Reticle handling system

Abstract

Multiple cover store positions are provided within an in-vacuum reticle library area of a lithographic apparatus. A system for handling a reticle includes a vacuum chamber, a library configured to hold reticle pods in vacuum in reticle pod positions disposed within the vacuum chamber, each reticle pod including a respective baseplate, reticle, and cover. The system includes an in-vacuum robot to selectively pick a reticle from the plurality of reticles and provide the picked reticle to a reticle exchange device, and a plurality of actuators, each actuator corresponding to a respective one of the pod positions, and each actuator being arranged to remove the cover from a corresponding reticle pod and move the cover into a cover storage position associated with the corresponding reticle pod.

Description

RETICLE HANDLING SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 537,233 which was filed on 8 September 2023, and which is incorporated herein in its entirety by reference.FIELD

[0002] The present disclosure relates generally to photolithography systems that make use of multiple reticles.BACKGROUND

[0003] 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 can 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., including 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. Modern high resolution tools are generally 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 substrate parallel or anti parallel to this direction.

[0004] Lithography tools have been developed to allow smaller and smaller devices to be patterned on a wafer. Lithographic tools and methods are being developed that utilize multiple exposure. During multiple exposure, two or more reticles are imaged sequentially based on reticle swapping between imaging. Multiple exposure is particularly advantageous in extreme ultra violet (EUV) imaging to overcome undesirably low kl imaging effects.

[0005] A solution to this problem has been implemented in which two or more reticles are stored in vacuum, allowing for faster swap between reticles.SUMMARY

[0006] In an aspect, a system for handling a reticle includes a vacuum chamber, a library configured to hold a plurality of reticle pods in vacuum in a plurality of reticle pod positions, disposed within the vacuum chamber, each reticle pod of the plurality of reticle pods comprising a respective baseplate, reticle, and cover, an in-vacuum robot, configured to selectively pick a reticle from the plurality of reticles and provide the picked reticle to a reticle exchange device, and a plurality ofactuators, each actuator corresponding to a respective one of the pod positions, and each actuator being configured to remove the cover from a corresponding reticle pod and move the cover into a cover storage position associated with the corresponding reticle pod.

[0007] In an aspect, at least one of the plurality of actuators includes a linear actuator disposed adjacent to a respective one of the pod positions, the linear actuator being actuatable to move a cover holding portion intothe respective reticle pod position to remove the cover from the reticle pod and to move the cover into the cover storage position

[0008] In an aspect, a method for handling reticles includes operating the above system to move the reticle pod into and out of a pod position, and to remove the cover from the corresponding reticle pod and move the cover into a cover storage position associated with the corresponding reticle pod.

[0009] In an aspect, there is provided a non-transitory computer program product comprising machine -readable instructions configured to cause a processor to cause performance of a method described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

[0011] Figure 1 schematically illustrates a lithographic cell for use in manufacturing substrates in integrated circuit manufacturing;

[0012] Figure 2 schematically illustrates a reticle handling subsystem of the lithographic cell of Figure 1;

[0013] Figure 3 schematically illustrates an in-vacuum portion of a reticle handling subsystem;

[0014] Figure 4 is an isometric exploded view of a reticle pod in accordance with an embodiment;

[0015] Figure 5 schematically illustrates a portion of an in-vacuum reticle library in accordance with an embodiment;

[0016] Figures 6A and 6B respectively are side and top schematic views of a cover store system in accordance with an embodiment;

[0017] Figures 7A and 7B respectively schematically illustrate the motion of a movable wing from a ready to a cover store position;

[0018] Figures 8A and 8B respectively are side and top schematic views of a cover store system in accordance with an embodiment;

[0019] Figures 9A and 9B respectively schematically illustrate the motion of a movable wing as in Figures 8A and 8B from a ready to a cover store position;

[0020] Figures 10A and 10B respectively schematically illustrate an alternate motion of a movable wing as in Figures 8A and 8B from a ready to a cover store position;

[0021] Figures 11 A and 1 IB respectively are top and side schematic views of a cover store systemin accordance with an embodiment;

[0022] Figures 12A and 12B respectively schematically illustrate an alternate motion of a movable wing as in Figures 11 A and 1 IB from a ready to a cover store position;

[0023] Figures 13A - 13C respectively are side schematic views of a cover store system in accordance with an embodiment, wherein Figure 13B and 13C illustrate variations on location and movement in the z-direction of a movable cover support.DETAILED DESCRIPTION

[0024] Before describing embodiments in detail, it is instructive to present an example environment in which embodiments may be implemented.

