US00396984]B2
`
`(12; United States Patent
`Smith
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,969,841 B2
`Mar. 3, 2015
`
`(54) LIGHT SOURCE FOR GENERATING LIGHT
`FROM A LASER SUSTAINED PLASMA IN A
`ABOVE-ATMOSPHERIC PRESSURE
`(j|[AM]}[.jR
`
`(71) Applicant: Encrgctiq Technology, Inc._. Woburn,
`MA (US)
`Inventor: Donald K. Smith, lioslon, MA (US)
`
`(72)
`
`(73) Assignee: Encrgctiq Technology, Int.-., Woburn,
`NIA
`
`[ * ) Notice:
`
`Subject to any disclaimer. the term ofthis
`patent is extended or adjusted under 35
`U.S.(f. l54(h) by 0 days.
`
`.
`(21) App]. No.. 141510.959
`
`(22)
`
`Filed:
`
`mi. 9, 2014
`
`(65)
`
`Prior Publication Data
`
`Us 20] 5,002] 500 A]
`
`Jam 22 201 5
`
`250504 R
`USPC
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U5‘ PATENT D0CUM|'iNTS
`3.826.996 A
`7.-"1974
`Jacgle ct al.
`4.088.966 A
`5.’'l978 % I
`4151525 A
`5.-‘[979 Co:;:(1
`4.179.566 A
`l2fl9T9
`'adelson
`
`4-493.039 A
`4.045.215 .-A
`R].-32.62t3 L
`
`2-{I935 Y0-Sl_1iZaW«'I C1 «'11.
`2-1193'?‘
`LICVIII CI 31.
`3.-1988 Yoshlzawa ct a].
`
`IP
`H,
`
`(comilllledl
`‘
`‘
`,
`‘
`_
`,
`‘
`‘
`,
`‘
`1
`‘
`_
`[-‘URl',l(rN PAI l',N l l)()(.UM[‘,N 15
`61 193358
`851936
`‘£96550
`“H939
`
`(Cmlimu-'d)
`OTHER PUBLICATIONS
`
`Beck, “Simple Pulse (jcncrator for Pulsing Xenon Arcs with High
`Repetition Rate." Rev. Sci‘. {osri'::iii.. vol. 45. No. 2. Feb. 19?’-4. pp.
`
`Related U.S. Application Data
`
`3 '83 '9‘
`
`(Continued)
`
`(63) Continuation of application No. 131964.938. filed on
`Aug. 12. 2013, which is a continuation ofapplication
`No. 13f(l24,()27_. liled on l"eb. 9, 2011, now Pat. No.
`8.525.138. wl1icl1
`is
`a
`continualion-in-part
`til‘
`
`(Continue-id)
`
`(51)
`
`Int‘ Cl‘
`GPIJ 3/10
`('21K 5/04
`(52) U-S-CL
`(-‘PC
`USPC
`(53) Field Of Clasfiificatiflfl S03“-‘ll
`CPC
`H01J 5i'00‘. H01] 61.962; H01] 15100;
`H01 .1 l5;"02;
`[ [05(i 2!'(l0
`
`(200601)
`(200601 )
`
`GZIK 5/040013-()1)
`2501504 R
`
`Primmj-‘ E.rami'r.'er — Nicole Ippolito
`Assistant E.raim'rrer — Jason McCorn1ack
`
`(74) Attorney‘. /Igc’J'i':', or F.I'rm — Proskatler Rose LLP
`
`(57)
`Al}S'l'RA(l'I‘
`An apparatus for producing light includes a chamber and an
`ignition source that ionizes a gas within the chamber. The
`apparatus also includes at least one laser that provides energy
`to the ionized gas within the chamber to produce a high
`hriglitness light. The laser can provide a subslzuilially con-
`linuous amount of energy to the ioniyed gas to generate a
`substantially continuous high brightness light.
