MEASUREMENT DEVICE AND METHOD FOR INSPECTING PHOTOMASKS FOR EUV MICROLITHOGRAPHY - Patent application

Abstract

To provide a measuring device and method for mask inspection, in which the risk of contamination is reduced.SOLUTION: A measuring device for inspecting photomasks comprises an illumination system (16), a projection lens (22), and an EUV image sensor (24). EUV radiation emitted by an EUV radiation source (14) is guided via the illumination system (16) to a photomask (17). EUV radiation reflected at the photomask (17) is guided via the projection lens (22) to the EUV image sensor (24) such that the photomask (17) is imaged on the EUV image sensor (24). The measuring device comprises a frame component part (27), the frame component part (27) carrying a pellicle (30). The pellicle (30) is arranged between the photomask (17) and the projection lens (22) such that the EUV radiation reflected at the photomask (17) passes through the pellicle (30). The invention also relates to a method for inspecting photomasks.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a metrology apparatus and method for inspecting photomasks for EUV microlithography. [Background technology]

[0002] In microlithography projection exposure apparatus, which are used to manufacture integrated circuits, particularly those with very small structures, photomasks are used that are irradiated with very short-wave extreme ultraviolet radiation (EUV) and imaged onto the lithography object in order to transfer the mask structure onto the lithography object.

[0003] To ensure a high quality of the image formed on the lithography object, the photomask needs to be true to size and not be adversely affected by contaminants. It is known practice to subject photomasks to inspection before operation in a microlithography projection exposure apparatus or during interruptions in operation. For this purpose, a so-called aerial image of the photomask or a part of the photomask is created, in which the photomask in question is imaged onto an EUV image sensor rather than onto the lithography object. Using the image on the EUV image sensor as a basis, the photomask can be assessed for defects and contaminants.

[0004] This mask inspection must be performed in such a way that the measurement results are not altered by contamination. Specifically, the photomask must be prevented from becoming contaminated as a result of the mask inspection procedure. Summary of the Invention

[0005] The present invention is based on the object of providing a measurement device and a method for mask inspection, in which the risk of contamination is reduced. This object is achieved by the features of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0006] A measurement device according to the present invention for inspecting a photomask includes an illumination system, a projection lens, and an EUV image sensor. EUV radiation emitted by an EUV radiation source is guided to the photomask through the illumination system. EUV radiation reflected from the photomask is guided to the EUV image sensor through the projection lens so that the photomask is imaged on the EUV image sensor. The measurement device includes a frame component part that carries a pellicle. The pellicle is positioned between the photomask and the projection lens so that the EUV radiation reflected from the photomask passes through the pellicle.

[0007] The use of measurement devices for the inspection of EUV photomasks has been found to carry a significant risk of contamination of the inspected photomask as a result of the inspection procedure. Although the inspection procedure is typically performed in a vacuum atmosphere, it is impossible to completely avoid particles. For example, particles are constantly generated due to friction when components of the measurement device are mechanically moved relative to one another. The present invention recognizes that the damaging effects of these unavoidable particles can be significantly reduced by avoiding situations in which particles can deposit on the photomask. The present invention proposes providing the measurement device with a pellicle positioned between the photomask and the projection lens, such that EUV radiation reflected from the photomask passes through the pellicle.

[0008] While this does not prevent the presence of particles in the measurement device, it does reduce the adverse effects of particles because they cannot deposit on the photomask, which can be particularly harmful because it can render entire batches of semiconductor component parts exposed using the contaminated photomask unusable.

[0009] The prior art discloses pellicles that are stretched directly over a photomask and also serve the purpose of protecting the photomask from particles. The pellicle according to the invention, which is a component of a measurement device, must be distinguished from these known pellicles. For example, the measurement device allows the photomask to be tested to be removed from the measurement device while the pellicle according to the invention remains.

[0010] A pellicle is a membrane designed to allow EUV radiation to pass through but prevent particles from passing through. Because materials are generally highly absorbent of EUV radiation, the material and structure of the pellicle must be carefully adapted for use in metrology systems for mask inspection. For example, unlike with visible light, it is not possible to use a glass plate as protection against contamination. The EUV radiation would be absorbed by the glass plate and would not reach the image sensor with sufficient intensity.

