CA1294352C - Light source for reduced projection - Google Patents
Light source for reduced projectionInfo
- Publication number
- CA1294352C CA1294352C CA000527873A CA527873A CA1294352C CA 1294352 C CA1294352 C CA 1294352C CA 000527873 A CA000527873 A CA 000527873A CA 527873 A CA527873 A CA 527873A CA 1294352 C CA1294352 C CA 1294352C
- Authority
- CA
- Canada
- Prior art keywords
- etalon
- light source
- laser device
- reduced projection
- output
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/08018—Mode suppression
- H01S3/08022—Longitudinal modes
- H01S3/08031—Single-mode emission
- H01S3/08036—Single-mode emission using intracavity dispersive, polarising or birefringent elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/08004—Construction or shape of optical resonators or components thereof incorporating a dispersive element, e.g. a prism for wavelength selection
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/22—Gases
- H01S3/223—Gases the active gas being polyatomic, i.e. containing two or more atoms
- H01S3/225—Gases the active gas being polyatomic, i.e. containing two or more atoms comprising an excimer or exciplex
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/22—Gases
- H01S3/223—Gases the active gas being polyatomic, i.e. containing two or more atoms
- H01S3/225—Gases the active gas being polyatomic, i.e. containing two or more atoms comprising an excimer or exciplex
- H01S3/2256—KrF, i.e. krypton fluoride is comprised for lasing around 248 nm
Abstract
ABSTRACT OF THE DISCLOSURE
A reduced projection light source comprises a laser device for emitting laser light having a lateral mode of multimodes, and an etalon located between a chamber of the laser device and a total reflection mirror. The light source is used as an exposure light source for transfer printing a ultrafine pattern on a semiconductor wafer.
A reduced projection light source comprises a laser device for emitting laser light having a lateral mode of multimodes, and an etalon located between a chamber of the laser device and a total reflection mirror. The light source is used as an exposure light source for transfer printing a ultrafine pattern on a semiconductor wafer.
Description
3r~2 rrhis invention relates to a light source for reduced projection suitable as an exposure light source for transfer printiny an extremely fine pattern on a semiconductor wafter.
According to this invention there is provided a light source for reduced projection comprising an excimer laser device inc]uding a total reflection mirror, a partial reflection output mirror having a reflective index of from 1-49~ and a chamber provided between said total reflection mirror and said output mirror, said laser device emitting laser light having a lateral mode of multimodes, and at least one etalon located between said chamber and said total reflection mirror.
The present invention wil] be further illustrated by way of the accompanying drawings in which:
Figs. 1 - 4 are diagrammatic side views respectively showing preferred embodiments of this invention;
Fig. 5 is a diagrammatic representation showing an arrangement wherein an etalon is disposed on the outside of the cavity of al~ excimer laser device;
Fig. 6 shows the construction of an air gap etalon arranged in multiple stages;
Fig. 7 is a diagrammatic representation of the construction o~ the reduced projection exposure device;
Fig. 8 is a graph showing the relation between the reflective index of an output mirror and a laser output;
Fig. 9 is a graph showing the relation between the reflective index of the output mirror and the spectrum line width;
lZ~9~3~2 Fig. ~0 is a yraph showing the relation between the reflective index of the output mirror and the laser output per unit line width; and Fig. 11 is a diagrammatic representation showing the construction of the injection lock type excimer laser device.
The light source of this type is required to have a narrow line Width of spectrum in order to provide a high resolution and it - la -.~
1 2~ ~ 3~
has been proposed to use an in;ection lock type excimer laser device as the light source.
As shown in Fig. 11, this laser device comprlses an oscillator 10 acting as a stable resonator and an amplifièr 20 actlng as a stable resonator.
In the oscillator an oscillation occurs between mirrors 11 and 12 and the wavelength of a light beam is selected by a dispersion prism 13. Since the light beam is throttled by apertures 14 and 15 so that laser light having a narrow spectrum line width and a coherent beam characteristic can be produced. This laser beam is pro~ected upon the amplifier through mirrors 17 and 18 with the result that the amplifier 20 undergoes a forced synchronous oscillation in a cavity mode.
The in~ection lock type excimer laser device can produce laser light having a narrow spectrum line width. ~owever, since the lateral mode of the laser light is of a single mode, where the laser device is used as the light source for reduced pro~ection, speckle ~interference fringe) are formed thus failing to provide a high resolution.
Accordingly, the present invention provides a light source for reduced pro~ection capable of producing laser light having a lateral mode of multimodes and a narrow spectrum line width thus enabling a high resolution.
According to the present invention there ls provided a light source for reduced pro~ection comprising a laser device lncluding a total reflection mirror, a partial reflection output m~rror and a chamber provided between said total reflection mirror and said output mirror, said laser device emitting laser light having a lateral mode of multimodes, and an etalon located between said chamber and said total reflection mirror. Suitably said etalon ~ 2 -,~QK,~
comprises an air gap etalon. Desirably said etalon comprises a solid etalon.
Thus according to this invention, there is provided an excimer laser device producing laser light whose lateral mode is multimodes, and an etalon lnterposed between a total reflection mirror and a chamber of the excimer laser device.
In one embodiment of the present invention a plurality of said etalons are used which are arranged in a plurality of stages.
Suitably said output mirror has a reflective index of from l to 49~. D~sirably the reduced pro;ection light source further comprises another etalon located on the outside of a cavity of said laser devlce. Suitably said laser device comprises an excimer laser device.
A preferred embodiment of this invention shown in Fig. 1 is constituted by an excimer laser device comprising a total reflection mirror 1 actlng as a rear mirror, an output mirror 2 acting as a front mirror and a chamber 3, and an air gap etalon 6~ disposed between the total reflection mirror l and the chamber 3. The chamber 3 is filled with a gaseous mixture of argon Ar and fluorine F, a gaseous mixture of krypton Kp and fluorine F.
Further, discharge electrodes, not shown for exciting these gases are contained in the chamber 3. Wlndows 5 and 5' are provided for the opposite ends of the chamber 3.
~ - 3 -lZ~35~
In the excimer laser device, a laser oscillation is produced between mirrors 1 and 2 wh~ch constitute a stable resonator so that laser light ls emitted ~rom the output mirror.
The lateral mode of the laser light produced by the excimer laser device has an extremely high order. In other words, the lateral mode is multiple modes which are very important for preventing the interference fringes in the spectrum at the time of the reduced projection.
In each of the other gas laser devices and an injec-tion lock type excimer laser device shown in Fig. 11, since their lateral mode is a single mode or a similar mode, such laser devices are not suitable for use in the reduced project~on.
