Patent Description:
Photolithography processes are widely used as one of the key steps in the manufacture of integrated circuits (ICs) and other semiconductor-related devices and/or structures. However, as the dimensions of features produced by such processes decrease, the importance of photolithography for the production of miniature ICs or other devices and/or structures rises.

In photolithography, a geometric pattern is transferred from a photomask (typically referred to as reticle) onto a substrate, for example a semiconductor wafer, by the use of light, a photosensitive layer and a subsequent etching step. Depending on the desired feature size on the substrate, the feature size of the reticle needs to be adapted as well as the wavelength of the light used for pattern transfer, with consideration of the Raleigh criterion.

In order to reduce the smallest achievable feature size, it has been proposed to use extreme ultraviolet (EUV) radiation. EUV radiation is electromagnetic radiation having a wavelength within the range of <NUM>-<NUM>, for example within the range of <NUM>-<NUM>.

Any contamination of the reticle may reduce the imaging performance of the photolithographic process and may in more serious cases require the reticle to be replaced. The reticle is typically expensive and therefore any reduction in the frequency with which it must be replaced is advantageous. Furthermore, replacement of the reticle is a time consuming process, during which the photolithographic process may have to be supported, thereby reducing its efficiency, which is undesirable.

For EUV applications, particle contamination with particle sizes of less than <NUM> as well as chemical contamination, for example by adsorption of volatile organic compounds, can be relevant.

The reticles used for such EUV applications are therefore typically stored in a storage stocker, and retrieved when needed in connection with the lithography exposure equipment. Usually, the reticles are contained in a double shell container (double pod) comprising a socalled EUV outer pod (EOP) and an EUV inner pod (EIP).

Such a double pod is described in further detail in <CIT>, for example.

Since the acceptable level of particle contamination is extremely small, friction (which leads to abrasion and thus particle generation) of the reticle against the container as well as friction of container components relative to one another needs to be avoided. Therefore, typical EIPs are designed so as to accommodate one reticle in such a way that it has only very limited possibilities to move therein. They are also equipped with additional reticle immobilization means to immobilize the reticle inside the EIP. In order to prevent contamination, the EIP is designed to enable a protective gas or vacuum to be applied to the reticle. To that end, typically orifices equipped with filter material are provided for the protective gas to enter from the EOP into the surroundings of the reticle contained in the respective EIP.

The EOP is equipped with actuation means adapted to bias the reticle immobilization means of the EIP into a retaining position, thereby immobilizing the reticle inside the EIP when the EOP is attached to the EIP. The EOP also functions to immobilize the typically two pieces of the EIP against one another to prevent friction induced abrasion.

A clamping device for immobilizing the EIP during times of storage, for example, are disclosed in <CIT>, in which systems and methods to protect a reticle from being contaminated by airborne particles are described. Those systems and methods include providing a reticle secured in a two-part cover. The two part cover includes a removable protection device used to protect the reticle from contaminants. The cover can be held inside a pod or box that can be used to transport the cover through a lithography system from an atmospheric section to a vacuum section. While in the vacuum section, the removable cover can be moved during an exposure process during which a pattern on the reticle can be formed on a wafer.

According to <CIT>, a reticle protection device capable of keeping a reticle therein is provided with an inner pod capable of keeping the reticle therein; an outer pod capable of keeping the inner pod therein; an electroconductive movable contact portion provided on at least one of the inner pod and the outer pod and being capable of coming into contact with an electroconductive film of the reticle; and a leaf spring for achieving electric conduction of the contact portion to at least one of the inner pod and the outer pod. The reticle is kept in the inner pod and the inner pod is kept in the outer pod, thereby enabling stable grounding of the reticle.

It is to be understood that the EIP components are moveable against one another as long as they are not immobilized from outside. In order to avoid friction induced abrasion caused by such movement, the EOP conventionally provides such immobilization functionality for the EIP while also providing protection against the surrounding atmosphere, which is necessary e.g. during transport between a storing position and process tools requiring reticles for operation.

EOPs are rather bulky, leading to high space requirements or "footprint" for stockers storing EUV reticles. Furthermore, they are made of polymeric material, which is also prone to abrasion and outgassing of volatile organic compounds.

The present invention attempts to solve these problems by providing methods, devices and systems with features according to the independent claims. Advantageous embodiments and additional features are provided in the dependent claims and discussed in the following description.

The present invention enables reducing the required space for storing reticles while ensuring at least the same level of contamination and damage protection provided by conventional systems. Chemical contamination during storage from outgassing EOPs is prevented and mechanical damage protection improved over storing reticles in double pods. For example, EOPs can easily be damaged during an earthquake, while devices according to the present invention are less fragile, even under such challenging conditions, as will be understood from the following description.

Aspects which need to be taken into account when developing such an improved storage concept include that it is highly undesirable to change the way the reticles are provided to the photolithographic process equipment, this typically being the most complicated and costly part of a semiconductor production facility.

Therefore, since the photolithographic process equipment is typically adapted to receive double pods, means for providing a conventional double pod to the photolithographic process equipment are advantageously provided with the improved reticle stocker.

