CA2063600A1 - Narrow band excimer laser and wavelength detecting apparatus - Google Patents
Narrow band excimer laser and wavelength detecting apparatusInfo
- Publication number
- CA2063600A1 CA2063600A1 CA 2063600 CA2063600A CA2063600A1 CA 2063600 A1 CA2063600 A1 CA 2063600A1 CA 2063600 CA2063600 CA 2063600 CA 2063600 A CA2063600 A CA 2063600A CA 2063600 A1 CA2063600 A1 CA 2063600A1
- Authority
- CA
- Canada
- Prior art keywords
- light
- wavelength
- laser
- detected
- etalon
- 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.)
- Abandoned
Links
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 claims abstract description 57
- 230000010355 oscillation Effects 0.000 claims abstract description 14
- 230000007480 spreading Effects 0.000 claims abstract description 5
- 239000013307 optical fiber Substances 0.000 claims description 14
- 230000004075 alteration Effects 0.000 claims description 8
- 230000003287 optical effect Effects 0.000 claims description 8
- 230000002194 synthesizing effect Effects 0.000 claims description 6
- 230000003405 preventing effect Effects 0.000 claims description 4
- 238000012937 correction Methods 0.000 claims description 3
- 230000000875 corresponding effect Effects 0.000 claims 2
- 230000009467 reduction Effects 0.000 abstract description 6
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000004065 semiconductor Substances 0.000 abstract description 4
- 238000001514 detection method Methods 0.000 description 13
- 238000000034 method Methods 0.000 description 10
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 7
- 229910052753 mercury Inorganic materials 0.000 description 7
- 238000010276 construction Methods 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 230000001965 increasing effect Effects 0.000 description 4
- 238000002347 injection Methods 0.000 description 4
- 239000007924 injection Substances 0.000 description 4
- 230000036961 partial effect Effects 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 229910021532 Calcite Inorganic materials 0.000 description 1
- 240000006829 Ficus sundaica Species 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 1
- 229910001634 calcium fluoride Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000005338 frosted glass Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000003449 preventive effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 230000002311 subsequent effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/7055—Exposure light control in all parts of the microlithographic apparatus, e.g. pulse length control or light interruption
- G03F7/70566—Polarisation control
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
- G01J9/0246—Measuring optical wavelength
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/7055—Exposure light control in all parts of the microlithographic apparatus, e.g. pulse length control or light interruption
- G03F7/70575—Wavelength control, e.g. control of bandwidth, multiple wavelength, selection of wavelength or matching of optical components to wavelength
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/7055—Exposure light control in all parts of the microlithographic apparatus, e.g. pulse length control or light interruption
- G03F7/70583—Speckle reduction, e.g. coherence control or amplitude/wavefront splitting
-
- 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
- H01S3/08009—Construction or shape of optical resonators or components thereof incorporating a dispersive element, e.g. a prism for wavelength selection using a diffraction grating
-
- 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
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/139—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length
- H01S3/1394—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length by using an active reference, e.g. second laser, klystron or other standard frequency source
-
- 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
- H01S3/0014—Monitoring arrangements not otherwise provided for
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Lasers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A narrow band excimer laser and a wavelength detecting apparatus are suitable for use as a light source of a reduction projection aligner of a semiconductor device manu-facturing apparatus. In the excimer laser, the ruling direction and the beam expanding direction of a prism beam expander are made substantially coincide with each other, and a polarizing element causing selective oscillation of a linearly polarized light wave substantially parallel with the beam spreading direction of a prism beam expander is contained in a laser cavity. A window at the front or rear side of a laser chamber is disposed such that the window make a Brewster's angle with respect to the axis of the laser beam in a plane containing the beam expanding direc-tion of the prism expander and the laser beam axis. An anti-reflection film which selectively prevents reflection of a polarized light component substantially parallel to the direction of beam expanding of a prism beam expander is coated on one surface of a prism that constitutes the prism beam expander. The wavelength detecting apparatus is con-structed to input a reference light and a light to be de-tected upon the etalon. The light transmitting through the etalon is condensed to focus on a light detector for detect-ing the wavelength of the laser beam based on interference fringe detected by the light detector.
A narrow band excimer laser and a wavelength detecting apparatus are suitable for use as a light source of a reduction projection aligner of a semiconductor device manu-facturing apparatus. In the excimer laser, the ruling direction and the beam expanding direction of a prism beam expander are made substantially coincide with each other, and a polarizing element causing selective oscillation of a linearly polarized light wave substantially parallel with the beam spreading direction of a prism beam expander is contained in a laser cavity. A window at the front or rear side of a laser chamber is disposed such that the window make a Brewster's angle with respect to the axis of the laser beam in a plane containing the beam expanding direc-tion of the prism expander and the laser beam axis. An anti-reflection film which selectively prevents reflection of a polarized light component substantially parallel to the direction of beam expanding of a prism beam expander is coated on one surface of a prism that constitutes the prism beam expander. The wavelength detecting apparatus is con-structed to input a reference light and a light to be de-tected upon the etalon. The light transmitting through the etalon is condensed to focus on a light detector for detect-ing the wavelength of the laser beam based on interference fringe detected by the light detector.
Description
2~3fiQ~i Specification TITLE OF THE INVENTION
NARROW BAND EXCIMER LASER AND
WAVELENGTH DETECTING APPARATUS
TECHNOLOGICAL FIELD
This invention relates to a narrow band excimer laser and a wavelength detection device, and more particularly, to a narrow band excimer laser suitable for a light source of a reduction projection aligner for use in manufacturing of semiconductors.
_ACKGROUND ART
An attention has been paid to the use of an excimer laser as a light source of reduction projection aligner (hereinafter called a stepper) for manufacturing semicon-ductor devices. This is because the excimer laser may possibly extend the light exposure limit to be less than 0.5 ~m since the wavelength of the excimer laser is short (for example the wavelength of KrF laser is about 248.4 nm), because with the same resolution, the focal depth is greater -than a g line or an i line of a mercury lamp conventionally used, because the numerical aperture (NA) of a lens can be made small so that the exposure region can be enlarged and large power can be obtained, and because many other advant-ages can be expected.
2~3~
An excimer laser utilized as a light source of the stepper is required to have a narrow bandwidth with a beam width of less than 3pm as well as a large output power.
A technique of narrowing the bandwidth of the excimer laser beam is known as the injection lock method. In the injection lock method, wavelength selecting element (etalon, diffraction grating, prism, etc.) are disposed in a cavity of an oscillation stage so as to generate a single mode oscillation by limiting the space mode by using a pin hole and to injection synchronize the laser beam in an amplifi-cation stage. With this method, however, although a rela-tively large output power can be obtained, there are such defects that a misshot occurs, that it is difficult to obtain 100% the locking efficiency, and that the spectrum purity degrades. Furthermore, in this method, the output light beam has a high degree of coherency so that when the output light beam is used as a light source of the reduction type projection aligner, a speckle pattern generates.
Generally it is considered that the generation of speckle pattern depends upon the number of space transverse modes.
When the number of space transverse modes contained in the laser light is small, the speckle pattern becomes easy to generate. Conversely, when the number of the space trans-verse modes increases, the speckle pattern becomes difficult to generate art. The injection lock method described above is a technique for narrowing the bandwidth by greatly : . .. . ..
. ~
.
-- :
.
2~3~ f3 decreasing the number of space transverse modes. Since generation of speckle pattern causes a serious problem, this technique can not be adopted in the reduction projection aligner.
Another projection technique for narrowing the band-width o the excimer layer beam is a technique utilizing a air gap etalon acting as a wavelength selective element. A
prior art technique utilizing the air gap etalon was devel-oped by AT & T Bell Laboratory wherein an air gap etalon is disposed between the front mirror and a laser chamber of an excimer laser device so as to narrow the bandwidth of the excimer laser. This system, however, cannot obtain a very narrow spectral bandwidth. In addition there are problems that the power loss is large due to the insertion of the air gap etalon. Further it is impossible to greatly increase the number of the space transverse modes. Furthermore, the air gap etalon has a problem of poor durability.
Accordingly, an excimer laser device has been proposed wherein a relatively high durable diffraction grating is used as the wavelength selective element.
In the excimer laser having a diffractive grating which acts as a wavelength selective element, a pin hole is provided in a resonator (laser cavity) to reduce the spread angle of the beam in the grating. Alternatively a beam expander is provided to expand the laser beam incident to the grating. For this beam expander, a prism expander ` ` 2 ~ ~ 3 ~
utilizing a prism is typically been used.
The narrow band excimer laser used as the stepper must not only have a narrow bandwidth with a line width of less than 3 pm but also must produce a large output.
In the construction in which a pin hole is disposed in a resonator, however, the output becomes greatly reduced and the number of space transverse modes necessary for prevent-ing generation of a speckle pattern decreases, so that such construction can not be used.
In the construction in which a prism beam expander is used, the expander must have a large magnifying power in order to narrow the line width.
However, when the magnifying power of the prism beam expander becomes large, the incident angle of the laser beam to a prism of the prism expander becomes large or it becomes necessary to increase the number of prisms, thereby increas-ing the loss. As a result, a large output cannot be pro-duced.
Furthermore, where a narrow band excimer laser is used as the light source of a stepper, it is necessary to narrow the bandwidth of the output laser beam and then to control the wavelength of the output laser beam whose bandwidth has been narrowed to a stable condition at a high accuracy.
