WO2020182540A1

WO2020182540A1 - Providing substantially laminar fluid flow in a lithographic apparatus

Info

Publication number: WO2020182540A1
Application number: PCT/EP2020/055562
Authority: WO
Inventors: Pepijn VAN DEN EIJNDEN; Erik Henricus Egidius Catharina Eummelen; Robin Bernardus Johannes KOLDEWEIJ; Cornelius Maria ROPS; Petrus Martinus Gerardus Johannes Arts; Nupur Rajan SUBHEDAR; Johannes MAESSEN
Original assignee: Asml Netherlands B.V.
Priority date: 2019-03-14
Filing date: 2020-03-03
Publication date: 2020-09-17
Also published as: TW202043946A

Abstract

The present invention provides a device for providing substantially laminar fluid flow in a lithographic apparatus. The device comprises an opening and a channel through which fluid flows to or from the opening, the channel defined within an enclosure formed by at least a first wall and a second wall. The device also comprises a flow laminating portion in the channel configured to provide the substantially laminar fluid flow through the opening. The flow laminating portion may comprise a plurality of pillars, and/or a plurality of sub-channels, and/or a porous layer across the channel.

Description

PROVIDING SUBSTANTIALLY LAMINAR FLUID

FLOW IN A LITHOGRAPHIC APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application no. 19162854.4, which was filed on 14 March 2019 and which is incorporated herein its entirety by reference.

FIELD

[0002] The present invention relates to devices for providing substantially laminar fluid flow, a fluid flushing apparatus, a lithographic apparatus and a method of generating at least one of the devices or the fluid flushing apparatus.

BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also often referred to as“design layout” or“design”) of a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer).

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as ‘Moore’s law’. To keep up with Moore’s law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which are patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm. A lithographic apparatus, which uses extreme ultraviolet (EUV) radiation, having a wavelength within a range of 4 nm to 20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm.

[0005] A lithographic apparatus may include an illumination system for providing a projection beam of radiation, and a support structure for supporting a patterning device. The patterning device may serve to impart the projection beam with a pattern in its cross-section. The apparatus may also include a substrate support for holding a substrate, a projection system for projecting the patterned beam onto a target portion of the substrate.

[0006] The projection system usually includes an optical component such as a lens for focusing the beam onto the target portion of the substrate. It is, however, as will be pointed out in slightly more detail further on in the specification, also possible to direct the beam via reflective components such as mirrors. The surfaces of these optical components may interact with gaseous contaminants in such a way that the transmission of light or the reflection of light occurs in a less accurate manner than would be the case had the surfaces of the optical components not interacted with these gaseous contaminants.

[0007] The result of the interaction may lead to a hindrance of the transmission or reflection of light via these optical components. That is, due to the interaction, a layer may be formed on or into the surface of optical component, changing the transmission coefficient or reflection coefficient of the optical component. This change may have a permanent nature. As the optical components are usually very expensive components of the apparatus, a reduction of the lifetime of these components due to interaction with these particles is highly undesirable. In this document often the term ‘particles’ is used generally to refer to contaminating gases. It should be understood that these particles may have molecular dimensions.

[0008] The gaseous contaminants interacting with these optical components may be released by the substrate, for example, before exposure of the substrate to the beam as a result of, for example, outgassing, during exposure of the substrate to the beam as a result of the removal of material from the substrate, or after exposure of the substrate to the beam as a result of, for example, baking out the substrate. These gaseous contaminants may also be present in the lithographic apparatus. Particles which may interact with the surface of an optical component can also be formed during, for example, production of UV radiation. The interaction of optical components may occur under the influence of radiation. Most often though, gases from the substrate or from elsewhere present in the lithographic apparatus interact under the influence of the radiation with a coating on the surface of an optical component. Due to a chemical reaction, crystals may form, which negatively affect the performance of the optical component. To remove these crystals, the apparatus has to be opened up, which results in downtime and hence expenses. Sometimes the crystals cannot be cleaned away and the optical element has to be replaced by a new one.

[0009] One way of preventing the interaction of gaseous contaminants with a surface of an optical component is carried out by flushing a flow of fluid along the surface of an optical component to drag away, within the flow of fluid, contaminating particles which are about to approach the surface of the optical component. It may also be useful to provide the flow of fluid across the patterned projection beam in order to prevent particles travelling along a path followed by the patterned projection beam from reaching a surface of the optical components. A flow of fluid may also be provided both across the patterned projection beam and along a surface of an optical component. If the flow of fluid is provided across the patterned projection beam, or any other beam of radiation for that matter, e.g. for use with a sensor, the flushing fluid is preferred to be substantially non-absorbent of the radiation used. The flow of fluid is also strongly preferred to be substantially laminar flow of fluid in order to improve the shielding effect of the flow of fluid.

[00010] US 2005/0264773 discloses a gas flushing device for flushing a substantially laminar flow of gas across a beam of radiation and or along a surface of an optical component. It is described that the gas flushing device may comprise a single gas outlet having an inner rim at a downstream end of the gas outlet, the inner rim defining a total gas outlet area of the gas flushing device. The gas flushing device may comprise a laminator at the downstream end of the gas outlet, the laminator having an effective area out of which the substantially laminar flow of gas flows, the laminator effective area comprising material having laminated openings. US 2005/0264773 is incorporated herein by reference.

[00011] Known gas flushing devices may comprise commercially available sieves, which are welded to a support construction, leading to a sieve assembly. The manufacturing involved in the production of the support for the sieves and the sieves themselves needs to be very accurate and very accurate welding techniques are required to attach the sieves to the support. Manual labour is required to attach the sieves to the support which results in high relative costs for providing the sieve assembly. Additionally, lead times can be very long, resulting in delays in providing an apparatus comprising the gas flushing device.

[00012] Alternative ways of providing a laminar flow may be provided. Advantages of such alternatives may include a device which is easier to manufacture, and thus which may be cheaper, more efficient and/or use less material. Additionally, alternatives may be beneficial in improving the laminar nature of the flow provided to improve the shielding effect of the flow of fluid.

SUMMARY

[00013] In the present invention, there is provided a device for providing substantially laminar fluid flow in a lithographic apparatus, the device comprising: an opening; a channel through which fluid flows to or from the opening, the channel defined within an enclosure formed by at least a first wall and a second wall; and a flow laminating portion in the channel configured to provide the substantially laminar fluid flow through the opening, wherein the flow laminating portion comprises a plurality of pillars formed between the first wall of the enclosure and the second wall of the enclosure.

[00014] According to the present invention, there is also provided a device for providing substantially laminar fluid flow in a lithographic apparatus, the device comprising: an opening; a channel through which fluid flows to or from the opening, the channel defined within an enclosure formed by at least a first wall and a second wall; and a flow laminating portion in the channel configured to provide the substantially laminar fluid flow through the opening, wherein the flow laminating portion comprises a plurality of sub-channels positioned to separate the fluid flow in the channel into the sub-channels, wherein at least one of the sub-channels has a cross-sectional area of less than or equal to approximately 5 mm² and the plurality of sub-channels have a length of greater than or equal to approximately 3 mm.

