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`US008525 l38B2
`
`(12)
`
`United States Patent
`Smith et al.
`
`(10) Patent No.:
`(45; Date of Patent:
`
`US 8,525,138 B2
`Sep. 3, 2013
`
`(54)
`
`(75)
`
`LASER-DRIVEN LIGHT SOURCE
`
`Iiivciitorsz Donald K. Smith. Boston. MA (US);
`Matthew Besen. Andover, MA (US);
`lluiling Zhu. Lexington. MA (US):
`Daniil Stelyarov. Reading, MA (US):
`lltmgke Ye. Clielinsford. MA (US):
`Gordon Hill. Arlington, MA (US); Ron
`Collins, Londonderry. NH (U S)
`
`(73)
`
`Assignee: Energetiq Technology, Inc.. Woburn.
`MA (US)
`
`(*1
`
`Notice:
`
`Subject to any disclaimer. the term of this
`patent
`is extended or adjusted under 35
`U.S.C. ]54[|3) by 0 days.
`
`(21)
`
`App1.N0.:
`
`l3l{|24.,027
`
`(22)
`
`Filed:
`
`‘ch. 9, 2011
`
`Prior Publication Data
`
`US 201li’0l8ll9] Al
`
`.I1:l.28, 2011
`
`Related U.S. Application Data
`
`Continuatimi-in-part of application No. 121166.918.
`filed on Jul. 2. 2008. now Pat. No. '!_.989.786. which is
`a contimiation-in-part ofapplication No. 111695.348.
`filed onApr. 2. 2007. now Pat. No. 7.786355. which is
`a continuation—in—part of application No. 112395.523.
`filed on Mar. 31. 2006. now Pat. No. 7.435.982.
`
`Provisional application No. 6li’302.797. filed on Feb.
`9. 2010.
`
`(65)
`
`(63)
`
`(60)
`
`(51)
`
`(52)
`
`(58) Field of Classification Search
`2501503.]. 504 R
`USPC
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U .S. PATI-ENT DOCIJMENTS
`4.088.966 A
`551918 Semis
`4.152.625 A "‘
`5-‘"1979 Cionrad
`4.498.029 A
`2.-‘"1985 Yoshizawa ct al.
`4.645.215 A
`23198? Levin ct al.
`Rlj32.626 1_'L
`3.-‘I988 Yoshizawa ctal.
`6.283.780 Bl
`9.-‘"2001 Fairiey et :11.
`6.417.625 B1
`‘#2002 Brooks el al.
`
`315.-'11I.7l
`
`JP
`JP
`JP
`W0
`
`[(‘ontimIed}
`FOREIGN PATENT DOCUMENTS
`61 |93358
`5191986
`04-14-4053
`511992
`U8-299951
`ll"l996
`20101093903
`8-"2010
`OTHER PUBLICATIONS
`
`Nakar. Radiometric Ch:uacl'eri'/.ation of llllraliigh Radiance Xenon
`Shorl—arc Discharge Lamps. Jan. 9. 2008. Applied Optics. vol. 4?.
`No. 2. pp. 224-2293‘
`
`[(‘o11ti1'11ied)
`
`Primary Excm.=:'r.rer — Robert Kim
`Assistant E.\'aim"ner — Jason Mi:C.‘0rmack
`
`(74) .4i'i'0me_i’. Agent. or Firiii — Proskauer Rose LLP
`
`ABSTRA(3'l'
`(57)
`An apparatus for producing light includes a cliambcr and an
`ignition source that ionizes a gas within the cllamber. The
`apparatus also includes at least one laser that provides energy
`to the ionized gas within the chamber to produce a high
`brightness light. The laser can provide a substantially con-
`tinuous amount of energy to the ionized gas to generate a
`substantially coiitinuolm high brighlilcss light.
`
`Int. (:1.
`can you
`us. (:1.
