Clamp and manufacturing method thereof

Abstract

A method includes bonding a first layer and a second layer of a jig by heating the first layer and the second layer to a holding temperature of at least 700 DEG C; maintaining the first layer and the second layer at the holding temperature during a holding time period; and cooling the first layer and the second layer at a cooling rate of at most 20 DEG C / hour for a cooling time period after the hold time has elapsed.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Application No. 63 / 432,112, filed on December 13, 2022, the entire disclosure of which is incorporated herein by reference. Technical field

[0002] The present disclosure relates to a fixture for supporting an object (e.g., a patterning device and / or a substrate) in a lithographic apparatus and a method of manufacturing the same. Background art

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. A lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device (which may alternatively be referred to as a mask or a reticle) may be used to generate a circuit pattern corresponding to an individual layer of the IC, and this pattern may be imaged onto a target portion (e.g., including a part of a die, one or several dies) of a substrate (e.g., a silicon wafer) having a layer of radiation-sensitive material (resist). Generally, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatuses include: so-called steppers, in which each target portion is irradiated by exposing the entire pattern at once onto the target portion; and so-called scanners, in which each target portion is irradiated by scanning the pattern through a beam in a given direction ("scan" direction) while synchronously scanning the substrate 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 regarded as one of the key steps in the manufacture of ICs and other devices and / or structures. However, as the dimensions of the features fabricated using lithography become smaller, lithography is becoming an even more critical factor in being able to fabricate micro-ICs or other devices and / or structures.

[0005] The theoretical estimate of the pattern printing limit can be given by the Rayleigh criterion for resolution as shown in Equation (1): (1) where λ is the wavelength of the radiation used, NA is the numerical aperture of the projection system used to print the pattern, k1 is a process-dependent adjustment factor, also known as the Rayleigh constant, and CD is the feature size (or critical dimension) of the printed feature. It can be seen from Equation (1) that a reduction in the minimum printable size of a feature can be obtained in three ways: by shortening the exposure wavelength λ, by increasing the numerical aperture NA, or by decreasing the value of k1.

[0006] To shorten the exposure wavelength and thus reduce the minimum printable size, the use of an extreme ultraviolet (EUV) radiation source has been proposed. EUV radiation is electromagnetic radiation having a wavelength in the range of 5 nm to 20 nm, for example, in the range of 13 nm to 14 nm, for example, in the range of 5 nm to 10 nm, such as 6.7 nm or 6.8 nm. Possible sources include, for example, laser-produced plasma sources, discharge plasma sources, or sources based on synchrotron radiation provided by an electron storage ring.

[0007] However, the radiation produced by such a source will not be only EUV radiation, and the source can also emit at other wavelengths including infrared (IR) radiation and deep ultraviolet (DUV) radiation. DUV radiation can be harmful to a lithography system because it can cause a loss of contrast. In addition, unwanted IR radiation can cause thermal damage to components within the system. Therefore, it is known to use a spectral purity filter to increase the proportion of EUV in the transmitted radiation and reduce or even eliminate unwanted non-EUV radiation, such as DUV and IR radiation.

[0008] A lithography apparatus using EUV radiation may require that the EUV radiation beam path or at least a substantial part thereof must be maintained in a vacuum during a lithography operation. In such a vacuum region of the lithography apparatus, an electrostatic chuck can be used to clamp an object (e.g., a patterning device and / or a substrate) to a structure of the lithography apparatus (e.g., a patterning device table and / or a substrate table), respectively.

[0009] In addition, a lithography apparatus using EUV radiation may require, for example, temperature regulation of the patterning device and / or the substrate. Due to the heat absorbed by the patterning device and / or the substrate, the heat generated by EUV radiation or unwanted non-EUV radiation may cause, for example, deformation in the patterning device and / or the substrate during a lithography operation. To reduce the deformation, a coolant can be circulated through the electrostatic chuck. However, an electrostatic chuck configured to circulate the coolant may generate stress in the chuck structure. This stress can be transmitted to the object clamped to the electrostatic chuck (e.g., a patterning device, a substrate), thereby causing deformation in the clamped object. SUMMARY OF THE INVENTION

[0010] Accordingly, there is a need for an electrostatic chuck that can be configured to firmly hold an object and prevent thermally induced and stress-induced deformation in the clamped object.

[0011] According to an embodiment, a method is provided. The method includes: bonding the first layer and the second layer of the fixture by 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 time period; and cooling the first layer and the second layer at a maximum cooling rate of 20°C per hour after the holding time has elapsed for a cooling time period.

[0012] In another embodiment, a lithographic apparatus is provided. The lithographic apparatus includes a chuck and an electrostatic chuck, the electrostatic chuck being coupled to the chuck and configured to releasably hold a patterning device. The electrostatic chuck includes 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 holding temperature of up to at least 700°C; maintaining the first layer and the second layer at the holding temperature during a holding time period; and cooling the first layer and the second layer at a maximum cooling rate of 20°C per hour after the holding time period has elapsed for a cooling time period.

[0013] In yet another embodiment, a fixture is provided. The fixture 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 holding temperature of up to at least 700°C; maintaining the first layer and the second layer at the holding temperature during a holding time period; and cooling the first layer and the second layer at a maximum cooling rate of 20°C per hour after the holding time has elapsed for a cooling time period.

[0014] Other features of the present disclosure and the structures and operations of various embodiments are described in detail below with reference to the accompanying drawings. Note that the present disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein only for illustrative purposes. Based on the teachings contained herein, additional embodiments will be apparent to those skilled in the relevant art(s). Description of the Drawings

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

[0016] Figure 1A A schematic diagram of a reflective lithographic apparatus is shown in accordance with some aspects of the present disclosure.

[0017] Figure 1B A schematic diagram of a transmissive lithographic apparatus is shown in accordance with some aspects of the present disclosure.

[0018] Figure 2 Shows a more detailed schematic illustration of a reflective lithography apparatus according to some aspects of the present disclosure.

[0019] Figure 3 Shows a schematic illustration of a lithography unit according to some aspects of the present disclosure.

[0020] Figure 4 Is a schematic illustration of a cross-sectional view of an electrostatic chuck according to some aspects of the present disclosure.

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

[0022] Figures 6A to 6N Is a schematic illustration of a cross-sectional view of an electrostatic chuck at a selection stage of its manufacturing process according to some aspects of the present disclosure.

[0023] Figure 7 Is a schematic illustration of a cross-sectional view of an electrostatic chuck during coupling with a chuck according to some aspects of the present disclosure.

[0024] Figure 8 Is a flowchart of a manufacturing process of an electrostatic chuck according to some aspects of the present disclosure.

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

[0026] Figure 10 Is a schematic illustration of a computer system according to some aspects of the present disclosure.

