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`Samsung Electronics Co., Ltd. v. Demaray LLC
`Samsung Electronic's Exhibit 1045
`Exhibit 1045 Page 1
`
`

`

`
`U.S. Patent
`
`
`
`
`May9, 2006
`
`
`
`
`
`Sheet 1 of 5
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`
`
`US 7,041,391 B2
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`
`FIG.
`
`7
`
`Ex. 1045, Page 2
`
`Ex. 1045, Page 2
`
`

`

`
`May9, 2006
`
`
`
`
`Sheet 2 of 5
`
`
`
`US 7,041,391 B2
`
`
`
`Tame
`
`f4N
`
`JOULNOD
`
`IWNOIS
`
`
`
`
`
`ddlLNdS-3ud
`
`
`
`
`U.S. Patent
`
`
`
`
`
`
`
`rrAAAAAPA
`
`
`
`Ex. 1045, Page 3
`
`

`

`
`U.S. Patent
`
`
`
`
`May9, 2006
`
`
`
`
`Sheet 3 of 5
`
`
`
`US 7,041,391 B2
`
`
`
`
`
`
`
`—N
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`
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`r
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`rc
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`~
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`h a
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`-
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`
`Ex. 1045, Page 4
`
`Ex. 1045, Page 4
`
`

`

`
`U.S. Patent
`
`
`
`
`May9, 2006
`
`
`
`
`Sheet 4 of 5
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`
`
`US 7,041,391 B2
`
`
`
`106
`
`
`
`
`
`
`
`Lo
`(as)
`Wo
`Cy
`Cy
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`LL
`iw
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`A
`
`Ex. 1045, Page 5
`
`Ex. 1045, Page 5
`
`

`

`
`U.S. Patent
`
`
`
`
`May9, 2006
`
`
`
`
`Sheet 5 of 5
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`US 7,041,391 B2
`
`:Qo.
`
`cCONTENTRATIO
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`FLUORINECONTENTRATIO(wt%)
`
`Ex. 1045, Page 6
`
`
`
`_o
`
`— p
`
`><
`
`O
`ow
`Ww
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`
`
`
`OPTICAL ABSORPTIVITY (%)
`
`- &
`
`
`
`Ex. 1045, Page 6
`
`

