Fluid purification system, projection system, illumination system, lithographic apparatus and method

Abstract

The invention provides a fluid purification system (100) for an optical element (30), comprising a ring and a fluid supply system (40). The ring is formed by a main body completely surrounding the optical element, the ring defining a space (5) radially inwardly and adjacent to the optical element. The ring is formed by at least one first wall portion (10) and at least one second wall portion (20A; 20B), wherein the average height of the first wall portion is greater than the average height of the second wall portion. The fluid supply system is positioned radially outwardly of the ring and is configured to supply fluid for passage through the at least one second wall portion to the space.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to EP application 20178213.3, filed on June 4, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to fluid purification systems, projection systems, irradiation systems, photolithography equipment and methods. Background Technology

[0004] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. Lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithography apparatus can project a pattern (often referred to as a “design layout” or “design”) from a patterning apparatus (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on a substrate (e.g., a wafer).

[0005] As semiconductor manufacturing processes continue to advance, the size of circuit components continues to shrink, while the number of functional elements (such as transistors) in each device steadily increases over decades, following a trend commonly known as "Moore's Law." To keep pace with Moore's Law, the semiconductor industry is seeking technologies capable of creating increasingly smaller features. To project patterns onto a substrate, photolithography equipment uses electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be patterned on the substrate. Typical wavelengths currently used are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm.

[0006] Photolithography equipment may include an irradiation system configured to modulate the radiation beam before it reaches a patterning apparatus. Once the radiation beam has been patterned by the patterning apparatus, a projection system directs the beam onto a substrate. Both the irradiation and projection systems include optical elements. Contamination of the optical elements can lead to reduced radiation beam uniformity, stray radiation loss from the system, or even reaching the substrate and causing errors, and / or contamination of the optical elements can cause contaminants to react with the surface of the optical elements, thereby reducing the lifetime of the optical elements. Such optical elements can be located in a clean fluid environment to extend the lifetime of the optical elements in the projection system. A clean fluid environment may be referred to as a protective environment or microenvironment. This environment can reduce optical element contamination (both cleanable and non-cleanable), thereby reducing the reduction in radiation beam uniformity, reducing the amount of stray radiation lost from the system, and increasing the lifetime of the optical elements.

[0007] Fluid flow within the microenvironment can affect purification performance. In conventional systems, fluid can be configured to flow through the microenvironment, creating stagnation points within the fluid. Such stagnation points are preferably avoided, as these are areas where the fluid does not move and therefore purification cannot be effectively performed. Backflow can also occur in conventional systems where the fluid containing contaminants flows in the reverse direction.

[0008] The system of the present invention provides a fluid flow over an optical element, which can improve the cleanliness of the optical element surface, for example, by reducing or avoiding stagnation points and / or backflow of contaminants in the fluid flow over the optical element. Summary of the Invention

[0009] One object of the present invention is to provide a fluid purification system for providing fluid from the outside of the microenvironment to optical elements to provide improved purification of the optical elements.

[0010] In this invention, a fluid purification system for an optical element is provided, comprising: an annular member formed entirely around a body of the optical element, the annular member defining a radially inward space adjacent to the optical element, the annular member being formed by at least one first wall and at least one second wall, wherein the average height of the first wall is greater than the average height of the second wall; and a fluid supply system positioned radially outside the annular member and configured to supply fluid for reaching the space through the at least one second wall.

[0011] In this invention, an irradiation system including a fluid purification system is provided.

[0012] In this invention, a projection system including a fluid purification system is also provided.

[0013] In this invention, a photolithography apparatus including a fluid purification system is also provided.

[0014] In this invention, a method for manufacturing a device using the aforementioned photolithography equipment is also provided.

[0015] Other embodiments, features, and advantages of the present invention will be described in detail below with reference to the accompanying drawings, as well as the structure and operation of various embodiments, features, and advantages of the present invention. Attached Figure Description

[0016] Embodiments of the invention will now be described by way of example only, with reference to the accompanying schematic diagrams, wherein corresponding reference numerals indicate corresponding parts, and wherein:

[0017] Figure 1 An overview of the photolithography equipment is schematically depicted;

[0018] Figure 2A , Figure 2B and Figure 2CA fluid purification system according to one embodiment is described;

[0019] Figure 3 A variation of a fluid purification system according to one embodiment is described;

[0020] Figure 4 Depicting Figure 2A A more detailed version; and

[0021] Figure 5 A variation of the annular component in a fluid purification system is depicted.

[0022] The features shown in the accompanying drawings are not necessarily drawn to scale, and the dimensions and / or arrangements depicted are not limiting. It should be understood that these drawings include optional features that are not essential to the present invention. Furthermore, not all features of the system and / or lithography apparatus are depicted in every drawing, and the drawings may show only some parts relevant to describing a particular feature. Detailed Implementation

[0023] In this document, the terms “radiation” and “beam” are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., with wavelengths of 436 nm, 405 nm, 365 nm, 248 nm, 193 nm, 157 nm, 126 nm, or 13.5 nm).

[0024] As used herein, the terms “mask,” “mask,” or “patterning apparatus” can be broadly interpreted to refer to a general patterning apparatus that can be used to impart a patterned cross-section to an incident radiation beam, the patterned cross-section corresponding to a pattern to be created in a target portion of a substrate. The term “optical valve” may also be used herein. Examples of such patterning apparatuses, in addition to classic masks (transmissive or reflective, binary, phase-shifting, hybrid, etc.), include programmable mirror arrays and programmable LCD arrays.

[0025] Figure 1A lithography apparatus is schematically depicted. The lithography apparatus includes: an irradiation system (also referred to as an irradiator) IL configured to modulate a radiation beam B (e.g., EUV or DUV radiation); a mask support (e.g., a mask stage) MT configured to support a patterning apparatus (e.g., a mask) MA and connected to a first positioner PM configured to precisely position the patterning apparatus MA according to certain parameters; a substrate stage WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to precisely position the substrate stage WT according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted by the radiation beam B by the patterning apparatus MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0026] In operation, the irradiation system IL receives the radiation beam B from the radiation source SO, for example, via the beam delivery system BD. The irradiation system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for guiding, shaping, and / or controlling the radiation. The irradiator IL can be used to adjust the radiation beam B to have a desired spatial and angular intensity distribution in a cross-section at the plane of the pattern forming apparatus MA.

[0027] As used herein, the term "projection system" PS should be interpreted broadly to encompass all types of projection systems, including refractive, reflective, antirefractive, distorting, magnetic, electromagnetic, and / or electrostatic optical systems, or any combination thereof, depending on the exposure radiation used and / or other factors suitable for use such as immersion liquids or vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0028] Photolithography apparatuses can be of the type in which at least a portion of the substrate W can be covered by an immersion liquid (e.g., water) having a relatively high refractive index to fill the immersion space between the projection system PS and the substrate W; this is also known as immersion lithography. Further information on immersion techniques is given in US 6,952,253, which is incorporated herein by reference.