[0011] In one embodiment, the pellicle is a CNT (carbon nanotube) pellicle, i.e., a membrane made of carbon nanotubes. The density and bundle structure of the carbon nanotubes can be selected so that the membrane is transparent to EUV radiation on the one hand, and particles are stopped by the membrane and cannot pass through the membrane on the other hand. The membrane can be provided with a coating to provide the membrane with sufficient resistance to radical ions and molecules. In another embodiment, the pellicle comprises a membrane made of silicon, silicon nitride, or any other silicon-containing material. If sufficiently thin, such a membrane made of a silicon material also provides sufficient transparency to EUV radiation.

[0012] The pellicle can be positioned so that EUV radiation reflected from the photomask passes through it before entering the projection lens. The projection lens can include multiple EUV mirrors through which EUV radiation is reflected between the photomask and the image sensor. The optical regions of the EUV mirrors can be formed with highly reflective coatings. These can be multilayer coatings, particularly multilayer coatings with alternating layers of molybdenum and silicon. Using such coatings, it is possible to reflect approximately 70% of the incident EUV radiation. The term EUV radiation is used to refer to electromagnetic radiation in the extreme ultraviolet spectral region, with wavelengths between 5 and 100 nm, particularly between 5 and 30 nm.

[0013] The projection lens can include a first mirror M1 that captures the EUV radiation reflected by the photomask. The numerical aperture NA of the projection lens is determined by the dimensions of the first mirror M1. The larger the area of ​​the first mirror M1, the higher the numerical aperture NA of the projection lens. A pellicle can be positioned between the photomask and the first mirror M1 of the projection lens such that the EUV radiation reflected by the photomask passes through the pellicle before the EUV radiation strikes the first mirror M1.

[0014] The EUV radiation reflected by the first mirror M1 can be directed via one or more further mirrors of the projection lens to an EUV image sensor, particularly such that an image of the photomask, and in particular the portion of the photomask to be inspected, appears on the image sensor.

[0015] The projection lens of the measurement device may have a high magnification, for example at least 50, preferably at least 100, more preferably at least 200. To be able to capture the test spot using EUV image recording, an image sensor with a large area compared to the spot to be imaged on the photomask is required.

[0016] For example, a photomask may have an edge length between 100 mm and 200 mm and / or a width of 100 cm 2 and 400cm 2 The area of ​​the area to be inspected may have an area between 0.1 mm and 5 mm, preferably between 0.5 mm and 3 mm. If the area is not square, this definition relates to the longer of the edge lengths. If the area is not rectangular, this definition relates to the largest dimension of the area. The sensor area of ​​the image sensor is preferably larger than the area to be inspected on the photomask in a manner corresponding to the magnification of the projection lens. The dimensions of the sensor area of ​​the image sensor, which are defined in the same way as the area to be inspected, may be, for example, between 50 mm and 500 mm, preferably between 100 mm and 20 mm.

[0017] The pellicle can also be positioned between the illumination system and the photomask such that EUV radiation coming from the illumination system passes through the pellicle before the EUV radiation is incident on the photomask, in other words, the pellicle can be positioned such that the EUV radiation passes through the pellicle twice along its path between the EUV radiation source and the EUV image sensor, specifically once before reflection from the photomask and once after reflection from the photomask.

[0018] The illumination system can be configured to illuminate a portion of the photomask, and the illumination system can be configured such that the intensity of the EUV radiation is substantially uniform within the illuminated portion.

[0019] The illumination system can include one or more EUV mirrors that reflect the EUV radiation on its path between the EUV radiation source and the photomask, and a pellicle can be positioned between the last EUV mirror in the illumination system and the photomask to prevent the EUV radiation from further reflections off other EUV mirrors in the illumination system before it strikes the photomask.

[0020] The measurement device can include a vacuum chamber in which a vacuum prevails during the measurement. The projection lens, the illumination system, the EUV radiation source and / or the photomask can be located within the vacuum chamber.

[0021] The measurement device according to the invention may include further pellicles arranged in one or more other sections of the EUV beam path, such that the EUV radiation can pass through multiple pellicles in succession. This may include further pellicles through which the EUV radiation passes exactly once. Additionally or alternatively, it may include pellicles arranged such that the EUV radiation passes through the relevant pellicle twice.

