Aperture, optical system and lithographic apparatus

Abstract

An aperture (300) for a lithographic apparatus (100A, 100B), in particular a numerical aperture aperture, a blocking aperture or a dummy aperture, comprises a light-transmissive aperture (302) and at least one aperture element (306, 308), the aperture (302) being disposed in or on the at least one aperture element (306, 308), wherein the aperture element (306, 308) is opaque and fluid-permeable outside the aperture (302).

Description

[0001] Cross-reference to related applications

[0002] The contents of priority application DE 10 2019 209 884.3, filed on July 4, 2019, are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates to apertures (particularly aperture stops, obscuration stops, or false-light stops) for photolithography apparatuses, optical systems having at least one such aperture, and photolithography apparatuses having at least one such aperture and / or at least one such optical system. Background Technology

[0004] Microlithography is used to produce microstructured components, such as integrated circuits. Microlithography processes are performed using a lithography apparatus equipped with an illumination system and a projection system. In this case, the image of a mask (mask master) illuminated by the illumination system is projected onto a substrate (e.g., a silicon wafer) coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system, thereby transferring the mask structure onto the photosensitive coating of the substrate.

[0005] Driven by the increasing demand for smaller structures in integrated circuit manufacturing, EUV lithography devices (extreme ultraviolet, EUV) that utilize light with wavelengths ranging from 0.1 nm to 30 nm (particularly 13.5 nm) are currently under development. In the case of such EUV lithography devices, since most materials have a high absorption rate for this wavelength of light, reflective optical units (i.e., mirrors) must be used instead of the previously used refractive optical units (i.e., lens elements). These mirrors operate with near-perpendicular or grazing incidence.

[0006] In DUV (deep ultraviolet) lithography apparatuses, airflow is frequently implemented through the system. "System" here can be understood to refer, for example, to the projection system of the lithography apparatus or the lithography apparatus itself. This airflow can be achieved, for example, by blowing in and expelling nitrogen or air. This airflow serves to cool the optical components (which are heated by the absorption of light) and to remove harmful substances that may accumulate in the system due to plant conditions or degassing.

[0007] Because EUV radiation has relatively low air transmittance, operation at EUV wavelengths is, in principle, carried out in a vacuum. However, low atmospheric pressures of approximately one Pascal are also common here. Hydrogen is preferably used for the gas flow. Providing the gas flow aids in photocleaning and occasionally achieves a limited cooling effect.

[0008] Airflow is achieved through several inlet locations and outlet openings, where the design challenge is to keep the number of such openings to a minimum. Therefore, the gas should flow through the system in a defined manner, particularly as freely as possible. However, at the same time, for example, the system may have multiple obstruction diaphragms (e.g., aperture diaphragms, blocking diaphragms, and / or virtual diaphragms), which could impede airflow.

[0009] The task of a numerical aperture stop is to adjust the working beam in the radial direction, referencing the beam path from the outside to the inside. Conversely, the task of an occlusion stop is to block obstructions in the beam path. To this end, the occlusion stop cuts out the interior portion of the working beam relative to the radial beam path. A virtual aperture stop is typically located in the intermediate image region or intermediate image plane. These stops provide a substantially field-constant exit pupil, which is important for the function of the lithography system. Furthermore, the virtual aperture stop ensures that background light, which contributes no useful imaging function and only reduces contrast, is filtered out.

[0010] Apertures are typically designed as thin metal plates with suitable geometry and aperture. Therefore, apertures are relatively lightweight and rigid, and do not introduce any unwanted substances into the system. Furthermore, this configuration allows for inexpensive and precise manufacturing. However, in this compact form, the aperture obstructs the desired gas flow through the system. This reduces the expected cooling and cleaning effect of the airflow due to the additional inlet and outlet openings, or necessitates greater system complexity. The goal is to reconcile these seemingly contradictory requirements of opacity and permeability. Summary of the Invention

[0011] In this context, the object of the present invention is to provide an improved aperture.

[0012] Therefore, an aperture for a photolithography apparatus is proposed, particularly a numerical aperture aperture, a blocking aperture, or a virtual aperture. The aperture includes a light-transmitting aperture and at least one aperture element, wherein the aperture is disposed within or above the at least one aperture element, and the aperture element is opaque and fluid-permeable outside the aperture.

[0013] Because the aperture element is fluid-permeable outside the aperture, it is possible to prevent the aperture from obstructing airflow through the optical system of the lithography apparatus, particularly through the projection system. In this way, the desired airflow cooling and cleaning effects can be maintained, thus eliminating the need for the increased system complexity resulting from additional inlet and outlet openings for airflow.