[0029] Photolithography equipment can be of the type having two or more substrate stages WT (also known as "dual stages"). In such a "multi-stage" machine, substrate stages WT can be used in parallel and / or the steps for preparing substrate W for subsequent exposure can be performed on substrate W located on one of the substrate stages WT, and another substrate W on another substrate stage WT can be used to expose a pattern on another substrate W.

[0030] In addition to the substrate stage (WT), lithography equipment can include a measurement stage ( Figure 1 (Not depicted in the text). The measurement stage is arranged to hold sensors and / or cleaning devices. Sensors may be arranged to measure the properties of the projection system PS or the properties of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning devices may be arranged to clean a portion of the lithography apparatus, such as a portion of the projection system PS or a portion of a system providing immersion liquid. The measurement stage may move below the projection system PS when the substrate stage WT is moved away from the projection system PS.

[0031] In operation, the radiation beam B is incident on a pattern forming apparatus (e.g., a mask) MA held on a mask support MT and patterned by a pattern (design layout) present on the pattern forming apparatus MA. After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of a second positioner PW and a position measurement system PMS, the substrate stage WT can be precisely moved, for example, to position different target portions C in the path of the radiation beam B at focused and aligned positions. Similarly, a first positioner PM and possibly another position sensor ( Figure 1 (Not explicitly depicted) can be used to precisely position the patterning apparatus MA relative to the path of the radiation beam B. The patterning apparatus MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 shown occupy dedicated target portions, they can be located in the space between the target portions. When the substrate alignment marks P1, P2 are located between the target portions C, they are referred to as scribing alignment marks.

[0032] In this specification, a Cartesian coordinate system is used. A Cartesian coordinate system has three axes: the x-axis, the y-axis, and the z-axis. Each of the three axes is orthogonal to the other two axes. A rotation about the x-axis is called an Rx rotation. A rotation about the y-axis is called an Ry rotation. A rotation about the z-axis is called an Rz rotation. The x-axis and y-axis define the horizontal plane, while the z-axis is in the vertical direction. The Cartesian coordinate system is not limiting of the invention and is only used for illustration. Instead, another coordinate system, such as a cylindrical coordinate system, can be used to illustrate the invention. The orientation of the Cartesian coordinate system can be different, for example, such that the z-axis has a component along the horizontal plane.

[0033] It is recognized that the optical performance of known systems can be affected by contamination of optical components, which can occur due to suboptimal cleanup performance. Typically, lens contamination is linearly proportional to the amount of certain types of light, and therefore any increase in the throughput of a lithography apparatus can lead to an increase in lens contamination and thus a greater deterioration in optical performance. This may result in some optical components needing to be replaced earlier due to potentially reduced component lifespan, or more frequent cleaning, which could impair equipment performance.

[0034] Therefore, protecting optical components (such as lenses) in photolithography equipment from contamination is beneficial. One known method for protecting such optical components is to place them in a semi-enclosed environment (which may otherwise be referred to as a clean volume, protective environment, microenvironment, or small environment). This semi-enclosed environment can be cleaned using a clean fluid (e.g., a clean gas), allowing contaminants on or around the optical component to be removed, or at least reduced to a level that allows for improved optical component lifespan. Therefore, the lifespan of the optical component may be related to the cleanliness of the semi-enclosed environment.

[0035] For some systems, purification performance (and therefore the lifespan of optical components) is related to many factors, such as refresh rate, overvoltage relative to the external environment, and purification uniformity.

[0036] Refresh rate is related to cleanup flow rate and cleanup length. Generally, a higher refresh rate means a shorter amount of time for contaminants to remain on the optical element, and therefore a shorter amount of time for any contaminant to react with the surface of the optical element, resulting in a lower contamination rate.

[0037] The pressure in a semi-closed environment is related to how the environment is closed, and the closure of the environment is related to the components that define the semi-closed environment. The average pressure of the cleaned volume within a semi-closed environment should generally be higher than that outside the environment, as this causes the cleaned fluid to flow out. This reduces the risk of cleaned fluid backflow, and therefore reduces the risk of contaminant backflow into the cleaned fluid.

[0038] Advantageously, the purification flow is evenly distributed along the optical element, as this reduces or avoids stagnation points, recirculation of the flow (which may contain contaminants), or turbulence of the purification fluid.

[0039] As described below, the present invention relates to a fluid purification system in which fluid is supplied to the outside of a semi-enclosed environment. This means that the purification fluid needs to traverse a small intermediate volume (which is part of the external environment) and cross the boundary of the semi-enclosed environment. Typically, the boundary of the semi-enclosed environment is flow-limiting, which can adversely affect purification performance. Nevertheless, providing the purification fluid outside the semi-enclosed environment has various advantages, meaning that it remains an attractive option despite such potential problems. Specifically, as described below, providing the purification fluid outside the semi-enclosed environment leads to easier decomposition and integration of system functions. Furthermore, in conventional systems, there are often problems in finding space to integrate purification hardware near its most critical areas, such as optical elements. Providing the purification fluid outside the semi-enclosed environment offers improved flexibility in resolving this volume conflict because it utilizes the available space outside the optical elements / semi-enclosed environment.

[0040] In some known systems, a fluid purification system is provided for optical elements (e.g., lenses), and this system is equipped with a gas inlet located outside a semi-closed environment; in other words, the gas inlet does not directly contact the semi-closed environment. The semi-closed environment can also be referred to as the purification volume. In such known systems, the semi-closed environment for the purified optical element is defined by an annular element that serves as the boundary of the semi-closed environment. The purification gas inlet (also referred to as the purification chamber) is radially mounted outside the semi-closed environment. As mentioned above, a problem with such known purification systems is that the purification gas may have difficulty crossing the flow-limiting boundary provided by the annular element, which can lead to suboptimal purification performance.

[0041] The annular element at the edge of the semi-closed environment restricts fluid inflow into the semi-closed environment, thereby maintaining sufficient overpressure within the semi-closed environment (i.e., the cleaned volume) relative to the environment outside the annular element. As mentioned above, this is beneficial for suppressing backflow and / or reverse diffusion contamination. However, while providing such a high flow restriction with the annular element is advantageous, such a flow-limiting boundary prevents cleaned fluid from entering the semi-closed environment. This can result in low cleaned flow rates and therefore low refresh rates within the cleaned volume, which should ideally be increased as described above.