In one aspect of the invention, a clamping device for an EUV inner pod (EIP) is provided, the EIP comprising two or more components and containing or adapted and configured to contain an EUV reticle, wherein the clamping device is configured to immobilize the two or more components of the EIP and the reticle relative to one another, and to only partially cover the EIP. For example, only a fraction amounting to less than <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% of an outer surface of the EIP is covered by the clamping device according to the invention. The clamping device, therefore, allows e.g. the atmosphere surrounding the clamping device to come into contact with the EIP, thus e.g. obviating the need for sophisticated supply means for protective gasses.

Be it noted that the clamping device can also be used for clamping the components of the EIP together, even if this does not hold a reticle. In this case, only the components of the EIP are immobilized relative to one another.

Advantageously, the clamping device is further configured to act upon a retention means of the EIP, the retention means being configured to immobilize the reticle therein, when acted upon from outside the EIP, to immobilize the reticle within the EIP. Therefore, the immobilization of the reticle within the EIP is effected through the clamping device acting upon the retention means provided with the EIP. This provides the advantage, that existing systems can continue to be used without the need for retrofitting, thus avoiding costly investments.

Advantageously, the clamping element is mainly made of metallic materials, the metallic materials comprising preferably at least <NUM> %, <NUM> %, <NUM> %, <NUM> % or <NUM> %, with respect to total device volume and/or mass. This mitigates the above mentioned problem of chemical contamination through outgassing of polymeric materials. Thereby the required amount of purging gases and the frequency of necessary reticle replacement can be reduced. Other possible materials with similar advantages are, for example, polycarbonates (PC), poly ethyl ether ketones (PEEK) or cyclo olefin (co)polymers (COC / COP). The uniting feature of these materials is a particularly low outgassing characteristic.

In a first alternative according to this invention, the clamping device is provided with two clamping elements comprising an upper clamping element and a lower clamping element which are configured to be attachable to one another while accommodating the EIP between them. Particularly, the movement required for assembling such a clamping device around an EIP is substantially normal towards a main surface of the EIP and lateral movements with respect to the EIP are substantially not required. This facilitates the assembly process and reduces the risk of friction induced particle generation (abrasion).

Advantageously, the upper clamping element is configured to act upon the retention means of the EIP to immobilize the reticle therein. It can thus replace or emulate the immobilization function that the EOP traditionally fulfils without the drawbacks in terms of chemical contamination and spatial footprint.

In a second alternative according to this invention, the clamping device comprises one clamping element and one, two or more fixation means, wherein the fixation means are biased towards a closed position and are configured to be moved into an open position; wherein the clamping device is configured to be attachable to an EIP, when the fixation means are in the open position and to immobilize the EIP components and the reticle relative to one another, when the fixation means are in and/or brought into the closed position In other words, the clamping device is provided as a single or one-piece clamping element comprising fixation means. The fixation means act upon an underside of an EIP, when the clamping device is attached to the EIP, and on a top side of the clamping element. Otherwise this single clamping element provides the same functionality as the upper clamping element described above. This one-piece-embodiment is favourable in terms of handling, since only one piece is required to provide the same functionality. This one piece is attached to the EIP from the top side of the EIP. Therefore, fewer handling steps are required for attaching the clamping device to an EIP, as compared to the two-piece embodiment described above.

Advantageously, the clamping device comprises actuators configured to act upon the retention means, when the clamping device is attached to the EIP.

Advantageously, the clamping device has an envelope volume of less than <NUM> %, <NUM> %, <NUM> %, <NUM> % or even less than <NUM> % of an envelope volume of an EIP to which the clamping device is attachable.

Particularly the clamping device has an envelope volume which is less than <NUM> %, <NUM> %, <NUM> % or <NUM> % of the envelope volume of the EIP, thus substantially reducing the spatial footprint of storing a reticle compared to storage within a double pod comprising an EIP and an EOP. This may also reduce the required amount of purging gases, as mentioned above. An envelope volume, for example, can be understood as describing the volume of the smallest possible cuboid completely containing a respective object.

The clamping device according to some embodiments may be equipped with an information carrying element, such as an RFID device or a visually detectable code such as a bar code, a QR code or other forms of 1D or 2D codes. This provides the advantage that information about the reticle can be associated with the corresponding clamping device. Therefore, it may be possible, for example, to identify a stored reticle solely by identifying the clamping device associated with it.

Furthermore, such information can be used for tracking purposes, for example to count the number of storage operations performed with a given clamping device. This is useful in order to determine the appropriate time for cleaning or replacement procedures or functionality tests.

In some embodiments, a sensor for monitoring certain conditions during storage and handling, such as humidity, temperature, pressure, acceleration or the concentration of certain chemical species in the storage atmosphere and the like is included in the clamping device. This provides the advantage of knowledge of influencing factors experienced by reticles throughout their storage history and can therefore improve the overall productivity of a production facility in which the present invention is used.

Such information can be stored and processed in a memory and/or processor provided with the clamping device or in a component of a machine or tool handling a storage system according to the invention.