[0027] When taken in conjunction with the accompanying drawings, the features of the present disclosure will become more apparent in accordance with the detailed description set forth below, wherein like reference numerals identify corresponding elements throughout. In the drawings, like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost digit(s) of a reference numeral identify the drawing in which the reference numeral first appears. Unless otherwise indicated, the drawings provided throughout the present disclosure should not be construed as being drawn to scale. Detailed Description

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

[0029] The described embodiments and references in the specification to "one embodiment", "an embodiment", "exemplary embodiment", etc., indicate that the described embodiments may include certain features, structures, or characteristics, but each embodiment may not necessarily include the particular features, structures, or characteristics. Further, such phrases do not necessarily refer to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that implementing such feature, structure, or characteristic in connection with other embodiments is within the knowledge of those skilled in the art, whether or not explicitly described.

[0030] To facilitate the description in the specification of the relationship of one element or feature illustrated in the figures to another element or feature(s), spatially relative terms (such as "below", "beneath", "lower", "above", "on", "upper", and the like) may be used herein. In addition to the orientation depicted in the figures, spatially relative terms are intended to encompass different orientations of the device in use or operation. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may be interpreted accordingly.

[0031] As used herein, the term "about" indicates a given value that may vary based on a particular technology. Based on the particular technology, the term "about" may indicate a given value that varies within, for example, 10% to 30% of the value (such as ±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, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). By way of example, a machine-readable medium may include: read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (such as carrier waves, infrared signals, digital signals, etc.) and others. Further, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such description is merely for convenience, and such actions are actually caused by a computing device, processor, controller, or other device that executes the firmware, software, routines, instructions, etc.

[0033] However, prior to describing such embodiments in more detail, it is beneficial to present an exemplary environment in which embodiments of the present disclosure may be implemented.

[0034] Exemplary lithography system

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

[0036] The illumination system IL may include various types of optical components, e.g., 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 depending 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 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 a frame or a table, e.g., which may be fixed or movable as required. By using sensors, the support structure MT can ensure that the patterning device MA is, e.g., in a desired position relative to the projection system PS.

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

[0039] The term "inspection device", "measurement system" or the like may be used herein to refer to, for example, a device or system for measuring properties of a structure (e.g., overlay error, critical dimension parameters) or for inspecting alignment in a lithographic apparatus (e.g., an alignment device) of a wafer.

[0040] The patterning device MA may be transmissive (as in the Figure 1B lithographic apparatus 100') or reflective (as in the Figure 1A lithographic apparatus 100). Examples of patterning devices MA include a reticle, a mask, a programmable mirror array or a programmable LCD panel. Masks are well known in lithography and include, for example, binary, alternating phase-shift or attenuated phase-shift mask types 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 tilted individually so as to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B which is reflected by the matrix of small mirrors.

[0041] The term "projection system" PS can encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems or any combination thereof, depending on the type of exposure radiation used or other factors (e.g., use of an immersion liquid on the substrate W or use of a vacuum). A vacuum environment may be used for EUV or electron beam radiation because other gases may absorb too much of the radiation or electrons. Thus, a vacuum environment can be provided to the entire beam path by means of a vacuum wall and a vacuum pump.

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

[0043] The lithographic apparatus may also be of the type in which at least a portion of the substrate can be covered by a liquid having a relatively high refractive index (e.g., water) so as to fill the space between the projection system and the substrate. The immersion liquid 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 the projection system. As used herein, the term "immersion" does not mean, for example, that the structure of the substrate must be immersed in the liquid, but only that the liquid is located between the projection system and the substrate during exposure.

[0044] Referring to Figure 1A and Figure 1B, the illuminator IL receives a radiation beam from a radiation source SO. For example, when the source SO is an excimer laser, the source SO and the lithographic apparatus 100, 100' can be separate physical entities. In such a case, the source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam B is delivered from the source SO to the illuminator IL by means of a beam delivery system BD (in Figure 1B ), which includes, for example, suitable directing mirrors and / or beam expanders. In other cases, for example, when the source SO is a mercury lamp, the source SO can be an integral part of the lithographic apparatus 100, 100'. If desired, the source SO and the illuminator IL together with the beam delivery system BD can be referred to as a radiation system.

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

[0046] Reference Figure 1A , the radiation beam B is incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a mask table) MT and is patterned by the patterning device MA. In the lithographic apparatus 100, the radiation beam B is reflected from the patterning device (e.g., a mask) MA. After reflection from the patterning device (e.g., a mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. By means of a second positioner PW and a position sensor IF2 (e.g., an interferometric device, a linear encoder, or a capacitive sensor), the substrate table WT can be accurately 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 can be used to accurately position the patterning device (e.g., a mask) MA relative to the path of the radiation beam B. The patterning device (e.g., a mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0047] Reference Figure 1B, a radiation beam B is incident on a patterning device (e.g., a mask MA) held on a support structure (e.g., a mask table MT) and is patterned by the patterning device. After traversing 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 conjugate PPU to an illumination system pupil IPU. Multiple portions of the radiation emanate from the intensity distribution at the illumination system pupil IPU, traverse the mask pattern without being affected by diffraction at the mask pattern, and create an image of the intensity distribution at the illumination system pupil IPU.

[0048] The projection system PS projects an image of the mask pattern MP onto a photoresist layer coated on the substrate W, where the image is formed by diffracted beams generated from the fiducial pattern MP by radiation from the intensity distribution. For example, the mask pattern MP may include an array of lines and spaces. Diffraction of the radiation at the array and different from the zero-order diffraction generates steering diffracted beams having a direction change in a direction perpendicular to the lines. The non-diffracted beam (i.e., the so-called zero-order diffracted beam) traverses the pattern without any change in the propagation direction. The zero-order diffracted beam traverses an upper lens or upper lens group of the projection system PS upstream of the pupil conjugate PPU of the projection system PS to reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zero-order diffracted beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. For example, an aperture device PD is disposed or substantially disposed at the plane including the pupil conjugate PPU of the projection system PS.

[0049] The projection system PS is arranged to capture not only the zero-order diffracted beam but also the first-order or first-order and 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 lines can be used to utilize the resolution enhancement effect of dipole illumination. For example, the first-order diffracted beam interferes with the corresponding zero-order diffracted beam at the level of the wafer W to produce an image of the line pattern MP at the highest possible resolution and process window (i.e., the available depth of focus combined with the tolerable exposure dose deviation). In some embodiments, astigmatism can be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. Additionally, in some embodiments, astigmatism can be reduced by blocking the zero-order beam in the pupil conjugate PPU of the projection system associated with the radiation poles in the opposite quadrants. This is described in more detail in US7,511,799B2 issued on March 31, 2009, which is incorporated herein by reference in its entirety.

[0050] With the aid of a second locator PW and a position sensor IFD (for example, an interferometric device, a linear encoder or a capacitive sensor), the substrate table WT can be accurately moved (for example, in order to position different target portions C in the path of the radiation beam B). Similarly, a first locator PM and another position sensor ( Figure 1B not shown in the figure) can be used to accurately position the mask MA relative to the path of the radiation beam B (for example, after mechanical retrieval from a mask library or during scanning).