`

`
`
`US 7,041,391 B2
`
`
`1
`METHOD FOR FORMING THIN FILMS
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`
`
`CROSS-REFERENCE TO THE RELATED
`
`
`APPLICATION
`
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`This application is a division of application Ser. No.
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`
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`08/821,435, now U.S. Pat. No. 6,383,346, filed on Mar. 21,
`
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`
`1997, which claimspriority to Japanese Patent Applications
`
`
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`
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`8-093535 filed Mar. 22, 1996 and 9-086123 filed Mar. 19,
`1997.
`
`
`BACKGROUND OF THE INVENTION
`
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`20
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`25
`
`
`30
`
`
`1. Field of the Invention
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`This invention relates to a method for forming thin films
`
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`that are used for optical parts as a reflection preventing film
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`or reflection enhancing film, and especially to a method for
`
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`forming thin films suitable for use in optical parts applicable
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`in ultraviolet and vacuum ultraviolet regions because they
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`have a good spectroscopic characteristics in the ultraviolet
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`region (wavelength of 230 to 400 nm) and vacuum ultra-
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`violet region (wavelength of 190 to 230 nm).
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`2. Related Background Art
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`Methods for forming thin films by sputtering are widely
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`used in the conventional art because they are rather easily
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`applicable for forming thin film of metals, insulators and
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`various kind of compounds. While there are a variety of
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`sputtering methods such as magnetron sputtering and facing
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`sputtering:
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`In the magnetron sputtering, known as a sputter capable
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`of a high speed deposition, electrons are confined by mag-
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`netic field to increase plasma density.
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`A method for forming a film of indium-tin mixed oxide
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`(ITO) by sputtering in a gas containing fluorine together
`
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`35
`with hydrogen and water is disclosed in Japanese Patent
`Publication No. 6-506266/International Publication WO
`
`
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`92/17620.
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`In U.S. Pat. No. 4,125,446, a method for forming a
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`metallic film of aluminum by sputtering in a gas containing
`water and Ar is disclosed.
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`In a sputtering process for forming oxide films like
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`alumina (Al,O,), alumina or aluminum (AJ) is used as a
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`target material and thin films are formed by a sputtering or
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`reactive sputtering in a mixed gas of argon (Ar) and oxygen
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`(O,). In the methods for forming thin films by sputtering or
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`reactive sputtering, a target material
`is ejected by ions
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`accelerated under an ion-sheath voltage.
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`Whenthe target material is composed of a compound, for
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`example an alumina (Al,O,) target, the sputtering particles
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`of alumina ejected from the target by an ion impact are
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`decomposed and ejected from the target. The sputtering
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`particles ejected are oxidized by colliding with oxygen or
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`the like in the plasma or on the surface of substrates.
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`The method for forming a thin film of aluminum oxideis
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`disclosed in Japanese Patent Application Laid-Open No.
`7-70749.
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`An example ofthe film-forming apparatus is a sputtering
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`system (an apparatus for forming sputtering thin films) in
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`which an ion source is mounted for the purpose of enhancing
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`the reactivity by an ion-assist effect by irradiating the ions to
`the substrate.
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`A sputtering system and method for forming sputtering
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`films are proposed in Japanese Patent Application Laid-
`
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`
`
`Open Nos. 7-258841 and 7-258845, wherein a positive
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`voltage is applied on a target electrode to prevent abnormal
`
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`electric discharge during sputtering. It was proved that a
`
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`SiOF film having a lower dielectric constant than that of
`
`40
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`45
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`50
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`55
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`60
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`65
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`2
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`conventional silicon oxide (SiO,) films is formed when a
`mixed material of oxides with fluorides is used. For
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`example, it was reported that SiOFfilms containing F atoms
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`was formed by a plasma chemical vapor deposition (CVD)
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`method by adding a mixed gas containing fluorine.
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`However, the alumina thin film formed by this method
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`contains unreacted bonds (dangling bonds) that are bond
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`deficiencies, thereby forming a film containing less numbers
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`of oxygen atoms than those required for satisfying a sto-
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`ichiometric oxygen content.
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`Recently, so called eximer stepper using an eximerlaser
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`that emits vacuum ultraviolet light having a short wave-
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`length range (190 to 230 nm) is used for a light source for
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`a projection aligner for producing semiconductor devices to
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`attain a high resolution.
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`Thethin films of alumina (Al,O,) formed by the conven-
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`tional method for forming thin sputtering films and system
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`for forming the same described above has a rather large
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`absorption in the ultraviolet wavelength region and, espe-
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`cially, in the vacuum ultraviolet wavelength region. There-
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`fore, it is difficult to use these thin films as optical thin films
`
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`for ArF eximer steppers.
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`Twenty to thirty pieces of lenses are usually combined in
`
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`the projection optical system for producing semiconductor
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`devices. It is important to form several to dozens of multi-
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`film layers of dielectric materials, as reflection preventing
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`layer, having different refractive indices with each other on
`the surface of each lens to reduce the reflection index of the
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`lens.
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`Supposethat 30 pieces of lenses are used in the projection
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`optical system and the absorption ofthe reflection prevent-
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`ing film on each lens is 1% in the working wavelength
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`region of ultraviolet and vacuum ultraviolet light. Then, the
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`intensity of the transmitted light is reduced to 54.7% (the
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`60th power of 0.99) of the incident beam since the light
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`transmittance decays in proportion to n-th power (n is the
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`numbers of the lens used) of transmittance. Moreover, when
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`the reflection preventing film has some degree of light
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`absorption, the absorbed light energy is transferred into heat
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`energy, which affect the quality of the printed images due to
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`distortion of the lens. The reflection preventing film at the
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`site where the eximer laser beam focuses may be broken.
`SUMMARY OF THE INVENTION
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`An object of the present invention is to provide an optical
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`thin film with little optical absorption and a good spectro-
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`scopic characteristics in the ultraviolet region and in the
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`vacuum ultraviolet region.
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`An another object of the present invention is to provide an
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`optical thin film comprising aluminum oxide containing
`fluorine.
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`Still another object of the present invention is to provide
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`an optical film comprising aluminum oxide havingthe ratio
`of the number of the atoms other than aluminum to the
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`numberof aluminum atomsis larger than 1.55 and smaller
`than 1.85.
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`Still further object of the present invention is to provide
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`an optical thin film comprising aluminum oxide prepared by
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`sputtering a target containing aluminum in a gas comprising
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`fluorine atoms in which, if required, oxygen, water and
`helium are added.
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
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`FIG. 1 is a schematic illustration of the system for
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`forming thin films according to the present invention.
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`Ex. 1045, Page 7
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`Ex. 1045, Page 7
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`

