NL2014324A - Housing for an array of densely spaced components and associated manufacturing method. - Google Patents

Description

HOUSING FOR AN ARRAY OF DENSELY SPACED COMPONENTS AND ASSOCIATED MANUFACTURING METHOD

The present invention relates to a housing for an array of densely spaced components, and an associated manufacturing method. In particular, the invention relates to a housing suitable for housing and cooling a suspension and actuator apparatus used, for example, to suspend and actuate optical elements forming part of an optical apparatus used in lithographic apparatus.

BACKGROUND

[0001] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned.

[0002] Lithography is widely recognized as one of the key steps in the manufacture of ICs and other devices and/or structures. However, as the dimensions of features made using lithography become smaller, lithography is becoming a more critical factor for enabling miniature IC or other devices and/or structures to be manufactured. A theoretical estimate of the limits of pattern printing can be given by the Rayleigh criterion for resolution as shown in equation (1):

(1) where λ is the wavelength of the radiation used, NA is the numerical aperture of the projection system used to print the pattern, kl is a process dependent adjustment factor, also called the Rayleigh constant, and CD is the feature size (or critical dimension) of the printed feature. It follows from equation (1) that reduction of the minimum printable size of features can be obtained in three ways: by shortening the exposure wavelength λ, by increasing the numerical aperture NA or by decreasing the value of kl.

[0003] In order to shorten the exposure wavelength and, thus, reduce the minimum printable size, it has been proposed to use an extreme ultraviolet (EUV) radiation source. EUY radiation is electromagnetic radiation having a wavelength within the range of 5-20 nm, for example within the range of 13-14 nm. It has further been proposed that EUV radiation with a wavelength of less than 10 nm could be used, for example within the range of 5-10 nm such as 6.7 nm or 6.8 nm. Such radiation is termed extreme ultraviolet radiation or soft x-ray radiation. Possible sources include, for example, laser-produced plasma sources, discharge plasma sources, or sources based on synchrotron radiation provided by an electron storage ring.

[0004] EUV radiation may be produced using a plasma. A radiation system for producing EUV radiation may include a laser for exciting a fuel to provide the plasma, and a source collector module for containing the plasma. The plasma may be created, for example, by directing a laser beam at a fuel, such as particles of a suitable material (e.g. tin), or a stream of a suitable gas or vapor, such as Xe gas or Li vapor. The resulting plasma emits output radiation, e.g., EUV radiation, which is collected using a radiation collector. The radiation collector may be a mirrored normal incidence radiation collector, which receives the radiation and focuses the radiation into a beam. The source collector module may include an enclosing structure or chamber arranged to provide a vacuum environment to support the plasma. Such a radiation system is typically termed a laser produced plasma (LPP) source.

[0005] In lithographic apparatuses typically many moving parts are provided with various degrees of freedom, and the positions (including linear and angular position (orientation), velocities and accelerations) are controlled automatically via numerous actuation (actuators) and suspension arrangements. Actuation and suspension arrangements may be electromagnetically operated, pneumatically of hydraulically operated. They are often constrained to effect movement in only one degree of freedom (linear or rotational). Where the moving parts are to be controlled in plural degrees of freedom, more complex mechanisms may be provided, or multiple single-degree mechanisms may be combined.

[0006] Because of the need for extreme accuracy, and because additionally of the need to work in a vacuum environment with high reliability, designing actuator and suspension arrangements for EUV lithography apparatus is particularly demanding.

[0007] An example where arrays of actuators and suspensions are required is in the facetted mirrors of an illumination system of an EUV optical system. Numerous individual mirror facets may be provided in an array, each of which may need to be oriented in different directions to effect different illumination profiles at a target location. Actuation and suspension arrangements for field facet mirrors are described for example in the published international patent application WO 2011/000671 Al.

[0008] Field facet mirrors (FFM) absorb some of the radiation incident upon them, which causes them to heat up. This heat needs to be transported away from the mirror to prevent overheating and/or distortions of the mirror. As EUV systems increase in output power, the heat load on each mirror increases and more heat needs to be transported away from the mirror.