[0051] Generally, the movement of the mask table MT can be achieved by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming part of the first locator PM. Similarly, the movement of the substrate table WT can be achieved using a long-stroke module and a short-stroke module forming part of the second locator PW. In the case of a stepper (as opposed to a scanner), the mask table MT can be connected only to a short-stroke actuator or can be fixed. The mask MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they can be located in the spaces between the target portions (referred to as scribe alignment marks). Similarly, in the case where more than one die is provided on the mask MA, the mask alignment marks can be located between the dies.

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

[0053] The lithographic apparatuses 100 and 100’ can be used in at least one of the following modes:

[0054] 1. In the step mode, the support structure (for example, the mask table) MT and the substrate table WT remain substantially stationary while the entire pattern imparted to the radiation beam B is projected onto the target portion C in one go (i.e., a single static exposure). The substrate table WT is then displaced in the X and / or Y direction so that different target portions C can be exposed.

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

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

[0057] Combinations and / or variations of the described usage modes and / or completely different usage modes can also be employed.

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

[0059] Figure 2 The lithographic apparatus 100 including a source collector apparatus SO, an illumination system IL, and a projection system PS is shown in more detail. The source collector apparatus SO is constructed and arranged such that a vacuum environment can be maintained in the enclosure structure 220 of the source collector apparatus SO. The EUV radiation emitting plasma 210 can be formed by a plasma source generated by a discharge. The EUV radiation can be generated from a gas or vapor (e.g., Xe gas, Li vapor, or Sn vapor), in which a very hot plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is generated by a discharge that causes at least partial ionization of the plasma, for example. To generate radiation effectively, 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, a plasma of excited tin (Sn) is provided to generate EUV radiation.

[0060] Radiation emitted by the hot plasma 210 is transferred from the source chamber 211 to the collector chamber 212 via a selected gas barrier or contaminant trap 230 (also referred to in some cases as a contaminant barrier or foil trap), which is positioned in or after an opening in the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further indicated herein includes at least a channel structure.

[0061] The 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 traversing the collector CO may be reflected from the grating spectral filter 240 to be focused in the virtual source point INTF. The virtual source point INTF is generally referred to as the intermediate focus, and the source collector device is arranged such that the intermediate focus INTF is located at or near the opening 219 in the enclosed structure 220. The virtual source point INTF is an image of the radiation-emitting plasma 210. The grating spectral filter 240 is specifically used to suppress infrared (IR) radiation.

[0062] Subsequently, the radiation traverses the 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 a desired uniformity of the radiation intensity at the patterning device MA. When the radiation beam 221 is reflected at the patterning device MA held by the support structure MT, a patterned beam 226 is formed, and the patterned beam 226 is imaged by the projection system PS via reflective elements 228, 229 onto a substrate W held by a wafer stage or a substrate stage WT.

[0063] There may generally be more elements in the illumination optics unit IL and the projection system PS than shown. Depending on the type of lithographic apparatus, the grating spectral filter 240 may optionally be present. In addition, there may be more mirrors than those Figure 2 shown, and for example, there may be one to six additional reflective elements in the projection system PS than those Figure 2 shown.

[0064] As Figure 2As illustrated, collector optics CO is depicted as a nested collector having grazing-incidence reflectors 253, 254, and 255, merely as an example of a collector (or collector mirror). The grazing-incidence reflectors 253, 254, and 255 are arranged axially symmetrically about the optical axis O, and this type of collector optics CO is preferably used in combination with a discharge-produced plasma source (commonly referred to as a DPP source).

[0065] Exemplary lithography cell

[0066] Figure 3 There is shown a lithography cell 300, sometimes also referred to as a lithography cell or cluster, according to some embodiments. A lithographic apparatus 100 or 100' may form part of the lithography cell 300. The lithography cell 300 may also include one or more apparatuses for performing pre-exposure and post-exposure processes on a substrate. Conventionally, these include a spin coater SC for depositing a resist layer, a developer DE for developing the 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 them between different processing apparatuses, and delivers them to the load port LB of the lithographic apparatus 100 or 100'. These apparatuses, commonly referred to as a track, are controlled by a track control unit TCU, which itself is controlled by a supervisory control system SCS, which also controls the lithographic apparatus via a lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0067] Exemplary embodiment of an electrostatic chuck

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

[0069] According to an embodiment, the electrostatic chuck 400 may include a multi-layer structure including a first layer 402 having opposite and parallel surfaces 402a and 402b, a second layer 404 having opposite and parallel surfaces 404a and 404b, and a third layer 406 having opposite and parallel surfaces 406a and 406b. According to an example of this embodiment, the first layer 402, the second layer 404, and the third layer 406 may have vertical dimensions in the ranges of about 1 mm to 4 mm, 1 mm to 4 mm, and 50 microns to 200 microns, respectively. The first layer 402 may be coupled to the second layer 404, where surface 402a is substantially in contact with surface 404b, and the third layer 406 may be coupled to the second layer 404, where surface 404a faces surface 406b. The surface 406a of the third layer 406 may define a clamping surface 406a of the electrostatic chuck 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 to the electrostatic chuck 400. The object 407 may be clamped to be substantially in contact with the clamping surface 406a. Optionally, the clamping surface 406a may include protrusions 405 configured to contact the object 407 during a clamping operation. The protrusions 405 may help provide less contaminated contact between the object 407 and the clamping surface 406a because less contaminants are likely to be on the smaller surface area of the protrusions 405 compared to the larger surface area of the clamping surface 406a.

[0070] In an embodiment, the first layer 402, the second layer 404, and the third layer 406 may include different materials from each other. In another embodiment, the first layer 402, the second layer 404, and the third layer 406 may be made of one or more dielectric materials configured to support an electrostatic field during operation of the electrostatic chuck 400, as further explained below. The dielectric material may have an ultra-low coefficient of thermal expansion that may be equal to or substantially zero, such as, but not limited to, an ultra-low expansion silicon-based material (e.g., ULE manufactured by Corning ® ), a glass material, a ceramic material, a silicon-based glass-ceramic material (e.g., ZERODUR manufactured by SCHOTT ® ), or a combination thereof. Any of these ultra-low expansion thermal materials may help reduce thermal stress in the structure of the electrostatic chuck 400 during manufacturing. Thermal stress in the electrostatic chuck 400, if not reduced, may cause one or more unwanted deformations in the first layer 402, the second layer 404, and / or the third layer 406, which may be transferred to the object 407 during a clamping operation.

[0071] In another embodiment, the first layer 402 and / or the second layer 404 can be made of one or more non-dielectric insulating materials having an ultra-low coefficient of thermal expansion.

