Measuring or inspecting apparatus and method for measuring or inspecting a surface

Abstract

To provide a measurement or inspection device, in particular a mask inspection device, comprising an object to be measured or inspected, a lens for measuring or inspecting a surface of the object, and a purging device for supplying a purge gas stream into an intermediate space between the surface of the object and the lens.SOLUTION: A measurement device comprises a component (18) that has a surface (18a) which is formed from the same material as a surface (2a) of an object (2) to be measured or inspected. A purging device (15) is designed to conduct a purge gas stream (16) along the surface (18a) of the component (18) before feeding the purge gas stream (16) into an intermediate space (17).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] [Reference to Related Applications] This application is the subject of German patent application no. 10 2019 203 880.8 of March 21, 2019. No. 6,313,535, filed on May 13, 2003, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a lens for measuring or inspecting a surface of an object to be measured or inspected, and a lens for measuring or inspecting the surface of the object. and a purge device for supplying a purge gas flow to an intermediate space between the surface of the lens and the lens. The present invention relates to a measuring or inspection apparatus, in particular a mask inspection apparatus. A method for measuring a surface of an object to be measured or inspected, which is placed on an object plane of a lens, Measuring or inspecting and an intermediate space between the surface of the object to be measured or inspected and the lens and providing a flow of purge gas to the [Background technology]

[0003] Surfaces for the semiconductor industry, in particular mirrors, lens elements, wafers, e.g. for the EUV wavelength range and lenses for UV and visible wavelengths for measurement, imaging and inspection of lithography masks. These lenses can be designed according to a variety of optical designs. (refraction, reflection, catadioptric). When inspecting the surface of an object, it is necessary to have a light source (e.g. in the form of particles) on the surface. ) feature is determined. During measurement, the actual size of the feature is measured (e.g. , line width, etc.).

[0004] Such lenses can be used in particular for measuring or inspecting unprotected surfaces. The object to be inspected or measured may be made of metal materials such as silicon, copper, aluminum, etc. Some of these materials, such as copper, react very sensitively to certain impurities, such as sulfur. To protect the object from this or other impurities, a purge gas flow can be introduced into the intermediate space between the object or the surface of the object and the lens. The purge gas is usually an inert gas, such as nitrogen, or a noble gas. However, it cannot be denied that the purge gas flow itself may contain impurities, such as a small amount of sulfur atoms.

[0005] Even when using low-sulfur steel for the metal mount that holds the optical glass used in the lens, it cannot be denied that a very small amount of sulfur, especially individual sulfur atoms, may leave the mount and reach the object through the purge gas flow. Therefore, the lens itself may also form a source of impurities. The deposition of even individual sulfur atoms on the object may render the area where the sulfur atoms are deposited unusable. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] An object of the present invention is to provide a measuring or inspecting apparatus, particularly a mask inspection apparatus, and a method for measuring or inspecting an object that can avoid the deposition of impurities on the surface of the object as much as possible during measurement or inspection. MEANS FOR SOLVING THE PROBLEMS

[0007] This object is achieved by a measuring or inspecting apparatus of the aforementioned type having at least one component having a surface made of the same material as the surface of the object to be measured or inspected, and a purge device designed to direct the purge gas along the surface of the component before introducing the purge gas into the intermediate space.

[0008] ​​​​​​​​According to the present invention, it is proposed to carry out a post-washing of the atmosphere, and thus a purge gas flow surrounding the surface of an object to be measured or inspected, for example a mirror or a mirror substrate or a mask. For this purpose, the purge gas flow is guided along at least one additional component made of the same material as the surface of the object to be measured or inspected. Impurities that are contained in the purge gas flow and that would otherwise enter the intermediate space between the lens and the object and deposit on the surface of the object, usually the surface of a mirror, mask, etc., are collected using the surface of the component. Guiding the purge gas flow along the surface is understood to mean bringing the purge gas flow into contact with the surface, and thus the purge gas flow does not necessarily have to proceed substantially parallel to the surface of the component. The purge gas flow can also strike the component substantially perpendicular to the surface. It is advantageous if the surface of the component made of the same material as the surface of the object has the maximum surface area in order to collect as many impurities as possible. A surface made of the same material as the surface of the object to be measured or inspected is understood in the sense of the present application to mean that the materials of the respective surfaces have the same chemical composition, i.e. both surfaces are made of, for example, Cu, Si, SiC, or Al. Needless to say, the material of the surface of the component means the material that is present before the surface absorbs impurities in the form of, for example, sulfur. The surface of the component can extend over the entire one side of the component, for example over the entire front side or the entire back side, but it is also possible for the surface to cover only partial regions on each side of the component.