[0042] Therefore, it is beneficial to reduce the current limiting provided by the ring, for example, by reducing the height of the ring. The height of the ring can be considered as the degree to which the ring protrudes from the surface surrounding the optics. Although reducing the height of the ring may make the boundaries of the semi-closed environment less restricted in order to increase the refresh rate, this may adversely affect overvoltage. Removing the ring will also adversely affect overvoltage, even if it does lead to an improvement in the refresh rate.

[0043] Furthermore, the ring-shaped element offers mechanical advantages because it can be used as a mechanical safety guard for optical elements. Specifically, because the height of the ring surrounding the optical element forms a physical barrier, the ring can protect the optical element during transportation and installation. This means that reducing the height of the ring may reduce the effectiveness of the protection it provides.

[0044] It should be noted that the surface opposite the annular element can be moved closer to or further away from the annular element to alter the amount of fluid that may enter the semi-closed environment. However, any change in the distance between the optical element and such an opposing surface may compromise optical performance.

[0045] This invention provides a fluid purification system, which will be described in detail below. The fluid purification system of this invention can solve some of the problems mentioned above.

[0046] The fluid purification system of the present invention can be, for example, as follows: Figure 2A and Figure 2B Provided as shown. Figure 2A A fluid purification system 100 is shown, and Figure 2B A cross-section of the fluid purification system 100 is shown.

[0047] The fluid purification system 100 is adapted to the lens 30. Therefore, the fluid purification system 100 can be used to provide purification fluid to the lens 30. Although the lens 30 is referred to below and shown in the corresponding figures, the lens 30 represents an optical element and can be replaced by any suitable optical element, including any refractive and reflective optical components. The optical element may include the lens 30 and / or may include another optical element, such as a projection lens or an illumination optics. The lens 30 is shown as having a convex shape, but the lens 30 may alternatively have a concave shape.

[0048] The fluid purification system 100 includes an annular member 1. The annular member 1 completely surrounds a lens 30. The lens 30 is radially inward of the annular member 1. The annular member 1 can completely surround the lens 30 in a cross-section spanning the annular member 1. In other words, the annular member 1 surrounds the lens 30. The annular member 1 surrounds the lens 30 because it surrounds the lens 30 without any gaps within the annular member 1. The annular member 1 completely surrounding the lens 30 means that at least a portion of the annular member 1 is formed radially outward of the lens 30. Therefore, the annular member 1 can be formed around the exterior of the lens 30. The annular member 1 can contact at least a portion of the outer edge of the lens 30. The annular member 1 can be positioned on and around the outer edge of the outer edge of the lens 30. The annular member 1 can be in direct contact with the lens 30, i.e., there are no gaps between the surface of the annular member 1 and the lens 30.

[0049] As described above, the annular member 1 can be formed from a body that completely surrounds the lens 30. In other words, the annular member 1 is formed as a single body that entirely surrounds the lens 30. In other words, the annular member 1 forms a continuous boundary surrounding the exterior of the lens 30. The annular member 1 can be formed as circular or elliptical. However, depending on the shape of the lens 30, other shapes can be used; that is, the shape of the annular member 1 can be consistent with the shape of the lens 30.

[0050] The annular member 1 defines its radially inward space 5. Therefore, the annular member 1 can form a continuous boundary surrounding the exterior of space 5. Space 5 is the radially inward volume of the annular member 1. The annular member 1 can completely surround space 5 in a cross-section passing through the annular member 1. In other words, the annular member 1 can form a continuous boundary surrounding space 5. In other words, the annular member 1 is formed as a single entity that can completely surround space 5. Lens 30 is adjacent to space 5. In other words, lens 30 can be located at the boundary of space 5. Lens 30 can protrude into space 5. For example, as... Figure 2B As shown, lens 30 is located inside the annular member 1 and protrudes from the bottom of the annular member 1. Figure 2B As shown, due to the convex shape of lens 30, the center of lens 30 protrudes inward into space 5. As mentioned above, lens 30 can also be concave, in which case the outer edge of lens 30 can protrude into space 5. The annular member 1 and lens 30 can define a space; that is, the boundary of space 5 can be formed at least partially by the annular member 1 and at least partially by lens 30. For example, space 5 can be defined by the inner surface of the annular member 1 and the surface of lens 30. Lens 30 can be part of the fluid purification system 100.

[0051] Space 5 may correspond to or form at least a portion of the aforementioned purification volume. Therefore, space 5 may correspond to or form at least a portion of the aforementioned semi-closed environment, microenvironment, protective environment, or small environment.

[0052] The annular member 1 is formed by at least one first wall portion 10 and at least one second wall portion 20. The at least one first wall portion 10 may also be referred to as a merlon. The at least one second wall portion 20 may also be referred to as a mortise. The average height of the first wall portion 10 is greater than the average height of the second wall portion 20. More generally, the annular member 1 may be formed as a boundary having at least one first wall portion and at least one second wall portion, the at least one first wall portion and the at least one second wall portion having different heights from each other. The average height of the first wall portion 10 and / or the second wall portion 20 may be determined using the same method or calculation. For example, the average height may be determined by dividing the volume of a wall portion by its cross-sectional area. The average height of the first wall portion 10 may be determined by the average height of the first wall portion 10 at the edge of the annular member 1 adjacent to the lens 30 (i.e., the average height of the inner edge of the first wall portion 10). Similarly, the average height of the second wall portion 20 may be determined by the average height of the second wall portion 20 at the edge of the annular member 1 adjacent to the lens 30 (i.e., the average height of the inner edge of the second wall portion 20). Because the first wall portion 10 has a greater average height than the second wall portion 20, the first wall portion 10 protrudes more than the second wall portion 20. Therefore, the first wall portion 10 can protrude more from the base of the annular member 1 over a given area than the second wall portion 20. In practice, when in use, the annular member 1 can be positioned on surface 75, such as... Figure 2C As shown, the first wall portion 10 protrudes further from the surface 75 than the second wall portion 20. The average height of the first wall portion 10 and the average height of the second wall portion 20 can be determined relative to the lens 30 (e.g., relative to the contact point between the lens 30 and the annular member 1).

[0053] The fluid purification system 100 includes a fluid supply system 40. The fluid supply system 40 is located radially outside the annular member 1. Therefore, the fluid supply system 40 is disposed outside the annular member 1. Thus, the fluid supply system 40 can correspond to the aforementioned purified gas inlet located outside the semi-closed environment. The fluid supply system 40 is configured to supply fluid for reaching the space 5 via at least one second wall portion 20. The fluid being supplied to the space 5 means that the fluid is configured to pass through the annular member 1 and the surface of the lens 30 located in or adjacent to the space 5. Therefore, the fluid supply system 40 is configured to provide fluid to the surface of the lens 30 adjacent to the space 5. The fluid supply system 40 is configured to provide fluid radially inward from the annular member 1.