[0072] In yet another embodiment, the first layer 402, the second layer 404, and the third layer 406 can be made of the same one or more ultra-low thermal expansion dielectric materials. Fabricating all three layers of the electrostatic chuck 400 from similar materials can help further reduce the thermal stress caused by the thermal expansion mismatch between different materials. In an example of this embodiment, the first layer 402, the second layer 404, and the third layer 406 can be made of ULE ® material, and the ULE ® material provides higher electrical stability than ZERODUR ® material.

[0073] As Figure 4 illustrated, according to an embodiment, the electrostatic chuck 400 further includes a composite layer 408 interposed between the second layer 404 and the third layer 406. In an example of this embodiment, the composite layer 408 can have a vertical dimension in the range of about 50 nm to 400 nm. The composite layer 408 includes conductive regions 410 and insulating regions 412 (also referred to herein as layers) arranged in an alternating configuration. One of the conductive regions 410 is electrically insulated from another conductive region through one of the insulating regions 412. Although Figure 4 only two conductive regions are illustrated, it should be understood that in other modifications of the present disclosure, the composite layer 408 can include a single or more than two conductive layers. In an embodiment, the conductive regions 410 and the insulating regions 412 are coplanar.

[0074] In various examples of this embodiment, any suitable conductive material (such as but not limited to aluminum, chromium, platinum, gold, or a combination thereof) can be used to form the conductive regions 410, and any suitable insulating material (such as silicon oxide or other insulating metal oxides) can be used to form the insulating regions 412. In another example, the conductive regions 410 can include a single metal layer, multiple identical metal layers, or multiple different metal layers.

[0075] According to an exemplary embodiment, the conductive regions 410 can be configured as electrodes 410 to generate an electrostatic field within the third layer 406 for clamping an object 407 to the clamping surface 406a. The electrostatic field can be generated by providing a clamping voltage to the electrodes 410. The clamping voltage can induce surface image charges on the conductive surface 407a of the object 407 to electrostatically attract and clamp the object 407 to the clamping surface 406a.

[0076] According to an embodiment, the electrostatic chuck 400 can alternatively include an intermediate layer 414 interposed between the composite layer 408 and the second layer 404, asFigure 4 as illustrated. The 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 the composite layer 414 to the second layer 404. In an example of this embodiment, the intermediate layer 414 may have a vertical dimension of from about 10 nm to 200 nm. Alternatively, the intermediate layer 414 may be interposed between the composite layer 408 and the third layer 406, as discussed in further detail below with reference to Figures 6J to 6K discussed further.

[0077] In another embodiment, the electrostatic chuck 400 includes a fluid channel 416, as Figure 4 illustrated. The fluid channel 416 may be configured to extend parallel to the surface 402a and carry a heat-regulating fluid (e.g., a liquid or a gas), such as but not limited to water, air, alcohol, glycol, or a phase-change coolant (e.g., Freon, carbon dioxide). A fluid regulation system 418 coupled to the electrostatic chuck 400 may be configured to regulate the heat-regulating fluid to a desired temperature before it enters the fluid channel 416 and circulate it through the electrostatic chuck 400. The circulating heat-regulating fluid may help regulate the temperature of the electrostatic chuck 400 to a desired temperature. The temperature regulation of the electrostatic chuck 400 may include absorbing unwanted heat from the electrostatic chuck 400 by the heat-regulating fluid. This unwanted heat may be transferred from the object 407 in the clamped state to the electrostatic chuck 400 through the clamping surface 406a and / or the protrusions.

[0078] In an example of this embodiment, the object 407 may be a patterning device, and the unwanted heat may be transferred from it, for example, during the operation of an illumination system and / or other systems of the lithographic apparatus 100. The presence of unwanted heat in the patterning device may cause deformation of the patterning device, which may lead to errors in the pattern transferred from the patterning device to the substrate. To prevent such deformation, according to various embodiments, the temperature of the patterning device may be maintained at substantially room temperature (about 22 degrees Celsius) or any other defined operating temperature. As discussed above, such temperature regulation of the patterning device may include transferring heat from the patterning device (e.g., through the clamping surface 406a, the protrusions 416) to the electrostatic chuck 400, and thereby reducing or eliminating thermally induced deformation of the patterning device.

[0079] Figure 5FIG. illustrates a schematic cross-sectional view of an electrostatic chuck 500 coupled to a chuck 520 according to an embodiment. According to an example of this embodiment, the electrostatic chuck 500 and the chuck 520 may be implemented as part of a lithographic apparatus 100. In an exemplary embodiment, the chuck 520 may be configured to couple the electrostatic chuck 500 to a substrate table WT and / or a support structure MA. Except for the differences described below, the electrostatic chuck 500 may be structurally and functionally similar to the electrostatic chuck 400. The fluid channel 522 may be configured to extend parallel to the surface 520a and carry a heat-regulating fluid as the fluid channel 416. A fluid regulating system 518 coupled to the chuck 520 may be configured to regulate the heat-regulating fluid to a desired temperature before it enters the fluid channel 522 and circulate it through the electrostatic chuck 500 and the chuck 504. The circulating heat-regulating fluid may help regulate the temperature of the electrostatic chuck 500 and the chuck 520 to a desired temperature. The temperature regulation of the electrostatic chuck 500 and the chuck 520 may include absorbing unwanted heat from the electrostatic chuck 500 and the chuck 520 by the heat-regulating fluid. As described above, the unwanted heat in the electrostatic chuck 500 may be transferred from the object 407, and the unwanted heat in the chuck 520 may be transferred from the electrostatic chuck 500 and / or other parts of the lithographic apparatus 100 coupled to the chuck 520.

[0080] Exemplary method for manufacturing an electrostatic chuck

[0081] Figures 6A to 6N FIG. illustrates a cross-sectional view of an electrostatic chuck 400 (as Figure 4 shown) at a selected stage in its manufacturing process.

[0082] Figures 6A to 6B FIG. illustrates a cross-sectional view of an electrostatic chuck 400 partially formed during the formation of a fluid channel 416 (as described above with reference to Figures 4 to 5 ). The formation of the fluid channel 416 may include forming a trench 630 (as Figure 6A shown) on the surface 402a of a first layer 402 and forming a stacked structure 632 (as Figure 6B shown).

[0083] According to an embodiment, the formation of the trench 630 may include polishing, machining, and etching of the surface 402a. The polishing of the surface 402a may be performed using any suitable polishing process (e.g., but not limited to a cerium oxide slurry polishing process) to obtain a smooth surface with a root mean square (RMS) roughness of about 0.5 mm or less. After polishing, the surface 402a may be machined using standard glass machining techniques and / or patterned and etched using standard lithography and glass etching processes to form the trench 630 (as Figure 6A shown). It should be noted that, asFigure 6A As illustrated, the rectangular cross-sectional shape of the groove 630 is for illustrative purposes and not restrictive. According to various embodiments, without departing from the spirit and scope of the present disclosure, the groove 630 may have other cross-sectional shapes (e.g., conical, trapezoidal). After machining, an acid etch can be performed on the machined surface 402a using an acid mixture including, for example, hydrofluoric acid. The acid etch can remove a layer 402 material of a few micrometers (e.g., about 5 micrometers) from the machined surface 402a. This removal of material from the machined surface 402a can help relieve stress that may be induced in the layer 402 by the machining process. The stress may be due to small deformations on the surface 402a caused by the physical forces of machining.