[0009] In one embodiment, the component is detachably fixed to the lens in particular. In principle

[0010] ​ It is not always necessary to fix the component to the lens, i.e., the component may be fixed to another holding structure of the measuring or inspection device. However, generally, the component is fixed to the lens, and in order to enable replacement of the component if necessary, it has been found that detachable fixing via, for example, screw connection, snap connection, etc. is advantageous. This may be necessary, for example, when the surface of the component has absorbed a very large amount of impurities and can no longer absorb impurities, thus losing the impurity recovery function. When measuring or inspecting an object having a surface made of a different material, it may be possible to replace the component or it may be necessary to replace it.

[0011] In yet another embodiment, the component forms a plate-shaped flow guide element attached between the final object-side optical element of the lens and the object. Such a flow guide element may be designed, for example, in the form of a circular or annular plate or disk. The flow guide element usually has a small thickness of less than about 3 mm, usually about 1 mm. Since the final object-side optical element of the lens has a relatively large diameter, the flow guide element may also have a relatively large diameter, for example, of about 60 mm or more. The purge gas flow is usually guided along the front side of the flow guide element, i.e., along the side of the flow guide element facing the final object-side optical element. Thus, this surface is usually made of the same material as the surface of the measurement or inspection object and has a relatively large surface area, which enhances the cleaning effect of the purge gas flow.

[0012] In yet another development, a gap width of less than 0.2 mm, particularly less than 0.1 mm, is preferred Alternatively, an annular gap is formed between the flow guiding element and the final object-side optical element. The length of the radial gap substantially corresponding to the radius of the final object-side optical element is relatively large compared to the width of the gap. Therefore, when there are substantially all atoms that can deposit on the surface of the object to be measured or inspected, the probability of contacting the surface of the flow guiding element and instead depositing on that surface becomes high.

[0013] In yet another development form, the flow guiding element has a particularly central opening for supplying a purge gas flow to the intermediate space. Generally, the purge gas flow in the gap proceeds substantially radially from the outside to the inside, leaves the gap, passes through the central opening, and reaches the intermediate space. The flow guiding element is usually made of a material that is not transparent to the radiation used for measuring or inspecting the object. Therefore, the opening of the flow guiding element also serves to allow the radiation to pass through for measuring or inspecting the surface of the object.

[0014] In yet another development form, the measuring or inspecting device further comprises at least one additional, particularly annular component having at least one additional inlet opening for supplying a purge gas flow to an annular space that at least partially surrounds the final object-side optical element annularly. The purge device generally has a purge gas reservoir from which the purge gas is taken out and supplied to the lens via one or more supply lines. In this case, the purge gas flow is supplied to the annular space via one or more usually radially extending inlet openings of the annular component. Ideally, from the annular space, the purge gas flow can enter the gap over the entire circular outer periphery of the final object-side optical element, and as a result, a substantially uniform purge gas flow is obtained in the gap. It occurs radially within the cup. However, there is a preferential direction in the purge gas flow that enters the intermediate space through the opening of the plate-shaped flow guide element, i.e., it does not flow uniformly towards the center of the opening. This is known to be advantageous. Otherwise, a stagnation point where the flow velocity of the purge gas flow is virtually zero is formed at the center of the opening or on the surface of the object to be measured or inspected. This is because of this. From.

[0015] In yet another development, a further component has its surface facing the annular space and / or the inside of the inlet opening made of the same material as the surface of the object to be measured or inspected. As an alternative to or in addition to the flow guide element, when other components of the lens guiding the purge gas flow are detachably fixed to the lens, for example, to the lens housing, in particular, these components can also have a surface made of the same material as the surface to be measured or inspected. This generally applies to the annular components where the plate-shaped flow guide element is usually attached or fixed. The flow guide element can be permanently connected to the annular component in particular. In this case, a further annular component is usually detachably connected to the lens, and as a result, when the fixing of the further component is released, the plate-shaped flow guide element is also removed from the lens.

[0016] In yet another development, the annular space has at least one further inlet opening for supplying a part of the purge gas flow into the lens. In this case, a part branches off from the purge gas flow and is used for purging inside the lens. The inside of the lens is formed by the intermediate space between the mount and the optical element of the lens. The space between the lens and the surface to be measured or inspected It has been found to be advantageous to use the annular space simultaneously for purging the intermediate space and for purging the interior of the lens. This has been found.

[0017] In yet another development, the distance between the flow guiding element and the object to be measured or inspected is 2.0 mm or less. For example, for the measurement or inspection of the surface of an object in the form of a mask or a mirror the lens to be used should have a relatively large object-side numerical aperture, and for this purpose a small actuation distance is generally required.

[0018] In yet another development, the final object-side optical element is a lens element. Lenses of different optical designs have different object-side apertures. It is important here that the required optically free diameter is not covered by the component.