In another aspect, the present invention provides a storage system comprising a clamping device as described above and an EIP. The EIP comprises two or more components, is configured to accommodate an EUV reticle and comprises a retention means configured to immobilize a reticle contained within the EIP when the retention means is acted upon from outside the EIP. The clamping device is attached to the EIP to immobilize the two or more components of the EIP relative to one another and acts upon the retention means, thus immobilizing the reticle within the EIP. Therefore, abrasion can be substantially avoided and contamination of the reticle by particles in a relevant size range minimized.

Typically, the retention means is provided in the form of one or more pistons penetrating one of the EIP components. Each of the pistons is elastically biased into a retracted position and is adapted to apply a normal force onto the reticle when acted upon from outside the EIP. At the same time, the retention means is in sealing engagement with the EIP component it penetrates in order to protect the reticle stored within the EIP from contamination with contaminants from outside the EIP.

In a preferred embodiment, the storage system has an envelope volume of less than <NUM> %, <NUM> %, <NUM> % or <NUM> %, compared to the envelope volume of the EIP. As such, the space required for storing a reticle is significantly reduced in relation to conventional storage systems in the form of a double pod comprising an EIP and an EOP.

Another aspect of the invention provides a method of operating an EUV reticle stocker, comprising storing reticles in the reticle stocker and retrieving reticles from the reticle stocker, wherein the storing comprises moving a storage system according to the invention containing a reticle to a storage position within the EUV reticle stocker; and the retrieving comprises removing a storage system according to the invention containing a reticle from its storage position. This reduces the required space for storing reticles in comparison to conventional storage methods.

The storing, before the step of moving to a storage position, according to the invention further comprises the steps of: receiving, from outside the stocker, a double pod comprising an EUV outer pod (EOP) and an EIP containing an EUV reticle, wherein the EIP is entirely contained within the EOP; opening the EOP; and attaching a clamping device to the EIP to immobilize EIP components relative to one another and to act upon the retention means provided in the EIP to immobilize the reticle relative to the EIP to provide the storage system.

Therefore, the storage system is provided by the improved stocker itself, making it possible to directly utilise the stocker in conjunction with an existing manufacturing process without substantially altering any process steps carried out outside the stocker.

In a preferred embodiment, receiving a double pod comprises accepting the double pod at an outwardly facing side of an entrance terminal comprising an airlock, opening a first shutter of the airlock, moving the double pod into the airlock, closing the first shutter, decontaminating an inner volume of the airlock, opening a second shutter of the airlock, moving the double pod through the second shutter to an inwardly facing side of the entrance terminal, and closing the second shutter. In other words, the double pod it is passed through the airlock from an outwardly facing side to an inwardly facing side of the entrance terminal, including a decontamination of the inner volume of the airlock, while the double pod is inside the airlock. This provides the advantage of avoiding contamination of the stocker.

Opening of an EOP may include unlocking the EOP, removing it from around the EIP and storing it in an EOP buffer stock. The EOP buffer stock is preferably separated from the storage positions for the storage system described above, in order to prevent cross contamination from the outer side of the EOP to the EIP. Thus, strict cleanliness requirements can be met while reducing the space needed for storing reticles.

The retrieving of reticles after the step of removing the storage system from its storage position preferably further comprises detaching the clamping device from the EIP, assembling an EOP around the EIP to immobilize the EIP components and the reticle contained within the EIP relative to each other, forming a double pod, and delivering the double pod to outside the stocker, preferably by passing it through an airlock in order to prevent contamination of the stocker atmosphere. This provides the advantage that standard double pods can be used with the production process in the facility, thereby enabling conventional process equipment to profit from the improved storage conditions provided in connection with this invention.

The EOP used for this assembling can preferably be retrieved from the above mentioned EOP buffer stock. This provides the advantage that an EOP is not required for every reticle to be stored, while ensuring timely supply of any reticles required for the manufacturing process. In other words, the number of reticles stored can significantly exceed the number of EOPs provided. In other words, only those reticles required outside the stocker at any given time require an EOP during that time.

Preferably, it is ensured, during any step performed at a time when the reticle is not immobilized relative to the EIP, that the reticle and/or EIP components are not moved relative to one another, in order to prevent abrasion and corresponding particle generation.

In cases in which the clamping device is provided with an information carrying element, as described above, the method can advantageously comprise one or more steps in which information carried by the clamping device is read, written, deleted or altered. In such steps information about the identity of a reticle associated with a handled clamping device, the storage conditions a reticle experienced or other pieces of information can be used for controlling the reticle stocker or other tools, machines or devices in order to provide improved overall performance of the production facility.

The method may further comprise reading, receiving or otherwise collecting information provided by the one or more sensors optionally provided with the clamping device in order to monitor a history of storage conditions, the reticle has experienced. This provides the advantage that those reticles which are more likely to have deficiencies regarding quality can, for example, be inspected prior to use in the manufacturing of semiconductor products to ensure their integrity. Thereby, the output of faulty products is minimized.