Let US describe the air gap etalon 6A acting as wave-length selecting means. Since the etalon 6A is disposed between the total reflection mirror 1 and the chamber 3 an extremely high wavelength selection effect can be obtained as will be described later, When the etalon is disposed at the position shown ln Fig. 1. The light generated in chamber 3 impinges upon the total reflection mirror after it has passed through the etalon 6A. The light reflected by the mlrror 1 passes again th~ etalon 6A and i8 then - amplified. In other words, the light is subiectea to the ~avelength selection operation of the etalon during it~ go and return passes. For th~s reason, ln th~s embodlment, laser llght having an extremely narrow spectrum light I
12~4352 can be produced.
Where the etalon 6A ls disp~sed between the output mirror 2 and the chamber 3, a st~ong wavelength selecting functlon described above can not be expec~ed so that it becomes impossible to reduce the spectrum line width.
~ 'ig. 2 shows a modified embodiment of thls lnvention in which in addition to the etal~n 6A described above, another etalon 6B is disposed on the outslde of the cavity of the excimer laser device. With this modification, the lo ~ser light produced by the laser device ~hown in Fig. 1 would pass through the additlonal etalon 6B.
Fig. 3 shows another modifica~ion of this invention wherein ~ (m ~ 2) etalons 6A are arranged between the total reflection mirror 1 and the chamber 3.
Fig. 4 ~hows another modi~ication in which m etalons 6A and m etalons 6B shown in Fi~. 2 are aisposed.
The spectrum line Width at the time of tlatural osc~llatlon (osclllatlon without the etalon) of the excimer laser device ranges:
lOOcm 1 to 120cm 1 at full width 50cm 1 to 70cm 1 at half width so that the optimum free spectrum range FSR of the etalon would be 50cm 1 < ~SR _ 120cm 1 '~ Where an air gap etalon is used as the etalon, ~here is the follo~ing relation between the air gap spaclng d and the free spectrum range FSR of the et~lon _ 5 _ I
12~43~2 FSR = 21d . . . . . (1) where n represents the refractive index of the air gap.
By ~electing n=l, a = ~
Consequently, the range of ~ir gap d necessary fox obtaining the optimum free spectrum range can be expressed by the following equation (2) 42~m < d _ lOO~m . . . . . (Z) Since there is a relation ~J 1 T F . . . . . ( 3 ) between the finesse F and the l1ne width (half width) a~
of the spectrum, the range of finesse F of the etalon necessary to reduce the spectrum line width ~a~ of the laser light spectrum to be less then 2 cm 1 (an optimum line width for reduced projection, we can obtain 25 < F <
60 by substituting ~a~ - 2cm 1 and 50cm 1 ~ FSR < 120cm 1 into equation l3) The finesse F of the alr gap etalon can be shown by the following equation ~4) in which FF represents the surface finesse in the air gaps of the etalon and FR
~epresents the finesse caused by reflection.
~ ~ total finesse Ft = (F~ ~ FR ) / . . . (4) 3~2 Consequently, it is suff.icient to set the finesse caused by the sur~ace finesse and the finesse FR caused by reflection such that the followlng relation is satisf~ed 2~ < ~F~ + F 2~ 1/2 < 6 Thus, ln the embodiment shown ln Fig. 1, the specl-fication of the et~lon 6A necessary to obtain a line width 2 cm 1 ls as follows. I
lo 1, free spectrum range: 50cm < FSR ~ 120cm 1 1¦
(the air gap space d is set to be ~2~m c d_ lOOl~m.
2. ef~ect~ve dlameter: larger than 2 mm 3. total finesse: 25 g Ft ~ 60 (FF and FR are set to satisfy a relation o ( F F~ ) ~.60 ) In the embodiment shown in Fig. 2, let us call the etalon 6A disposed in the cavity of the excimer laser device as an internal etalon and call the etalon 6B
disposed or the outslde of the cavity as an external etalon~ the specification of the internal and external etalon 6A and 6B necessary to obtain a spectruM line width of 2 cm 1 ls as follows.
Internal etalon 6A
1. free spectrum range: 50cm 1 < FSR < 120cm 1 (when the air gap spaciny d is set to 42~m < d < lOO~m,) 129~3~2 2. effective diameter: laryer th~n 2 mm 3. total finesse: 5 ~ Ft ~ 60 (FF and FR are set to satisfy a ~elation '= F R -- ) External etalon 6B
1. free spectrum range: lOcm 1 < Ft < 20cm (when t~e air gap spacing d is set to be 208~m - 2500~m.) 2. effective dlameter: larger than 2 mm 3 the overall finesse FaQ = Fin.FoUt, product of the total finesse Ft ~ Fin of the internal etalon 6A and the total ~inesse Ft = FoUt of etalon 6B ls ~et to satisfy the following relation 25 ~ Fl F ~ 60 ( FF and FR are set to satisfy a relation 25 < (FF2 + FR2) 1/2-Fin < 60 ) In the embodiment shown in Fig. 3, the specificatlon for m etalons is aq follows.
As shown in Fig. 6, where m air gap etalons 6 are arranged in multi-stages, according to equation (l), the free spectrum range ~CRl of the first etalon is expressed by FSRl = 1/2 ndl . . . . . (S) wherea~ the spectrum range of the k-th etalon (k 5 2-m) ls ~ . .
3~i:
shown by FSRl~ = l/(Fl-F2'~'Fk~ 2 n 1 where Fl and Fk represent the finesses of the first and k-th etalons. To obtain the spectrum line width of 2 cm 1, the fr~e spectrum range FSRl shown ~n equation (5) may be in a range of 50cm 1 _ 120cm 1 when n-l. Further-more, equation (6) shows that the k-th free spectrum range may satlsfy a relation 50cm~l ~ FSRk ~ F2 Fm) _ The overall finesse of respective etalons is ex-pressed by FaQ = Fl~F2 Fm . . . . . (8) ln other words, in order to obtain a spectrum line wldth of 2 cm 1, the overall finesse Fa may be in a range of 25-60.
Accordingly, the speclfication for the m etalons 6A
of the embodiment shown in Fig. 3 is a~ follows.
1, The free spectrum range of the first etalon is 6Qt to satisfy a relation 50 < FSRl c 120, while that of the k-th etalon is set to satisfy equation (8~
(in other words, the air gap spacing of the flrst etalon ~is set to satisfy a relation 42 ~ dl c 100 and that of the k-th etalon is set to satisfy a ~elation 42 < dk / Fl F2 -Fk_l) C 100) 12~4352 2. The effective diameter of ea~h etalon larger than 2 mm 3. The overall f~nesse - FaQ is set to satisfy a relation ~5 _ Fl'F2' ~ 'Fm < 60 Although in this embodiment~ the first to m-th etalons are arranged in the order of incident of oscil-lation light, This is only the purpose of the descrip-tion, and it is clear that othex orders o arrangement can be used. Thus so long as each etalon satisfies the above described specification, the order of arrangement may be random.
The following ~able I shows examples 1 - 12 of the specifications of respective air gap etalons 6A and 68.