[0084] According to an embodiment, the acid etch process may subsequently bond the layer 402 to a second layer 404 to form a stacked structure 632, as Figure 6B illustrated. The bonding process may include polishing the surface 604b, cleaning the surfaces 402a and 404b, and subsequently directly bonding the first layer 402 to the second layer 404. The surface 404b can be polished to a root mean square (RMS) roughness of about 0.5 mm or less using any suitable polishing process (e.g., but not limited to a cerium oxide slurry polishing process). After machining the groove 630, the surface 402a can be ground and polished. Subsequently, the first layer 402 can be directly bonded to the second layer 404 to form the stacked structure 632 by pressing the surface 402a against the surface 404b under a pressure suitable for the layer materials used. Optionally, the stacked structure 632 can be annealed at a temperature in the range of about 350 degrees Celsius (°C) to 900 degrees Celsius (°C) to strengthen the direct bonding interface between the first layer 402 and the second layer 404. In some aspects, the bonding methods described later herein can be applied.

[0085] According to an embodiment, the direct bonding herein can refer to optical contact bonding, which is a bonding between substantially defect-free and highly polished surfaces (e.g., surfaces 402a and 404b) without using any bonding materials, such as epoxy resin or any other adhesive material. Optical contact bonding can be produced by attractive intermolecular electrostatic interactions, such as van der Waals forces between the bonding surfaces (e.g., surfaces 402a and 404b). Annealing the optical contact bonding (as described above) can transform, for example, the van der Waals bonds between the bonding surfaces into stronger covalent bonds and thereby strengthen the optical contact bonding structure.

[0086] According to an embodiment, forming the fluid channel 416 may subsequently involve thinning the layer 404 to approximately 2 mm. Any suitable polishing and / or grinding techniques can be used to polish the surface 404b to thin the second layer 404. Alternatively, the thinning process of the second layer 404 can be performed by polishing the surface 404a and / or the surface 404b before forming the fluid channel 416.

[0087] Figures 6C to 6D A cross-sectional view of an electrostatic chuck 400 partially formed during the formation of the conductive region 410 according to an embodiment is illustrated. The formation of the conductive region 410 can include, for example, depositing one or more metal layers 610 on the third layer 406, as Figure 6C shown. This metal deposition may subsequently be followed by patterning and etching processes to define the conductive region 410, as Figure 6D shown. The deposition of the layer 610 can 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 can be performed by conventional lithography processes, and the etching process can be performed by wet etching methods or dry etching methods (such as, but not limited to, reactive ion etching (RIE)).

[0088] Figures 6E to 6F A cross-sectional view of an electrostatic chuck 400 partially formed during the formation of the insulating region 412 according to an embodiment is illustrated. The conductive region 410 can be covered with photoresist, and a dielectric can be deposited, and the insulating region can be deposited coplanarly with the top of the conductive region 410. In some aspects, the photoresist is subsequently removed using a suitable organic solvent or the photoresist is digested using a strong oxidizing agent. In some embodiments, other techniques known in the art can be used to form the insulating region.

[0089] Figures 6G to 6H A cross-sectional view of an electrostatic chuck 400 partially formed during the bonding of the composite layer 408 to the stacked structure 632 (as described with reference to Figure 6B is illustrated. The bonding process can include depositing an intermediate layer 414 on the composite layer 408, as Figure 6G shown. The intermediate layer 414 can help provide a bonding surface 414a for the composite layer 408 that is compatible with direct bonding to the surface 404a. Any suitable method for depositing, for example, silicon oxide (such as a CVD process) can be used to deposit the intermediate layer 414. The bonding process can further include pressing the Figure 6G combined structure against the stacked structure 632 to bond the surface 414a to the surface 404a, as Figure 6HAs shown. To strengthen the bonding interface between surface 414a and surface 304a, the bonding structure can be annealed at a temperature in the range of about 350°C to 900°C.

[0090] Optionally, according to an embodiment, the bonding process can be followed by a process of thinning the third layer 406 to a vertical dimension in the range of about 50 microns to 200 microns. Any suitable polishing and / or grinding techniques can be used to polish surface 406a to thin layer 406. Alternatively, the thinning process of the third layer 406 can be performed by polishing surface 406a and / or surface 406b before forming the composite layer 408.

[0091] Figures 6I to 6J Illustrated is a cross-sectional view of the electrostatic chuck 400 during the formation of the protrusion 405 on the clamping surface 406a according to an embodiment. The protrusion 405 can be formed by depositing, for example, a polymer layer 605, as Figure 6I shown. This deposition can be followed by patterning and etching the polymer layer 605 to define the protrusion 405, as Figure 6J shown. The patterning and etching processes can be performed by the methods mentioned above. It should be noted that the rectangular cross-sectional shape of the protrusion 405 is for illustrative purposes and not restrictive. According to various embodiments, the protrusion 405 can have other cross-sectional shapes (e.g., spherical, conical, trapezoidal).

[0092] According to an embodiment, in an alternative method, a composite layer 408 and an intermediate layer 414 can be formed on the surface 404a of the stacked structure 632, as Figure 6K illustrated. The third layer 406 can be directly bonded to the intermediate layer 414 and thinned to a vertical dimension in the range of about 50 microns to 200 microns, as Figure 6L shown. The direct bonding and thinning can be performed by the methods mentioned above.

[0093] As Figure 6M illustrated, according to an embodiment, in another alternative method, a first portion 608a and a second portion 608b of the composite layer 408 can be formed on the surface 406b and the surface 404a, respectively. The first portion 608a and the second portion 608b can be heat-fused together to form the composite layer 408, as Figure 6N shown.

[0094] Exemplary method for coupling an electrostatic chuck to a chuck

[0095] Figure 7 Illustrated is a cross-sectional view of the electrostatic chuck 400 during the connection of the electrostatic chuck 400 to the chuck 720. The chuck 720 can be structurally and functionally similar to the chuck 520, as previously referenced Figure 5As described. In an embodiment, the joining process can include polishing and cleaning surfaces 402b and 720a, followed by directly bonding these surfaces. Any suitable polishing process (e.g., but not limited to cerium oxide slurry polishing process) can be used to polish surfaces 402b and 720a to a root mean square (RMS) roughness of about 0.5 mm or less. Subsequently, surfaces 402b and 720a can be pressed together to form a direct bond between surfaces 402b and 720a. As will be appreciated by those skilled in the relevant art(s), other types of bonding or joining can be used to couple electrostatic chuck 400 to chuck 720.