A monitor etalon has been used for measuring the line width of the output beam and for detecting the wavelength.
The monitor etalon is constituted by an air gap etalon , ,. - ;~ '' , . ;., . ' :: . ~ . , .. -., . ~ , :: , , :
. .
2~3~3~3~
wherein a pair of partial reflective mirrors are disposed to confront each other with a predetermined air gap therebet-ween. The transmissive wavelength of this air gap etalon is expressed by the following equation m~ = 2nd cos 3 where m represents the order, d the partial mirrors spacing, n the refractive index of the medium the par ial reflective mirrors, and ~ an angle between the normal of the etalon and the axis of the incident light.
This equation shows that where n, d and m are constant, as the wavelength varies, the angle 3 changes. The monitor etalon detects the wavelength of the beam by utilizing this characteristics. In the monitor etalon described above, when the pressure in the air gap and the ambient temperature vary, the angle ~ varies even when the wavelength is con-stant. Accordingly, where the monitor etalon is used for detectiny the wavelength, the pressure in the air gap and the ambient temperature are controlled to be constant.
However, it is difficult to precisely control the pressure in the air gap and the ambient temperature.
Therefore, it is impossible to detect the absolute wave-length at a high accuracy.
For this reason, apparatus has been proposed wherein the beam to be detected is inputted to the monitor etalon together with a reference beam having a known wavelength, and the wavelength of the beam is detected by detecting a wavelength of the beam relative to the reference beam.
In this apparatus, a light beam transmitting through the monitor etalon is directly inputted to a beam detector such as CCD image sensor.
However, in this apparatus, since the output of the monitor etalon is directly inputted to the beam detector, the beam to be detected and the reference beam cannot be inputted to the beam detector with a sufficient beam quan-tity, and an interference fringe cannot be formed on the beam detector.
Accordingly, it is an object of this invention to provide a novel narrow band excimer laser of the type using a prism beam expander and a diffraction grating as a band-narrowing element, capable of preventing increase of loss even when the magnifying power of the prism expander is increased.
Another object of this invention is to provide a novel wavelength detecting apparatus of a narrow band excimer laser capable of inputting a reference beam and a beam to be detected into a beam detector with a sufficient quantity and capable of detecting the interference fringes of both beams at a high accuracy.
DISCLOSURE OF THE INVENTION
According to one aspect of this invention, there is provided a narrow band oscillation excimer laser comprising ' 2n~60~
a prism beam expander and a diffractive grating which are used as a bandwidth narrowing element, the ruling direction o the grating and the beam spreading direction of the prism beam expander being substantially coincided with each other;
and selective oscillation means for selectively oscillating a linearly polarized wave which is substantially parallel with the beam expanding direction of the prism beam ex-pander. The selective oscillation means may be constructed by a polarizing element disposed in the laser cavity.
The selective oscillation means may be constructed by a window provided on a rear side or a front side of the laser chamber in such a manner that the window is inclined with a Brewster's angle with respect to the optical axis of the laser beam in a plane containing the beam expanding direc-tion of the prism expander and the optical axis of the laser beam.
The selective oscillation means may include a prism beam expander in which one surface of a prism is coated with a reflection preventive film for selectively preventing a reflection of a polarized component which is parallel with the beam expanding direction of the prism beam expander.
By selectively oscillating a linearly polarized wave which is substantially parallel with the beam expanding direction of the prism beam expander, the loss can be reduced even though the incident angle to the prism is large or the number of the prisms is increased. This is because a 20~3~
linearly polarized wave parallel with the beam expanding direction of the prism beam expander has a large transmis-sivity even the incident angle to the prism islarge. With this construction, the narrow ban laser device can generate a large output with a small spectrum line width.
According to the other aspect of this invention there is provided a wavelength detecting apparatus for use in a narrow band oscillation excimer laser, comprising an etalon, light incidence means for projecting a reference light generated by a source of reference light and a laser beam to be detècted upon the etalon; light condensing means for condensing lights passed through the etalon; light detecting means disposed in a rear side focal plane of the light condensing means for detecting an interference fringe of lights condensed by the light condensing means.
The reference light and the light to be detected are passed through the light condensing means, and then focused on the detection surface of the light detecting means disposed on the focal plane of the light condensing means.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
Fig. l(a) is a plan view showing one embodiment of a narrow band excimer laser according to this invention;
Fig. l(b) is a side view of the embodiment shown in Fig. l(a);
..
. ~ ~ , . . . . .. .... .
2~3~
Fig. 2(a) is a plan view showing another embodiment of the narrow band excimer laser according to this invention;
Fig. 2~b) is a side view showing the another embodiment shown in Fig. 2(a);
Fig. 3~a) is a plan view showing a still another embodiment of the narrow band excimer laser;
Fig. 3~b) is a side view of the embodiment shown in Fig. 3~a);
Fig. 4 is a diagrammatic representation showing one embodiment of the wavelength detecting apparatus for the narrow band excimer laser of this invention;
Fig. S is a diagrammatic representation showing another embodiment of the wavelength detecting apparatus for the narrow band excimer laser using a beam condensing mirror;
Fig. 6 is a diagrammatic representation showing still another embodiment of the wavelength detecting apparatus for narrow band excimer laser using a converging type light filter;
Fig. 7 is a diagrammatic representation showing a further embodiment of the wavelength detecting apparatus for the narrow band excimer laser using a lamp as a source of reference light;
Fig. 8 is a diagrammatic representation showing a still of the wavelength detecting apparatus using a lamp and an optical fiber;
, , : . . :~ - : .
, : ... . . , . : :.
. .
::, : : . . :: .:, . -:. . .. - ;: :~ :
.. .. . . . .. . . : :
- . .: - .
: : . ::
2.f~ 3'~
Fig. 9 is a diagrammatic representation showing another wavelength detecting apparatus for the narrow band excimer laser in which a shutter and a filter are inserted;
Fig. 10 is a flow chart showing one example of the main routine for detecting a wavelength when the wavelength detecting apparatus shown in Fig. 9 is used;
Fig. 11 is a flow chart showing and example of a reference light detecting subroutine; and Fig. 12 is a flow chart showing one example of a light detecting subroutine.
' BEST MODE FOR CARRYING OUT THE INVENTION
The embodiments--o`fthis invention will now be described with reference to the accompanying drawings. The narrow band excimer laser shown in Figs. l(a) and l(b) comprises a front mirror 1, and a grating 6 acting as a rear mirror and a wavelength selective element. Between the front mirror 1 and the grating 6, a laser chamber 3, a polarizing element 4, and two prisms 5a and Sb acting as a beam expander (prism beam expander) are provided. -Thus, a laser cavity is 20 constructed between the front mirror 1 and the grating 6.
The laser chamber 3 is filled with a laser gas contain-ing KrF, etc. which can circulate in the chamber. For the purpose of exciting the laser gas, discharge electrodes, not shown, are provided in the laser chamber 3. Windows 2a and 2b are provided at both ends of the laser chamber 3 at . . .
.. ., .. . . :
~ - , - . ~
: . , . - . . - : .
2~3~
predetermined angles.
The purpose of the grating 6 is to select a beam having a specific wavelength by utilizing diffraction of light beam.
The grating 6 is provided with a number of grooves directed in the same direction. In this specification, the direction perpendicular to these grooves is termed a ruling direction.
By changing the angle of grating 6 with respect to an incident beam within a plane containing the ruling direction of the grating 6, a beam having a specific wavelength can be selected. In other words, the grating 6 reflects only a specific diffracted light in a predetermined direction (in this case, the direction of incident beam), the specific diffracted light corresponding to the angle of the grating with respect to the incident beam. As a consequence, a beam having a specific wavelength can be selected.
The prism beam expander including prisms 5a and 5b is disposed such that its beam expanding direction substan-tially coincides with the ruling direction of the grating 6.
The grating 6 is irradiated by the laser beam expanded by the prism beam expander.
The polarizing element 4 selectively transmit only the polarized beam which is substantially parallel with the beam expanding direction of prism beam expander made up of prisms 5a and 5b. The polarizing element 4 may be constructed, for example, by a polarizing prism utilizing a birefringence material (crystal, calcite, etc.), A brewster's dispersion . : . . ~ . . , ~ : :: :
, -....... .. : . . ~ - : . :
:
. . .
2~3~3~0~
prism, a glass substrate (quarts, CaF2 or MgF2), which is arranged at a Brewster's angle or a glass substrate coated such that it transmits a certain polarized light component~
With such construction, the apparatus shown in Figs.
l~a) and l(b) selectively oscillates a linearly polarized light wave parallel to the beam spreading direction by the prism beam expander made up of prisms Sa and Sb. The linearly polarized light wave parallel with the beam expand-ing direction of the prism beam expander has a large trans-missivity even when the incident angle of the beam to the prism is large. Therefore, even when the magnifying power of the beam expander is made large for line-narrowing, the loss does not increase greatly. In other words, according to this invention, it is possible to construct a narrow band excimer laser with a small loss.
The modified embodiment of this invention shown in Figs. 2(a) and 2(b) is constructed such that a specific linearly polarized light wave can be selected by a rear side window of the laser chamber 3. In this embodiment, the rear side window 2b of the laser chamber 3 makes substantially the Brewster's angle ~ with respect to the beam expanding direction of the prism beam expander constructed by pri~ms Sa and 5b, in a plane including the beam expanding direction of the beam expander and the optical axisofthe laser beam.
