NL2006106A - Lithographic apparatus. - Google Patents

Description

LITHOGRAPHIC APPARATUS

FIELD

[0001] The present invention relates 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):

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, /n 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 K, by increasing the numerical aperture NA or by decreasing the value of/ci.

[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.

SUMMARY OF INVENTION

[0008] In an aspect of the present invention, there is provided a lithographic apparatus which obviates or mitigates a problem of the prior art, whether identified herein or elsewhere, or provides an alternative to an existing lithographic apparatus.

[0009] According to an aspect of the invention, there is provided a lithographic apparatus including: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate; and a contaminant barrier arrangement configured to provide a region of radiation in a flight path of contamination, in order to reduce an amount of contamination passing from a first region of the lithographic apparatus to a second region of the lithographic apparatus.

[00010] The region of radiation may be configured to at least partially evaporate contamination, at least partially vaporize contamination, at least partially explode contamination, and/or at least partially deflect radiation.

[00011] The first region of the lithographic apparatus may be upstream of a part of the projection system and/or the illumination system, and the second region of the lithographic apparatus may be or include of a part of the projection system and/or the illumination system.

[00012] The first region of the lithographic apparatus may be located in a radiation source configured to provide the radiation beam.

[00013] The region of radiation may be located upstream and/or downstream of an intermediate focus of the lithographic apparatus.

[00014] The region of radiation may be adjacent to an intermediate focus of the lithographic apparatus, or may traverse an intermediate focus of the lithographic apparatus.

[00015] The region of radiation may traverse a cross-section of the radiation beam.

[00016] The contaminant barrier arrangement may include a laser cavity, or a laser beam.

[00017] The contaminant barrier arrangement may be configured to provide a region of radiation having a power of between 0.1 kW and 10kW.

[00018] The contaminant barrier arrangement may be configured to provide a region of radiation having a wavelength of between 100nm and 20,000nm.

[00019] The contaminant barrier arrangement may be configured to provide a region of radiation that extends in a direction of flight of the contamination.

[00020] The contaminant barrier arrangement may be configured to provide a region of radiation that extends in a direction of flight of the contamination over a distance of between 0.5 cm and 10 cm.

[00021] The lithographic apparatus may include, or be in connection with a radiation source.

[00022] The lithographic apparatus may include, or be in connection with an LPP radiation source, or a DPP radiation source.

[00023] The radiation beam may include of radiation having a wavelength in the EUV part of the electromagnetic spectrum, such as a wavelength in the range of 5-20nm, in the range of 13-14nm, in the range of 6-7nm, or in the range of 6.6-6.9nm.

[00024] According to an aspect of the invention, there is provided a radiation source, including:an arrangement for providing a beam of radiation; and a contaminant barrier arrangement configured to provide a region of radiation in a flight path of contamination, in order to reduce an amount of contamination passing from a first region to a second region. The first region may be located within the radiation source, and the second region may be located outside of the radiation source.

[00025] The second aspect of the invention may include one or more additional features of the first aspect of the invention, where appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

[00026] 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:

[00027] Figure 1 schematically depicts a lithographic apparatus according to an embodiment of the invention;

[00028] 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 in accordance with an embodiment of the invention;

[00029] 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 (LPP) source collector module in accordance with an embodiment of the invention;

[00030] Figure 4 schematically depicts part of a radiation source, and also a contaminant barrier arrangement in accordance with an embodiment of the present invention;

[00031] Figure 5 schematically depicts an alternative contaminant barrier arrangement to that shown in Figure 4 in accordance with an embodiment of the invention; and

[00032] Figure 6 schematically depicts an alternative view of the contaminant barrier arrangement of Figure 4 or Figure 5 in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

[00033] 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 patterning device support or 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.

[00034] 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, to direct, shape, or control radiation.

[00035] The patterning device support 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 patterning device support MT can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device MA. The patterning device support MT may be a frame or a table, for example, which may be fixed or movable as required. The patterning device support MT may ensure that the patterning device MA is at a desired position, for example with respect to the projection system PS.

[00036] 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.

[00037] 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.

[00038] 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.

[00039] As here depicted, the apparatus is of a reflective type (e.g. employing a reflective mask).

[00040] 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.

[00041] 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, 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 CO2 laser is used to provide the laser beam for fuel excitation.

[00042] 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.

[00043] 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.

[00044] The radiation beam B is incident on the patterning device (e.g. mask) MA, which is held on the patterning device support (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 M1, M2 and substrate alignment marks P1, P2.

[00045] The depicted apparatus could be used in at least one of the following modes: 1. In step mode, the patterning device support (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 patterning device support (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 patterning device support (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 patterning device support (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.

[00046] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

[00047] 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.

[00048] 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.

[00049] 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).

[00050] 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 patterning device support 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.

[00051] 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.

[00052] 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 is preferably used in combination with a discharge produced plasma source, often called a DPP source.

[00053] 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).

[00054] 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.