[0054] The fluid can be any suitable fluid. The fluid can be a gas, such as N2, He, Ar, Kr, Ne, Xe, air, CDA, and XCDA. In this case, a gas can be used instead of a reference fluid. In this case, the fluid purification system 100 can be a gas purification system, and the fluid supply system 40 can be a gas supply system. The fluid can be a clean gas. The fluid can be a liquid, such as ultra-clean water.

[0055] The fluid purification system 100 of the present invention is advantageous in making it easier to allow fluid to enter and exit the space 5, and thus can improve the refresh rate of the fluid on the purification lens 30. This is because the annular member 1 has at least one first wall portion 10 and at least one second wall portion 20, wherein the first wall portion 10 has a larger average height than the second wall portion 20, and the fluid supply system 40 is configured to supply fluid to the space 5.

[0056] At least one first wall 10 can be configured to restrict the inflow or outflow of fluid into or out of space 5. In other words, at least one first wall 10 can reduce fluid flow from the outside of the annular member 1 into space 5 and / or reduce fluid flow from space 5 to the outside of the annular member 1. Therefore, at least one first wall 10 can serve as a height-restricted flow barrier. This is beneficial for providing sufficient overpressure in space 5 relative to the external environment of the annular member 1. Preferably, the height of the first wall 10 is as high as possible (taking into account the position of the annular member 1 and other components) so that inflow above the first wall 10 can be reduced or minimized. For example, at least one first wall portion 10 may be at least about 5 mm from the base of the annular member 1, or preferably at least about 6 mm, or preferably at least about 7 mm, or preferably at least about 8 mm, or preferably at least about 9 mm, or preferably at least about 10 mm, or preferably at least about 11 mm, or preferably at least about 12 mm, or preferably at least about 15 mm, or preferably at least about 20 mm, or preferably at least about 30 mm, or preferably at least about 40 mm. This height may refer to the average height of at least one first wall portion 10, for example, over the entire area of ​​the first wall portion 10, at its inner edge, or at the highest point of at least one first wall portion 10. At least one second wall portion 20 may be at least about 2 mm from the base of the annular member 1, or preferably at least about 3 mm, or preferably at least about 4 mm, or preferably at least about 5 mm, or preferably at least about 6 mm, or preferably at least about 7 mm, or preferably at least about 8 mm, or preferably at least about 9 mm, or preferably at least about 10 mm, or preferably at least about 15 mm, or preferably at least about 20 mm, or preferably at least about 25 mm, or preferably at least about 30 mm. This height may refer to the average height of at least one second wall portion 20, for example, over the entire area of ​​the second wall portion 20, or at the inner edge of the second wall portion 20, and / or at the highest point of at least one second wall portion 20.

[0057] The average height of at least one first wall portion 10 is greater than the average height of at least one second wall portion 20, and can be up to approximately four times the average height of at least one second wall portion 20. The ratio of the average height of at least one first wall portion 10 to the average height of at least one second wall portion is greater than 1:1, or preferably greater than or equal to about 2:1, or preferably greater than or equal to about 3:1, or preferably greater than or equal to about 4:1. It should be noted that these are merely example values, as the appropriate dimensions and heights of the first wall portion 10 and the second wall portion 20, as well as the height ratio of these walls, will depend on how each annular member 1 is used.

[0058] Because the average height difference between the first wall portion 10 and the second wall portion 20 results in a height difference around the space 5, the height difference between the first wall portion 10 and the second wall portion 20 may have a greater impact on controlling the fluid flow than the total average height of the first wall portion 10 and the second wall portion 20 relative to the base of the annular member 1. The height difference between the first wall portion 10 and the second wall portion 20 may be at least about 2 mm, or preferably at least about 3 mm, or preferably at least about 4 mm, or preferably at least about 5 mm, or preferably at least about 6 mm, or preferably at least about 7 mm, or preferably at least about 8 mm, or preferably at least about 9 mm, or preferably at least about 10 mm, or preferably at least about 11 mm, or preferably at least about 12 mm, or preferably at least about 15 mm, or preferably at least about 25 mm, or preferably at least about 30 mm.

[0059] At least one first wall portion 10 is also advantageous because it can provide a physical barrier around the lens 30. Therefore, at least one first wall portion 10 can provide mechanical safety protection for the optical element (e.g., the lens 30 as described above), particularly during installation and transport. For example, during transport of the lens 30, a mechanical cover can be placed on top of the lens 30 for protective purposes. The mechanical cover can be provided using a support feature with sufficient height between the lens 30 and the cover. At least one first wall portion 10 can serve as such a mechanical support feature to support the mechanical cover.

[0060] At least one second wall portion 20 can serve as a low-limit flow inlet to space 5. This facilitates easier flow of fluid into space 5. At least one second wall portion 20 can also serve as a low-limit flow outlet from space 5. This facilitates easier flow of fluid out of space 5, particularly in a defined and controlled manner and at a predetermined location. At least one second wall portion 20 can serve as a low-limit flow inlet to space 5, and at least one second wall portion can also serve as a low-limit flow outlet from space 5. This facilitates easier flow of fluid into and out of space 5, and thus improves the refresh rate of the purified fluid on lens 30.

[0061] Preferably, the fluid supply system 40 and the annular member 1 are arranged such that most of the fluid from the fluid supply system 40 flows radially inward through the annular member 1, while the remaining fluid from the fluid supply system 40 flows around the outer periphery of the annular member 1. This is advantageous because the flow around the outer periphery reduces or prevents fluid from outside the fluid purification system 100 from being entrained by the fluid flowing into the space 5 in the annular member 1. This reduces or prevents the possibility of contaminants from outside the annular member 1 being moved into the interior of the annular member 1 by the fluid. Additionally, contaminants can be removed from the outside of the annular member 1 and can be removed from the lens 30. The arrangement of the fluid supply system 40 and the annular member 1 can be configured such that the fluid supply system 40 is aligned with at least one second wall portion 20. In other words, the fluid supply system 40 can be positioned to supply fluid toward the space 5 across at least one second wall portion 20. This can be advantageous because most of the fluid can flow radially inward through the annular member 1, i.e., across at least one second wall portion 20, to reach the space 5. The fluid supplied by the fluid supply system 40 can be provided in the form of a fluid flow, and the fluid flow can be wider than at least the second wall 20 at the point of entry across the annular member 1. For example, the fluid supply system 40 can have a length across which it supplies fluid, wherein the length is greater than the width of at least the second wall 20. In this case, most of the fluid from the fluid supply system 40 will be directed into the interior of the annular member 1. Some fluid can be redirected around the outer periphery of the annular member 1 by the higher portion of the annular member 1 at the edge of the second wall 20 (i.e., the first wall 10). Additionally or alternatively, the fluid supply system 40 can supply a fluid flow such that the fluid flow diffuses outward as it approaches the annular member 1, and thus at least some of the fluid flow can flow around the outer periphery of the annular member 1.