[0022] In one embodiment, the measurement device includes a first pellicle and a second pellicle, where the first pellicle is positioned between the photomask and the projection lens and the second pellicle is positioned between the illumination system and the photomask. Two separate pellicles can protect the photomask from particle contamination from both the illumination system and the projection lens. The first and second pellicles can be positioned such that EUV radiation passes through them exactly once.

[0023] The present disclosure encompasses further embodiments in which one such pellicle is disposed between the illumination system and the photomask, and no pellicle is disposed between the photomask and the projection lens, which can be particularly advantageous if passage of particles from the projection lens to the photomask is prevented in a different manner.

[0024] The pellicle can be secured to a frame component such that the pellicle covers an opening through which the frame spans. Connection to a measurement device can be established through the frame. The pellicle can be a consumable item designed to be replaced periodically within a maintenance regime. The pellicle may need to be replaced if it becomes contaminated after the pellicle has been in use for a period of time.

[0025] The frame component part can be attached to a carrying structure of the measurement device when the measurement device is in operation. The carrying structure refers to a part of the measurement device that is used to mechanically hold the components of the measurement device in place relative to each other. The carrying structure can hold in place an EUV mirror of the projection lens. Additionally or alternatively, the carrying structure could hold in place an EUV mirror of the illumination system.

[0026] The connection between the frame component part and the carrier structure can be a detachable connection. The detachable connection can be designed so that when the measurement apparatus undergoes maintenance, the frame component part can be removed from the carrier structure to replace the used pellicle with a new one. The new pellicle can be inserted into the measurement device together with the new frame component part. The maintenance procedure can be performed after a relatively long operating phase of the measurement device, for example of at least several months, and may include maintenance of further components of the measurement device.

[0027] Components used to hold the photomask in place during measurement are also part of the carrying structure of the measurement device. Specifically, the measurement device may include a carrying component that holds the photomask during measurement. In one embodiment, the frame component part is attached to the carrying component during operation of the measurement device.

[0028] The carrier component may be a component part of a loading mechanism for transferring the photomask into and out of the measurement device. The measurement device may include an airlock in which pressure regulation is performed. In a first state of the airlock, the same pressure may exist in both the airlock chamber and the vacuum chamber, so that the photomask can be transferred without a pressure difference between the airlock chamber and the vacuum chamber. In a second state of the airlock, a pressure higher than the vacuum pressure may exist in the airlock chamber, corresponding to the pressure around the airlock. In one embodiment, the pressure in the second state of the airlock corresponds to atmospheric pressure. In the second state of the airlock, the photomask can be transferred without a pressure difference between the airlock chamber and the airlock's surroundings.

[0029] The loading mechanism can be designed to transport the photomask between a measurement position precisely defined relative to the illumination system and projection lens and a position within the airlock chamber. The loading mechanism can include an actuator suitable for this purpose. The measurement device can include a control unit used to drive the actuator.

[0030] The loading mechanism can be designed to transport the carrier component together with the photomask into the airlock chamber. If a pellicle is connected to the carrier component, the pellicle is also transported together with the carrier component into the airlock chamber. The carrier component can be designed so that the photomask unloaded from the measurement device can be removed from the carrier component while the pellicle remains with the carrier component. This can be standard during operation of the measurement device, so that new photomasks can be repeatedly transported into the measurement device while the pellicle remains the same. In this case, the pellicle is replaced only after it has worn out after inspecting multiple photomasks. It is also possible to replace the pellicle each time a new photomask is introduced into the measurement device. In all cases, replacement is facilitated if the pellicle is located outside the measurement device together with the carrier component during replacement. For pellicle replacement, the frame component part together with the pellicle can be removed from the carrier component and replaced with a new pellicle with a new frame component part. This replacement of the pellicle can be performed manually or automatically.

[0031] The region of the vacuum chamber in which the photomask is placed during measurement can be designed so that, firstly, the same pressure as the rest of the vacuum chamber prevails there, and secondly, the ingress of particles from the rest of the vacuum chamber into this region of the vacuum chamber is largely avoided. For this purpose, the photomask can be arranged in a partial chamber that is separated from the rest of the vacuum chamber by a housing wall. The housing wall can be provided with a pressure equalization channel, by means of which the pressure is equalized between the partial chamber and the rest of the vacuum chamber. The partial chamber can include an opening through which EUV radiation coming from the illumination system enters the partial chamber and / or through which EUV radiation reflected by the projection lens exits.