[00015] According to the present invention, there is also provided device for providing substantially laminar fluid flow in a lithographic apparatus, the device comprising: an opening; a channel through which fluid flows to or from the opening, the channel defined within an enclosure formed by at least a first wall and a second wall; and a flow laminating portion in the channel configured to provide the substantially laminar fluid flow through the opening, wherein the flow laminating portion comprises a porous layer across the channel with openings throughout the porous layer, the porous layer having a thickness of at least approximately 0.2 mm.

[00016] According to the present invention, there is also provided a fluid flushing apparatus comprising: at least one device as above; and a further opening through which a radiation beam can pass through when the lithographic apparatus is in use.

[00017] According to the present invention, there is also provided a lithographic apparatus comprising the device or the fluid flushing apparatus as above..

[00018] According to the present invention, there is also provided a method of generating the device or the fluid flushing apparatus as above, the method comprising applying successive layers of material to form the device or the fluid flushing apparatus.

[00019] Further embodiments, features and advantages of the present invention, as well as the structure and the operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[00020] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

Figure 1 depicts a schematic overview of a lithographic apparatus;

Figure 2 depicts an internal gaseous environment and first and second planar elements on an upper side of the support for the patterning device;

Figure 3 depicts an internal gaseous environment and first and second planar elements on a lower side of the support;

Figures 4A, 4B, 5A, 5B, 5C, 5D, 6A, 6B, 7, 8A and 8B depict variations of a first embodiment of the present invention;

Figures 9A and 9B depict a second embodiment of the present invention;

Figures 10A and 10B depict a third embodiment of the present invention; and

Figures 11 A and 1 IB depict an embodiment of the present invention.

DETAIFED DESCRIPTION

In the present document, the terms“radiation” and“beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g. with a wavelength of 365, 248, 193,

157 or 126 nm) and EUV (extreme ultra-violet radiation, e.g. having a wavelength in the range of about 5-100 nm).

[00021] The term“reticle”,“mask” or“patterning device” as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term“light valve” can also be used in this context. Besides the classic mask (transmissive or reflective, binary, phase- shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable LCD array.

[00022] Figure 1 schematically depicts a lithographic apparatus LA. The lithographic apparatus LA includes an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation or EUV radiation), a patterning device support (e.g., a mask table) MT constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA in accordance with certain parameters, a substrate support (e.g., a wafer table) WT constructed to hold a substrate (e.g., a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate support in accordance with certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[00023] In operation, the illumination system IL receives a radiation beam from a radiation source SO, e.g. via a beam delivery system BD. The illumination 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 directing, shaping, and or controlling radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at a plane of the patterning device MA.

[00024] The term“projection system” PS used herein should be broadly interpreted as encompassing various types of projection system, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and/or electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, and or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the more general term“projection system” PS.

[00025] The lithographic apparatus LA may be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system PS and the substrate W - which is also referred to as immersion lithography. More information on immersion techniques is given in US6952253, which is incorporated herein by reference.

[00026] The lithographic apparatus LA may also be of a type having two or more substrate supports WT (also named“dual stage”). In such“multiple stage” machine, the substrate supports WT may be used in parallel, and or steps in preparation of a subsequent exposure of the substrate W may be carried out on the substrate W located on one of the substrate support WT while another substrate W on the other substrate support WT is being used for exposing a pattern on the other substrate W. [00027] In addition to the substrate support WT, the lithographic apparatus LA may comprise a measurement stage. The measurement stage is arranged to hold a sensor and/or a cleaning device.

The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning device may be arranged to clean part of the lithographic apparatus, for example a part of the projection system PS or a part of a system that provides the immersion liquid. The measurement stage may move beneath the projection system PS when the substrate support WT is away from the projection system PS.

[00028] In operation, the radiation beam B is incident on the patterning device, e.g. mask, MA which is held on the patterning device support MT, and is patterned by the pattern (design layout) present on patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and a position measurement system IF, the substrate support WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B at a focused and aligned position. Similarly, the first positioner PM and possibly another position sensor (which is not explicitly depicted in figure 1) may be used to accurately position the patterning device MA with respect to the path of the radiation beam B.

Patterning device MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks PI, P2. Although the substrate alignment marks PI, P2 as illustrated occupy dedicated target portions, they may be located in spaces between target portions. Substrate alignment marks PI, P2 are known as scribe-lane alignment marks when these are located between the target portions C.

[00029] To clarify the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axis, i.e., an x-axis, a y-axis and a z-axis. Each of the three axis is orthogonal to the other two axis. A rotation around the x-axis is referred to as an Rx-rotation. A rotation around the y- axis is referred to as an Ry -rotation. A rotation around about the z-axis is referred to as an Rz- rotation. The x-axis and the y-axis define a horizontal plane, whereas the z-axis is in a vertical direction. The Cartesian coordinate system is not limiting the invention and is used for clarification only. Instead, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example, such that the z-axis has a component along the horizontal plane.

[00030] As mentioned above, it may be desirable to maintain a controlled internal gaseous environment in a region of a lithographic apparatus. This will be described in relation to a region of the patterning device MA (above and/or below the patterning device MA). Figure 2 depicts an arrangement, explaining in general how control of an internal gaseous environment 4 can be achieved in a region above, for example, the patterning device support MT. It should be appreciated that such an internal gaseous environment 4 may desirably also be provided in other parts of a lithographic apparatus, for example in the region of the substrate and/or substrate support, or a part thereof. For example, it may be desirable to control a gaseous environment around a sensor such as a position sensor. It will be appreciated that the invention described below may therefore be used in such other contexts, namely is not limited to the contexts used below to describe the invention.

[00031] The internal gaseous environment 4 in this example is located between the patterning device MA and patterning device support MT on one side, and a final element (and surrounding hardware) 2 of the illumination system IL on the other side. The internal gaseous environment 4 depicted is thus a volume through which the radiation beam will pass before it encounters the patterning device MA.

[00032] In this example, a gas supply system 5 is provided for supplying gas via an outlet 7 to the internal gaseous environment 4. The gas may be supplied with a controlled composition and/or at a controlled flow rate. Optionally, an overpressure is maintained within the internal gaseous environment 4. The overpressure results in an outward flow of gas, as shown schematically by arrows 6. The gas supply system 5 and/or outlet 7 may be mounted within the patterning device support MT (as shown) and/or within an element above and/or below the patterning device support MT. For example, the gas supply system 5 and or outlet 7 may be mounted within the final element 2 of the illumination system IL. Alternatively or additionally, the gas supply system 5 and or outlet 7 may be mounted within a first element 3 of the projection system PS.

[00033] The spatial distribution of flows/velocities can be controlled by first and second planar elements 8, 10. The first planar element 8 is such as to present a first flow-restricting surface 8a. The second planar element 10 is such as to present a second flow-restricting surface 10a. The planar elements 8, 10 are typically configured such that the first and second flow-restricting surfaces 8a, 10a are generally planar, i.e. planar within standard engineering tolerances and disregarding deliberately formed projections and/or recesses that may be provided in order to restrict further the gas flow between the flow restriction surfaces 8a, 10a. Either or both of the planar elements 8, 10 may be formed as a separate element, for example as a plate, and attached to a component of the lithographic apparatus (e.g. the patterning device support MT in the case of the first planar element 8).