[0019] In one embodiment, the component and / or a further component has a surface in the form of a coating made of the same material as the surface of the object to be measured or inspected. The coating is generally applied to each surface of the body of the component made of a material different from that of the surface of the object to be measured or inspected. The coating is applied using conventional coating methods, such as deposition from the gas phase, in particular sputtering, etc. The application of the coating is particularly useful when, for example, the material of the coating is a semiconductor such as silicon, and this material does not have suitable mechanical properties so that it is not suitable for manufacturing the entire component from this material. This is the case when, for example, the material of the coating is a semiconductor such as silicon, and this material does not have suitable mechanical properties so that it is not suitable for manufacturing the entire component from this material. .

[0020] In yet another embodiment, the component and / or a further component , is made of the same material as the surface of the object to be measured or inspected. In this case, the entire component, or in the case of a multi-component component, at least one component having a surface is made of the same material as the surface of the object to be measured or inspected, meaning that there is no need to apply a coating. When the material of the surface of the object is a metallic material, such as copper, for example, this is usually advantageous because it usually has sufficient mechanical stability to manufacture components in the form of, for example, plate-shaped flow guide elements. In one embodiment, the material of the surface of the object to be measured or inspected is selected from the group comprising metals, in particular copper, semiconductors, in particular silicon, silicon carbide, or aluminum. The measurement or inspection of the object can be carried out on an uncoated object. The material of the surface of the object corresponds in this case to the material forming the entire object. When the object has a plurality of layers or plies, the material of the surface of the object corresponds to the material of the uppermost layer of the object. In principle, it is also possible to carry out the measurement or inspection on a coated object. In this case, the material of the surface corresponds to the material of the uppermost ply of the coating. The invention also relates to a method of the aforementioned type, in which the purge gas flow is guided along the surface of the component before the introduction of the purge gas flow into the intermediate space, the said surface being made of the same material as the surface of the object to be measured or inspected. In this way, impurities which would otherwise deposit on the surface of the object are collected on the surface of the component, so that a post-washing of the purge gas flow can be carried out during the measurement or inspection of the object.

[0021] In one variant, the method involves rinsing the component before the measurement or inspection of the surface of the object.

[0022]

[0023] ​ includes a step of detachably fixing to the lens. In this case, on the surface of each object to be measured or inspected Depending on the material, several components with different materials for guiding the purge gas flow on the surface From a group of components, it is possible to select each component having a surface made of the same material However, generally, copper becomes a contaminant for objects made of other materials, so the lens used for measuring or inspecting copper objects will not be used for measuring or inspecting such objects, for example, Si objects. When the ability to accommodate or absorb impurities on the surface is exceeded, the component can also be replaced.

[0024] Still other features and advantages of the present invention will become apparent from the following description of exemplary embodiments of the present invention with reference to the drawings showing details essential to the present invention and the claims. Each feature can be implemented alone or in any arbitrary combination of a plurality in one variant form of the present invention respectively.

[0025] Exemplary embodiments are shown in schematic diagrams and will be described in the following description.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0027] In the following description of the drawings, the same reference numerals are used for the same or functionally identical components exists.

[0028] FIG. 1 schematically shows an inspection apparatus 1 for inspecting an object 2 in the form of a mask. The object 2, or more precisely the surface 2a of the object 2 to be inspected, is disposed on the object surface 3 of a reflection-refraction lens 4. The lens 4 has an optical assembly 5 disposed adjacent to the object surface 3. The lens 4 has a plurality of mirrors 5a, b and a plurality of lens elements 6, 7, 8 for imaging the surface 2a of the object to be inspected. The individual lens elements 6, 7, 8 and / or mirrors 5a, b of the lens 4 can in this case be arranged symmetrically with respect to the central axis 13 of the lens 4. It should be noted that the number of lens elements and mirrors of the lens 4 is not limited to the number shown in the figure. It is also possible to provide more or fewer lens elements and / or mirrors. Furthermore, the mirrors 5a, b are generally curved on the front side for beam shaping. In particular, the mirrors 5a, b can be omitted, that is, the lens 4 can be designed as a refractive type.

[0029]

[0030] In addition to the lens 4, the mask inspection apparatus 1 has refractive and / or transmissive optical elements disposed in the beam path upstream of the lens 4, but these are not shown in FIG. 1 for simplicity. The lens 4 shown in FIG. 1 is designed to operate with broadband UV radiation of less than 400 nm, less than 300 nm, or in some cases less than 200 nm. Broadband UV radiation is understood to generally encompass a wavelength range of several nanometers, and in some cases several tens of nanometers.

[0031] FIG. 2 shows the final object-side optical element of the lens 4 and is disposed opposite the surface 2a of the object 2. One of the lens elements 8 as the optical element taken makes it possible to very roughly show the details of the lens from FIG. 1. The inspection device 1 also has a purge device 15 shown very schematically in FIG. 2. The purge device 15 functions to supply a purge gas flow 16 to the intermediate space 17 between the lens 4 and the surface 2a of the object 2 to be inspected. The purge device 15 has a purge gas reservoir (not shown), from which a purge gas, for example in the form of nitrogen, can be taken out. The purge gas or the purge gas flow 16 is supplied to the lens 4 by the purge device 15 via a supply line (not shown).