`

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`US 7,041,391 B2
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`
`3
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`FIG. 2 is a chart for describing the operation of the
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`apparatus illustrated in FIG. 1.
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`FIG.3 is a schematic illustration of one example of a thin
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`film forming system usedin the present invention equipped
`with a fluorine monitor.
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`FIG.4 is a schematic illustration of another example of a
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`thin film forming system used in the present invention.
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`FIG.5 is a graph indicating the relation of the contents of
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`fluorine and hydroxyl groups in alumina with the optical
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`absorptivity.
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`DETAILED DESCRIPTION OF THE
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`PREFERRED EMBODIMENT
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`4
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`films are formed. Fluorine atoms, fluoride ions and fluoride
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`radicals are formed through a complex decomposition reac-
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`tion of fluorine or fluoride compounds added during the
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`plasma discharge. The monovalent fluorine atoms, fluoride
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`ions and fluorine radicals formedare so reactive that they are
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`liable to be involved in bond terminations by reacting with
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`the unreacted bonds (dangling bonds) of bond deficiencies in
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`the thin film formed by sputtering.
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`temporarily
`When the self-bias during sputtering is
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`adjusted to the potential near the earth potential, sputtering
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`is suppressed, though the plasmais continuing, and few thin
`films are formed because ion acceleration to the surface of
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`the target diminishes. When gasses supplemented with fluo-
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`rine or fluoride compoundsare introduced by synchronizing
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`with adjusting the self-bias close to the earth potential, they
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`are decomposed in the plasma and fluorine atoms, fluoride
`ions andfluoride radicals formed react with unreacted bonds
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`(dangling bonds) in bond deficiencies on the surface of the
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`substrates, thereby terminating the chemical bonds.
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`Byalternately repeating the steps for film formations and
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`for reactions on the surface of the substrate, the density of
`the bond deficiencies in the films formed can be decreased.
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`An excellent optical thin film having low absorption in
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`ultraviolet and vacuum ultraviolet regions and being durable
`to irradiation of ultraviolet or vacuum ultraviolet laser is
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`obtained by the process described above.
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`FIG. 2 is a time chart describing various operations in
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`forming a thin film of aluminaon the substrate 5 according
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`to the present embodiment. The figure contains a time chart
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`representing a high frequency voltage having an amplitude
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`of Vrf that is applied at the beginning ofelectric discharge,
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`at a pre-sputtering stage and at an initial stage of thin film
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`formation, a control signal for the switch 10, and a gas
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`supply (O, and NF, gases) configuration from the gas feed
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`means. Whena high frequency voltage having an amplitude
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`of Vrfis applied to the target 4 before the electric discharge
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`starts, electrons with a small mass follow along with the
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`electric field and generates a plasma by colliding with
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`gaseous molecules having heavy masses. Electrons are accu-
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`mulated on the surface of the target 4 due to a difference in
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`mobility between electrons and ions, which imparts negative
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`vias (Vb) to the target.
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`After the pre-sputtering step has completed, formation of
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`thin films on the substrate 5 starts by opening the shutter
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`plate 16. After starting to form thin films, a control signalis
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`applied from the control system 15 for 5 sec. to the switch
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`10 and the mass flow controller 14 for adjusting NF, gas
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`feed. The switch 10 turns close for 5 sec. by the control
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`signal applied to the mass flow controller 14,
`thereby
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`supplying fluoride gas. A DC voltage is supplied from the
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`DC powersource 11. The prescribed output level of this DC
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`voltage is adjusted to an approximately equal level with the
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`self-bias voltage butits polarity is reversed. Electrons accu-
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`mulated on the surface of the target 4 flows through the
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`cathode electrode 3, low-passfilter 9 and switch 10 to the
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`DC power source 11 and the bias potential is made to the