[0062] The fluid purification system 100 can be configured such that the space 5 is maintained at a pressure greater than that outside the space 5. The pressure of the space 5 can be controlled by the fluid supplied to the space 5 by the fluid supply system 40 and by the shape of the annular member 1 as described with respect to the invention. Advantageously, a higher refresh rate is provided while simultaneously providing a higher fluid pressure on the lens 30. It is particularly advantageous to increase and / or optimize the fluid flow rate in the middle of the lens 30, i.e., the fluid flow rate towards the center of the lens 30, which may correspond to the exposure slit, as this is the critical area through which radiation in the lithography apparatus can pass. In known systems, the effectiveness of the purified fluid is lower in the middle of the lens 30 due to the geometry of the lens 30, and therefore the fluid purification system 100 of the present invention is particularly advantageous in improving the airflow velocity in the middle of the lens 30.

[0063] Due to overpressure in space 5, small outflows may occur above the two first walls 10A, 10B. Preferably, at least two first walls 10A, 10B are configured such that the amount of fluid flowing through the two first walls 10A, 10B is less than the amount of fluid flowing through at least one second wall 20. Therefore, the first walls 10A, 10B provide greater flow restriction than the second wall 20, allowing more fluid to flow through a second wall 20 than through the two first walls 10A, 10B. Preferably, the amount of fluid flowing through the two first walls 10A, 10B is significantly less than the amount of fluid flowing through the second wall 20.

[0064] Preferably, the fluid supply system 40 is configured to supply fluid at a rate of approximately 20 nlpm (standard liters per minute) to 150 nlpm, or preferably from approximately 70 nlpm to approximately 110 nlpm. The fluid supply system 40 can supply fluid at any suitable rate. Preferably, the fluid supply system 40 is configured to supply fluid at a rate of approximately greater than or equal to 20 nlpm, or preferably approximately greater than or equal to 45 nlpm, or preferably approximately greater than or equal to 70 nlpm, or preferably approximately greater than or equal to 90 nlpm. Preferably, the fluid supply system 40 is configured to supply fluid at a rate of approximately less than or equal to 150 nlpm, or preferably approximately less than or equal to 110 nlpm, or preferably approximately less than or equal to 90 nlpm. These fluid flow rates can be used for any suitable fluid, but are particularly suitable for one of the gases mentioned above, such as N2, He, Ar, Kr, Ne, Xe, air, CDA, and XCDA, and the fluid flow rate expressed herein in standard liters per minute (nlpm) is assumed to be set at 0°C and 1 atmosphere. Of course, the fluid can be supplied at any other suitable temperature and / or pressure.

[0065] The fluid purification system 100 may further include a fluid extraction system 50. The fluid extraction system 50 is... Figure 2A and Figure 2B The fluid extraction system 50 can be configured to extract fluid from the space 5. The fluid extraction system 50 can be configured to extract fluid from the space 5 at the same or similar rate as the fluid supply system 40 supplies fluid to the space 5. The fluid extraction system 50 can be positioned on the side of the annular member 1 opposite to the fluid supply system 40. The fluid extraction system 50 and the fluid supply system 40 can be positioned symmetrically about the center of the annular member 1. Although in Figure 2A and Figure 2B The fluid extraction system 50 is shown in the figures, but the fluid extraction system 50 is optional and other features shown and described in these figures may be provided without the fluid extraction system 50.

[0066] The annular member 1 includes at least one first wall portion 10 and at least one second wall portion 20. Therefore, the annular member 1 may include only one first wall portion 10 or multiple first wall portions 10. All of the multiple first wall portions 10 may have the same height as each other. The annular member 1 may have only one second wall portion 20 or multiple second wall portions 20. All of the multiple second wall portions 20 may have the same height as each other. Figure 2A As shown, the annular member 1 can be formed by two first wall portions 10A, 10B and two second wall portions 20A, 20B. Preferably, the annular member 1 includes two or more first wall portions 10. Preferably, the annular member 1 includes two or more second wall portions 20. In such a way... Figure 2A and Figure 3 In the illustrated embodiment, the two first wall portions 10A, 10B and the two second wall portions 20A, 20B can be arranged alternately along the circumference of the annular member 1.

[0067] Preferably, the two first wall portions 10A, 10B are disposed on opposite sides of the annular member 1. This is in Figure 2A and Figure 3 As shown, one first wall portion 10A is opposite to another first wall portion 10B. Preferably, the two second walls 20A, 20B are disposed on opposite sides of the annular member 1. This is in Figure 2A and Figure 3 As shown, one of the second wall portions 20A is opposite to another second wall portion 20B.

[0068] Preferably, one of the second wall portions 20 is aligned with the fluid supply system 40 to provide a fluid inlet to the space 5. This is in Figure 2A and Figure 2B As shown, the fluid supply system 40 is configured such that fluid from the fluid supply system 40 is directed to one of at least two wall portions 20A. More generally, the location of at least one second wall portion 20 may be aligned with a fluid inlet to minimize hydraulic resistance to the flow from the fluid supply system 40 to the lens 30. This will increase the fluid flow rate and refresh rate in the space 5. Multiple second wall portions 20 may be used as fluid inlets.

[0069] Preferably, one of the second wall portions 20 provides a fluid outlet from the space 5. This can be achieved... Figure 2A and Figure 2BAs seen in the diagram, other second wall portions 20B allow fluid to move from space 5 to the environment outside the annular member 1. The location of at least one second wall portion 20, which can serve as a fluid outlet for space 5, can be selected to guide fluid flow within space 5. When a fluid flow pattern with minimal purification length is desired (e.g., to achieve an increased or optimal refresh rate), for example, based on the flow at the inlet of space 5, at least one of the second wall portions 20 used as an outlet can be aligned with the expected flow direction across space 5. If the overall hydraulic resistance of space 5 is too high, this can result in low fluid velocity and low refresh rate within space 5. Using at least one second wall portion 20 as a fluid outlet can be beneficial because it provides a low-restriction outlet. This is also beneficial in reducing or avoiding flow stagnation points in the fluid flow within space 5. Multiple second wall portions 20 can be used as fluid outlets.

[0070] It is advantageous to use at least one of the second wall portions 20 as a fluid inlet and at least one of the second wall portions 20 as a fluid outlet because the total hydraulic resistance of the space 5 can be low enough to ensure high flow rates and refresh rates in the space 5. Specifically, as Figure 2A and Figure 2B As shown, it may be particularly advantageous to provide two second walls 20 having a second wall 20A as a fluid inlet and a second wall 20B as a fluid outlet, because this may cause any stagnant area above the lens 30 to form away from the center of the lens (i.e., away from the exposure slit), which can thus reduce the negative impact of such stagnant areas.

