NL2024436A - Direct drive reticle safety latch - Google Patents

Abstract

Embodiments herein describe a safety device used to provide support for an object. The safety device includes a housing having a rotating shaft extending along a length of the housing. The safety device also includes a rotary motor that is coupled to a first end of the rotating shaft 5 and a safety latch that is coupled to a second end of the rotating shaft opposite from the first end of the rotating shaft. Rotation of the rotating shaft causes the safety latch to rotate. The safety latch extends away from the rotating shaft in a radial direction. The safety latch includes a foot portion at a distal end of the safety latch away from the rotating shaft. The foot portion is designed to act as a contact point for the object.

Description

DIRECT DRIVE RETICLE SAFETY LATCH FIELD

[0001] The present disclosure relates to safety mechanisms, such as a safety mechanism for the retention of a patterning device in a lithography system.

BACKGROUND

[0002] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the target portions parallel or anti-parallel to this scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0003] Lithography is widely recognized as one of the key steps in the manufacture of ICs and other devices and/or structures. However, as the dimensions of features made using lithography become smaller, lithography is becoming a more critical factor for enabling miniature IC or other devices and/or structures to be manufactured.

[0004] A theoretical estimate of the limits of pattern printing can be given by the Rayleigh criterion for resolution as shown in equation (1): CD =k + NM (1) where 4 is the wavelength of the radiation used, NA is the numerical aperture of the projection system used to print the pattern, ky is a process dependent adjustment factor, also called the

Rayleigh constant, and CD is the feature size (or critical dimension) of the printed feature. It follows from equation (1) that reduction of the minimum printable size of features can be obtained in three ways: by shortening the exposure wavelength 4, by increasing the numerical aperture NA, or by decreasing the value of ki.

[0005] In order to shorten the exposure wavelength, and thus, reduce the minimum printable size, it has been proposed to use an extreme ultraviolet (EUV) radiation source. EUV radiation is electromagnetic radiation having a wavelength within the range of 5-20 nm, for example within the range of 13-14 nm, for example within the range of 5-10 nm such as 6.7 nm or

6.8 nm. Possible sources include, for example, laser-produced plasma sources, discharge plasma IO sources, or sources based on synchrotron radiation provided by an electron storage ring.

[0006] The radiation generated by such sources will not, however, be only EUV radiation and the source may also emit at other wavelengths including infra-red (IR) radiation and deep ultra-violet (DUV) radiation. DUV radiation can be detrimental to the lithography system as it can result in a loss of contrast. Furthermore unwanted IR radiation can cause heat damage to components within the system. It is therefore known to use a spectral purity filter to increase the proportion of EUV in the transmitted radiation and to reduce or even eliminate unwanted non- EUV radiation such as DUV and IR radiation.

[0007] A lithographic apparatus using EUV radiation may require that the EUV radiation beam path, or at least substantial parts of it, must be kept in vacuum during a lithographic operation. In such vacuum regions of the lithographic apparatus, an electrostatic clamp may be used to clamp an object, such as a patterning device and/or a substrate to a structure of the lithographic apparatus, such as a patterning device table and/or a substrate table, respectively.

[0008] Conventional patterning devices, such as reticles, are very costly. As such, extreme care is taken when handling the reticles within the lithographic apparatus. Although the reticle is usually clamped to a chuck structure, it is desirable to include safety mechanisms in the event that the clamping fails. Otherwise, the reticle may fall and cause damage not only to the reticle itself, but also to other costly optics within the lithographic apparatus.

SUMMARY

[0009] Conventional safety designs used to ensure that a patterning device, such as a reticle, does not inadvertently fall away from a chuck typically use electromagnets to open or closemetallic arms to “catch” the reticle if it were to fall. These designs are not very efficient as they require a large motor to generate the force necessary to open the arms and also require constant power consumption to keep the arms in the open position. Embodiments herein describe systems and methods for an improved safety device that does not require electromagnets.

[0010] In some embodiments, a safety device used to provide support for an object includes a housing having a rotating shaft extending along a length of the housing. The safety device also includes a rotary motor that is coupled to a first end of the rotating shaft and a safety latch that is coupled to a second end of the rotating shaft opposite from the first end of the rotating shaft. Rotation of the rotating shaft causes the safety latch to rotate. The safety latch extends away from the rotating shaft in a radial direction. The safety latch includes a foot portion at a distal end of the safety latch away from the rotating shaft. The foot portion is designed to act as a contact point for the object.

