Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 1 of 171
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`Sample No.
`
`Target
`
`Substrate
`· temperature (°C)
`
`Table 7
`
`Surrounding gas
`composition,
`oxygen/ argon
`(vol%)
`
`Crystaflinity
`
`Comparative
`Sample 5
`
`Comparative
`Sample 6
`
`titanium metal
`
`titanium metal
`
`230
`
`350
`
`100/0
`
`100/0
`
`anatase
`
`anatase
`
`Titanium oxide film
`
`Triolein-
`decomposing
`ability, residual
`amount(%)
`89
`
`75
`
`Contact angle with
`water (degree)
`
`Anti-fouling ·
`performance
`
`22
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`19
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`Page 459 of 1053
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 2 of 171
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`...
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`EP 1068899 A1
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`[0067] The above results show that in order for the conventional reactive sputtering method using titanium metal as
`a target to obtain a titanium oxide film having photocatalytic activity, the substrate should be heated to a temperature
`as high as 350°C, and that the photocatalytic activity thus obtained is not so high. The results further show that a
`titanium oxide film having photocatalytic activity cannot be obtained at a substrate temperature of 230"C, i.e., a titanium
`oxide film having high catalytic activity cannot be obtained at low temperatures.
`[0068] The above Examples and Comparative Examples demonstrate that according to the process of the present
`invention for producing a multilayer structure, films having high catalytic activity can be obtained at relatively low sub(cid:173)
`strate temperatures of 270"C or lower. The Examples further demonstrate that the photocatalytically active titanium
`oxide films obtained have antifouling properties and are practically useful.
`[0069] According to the process of the present invention for producing a multilayer structure, a photocatalylically
`active titanium oxide film is formed on a substrate by sputtering in an atmosphere capable of having a regulated vacuum
`using a conductiVe sinter target obtained by sintering a mixture of particles of titanium oxide and particles of at least
`one metal oxide selected from the group consisting of niobium oxide, tantalum oxide, vanadium oxide, zirconium oxide,
`tin oxide, chromium oxide and copper oxide. Consequently, a multilayer structure having a photocatalytically active
`film can be produced at high rate without the necessity of heating the substrate at high temperature.
`[0070] As a result, it has become possible to produce a multilayer structure using a large glass plate as a substrate,
`such as a window glass, using a sputtering apparatus having a simplified heating mechanism. The equipment cost
`can hence be reduced.
`[0071] Since lower substrate temperatures can be used in substrate heating, a photocatalytically active film can be
`formed on organic resin substrates and the like.
`[0072] Furthermore, by regulating the conductivity of the sinter target so that the surface resistance thereof is 500
`Q/D or lower. not only a multilayer structure can be produced with a direct current glow discharge continuing stably.
`but also a film having enhanced catalytic activity can be obtained when the substrate is heated to 170 to 27r1'C.
`[0073] The multilayer structure of the present invention has a titanium oxide film which contains as a minor component
`at least one metal oxide selected from the group consisting of niobium oxide. tantalum oxide, vanadium oxide, zirconium
`oxide, tin oxide, chromium oxide and copper oxide, and which is substantially amorphous when analyzed by the X-ray
`diffraction method. Due to this constitution, the multilayer structure has high photocatalytic activity.
`[0074] By regulating the content of the metal oxide(s) as the minor component to 1 to 10% by weight, the titanium
`oxide film can be an amorphous film having high photocatalytic activity.
`[0075] Furthermore, by interposing, between the substrate and the titanium oxide film, a primer film which serves to
`prevent any alkali component of the substrate from dissolving in the titanium oxide film, the photocatalytic activity of
`the multilayer structure can be made to last over long period of time. Moreover, by partly or wholly coating the titanium
`oxide film with a hydrophilic film, the surface of the multilayer structure can be made more hydrophilic and the antifouling
`properties can be enhanced.
`
`Claims
`
`1. A process for producing a multilayer structure comprising a substrate and formed thereon a film mainly comprising
`titanium oxide and having photocatalytic activity, which comprises forming the film by sputtering a conductive sinter
`target obtained by sintering a mixture of particles of titanium oxide and particles of at least one metal oxide selected
`from the group consisting of niobium oxide, tantalum oxide, vanadium oxide, zirconium oxide, tin oxide, chromium
`oxide and copper oxide, in an atmosphere capable of having a regulated vacuum.
