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`
`US008309943B2
`
`(12; United States Patent
`Smith et al.
`
`(10) Patent No;
`
`(45) Date of Patent:
`
`US 8,309,943 B2
`Nov. 13, 2012
`
`LASl1lR-I)R[\"E:\’ LIGHT SOURCE
`
`(56)
`
`References (fited
`
`l1’t‘\“C11101‘S2 Donald K. Smith. Bostoti. MA (US);
`William NI. Hoiber. Witicitester. MA
`(US): Jeffrey A. (Tasty, Winciicster. MA
`(US)
`
`.‘\$Sig1’1Ci32
`
`Eitcrgetiq Tecltnnlogy. [nc.. Wobum.
`(US)
`
`Notice:
`
`Subject to any disciaimer. the term ofthis
`patent is extended or adjusted under 35
`U.S.(.‘. 154(1)) by 41 days.
`
`Appl. Nix: 13/099,823
`
`17‘i1et1:
`
`May 3, 2011
`
`Prior Publication Data
`
`US 2()11/02()4265 A1
`
`Aug. 25, 2011
`
`Related
`
`.-ixpplication Data
`
`Ctmtiinizttion ofappliczttioii No. 12/166918. filed on
`Jul. 2. 2008. nnw P211. N0.
`'.3’.989.786. which is 21
`contimitation-in-part ofapplicatiuii No. 11/695.3-'18.
`filed onApr. 2. 2007. now Pat. No. 7.786.455. which is
`E1 continuzitimi-iii-part of zipplication No. 113595.523.
`filed on l\/liil‘. 31. 2()t)6. now Pat. No. 7.435.982.
`
`Int. Cl.
`IIOIJ 63/(I8
`[1051] 1/24
`11051} 31/00
`US. (71.
`
`(2006.()1)
`{2006.().l)
`(200601 )
`250/493.1: 250/504 R1250/503.1;
`
`
`25('),’“65‘. 315/149: 315511 1.21: 313/231.31
`Field of (Tlassificatiun Search
`.
`1
`'” .
`.
`.
`
`250/50-'1R.365. 493.1. 31../149. 111.21:
`313./231.31
`
`applicz-ition tile for complete Search history.
`
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`22001 Sziwatlzi ct al.
`6.233.? 30 El
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`9?O()4 Lzmgc
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`5‘2006 Owa C1 211.
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`9V20()2"s'
`I10ldei'et:»il.
`7.429.818 B2
`9,'2()O8 Cltzmg ct Al.
`
`7.4?" 982 B2 “"
`1032008 Smith
`").71,\'6 B2 *
`82011 Smith ex 211.
`Z0()'.Z'O02l5l)S Al
`‘Z2002
`lshihzirzt
`2()03'{)1t389X2 A1
`9‘2()()3 Kim
`2003 (J131<1£>6 A1
`12"2(1()3 Sam Ct :11.
`
`350 222 2
`
`250504 R
`.............. .. 250 503.1
`
`(i(i'0I1111'11lL“.(l)
`
`JP
`
`l7()R1~5lCiN l’.~Vi'}Ei;7\i"l" l)C')(_‘Ui\'1i7.N'l'S
`61-193358
`<‘$'19S6
`
`(Ti ‘PIER PUB l... IC'A'I‘I()NS
`
`Beck. “Siniplc Pulsc Generator 1'01 Pulsing Xenon Arcs with High
`Repetition Rate.” Rena Sci. InsIm.rn.. vol. 45, ;\'0. 2. Feb. 19741. pp.
`318-319.
`
`(Continued)
`
`.E.x'cm1;'1z<*r Nikita \VClls
`I’r'€1r:<1;jt'
`(74) .—'1IIOr‘rz({t'. xlgwzt, or Firnz M Proskziucr Rose 1.1.1’
`
`1 57’)
`
`.:\BS'I‘R.-'\([,'T
`
`An zippamttis for producing iight includes a cliambcr and an
`ignition source that ionizes 21 gas within the c11amber. The
`zzpparziuis also includes at least one lasertliat pmvicles energy
`to the i0ni7.cd gas within 111:: chamber to produce 21 high
`brightness light. The laser can provide 21 SL1bS1Z1111iZ1ll_V‘ con-
`tinuou:s' zmiount 01' C11€3I‘g}‘
`to the ioni‘/,..c:1 gas to gcncr;ite 2:
`substzuitially comimiuus high briglitness light.