[0011] In some embodiments, a lithographic apparatus includes an illumination system, a support structure, and one or more safety devices. The illumination system conditions a radiation beam. The support structure is constructed to support a patterning device that is capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam. The one or more safety devices are coupled to the support structure and each includes a housing, a rotary motor, and a safety latch. The housing has a rotating shaft extending along a length of the housing. The rotary motor is coupled to a first end of the rotating shaft. The safety latch is coupled to a second end of the rotating shaft opposite from the first end of the rotating shaft. Rotation of the rotating shaft causes the safety latch to rotate. The safety latch extends away from the rotating shaft in a radial direction. The safety latch includes a foot portion at a distal end of the safety latch away from the rotating shaft. The foot portion is designed to act as a contact point for the patterning device.

[0012] In some embodiments, a method includes determining a rotational position of a safety latch on a safety device that is coupled to a chuck, and translating a reticle towards the chuck. The method also includes coupling the reticle onto a surface of the chuck, and rotating the safety latch such that a foot portion at a distal end of the safety latch is rotated to a position beneath the reticle.

[0013] Further features and advantages, as well as the structure and operation, of various embodiments of the invention are described in detail below with reference to the accompanyingdrawings. It is noted that the invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0014] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention.

[0015] FIG. 1 is a schematic illustration of a lithographic apparatus, according to an exemplary embodiment.

[0016] FIG. 2 is a perspective schematic illustration of a reticle stage, according to an exemplary embodiment.

[0017] FIG. 3 is a top plan view of the reticle stage of Figure 2.

[0018] FIG. 4 is a schematic illustration of a safety device, according to an exemplary embodiment.

[0019] FIG. 5 is a partial perspective schematic illustration of the safety device of Figure

2.

[0020] FIG. 6 is a schematic illustration of rotating the safety latch, according to an exemplary embodiment.

[0021] FIG. 7 is a schematic illustration of a cross section of a portion of the safety latch, according to an exemplary embodiment.

[0022] FIGs. 8A — 8C are schematic illustrations of loading a patterning device onto a chuck, according to some embodiments. 10023] FIG. 9 is a schematic illustration of a flowchart for operating the safety latch, according to an exemplary embodiment.

[0024] The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similarelements. Unless otherwise indicated, the drawings provided throughout the disclosure should not be interpreted as to-scale drawings.

DETAILED DESCRIPTION 5 [0025] This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodiment(s) merely exemplify the invention. The scope of the invention is not limited to the disclosed embodiment(s). The invention is defined by the clauses appended hereto.

[0026] The embodiment(s) described. and references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it 1s understood that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0027] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0028] The term “about” as used herein indicates the value of a given quantity that can vary based on a particular technology. Based on the particular technology, the term “about” can indicate a value of a given quantity that varies within, for example, 10-30% of the value (e.g., +10%, 220%, or £30% of the value).

[0029] Embodiments of the disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing ortransmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, and/or instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.

[0030] Before describing such embodiments in more detail, however, it is instructive to present an example environment in which embodiments of the present disclosure may be implemented.

[0031] Example Lithographic System

[0032] FIG. 1 shows a lithographic system comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and to supply the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

[0033] The illumination system IL is configured to condition the EUV radiation beam B before the EUV radiation beam B is incident upon the patterning device MA. Thereto, the illumination system IL may include a facetted field mirror device 10 and a facetted pupil mirror device 11. The faceted field mirror device 10 and faceted pupil mirror device 11 together provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution.

The illumination system IL may include other mirrors or devices in addition to, or instead of, the faceted field mirror device 10 and faceted pupil mirror device 11.

[0034] After being thus conditioned, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B’ is generated. The projection system PS is configured to project the patterned EUV radiation beam B’ onto the substrate W. For that purpose, the projection system PS may comprise a plurality of mirrors 13, 14 which are configured to project the patterned EUV radiation beam B’ onto thesubstrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B’, thus forming an image with features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is illustrated as having only two mirrors 13, 14m FIG. 1, the projection system PS may include a different number of mirrors (e.g. six or eight Mirrors).