[0032] In the example shown in FIG. 2, a component in the form of a plate-shaped flow guide element 18 is attached to the lens 4. The flow guide element 18 is attached to a further annular component 19, which has a plurality of radially extending inlet openings 20 for supplying the purge gas flow 16 to the lens 4. The further component 19 is detachably connected to the lens 4, more precisely to the substantially cylindrical housing 21 of the lens 4, via a screw connection or the like. The flow guide element 18 and the annular component 19 can be removed together (non-destructively) from the lens 4. The plate-shaped flow guide element 18 functions as a closing element of the lens 4, i.e., as a partition of the lens 4 against the surroundings.

[0033] The purge gas flow 16 supplied to the annular component 19 via the inlet openings 20 by the purge device 15 first enters the annular space 22, which does not reach the full height of the final object-side optical element 8 but surrounds the final object-side optical element 8 of the lens 4 in a ring shape. Starting from the annular space 22, the purge gas flow 16 passes between the back side 8b of the final object-side optical element 8 of the lens and the lens 4. ​ enters an annular gap 23 formed between the surface 18a of the plate-shaped flow guide element 18 facing the back side 8b of the final object-side optical element 8. The annular gap 23 usually has a substantially constant gap width B of less than about 0.2 mm. The purge gas flow 16 enters the intermediate space 17 from the gap 23 through a central opening 24 formed in the plate-shaped flow guide element 18. The central opening 24 of the flow guide element 18 has a diameter slightly larger than the optical effective diameter of the final object-side optical element 8 so that the UV radiation incident on the surface 2a of the object 2 is not blocked by the flow guide element 18. enters an annular gap 23 formed between the surface 18a of the plate-shaped flow guide element 18 facing the back side 8b of the final object-side optical element 8. The annular gap 23 usually has a substantially constant gap width B of less than about 0.2 mm. The purge gas flow 16 enters the intermediate space 17 from the gap 23 through a central opening 24 formed in the plate-shaped flow guide element 18. The central opening 24 of the flow guide element 18 has a diameter slightly larger than the optical effective diameter of the final object-side optical element 8 so that the UV radiation incident on the surface 2a of the object 2 is not blocked by the flow guide element 18. enters an annular gap 23 formed between the surface 18a of the plate-shaped flow guide element 18 facing the back side 8b of the final object-side optical element 8. The annular gap 23 usually has a substantially constant gap width B of less than about 0.2 mm. The purge gas flow 16 enters the intermediate space 17 from the gap 23 through a central opening 24 formed in the plate-shaped flow guide element 18. The central opening 24 of the flow guide element 18 has a diameter slightly larger than the optical effective diameter of the final object-side optical element 8 so that the UV radiation incident on the surface 2a of the object 2 is not blocked by the flow guide element 18. enters an annular gap 23 formed between the surface 18a of the plate-shaped flow guide element 18 facing the back side 8b of the final object-side optical element 8. The annular gap 23 usually has a substantially constant gap width B of less than about 0.2 mm. The purge gas flow 16 enters the intermediate space 17 from the gap 23 through a central opening 24 formed in the plate-shaped flow guide element 18. The central opening 24 of the flow guide element 18 has a diameter slightly larger than the optical effective diameter of the final object-side optical element 8 so that the UV radiation incident on the surface 2a of the object 2 is not blocked by the flow guide element 18. enters an annular gap 23 formed between the surface 18a of the plate-shaped flow guide element 18 facing the back side 8b of the final object-side optical element 8. The annular gap 23 usually has a substantially constant gap width B of less than about 0.2 mm. The purge gas flow 16 enters the intermediate space 17 from the gap 23 through a central opening 24 formed in the plate-shaped flow guide element 18. The central opening 24 of the flow guide element 18 has a diameter slightly larger than the optical effective diameter of the final object-side optical element 8 so that the UV radiation incident on the surface 2a of the object 2 is not blocked by the flow guide element 18. enters an annular gap 23 formed between the surface 18a of the plate-shaped flow guide element 18 facing the back side 8b of the final object-side optical element 8. The annular gap 23 usually has a substantially constant gap width B of less than about 0.2 mm. The purge gas flow 16 enters the intermediate space 17 from the gap 23 through a central opening 24 formed in the plate-shaped flow guide element 18. The central opening 24 of the flow guide element 18 has a diameter slightly larger than the optical effective diameter of the final object-side optical element 8 so that the UV radiation incident on the surface 2a of the object 2 is not blocked by the flow guide element 18. enters an annular gap 23 formed between the surface 18a of the plate-shaped flow guide element 18 facing the back side 8b of the final object-side optical element 8. The annular gap 23 usually has a substantially constant gap width B of less than about 0.2 mm. The purge gas flow 16 enters the intermediate space 17 from the gap 23 through a central opening 24 formed in the plate-shaped flow guide element 18. The central opening 24 of the flow guide element 18 has a diameter slightly larger than the optical effective diameter of the final object-side optical element 8 so that the UV radiation incident on the surface 2a of the object 2 is not blocked by the flow guide element 18.