Alternatively or additionally, either or both of the planar elements 8, 10 may be formed as an integral part of another component. Either or both of the planar elements 8, 10 may comprise two substantially parallel, planar surfaces that are spaced apart from each other parallel to the Z-axis. Alternatively, either or both of the planar elements 8, 10 may comprise only a single planar surface (which would be the flow-restricting surface 8a, 10a in this case).

[00034] The flow-restricting surfaces 8a, 10a face each other and are configured to resist inward and outward gas flow through the gap between them. Resisting inward gas flow helps to reduce contamination of the internal gaseous environment 4. Resisting outward gas flow helps the gas supply system 5 maintain a stable overpressure in the internal gaseous environment 4. The flow- restricting surfaces 8a, 10a also present a relatively small gap through which the outflow of gas must pass. This results in an increase in velocity of the outflow of gas. The increase in velocity counters diffusion of contaminants inwards. Also a higher outflow velocity is beneficial for the following reason. When the patterning device support MT is moved along Y in a first sense, it creates a lower pressure region in its wake, which tends to be filled by environmental air (which it is desirable to keep out of the internal gaseous environment 4). When the patterning device support MT then scans back in the opposite direction, it is desirable that the output velocity should be higher at least than the scan speed of the patterning device support MT (and preferably higher than the scan speed plus the maximum velocity of inflow of environmental air into the lower pressure region) in order to minimise or completely avoid significant inflow of the environment air into the internal gaseous environment 4.

[00035] The flow-restricting surfaces 8a, 10a are typically arranged to be substantially parallel to each other. The spacing between the flow-restricting surfaces 8a, 10a is small enough to provide the desired level of outflow velocity for a given supply of gas via the gas supply system 5 and/or outlet 7 used to establish the overpressure in the internal gaseous environment 4.

[00036] Figure 3 depicts an arrangement corresponding to the arrangement of figure 2 except that the internal gaseous environment 4 is located below the patterning device MA. The internal gaseous environment 4 depicted is thus a volume through which the radiation beam will pass after it has encountered the patterning device MA. The internal gaseous environment 4 is contained by the patterning device support MT and patterning device MA on one side and by a first element (and surrounding hardware) 3 of the projection system PS on the other side. The patterning device support MT in this example comprises a first planar element 9 formed in a lower portion thereof. The first planar element 9 has a first flow-restricting surface 9a. The first element of the projection system PS has a second planar element 11 attached to an upper surface thereof. The second planar element 11 has a second flow-restricting surface 11a. The second flow-restricting surface 11a is configured to face the first flow-restricting surface 9a. Either or both of the planar elements 9, 11 may comprise two substantially parallel, planar surfaces that are spaced apart from each other parallel to the Z-axis. Alternatively, either or both of the planar elements 9, 11 may comprise only a single planar surface (which would be the flow-restricting surface 9a, 1 la in this case). As with the arrangement of figure 2 discussed above, the distribution of flows/velocities can be controlled by the arrangement of the first and second planar elements 9, 11.

[00037] In both the arrangement of figure 2 and the arrangement of figure 3, arrows 6 show schematically the flow of gas from the outlet 7 of the gas supply system 5 through a central region of the internal gaseous environment 4 and out through the gap between the flow-restricting surfaces 8a, 9a, 10a, 1 la to the region outside the internal gaseous environment 4.

[00038] The internal gaseous environments 4 of figures 2 and 3 are shown in separate locations. However, it is not essential that the internal gaseous environments 4 be isolated from each other. The internal gaseous environments 4 could be connected together. In this case, a single gas supply system 5 could be provided. The single gas supply system 5 could have a single outlet 7 either above or below the patterning device MA. Gas would be able to flow between the internal gaseous environment 4 above the patterning device MA and the internal gaseous environment 4 below the patterning device MA by connections between the internal gaseous environment 4 above the patterning device MA and the internal gaseous environment 4 below the patterning device MA. Alternatively, the single gas supply system 5 could have a plurality of outlets 7 below, above, or below and above the patterning device MA.

[00039] In the example shown, the gas supply system 5 and outlet 7 are incorporated into the patterning device support MT. However, this is not essential. The gas supply system 5 and/or outlet 7 could be mounted to other components. For example, the gas supply system 5 and or outlet 7 could be attached to the final element (or surrounding hardware) 2 of the illumination system IL and/or the first element (or surrounding hardware) 3 of the projection system PS.

[00040] As already described, presently known devices used for laminating the airflow may be costly (in terms of time and or money) to produce. Additionally, due to the manufacturing complexity, relatively little design space is generally available for performance optimization. If the gas flow is not conditioned correctly, a component (such as an optical component, e.g. a lens) can be contaminated both through outside air and resist outgassing of the substrate. Having a functioning device for providing substantially laminar gas flow considerably improves contamination reduction. However, even with the better known pre-existing options, a small amount of contamination may arise. Thus, there is room for improvement.

[00041] The present invention includes a device for providing substantially laminar fluid flows in a lithographic apparatus. In general, the device may be useful for providing channels for fluid supply and exhaust, shielding a radiation beam from external unconditioned flows, and/or shielding a component, such as an optical component, from contaminants. The device may thus improve overlay performance due to better thermal conditioning, and may reduce contamination resulting in reduced stray radiation, which can for example, affect critical dimension uniformity. The device may improve the lifetime of certain components.

[00042] As will be described below, the device comprises a flow laminating portion. The flow laminating portion may be arranged in many different ways. The arrangement of the flow laminating portion may be selected to impart desired properties on fluid flow passing through the flow laminating portion, for example, to provide flow with a desired uniformity and or vorticity. The flow laminating portion may be used to improve desirable flow properties and reduce or prevent undesired flow properties. Thus, the flow laminating portion may be arranged to optimize certain properties of the flow as desired. The flow may be optimized by using computer analysis of flow in a channel and determining the arrangement of the flow laminating portion which could be used to provide the optimum flow. The flow laminating portion may provide physical flow structures over a certain length of the channel which ideally reduce vorticity and improve homogeneity of the flow at an optimized pressure drop. [00043] The device of the present invention is suitable for providing substantially laminar fluid flow. For example, if fluid is passed through the device, the fluid exiting the device may be substantially laminar. Alternatively, if the fluid is drawn into the device, the fluid flowing into the device may be made substantially laminar by the device. The device may have more impact on flow which passes through and exits the device, rather than flow being drawn into the device. The device may be configured to provide substantially laminar flow due to the flow laminating portion described below.

[00044] For example only, the device may be provided adjacent to a final element 2 of the illumination system IL. The device may be provided as part of, or instead of, the planar elements 8 and 10 and/or the planar elements 9 and 11 of figures 2 or 3. Alternatively, the device may be positioned in another location to maintain a controlled gaseous environment in any other region, as indicated above. For example, the device may be provided to control fluid flow in a region of a substrate, substrate support, a sensor, etc..

[00045] The device comprises an opening and a channel through which fluid flows to or from the opening. The fluid flow in the channel is to or from the opening. The channel is defined within an enclosure formed by at least a first wall and a second wall. It will be understood that the first wall and the second wall may be integral with each other. However, the first wall may provide one side of the channel and the second wall may provide the other side of the channel. For example only, the first wall may be considered as a roof or ceiling portion of the channel. For example only, the second wall may be considered as a base or floor portion of the channel.

