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  • 专利说明
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    • 专利摘要:

    公开号:NL2013246A
    申请号:NL2013246
    申请日:2014-07-24
    公开日:2015-03-02
    发明作者:Oscar Noordman；Markus Eurlings
    申请人:Asml Netherlands Bv；
    IPC主号:
    专利说明:

    RADIATION SOURCE AND LITHOGRAPHIC APPARATUS
    FIELD
    [0001] The present invention relates to a radiation source and 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 isalternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to beformed 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 ofthe pattern is typically via imaging onto a layer of radiation-sensitive material (resist) providedon the substrate. In general, a single substrate will contain a network of adjacent target portionsthat are successively patterned.
    [0003] Lithography is widely recognized as one of the key steps in the manufacture of ICsand other devices and/or structures. However, as the dimensions of features made usinglithography become smaller, lithography is becoming a more critical factor for enablingminiature IC or other devices and/or structures to be manufactured.
    [0004] A theoretical estimate of the limits of pattern printing can be given by the Rayleighcriterion for resolution as shown in equation (1):
    where λ is the wavelength of the radiation used, NA is the numerical aperture of the projectionsystem used to print the pattern, k is a process dependent adjustment factor, also called theRayleigh constant, and CD is the feature size (or critical dimension) of the printed feature. Itfollows from equation (1) that reduction of the minimum printable size of features can beobtained in three ways: by shortening the exposure wavelength A, by increasing the numericalaperture NA or by decreasing the value of k.
    [0005] In order to shorten the exposure wavelength and, thus reduce the minimum printablesize, 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 examplewithin the range of 13-14 nm, for 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 sources, discharge plasma 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 producingEUV radiation may include a laser source for exciting a fuel to provide the plasma, and a sourcecollector module for containing the plasma. The plasma may be created, for example, bydirecting a laser beam at a fuel, such as droplets of a suitable material (e.g., tin), or a stream of asuitable 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 maybe a mirrored normal incidence radiation collector, which receives the radiation and focuses theradiation into a beam. The source collector module may include an enclosing structure orchamber arranged to provide a vacuum environment to support the plasma. Such a radiationsystem is typically termed a laser produced plasma (LPP) source.
    [0007] Another known method of producing EUV radiation is known as dual laser pulsing(DLP). In the DLP method droplets are pre-heated, for instance by a neodymium-doped yttriumaluminium garnet (Nd:YAG) laser to cause the droplet (e.g., a tin droplet) to decompose intovapor and small particles that are then heated to a very high temperature by a CO2 laser.
    [0008] In known methods such as LPP and DLP methods, a stream of droplets is generated.The droplets may be generated as either a continuous stream or in pulses.
    [0009] For example, in one known method that is used in particular for LPP methods, aheated container is filled with molten tin that passes from the container to a capillary via a filterand a piezoelectric actuator. A continuous jet exits from the end of the capillary that ismodulated in velocity by the piezoelectric actuator. During flight, this jet decomposes into smalldroplets and due to the modulated velocity, these smaller droplets merge into larger dropletsspaced at larger distances.
    [0010] The laser beam that pre-heats the droplet to cause the droplet to decompose into vaporand small particles may be slightly misaligned with respect to the droplet it pre-heats. Such slightmisalignment may cause further misalignment when the CO2 laser heats the vapor and the smallparticles to the very high temperature. Such further misalignment may be detrimental to theamount of EUV radiation emitted by the resulting plasma.
    SUMMARY
    [0011] According to an aspect of the invention, there is provided a radiation source thatincludes a nozzle configured to direct a stream of fuel droplets along a droplet path towards aplasma formation location. The radiation source is configured to receive a gaussian radiationbeam having gaussian intensity distribution, having a predetermined wavelength and propagatingalong a predetermined trajectory. The radiation source is further configured to focus theradiation beam on a fuel droplet at the plasma formation location. The radiation source includesa phase plate structure comprising one or more phase plates. The phase plate structure has a firstzone and a second zone. The zones are arranged such that radiation having the predeterminedwavelength passing through the first zone and radiation having the predetermined wavelengthpassing through the second zone propagate along respective optical paths having different opticalpath lengths. A difference between the optical path lengths between the radiation passingthrough the first zone and the radiation passing through the second zone is an odd number oftimes half the predetermined wavelength when the radiation passing through the first zone andthe radiation passing through the second zone hit one of the fuel droplets at the plasma formationlocation.
