 400. The dielectric material may have an ultra-low coefficient of thermal expansion, such as zero or substantially equal to zero. In some embodiments, the bonding profile described above may be tailored based on the materials used, and therefore have minimal impact on the coefficient of expansion.

[0108] Example steps for manufacturing an electrostatic clamp

[0109] Figure 8 shows a flow chart for fabricating an electrostatic clamp 400 and coupling the electrostatic clamp 400 to a chuck according to one embodiment. For illustrative purposes only, the steps shown in Figure 8 are described with reference to the example fabrication process shown in Figures 6A-6N and 7. The steps may be performed in a different order or not, depending on the particular application.

[0110] In step 802, a trench is formed in a first layer. For example, as shown in Figure 6A, a trench such as trench 630 may be formed in a first layer such as first layer 402. Trench 630 may be formed using standard glass processing techniques.

[0111] In step 804, the first layer is bonded with a second layer to form a laminate structure. For example, a second layer, such as second layer 404, may be bonded with first layer 402 to form a laminate structure similar to laminate structure 632 shown in FIG. 6B. The bonding process may include direct bonding of surface 402a and surface 404b. Direct bonding may be performed by pressing surface 402a against surface 404b under pressure appropriate for the layer materials used. Laminate structure 632 may be annealed at a temperature in the range of approximately 350-900°C.

[0112] In step 806, a composite layer is formed on the third layer. For example, a composite layer similar to composite layer 408 may be formed on the third layer 406, as shown in FIGS. 6C-F. Composite layer 408 may be formed by depositing, patterning, and etching a metal layer, such as metal layer 610, on the third layer 406, followed by depositing, patterning, and etching a dielectric layer, such as dielectric layer 612. Deposition of metal layer 610 may be performed using, for example, sputtering, thermal evaporation, atomic layer deposition (ALD), or chemical vapor deposition (CVD). Deposition of dielectric layer 612 may be performed using, for example, a CVD process, magnetron sputtering, thermal evaporation, or electron beam evaporation.

[0113] In step 808, an intermediate layer is formed on the composite layer. For example, an intermediate layer similar to intermediate layer 414 may be formed on composite layer 408, as shown in Figure 6G. Intermediate layer 414 may be deposited using, for example, a CVD process.

[0114] In step 810, the third layer 406 is bonded to the laminate structure 632 to form an electrostatic clamp. For example, as shown in FIG. 6H, the third layer 406 may be bonded to the laminate structure 632 by bonding the intermediate layer 414 directly to the surface 404a of the laminate structure.

[0115] In optional step 812, burls are formed on the clamping surface of the clamp. For example, burls such as burls 405 may be formed on a clamping surface such as clamping surface 406a of third layer 406, as shown in Figures 6I-J. Burls 405 may be formed by depositing, patterning, and etching polymer layer 605.

[0116] In optional step 814, the electrostatic clamp is coupled to a chuck. For example, electrostatic clamp 400 may be coupled to a chuck similar to chuck 720, as shown in Figure 7. Coupling may be performed by directly bonding surface 402b of clamp 400 to surface 720a of chuck 720.

[0117] FIG. 9 shows a flow chart of a bonding method 900 according to one embodiment.

[0118] In step 902, first and second layers of a structure (e.g., a clamp) are heated to a holding temperature (e.g., first layer 402 and second layer 404 to join surfaces 402a and 402b in FIG. 4, first portion 608a and second portion 608b in FIG. 6M). In some embodiments, the holding temperature is at least 700°C.

[0119] In step 904, the first layer and the second layer are maintained at the hold temperature for a hold period. In some embodiments, the hold period is at least 5 hours.

[0120] In step 906, the first and second layers are cooled at a cooling rate during a cooling period after the hold time. The cooling rate may be up to 20°C / hour during the cooling period. In some embodiments, the cooling period is at least 10 hours. In some embodiments, the first and second layers are cooled at a cooling rate to a temperature of 700°C or less.

[0121] Exemplary Computing System

[0122] Aspects of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. For example, the design of one or more of the hold temperature, hold period, cooling time, and / or cooling rate may be implemented using hardware, firmware, software, or any combination thereof.

[0123] 10 illustrates a computer system 1000 according to some embodiments. Various embodiments and components thereof may be implemented using, for example, computer system 1000 or any other known computer system. For example, the method steps of FIG. 9 may be implemented via computer system 1000.

[0124] In some embodiments, computer system 1000 may include one or more processors (also referred to as central processing units or CPUs), such as processor 1004. Processor 1004 may be connected to a communications infrastructure or bus 1006.