The specifications for the m internal etalons and m external etalons of the embodiment shown in Fig. 4 are the same as the specification for the m external etalons 6A of the embodiment shown in Fig. 3. In this embodiment too, the order of arrangement of the internal etalons may be random so long as thc specificatlon described above is fulfilled.
I
1~43~:~
Table I
~xample of Air ~eflec~ Surface ~ffec- Total Free Speciica- Gap tion Fineness tive Finesse Spectrum tion Index Dla- l~ange meter l~m] [%] [6328nm] tmm] ~ ~t [cm-l]
, _., ,. ._ _ 1 lO0 60 ~ l 50 3~ 5.2 50 2 100 70 A / 30 ~0~ 4.9 5 ... .. ...
3 100 80 ~ / 30 30~ 5,44 50 . I
~ 100 90 ~ / 30 30~ 5-77 50 100 so ~ / 50 30~ 9.3 so 6 100 95 A / 30 30~ 5.~6 50 .. .... . . _ . . .. . . .. .
7 42 90 ~ / 50 30~ 9.3 120 8 38S 73 A / 50 30~ 7.0 13 _ _ _ _ _ 9 500 ~0 ~ / 30 30~ 5.44 10 .... . . . .. _ . . . .
lo 500 62 ~ ~ 50 30~ 5.5 10 . . . ~
11 625 ~ 60 A / 30 30~ 4.23 8.0 12 926 50 ~ / 20 30~ 3 5,4 In this Table the surface ~inesse is represented by uslng the oscillation wavélength ~ ~ 632.8 nm of a He - Ne laser device.
The following Table II ~hows the lasex light spectrum line wldth and the output ratio in cases ~here tlle inter-nal etalon 6A and the external etalon 6B ~hown ln Fig. 2 and satlsfying the examples o the specifications shown in ~able ~ are suitably combined.
In Table II, the output ratlo means the ratlo of the oscillation output when etalon~ 6A and 6B are not used to ~2~4352 that when the etalons are used.
Table II
Example of Speclflcation Specification L~ne Outp~t Combination of Internal of External ~idth Ratio Etalon Etalon ~cm 1] 1 % ]
1 1 2 1.5 30 2 1 10 1.1 16 _ .
. 3 2 9 1.2 12 4 2 10 1.1 14 3 9 1.0 14 6 3 10 1.3 11 I
7 4 _ 1.5 50 8 4 11 1.1 20 9 5 11 0.8 18 _ ~
6 10 oscillate ~ .
11 7 8 1.8 10 In example 10 of Table II, since the reflective index of the internal etalon 6A is about 95%, the throughput becomes small thus disenabling osclllation, but in other examples, a line width of less than 2 cm 1 can be obtained. The interference was investigated by passing the laser lights o~ respective combinations through a pin-hole and ~ound that no interference fringe was formed.
Thus it was found that the lateral mode of the laser llght li~ of the multimodes that is there are sufficiently large number of lateral modes.
- 12 _ ~ .
.
The term "throughput" means the ratio of strength of the inpu~ light when light of a selected wavelength is passed through an etalon to the s~rength of the outpUt light ls defined by the ~ollowing equation ~ 2 t = (1- ) where A s absorption index R: ~eflective index The following Table III show~ the result of experi-ment~ where the number of internal etalons of the embodi-ment shown in Fig. 3 was made to be m=2, and the specifi-cations of the one and other internal etalons were suit-ably selected and combined from Table I.
Table III
Example of Speciflcation Specification Line Output Comblnation of Internal of External Width Ratio EtalonEtalon [Cm-1] [ ~ 1 1 1 9 0.8 38 2 1 10 0.9 47 3 2 9 0.9 30 4 2 10 0.9 28 3 9 0.8 23 .
6 3 10 0.9 24 .
7 4 9 1,0 14 8 4 11 1.0 18 ~9 5 11 0.7 14 _ 7 a l.o 13 ~ - 13 -lZ94352 As shown in Table III ~n each of the combinations 1 10 a line width of less than 2 c~ 1 was obtained. Compar-ison of these experimental data with those shown in Table Il clearly shows that the . 5 constru~tion shown in Fig. 3 has smaller power loss than that shown in Flg. ~. Furthermore, a sufflc~ent number of lateral mode~ was obtained with the combinations shown in Table III.
The following Table IV shows the resl~lt of experiment 10 where only two external etalons were used as shown in Fig, 5.
Table IV
~ Example of Specif~ation speci~ation ~ine Output ! Combination of ~nternal of External ~idth Ratio EtalonEtalon ~cm 1] [ ~ ]
I 1 1 9 1.8 3 r 2 1 10 1.9 2 3 ~ 9 1.9 2 4 2 lo 2 3 3 9 l.a 2 , 6 3 1 0 1 . 8 2 7 4 9 1.9 2 8 4 11 1.9 2 9 5 11 1.8 2 o 6 lo 1 . 9 1 7 8 1 . 8 31 29~35~:
As shown in Table IV, in each one of the combinations 1-11, a line width of less than Z cm 1 was ob~ained, but I the output ratio was decreased slightly (1-3%) than the ¦ experimental data shown in Table II. This sho~s that when ¦ 5 only the external etalon 6B is used for decreasing the ¦ spectrum line width the power loss becomes large thus I preventing practical use.
¦ Although in each embodiment shown in Figs 1-4, an ¦ air gap etalon was used as the etalon 6A, a solid etalon I 10 can be substituted for the air gap etalon. However, it is ¦ necessary to use a solid etalon of the same specification as the air gap etalon.
In the embodiments described above, the effective diameter of windows 5 and 5' was set to be larger than 2 mm and a slit (aperture) of less than 2 mm was not instal-led in the cavity of the excimer laser device.
Fig, 7 dia~rammatically sho~s a reduced projectio~
exposure device wherein light projected from a reduced projection iight source 30 ls co~veyed to a wafer 36 through an integrator 31, a reflecting mirror 32, a conden~er lens 33, a reticle 34 and a reduced projection lens 35 so as to project a pattern on the rectile 34 upon the wafer 36.
In thls apparatu9, where a high pr~sure mercury lamp, for example, is used as the light source, it is impo~sible to expo6e a fine pattern because thc maxlmum resolution ~s only about 5.0 ~m. Furthermore, as the ~L2~4~S2 spectrum line width of the mercu~y lamp is relatively wide, a color aberration compensation is necessary. For this reason, it is necessary to ~se a reduced projection lens 35 of a complicated construction comprising a com-bination of glasses havlng d~fferent refr~ctlve lndices.ThiS not only makes difficult to design lens 35 but also increases lts manufacturing cost.