    [0012] An effect of this aspect is that it offers the possibility to adjust a profile of theradiation beam such that, at the plasma formation location, the profile is flatter and wider.
    [0013] Increasing the tolerance in the alignment requirement for the radiation beam withrespect to the droplet may solve the issue that a slight misalignment will be detrimental to theamount of EUV radiation emitted.
    [0014] The radiation passing through the first zone and the radiation passing through thesecond zone may be different parts of the gaussian radiation beam. The radiation passing throughthe first zone may include at least a top of the intensity distribution. The radiation passingthrough the second zone may be located at a distance from a top of the intensity distribution,which may offer the possibility of bringing at least part of the sides of the curve of the gaussiandistribution in antiphase with the top of the intensity distribution [0015] According to an aspect of the invention, the phase plate structure includes two phaseplates, at least one of the phase plates including at least a first area and a second area, whereinradiation having the predetermined wavelength passing through the first area and radiationhaving the predetermined wavelength passing through the second area propagate along respective optical paths, a difference between the optical path lengths between the radiationpassing through the first area and the radiation passing through the second area being an oddnumber of times half the predetermined wavelength at a location on the trajectory of theradiation beam downstream relative to the phase plate.
    [0016] According to an aspect of the invention, the phase plate structure includes two phaseplates, at least two of the phase plates including at least a first area and a second area, whereinradiation having the predetermined wavelength passing through the first area and radiationhaving the predetermined wavelength passing through the second area propagate alongrespective optical paths, a difference between the optical path lengths between the radiationpassing through the first area and the radiation passing through the second area being an oddnumber of times half the predetermined wavelength at a location on the trajectory of theradiation beam downstream relative to the phase plate.
    [0017] The one or more phase plates may be made of ZnSe and/or ZnS.
    [0018] Further features and advantages as well as the structure and operation of variousembodiments are described in detail below with reference to the accompanying drawings. It isnoted that the invention is not limited to the specific embodiments described herein. Suchembodiments are presented herein for illustrative purposes only. Additional embodiments will beapparent to persons skilled in the relevant art(s) based on the teachings contained herein.
    BRIEF DESCRIPTION OF THE DRAWINGS
    [0019] Embodiments of the invention will now be described, by way of example only, withreference to the accompanying schematic drawings in which corresponding reference symbolsindicate corresponding or functionally similar parts, and in which: [0020] Figure 1 schematically depicts a lithographic apparatus according to an embodiment ofthe invention; [0021] Figure 2 depicts a more detailed view of the apparatus of Figure 1 including a sourcecollector module having a normal incidence mirror; [0022] Figure 3 schematically depicts a beam delivery system of the source collector moduleshown in Figure 2; and [0023] Figure 4 schematically depicts a phase plate structure of the beam delivery system ofFigure 4.
    DETAILED DESCRIPTION
    [0024] It is noted that reference in this specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment described may include a particularfeature, structure, or characteristic, but not every embodiment may necessarily include theparticular feature, structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature, structure, or characteristic,is described in connection with an embodiment, it is submitted that it is within the knowledge ofone skilled in the art to effect such feature, stmcture, or characteristic, in connection with otherembodiments whether or not explicitly described.
    [0025] Figure 1 schematically depicts a lithographic apparatus 100 according to anembodiment. The lithographic apparatus includes an EUV radiation source. The apparatuscomprises: 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 apatterning device (e.g., a mask or a reticle) MA and connected to a first positioner PMconfigured to accurately position the patterning device; a substrate table (e.g., a wafer table) WTconstructed to hold a substrate W (e.g., a resist-coated wafer) and connected to a secondpositioner PW configured to accurately position the substrate; and a projection system (e.g., areflective projection system) PS configured to project a pattern imparted to the radiation beam Bby patterning device MA onto a target portion C (e.g., comprising one or more dies) of thesubstrate W.
    [0026] The illumination system may include various types of optical components, such asrefractive, reflective, magnetic, electromagnetic, electrostatic or other types of opticalcomponents, or any combination thereof, for directing, shaping, or controlling radiation.