[0096] Overview of the combination

[0097] Reference Figure 4 、 Figure 6H and Figure 6M and, one or more layers previously described herein can be processed by heat treatment. Heat treatment can be used to form a durable connection, also referred to as a bond, between the layers of the stacked structure. In some aspects, first layer 402 and second layer 404 can be subjected to heat treatment to bond Figure 4 surfaces 402a and 404b. In additional aspects, heat treatment can be applied to structure 632 to bond surface 414a to Figure 6H surface 404a of, applied to third layer 406 to bond with intermediate layer 414, and applied to Figure 6M first part 608A and second part 608B of.

[0098] A structure (i.e., one or more layers) can be heated in a bonding furnace. The structure can be heated up to a holding temperature. In some aspects, the structure can be heated to the holding temperature at a heating rate. In some aspects, the holding temperature can be greater than about 350 °C. In some aspects, the holding temperature can 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, about 805 °C, about 810 °C, or about 815 °C. In some aspects, the heating rate can be from about 2 °C / hour to about 60 °C / hour, from about 10 °C / hour to about 55 °C / hour, less than 60 °C / hour, or less than 55 °C / hour.

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

[0100] In some aspects, 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 is from about 1 °C / hour to about 5 °C / hour or from about 2 °C / hour to about 4 °C / hour. In some aspects, the intermediate temperature can be lower than the holding temperature by from about 5 °C to about 20 °C. For example, the holding 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 can be maintained at the holding temperature for a holding time period. In some aspects, the holding time period can be at least 5 hours, at least 10 hours, at least 15 hours, or at least 20 hours. In some aspects, the holding time period can 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] After the holding time has elapsed, the structure can be cooled. The temperature can be reduced from the holding temperature to room temperature. In some aspects, the structure can be cooled at different cooling rates until the desired temperature or room temperature is reached. That is, the temperature of the structure can be reduced at different cooling rates. For example, one or more cooling rates can be used. In some aspects, the structure is cooled at a first cooling rate until the desired temperature is reached. Then, the cooling can proceed at any cooling rate until room temperature is reached (i.e., uncontrolled).

[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 aspects, the desired temperature can be lower than the holding temperature by about 100 °C. For example, when the holding temperature is about 810 °C, the desired temperature can be about 700 °C. In some aspects, the desired temperature can be equal to about 700 °C, about 600 °C, about 500 °C, about 400 °C, or about 300 °C.

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

[0105] In some embodiments, the structure can be cooled at a first cooling rate until a first desired temperature is reached, then cooled at a second cooling rate until a second desired temperature is reached. Then, the structure can be cooled at a third cooling rate until a third desired temperature is reached. Once the third desired temperature is reached, the structure can be cooled without restrictions on the cooling rate until room temperature is reached. In some aspects, the second cooling rate can be greater than the first cooling rate, and the third cooling rate can be greater than the second cooling rate. For example, the first cooling rate can be from about 5 °C / hour to about 15 °C / hour, and the second cooling rate can be from about 40 °C / hour to about 60 °C / hour. In some aspects, the third cooling rate can be from about 80 °C / hour to about 120 °C / hour. In some embodiments, the first desired temperature can be from about 650 °C to about 750 °C, and the second desired temperature can be from about 550 °C to about 450 °C. In some aspects, the third desired temperature can be from about 350 °C to about 250 °C.

[0106] In some embodiments, the structure can be cooled at a controlled rate for a first period. In some aspects, the first period can 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 period time can be selected based on the material properties of the layers of the structure. For example, measurements can be performed to determine one or more properties of the material, and the cooling rate can be selected based on the measured properties. As previously described herein, the layers of the structure (fixture) can be made of one or more dielectric materials that are configured to support an electrostatic field during operation of the fixture 400. The dielectric material can have an ultra-low coefficient of thermal expansion that can be equal to or substantially zero. In some aspects, the bonding profile described above has a minimal impact on the coefficient of thermal expansion because it can be adjusted based on the materials used.

[0108] Exemplary steps for manufacturing an electrostatic chuck

[0109] Figure 8 Illustrated is a flowchart for manufacturing an electrostatic chuck 400 and coupling the electrostatic chuck 400 to a chuck according to an embodiment. For illustrative purposes only, reference will be made to the exemplary fabrication process illustrated in Figures 6A to 6N and Figure 7 to describe the steps illustrated in Figure 8 The steps may be performed in a different order or not performed depending on the specific application.

[0110] In step 802, a trench is formed in a first layer. For example, a trench (e.g., trench 630) may be formed in the first layer (e.g., first layer 402) as illustrated in Figure 6A Standard glass machining techniques may be used to form trench 630.

[0111] In step 804, the first layer is coupled to a second layer to form a stacked structure. For example, the second layer (e.g., second layer 404) may be coupled to the first layer 402 to form a stacked structure similar to stacked structure 632 as illustrated in Figure 6B The coupling process may include direct bonding of surfaces 402a and 404b. The direct bonding may be performed by pressing surface 402a against surface 404b under a pressure suitable for the layer materials used. The stacked structure 632 may be annealed at a temperature in the range of about 350 degrees Celsius to 900 degrees Celsius.

[0112] In step 806, a composite layer is formed on a third layer. For example, a composite layer similar to composite layer 408 may be formed on the third layer 406 as illustrated in Figures 6C to 6F The composite layer 408 may be formed by depositing, patterning, and etching a metal layer (e.g., metal layer 610) on the third layer 406, followed by depositing, patterning, and etching a dielectric layer (e.g., dielectric layer 612). Deposition of the metal layer 610 may be performed using, for example, sputtering, thermal evaporation, atomic layer deposition (ALD), or chemical vapor deposition (CVD). Deposition of the 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 the composite layer 408 as illustrated in Figure 6G The intermediate layer 414 may be deposited using, for example, a CVD process.

[0114] In step 810, the third layer is coupled to the stacked structure to form an electrostatic chuck. For example, the third layer 406 may be coupled to the stacked structure 632 by directly bonding the intermediate layer 414 to the surface 404a of the stacked structure, asFigure 6H as illustrated.

[0115] In the selection step 812, protrusions are formed on the clamping surface of the fixture. For example, protrusions (e.g., protrusion 405) can be formed on the clamping surface (e.g., the clamping surface 406a of the third layer 406), as Figures 6I to 6J illustrated. The protrusion 405 can be formed by depositing, patterning, and etching the polymer layer 605.

[0116] In the selection step 814, the electrostatic chuck is coupled to the chuck. For example, the electrostatic chuck 400 can be coupled to a chuck similar to the chuck 720, as Figure 7 illustrated. The coupling can be performed by directly bonding the surface 402b of the chuck 400 to the surface 720a of the chuck 720.

[0117] Figure 9 A flowchart of an integration method 900 according to an embodiment is illustrated.