Where the light source described above is used in the embodiments shown in Figs. 1-4 laser light having spectrum line widih of less than 2 cm 1 can be o~tained so that no color aberration compensation is necessary. Accordingly, it is possible to fa~ricate the projection lens with quartz above, whereby the lens can be deslgned readily and manufactured a~ a low cost.
With this embodiment, as it i3 possible to decrease the spectrum line wldth without decreasing the number of the lateral modes there is no fear of producing such problem as speckle at the time of projection.
Accordingly, it is possible to construct projection apparatus of high resolution.
In an excimer laser device, since the reflective lndex of the output mirror has an influence upon the output efficiency thereof, the laser outp~t ~ould decrease unless the reflective index is optimum.
~ Let us consider how to opti~ize the reflective index of the output mirror in order to efficiently deriving out the laser output of the excimcr laser device.
~2~435Z
In the embodiment shown in Fig. 1, an air gap etalon having a free spectrum range of 42 cm 1, a finesse of 1.7, and an effective diameter of 30 mm was used and an I experiment Was carried out for investi~ating ~he relation between the reflective index of the output mirror 2 and an excimer laser device utilizing Kr ~nd F.
Fig. 8 ~hows the resul~ of this experiment ~howing that a maximum output ~180 mJ) can be taken out when the output mirror 2 has a reflective index of about 8~.
According to this invention there is provided a light source for reduced projection comprising an excimer laser device inc]uding a total reflection mirror, a partial reflection output mirror having a reflective index of from 1-49~ and a chamber provided between said total reflection mirror and said output mirror, said laser device emitting laser light having a lateral mode of multimodes, and at least one etalon located between said chamber and said total reflection mirror.
The present invention wil] be further illustrated by way of the accompanying drawings in which:
Figs. 1 - 4 are diagrammatic side views respectively showing preferred embodiments of this invention;
Fig. 5 is a diagrammatic representation showing an arrangement wherein an etalon is disposed on the outside of the cavity of al~ excimer laser device;
Fig. 6 shows the construction of an air gap etalon arranged in multiple stages;
Fig. 7 is a diagrammatic representation of the construction o~ the reduced projection exposure device;
Fig. 8 is a graph showing the relation between the reflective index of an output mirror and a laser output;
Fig. 9 is a graph showing the relation between the reflective index of the output mirror and the spectrum line width;
lZ~9~3~2 Fig. ~0 is a yraph showing the relation between the reflective index of the output mirror and the laser output per unit line width; and Fig. 11 is a diagrammatic representation showing the construction of the injection lock type excimer laser device.
The light source of this type is required to have a narrow line Width of spectrum in order to provide a high resolution and it - la -.~
1 2~ ~ 3~
has been proposed to use an in;ection lock type excimer laser device as the light source.
As shown in Fig. 11, this laser device comprlses an oscillator 10 acting as a stable resonator and an amplifièr 20 actlng as a stable resonator.
In the oscillator an oscillation occurs between mirrors 11 and 12 and the wavelength of a light beam is selected by a dispersion prism 13. Since the light beam is throttled by apertures 14 and 15 so that laser light having a narrow spectrum line width and a coherent beam characteristic can be produced. This laser beam is pro~ected upon the amplifier through mirrors 17 and 18 with the result that the amplifier 20 undergoes a forced synchronous oscillation in a cavity mode.
The in~ection lock type excimer laser device can produce laser light having a narrow spectrum line width. ~owever, since the lateral mode of the laser light is of a single mode, where the laser device is used as the light source for reduced pro~ection, speckle ~interference fringe) are formed thus failing to provide a high resolution.
Accordingly, the present invention provides a light source for reduced pro~ection capable of producing laser light having a lateral mode of multimodes and a narrow spectrum line width thus enabling a high resolution.
According to the present invention there ls provided a light source for reduced pro~ection comprising a laser device lncluding a total reflection mirror, a partial reflection output m~rror and a chamber provided between said total reflection mirror and said output mirror, said laser device emitting laser light having a lateral mode of multimodes, and an etalon located between said chamber and said total reflection mirror. Suitably said etalon ~ 2 -,~QK,~
comprises an air gap etalon. Desirably said etalon comprises a solid etalon.
Thus according to this invention, there is provided an excimer laser device producing laser light whose lateral mode is multimodes, and an etalon lnterposed between a total reflection mirror and a chamber of the excimer laser device.
In one embodiment of the present invention a plurality of said etalons are used which are arranged in a plurality of stages.
Suitably said output mirror has a reflective index of from l to 49~. D~sirably the reduced pro;ection light source further comprises another etalon located on the outside of a cavity of said laser devlce. Suitably said laser device comprises an excimer laser device.
A preferred embodiment of this invention shown in Fig. 1 is constituted by an excimer laser device comprising a total reflection mirror 1 actlng as a rear mirror, an output mirror 2 acting as a front mirror and a chamber 3, and an air gap etalon 6~ disposed between the total reflection mirror l and the chamber 3. The chamber 3 is filled with a gaseous mixture of argon Ar and fluorine F, a gaseous mixture of krypton Kp and fluorine F.
Further, discharge electrodes, not shown for exciting these gases are contained in the chamber 3. Wlndows 5 and 5' are provided for the opposite ends of the chamber 3.
~ - 3 -lZ~35~
In the excimer laser device, a laser oscillation is produced between mirrors 1 and 2 wh~ch constitute a stable resonator so that laser light ls emitted ~rom the output mirror.
The lateral mode of the laser light produced by the excimer laser device has an extremely high order. In other words, the lateral mode is multiple modes which are very important for preventing the interference fringes in the spectrum at the time of the reduced projection.
In each of the other gas laser devices and an injec-tion lock type excimer laser device shown in Fig. 11, since their lateral mode is a single mode or a similar mode, such laser devices are not suitable for use in the reduced project~on.
Let US describe the air gap etalon 6A acting as wave-length selecting means. Since the etalon 6A is disposed between the total reflection mirror 1 and the chamber 3 an extremely high wavelength selection effect can be obtained as will be described later, When the etalon is disposed at the position shown ln Fig. 1. The light generated in chamber 3 impinges upon the total reflection mirror after it has passed through the etalon 6A. The light reflected by the mlrror 1 passes again th~ etalon 6A and i8 then - amplified. In other words, the light is subiectea to the ~avelength selection operation of the etalon during it~ go and return passes. For th~s reason, ln th~s embodlment, laser llght having an extremely narrow spectrum light I
12~4352 can be produced.
Where the etalon 6A ls disp~sed between the output mirror 2 and the chamber 3, a st~ong wavelength selecting functlon described above can not be expec~ed so that it becomes impossible to reduce the spectrum line width.
~ 'ig. 2 shows a modified embodiment of thls lnvention in which in addition to the etal~n 6A described above, another etalon 6B is disposed on the outslde of the cavity of the excimer laser device. With this modification, the lo ~ser light produced by the laser device ~hown in Fig. 1 would pass through the additlonal etalon 6B.