[0025] As shown in Figure 1, a lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to as a lithocell or lithocluster, which also includes apparatus to perform one or more pre- and post-exposure processes on a substrate. Conventionally these include one or more spin coaters SC to deposit a resist layer, one or more developers DE to develop exposed resist, one or more chill plates CH and one or more bake plates BK. A substrate handler, or robot, RO picks up a substrate from input / output ports I / Ol, I / O2, moves it between the different process devices and delivers it to the loading bay LB of the lithographic apparatus. These devices, which are often collectively referred to as the track, are under the control of a track control unit TCU which is itself controlled by the supervisory control system SCS, which also controls the lithographic apparatus via lithographic control unit LACU. Thus, the different apparatus may be operated to maximize throughput and processing efficiency.

[0026] Generally, a lithography tool LA can include an exposure chamber, a projection optical system that projects EUV and / or DUV light through a reticle mounted on a reticle stage onto a wafer to print images of a layer of, e.g., an integrated circuit. The lithography tool LA further may include a reticle handling system that exchanges the reticle being exposed as prescribed by the user of the lithography tool LA.

[0027] Reticle handling for use in EUV and / or DUV apparatus requires at least some steps wherein the reticles are handled in vacuum. For this purpose, within the lithographic apparatus, a reticle handling subsystem 200 as shown in Figure 2 may be included. The reticle handling subsystem may include a pod transport system 202, which may be an integrated pod transport and manual load station combined. The pod transport system interfaces with an atmospheric module 204. The atmospheric module 204 includes one or more load locks 206 which allow it to load reticles into the vacuum module 208. The load lock acts as a pressure-controlled input section to allow movement from atmospheric pressure in the atmospheric module 204 into vacuum in the vacuum module 208.

[0028] Within the vacuum module 208, may be an inspection station 210, which may include functionality to identify the input reticles, inspect the reticle, measure aspects such as the reticle's thickness, cleaning the reticle, and / or aligning the reticle relative to the lithography tool. Holdingreticles in vacuum can be used to condition them prior to use, such that they do not introduce contaminants in the form of outgassed material that has, for example, adsorbed while the reticles are held in atmosphere. In addition, there is a reticle library 212 for storing at least one extra reticle, such that the reticle is quickly available for exchange. Also, based on information gathered at the inspection station, a processing station, and / or a location of the reticle in the reticle library, the stored reticle can be indexed to aid in retrieving the reticles during exposure.

[0029] Within the vacuum module 208 there is further an in vacuum robot 220 for moving reticles into and out of reticle pod positions 222 of the reticle library 212. The reticle library stores one or more reticles for use in exposures, for example for use in multiple exposure imaging techniques, or for exposing different layers or patterns onto the wafer for different manufacturing steps.

[0030] The in vacuum robot 220 exchanges reticles via a reticle exchange device 230 that is adapted to transfer reticles to the reticle stage of the lithography apparatus LA. The reticle exchange device may include one or more arms for holding reticles during loading, unloading, and exchanges.

[0031] Figure 3 illustrates in greater detail a portion of a vacuum module 208. The in vacuum robot 220 is located centrally and movable among various stations within the vacuum module 208. In particular, it is configured to allow for moving reticles into and out of the reticle pod positions 222 of the reticle library, or to and from the inspection station 210 and to and from the load locks (not seen in this figure). The in vacuum robot includes an arm 230 having an end effector 232 (which may also be referred to as a gripper, or holder). While the in vacuum robot 220 is shown as having a single end effector 232, it may in principle have multiple end effectors, allowing it to grip more than one item at a time, for example.