`
`2. The process for producing a multilayer structure as claimed in claim 1. wherein the target has a conductivity such
`that the surface resistance thereof is 500 Q/D or lower. and the sputtering is conducted with a direct current glow
`discharge.
`
`s ·
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`3. The process for producing a multilayer structure as claimed in claim 1, wherein the film mainly comprising titanium
`oxide is formed while heating the substrate at a temperature of from 170 to 270"C.
`
`50
`
`4. The process for producing a multilayer structure as claimed in claim 3, wherein the film mainly comprising titanium
`oxide is formed while heating the substrate at a temperature of from 200 to 250"C.
`
`55
`
`5. The process for producing a multilayer structure as claimed in claim 1, wherein the metal oxide is niobium oxide.
`
`6. A multilayer structure comprising a substrate and formed thereon a film mainly comprising titanium oxide and
`having photocatalytic activity, said film containing as a minor component at least one metal oxide selected from
`
`lOCID: <EP ___ 1088899A1_1_>
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 3 of 171
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`EP 1068899 A1
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`the group consisting of niobium oxide, tantalum oxide, vanadium oxide, zirconium oxide, tin oxide, chromium oxide
`and copper oxide, and being substantially amorphous when analyzed by the X-ray diffraction method.
`
`7. The multilayer structure as claimed in claim 6, Wherein the substantially amorphous tilm mainly comprising titanium
`oxide comprises an amorphous matrix containing microcrystals.
`
`5
`
`·
`
`8. The multilayer structure as claimed in claim 6, wherein the content of the metal oxide as the minor component in
`the film mainly comprising titanium oxide is from 1 to 10% by weight.
`
`10
`
`9. The multilayer structure as claimed in claim 8, wherein the metal oxide as the minor component is niobium oxide.
`
`10. The multilayer structure as claimed in claim 6, which has, interposed between tho substrate and the film consisting
`mainly of titanium oxide, a primer film which serves to prevent any alkali component of the substrate from dissolving
`in the film mainly comprising titanium oxide.
`·
`
`15
`
`11. The mul1ilayer structure as claimed in claim 6, wherein the film mainly comprising titanium oxide is coated with a
`hydrophilic film.
`
`12. The multilayer structure as claimed in claim 11, wherein the primer film and the hydrophilic film each is a film of
`silicon dioxide.
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 4 of 171
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`EP 1068899 A1
`
`FIG. 1
`
`1
`~
`
`FIG. 2
`
`5
`
`3
`
`4
`
`2
`
`100
`
`90
`
`80
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`70
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`60
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`16
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 5 of 171
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`FIG. 3
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`Page 463 of 1053
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 6 of 171
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`. . •.
`
`EP 1068899 A1
`
`European Patent
`Office
`
`EUROPEAN SEARCH REPORT
`
`ApplloatlCln Number
`EP 00 11 4185
`
`Relevant
`to daim
`
`CLASSIFICATION OF THE
`APPLICATION Ont.Cl7)
`
`B01J35/00
`801J37/34
`
`TECHNICAL FIELDS
`SEARCHED
`(lnt.Cl.7)
`BOIJ
`
`Category
`
`A
`
`A
`
`A
`
`A
`
`DOCUMENTS CONSIDERED TO BE RELEVANT
`Citation of document with indication. where appropriate.