[0034] The annular space 22 is usually higher than the annular gap 23, and the height of the annular space 22 can be, for example, about 0.6 mm or more. In the annular space 22, a further inlet opening 26 is formed between the mount 25 and the final object-side optical element 8, and a part 16a of the purge gas 16 branches through this and is supplied to its interior 27 to purge the lens 4. However, needless to say, the purge of the lens 4 does not have to be performed using the branched purge gas flow 16a shown in FIG. 2, and other purge gas flows can be used for this purpose if desired. The annular space 22 is usually higher than the annular gap 23, and the height of the annular space 22 can be, for example, about 0.6 mm or more. In the annular space 22, a further inlet opening 26 is formed between the mount 25 and the final object-side optical element 8, and a part 16a of the purge gas 16 branches through this and is supplied to its interior 27 to purge the lens 4. However, needless to say, the purge of the lens 4 does not have to be performed using the branched purge gas flow 16a shown in FIG. 2, and other purge gas flows can be used for this purpose if desired. The annular space 22 is usually higher than the annular gap 23, and the height of the annular space 22 can be, for example, about 0.6 mm or more. In the annular space 22, a further inlet opening 26 is formed between the mount 25 and the final object-side optical element 8, and a part 16a of the purge gas 16 branches through this and is supplied to its interior 27 to purge the lens 4. However, needless to say, the purge of the lens 4 does not have to be performed using the branched purge gas flow 16a shown in FIG. 2, and other purge gas flows can be used for this purpose if desired. The annular space 22 is usually higher than the annular gap 23, and the height of the annular space 22 can be, for example, about 0.6 mm or more. In the annular space 22, a further inlet opening 26 is formed between the mount 25 and the final object-side optical element 8, and a part 16a of the purge gas 16 branches through this and is supplied to its interior 27 to purge the lens 4. However, needless to say, the purge of the lens 4 does not have to be performed using the branched purge gas flow 16a shown in FIG. 2, and other purge gas flows can be used for this purpose if desired. The annular space 22 is usually higher than the annular gap 23, and the height of the annular space 22 can be, for example, about 0.6 mm or more. In the annular space 22, a further inlet opening 26 is formed between the mount 25 and the final object-side optical element 8, and a part 16a of the purge gas 16 branches through this and is supplied to its interior 27 to purge the lens 4. However, needless to say, the purge of the lens 4 does not have to be performed using the branched purge gas flow 16a shown in FIG. 2, and other purge gas flows can be used for this purpose if desired. The annular space 22 is usually higher than the annular gap 23, and the height of the annular space 22 can be, for example, about 0.6 mm or more. In the annular space 22, a further inlet opening 26 is formed between the mount 25 and the final object-side optical element 8, and a part 16a of the purge gas 16 branches through this and is supplied to its interior 27 to purge the lens 4. However, needless to say, the purge of the lens 4 does not have to be performed using the branched purge gas flow 16a shown in FIG. 2, and other purge gas flows can be used for this purpose if desired. The annular space 22 is usually higher than the annular gap 23, and the height of the annular space 22 can be, for example, about 0.6 mm or more. In the annular space 22, a further inlet opening 26 is formed between the mount 25 and the final object-side optical element 8, and a part 16a of the purge gas 16 branches through this and is supplied to its interior 27 to purge the lens 4. However, needless to say, the purge of the lens 4 does not have to be performed using the branched purge gas flow 16a shown in FIG. 2, and other purge gas flows can be used for this purpose if desired.