[00046] The device comprises a flow laminating portion in the channel configured to provide the substantially laminar fluid flow through the opening. The flow laminating portion may be provided by a plurality of different physical structures. These will be described in the embodiments below. Overall, the flow laminating portion may provide a physical barrier to redirect the flow through the channel in a desired way. In particular, the flow laminating portion may redirect the flow to make the flow more laminar.

[00047] The flow laminating portion as described in any of the embodiments below may be integral with the walls forming the channel. In other words, the components of the flow laminating portion as described below and the walls defining the channel may be made from a single component, i.e. one piece of material. The flow laminating portion may be easier to manufacture than known systems. Using such a device which is easier to manufacture can reduce the cost of the goods and or make the process of manufacture more efficient. The flow laminating portion as described in any of the embodiments below may usefully be used to provide a device which is lower in cost to produce, has fewer parts than other known devices, can be assembled more quickly than other known devices and or has a shorter lead-time.

[00048] In a first embodiment, as shown in figures 4A and 4B, the flow laminating portion 30 comprises a plurality of pillars 30a formed between the first wall 23 of the enclosure and the second wall 24 of the enclosure. The device 20 is shown in cross-section in section 4A. A cross-section through A- A of figure 4A is shown in figure 4B. The flow of fluid in the channel 22 is indicated by the double-ended arrow shown in figure 4A. Side walls are shown by third wall 25 and fourth wall 26b in figure 4B.

[00049] The height of the channel 22 may be the distance between the first wall 23 and the second wall 24. The height of the channel 22 is indicated by the dimension h in figure 4A. The height h of the channel 22 may be substantially uniform, or may vary over the length of the channel 22. The channel 22 may have a height h of approximately 3.5 mm, however, this is for example only. The height h of the channel 22 may be greater than or equal to approximately 1mm, or preferably greater than or equal to approximately 2 mm, or preferably greater than or equal to approximately 3 mm. The height h of the channel 22 may be any appropriate height and may be significantly larger than 3 mm.

[00050] As depicted in figure 4A, the plurality of pillars 30a extend from the first wall 23 to the second wall 24, i.e. the plurality of pillars 30a are connected to both the first wall 23 and the second wall 24. Thus, the plurality of pillars 30a are provided across the length of the opening 21. Although all the pillars 30a in figure 4A are shown to extend the full length of the gap between the first wall 23 and the second wall 24, this is not necessary and some of the pillars 30a may be shorter than the length so that they are in contact with only one of the first wall 23 and/or the second wall 24.

[00051] The plurality of pillars 30a may be provided in various configurations. The plurality of pillars 30a may be provided in a uniform pattern, in a non-uniform pattern, having a variety of cross- sectional shapes, being at an angle to the first wall 23 and/or the second wall 24, being aligned with each other and or at least partly staggered and having a range of different sizes. Some of these variations will be described below. Other variations are also possible. Overall, the arrangement of the pillars may be selected by predicting the effect of a particular configuration on the fluid flow and providing such an arrangement, for example, to optimize the laminar nature of the fluid flow to or from the opening 21.

[00052] Most generally, the plurality of pillars 30a may be provided along the length of the channel 22 (i.e. in the X direction shown in figures 4A and 4B) and or the plurality of pillars 30a may be provided across the width of the channel 22 (i.e. in the Y direction shown in figure 4B). For example only, as shown in figure 4A, there are 4 rows of pillars 30a along the length of the channel 22. As depicted in figure 4B, each row comprises 4 pillars 30a across the width of the opening 21. Thus, the plurality of pillars 30a can be spaced out to affect the flow across the whole width of the channel 22. Providing multiple pillars 30a along the length of the channel 22 (rather than a single row) may increase the impact of the plurality of pillars 30a on the flow as the flow is redirected by multiple pillars 30a as it travels along the channel 22. Providing multiple pillars 30a across the width of the channel 22 may increase the impact of the plurality of pillars 30a on the flow because more of the flow may interact and be affected by the pillars 30a. [00053] As shown in figure 4A, the plurality of pillars 30a may be arranged along the channel 22. Thus, the plurality of pillars 30a are generally arranged along the direction of flow to or from the opening 21. A length L of the channel 22 comprising the plurality of pillars 30a may be greater than or equal to approximately 3 mm. In other words, the plurality of pillars 30a extend over distance L in the channel 22. Thus, the distance in which the plurality of pillars 30a are arranged within the enclosure is generally greater than or equal to approximately 3 mm, or preferably greater than or equal to approximately 10 mm, or preferably greater than or equal to approximately 20 mm, or preferably, greater than or equal to approximately 30 mm, or preferably, greater than or equal to approximately 40 mm, or preferably, greater than or equal to approximately 50 mm. The plurality of pillars 30a may be more spaced out, i.e. L may be larger for a given number of pillars 30a, to increase the effect of the pillars 30a on the flow. Alternatively, L may be larger due to a greater number of pillars 30a, to increase the effect of the pillars on the flow.

[00054] The pitch may be the distance between each of the pillars 30a and may be variable. The pitch may be the distance between each of the pillars 30a along the length L of the channel 22, i.e. in the X direction. The pitch may be the distance between each of the pillars 30a across the width of the channel 22, i.e. in the Y direction. The pitch may be specifically defined as the distance from the centre of one pillar to the centre of a next pillar in the relevant direction, e.g. in the Y direction. The pitch will be determined by the number of pillars 30a and the placement of the pillars 30a. The pitch in the X and/or Y direction may be specifically selected/controlled.

[00055] The plurality of pillars 30a may be non-perpendicular to the first wall 23 and or the second wall 24 of the enclosure. Examples are depicted in figures 5A, 5B, 5C and 5D. The plurality of pillars 30b in figures 5A and 5B and the plurality of pillars 30c in figures 5C and 5D may be substantially the same as the plurality of pillars 30a in figures 4A and 4B, except for the angles to the walls of the enclosure as described below.

[00056] In figures 5A and 5B, the plurality of pillars 30b are provided at a first angle a relative to the first wall 23 and at a second angle b relative to the second wall 24. If the first wall 23 and the second wall 24 are parallel to each other and the plurality of pillars 30b are straight between the first wall 23 and the second wall 24, then the first angle a will be the same as the second angle b. In this example, the plurality of pillars 30b are slanted in the X-Z plane, i.e. slanted along the length of the channel 22. As shown in figure 5B, even though the plurality of pillars 30b are slanted in the X-Z plane, they may be perpendicular in the Z-Y plane, i.e. from a front view of the opening 21. Thus, the plurality of pillars 30b may be perpendicular to the first wall 23 and the second wall 24 in one plane (as shown in figure 5B) and slanted in another plane (as shown in figure 5A).

[00057] In figures 5C and 5D, the plurality of pillars 30c are provided at a first angle Q relative to the first wall 23 and at a second angle g relative to the second wall 24. If the first wall 23 and the second wall 24 are parallel to each other and the plurality of pillars 30c are straight between the first wall 23 and the second wall 24, then the first angle Q will be the same as the second angle g. In this example, the plurality of pillars 30c are slanted in the Z-Y plane, i.e. slanted across the width of the channel 22. As shown in figure 5C, even though the plurality of pillars 30c are slanted in the Z-Y plane, they may be perpendicular in the Z-X plane, i.e. along the length of the channel 22. Thus, the plurality of pillars 30b may be perpendicular to the first wall 23 and the second wall 24 in one plane (as shown in figure 5C) and slanted in another plane (as shown in figure 5D).