[0071] The fluid purification system 100 may include another surface 70 opposite to the annular member 1. In other words, the other surface 70 may face the lens 30. Fluid can therefore pass between the other surface 70 and the lens 30. In other words, restriction of fluid flow above the lens 30 can be provided by the annular member 1 and the other surface 70. Therefore, the boundary of the space 5 can be defined at least partially by the annular member 1 and the other surface 70. The other surface 70 in Figure 2C As shown in the figure, another surface 70 opposite to the annular member 1 and the lens 30 can be moved closer to or further away from the annular member 1 to change the amount of fluid that may enter the semi-closed environment. The other surface 70 can be the surface of another optical element (such as a lens) through which radiation can pass. As shown, the fluid purification system 100 may include a surface 75, on which, for example, the annular member 1 can be positioned. The other surface 70 can face surface 75, i.e., opposite to surface 75. Any one or all of the fluid supply system 40, another fluid supply system 60, and / or the fluid extraction system 50 can be positioned on surface 75.

[0072] The annular member 1 can be provided around the lens 30 in any suitable configuration. For example, as... Figure 2Band Figure 2C As shown, lens 30 can be positioned within the inner surface of annular member 1. For example, as... Figure 4 As shown, the lens 30 can be positioned within a slit in a recess on the inner surface of the annular member 1. Any suitable manner can be used to provide the annular member 1 around the lens 30. Figure 2B and Figure 2C The variations shown can be used in combination with any variations shown or described with respect to other figures. Figure 4 The variations shown can be used in combination with any variations shown or described with respect to other figures.

[0073] In the above variation, the fluid purification system 100 is provided with a fluid supply system 40 and a fluid extraction system 50. However, the fluid purification system 100 may be provided with a fluid supply system 40 but without a fluid extraction system 50. Additionally or alternatively, the fluid purification system 100 may include another fluid supply system 60. This is in Figure 3 As shown in the figure. Another fluid supply system 60 can be radially positioned outside the annular member 1. Fluid supply system 40 can be configured to supply fluid for entering space 5 through one of at least two second walls 20A. Another fluid supply system 60 can be configured to supply fluid for entering space 5 through the other of at least two second walls 20B.

[0074] Another fluid supply system 60 can be configured to supply fluid at a rate of approximately 20 nlpm to 150 nlpm, or preferably from approximately 70 nlpm to approximately 110 nlpm. The other fluid supply system 60 can supply fluid at any suitable rate. Preferably, the other fluid supply system 60 is configured to supply fluid at a rate of approximately greater than or equal to 20 nlpm, or preferably approximately greater than or equal to 45 nlpm, or preferably approximately greater than or equal to 70 nlpm, or preferably approximately greater than or equal to 90 nlpm. Preferably, the other fluid supply system 60 is configured to supply fluid at a rate of approximately less than or equal to 150 nlpm, or preferably approximately less than or equal to 110 nlpm, or preferably approximately less than or equal to 90 nlpm. These fluid flow rates can be used for any suitable fluid, particularly for one of the gases mentioned above, such as N2, He, Ar, Kr, Ne, Xe, air, CDA, and XCDA, and the fluid flow rates expressed herein in standard liters per minute (nlpm) are assumed to be set at 0°C and 1 atmosphere. Of course, the fluid can be supplied at any other suitable temperature and / or pressure.

[0075] While providing fluid supply system 40 and another fluid supply system 60 may be beneficial, there is also a risk that multiple fluid flows entering space 5 may introduce flow stagnation points in the middle of space 5 (i.e., in an area that may be particularly important for lens performance). Such flow stagnation can be reduced or controlled by selecting the positions of at least one first wall portion 10 around annular member 1, the positions of at least one second wall portion 20 around annular member 1, the positions of fluid supply system 40 relative to annular member 1, and the positions of another fluid supply system 60 relative to annular member 1.

[0076] In a preferred embodiment, the fluid purification system 100 is provided with only the fluid supply system 40 (i.e., no other fluid supply system 60 and no fluid extraction system 50). This is beneficial in reducing stagnation points on the lens 30 (especially in the middle of the lens 30), as this is the critical area of ​​the lens 30 through which radiation can pass through the lithography apparatus.

[0077] Figure 4 As shown Figure 2A and Figure 2B A more detailed view of the annular member 1 is shown. Additional details of at least one first wall portion 10 and at least one second wall portion 20 can be found in... Figure 4 The distinction is clearer in Chinese.

[0078] The height of at least one first wall portion 10 can vary in the radial direction. In other words, the height of at least one first wall portion 10 varies from the inside of the annular member 1 to the outside of the annular member 1. The height can vary relative to the portion of the annular member 1 that contacts the lens 30. For example, as Figure 4 As shown, the inner edge 11A of at least one first wall portion 10A may be higher than the outer edge 12A of at least one first wall portion 10A. Alternatively, the inner edge 11A of at least one first wall portion 10A may be lower than the outer edge 12A of at least one first wall portion 10A, which may help reduce unwanted fluid flow leakage into the space 5.

[0079] The height of at least one second wall portion 20 can vary in the radial direction. In other words, the height of at least one second wall portion 20 varies from the inside of the annular member 1 to the outside of the annular member 1. The height can vary relative to the portion of the annular member 1 that contacts the lens 30. Preferably, the height of at least one second wall portion 20 increases from the outer radius of the annular member 1 to the inner radius of the annular member 1. In other words, preferably, at least one second wall portion 20 further protrudes from the base of the annular member 1 at the inner side of the annular member 1. In other words, the inner edges 21A, 21B of at least one second wall portion 20A, 20B are higher than the outer edges 22A, 22B of at least one second wall portion 20A, 20B.

[0080] Preferably, at least one edge of the second wall portion 20 is rounded. For example, the inner edge 21A of one of the second wall portions 20A may be rounded. Additionally or alternatively, the inner edge 21B of another of at least one of the second wall portions 20B may be rounded. The outer edge 22A of one of the second wall portions 20A may be rounded. Additionally or alternatively, the outer edge 22B of another of at least one of the second wall portions 20B may be rounded. Providing at least one second wall 20A, 20B with rounded inner edges is advantageous in reducing hydraulic resistance and reducing flow stagnation points above the surface of the lens 30. Preferably, the inner edges 21A, 21B and the outer edges 22A, 22B of at least one second wall portion 20A, 20B are rounded. Preferably, the inner edges 21A, 21B and the outer edges 22A, 22B of all the second wall portions 20A, 20B are rounded. By way of example only, the radius of curvature of any of the aforementioned rounded edges can range from approximately 0.5 mm to approximately 4 mm.

