NL2005763A - Lithographic apparatus. - Google Patents

Description

Lithographic apparatus

BACKGROUND

Field

[0001] Embodiments of the present invention relate to a lithographic apparatus.

Background

[0002] 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. including 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.

[0003] 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.

[0004] A theoretical estimate of the limits of pattern printing (i.e. pattern application) 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 (i.e. apply) the pattern, k\ is a process dependent adjustment factor, also called the Rayleigh constant, and CD is the feature size (or critical dimension) of the printed (i.e. applied) feature. It follows from equation (1) that reduction of the minimum printable (i.e. applicable) 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 k\.

[0005] In order to shorten the exposure wavelength and, thus, reduce the minimum printable (i.e. applicable) feature size, it has been proposed to use an extreme ultraviolet (EUV) radiation source. EUV radiation is electromagnetic radiation having a wavelength within the range of 5-20 nm, for example within the range of 13-14 nm. or example within the range of 5-10 nm such as 6.7 nm or 6.8 nm. Possible sources include, for example, laser-produced plasma (LPP) sources, discharge plasma (DPP) sources, or sources based on synchrotron radiation provided by an electron storage ring.

[0006] 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 vapour, such as Xe gas or Li vapour. 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.

[0007] Radiation sources are used to generate a radiation beam. At the same time, however, radiation sources may also generate contamination in the form of particles or the like. For example, such generation of contamination is a particular problem associated with the generation of radiation in laser produced plasma sources (LPP sources) or discharge produced plasma sources (DPP radiation sources). This is because in such sources material is vaporized or the like using radiation or electrical discharge. The vaporization results in the generation of a plasma and subsequent radiation, but also the generation of contamination. Contamination generated by any radiation source may have a flight path that coincides with the beam path of the radiation beam that is generated by that source. Thus, the contamination may be directed towards any object that the radiation beam is also directed towards, for example one or more optical elements of a lithographic apparatus. If the contamination is incident upon these optical elements, the contamination can damage or degrade the optical elements, degrading the optical performance of the optical element and thus the lithographic apparatus as a whole. This is undesirable.

BRIEF SUMMARY

[000S] A lithographic apparatus is provided which obviates or mitigates the afore mentioned problems or provides an alternative to an existing lithographic apparatus.

[0009] According to a first aspect of the invention, there is provided a module including a normal-incidence collector mirror constructed and arranged to reflect radiation emitted from a first focal point to a second focal point and a barrier structure including one or more surfaces, the surfaces being oriented to allow radiation emitted from the first focal point to substantially transmit through the barrier structure to the second focal point and/or to allow radiation emitted from the first focal point to the second focal point to substantially transmit through the barrier structure from the second focal point, the surfaces further being constructed and arranged to intercept particles directly emanating from the first focal point.

[0010] The module may be a plasma radiation source arranged to generate an EUV-emitting plasma at the first focal point.

[0011] The module may include one or more conically-shaped elements.

[0012] The barrier structure may include one or more of the surfaces, where the surfaces are surfaces of the conically-shaped elements. The conically-shaped elements may be concentrically positioned with respect to each other.

[0013] A lithographic projection apparatus may include a module having a normal-incidence collector mirror constructed and arranged to reflect radiation emitted from a first focal point to a second focal point and a barrier structure having one or more surfaces, the surfaces being oriented to allow radiation emitted from the first focal point to substantially transmit through the barrier structure to the second focal point and/or to allow radiation emitted from the first focal point to the second focal point to substantially transmit through the barrier structure from the second focal point, the surfaces further being constructed and arranged to intercept particles directly emanating from the first focal point.

[0014] Usually, the majority of debris from the EUV-emitting plasma originates directly from the plasma and only a small portion is deflected off the normal-incidence collector mirror. Thus, owing to the orientation of the surfaces, such majority of particles may be intercepted and will remain in the module. They will not enter another part of the lithographic projection apparatus, if the module is included in such a lithographic projection apparatus.

