(19) Japan Patent Office (JP)
`
`(1 1) Japanese Unexamined Patent
`Application Publication Number
`
`(12) Japanese Unexamined Patent
`Application Publication (A)
`
`S61—193358
`
`(51) Int. Cl.“
`H 01 J 65/O0
`H 01 L 21/30
`// H 01 S 3/101
`
`Identification codes
`
`JPO file numbers
`7825-5C
`Z—7376-5F
`7113-5F
`
`(43) Publication date August 27, 1986
`
`Request for examination: Not yet requested Number of Claims: 1 (Total of 3 Pages)
`
`(54) Title of the invention
`
`LIGHT SOURCE DEVICE
`
`(72) Inventor
`
`(71) Applicant
`(74) Agent
`
`(21) Japanese Patent Application
`(22) Date of Application
`SATO, Yasue
`
`Canon Corporation
`Patent attorney ITO, Tatsuo
`
`S60~32845
`
`February 22, 1985
`% Canon Corporation, Kosigi Works
`53 Imaikami-Cho, Nakahara—Ku, Kawasaki City
`3-30-2 Shimomarkuko, Ota-Ku, Tokyo
`and 1 other
`
`SPECIFICATION
`
`1 . TITLE OF THE INVENTION
`Light Source Device
`2. SCOPE OF PATENT CLAIMS
`
`1. A light source device comprising:
`a gas—filled tube bulb;
`a laser oscillator for excitation: and
`
`an optical system device for focusing, onto the tube
`bulb, a laser beam from the laser emitting device:
`configured so as to emit light through excitation of
`the filled gas in the tube bulb by the focused laser
`beam.
`
`2. A light source device as set forth in Claim 1,
`wherein:
`
`the filled gas is a gas a for emitting ultraviolet or
`deep ultraviolet light, such as a noble gas, halogen
`gas, argon gas, mercury vapor, or the like, where the
`tube ‘bulb is structured from a material that transmits
`
`light in the ultraviolet or deep ultraviolet domain,
`such as calcium fluoride, lithium fluoride,
`magnesium fluoride, quartz glass, sapphire, or the
`like.
`3. DETAILED EXPLANATION OF THE INVENTION
`
`[FIELD OF USE OF THE INVENTION]
`The present invention relates to a light source
`device, and, more particularly,,relates to a light
`source device that is well suited as an ultraviolet/deep
`ultraviolet light source, in particular, for causing
`sealed gas to emit plasma through excitation with a
`laser beam.
`
`[PRIOR ART]
`In light source devices in semiconductor
`manufacturing equipment such as optical exposure
`
`devices, and the like, there are a variety of
`requirements, such as a long service life, stability of
`the position of the center of light emission, and the
`like, in addition to adequate strength of light emission
`add to the desired wavelength.
`Conventionally, that which has been used as an
`ultraviolet or deep ultraviolet light source for
`photolithography has been of a type that produces an
`arc discharge between electrodes within a gas tube
`bulb that is filled with mercury gas or a noble gas
`(such as Xe gas, or the like), where because the
`electrodes are exposed to the arc discharge, they
`become extremely hot and gradually are vaporized,
`. or are sputtered by high velocity electrons that are
`produced by the arc, and thus unavoidably the
`electrodes wear out, and the metal that is vaporized
`or produced through sputtering coats the inner wall
`surfaces of the tube bulb, and have an effect on the
`transparency for wavelengths in the ultraviolet
`domain, so that as time passes, the intensity and
`spectrum of the light emission changes gradually, and,
`at the same time, there are changes in the shape of the
`arc and changes in the position of the center of the
`light emission, due to the changes in the shape of the
`electrodes‘, and thus typically the service life is
`limited to several hundred hours, and thus it is
`necessary to stop the semiconductor manufacturing
`equipment frequently in Order to change the tube bulb.
`Moreover, even when replacing the tube bulb, there
`are fine differences in the positions of the electrodes
`from bulb to bulb, requiring fine adjustments in the
`positions of the tube bulb each time a tube bulb is
`replaced.
`
`ASML 1317
`
`