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`level close to the earth potential. The plasmais still con-
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`tinuing because the high frequency voltage is being
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`impressed on the target 4.
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`NF, gas with a prescribed flow rate is supplied in the
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`vacuum vessel 1 for 5 sec. when a control signal synchro-
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`nized with the signal from the switch 10 is supplied to the
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`massflow controller 14 for adjusting the supply of NF, gas.
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`The NF, gas supplied is decomposed into highly reactive
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`monovalent fluorine atoms, fluorine radicals and fluoride
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`ions in the plasma 18, which react with the unreacted bonds
`of the bond deficiencies in the thin films of alumina formed
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`FIG. 1 is a schematic illustration of the main components
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`of the system for forming sputtering thin films according to
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`the present invention. In the figure, numeral 1 is a vacuum
`vessel as a reaction chamber. Mounted in the vacuum vessel
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`1 are an evacuation means 2 for evacuating the air in the
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`vessel, a gas feed means 12 for introducing various gases
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`into the vessel, and a shutter driving system 17 for driving
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`a shutter plate 16 equipped in the vessel. A cathode electrode
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`3 and a substrate holder 5 for holding a substrate 6 at a
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`position opposed to the cathode electrode 3 are disposed in
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`the vacuum vessel 1. An aluminum target 4 that serves as a
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`target material is attached to the cathode electrode 3. The
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`substrate holder 5 has a device for heating the substrate 6
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`attached to it. The shutter plate 16 is disposed at the foot of
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`the substrate 6 to control the timing for forming thin films
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`(thin films of alumina) on the substrate 6.
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`A high frequency power source 8 is connected to the
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`cathode electrode 3 via a matching box 7 for matching
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`discharge impedance. One terminal of a switch 10 is con-
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`nected to the cathode electrode 3 via a low passfilter 9 for
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`cutting high frequency components off from the high fre-
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`quency power source 8. The other terminal of the switch 10
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`is connected to a DC power source 11 for applying DC
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`voltage equal to the self-bias potential of plasma.
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`Sputtering gases, oxygen (O,) and NF, gas containing
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`fluorine, are piped to the gas feed means 12 via mass flow
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`controllers (MFC) 13 and 14 for adjusting gas supply. The
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`massflow controller 14 is provided for adjusting the supply
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`of NF, gas containing fluorine while a control system 15 is
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`also provided for controlling the switch 10.
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`In the present embodiment, 200 sccm of oxygen gas (O3)
`is introduced into the vacuum vessel 1 via the mass flow
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`controller 13 in the gas inlet means 12 after sufficiently
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`evacuating the air inside of the vacuum vessel 1 by the
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`evacuation means 2. Argon gas may be incorporated in the
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`oxygen gas. A plasma 18 is generated by supplying a high
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`frequency electric power to the cathode electrode 3 and Al
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`target 4 from the high frequency power source 8 via the
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`matching box 7. The high frequency electric power is
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`supplied up to a prescribed level while adjusting the match-
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`ing so that the intensity of reflected high frequency wave
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`will be kept to its minimum value. After completing a
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`pre-sputtering step for cleaning the surface of the target 4
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`and for stabilizing discharge, the shutter plate 16 is turned
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`open bythe driving force of the shutter driving system 17 to
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`start forming thin films on the substrate 5.
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`The elements 9, 10, 11 and 15 described above form a
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`means for temporarily keeping the repeating self-bias near
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`the earth potential while the target material is subjected to a
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`sputtering discharge at metal materials (Al).
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`In the system for forming sputtering thin films according
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`to the present embodiment, means for adding fluorine or
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`gases of fluoride compounds are used when sputtering thin
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`55
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`60
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`65
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`Ex. 1045, Page 8
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`Ex. 1045, Page 8
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`