[0118] In step 902, the first and second layers of a structure (e.g., a chuck) are heated to up to a holding temperature (e.g., heating the first layer 402 and the second layer 404 to bond Figure 4 the surfaces 402a and 404b, Figure 6M the first part 608a and the second part 608b of). In some aspects, the holding temperature is at least 700 °C.

[0119] In step 904, the first and second layers are maintained at the holding temperature during a holding time period. In some aspects, the holding time period is at least 5 hours.

[0120] In step 906, after the holding time has elapsed, the first and second layers are cooled at a cooling rate for a cooling time period. For the cooling time period, the cooling rate can be a maximum of 20 °C / hour. In some aspects, the cooling time period is at least 10 hours. In some aspects, the first and second layers are cooled to a temperature of 700 °C or lower at the cooling rate.

[0121] Exemplary computing system

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

[0123] Figure 10FIG. 1000 shows a computer system 1000 according to some embodiments. For example, the computer system 1000 or any other well-known computer system can be used to implement various embodiments and components thereof. For example, Figure 9 the method steps of can be implemented via the computer system 1000.

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

[0125] In some embodiments, one or more of the processors 1004 may each be a graphics processing unit (GPU). In an embodiment, a GPU is a processor that is a dedicated electronic circuit designed to process mathematically intensive applications. The GPU may have a parallel architecture that is effective for parallel processing of large data blocks, e.g., common mathematically intensive data such as computer graphics applications, images, videos, etc.

[0126] In some embodiments, the computer system 1000 may further include (a plurality of) user input / output devices 1003 that communicate with the communication infrastructure 1006 via (a plurality of) user input / output interfaces 1002, e.g., monitors, keyboards, pointing devices, etc. The computer system 1000 may further include a main memory or primary storage 1008, e.g., random access memory (RAM). The main memory 1008 may include one or more levels of cache. Control logic (i.e., computer software) and / or data has been stored therein in the main memory 1008.

[0127] In some embodiments, the 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 tape drive, a CD drive, an optical storage device, a tape backup device, and / or any other storage device / drive. The removable storage drive 1014 may interact with a removable storage unit 1018. The removable storage unit 1018 may include a computer-usable or readable storage device on which computer software (control logic) and / or data has been stored. The removable storage unit 1018 may be a floppy disk, a tape, a CD, 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, the secondary memory 1010 may include other devices, means, or other methods for allowing a computer system 1000 to access computer programs and / or other instructions and / or data. Such devices, means, or other methods may include, for example, 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 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, the computer system 1000 may further include a communication or network interface 1024. The communication interface 1024 enables the computer system 1000 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (collectively and individually referred to by reference numeral 1028). For example, the communication interface 1024 may allow the computer system 1000 to communicate with a remote device 1028 via a communication path 1026, which may be wired and / or wireless, and the communication path 1026 may include any combination of LAN, WAN, the Internet, etc. Control logic and / or data may be transmitted to and from the computer system 1000 via the communication path 1026.

[0130] In some embodiments, a non - transitory tangible device or article including 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. This includes, but is not limited to, the computer system 1000, main memory 1008, secondary memory 1010, and removable storage units 1018 and 1022, and tangible articles implementing any combination of the foregoing. When executed by one or more data processing devices (such as the computer system 1000), such control logic causes such data processing devices to operate as described herein.

[0131] Based on the teachings contained in this disclosure, it will be apparent to those of ordinary skill in the relevant art(s) how to make and use embodiments of this disclosure using data processing devices, computer systems, and / or computer architectures different from those Figure 9 shown herein. Specifically, embodiments may operate with software, hardware, and / or operating system implementations other than those described herein.

[0132] Embodiments may be further described using the following aspects: 1. A method, comprising: The first layer and the second layer of the fixture are joined by 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 time period; and after the holding time has elapsed, cooling the first layer and the second layer at a maximum cooling rate of 20 °C / hour for a cooling time period. 2. The method according to aspect 1, wherein the holding temperature is from about 700 °C to about 900 °C. 3. The method according to aspect 2, wherein the holding temperature is from about 750 °C to about 850 °C. 4. The method according to aspect 3, wherein the holding temperature is about 810 °C. 5. The method according to aspect 1, wherein the holding time period is at least 5 hours. 6. The method according to aspect 5, wherein the holding time period is from about 5 hours to about 30 hours. 7. The method according to aspect 1, further comprising: heating the first layer and the second layer to a first temperature below the holding temperature at a first rate and to the holding temperature at a second rate, wherein the first rate is higher than the second rate. 8. The method according to aspect 1, wherein the first layer and the second layer are heated at a rate from about 2 °C / hour to about 60 °C / hour. 9. The method according to aspect 1, further comprising: cooling the first layer and the second layer at another rate during another cooling period after the cooling period, wherein the rate is lower than the other rate. 10. The method according to aspect 1, wherein the cooling rate is from about 5 °C / hour to about 20 °C / hour. 11. The method according to aspect 1, wherein the cooling time period is at least 10 hours. 12. The method according to aspect 1, wherein the first layer and the second layer are cooled to a temperature of 700 °C or lower at the cooling rate. 13. A lithographic apparatus, comprising: a chuck; and an electrostatic chuck coupled to the chuck, the electrostatic chuck being configured to releasably hold a patterning device, the electrostatic chuck comprising: A first layer and a second layer, wherein the first layer and the second layer are joined together using heat treatment, and wherein 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 time period; and cooling the first layer and the second layer at a maximum cooling rate of 20 °C per hour for a cooling time period after the holding time period has elapsed. 14. The lithographic apparatus according to aspect 13, wherein the holding temperature is from about 700 °C to about 900 °C. 15. The lithographic apparatus according to aspect 14, wherein the holding temperature is from about 750 °C to about 850 °C. 16. The lithographic apparatus according to aspect 13, wherein the holding time period is at least 5 hours. 17. The lithographic apparatus according to aspect 16, wherein the holding time period is from about 5 hours to about 30 hours. 18. The lithographic apparatus according to aspect 13, wherein the cooling rate is from about 5 °C per hour to about 20 °C per hour. 19. The lithographic apparatus according to aspect 13, wherein the cooling time period is at least 10 hours. 20. A fixture comprising: A first layer and a second layer, wherein the first layer and the second layer are joined together using heat treatment; and wherein 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 time period; and cooling the first layer and the second layer at a maximum cooling rate of 20 °C per hour for a cooling time period after the holding time has elapsed.

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

[0134] Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described in this text may have other applications, such as the manufacture of integrated optical systems, the guiding and detecting patterns for magnetic domain memories, flat panel displays, liquid crystal displays, thin film magnetic heads, etc. Those skilled in the art will appreciate that in the context of such alternative applications, any use of the terms "wafer" or "die" in this text may be considered synonymous with the more general terms "substrate" or "target portion" respectively. The substrates referred to in this text may be processed in, for example, a track (a tool that typically applies a resist layer to a substrate and develops the exposed resist), a metrology tool, and / or an inspection tool, either before or after exposure. Where applicable, the disclosures in this text may be applied to such and other substrate processing tools. In addition, the substrate may be processed more than once, for example, to produce a multi-layer IC, such that the term substrate as used in this text may also refer to a substrate that already contains multiple processed layers.