[00055] According to an embodiment of the present invention, the problems discussed above can be obviated or mitigated by the inclusion in the lithographic apparatus (or the radiation source itself, or between the radiation source and the lithographic apparatus) of a contaminant barrier arrangement configured to provide a region of radiation in the flight path of the contamination. The region of radiation is arranged to reduce an amount of contamination passing from a first region of the lithographic apparatus to a second region of the lithographic apparatus (or other regions, for example from within a radiation source to outside of that radiation source, or the like). The region of radiation may be configured to at least partially evaporate contamination, at least partially vaporize contamination, at least partially explode contamination, and/or at least partially deflect radiation, in order to reduce the amount of contamination passing from a first region of the lithographic apparatus to a second region of the lithographic apparatus. Deflection, for example, may prevent contamination from passing through an aperture, through which the radiation beam may pass.

[00056] The first region of the lithographic apparatus may be, for example, upstream of the projection system of the lithographic apparatus. The second region of the lithographic apparatus may be, for example, the projection system and/or illumination system itself, or a part thereof. Alternatively or additionally, the first region of the lithographic apparatus may be located in a radiation source configured to provide the radiation beam. Such arrangements may reduce or eliminate an amount of contamination entering the projection system and/or illumination system of the lithographic apparatus, and thus reduce the risk of such contamination damaging or degrading the sensitive optical elements located in the projection system and/or illumination system.

[00057] The region of radiation provided, in use, by the contaminant barrier arrangement may traverse a cross-section of the radiation beam. This will ensure that any contamination having a flight path that coincides with a beam path of the radiation beam will pass through the region of radiation. The region of radiation may be located upstream and/or downstream of an intermediate focus of the lithographic apparatus. Preferably, the region of radiation is adjacent to an intermediate focus of the lithographic apparatus, and/or traverses an intermediate focus of the lithographic apparatus. A cross-section of the radiation beam passing through the lithographic apparatus might be smaller adjacent to the intermediate focus, or at the intermediate focus, than the cross-section might be at other points in the lithographic apparatus. The smaller cross-section of the radiation beam adjacent to or at the intermediate focus means that a smaller region of radiation provided by the contaminant barrier arrangement is required to traverse that cross-section. This may result in space savings, and/or costs savings for the contaminant barrier arrangement.

[00058] The contaminant barrier arrangement may be or include of any appropriate radiation generation arrangement that is sufficient to reduce or eliminate the contamination. For example, the contaminant barrier arrangement may be or include of one or more lasers, laser cavities, or laser beams. The region of radiation may be arranged to include of radiation having a wavelength of, for example, between 100 nm and 20,000 nm. The region of radiation may have a (radiative) power of between 0.1 kW and 10 kW. The region of radiation may have a different radiative power. The region of radiation will preferably extend in the direction of flight of the contamination, for example over a distance of 0.5 cm and 10 cm, so that the contamination has a flight time in the region of radiation that is sufficient to ensure that the contamination (or a proportion thereof) is sufficiently suppressed, for example due to appropriate vaporization, evaporation, explosion, or deflection of the contamination.

[00059] The contaminant barrier may be used in conjunction with any appropriate contamination. The contamination may be generated by a radiation source. The radiation source may be, for example, an LLP source or a DPP source, both of which are well known to generate contamination as well as radiation. The contamination might include tin, often used in an LLP source or a DPP source.

[00060] The contaminant barrier may find use in a lithographic apparatus, a radiation source, or in between a radiation source and a lithographic apparatus.

[00061] Specific embodiments of the present invention will now be described, with reference to Figures 4-6. In these Figures, like features are given like reference numerals for consistency and clarity. The Figures have not been drawn to scale. The embodiments are given by way of example only.

[00062] Figure 4 schematically depicts a normal incidence collector 300, for example, the collector shown above in relation to Figure 3. Radiation 302 is collected and directed by the collector 300 to an intermediate focus 304. A contaminant barrier arrangement consisting of a laser cavity 306 traverses the radiation 302 at a point adjacent to, and upstream of (in terms of the propagation of the radiation 302), the intermediate focus 304. In this embodiment, the amount of contamination passing to, through and beyond the intermediate focus 304 may thus be reduced by the presence of the contaminant barrier arrangement consisting of the laser cavity 306.

[00063] In this embodiment, the first region of the lithographic apparatus, as discussed above, may be the radiation source, or a part thereof, including the collector 300 and a radiation emission point or the like. A second region of the lithographic apparatus, as discussed above, may be outside of the radiation source, may be the intermediate focus 304 itself, a (downstream) illumination system, and/or a (downstream) projection system of the lithographic apparatus.

[00064] Figure 5 shows a similar arrangement to that shown in Figure 4. Flowever, in Figure 5 a contaminant barrier arrangement takes the form of one or more laser cavities 308 which substantially surrounds the intermediate focus 304. In an alternative embodiment (not shown), a laser cavity may be located upstream of the intermediate focus 304 and downstream of the intermediate focus 304. In either embodiment, multiple regions of radiation are thus provided for suppressing the contamination.