[0014] The aperture is transmissive, especially for EUV or DUV radiation. The aperture can be a perforation of any desired shape within the aperture element, or a cutout of any desired shape within the aperture element. A “perforation” should be understood as any desired shape of geometry passing through the aperture element and having a completely closed boundary or edge. In contrast, a “cutout” should be understood as a geometry passing through the aperture element without a closed boundary or edge. In other words, such a cutout is located on the periphery of the aperture element and extends from the periphery into the aperture element.

[0015] Specifically, at least one aperture element is provided. However, multiple aperture elements may also be provided, such as two or three aperture elements. However, the number of aperture elements is arbitrary. The aperture disposed in or on the aperture element should be understood in particular to indicate that the aperture is completely surrounded by the material of the aperture element (as explained just with reference to the perforation) and therefore located in the aperture element, or the aperture is not completely surrounded by the material of the aperture element (as explained just with reference to the cut) and therefore located on the aperture element.

[0016] The “outside” of the aperture refers to the area within or above the diaphragm element where no aperture is located. For example, this could be the area adjacent to the aperture, completely or partially surrounding it. “Opaque” in this context should be understood specifically to mean opaque to EUV and / or DUV radiation. That is, the diaphragm element transmits light only at the aperture, particularly for EUV and / or DUV radiation.

[0017] The term "fluid-permeable" for an aperture element should be understood to mean that a fluid (e.g., a gas, particularly air, nitrogen, or hydrogen) or liquid can flow from the front of the aperture element through it to the rear, and vice versa. The fluid does not flow through the aperture itself, but rather flows outside or alongside the aperture through the material of the aperture element itself. However, this does not preclude the possibility of fluid flowing through the aperture separately.

[0018] According to one embodiment, the aperture is designed to deflect the fluid flow passing through it several times.

[0019] An aperture deflects the fluid flow, for example, at least once. On the other hand, light incident on an aperture element next to the aperture is not deflected by the aperture element, but is blocked by it.

[0020] According to another embodiment, at least one aperture element has a plurality of openings configured such that at least one aperture element is opaque and fluid-permeable.

[0021] Specifically, the openings are offset from each other in the direction in which light is incident on the aperture. As a result, the fluid flow is deflected as it flows through the aperture element. Conversely, the light is blocked by the offset configuration of the openings.

[0022] According to another embodiment, the opening fluidly connects the front and rear sides of the aperture to each other.

[0023] In other words, fluid can flow from the front to the back through the opening, and vice versa.

[0024] According to another embodiment, the cross-section of the opening is circular or rectangular.

[0025] However, the opening can also have any other geometry. For example, the opening can be triangular or elliptical. In the present context, "opening" should be understood specifically as a gap or perforation through the aperture element.

[0026] According to another embodiment, the aperture further includes a first aperture element having a first opening and a second aperture element having a second opening, wherein the first opening and the second opening are configured to be offset relative to each other.

[0027] The "offset configuration" of the openings specifically refers to the fact that the first and second openings do not overlap, so that the fluid flow is deflected at least once when flowing from the first opening to the second opening. The number of aperture elements is arbitrary. Exactly two aperture elements can be used. However, it is also possible to use three or four aperture elements.

[0028] According to another embodiment, the first opening and the second opening are configured offset relative to each other, such that the first aperture element completely covers the second opening, and the second aperture element completely covers the first opening.

[0029] Specifically, the aperture element covers a corresponding opening in the direction in which light is incident on the aperture, allowing light to still pass through the first opening and enter the second aperture element, but which then blocks it. Simultaneously, the fluid is deflected at the second aperture element and flows through the second opening to the rear of the aperture.

[0030] According to another embodiment, the first aperture element is disposed at a distance from the second aperture element.

[0031] Therefore, an intermediate space is provided between the first and second aperture elements. The size of this distance allows fluid to flow freely between the first and second aperture elements. This distance can range from a fraction of a millimeter to several millimeters.

[0032] According to another embodiment, the opening is slit-shaped and passes through at least one aperture element at an angle.

[0033] In this case, a single, monolithic aperture element is specifically chosen. A seamless frame extends around the opening, ensuring sufficient stability of the aperture.

[0034] According to another embodiment, at least one aperture element is made of a porous material, which is fluid-permeable due to its porous structure.

[0035] In this case, exactly one aperture element can also be used. For example, the aperture element is made of ceramic or metal. For example, for this purpose, particles of, for example, metal powder or ceramic powder can be sintered together. This provides an open structure that allows fluid to pass through but is not transparent.

[0036] According to another embodiment, the pore size is fluid permeable.

[0037] This means that both the aperture element itself and the aperture set in or on the aperture element are fluid-permeable.

[0038] According to another embodiment, the aperture is defined by means of a light-determining edge, wherein the light-determining edge is either closed or open with respect to its perimeter.