[0009] Similarly, motors comprised within the actuators, and configured to drive (for example) FFMs, heat up when energized. Currently, motor cooling systems, specifically designed for cooling motors of FFM actuators, comprise a dense web of small cooling pipes, resulting in a limited heat transfer area. Consequently, the performance of current cooling systems may be inefficient; for instance, insufficient cooling and temperature control is provided for arrangements comprising a densely packed array of actuators.

SUMMARY

[0010] It is desirable to improve the cooling of components such as motors of an array of actuators configured to move optical components such as field facet mirrors.

[0011] In a first aspect of the invention there is provided a housing for an array of components, said housing being operable to provide cooling to said components, said housing comprising: an array of component apertures, each component aperture for receiving at least one of said components; and wherein: a wall of said component aperture comprises at least one cooling channel defined by an inner layer and an outer layer; and the outer layer of the at least one cooling channel comprises one or more fluid flow apertures enabling fluid flow between the at least one cooling channel of the component aperture and an at least one cooling channel of an adjacent component aperture, said cooling channels and fluid flow apertures defining a cooling path for a coolant between an inlet and an outlet.

[0012] Also disclosed is a method of manufacture of such a housing and various apparatuses comprising said housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figure 1 depicts a lithographic apparatus according to an embodiment of the invention;

Figure 2 is a more detailed view of the apparatus 100:

Figure 3 is a more detailed view of the source collector module SO of the apparatus of Figures 1 and 2;

Figure 4 depicts an alternative example of an EUV lithographic apparatus;

Figure 5a is a first cross sectional view of part of an illumination system of a lithographic apparatus in which methods and apparatuses embodying an embodiment of the invention may be used;

Figure 5b is a second cross sectional view of the apparatus of Figure 5 a showing adjustment of a field facet mirror to address two associated pupil facet mirrors;

Figure 6(a) illustrates an actuator and suspension arrangement of a field facet mirror module in a lithographic apparatus; (b) is a more detailed view of one actuator in the mirror module of (a);

Figure 7 illustrates an actuator and suspension arrangement of a field facet mirror module in accordance with an embodiment of the invention;

Figure 8 is a flowchart describing a method of manufacture of a housing in accordance with an embodiment of the invention;

Figures 9(a) and 9(b) illustrate in two views the incomplete housing following step 810 of Figure 8;

Figures 10(a) and 10(b) illustrate in two views the incomplete housing following step 820 of Figure 8;

Figures 11(a) and 11(b) illustrate in two views the housing following step 830 of Figure 8; and

Figure 12 illustrates the cooling path within a housing according to an embodiment of the invention.

DETAILED DESCRIPTION

[0014] Figure 1 schematically depicts a lithographic apparatus 100 including a source collector module SO according to one embodiment of the invention. The apparatus comprises: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. EUV radiation). a support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask or a reticle) MA and connected to a first positioner PM configured to accurately position the patterning device; a substrate table (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; and a projection system (e.g. a reflective projection 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.

[0015] The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation.

[0016] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system.

[0017] The term “patterning device” should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. The pattern imparted to the radiation beam may correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

[0018] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.

[0019] The projection system, like the illumination system, may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of a vacuum. It may be desired to use a vacuum for EUV radiation since other gases may absorb too much radiation. A vacuum environment may therefore be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps.

[0020] As here depicted, the apparatus is of a reflective type (e.g. employing a reflective mask).

[0021] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more mask tables). In such “multiple stage” machines the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure.

[0022] Referring to Figure 1, the illuminator IL receives an extreme ultra violet radiation beam from the source collector module SO. Methods to produce EUV light include, but are not necessarily limited to, converting a material into a plasma state that has at least one element, e.g., xenon, lithium or tin, with one or more emission lines in the EUV range. In one such method, often termed laser produced plasma ("LPP") the required plasma can be produced by irradiating a fuel, such as a droplet, stream or cluster of material having the required line-emitting element, with a laser beam. The source collector module SO may be part of an EUV radiation system including a laser, not shown in Figure 1, for providing the laser beam exciting the fuel. The resulting plasma emits output radiation, e.g., EUV radiation, which is collected using a radiation collector, disposed in the source collector module. The laser and the source collector module may be separate entities, for example when a C02 laser is used to provide the laser beam for fuel excitation.