Fig. 3 shows another modifica~ion of this invention wherein ~ (m ~ 2) etalons 6A are arranged between the total reflection mirror 1 and the chamber 3.
Fig. 4 ~hows another modi~ication in which m etalons 6A and m etalons 6B shown in Fi~. 2 are aisposed.
The spectrum line Width at the time of tlatural osc~llatlon (osclllatlon without the etalon) of the excimer laser device ranges:
lOOcm 1 to 120cm 1 at full width 50cm 1 to 70cm 1 at half width so that the optimum free spectrum range FSR of the etalon would be 50cm 1 < ~SR _ 120cm 1 '~ Where an air gap etalon is used as the etalon, ~here is the follo~ing relation between the air gap spaclng d and the free spectrum range FSR of the et~lon _ 5 _ I
12~43~2 FSR = 21d . . . . . (1) where n represents the refractive index of the air gap.
By ~electing n=l, a = ~
Consequently, the range of ~ir gap d necessary fox obtaining the optimum free spectrum range can be expressed by the following equation (2) 42~m < d _ lOO~m . . . . . (Z) Since there is a relation ~J 1 T F . . . . . ( 3 ) between the finesse F and the l1ne width (half width) a~
of the spectrum, the range of finesse F of the etalon necessary to reduce the spectrum line width ~a~ of the laser light spectrum to be less then 2 cm 1 (an optimum line width for reduced projection, we can obtain 25 < F <
60 by substituting ~a~ - 2cm 1 and 50cm 1 ~ FSR < 120cm 1 into equation l3) The finesse F of the alr gap etalon can be shown by the following equation ~4) in which FF represents the surface finesse in the air gaps of the etalon and FR
~epresents the finesse caused by reflection.
~ ~ total finesse Ft = (F~ ~ FR ) / . . . (4) 3~2 Consequently, it is suff.icient to set the finesse caused by the sur~ace finesse and the finesse FR caused by reflection such that the followlng relation is satisf~ed 2~ < ~F~ + F 2~ 1/2 < 6 Thus, ln the embodiment shown ln Fig. 1, the specl-fication of the et~lon 6A necessary to obtain a line width 2 cm 1 ls as follows. I
lo 1, free spectrum range: 50cm < FSR ~ 120cm 1 1¦
(the air gap space d is set to be ~2~m c d_ lOOl~m.
2. ef~ect~ve dlameter: larger than 2 mm 3. total finesse: 25 g Ft ~ 60 (FF and FR are set to satisfy a relation o ( F F~ ) ~.60 ) In the embodiment shown in Fig. 2, let us call the etalon 6A disposed in the cavity of the excimer laser device as an internal etalon and call the etalon 6B
disposed or the outslde of the cavity as an external etalon~ the specification of the internal and external etalon 6A and 6B necessary to obtain a spectruM line width of 2 cm 1 ls as follows.
Internal etalon 6A
1. free spectrum range: 50cm 1 < FSR < 120cm 1 (when the air gap spaciny d is set to 42~m < d < lOO~m,) 129~3~2 2. effective diameter: laryer th~n 2 mm 3. total finesse: 5 ~ Ft ~ 60 (FF and FR are set to satisfy a ~elation '= F R -- ) External etalon 6B
1. free spectrum range: lOcm 1 < Ft < 20cm (when t~e air gap spacing d is set to be 208~m - 2500~m.) 2. effective dlameter: larger than 2 mm 3 the overall finesse FaQ = Fin.FoUt, product of the total finesse Ft ~ Fin of the internal etalon 6A and the total ~inesse Ft = FoUt of etalon 6B ls ~et to satisfy the following relation 25 ~ Fl F ~ 60 ( FF and FR are set to satisfy a relation 25 < (FF2 + FR2) 1/2-Fin < 60 ) In the embodiment shown in Fig. 3, the specificatlon for m etalons is aq follows.
As shown in Fig. 6, where m air gap etalons 6 are arranged in multi-stages, according to equation (l), the free spectrum range ~CRl of the first etalon is expressed by FSRl = 1/2 ndl . . . . . (S) wherea~ the spectrum range of the k-th etalon (k 5 2-m) ls ~ . .
3~i:
shown by FSRl~ = l/(Fl-F2'~'Fk~ 2 n 1 where Fl and Fk represent the finesses of the first and k-th etalons. To obtain the spectrum line width of 2 cm 1, the fr~e spectrum range FSRl shown ~n equation (5) may be in a range of 50cm 1 _ 120cm 1 when n-l. Further-more, equation (6) shows that the k-th free spectrum range may satlsfy a relation 50cm~l ~ FSRk ~ F2 Fm) _ The overall finesse of respective etalons is ex-pressed by FaQ = Fl~F2 Fm . . . . . (8) ln other words, in order to obtain a spectrum line wldth of 2 cm 1, the overall finesse Fa may be in a range of 25-60.
Accordingly, the speclfication for the m etalons 6A
of the embodiment shown in Fig. 3 is a~ follows.
1, The free spectrum range of the first etalon is 6Qt to satisfy a relation 50 < FSRl c 120, while that of the k-th etalon is set to satisfy equation (8~
(in other words, the air gap spacing of the flrst etalon ~is set to satisfy a relation 42 ~ dl c 100 and that of the k-th etalon is set to satisfy a ~elation 42 < dk / Fl F2 -Fk_l) C 100) 12~4352 2. The effective diameter of ea~h etalon larger than 2 mm 3. The overall f~nesse - FaQ is set to satisfy a relation ~5 _ Fl'F2' ~ 'Fm < 60 Although in this embodiment~ the first to m-th etalons are arranged in the order of incident of oscil-lation light, This is only the purpose of the descrip-tion, and it is clear that othex orders o arrangement can be used. Thus so long as each etalon satisfies the above described specification, the order of arrangement may be random.
The following ~able I shows examples 1 - 12 of the specifications of respective air gap etalons 6A and 68.
The specifications for the m internal etalons and m external etalons of the embodiment shown in Fig. 4 are the same as the specification for the m external etalons 6A of the embodiment shown in Fig. 3. In this embodiment too, the order of arrangement of the internal etalons may be random so long as thc specificatlon described above is fulfilled.
I
1~43~:~
Table I
~xample of Air ~eflec~ Surface ~ffec- Total Free Speciica- Gap tion Fineness tive Finesse Spectrum tion Index Dla- l~ange meter l~m] [%] [6328nm] tmm] ~ ~t [cm-l]
, _., ,. ._ _ 1 lO0 60 ~ l 50 3~ 5.2 50 2 100 70 A / 30 ~0~ 4.9 5 ... .. ...
3 100 80 ~ / 30 30~ 5,44 50 . I
~ 100 90 ~ / 30 30~ 5-77 50 100 so ~ / 50 30~ 9.3 so 6 100 95 A / 30 30~ 5.~6 50 .. .... . . _ . . .. . . .. .