`
`21 Claims, 17 Drawing Sheets
`
`
`‘S10
`
`'1"
`
`<——: 155
`
`ASML 1201
`
`
`
`
`
`’2
`
`

`
`US 8,309,943 B2
`Page 2
`
`U .S. 1’:'XT1‘:'.N'1‘ 1.)(.')(',‘U.
`200450026512 A1
`2.2004 (f){:;ubo
`2004-’O264512 A1
`12,2004 Hzirlloxrc £1111.
`20050167618 ..»‘\1
`8,2005 Hoshino at 211.
`20110181191 AU‘
`T2011 Smithct 211.
`................. .. 315149
`
` LNTS
`
`C)'1‘1'1111{ 1’U1;3I .1(7;'\£1"1()NS
`
`C‘ar1110f1‘c1 :11. “Continuous (')pti<;a1 1)ischarg,cs at V-hr)-‘ High Pres-
`sure." Pi2,_1:s'i('c2 103C. 1981. pp. 4339447.
`C1'L’11’1C1'>‘- ct .11.. "1?Iva1uati<sn ufthc Cfominumns Opticzii 1)isc1:arge for
`Spcc1mc11cxnic211 Analysis.” .Sp:rz*r:-r::~/tizrzica .-117:1. vol. 4013. No. 4.
`1985. pp. 665-679.
`Ficdormvim. cl 211.. “X-Ray Emission form Laser-I.rrac1iatcd Gas 1’u‘1T
`"l"a.rgets.".-zppi. P/:y.s-. Lon. 62 22'). May 31. 1993. pp. 3778-2780.
`17mn;cen. “CW Gas B1'€Zlk(10”Wl1
`in Argon Using 10.6» 3.1m I.as<:r
`
`RZl(11E1t1()n ",4;);)I,1’!(i's’. l,<.>II,. vol. 31. .\Io. 3. Jul. 1*.
`1‘
`pp. 62-64.
`(.}c:ncra1m= ex 211.. “Continuous ()p1ica1 1)ischargc,
`/./1521:" Pis’. Red.
`11. .\'0. 9. :‘VIny 5. 1‘)',7(1. pp. 302-304.
`Cicncmlov at 31.. “1}Ixpc1'i1ncnm1 1n\’€i'-'11gél11(.\i'1 01:1 C<..>minu<>us Opti-
`cal 1’)ischzu'gL‘.” Sovivl I’h)§'.s'1'<.'..\‘ .115.‘ 77’. V01. 34. \'n. 4. Apr. 1973. pp.
`763-769.
`1-Iccht. “Rcfrac1ion"’. Optic-s (_ Tixird li'diti(»I'). 1998. Chapter 4. pp.
`100-101.
`Jcng at 211.. "Theoretical Invcstigzuion of[..2iscr—Sustained Aigon Plas-
`111215."./. xiggvl. Plr_r.<. 60 (7). Oct. 1. 1936. pp. 2.'Z72—2279.
`
`Keefer. "1.zxser~SusI.'-iincil P1asm:1s." [,tz.w1‘—Ir2r1z¢r'<r¢i Pla.wmz.\' am!
`.411}?/i(.‘(1:’ic.m.s‘. published by .\-inrccl 1)c1;kcr. edited by Rzld‘/..ic.mski c1
`:11. 1989. pp. 169-206.
`Kc<:1'cx' at 31.. “1}Lxpcrimcnta1 Siudy 012: Starionzuy 1..E1.$€1‘-SUS{Z11n€(1
`Air Plasxna." .iournal cg/‘./1;>[1i:‘:*d}’!zysiz;'s. V01. 46. ;\’o. 3. Mar. 1975.
`pp. 1(18()~1083.