[0039] The "light-determining edge" is the profile of the aperture, which helps adjust the beam path. "Closed in terms of its perimeter" means that the light-determining edge completely surrounds the aperture. "Open in terms of its perimeter" specifically indicates that the light-determining edge does not completely surround the aperture.

[0040] Furthermore, an optical system for a photolithography apparatus is proposed. The optical system includes an object plane, a field plane, an intermediate image plane disposed between the object plane and the field plane, and at least one aperture as described above, wherein the aperture is disposed in the intermediate image plane to filter out virtual light from the beam path of the optical system upstream of the field plane during operation of the optical system.

[0041] Object points from the object plane (in which an object, for example, in the form of a photomask, is disposed) are imaged onto the field plane and the intermediate image plane. The wafer to be exposed can be placed in the field plane. A pupil plane with a numerical aperture stop can be positioned between the object plane and the intermediate image plane.

[0042] According to one embodiment, the optical system further includes a plurality of apertures arranged sequentially along the beam path.

[0043] The number of aperture stops is arbitrary. Numerical aperture stops, blocking stops, scattering stops, or virtual stops can be set.

[0044] Furthermore, a photolithography apparatus having at least one such aperture and / or having at least one such optical system is proposed.

[0045] The lithography apparatus can be either an EUV lithography apparatus or a DUV lithography apparatus. EUV stands for "Extreme Ultraviolet Light" and indicates that the wavelength of the working light is between 0.1 nm and 30 nm. DUV stands for "Deep Ultraviolet Light" and indicates that the wavelength of the working light is between 30 nm and 250 nm.

[0046] In the present context, the term “one; one” should not necessarily be construed as limiting it to only one element. On the contrary, multiple elements may be provided, such as two, three, or more. Any other quantity used herein should not be construed as a limitation on the exact number of elements stated. Rather, upward and downward numerical deviations are possible unless otherwise stated.

[0047] The embodiments and features described for the aperture are accordingly applicable to the proposed optical system and, respectively, to the proposed lithography apparatus, and vice versa.

[0048] Other possible embodiments of the invention also include combinations of features or embodiments not explicitly mentioned in the foregoing or hereinafter described with respect to exemplary embodiments. In such cases, those skilled in the art will also add various aspects as improvements or supplements to the various basic forms of the invention. Attached Figure Description

[0049] Other advantageous constructions and aspects of the invention are the subject of the dependent claims and the exemplary embodiments described below. Hereinafter, the invention will be explained in more detail based on preferred embodiments and with reference to the accompanying drawings:

[0050] Figure 1A A schematic diagram of an embodiment of an EUV lithography apparatus is shown;

[0051] Figure 1B A schematic diagram of one embodiment of a DUV lithography apparatus is shown;

[0052] Figure 2 Showing the use of Figure 1A or Figure 1B A schematic diagram of an embodiment of the optical system of a photolithography apparatus;

[0053] Figure 3 Showing the use of Figure 2 A schematic diagram of the exit pupil of the optical system;

[0054] Figure 4 Showing the use of Figure 2 A schematic diagram of an embodiment of the aperture of the optical system;

[0055] Figure 5 Showing along Figure 4 A schematic cross-sectional view of the aperture with cross-section line VV in the diagram;

[0056] Figure 6 Showing the use of Figure 2 A schematic diagram of another embodiment of the aperture of the optical system;

[0057] Figure 7 Showing along Figure 6 A schematic cross-sectional view of the aperture along section line VII-VII in the diagram;

[0058] Figure 8 Showing the use of Figure 2 A schematic diagram of another embodiment of the aperture of the optical system;

[0059] Figure 9 Showing along Figure 8 A schematic cross-sectional view of the aperture along the cross-section line IX-IX;

[0060] Figure 10 Showing the use of Figure 2 A schematic diagram of another embodiment of the aperture of the optical system; and

[0061] Figure 11 Showing along Figure 10 A schematic cross-sectional view of the aperture along the cross-section line XI-XI.

[0062] Unless otherwise indicated, identical elements or elements having the same function in the figures have the same reference numerals. It should also be noted that the illustrations in the figures are not necessarily drawn to scale. Parts that are obscured are shown in dashed lines in the figures. Detailed Implementation

[0063] Figure 1A A schematic diagram of an EUV lithography apparatus 100A is shown, comprising a beam shaping and illumination system 102 and a projection system 104. In this case, EUV stands for "extreme ultraviolet light," indicating that the wavelength of the working light is between 0.1 nm and 30 nm. The beam shaping and illumination system 102 and the projection system 104 are respectively housed in vacuum chambers (not shown), each of which is evacuated with the assistance of a evacuation device (not shown). The vacuum chambers are surrounded by a machine room (not shown), which houses drive devices for mechanically moving or setting optical elements. Additionally, electronic controllers, etc., may also be housed in this machine room.