[0035] The substrate W may include previously formed patterns. Where this is the case, the lithographic apparatus LA aligns the image, formed by the patterned EUV radiation beam B’, with a pattern previously formed on the substrate W.

[0036] A relative vacuum, i.e. a small amount of gas (e.g. hydrogen) at a pressure well below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL, and/or in the projection system PS.

[0037] The radiation source SO may be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL), or any other radiation source that is capable of generating EUV radiation.

{0038] Example Reticle Stage and Safety Device Systems

[0039] FIGs. 2 and 3 show schematic illustrations of an exemplary reticle stage 200, according to some embodiments of this disclosure. Reticle stage 200 can include top stage surface 202, bottom stage surface 204, side stage surfaces 200, reticle 208, and safety device 300. In some embodiments, reticle stage 200 with reticle 208 can be implemented in lithographic apparatus LA. For example, reticle stage 200 can represent support structure MT and reticle 208 can represent patterning device MA in lithographic apparatus LA. In some embodiments, reticle 208 and a plurality of safety devices 300 can be disposed on top stage surface 202. For example, as shown in FIG. 2, reticle 208 can be disposed at a center of top stage surface 202 with safety devices 300 disposed adjacent to each corner of reticle 208.

[0040] In some lithographic apparatuses, for example, lithographic apparatus LA, a reticle stage or chuck 200 can be used to hold and position a reticle 208 for scanning or patterning operations. Reticle stage 200 requires powerful drives, large balance masses, and heavy frames to support it. Reticle stage 200 has a large inertia and can weigh over 500 kg to propel and position reticle 208 weighing about 0.5 kg. To accomplish reciprocating motions of reticle 208, which aretypically found in lithographic scanning or patterning operations, accelerating and decelerating forces can be provided by linear motors that drive reticle stage 200.

[0041] During a catastrophic failure of reticle stage 200, for example, by major power loss or serious system failure, the accelerating and decelerating forces of reticle stage 200 can be transferred to reticle 208 and result in a reticle crash. Reticle 208 can crash into other components of reticle stage 200, causing damage to reticle 208 and/or other nearby components. Reticle 208 can crash at a high force (i.e., high acceleration) depending on the pre-crash motion and momentum of reticle stage 200. Softer reticle flexure can lead to metal breaks (e.g., pattern damage), while harder reticle flexure can lead to glass breaks (e.g., cracks in reticle). Current methods use some form of a safety mechanism to reduce or decrease the force of a reticle during a crash. However, due to the high impact stress (force) of the reticle in worst case crashes, damage can still occur to the reticle and/or current safety mechanisms.

[0042] One possible solution is to position a safety mechanism, for example, safety devices 300 around reticle 208 to act as a shock absorber to reduce an impact force of reticle 208 during a crash. For example, a bumper apparatus 201 with shock absorbers can be used around reticle 208 to absorb possible forces or shocks occurring from a crash such that damage to reticle 208 and safety devices 300 can be reduced or eliminated completely. According to an embodiment, safety devices 300 can also each include a safety latch (not shown) that is rotated in place beneath reticle 208 such that the safety latch prevents reticle 208 from falling away from reticle stage 200. Reticle 208 may be restrained by four safety devices 300, for example, arranged adjacent to the corners of reticle 208. In an embodiment, safety devices 300 may act like a “cage” used to contain an object from shifting or falling. When safety devices 300 are used to provide emergency support for a reticle, they may be collectively called a reticle cage, but safety devices 300 can also be used to support other types of patterning devices, or any other type of clamped object.

[0043] In some embodiments, as shown in FIGS. 2 and 3, reticle stage 200 can include first encoder 212 and second encoder 214 for positioning operations. For example, first and second encoders 212, 214 can be interferometers. First encoder 212 can be attached along a first direction, for example, a transverse direction (i.e., X-direction) of reticle stage 200 and second encoder 214 can be attached along a second direction, for example, a longitudinal direction (i.e, Y-direction) of reticle stage 200. In some embodiments, as shown in FIGS. 2 and 3, first encoder 212 can be orthogonal to second encoder 214.