`Kw/.1mv' et ai.. “Rziciizxtivc 1..<>sse.< by .»'—\rg(.>n Plasma and the: Emiss‘ c
`
`Model ofa Continumls ()pt1ca1 Disch21r<_.:w:.".‘5'o1z 1~’/sum". ./.E'[‘P. vol. 3‘).
`,\"n.
`Scp. 1‘)7r=1.pp. 463-463.
`Koz.1m' et .11.. “Susiaixieai ()pIic:11 Dischzu‘ges in Molccxniai‘ (iases.”
`50;: Plzgxs.
`7E’(.‘I1’. P/:y.v. 49(11). ?\'o\=. 1979. pp. 1283-1“v"\’7.
`.\=1oody. “;\/Iaintcnamze 01:1 Gas Brca1c(1owninArgon Li sing 10.6-_u cw
`Radiation." Journal (gf'Ap;2lic*(I' Plz,r.s’ic‘$. vol. 46. N0. 6. Jun. ,1 975. pp.
`.‘;475—24S2.
`11:1
`er. “( )p!ica1 1)ischm‘ges.“.S'oi< l’Iz}'..V. 1 *'.\p. 23(1 1). .\f0v. 1980. pp.
`7S9—2s'O6.
`1— 16.
`“Super-Quit-1 Xenon Lamp Super-(;)_uic1 :‘v1crcury~.7"\'cnon
`1,:unp." !I(znzanz(zr.m l’r0dmv' 1111211-1z2zz.'1aI:. ;\'o\‘. 2005. pp. 1»1(3.
`V‘v"i1bcrs «:1 111.. “The (ffmninuxnn kimission of an Arc 1’1asmzi." .7.
`Quani. $;)e(’(r'r>.vc‘. Radiai. Tran.
`'
`v01.4.">. No. 1. 1991. pp. 140.
`
`Wilbers at 211.. “The V1 7V’ F.mi..
`it}-‘ of :1 High—Pressure Cascade
`Argon Arc from 12510 200 nm.“.l. Qzmm‘. .S:!2<>z?m>sc. Radial. 1}'(z:z.v-
`fér. vol. 46. 1991. pp. 299-308.
`
`*1‘ cited by cxzunincr
`
`

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`Nov.13,2012
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`Rlil <\"l'l Ell’) Al’l’l._.l(.‘.='\'li'l()N S
`
`No. llllob.
`"lhis application is El continuation ol‘U.S.
`918. tiled on Jul. 7 2008 which is at continuzttion—in—part of
`
`
`U.
`.Ser. No. 1 1/69
`48. filed on Apr. 2, 2007. now US. Pat.
`No. 7.786.455. which is a continuation—in—part ol‘U.S.
`No. llt'395.523. filed on Mar. 31. 2006. now US. Pat. No.
`7.435.982. the entire disclosures ofwhich are hereby incor-
`porated by reference herein.
`
`l’ll".l,,,l') Oi" ll ll? lN\"l.E.N'l‘il()N
`
`The invention relates to methods and apparatus tor provid-
`ing a laser—driven light source.
`
`l3_<\(.‘K('iR()l.?Nl) Oi" ’l"l"ll‘Ff lN\~'FiN'l‘lC).N
`
`High brightness light sources can be used in it variety ol‘
`appliczttions. For example. a high briglitncss light source can
`be used for inspection. testing or xi1e;isttt‘ir1g properties asso-
`ciated with semiconductor waters or materials used in the
`fabrication of wafers
`rcticles and pliotomasksl. The
`electromagnetic energy produced by high brightness light
`
`sources can. alternatively. be used as
`source ofillumination
`in a lithography systctn used in the fabrication o,l"wafer.s. a
`microscopy system. or a photoresist curing. system. The
`parameters {e.g.. wavelength. power level and briglnncss) o l‘
`the light vary depending, upon the application.
`'-
`the state oltlic art in. for cxatnple. wafer inspection
`tcms involves‘ the use of xenon or mercury arc lamps to
`produce light. ilhc arc lamps include an anode and cathode
`that are used to excite xenon or mercury gas located in ‘d
`chamber of the lamp. :\.n electrical discliarge is generated
`between the zmodc and cathode to provide power to the
`excited (fc.g.. ionized‘) gas to sustain the light emitted by the
`ionized gas during operation ol‘ the light source. During
`operation.