[0032] The pellicle can be stretched over the opening so that all EUV radiation entering the partial chamber through the opening passes through, i.e., propagates through, the pellicle. The pellicle can be sealingly flush with an edge of the housing surrounding the opening so that passage of particles between the partial chamber and the remainder of the vacuum chamber is prevented at the transition between the pellicle and the housing.

[0033] In addition to or instead of such a pellicle, other means may be provided to prevent particles from depositing on the photomask. For example, the measurement device may include a particle trap in which an electromagnetic beam is formed to deflect the particle's direction of movement. The electromagnetic beam may have a propagation direction that intersects with the EUV beam path. The electromagnetic beam may form an angle of at least 30°, preferably at least 60°, with the EUV beam path.

[0034] To prevent particles from entering an area of ​​the measurement device, such as through an opening in a partial chamber, multiple electromagnetic beams can be formed, which can be parallel to one another. It is also possible to change the propagation direction of a single electromagnetic beam during a scanning procedure so that the beam covers the area. The EUV beam path can intersect the area, particularly in a section of the EUV beam path located between the illumination system and the photomask and / or between the photomask and the projection lens. This area can form an angle of at least 30°, preferably at least 60°, with the EUV beam path. For example, the wavelength of the electromagnetic radiation can be between 300 nm and 1200 nm, preferably between 700 nm and 1100 nm. For example, the power of the electromagnetic beam can be between 0.08 W and 1.2 W.

[0035] There may also be a particle trap in which particles are guided along the surface of the measurement device until they are within a region where particles are not desirable. This surface may be substantially horizontal so that particles are deposited on the surface under the influence of gravity. A volumetric flow that condenses the moving particles can be formed in a vacuum atmosphere so that the particles move over the surface. The particles can be collected in a region of the measurement device where particles are not desirable and / or the particles can be sucked out of the interior of the measurement device. For this purpose, a vacuum pump that generates a pressure lower than the pressure prevailing in the vacuum chamber of the measurement device can be used. The particle trap can be positioned at a radial distance from the section of the EUV beam path so that the particles remain outside the region where they can move along the EUV beam path toward the photomask. The volumetric flow formed to move the particles can intersect the direction of the EUV beam path and form an angle of at least 30°, preferably at least 60°, with the section of the EUV beam path.

[0036] It is also possible to provide a particle trap formed in a volumetric flow guided through the mesh structure before crossing the EUV beam path inside the measurement device. The volumetric flow can pass through the mesh structure in such a way that particles carried by the volumetric flow are deposited on the mesh structure. In this way, particles can be prevented from entering the region of the EUV beam path.

[0037] When such a particle trap is used with a pellicle of the present invention, the volumetric flow generated for the particle trap and / or the electromagnetic beam generated for the particle trap can extend parallel to the pellicle, preferably in a manner that does not create a pressure difference above the pellicle.

[0038] In one embodiment, the device includes an XY positioning mechanism by which the position of the photomask can be changed in an XY plane relative to the incoming EUV beam path. The XY plane can correspond to the plane of the photomask. The XY positioning mechanism can be implemented to move the photomask linearly in the XY plane. This can be used for a scanning procedure, in which multiple EUV image records belonging to the same portion of the photomask are recorded during the linear movement of the photomask.

[0039] Additionally or alternatively, the XY positioning mechanism can be used to move the photomask relative to the incident EUV beam path so that aerial images of different portions of the photomask can be formed. Specifically, the XY positioning mechanism can be designed to allow inspection of each portion of the photomask.

[0040] Additionally or alternatively, the XY positioning mechanism can be used to obtain information about the state of the pellicle. To this end, a reference mask with a known surface structure, for example a uniform surface structure, can be introduced into the measurement device. Depending on how the image recording changes when the reference mask is moved in the XY plane, a description of the state of the pellicle can be made.

[0041] The present invention also relates to a method for inspecting a photomask, in which EUV radiation emitted by an EUV radiation source is directed to the photomask through an illumination system. EUV radiation reflected from the photomask is directed to an EUV image sensor through a projection lens (22) so that the photomask is imaged on the image sensor. A frame component of the measurement device carries a pellicle positioned between the photomask and the projection lens (22). The EUV radiation passes through the pellicle.

[0042] The present disclosure encompasses the development of a method having the features described in the context of a measuring device according to the present invention.The present disclosure encompasses the development of a measuring device having the features described in the context of a method according to the present invention.