[0044] Safety devices 300 can be configured to secure and reduce damage to reticle 208 during a crash. Safety devices 300 can be configured to uniformly distribute an impact force of reticle 208 during a crash. In some embodiments, a plurality of safety devices 300 can be disposed in top stage surface 202 and arranged around a perimeter of reticle 208. For example, multiple safety devices 300 can be disposed adjacent each corner of reticle 208 to uniformly distribute an impact force of reticle 208 over a plurality of impact locations.

[0045] Design of Reticle Cage with a Safety Latch

[0046] FIG. 4 illustrates an isometric view of one safety device 300, according to an embodiment. As noted above in FIGs. 2-3, one or more of safety device 300 may be disposed around reticle 208 and coupled to a chuck (e.g., reticle stage 200.) Safety device 300 includes a housing 402 that has a longest length along the Z-direction, and is provided to protect moving components disposed inside. Housing 402 may be an injection molded material, such as a polymer material, or housing 402 may be machined metal. In some embodiments, housing 402 has a length along the Z-direction of about 60 millimeters.

[0047] According to an embodiment, Safety device 300 includes a rotary motor 404 that is coupled to a shaft 406. Shaft 406 is disposed within housing 402 while rotary motor is coupled to one end of shaft 406 outside of housing 402. Shaft 406 may extend along the length of housing

402.

[0048] Rotary motor 404 may be a bi-stable friction drive motor. Alternatively, a rotary solenoid may be used instead of a motor, or another electrical rotary motor with a braking mechanism. The bi-stable nature of rotary motor 404 means that motion of the motor only occurs while under power. No power is consumed by rotary motor 404 while it is fixed in a given position. Rotary motor 404 may be a piezoelectric motor or DC motor.

[0049] Bushings 408 may also be included as part of the motor design and disposed within housing 402. Any type of bushing or bearing design may be used. According to some embodiments, bushings 408 are designed to reduce the expulsion of any particles generated from the moving parts out into the area around reticle cage 300. Any particles produced by the operation of safety device 300 that end up on the surface of a neighboring patterning device would be highly detrimental to forming the correct pattern on a substrate. Accordingly, bushings 408 may be designed to include particle traps, such as small spacings between moving parts that make it difficult for particles to escape.

[0050] Rotary motor 404 may include a plurality of electrical connections 410. Electrical connections 410 provide power to Rotary motor 404. According to some embodiments, rotary motor 404 may receive signals via electrical connections 410 from a microcontroller or other type of control device to control operation of rotary motor 404.

[0051] Safety device 300 also includes a safety latch 412 that is coupled to an opposite end of shaft 406 from the end coupled to rotary motor 404. Safety latch 412 rotates along with rotating shaft 406. In some embodiments, safety latch 412 can rotate a full 360 degrees beneath housing 402 about an axis parallel to the Z-direction. Safety latch 412 extends outward radially from shaft 406 and may have a length of less than 60 mm. The exact illustrated design of safety latch 412 is only one example and is not intended to be limiting. Safety latch 412 may include two or more separate beams as illustrated in FIG. 4, or it may be one solid piece.

[0052] A foot region 414 is disposed at a distal end of safety latch 412, according to some embodiments. Foot region 414 may be substantially flat and designed to contact a portion of a patterning device. According to some embodiments, foot region 414 is the only portion of safety latch 412 that would have any contact with a patterning device if the device were to fall in the Z- direction from its clamped position. Foot region 414 may be bent away from a remainder of safety latch 412 at an angle, such as about a 90 degree angle. According to some embodiments, a sloped member 415 may connect safety latch 412 to foot region 414, such that foot region 414 is disposed at a lower, parallel plane than safety latch 412.

[0053] Safety device 300 can also include safety bumpers 201, as discussed above. Safety bumpers 201 are not the focus of this disclosure, but are described in more detail in co-pending Attorney Docket Number 2857.6980000, which is incorporated by reference herein in its entirety.