In the modification shown in Fig. 2, only the rear side `
2~6~r3 window 2b is set to make the Brewster's angle. However, it is possible to arrange both the rear side window 2b and the front side window 2a can be set to make the Brewster's angle. It is also possible to set only the front side window 2a to make the Brewster's angle.
A still another embodiment shown in Figs. 3(a~ and 3(b) is constructed such that by coating the prisms 5a and Sb which constitute the prism beam expander with an anti-reflec-tion coating film that selectively transmits only the polar-ized light component parallel to the beam expanding directionof the prism ~eam expander. In Fig. 3(b), portions 5c and 5b shown by dotted lines indicate these coated portions.
The coating can be applied to one beam transmitting surface of at least one prism. With this consturction, even when the incident angle increases, the transmissivity is higher than 99%.
Fig. 4 shows one embodiment of a wavelength detecting apparatus for the narrow band excimer laser according to this invention. In this embodiment, as the beam to be detected, the output beam La of the narrow band excimer laser 10 is used, and as a reference light source 20, a He-Ne laser or an Ar laser or other types of laser is used.
The reference laser beam generated by the reference light source 20 and the excimer laser beam hàve different wave-length.
A part of the laser beam La outputted from the narrow - . .~ ` `
:~ : ' ' . . "' :
:
band excimer laser 10 is sampled by a beam splitter 30, and this sampled beam is inputted to a beam splitter 40. The reference beam Lb generated by the reference light source 20 is inputted to the other surface of the beam splitter 40.
The beam splitter 40 transmits a part of the sampled beam La outputted from the beam splitter 30 and reflects a part of the reference beam Lb outputted by the reference beam source 20, thus combining the sampled beam with the reference beam. The combined beam outputted from the beam splitter 40 is spreaded by a concave lens 50, and the spread beam is inputted to an etalon 60.
The etalon 60 is constituted by two transparent plates 60a and 60b whose inner surfaces are made to act as partial reflecting mirrors. The wavelength of the beam transmitted through the etalon 60 varies corresponding to the angle of incident light to the etalon. Thus, the reflecting films are coated on the etalon plates in 2-wavelength coating so as to partially reflect both the reference beam Lb and the excimer laser beam La having different wavelengths from the reference beain Lb.
The beams transmitted through the etalon 60 are input-ted to a condenser lens 70. The condenser lens 70 may be an achromatic lens to which correction for color aberration is performed. When the laser beam transmits through the achro-matic condenser lens 70, the color aberration is compensated for.
`
20~3~0~
The beam detector 80 is disposed at the focal point of the condenser lens 70 so that the light beam passed through the condenser lens 70 is focused on the beam detector 80. On the detecting surace of the beam detector 80, a first interference fringe corresponding to the reference beam and a second interference fringe corresponding to the beam to be detected are formed. Base on these first and second inter-ference fringes, the beam detector 80 detects the relative wavelength of the beam to be detected with respect to the wavelength of the reference beam. Thus, the beam detector 80 can detect the absolute wavelength of a beam to be detected when the wavelength of the reference beam is known.
detected wavelength.
The beam detector 80 may be constituted by a one-dimensional or two-dimensional image sensor, a diode array or a position sensitive detector (PSD).
As above described, the beams are inputted to the etalon 60 after being spread with the concave lens 50, and the beams transmitted through the etalon 60 are focused on the beam detector 80 with the condenser lens 70. Therefore, a sufficient quantity of beams are inputted to the beam detector 80 and the interference f~inges of both beams can be clearly formed.
Fig. 5 illustrates another embodiment of the wavelength detecting apparatus of the narrow band excimer laser accord-ing to this invention. For convenience of description, , ' ~f;,'~3,~t~ ~3 elements doing the same performance are designated by the same reference numerals and characters in Fig. 5 and sub-sequent drawings.
In the embodiment shown in Fig. 5, instead of the achromatic condenser lens 70, such condenser mirror 90 as a concave mirror or an eccentric parabolic mirror is used.
More particularly, a reference beam Lb and an excimer laser beam La are inputted to an etalon 60 through a concave lens 50, and the beam transmitted through the etalon 60 is reflected by the condenser mirror 90. The reflected light beam is inputted to the detecting surface of a beam detector 80 disposed at the focus of the condenser mirror 90. Since the condenser mirror 90 having a reflecting surface is used, there is no achromatic aberration so that it is possible to focus the interference fringes of the excimer laser beam La and the reference laser beam Lb at the same position, that is, on the beam detector 80 disposed at the focal point of the mirror 90.
In this embodiment shown in Fig. 5, it is possible to detect at a high accuracy the interference fringes of a sufficient light quantity by using the concave lens 50 and the condenser mirror 90 as in the previous embodiment.
Fig. 6 shows a still another embodiment of the wave-length detecting apparatus of the narrow band excimer laser according to this invention.
In this embodiment, the excimer laser beam La and the 3~a reference laser beam Lb are synthesized by using a synthe-sizer type optical fiber 40a. More particularly, the excimer laser beam La sampled by a beam splitter 30 is applied to a beam-synthesizer 14 through a condenser lens 11, an optical fiber sleeve 12 and an optical fiber 13, while the reference laser beam Lb generated by the reference light source 20 is applied to the beam synthesizer 14 via condenser lens 15, an optical fiber sleeve 16 and an optical fiber 17. The beam synthesizer 14 synthesizes these two beams La and Lb, and the beam thus synthesized is inputted to an optical fiber 18, and the beam spread by a sleeve 19 is inputted to a monitor etalon 60. The beam transmitted through the monitor etalon 60 is focused on the beam detec-tor 80 through an achromatic condenser lens 70.
In the embodiment shown in Fig. 6, the position of the interference fringe is not influenced by the position of the synthesizing type optical fiber 10, but is solely determined by the positional relation among the etalon 60, the con-denser lens 70 and the beam detector 80. Therefore, there is an advantage that the optical system can be adjusted easily, in addition to the advantages of the previous embodiments.
Although in the embodiment shown in Fig. 6, correction of the color aberration is performed by using the achromatic lens 70, this lens can be substitu~ed by the concave mirror or the eccentric parabolic mirror 90 shown in Fig. 5.
~, .
2 ~ n Fig. 7 shows further embodiment showing the wavelength detecting apparatus of the narrow band excimer laser in which a plane light source, that is a lamp 20a is used as the reference light source. This lamp 20a may be a mercury lamp generating a reference light having a wavelength of 253.7 nm, for example. More particularly, the excimer laser beam La sampled by a beam splitter 30 is spread by a concave lens 21 and then applied to a beam splitter 40 which synthe-sizes the spread beam with the reference beam Lc from the mercury lamp 20. The synthesized beam is inputted to an etalon 60. The beam transmitted through the etalon 60 is focused on the beam detector 80 through an achromatic -~ condenser lens 70.
In the embodiment shown in Fig. 7, the color aberration is corrected by using the achromatic condenser lens 70.
However, this lens can be substituted by the concave mirror or the eccentric parabolic mirror 90 shown in Fig. 5.
Fig. 8 illustrates yet another embodiment of the wavelength detecting apparatus of the narrow band excimer laser of this invention in which a mercury lamp 20a is used as the reference light source. In this embodiment, the excimer laser beam La is guided to a beam splitter 40 by using an optical fiber 23. More particularly, the excimer laser beam sampled by a beam splitter 30 is inputted to a sleeve 22 through a condenser lens 11. Thereafter, the beam is outputted from a sleeve 24 through an op~ical fiber 23.
2~3~
The beam which is spread by passing through the sleeve 24 is - applied to a beam splitter 40 where the beam is synthesized with the reference light beam Lc from the mercury lamp 20 and is then inputted to an etalon 60. The light beam transmitted through the etalon 60 is focused on a beam detector 80 via an achromatic condenser lens 70.
In the embodiment shown in Fig. 8, the achromatic condenser lens 70 may be substituted by a concave mirror or an eccentric parabolic mirror 90 shown in Fig. S.
Fig. 9 shows another embodiment of the wavelength detecting apparatus of the narrow band excimer laser. In this embodiment, the achromatic condenser lens 70 in Fig. 8 is replaced with a condenser mirror 90 such as a concave - mirror or an eccentric parabolic mirror. In addition, a filter 41, shutters 42 and 43 are added.
More particularly, a filter 41 which selects only a light beam having a predetermined wavelength among the reference light beams Lc generated by the mercury lamp 20a is provided between a shutter 42 and a beam splitter 40.
Thus, only the reference light beam having the predetermined wavelength is inputted to beam splitter 40. For example, where the apparatus is used as the wavelength detector of the beam (having a wavelength of 248.4 nm) generated by a KrF narrow band excimer laser, a mercury lamp is used as the lamp 20a, and an interference filter for a beam having a wavelength of 253.7 nm, which is close to that of the ~' ':
`, . ~g~3~.~?~
excimer laser, is used as the filter 16. Shutters 42 and 43 are provided for the purpose of independently detect the reference light beam and the light beam to be detected (the laser beam of excimer laser). For detecting the reference light beam, the shutter 42 is opened and the shutter 43 is closed. For detecting the light beam to be detected, the shutter 43 is opened and the shutter 42 is closed.