`the anode and cathode become very’ hot due to
`electrical discharge delivered to the ionized
`located
`between the anode and cathode. As it result. the anode and/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 arc latnps do not provide sufficient bright-
`ness for some applications. especially in the ultmviolct spec-
`trum. Further. the position olthc arc can be unstable in these
`lamps.
`Accordiitgly. a need tltcreforc exists for improved high
`brightness light sources. A need also exists for improved hi gh
`brightness light sources that do not rely on an electrical dis~
`charge to maintain a plasma that generates a high briglitness
`light.
`lhc properties of light produced by mzuty light sources
`(e.g.. arc lamps. tiiicroxvave lamps) are allectcd when the light
`passes through a wall of. for example. 21 cltantber that includes
`the location from which the light is emitted.
`Accordingly. 21 need therefore exists for an improved light
`source whose emitted light is not significantly affected when
`the light passes tltrongh a wall o la chamber that includes the
`location from which the light is emitted.
`
`SUl\-'ll\/lA RY (').l-" 'l‘l*ll'.i [N \-'l:'IN‘l'l(_)N
`
`The present invention feat'ttres a light source for generating
`a high brightness light.
`Tlie invention. in one aspect. features a light source having
`a chamber. The light source also includes an ignition source
`
`20
`
`lor ionizing a gas within the chamber. The light source also
`includes at least one laser for providing energy to the ionized
`gar Wllllitl the chamber to produce 21 hi gh brightness light.
`In some embodiments. the at least one laser is 2-1 plurality of
`lasers directed at a region from which the higlt brightness
`light originates. In some embodiments. the light source also
`includes at least one optical element for itiodifyiiig a property
`ollthe laser energy provided to the ionized gas. The optical
`element can be. for example. a lens (c.g.. an nplanatic lens. an
`achromatic letis. a single element lens. and a liresnel lens) or
`mirror
`a coated mirror. it dielectric coated mirror.
`in
`narrow band mirror. and an ultraviolet transparent inlirared
`reflecting mirror). in some embodiments. the optical element
`one or more fiber optic elcntents for directing the laser
`energy to the gas.
`The chaniber can include an ultraviolet transparent regititi.
`The chamber or a vvindou— in the chamber can include a
`matcn'al selected from the group consisting ol‘quart7.. Supra-
`silJt'<‘ quartz tllcraeus Quartz. skmcrica.
`l,l,,(“. Buford. (izn).
`sapphire. lv
`‘
`. diamond. and Cal" ,. In some embodiments.
`
`
`the chamber is a sealed cltamber. In some €II‘tl’70(llt11€t1lS.Tl'l€
`chamber is capable of being actively pumped.
`In some
`embodiments.
`the chamber includes a dielectric material
`( quartz). The chamber can be, for example, a glass bulb.
`In some embodiments. the chamber is an ultraviolet transpar—
`cut dielectric chamber.
`Kr.
`The gas can
`one or more ola noble gas. Xe. Ar.
`
`He. D2, H2. C _,. F2. 2: metal halide, a halogen. Hg‘ Cd. Zn. Sn.
`Ga. Fe. Li. Na. an excimer lorming.
`air. a vapor. a metal
`oxide. an aerosol. a flowing media. or a recycled media. 'lhc
`gas can he produced by at pulsed laser beam that impacts 21
`target 1] a solid or liquid) in the chamber. The target can be
`a pool or film of metal. In some cinbodiitteiits. the target is
`capable olimoving. 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 some
`enibodiruents. the at least one laser includes a pulse or con-
`tinuous wave laser. In some cmboditncntsz. the at least one
`laser is an IR laser. a diode laser. a fiber laser. an ytterbium
`laser. at 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
`absorbetl by the ioni/.cd mcdiuin.
`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 itticrowzivc
`ignition source. a flash lamp. 3 pulsed laser. or a pulsed lamp.