`
`30 Claims, 39 Drawing Sheets
`
`116
`
`11?.‘
`
`ASML 1201
`ASML 1201
`
`

`
`US 8,969,841 B2
`Page 2
`
`Related U.S. A]Jp11I:atiI)l'l Data
`
`application No. 127166.918, filed on Jul. 2. 2008, now
`Pat. No. 7,989.786. which is a co11Ii11ua1ion-in-part of
`application No. 1 17695,?-48, filed onApr. 2, 2007, now
`Pat. No. 7.786.455. which is a continuation—in—part of
`application No. 117395.523. filed on Mar. 31, 2006.
`now Pat. No. 7,435,982.
`
`JP
`JP
`JP
`JP
`JP
`JP
`W0
`
`(60) Provisional application No. 617302.797. filed o11 Feb.
`9. 2010.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4.780.608 A "‘
`4.789.788 A
`4.868.458 A
`5.801.495 A
`6.184.517 Bl
`6.288.780 131
`6.417.625 Bl
`6.541.924 131*
`6.788.404 132
`0.956.329 F12
`7.050.149 B2
`7.427.167 132
`7.429.818 132
`7.652.430 131
`200270021508 Al
`200270044-629 Al
`200270080834 Al
`200270172235 A1
`200370052609 A1 "‘
`200370068012 A1
`200370147499 Al '1’
`200370168982 Al
`200370231496 A 1
`200470016894 A 1
`200470026512 Al
`200470129896 Al
`200470183038 Al
`200470238762 A 1
`200470264512 A1
`2005701 676.18 A1
`200570199829 A1
`20057020581] Al
`200570243390 A 1
`200670039435 A 1
`200670131515 A1
`200670152128 Al "
`200670186356 Al
`200670192152 Al‘
`200670219957 Al‘
`200770228288 A1
`200770228300 AI
`200770285921 A1
`200970032740 Al
`
`............ .. 3137634
`
`................. .. 2507281
`
`1071988 Cross et al.
`1271988 Cox
`971989 Davenport et al.
`971998 Smolka et al.
`272001 Sawada
`972001 Fairley et al.
`772002 Brooks et al.
`472003 Kaneci al.
`.................. .. 3157246
`972004 Lange
`1072005 Brooks et al.
`572006 Owa et al.
`972008 Ilolder et al.
`972008 Chang et al.
`172010 Delgado
`272002 Ishiliara
`472002 Hen‘). el al.
`672002 Kusunose
`1172002 Changeta].
`372003 Eastlllnd et a].
`472003 Ahmad et al.
`872003 Kondo ........................ .. 3787119
`972003 Kim
`1272003 Sato et al.
`172004 Westcr
`272004 Otsuho
`772004 Schinidtetal.
`972004 Hiramoto etal.
`1272004 Mizoguchieta].
`1272004 tlartlove ct al.
`872005 Iloshino eta].
`972005 Partloet al.
`972005 Parlloet al.
`1172005 Tejnil
`272006 Cheymol etal.
`672006 1-‘artlo et al.
`772006 Manning 3137113
`872006 lamiet al.
`872006 Ershovetal.
`1072006 Ershov et al.
`1072007 Smith
`1072007 Srnilh
`1272007 Zulim et al.
`272009 Smith et al.
`
`250.-’503.1
`........... .. 2507504 R
`
`1'-‘()Rl".lGN PA'1‘lF.N'l‘ DOCU IV1ljN'l'S
`
`04-144053
`05-82087
`08—299951
`09—288995
`2006- 10675
`2006-080255
`20107093903
`
`571992
`471993
`1171996
`1171997
`172006
`3.-"2006
`8.-"2010
`
`OTHER PUB LICATIONS
`
`Bussiahn. R.. et. al.. “Experimental and theoretical investigations of
`a low—pressure He—Xe discharge for lighting purpose.” Journal ()1
`Applied Physics. vol. 95. No. 9. May 1. 2004. pp. 4627-4634.