In this embodiment, the filter 41 is disposed between the beam splitter 40 and the shutter 42. However, the filter 41 may be disposed between the lamp 20a and the - shutter 42. Furthermore, where the wavelengths of the reference light beam and of the beam to be detected are close to each other, and where the beam to be detected transmits through the filter 41, the filter 41 may be placed at a suitable position in the light path between the beam splitter 40 and the light beam detector 80.
The detecting operation of the reference light beam and the beam to be detected of this embodiment shown in Fig. 9 will now be described with reference to the flow charts shown in Figs. 10 - 12.
Fig. 10 shows the main routine for the wavelength detection. First, the reference light beam detection subroutine is executed at step 100. As shown in Fig. 11, in this subroutine, the shutter 43 on the side of the beam to be detected is closed while the shutter 42 on the side of the reference light beam is opened so as to input only the ~f3~36~
reference light beam Lc to the beam detector 80 via the etalon 60 at steps 200 and 210. Then, the radius Rs of the interference fringe of the reference beam formed on the beam detector 80 is detected and stored in a memory, not shown, at step 220.
Upon completion of this reference beam detection subroutine, the count value T of a timer, not shown, is : cleared to zero at step 110. Then, at step 120, a judgement is made as to whether the count value T is larger than a predetermined preset time K (for example, several minutes).
Where T < K, the detection subroutine for detecting the beam . to be detected is executed at step 140. In this detection subroutine, as shown in Fig. 12, by closing the shutter 42 on the side of the reference light beam and opening the shutter 43 on the side of the beam to be detected, only the beam La to be detected is applied to the beam detector 80 at steps 300 and 310. Then, the radius Re of the interference fringe of the beam to be detected formed on the surface of the beam detector 80 is detected at step 320.
Upon completion of the detection subroutine for detect-ing the beam to be detected, the radius Re determined by this subroutine is compared with the radius Rs which has been determined and stored in the previous reference beam subroutine so as to detect the absolute wavelength of the beam to be detected at step 150. Thereafter, the executions of steps 140 and 150 are repeated until a condition T ~ K is obtained.
: , ~.
2~ 33~
When T ~ K at step 120, the reference beam detection subroutine shown in Fig. 11 is executed again and the stored data Rs is renewed by the radius Rs of the interference fringe of the reference beam determined by the subroutine.
Then, after the count value T of the timer is cleared to zero, the subroutine for detecting the beam to be detected is executed again.
All processings described above are executed automatic-ally.
More particularly, in the wavelength detection process-ing described above, where the wavelengths of the reference beam and the beam to be detected are close to each other, it is difficult to simultaneously detect the interference fringes of both beams. Therefore, the interference fringes are independently detected by using the shutters 42 and 43.
; Since the reference beam is relatively stable, it is advan-tageous to detect the interference fringe in a relatively long preset period K. In a case other than detecting the reference beam, it is designed that the beam to be detected is always detected. In other words, the detection period for the reference beam is set to be sufficiently longer than the detection period for the beam to be detected.
In this embodiment, the radius of an interference fringe is detected. However, the absolute wavelength of the beam to be detected can also be obtained by detecting the diameter or position of the interference fringe.
'', ' 2g~J~3~
In the embodiments shown in Figs. 4 - 9, when the light quantities of the reference beam and the beam to be detected are small so that the detection of the interference fringes is difficult, a collimator lens may be disposed in front of the etalon 60 so as to apply parallel light to the etalon, thus increasing the light quantity.
In the embodiments shown in Figs. 4 - 9, the beam splitter 40 is disposed such that the beam to be detected is applied to the beam transmissive side while the reference beam is applied to the opposite side. However, their positional relationship may be reversed. Where the wave-lengths of the reference beam and of the beam to be detected are close to each other, a partial reflection mirror may be used, whereas where the difference between wavelengths are large, a dichroic mirror may be used.
The embodiments described above are constituted by using an air gap etalon. However, it may be substituted by a solid etalon.
In the above described embodiments, the focused positions of the reference beam and of the beam to be detected are made to coincide with each other by correcting the color aberration of the condenser lens 70, or by using the condenser mirror 90. However, it may be so constructed that the condensing lens 70 or the beam detector 80 is disposed movable in the direction of the optical axis so as to correct the focused position.
- 23 ~
2f3é~3~
Where the waveleng~sof the reference beam and the beam to be detected are close to each other in the embodi-ments shown in Figs. 4, 6, 7 and 8, a condenser lens whose color aberration is not corrected may be inserted between the etalon 60 and the beam detector 80.
In the embodiments shown in Figs. 4, 5, and 7, the laser beam La is spread by the concave lens 50 or 21 and the spread laser beam is inputted to the etalon 60. However, the concave lens may be substituted with a convex lens.
According to this modification the laser beam is condensed at first by the convex lens and then spread. The spread beam is inputted to the etalon 60. Furthermore, instead of using the concave lens 50, adiffusion plate (e.g., a frosted glass) may be used.
FIELD OF APPLICATION IN INDUSTRY
As above described, in the narrow band excimer laser according to this invention, by substantially coinciding the ruling direction of the grating with the beam expanding direction of the prism beam expander and by providing selec-tive oscillation means for selectively oscillating a linear-ly polarized light wave substantially parallel with the beam spreading direction of a prism beam expander, it becomes possible to greatly decrease the loss in the prism beam expander. For this reason, it becomes possible to narrow the spectrum line width and to obtain a large output.
~3~,~0 Further, according to the wavelength detecting appara-tus of the narrow band excimer laser of this invention, with a simple construction of providing a light condensing device on the rear side of an etalon, a sufficient quantity of light can be applied to a light detector. As a result, it becomes possible to form clear interference fringes on the light detector, thus enabling to detect the absolute wave-length of the beam to be detected at a high accuracy.
Especially, by using an achromatic lens or a light condens-ing mirror as light condensing means, even when the wave-lengths of the reference beam and that of the detected beam are not equal, the absolute wavelength can be accurately detected without constructing the optical system to be movable.
The narrow band excimer laser and the wavelength detecting apparatus of the excimer laser are especially suitable to use as a light source of a reduction projection aligner for use in manufacturing semiconductor devices.
`
NARROW BAND EXCIMER LASER AND
WAVELENGTH DETECTING APPARATUS
TECHNOLOGICAL FIELD
This invention relates to a narrow band excimer laser and a wavelength detection device, and more particularly, to a narrow band excimer laser suitable for a light source of a reduction projection aligner for use in manufacturing of semiconductors.
_ACKGROUND ART
An attention has been paid to the use of an excimer laser as a light source of reduction projection aligner (hereinafter called a stepper) for manufacturing semicon-ductor devices. This is because the excimer laser may possibly extend the light exposure limit to be less than 0.5 ~m since the wavelength of the excimer laser is short (for example the wavelength of KrF laser is about 248.4 nm), because with the same resolution, the focal depth is greater -than a g line or an i line of a mercury lamp conventionally used, because the numerical aperture (NA) of a lens can be made small so that the exposure region can be enlarged and large power can be obtained, and because many other advant-ages can be expected.
2~3~
An excimer laser utilized as a light source of the stepper is required to have a narrow bandwidth with a beam width of less than 3pm as well as a large output power.
A technique of narrowing the bandwidth of the excimer laser beam is known as the injection lock method. In the injection lock method, wavelength selecting element (etalon, diffraction grating, prism, etc.) are disposed in a cavity of an oscillation stage so as to generate a single mode oscillation by limiting the space mode by using a pin hole and to injection synchronize the laser beam in an amplifi-cation stage. With this method, however, although a rela-tively large output power can be obtained, there are such defects that a misshot occurs, that it is difficult to obtain 100% the locking efficiency, and that the spectrum purity degrades. Furthermore, in this method, the output light beam has a high degree of coherency so that when the output light beam is used as a light source of the reduction type projection aligner, a speckle pattern generates.
Generally it is considered that the generation of speckle pattern depends upon the number of space transverse modes.
When the number of space transverse modes contained in the laser light is small, the speckle pattern becomes easy to generate. Conversely, when the number of the space trans-verse modes increases, the speckle pattern becomes difficult to generate art. The injection lock method described above is a technique for narrowing the bandwidth by greatly : . .. . ..
. ~
.
-- :
.
2~3~ f3 decreasing the number of space transverse modes. Since generation of speckle pattern causes a serious problem, this technique can not be adopted in the reduction projection aligner.
Another projection technique for narrowing the band-width o the excimer layer beam is a technique utilizing a air gap etalon acting as a wavelength selective element. A
prior art technique utilizing the air gap etalon was devel-oped by AT & T Bell Laboratory wherein an air gap etalon is disposed between the front mirror and a laser chamber of an excimer laser device so as to narrow the bandwidth of the excimer laser. This system, however, cannot obtain a very narrow spectral bandwidth. In addition there are problems that the power loss is large due to the insertion of the air gap etalon. Further it is impossible to greatly increase the number of the space transverse modes. Furthermore, the air gap etalon has a problem of poor durability.
Accordingly, an excimer laser device has been proposed wherein a relatively high durable diffraction grating is used as the wavelength selective element.
In the excimer laser having a diffractive grating which acts as a wavelength selective element, a pin hole is provided in a resonator (laser cavity) to reduce the spread angle of the beam in the grating. Alternatively a beam expander is provided to expand the laser beam incident to the grating. For this beam expander, a prism expander ` ` 2 ~ ~ 3 ~
utilizing a prism is typically been used.