`USPC
`
`(2006.01)
`
`250i'503.1:2501504R: 313667
`
`2'? Claims, 39 Drawing Sheets
`
`140
`
`
`
`108
`
`112
`
`104
`
`ASML 1101
`
`ASML 1101
`
`

`
`US 8,525,138 B2
`Page 2
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5388.404 B2
`5.955.329 B2
`7.050.149 B2
`7.42116? B2
`7.429.818 B2
`7.652.430 Bl
`20020021508 Al
`200150080834 A1"
`2002.-'01'r'2235 A1"
`2003.-"0168982 A1
`2003.-0231496 Al
`2004.-"002-5512 Al
`2004.-’0264St2 Al
`2005.-"0167Gl8 Al
`2006.-0039435 Al‘
`2007»"0228288 Al
`200'?r'0228300 Al
`200'.-‘.-"0285921 A1
`2009.-"0032'i40 A1
`
`‘X2004 Lange
`l0."20U5 Brooks et al.
`5.52005 Owa et al.
`9.’2008 llelderetal.
`9a’2008 Changetal.
`H2010 Delgado
`2»"20()2
`lshihara
`6.-‘Z002 Kusunose
`11.52002 Changetal.
`9e"2003 Kim
`l2e"2003 Satoet al.
`2.-"2004 Otsubu
`12.-"2004
`I-Iarttove etal.
`8e"2005 Hoshino etal.
`F2006 Cheymel et al.
`l0.’200':' Smith
`l0.-“200? Smith
`12.900? Zulimetal.
`2.’2009 Smith etal.
`
`372.-"25
`.. 3'i'2a’5
`
`372.-"55
`
`OTHER PUBLICATIONS
`
`Nakar et al.. Radiometric Characterization o1‘Ultra.high Radiance
`Xenon Short-Arc Discharge Lamps. Ben-Gurion University. Jan. 9.
`2008.’'‘
`Beck. "Simple Pulse Generator for Pulsing Xenon Ares with High
`Repetition Rale." Rev. Sci. hm‘:-niri.. vol. 45. No. 2. Feb. 1934. pp.
`3 18-319.
`Bussiahn. R... et. al.. “Experimental and theoretical i_r:ivestigatiens of
`a low-pressure He-Xe discharge for lighting purpose.“ Journal of
`Applied Physics. vol. 95. No. 9. May 1. 2004. pp. 462'.-‘-4634.
`Carlhelf et al.. “Continuous Optical Discharges at Very High Pres-
`sure." Physi't'a 103C. I981. pp. 439-44?.
`Cremers et al.. "Evaluation of the Continuous Optical Discharge for
`Speetrochemieal Analysis.” Specrrrnchrrrrirrzz .4'(.'.'rz. vol. 40B. No. 4,
`1985, pp. 5654379.
`
`Fiedorowicz et al .. “X-Ray Emission form Laser-Irradiated Gas Pufl‘
`Targets," Appl. Phys. Left‘. 62 (22). May 31, 1993. pp. 2778-2780.
`Franzen. "CW Gas Breakdown in Argon Using 10.6-pm Lmer Radia-
`tion."Appt'. Phys. Lem. vol. 21. No. 2. Jul. 15. 1972. pp. 62-64.
`Generalov et al.. "Continuous Optical Discharge." Zhf:'TF Pis. Red.
`1 1. No. 9. May 5. 1930. pp. 302-304.
`Generalov et al.. “lixperimental Investigation of a Continuous Opti-
`cal Discharge." Soviet Physics JETP. vol. 34, No. 4. Apr. 19'i2. pp.
`763-769.
`Hamasnatsu Product Information. "Super-Quiet Xenon Lamp Super-
`Quiet Mercury-Xenon Lamp.” Nov. 2005. pp. 1-16.
`I-Iecht. “Refraction". Optics (Third Edifiori). 1998. Chapter 4. pp.
`I00-101.
`Jerlg el al.. "Theoretical Investigation ofl..aser—SLIslainecl Argon Plas-
`mas." .I. Appf. Phys. 60 (7). Oct.
`1._ 1986. pp. 2272-2279.
`Keefer et al.. “Experimental Study of a Stationary Laser-Sustained
`Air Plasma.” Joimrm’ q!'.4pph'ed P.t.=ysr'cs-. vol. 46. No. 3. Mar. t9'.l5,
`pp. 1080-1083.
`Keefer. "l_.aser-Sustained Plasmas.“ Laser‘-Iriditced Plasmas and
`Appficarioris. published by Marcel Dekker. edited by Radziemski et
`al.. 1989. pp. 169-206.
`Kozlov et al.. “Radiative Losses by Argon Plasma and the Emissive
`Model of a Continuous Optical Discharge.“ Sou Phys. JEEP. vol. 39.