`of relevam oassaaes
`DATABASE WPI
`Section Ch, Week 199930
`Derwent Publications Ltd., London, GB;
`Class 015, AN 1999-352578
`XP002149112
`& JP 11 130434 A (BRIDGESTONE CORP),
`18 May 1999 {1999-05-18)
`* abstract *
`DATABASE WPI
`Section Ch, Week 199924
`Derwent Publications Ltd., London, GB;
`Class DIS, AN 1999-283348
`XP002149113
`& JP 11 092176 A (BRIDGESTONE CORP),
`6 April 1999 (1999-04-06)
`• abstract *
`DATABASE WPI
`Section Ch, Week 199901
`Derwent Publications Ltd., London. GB;
`Class J04, AN 1999-003984
`XP002149114
`& JP 10 278165 A (ASAHI GLASS CO LTD),
`20 October 1998 (1998-10-20)
`* abstract *
`DATABASE WPI
`Section Ch. Week 199706
`Derwent Publications Ltd., London, GB;
`Class 015, AN 1997-060199
`XP00214911S
`& JP 08 309204 A (BRIDGESTONE CORP),
`26 November 1996 (1996-11-26)
`* abstract *
`
`The present search report has been drawn up for all claims
`
`PlaceclAmdl
`
`I
`I
`°""""'-= ... -
`gi----------------------__,_ ______________________ ......_ ____________________ --1
`B
`THE HAGUE
`4 October 2000
`Thi on, M
`li:l
`CATEGORY OF CITED DOCUMENTS
`T : lhe-ory or pitncil)le ...aerlying the trwenlion
`g
`E : earlier patent doarnenl, but iU>liShed on. or
`X : parUc:Uarly rele\;ant I laken alone
`alter Ille filing dale
`~
`Y : paJtic:Uarly relevant I c~ Wllh ~ 0 : document cited in !he ~ICJ!llicn
`docunwtt of the same categoiy
`L: document cited tor olher reasons
`~
`~ ~ ::n"::~rtUld
`a··;;;;;;i;~·~·tt;;m;;·;~;;-im;;;iy:·;;:;~;;;--··-····-·
`...._ __________________________________________________________________ __,
`
`~
`
`P : ntenne<iate document
`
`dC'c:um«rt
`
`OOCIO: <EP __ t068899At_I_>
`
`18
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 7 of 171
`
`..
`
`EP 1068899 A1
`
`ANNEX TO THE EUROPEAN SEARCH REPORT
`ON EUROPEAN PATENT APPLICATION NO.
`
`EP 00 11 4185
`
`This annex lists the patent lamily members relating to the patent documents cited in the above-mentioned European search report.
`The members are as contained in the European Patent Office EDP tae ;:in
`The European Patent Office 1s in no way liable for these particulars which are merely given for ltle purpose ol information.
`04-10-2000
`
`Patent document
`cited in search report
`
`JP 11130434
`
`JP 11092176
`
`JP 10278165
`
`JP 8309204
`
`A
`
`A
`
`A
`
`A
`
`I Publication
`
`date
`
`18-05-1999
`
`06-04-1999
`
`20-10-1998
`
`26-11-1996
`
`I
`
`Publicahon
`dale
`
`I
`
`Patent family
`member(s)
`
`NONE
`NONE
`
`NONE
`
`NONE
`
`19
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 8 of 171
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`Th~s Page Blank (uspto)
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 9 of 171
`
`Europaisches Patentamt
`
`European Patent Office ·
`
`Office europeen des brevets
`
`I mllll llllll Ill lllll lllll lllll llll ll~l llll lllll lllll llllll llll llll llll
`0 639 655 A1
`
`@ Publication number:
`
`©
`
`EUROPEAN PATENT APPLICATION
`
`@ Application number: 94111669.1
`
`@ Date of filing: 26.07.94
`
`<§) Priority: 28.07.93 JP 205704/93
`
`@ Date of publication of application:
`22.02.95 Bulletin 95/08
`
`@ Designated Contracting States:
`BE OEFR GB
`
`@ Applicant: ASAHI GLASS COMPANY LTD.
`1-2, Marunouchi 2-chome
`Chiyoda-ku
`Tokyo 100 (JP)
`
`@ Inventor: Shimizu, Junichi, Asahi Glass
`Company Ltd.
`Chuo Kenkyusho,
`1150, Hazawa-cho,
`Kanagawa-ku
`Yokohama-shi,
`Kanagawa-ken (JP)
`Inventor: Watanabe, Shujiro, Asahi Glass
`Company Ltd.
`Chuo Kenkyusho,
`1150, Hazawa-cho,
`Kanagawa-ku
`Yokohama-shi,
`Kanagawa-ken (JP)
`Inventor: Takaki, Satoru, AG TECHNOLOGY
`CO., LTD.
`1160, Matsubara
`Hazawa-cho,
`
`@ Method and apparatus for sputtering.
`
`@ Int. Cl.B: C23C 14/00, C23C 14/34, .