[0023] In such cases, the laser is not considered to form part of the lithographic apparatus and the radiation beam is passed from the laser to the source collector module with the aid of a beam delivery system comprising, for example, suitable directing mirrors and/or a beam expander. In other cases the source may be an integral part of the source collector module, for example when the source is a discharge produced plasma EUV generator, often termed as a DPP source.

[0024] The illuminator IL may comprise an adjuster for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may comprise various other components, such as facetted field and pupil mirror devices. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

[0025] The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. After being reflected from the patterning device (e.g. mask) 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 position sensor PS2 (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor PS1 can be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam B. Patterning device (e.g. mask) MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks PI, P2.

[0026] The depicted apparatus could be used in at least one of the following modes: 1. In step mode, the support structure (e.g. mask table) MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C can be exposed. 2. In scan mode, the support structure (e.g. mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (e.g. mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. 3. In another mode, the support structure (e.g. mask table) MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0027] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

[0028] Figure 2 shows the apparatus 100 in more detail, including the source collector module SO, the illumination system IL, and the projection system PS. The source collector module SO is constructed and arranged such that a vacuum environment can be maintained in an enclosing structure 220 of the source collector module SO. An EUV radiation emitting plasma 210 may be formed by a discharge produced plasma source. EUV radiation may be produced by a gas or vapor, for example Xe gas, Li vapor or Sn vapor in which the very hot plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is created by, for example, an electrical discharge causing an at least partially ionized plasma. Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapor or any other suitable gas or vapor may be required for efficient generation of the radiation. In an embodiment, a plasma of excited tin (Sn) is provided to produce EUV radiation.

[0029] The radiation emitted by the hot plasma 210 is passed from a source chamber 211 into a collector chamber 212 via an optional gas barrier or contaminant trap 230 (in some cases also referred to as contaminant barrier or foil trap) which is positioned in or behind an opening in source chamber 211. The contaminant trap 230 may include a channel structure. Contamination trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further indicated herein at least includes a channel structure, as known in the art.

[0030] The collector chamber 211 may include a radiation collector CO which may be a so-called grazing incidence collector. Radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation that traverses collector CO can be reflected off a grating spectral filter 240 to be focused in a virtual source point IF. The virtual source point IF is commonly referred to as the intermediate focus, and the source collector module is arranged such that the intermediate focus IF is located at or near an opening 221 in the enclosing structure 220. The virtual source point IF is an image of the radiation emitting plasma 210.

[0031] Subsequently the radiation traverses the illumination system IL, which may include a facetted field mirror device 22 and a facetted pupil mirror device 24 arranged to provide a desired angular distribution of the radiation beam 21, at the patterning device MA, as well as a desired uniformity of radiation intensity at the patterning device MA. Upon reflection of the beam of radiation 21 at the patterning device MA, held by the support structure MT, a patterned beam 26 is formed and the patterned beam 26 is imaged by the projection system PS via reflective elements 28, 30 onto a substrate W held by the wafer stage or substrate table WT.

[0032] More elements than shown may generally be present in illumination optics unit IL and projection system PS. The grating spectral filter 240 may optionally be present, depending upon the type of lithographic apparatus. Further, there may be more mirrors present than those shown in the Figures, for example there may be 1- 6 additional reflective elements present in the projection system PS than shown in Figure 2.

[0033] Collector optic CO, as illustrated in Figure 2, is depicted as a nested collector with grazing incidence reflectors 253, 254 and 255, just as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are disposed axially symmetric around an optical axis O and a collector optic CO of this type is preferably used in combination with a discharge produced plasma source, often called a DPP source.

[0034] Alternatively, the source collector module SO may be part of an LPP radiation system as shown in Figure 3. A laser LA is arranged to deposit laser energy into a fuel, such as xenon (Xe), tin (Sn) or lithium (Li), creating the highly ionized plasma 210 with electron temperatures of several 10's of eV. The energetic radiation generated during de-excitation and recombination of these ions is emitted from the plasma, collected by a near normal incidence collector optic CO and focused onto the opening 221 in the enclosing structure 220.