In a further aspect of the invention, a stocker for storing at least one EUV reticle is provided, wherein each of the at least one reticle is stored or adapted and configured to be stored in one respective EUV inner pod (EIP), wherein the EIP comprises two or more EIP components which are immobilized relative to one another by a clamping device, wherein the EIP comprises retention means configured to immobilize the reticle stored inside the EIP relative to the EIP, when acted upon from outside the EIP, wherein the clamping device acts upon the retention means to immobilize the reticle stored within the EIP, the stocker comprising: a loading port (also referred to as entrance terminal in the language of this disclosure) comprising an airlock and an assembler; a storage unit configured to store EIPs each immobilized by one clamping device and each containing one reticle; and a handler configured to move the clamped EIP containing the reticle to and from a storage position within the stocker; wherein the airlock is configured to receive a double pod comprising an EUV outer pod (EOP) and an EIP containing a reticle from outside the stocker, wherein the EOP acts upon the retention means; and the assembler is configured to open the EOP without causing movement of EIP components and the reticle relative to one another; to attach said clamping device to and remove the clamping device from said EIP without causing movement of the EIP components and the reticle relative to one another; and to assemble an EOP around the unclamped EIP.

Advantageously, the stocker further comprises an EOP buffer stock, configured to store a number of EOPs in a controlled atmosphere with handling means configured to place an EOP into and retrieve an EOP from the EOP buffer stock.

In other words, the stocker is adapted to implement the above described method(s) and therefore profits from the same advantages as the method described above.

Advantages and further aspects of the invention will now be discussed in further detail with reference to the accompanying drawings, wherein.

Two embodiments A, B of a conventional EIP generally designated <NUM> are shown in <FIG>. Each EIP <NUM> comprises an upper component <NUM> and a lower component <NUM>. The upper component <NUM> comprises one or more orifices <NUM>, retention means <NUM> and pressure points <NUM>.

The retention means <NUM> are provided in the form of four pistons, biased into a retracted position by elastic elements and connected to the upper component <NUM> in a sealing manner by elastic sealing means to prevent particulate contaminants from entering the inside of the EIP.

The orifices <NUM> are equipped with filter material also preventing particulate contaminants from entering the inside of the EIP while providing access for purging and/or protective gas(es) such as nitrogen.

The pressure points <NUM> are provided for immobilizing the two components <NUM>, <NUM> relative to one another and the retention means are provided for immobilizing a reticle inside the EIP when acted upon from outside the EIP.

Pressure points similar to the pressure points <NUM> of the upper component <NUM> may also be provided with the lower component <NUM>.

In embodiment A of EIP <NUM>, the pressure points <NUM> are spatially separated from the retention means <NUM>, while in embodiment B, the retention means <NUM> are provided within the same area as the pressure points <NUM> and extend through the pressure points <NUM>.

In <FIG> and <FIG> clamping devices <NUM> usable in connection with embodiments A, B of EIP <NUM> are schematically depicted.

The clamping device <NUM> comprises two elements <NUM>, <NUM> made of sheet metal, one of which is an upper clamping element <NUM> featuring an orifice <NUM> substantially corresponding to the one or more orifices <NUM> of the EIP in terms of location and is formed to fit onto EIP <NUM>. The part of the surface of EIP <NUM>, which corresponds to the orifice <NUM> in terms of location, is referred to as "not covered" in the language of this disclosure, while particularly portions of the surface of EIP <NUM>, which are in contact with or located directly opposite or under a material surface of the clamping device, are considered to be "covered". Therefore, according to the invention, clamping device <NUM> is configured to only partially cover EIP <NUM>. The orifice <NUM> can especially take up more than <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% of the surface area of the upper clamping element <NUM>. Furthermore, a similar orifice may also be provided in the lower clamping element <NUM> (not shown in the figures). Additionally, a sideways facing surface of EIP <NUM>, which is in correspondence with neither of the upper <NUM> or lower <NUM> clamping elements is also considered "not covered".

Second element <NUM> forming a lower clamping element is essentially flat and corresponds to the upper clamping element <NUM> in size and shape and contour.

The upper <NUM> and lower <NUM> clamping elements are attachable to one another and are configured to accommodate and immobilize the EIP <NUM> between them when attached to one another. To that end, the upper and lower clamping elements are both equipped with pressing means <NUM>, which are configured to press against the respective pressure points <NUM> of the upper and lower components <NUM>, <NUM> of the EIP <NUM> to immobilize the EIP components <NUM>, <NUM> relative to one another.

Further, actuators <NUM> are provided with the upper clamping element <NUM> for embodiment A of EIP <NUM> which are configured to act upon the retention means <NUM> of the upper component <NUM> of embodiment A of EIP <NUM>, when the clamping device <NUM> is attached to EIP <NUM>.

In the clamping device <NUM> adapted for use with embodiment B of EIP <NUM>, pressing means <NUM> simultaneously fulfil the function of actuators <NUM>. Thus, each pressing means <NUM> also constitutes an actuator <NUM>.

For both embodiments shown, by acting upon the retention means <NUM> of EIP <NUM>, the clamping device <NUM> immobilizes the reticle contained within EIP <NUM> relative to the EIP <NUM>.