`H01J 37/32
`
`Kanagawa-ku
`Yokohama-sh I,
`Kanagawa-ken (JP)
`Inventor: Osaki, Hisashi, Asahi Glass
`Company Ltd.
`Chuo Kenkyusho,
`1150, Hazawa-cho,
`Kanagawa-ku
`Yokohama-shi,
`Kanagawa-ken (JP)
`Inventor: Oyama, Takuji, Asahi Glass
`Company Ltd.
`Chuo Kenkyusho,
`1150, Hazawa-cho,
`Kanagawa-ku
`Yokohama-shi,
`Kanagawa-ken (JP)
`Inventor: Ando, Eiichi, Asahi Glass Company
`Ltd.
`Kashima Kojo,
`25, Oaza-higashiwada,
`Kamisu-cho,
`Kashima-gun,
`lbaraki-ken (JP)
`
`® Representative: Wachtershauser, Gunter, Prof.
`Dr.
`Patentanwalt
`Tal29
`D-80331 Munchen (DE)
`
`® A sputtering method comprises applying a negative voltage intermittently in a constant periodic cycle to a
`cathode disposed in a vacuum chamber, wherein the negative voltage is intermittently applied so that a time
`during which the negative voltage is not applied includes a time during which the voltage is controlled to be zero
`volt in a range of from 10 us to 10 ms, and the zero voltage time is equal to or longer than the time required by
`one arcing from its generation to extinction.
`
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`13. 10/3.09/3.3 ... l
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`Case 6:20-cv-00636-ADA Document 75 Filed 03/10/21 Page 11 of 171
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`EP 0 639 655 A1
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`5
`
`The present invention relates to a sputtering method in which a pulse-like DC voltage is applied, a film(cid:173)
`deposition method by sputtering, an apparatus for obtaining sputtering and a power processing portion for
`sputtering.
`A cathode for DC sputtering (hereinbelow, referred to as sputtering) can not be used for forming a film
`of high quality at a high deposition rate unless a problem of abnormal discharge is overcome.
`Various causes are considered concerning the abnormal discharge occurring around the cathode
`(hereinbelow, referred to as arcing). As one of the causes, electric charges are accumulated on a small
`insulating substance, which is deposited or grown on the surface of a target material, and the electric
`charges cause arcing to a potentially opposite site, e.g. a substrate on which a film is to be formed, an
`10 anode electrode. the inner wall of a vacuum chamber or the surface of the target.
`The arcing occurs frequently in a case that an insulating film is produced from a conductive target
`material by reactive sputtering. When the arcing is generated, arcing energy concentrates locally to a
`portion of the target surface in a reactive gas atmosphere, this forming an insulation or insulations, whereby
`the arcing happens frequently in a series. Accordingly, a stable glow discharge effective to sputtering can
`15 not be maintained; a sputtering rate becomes unstable and the production of films of uniform quality is
`impossible. Occasionally. a substrate on which a film is formed is damaged by arcing, or a mechanical
`component constituting a cathode or a target material or a cathode is molten by arcing.
`In order to avo1j. the above-mentioned disadvantage, a method of using electric power of a high
`frequency su.:-t· as t 3 56 MH.: has been used.
`Recently a tt ... ~hn·qu.-1 ot preventir;ig arcing by using a waveform proposed in Japanese Unexamined
`Paten1 P.1t11r.-=t·,...,,
`,.,.,,, UN..l4 1993 and 331634/1993 or using a device to obtain such waveform (the
`device is .-.·.mrn • .rr.;.1o.·,-,.1 ~<. SPARC-LE by Advanced Energy in U.S.A. Namely, the waveform having a
`frequency c 1 • • ·v'"' a
`.. ~t.-
`is comparable to the effect obtained by a discharge in 13.56 MHz by
`,,..,., t
`applying a pu1~ .. -1,; ... , ,.·,s•ln...- ciectric potential of about 5 us-10 us is applied in a periodic cycle to a
`cathode so that r•,s•t•vt:: .. ,t. .. :tric charges accumulated on a small insulating substance, which is deposited
`or grown on m .. · swtace ot a t.lrget material are neutralized by attracting electrons in plasma.