`No. 3. Sep. 1974. pp. 463-468.
`Kozlov et al.. "Sustained Optical Discharges in Molecular Gases.”
`So-2 Phys. Teeth. Phys. 49(ll). Nov. 1979. pp. 1283-1281
`Moody. "Maintenance ofa Gas Breakdown in Argon Using 10.6-p cw
`Radiation." Jcmrnm‘ ofxffrpiied Physics. vol. 46. No. I5. Jun. 1975. pp.
`2475-2482.
`Rélizer. “Optical l')iscl1.1.rges." Sm! Phys. Usp. 23f_l I ). Nov. I980. pp.
`789-806.
`Wilbers et al.. “'I'l1e Continuum Emission of an Arc Plasma.“ J.
`Qriam. Specrnosc. Radirzt. Tr'ansfe.r'. vol. 45. No. 1. 1991. pp. 1-10.
`Wilbers et al.. "The VUV Emissivity ot'a High-Pressure Cascade
`Argon Arc from I25 to 200 nm.”J. Qnam. Specrnose. Radiar.
`i’i'a.ri.v-
`fer. vol. 46. I991. pp. 299-308.
`
`“ cited by exanliner
`
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`Sheet 29 of 39
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`U.S. Patent
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`Sep. 3, 2013
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`Sheet 34 of 39
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`US 8,525,138 B2
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`U.S. Patent
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`Sep. 3, 2013
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`Sheet 35 of 39
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`Sep. 3, 2013
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`Sep. 3, 2013
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`U.S. Patent
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`Sep. 3, 2013
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`Sheet 33 of 39
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`U.S. Patent
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`Sep. 3, 2013
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`Sheet 39 of 39
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`US 8,525,138 B2
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`

`
`1
`LASER-DRIVEN LIGHT SOURCE
`
`RELATED APPLICATIONS
`
`This application is a continuation-in-part of U.S. Ser. No.
`I22’ I 66,91 8. filed on Jul. 2, 2008. which is a continuation-iru
`part of ll.S. Set". No. I lr"695.348, filed o11Apr. 2, 2007. which
`is a continuation-in-part ofU.S. Ser. No. 1 1895.523. filed on
`Mar. 31. 2006. the entire disclosures of which are it1corpo-
`rated by reference herein. This application claims the benefit
`of. and priority to U.S. Provisional Patent Application No.
`611302.797. filed on Feb. 9, 2010. the entire disclosure of
`which is incorporated by reference herein.
`
`FIELD OF THE INVENTION
`
`The invention relates to methods and apparatus for provid-
`ing a laser-driven light source.
`
`IMICKGROUND OF Tl Ill. INVl.7.N'l‘l()N
`
`High brightness ligltt sources can be used in a variety of
`applications. For example. a higlt brightness light source can
`be used for inspection. testing or measuring properties asso-
`ciated with semiconductor wafers or materials used in the
`
`fabrication of wafers (e.g., reticles and pliotontasl-ts). The
`electromagnetic energy produced by high brightness light
`sources can. alternatively. be used as a source of illumination
`in a lithography system used in the fabrication of wafers. a
`microscopy system. or a photoresist curing system. The
`parameters (e.g., wavelength. power level and brightness) of
`the light vary depending upon the application.
`The state of the art in, for example, wafer inspection sys-
`tems ittvolves the use of xenon or mercury arc lamps to
`produce light. The are 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 (e.g.. 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 chic to
`electrical discharge delivered to the ionized
`located
`between the anode and cathode. As a result, the anode andfor
`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 sttlficient bright-
`ness for sonte applications. especially in the ttltraviolet spec-
`trum. Further. the position of the arc can be unstable 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 maintaitt a plasma that generates a high brightness
`light.
`The properties of light produced by litany light sources
`(e.g.. arc lamps. microwave lamps) are allected wlten the light
`passes through a wall of. for example. a chamber that includes
`the location from which the light is emitted.
`Accordingly. a need tlterefore exists for an improved light
`source whose emitted light is not signj ficantly affected when
`the light passes through a wall ofa chamber that includes the
`location from which the light is entitled.
`
`SUIVIMARY OF THE INVENTION
`
`The present invention features a light source for generating
`El high brightness light.
`
`US 8,525,138 B2
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`2
`
`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.