`The ignition source can be a continuous wave (CTW ) or pulsed
`laser impinging on a solid or liqti id target in the chamber. The
`ignition source can be external or internal to the chamber.
`The light source can include at least one optical element for
`modifying a property o fclcctroxttagtietic radiation emitted by
`the l0Ill'/.i)(l gas. The optical element can be, for c>;amplc. one
`or more mirrors or lenses. In some embodiments. the optical
`element is configured to deliver the electrotnagnetic radiation
`emitted by the ionized gas to a tool {e.g.. a wafer inspection
`tool. a microscope. at mctrology tool. a lithography tool. or an
`endoscopic tool).
`The invention. in another aspect. relates to :1 method for
`producing light. The method involves ioni’/,.'.ing with an igni-
`tion source a gas within it 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 ericrgy through at
`least one optical element for
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`US 8.309.943 B2
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`3
`modifying 2: property of the laser energy provided to the
`ionized gas. In some embodiments. the method also involves
`actively pumping the chamber. "lite ionirable 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 11 property ofthe light. in some
`ernbodiments. the method also involves delivering the high
`
`brightness light emitted by the ionized medium to at tool {en ..
`2! wafer inspection tool. a microscope. a metrology tool. a
`lithograplty tool. or an endoscopic tool).
`ln another aspect. the invention features a light source. Tlie
`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 prox-riding substan-
`tially continuous energy to the ionized medium Within the
`chamber to produce a high brightness light.
`In some emboclitnents. 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 ofcttcrgy to the ionized medium so the high brightness
`light is substantially continuous. In some embodiments. the
`magititude ofthe high brightness light does not vary by more
`than about F)()% during operation. In some embodiments. the
`at least one laser provides energy sttbstaittiztlly continuously
`to minimize cooling of the ionized medium when ettergy is
`not provided to the ionized medium.
`‘
`In some embodiments. the light sottrcc can include at least
`one optical element
`a lens or mirror) for modifying a
`property olithe laser criergy provided to the ionized medium.
`The optical element can be. for example. an aplanutic lens. an
`achromatic lens. £1 single element lens. a Fresnel lens. a coated
`mirror. a dielectric coated in irror. a narrow band mirror. or an
`ultraviolet
`transparent
`infrared retlccting mirror.
`In some
`embodiments. the optical element is one or more libcr optic
`elements for directing the laser energy to the ionizztble
`medium.
`In some embodiments. the chamber includes an ultraviolet
`transparent region. ln some eittbodimeuts. the chamber or a
`tt'iudovt‘ in the chamber includes a quart’/. niaterial. suprasil
`quart:/. materia
`sapphire material. Mgl’ material. diamond
`
`ntateriail, or Ca material. In some embodiments. the cham-
`ber is a sealed chzm1ber.'l"he chamber can be capable ofbeing
`actively pumped.
`In some embodiments,
`the chamber
`includes a dielectric material (e.g.. quztrtz). In some embodi-
`ments. the chamber is a glass bulb. In some embodiments. the
`chamber is an ultraviolet ‘transparent dielectric chamber.
`"lhe ionizable medium can be a solid. liquid or gas. lite
`ioni7,able medium can include one or more olia noble gets.
`Ar. Ne. Kr. He. 1).. lvl.__. O2. 19., a metal halide. a halogen. lrlg.
`Cd, Zn. Sn. Ga, I-re. Li, Na. an excinter forming gas. air. a
`vapor. a metal oxide. an aerosol. a flowing media. a recycled
`media. or an evaporating target. In some embodiments. the
`itiitizable medium is a target in the chamber and the ignition
`source is a pulsed laser that provides it pulsed laser beam that
`strikes the target. The target can be a pool or lilm oi‘ metal. In
`some embodintents. the target is capable of moving.
`In some embodiments. the at least one laser multiple
`diode lasers coupled into a fiber optic element. The at least
`one laser can emit at least one wavelength ofelect,rotnagnetic
`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 itticrovrave
`ignition source. a llash 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 element (eg. a mirror or lens) for modi jing a prop-
`
`2;»
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`erty of electromagnetic rt’-tdiation emitted by the ionized
`medium. The optical element can be configured to deliver the
`electromagnctie radiation emitted by the ionized medium to a
`tool (_e.g.. at wafer inspection tool. 2! microscope. at metrology
`tool. a lithography tool. or an endoscopic tool).