[0064] EUV lithography apparatus 100A includes an EUV light source 106A. For example, a plasma source (or synchrotron) that provides radiation 108A within the EUV range (limiting ultraviolet range), i.e., in the wavelength range of 5 nm to 20 nm, can serve as the EUV light source 106A. In the beam shaping and illumination system 102, the EUV radiation 108A is focused, and the desired operating wavelength is filtered from the EUV radiation 108A. The EUV radiation 108A generated by the EUV light source 106A has a relatively low air transmittance; therefore, the beam guiding space in the beam shaping and illumination system 102 and the projection system 104 is evacuated.

[0065] Figure 1A The beamforming and illumination system 102 shown has five mirrors 110, 112, 114, 116, and 118. After passing through the beamforming and illumination system 102, EUV radiation 108A is guided onto a photomask (mask master) 120. The photomask 120 is also implemented as a reflective optical element and can be configured externally to systems 102 and 104. Furthermore, EUV radiation 108A can be guided onto the photomask 120 via mirror 122. The photomask 120 has a structure that images onto a wafer 124 or the like in a reduced manner via projection system 104.

[0066] The projection system 104 (also called a projection lens) has six mirrors M1 to M6 for imaging the photomask 120 onto the wafer 124. In this case, the individual mirrors M1 to M6 of the projection system 104 can be symmetrically arranged with respect to the optical axis 126 of the projection system 104. It should be noted that the number of mirrors M1 to M6 in the EUV lithography apparatus 100A is not limited to the indicated number. More or fewer mirrors M1 to M6 may also be provided. Furthermore, the mirrors M1 to M6 are typically bent on their front side for beam shaping.

[0067] Figure 1B A schematic diagram of a DUV lithography apparatus 100B is shown, which includes a beam shaping and illumination system 102 and a projection system 104. In this case, DUV stands for "deep ultraviolet light," and indicates that the wavelength of the working light is between 30 nm and 250 nm. (See reference...) Figure 1A As described, the beam shaping and illumination system 102 and the projection system 104 may be configured in a vacuum housing and / or surrounded by a machine room with corresponding drive units.

[0068] The DUV lithography apparatus 100B has a DUV light source 106B. For example, an ArF excimer laser that emits radiation 108B in the DUV range, for example, at 193 nm, can be provided as the DUV light source 106B.

[0069] Figure 1B The beam shaping and illumination system 102 shown directs DUV radiation 108B onto a photomask 120. The photomask 120 is implemented as a transmissive optical element and can be configured externally to systems 102 and 104. The photomask 120 has a structure that images onto a wafer 124 or the like in a reduced manner via a projection system 104.

[0070] The projection system 104 has a plurality of lens elements 128 and / or mirrors 130 for imaging the photomask 120 onto the wafer 124. In this case, the individual lens elements 128 and / or mirrors 130 of the projection system 104 may be symmetrically arranged with respect to the optical axis 126 of the projection system 104. It should be noted that the number of lens elements 128 and mirrors 130 of the DUV lithography apparatus 100B is not limited to the number shown. More or fewer lens elements 128 and / or mirrors 130 may also be provided. Furthermore, the mirrors 130 are typically bent on their front side for beam shaping.

[0071] The air gap between the last lens element 128 and the wafer 124 can be replaced by a liquid medium 132 with a refractive index >1. For example, the liquid medium 132 can be high-purity water. This configuration is also called immersion lithography and has improved lithographic resolution. The medium 132 can also be called an immersion liquid.

[0072] Figure 2 A schematic diagram of the optical system 200 is shown. As described above, the optical system 200 is part of the EUV lithography apparatus 100A or the DUV lithography apparatus 100B. The optical system 200 may be, in particular, the projection system 104 as described above, or a part of such a projection system 104.

[0073] Optical system 200 includes, for example, an object plane 202, a pupil plane 204, an image or intermediate image plane 206, and a field plane 208. Another pupil plane 204 (however, it is not shown in the image) Figure 2 The image plane (206) can be positioned between the intermediate image plane 206 and the field plane 208. Multiple object points O are positioned in the object plane 202 (however, in...). Figure 2 The object field or field of use 210 is indicated by only one of the reference numerals in the figure. With the assistance of the pupil plane 204, the object point O is imaged onto the field point F1 in the field plane 208 and onto the field point F2 in the intermediate image plane 206.

[0074] An object (not shown) is located in object plane 202. The object may be a photomask 120. A field 210 is positioned at or on the object, or at or on the photomask 120. For example, the wafer 124 to be exposed is positioned in field plane 208. In principle, field plane 208 may also be an image plane or an intermediate image plane.

[0075] Instead of object plane 202, a field plane may also be provided, in which the image is imaged onto field plane 208 and intermediate image plane 206. Pupil plane 204 is preferably disposed between object plane 202 and field plane 208. Therefore, pupil plane 204 is neither disposed on the object side nor on the image side.