`Carlhoff et al.. “Continuous Optical Discharges at Very High Pres-
`sure.“ Physfcvz 103C. 1981. pp. 439-447.
`Crerners et al.. “Evaluation of the Continuous Optical Di scharge for
`Spcctrochemical Analysis.” Sp(?m1oc‘h7a17ca Acre. vol. 4013. No. 4.
`1985. pp. 665-679.
`Fiedorowicv. et al.. "X—Ray Emission form l,aser-1rradia1edGas Pull‘
`'1'a.rgets,” Appl. Phys. Len. 62 (22). May 31. 1993. pp. 2778-2780.
`Franzen. “CW Gas Breakdown in Argon Using 10.6-pm Laser Radia-
`lion." /1',r.7p7'. Phys’. 7.977.. vol. 21. No. 2. Jul. 15. 1972. pp. 62-64.
`Generalov el al.. "Corllinllous Optical Discharge.” 7.71737}-" Pix’. Red.
`11. No. 9. May 5. 1970. pp. 302-304.
`Gerleralov et al., “F.xperi1nental Invest igal ion ofa Corllinuous Opti-
`cal Discharge.” S0171'c.t P7:y.s'7.r.'.\‘ .7E'TP. vol. 34. No. 4. Apr. 1972. pp.
`763-769.
`Harnzunatsu Product Information. “Super-Quiet Xenon Lamp Super-
`Quiet l\71ercury—Xenon lzunp." Nov. 2005. pp. 1-16.
`llecht. "Refraction". Optics (7711'm‘ .[:'d7r7on]. 1998. Chapter 4. pp.
`100-101.
`Jeng et al.. “Tlieolietical Investigation o1'1..a_ser—S11slaine(l Argon Plas-
`mas.”.7. Appl. Phys. 60 (7). Oct. 1. 1986. pp. 2272-2279.
`Keefer el al.. “Experimental Slutty of'a l.aser—S11s1ainer.l Air Plasma.”
`.7r.>m'm17r.gfA,71p77ez7P71)-:v7(.1v. vol. 46. No.3. Mai‘. 1975. pp. 1080-1083.
`Keefer, “Laser-Sustained Plasmas." Laser‘-Iriduced Plasrims and
`App.l'7r.'a1f7r)m'. published by Marcel Dekker. edited by Radziemski el
`al.. 1989. pp. 169-206.
`Kozlov et al.. "Radiative Losses by Argon Plasma and the llmissive
`Mode] ofa Continuous Optical Discharge.” Sov. Phys. .77.-I 77-’. vol. 39,
`No. 3. Sep. 1974. pp. 463-468.
`Kozlov el al.. “Suslairled Optical Discharges in Molecular Gases.”
`Sou Phys. 7i2c71.P71ys.49(l1). Nov. 1979. pp. 1283-1287.
`Moody. "Maintenance 01:1 Gas Breakdown in Argon Using 10.6 -11 cw
`Radiation.” .7om'mz7 0fA'p;)71'ed Phy.w'c.r. vol. 46. No. 6. J11n. 1975. pp.
`2475-2482.
`Nakr. “Radiometric Characterization of Ultrahigh Radiance Xenon
`Short-acr Dichage Lamps”. App77erJ O,r11‘7.L's. vol. 47. No. 2. Jan. 9,
`2008. pp. 224-229.
`Raizer. “Optical Discharges.“ S01: Phys. Usp. 23(11). Nov. 1980. pp.
`789-806.
`Wilbers et al.. “The Continuum Emission of an Arc Plasma." .7’.
`Qmzm. .5-pecmosc. Rad1':z.'. 7l"¢:msfizr'. vo].45. No. 1. 1991. pp. 1-10.