    [0027] The support structure MT holds the patterning device MA in a manner that depends onthe orientation of the patterning device, the design of the lithographic apparatus, and otherconditions, such as for example whether or not the patterning device is held in a vacuumenvironment. The support structure can use mechanical, vacuum, electrostatic or other clampingtechniques to hold the patterning device. The support structure may be a frame or a table, forexample, which may be fixed or movable as required. The support structure may ensure that thepatterning device is at a desired position, for example with respect to the projection system.
    [0028] The term “patterning device” should be broadly interpreted as referring to any devicethat can be used to impart a radiation beam with a pattern in its cross-section such as to create apattern in a target portion of the substrate. The pattern imparted to the radiation beam maycorrespond to a particular functional layer in a device being created in the target portion, such asan integrated circuit.
    [0029] The patterning device may be transmissive or reflective. Examples of patterningdevices include masks, programmable mirror arrays, and programmable LCD panels. Masks arewell known in lithography, and include mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An example of a programmablemirror array employs a matrix arrangement of small mirrors, each of which can be individuallytilted so as to reflect an incoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirror matrix.
    [0030] The projection system, like the illumination system, may include various types ofoptical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic orother types of optical components, or any combination thereof, as appropriate for the exposureradiation being used, or for other factors such as the use of a vacuum. It may be desired to use avacuum for EUV radiation since other gases may absorb too much radiation. A vacuumenvironment may therefore be provided to the whole beam path with the aid of a vacuum walland vacuum pumps.
    [0031] As here depicted, the apparatus is of a reflective type (e.g., employing a reflectivemask).
    [0032] The lithographic apparatus may be of a type having two (dual stage) or more substratetables (and/or two or more mask tables). In such “multiple stage” machines the additional tablesmay be used in parallel, or preparatory steps may be carried out on one or more tables while oneor more other tables are being used for exposure.
    [0033] Referring to Figure 1, the illuminator IL receives an extreme ultraviolet (EUV)radiation beam from the source collector module SO. Methods to produce EUV radiationinclude, but are not necessarily limited to, converting a material into a plasma state that has atleast 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 desired plasma can beproduced by irradiating a fuel, such as a droplet of material having the desired line-emitting element, with a laser beam. The source collector module SO may be part of an EUV radiationsource 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 aradiation collector, disposed in the source collector module SO.
    [0034] The laser and the source collector module may be separate entities, for example whena CO2 laser is used to provide the laser beam for fuel excitation. In such cases, the radiationbeam is passed from the laser to the source collector module with the aid of a beam deliverysystem comprising, for example, suitable directing mirrors and/or a beam expander. The laserand a fuel supply may be considered to comprise an EUV radiation source.
    [0035] The illuminator TL may comprise an adjuster for adjusting the angular intensitydistribution 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 apupil plane of the illuminator can be adjusted. In addition, the illuminator IL may comprisevarious other components, such as facetted field and pupil mirror devices. The illuminator maybe used to condition the radiation beam, to have a desired uniformity and intensity distribution inits cross-section.
    [0036] The radiation beam B is incident on the patterning device (e.g., mask) MA, which isheld 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 passesthrough the projection system PS, which focuses the beam onto a target portion C of thesubstrate W. With the aid of the second positioner PW and position sensing system PS2 (e.g.,using interferometric devices, linear encoders or capacitive sensors), the substrate table WT canbe moved accurately, e.g., so as to position different target portions C in the path of the radiationbeam B. Similarly, the first positioner PM and another position sensing system PS1 can be usedto accurately position the patterning device (e.g., mask) MA with respect to the path of theradiation beam B. Patterning device (e.g., mask) MA and substrate W may be aligned usingmask alignment marks Ml, M2 and substrate alignment marks PI, P2.
    [0037] The depicted apparatus could be used in at least one of the following modes: [0038] 1. In step mode, the support structure (e.g., mask table) MT and the substrate tableWT 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 tableWT is then shifted in the X and/or Y direction so that a different target portion C can be exposed.
    [0039] 2. In scan mode, the support structure (e.g., mask table) MT and the substrate tableWT are scanned synchronously while a pattern imparted to the radiation beam is projected onto atarget portion C (i.e., a single dynamic exposure). The velocity and direction of the substratetable 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.