[0081] The dimensions of at least one first wall portion 10A, 10B and at least one second wall portion 20A, 20B can be related to how to optimize flow above the lens 30. The dimensions of at least one first wall portion 10A, 10B and at least one second wall portion 20A, 20B will be related to the radius and angle of the annular member 1. The radius of the annular member 1 will be related to the application scenario and size of the lens 30 (or other optical elements), and can also be related to the required fluid flow in space 5. For example, the radius of the annular member 1 can be on the order of tens or hundreds of millimeters, but this is not necessary. Figure 5 Depicting Figure 2A - Figure 4 The simplified form of the annular member 1. Angles β1, β2, β3, and β4 represent the dimensions of the second wall portions 20A and 20B. (Example) Figure 5 As shown, one of the second wall portions 20A can be formed with angles β1 and β2, while the other of the second wall portions 20B can be formed with angles β3 and β4. Angles β1, β2, β3, and β4 can be determined relative to an axis passing through the center of the annular member 1. The axis is shown as a horizontal axis. Typically, as... Figure 5 Each of the angles β1, β2, β3, and β4 shown can be independent of each other. Each of the angles β1, β2, β3, and β4 can be between approximately 5° and 80°. Therefore, at least one of the second wall portions 20A and 20B can form an angle of approximately 10° to 160° with the center of the annular member 1. Therefore, at least one of the first wall portions 10A and 10B can form an angle of approximately 170° to 20° with the center of the annular member 1.

[0082] Note that, as shown in the figure, the edges at the transition between at least one first wall portion 10A, 10B and at least one second wall portion 20A, 20B are arranged in the radial direction. In other words, the edges between at least one first wall portion 10A, 10B and at least one second wall portion 20A, 20B form a plane passing through the central longitudinal axis of the annular member 1. However, this is not necessary. For example, in Figure 2A , Figure 3 or Figure 5 In any one of them, the edge at the transition between at least one first wall portion 10A, 10B and at least one second wall portion 20A, 20B can be horizontal or vertical. For example, a horizontal edge can be provided between the wall portions (e.g., Figure 5 (As shown by the dashed edge) This means that the inlet and / or outlet can be more aligned with the fluid supply system 40 and / or the fluid extraction system 50 and / or another fluid supply system 60. This can result in a better flow profile for the fluid in space 5.

[0083] Typically, in the above embodiments, the annular member 1 includes two first wall portions 10A and 10B and two second wall portions 20A and 20B. However, other configurations are possible, and the embodiments described with respect to the drawings may have only one first wall portion 10 and only one second wall portion 20, or more than two first wall portions 10 and more than two second wall portions 20. For example, the annular member 1 may have at least three, four, five, or six first wall portions 10. For example, the annular member 1 may have at least three, four, five, or six second wall portions 20. The annular member 1 may have the same number of first wall portions 10 and second wall portions 20.

[0084] The plurality of first wall portions 10 may all have similar shapes and, specifically, may have the same height as each other. The plurality of second wall portions 20 may all have similar shapes and, specifically, may have the same height as each other. The annular member 1 may include other wall portions, such as at least one third wall portion, whose height differs from the height of at least one first wall portion 10 and the height of at least one second wall portion 20.

[0085] When the lens 30 is positioned in or at the edge of the space 5, the shape of the surface of the lens 30 (e.g., related to whether the lens 30 is concave or convex) can alter the fluid flow over the surface of the lens 30. Therefore, the shape of the annular member 1 described above is merely an example, as variations of at least the first wall portion 10 and at least the second wall portion 20 can be selected based on the shape of at least the lens 30 and the interaction of the fluid flowing through the lens 30 and the annular member 1. For example, the dimensions of at least the first wall portion 10 and at least the second wall portion 20 can be selected to optimally guide fluid flow across the surface of a particular lens 30.

[0086] The fluid purification system 100 can be provided as part of various other systems. For example, the present invention can provide a projection system PS that can have the components described above, and the projection system PS can include the fluid purification system 100 described in any of the above embodiments or variations. The present invention can provide an irradiation system IL that can have the components described above, and the irradiation system IL can include the fluid purification system 100 described in any of the above embodiments or variations. The present invention can provide a lithography apparatus that can have the components described above, and the lithography apparatus can include the fluid purification system 100 described in any of the above embodiments or variations. The present invention can provide a method of manufacturing a device using the lithography apparatus, wherein a fluid supply system 40 provides fluid for reaching the space 5 through at least one second wall portion 20 of the annular member 1.

[0087] It is understood that any of the above features may be used in conjunction with any other features, and that such combinations are those explicitly described and covered in this application.

[0088] While specific references may be made herein to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein may have other applications, such as the fabrication of integrated optical systems, the guiding and detection of patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc. Those skilled in the art will understand that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered synonymous with the more general terms “substrate” or “target portion,” respectively. Substrates mentioned herein may be processed before or after exposure in, for example, in tracks (tools typically used to apply a resist layer to the substrate and develop the exposed resist), metrology tools, and / or inspection tools. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Furthermore, for example, to create multilayer ICs, substrates may be processed more than once, such that the term “substrate” as used herein may also refer to a substrate that has contained one or more processed layers.

[0089] One or more embodiments of the present invention can be applied to any dry lithography apparatus. One or more embodiments of the present invention can be applied to any immersion lithography apparatus, specifically, but not exclusively, to the types of lithography apparatus described above, regardless of whether the immersion liquid is provided in the form of a tank, provided only on a localized surface area of ​​the substrate, or provided unconstrained. In an unconstrained arrangement, the immersion liquid can flow on the surface of the substrate and / or substrate stage, such that substantially the entire uncovered surface of the substrate stage and / or substrate is wetted. In such an unconstrained immersion system, the liquid supply system may not constrain the immersion liquid, or it may provide a proportionate constraint on the immersion liquid, but not substantially complete constraint.

[0090] The liquid supply system considered herein should be interpreted broadly. In some embodiments, it can be a combination of mechanisms or structures that supply liquid to the space between the projection system and the substrate and / or substrate stage. It can include a combination of one or more structures, one or more fluid openings including one or more liquid openings, one or more gas openings, or one or more openings for two-phase flow. The openings can each be an inlet into the immersion space (or an outlet from the liquid handling structure) or an outlet out of the immersion space (or an inlet into the liquid handling structure). In one embodiment, the surface of the space can be part of the substrate and / or substrate stage, or the surface of the space can completely cover the surface of the substrate and / or substrate stage, or the space can surround the substrate and / or substrate stage. The liquid supply system may optionally further include one or more elements for controlling the position, quantity, quality, shape, flow rate, or any other characteristic of the liquid.