The pressing means <NUM> and the actuators <NUM> are provided in the form of tongue shaped cut-outs and can be configured to apply predetermined forces to the pressure points <NUM> and the retention means <NUM>, respectively. Advantageously the pressing means <NUM> are configured to apply a predetermined force to each of the pressure points <NUM>. In the clamping device for use with embodiment A of EIP <NUM>, this force applied to the pressure points may be different from the predetermined force the actuators <NUM> apply to the retention means <NUM>. As such, the forces applied to the retention means <NUM> and the pressure points <NUM> can be adapted to the required forces needed for immobilizing the respective parts relative to one another. Typically, the forces required for immobilizing the reticle within the EIP are smaller than the forces required for immobilizing the upper component <NUM> relative to the lower component <NUM>. Therefore, a tongue shaped cut-out forming an actuator <NUM> may be longer and/or narrower than a cut-out forming a pressing means <NUM>.

In the clamping device adapted to be usable with embodiment B of EIP <NUM>, it is also possible to apply different forces to the pressure points <NUM> and the retention means <NUM>, respectively, for example by providing an additional tongue shaped cut-out (not shown in the figures) within the pressing means <NUM>, so that a smaller force may be applied to the retention means <NUM> as compared to the force applied to the pressure points <NUM>. In other words, even though the pressure points <NUM> and retention means <NUM> in the embodiment B of EIP <NUM> are in close proximity, it is still possible to provide pressing means <NUM> and actuators <NUM> separately from one another.

The upper clamping element <NUM> is provided with fixation means <NUM> which are configured to fixedly attach the upper clamping element <NUM> to the lower clamping element <NUM> so as to provide the clamping device <NUM>. In the example shown in <FIG> and <FIG>, the fixation means <NUM> are provided in the form of a latch, but other forms of fixation means are also possible.

In <FIG> a storage system <NUM> comprising an EIP <NUM> and a two-piece clamping device <NUM> with upper <NUM> and lower <NUM> clamping elements is shown in an assembled state. The lower clamping element <NUM> is not visible in <FIG> as it is covered by the EIP <NUM>.

In <FIG> a further advantageous embodiment of a clamping device <NUM> is schematically shown in perspective and plan views.

In contrast to the clamping device <NUM> shown in <FIG> and <FIG> the clamping device <NUM> comprises only one clamping element with at least two fixation means <NUM>. Furthermore one or more pressing means <NUM> are provided, which are configured to press against the respective pressure points <NUM> of the upper component <NUM> of EIP <NUM> to immobilize the EIP components <NUM>, <NUM> relative to one another. The fixation means <NUM> are configured to press against a top side of the clamping element <NUM> and against an underside of the lower component <NUM> of the EIP <NUM>, when the clamping device <NUM> is attached to the EIP <NUM>. Similar to the clamping device <NUM>, in the clamping device <NUM> actuators <NUM> are provided to immobilize the reticle within the EIP <NUM>. The immobilization of the reticle within the EIP <NUM> is effected by an interaction between the actuators <NUM> with the retention means <NUM> of the EIP <NUM> when the clamping device <NUM> is attached to the EIP <NUM>.

It is noted that the clamping device <NUM> shown in <FIG> is adapted to be usable with embodiment A of EIP <NUM>. It is, however, to be understood that a similar one-piece clamping device <NUM> can be provided for embodiment B of EIP <NUM>.

In <FIG> the fixation means <NUM> are shown in a closed position. In this particular embodiment fixation means <NUM> are provided on two sides of the clamping device <NUM> essentially in the form of a flat spring with handling and fixing elements. When attached to an EIP <NUM>, the fixing elements of the fixation means <NUM> fulfil the above described function of pressing against the top side of the clamping element and the underside of the lower component <NUM> of EIP <NUM>.

In <FIG> the fixation means <NUM> are shown in an open position. In this position, the fixation means <NUM> are spaced from the clamping element in such a way that the space between fixing elements <NUM> on two opposite sides of the clamping device <NUM> is large enough for an EIP <NUM> to be moved between them. Therefore, when the fixation means <NUM> are in the open position, the clamping device <NUM> may be attached to an EIP <NUM>.

The fixation means <NUM> in the form of a flat spring are biased against the closed position so that, in order to be attached to the EIP <NUM>, a lateral force has to be applied to the fixation means <NUM> in order to bring them into the open position.

The clamping element of the clamping device <NUM> is preferably essentially made of sheet metal, while the fixation means <NUM> can be provided in the form of flat springs of metal, a plastic or any other suitable single material or combination of materials.

The actuators <NUM> and pressing means <NUM> are preferably provided in the form of tongue shaped cut-outs, essentially as described above in connection with the embodiment of <FIG>.

When the clamping device <NUM> is to be attached to an EIP <NUM>, the fixation means <NUM> are forced into the open position. This may be achieved by pulling the handling elements of the fixation means in a substantially lateral direction with respect to the clamping device <NUM>. The clamping device <NUM> with the fixation means <NUM> held in the open position is then placed on the EIP and pressed downwardly against the EIP with a preload force. Thereby, the pressing means <NUM> and the actuators <NUM> of the clamping device <NUM> are brought into contact with the pressing points <NUM> and the retention means <NUM> of the EIP <NUM>, respectively. Thus, the EIP components <NUM>, <NUM> and the reticle contained within the EIP <NUM> are immobilized relative to one another by the interaction of the clamping device <NUM> with the EIP <NUM> as soon as the preload force is applied.