`Wilbcrs ct al.. "The VUV ljrnissivity of a High-Pressure Cascade
`Argon Arc from 125 to 200 nm.”.7'_ Quamt S17er.“1‘:'r).i'(.‘. Radiar. 77'<'m.s'—
`fin‘. vol. 46. 1991. pp. 299-308.
`
`* cited by examiner
`
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`US 8,969,841 B2
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`1
`I.l(}lI'l‘ SOURCE FOR GENERA'l‘[NG LIGIIT
`FROM A LASER SUSTAINED PLASMA IN A
`ABOVE-ATMOSPHERIC PRESSURE
`CHAIVIBER
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`2
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`Accordingly, a need therefore exists for an improved light
`source whose emitted light is not significantly affected when
`the light passes through a wall of a chamber that includes the
`location from which the light is emitted.
`
`RlF.l.A'l‘l.i|') 2\PPl.IC.‘.AT[()NS
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`SUMMARY ()1-‘ Tl'Il"l lNVI€N'l"[()N
`
`This application is a continuation ofU.S. Ser. No. 13.1964,
`938, filed on Aug. 12, 2013, which is a continuation ofU.S.
`Ser. No. 13r’024,027, filed on Feb. 9, 201 1, now U.S. Pat. No.
`8,525,138, which claims the benefit of, and priority to U.S.
`Provisional Patent Application No. 61!’302,797. liled on l"eb.
`9, 2010, the entire disclosure of which is incorporated by
`reference herein, Ser. No. 131024.027 is also a contin1Iation—
`in—part ofU.S. Ser. No. 12! 166.918. filed on Jul. 2, 2008. now
`U.S. Pat. No. 7,989,786, which is a continuation—in—part of
`IJ.S. Ser. No. 1 li’695,348, filed on Apr. 2, 2007. now U.S. Pat.
`No. 7,786,455, which is a continuation-in-part of U.S. Ser.
`No. lli'395,523_. filed oi1 Mar. 31. 2006. now U.S. Pat. No.
`7,435,982, the entire disclosures ofeach of which are hereby
`incorporated by reference herein.
`
`I-‘Il€I..l) O1’ Tlllfi lNV'liN'l'l()N
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`The invention relates to methods and apparatus for provid-
`ing a laser—driven light source.
`
`l3A(.‘KGR()UNl) 01-’ TI [Ii INVl7.NTl()N
`
`High brightness light sources can be used m a variety of
`applications. For example, a high brightness light source can
`be used for inspection, testing or measuring properties asso-
`ciated with semiconductor wafers or 111aterials used in tlie
`fabrication of wafers (e.g.. reticles and photomasks). The
`electromagnetic energy produced by high brightness light
`sources can, alternatively, be used as a source ofillumination
`in a lithography system used in the fabrication of wafers, a
`microscopy system, or a photoresist curing system. The
`parameters (eg, wavelength, power level and brightness) of
`the light vary depending upon the application.
`The state of the an in, for example, wafer inspection sys-
`tems involves the Lise of xenon or mercury arc lamps to
`produce light. Tl1e arc lamps include an anode and cathode
`that are used to excite xenon or mercury gas located in a
`chamber of the lamp. An electrical discharge is generated
`between the anode and cathode to provide power to the
`excited
`ionized) gas to sustain the light emitted by the
`ionized gas during operation of the light source. During
`operation, the anode and cathode become very hot due to
`electrical discharge delivered to the ionized gas located
`between the anode and cathode. As a result. l.l1e anode andi"or
`cathode are prone to wear and may emit particles that can
`contaminate the light source or result in failure of the light
`source. Also. these are lamps do not provide sufficient bright-
`ness for some applications, especially in the ultraviolet spec-
`trum. l’ur1her. the position of the arc can be tmstable in these
`lamps.
`Accordingly, a need therefore exists for improved high
`brightness light sources. A need also exists for improved high
`brightness light sources that do not rely on an electrical dis-
`charge to maintain a plasma that generates a high brightness
`light.