[0035] Figure 4 shows an alternative arrangement for an EUV lithographic apparatus in which the spectral purity filter SPF is of a transmissive type, rather than a reflective grating. The radiation from source collector module SO in this case follows a straight path from the collector to the intermediate focus IF (virtual source point). In alternative embodiments, not shown, the spectral purity filter 11 may be positioned at the virtual source point 12 or at any point between the collector 10 and the virtual source point 12. The filter can be placed at other locations in the radiation path, for example downstream of the virtual source point 12.

Multiple filters can be deployed. As in the previous examples, the collector CO may be of the grazing incidence type (Figure 2) or of the direct reflector type (Figure 3).

[0036] The following description presents optical apparatus and methods that can condition a radiation beam being directed at a target location on an object. The object can be, for example, a lithographic patterning device MA for generating a circuit pattern to be formed on an individual layer in an integrated circuit, or a substrate W on a substrate table WT of a lithographic apparatus. The target location may be an area of the patterning device MA illuminated by the illumination system IL. Example patterning devices include a mask, a reticle, or a dynamic patterning device. The reticles can also be for use within any lithography process, while the emphasis in this application will be on EUV lithography. Within the illumination system, actuators with suspension arrangements embodying the novel principles described above are used to move reflective elements so as to select different illumination modes.

[0037] Figure 5 a schematically shows a cross sectional view of an exemplary optical apparatus 20 for conditioning a radiation beam in the illumination system IL of a lithographic apparatus of the type shown in Figures 1 to 4. Apparatus 20 includes a first optical component in the form of facetted field mirror device 22 and a second optical component in the form of facetted pupil mirror device 24. Facetted field mirror device 22 comprises a plurality of primary optical elements, some particular ones schematically indicated in Figure 5a and referred to as field facet mirror elements 22a, 22b, 22c and 22d. The second optical component 24 comprises a plurality of secondary optical elements including, for example, the particular secondary optical elements referred to as pupil facet mirror elements 24a, 24b, 24c, 24d, and 24a’, 24b’, 24c', 24d’.

[0038] Generally, the field facet mirror elements 22a-d direct respective parts of incoming radiation beam B towards the pupil facet mirror elements 24a-d, 24a’-d’. Although only four field facet mirror elements 22a-d are shown, any number of field facet mirror elements may be provided. The field facet mirror elements may be arranged in a generally two-dimensional array , which does not mean that they should lie strictly in a flat plane. Although only eight pupil facet mirror elements 24a-d, 24a’-d’ are shown, any number of pupil facet mirror elements may be provided, the number being typically a multiple of the number of field facet mirror elements. The pupil facet mirror elements may be arranged in a two-dimensional array. The shapes and configurations of the field facet mirror elements and pupil facet mirror elements may be square, rectangular, circular, or more complicated in shape, according to design.

[0039] Each field facet mirror element 22a-d reflects a portion of the radiation beam B received by the first reflective component (22) in the form of a sub-beam of radiation towards a different pupil facet mirror element 24a-d of the pupil mirror device 24. For example, a first sub-beam Ba is directed by a first field facet mirror element 22a to a first pupil facet mirror element 24a. Second, third and fourth sub-beams Bb, Be and Bd are directed by second, third and fourth field facet mirror elements 22b, 22c, and 22d respectively to second, third and fourth pupil facet mirror elements 24b, 24c, and 24d. The spatial intensity distribution of the radiation beam B at the pupil mirror device 24 cA define an illumination mode of the lithographic apparatus. In one embodiment, the field facet mirror elements 22a-d have adjustable orientations, and they may be used with different ones of the pupil facet mirror elements 24a-d, 24a’-d’, to form different spatial intensity distributions at the pupil plane P, thereby providing different illumination modes. This option, which is known per se, will be described later with reference to Figure 5b. The pupil facet mirror elements 24a-d may also be adjustable in orientation.