The preload force is chosen such that the clamping device <NUM> is moved towards the EIP <NUM> in a normal direction relative to its main plane of extension to such an extent that the fixation means <NUM> can be released into the closed position without the fixation means <NUM> coming into contact with any part of the EIP <NUM>. Hereby, as long as the preload force is applied, no friction is induced by the movement of the fixation means <NUM> into the closed position. Therefore, particle generation is effectively prevented.

As long as the preload force is applied to the clamping device <NUM>, the fixation means <NUM> remain spaced from the EIP <NUM> and the top side of the clamping device <NUM> in the normal direction.

Once the fixation means <NUM> have reached the closed position, the applied preload force is released, so that the clamping device <NUM> moves away from the EIP <NUM>, until the fixation means <NUM> restrict further displacement of the clamping device <NUM> relative to the EIP <NUM> by pressing against the top side of the clamping device and the underside of the lower component <NUM> of the EIP <NUM>.

After the preload force has been removed from the top side of the clamping device <NUM>, the actuators <NUM> and pressing means <NUM> still apply immobilizing forces in the normal direction to the retention means <NUM> and pressing points <NUM>, respectively. These immobilizing forces are somewhat smaller than the preload force. However, the actuators <NUM> and retention means <NUM> are each designed such that the immobilizing forces effected by each of them are sufficient to immobilize the reticle within and the components <NUM>, <NUM> of the EIP <NUM> relative to one another. For example, the pressing means <NUM> of one clamping element <NUM> effect a normal immobilization force on the pressing points <NUM> in the range of <NUM> N to <NUM> N, preferably in the range of <NUM> N to <NUM> N, e. about <NUM> N ± <NUM> N, for example <NUM> N, collectively or on each individual pressing point <NUM>. This collective immobilization force is preferably equally distributed over the entirety of single pressing means <NUM>. In the illustrated example, a quarter of the collective immobilization force is applied to each of the pressing points <NUM>, since four pressing means <NUM> are provided with the clamping device <NUM>.

As discussed above, the immobilization force applied to the reticle through the retention means <NUM> is preferably smaller than the one applied to the EIP components <NUM>, <NUM> through the pressing points <NUM>. For example, the immobilization force applied to the retention means <NUM> collectively or to each individual retention means <NUM> may be selected from the range of <NUM> N to <NUM> N, preferably from the range of <NUM> N to <NUM> N, and may, for example, amount to about <NUM> N ± <NUM> N, e.g. <NUM> N. This force is preferably equally distributed across all of the provided actuators <NUM>, in a similar manner as described with reference to the pressing means <NUM>.

As mentioned above, this one-piece clamping device <NUM> is not limited for using with embodiment A of EIP <NUM>. Different configurations, e.g. also allowing the one-piece clamping device <NUM> to be used with embodiment B of EIP <NUM>, are also provided according to the present disclosure. Those embodiments of the clamping device <NUM> usable with embodiment B of EIP <NUM> essentially correspond to the clamping device <NUM> usable with embodiment B of EIP <NUM> described above, but are provided in the form of a one-piece clamping device similar to that of the one-piece clamping device <NUM> as described.

It is to be understood that, in comparison with the two-piece clamping device <NUM>, the one-piece clamping device <NUM> covers less of the surface of EIP <NUM>, since it leaves substantially the whole of the lower component <NUM> of EIP <NUM> uncovered. Thus, a clamping device <NUM> with an orifice of the same size as the orifice <NUM> of clamping device <NUM> covers substantially less of EIP <NUM>. For example, when attached to EIP <NUM>, clamping device <NUM> leaves at least <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% of EIP <NUM> uncovered. In some embodiments, clamping device <NUM> (or <NUM>) leaves at least the orifice(s) <NUM> of EIP <NUM> uncovered, so that fluid access from the atmosphere surrounding the clamping device <NUM> (or <NUM>) towards the orifice(s) <NUM> is substantially unhindered.

<FIG> is a schematic representation of storage systems <NUM> each comprising an EIP <NUM> and a clamping device <NUM> as described above. The fixation means <NUM> of the clamping device <NUM> are in the closed position and the pressing means <NUM> act upon the pressing points <NUM> to immobilize the EIP components <NUM>, <NUM> relative to one another. The actuators <NUM> act upon the retention means <NUM> to immobilize the reticle within the EIP <NUM>.

As with the two-piece clamping device <NUM>, one-piece clamping device <NUM> adapted to be usable with embodiment B of EIP <NUM> features pressing means <NUM> which simultaneously function as actuators <NUM>. Similar to the clamping device <NUM>, the actuators <NUM> of the clamping device <NUM> can also be provided separately from the pressing means <NUM>, for example in the form of tongue shaped cut-outs within the pressing means <NUM>, or in the form of cut-outs extending in an opposite direction as the pressing means <NUM>. These modifications are not illustrated in the figures, but provide the advantage, that the force applied to the pressing points <NUM> can be adjusted separately from the force acting upon the retention means <NUM> of EIP <NUM>.

As can be inferred from <FIG> and <FIG>, the clamping device <NUM>, <NUM> is of small size. Thus, the storage system <NUM>, <NUM> takes up essentially the same volume as the EIP <NUM> on its own.