The narrow band excimer laser used as the stepper must not only have a narrow bandwidth with a line width of less than 3 pm but also must produce a large output.
In the construction in which a pin hole is disposed in a resonator, however, the output becomes greatly reduced and the number of space transverse modes necessary for prevent-ing generation of a speckle pattern decreases, so that such construction can not be used.
In the construction in which a prism beam expander is used, the expander must have a large magnifying power in order to narrow the line width.
However, when the magnifying power of the prism beam expander becomes large, the incident angle of the laser beam to a prism of the prism expander becomes large or it becomes necessary to increase the number of prisms, thereby increas-ing the loss. As a result, a large output cannot be pro-duced.
Furthermore, where a narrow band excimer laser is used as the light source of a stepper, it is necessary to narrow the bandwidth of the output laser beam and then to control the wavelength of the output laser beam whose bandwidth has been narrowed to a stable condition at a high accuracy.
A monitor etalon has been used for measuring the line width of the output beam and for detecting the wavelength.
The monitor etalon is constituted by an air gap etalon , ,. - ;~ '' , . ;., . ' :: . ~ . , .. -., . ~ , :: , , :
. .
2~3~3~3~
wherein a pair of partial reflective mirrors are disposed to confront each other with a predetermined air gap therebet-ween. The transmissive wavelength of this air gap etalon is expressed by the following equation m~ = 2nd cos 3 where m represents the order, d the partial mirrors spacing, n the refractive index of the medium the par ial reflective mirrors, and ~ an angle between the normal of the etalon and the axis of the incident light.
This equation shows that where n, d and m are constant, as the wavelength varies, the angle 3 changes. The monitor etalon detects the wavelength of the beam by utilizing this characteristics. In the monitor etalon described above, when the pressure in the air gap and the ambient temperature vary, the angle ~ varies even when the wavelength is con-stant. Accordingly, where the monitor etalon is used for detectiny the wavelength, the pressure in the air gap and the ambient temperature are controlled to be constant.
However, it is difficult to precisely control the pressure in the air gap and the ambient temperature.
Therefore, it is impossible to detect the absolute wave-length at a high accuracy.
For this reason, apparatus has been proposed wherein the beam to be detected is inputted to the monitor etalon together with a reference beam having a known wavelength, and the wavelength of the beam is detected by detecting a wavelength of the beam relative to the reference beam.
In this apparatus, a light beam transmitting through the monitor etalon is directly inputted to a beam detector such as CCD image sensor.
However, in this apparatus, since the output of the monitor etalon is directly inputted to the beam detector, the beam to be detected and the reference beam cannot be inputted to the beam detector with a sufficient beam quan-tity, and an interference fringe cannot be formed on the beam detector.
Accordingly, it is an object of this invention to provide a novel narrow band excimer laser of the type using a prism beam expander and a diffraction grating as a band-narrowing element, capable of preventing increase of loss even when the magnifying power of the prism expander is increased.
Another object of this invention is to provide a novel wavelength detecting apparatus of a narrow band excimer laser capable of inputting a reference beam and a beam to be detected into a beam detector with a sufficient quantity and capable of detecting the interference fringes of both beams at a high accuracy.
DISCLOSURE OF THE INVENTION
According to one aspect of this invention, there is provided a narrow band oscillation excimer laser comprising ' 2n~60~
a prism beam expander and a diffractive grating which are used as a bandwidth narrowing element, the ruling direction o the grating and the beam spreading direction of the prism beam expander being substantially coincided with each other;
and selective oscillation means for selectively oscillating a linearly polarized wave which is substantially parallel with the beam expanding direction of the prism beam ex-pander. The selective oscillation means may be constructed by a polarizing element disposed in the laser cavity.
The selective oscillation means may be constructed by a window provided on a rear side or a front side of the laser chamber in such a manner that the window is inclined with a Brewster's angle with respect to the optical axis of the laser beam in a plane containing the beam expanding direc-tion of the prism expander and the optical axis of the laser beam.
The selective oscillation means may include a prism beam expander in which one surface of a prism is coated with a reflection preventive film for selectively preventing a reflection of a polarized component which is parallel with the beam expanding direction of the prism beam expander.
By selectively oscillating a linearly polarized wave which is substantially parallel with the beam expanding direction of the prism beam expander, the loss can be reduced even though the incident angle to the prism is large or the number of the prisms is increased. This is because a 20~3~
linearly polarized wave parallel with the beam expanding direction of the prism beam expander has a large transmis-sivity even the incident angle to the prism islarge. With this construction, the narrow ban laser device can generate a large output with a small spectrum line width.
According to the other aspect of this invention there is provided a wavelength detecting apparatus for use in a narrow band oscillation excimer laser, comprising an etalon, light incidence means for projecting a reference light generated by a source of reference light and a laser beam to be detècted upon the etalon; light condensing means for condensing lights passed through the etalon; light detecting means disposed in a rear side focal plane of the light condensing means for detecting an interference fringe of lights condensed by the light condensing means.
The reference light and the light to be detected are passed through the light condensing means, and then focused on the detection surface of the light detecting means disposed on the focal plane of the light condensing means.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
Fig. l(a) is a plan view showing one embodiment of a narrow band excimer laser according to this invention;
Fig. l(b) is a side view of the embodiment shown in Fig. l(a);
..
. ~ ~ , . . . . .. .... .
2~3~
Fig. 2(a) is a plan view showing another embodiment of the narrow band excimer laser according to this invention;
Fig. 2~b) is a side view showing the another embodiment shown in Fig. 2(a);
Fig. 3~a) is a plan view showing a still another embodiment of the narrow band excimer laser;
Fig. 3~b) is a side view of the embodiment shown in Fig. 3~a);
Fig. 4 is a diagrammatic representation showing one embodiment of the wavelength detecting apparatus for the narrow band excimer laser of this invention;
Fig. S is a diagrammatic representation showing another embodiment of the wavelength detecting apparatus for the narrow band excimer laser using a beam condensing mirror;
Fig. 6 is a diagrammatic representation showing still another embodiment of the wavelength detecting apparatus for narrow band excimer laser using a converging type light filter;
Fig. 7 is a diagrammatic representation showing a further embodiment of the wavelength detecting apparatus for the narrow band excimer laser using a lamp as a source of reference light;
Fig. 8 is a diagrammatic representation showing a still of the wavelength detecting apparatus using a lamp and an optical fiber;
, , : . . :~ - : .
, : ... . . , . : :.
. .
::, : : . . :: .:, . -:. . .. - ;: :~ :
.. .. . . . .. . . : :
- . .: - .
: : . ::
2.f~ 3'~
Fig. 9 is a diagrammatic representation showing another wavelength detecting apparatus for the narrow band excimer laser in which a shutter and a filter are inserted;
Fig. 10 is a flow chart showing one example of the main routine for detecting a wavelength when the wavelength detecting apparatus shown in Fig. 9 is used;
Fig. 11 is a flow chart showing and example of a reference light detecting subroutine; and Fig. 12 is a flow chart showing one example of a light detecting subroutine.
' BEST MODE FOR CARRYING OUT THE INVENTION
The embodiments--o`fthis invention will now be described with reference to the accompanying drawings. The narrow band excimer laser shown in Figs. l(a) and l(b) comprises a front mirror 1, and a grating 6 acting as a rear mirror and a wavelength selective element. Between the front mirror 1 and the grating 6, a laser chamber 3, a polarizing element 4, and two prisms 5a and Sb acting as a beam expander (prism beam expander) are provided. -Thus, a laser cavity is 20 constructed between the front mirror 1 and the grating 6.
The laser chamber 3 is filled with a laser gas contain-ing KrF, etc. which can circulate in the chamber. For the purpose of exciting the laser gas, discharge electrodes, not shown, are provided in the laser chamber 3. Windows 2a and 2b are provided at both ends of the laser chamber 3 at . . .
.. ., .. . . :
~ - , - . ~
: . , . - . . - : .
2~3~
predetermined angles.
The purpose of the grating 6 is to select a beam having a specific wavelength by utilizing diffraction of light beam.
The grating 6 is provided with a number of grooves directed in the same direction. In this specification, the direction perpendicular to these grooves is termed a ruling direction.
By changing the angle of grating 6 with respect to an incident beam within a plane containing the ruling direction of the grating 6, a beam having a specific wavelength can be selected. In other words, the grating 6 reflects only a specific diffracted light in a predetermined direction (in this case, the direction of incident beam), the specific diffracted light corresponding to the angle of the grating with respect to the incident beam. As a consequence, a beam having a specific wavelength can be selected.
The prism beam expander including prisms 5a and 5b is disposed such that its beam expanding direction substan-tially coincides with the ruling direction of the grating 6.
The grating 6 is irradiated by the laser beam expanded by the prism beam expander.
The polarizing element 4 selectively transmit only the polarized beam which is substantially parallel with the beam expanding direction of prism beam expander made up of prisms 5a and 5b. The polarizing element 4 may be constructed, for example, by a polarizing prism utilizing a birefringence material (crystal, calcite, etc.), A brewster's dispersion . : . . ~ . . , ~ : :: :
, -....... .. : . . ~ - : . :
:
. . .