[0076] One or more aperture stops are configured in the pupil plane 204. According to an exemplary embodiment, a numerical aperture stop 212 (NA stop) is provided. Additionally, an occlusion stop (not shown) may be provided. The NA stop 212 includes an aperture 214 defined by an optically determining edge 216. The optically determining edge 216 may be closed. The aperture 214 may have any desired geometry. The NA stop 212 may be made of multiple parts, meaning the geometry of the aperture 214 is adjustable.

[0077] The NA stop 212, together with planes 202, 204, 206, and 208, defines the beam path 218 along which the working beam 220 travels through the optical system 200. Instead of or supplementing the NA stop 212, it is also possible to place a scattering stop and / or a virtual stop (not shown) in the pupil plane 204 or at different locations (particularly in the intermediate image plane 206), as explained below with reference to the intermediate image plane 206.

[0078] Here, the working light 220 includes, for example, light rays S1 and S2, which describe the imaging of the object point O on the intermediate image plane 206 and on the field plane 208. The figure is only schematic and illustrates that multiple optical elements (e.g., mirrors, lens elements, gratings, and / or the like) may be configured between the object plane 202 and the pupil plane 204, between the pupil plane 204 and the intermediate image plane 206, and between the intermediate image plane 206 and the field plane 208. The optical elements may include, for example, mirrors M1 to M6, 110, 112, 114, 116, 118, 130, and / or lens element 128.

[0079] The task of the NA stop 212 is to adjust the working light 220 in the radial direction R relative to the beam path 218 from the outside to the inside, thereby defining the maximum half-image-side aperture angle θmax of the light-filling angle space W1 assigned to the field point F1. The aperture angle θmax, in turn, specifies the numerical aperture of the optical system 200. For large numerical apertures, the aperture angle θmax is very large, and the angle space W1 therefore has a flat, tapered geometry. For small numerical apertures, the aperture angle θmax is very small, and the angle space W1 therefore has a sharp, tapered geometry.

[0080] Field point F1 is assigned an exit pupil AP1. The exit pupil AP1 is the image-side representation of the NA stop 212. Figure 2The entrance pupil EP1 for object point O is further shown. The entrance pupil EP1 is the object-side imaging representation of the NA stop 212. Each field point F1 is assigned an exit pupil AP1. Each object point O is assigned an entrance pupil EP1.

[0081] The exit pupil AP1 defines the light-filling angle space W1 via the field point F1. The angle space W1 is defined by edge (light) rays S3 and S4. These rays, in each case, are incident on the field point F1 with half of the image-side maximum aperture angle θmax. The maximum aperture angle θmax is measured between the corresponding edge rays S3 and S4 and the central (light) ray S5 arriving at the field point F1. The central ray S5 intersects the center point M of the exit pupil AP1. The field point F2 is assigned the intermediate image pupil AP2, which defines the angle space W2. The entrance pupil EP1 is similarly assigned this angle space W3.

[0082] like Figure 3 As shown, each point P of the exit pupil AP1 can be described with the assistance of the direction vector V. The direction vector V has an opening angle θ relative to the central ray S5. The direction vector V further has a circumferential angle in the circumferential direction around the center point M. In principle, each ray in the exit pupil AP1 (composed of angle θ, ...) (Description) A position is assigned in the pupil plane 204. In other words, therefore, every field point F1 in the field plane 208 sees all the light spots in the pupil plane 204. Conversely: light in the angular space on the pupil plane 204 is assigned a position in the field plane 208. Therefore, the exit pupil AP1 is field constant. For each field point F1, the light incident on the field plane 208 is constant.

[0083] As described above, the incident pupil EP1 is the object-side imaging representation of the NA aperture 212. The incident pupil EP1 can also be referred to as the usable aperture or something equivalent. During the operation of the photolithography apparatuses 100A and 100B, light also diffracts at an angle greater than the usable aperture at the photomask 120 located in the object plane 202. In other words, light diffracts at an angle greater than the maximum aperture angle θmax (defined by the NA aperture 212). This is in Figure 2 The reference light ray S6 is shown in the middle. This can occur at a higher diffraction order on the regular imaging structure of the photomask 120, and can also occur at auxiliary structures such as the so-called SRAF (Secondary Resolution Auxiliary Feature).

[0084] These are designed to redistribute light so that the structure being imaged is formed without end-tapering or other errors. However, they should themselves be invisible in the image (i.e., in field plane 208). Therefore, they are chosen to be small so that all diffraction orders capable of being imaged are located outside the incident pupil EP1 or outside the usable aperture, and ideally blocked at the NA stop 212. In other words, light rays with an aperture angle θ larger than the maximum aperture angle θmax determined by the NA stop 212 are blocked at the NA stop 212.