`Recently. anothc• tectrncue of neutralization of a potential difference on the target surface has been
`developed as s .... ~n m USP. 5,082,546. Namely, an alternating current having an intermediate frequency
`such as sever al :ens l<.H.' is applied to a pair of closely disposed cathodes to ignite glow discharges
`30 between the two cathoocs alternately. In this case, when the electric potential of the cathodes is negative,
`sputtering is conducted. and when the electric potential is positive, positive electric charges accumulated on
`a small insulating substance. which is deposited or grown on the surface of a target material are neutralized
`by attracting electrons in plasma.
`The sputtering method using a radio frequency power source having 13.56 MHz is believed to suppress
`35 arcing because an insulation can be sputtered. However, it is difficult to form a sputtering apparatus using a
`radio frequency power source of 13.56 MHz because a power source having an output of 10 kW or more is
`large and expensive. and an impedance-matching circuit of high voltage and large current is needed.
`·
`A sputtering method wherein DC power is used to apply a positive potential intermittently and the·
`power is intermittently off is a useful technique because a potential difference on the target surface can be
`40 neutralized and the generation of arcing at the initial stage can be suppressed. Thus, the generation of
`arcing could be effectively suppressed. in comparison with the ordinary DC sputtering method. However,
`this method has no ability of sputtering an insulating substance unlike the sputtering method using 13.56
`MHz, and accordingly, arcing occurs when a continuous discharge is conducted for a long time. When the
`arcing is generated. discharge energy concentrates locally on the target. surface in a reactive gas
`45 atmosphere, which further forms an insulation or insulations and results in arcing frequently in a series.
`Namely, the neutralization of potential difference on the target surface by applying a positive voltage or
`O voltage intermittently is effective only to a small insulating substance accumulated with a small amount of
`electric charges if the application time of positive voltage or O voltage is short. Accordingly, it is impossible
`to obtain complete neutralization of an insulating substance accumulated with a large amount of electric
`charges by sputtering for a long time or of an insulating substance having a large amount of electric
`charges produced by arcing, with use of a simple intermittent DC power.
`In the sputtering method of applying an alternating current to the two closely disposed cathodes, an
`alternating current of several tens kHz is used. -Accordingly, it can be said that this method uses the same
`principle as the sputtering method with use of the before-mentioned intermittent DC power, i.e. a potential·
`55 difference on the target surface is neutralized. Further, in this method, the same electrode is used as a
`cathode and an anode. Accordingly, there is an advantage that when the electrode is used as a cathode,
`the surface of it is sputtered and cleaned, and when it is used as an anode, the surface is always cleaned
`whereby a continuous discharge can be stably carried out for a long time. However, this method requires
`
`20
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`
`50
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`EP 0 639 655 A1
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`s
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`the two closely disposed cathodes and an AC power source of several tens kHz. Accordingly, it is
`impossible to suppress arcing and stabilize a normal discharge in a simple manner with use of a currently
`used DC sputtering apparatus.
`As another cause of the occurrence of arcing, when a target material is eroded by sputtering, minute
`protrusions appear in the surface of the target material depending on the kind of material. An electric field
`concentrates to the protrusions whereby arcing occurs at a local portion. Accordingly, the composition of
`the target material is changed whereby a portion having a different sputtering yield may appear and uniform
`sputtering of target surface can not be obtained.
`In particular, when an ITO (indium-tin-oxide) film is to be produced by the sputtering method. and when
`10 an ITO target or an IT (indium-tin) target is used, indium oxide which is believed to be sub oxide, or a large
`number of minute black protrusions (hereinbelow, referred to as nodules), are produced on the target
`surface during continuous sputtering, and the deposition rate of the ITO film is gradually decreased. Further,
`the arcing frequently occurs, whereby small pieces of the target material scattering by the arcing deposit on
`the substrate to reduce the quality of the ITO film.
`As a common technique to remove the protrusions formed by the erosion of the target is to physically
`remove them by causing a discharge in an inert gas atmosphere such as Ar gas, i.e. sputter-etching.
`Further, when the ITO target is used, a method of removing the nodules by a discharge in a N2 gas
`atmosphere is proposed in Japanese Unexamined Patent Publication No. 293767/1992.