[0054] As shown, for example in FIG. 5, safety device 300 having housing 402 can also include a securing mechanism 304, safety latch 412, and bumper apparatus 201. Safety device 300 can be a rigid material, for example, a metal or a ceramic. In some embodiments. housing 302 of safety device 300 can extend through a portion of reticle stage 200. For example, housing 302 can be cylindrical and extend through top stage surface 202 for rigid alignment with a corner of reticle

208. In some embodiments, safety device 300 can be secured to top stage surface 202 with one or more securing mechanisms 304. For example, securing mechanism 304 can be a bolt. In some embodiments, safety latch 412 can be configured to secure (i.e, catch) and reduce damage to reticle 208 during a crash. For example, a foot region 414 of safety latch 412 can extend over a topsurface of reticle 208 and be configured to prevent movement of reticle 208 in a direction perpendicular to top stage surface 202 (i.e., Z-direction).

[0055] FIG. 6 illustrates a top-down view of patterning device 208 and safety device 300 adjacent to one corner of patterning device 208, according to an embodiment. It should be noted that FIG. 6 is not drawn to scale and that certain features have been made larger for clarity. Furthermore, the location of safety device 300 with respect to patterning device 208 is not intended to be limiting — safety device 300 may be located anywhere around the perimeter of patterning device 208.

[0056] As shown in FIG. 6, safety latch 412 of safety device 300 rotates between a first position shown on the left and a second position shown on the right. In the first position, foot region 414 is aligned beneath patterning device 208, such that patterning device 208 contacts foot region 414 if patterning device 208 detaches from the chuck (not shown in FIG. 6) and fell in the Z-direction. In the second position, safety latch 412 has rotated away from patterning device 208, such that no part of safety latch 412 is below patterning device 208. According to an embodiment, safety latch 412 would be rotated into the first position while patterning device 208 is clamped to the chuck. According to an embodiment, safety latch 412 would be rotated into the second position during either loading or removal of patterning device 208 from the chuck. An angle of rotation 6 for safety latch 412 between the first position and the second position may be between 5 degrees and 20 degrees. Other rotation angles are possible as well based on the length of safety latch 412.

[0057] According to an embodiment, one advantage of using a friction drive motor to rotate safety latch 412 is that the motor only consumes power during the rotation and not while safety latch 412 is stationary in either the first position or the second position. Additionally, safety device 300 does not rely on rotary or compression springs to provide the force for maintaining safety latch 412 in the first position. In an embodiment, safety device 300 provides a force of at least 1.5 N when “closing” safety latch 412 into the first position. Due in part to the use of a friction drive motor, safety latch 500 has a lower overall volume and mass compared to previous safety designs.

[0058] FIG. 7 illustrates a cross-section view of a lower portion of safety device 300 where shaft 406 couples with safety latch 412. As is shown in FIG. 7, shaft 406 extends through housing 402 and couples with safety latch 412, which rotates beneath housing 402 about an axis ‘A’ passing through a center of shaft 406 and parallel to the Z-direction.

[0059] Safety latch 412 may include an annular bearing 702 that includes an annular ridge 704 protruding up into an annular recess 706 in the bottom portion of housing 402. It is not required that ridge 704 be an annular shape and other designs are possible as well that still stabilize the rotation of safety latch 412.

[0060] According to an embodiment, a spacing between ridge 704 and recess 706 is designed such that particles generated from the moving parts during rotation of safety latch 412 remain trapped within housing 402 and are not expelled out into the space around safety device

300. The spacing between ridge 704 and recess 706 may be designed to be between about 0.5mm and about 2mm.

[0061] Example Methods of Operation

[0062] FIGs. 8A — 8C illustrate an example procedure for loading reticle 208 to chuck 200, according to some embodiments. During the loading procedure, the rotated orientation of safety device 300 changes. In FIG. 8A, reticle 208 is translated towards chuck 200 using a reticle arm

802. Reticle arm 802 may be a robotic arm used to safely transfer patterning devices, such as reticle 802, to various positions within a lithographic apparatus. For example, reticle 208 may be removed from its stored position by reticle arm 802 and translated up towards chuck 200 where reticle 208 can be clamped to a surface of chuck 200.

[0063] During the translation of reticle 208 towards chuck 802, the rotated orientation of safety device 300 is checked to determine if safety latch 412 is rotated out of the way such that it will not impede the progress of loading reticle 208. If safety latch 412 is in a position that would cause any part of reticle 208 or reticle arm 802 to strike safety latch 412, then it is rotated to a safe position.