In <FIG>, a preferred method of operating a reticle stocker <NUM> for storing reticles is illustrated in a flow diagram and collectively referred to with reference numeral <NUM>. A corresponding reticle stocker is schematically depicted in <FIG>.

The method will be described in the following with regard to a clamping device <NUM> as discussed in relation to <FIG> and <FIG>. It is, however, to be understood, that corresponding steps are undertaken when using a clamping device <NUM> to afford a storage system <NUM> as described above.

In step <NUM>, a double pod comprising an EUV outer pod (EOP) <NUM> and an EIP <NUM> contained within the EOP <NUM> is received from outside the stocker <NUM>. The double pod is accepted at an outwardly facing side of an entrance terminal comprising an airlock <NUM> and passed through the airlock <NUM> to an inwardly facing side of the entrance terminal. During passing through the airlock <NUM>, the inner volume of the airlock <NUM> is decontaminated, thereby ensuring that the atmosphere inside the reticle stocker <NUM> is not adversely affected by the receiving of the double pod.

Decontaminating the airlock <NUM> may comprise evacuating the airlock <NUM>, flushing it with a fluid such as a gas, particularly an inert gas, and/or purging it with a fluid, especially an inert gas.

In step <NUM>, the double pod is opened. Opening the double pod in this example comprises unlocking the EOP <NUM>, removing the EOP <NUM> from its position surrounding the EIP <NUM> and moving the EOP <NUM> to an EOP buffer stock <NUM>, where it may be stored until it is needed again. When the EOP <NUM> is removed from the EIP <NUM>, the pressure points <NUM> and the retention means <NUM> are no longer acted upon. Therefore, at that time, the EIP components <NUM>, <NUM> and the reticle contained therein are no longer immobilized relative to one another.

In step <NUM>, a clamping device <NUM> is attached to the EIP <NUM>. Thereby, a storage system <NUM> as shown in <FIG> is provided. Attaching the clamping device <NUM> may particularly be effected by placing the EIP <NUM> onto a lower clamping element <NUM>, then covering the EIP <NUM> with an upper clamping element <NUM> and attaching the lower and upper clamping elements to one another. Preferably, placing the EIP <NUM> onto the lower clamping element <NUM> and covering the EIP <NUM> with the upper clamping element <NUM> is carried out in a manner such that essentially only normal forces are applied to the EIP <NUM> and torsional and lateral forces are avoided. Once the clamping device <NUM> is mounted to the EIP <NUM>, the immobilization function effected by the EOP <NUM> before opening the double pod is effectively reinstated or emulated by the clamping device <NUM>.

The step <NUM> of attaching a clamping device is performed in a slightly different way when a one-piece clamping device <NUM> is used. In such a case, the fixation means <NUM> of the clamping device <NUM> are forced into the open position as shown in <FIG>. The clamping device <NUM> is then moved onto the EIP <NUM> and pressed towards the EIP <NUM> with a predefined preload force in the direction perpendicular to the main plane of extension ("normal direction") of the clamping device <NUM>. Then the fixation means <NUM> are released into the closed position and the preload force is released from the clamping device <NUM>. Thereby a storage system <NUM> as described above is formed.

In step <NUM> the storage system <NUM>, <NUM> is moved to a storage position within the reticle stocker.

All of the steps, especially steps <NUM> and <NUM>, are carried out in such a way that the reticle contained with the EIP <NUM> is not moved with respect to the EIP <NUM> in order to prevent friction induced particle generation, as described above.

In <FIG>, a preferred method of operating a reticle stocker for retrieving reticles is illustrated in a flow diagram and collectively referred to with reference numeral <NUM>.

In step <NUM>, a storage system <NUM> is removed from its storage position.

In step <NUM>, the clamping device <NUM> is removed from the EIP <NUM> to disassemble the storage system <NUM>. To that end, the upper and lower clamping elements <NUM>, <NUM> are detached from one another and the upper clamping element <NUM> is lifted off the EIP <NUM>, thereby releasing the pressure points <NUM> and the retention means <NUM>. At that point, the immobilization of the reticle within the EIP <NUM> is no longer effective.

Again, step <NUM> is performed in a slightly modified way, when a storage system <NUM> is disassembled: the clamping device <NUM> is removed from the EIP <NUM> by first applying the preload force to the clamping device <NUM> so that the fixation means <NUM> are no longer in contact with the EIP <NUM> or the top side of the clamping device <NUM>. Then the fixation means <NUM> are forced into the open position and the preload force is released. The clamping device <NUM> is then lifted off the EIP <NUM>, thereby releasing the pressure points <NUM> and the retention means <NUM>.

In the case of a one-piece clamping device <NUM> being used, the steps <NUM> and <NUM> can be carried out without moving the EIP <NUM> at all. This can be achieved by leaving the EIP <NUM> on the lower component of the EOP <NUM> when attaching the clamping device <NUM> to the EIP <NUM> or placing it on the lower component of EOP <NUM> before detaching the clamping device <NUM>, respectively. This is particularly favourable because it effectively prevents relative movement of the EIP components <NUM>, <NUM> and the reticle, respectively.