[0125] In some embodiments, each of the one or more processors 1004 may be a graphics processing unit (GPU). In one embodiment, a GPU is a processor that is a specialized electronic circuit designed to process mathematically intensive applications. A GPU may have a parallel structure that is efficient for parallel processing of large blocks of data, such as mathematically intensive data common in computer graphics applications, images, video, etc.

[0126] In some embodiments, computer system 1000 may further include user input / output devices 1003, such as a monitor, keyboard, pointing device, etc., which communicate with communications infrastructure 1006 via user input / output interface 1002. Computer system 1000 may also include main or primary memory 1008, such as random access memory (RAM). Main memory 1008 may include one or more cache levels. Main memory 1008 stores control logic (i.e., computer software) and / or data.

[0127] In some embodiments, computer system 1000 may further include one or more secondary storage devices or memories 1010. The secondary memory 1010 may include, for example, a hard disk drive 1012 and / or a removable storage device or drive 1014. The removable storage drive 1014 may be a floppy disk drive, a magnetic tape drive, a compact disk drive, an optical storage device, a tape backup device, and / or any other storage device / drive. The removable storage drive 1014 may interface with a removable storage unit 1018. The removable storage unit 1018 may include computer usable or readable storage devices on which computer software (control logic) and / or data are stored. The removable storage unit 1018 may be a floppy disk, magnetic tape, a compact disk, a DVD, an optical storage disk, and / or any other computer data storage device. The removable storage drive 1014 reads from and / or writes to the removable storage unit 1018 in a well-known manner.

[0128] In some embodiments, secondary memory 1010 may comprise other means, devices, or other techniques that allow computer programs and / or other instructions and / or data to be accessed by computer system 1000. Such means, devices, or other techniques may include, for example, a removable storage unit 1022 and interface 1020. Examples of removable storage unit 1022 and interface 1020 may include a program cartridge and cartridge interface (such as those found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and / or any other removable storage unit and associated interface.

[0129] In some embodiments, computer system 1000 may further comprise a communications or network interface 1024. Communications interface 1024 enables computer system 1000 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referred to as 1028). For example, communications interface 1024 may enable computer system 1000 to communicate with remote devices 1028 over communications path 1026, which may be wired and / or wireless and may comprise any combination of a LAN, a WAN, the Internet, etc. Control logic and / or data may be transmitted to and from computer system 1000 over communications path 1026.

[0130] In some embodiments, a non-transitory, tangible device or article of manufacture comprising a non-transitory, tangible, computer-usable or readable medium having control logic (software) stored thereon is also referred to herein as a computer program product or program storage device, including, but not limited to, a tangible article of manufacture embodying computer system 1000, main memory 1008, secondary memory 1010, and removable storage units 1018 and 1022, as well as any combination thereof. Such control logic, when executed by one or more data processing devices (e.g., computer system 1000), causes those data processing devices to operate as described herein.

[0131] Based on the teachings contained herein, it will be apparent to one skilled in the relevant art how to make and use embodiments of the present disclosure using data processing devices, computer systems, and / or computer architectures other than those shown in Figure 9. In particular, embodiments may operate with software, hardware, and / or operating system implementations other than those described herein.