[00058] It may be preferable that the pillars slanted (i.e. at an angle which is not perpendicular or parallel) in at least one plane as shown in figures 5A and 5D. This may make the flow laminating portion 30 easier to manufacture. For example, the pillars may be angled at approximately 45 ° to the first wall 23 and/or the second wall 24, i.e. a ~ 45° and/or b~ 45° and or Q ~ 45° and/or g ~ 45°. In particular, if the pillars are manufactured by additive manufacturing (for example, 3-D printing) as described below, then slanting the pillars in such a way may improve the reliability of the manufacturing and may allow more freedom in how the pillars are printed. For example, the device 20 may be printed in a greater variety of orientations if the pillars are slanted in at least one plane.

[00059] At least one of the plurality of pillars may be substantially perpendicular to the first wall 23 and or the second wall 24 as shown in figure 4A without slanting in any plane. At least one of the plurality of pillars may be slanted in the Z-X plane as shown in figure 5A and or the Z-Y plane, as shown in figure 5D. Some pillars may be slanted in one direction and one plane, and other pillars may be slanted in another way and or in a different plane. All the pillars may be uniform, in that all the pillars may have the same angle with respect to the first wall 23 and or the second wall 24. The pillars may be slanted in multiple planes.

[00060] As shown in figure 4B, at least a portion of the plurality of pillars 30a are arranged in a uniform pattern in plan view. In other words, at least a portion of the pillars 30a may be arranged in a uniform pattern in the X-Y plane shown in figure 4B. More generally, at least a portion of the plurality of pillars 30a may be arranged in a uniform pattern in at least one plane. For example, this could be any of the Z-X, Z-Y or X-Y planes shown in the figures. Figure 4B shows a cross-section through the device 20 and in this instance shows a uniform set of rows and columns forming the plurality of pillars 30a in the flow laminating portion 30. Of course, although it may be preferred that the plurality of pillars are in a uniform pattern, the plurality of pillars may also be arranged in a non- uniform pattern.

[00061] The plurality of pillars may comprise multiple sets of pillars. A set of pillars may be a subset of the plurality of pillars, i.e. including some but not all of the plurality of pillars. A first set of pillars may be arranged in a first pattern, and a second set of pillars may be arranged in a second pattern. The first pattern may be a predetermined pattern in plan view (i.e. in the X-Y plane). The second pattern may be a predetermined pattern in plan view. Thus, the pillars may be provided as a first set of pillars arranged in a first pattern in plan view and a second set of pillars arranged in a second pattern in plan view, wherein the second pattern is different from the first pattern. This is depicted in figures 6A and 6B. As can be seen in figures 6A and 6B, a first set of pillars 30d is provided and a second set of pillars 30e is provided. The first set of pillars 30d are more widely spaced along the length of the channel 22 and across the width of the channel 22 than the second set of pillars 30e. The first set of pillars 30d are in a first pattern in plan view and the second set of pillars 30e are in a second pattern in plan view, the second pattern being different from the first pattern.

[00062] The first set of pillars 30d may be different from the second set of pillars 30e in multiple ways. The first set of pillars 30d may differ from the second set of pillars 30e in only one way. For example, the first set of pillars 30d may differ from the second set of pillars 30e by having different cross-sectional areas, different cross-sectional shapes, different patterns in plan view, different patterns in side view, different spacing, different angles with respect to the first wall 23 and/or the second wall 24. Any variation of patterns may be provided for at least one set of pillars. Any of the first set of pillars 30d and/or the second set of pillars 30e may be arranged in a non-uniform pattern in plan view. The different sets of pillars may be particularly beneficial in affecting particular properties of the flow through the channel 22. For example, a subset of pillars (e.g. the first set of pillars 30d) may reduce or remove upstream vorticity, whilst a further subset of pillars (e.g. the second set of pillars 30e) with different characteristics, may increase uniformity of the flow without introducing new vortices.

[00063] Generally, the plurality of pillars may be arranged to affect the flow through the flow laminating portion 30 as desired. Thus, as described by the exemplary inclusion of subsets of pillars, the position and arrangement of each of the plurality of pillars may be selected to provide a desired functionality, i.e. to impact the flow within the channel 22 in a certain way.

[00064] As shown by the plurality of pillars in figure 7, at least some of the plurality of pillars may be arranged in a staggered pattern. Thus, the plurality of pillars may comprise a first row of pillars 31 and a second row of pillars 32, wherein the first row of pillars 31 is offset from the second row of pillars 32. In other words, adjacent rows of pillars may be offset, i.e. not aligned, from each other in the Y-direction. Staggering the pillars may be particularly useful in homogenizing the flow and reducing initial vorticity.

[00065] The cross-sectional area of the pillars may be selected depending on the effect on the flow in the channel 22. The cross-sectional area of the plurality of pillars may be circular as shown in figures 4B, 6B and 7. However, this is not necessary. The cross-sectional area of at least one of the plurality of pillars may be hexagonal, square, rectangular, oval or triangular, or any other appropriate shape. At least one of the plurality of pillars may have a different cross-sectional shape from other pillars in the plurality of pillars. The cross-sectional area of a pillar does not have to be uniform, and thus, the cross-sectional area and or shape may vary along the length of an individual pillar.

[00066] At least one of the plurality of pillars may have a cross-sectional width of greater than or equal to 0.2 mm. This is indicated by the width e measured of one of the plurality of pillars 30a in figure 4A. The cross-sectional width e may effectively be the diameter of the pillar 30a, if the cross- sectional area of the pillar 30a is circular. If other cross-sectional shapes are used, the cross-sectional width may be considered as the shortest distance across the cross-section of the pillar through the middle of the cross-section. Preferably, the cross-sectional width of the pillars is as small as possible. The cross-sectional width may be less than 0.2 mm. The cross-sectional width may be greater than or equal to approximately 0.2 mm, or greater than or equal to approximately 0.3 mm, or greater than or equal to approximately 0.4 mm, or greater than or equal to approximately 0.5 mm, or greater than or equal to approximately 0.6 mm, or greater than or equal to approximately 0.7 mm, or greater than or equal to approximately 0.8 mm, or greater than or equal to approximately 0.9 mm, or greater than or equal to approximately 1.0 mm. The cross-section area of the pillar may be elongated, for example in a rectangular or oval shape. The cross-sectional length of the pillar may be approximately double the cross-sectional width of the pillar. For example, the cross-sectional length of the pillar may be greater than or equal to approximately 1 mm, or greater than or equal to approximately 1.5 mm, or greater than or equal to approximately 2 mm.

[00067] In the first embodiment, the plurality of pillars may be arranged and have features as described above. The plurality of pillars may comprise an end row of pillars which are substantially perpendicular to the first wall 23 and/or the second wall 24 in the X-Z plane and the Y-Z plane. The end row of pillars may be positioned along the channel 22 at the furthest distance from the opening 21 in the flow laminating portion 30. In other words, the rest of the plurality of pillars may be positioned between the end row of pillars and the opening 21.