2~3~3~0~
prism, a glass substrate (quarts, CaF2 or MgF2), which is arranged at a Brewster's angle or a glass substrate coated such that it transmits a certain polarized light component~
With such construction, the apparatus shown in Figs.
l~a) and l(b) selectively oscillates a linearly polarized light wave parallel to the beam spreading direction by the prism beam expander made up of prisms Sa and Sb. The linearly polarized light wave parallel with the beam expand-ing direction of the prism beam expander has a large trans-missivity even when the incident angle of the beam to the prism is large. Therefore, even when the magnifying power of the beam expander is made large for line-narrowing, the loss does not increase greatly. In other words, according to this invention, it is possible to construct a narrow band excimer laser with a small loss.
The modified embodiment of this invention shown in Figs. 2(a) and 2(b) is constructed such that a specific linearly polarized light wave can be selected by a rear side window of the laser chamber 3. In this embodiment, the rear side window 2b of the laser chamber 3 makes substantially the Brewster's angle ~ with respect to the beam expanding direction of the prism beam expander constructed by pri~ms Sa and 5b, in a plane including the beam expanding direction of the beam expander and the optical axisofthe laser beam.
In the modification shown in Fig. 2, only the rear side `
2~6~r3 window 2b is set to make the Brewster's angle. However, it is possible to arrange both the rear side window 2b and the front side window 2a can be set to make the Brewster's angle. It is also possible to set only the front side window 2a to make the Brewster's angle.
A still another embodiment shown in Figs. 3(a~ and 3(b) is constructed such that by coating the prisms 5a and Sb which constitute the prism beam expander with an anti-reflec-tion coating film that selectively transmits only the polar-ized light component parallel to the beam expanding directionof the prism ~eam expander. In Fig. 3(b), portions 5c and 5b shown by dotted lines indicate these coated portions.
The coating can be applied to one beam transmitting surface of at least one prism. With this consturction, even when the incident angle increases, the transmissivity is higher than 99%.
Fig. 4 shows one embodiment of a wavelength detecting apparatus for the narrow band excimer laser according to this invention. In this embodiment, as the beam to be detected, the output beam La of the narrow band excimer laser 10 is used, and as a reference light source 20, a He-Ne laser or an Ar laser or other types of laser is used.
The reference laser beam generated by the reference light source 20 and the excimer laser beam hàve different wave-length.
A part of the laser beam La outputted from the narrow - . .~ ` `
:~ : ' ' . . "' :
:
band excimer laser 10 is sampled by a beam splitter 30, and this sampled beam is inputted to a beam splitter 40. The reference beam Lb generated by the reference light source 20 is inputted to the other surface of the beam splitter 40.
The beam splitter 40 transmits a part of the sampled beam La outputted from the beam splitter 30 and reflects a part of the reference beam Lb outputted by the reference beam source 20, thus combining the sampled beam with the reference beam. The combined beam outputted from the beam splitter 40 is spreaded by a concave lens 50, and the spread beam is inputted to an etalon 60.
The etalon 60 is constituted by two transparent plates 60a and 60b whose inner surfaces are made to act as partial reflecting mirrors. The wavelength of the beam transmitted through the etalon 60 varies corresponding to the angle of incident light to the etalon. Thus, the reflecting films are coated on the etalon plates in 2-wavelength coating so as to partially reflect both the reference beam Lb and the excimer laser beam La having different wavelengths from the reference beain Lb.
The beams transmitted through the etalon 60 are input-ted to a condenser lens 70. The condenser lens 70 may be an achromatic lens to which correction for color aberration is performed. When the laser beam transmits through the achro-matic condenser lens 70, the color aberration is compensated for.
`
20~3~0~
The beam detector 80 is disposed at the focal point of the condenser lens 70 so that the light beam passed through the condenser lens 70 is focused on the beam detector 80. On the detecting surace of the beam detector 80, a first interference fringe corresponding to the reference beam and a second interference fringe corresponding to the beam to be detected are formed. Base on these first and second inter-ference fringes, the beam detector 80 detects the relative wavelength of the beam to be detected with respect to the wavelength of the reference beam. Thus, the beam detector 80 can detect the absolute wavelength of a beam to be detected when the wavelength of the reference beam is known.
detected wavelength.
The beam detector 80 may be constituted by a one-dimensional or two-dimensional image sensor, a diode array or a position sensitive detector (PSD).
As above described, the beams are inputted to the etalon 60 after being spread with the concave lens 50, and the beams transmitted through the etalon 60 are focused on the beam detector 80 with the condenser lens 70. Therefore, a sufficient quantity of beams are inputted to the beam detector 80 and the interference f~inges of both beams can be clearly formed.
Fig. 5 illustrates another embodiment of the wavelength detecting apparatus of the narrow band excimer laser accord-ing to this invention. For convenience of description, , ' ~f;,'~3,~t~ ~3 elements doing the same performance are designated by the same reference numerals and characters in Fig. 5 and sub-sequent drawings.
In the embodiment shown in Fig. 5, instead of the achromatic condenser lens 70, such condenser mirror 90 as a concave mirror or an eccentric parabolic mirror is used.
More particularly, a reference beam Lb and an excimer laser beam La are inputted to an etalon 60 through a concave lens 50, and the beam transmitted through the etalon 60 is reflected by the condenser mirror 90. The reflected light beam is inputted to the detecting surface of a beam detector 80 disposed at the focus of the condenser mirror 90. Since the condenser mirror 90 having a reflecting surface is used, there is no achromatic aberration so that it is possible to focus the interference fringes of the excimer laser beam La and the reference laser beam Lb at the same position, that is, on the beam detector 80 disposed at the focal point of the mirror 90.
In this embodiment shown in Fig. 5, it is possible to detect at a high accuracy the interference fringes of a sufficient light quantity by using the concave lens 50 and the condenser mirror 90 as in the previous embodiment.
Fig. 6 shows a still another embodiment of the wave-length detecting apparatus of the narrow band excimer laser according to this invention.
In this embodiment, the excimer laser beam La and the 3~a reference laser beam Lb are synthesized by using a synthe-sizer type optical fiber 40a. More particularly, the excimer laser beam La sampled by a beam splitter 30 is applied to a beam-synthesizer 14 through a condenser lens 11, an optical fiber sleeve 12 and an optical fiber 13, while the reference laser beam Lb generated by the reference light source 20 is applied to the beam synthesizer 14 via condenser lens 15, an optical fiber sleeve 16 and an optical fiber 17. The beam synthesizer 14 synthesizes these two beams La and Lb, and the beam thus synthesized is inputted to an optical fiber 18, and the beam spread by a sleeve 19 is inputted to a monitor etalon 60. The beam transmitted through the monitor etalon 60 is focused on the beam detec-tor 80 through an achromatic condenser lens 70.
In the embodiment shown in Fig. 6, the position of the interference fringe is not influenced by the position of the synthesizing type optical fiber 10, but is solely determined by the positional relation among the etalon 60, the con-denser lens 70 and the beam detector 80. Therefore, there is an advantage that the optical system can be adjusted easily, in addition to the advantages of the previous embodiments.
Although in the embodiment shown in Fig. 6, correction of the color aberration is performed by using the achromatic lens 70, this lens can be substitu~ed by the concave mirror or the eccentric parabolic mirror 90 shown in Fig. 5.
~, .
2 ~ n Fig. 7 shows further embodiment showing the wavelength detecting apparatus of the narrow band excimer laser in which a plane light source, that is a lamp 20a is used as the reference light source. This lamp 20a may be a mercury lamp generating a reference light having a wavelength of 253.7 nm, for example. More particularly, the excimer laser beam La sampled by a beam splitter 30 is spread by a concave lens 21 and then applied to a beam splitter 40 which synthe-sizes the spread beam with the reference beam Lc from the mercury lamp 20. The synthesized beam is inputted to an etalon 60. The beam transmitted through the etalon 60 is focused on the beam detector 80 through an achromatic -~ condenser lens 70.
In the embodiment shown in Fig. 7, the color aberration is corrected by using the achromatic condenser lens 70.
However, this lens can be substituted by the concave mirror or the eccentric parabolic mirror 90 shown in Fig. 5.
Fig. 8 illustrates yet another embodiment of the wavelength detecting apparatus of the narrow band excimer laser of this invention in which a mercury lamp 20a is used as the reference light source. In this embodiment, the excimer laser beam La is guided to a beam splitter 40 by using an optical fiber 23. More particularly, the excimer laser beam sampled by a beam splitter 30 is inputted to a sleeve 22 through a condenser lens 11. Thereafter, the beam is outputted from a sleeve 24 through an op~ical fiber 23.
2~3~
The beam which is spread by passing through the sleeve 24 is - applied to a beam splitter 40 where the beam is synthesized with the reference light beam Lc from the mercury lamp 20 and is then inputted to an etalon 60. The light beam transmitted through the etalon 60 is focused on a beam detector 80 via an achromatic condenser lens 70.
In the embodiment shown in Fig. 8, the achromatic condenser lens 70 may be substituted by a concave mirror or an eccentric parabolic mirror 90 shown in Fig. S.
Fig. 9 shows another embodiment of the wavelength detecting apparatus of the narrow band excimer laser. In this embodiment, the achromatic condenser lens 70 in Fig. 8 is replaced with a condenser mirror 90 such as a concave - mirror or an eccentric parabolic mirror. In addition, a filter 41, shutters 42 and 43 are added.