[0132] The embodiments may be further described using the following clauses. (Item 1) joining the first and second layers of the clamp by heating the first and second layers to a holding temperature of at least 700°C; maintaining the first layer and the second layer at the hold temperature for a hold period; cooling the first layer and the second layer at a maximum cooling rate of 20°C / hour during a cooling period after the holding period has elapsed; A method for providing (Item 2) The method according to Item 1, wherein the holding temperature is from about 700°C to about 900°C. (Item 3) The method according to Item 2, wherein the holding temperature is from about 750°C to about 850°C. (Item 4) The method according to Item 3, wherein the holding temperature is about 810°C. (Item 5) The method of item 1, wherein the retention period is at least 5 hours. (Item 6) The method according to Item 5, wherein the retention period is from about 5 hours to about 30 hours. (Item 7) The method of item 1, further comprising heating the first layer and the second layer to a first temperature lower than the holding temperature at a first rate and heating them to the holding temperature at a second rate, wherein the first rate is higher than the second rate. (Item 8) The method of item 1, wherein the first layer and the second layer are heated at a rate of about 2°C / hour to about 60°C / hour. (Item 9) The method described in Item 1, further comprising cooling the first layer and the second layer at a different rate in another cooling period after the cooling period, wherein the cooling rate is lower than the other rate. (Item 10) The method according to Item 1, wherein the cooling rate is from about 5°C / hour to about 20°C / hour. (Item 11) The method of item 1, wherein the cooling period is at least 10 hours. (Item 12) The method according to Item 1, wherein the first layer and the second layer are cooled to a temperature of 700°C or less at the cooling rate. (Item 13) A zipper, an electrostatic clamp coupled to the chuck and configured to releasably hold a patterning device; the electrostatic clamp comprises a first layer and a second layer, the first layer and the second layer being bonded together using a heat treatment comprising heating the first layer and the second layer to a holding temperature of at least 700°C, maintaining the first layer and the second layer at the holding temperature during a holding period, and cooling the first layer and the second layer at a cooling rate of up to 20°C / hr during a cooling period after the holding period; Lithography equipment. (Item 14) A lithographic apparatus according to item 13, wherein the holding temperature is from about 700°C to about 900°C. (Item 15) A lithographic apparatus according to item 14, wherein the holding temperature is from about 750°C to about 850°C. (Item 16) The lithographic apparatus according to item 13, wherein the holding period is at least 5 hours. (Item 17) The lithographic apparatus according to item 16, wherein the holding period is from about 5 hours to about 30 hours. (Item 18) The lithographic apparatus according to item 13, wherein the cooling rate is from about 5°C / hour to about 20°C / hour. (Item 19) The lithographic apparatus according to item 13, wherein the cooling period is at least 10 hours. (Item 20) A first layer and a second layer are provided, the first layer and the second layer are bonded together using a heat treatment; the heat treatment comprises heating the first layer and the second layer to a holding temperature of at least 700°C, maintaining the first layer and the second layer at the holding temperature during a holding period, and cooling the first layer and the second layer at a cooling rate of up to 20°C / hour during a cooling period after the holding period. Clamp.

[0133] Although specific reference is made in this text to the use of electrostatic clamps in lithographic apparatus, it should be understood that the electrostatic clamps described herein may have other applications, such as in mask inspection apparatus, wafer inspection apparatus, aerial image metrology apparatus and more generally in any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices) in vacuum or ambient (non-vacuum) conditions, such as, for example, a plasma etching or deposition apparatus.

[0134] Although specific reference is made herein to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc. Those skilled in the art will understand that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered synonymous with the more general terms “substrate” or “target portion,” respectively. Substrates referred to herein may be processed, before or after exposure, for example, in a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool, and / or an inspection tool. Where applicable, the disclosure herein may apply to such and other substrate processing tools. Furthermore, a substrate may be processed multiple times, for example to create multi-layer ICs, and thus the term substrate, as used herein, may refer to a substrate already including multiple processed layers.

[0135] Although specific reference has been made above to using embodiments of the present disclosure in the context of optical lithography, it will be understood that the present disclosure may be used in other applications, for example imprint lithography, and is not limited to optical lithography where the context allows. In imprint lithography, a shape (topography) of a patterning device defines the pattern formed on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist may be cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is then removed from the resist leaving a pattern behind after the resist is cured.

[0136] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, and therefore should be interpreted by one skilled in the relevant art in light of the teachings herein.

[0137] As used herein, the terms "radiation" and "beam" encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength of 365, 355, 248, 193, 157 or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having a wavelength in the range of 5-20 nm), as well as charged particle beams such as ion beams and electron beams.

[0138] The term "lens", where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

[0139] As used herein, the terms "etching" or "etching" or "etch-back" generally refer to a manufacturing process in which a material is patterned such that at least a portion of the material remains after the etching is complete. For example, the process of etching a material generally involves patterning a masking layer (e.g., photoresist or hard mask) over the material, followed by removing areas of the material that are no longer protected by the mask layer, and optionally removing remaining portions of the mask layer. Typically, the removal step is performed using an "etchant" that is more "selective" to the material than to the mask layer. Thus, areas of the material protected by the mask remain after the etching process is complete. However, the above is for purposes of illustration and not limitation. In another example, etching may refer to a process that does not use a mask, but in which at least a portion of the material remains after the etching process is complete.

[0140] The above explanation is intended to distinguish between the terms "etching" and "removing." In certain embodiments, when etching a material, at least a portion of the material remains after the process is completed. In contrast, when removing a material, substantially all of the material is removed in the process. However, in other embodiments, "removing" may include etching.

[0141] As used herein, the terms "depositing" or "disposing" refer to the act of applying a layer of material to a substrate. These terms are meant to refer to any possible layer formation technique, including, but not limited to, thermal growth, sputtering, evaporation, chemical vapor deposition, epitaxial growth, atomic layer deposition, electroplating, etc.