In step <NUM>, an EOP <NUM> is retrieved from the EOP buffer stock <NUM> and assembled around the EIP <NUM> to provide a double pod. When the double pod is fully assembled, the immobilization function effected by the clamping device <NUM> during the time of storage is provided by the EOP.

In step <NUM>, the double pod formed in step <NUM> is delivered to outside the stocker <NUM>. This may include passing the double pod through the airlock <NUM> mentioned above to the outwardly facing side of the entrance terminal. The airlock <NUM> can be purged or flushed during the passage of the double pod so as to prevent contaminants from entering the entrance terminal.

As shown in <FIG>, the reticle stocker <NUM> comprises the already mentioned airlock <NUM>, an assembler <NUM>, which is configured to perform the steps <NUM>, <NUM>, <NUM> and <NUM> of the above described methods <NUM>, <NUM>, the EOP buffer stock <NUM>, in which a number of EOPs <NUM> can be stored, and a storage unit <NUM> in which storage systems <NUM>, <NUM> can be stored in a number of storage positions <NUM>. A handler <NUM> is provided with the stocker <NUM> for moving the storage systems <NUM>, <NUM> to and from their respective storage positions <NUM>.

It is to be noted that the number of storage positions <NUM> can substantially exceed the number of EOPs <NUM> storable in the EOP buffer stock <NUM>. As described above, only reticles which are needed outside the stocker <NUM> require an EOP <NUM>. Therefore, a (small) number of EOPs <NUM> are stored in the EOP buffer stock <NUM>, so that a double pod can be assembled on request for a reticle. However, since typically all the reticles are never required at the same time, there is no need to store an EOP <NUM> for each reticle stored within the storage unit <NUM>.

In <FIG>, <FIG> and <FIG>, the clamping device <NUM>, <NUM> is additionally provided with a logging element <NUM>, <NUM> (schematically shown) comprising an identification device, such as an RFID device, and one or more sensors. The RFID device <NUM>, <NUM> is an information carrying element which is provided with an identification number so that each clamping device <NUM>, <NUM> is distinguishable from other clamping devices <NUM>, <NUM> by reading the RFID device <NUM>, <NUM>.

The one or more sensors included in the logging element <NUM>, <NUM> are configured to detect or measure, for example, a temperature, a composition of an atmosphere surrounding the clamping device <NUM>, <NUM>, a pressure and/or an acceleration acting on the clamping device <NUM>, <NUM>. The logging element <NUM>, <NUM> in this example is further configured to store readings of the one or more sensors and/or to make these readings available for further processing.

In the case of clamping devices <NUM>, <NUM> being equipped with an RFID device <NUM>, <NUM>, for example, the method <NUM> can comprise providing an association of a reticle stored in combination with a certain clamping device <NUM>, <NUM> with an identification number provided with the RFID device <NUM>, <NUM> of the used clamping device <NUM>, <NUM>. This association can be stored, for example, in a central memory of the reticle stocker and/or within a central computing device of the production facility. This provides the advantage that a reticle is identifiable by the clamping device <NUM>, <NUM>, used for its storage and can therefore be identified while still being safely contained within the respective EIP <NUM>.

The method may further comprise collecting data from the one or more sensors and using this data, for example to assess if further action, e.g. an inspection of a retrieved reticle, is necessary.

Advantageously, the method <NUM> then uses this RFID device <NUM>, <NUM> of the clamping device <NUM>, <NUM> in order to retrieve the reticle associated with the clamping device <NUM>, <NUM>. Thereby, a verification mechanism can be realised. For example, it is possible, that a storage position <NUM> of a given reticle within the stocker <NUM> is used for identifying a reticle to be retrieved from the stocker <NUM>. When retrieving the reticle from that storage position <NUM>, the RFID device <NUM>, <NUM> of the clamping device <NUM>, <NUM> can be read and the association of the identification number of the clamping device <NUM>, <NUM> with the stored reticle can be checked, in order to verify, that the correct reticle is being retrieved. If the identity of the reticle stored at the specific storage location and the reticle associated with the clamping device <NUM>, <NUM> differ, an identification procedure is triggered and a warning signal can be generated, so that the production does not use the reticle before its identity has been verified. This provides the advantage of a higher overall reliability of the reticle identification.

Claim 1:
Clamping device for an EUV inner pod (EIP), the EIP (<NUM>) comprising two or more components and containing an EUV reticle, wherein the clamping device (<NUM>, <NUM>)
is configured to immobilize the two or more components (<NUM>, <NUM>) of the EIP (<NUM>) and the reticle relative to one another; and
to only partially cover the EIP (<NUM>), further comprising
an upper clamping element (<NUM>) and a lower clamping element (<NUM>), wherein the upper (<NUM>) and the lower (<NUM>) clamping elements are configured to be attachable to one another while accommodating the two or more EIP components (<NUM>, <NUM>) between them.,
or further comprising one clamping element with one, two or more fixation means (<NUM>), wherein the fixation means (<NUM>) are biased towards a closed position and are configured to be moved into an open position; wherein the clamping device (<NUM>) is configured to be attachable to an EIP (<NUM>), when the fixation means are in the open position and to immobilize the EIP components (<NUM>, <NUM>) and the reticle relative to one another, when the fixation means (<NUM>) are in the closed position.