`
`Japanese Unexamined Patent Application Publication S6l~l93358 (2)
`
`[OBJECT OF THE PRESENT INVENTION, AND SUMMARY
`THEREOF]
`In order to solve the problem with the conventional
`technology, set forth above, the present invention
`provides a light source of device wherein there is
`little change over time in the intensity or spectrum of
`the light that is produced and wherein the position of
`the center of light emission is stabilized by an
`external optics system, wherein, through focusing a
`laser beam, from the outside, into a gas that is filled
`into a tube bulb, electrodischarge breakdown of the
`filled gas is produced through excitation by the laser
`beam, to cause the production of a high—temperature
`plasma of the filled gas at the focal position of the
`condensed laser beam within the tube, to produce a
`light source with a stabilized light emission intensity
`and the light emission central position with a spectral
`distribution that depends on the constituents of the
`filled gas.
`'
`In the light source device according to the present
`invention, there are no electrodes within the tube bulb,
`so there is no change in the intensity of light
`production nor in the spectrum due to the effects of
`evaporation or sputtering thereof, making it possible
`to produce a long service life, and, additionally,
`because the position of the center of the light
`emission is determined by the position of the focal
`point of the laser beam, it is always preserved with
`stability, and there is no change, even when the tube
`bulb is replaced, In the present invention, the spectral
`distribution of the light emission is determined by the
`composition of the filled gas, and when used in, for
`example, the ultraviolet or deep ultraviolet domain, a
`noble gas, such as Xe, a halogen gas, argon gas,
`mercury vapor, or the like, may be filled in a specific
`composition. Moreover, in this case, for the tube bulb
`itself, the material may be selected depending on the
`transparency in relation to the target wavelength
`domain, where, for example, calcium fluoride,
`lithium fluoride, magnesium fluoride, quartz glass,
`sapphire, or the like, may be used for ultraviolet or
`deep ultraviolet.
`[EMBODIMENTS]
`An embodiment of the present invention is
`provided as follows.
`I
`FIG. 1 is a structural diagram illustrating a basic
`structural example of a light source device according
`to the present embodiment, wherein a laser oscillator
`l emits a continuous or pulsed laser beam of an
`intensity that is adequate to excite electrodischarge of
`' the filled gas. 2 and 3 are optical system elements for
`forming and projecting a laser beam in an appropriate
`shape for easy handling, where the projected laser
`' beam is focused onto the position of the focal point
`within the tube bulb 5 by a focusing optical system
`element 4. The tube bulb 5 has deep ultraviolet
`
`radiation transparent material properties and is filled
`with, for example, aanoble gas such as Xe, argon gas,
`mercury vapor, or the like, as a light-emitting gas. 6
`is a reflective optical system element for reflecting
`again the laser beam that has passed through the tube
`bulb 5, and is conjugate with the focusing optical
`system element 4.
`The laser beam from the laser oscillator l
`
`undergoes appropriate beam forming by the optical
`system elements 2 and 3 to pass through a specific
`light path to be focused onto a focal point position
`within the tube bulb 5, focused by the focusing
`optical system element 4. At the focal point that is
`determi'ned in essentially the central position of the
`tube bulb 5, an electromagnetic field is produced with
`enough intensity to stimulate electrodischarge of the
`filled gas, through the strong energy of the laser
`beam, and a spectrum that includes ultraviolet and
`deep ultraviolet radiation is emitted from the high
`temperature plasma of the filled gas that is produced
`by the electrodischarge. In this case, the laser beam
`that has not contributed to the stimulation of the
`
`.
`
`electrodischarge is incident into the reflecting optical
`system component 6, and is reflected thereby to be
`focused again onto the focal point of the tube bulb.
`The lightsource device of the present invention is
`well-suited to semiconductor manufacturing
`equipment, in particular, due to the stability of the
`light emission intensity, spectrum, and central
`position of the light emission, where an example of
`application to exposure equipment is presented in
`FIG. 2 as a specific example of application thereof. In
`FIG. 2, those parts given the same symbols as in FIG.
`1 have the same effects, where, additionally, 7 is an
`elliptical mirror for focusing, 8 is an illumination
`optical system device for the exposure equipment, 9
`is a mask, and 10 is a wafer. When the deep
`ultraviolet radiation that is emitted from the tube bulb
`
`5 is focused by the elliptical mirror 7 and projected
`onto the mask 9 by the illumination optics system
`device 8, the circuit patterns of the mask 9 are
`transferred onto the wafer 10, which has been coated
`with photoresist.
`[EFFECTS OF THE INVENTION]
`As described above, given the present invention,
`the sealed gas is excited by the laser beam within the
`tube bulb to undergo plasma emission of light, and
`thus there is no need to provide electrodes within the
`tube bulb, making it possible to solve all at once in
`the various problems with the conventional
`technology that have occurred due to the existence of
`the electrodes, making it possible to produce a light
`source device with a long service life wherein there is
`little change in the intensity of light produced or in
`the spectrum as time passes, where the position of the
`center of light emission is also determined by the
`
`

`
`Japanese Unexamined Patent Application Publication S61-193358 (3)
`
`application to semiconductor manufacturing
`equipment.
`_
`1: Laser Oscillator
`2, 3: Optical System Components
`4: Focusing Optical System Component
`5: Tube Bulb
`6: Reflecting Optical System Element
`
`Patent Applicant: Canon Corporation
`Agent: Patent Atty. ITO, Tatsuo
`Agent: Patent Atty. ITO, Tetsuya
`
`position of the focal point of the external focusing
`optics system, regardless of the tube bulb, and so not
`only is always stable, but does not change, even when
`the tube bulb is replaced, making replacement of the
`tube bulb easy, and thus it is also easy to prepare tube
`bulbs with a Variety of filled gases to make it possible
`to selectively obtain light sources for beams of
`different spectral distributions.
`4. BRIEF DESCRIPTIONS or THE DRAWINGS
`FI_G. 1 is a structural diagram illustrating one
`embodiment of the presentinvention, and FIG. 2 is a
`structural diagram illustrating an example of
`
`FIG. I
`
`
`
`1: Laser Oscillator
`
`FIG. 2
`
`
`
`1: Laser Oscillator
`
`

`
`
`
`County of New York
`State of New York
`
`Date: November 2, 2015
`
`To whom it may concern:
`
`This is to certify that the attached translation from Japanese into English is an accurate
`
`representation of the documents received by this office.
`
`The documents are designated as:
`
`0
`
`Japanese Unexamined Patent Application Publication Number S61—193358
`
`Abe Holczer, Project Manager in this company, attests to the following:
`
`"To the best of my knowledge, the aforementioned documents are a true, full and accurate
`
`translation of the specified documents.”
`
`
`
`Signature of Abe Holczer
`
`4 ‘
`
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