[0015] Further features and advantages of embodiments of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. It is noted that the invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0016] 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:

[0017] Figure 1 schematically depicts a lithographic apparatus according to an embodiment of the invention;

[0018] Figure 2 is a more detailed view of the lithographic apparatus shown in Figure 1, including a discharge produced plasma (DPP) source collector module SO according to an embodiment of the invention;

[0019] Figure 3 is a view of an alternative source collector module SO of the apparatus of Figure 1, the alternative being a laser produced plasma (FPP) source collector module, according to an embodiment of the invention;

[0020] Figure 4 schematically depicts a module in accordance with an embodiment of the present invention;

[0021] Figure 5 schematically depicts an alternative module to that shown in Figure 4, according to an embodiment of the invention;

[0022] Figure 6a schematically depicts another alternative module to that of Figures 4 and 5, according to an embodiment of the invention;

[0023] Figure 6b schematically depicts a cross-section of the barrier structure shown in Figure 6a, according to an embodiment of the invention;

[0024] Figure 7 schematically depicts a cross-section of yet another alternative module to that of Figures 4, 5 and 6a-b, according to an embodiment of the invention; and

[0025] Figure 8 schematically depicts a cross-section of a modification of the module of Figure 7, according to an embodiment of the invention.

[0026] The features and advantages of embodiments of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.

DETAILED DESCRIPTION

[0027] This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodiment(s) merely exemplify the invention. The scope of the invention is not limited to the disclosed embodiment(s). The invention is defined by the clauses appended hereto.

[0028] The embodiment(s) described, and references in the specification to "one embodiment", "an embodiment", "an example embodiment", etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0029] Before describing such embodiments in more detail, however, it is instructive to present an example environment in which embodiments of the present invention may be implemented.

[0030] Figure 1 schematically depicts a lithographic apparatus 100 including a source collector module SO according to one embodiment of the invention. The apparatus includes: an illumination system (sometimes referred to as an 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 MA; 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 W; 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. including one or more dies) of the substrate W.

[0031] The illumination system IL 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.

[0032] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA, the design of the lithographic apparatus 100, and other conditions, such as for example whether or not the patterning device MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device MA. The support structure MT may be a frame or a table, for example, which may be fixed or movable as required. The support structure MT may ensure that the patterning device MA is at a desired position, for example with respect to the projection system PS.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] As here depicted, the apparatus is of a reflective type (e.g. employing a reflective mask).

[0037] 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.

[0038] Referring to Figure 1, the illumination system IL receives an extreme ultra violet (EUV) 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 (Xe), lithium (Li), or tin (Sn), 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 CO2 laser is used to provide the laser beam for fuel excitation.

[0039] 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 including, 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.

[0040] The illumination system IL may include an adjuster for adjusting the angular intensity distribution of the radiation beam B. 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 illumination system IL can be adjusted. In addition, the illumination system IL may include various other components, such as facetted field and pupil mirror devices. The illumination system may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

[0041] 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.

[0042] 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 B 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 (e.g. in the X or Y direction) 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.

[0043] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

[0044] 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 (DPP) source. EUV radiation may be produced by a gas or vapour, for example Xe gas, Li vapour or Sn vapour 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 creating an at least partially ionized plasma. Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapour or any other suitable gas or vapour may be required for efficient generation of the radiation. In an embodiment, a plasma of excited tin (Sn) is provided to produce EUV radiation.

[0045] The radiation emitted by the 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.

[0046] The collector chamber 212 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 SO 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. Before passing through the opening 221, the radiation may pass through an optional spectral purity filter SPF. In other embodiments, the spectral purity filter SPF may be located in a different part of the lithographic apparatus (e.g. outside of the source collector module SO).

[0047] 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.

[0048] 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 reflective elements (e.g. mirrors or the like) 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.

[0049] Collector 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 CO of this type may be used in combination with a discharge produced plasma source, often called a DPP source.

[0050] Alternatively, the source collector module SO may be part of, include or form an LPP radiation system as shown in Figure 3. Referring to Figure 3, a laser LA is arranged to deposit laser energy into a fuel, such as a droplet or region or vapour of 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 210, collected by a near normal incidence collector CO and focused onto the opening 221 in the enclosing structure 220. Before passing through the opening 221, the radiation may pass through an optional spectral purity filter SPF. In other embodiments, the spectral purity filter SPF may be located in a different part of the lithographic apparatus (e.g. outside of the source collector module SO).

[0051] The LPP and DPP radiation sources discussed above are known to generate contamination (in the form of particles or the like), and this contamination may have a flight path which coincides with a path of radiation generated by the radiation sources.

It is desirable to reduce or eliminate this contamination, and thus reduce the risk of the contamination passing through the lithographic apparatus and onto optical elements or the like of the lithographic apparatus. Reducing or eliminating the contamination will reduce the risk of the optical elements of the lithographic apparatus becoming damaged or degraded by that contamination, and thus degrading the optical performance of the lithographic apparatus as a whole.