[0035] As can also be seen in FIG. 2, the distance A between the flow guide element 18, more precisely the back side 18b of the flow guide element 18 facing the object 2, and the surface 2a of the inspection target on the front side of the object 2 is relatively small, generally about 2.0 mm or less. The distance A corresponds to the width of the intermediate space 17 into which the purge gas flow 16 is supplied through the central opening 24 of the flow guide element 18. In the example shown in FIG. 2, the purge gas flow 16 passes through the opening 24 completely symmetrically in the radial direction through the gap 23. As can also be seen in FIG. 2, the distance A between the flow guide element 18, more precisely the back side 18b of the flow guide element 18 facing the object 2, and the surface 2a of the inspection target on the front side of the object 2 is relatively small, generally about 2.0 mm or less. The distance A corresponds to the width of the intermediate space 17 into which the purge gas flow 16 is supplied through the central opening 24 of the flow guide element 18. In the example shown in FIG. 2, the purge gas flow 16 passes through the opening 24 completely symmetrically in the radial direction through the gap 23. As can also be seen in FIG. 2, the distance A between the flow guide element 18, more precisely the back side 18b of the flow guide element 18 facing the object 2, and the surface 2a of the inspection target on the front side of the object 2 is relatively small, generally about 2.0 mm or less. The distance A corresponds to the width of the intermediate space 17 into which the purge gas flow 16 is supplied through the central opening 24 of the flow guide element 18. In the example shown in FIG. 2, the purge gas flow 16 passes through the opening 24 completely symmetrically in the radial direction through the gap 23. As can also be seen in FIG. 2, the distance A between the flow guide element 18, more precisely the back side 18b of the flow guide element 18 facing the object 2, and the surface 2a of the inspection target on the front side of the object 2 is relatively small, generally about 2.0 mm or less. The distance A corresponds to the width of the intermediate space 17 into which the purge gas flow 16 is supplied through the central opening 24 of the flow guide element 18. In the example shown in FIG. 2, the purge gas flow 16 passes through the opening 24 completely symmetrically in the radial direction through the gap 23. As can also be seen in FIG. 2, the distance A between the flow guide element 18, more precisely the back side 18b of the flow guide element 18 facing the object 2, and the surface 2a of the inspection target on the front side of the object 2 is relatively small, generally about 2.0 mm or less. The distance A corresponds to the width of the intermediate space 17 into which the purge gas flow 16 is supplied through the central opening 24 of the flow guide element 18. In the example shown in FIG. 2, the purge gas flow 16 passes through the opening 24 completely symmetrically in the radial direction through the gap 23. Rather, it has a preferential direction. Such a preferential direction can be generated, for example, by appropriately structuring the back side 8a of the final object-side optical element 8 and / or the front side of the plate-shaped flow guide element 18. This can be achieved by appropriately structuring the back side 8a of the final object-side optical element 8 and / or the front side of the plate-shaped flow guide element 18. The generation of the preferential direction of the purge gas flow 16 is for preventing the formation of stagnation points of the purge gas flow 16 in the region of the opening 24. This can be achieved by appropriately structuring the back side 8a of the final object-side optical element 8 and / or the front side of the plate-shaped flow guide element 18.

[0036] The purge gas flow 16 is for reliably removing impurities on the surface 2a of the object 2. However, the purge gas flow 16 itself may contain impurities, for example, a small amount of sulfur. These impurities can be emitted, for example, in the supply line of the purge device 15 or the lens 4 when stray light is incident on the metal mount of the lens 4 containing, for example, a small amount of sulfur. This can be achieved by appropriately structuring the back side 8a of the final object-side optical element 8 and / or the front side of the plate-shaped flow guide element 18.

[0037] Therefore, before the purge gas flow 16 is introduced into the intermediate space 17 through the opening 24 of the flow guide element 18, the purge gas flow 16 is pre-cleaned by being guided along the front side of the plate-shaped flow guide element 18. In the example shown in FIG. 2, the surface 18a on the front side of the flow guide element 18 is designed as a coating made of the same material as the surface 2a of the object 2, that is, the surface 18a of the flow guide element 18 acts as a collector ("getter") of impurities. Thus, if the purge gas flow 16 is not cleaned, the same impurities as on the surface 2a of the object 2 will accumulate on the surface 18a of the flow guide element 18. In the example shown in FIG. 2, the object 2 is a mask containing copper, and the surface 18a or the coating on the front side of the plate-shaped flow guide element 18 is also made of copper. In the example shown in FIG. 2, the surface 18a on the front side of the flow guide element 18 is designed as a coating made of the same material as the surface 2a of the object 2, that is, the surface 18a of the flow guide element 18 acts as a collector ("getter") of impurities. Thus, if the purge gas flow 16 is not cleaned, the same impurities as on the surface 2a of the object 2 will accumulate on the surface 18a of the flow guide element 18. In the example shown in FIG. 2, the object 2 is a mask containing copper, and the surface 18a or the coating on the front side of the plate-shaped flow guide element 18 is also made of copper. if the purge gas flow 16 is not cleaned, the same impurities as on the surface 2a of the object 2 will accumulate on the surface 18a of the flow guide element 18. In the example shown in FIG. 2, the object 2 is a mask containing copper, and the surface 18a or the coating on the front side of the plate-shaped flow guide element 18 is also made of copper. if the purge gas flow 16 is not cleaned, the same impurities as on the surface 2a of the object 2 will accumulate on the surface 18a of the flow guide element 18. In the example shown in FIG. 2, the object 2 is a mask containing copper, and the surface 18a or the coating on the front side of the plate-shaped flow guide element 18 is also made of copper. As an alternative, the object 2 can be a mirror, for example, a copper mirror, or a substrate for a mirror made of, for example, copper. In the example shown in FIG. 2, the object 2 is a mask containing copper, and the surface 18a or the coating on the front side of the plate-shaped flow guide element 18 is also made of copper. As an alternative, the object 2 can be a mirror, for example, a copper mirror, or a substrate for a mirror made of, for example, copper. This can be achieved by appropriately structuring the back side 8a of the final object-side optical element 8 and / or the front side of the plate-shaped flow guide element 18.