    [0040] 3. In another mode, the support structure (e.g., mask table) MT is kept essentiallystationary holding a programmable patterning device, and the substrate table WT is moved orscanned while a pattern imparted to the radiation beam is projected onto a target portion C. Inthis mode, generally a pulsed radiation source is employed and the programmable patterningdevice is updated as required after each movement of the substrate table WT or in betweensuccessive radiation pulses during a scan. This mode of operation can be readily applied tomaskless lithography that utilizes a programmable patterning device, such as a programmablemirror array of a type as referred to above.
    [0041] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.
    [0042] Figure 2 shows the lithographic apparatus 100 in more detail, including the sourcecollector module SO, the illumination system IL, and the projection system PS. The sourcecollector module SO is constructed and arranged such that a vacuum environment can bemaintained in an enclosing structure 220 of the source collector module.
    [0043] A laser source LA is arranged to deposit laser energy via a laser beam 205 into a fuel,such as xenon (Xe), tin (Sn) or lithium (Li) which is provided from a fuel droplet streamgenerator 200 having a nozzle configured to direct a stream of droplets along a path toward aplasma formation location 211. This creates a highly ionized plasma 210 at the plasmaformation location 211 which has electron temperatures of several 10’s of eV. The energeticradiation generated during de-excitation and recombination of these ions is emitted from theplasma, collected and focused by a near normal incidence radiation collector CO. The lasersystem LA and fuel droplet stream generator 200 may together be considered to comprise anEUV radiation source. The EUV radiation source may be referred to as a laser produced plasma(LPP) source.
    [0044] Radiation that is reflected by the radiation collector CO is focused at a virtual sourcepoint IF. The virtual source point IF is commonly referred to as the intermediate focus, and thesource collector module SO is arranged such that the intermediate focus IF is located at or nearto an opening 221 in the enclosing structure 220. The virtual source point IF is an image of theradiation emitting plasma 210.
    [0045] Subsequently the radiation traverses the illumination system IL, which may include afacetted field mirror device 22 and a facetted pupil mirror device 24 arranged to provide adesired angular distribution of the radiation beam 21 at the patterning device MA, as well as adesired uniformity of radiation intensity at the patterning device MA. Upon reflection of thebeam of radiation 21 at the patterning device MA, held by the support structure MT, a patternedbeam 26 is formed and the patterned beam 26 is imaged by the projection system PS viareflective elements 28, 30 onto a substrate W held by the wafer stage or substrate table WT.
    [0046] The laser system LA may be used to preheat the fuel. This is depicted in Figure 3.Figure 3 schematically discloses the laser system LA. The laser source LA comprises two lasersources 301a, 301b constructed and arranged to generate radiation beams 303a, 303b in pulsedform. Main pulse laser source 301a may be configured to generate radiation having a wavelengthof 10.59 pm and pre-pulse laser source 301b may be configured to generate radiation having awavelength of 10.23 pm. Mirror 302a and beam splitter 302b reflect the radiation having awavelength of 10.23 pm as shown in Figure 3.
    [0047] The embodiment of Figure 3 is configured such, that, in use, laser source 301b istriggered first to generate a pulse and, for instance, 1 ps later, the laser source 301a is triggeredto generate a pulse.
    [0048] The laser system LA comprises a beam delivery system 305. The beam deliverysystem 305 includes reflectors 307, 309 and beam splitters 311, 313, 315. The reflectors 307, 309and the beam splitters 311, 313, 315 are configured such that the radiation beam propagatesalong a predetermined main trajectory 317 and a predetermined pre-pulse trajectory 319. Thebeam splitter 311 is configured to reflect radiation having a wavelength of about 10.59 pm andtransmit radiation having a wavelength about 10.23 pm. Thus, pulses generated by laser source301a propagate along trajectory 317 and pulses generated by laser source 301b propagate alongtrajectory 319. Both trajectories 317, 319 pass through focusing unit 320, which focuses theradiation beam at the plasma formation location 211 to hit one of the droplets 322.
    [0049] The beam delivery system 305 of Figure 3 includes a phase plate structure 321, whichis depicted in more detail in Figure 4. The phase plate structure 321 includes a first phase plate323 and a second phase plate 325. Each of the phase plates 323, 325 includes a first area 327,329 and a second area 331, 333. The phase plates 323, 325 are positioned and oriented such thata part of the laser beam 303 propagating along the predetermined pre-pulse trajectory 319propagates through both the first phase plate 323 and the second phase plate 325.