`The properties of light produced by many light sources
`(e.g.. arc lamp s. microwave lamp s) are affected when the light
`pas through a wall of, for example, a chamber that includes
`the location from which the light is emitted.
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`The present invention features a light source for generating
`a high brightness light.
`The invention. in one aspect, features a light source having
`a chamber. The light source also includes an ignition source
`for ionizing a gas within the chamber. The light source also
`includes at least one laser for providing energy to the ionized
`gas within the chamber to produce a high brightness light.
`In some embodiments. the at least one laser is a plurality of
`lasers directed at a region from which the high brightness
`light originates. In some embodiments, the light source also
`includes at least one optical element for modifying a property
`of tile laser energy provided to the ionized gas. The optical
`element can be, for example, a lens [e.g., an aplanatic lens, an
`achromatic lens, a single element lens, and a fresnel lens) or
`mirror (e.g., a coated mirror, a dielectric coated mirror, a
`narrow band mirror, and an ult.raviolet transparent infrared
`reflecting mirror). ln some embodiments, the optical element
`is one or more fiber optic elements [or directing the laser
`energy to the gas.
`The chamber can include an ultraviolet transparent region.
`The chamber or a window in the chamber can include a
`
`material selected from the group consisting of quartz. Supra-
`sil® quartz (Heraeus Quartz America. LLC. Buford, Ga.),
`sapphire, MgF3, diamond, and CaF2. In sortie embodiments,
`the chamber is a sealed chamber. In some embodiments. the
`chamber is capable of being actively pumped.
`in some
`embodiments,
`the chamber includes a dielectric material
`(eg. quartz). The chamber can be. for example, a glass bulb.
`In some embodiments. the chamber is an ultraviolet transpar-
`ent dielectric chamber.
`Xe, Ar, Ne. Kr.
`The gas can be one or more ofa noble
`Ile. D2, I13. 02, 1372, a metal halide, a halogen, llg, Cd, Zn. Sn,
`Ga, Fe. Li. Na. an excimer forming gas. air, a vapor. a metal
`oxide, an aerosol, a flowing media, or a recycled media. The
`gas can be produced by a pulsed laser beam that impacts a
`target (e.g.. a solid or liquid] in the chamber. The target can be
`a pool or film of metal. I11 some embodiments, the target is
`capable of moving. For example. the target may be a liquid
`that is directed to a region from which the high brightness
`light originates.
`In some embodiments. die at least one laser is multiple
`diode lasers coupled into a fiber optic element. In some
`embodiments. the at least one laser includes a pulse or con-
`tinuous wave laser. In some embodiments, the at least one
`laser is a11 IR laser. a diode laser, a fiber laser, tut ytterbium
`laser. a C02 laser, a YAG laser, or a gas discharge laser. In
`some embodiments, the at least one laser emits at least one
`wavelength of electromagnetic energy that
`is strongly
`absorbed by the ionized medium.
`The ignition source can be or can include electrodes, an
`ultraviolet ignition source. a capacitive ignition source. all
`inductive ignition source, an RF ignition source, a microwave
`ignition source, a flash lamp. a pulsed laser. ora pulsed lamp.
`The ignition source can be a continuous wave (CW) or pulsed
`laser impinging on a sol id or liquid target in the chamber. The
`ignition source can be extemal or internal to the chamber.
`The light source can include at least one optical element for
`modifying a property ofelectromagnetic radiation emitted by
`the ionized gas. The optical element can be. for example. one
`or more mirrors or lenses. In some embodiments, the optical
`
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`US 8,969,841 B2
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`element is configured to deliver the electromagnetic radiation
`emitted by the ionized gas to a tool (e.g., a wafer inspection
`tool, a microscope, at tnetrology tool. a lithography tool. or an
`endoscopic tool).
`in another aspect, relates to a method for
`The invention.