[0038] The gap 23 between the final object-side optical element 8 and the plate-shaped flow guide element 18 is relatively small. It has a relatively small gap width B. Further, the final object-side optical element 8 has a relatively large radius (substantially corresponding to the length of the radial gap 23 from the annular space 22 to the central axis 13), for example, about 30 mm or more. Therefore, when there are individual sulfur atoms, the probability of their hitting and adhering to the copper surface 18a of the plate-shaped flow guide element 18 is very high. Thus, sulfur is captured by the copper material on the surface 18a of the plate-shaped flow guide element 18 before reaching the copper surface 2a of the object 2. As an alternative to the above-described configuration of the surface 18a in the form of coating, the entire plate-shaped flow guide element 18, or in some cases, particularly a part of its front side, may be made of the same material as the surface 2a of the object 2. For example, the plate-shaped flow guide element 18 can be designed as a copper plate. In the illustrated example, the flow guide element 18 has a conical portion in the region of the gap 23 that conforms to the curvature of the lens element 8. Needless to say, in the case of the final optical element having a planar back side 8b, the conical portion of the flow guide element 18 can be omitted. If the copper surface 18a of the plate-shaped flow guide element 18 absorbs so much sulfur at a certain point that new sulfur cannot reach the surface 2a of the object 2, the plate-shaped flow guide element 18 can be removed from the lens 4 and replaced with another plate-shaped flow guide element 18 that has not yet absorbed sulfur. For this purpose, in particular, an additional annular component 19 can be removed from the lens 4. When inspecting different types of objects 2 or objects 2 with different materials of the surface 2a by the inspection apparatus 1

[0039]

[0040] ​​​​​​​​​​When doing so, the plate-shaped flow guide element 18 shown in Fig. 2 having a copper surface 18a can be replaced with a flow guide element 18 made of a different material. For example, for the inspection of an object 2 having a silicon surface 2a, in order to capture impurities in the form of atoms or molecules that should not be deposited on the surface 2a of the object 2 made of silicon, a silicon surface 18a or a silicon coating can be provided on the front side of the plate-shaped flow guide element 18. Copper is an impurity for most of the other materials usually used to form the object 2, such as aluminum, or semiconductors, such as Si, SiC, etc. Therefore, usually, the lens 4 used for the inspection or measurement of an object 2 made of copper is not used for the inspection or measurement of other types of objects 2. Thus, usually, the plate-shaped flow guide element 18 having a copper surface 18a is attached to the lens 4 only when it is certain that the lens 4 is used only for the inspection or measurement of a copper object 2 and not for the inspection or measurement of other types of objects 2. During the manufacture of the lens 4, since it is not known whether the lens 4 will be used for the measurement or inspection of a copper object, it is not advisable to use copper during the manufacture of the lens 4. For these reasons too, it is advantageous if the flow guide element 18 is detachably attached to the lens 4. In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this

[0041] Copper is an impurity for most of the other materials usually used to form the object 2, such as aluminum, or semiconductors, such as Si, SiC, etc. Therefore, usually, the lens 4 used for the inspection or measurement of an object 2 made of copper is not used for the inspection or measurement of other types of objects 2. Thus, usually, the plate-shaped flow guide element 18 having a copper surface 18a is attached to the lens 4 only when it is certain that the lens 4 is used only for the inspection or measurement of a copper object 2 and not for the inspection or measurement of other types of objects 2. During the manufacture of the lens 4, since it is not known whether the lens 4 will be used for the measurement or inspection of a copper object, it is not advisable to use copper during the manufacture of the lens 4. For these reasons too, it is advantageous if the flow guide element 18 is detachably attached to the lens 4. In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this

[0042] In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this In addition to or as an alternative to the plate-shaped flow guide element 18, surfaces made of a material corresponding to the material of the surface 2a of the object 2 can also be provided on other components of the lens 4. For example, the annular component 19 to which the plate-shaped flow guide element 18 is fixed can have the same material as the surface 2a of the object 2 on its surface 19a facing the annular opening 22 and / or the inner side 19b of the inlet opening 26. Since the annular component 19 is also detachably fixed to the lens 4, this is advantageous. However, it goes without saying that components permanently connected to the lens 4 can also optionally have a surface through which the purge gas stream 16 flows and which can be used for