[0032] The end effector is configured to hold a EUV inner pod (EIP, as seen best in Figure 4) 250 which typically includes a baseplate 252, a reticle 254, and a cover 256. In other embodiments, the end effector may be configured to hold an inner pod used in any lithographic apparatus. The cover 256 may include tabs or wings 258 that allow the cover to be lifted from the EIP 250. The baseplate 252 may include one or more containment pins 260 for guiding the reticle 254 into its proper position when it is subject to lateral displacement. Likewise, the cover 256 may include projections 262 that engage with the baseplate 252 to bear the weight of the cover 256, and to keep the cover 256 from touching the reticle 254.

[0033] Figure 5 is a partial view of the vacuum module 208, and in particular illustrating the reticle library 212. Three reticle pod positions 222a-222c of the reticle library are shown, and the end effector 232 of the in vacuum robot 220 is shown in one of the reticle pod positions. Adjacent to each of the three reticle pod positions 222 is a respective pair of positions corresponding to each pod position. Specifically, locations Al and A2 are adjacent to reticle pod position 222a, Bl and B2 are adjacent to reticle pod position 222b, and Cl and C2 are adjacent to reticle pod position 222c. As shown in the figure, the locations are substantially horizontally adjacent to each respective reticle pod position 222a-c, but in principle they may be horizontally or vertically adjacent as desired. The amount of room available between pod positions, for example, may be small, requiring a vertical displacement rather than, or in addition to, a horizontal displacement. Irrespective of the direction of the displacement, the movement may be considered to be to a position adjacent to the pod position.

[0034] Figures 6A and 6B schematically illustrate an embodiment of a mechanism for moving a cover into a cover store position suitable for positions Al and C2, for example. Within a frame portion 270 there is a movable wing 272 that is actuatable to move into and out of the library area. The movable wing 272 is further movable into and out of a pocket area 278, as described in greater detail below. In an embodiment, the movable wing 272 may include a kinematic mount 274 and / or a sensor 276 for determining the presence of the cover on the wing 272. The sensor may be, for example, a reflective beam sensor, capacitive sensor, triangulation sensor, pressure sensor, strain gauge, or any other suitable sensor.

[0035] The movable wing 272 is actuatable along a direction 280 by way of at least one linear actuator 284. As seen in Figure 7A, the movable wing 272 may be an L-shaped member, and the L- shaped member is configured to pivot about a point of rotation 286. In this embodiment, one leg 290 of the movable wing 272 is engaged or engagable with an end of the linear actuator 284 such that as the linear actuator 284 pushes on the leg 290 of the movable wing 272 the wing rotates about the point of rotation 286 which in turn rotates the other leg, containing the kinematic mount 274 and the sensor 276 out of the pocket area 278. This rotational movement of the movable wing 272 results in the configuration illustrated in Figure 7B. Likewise, retraction of the linear actuator 284 rotates the movable wing 272 in the opposite direction, returning the movable wing to its storage position within the pocket area 278 as shown in Figure 7A. The movable wing 272 need not be strictly L-shaped, and other shapes that allow for a similar conversion of linear movement of the actuator into rotational movement such as cammed shapes or the like may be used. A linear actuator as described above may be, for example, a voice coil actuator, which have good vacuum compatibility and therefore are well- suited to use in the in-vacuum library area of the system.

[0036] In this embodiment, the pocket area 278 is disposed adjacent to its respective pod position 222, and the actuator is actuatable as described to move a cover holding portion, i.e., the kinematic mount end of the movable wing 272, into the reticle pod position 222 to remove a cover 256 from a reticle pod 250, and after engaging the wing 258 with the kinematic mount 274, to move the cover 256 into a cover storage position. The wing should be engineered to include sufficient stiffness in the z- direction to effectively support itself and the cover.