[0040] Each of the field facet mirror elements 22a-d is shaped so as to form an image of the intermediate focus IF at a different pupil facet mirror element 24a-d, of the pupil mirror device 24. In practice, the intermediate focus IF will be a virtual image of the plasma source, the image having a finite diameter (e.g. 4-6 mm). Consequently, each field facet mirror element 22a-d will form an image of the virtual source point IF which has a finite diameter (e.g. 3-5 mm) at the pupil facet mirror elements 24a-d. The pupil facet mirror elements 24a-d, may each have a diameter which is larger than the aforementioned image diameter (to avoid radiation falling between pupil facet mirror elements and thereby being lost). The intermediate focus IF and images of the intermediate focus IF are shown as points in the figures for ease of illustration only.

[0041] The facetted mirror devices 22 and 24 together form a so-called “fly’s eye” illuminator, by which non-uniformities present in the radiation source are eliminated to illuminate area E with more even distribution, and with more control. Each one of the pupil facet mirror elements 24a-d may form an image of its associated field facet mirror element 22a-d at or near the field plane wherein the patterning device MA is located during exposure of a substrate. These images are substantially overlapping and together form an illumination area E. As a result, a spatially non-uniform intensity distribution in a cross section of the radiation B as emanating from the source SO and received by the apparatus 20 is conditioned to have a substantially spatially uniform intensity distribution in the illumination area E. The shape of the illumination area E is determined by the shape of the field facet mirror elements 22a-d. In a scanning lithographic apparatus the illumination area E may for example be a rectangle or a curved band, when viewed in two dimensions which in the scanning direction has a width narrower than the width in a direction perpendicular to the scanning direction.

[0042] A wavelength of the desired part of radiation may be an EUV wavelength in the range 5-20nm, for example 13.5nm. The beam B may also include large amounts of unwanted radiation, for example at DUV wavelengths. Other patent publications disclose techniques for reducing the transmission of unwanted radiation through the illuminator.

[0043] As mentioned already, each field facet mirror element 22a-d of field mirror device 22 may have more than one associated pupil facet mirror elements of pupil mirror device 24. A field facet mirror element 22a of field mirror device 22 can be controlled to cooperate with different ones of its associated pupil facet mirror elements 24a at different times. For example, as shown in Figure 5b, field facet mirror element 22a has two associated pupil facet mirror elements 24a and 24a’. These are used in different illumination modes of illuminator 20. Field facet mirror element 22a may thus be controlled in a second mode to direction EUV radiation towards pupil facet mirror element 24a’ instead of 24a, while radiation with an undesired wavelength, such as DUV radiation may be scattered to fall onto neighboring pupil facet mirror elements like 24c, 24d, 24b’ or 24c’. In some embodiments, pupil facet mirror elements may also have controllable orientation. Again, the design can be made such that the pupil facet mirror elements most closely surrounding the associated mirror will direct the scattered DUV radiation away from the target (illumination area E).