`producing light. The method involves ionizing with an ig11i-
`tion source a gas within a chamber. The method also involves
`providing laser energy to the ionized gas in the chamber to
`produce a high brightness light.
`In some embodiments, the method also involves directing
`the laser e11ergy through at least one optical element for
`modifying a property of the laser energy provided to the
`ionized gas. In some embodiments. the method also involves
`actively pumping the chamber. The ionizable medium can be
`a moving target. In some embodiments, the method also
`involves directing the high brightness light through at least
`one optical element to modify a property ofthe ligltt. In sonte
`embodiments, the method also involves delivering the high
`brightness light emitted by the ionized n1ediLu11 to a tool (e.g.,
`a wafer inspection tool. a microscope. a metrology tool. a
`litltograplty tool, or an endoscopic tool).
`In another aspect, the invention features a ligltt source. The
`lights source includes a chamber and an ignition source for
`ionizing an ionizable medium wil.hin the chamber. The light
`source also includes at least one laser for providing sttbstan-
`tially continuous energy to the ionized medium within the
`chamber to produce a high brightness ligltt.
`In solne embodiments, the at least one laser is a continuous
`wave laser or a high pulse rate laser. I11 some embodiments,
`the at least one laser is a high pulse rate laser that provides
`pulses ofenergy to the ionized medium so the high brightness
`light is substantially continuous. In some embodiments, the
`magnitttde ofthe high brightness light does not vary by n1o1‘e
`than about 90% during operation. [11 some embodiments, tl1e
`at least one laser provides energy substantially continuously
`to minimize cooling of the ionized medium when energy is
`not provided to the ionized medium.
`In some embodiments, the light source can include at least
`one optical element (e.g.. a lens or minor) for modifying a
`property oftlte laser energy provided to the ionized medium.
`The optical element can be, for example, an aplanatic lens, an
`achromatic lens, a single element lens. a fresnel lens. a coated
`mirror, a dielectric coated mirror, a nanow band mirror. or an
`ultraviolet transparent
`infrared reflecting mirror.
`In some
`embodiments. the optical eletnent is one or more fiber optic
`elements for directing the laser energy to the ionizable
`medium.
`In some elnbodiments, the chamber includes an ultraviolet
`transparent region. In some embodiments, the chamber or a
`window i11 the chamber includes a quartz material, suprasil
`quartz material, sapphire material, MgF2 material, diamond
`material, or (.'aF2 material. In some embodiments, the cham-
`ber is a sealed chamber. The chamber can be capable ofheing
`actively pumped.
`In sonte embodiments,
`the chamber
`includes a dielectric material (e.g.. quartz). In some embodi-
`ments, the chamber is a glass bulb. ln son1e embodiments, the
`chamber is an ultraviolet transparent dielectric chamber.
`The ionizable lnedittm can be a solid, liqttid or gas. The
`ionizable medium can include one or more ofa noble gas, Xe,
`Ar, Ne, Kr, He. D2, H2, 02, F2, a metal halide, a halogen, Hg,
`Cd, Zn, Sn, (la, I"e. Li, Na. an excimer fomtirlg gas. ail‘. a
`vapor. a metal oxide, an aerosol. a flowing media, a recycled
`media, or an evaporating target. In some embodiments, the
`ionizable medium is a target in the chamber and the ignition
`source is a pulsed laser that provides a pulsed laser beam that
`strikes the target. The target can be a pool or film of metal. In
`some embodiments, the target is capable of moving.
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`I11 solne embodiments, the at least one laser is multiple
`diode lasers coupled into a fiber optic element. The at least
`one laser can emit at least one wavelength ofelectromagnetic
`energy that is strongly absorbed by the ionized medium.
`The ignition source can be or can inclttde electrodes, an
`ultraviolet ignition source. a capacitive ignition source, an
`inductive ignition source, an RF ignition source, a microwave
`ignition source, a flash lamp, a pulsed laser, ora pulsed lamp.