[00068] The figures depicting the first embodiment show a variety of arrangements of a few pillars. There may be a much larger number of pillars than shown. There may be any appropriate number of pillars. For example only, the flow laminating portion 30 may comprise more than or equal to approximately 5 pillars, or more than or equal to approximately 10 pillars, or more than or equal to approximately 20 pillars, or more than or equal to approximately 50 pillars, or more than or equal to approximately 100 pillars, or more than or equal to approximately 200 pillars, or more than or equal to approximately 500 pillars, or more than or equal to approximately 1000 pillars.

[00069] It will be understood that where at least one is referred to above may mean 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more, or may mean all of the group or sub-group/set being referred to.

[00070] The plurality of pillars may have any combination of features described above. For example, at least one of the pillars may have a cross-sectional shape and/or area as described in combination with any slant with respect to the first wall 23 and or the second wall 24 as shown, etc..

[00071] The first wall 23 and the second wall 24 are shown as being of approximately the same length in figures 4A-7, however, this is not necessary. For example, the second wall 24 may extend further than the first wall 23. The opening 21 may thus be formed at a diagonal between the first wall 23 and the second wall 24. For example, as shown in figure 8A, the second wall 24 may extend outwards of the channel 22 by an additional distance d. The shape of the first wall 23 and the second wall 24 at the opening may be selected to alter the effect on the flow of fluid into or out of the opening 21. Although the ends of the first wall 23 and the second wall 24 are generally shown as being aligned in figures 4A to 7, this may not be the case and the end of the first wall 23 and the second wall 24 may be more similar to the formation shown in figure 8A.

[00072] The first wall 23 and/or the second wall 24 may be substantially planar (i.e. flat) on the inside as shown in at least figures 4A and 5A. In other words, the inwardly facing surfaces 23A and or 24A of the first wall 23 and or the second wall 24 respectively may be planar. The first wall 23 and the second wall 24 may generally form a rectangular enclosure. The enclosure may be any appropriate shape, for example, square, oval, rectangular, circular, etc.. The channel 22 may be defined within an enclosure formed by the first wall 23, second wall 24, third wall 25 and fourth wall 26. The first wall 23, second wall 24, third wall 25 and fourth wall 26 are generally referred to as separate walls. However, these walls may be integral with one another, i.e. a solid piece may form the first wall 23, second wall 24, third wall 25 and fourth wall 26 to define a channel 22 within the walls. Although the walls are generally shown as straight and uniform in figures 4 A to 7B, this is not necessary. For example, as shown in figure 8B, the channel 22 may have curved sides, i.e. at least one of the inwardly facing surfaces 23A and or 24A maybe curved. The shape of the sides of the channel 22, formed by at least the first wall 23 and the second wall 24 may be predetermined to alter the effect on the flow of fluid in the channel 22. The cross-sectional area of the channel 22 formed by at least the first wall 23 and the second wall 24 may increase towards the opening 21.

[00073] As shown in figure 8B, the second wall 24 may extend at the opening by a distance d more than the first wall 23. Preferably the distance d is between approximately 1mm and 20 mm, or more preferably between approximately 5 mm and 15 mm. As shown in figure 8B, the end of the first wall 23 and the end of the second wall 24 may be sloped to form a diagonal with the opening 21 from the first wall 23 to the second wall 24. However, the difference d in length and/or the sloped ends shown in figure 8B is optional and the end of the first wall 23 and the end of the second wall 24 may be aligned in the X-direction as in figure 8A or 4A even if the channel 22 has curved walls as in figure 8B. The straight end walls as shown in figure 4A-7 may be preferable in that contamination may be reduced compared to the angled end shown in at least figures 8A and 8B. However, the angled ends shown in figures 8A and 8B may be easier, quicker and/or cheaper to manufacture.

[00074] At least one of the plurality of pillars may extend between any two of the first, second, third or fourth walls. In other words, at least one of the plurality of pillars may be connected to one of the first, second, third or fourth walls at a first end of the at least one pillar and connected to a different one of the first, second, third or fourth walls at a second end of the at least one pillar. The pillars being arranged in this way may still provide the advantages described above.

[00075] More specifically, in any of the above embodiments, at least one of the plurality of pillars may be formed to extend between the third wall 25 and the fourth wall 26. Thus, the pillars may extend in substantially the Y direction shown in the figures. In other words, the pillars may be formed substantially horizontally, rather than substantially vertically as shown in in at least figures 5A to 5D for example. In this case, the third wall 25 and the fourth wall 26 may otherwise be referred to as a first wall and a second wall.

[00076] In a second embodiment, the flow laminating portion 30 comprises a plurality of sub channels 30f positioned to separate the fluid flow in the channel 22 into the sub-channels. Thus, the flow laminating portion 30 may separate the fluid flow into smaller sub-sections along the length of the channel 22. An example showing the plurality of sub-channels 30f is depicted in figures 9A and 9B.

[00077] At least one of the plurality of sub-channels 30f may have a cross-sectional area A of less than or equal to approximately 5 mm² , or preferably less than or equal to approximately 4 mm², or preferably less than or equal to approximately 3 mm², or preferably less than or equal to

approximately 2 mm², or preferably less than or equal to approximately 1 mm², or preferably less than or equal to approximately 0.5 mm² or preferably less than or equal to approximately 0.2 mm². The shape of the cross-sectional area of the sub-channels 30f may be selected as desired. The cross- sectional area A depicted in figure 9A is hexagonal but this is optional. At least one of the plurality of sub-channels 30f may have a cross-sectional area A which is hexagonal, circular, square, rectangular, oval or triangular. The plurality of sub-channels 30f may all have the same cross-sectional shape and/or size. The plurality of sub-channels 30f may have some sub-channels 30f with different cross- section shapes and/or sizes. The plurality of sub-channels 30f may form at least two sets of sub channels 30f wherein at least one characteristic, e.g. cross-sectional shape or size or pattern differs between the sets.

[00078] The plurality of sub-channels 30f may have a length L in the direction of the channel (i.e. in the X direction as shown in the figures) of greater than or equal to approximately 3 mm, or preferably greater than or equal to approximately 10 mm, or preferably greater than or equal to approximately 20 mm, or preferably, greater than or equal to approximately 30 mm, or preferably, greater than or equal to approximately 40 mm, or preferably, greater than or equal to approximately 50 mm.

[00079] The plurality of sub-channels 30f are preferably substantially parallel to the first wall 23 and/or the second wall 24 of the enclosure, for example, as depicted in figures 9 A and 9B.

[00080] Preferably, the plurality of sub-channels 30f are arranged in a uniform pattern. For example, as depicted in figure 9A, the plurality of sub-channels 30f may be provided in a honeycomb pattern. In other words, in a cross-section across the channel (i.e. in the Y direction in figure 9A), the plurality of sub-channels 30f may form adjacent rows of sub-channels 30f in which each row of sub channels is offset from the adjacent rows of sub-channels 30f.

[00081] As shown in figure 9B, one end of the plurality of sub-channels 30f may be near the opening 21 and the other end of the plurality of sub-channels 30f may be further from the opening 21. The other end of the plurality of sub-channels 30f (away from the opening 21) may be formed as a straight line in the X-Z plane. Alternatively, the other end of the plurality of sub-channels 30f may be formed in a pattern such as a chevron shape, as shown in figure 9B, which may make manufacture of the plurality of sub-channels 30f easier. This is optional and the end of the plurality of sub-channels 30f may be in any shape.