[0085] However, structurally, a housing 222 is required for the beam path 218, at least in the region of the photomask 120. The housing 222 serves to maintain a vacuum and prevent contamination. However, grazing incidence reflection can occur at this housing 222. This reflection alters the beam angle within a selected angular range, causing the reflected light to reappear within the working aperture EP. However, the light now appears to originate from a virtual object point OV outside the working field 210. The virtual object point OV is assigned a virtual incident pupil EP2 that defines the angular space W4.

[0086] exist Figure 2 In the diagram, the light ray S6, after reflection at housing 222, is designated by reference symbol S6'. The extension of light ray S6' in the direction of object plane 202 will guide to the virtual object point OV. The extension of light ray S6 beyond housing 222 is designated by reference symbol S6”. Now, NA aperture 212 can no longer intercept the virtual light in the form of reflected light ray S6' because the aperture angle θ after reflection at housing 222 appears to be “right”. This means that the aperture angle θ is less than the maximum aperture angle θmax defined by NA aperture 212. As a result, not only light L1 from object point O in use field 210 passes through NA aperture 212, but also light L2 from virtual object point OV outside use field 210. Light L2 can also be referred to as superaperture light or virtual light.

[0087] The objective is to prevent the spectral ray L2 from reaching the field plane 208. The spectral ray L2 provides no useful imaging information and only contributes to a background with reduced contrast in the field plane 208. Therefore, the spectral ray L2 must be filtered out upstream of the field plane 208. To this end, the object point O is imaged as field point F2 in the intermediate image plane 206, and the dummy object point OV is imaged as field point F3. Field point F3 is assigned an intermediate image pupil AP3, which defines the angular space W5.

[0088] An aperture stop 300, specifically a virtual or scattered light stop, is now positioned in the intermediate image plane 206 to filter out the virtual light L2 from the beam path 218. In other words, the virtual object point OV is imaged as the field point F3 on the aperture stop 300. The virtual light L2 can therefore no longer reach the field plane 208. The aperture stop 300 includes an aperture 302 defined by the light-determining edge 304.

[0089] In the DUV lithography apparatus 100B, airflow through the system is frequently achieved. This can be accomplished, for example, by blowing in and out nitrogen or air. This airflow cools the optical components (which are heated by light absorption) and removes harmful substances (which may accumulate in the system due to plant conditions or degassing). As mentioned in the introduction, operation at EUV wavelengths is, in principle, carried out under vacuum. However, low pressures of approximately one Pascal are also common here. Hydrogen is preferred. The airflow is provided to aid in photocleaning and occasionally to achieve a limited cooling effect.

[0090] Airflow is achieved through several inlet locations and outlet openings, where the design challenge is to keep the number of such openings to a minimum. Therefore, the gas should flow through the optical system 200 in a defined manner, particularly as freely as possible. However, as mentioned above, the optical system 200 also has multiple apertures 212, 300, which may obstruct airflow.

[0091] Apertures 212 and 300 are typically designed as thin metal plates with suitable geometries and apertures 214 and 302. Therefore, apertures 212 and 300 are relatively lightweight and rigid, and do not introduce any unwanted material into the optical system 200. Furthermore, this arrangement allows for inexpensive and precise manufacturing. However, in this compact form, apertures 212 and 300 obstruct the required gas flow through the optical system 200. This reduces the desired cooling and cleaning effect of the airflow due to the additional inlet and outlet openings, or necessitates greater system complexity. The goal is to reconcile these seemingly contradictory requirements of opacity and permeability. The following explanation, with reference to aperture 300, illustrates how apertures 212 and 300 can meet these requirements.

[0092] Figure 4 A schematic, highly simplified detail of an embodiment suitable for use with an aperture 300 in the intermediate image plane 206 is shown. Figure 5 Showing along Figure 4 A schematic cross-sectional view of the aperture 300 along the cross-section line VV. See also the following text. Figure 4 and Figure 5 .

[0093] As described above, the aperture 300 includes an aperture 302 having a light-determining edge 304 that defines the aperture 302. The light-determining edge 304 may be curved or at least partially curved. However, the light-determining edge 304 may also be straight or at least partially straight. The aperture 302 can therefore have any desired geometry.

[0094] The aperture 300 is provided with a first aperture element 306 and a second aperture element 308, which are arranged along the beam path 218 at a distance A from each other, especially when viewed along the light direction LR. The number of aperture elements 306 and 308 is, in principle, arbitrary. However, at least two aperture elements 306 and 308 are provided. The distance A can be from a fraction of a millimeter to several millimeters. An intermediate space 310 is provided between the aperture elements 306 and 308.