[0043] The invention will now be described by way of example on the basis of advantageous embodiments with reference to the accompanying drawings, in which: FIG. [Brief explanation of the drawings]

[0044] [Figure 1] FIG. 1 shows a schematic diagram of a measuring device according to the invention. [Figure 2] FIG. 1 is a diagram showing a schematic diagram of a photomask. [Figure 3] FIG. 2 shows an enlarged view of a detail of the device of FIG. 1. [Figure 4] FIG. 4 shows a view from the perspective according to FIG. 3 in an alternative embodiment of the present invention. [Figure 5] 1 shows a schematic diagram of an alternative embodiment of a measuring device according to the invention; [Figure 6] FIG. 4 shows a view from the perspective of FIG. 3 in an alternative embodiment of the present invention. [Figure 7] FIG. 4 shows a view from the perspective of FIG. 3 in an alternative embodiment of the present invention. [Figure 8] FIG. 4 shows a view from the perspective of FIG. 3 in an alternative embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0045] The measurement device according to the present invention can be used to inspect a microlithography photomask 17 .

[0046] Typically, a microlithography photomask 17 is provided for use in a microlithography projection exposure apparatus (not shown here). In the microlithography projection exposure apparatus, the photomask 17 is irradiated with extreme ultraviolet radiation (EUV radiation), for example at a wavelength of 13.5 nm, in order to image structures formed on the photomask 17 onto the surface of a lithography object in the form of a wafer. The wafer is coated with a photoresist that is sensitive to EUV radiation. A measuring device is used to check whether the measuring device meets requirements and is free of contamination.

[0047] According to FIG. 1, the photomask 17 is arranged in the measurement device such that the EUV beam path 15 from the EUV radiation source 14 is guided to the photomask 17 via the illumination system 16. The illumination system 16 is used to shape the EUV radiation to form a beam that is used to illuminate an inspection field 20 on the surface of the photomask 17 with uniform brightness. The inspection field 20, which is small compared to the area of ​​the photomask 17, is shown in FIG. 2 in a not-to-scale illustration. For example, the illumination area 20 may have dimensions of 0.5 mm by 0.8 mm. The edge length of the photomask 17 may be, for example, between 100 mm and 200 mm. A field stop is arranged in the illumination system 16, which is used to delimit the illumination area into inspection fields 20 on the surface of the photomask 17. To bring different inspection fields 20 into the area of ​​the EUV beam path, the photomask can be moved in the XY plane using an XY positioning mechanism 37.

[0048] The EUV beam path 15 reflected by the photomask 17 continues through a projection lens 22 to an EUV camera 23 equipped with an image sensor 24. The projection lens is used to image an inspection field 20 of the photomask 17 onto the image sensor 24 of the EUV camera 23. An aperture stop 25 (see FIG. 3 ), whose aperture corresponds to the first mirror M1 of the projection lens 22, is arranged between the photomask 17 and the first mirror M1. The EUV radiation source 14, the illumination system 15, the photomask 17, the projection lens 22 and the EUV camera 23 are arranged in a vacuum housing 40 in which a negative pressure prevails during operation of the measurement device.

[0049] The EUV radiation source 14 is a plasma radiation source in which EUV radiation is emitted from the plasma at a wavelength of 13.5 nm. Tin is a medium that can be used to generate a plasma suitable for emitting such EUV radiation. A laser beam can be formed to strike droplets of the medium to generate the plasma.

[0050] The mirrors in the illumination system 16 and the projection lens 22 are designed as EUV mirrors with a particularly high reflectivity for EUV radiation. The optical regions of the EUV mirrors can be formed by high-reflectivity coatings. These can be multilayer coatings, in particular multilayer coatings with alternating layers of molybdenum and silicon. Using such coatings, it is possible to reflect approximately 70% of the incident EUV radiation.

[0051] The projection lens 22 has a magnification of more than 100. The area of ​​the image sensor 24 is larger than the area of ​​the inspection field 20 according to the magnification so that the entire generated image of the inspection field 20 of the photomask 17 can be recorded. For example, the image sensor 24 can have dimensions on the order of 100 mm to 200 mm.