`The ignition source can be external or internal to the chamber.
`In some embodiments, the light source includes at least one
`optical elelnent (eg. a mirror or lens) lor modifying a prop-
`erty of electromagnetic radiation emitted by the ionized
`medium. The optical element can be configured to deliver the
`electromagnetic radiation emitted by the ionized medium to a
`tool (e.g., a wafer inspection tool. a microscope. a metrology
`tool, a litltography tool, or an endoscopic tool).
`The invention, in another aspect relates to a method for
`producing light. The method involves ionizing with an igni-
`tion source an ionizable medium wil.hin a chamber. The
`method also involves providing substantially continuous
`laser energy to the ionized medium in the chamber to produce
`a high brightness light.
`In some embodilnents, the method also involves directing
`the laser energy through at least one optical element [or
`modifying a proper1y of the laser energy provided to the
`ionizable medium. The method also can involve actively
`pumping the chamber. In some embodiments, the ionizable
`medium is a moving target. The ionizable medium can
`include a solid,
`liqttid or
`In some embodiments. the
`method also involves directing the high brightness light
`through at least one optical elentent to modify a property of
`the light. In sonte embodiments, the method also involves
`delivering the high brightness light emitted by the ionized
`medium to a tool.
`The invention. itt another aspect, features a ligltt source
`having a chamber. The light source includes a first ignition
`means for ionizing an ionizable medium within the chamber.
`The light source also includes a means for providing substan-
`tially continuous laser energy to the ionized medium within
`the chamber.
`
`The invention, in another aspect, features a ligltt source
`having a chamber l.l1at includes a reflective surface. The light
`source also includes an ignition source for ionizing a gas
`within the chamber. The light source also includes a reflector
`that at least substantially reflects a first set of predefined
`wavelengths of electromagnetic energy directed toward the
`reflector and at least substantially allows a second set of
`predefined wavelengths of electromagnetic energy to pass
`through the reflector. The light source also includes at least
`one laser (e.g.. a conti11uous—wave fiber laser) external to the
`chamber for providing electromagnetic energy to the ionized
`gas within the chamber to produce a plasma that generates a
`high brightness light. A continuous-wave laser emits radia-
`tion continuously or substantially continuously rather than in
`short bursts, as iii a pulsed laser.
`In some etnboditnents, at least one laser directs a first set of
`wavelengths of electromagnetic energy through the reflector
`toward the reflective surface (e.g., inner surface) o fthe cham-
`ber and the reflective surface directs at least a portion of the
`first set ofwavelengths of electromagnetic energy toward the
`plasma. In some embodiments, at least a portion of the high
`brightness light is directed toward the reflective surface of the
`chamber, is reflected toward the reflector, and is reflected by
`the reflector toward a tool. In some embodiments, at least one
`laser directs a first set of wavelengths of electromagnetic
`energy toward the reflector, the reflector reflects at least a
`por1ion of the first wavelengths of electromagnetic energy
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`US 8,969,841 B2
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`towards the reflective surface of the chamber, and the reflec-
`tive surface directs a portion of the first set of wavelengths of
`electromagnetic energy toward the plasma.
`In some embodiments, at least a portion ofthe high bright-
`ness light is directed toward the reflective surface of the
`chamber, is reflected toward the reflector, and passes through
`the reflector toward an output of the light source. In some
`embodiments, the light source comprises a microscope. ultra-
`violet microscope, wafer inspection system, reticle inspec-
`tion system or lithography system spaced relative to the out-
`put ofthe light source to receive the high brightness light. In
`some embodiments. a portion of the high brightness light is
`directed toward the reflective surface of the chamber. is
`reflected toward the reflector. and electromagnetic energy
`comprising the second set ofpredefined wavelengths ofelec-
`troinagnetic energy passes through the reflector.