[0135] Although the above has specifically referred to the use of embodiments of the present disclosure in the context of optical lithography, it will be appreciated that the present disclosure may be used in other applications (such as, for example, imprint lithography), and is not limited to optical lithography where the context permits. In imprint lithography, the topography in the patterning device defines the pattern created on the substrate. The topography of the patterning device may be pressed into a resist layer supplied to the substrate, and then the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is removed from the resist, thereby leaving a pattern therein.

[0136] It should be understood that the language or terminology in this text is for the purpose of description rather than limitation, such that the terminology or language of this specification will be interpreted by those skilled in the relevant art(s) in light of the teachings in this text.

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

[0138] Where the context permits, the term "lens" may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electro - static optical components.

[0139] As used herein, the terms "etch", "etching", or "etch back" generally describe a fabrication process for patterning a material such that at least a portion of the material remains after the etching is complete. By way of example, typically, the process of etching a material involves the following steps: patterning a mask layer (e.g., photoresist or hard mask) over the material; subsequently removing the areas of the material that are no longer protected by the mask layer; and optionally removing the remaining portion of the mask layer. Typically, an "etchant" that is "selective" to the material over the mask layer is used for the removal step. Thus, after the etching process is complete, the areas of the material protected by the mask will remain. However, the foregoing is provided for illustrative purposes and not limiting. In another example, etching can also refer to a process that does not use a mask but still leaves at least a portion of the material after the etching process is complete.

[0140] The foregoing specification is used to distinguish the term "etch" from "remove". In an embodiment, when etching a material, at least a portion of the material remains after the process is complete. In contrast, when removing a material, substantially all of the material is removed during the process. However, in other embodiments, "removing" can be incorporated into etching.

[0141] As used herein, the terms "deposit" or "set" describe the act of applying a layer of material to a substrate. Such terms are meant to describe 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" describes the material onto which subsequent layers of material are added. In an embodiment, the substrate itself may be patterned, and the material added on top of it may also be patterned, or may remain unpatterned.

[0143] As used herein, the terms "substantially" or "substantially in contact" generally describe that elements or structures are physically substantially in contact with each other, where they are only slightly separated, which is typically caused by fabrication and / or misalignment tolerances. It should be understood that the relative spatial descriptions between one or more specific features, structures, or characteristics used herein (e.g., "vertically aligned", "substantially in contact", etc.) are for illustrative purposes only, and the actual implementations of the structures described herein may include fabrication and / or misalignment tolerances without departing from the spirit and scope of the present disclosure.

[0144] Although specific embodiments of the present disclosure have been described above, it will be understood that embodiments of the present disclosure may be practiced in a manner different from that described. The description is intended to be illustrative rather than restrictive. Thus, it will be apparent to those skilled in the art that modifications may be made to the present disclosure as described without departing from the scope of the claims set forth herein.

[0145] It should be understood that the detailed description section, rather than the summary and abstract sections, is intended to be used to interpret the claims. The summary and abstract sections may set forth one or more but not all exemplary embodiments of the present disclosure as contemplated by the (one or more) inventors, and are therefore not intended to limit the present disclosure and the appended claims in any way.

[0146] The present disclosure has been described above by means of functional building blocks of embodiments that illustrate specific functions and their relationships. For convenience of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries may be defined so long as the specified functions and their relationships are appropriately performed.

[0147] The foregoing description of specific embodiments will fully disclose the general nature of the present disclosure, such that others may, by applying knowledge within the scope of the art, readily modify and / or adapt various applications of such specific embodiments without undue experimentation, without departing from the general concept of the present disclosure. Thus, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments based on the teachings and guidance presented herein.

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

Claims

1. A method, comprising: bonding a first layer and a second layer of a fixture by heating the first layer and the second layer to a holding temperature of up to at least 700 °C; maintaining the first layer and the second layer at the holding temperature during a holding time period; and after the holding time has elapsed, cooling the first layer and the second layer at a maximum cooling rate of 20 °C / hour during a cooling time period.

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

3. The method according to claim 2, wherein The holding temperature is from about 750 °C to about 850 °C.

4. The method according to claim 3, wherein The holding temperature is about 810 °C.

5. The method according to claim 1, wherein The holding time period is at least 5 hours.

6. The method according to claim 5, wherein The holding time period is from about 5 hours to about 30 hours.

7. The method according to claim 1, further comprising: heating the first layer and the second layer to a first temperature below the holding temperature at a first rate and heating the first layer and the second layer to the holding temperature at a second rate, wherein the first rate is higher than the second rate.

8. The method according to claim 1, wherein heating the first layer and the second layer at a rate from about 2 °C / hour to about 60 °C / hour.

9. The method according to claim 1, further comprising: after the cooling cycle, cooling the first layer and the second layer at another rate during another cooling cycle, wherein the cooling rate is lower than the another rate.

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

11. The method according to claim 1, wherein, The cooling time period is at least 10 hours.

12. The method according to claim 1, wherein, cooling the first layer and the second layer to a temperature of 700 °C or lower at the cooling rate.

13. A lithographic apparatus, comprising: a chuck; and an electrostatic chuck coupled to the chuck, the electrostatic chuck being configured to hold a patterning device in a releasable manner, the electrostatic chuck comprising: a first layer and a second layer, wherein the first layer and the second layer are bonded together using a heat treatment, and wherein the heat treatment comprises: heating the first layer and the second layer to a holding temperature of up to at least 700 °C; maintaining the first layer and the second layer at the holding temperature during a holding time period; and after the holding time period has elapsed, cooling the first layer and the second layer at a maximum cooling rate of 20 °C / hour during a cooling time period.

14. A lithographic apparatus according to claim 13, wherein, The holding temperature is from about 700 °C to about 900 °C.

15. A lithographic apparatus according to claim 14, wherein, The holding temperature is from about 750 °C to about 850 °C.

16. A lithographic apparatus according to claim 13, wherein, The holding time period is at least 5 hours.

17. A lithographic apparatus according to claim 16, wherein, The holding time period is from about 5 hours to about 30 hours.

18. A lithographic apparatus according to claim 13, wherein The cooling rate is from about 5 °C / hour to about 20 °C / hour.

19. A lithographic apparatus according to claim 13, wherein, The cooling time period is at least 10 hours.

20. A fixture, comprising: a first layer and a second layer, wherein the first layer and the second layer are bonded together using a heat treatment; and Wherein, the heat treatment includes: 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 time period; and cooling the first layer and the second layer at a cooling rate of at most 20 °C / hour during a cooling time period after the holding time period has elapsed.

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