[0064] In FIG. 8B, reticle arm 802 has brought reticle 208 into contact with chuck 200. At this point, reticle 208 may be clamped to chuck 200 using any known method. Some common clamping techniques include using vacuum pressure to retain reticle 208, or using electrostatic charge to retain reticle 208.

[0065] In FIG. 8C, reticle arm 802 pulls away from reticle 208, now clamped to chuck 200, and safety latch 418 is rotated to a position beneath a portion of reticle 208, according to an embodiment. The rotation angle between the first “safe” position and the second position beneath reticle 208 may be between 5 degrees and 20 degrees and could vary further depending on thelength of the latch (already mentioned in earlier section). Each safety device 300 positioned around reticle 208 may rotate its respective safety latch in unison.

[0066] FIG. 9 is a flowchart of an exemplary method 900 for operating a safety latch on a safety device, according to an embodiment. Method 900 may describe the operation of safety device 300 and its corresponding safety latch 412 as discussed above with reference to FIGs. 2-8 (908 and 910 are reversed, latch is rotated first, then positioning arm is removed). It should be understood that the operations shown in method 900 are not exhaustive and that other operations can be performed as well before, after, or between any of the illustrated operations. In various embodiments of the present disclosure, the operations of method 900 can be performed in a different order and/or vary.

[0067] In operation 902, the position of the safety latch is determined. If the safety latch position would cause it to be struck by a reticle or reticle arm when loading the reticle to a reticle chuck, then the safety latch is rotated until it is no longer in the path of the reticle. This may be considered equivalent to rotating the safety latch to an “open” position. If the safety latch is already in the “open” position, then no further movement of the safety latch needs to occur. It should be understood that any position of the safety latch may be considered an “open” position so long as the safety latch is not in the way of loading a reticle to the reticle chuck.

[0068] In operation 904, the reticle is translated towards the reticle chuck using a movable arm. The movable arm may be designed to support the reticle at one end of the arm and to carry the reticle through the interior of a lithographic apparatus. The movable arm may first align the reticle with the reticle chuck, and then translate the reticle towards the reticle chuck.

[0069] In operation 906, the reticle is clamped to a surface of the reticle chuck. The clamping may be performed using vacuum pressure or electrostatic force. In some other examples, the reticle is mechanically clamped using a fixture on the reticle chuck.

[0070] In operation 908, the movable arm is removed from the reticle. The clamped reticle remains in place against the surface of the reticle chuck. The movable arm may be translated away from the reticle in the opposite direction used to load the reticle. This operation happens after 910

[0071] In operation 910, the safety latch of one or more of the safety devices arranged around the reticle is rotated such that a portion of the safety latch is beneath the reticle. The portion of the safety latch may be a foot region on the safety latch that is designed to safely and securely hold the weight of the reticle if it were to fall away from the reticle chuck. The safety latch maybe rotated between a first “open” position and a second “closed” position, with the first and second positions being separated by anywhere from 5 degrees to 20 degrees. This operation happens before 908

[0072] Final Remarks

[0073] Although specific reference may be made in this text to a “reticle,” it should be understood that this is just one example of a patterning device and that the embodiments described herein may be applicable to any type of patterning device. Additionally, the embodiments described herein may be used to provide safety support for any object to ensure a clamping failure does not cause the object to fall and damage either itself or other equipment.

[0074] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, LCDs, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology unit and/or an inspection unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0075] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0076] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0077] The term “substrate” as used herein describes a material onto which material layers are added. In some embodiments, the substrate itself may be patterned and materials added on top of it may also be patterned, or may remain without patterning.

[0078] Embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or IO more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical, or other forms of propagated signals, and others. Further, firmware, software, routines, and/or instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, and/or instructions.

[0079] The following examples are illustrative, but not limiting, of the embodiments of this disclosure. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the field, and which would be apparent to those skilled in the relevant art(s), are within the spirit and scope of the disclosure.