[0044] Figure 6 (a) shows a flexible actuation and suspension apparatus 600. Actuators 605 are applied to effect movement of reflecting elements serving as FFM components 22a in the illumination system of an EUV lithography apparatus such as the ones described above. Figure 6 (b) illustrates a detail of one of the actuator 605. Figure 6 portions of actuator 605 are broadly identified as corresponding to the motor M, chassis C and suspension R. The actuator 600 has a head 650 on which an FFM component 22a is mounted. In this example, the body and actuator provide two rotational degrees of freedom centred on a virtual pivot point 624. Two narrower bellows 651a and 651b extend between the actuator head 650 and two opposite sides of a chassis part 652. Four tendons 642, two of which are in the centre of the bellows 651a and 65 lb, extend from anchoring points on the chassis part 652 to the head 650. These tendons 642 point towards the virtual pivot point 624, and define the x, y, z position of this point. The bellows 651a and 651b constrain the Rz degree of freedom. It will be understood that any component, not only a mirror, may be attached to the head 722 to be moved by an actuator of this type. The suspension arrangement in this example comprises a tetrapod of tendons in tension, and two bellows in V-shape that prevent rotation along the Z axis. The tendons are uniformly spaced around the actuator’s central (Z) axis 626. The suspension arrangement again provides two degrees of freedom for tilting the body 650 in direction Rx and Ry. Movement in the Z direction as well as translation in X and Y are substantially or completely prevented. The bellows 651a, 651b in this example can be filled with Litz wire, or fluid filled so as to serve as thermal conductors instead of the Litz wire. They may also be constructed as heat pipes for greater heat conduction. A further magnet (not shown) may be provided within a cavity in the chassis part 652, to provide magnet counter-bias. Concerning the motor part of the actuator, moving magnet 654 is attached to the moving shaft 632 of the actuator 605, and its movements are controlled by a first electromagnet comprising coils 670 for displacement in the X direction (rotation Ry) and a second electromagnet comprising coils 671 for displacement the Y direction (rotation Rx). The motor has a single core base 674. This core base 774 is provided with an aperture to allow an optical sensor (not shown) to measure the tilt of the actuator in two dimensions. The position sensor can be provided at another place in the mechanism, if space permits. As can be seen from the inset detail on Figure 6(b), looking down onto the face of pole shoes 680, 682. Each pole face substantially fills a quadrant of an annulus, and that annulus in turn encompasses all desired positions of the moving magnet 654. The pole shoes are not touching one another, to ensure that they can be magnetized independently, but the gaps between them are limited to maximize coverage of the annular area. Similarly, the central opening is minimized, permitting just enough space for the optical position sensor to ‘see’ the moving magnet 654.

[0045] Coils 670,671, when energized, constitute an additional source of heat. As mentioned, current cooling systems can be inefficient at removing this additional heat.

[0046] The present document discloses a component housing operable to cool the components housed, and an associated method of manufacturing thereof. The housing may be particularly suitable for components arranged in a densely packed manner. The component housing may be used, for example, for the housing and cooling of motors M forming part of actuators 605 as illustrated in Figure 6, and in particular for housing and cooling said motors when forming part of an array of densely packed actuators.

[0047] Figure 7 shows an apparatus comprising a densely packed array of actuators 605, for actuating field facet mirrors 22a, and a component housing 701 for housing and cooling the components comprised within actuators 605.Component housing 701 comprises a plurality of component apertures 705, each one for receiving one or more components such as an actuator 605 or part thereof (specifically here the actuator motor).

[0048] Figure 8 is a flowchart describing manufacturing steps for manufacturing the component housing 701 and a complete actuator assembly comprising said housing 701. Figures 9 to 11 illustrate the component housing after each of these steps.

[0049] At step 810, the housing block from which the housing is to be formed is machined to form bores 905. The resulting part complete housing is illustrated in Figures 9(a) and (b), where Figure 9(b) is a section view through A-A of Figure 9(a). The part complete housing 901 comprises bores 905 into which component apertures 705 will be formed. In the embodiment depicted, the bores 905 are arranged in a densely packed arrangement. Inlet and outlet apertures 910a and 910b provide an inlet and outlet for a cooling medium.

[0050] The cooling medium circulates through the housing by means of fluid flow apertures 920 which permit fluid flow between each component aperture 705 and its nearest adjacent component aperture(s) 705. The fluid flow apertures 920 may be formed within cooling channels which in this example take the form of indented rings 930a, 930b cut into the walls of the bores 905. In this specific embodiment, each of said bores 905 comprises two such indented rings 930a, 930b an upper ring 930a and a lower ring 930b. The upper rings 930a of all the bores 905 are each at a common height, as are all the lower rings 930b. The (inner) diameter of the bores 905 may be larger between upper ring 930a and a lower ring 930b than it is above and below these rings. Of course, where the component apertures are not cylindrical, one or more dimensional parameters other than diameter (in the XY plane) can be be larger between the rings.

[0051] The indented rings 930a, 930b are sufficiently deep such that the fluid flow apertures 920 are formed between the indented rings 930a, 930b of diagonally adjacent bores 905, that is at the points where distance between adjacent (in all directions) component apertures 705 will be at a minimum. Consequently, the distance between the centre axes of each bore 905 and its nearest adjacent bore(s) 905 should be slightly less than the diameter of the indented rings 930a, 930b, but slightly greater than the diameter of the bores 905 along their height other than at the positions of the indented rings 930a, 930b.