`ltt some e1nboditttents_.tl1e at least one laser is a plurality of
`lasers directed at a region frotn which the high brightness
`light originates. In some embodiments. the light source also
`includes at least one optical element for modifyinga property
`of the 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 at fresnel lens) or
`mirror (e.g., a coated mirror. a dielectric coated mirror, a
`narrow band mirror, and an ultraviolet transparent infrared
`reflecting mirror). In some embodiments. the optical element
`is one or more fiber optic elements for directing the laser
`energy to the gas.
`The chamber catt include an ultraviolet transparent region.
`The chamber or El window in the chamber can include a
`
`material selected from the group consisting ofquartz. Supra-
`sil® quartz (Heraeus Quartz An1erica_. LLC. Buford, Ga.)_.
`sapphire. MgF2. diamond. and CaF3. In sotne 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
`(e.g.. quartz). The chamber catt be. fin‘ example, a glass bttlb.
`In some embodiments. the chamber is an ultraviolet transpar-
`ent dielectric chamber.
`
`The gas can be one or more ofa noble gas. Xe, Ar. Ne. Kr,
`lie, 1):, llg. ()2, 172, a metal halide, a halogen. I-lg, Cd. Z11, 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 beatn that impacts a
`target (e.g.. a solid or liquid) in the chtunber. The target can be
`a pool or film of metal. In sotne 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. the at least one laser is multiple
`diode lasers coupled into a fiber optic element. In sotne
`etnbodintents. the at least one laser includes a pulse or con-
`tinuous wave laser. In some entbodintents. the at least one
`laser is an IR laser. a diode laser, a fiber laser. an ytterbium
`laser. a C03 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, an
`inductive ignition source, an RF ignition source. a microwave
`ignition source. a flash Iamp_. a pulsed laser. or a pulsed lamp.
`The ignition source can be a continuous wave (CW) or pulsed
`laser impinging on a solid or liquid target in the chamber. The
`ignitiott source can be external or intental 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 tttirrors or lenses. In sotne embodirnen1s_. the optical
`element is configured to deliver the electromagnetic radiation
`emitted by the ionized gas to a tool (e.g.. a wafer inspection
`tool. a microscope. £1 ntetrology tool. a lithography 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 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.
`
`5
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`In some embodiments. the n1etl1od also involves directing
`the laser energy 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 ioni':.able 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 light. In some
`embodiments, the method also involves delivering the high
`brightness light emitted by the ionized medium to a tool {e.g..
`a wafer inspection tool, a microscope. at metrology tool. a
`lithography tool. or an endoscopic tool).
`In another aspect, the invention features a light source. The
`lights source includes a chamber and an ignition source for
`ionizing an ionizable medium within the chamber. The light
`source also includes at least one laser for providing substan-
`tially continuous energy to the ionized medium within the
`chamber to produce a high brightness light.
`In some embodiments. the at least one laser is a continuous
`
`wave laser or a high pulse rate laser. In 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
`magnitude of the high brightness light does not vary by more
`than about 90% during operation. In some embodiments. the
`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 mirror) for modifying a
`property of the laser energy provided to the ionized medium.
`The optical element can be, for exzuuple, an aplanatic lens. an
`achromatic lens. a single element lens. a fresnel lens. a coated
`mirror. a dielectric coated mirror. a narrow band mirror. or an
`ultraviolet transparent infrared reflecting, mirror. In some
`embodiments. the optical element is one or 111ore fiber optic
`elements for directing the laser energy to the ionizable
`medium.
`In some embodiments, the chamber includes an ultraviolet
`transparent region. In some embodiments. the chamber or a
`window in the chamber includes a quartz material, supmsil
`quartz material, sapphire material. MgF2 material, diamond
`material. or CaF2 material. In some embodiments. the cham-
`ber is a sealed chamber. The chamber can be capable ofbeing
`actively pumped.
`In some embodiments,
`the chamber
`includes a dielectric material (e.g.. quartz). In some embodi-
`ments, the chamber is a glass bulb. In some embodiments. the
`chamber is an ultraviolet transparent dielectric cltamber.
`The ionizable medium can be a solid. liquid or gas. The
`ionizable medium can include one or more ofa noble gas. Xe,
`Ar, Ne. Kr, He, D3, H2. 03, F2, a metal halide, a halogen. Hg.