[00082] The plurality of sub-channels 30f may be provided as well as, or in addition to, the plurality of pillars of the first embodiment. For example, a plurality of pillars as in any of the variations in the first embodiment may be provided between the opening 21 and the sub-channels 30f. Alternatively, the sub-channels 30f of the second embodiment may be provided between a plurality of pillars as in any of the variations in the first embodiment and the opening 21. Alternatively, the sub-channels 30f of the second embodiment may be provided with a plurality of pillars as in any variation of the first embodiment on either side of the sub-channels 30f.

[00083] In a third embodiment, the flow laminating portion 30 comprises a porous layer 30g, as shown in figures 10A and 10B. The porous layer 30g may remove or reduce vorticity in the flow.

The porous layer 30g may provide a desired pressure drop and thus improve uniformity of the flow. The porous layer 30g may be provided across the channel 22 with openings 33 throughout the porous layer 30g, the porous layer 30g having a thickness t of greater than or equal to approximately 0.2 mm, or greater than or equal to approximately 0.3 mm, or greater than or equal to approximately 0.4 mm, or greater than or equal to approximately 0.5 mm, or greater than or equal to approximately 0.6 mm, or greater than or equal to approximately 0.7 mm, or greater than or equal to approximately 0.8 mm, or greater than or equal to approximately 0.9 mm, or greater than or equal to approximately 1.0 mm.

[00084] The porous layer 30g may be provided with any of the variations described in the first and/or second embodiment.

[00085] The porous layer 30g may be provided across the opening 21. The porous layer 30g may be provided across the whole width of the channel 22. The porous layer 30g may be connected to the walls forming the enclosure around the whole of the channel 22 at the opening 21.

[00086] The porous layer 30g may be integral with at least the first wall 23 and/or the second wall 24. The porous layer 30g may be integral with all the walls forming the channel 22.

[00087] The openings 33 of the porous layer 30g may be arranged in a non-uniform pattern.

Specifically, the desired flow and effect of the porous layer 30g may be determined and the openings may be determined based on the desired flow through the porous layer 30g. Thus, the openings 33 of the porous layer 30g may be tailored for a specific situation.

[00088] The openings 33 may comprise at least 1% of the volume of the porous layer 30g. The openings 33 may comprise at least 5% of the volume of the porous layer 30g. The openings 33 may comprise at least 10% of the volume of the porous layer 30g. Preferably, the openings 33 comprise less than 70% of the volume of the porous layer 30g, and more preferably, less than 50% of the volume of the porous layer 30g.

[00089] The porous layer 30g is shown as slanted in the figures 10A and 10B. In other words, the ends of the first wall 23 and the second wall 24 are not aligned and may have a different of distance d as in figures 8A and 8B. In figures 10A and 10B, the porous layer 30g is connected to across the opening 21 at the end of the walls. However, this is not necessary. However, the porous layer 30g may be provided as substantially vertical between the first wall 23 and the second wall 24. In other words, the porous layer 30g may be approximately perpendicular to the first wall 23 and/or the second wall 24. Thus, the end of the walls may be aligned, or the porous layer 30g may not be attached to the ends of the walls.

[00090] The device 20 of any of the previous embodiments may further comprise a fluid supply configured to supply fluid to the channel 22. The fluid supplied by the fluid supply may be a gas, for example, such as filtered (i.e. cleaned, possibly extremely clean) humidified or dry air. Additionally or alternatively, other fluids such as nitrogen, CO2, water or normal air may be used. Any reference to a fluid in the application may more specifically mean a gas, and any reference to a gas in the application can be replaced with a fluid. The fluid supply may be at a first end of the channel 22 and the opening 21 may be at a second end of the channel 22. Alternatively, the device 20 of any of the previous embodiments may further comprise a fluid extractor configured to extract the fluid from the channel 22. The fluid extractor may be at a first end of the channel 22 and the opening 21 may at a second end of the channel 22. The fluid extractor may result in the flow of fluid remaining laminar over a much longer path as compared to a situation without a fluid extractor for extracting the flow of fluid.

[00091] In a further embodiment, a fluid flushing apparatus is provided. The fluid flushing apparatus comprises any of the devices described above. The fluid flushing apparatus further comprises a further opening through which a radiation beam can pass through when the lithographic apparatus is in use. The at least one device may be integral with the fluid flushing apparatus. It may be beneficial to provide the fluid flushing apparatus because it can further reduce the number of separate parts required and thus may further reduce the number of assembly steps, lead-time and/or cost.

[00092] Figure 11 A shows an example of the fluid flushing apparatus 40 situated at the bottom of the projection system PS. Figure 1 IB shows a cross section through C-C of figure 11 A. The fluid flushing apparatus 40 may be located elsewhere, e.g. near a patterning device and/or sensor as described above.

[00093] As depicted in figures 11 A and 1 IB, the fluid flushing apparatus 40 may comprise a first device 20A comprising a fluid supply FS configured to supply the fluid to the channel 22 in which the fluid flow passes from the corresponding opening and a second device 20B comprising a fluid extractor FE configured to extract the fluid from the channel 22 in which the fluid flow passes to the corresponding opening. In this way, fluid can be supplied to the further opening 50 from the fluid supply FS and through a first device 20A and can be extracted from the further opening 50 by the fluid extractor FE via the second device 20B. The fluid supplied by the fluid supply FS may be a gas, for example, such as filtered (i.e. cleaned, possibly extremely clean) humidified or dry air.

Additionally or alternatively, other fluids such as nitrogen , CO2, water or normal air may be used. The first device 20A and the second device 20B may each correspond to any combination or variation of the device 20 described in first, second and/or third embodiments above. The first device 20A and the second device 20B may each have a corresponding flow laminating portion 30. At least one of these corresponding flow laminating portions 30 may comprise a plurality of pillars as described in any of the variations above. Both of the corresponding flow laminating portions 30 may comprise a plurality of pillars.

[00094] Preferably, the flow laminating portion 30 of the first device 20A corresponding to the fluid supply FS comprises a greater number of pillars that than the flow laminating portion 30 of the second device 20B corresponding to the fluid extraction FE, and or the plurality of pillars of the flow laminating portion 30 of the first device 20A corresponding to the fluid supply FS may be more densely positioned (i.e. with smaller pitch along the length of the channel 22 or across the width of the channel 22) than the flow laminating portion 30 of the second device 20B corresponding to the fluid extraction FE.

[00095] In the configuration shown in figures 11 A and 1 IB, the fluid flushing apparatus 40 is above a substrate W which may be moved relative to the fluid flushing apparatus 40 in the direction of the double headed arrow. Fluid may be introduced from the fluid supply FS as indicated by FI and may be extracted by the fluid extractor as indicated by F2. Ideally, the fluid flow from FI to F2 is substantially laminar across the further opening 50 due to the flow laminating portions (not shown) of the first device 20 A and the second device 20B. Optionally, additional fluid flow may be provided as shown by F3 and F4 from the gap between the fluid flushing device 40 and the substrate W.