`The chamber of the light source can include a window. In
`some embodiments, the chamber is a sealed chamber. In some
`embodiments. the reflective surface of the chamber coni-
`prises a curved shape, parabolic shape, elliptical shape,
`spherical shape or asplierical shape. In some embodiments,
`the chamber has a reflective inner surface. In some embodi-
`ments, a coating or film is located on the outside of the
`chamber to produce the reflective surface. In some enibodi-
`merits, a coating or film is located on the inside o fthe chamber
`to produce the reflective surface. In some embodiments, the
`reflective surface is a structure or optical element that is
`distinct from the inner surface of the chamber.
`The light source can include an optical element disposed
`along a path the electromagnetic energy from the laser travels.
`In some embodiments, the optical element is adapted to pro-
`vide electromagnetic energy from the laser to the plasma over
`a large solid angle. In some embodilneiits, the reflective sur-
`face of the chamber is adapted to provide electromagnetic
`energy from the laser to the plasma over a large solid angle. In
`some embodiments, the reflective surface of the chamber is
`adapted to collect the high brightness light generated by the
`plasma over a large solid angle. In some embodiments. one or
`more of the reflective surface, reflector and the window
`include (e.g._. are coated or include) a material to filter pre-
`defined wavelengths (e.g., infrared wavelengths of electro-
`magnetic energy) of electromagnetic energy.
`The invention, in another aspect. features a light source that
`includes a chamber that has a reflective stirface. The light
`source also includes an ignition source for ionizing a gas
`within the chamber. The light source also includes at least one
`laser external to the chamber for providing electromagnetic
`energy to the ionized gas within the chamber to produce a
`plasma that generates a high brightness light. The light source
`also includes a reflector positioned along a path that the
`electromagnetic energy travels from the at least one laser to
`the reflective surface of the chamber.
`In some embodiments. the reflector is adapted to at least
`substantially reflect a first set of predefined wavelengths of
`electromagnetic energy directed toward the reflector and at
`least substantially allow a second set of predefined wave-
`lengths ofelectromagnetic energy to pass through the reflec-
`tor.
`
`The invention, in another aspect, relates to a method for
`producing light. The method involves ionizing with an igni-
`tion sotirce a gas within a chamber that has a reflective sur-
`face. The method also involves providing laser energy to the
`ionized gas in the chamber to produce a plasma that generates
`a high brightness light.
`In some embodiments, the method involves directing the
`laser energy comprising a first set of wavelengths ofelectro-
`magnetic energy through a reflector toward the reflective
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`surface of the chamber, the reflective surface reflecting at
`least a portion of the first set of wavelengths of electromag-
`netic energy toward the plasma. In some embodiments, the
`method involves directing at least a portion ofthe high bright-
`ness light toward the reflective surface ofthe chamber which
`is reflected toward the reflector and is reflected by the reflec-
`tor toward a tool.
`
`In some embodiments. the method involves directing the
`laser energy Comprising a first set of wavelengths of electro-
`inagnetic energy toward the reflector, the reflector reflects at
`least a portion of the first wavelengths of electromagnetic
`energy toward the reflective surface of the chamber, the
`reflective surface directs a portion of the first set of wave-
`lengths ofelectromagnetic energy toward the plasma. In some
`embodiments, the method involves directing a portion ofthe
`high brightness light toward the reflective surface of the
`chamber which is reflected toward the reflector and, electro-
`magnetic energy comprising the second set of predefined
`wavelengths of electromagnetic energy passes through the
`reflector.
`
`The method can involve directing the laser energy through
`an optical element that modifies a property of the laser energy
`to direct the laser energy toward the plasma over a large solid
`angle. In some embodiments. the method involves directing
`the laser energy through an optical element that modifies a
`property of the laser energy to direct the laser energy toward
`the plasma over a solid angle of approximately 0.012 stera-
`dians. In some embodiments, the method involves directing
`the laser energy through an optical element |.hat modifies a
`property of the laser energy to direct the laser energy toward
`the plasma over a