[0052] A pellicle unit 26 including a frame component part 27 and a pellicle 30 held by the frame component part is disposed above the photomask 17. See FIG. 3 . The pellicle unit 26 is disposed both between the photomask 17 and the illumination system 16 and between the photomask 17 and the projection lens 22. The pellicle is positioned between the last mirror 19 of the illumination system 16 and the photomask. This means that the EUV beam path 15 passes through the pellicle 30 twice, specifically, once as an incoming EUV beam path 15 coming from the illumination system 16 and once as an outgoing EUV beam path 15 reflected by the photomask 17, before propagating toward the image sensor 24.

[0053] A frame component part 27 of the pellicle unit 26 is mounted to a carrying structure 28 of the measurement device using a threaded connection. The carrying structure 28 also holds the mirrors in the projection lens 22 and the illumination system 16 in position relative to each other.

[0054] Pellicle 30 is an extremely thin film of carbon nanotube material that is transparent to EUV radiation but blocks the passage of particles. Pellicle 30 is used to protect photomask 17 from particle contamination. Particles originating in illumination system 16 or projection lens 22 and traveling toward photomask 17 strike and deposit on pellicle 30 before they can reach the photomask.

[0055] The frame component part 27 of the pellicle unit 26 can be removed from the carrying structure 28 of the measurement device during maintenance of the measurement device in order to replace the worn pellicle 30 with a new pellicle. The new pellicle 30 can be inserted into the measurement device together with the new frame component part 27 and connected to the carrying structure 28.

[0056] In the exemplary embodiment according to FIG. 4 , the pellicle unit 26 is connected to another part of the carrier structure 28, specifically to a carrier component 29 that carries the photomask 17. Together with the pellicle unit 26, the carrier component 29 forms a partial chamber 33 within the vacuum housing 40. The carrier component 29 surrounds an opening 32 through which the EUV beam path 15 enters and exits the partial chamber 33. The opening 32 is surrounded by a housing edge of the carrier component 29, to which a frame component part 27 of the pellicle unit 26 is attached. Together with the pellicle unit 26, the carrier component 29 forms a sealing sleeve for the partial chamber 33, which is interrupted only by a pressure equalization channel 31. The pressure between the partial chamber 33 and the remaining area of ​​the vacuum housing 40 can be equalized via the pressure equalization channel 31.

[0057] The carrier component 29 is a component of a loading mechanism 35, by means of which the photomask 17 is introduced into and removed from a vacuum housing 40. The loading mechanism 35 includes an airlock chamber 34 adjacent to the vacuum housing 40. The airlock chamber 34 is evacuated to the same pressure that prevails in the vacuum housing 40. The carrier component 29, together with the photomask 17 and the pellicle unit 26, is moved into the airlock chamber 34. The connecting opening between the vacuum housing 40 and the airlock chamber 34 is then closed, and the airlock chamber 34 is brought to atmospheric pressure. The pressure from the airlock chamber 34 is transferred to the interior of the carrier component 29 via the pressure equalization channel 31. At atmospheric pressure, the airlock chamber 34 can be opened, and the photomask 17 can be removed from the carrier component 29. An opening (not shown in the drawings) in the sidewall of the carrier component 29 is opened for this purpose.

[0058] The loading mechanism 35 is operated multiple times to introduce new photomasks 17 into the vacuum chamber 40, while the pellicle unit 26 remains unchanged. After the pellicle 30 is worn out after inspecting multiple photomasks 17, the pellicle unit 28 is replaced. This is performed in an automated process where, at atmospheric pressure, the pellicle unit 26 is removed from the carrying component 29 and replaced by a new pellicle unit. The carrying component 29 is then ready for inspecting multiple additional photomasks 17.

[0059] 6 shows an embodiment in which a particle trap is present in addition to the pellicle unit to protect the photomask 17 from contamination. The support structure 28 of the measurement device includes a housing portion 35 that extends around the photomask 17. The housing portion 35 has a horizontal, upward-facing surface 36 on which particles can be placed next to the pellicle unit 26. By applying negative pressure to the gap 41 that exists between the housing portion 35 and the support component 29, particles are sucked from the surface 36 and removed from the measurement device. The negative pressure is lower than the pressure prevailing in the vacuum housing 40 to create a volumetric flow in the desired direction.