[00096] The fluid extractor FE may be situated opposite the fluid supply FS, as in figures 11 A and 1 IB. The fluid extractor FE and the fluid supply FS may be provided on either side of the further opening 50. Preferably, the fluid extractor FE is, in terms of its dimensions, similar to the fluid supply FS. Ideally, fluid in the space between the first device 20A comprising the fluid supply FS and the second device 20B comprising the fluid extractor FE is substantially laminar.

[00097] The device 20 and or fluid flushing apparatus 40 can be made from any appropriate material. For example, the material may be easily machinable and allow for production of a relatively stiff fluid flushing device. The material may comprise at least one metal and/or at least one polymer and or at least one ceramic.

[00098] In an embodiment, a lithographic apparatus is provided comprising a device or fluid flushing apparatus as described above.

[00099] In an embodiment, a method of generating any one of the above described devices 20 and or fluid flushing apparatus 40 is provided. The method comprising additive manufacturing, i.e. applying successive layers of material to form the device 20 or the fluid flushing apparatus 40. This may otherwise be known as 3-D printing. Thus, the device 20 and or fluid flushing apparatus 40 can be manufactured using a variety of materials. The devices 20 and fluid flushing apparatus 40 described above may be particularly suited to this type of additive manufacture. The additive manufacturing technique allows complex structures to be manufactured in one piece at relatively low cost. The additional design freedom and short development times allow optimal flow investigation opportunities on offline tools and within machine tests.

[000100] In further detail, using additive manufacturing to produce the devices 20 and/or fluid flushing apparatus 40 described above have various advantages. There is more design freedom, to be able to fit a device 20 or fluid flushing apparatus 40 in a tight volume, and tweak pressure drop/flow uniformity according specific situations. Manufacturing in this way leads to reduced or minimal rejection. Due to crack formation in presently known devices, such as current sieve assemblies, there is a large amount of rejection and need to re-assemble parts. This leads to extra cost and lead-time. Manufacturing as in the present invention is less expensive than currently used methods, because currently the assembly is composed out of many small parts that need to be assembled accurately. These high costs can be completely be circumvented by additive manufacturing the device 20 and or fluid flushing apparatus 40 as described in the present invention. Using additive manufacturing as in the present invention can result in reduced lead-times. For example, devices 20 and or fluid flushing apparatus 40 include new designs for the flow laminating portion 30 can be printed immediately and do not require third party manufacturers to make different component parts.

[000101] There may also be other methods of generating the device 20 and or fluid flushing apparatus 40. For example, other methods may include milling, wire eroding and/or laser ablation.

[000102] The device 20 and or apparatus 40 may be usefully provided in various sections and machines. As described above the device 20 and/or apparatus 40 may be positioned for controlling flow over a patterning device in a patterning device support micro environment, or the substrate W. Additionally or alternatively, the device 20 and or apparatus 40 could be provided may be positioned for controlling flow over an optical component, such as lens 2, or any part of a substrate support WT, sensor, or component of a lithographic apparatus which may benefit from substantially laminar flow.

[000103] Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc.

[000104] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions or ambient (non- vacuum) conditions.

[000105] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention, where the context allows, is not limited to optical lithography and may be used in other applications, for example imprint lithography.

[000106] Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine -readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.

[000107] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

1. A device for providing substantially laminar fluid flow in a lithographic apparatus, the device comprising:

an opening;

a channel through which fluid flows to or from the opening, the channel defined within an enclosure formed by at least a first wall and a second wall; and

a flow laminating portion in the channel configured to provide the substantially laminar fluid flow through the opening, wherein the flow laminating portion comprises a plurality of pillars formed between the first wall of the enclosure and the second wall of the enclosure.

2. The device of claim 1, wherein the plurality of pillars are arranged along the channel and a length of the channel comprising the plurality of pillars is greater than or equal to approximately 3 mm, and/or wherein the plurality of pillars are non-perpendicular to the first wall and or the second wall of the enclosure, and/or wherein the plurality of pillars comprise a first set of pillars arranged in a first pattern in plan view, and a second set of pillars arranged in a second pattern in plan view, different from the first pattern, and or wherein the plurality of pillars are arranged in a staggered pattern, comprising a first row of pillars and a second row of pillars, wherein the first row of pillars is offset from the second row of pillars.

3. The device of claim 1 or 2, wherein at least a portion the plurality of pillars are arranged in a uniform pattern in plan view, and/or wherein at least one of the plurality of pillars has a cross- sectional width of greater than or equal to 0.2 mm, and/or wherein at least one of the plurality of pillars has a cross-sectional area which is hexagonal, circular, square, rectangular, oval or triangular.

4. A device for providing substantially laminar fluid flow in a lithographic apparatus, the device comprising:

an opening;

a flow laminating portion in the channel configured to provide the substantially laminar fluid flow through the opening, wherein the flow laminating portion comprises a plurality of sub-channels positioned to separate the fluid flow in the channel into the sub-channels, wherein at least one of the sub-channels has a cross-sectional area of less than or equal to approximately 5 mm² and the plurality of sub-channels have a length of greater than or equal to approximately 3 mm.

5. The device of claim 4, wherein the plurality of sub-channels are substantially parallel to the first wall and/or the second wall of the enclosure, and/or wherein the plurality of sub-channels are arranged in a uniform pattern.

6. The device of claim 4 or 5, wherein at least one of the plurality of sub-channels has a cross- sectional area which is hexagonal, circular, square, rectangular, oval or triangular.

7. A device for providing substantially laminar fluid flow in a lithographic apparatus, the device comprising:

an opening;

a flow laminating portion in the channel configured to provide the substantially laminar fluid flow through the opening, wherein the flow laminating portion comprises a porous layer across the channel with openings throughout the porous layer, the porous layer having a thickness of at least approximately 0.2 mm.

8. The device of any of claims 1 to 7, wherein the flow laminating portion further comprises a porous layer across the channel with openings throughout the porous layer, the porous layer having a thickness of at least approximately 0.2 mm, and or wherein the flow laminating portion is integral with at least the first wall and/or the second wall, and/or wherein the flow laminating portion is provided across the width of the channel.

9. The device of claim 7 or 8, wherein the openings throughout the porous layer are arranged in a non-uniform pattern.

10. The device of any of claims 1-9, further comprising a fluid supply configured to supply the fluid to the channel, wherein the fluid supply is at a first end of the channel and the opening is at a second end of the channel and/or further comprising a fluid extractor configured to extract the fluid from the channel, wherein the fluid extractor is at a first end of the channel and the opening is at a second end of the channel.

11. A fluid flushing apparatus comprising:

at least one device according to any preceding claim; and

a further opening through which a radiation beam can pass through when the lithographic apparatus is in use.

12. The fluid flushing apparatus of claim 11, wherein the at least one device is integral with the fluid flushing apparatus.

13. The fluid flushing apparatus of claim 11 or 12, wherein the fluid flushing apparatus comprises a first device according to claim 18 in which the fluid flow passes from the corresponding opening and a second device according to claim 19 in which the fluid flow passes to the corresponding opening.

14. A lithographic apparatus comprising

the device of any of claims 1 to 10 or the fluid flushing apparatus of any of claims 11 to 13.

15. A method of generating the device of any of claims 1 to 10 or the fluid flushing apparatus of any of claims 11 to 13, the method comprising applying successive layers of material to form the device or the fluid flushing apparatus.