`However, the above-mentioned methods are only effective under the condition that a vacuum chamber
`is maintained vacuum after the nodules have been formed, and they can not suppress the occurrence of
`arcing and can not realize a method of a long time stably discharge.
`As another technique, there is a method of improving the surface condition of the target formed by the
`erosion of the target, by increasing the density of a target material of ITO in sintering. However, this method
`pushes up the cost of the target material and effect can not be expected.
`As another technique, there is a method of increasing the density of power at the sputtering to change
`the erosion of the target. When the density of power is simply increased, the frequency of occurrence of
`arcing increases and a discharge energy of arcing also increases. So, this method increases adverse
`effects of the arcing.
`It is an object of the present invention to provide a sputtering method, a film-deposition method by
`sputtering, an apparatus for obtaining sputtering and a power processing portion for sputtering whereby
`arcing is effectively controlled and a larger power can be supplied quickly to deposit a film of high quality
`with high deposition rate for a long time.
`In accordance with the present invention, there is provided a sputtering method, a film-forming method
`by sputtering and an apparatus for sputtering and a power processing part for sputtering wherein the
`35 negative voltage is intermittently applied so that a time during which the negative voltage is not applied
`includes a time during which the voltage is controlled to be zero volt in a range of from 10 us to 10 ms, and
`the zero voltage time is equal to or longer than the time required by one arcing from its generation to
`extinction.
`It is possible in principle to realize the above-mentioned methods, apparatus and the power processing
`portion of the present invention with use of an ordinary DC power source if such a function that the arcing at
`the initial stage is detected to quickly stop the output and the output is again produced after the passing of
`the time of the extinction of arcing, is added to a DC power source. However, when a detection circuit of
`arcing is actually installed in the power source, it is necessary to detect through a power source cable an
`abnormal condition of current or voltage supplied from the positive pole to the negative pole by the power
`source.
`Such method of detection can only detect arcing between the cathode electrode as a target material
`and the anode electrode disposed near the target material. However, a slight arcing at the initial stage which
`starts on the surface of the cathode material can not be detected because the slight arcing is filtered by the
`impedance of the power source cable and the circuit constant of the power source circuit. Namely, only a
`relatively large arcing which is produced as a result of the slight arcing at the initial stage can be detected.
`Since the time of extinction of the relatively large arcing between the cathode and anode is in the order
`of ms, it is necessary to stop the output from the power source for more than several ms. Further, since the
`size of an insulation formed on the surface of the target material at the time of generation of arcing already
`becomes large, the arcing occurs frequently. Accordingly, an abnormal state of output is detected from the
`55 DC power source, the shut-off of several ms is repeated, and it is very difficult to continue the normal
`sputtering operation.
`For the above-mentioned reasons, the slight arcing can not be detected in a case that the ordinary DC
`power source is used for sputtering, and there will be a problem such that the shutting-off of more than
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`several ms is repeated when a large arcing occurring subsequent to the slight arcing takes place.
`The inventors of this application have found through intensive observations of the waveform of arcing
`that the crest value (the maximum value of the waveform of current) in initial arcing before a large arcing
`takes place in a series and the time of extinction of the initial arcing are substantially constant when the
`same apparatus is used.
`Therefore, they have found that the progress of arcing in a series can be prevented by minimizing the
`energy of arcing. Specifically, the sputtering method comprises applying a negative voltage intermittently in
`a constant periodic cycle to a cathode disposed in a vacuum chamber, wherein the negative voltage is
`intermittently applied so that a time during which the negative voltage is not applied includes a time during
`10 which the voltage is controlled to be zero volt in a range of from 10 u.s to 10 ms, and the zero voltage time
`is equal to or longer than the time required by one arcing from its generation to extinction.
`The slight arcing can be seen with a waveform observing device such as an oscilloscope or the like.
`Further, they have found through intensive observations of the waveform of arcing that a time from the
`application of a negative voltage to the generation of the initial arcing is substantially constant when the
`construction of the apparatus is the same.
`Therefore, they have found that by using a voltage waveform wherein the time during which the
`negative voltage is intermittently applied is within a range of from 10 us to 10 ·ms and is equal to or shorter
`than the period of time from the application of the negative voltage to the generation of arcing, the
`accumulation of electric charges on an insulation having a small surface area on the surface of a target can
`20 be minimized; the voltage is controlled to be zero volt before the arcing takes place, and the electric
`charges are neutralized by plasma near the target, whereby the frequency of occurrence of the initial arcing
`can be reduced.