[0060] 7, a volumetric flow is created that is oriented parallel to the pellicle 30 and extends above and below the pellicle 30. Before entering the region of the pellicle 30, the volumetric flow is directed through a mesh structure 38 that allows the volumetric flow to pass but can retain particles. This can also help protect the pellicle 30 and photomask 17 from particle contamination.

[0061] The embodiment according to Figure 8 includes a laser 39 that emits a laser beam 41. A scanning device 40 is used to deflect the laser beam 41 in a plane parallel to the pellicle 30 so that the laser beam 41 passes over the area where the pellicle 30 is stretched. As a result of interaction with the laser beam 41, particles are deflected to the side so that they cannot adversely affect the pellicle 30. [Explanation of symbols]

[0062] 14 EUV radiation source 15 EUV beam path 16 Irradiation system 17 Photomask 19 The Last Mirror 20 Inspection field, irradiation area 22 Projection lens 23 EUV camera 24 image sensors 25 aperture stop 26 Pellicle Unit 27 Frame component section 28 Support structure 29 Supporting Components 30 Pellicle 31 Pressure Equalization Channel 32 Aperture 33 Partial Chamber 34 Airlock Chamber 35 Loading mechanism, housing section 36 Surface 37 XY positioning mechanism 38 Mesh Structure 39 Laser 40 Vacuum housing, vacuum chamber, scanning device 41 Gap, laser beam

Claims

1. a measuring device for inspecting a photomask, the measuring device comprising an illumination system (16), a projection lens (22), and an EUV image sensor (24), wherein EUV radiation emitted by an EUV radiation source (14) is directed to a photomask (17) via the illumination system (16), and EUV radiation reflected by the photomask (17) is directed to the EUV image sensor (24) via the projection lens (22) such that the photomask (17) is imaged on the EUV image sensor (24); the measuring device a support component (29) surrounding the periphery of the photomask (17) and supporting the photomask (17); a frame component part (27) connected to the support component (29) and supporting a pellicle (30) on the photomask (17); a housing portion (35) surrounding the carrying component (29); wherein the pellicle (30) is arranged between the photomask (17) and the projection lens (22) such that the EUV radiation reflected by the photomask (17) passes through the pellicle (30), and a negative pressure is applied to a gap (41) between the carrying component (29) and the housing part (35).

2. 2. The measuring device of claim 1, wherein the pellicle (30) is arranged between the illumination system (16) and the photomask (17) such that EUV radiation coming from the illumination system (16) passes through the pellicle (30).

3. 3. The measuring device according to claim 1, further comprising a vacuum chamber (40) in which the projection lens (22), the illumination system (16), the EUV radiation source (14) and / or the photomask (17) are arranged.

4. 3. A measuring device according to claim 1 or 2, wherein the frame component part (27) is removably connected to a carrying structure (28) of the measuring device.

5. 5. A measuring device according to claim 4, wherein the frame component part (27) is removably connected to the carrying component (29) which is an integral part of a loading mechanism (35) of the measuring device.

6. 6. The measuring device of claim 5, further comprising an airlock chamber (34), wherein the loading mechanism (35) is designed to transfer the pellicle (30) into the airlock chamber (34).

7. 3. The measuring device according to claim 1, wherein the photomask is arranged in a partial chamber (33) of the vacuum chamber (40), the partial chamber (33) being separated from other areas of the vacuum chamber (40) by a housing wall.

8. 8. The measuring device according to claim 7, wherein the partial chamber (33) comprises an opening (32) through which EUV radiation coming from the irradiation system (16) enters the partial chamber (33) and / or through which the EUV radiation reflected by the projection lens (22) exits.

9. 9. The measurement device of claim 8, wherein the pellicle (30) is stretched over the opening (32).

10. 10. The measuring device of claim 9, wherein the pellicle (30) is sealingly flush with a housing edge surrounding the opening (32).

11. 3. The measurement system according to claim 1, wherein the pellicle (30) is made of a silicon material.

12. 1. A method for inspecting a photomask, comprising: directing EUV radiation emitted by an EUV radiation source to a photomask via an illumination system; directing EUV radiation reflected from the photomask via a projection lens to an image sensor such that the photomask is imaged on the EUV image sensor, with a frame component part of the measurement device carrying a pellicle arranged between the photomask and the projection lens; and applying a negative pressure to a gap between a carrying component carrying the photomask and a housing part surrounding the carrying component, the EUV radiation passing through the pellicle.

Images