[0080] Although specific reference may be made in this text to the use of the apparatus and/or system according to the invention in the manufacture of ICs, it should be explicitly understood that such an apparatus and/or system has many other possible applications. For example, it can be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, LCD panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle,” “wafer,” or “die” in this text should be considered as being replaced by the more general terms “mask,” “substrate,” and “target portion,” respectively.

[0081] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The description is not intended to limit the invention.

[0082] It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the clauses. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended clauses in any way.

[0083] The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0084] The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0085] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following clauses and their equivalents. Other aspects of the invention are set out as in the following numbered clauses.

1. A safety device used to provide support for an object, comprising: a housing comprising a rotating shaft extending along a length of the housing; a rotary motor coupled to a first end of the rotating shaft; and a safety latch coupled to a second end of the rotating shaft opposite from the first end of the rotating shaft, such that rotation of the rotating shaft causes the safety latch to rotate, the safety latch extending away from the rotating shaft in a radial direction, wherein the safety latch comprises a foot portion at a distal end of the safety latch away from the rotating shaft, the foot portion being configured to act as a contact point for the object.

2. The safety device of clause 1, wherein the safety latch further comprises an annular ridge that fits into an annular recess at a bottom surface of the housing.

3. The safety device of clause 2, wherein a space between the annular ridge and the annular recess is between 0.5 and 2 millimeters.

4. The safety device of clause 1, wherein the foot portion is disposed at the distal end of the safety latch at an angle from a remainder of the safety latch.

5. The safety device of clause 4, wherein the angle is around 90 degrees.

6. The safety device of clause 1, wherein the safety latch is configured to rotate between a first position and a second position, the first position and the second position being separated by anywhere between about 5 degrees and about 20 degrees.

7. The safety device of clause 1, wherein the rotary motor comprises a friction drive motor or any rotary motor with a brake.

8. The safety device of clause 1, wherein the object is a patterning device.

9. A lithographic apparatus, comprising: an illumination system configured to condition a radiation beam; a support structure constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; one or more safety devices coupled to the support structure, each of the one or more safety devices comprising: a housing comprising a rotating shaft extending along a length of the housing; a rotary motor coupled to a first end of the rotating shaft; anda safety latch coupled to a second end of the rotating shaft opposite from the first end of the rotating shaft, such that rotation of the rotating shaft causes the safety latch to rotate, the safety latch extending away in a radial direction from the rotating shaft, wherein the safety latch comprises a foot portion at a distal end of the safety latch away from the rotating shaft, the foot portion being configured to act as a contact point for the patterning device.

10. The lithographic apparatus of clause 9, wherein the safety latch further comprises an annular ridge that fits into an annular recess at a bottom surface of the housing.

11. The lithographic apparatus of clause 10, wherein a space between the annular ridge and the annular recess is between 0.5 and 2 millimeters.

12. The lithographic apparatus of clause 9, wherein the foot portion is disposed at the distal end of the safety latch at an angle from a remainder of the safety latch.

13. The lithographic apparatus of clause 12, wherein the angle is around 90 degrees.

14. The lithographic apparatus of clause 12, wherein the safety latch is configured to rotate between a first position and a second position, the first position and the second position being separated by anywhere between about 5 degrees and about 20 degrees.

15. The lithographic apparatus of clause 12, wherein the rotary motor comprises a friction drive motor or any rotary motor with a brake.

16. A method, comprising: determining a rotational position of a safety latch on a safety device that is coupled to a chuck; translating a reticle towards the chuck; coupling the reticle onto a surface of the chuck; androtating the safety latch such that a foot portion at a distal end of the safety latch is rotated to a position beneath the reticle.

17. The method of clause 16, wherein the translating comprises elevating the reticle towards the chuck using a robotic arm.

18. The method of clause 16, wherein the coupling comprises electrostatically clamping the reticle onto the surface of the chuck.

19. The method of clause 16, wherein the rotating comprises rotating the safety latch between a first position and second position separated by anywhere between about 5 degrees and about 20 degrees.

20. The method of clause 16, wherein the determining comprises: determining whether the safety latch would be struck by the reticle as it is translated towards the chuck; and if the safety latch would be struck by the reticle, rotating the safety latch to a position where it would not be struck by the reticle as it is translated towards the chuck.

Claims (1)

CONCLUSION 1. A device arranged for exposing a substrate.