`The invention.
`in another aspect relzttes to a rnethod for
`producing light. The method involves ionizing with an igni-
`tion source an ioniznble medium within it chamber. The
`method also i1‘tV'OlVL’S providing stthstantiztlly continuous
`laser energy to the ionized medium in the chamber to produce
`a high brightness light.
`In some embodiments. the method also involves directing
`the laser energy through at
`one optical element for
`
`modifying a property of the laser energy pro\'
`=d to the
`ionizable medium. The tnetliod also can involve actively
`pumping the chamber. In some embodiments. the ionizable
`medium is a moving target. ‘the ionixable 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 _n1odif‘y 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.
`Tlie invention. in another aspect. features a light source
`having a chamber. The light source includes a first ignition
`means fiir ionizing. an ionizable medium within the chamber.
`The light source also includes a means for prtwiding substan-
`tially continuous laser energy to the ionized medium within
`the chamber.
`The invention. in another aspect. features E3 light source
`having at chamber that includes :1 reflective surface The light
`source also includes an ignition source for ionizing a gas
`within the chamber. Tlic light source also includes a reflector
`that at leas
`substantially rcllects at first
`of predefined
`wavelengths of electroinagnctic ertergy directed toward the
`rellector 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 t_'c.g.. a contitntotis—Wu\»=e 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 substantiall_\;' continuously rather than in
`short bursts. as in a pulsed laser.
`In sotne embodiments. at least one laser directs a first set of
`wavelengths of electromagnetic energy through the reflector
`toV\=;u'd the rcllective surface ( inner stu'f'ace) ofthe chain-
`bcr and the reflective surface directs at least a portion of the
`first set ol‘\x'a\/elettgtlts ofelectromagnetic energy toward the
`plasma. In some embodiments. at least a portion of the high
`brightness light is directed toward the reflective surface of the
`cliamber. is reflected toward the reflector. and is reflected by
`the reflector toward a tool. In some embodiments. at least one
`laser directs at first set of wavelengths of electromagnetic
`energy toward the rellector. the rellcctor rellects at least at
`portion of the first wax»-‘elengtlts of electromagnetic energy
`towards the reflective surface ofthe chamber. and the reflec-
`tive surface directs a portion ofthe first set of wavelengths of
`electromagnetic energy tovvard the plztsnta.
`In some embodiments. at least a portion of the high bright-
`ness light
`is directed toward the reflective surfiace of the
`chtunbcr. is rellected toward the rellector. 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 .
`fem or lithography system spaced relative to the out-
`put ofthc light source to receive the high brightness light. ln
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`US 8,309,943 B2
`
`5
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`some enibocliments. a portion ofthe 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 o f‘ elec-
`tromagnetic energy passes through the reflector.
`The chamber o l’ the light source can include a window. in
`some embodiments. the chamber is a sea led chamber. l it some
`embodiments. the reflective surface of the chamber com-
`
`pris s a curved shape. parabolic shape. elliptical shape.
`spherical shape or aspherical 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 embodi-
`ments. a coating or film is located on the inside ofthe chamber
`to produce the reflective surface. In some embodiuients. 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.
`ln some embodiments. the optical element is adapted to pro-
`vide electrotnagnetic energy from the laser to the plasma over
`a large solid angle, In some embodiments. the reflective stir-
`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 surfiice ofthe chamber is
`adapted to collect the high brightness light generated by the
`plasnta 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 (cg. infrared wavelengths oi‘electro-
`rnagnetic energy) o f‘ electromagnetic energy.
`The invention. in another aspect. features a light 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. "fhe 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. Tltc light source
`also includes a reflector positioned along a path that the
`clcctrontagnetic 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
`of predefined waveleiigtlts of
`electromagnetic energy directed toward the reflector and at
`least substantially allow a second set of predefined wave-
`lengths ofelectromagnctic 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 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 brightness light.