[0091] While specific embodiments of the invention have been described above, it should be understood that the invention can be implemented in ways other than those described. Aspects of the invention are set forth in the following provisions.

[0092] 1. A fluid purification system for an optical element, comprising: an annular member formed entirely around a body of the optical element, the annular member defining a space radially inward and adjacent to the optical element, the annular member being formed by at least one first wall and at least one second wall, wherein the average height of the first wall is greater than the average height of the second wall; and a fluid supply system positioned radially outside the annular member and configured to supply fluid for reaching the space through the at least one second wall.

[0093] 2. The fluid purification system according to Clause 1, wherein at least one first wall is configured to restrict flow into or out of the space.

[0094] 3. The fluid purification system according to clause 1 or 2, wherein the optical element includes a lens.

[0095] 4. The fluid purification system according to any one of the preceding clauses, wherein the fluid supply system and the annular member are arranged such that a majority of the fluid from the fluid supply system flows radially inward through the annular member, and the remaining fluid from the fluid supply system flows around the outer periphery of the annular member.

[0096] 5. The fluid purification system according to any one of the preceding clauses, wherein the annular member comprises at least two first walls and at least two second walls.

[0097] 6. The fluid purification system according to Clause 5, wherein two first walls are disposed on opposite sides of the annular member, and two second walls are disposed on opposite sides of the annular member.

[0098] 7. The fluid purification system according to Clause 5 or 6, wherein one of at least two second walls is aligned with a fluid supply system to provide a fluid inlet to the space, and the other of at least two second walls provides a fluid outlet from the space.

[0099] 8. The fluid purification system according to Clause 5 or 6 further includes another fluid supply system radially positioned outside the annular member, wherein the fluid supply system is configured to supply fluid for entering the space through one of at least two second walls, and the other fluid supply system is configured to supply fluid for entering the space through the other of at least two second walls.

[0100] 9. The fluid purification system according to any one of Clauses 5-7 further includes a fluid extraction system configured to extract fluid from space.

[0101] 10. The fluid purification system according to any one of clauses 5-9, wherein at least two first walls are configured such that the amount of fluid flowing through the two first walls is less than the amount of fluid flowing through at least one second wall.

[0102] 11. The fluid purification system according to any one of the preceding clauses is configured such that the space is maintained at a pressure greater than that outside the space.

[0103] 12. The fluid purification system according to any one of the preceding clauses, wherein at least one edge of the second wall is rounded.

[0104] 13. The fluid purification system according to any one of the preceding clauses further includes a surface opposite the annular element, wherein fluid in the space passes between the surface and the optical element.

[0105] 14. The fluid purification system according to any one of the preceding clauses, wherein the fluid supply system is configured to supply fluid at a rate of about 20 nlpm to 150 nlpm or preferably about 70 nlpm to 110 nlpm.

[0106] 15. A projection system comprising a fluid purification system according to any one of the preceding clauses.

[0107] 16. An irradiation system comprising a fluid purification system according to any one of clauses 1 to 14.

[0108] 17. A photolithography apparatus comprising a fluid purification system according to any one of Clauses 1 to 14.

[0109] 18. A method of manufacturing a device using a lithography apparatus according to Clause 17, wherein a fluid supply system provides fluid for reaching a space through at least one second wall of an annular member.

[0110] The above description is intended to be illustrative and not limiting. Therefore, it will be apparent to those skilled in the art that modifications can be made to the described invention without departing from the scope of the following claims.

Claims

1. A fluid purification system for optical components, comprising: An annular member formed entirely around the body of the optical element, the annular member defining a radially inward space adjacent to the optical element, the annular member being formed by at least one first wall portion and at least one second wall portion, wherein the average height of the first wall portion is greater than the average height of the second wall portion; A fluid supply system, positioned radially outside the annular member and configured to supply fluid for reaching the space via the at least one second wall portion, and The at least one second wall portion has a height that changes in the radial direction.

2. The fluid purification system of claim 1, wherein the at least one first wall is configured to restrict flow into or out of the space.

3. The fluid purification system according to claim 1 or 2, wherein the optical element comprises a lens.

4. The fluid purification system according to any one of the preceding claims, wherein the fluid supply system and the annular member are arranged such that a majority of the fluid from the fluid supply system flows radially inward through the annular member, and the remaining fluid from the fluid supply system flows around the outer periphery of the annular member.

5. The fluid purification system according to any one of the preceding claims, wherein the annular member comprises at least two first walls and at least two second walls.

6. The fluid purification system according to claim 5, wherein the two first wall portions are disposed on opposite sides of the annular member, and the two second wall portions are disposed on opposite sides of the annular member.

7. The fluid purification system of claim 5 or 6, wherein one of the at least two second walls is aligned with the fluid supply system to provide a fluid inlet to the space, and the other of the at least two second walls provides a fluid outlet from the space.

8. The fluid purification system according to claim 5 or 6 further comprises another fluid supply system radially positioned outside the annular member, wherein the fluid supply system is configured to supply fluid for entering the space through one of the at least two second walls, and the other fluid supply system is configured to supply fluid for entering the space through the other of the at least two second walls.

9. The fluid purification system according to any one of claims 5-7, further comprising a fluid extraction system configured to extract the fluid from the space.

10. The fluid purification system according to any one of claims 5-9, wherein the at least two first walls are configured such that the amount of fluid flowing through the two first walls is less than the amount of fluid flowing through the at least one second wall.

11. The fluid purification system according to any one of the preceding claims, configured such that the space is maintained at a pressure greater than that outside the space.

12. The fluid purification system according to any one of the preceding claims, wherein the edge of the at least one second wall portion is rounded.

13. The fluid purification system according to any one of the preceding claims further includes a surface opposite to the annular member, wherein the fluid in the space passes between the surface and the optical element.

14. The fluid purification system according to any one of the preceding claims, wherein the at least one first wall portion has a height that varies in the radial direction.

15. The fluid purification system according to any one of the preceding claims, wherein the height of the at least one second wall portion increases from the outer diameter of the annular member to the inner diameter of the annular member.

16. The fluid purification system according to any one of the preceding claims, wherein at least one of the second wall portions forms an angle of approximately 10° to 160° with the center of the annular member.

17. The fluid purification system according to any one of the preceding claims further includes at least one third wall portion having a height different from the height of the at least one first wall portion and the height of the at least one second wall portion.

18. A projection system comprising a fluid purification system according to any one of the preceding claims.

19. An irradiation system comprising a fluid purification system according to any one of claims 1 to 17.

20. A photolithography apparatus comprising a fluid purification system according to any one of claims 1 to 17.

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