[0037] An alternate approach is illustrated in Figures 8 A and 8B. In this embodiment, rather than a linear actuator 284, the actuator may include a rotational actuator 292 configured to rotate the movable wing 272 about the point of rotation 286. In this case, rather than the direction 280 of Figures 6A and 6B, the rotational actuator 292 is actuatable in a rotational direction 294. The actuator 292 may rotatean L-shaped movable wing 272 as in the previous embodiment and as illustrated in Figures 9A and 9B, or alternately may use a relatively linear wing 296 as shown in Figures 10A and 10B. Other than the specific direction of motion of the actuator, the operation of the embodiment of Figures 8 A, 8B - 10A, 10B is similar to that of the embodiment shown in Figures 6A, 6B - 7A, 7B.

[0038] In another embodiment, rather than a rotational in-plane movement as described above, a hanging bridge movable wing 296 may be implemented. In this embodiment, illustrated in Figures 11 A, 1 IB - 12A, 12B, the hanging bridge movable wing 296 is configured to rotate, either up or down, out of its plane when it is in its storage position within the pocket area 278. An actuator (not illustrated) is configured to rotate it from its vertical storage position into a horizontal cover store position as seen in Figures 12A and 12B. That is, the hanging bridge movable wing 296 is rotatable between a first position, out of a plane of the pod position, and a second position, in the plane of the pod position, and into its respective reticle pod position to remove the cover from the reticle pod and to move the cover into the cover storage position In other respects, the hanging bridge movable wing 296 is similar to the movable wing 272 in that it may include a similar kinematic mount 274 and sensor 276.

[0039] A further embodiment may find particular application in regions where there is insufficient room within a wall of the frame to place the foregoing embodiments. For example, this approach may be suited to positions A2, Bl, B2, and Cl where vertical space is more easily identified than frame space may be.

[0040] In this embodiment, a pair of vertical cover store positions may be provided for by including an upper movable wing 300 and a lower movable wing 302 in a z-lift approach. Each is actuated by way of an actuator 304, which may be, for example, a linear actuator. The linear actuator 304 is configured to move from a first, ready position to a second, cover store position as illustrated in Figures 13A - 13C. Figure 13A illustrates the upper and lower movable wings 302, 304 in their ready positions, while 13B illustrates the same wings actuated into their cover store positions. The kinematic mount 274 and sensor 276 may be similar to those used in the above embodiments. Figure 13C illustrates an alternate upper and lower position for the upper movable wing 300 and the lower movable wing 302, wherein their respective actuators are held on a common base.

[0041] In an embodiment that may be combined with any of the foregoing embodiments, facility for storing two covers adjacent some or each of the reticle pod positions 222 within the library may be provided. This can simplify the process of returning one pod to the library in an exchange operation where a cover is already stored in that position from a different pod.

[0042] In an embodiment, the cover store itself may include actuators. In this approach, could include, for example, z-actuators such that the in vacuum robot may be stationary in the z-direction, while the actuators of the cover store moves the movable wing and takes the cover from the robot. This may allow, for example, reduced vibration of the robot in the z direction.

[0043] As may be appreciated, certain of the above-described approaches may be better suited toone or more particular locations within the IVL. For example, the embodiments using a lateral pocket with a movable wing, swing out arm, or swing bridge may best fit at locations Al and C2 of an IVL as shown in view of the possibility of using lateral space adjacent the outermost of the reticle pod positions. The use of z-lift approaches may best fit at locations A2, Bl, B2, Cl, in between reticle pod positions, where lateral space may be at a premium. The precise combination of approaches taken will depend on the specifics of the space available within the IVL volume, and differences in designs of the reticle pod positions may make additional room for side pockets more or less available than as in the configuration shown.