[0142] As used herein, the term "substrate" refers to a material onto which subsequent layers of material are added. In embodiments, the substrate itself may be patterned, or the material added onto the substrate may also be patterned or may remain unpatterned.

[0143] As used herein, the terms "substantial" or "substantially in contact" generally refer to elements or structures in substantial physical contact with one another, typically with only a small amount of separation due to manufacturing and / or misalignment tolerances. It should be understood that any relative spatial descriptions between one or more particular features, structures, or characteristics used herein (e.g., "vertically aligned," "substantially in contact," etc.) are for illustrative purposes only, and that actual implementations of the structures described herein may include manufacturing and / or misalignment tolerances without departing from the spirit and scope of the present disclosure.

[0144] While specific embodiments of the present disclosure have been described above, it will be understood that the embodiments of the present disclosure may be practiced otherwise than as described. The description is for purposes of illustration and not limitation. Thus, it will be apparent to those skilled in the art that modifications may be made to the described embodiments without departing from the scope of the claims set forth below.

[0145] It is noted that the intention is to use the Detailed Description, rather than the Summary and Abstract, to interpret the claims. While the Summary and Abstract may describe one or more exemplary embodiments of the disclosure as contemplated by the inventors, they are not exhaustive and are not intended to limit the disclosure and the appended claims in any way.

[0146] The present disclosure has been described above using functional blocks that illustrate implementation of specific functions and relationships thereof. The boundaries of these functional blocks are arbitrarily defined herein for the convenience of description. Alternative boundaries may be defined as long as the specific functions and relationships thereof are appropriately performed.

[0147] The foregoing descriptions of specific embodiments fully demonstrate the general nature of the present disclosure, and those skilled in the art can, by applying their knowledge in the art, readily modify and / or adapt such specific embodiments for various applications without undue experimentation and without departing from the general concepts of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0148] The breadth and scope of protected subject matter should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. bonding the first and second layers of the clamp by heating the first and second layers to a holding temperature of at least 700°C; maintaining the first layer and the second layer at the hold temperature for a hold period; cooling the first layer and the second layer at a maximum cooling rate of 20°C / hour during a cooling period after the holding period has elapsed; A method for providing the above.

2. The holding temperature is from about 700°C to about 900°C. The method of claim 1.

3. The holding temperature is about 750°C to about 850°C. The method of claim 2.

4. The holding temperature is about 810°C. The method of claim 3.

5. The holding period is at least 5 hours. The method of claim 1.

6. The holding period is from about 5 hours to about 30 hours. The method of claim 5.

7. heating the first layer and the second layer at a first rate to a first temperature that is lower than the holding temperature, and heating the first layer and the second layer at a second rate to the holding temperature, the first rate being higher than the second rate; The method of claim 1.

8. the first layer and the second layer are heated at a rate of about 2° C. / hour to about 60° C. / hour; The method of claim 1.

9. further comprising cooling the first layer and the second layer at a different rate in another cooling period after the cooling period, the cooling rate being lower than the other rate. The method of claim 1.

10. The cooling rate is from about 5°C / hour to about 20°C / hour. The method of claim 1.

11. The cooling period is at least 10 hours. The method of claim 1.

12. the first layer and the second layer are cooled at the cooling rate to a temperature of 700°C or less; The method of claim 1.

13. Chuck and an electrostatic clamp coupled to the chuck and configured to releasably hold a patterning device; the electrostatic clamp comprises a first layer and a second layer, the first layer and the second layer being bonded together using a heat treatment comprising: heating the first layer and the second layer to a holding temperature of at least 700°C; maintaining the first layer and the second layer at the holding temperature during a holding period; and cooling the first layer and the second layer at a cooling rate of up to 20°C / hr during a cooling period after the holding period. Lithography equipment.

14. The holding temperature is from about 700°C to about 900°C. The lithographic apparatus of claim 13.

15. The holding temperature is about 750°C to about 850°C. The lithographic apparatus of claim 14.

16. The holding period is at least 5 hours. The lithographic apparatus of claim 13.

17. The holding period is from about 5 hours to about 30 hours.

17. A lithographic apparatus according to claim 16.

18. The cooling rate is from about 5°C / hour to about 20°C / hour. The lithographic apparatus of claim 13.

19. The cooling period is at least 10 hours. The lithographic apparatus of claim 13.

20. comprising a first layer and a second layer; the first layer and the second layer are bonded together using a heat treatment; the heat treatment comprises heating the first layer and the second layer to a holding temperature of at least 700°C, maintaining the first layer and the second layer at the holding temperature during a holding period, and cooling the first layer and the second layer at a cooling rate of up to 20°C / hour during a cooling period after the holding period. Clamp.

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