`Cd. Zn, Sn, Ga, Fe, Li. Na, an excimer fomting gas, air, 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 ofmetal. In
`some embodiments, the target is capable of moving.
`In seine 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 include electrodes, an
`ultraviolet ignition source, a capacitive ignition source, an
`inductive ignition source, an RF ignition source, a microwave
`ignition source, a flash lzuup. a pulsed laser. or a pulsed lamp.
`The ignition source can be extcmal or internal to the chamber.
`
`In some embodiments, the light source includes at least one
`optical element {e.g._. a mirror or lens] for 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 (c.g.. a wafer inspection tool. a rnicroscope, a metrology
`tool, a lithography 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 within a chamber. The
`
`1U
`
`method also involves providing substantially continuous
`laser energy to the ionized medium in the chamber to produce
`at high brightness light.
`In some embodiments. the method also involves directing
`the laser energy through at least one optical element for
`modifying a property 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. liquid or gas. In some embodiments. the
`method also involves directing the high brightness light
`through at least one optical element to modify a property of
`the light. In some embodiments, the method also involves
`delivering the high brightness light emitted by the ionized
`medium to a tool.
`
`The invention, in another aspwt, features a light 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.
`
`3U
`
`The invention. in another aspect, features a light source
`having a chamber that includes a ref'lect'ive 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
`rellector and at least substantially allows a second set of
`predefined wavelengtlis of electromagnetic energy to pass
`through the reflector. The light source also includes at least
`one laser (e.g.. a continuous-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 in a pulsed laser.
`In some embodiments, at least one laser directs a lirst set of
`wavelengths o f electromagnetic energy through the reflector
`toward the reflective surface (e.g.. irmer surface) ofthe cham-
`ber and the reflective surface directs at least a portion of the
`first set ofwavelengths of electromagnetic energy toward the
`plasma. In some embodirrrents. at least a portion of the high
`brightness light is directed toward the reflective surface ofthe
`chamber. is reflected toward the reflector, and is reflected by
`the rcllwtortoward a too]. 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
`portion of the first wavelengths of electromagnetic energy
`towards the reflective surface of the chamber, and the reflec-
`tive surface directs a portion of the first set of wavelengths of
`electrontagnctic energy toward the plasma.
`In some embodiments. at least a portion of the 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-
`
`4U
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`5
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`6
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`US 8,525,138 B2
`
`tion system or lithography system spaced relative to the out-
`put of the 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 of predefined wavelengths ofclec-
`tromagnetic energy passes through the reflector.
`Tl1e cliamber of the light source can include a window. In
`sortie embodiments, the chamber is a sealed chamber. In some
`embodiments. the reflective surface of the chamber com-
`
`shape_.
`prises a curved shape, parabolic shape, elliptical
`spherical shape or aspherical shape. In some embodiments.
`tl1e 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 embodi-
`ments, a coating or film is located on the inside ofthe 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 tl1e 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 embodirnents. 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 ernbodilnents, 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 liglu source that
`includes a chamber that has a reflective surface. 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.
`
`111 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 of electromagnetic 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 in '-
`tion source 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 briglttness light.
`In some embodiments. the method involves directing the
`laser energy comprising a first set ofwavelengths of electro-
`magnetic energy through a reflector toward the reflective
`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. I11 some embodiments. the
`method involves directing at least a portion of the high bright-
`ness light toward the reflective surface of the chamber which
`is reflected toward the reflector and is reflected by the reflec-
`tor toward a tool.
`[11 some embodiments. the method involves directing the
`laser energy comprising a first set of wavelengths of electro-
`
`magnetic 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
`einbodiments, the method involves directing a portion of the
`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.
`
`1U
`
`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 modi fies 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 that modifies a
`property of the laser energy to direct the laser energy toward
`the plasma over a solid angle of approximately 0,048 stem-
`dians. 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 greater than about 2rr (about
`6.28] steradians. In some cntbodiments, the reflective surface
`of the chamber is adapted to provide the laser energy 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 flu: plasma over a large solid
`angle.
`The invention. in another aspect. relates to a method for
`producing light. The method involves ionizing with an igni-
`tion source a gas within a chamber that has a reflective sur-
`face. The method also involves directing electromagnetic
`energy from a laser toward a reflector that at least substan-
`tially reflects a first set of wavelengths of electromagnet