[00065] Figure 6 shows a cross sectional view through a region of radiation provided by a contaminant barrier arrangement consisting of a laser cavity as shown in Figure 4 or Figure 5, at a point where the region of radiation traverses the radiation beam provided by a radiation source.

[00066] The laser cavity 306, 308 is shown as traversing a cross-section 310 of the beam of radiation in the vicinity of (e.g. adjacent to) the intermediate focus 304. It can be seen that the region of radiation provided by the laser cavity 306,308 extends entirely across the cross-section of the radiation beam 310, thus ensuring that any contamination having a flight path which coincides with the beam path of the radiation beam will also pass through the region of radiation and thus be appropriately vaporized, evaporated, exploded, or deflected.

[00067] In order to sufficiently vaporize contamination, the beam of radiation provided by any contaminant barrier arrangement will need to provide an amount of energy which is sufficient to vaporize the contamination. In another embodiment, total vaporization (or even vaporization in general) may not be required. However, in order to provide evidence of the potential effectiveness of the present invention, a table (TABLE 1) is included below which demonstrates that for a tin contaminant particle (which may be generated by an LLP or DPP radiation source which uses tin droplets, vapour or liquid or the like to generate a plasma) a laser cavity is able to provide sufficient vaporization energy to vaporize a tin particulate contaminant having typical dimensions.

TABLE 1

[00068] It can be seen that from the table that the vaporization energy that may be provided (5.00x1010J) exceeds the vaporization energy that may be required (1.79x1011J) to totally vaporize the tin particle.

[00069] In other embodiments (not shown), more than one contaminant barrier may be provided. In other embodiments (not shown), one or more contaminant barriers may provide one or more regions of radiation for suppressing contamination.

[00070] 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 1C, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[00071] 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 lithographic apparatus comprising: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate; and a contaminant barrier arrangement configured to provide a region of radiation in a flight path of contamination, in order to reduce an amount of contamination passing from a first region of the lithographic apparatus to a second region of the lithographic apparatus.

2. The lithographic apparatus of clause 1, wherein the region of radiation is configured to at least partially evaporate contamination, at least partially vaporize contamination, at least partially explode contamination, and/or at least partially deflect radiation.

3. The lithographic apparatus of any preceding clause, wherein the first region of the lithographic apparatus is upstream of a part of the projection system and/or the illumination system, and the second region of the lithographic apparatus comprises a part of the projection system and/or the illumination system.

4. The lithographic apparatus of any preceding clause, wherein the first region of the lithographic apparatus is located in a radiation source configured to provide the radiation beam.

5. The lithographic apparatus of any preceding clause, wherein the region of radiation is located upstream and/or downstream of an intermediate focus of the lithographic apparatus.

6. The lithographic apparatus of any preceding clause, wherein the region of radiation is adjacent to an intermediate focus of the lithographic apparatus, or traverses an intermediate focus of the lithographic apparatus.

7. The lithographic apparatus of any preceding clause, wherein the region of radiation traverses a cross-section of the radiation beam.

8. The lithographic apparatus of any preceding clause, wherein the contaminant barrier arrangement comprises a laser cavity, or a laser beam.

9. The lithographic apparatus of any preceding clause, wherein the contaminant barrier arrangement is configured to provide a region of radiation having a power of between 0.1 kW and 10kW.

10. The lithographic apparatus of any preceding clause, wherein the contaminant barrier arrangement is configured to provide a region of radiation having a wavelength of between 100nm and 20,000nm.

11. The lithographic apparatus of any preceding clause, wherein the contaminant barrier arrangement is configured to provide a region of radiation that extends in a direction of flight of the contamination.

12. The lithographic apparatus of any preceding clause, wherein the contaminant barrier arrangement is configured to provide a region of radiation that extends in a direction of flight of the contamination over a distance of between 0.5 cm and 10 cm.

13. The lithographic apparatus of any preceding clause, wherein the lithographic apparatus comprises, or is in connection with a radiation source.

14. The lithographic apparatus of any preceding clause, wherein the lithographic apparatus comprises, or is in connection with an LPP radiation source, or a DPP radiation source.

15. The lithographic apparatus of any preceding clause, wherein the radiation beam comprises radiation having a wavelength in the EUV part of the electromagnetic spectrum.

16. The lithographic apparatus of clause 15, wherein the radiation beam has a wavelength in the range of 5-20nm, in the range of 13-14nm, in the range of 6-7nm, or in the range of 6.6-6.9nm.

17. A radiation source, comprising: an arrangement configured to provide a beam of radiation; and a contaminant barrier arrangement configured to provide a region of radiation in a flight path of contamination, in order to reduce an amount of contamination passing from a first region to a second region.

18. The radiation source of clause 17, wherein the first region is located within the radiation source, and the second region is located outside of the radiation source.

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.