[0052] In the particular example array arrangement shown here, each component aperture 705, except those at the periphery of the array, will comprise fluid flow apertures 920 which permit direct fluid flow between that component aperture 705 and four other adjacent component apertures 705.

[0053] The shape, structure, material and or dimensions of housing 901 may be adapted to hold components other than circular shaped motors M, depending on the application.

[0054] At step 820, (e.g. cylindrical) sleeves are brazed (or otherwise assembled) into the bores 905 to form component apertures 705. The housing 1001 following this step is illustrated in Figures 10(a) and 10(b), where Figure 10(b) is a section view through A-A of Figure 10(a).

[0055] The sleeves 1005 are such that they are flush against the inner wall of bores 905 above the upper ring 930a and below the lower ring 930b. The upper ring 930a and lower ring 930b is each defined by an inner layer 1020a and an outer layer 1020b thereby defining a cooling channel. In this embodiment, between upper ring 930a and lower ring 930b there is a gap 1013 due to the larger diameter of the bores 905 in this region. This gap 1013 defines a cooling layer around the circumference of the component aperture 705 through which coolant flows.

[0056] In an alternative embodiment to that shown, no gap is provided and the cooling is provided only by the upper ring 930a and lower ring 930b; or by only one cooling channel, for example in an embodiment where each component aperture 705 has only one ring. In another alternative embodiment, instead of there being a gap 1013 around the full circumference of the component aperture 705, there is provided one or more cooling channels between upper ring 930a and lower ring 930b, allowing coolant flow between these rings.

[0057] At step 830, the completed component housing 701 is formed by machining the top and bottom surfaces, such that the housing 701 and sleeves 1005 are flush at the top and bottom of the housing 701. The housing 701 following this step is illustrated in Figures 11(a) and 11(b), where Figure 11(b) is a section view through A-A of Figure 11(a).

[0058] Finally at step 840, the completed component housing 701 is assembled with the actuator assembly to obtain the complete assembly depicted in Figure 7.

[0059] Figure 12 is a cross section through B-B of Figure 11, but showing only the coolant path formed within the component housing 710. Aperture 910a defines a low resistance inlet for the cooling medium, for example, water. The cooling medium spreads quickly through the system via upper and lower rings 930a, 930b, the gaps (cooling layer) 1013 between the bore 905 wall and sleeve 1005, and fluid flow apertures 920. The gaps 1013 provide a thin cooling layer around the central region of each component aperture 705. The cooling medium exits the system via outlet defined by aperture 910b. Note that the resistance of the cooling path can be modified by varying the thickness of gap 1013, to compensate, for example, for the bigger flow that might be expected at positions near to the inlet and outlet.

[0060] Motors M may be inserted within the sleeves 1005 and therefore will be isolated from their surroundings. Also replacement and/or removal of motors can be performed without opening the cooling circuit.

[0061] The housing described herein may be easily implemented to house, for example, an array of actuators so as to provide an efficient cooling of motors. In addition, the flow of the cooling medium around each of the motors isolates them from surrounding structures/components. Consequently, a better control of the thermal expansion of surrounding structures/components is also achieved. The reduction in the temperature rise of actuators, for example controlling the movement of FFMs, helps prevent the generation of an additional heat source that may be transferred to the field facet mirror elements and helps prevent failure of actuators in case of excessive temperature rise.

[0062] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as 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. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion", respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0063] Although specific reference may have been made above to the use of embodiments of the invention in the context of EUV optical systems, it will be appreciated that the invention may be used in other applications, whether in optical systems, whether in lithography or completely different applications, and whether in vacuum or other environments.