[0095] Aperture elements 306 and 308 each have multiple perforations or openings 312, 314, 316, and 318, which are offset relative to each other, allowing fluid flow 320 to pass through the openings 312, 314, 316, and 318, while blocking the virtual light L2. The fluid flow 320 is specifically a gas flow, or may be referred to as a gas flow. Simultaneous opacity and fluid permeability are achieved by the following: the first openings 312 and 314 in the first aperture element 306 are blocked by the second aperture element 308 located behind the first aperture element 306, and the second openings 316 and 318 in the second aperture element 308 are blocked by the first aperture element 306 located in front of the second aperture element 308. Therefore, with the assistance of the openings 312, 314, 316, and 318, fluid connection is achieved between the front side 322 and the rear side 324 of the aperture 300, and vice versa.

[0096] The propagation of the virtual light L2 is blocked, and except for minimal diffraction, its propagation is in a straight line. However, due to the openings 312, 314, 316, and 318, gas molecules can move through the aperture 300 by changing direction multiple times. Depending on the geometry and the specific gas and gas pressure used, the geometry, number, size, and / or distribution of the openings 312, 314, 316, and 318 can be adjusted as needed.

[0097] The number and size of openings 312, 314, 316, and 318 are arbitrary. Openings 312, 314, 316, and 318 can be configured in the form of a grid or pattern, thus allowing them to be regularly spaced apart. Alternatively, openings 312, 314, 316, and 318 can also be configured irregularly or randomly. Openings 312, 314, 316, and 318 can have a rectangular (especially square) geometry. However, openings 312, 314, 316, and 318 can also have any other geometry. For example, openings 312, 314, 316, and 318 can be introduced into aperture elements 306 and 308 by means of a laser method.

[0098] Figure 6 A schematic, highly simplified detail of another embodiment of the aperture 300 is shown. Figure 7 Showing according to Figure 6 A schematic cross-sectional view of aperture 300 along section line VII-VII in the diagram. See also the following text. Figure 6 and Figure 7 .

[0099] according to Figure 6 and Figure 7 Embodiments of aperture 300 and according to Figure 4 and 5 The only difference in the embodiment of the aperture 300 is that the openings 312, 314, 316, and 318 are not rectangular but annular, and especially circular. However, the openings 312, 314, 316, and 318 may also be, for example, elliptical.

[0100] Figure 8 A schematic, highly simplified detail of another embodiment of the aperture 300 is shown. Figure 9 Showing according to Figure 8 A schematic cross-sectional view of aperture 300 along section line IX-IX is shown below. (See also: [reference needed]) Figure 8 and Figure 9 .

[0101] according to Figure 8 and Figure 9 Embodiments of aperture 300 and according to Figure 4 and 5 The difference in the embodiment of the aperture 300 is that only one aperture element 306 is provided, which includes slit-type openings 312, 314, 316, and 318. The openings 312, 314, 316, and 318 are inclined at an angle α relative to the light direction LR. It can be understood that the openings are guided at an angle through the aperture 300, or at an angle through the aperture element 306. Therefore, the aperture 300 or the aperture element 306 is a single component. For mechanical stability purposes, a solid closed frame is provided around the openings 312, 314, 316, and 318.

[0102] Figure 10 A schematic, highly simplified detail of another embodiment of the aperture 300 is shown. Figure 11 Showing according to Figure 10 A schematic cross-sectional view of aperture 300 along section line XI-XI. See also the following text. Figure 10 and Figure 11 .

[0103] In this embodiment of the aperture 300, only one aperture element 306 is provided, which is made of a porous material. The fluid flow 320 can pass through the porous material, while the virtual light L2 is blocked. The porous material can be, for example, sintered metal powder or ceramic powder. For example, the aperture element 306 or the aperture 300 can be composed of fixedly connected (especially sintered) granular particles 326, in which the fluid flow 320 can flow almost freely.

[0104] Although the present invention has been described based on exemplary embodiments, the present invention can be modified in various ways.