More particularly, a filter 41 which selects only a light beam having a predetermined wavelength among the reference light beams Lc generated by the mercury lamp 20a is provided between a shutter 42 and a beam splitter 40.
Thus, only the reference light beam having the predetermined wavelength is inputted to beam splitter 40. For example, where the apparatus is used as the wavelength detector of the beam (having a wavelength of 248.4 nm) generated by a KrF narrow band excimer laser, a mercury lamp is used as the lamp 20a, and an interference filter for a beam having a wavelength of 253.7 nm, which is close to that of the ~' ':
`, . ~g~3~.~?~
excimer laser, is used as the filter 16. Shutters 42 and 43 are provided for the purpose of independently detect the reference light beam and the light beam to be detected (the laser beam of excimer laser). For detecting the reference light beam, the shutter 42 is opened and the shutter 43 is closed. For detecting the light beam to be detected, the shutter 43 is opened and the shutter 42 is closed.
In this embodiment, the filter 41 is disposed between the beam splitter 40 and the shutter 42. However, the filter 41 may be disposed between the lamp 20a and the - shutter 42. Furthermore, where the wavelengths of the reference light beam and of the beam to be detected are close to each other, and where the beam to be detected transmits through the filter 41, the filter 41 may be placed at a suitable position in the light path between the beam splitter 40 and the light beam detector 80.
The detecting operation of the reference light beam and the beam to be detected of this embodiment shown in Fig. 9 will now be described with reference to the flow charts shown in Figs. 10 - 12.
Fig. 10 shows the main routine for the wavelength detection. First, the reference light beam detection subroutine is executed at step 100. As shown in Fig. 11, in this subroutine, the shutter 43 on the side of the beam to be detected is closed while the shutter 42 on the side of the reference light beam is opened so as to input only the ~f3~36~
reference light beam Lc to the beam detector 80 via the etalon 60 at steps 200 and 210. Then, the radius Rs of the interference fringe of the reference beam formed on the beam detector 80 is detected and stored in a memory, not shown, at step 220.
Upon completion of this reference beam detection subroutine, the count value T of a timer, not shown, is : cleared to zero at step 110. Then, at step 120, a judgement is made as to whether the count value T is larger than a predetermined preset time K (for example, several minutes).
Where T < K, the detection subroutine for detecting the beam . to be detected is executed at step 140. In this detection subroutine, as shown in Fig. 12, by closing the shutter 42 on the side of the reference light beam and opening the shutter 43 on the side of the beam to be detected, only the beam La to be detected is applied to the beam detector 80 at steps 300 and 310. Then, the radius Re of the interference fringe of the beam to be detected formed on the surface of the beam detector 80 is detected at step 320.
Upon completion of the detection subroutine for detect-ing the beam to be detected, the radius Re determined by this subroutine is compared with the radius Rs which has been determined and stored in the previous reference beam subroutine so as to detect the absolute wavelength of the beam to be detected at step 150. Thereafter, the executions of steps 140 and 150 are repeated until a condition T ~ K is obtained.
: , ~.
2~ 33~
When T ~ K at step 120, the reference beam detection subroutine shown in Fig. 11 is executed again and the stored data Rs is renewed by the radius Rs of the interference fringe of the reference beam determined by the subroutine.
Then, after the count value T of the timer is cleared to zero, the subroutine for detecting the beam to be detected is executed again.
All processings described above are executed automatic-ally.
More particularly, in the wavelength detection process-ing described above, where the wavelengths of the reference beam and the beam to be detected are close to each other, it is difficult to simultaneously detect the interference fringes of both beams. Therefore, the interference fringes are independently detected by using the shutters 42 and 43.
; Since the reference beam is relatively stable, it is advan-tageous to detect the interference fringe in a relatively long preset period K. In a case other than detecting the reference beam, it is designed that the beam to be detected is always detected. In other words, the detection period for the reference beam is set to be sufficiently longer than the detection period for the beam to be detected.
In this embodiment, the radius of an interference fringe is detected. However, the absolute wavelength of the beam to be detected can also be obtained by detecting the diameter or position of the interference fringe.
'', ' 2g~J~3~
In the embodiments shown in Figs. 4 - 9, when the light quantities of the reference beam and the beam to be detected are small so that the detection of the interference fringes is difficult, a collimator lens may be disposed in front of the etalon 60 so as to apply parallel light to the etalon, thus increasing the light quantity.
In the embodiments shown in Figs. 4 - 9, the beam splitter 40 is disposed such that the beam to be detected is applied to the beam transmissive side while the reference beam is applied to the opposite side. However, their positional relationship may be reversed. Where the wave-lengths of the reference beam and of the beam to be detected are close to each other, a partial reflection mirror may be used, whereas where the difference between wavelengths are large, a dichroic mirror may be used.
The embodiments described above are constituted by using an air gap etalon. However, it may be substituted by a solid etalon.
In the above described embodiments, the focused positions of the reference beam and of the beam to be detected are made to coincide with each other by correcting the color aberration of the condenser lens 70, or by using the condenser mirror 90. However, it may be so constructed that the condensing lens 70 or the beam detector 80 is disposed movable in the direction of the optical axis so as to correct the focused position.
- 23 ~
2f3é~3~
Where the waveleng~sof the reference beam and the beam to be detected are close to each other in the embodi-ments shown in Figs. 4, 6, 7 and 8, a condenser lens whose color aberration is not corrected may be inserted between the etalon 60 and the beam detector 80.
In the embodiments shown in Figs. 4, 5, and 7, the laser beam La is spread by the concave lens 50 or 21 and the spread laser beam is inputted to the etalon 60. However, the concave lens may be substituted with a convex lens.
According to this modification the laser beam is condensed at first by the convex lens and then spread. The spread beam is inputted to the etalon 60. Furthermore, instead of using the concave lens 50, adiffusion plate (e.g., a frosted glass) may be used.
FIELD OF APPLICATION IN INDUSTRY
As above described, in the narrow band excimer laser according to this invention, by substantially coinciding the ruling direction of the grating with the beam expanding direction of the prism beam expander and by providing selec-tive oscillation means for selectively oscillating a linear-ly polarized light wave substantially parallel with the beam spreading direction of a prism beam expander, it becomes possible to greatly decrease the loss in the prism beam expander. For this reason, it becomes possible to narrow the spectrum line width and to obtain a large output.
~3~,~0 Further, according to the wavelength detecting appara-tus of the narrow band excimer laser of this invention, with a simple construction of providing a light condensing device on the rear side of an etalon, a sufficient quantity of light can be applied to a light detector. As a result, it becomes possible to form clear interference fringes on the light detector, thus enabling to detect the absolute wave-length of the beam to be detected at a high accuracy.
Especially, by using an achromatic lens or a light condens-ing mirror as light condensing means, even when the wave-lengths of the reference beam and that of the detected beam are not equal, the absolute wavelength can be accurately detected without constructing the optical system to be movable.
The narrow band excimer laser and the wavelength detecting apparatus of the excimer laser are especially suitable to use as a light source of a reduction projection aligner for use in manufacturing semiconductor devices.
`
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-
1. A narrow band excimer laser comprising:
a line-narrowing element including a prism beam expander and a grating, a ruling direction of said grating and a beam expanding direction of said prism beam expander being substantially coincided with each other; and selective oscillation means for selectively oscillating a linearly polarized light wave which is substantially parallel with said beam spreading direction of said prism beam expander.
a line-narrowing element including a prism beam expander and a grating, a ruling direction of said grating and a beam expanding direction of said prism beam expander being substantially coincided with each other; and selective oscillation means for selectively oscillating a linearly polarized light wave which is substantially parallel with said beam spreading direction of said prism beam expander.
2. The narrow band excimer laser according to claim 1 wherein said selective oscillation means comprises a polar-izing light element disposed in a laser cavity.
3. The narrow band excimer laser according to claim 1 wherein said selective oscillation means comprises a window provided on either rear and front side of a laser chamber disposed such that said window makes Brewster's angle with respect to an optical axis of laser beam in a plane defined by a beam expanding direction of said prism beam expander and the optical axis of the laser beam.
4. The narrow band excimer laser according to claim 1 wherein said selective oscillation means comprises an anti-reflection film coated on at least one surface of a prism constituting said prism beam expander, said anti-reflection film selectively preventing reflection of only a polarized light component substantially parallel with a beam expanding direction of said prism beam expander.
5. A wavelength detecting apparatus for use in a narrow band excimer laser, comprising:
input means for inputting a reference light generated by a reference light source and a laser beam to be detected outputted from said excimer laser into an etalon;
light condensing means for condensing light transmit-ting through said etalon;
light detecting means disposed in a rear side focal plane of said light condensing means, for detecting an interference fringe of light condensed by said light con-densing means;
said wavelength detecting apparatus detecting a wave-length of said light to be detected base on output of said light detecting means.
input means for inputting a reference light generated by a reference light source and a laser beam to be detected outputted from said excimer laser into an etalon;
light condensing means for condensing light transmit-ting through said etalon;
light detecting means disposed in a rear side focal plane of said light condensing means, for detecting an interference fringe of light condensed by said light con-densing means;
said wavelength detecting apparatus detecting a wave-length of said light to be detected base on output of said light detecting means.
6. The wavelength detecting apparatus according to claim 5 wherein said reference light source comprises a reference laser beam source for generating a reference laser beam.