7 42 90 ~ / 50 30~ 9.3 120 8 38S 73 A / 50 30~ 7.0 13 _ _ _ _ _ 9 500 ~0 ~ / 30 30~ 5.44 10 .... . . . .. _ . . . .
lo 500 62 ~ ~ 50 30~ 5.5 10 . . . ~
11 625 ~ 60 A / 30 30~ 4.23 8.0 12 926 50 ~ / 20 30~ 3 5,4 In this Table the surface ~inesse is represented by uslng the oscillation wavélength ~ ~ 632.8 nm of a He - Ne laser device.
The following Table II ~hows the lasex light spectrum line wldth and the output ratio in cases ~here tlle inter-nal etalon 6A and the external etalon 6B ~hown ln Fig. 2 and satlsfying the examples o the specifications shown in ~able ~ are suitably combined.
In Table II, the output ratlo means the ratlo of the oscillation output when etalon~ 6A and 6B are not used to ~2~4352 that when the etalons are used.
Table II
Example of Speclflcation Specification L~ne Outp~t Combination of Internal of External ~idth Ratio Etalon Etalon ~cm 1] 1 % ]
1 1 2 1.5 30 2 1 10 1.1 16 _ .
. 3 2 9 1.2 12 4 2 10 1.1 14 3 9 1.0 14 6 3 10 1.3 11 I
7 4 _ 1.5 50 8 4 11 1.1 20 9 5 11 0.8 18 _ ~
6 10 oscillate ~ .
11 7 8 1.8 10 In example 10 of Table II, since the reflective index of the internal etalon 6A is about 95%, the throughput becomes small thus disenabling osclllation, but in other examples, a line width of less than 2 cm 1 can be obtained. The interference was investigated by passing the laser lights o~ respective combinations through a pin-hole and ~ound that no interference fringe was formed.
Thus it was found that the lateral mode of the laser llght li~ of the multimodes that is there are sufficiently large number of lateral modes.
- 12 _ ~ .
.
The term "throughput" means the ratio of strength of the inpu~ light when light of a selected wavelength is passed through an etalon to the s~rength of the outpUt light ls defined by the ~ollowing equation ~ 2 t = (1- ) where A s absorption index R: ~eflective index The following Table III show~ the result of experi-ment~ where the number of internal etalons of the embodi-ment shown in Fig. 3 was made to be m=2, and the specifi-cations of the one and other internal etalons were suit-ably selected and combined from Table I.
Table III
Example of Speciflcation Specification Line Output Comblnation of Internal of External Width Ratio EtalonEtalon [Cm-1] [ ~ 1 1 1 9 0.8 38 2 1 10 0.9 47 3 2 9 0.9 30 4 2 10 0.9 28 3 9 0.8 23 .
6 3 10 0.9 24 .
7 4 9 1,0 14 8 4 11 1.0 18 ~9 5 11 0.7 14 _ 7 a l.o 13 ~ - 13 -lZ94352 As shown in Table III ~n each of the combinations 1 10 a line width of less than 2 c~ 1 was obtained. Compar-ison of these experimental data with those shown in Table Il clearly shows that the . 5 constru~tion shown in Fig. 3 has smaller power loss than that shown in Flg. ~. Furthermore, a sufflc~ent number of lateral mode~ was obtained with the combinations shown in Table III.
The following Table IV shows the resl~lt of experiment 10 where only two external etalons were used as shown in Fig, 5.
Table IV
~ Example of Specif~ation speci~ation ~ine Output ! Combination of ~nternal of External ~idth Ratio EtalonEtalon ~cm 1] [ ~ ]
I 1 1 9 1.8 3 r 2 1 10 1.9 2 3 ~ 9 1.9 2 4 2 lo 2 3 3 9 l.a 2 , 6 3 1 0 1 . 8 2 7 4 9 1.9 2 8 4 11 1.9 2 9 5 11 1.8 2 o 6 lo 1 . 9 1 7 8 1 . 8 31 29~35~:
As shown in Table IV, in each one of the combinations 1-11, a line width of less than Z cm 1 was ob~ained, but I the output ratio was decreased slightly (1-3%) than the ¦ experimental data shown in Table II. This sho~s that when ¦ 5 only the external etalon 6B is used for decreasing the ¦ spectrum line width the power loss becomes large thus I preventing practical use.
¦ Although in each embodiment shown in Figs 1-4, an ¦ air gap etalon was used as the etalon 6A, a solid etalon I 10 can be substituted for the air gap etalon. However, it is ¦ necessary to use a solid etalon of the same specification as the air gap etalon.
In the embodiments described above, the effective diameter of windows 5 and 5' was set to be larger than 2 mm and a slit (aperture) of less than 2 mm was not instal-led in the cavity of the excimer laser device.
Fig, 7 dia~rammatically sho~s a reduced projectio~
exposure device wherein light projected from a reduced projection iight source 30 ls co~veyed to a wafer 36 through an integrator 31, a reflecting mirror 32, a conden~er lens 33, a reticle 34 and a reduced projection lens 35 so as to project a pattern on the rectile 34 upon the wafer 36.
In thls apparatu9, where a high pr~sure mercury lamp, for example, is used as the light source, it is impo~sible to expo6e a fine pattern because thc maxlmum resolution ~s only about 5.0 ~m. Furthermore, as the ~L2~4~S2 spectrum line width of the mercu~y lamp is relatively wide, a color aberration compensation is necessary. For this reason, it is necessary to ~se a reduced projection lens 35 of a complicated construction comprising a com-bination of glasses havlng d~fferent refr~ctlve lndices.ThiS not only makes difficult to design lens 35 but also increases lts manufacturing cost.
Where the light source described above is used in the embodiments shown in Figs. 1-4 laser light having spectrum line widih of less than 2 cm 1 can be o~tained so that no color aberration compensation is necessary. Accordingly, it is possible to fa~ricate the projection lens with quartz above, whereby the lens can be deslgned readily and manufactured a~ a low cost.
With this embodiment, as it i3 possible to decrease the spectrum line wldth without decreasing the number of the lateral modes there is no fear of producing such problem as speckle at the time of projection.
Accordingly, it is possible to construct projection apparatus of high resolution.
In an excimer laser device, since the reflective lndex of the output mirror has an influence upon the output efficiency thereof, the laser outp~t ~ould decrease unless the reflective index is optimum.
~ Let us consider how to opti~ize the reflective index of the output mirror in order to efficiently deriving out the laser output of the excimcr laser device.
~2~435Z
In the embodiment shown in Fig. 1, an air gap etalon having a free spectrum range of 42 cm 1, a finesse of 1.7, and an effective diameter of 30 mm was used and an I experiment Was carried out for investi~ating ~he relation between the reflective index of the output mirror 2 and an excimer laser device utilizing Kr ~nd F.