`

`
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`US 7,041,391 B2
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`5
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`on the substrate 5. While nitrogen atoms and nitrogen
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`radicals are also formed in the plasma 18, their reactivities
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`are so low compared with oxygenation or fluorination reac-
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`tions that a nitrogenation reaction with the thin films of
`alumina formed on the substrate 5 does notstart.
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`An excellent thin film with few bond deficiencies can be
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`formed byalternately repeating the steps mainly for film
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`formation and mainly for reactions.
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`The signal cycle of the control signals from the control
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`system 15 has a close relation with the film-forming rate. A
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`signal cycle of 0.1 Hz or less is preferable. Since the
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`film-forming rate of the Al,O, thin film is 0.03 nm/sec when
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`2.5 kw of high frequency poweris supplied to the Altarget
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`4 with an area of 5x15 square inches while the size of the
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`alumina molecule is several tenth nm, the reaction process
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`wasset to start after forming a single layer in this preferred
`embodiment.
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`Because fluorine series of gases with high reactivities are
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`introduced in the film formation according to the present
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`embodiment,it is preferable to use aluminum (Al) materials,
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`whichareresistive to fluorine and do not cause any problems
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`when the materials migrate into the film as contaminants,for
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`the vacuum vessel 1 and for the components in the vacuum
`vessel 1.
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`The mass flow controller 14 for adjusting the supply of
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`NF, gas from the gas feed means 12 should bedisposed as
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`close as possible to the vacuum vessel 1 to minimize the
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`delay time for introducing the gas. It is also preferable that
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`signals are applied from the control system 15 to the mass
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`flow controller 14 by taking the delay time for introducing
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`the gas into account.
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`Although NF, gas was used as a gas containing fluoride
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`compounds, F,, SiF,, CF,, C.F, or C,F, may be used
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`instead of NF, gas. These gases were selected from those
`35
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`satisfying the conditions below.
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`(1-a) The gases should contain fluorine or fluoride com-
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`pounds because the unreacted chemical bonds (dangling
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`bonds) in the bond deficiencies are terminated by bonding
`with fluorine atoms.
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`(1-b) In the case of gases of fluoride compounds, the
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`absorption edge of the compounds formed by oxidizing the
`atoms bonded to fluorine atom should be in the vacuum
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`ultraviolet region.
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`the
`(1-c) In the case of gases of fluoride compounds,
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`atoms bondingto fluorine atom should have low reactivities
`than oxidation reactions or fluorination reactions.
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`In the process for forming sputtering thin films described
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`above, the amount of fluorine or gases of fluoride com-
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`pounds addedis preferably from 0.5% to 20% of the amount
`50
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`of the sputtering gas. When the amountis 0.5% or more, the
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`gas exhibits a termination effect that allows the gasto react
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`with the unreacted chemical bonds (dangling bonds) of the
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`bond deficiencies in the thin film formed, thereby making it
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`possible to obtain a film without any optical absorption in
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`the wavelength range from the ultraviolet region having a
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`wavelength of 300 nm or below to the vacuum ultraviolet
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`region having a wavelength of 193 nm.
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`When the amount of fluorine or gases of fluoride com-
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`pounds added is more than 20%, sometroubles as described
`60
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`below are seen in the process for forming thin films of
`alumina.
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`(2-a) When the film-forming rate of aluminum fluoride
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`(AIF,) is very rapid and the amount of the gases added is
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`large during pulse-wise introduction of the reaction gases, a
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`large amount of aluminum fluoride (AIF,) is formed in the
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`sputtering thin film of alumina by the effect of residual
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`fluorine. Aluminum fluoride (AIF;) has an inherent deli-
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`20
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`25
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`30
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`40
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`45
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`55
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`65
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`6
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`quescence that allows the material to be dissolved out by
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`absorbing moisturein theair, thereby causing environmental
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`problemsas well as deteriorating durability.
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`(2-b) Both of the materials having a high refractive
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`indices and low refractive indices are required for preparing
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`a film having such optical characteristics as reflection pre-
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`venting films in the regions from the ultraviolet wavelength
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`of 300 nm or below to the vacuum ultraviolet wavelength of
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`193 nm. However, any optical materials having a high
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`refractive indices suitable for use in the wavelength region
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`described above are not available today. Therefore,
`the
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`required optical characteristics are only attained by using
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`alumina (Al,O,) that is an intermediate refraction material
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`havinga refractive index of n=1.85 at 193 nm. For example,
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`a material with excellent optical characteristics suitable for
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`forming a reflection preventing film in a broad wavelength
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`range can be obtained by a combination of the materials
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`having a large difference between an intermediate refractive
`index and a low refractive index. Since aluminum fluoride
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`(AIF;) has a low refractive index of n=1.45 at a wavelength
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`of 193 nm, the refractive index (n) of the alumina film
`becomes 1.77 or less when the content of fluoride after
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`forming the sputtering thin film of alumina exceeds 20% by
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`weight. The difference between the refractive index of
`alumina thus formed and that of the material with a low
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`refractive index—sSiO,, MgF, or CaF,—is so small thatit is
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`difficult to obtain an excellent optical characteristics.
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`In the present embodiment, optical parts like lenses and
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`mirrors, on which a thin film of alumina obtained by using
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`the method and system for forming sputtering thin films
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`described above is applied, are used for optical projection
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`systemsfor effectively producing semiconductor devices.
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`According to the embodiments of the present invention, a
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`sputtering thin film which is suitable for optical systems
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`used in the ultraviolet and vacuum ultraviolet regions can be
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`produced by appropriately selecting each element of the
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`system and steps for forming a thin film on the substrate,
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`especially by film-forming an alumina (AI1,O,) thin film on
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`the substrate. This film has little absorptionin the ultraviolet
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`and vacuum ultraviolet regions and other characteristics
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`required for use described above.
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`Thin films of alumina formed by the conventional sput-
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`tering methods or reactive sputtering methods have unre-
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`acted bonds (dangling bonds) due to the bonddeficiencies in
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`the film. A high absorption of the film in the ultraviolet and
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`vacuum ultraviolet regions is ascribed to the presence of
`these deficiencies.
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`According to the present embodiment, on the other hand,
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`fluorine or gases of fluoride compounds are added by
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`synchronizing with the self-bias control of the target during
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`the process for forming thin films of alumina when unre-
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`acted bonds (dangling bonds) due to bond deficiencies are
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`liable to be formed. The process is divided into alternately
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`repeating two steps of mainly forming the films and mainly
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`allowing to react the gases on the surface of the substrate,
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`thereby reducing the density of the bond deficiencies in the
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`film formed and obtaining thin films with little optical
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`absorption in the ultraviolet region and vacuum ultraviolet
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`region.
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`Thethin films of alumina with low absorption obtained by
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`the embodiments of the present invention havea resistivity
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`against irradiation by a ultraviolet or vacuum ultraviolet
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`lasers like KrF or ArF eximerlasers. Further, the films have
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`high refractive indices when applied on the optical parts to
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`be used in the ultraviolet region (300 nm or below) and
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`vacuum ultraviolet region. When the film is combined with
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`the materials having low refractive indices such as SiO,,
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`Ex. 1045, Page 9
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`Ex. 1045, Page 9
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`