[0044] Various embodiments of the present apparatuses, systems and methods are disclosed in the subsequent list of numbered clauses:1. A system for handling a reticle, comprising: a vacuum chamber; a library configured to hold a plurality of reticle pods in vacuum in a plurality of reticle pod positions, disposed within the vacuum chamber, each reticle pod of the plurality of reticle pods comprising a respective baseplate, reticle, and cover; an in-vacuum robot, configured to selectively pick a reticle pod from the plurality of reticle pods and provide the picked reticle pod to a reticle exchange device; and a plurality of actuators, each actuator corresponding to a respective one of the pod positions, and each actuator being configured to remove the cover from a corresponding reticle pod and move the cover into a cover storage position associated with the corresponding reticle pod.2. A system as in clause 1, wherein each cover storage position is adjacent to a respective one of the pod positions.3. A system as in clause 1, wherein at least one of the plurality of actuators comprises a linear actuator disposed adjacent to a respective one of the reticle pod positions, the linear actuator being actuatable to move a cover holding portion into the respective reticle pod position to remove the cover from the reticle pod and to move the cover into the cover storage position.4. A system as in clause 2, wherein the linear actuator is actuatable to rotatably move the cover holding portion.5. A system as in any of clauses 1 or 2, wherein at least one of the plurality of actuators comprises a rotational actuator disposed adjacent to a respective one of the pod positions, the rotational actuator being actuatable to move a cover holding portion into the respective reticle pod position to remove the cover from the reticle pod and to move the cover into the cover storage position.6. A system as in clause 5, wherein the cover holding portion comprises an L-shaped member, wherein the rotational actuator is operably connected to a first leg of the L-shaped member, and a second leg of the L-shaped member comprises a mount for holding the cover.7. A system as in clause 6, wherein the cover holding portion comprises an elongated member, wherein the rotational actuator is operably connected to a first end of the elongated member, and amount for holding the cover is positioned at a second end of the elongated member.8. A system as in clause 1, wherein at least one of the plurality of actuators comprises a cover holding portion having a first position, rotated out of a plane of the pod position, and a second position, rotated into a plane of the pod position and into a respective reticle pod position to remove the cover from the reticle pod and to move the cover into the cover storage position.9. A system as in any of clauses 1-8, wherein at least one of the plurality of actuators comprises a linear actuator configured to move in a direction perpendicular to a plane of the reticle pod.10. A system as in any of clauses 1-9, wherein each actuator comprises: a mount, configured to support the cover in the cover storage position; and a sensor, configured to sense the presence of the cover on the mount.11. A system as in any of clauses 1-10, wherein the library comprises a frame, and a portion of the frame adjacent each reticle pod position comprises a holding chamber for a respective actuator.12. A system as in any of clauses 1-11, wherein each reticle pod position corresponds to two respective cover storage positions.13. A system as in any of clauses 1-12, further comprising: an in-vacuum robot, configured to move an uncovered reticle to a reticle exchange device for use in a lithographic imaging operation.14. A system as in any of clauses 1-13, further comprising: at least one load lock for accepting reticle pods from an atmospheric module for placement into the library.

[0045] The terms “optimize”, “optimizing” and “optimization” as used herein mean adjusting a lithographic process parameter such that results and / or processes of lithography have a more desirable characteristic, such as higher accuracy of projection of a design layout on a substrate, a larger process window, etc.

[0046] An embodiment of the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed herein, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein. Further, the machine readable instruction may be embodied in two or more computer programs. The two or more computer programs may be stored on one or more different memories and / or data storage media.

[0047] This computer program may be included, for example, with or within the inspection apparatus and / or with or within the control unit LACU of Figure 1. Where an existing apparatus, for example of the type shown in Figures 2 and 3, is already in production and / or in use, an embodiment can be implemented by the provision of updated computer program products for causing a processor of the apparatus to perform a method as described herein.

[0048] Any controllers described herein may each or in combination be operable when the one ormore computer programs are read by one or more computer processors located within at least one component of the inspection apparatus. The controllers may each or in combination have any suitable configuration for receiving, processing, and sending signals. One or more processors are configured to communicate with the at least one of the controllers. For example, each controller may include one or more processors for executing the computer programs that include machine-readable instructions for the methods described above. The controllers may include data storage medium for storing such computer programs, and / or hardware to receive such medium. So the controller(s) may operate according the machine readable instructions of one or more computer programs.