Fig. 8 ~hows the resul~ of this experiment ~howing that a maximum output ~180 mJ) can be taken out when the output mirror 2 has a reflective index of about 8~.
10 Taking one hal~ value t90 mJ) of the maximum output as a threshold value Tl, for judging high o~ low of the effi-¦ ciency of the excimer laser device, as can be noted from Fig. 8, a sufficiently practical output can be efficient~y taken ou~ when the reflective index of the oUtput mirror lies ln a range between 2~ and 43~.
As the reflective index of the output mirror isincreased, the number of turns of light in the cavity ~, lncreases 60 that the spectrum llne width of the laser light becomes narrow. Fig. 9 is a graph showing the reflective index of the output mirror 2 and the spectrum llne width.
Fig. 10 shows a graph obtained by dividlng the laser output showing ~ig. 8 with the spectrum llne width shown in Fig. 9, the qraph showin~ the relation between the ~reflective index of the output mirror 2 and the laser device output per un~t spectrunl llne width.
Fig. 10 ~hows that the laser output per unit line 1~9~352 wiath becomes a maximum (8.6 mJ/cm 1~ whe~ the reflective index o~ the o~tput mirror is about 20%. Taking one half value ~4.3 mJ/cm 1) of the maximum laser output per unit line width as a threshold value T2 for ju~ging high or low of the efficiency of the laser output per unit line width, it is possible to efficiently take out the laser output per unit line width when the reflective index of the output mirror lies i~ a range of from 1~ to 49~, as can be noted from the graph.
Tt should be understood that the relation shown in Fig. 1~ also holds true for the embodiments shown in Figs 1-4, Brlefly stated, in the above described embodiments employing internal etalon 6A, 80 long as the re~lective ) ~ndex of the output mlrror 2 is set in a range of from 1 to 49~, it ls possible to obtain sufficient laser output per unit spect~um llne wi~th.
- lB -
As the reflective index of the output mirror isincreased, the number of turns of light in the cavity ~, lncreases 60 that the spectrum llne width of the laser light becomes narrow. Fig. 9 is a graph showing the reflective index of the output mirror 2 and the spectrum llne width.
Fig. 10 shows a graph obtained by dividlng the laser output showing ~ig. 8 with the spectrum llne width shown in Fig. 9, the qraph showin~ the relation between the ~reflective index of the output mirror 2 and the laser device output per un~t spectrunl llne width.
Fig. 10 ~hows that the laser output per unit line 1~9~352 wiath becomes a maximum (8.6 mJ/cm 1~ whe~ the reflective index o~ the o~tput mirror is about 20%. Taking one half value ~4.3 mJ/cm 1) of the maximum laser output per unit line width as a threshold value T2 for ju~ging high or low of the efficiency of the laser output per unit line width, it is possible to efficiently take out the laser output per unit line width when the reflective index of the output mirror lies i~ a range of from 1~ to 49~, as can be noted from the graph.
Tt should be understood that the relation shown in Fig. 1~ also holds true for the embodiments shown in Figs 1-4, Brlefly stated, in the above described embodiments employing internal etalon 6A, 80 long as the re~lective ) ~ndex of the output mlrror 2 is set in a range of from 1 to 49~, it ls possible to obtain sufficient laser output per unit spect~um llne wi~th.
- lB -
Claims (5)
1. A light source for reduced projection comprising an excimer laser device including a total reflection mirror, a partial reflection output mirror having a reflective index of from 1-49% and a chamber provided between said total reflection mirror and said output mirror, said laser device emitting laser light having a lateral mode of multimodes, and at least one etalon located between said chamber and said total reflection mirror.
2. The reduced projection light source as set forth in claim 1 wherein said etalon comprises an air gap etalon.
3. The reduced projection light source as set forth in claim 1 wherein said etalon comprises a solid etalon.
4. The reduced projection light source as set forth in claim 1 wherein said at least one etalon comprises a plurality of said etalons which are arranged in a plurality of stages.
5. The reduced projection light source as set forth in claim 1 further comprising another etalon located on the outside of a cavity of said laser device.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11765/1986 | 1986-01-22 | ||
| JP61011765A JPS62111228A (en) | 1985-07-02 | 1986-01-22 | Light source for reduction projection |
| JP39455/1986 | 1986-02-25 | ||
| JP61039455A JP2623085B2 (en) | 1986-02-25 | 1986-02-25 | Excimer laser |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1294352C true CA1294352C (en) | 1992-01-14 |
Family
ID=26347287
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000527873A Expired - Fee Related CA1294352C (en) | 1986-01-22 | 1987-05-25 | Light source for reduced projection |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4856018A (en) |
| EP (1) | EP0230302A3 (en) |
| CA (1) | CA1294352C (en) |
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| US20010046088A1 (en) | 1994-02-14 | 2001-11-29 | Naoto Sano | Exposure apparatus and device manufacturing method using the same |
| DE19603637C1 (en) | 1996-02-01 | 1997-07-31 | Lambda Physik Gmbh | Narrow band radiation emitting laser |
| US6014398A (en) * | 1997-10-10 | 2000-01-11 | Cymer, Inc. | Narrow band excimer laser with gas additive |
| US7006541B2 (en) * | 1998-06-01 | 2006-02-28 | Lambda Physik Ag | Absolute wavelength calibration of lithography laser using multiple element or tandem see through hollow cathode lamp |
| US6580517B2 (en) | 2000-03-01 | 2003-06-17 | Lambda Physik Ag | Absolute wavelength calibration of lithography laser using multiple element or tandem see through hollow cathode lamp |
| US6160832A (en) | 1998-06-01 | 2000-12-12 | Lambda Physik Gmbh | Method and apparatus for wavelength calibration |
| US6490307B1 (en) | 1999-03-17 | 2002-12-03 | Lambda Physik Ag | Method and procedure to automatically stabilize excimer laser output parameters |
| US6345065B1 (en) | 1998-06-04 | 2002-02-05 | Lambda Physik Ag | F2-laser with line selection |