`in some embodiments. the method ittvolvcs directing the
`laser energy‘ comprising at first set ofwavelengths ofclectro-
`magnetic energy through a reflector toward the reflective
`surface of the chamber. the reflective surface reflecting 2
`least a portion of the first set 0fW8V’el€ttgtl1S of'electromag-
`netic energy toward the plasma. In some embodiments. the
`method involves directing at least a portion o fthc high bright-
`ness light toward the reflective surface o f‘ the chamber which
`reflected toward the reflector and is reflected by the reflec-
`tor toward a tool.
`fit 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
`
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`
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`
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`6
`energy toward the reflective surface of the chamber. the
`reflective surface directs a portion of the first
`oftvavc-
`lengths ofelcctromagnetic energy totvard the plasma. ln 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.
`The method can involve directing the laser energy through
`an optical element that modifies a property ofthe laser energy
`to direct the laser energy toward the plasma over a large solid
`angle. In sortie 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 plasrna over a solid angle of approximately 0.0l2 stora-
`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 ofappro:-timately 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 2:: (about
`6.28) steradians. in some embodiments. 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 ofthc chamber is adapted to collect the high
`brightness light generated by the plasma over a large solid
`angle.
`The invention. in another aspect. relates to a method for
`producing light. The method involtcs ionizing with an igni~
`tion source a gas within a chamber that has a reflective sur-
`face. "lite method also involves directing elcctrornaguctic
`energy from a laser toward a reflector that at least substan-
`tially reflects a first set of'waveletigt_lis of electromagnetic
`euertvv toward the ionized gas in the chamber to produce a
`plasma that generates a high brightness light.
`In some embodiments. the electromagnetic energy from
`the laser first is reflected by the reflector toward the reflective
`surface of the chamber. in some embodiments. the electro-
`magnetic energy directed toward the reflective surface of the
`chamber is reflected toward the plasma. In some embodi-
`ments. 2: portion ofthe high brightness light is directed toward
`the reflective surface of the chzunber. reflected toward the
`reflector and passes through the reflector.
`In some embodiments. the electromagnetic energy from
`the laser first passes through the reflector and travels toward
`the reflective surface of the chamber. In some embodiments.
`the electromagnetic energy directed toward the reflective sur-
`face of the cliamloer is reflected toward the plasma. In some
`embodiments. a portion ofthc high brightness light is directed
`toward the reflective surface ofthe chamber. reflected toward
`the reflector and reflected by the reflector.
`The invention. in another aspect. features a light source that
`includes :2 chamber having a reflective surface. The light
`source also includes a means for ionizing a gas within the
`chamber. The light source also includes a means for at least
`substantially reflecting a first set o fipredcfiued wavelengths of
`electromagnetic energy directed toward the reflector and at
`least substantially allowing a second set of predefined waxe-
`lcngths ofclcctrornagnetic energy to pass through the reflec-
`tor. The light source also includes a means for providing
`electromagnetic energy to the ionized gas Within the chamber
`to produce 3 plasma that generates a high brightness light.
`The invention. in anothcrztspect. features a light source that
`includes a sealed chamber. The light source also includes an
`
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`US 8,309,943 B2
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`7
`
`ignition source for ionizing a gas within the chamber. The
`light source also includes at least one laser external to the
`sealed chamber for providing electromagnetic energy to the
`ionizec gas within the chamber to produce a plasma that
`generates a high brightness light. The light source also
`includes a cttrvecl reflective surfhce disposed external to the
`sealed chamber to receive at lens a portion of the high bright—
`ness light emitted by the sealed chamber and reflect the high
`brightness light toward an output ofthc light source.
`in some embodiments. the light source includes an optical
`element disposed along a path the electromagnetic energy
`from the laser travels.
`In some embodiments.
`the sealed
`chamber includes a support element that locates the sealed
`chamber relative to the curved reflective sttrlace.
`in some
`emhodintents, the sealed chamber is a quartz bulb. in sortie
`embodiments. the light source includes a second curved
`reflective surface disposed internal or external to the sealed
`chamber to receive at least a portion oft