`As described above, it is possible to continue sputtering operations for a long time by specifying the
`time during which the voltage is controlled to zero volt, and this effect can be increased by specifying the
`time during which the negative voltage is intermittently applied.
`In drawings:
`Figure 1 is a diagram showing intermittent waveforms ·according to an embodiment of the present
`invention;
`Figure 2 is a diagram showing intermittent waveforms in a case of applying a positive potential according
`to an embodiment of the present invention;
`Figure 3 is a diagram showing a sputtering apparatus according to a first embodiment of the present
`invention;
`Figure 4 is a circuit diagram showing an embodiment of an intermittent power processing portion of the
`present invention;
`Figure 5 is a diagram showing the sputtering apparatus according to a second embodiment of the
`present invention;
`Figure 6 is a first graph showing the effect of the present invention;
`Figure 7 is a second graph showing the effect of the present invention;
`Figure 8 is a diagram showing the sputtering apparatus according to a third embodiment of the present
`invention;
`Figure 9 is a diagram showing an intermittent waveform of an embodiment of the present invention;
`Figure 10 is a diagram showing an intermittent waveform according to an embodiment of the present
`invention; and
`Figure 11 is a diagram showing an intermittent waveform according to an embodiment of the present
`invention.
`Preferred embodiments of the present invention will be described with reference to the drawings.
`Figure 1 shows waveforms according to an embodiment of the present invention wherein the upper
`portion shows a waveform of voltage and the lower portion shows a waveform of current. Reference numeral
`1 indicates a time during which a negative voltage is intermittently applied (hereinbelow, referred to as an
`5o ON time), numeral 2 designates a time during which the voltage is controlled to be zero voltage
`(hereinbelow, referred to as a zero volt time) and numeral 3 shows a waveform produced when arcing takes
`place. In Figure 1, when the zero volt time is longer than the ON time, power efficiency becomes poor.
`However, the waveform is simple because the power is simply turning-on and off. Accordingly, it is
`advantageous in construction when the power source portion has a sufficient capacity.
`On the other hand, the inventors of the present invention have found that the neutralization of charging
`to an insulation can be effectively done in a shorter time by using a voltage waveform wherein there is a
`time during which a positive voltage is applied in a range of from 1 u.s to 20 us in part of the zero volt time~
`By combining this waveform with the above-mentioned specified ON time, a waveform having excellent
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`power efficiency can be obtained.
`Further, they have found to suppress the occurrence of arcing for a long time and with excellent power
`efficiency by suitably determining the zero volt time, which is equal to or longer than the time of extinction
`of arcing, only just after the arcing.
`Figure 2 shows the waveform obtained by the application of a positive voltage. In Figure 2, the upper
`portion shows the waveform of voltage and the lower portion shows the waveform of current. Reference
`numeral 21 indicates an ON time which is in a range of from 10 µs to 10 ms and which is equal to or
`shorter than the time from the rise of voltage to the generation of an arc discharge in the initial arcing.
`Numeral 22 indicates a zero volt time, which is determined by a time 23 during which a positive
`10 potential is applied and a time 26 for a zero volt after the time 23.
`The zero volt time just before the time 23 during which a positive potential is applied is preferably short.
`However, a constant time of 1 IJ.S to 2 IJ.S is actually set to protect the switching element.
`It is not necessary that the time 23 during which a positive potential is applied is a long time, but it may
`be a time which is sufficient to apply the voltage to a large-sized target, and a time of about 5 µs to 20 u.s
`is preferable. The value of a positive potential can be a potential sufficient to apply the voltage to an actual
`target, and may be 200 V or lower.
`It is desirable tnat the zero volt time 22 can be adjusted depending on a situation of process by
`adjusting the time 26 after the application of a positive potential.
`Namely. a tksrrable rcsLlt can be obtained by adjusting the zero volt time 26 so as to form the zero
`volt time ?? equal to °' lon]C't than the time of extinction of a slight arcing even when a slight arcing
`smaller than a n-1.-u-nr ,.. va1 .... "" netection set in a detection circuit takes pla