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`US 7,041,391 B2
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`7
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`MgF, and CaF, that are suitable for use in the wavelength
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`region described above, optical elements having low reflec-
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`tive indices in a wide wavelength region can be easily
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`prepared.
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`FIG. 3 showsa system for forming thin films according to
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`the another embodiment of the present invention. This is a
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`system by which the amountof fluorine is monitored during
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`the film-forming process, provided with: a film-forming
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`chamber 1 that is evacuated with a vacuum pump as an
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`evacuation means 2 connected to an exhaustport, a substrate
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`holder 5 as holding means disposed in the chamber, a rotary
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`target unit 3 as generator meansfor film-forming particles
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`opposedto the substrate holder 5, power sources 8 and 11 for
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`supplying electric current to the target, reaction gas feed
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`means provided with reaction gas feed lines 13a, 14a and
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`19a for introducing the reaction gases into the film-forming
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`chamber 1 via the mass flow controllers 13, 14 and 19, a
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`mass spectrometer 21 as a detection meansfor fluorine in the
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`atmosphere of the film-forming chamber 1 and CPU 15 as
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`control means connected to the mass spectrometer. This
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`CPU controls a heater 20 for heating the inside of the
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`film-forming chamber 1, the mass flow controllers 13, 14
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`and 19 in each reaction gas feed line 13a, 14a and 19a and
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`power sources 8 and 11.
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`The substrate holder 5 has a heater 5a for heating a
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`substrate 6 as a base body mounted thereon, and rotates
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`around an axis O, by a rotary driving means (not shown).
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`The rotary target unit 3 has a target holder freely rotating
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`around an axis O, perpendicular to the axis O, of the
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`substrate holder 5, and onepair oftarget 4 held thereon. Both
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`targets 4 are provided with magnets 4a, on their opposed
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`faces. When alternating multi-layers are formed by using
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