[0105] Explanation of the attached figure label list

[0106] 100A EUV lithography apparatus

[0107] 100B DUV lithography apparatus

[0108] 102 Beam shaping and illumination systems

[0109] 104 Projection System

[0110] 106A EUV light source

[0111] 106B DUV light source

[0112] 108A EUV radiation

[0113] 108B DUV radiation

[0114] 110 Reflector

[0115] 112 Reflector

[0116] 114 Reflector

[0117] 116 Reflector

[0118] 118 Reflector

[0119] 120 photomask

[0120] 122 Reflector

[0121] 124 chips

[0122] 126 optical axes

[0123] 128 Lens element

[0124] 130 reflector

[0125] 132 Medium

[0126] 200 Optical System

[0127] 202 Object Plane

[0128] 204 Pupil Plane

[0129] 206 Intermediate Image Plane

[0130] 208 field plane

[0131] 210 Usage Area

[0132] 212 NA aperture

[0133] 214 aperture

[0134] 216 Light determines the edge

[0135] 218 Beam Path

[0136] 220 working light

[0137] 222 Housing

[0138] 300 aperture

[0139] 302 aperture

[0140] 304 Light determines the edge

[0141] 306 Aperture Element

[0142] 308 Aperture Element

[0143] 310 Intermediate Space

[0144] 312 Opening

[0145] 314 Opening

[0146] 316 Opening

[0147] 318 Opening

[0148] 320 Fluid Flow

[0149] 322 Front

[0150] 324 rear side

[0151] 326 Granular particles

[0152] A distance

[0153] AP1 Exit Illumination

[0154] AP2 Center Like Pupil

[0155] AP3 Center Like a Pupil

[0156] EP1 Entrance Pupil

[0157] EP2 Entrance Pupil

[0158] F1 track points

[0159] F2 track

[0160] F3 venue

[0161] LR light direction

[0162] L1 light

[0163] L2 False light

[0164] M center point

[0165] M1 reflector

[0166] M2 reflector

[0167] M3 reflector

[0168] M4 reflector

[0169] M5 reflector

[0170] M6 reflector

[0171] O object point

[0172] OV Virtual Object

[0173] Point P

[0174] R direction

[0175] S1 light rays

[0176] S2 light rays

[0177] S3 light rays

[0178] S4 light rays

[0179] S5 light rays

[0180] S6 light rays

[0181] S6' light rays

[0182] S6” light rays

[0183] V direction vector

[0184] W1 Angular Space

[0185] W2 Angular Space

[0186] W3 Angle Space

[0187] W4 Angle Space

[0188] W5 Angle Space

[0189] α Inclination angle

[0190] θ opening angle

[0191] θmax opening angle

[0192] Inscribed angle

Claims

1. An aperture (300) for a photolithography apparatus (100A, 100B), comprising: Light transmission aperture (302), and At least one aperture element (306, 308) is disposed therein or thereon, wherein the aperture (302) is opaque and fluid-permeable outside the aperture (302). The at least one aperture element (306, 308) has a plurality of openings (312, 314, 316, 318) configured such that the at least one aperture element (306, 308) is opaque and fluid-permeable.

2. The aperture as described in claim 1, wherein the aperture is a numerical aperture aperture, an obstruction aperture, or a virtual aperture.

3. The aperture as claimed in claim 1, wherein the aperture (300) is designed to deflect the fluid flow (320) flowing through the aperture (300) multiple times.

4. The aperture as claimed in any one of claims 1 to 3, wherein the opening (312, 314, 316, 318) fluidly connects the front side (322) and the rear side (324) of the aperture (300) to each other.

5. The aperture as claimed in any one of claims 1 to 3, wherein the cross-section of the opening (312, 314, 316, 318) is circular or rectangular.

6. The aperture as claimed in any one of claims 1 to 3, further comprising a first aperture element (306) having a first opening (312, 314) and a second aperture element (308) having a second opening (316, 318), wherein the first opening (312, 314) and the second opening (316, 318) are configured to be offset relative to each other.

7. The aperture of claim 6, wherein the first opening (312, 314) and the second opening (316, 318) are configured to be offset relative to each other such that the first aperture element (306) completely covers the second opening (316, 318) and the second aperture element (308) completely covers the first opening (312, 314).

8. The aperture as claimed in claim 6, wherein the first aperture element (306) is disposed at a distance (A) from the second aperture element (308).

9. The aperture as claimed in any one of claims 1 to 3, wherein the opening (312, 314, 316, 318) is slit-shaped and passes through the at least one aperture element (306, 308) at an angle (α).

10. The aperture as claimed in any one of claims 1 to 3, wherein the at least one aperture element (306, 308) is made of a porous material that is fluid-permeable due to its porous structure.

11. The aperture as claimed in any one of claims 1 to 3, wherein the aperture (302) is fluid permeable.

12. The aperture (302) of any one of claims 1 to 3, wherein the aperture (302) is defined by means of a light-determining edge (304), and wherein the light-determining edge (304) is closed or open with respect to its periphery.

13. An optical system (200) for a photolithography apparatus (100A, 100B), comprising: Object plane (202), Field plane (208), An intermediate image plane (206) is disposed between the object plane (202) and the field plane (208), and At least one aperture (300) as claimed in any one of claims 1 to 9, The aperture (300) is disposed in the intermediate image plane (206) to filter out virtual light (L2) from the beam path (218) of the optical system (200) upstream of the field plane (208) during operation of the optical system (200).

14. The optical system of claim 13 further includes a plurality of aperture stops (300) arranged sequentially on the beam path (218).

15. A photolithography apparatus (100A, 100B) having at least one aperture (300) as claimed in any one of claims 1 to 12 and / or at least one optical system (200) as claimed in claims 13 or 14.

Images