[0064] The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

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 clauses set out below. Other aspects of the invention are set-out as in the following numbered clauses. 1. A housing for an array of components, said housing being operable to provide cooling to said components, said housing comprising: an array of component apertures, each component aperture for receiving at least one of said components; and wherein: a wall of said component aperture comprises at least one cooling channel defined by an inner layer and an outer layer; and the outer layer of the at least one cooling channel comprises one or more fluid flow apertures enabling fluid flow between the at least one cooling channel of the component aperture and an at least one cooling channel of an adjacent component aperture, said cooling channels and fluid flow apertures defining a cooling path for a coolant between an inlet and an outlet. 2. A housing as claimed in clause 1 wherein said array of component apertures comprises a two-dimensional array of component apertures, for housing a two-dimensional array of densely packed components. 3. A housing as claimed in clause 1 or 2 wherein the each cooling channel completely surrounds at least a section of its component aperture. 4. A housing as claimed in any preceding clause wherein each fluid flow aperture comprises a common aperture in the outer layers of cooling channels of two adjacent component apertures without any intervening conduit. 5. A housing as claimed in any preceding clause wherein said component apertures are cylindrical. 6. A housing as claimed in clause 5 wherein said at least one cooling channel is ring shaped. 7. A housing as claimed in any preceding clause wherein each component aperture comprises a plurality of said cooling channels. 8. A housing as claimed in any preceding clause wherein said component apertures are formed within bores formed in a housing block, and said outer layer is defined by an indented inner wall of said bore and said inner layer is defined by a sleeve introduced into said bore. 9. A housing as claimed in clause 8 wherein each component aperture comprises two cooling channels, an upper cooling channel and a lower cooling channel. 10. A housing as claimed in clause 9 comprising one or more further cooling channels between said upper cooling channel and a lower cooling channel, thereby enabling coolant flow between said upper cooling channel and a lower cooling channel. 11. A housing as claimed in clause 9 comprising a cooling layer through which coolant can flow between said upper cooling channel and a lower cooling channel, the wall of said component aperture between said upper cooling channel and a lower cooling channel being comprised of said cooling layer. 12. A housing as claimed in clause 11 wherein the diameter of said bore in an intermediate section of said bore between said upper cooling channel and a lower cooling channel is larger than the diameter of the bore above said upper cooling channel and the diameter of the bore below said lower cooling channel, thereby forming said cooling layer between the inner wall of the bore and said sleeve at said intermediate section. 13. A housing as claimed in any preceding clause wherein the fluid path between an inlet and an outlet comprises only the cooling channels and, where present, said cooling layers of each one of said component apertures, and said fluid flow apertures. 14. A housing as claimed in any preceding clause wherein said fluid flow apertures are arranged such that, for every component aperture, coolant is able to flow between that component aperture and each component aperture adjacent to it. 15. An actuator and suspension arrangement comprising: a plurality of densely packed actuator and suspension devices, a housing as claimed in any preceding clauses, wherein each of said component apertures receives one of said actuator and suspension devices. 16. An optical device comprising: an optical component arranged to receive a radiation beam from a radiation source to process and deliver the beam to a target location, wherein said optical component includes one or more movable optical components mounted on the actuator and suspension arrangement as claimed in clause 15. 17. A lithographic apparatus, comprising: an illumination system configured to condition a radiation beam; said illumination system comprising an optical device as claimed in clause 16. 18. A method of manufacturing a housing as claimed in any of clauses 1 to 14 comprising: forming an array of bores within a housing block, and introducing a sleeve into each bore; such that said outer layer is defined by the housing block and said inner layer is defined by said sleeve. 19. A method as claimed in clause 18 comprising forming said bore with an intermediate section which has a diameter greater than the diameter at either end of said bore, said sleeve being located flush against the inner wall of the bore at either end of said bore. 20. A method as claimed in clause 18 or 19 comprising forming at least one ring indented into said inner wall of said bore such that the diameter of the bore is widest at the position of said indented ring, the diameter of said indented ring being such that said fluid flow apertures are formed between the rings of adjacent bores at the points where the distance between adjacent bores is smallest.

Claims (1)

A lithography device comprising: an exposure device adapted to provide a radiation beam; a carrier constructed to support a patterning device, the patterning device being capable of applying a pattern in a section of the radiation beam to form a patterned radiation beam; a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto a target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.