[0043] capturing impurities. It is also understood that the inspection device 1 or the lens 4 does not necessarily have the optical design shown in FIG. 1 and can be designed in any different way. The larger the diameter of the final object-side optical element 8, the larger the surface 18a of the plate-shaped flow guide element 18, and the better the purge gas stream 16 is cleaned (at the same gap width B). Instead of the object 2 in the form of a lithography mask mirror, for example an EUV mirror, other objects used in the semiconductor industry,

Claims

1. a lens (4) for measuring or inspecting a surface (2a) of an object (2) to be measured or inspected; a purge device (15) for supplying a purge gas flow (16) to an intermediate space (17) between the surface (2a) of the object (2) and the lens (4); a component (18) forming a plate-like flow guide element mounted between the object (2) and a final object-side optical element (8) of the lens (4); A measuring or inspection device (1) comprising: the component (18) is selected according to the surface (2a) of the object (2) comprising at least one of the following materials: metal, semiconductor; and a component (18) having a surface (18a) made of the material contained in the surface (2a) of the object (2), The purge device (15) is designed to direct the purge gas flow (16) along the surface (18a) of the component (18) prior to introduction of the purge gas flow (16) into the intermediate space (17).

2. 2. The measuring or inspection device according to claim 1, wherein the component (18) is removably fixed to the lens (4).

3. 3. The measuring or inspection device according to claim 1 or 2, wherein an annular gap (23) having a gap width (B) of less than 0.2 mm is formed between the flow guiding element (18) and the final object-side optical element (8).

4. 4. The measuring or inspection device according to claim 1, wherein the flow guiding element (18) has a central opening (24) for supplying the purge gas flow (16) to the intermediate space (17).

5. 5. The measuring or inspection apparatus according to claim 1, further comprising an annular further component (19) having at least one further inlet opening (20) for supplying the purge gas flow (16) to an annular space (22) at least partially annularly surrounding the final object-side optical element (8).

6. 6. A measuring or inspection device as claimed in claim 5, in which a further component (19) is selected, the further component (19) having its surface (19a) facing the annular space (22) and / or the inside (19b) of the inlet opening (20) made of the material contained in the surface (2a) of the object (2) to be measured or inspected.

7. 6. The measuring or inspection device according to claim 5, wherein the annular space (22) has at least one further inlet opening (26) for supplying a portion (16a) of the purge gas flow (16) to an interior (25) of the lens (4).

8. 8. A measuring or inspection device according to any one of the preceding claims, wherein the distance (A) between the flow guiding element (18) and the object (2) to be measured or inspected is equal to or less than 2.0 mm.

9. Measuring or inspection device according to any one of the preceding claims, wherein the final object side optical element forms a lens element (8).

10. 10. The measuring or inspection device according to any one of claims 1 to 9, wherein the component (18) and / or the further component (19) has a coating made of the material contained in the surface (2a) of the object (2) to be measured or inspected.

11. A measuring or inspection device according to any one of claims 1 to 10, wherein the component (18) and / or the further component (19) are made of the material contained in the surface (2a) of the object (2) to be measured or inspected.

12. 12. The measuring or inspection device according to any one of the preceding claims, wherein the surface (2a) of the object (2) to be measured or inspected comprises copper.

13. A measuring or inspection apparatus as claimed in any one of claims 1 to 12, wherein the component (18) is made of copper or the component (18) has a coating made of copper.

14. A method for measuring or inspecting an object (2), comprising the steps of: - measuring or inspecting a surface (2a) of an object (2) to be measured or inspected, the surface (2a) being arranged in an object plane (3) of a lens (4); providing a purge gas flow (16) into an intermediate space (17) between the surface (2a) of the object (2) to be measured or inspected and the lens (4); In a method comprising: The surface (2a) of the object (2) to be measured or inspected comprises at least one material selected from the group consisting of metal and semiconductor; 2. The method of claim 1, further comprising: guiding said purge gas flow (16) along a surface (18a) of a component (18) made of said material contained in said surface (2a) of said object (2) to be measured or inspected prior to introduction of said purge gas flow (16) into said intermediate space (17), said surface (18a) being made of said material contained in said surface (2a) of said object (2) to be measured or inspected, said component forming a plate-like flow guiding element (18) mounted between a final object-side optical element (8) of said lens (4) and said object (2).

15. 15. The method of claim 14, Removably fixing the component (18) to the lens (4) prior to measuring or inspecting the surface (2a) of the object (2). The method further comprises:

16. A method according to claim 14 or 15, wherein the surface (2a) of the object (2) to be measured or inspected comprises copper.

17. A method according to any one of claims 14 to 16, wherein the component (18) is made of a material selected from copper, or the component (18) has a coating made of a material selected from copper.

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