    [00501 Each of the phase plates 323, 325 is constructed and arranged such that radiation fromthe radiation beam 303 passing through the first area 327, 329 and radiation having radiationfrom the radiation beam 303 passing through the second area 331, 333 have a difference inoptical path length. This difference may be an odd number of times half the wavelength of theradiation beam 303. Such a wavelength may be the wavelength of the radiation of the pre-pulselaser source 301b, in this embodiment about 10.23 pm.
    [0051] In Figure 4, a cross-section 335 of the radiation beam 303 is shown. A part of theradiation beam passes through a first zone 337 and another part of the radiation beam passesthrough a second zone 339. As a skilled person will readily acknowledge, this results in a phaseshift that causes the radiation that was transmitted through the first zone 337 to be in antiphasewith respect to the radiation that was transmitted through the second zone 339, if the radiation ofthe radiation beam 303 was in-phase upstream with respect to the phase plate stmcture 321. Thesize of the first zone 337 is determined by the position of the first phase plate 323 and the secondphase plate 325, one or both of which are determined by an actuator system 341 shown in Figure 3.
    [0052] Going back to Figure 3, the final focus metrology unit 343 which provides data 345concerning an intensity profile and a wavefront of the radiation beam 303. A data processingsystem 347 calculates a beam profile near a focus of the combination of the focusing unit 320and beam splitters 313, 315. This may be where the radiation beam passes through the phaseplate structure 321. The data processing system 347 operates the actuator system 341 thatpositions the phase plates 323, 325 with respect to part of the radiation beam that passes alongtrajectory 319.
    [0053] The position of the phase plates 323, 325 is operated in such a way that the beamcross-section in the plasma formation location 211 that propagated along pre-pulse trajectory 319is not gaussian, but has a more flattened profile.
    [0054] In operation, pre-pulse laser source 302b generates a pulse first. The pulse propagatesalong the trajectory 319 through the phase plate structure 321. This causes the wavefront of thepulse to be flattened as explained above. The pulse irradiates a droplet 322 which vaporizes intoa pancake-shaped cloud. Then, the main pulse laser source 302a is triggered and generates apulse which propagates along the trajectory 317 and hits the cloud to generate an EUV-emittingplasma. Γ00551 It should be understood that many variations and modifications are possible withoutdeviating from the invention. Instead of the pre-pulse laser source mentioned above which maybe a CO2 laser, a neodymium-doped yttrium aluminium garnet (Nd:YAG) laser may be usedgenerating radiation having a wavelength of, for instance about 1.064 pm.
    [0056] More elements than shown may generally be present in the illumination system IL andprojection system PS. Furthermore, there may be more mirrors present than those shown in thefigures, for example there may be 1- 6 additional reflective elements present in the projectionsystem PS than shown in Figure 2. One feature of the source collector module SO which isworthy of note is that the laser source is angled which means that the stream of fuel dropletssupplied to the laser source LA should be substantially horizontal to avoid fuel droplets strikingthe collector CO.
    [0057] Although specific reference may be made in this text to the use of lithographicapparatus in the manufacture of ICs, it should be understood that the lithographic apparatusdescribed herein may have other applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories, flat-panel displays,liquid-crystal displays (LCDs), thin-film magnetic heads, LED’s, solar cells, photonic devices,etc. The skilled artisan will appreciate that, in the context of such alternative applications, anyuse of the terms “wafer” or “die” herein may be considered as synonymous with the moregeneral terms “substrate” or “target portion”, respectively. The substrate referred to herein maybe processed, before or after exposure, in for example a track (a tool that typically applies a layerof resist to a substrate and develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such and other substrateprocessing tools. Further, the substrate may be processed more than once, for example in orderto create a multi-layer IC, so that the term substrate used herein may also refer to a substrate thatalready contains multiple processed layers.
    [0058] The term “lens”, where the context allows, may refer to any one or combination ofvarious types of optical components, including refractive, reflective, magnetic, electromagneticand electrostatic optical components.