[0049] Although specific reference may have been made above to the use of embodiments in the context of lithography using radiation, it will be appreciated that an embodiment of the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to lithography using radiation. 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.

[0050] Further, 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, liquid-crystal 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 (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and / or an inspection tool. Where applicable, the disclosure herein may 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.

[0051] The patterning device described herein may be referred to as a lithographic patterning device. Thus, the term “lithographic patterning device” may be interpreted as meaning a patterning device which is suitable for use in a lithographic apparatus.

[0052] The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 355, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5- 20 nm), as well as particle beams, such as ion beams or electron beams.

[0053] The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

[0054] The embodiment(s) described, and references in the specification to an “embodiment”, “example,” etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0055] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below. For example, one or more aspects of one or more embodiments may be combined with or substituted for one or more aspects of one or more other embodiments as appropriate. 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. It is to be understood that the phraseology or terminology herein is for the purpose of description by example, and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. The breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

CLAIMS1. A system for handling a reticle, comprising: a vacuum chamber; a library configured to hold a plurality of reticle pods in vacuum in a plurality of reticle pod positions, disposed within the vacuum chamber, each reticle pod of the plurality of reticle pods comprising a respective baseplate, reticle, and cover; an in-vacuum robot, configured to selectively pick a reticle pod from the plurality of reticle pods and provide the picked reticle pod to a reticle exchange device; and a plurality of actuators, each actuator corresponding to a respective one of the pod positions, and each actuator being configured to remove the cover from a corresponding reticle pod and move the cover into a cover storage position associated with the corresponding reticle pod.

2. A system as in claim 1, wherein each cover storage position is adjacent to a respective one of the pod positions.

3. A system as in claim 1, wherein at least one of the plurality of actuators comprises a linear actuator disposed adjacent to a respective one of the reticle pod positions, the linear actuator being actuatable to move a cover holding portion into the respective reticle pod position to remove the cover from the reticle pod and to move the cover into the cover storage position.

4. A system as in claim 2, wherein the linear actuator is actuatable to rotatably move the cover holding portion.

5. A system as in any of claims 1 or 2, wherein at least one of the plurality of actuators comprises a rotational actuator disposed adjacent to a respective one of the pod positions, the rotational actuator being actuatable to move a cover holding portion into the respective reticle pod position to remove the cover from the reticle pod and to move the cover into the cover storage position.

6. A system as in claim 5, wherein the cover holding portion comprises an L-shaped member, wherein the rotational actuator is operably connected to a first leg of the L-shaped member, and a second leg of the L-shaped member comprises a mount for holding the cover.

7. A system as in claim 6, wherein the cover holding portion comprises an elongated member, wherein the rotational actuator is operably connected to a first end of the elongated member, and a mount for holding the cover is positioned at a second end of the elongated member.

8. A system as in claim 1, wherein at least one of the plurality of actuators comprises a cover holding portion having a first position, rotated out of a plane of the pod position, and a second position, rotated into a plane of the pod position and into a respective reticle pod position to remove the cover from the reticle pod and to move the cover into the cover storage position.

9. A system as in any of claims 1-8, wherein at least one of the plurality of actuators comprises a linear actuator configured to move in a direction perpendicular to a plane of the reticle pod.

10. A system as in any of claims 1-9, wherein each actuator comprises: a mount, configured to support the cover in the cover storage position; and a sensor, configured to sense the presence of the cover on the mount.

11. A system as in any of claims 1-10, wherein the library comprises a frame, and a portion of the frame adjacent each reticle pod position comprises a holding chamber for a respective actuator.

12. A system as in any of claims 1-11, wherein each reticle pod position corresponds to two respective cover storage positions.

13. A system as in any of claims 1-12, further comprising: an in-vacuum robot, configured to move an uncovered reticle to a reticle exchange device for use in a lithographic imaging operation.

14. A system as in any of claims 1-13, further comprising: at least one load lock for accepting reticle pods from an atmospheric module for placement into the library.

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