[0052] Figure 4 depicts a module in accordance with an embodiment. The module may be a plasma radiation source arranged to generate an EUV-emitting plasma at a first focal point 9. The module includes a normal-incidence collector mirror 1 constructed and arranged to reflect radiation 2 emitted from first focal point 9 to a second focal point 3, which is often also referred to as the intermediate focus (IF). The module also includes a barrier structure 4 including one or more conically-shaped elements having several surfaces 4’. In the embodiment of Figure 4, the conically-shaped elements are concentrically positioned with respect to each other. These surfaces 4’ are oriented to allow radiation emitted from the first focal point 9 to substantially transmit through the barrier structure 4 to the second focal point 3. Also, the surfaces 4’ are constructed and arranged to intercept particles directly emanating from the first focal point 9.

[0053] In this embodiment, the surfaces 4’ are oriented to allow radiation emitted from the first focal point 9 to substantially transmit through the barrier structure to the second focal point 3. However, as an alternative, the surfaces may be oriented to allow radiation emitted from the first focal point to the second focal point 3 to substantially transmit through the barrier structure from the second focal point 3 to another part of a lithographic apparatus.

[0054] Figures 5 and 6a depict embodiments which are similar to the embodiment depicted by Figure 4. Both the embodiments of Figure 5 and Figure 6a include a solid obscuration 8 for the central area. Figure 6b depicts a cross-section of the module of Figure 6a.

[0055] Figure 7 schematically depicts a cross-section of yet another alternative embodiment. A cross-section of the EUV-radiation emitted by the plasma is indicated with reference numeral 11. Instead of conically-shaped elements, radial vanes 10 are employed, in this embodiment extending from the central obscuration 8.

[0056] Figure 8 schematically depicts a cross-section of a modification of the module of Figure 7. In this modification, additional vanes 12 are provided to the barrier structure in order to compensate the effect that the vanes extending from the central obscuration 8 are further apart at a long distance from the central obscuration 8 than they are at a close distance from it.

[0057] In other embodiments (not shown), more than one barrier structure may be provided. In other embodiments (not shown), one or more barrier structure may provide one or more regions of radiation for suppressing contamination. The may be positioned in the source near the intermediate focus of a lithographic apparatus, or in an illuminator near the intermediate focus of the lithographic apparatus. Alternatively or additionally, the barrier structure may be located near a mask table upstream or downstream in an optical path of the radiation emitted by EUV-plasma.

[0058] 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.

[0059] 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.

[0060] 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.

Conclusion

[0061] It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the clauses. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended clauses in any way.

[0062] Embodiments of the present invention have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0063] The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.

[0064] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following clauses and their equivalents. Other aspects of the invention are set out as in the following numbered clauses: 1. A module comprising a normal-incidence collector mirror constructed and arranged to reflect radiation emitted from a first focal point to a second focal point, a barrier structure comprising one or more surfaces, the surfaces being oriented to allow radiation emitted from the first focal point to substantially transmit through the barrier structure to the second focal point and/or to allow radiation emitted from the first focal point to the second focal point to substantially transmit through the barrier structure from the second focal point, the surfaces further being constructed and arranged to intercept particles directly emanating from the first focal point.

2. The module according to clause 1, wherein the module is a plasma radiation source arranged to generate an EUV-emitting plasma at the first focal point.

3. The module according to clause 1 or clause 2, wherein the barrier structure comprises one or more conically-shaped elements.

4. The module according to clause 3, wherein one or more of the surfaces are surfaces of the conically-shaped elements.

5. The module according to clause 3 or 4, wherein the conically-shaped elements are concentrically positioned with respect to each other.

6. A lithographic projection apparatus comprising a module according to any one of the preceding clauses.

7. A module comprising a normal-incidence collector mirror constructed and arranged to reflect radiation emitted from a first focal point to a second focal point, and a barrier structure comprising one or more surfaces, the surfaces being oriented to at least one of allow radiation emitted from the first focal point to substantially transmit through the barrier structure to the second focal point and to allow radiation emitted from the first focal point to the second focal point to substantially transmit through the barrier structure from the second focal point, the surfaces further being constructed and arranged to intercept particles directly emanating from the first focal point.

8. The module according to clause 7, wherein the module is a plasma radiation source arranged to generate an EUV-emitting plasma at the first focal point.

9. The module according to clause 7, wherein the barrier structure comprises one or more conically-shaped elements.

10. The module according to clause 9, wherein one or more of the surfaces are surfaces of the conically-shaped elements.

11. The module according to clause 9, wherein the conically-shaped elements are concentrically positioned with respect to each other.

12. A lithographic projection apparatus comprising a module according to clause 7.

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.