    [0059] While specific embodiments of the invention have been described above, it will beappreciated that the invention may be practiced otherwise than as described. The descriptionsabove are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in theart that modifications may be made to the invention as described without departing from thescope of the clauses set out below. Other aspects of the invention are set out as in the followingnumbered clauses: 1. A radiation source comprising: a nozzle configured to direct a stream of fuel droplets along a droplet path towards aplasma formation location; the radiation source being configured to receive a gaussian radiation beam havinggaussian intensity distribution, having a predetermined wavelength and propagating along apredetermined trajectory, the radiation source further being configured to focus the radiationbeam on a fuel droplet at the plasma formation location; a phase plate structure comprising one or more phase plates, the phase plate structurehaving a first zone and a second zone, the zones being arranged such that radiation having thepredetermined wavelength passing through the first zone and radiation having the predeterminedwavelength passing through the second zone propagate along respective optical paths havingdifferent optical path lengths, wherein a difference between the optical path lengths between the radiation passingthrough the first zone and the radiation passing through the second zone is an odd number oftimes half the predetermined wavelength when the radiation passing through the first zone andthe radiation passing through the second zone hit one of the fuel droplets at the plasma formationlocation. 2. The radiation source of clause 1, wherein the radiation passing through the first zone andthe radiation passing through the second zone are different parts of the gaussian radiation beam. 3. The radiation source of clause 2, wherein the radiation passing through the first zonecomprises at least a top of the intensity distribution. 4. The radiation source of clause 2 or 3, wherein the radiation passing through the secondzone is located at a distance from a top of the intensity distribution. 5. The radiation source of any preceding clause, wherein the phase plate structure comprisestwo phase plates, at least one of the phase plates comprising at least a first area and a secondarea, wherein radiation having the predetermined wavelength passing through the first area andradiation having the predetermined wavelength passing through the second area propagate alongrespective optical paths, a difference in optical path length between the radiation passing throughthe first area and the radiation passing through the second area being an odd number of timeshalf the predetermined wavelength at a location on the trajectory of the radiation beamdownstream relative to the phase plate. 6. The radiation source of any preceding clause, wherein the phase plate structure comprisestwo phase plates, at least two of the phase plates comprising at least a first area and a secondarea, wherein radiation having the predetermined wavelength passing through the first area andradiation having the predetermined wavelength passing through the second area propagate alongrespective optical paths, a difference between the optical path lengths between the radiationpassing through the first area and the radiation passing through the second area being an oddnumber of times half the predetermined wavelength at a location on the trajectory of theradiation beam downstream relative to the phase plate. 7. The radiation source of clause 6, wherein the at least two phase plates determine thedifference between the optical path lengths between the radiation passing through the first zoneand the radiation passing through the second zone. 8. The radiation source of clause 7, wherein the at least two phase plates are moveable withrespect to the radiation beam in a direction transverse to the radiation beam such that a sizeand/or location of the first zone and/or a size and/or location of the second zone is/are adjustable. 9. The radiation source of any preceding clause, wherein the predetermined wavelength isbetween 9 pm and 11 pm. 10. The radiation source of any preceding clause, wherein the predetermined wavelength isbetween 900 nm and 1100 nm. 11. A radiation system constructed and arranged to generate extreme ultraviolet radiation, theradiation system comprising a radiation source of any preceding clause and a laser source, suchas a CO2 laser source or an yttrium aluminum garnet laser source. 12. The radiation system of any one of clause 11, wherein the radiation system is constructedand arranged to provide a pre-pulse to hit the fuel droplet at the plasma formation location and asubsequent main pulse to hit said fuel droplet at the plasma formation location, after the fueldroplet has been hit by the pre-pulse, to generate an extreme ultraviolet radiation-generatingplasma. 13. The radiation system of clause 12, wherein the radiation system is configured such that,in use, the laser source generates the pre-pulse and the subsequent main pulse. 14. The radiation system of clause 12, wherein the radiation system is configured such that,in use, the laser source generates the pre-pulse and wherein the radiation system comprises afurther laser source, the radiation system being configured such that, in use, the further lasersource generates the main pulse. 15. A lithographic apparatus comprising a radiation source according to any one of thepreceding clauses.
    权利要求:
    Claims (1)
    [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 cross-section of the radiation beam forming 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.
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    法律状态:
    2015-06-10| WDAP| Patent application withdrawn|Effective date: 20150501 |
    优先权:
    申请号 | 申请日 | 专利标题
    US201361870128P| true| 2013-08-26|2013-08-26|
    US201361870128|2013-08-26|
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