| US6476987B1 (en) | 1999-08-04 | 2002-11-05 | Lambda Physik Ag | Excimer laser with line narrowing |
| US6424666B1 (en) | 1999-06-23 | 2002-07-23 | Lambda Physik Ag | Line-narrowing module for high power laser |
| US6795473B1 (en) | 1999-06-23 | 2004-09-21 | Lambda Physik Ag | Narrow band excimer laser with a prism-grating as line-narrowing optical element |
| US6381256B1 (en) | 1999-02-10 | 2002-04-30 | Lambda Physik Ag | Molecular fluorine laser with spectral linewidth of less than 1 pm |
| US6426966B1 (en) | 1999-02-10 | 2002-07-30 | Lambda Physik Ag | Molecular fluorine (F2) laser with narrow spectral linewidth |
| US6421365B1 (en) | 1999-11-18 | 2002-07-16 | Lambda Physik Ag | Narrow band excimer or molecular fluorine laser having an output coupling interferometer |
| US6154470A (en) * | 1999-02-10 | 2000-11-28 | Lamba Physik Gmbh | Molecular fluorine (F2) laser with narrow spectral linewidth |
| US6965624B2 (en) * | 1999-03-17 | 2005-11-15 | Lambda Physik Ag | Laser gas replenishment method |
| US6717973B2 (en) | 1999-02-10 | 2004-04-06 | Lambda Physik Ag | Wavelength and bandwidth monitor for excimer or molecular fluorine laser |
| US6463086B1 (en) * | 1999-02-10 | 2002-10-08 | Lambda Physik Ag | Molecular fluorine laser with spectral linewidth of less than 1 pm |
| US6678291B2 (en) | 1999-12-15 | 2004-01-13 | Lambda Physik Ag | Molecular fluorine laser |
| US6546037B2 (en) | 1999-02-10 | 2003-04-08 | Lambda Physik Ag | Molecular fluorine laser with spectral linewidth of less than 1 pm |
| US6389052B2 (en) | 1999-03-17 | 2002-05-14 | Lambda Physik Ag | Laser gas replenishment method |
| US6393040B1 (en) | 1999-02-24 | 2002-05-21 | Lambda Physik Ag | Molecular fluorine (F2) excimer laser with reduced coherence length |
| US6298080B1 (en) | 1999-03-12 | 2001-10-02 | Lambda Physik Ag | Narrow band excimer or molecular fluorine laser with adjustable bandwidth |
| US6700915B2 (en) | 1999-03-12 | 2004-03-02 | Lambda Physik Ag | Narrow band excimer laser with a resonator containing an optical element for making wavefront corrections |
| US6727731B1 (en) | 1999-03-12 | 2004-04-27 | Lambda Physik Ag | Energy control for an excimer or molecular fluorine laser |
| US6714577B1 (en) | 1999-03-17 | 2004-03-30 | Lambda Physik Ag | Energy stabilized gas discharge laser |
| DE29907349U1 (en) | 1999-04-26 | 2000-07-06 | Lambda Physik Gmbh | Laser for generating narrow-band radiation |
| US6594291B1 (en) * | 1999-06-16 | 2003-07-15 | Komatsu Ltd. | Ultra narrow band fluorine laser apparatus and fluorine exposure apparatus |
| JP2001024265A (en) * | 1999-07-05 | 2001-01-26 | Komatsu Ltd | Very narrow-band fluorine laser device |
| US6785316B1 (en) | 1999-08-17 | 2004-08-31 | Lambda Physik Ag | Excimer or molecular laser with optimized spectral purity |
| US6553050B1 (en) | 1999-11-18 | 2003-04-22 | Lambda Physik Ag | Narrow band excimer or molecular fluorine laser having an output coupling interferometer |
| US6603788B1 (en) | 1999-11-23 | 2003-08-05 | Lambda Physik Ag | Resonator for single line selection |
| DE10190427T1 (en) | 2000-01-25 | 2002-06-06 | Lambda Physik Ag | Energy monitoring device for a fluoromolecular laser |
| US6735232B2 (en) | 2000-01-27 | 2004-05-11 | Lambda Physik Ag | Laser with versatile output energy |
| US6542243B2 (en) | 2000-01-27 | 2003-04-01 | Lambda Physik Ag | Resonator optics monitoring method |
| US7075963B2 (en) | 2000-01-27 | 2006-07-11 | Lambda Physik Ag | Tunable laser with stabilized grating |
| US6597462B2 (en) | 2000-03-01 | 2003-07-22 | Lambda Physik Ag | Laser wavelength and bandwidth monitor |
| US6941259B2 (en) * | 2000-03-01 | 2005-09-06 | Lamda Physik Ag | Laser software control system |
| US6618403B2 (en) | 2000-03-16 | 2003-09-09 | Lambda Physik Ag | Method and apparatus for compensation of beam property drifts detected by measurement systems outside of an excimer laser |
| US20010049618A1 (en) * | 2000-03-23 | 2001-12-06 | Rainer Patzel | Method for allocating predictable costs for consumable items |
| US6834066B2 (en) | 2000-04-18 | 2004-12-21 | Lambda Physik Ag | Stabilization technique for high repetition rate gas discharge lasers |
| US6862307B2 (en) | 2000-05-15 | 2005-03-01 | Lambda Physik Ag | Electrical excitation circuit for a pulsed gas laser |
| US6577663B2 (en) | 2000-06-19 | 2003-06-10 | Lambda Physik Ag | Narrow bandwidth oscillator-amplifier system |
| US6603789B1 (en) | 2000-07-05 | 2003-08-05 | Lambda Physik Ag | Narrow band excimer or molecular fluorine laser with improved beam parameters |
| US6721345B2 (en) | 2000-07-14 | 2004-04-13 | Lambda Physik Ag | Electrostatic precipitator corona discharge ignition voltage probe for gas status detection and control system for gas discharge lasers |
| US6807205B1 (en) | 2000-07-14 | 2004-10-19 | Lambda Physik Ag | Precise monitor etalon calibration technique |
| US6801561B2 (en) | 2000-09-25 | 2004-10-05 | Lambda Physik Ag | Laser system and method for spectral narrowing through wavefront correction |
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| US6998620B2 (en) * | 2001-08-13 | 2006-02-14 | Lambda Physik Ag | Stable energy detector for extreme ultraviolet radiation detection |
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|---|---|---|---|---|
| GB1443127A (en) * | 1973-05-23 | 1976-07-21 | Us Energy Research Dev Adminis | Pulsed multiline co2 laser oscillator spparatus and method |
| US3919665A (en) * | 1974-07-02 | 1975-11-11 | Zeiss Stiftung | Laser with transverse mode and frequency selection |
| DE3588012T2 (en) * | 1984-06-21 | 1995-09-14 | At & T Corp | Lithography in the far UV region. |
| JPS6197981A (en) * | 1984-10-19 | 1986-05-16 | Japan Atom Energy Res Inst | Optical pumping laser |
| US4689794A (en) * | 1985-01-28 | 1987-08-25 | Northrop Corporation | Injection locking a xenon chloride laser at 308.4 nm |
-
1987
- 1987-01-20 US US07/005,226 patent/US4856018A/en not_active Expired - Lifetime
- 1987-01-20 EP EP87100681A patent/EP0230302A3/en not_active Withdrawn
- 1987-05-25 CA CA000527873A patent/CA1294352C/en not_active Expired - Fee Related
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| EP0230302A3 (en) | 1989-11-15 |
| US4856018A (en) | 1989-08-08 |
| EP0230302A2 (en) | 1987-07-29 |
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