7. The wavelength detecting apparatus according to claim 6 wherein said input means comprises:
a beam splitter for synthesizing said reference laser beam generated by said reference laser beam source, and a concave lens interposed between said beam splitter and said etalon.
a beam splitter for synthesizing said reference laser beam generated by said reference laser beam source, and a concave lens interposed between said beam splitter and said etalon.
8. The waveform detecting apparatus according to claim 6 wherein said input means comprises:
a beam splitter for synthesizing a reference laser beam generated by said reference laser beam source and said laser beam to be detected, and a light diffusing plate interposed between said beam splitter and said etalon.
a beam splitter for synthesizing a reference laser beam generated by said reference laser beam source and said laser beam to be detected, and a light diffusing plate interposed between said beam splitter and said etalon.
9. The wavelength detecting apparatus according to claim 6 wherein said input means comprises:
synthesizing type optical fiber means for receiving said laser beam to be detected via a first input side and said reference laser beam via a second input side, for projecting a synthesized beam obtained by combining said laser beam to be detected and said reference laser beam onto said etalon.
synthesizing type optical fiber means for receiving said laser beam to be detected via a first input side and said reference laser beam via a second input side, for projecting a synthesized beam obtained by combining said laser beam to be detected and said reference laser beam onto said etalon.
10. The wavelength detecting apparatus according to claim 5 wherein said reference light source comprises a lamp.
11. The wavelength detecting apparatus according to claim 10 wherein said input means comprises:
a concave lens to which said laser beam to be detected is inputted; and a beam splitter disposed at a rear stage of said concave lens, for synthesizing said reference light gener-ated by said lamp and an output light of said concave lens.
a concave lens to which said laser beam to be detected is inputted; and a beam splitter disposed at a rear stage of said concave lens, for synthesizing said reference light gener-ated by said lamp and an output light of said concave lens.
12. The wavelength detecting apparatus according to claim 10 wherein said input means comprises:
an optical fiber for transmitting said laser beam to be detected;
an optical fiber sleeve provided at an input end of said optical fiber; and a beam splitter for synthesizing an output light of said optical fiber sleeve and said reference light to obtain a synthesized light and for projecting said synthesized light upon said etalon.
an optical fiber for transmitting said laser beam to be detected;
an optical fiber sleeve provided at an input end of said optical fiber; and a beam splitter for synthesizing an output light of said optical fiber sleeve and said reference light to obtain a synthesized light and for projecting said synthesized light upon said etalon.
13. The wavelength detecting apparatus according to claim 10 which further comprises a filter for selecting only a light beam having a predetermined wavelength among the light generated by said lamp and said laser beam to be detected, said filter being disposed in a light path extend-ing between said lamp and said light detecting means.
14. The wavelength detecting apparatus according to claim 5 wherein said input means comprises:
first shutter means intercepting a reference light generated by said reference light source; and second shutter means for intercepting said light to be detected.
first shutter means intercepting a reference light generated by said reference light source; and second shutter means for intercepting said light to be detected.
15. The wavelength detecting means according to claim 5 wherein said light condensing means comprises an achro-matic lens to which color aberration correction is per-formed.
16. The wavelength detecting apparatus according to claim 5 wherein said light condensing means comprises a light condensing mirror for reflecting a light beam trans-mitted through said etalon into said light detecting means.
17. The wavelength detecting apparatus according to claim 16 wherein said light condensing mirror comprises a concave mirror.
18. The wavelength detecting apparatus according to claim 16 wherein said light condensing mirror comprises an eccentric parabolic mirror.
19. A wavelength control apparatus for use in a narrow band excimer laser for use in a wavelength detecting appara-tus wherein a reference light beam generated by a reference light source and a light beam to be detected are projected upon an etalon; and a first interference fringe correspond-ing to said reference light and a second interference fringe corresponding to said light to be detected are detected by light detecting means so as to detect a wavelength of said light to be detected, said first and second interference fringes being respectively formed by light transmitting through said etalon, said first and said second interference fringes being detected at different times, a detecting period of said first interference fringe being longer than a detecting period of said second interference fringe.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1181680A JP2688991B2 (en) | 1989-07-14 | 1989-07-14 | Narrow-band oscillation excimer laser |
| JP181680/1989 | 1989-07-14 | ||
| JP208762/1989 | 1989-08-11 | ||
| JP1208762A JP2614768B2 (en) | 1989-08-11 | 1989-08-11 | Wavelength detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2063600A1 true CA2063600A1 (en) | 1991-01-15 |
Family
ID=26500765
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2063600 Abandoned CA2063600A1 (en) | 1989-07-14 | 1990-07-12 | Narrow band excimer laser and wavelength detecting apparatus |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA2063600A1 (en) |
| DE (1) | DE4091247T1 (en) |
| WO (1) | WO1991001579A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4401131C2 (en) * | 1994-01-17 | 2003-07-03 | Lambda Physik Ag | Laser for generating narrowband and tunable emissions |
| DE102004010825A1 (en) * | 2004-02-27 | 2005-04-21 | Zeiss Carl Smt Ag | Radiation coherence determination procedure for photolithographic light sources measures amplitude modulation with inserted grating mask |
| TWI725827B (en) * | 2020-04-24 | 2021-04-21 | 力晶積成電子製造股份有限公司 | Image sensing module |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5120691A (en) * | 1974-08-13 | 1976-02-19 | Mitsubishi Electric Corp | REEZA HATSUSHI NKI |
| US4016504A (en) * | 1976-04-12 | 1977-04-05 | Molectron Corporation | Optical beam expander for dye laser |
| US4173442A (en) * | 1977-05-27 | 1979-11-06 | The United States Of America As Represented By The Secretary Of Commerce | Apparatus and method for determination of wavelength |
| JPS6046837B2 (en) * | 1980-03-11 | 1985-10-18 | 日本電気株式会社 | Laser device |
| US4601036A (en) * | 1982-09-30 | 1986-07-15 | Honeywell Inc. | Rapidly tunable laser |
| JPS63107177A (en) * | 1986-10-24 | 1988-05-12 | Komatsu Ltd | Device for detecting wavelength of laser beam |
| JPH01183873A (en) * | 1988-01-18 | 1989-07-21 | Mitsubishi Electric Corp | Laser-wavelength stabilizing method and wavelength stabilized laser device |
| JP2649378B2 (en) * | 1988-04-27 | 1997-09-03 | 株式会社小松製作所 | Wavelength anomaly detector for narrow band oscillation excimer laser |
| US4942583A (en) * | 1988-06-17 | 1990-07-17 | Hewlett-Packard Company | Misalignment-tolerant, grating-tuned external-cavity laser |
| JPH0244219A (en) * | 1988-08-04 | 1990-02-14 | Matsushita Electric Ind Co Ltd | wavelength detection device |
| JPH02121380A (en) * | 1988-10-29 | 1990-05-09 | Toshiba Corp | Narrowband laser device |
-
1990
- 1990-07-12 WO PCT/JP1990/000900 patent/WO1991001579A1/en active Application Filing
- 1990-07-12 CA CA 2063600 patent/CA2063600A1/en not_active Abandoned
- 1990-07-12 DE DE19904091247 patent/DE4091247T1/de not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| WO1991001579A1 (en) | 1991-02-07 |
| DE4091247T1 (en) | 1992-04-23 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5404366A (en) | Narrow band excimer laser and wavelength detecting apparatus | |
| US5373515A (en) | Laser wavelength controlling apparatus | |
| US4829536A (en) | Multi-mode narrow-band oscillation excimer laser | |
| US5243614A (en) | Wavelength stabilizer for narrow bandwidth laser | |
| JP3927753B2 (en) | Exposure apparatus and device manufacturing method | |
| US4975919A (en) | Laser wavelength control apparatus | |
| US6160831A (en) | Wavelength calibration tool for narrow band excimer lasers | |
| JP3624783B2 (en) | Double pass etalon spectrometer | |
| US5387974A (en) | Laser apparatus including Fabry-perot wavelength detector with temperature and wavelength compensation | |
| EP1063503B1 (en) | Wavelength monitoring apparatus for laser light for semiconductor exposure | |
| JPH06302491A (en) | Exposure quantity controller | |
| US4922290A (en) | Semiconductor exposing system having apparatus for correcting change in wavelength of light source | |
| US6621847B1 (en) | Narrow-band excimer laser apparatus | |
| CN111006776B (en) | Atomic absorption-based FP wavelength Ji Wenpiao calibration device and method | |
| CN113659417A (en) | High-stability excimer laser device | |
| JP4197816B2 (en) | Wavelength detector | |
| CA2063600A1 (en) | Narrow band excimer laser and wavelength detecting apparatus | |
| US6542243B2 (en) | Resonator optics monitoring method | |
| JP2631553B2 (en) | Laser wavelength controller | |
| US6456361B1 (en) | Method and instrument for measuring vacuum ultraviolet light beam, method of producing device and optical exposure apparatus | |
| JP2661082B2 (en) | Laser wavelength control apparatus and exposure apparatus using the same | |
| JP2617320B2 (en) | Laser wavelength controller | |
| JP2649378B2 (en) | Wavelength anomaly detector for narrow band oscillation excimer laser | |
| JP2913725B2 (en) | Exposure equipment | |
| JP2537970B2 (en) | Wavelength tunable laser device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |