WORLD INTELLECTUAL PROPERT
`
`PCT
`International Burea
`INTERNATIONAL APPLICATION PUBLISHED UNDER Ti
`(51) International Patent Classification 6 :
`(11) International Publication Number:
`C23C 14/34, G02F 1/163
`
`WO 9606203A1
`WO 96/06203
`
`(43) International Publication Date: 29 February 1996 (29.02.96)
`
`(21) International Application Number:
`
`PCT/US95/10597
`
`(22) Internationa] Filing Date:
`
`17 August 1995 (17.08.95)
`
`(81) Designated States: JP, European patent (AT, BE, CH, DE, DK,
`ES, FR, GB, GR, IE, IT, LU, MC. NL, PT, SE).
`
`Published
`With international search report.
`Before the expiration of the time limit for amending the
`claims and to be republished in the event of the receipt of
`amendments.
`
`(30) Priority Data:
`293,129
`
`19 August 1994 (19.08.94)
`
`US
`
`(71) Applicant: OPTICAL COATING LABORATORY, INC.
`[US/US]; 2789 Northpoint Parkway, Santa Rosa, CA
`95407-7397 (US).
`
`(72) Inventors: O’BRIEN, Nada, A.; 2322 Maher Drive, Santa
`Rosa, CA 95405 (US). MATHEW, John, G., H.; 2342 S.
`Hampton Circle, Santa Rosa, CA 95401 (US). HICHWA,
`Bryant, P.; 4100 Pressley Road, Santa Rosa, CA 95404
`(US). ALLEN, Thomas, H.; 300 California Avenue, Santa
`Rosa, CA 95405 (US).
`
`(74) Agents: SEELEY, David, O. et al.; Workman, Nydegger &
`Seeley, 1000 Eagle Gale Tower, 60 East South Temple, Salt
`Lake City, UT 84111 (US).
`
`(54) Title: ELECTROCHROMIC MATERIALS AND DEVICES, AND METHOD
`
`(57) Abstract
`
`A process for manufacturing electrochromic layers/devices at high rates and low deposition temperatures is described. The method
`utilizes the magnetron enhanced sputtering technique in which a substrate (36) is rotated past sputter cathodes (38, 40, 42, 44, 46) and past
`a reactive ion source (48) in order to deposit a layered electrochromic device. The process uses high system pressure and large reaction gas
`flow rates, but relatively low reactive gas partial pressures at the sputter cathodes (38, 40, 42, 44, 46) to reproducibly form electrochromic
`materials and devices which exhibit excellent optical and physical properties.
`
`Page 1 of 42
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`APPLIED MATERIALS EXHIBIT 1051
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`

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`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international
`applications under the PCT.
`
`AT
`AL
`BB
`BE
`BF
`BG
`BJ
`BR
`BY
`CA
`CF
`CG
`CH
`CI
`CM
`CN
`CS
`CZ
`DE
`DK
`ES
`FI
`FR
`GA
`
`Austria
`Australia
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Côte d’Ivoire
`Cameroon
`China
`Czechoslovakia
`Czech Republic
`Germany
`Denmark
`Spain
`Finland
`France
`Gabon
`
`GB
`GE
`GN
`GR
`HU
`IE
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`LI
`LK
`LU
`LV
`MC
`MD
`MG
`ML
`MN
`
`United Kingdom
`Georgia
`Guinea
`Greece
`Hungary
`Ireland
`Italy
`Japan
`Kenya
`Kyrgystan
`Democratic People’s Republic
`of Korea
`Republic of Korea
`Kazakhstan
`Liechtenstein
`Sri Lanka
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`Mali
`Mongolia
`
`MR
`MW
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SI
`SK
`SN
`TD
`TG
`TJ
`TT
`UA
`US
`UZ
`VN
`
`Mauritania
`Malawi
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Slovenia
`Slovakia
`Senegal
`Chad
`Togo
`Tajikistan
`Trinidad and Tobago
`Ukraine
`United States of America
`Uzbekistan
`Viet Nam
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`WO 96/06203
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`PCT/US95/10597
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`ELECTROCHROMIC MATERIALS AND DEVICES, AND METHOD
`
`I
`
`1. BACKGROUND OF THE INVENTION
`
`A. Field of the Invention
`The present invention relates to electrochromic and electrochromically active
`materials and devices and to methods and processes for making such materials and
`devices.
`
`B. Description of the Related Technology
`Electrochromic or electrochromically active (EC) materials change their refractive
`index (real and imaginary) as the result of a voltage potential-induced injection (or
`rejection) of ions induced by the application of an electric potential. Charge neutrality
`is maintained by a balanced and oppositely directed flow of electrons from the potential
`source. The change in refractive index results in a change in the transmission and/or the
`reflection characteristics of the film, often resulting in a visible change of color. So-
`called anodic and cathodic electrochromic materials/devices color when a positive or
`negative voltage of appropriate magnitude and duration is applied.
`Because ion transfer is required to induce the change in the index of refraction,
`reversible electrochromic devices contain both a source of ions and a sink. Typically,
`this necessitates a multiple-material, multi-layer structure comprising electrochromic and
`ion conductive materials. See for example, Large Area Chromogenics: Materials and
`Devices for Transmittance Control. Ed. C.M. Lampert and C.G. Granqvist. SPIE 1990.
`The typical device structure used and the associated electrochemical processes are
`equivalent to those of a rechargeable battery for which the degree of color is an indication
`of the state of charge. Consequently, many of the electrochromic materials, fabrication
`methods and analysis techniques are similar or identical to those used for the manufacture
`of batteries.
`FIGS. 1A and IB (collectively, FIG. 1) schematically depict key components of
`two common types of reversible EC devices. Please note, these figures are not to scale.
`Layer thicknesses are chosen in part for ease of illustration and to help in distinguishing
`adjacent layers. Furthermore, except as noted, the cross-hatching is selected primarily
`merely to visually distinguish adjacent layers.
`Referring initially to FIG. 1 A. there is shown a typical laminated device 1 which
`incorporates polymer ion conducting material. The laminated device 1 comprises
`supportive substrates 2 and 8, of material such as glass, at the opposite ends or sides
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`thereof. Conductor layers 3 and 7 on the interior sides of the substrates apply voltage
`from source 9 across the EC structure which is positioned therebetween. The EC
`structure comprises an EC layer 6 next to the conductor layer 7, a so-called ion storage
`layer 4 next to the conductor layer 3 and polymer ion conducting layer 5 sandwiched
`between the EC and ion storage layers. Suitable ion conductor polymer materials include
`proton conducting polymer such as poly AMPS (2-acrylamido-2-methylpropanesulfonic
`acid), and Li" conducting polymer such as PMMA (poly methyl methacrylate) doped
`with LiClO4.
`The EC layer 6 is the primary electrochromic layer in that most of the color
`change occurs within this layer. The ion conducting layer 5 which separates the EC layer
`and the ion storage layer functions both as an ion conducting layer and an electronic
`insulator. Ion storage layer 4 functions as a sink and as a source of ions for the primary
`EC layer 6. In fact, the ion storage layer 4 often is an EC material whose color change
`augments that of the primary EC layer 6. This can be achieved using an EC layer 6 that
`colors as the result of the injection of ions and an ion storage layer 4 of different EC
`material that colors upon the loss of the transported ions.
`FIG. IB schematically illustrates a so-called solid state stack EC device 10. (This
`device is of the greater interest here, because the components can be formed using the
`techniques developed for forming optical thin film coatings.) The thin film device 10
`comprises a substrate 12 of material such as glass; first conductor layer 13 on the
`substrate; ion storage layer 14 formed next to the conductor 13; electrochromic layer 16;
`ion conducting layer 15 between the electrochromic layer and the ion storage layer;
`second conductor 17; and a substrate 18 formed on the opposite end/side of the device
`from the substrate 12. As indicated in the figure, one or both the substrates may be used.
`Voltage source 19 is connected to the conductors 13 and 17 for supplying the required
`voltage across the EC structure. The arrows (see also FIG. 1A) indicate a typical
`potential-induced flow of electrons (e ) and ions (M4) during coloring. Examples of
`suitable ion conductor thin film materials include Ta3O5, MgF2, LiNbO3, etc.
`In so-called window (optically transmissive) versions of the devices 1 and 10,
`both conductors 13 and 17, FIG. IB (also 3 and 7. FIG. 1A). are transparent layers of
`material such as tin oxide SnO2, indium tin oxide (In2O3:Sn or ITO), fluorine-doped tin
`oxide (SnO2:F) , aluminum-doped zinc-oxide (ZnO:Al), etc. In mirror (reflective)
`devices, one of the transparent conductors 13 or 17 (3 or 7) typically is replaced with a
`reflective conductor layer, for example, a metal such as aluminum. In both window and
`mirror devices, the other constituent layers preferably are transparent. Examples of
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`suitable materials for the electrochromic (electrochromic and ion storage) layers 14 and
`16 (4 and 6) include WO3, MoO3, Nb2O5, V2O5, Cr2O3, TiO2, IrO2, NiO, Rh2O3, etc.
`One suitable construction for device 10 uses a glass substrate; an ITO
`conductors); a nickel oxide (NiO) ion storage layer; a tantalum pentoxide (Ta2O5) ion
`5 conducting layer; and a tungsten oxide (WO3 ) electrochromic layer.
`Several processes are reported to have been used to manufacture electrochromic
`materials, including the electrochromic components of the exemplary EC devices 1
`and/or 10. These processes include sol-gel deposition, electrodeposition, and vacuum
`deposition techniques such as plasma-enhanced chemical vapor deposition (PECVD),
`10 electron beam evaporation, reactive ion plating, and reactive sputtering.
`U.S. Patent No. 5,277,986 describes sol gel deposition of the tungsten oxide.
`Reported advantages include low cost of operation, at least in part because the process
`can be effected at ambient atmospheric pressures, thus eliminating the time and expensive
`apparatus required for vacuum processing. However, sol gel deposition requires the use
`15 of high temperatures to evaporate and decompose the solvent and organic materials,
`respectively. As a result, this approach is unsuitable for temperature-sensitive materials
`such as many plastics and for coating electrochromic layers/devices on plastics.
`U.S. Patent No. 4,282,272 describes the use of reactive evaporation for forming
`on a heated substrate a film of electrochromically active, amorphous WO, or of WO,
`20 containing TiO2, Ta2O5, Nb2O5,, V2O5. or B2O3. Reactive evaporation has the advantage
`of high deposition rates, here about 5A/sec., but requires heating the substrate to elevated
`temperatures ranging from about 250°C to 350°C. which prevents coating electrochromic
`layers/devices on plastics.
`Plasma-enhanced chemical vapor deposition of electrochromic transition metal
`25 oxide materials is described in U.S. Patent No. 4,687,560. PECVD has the advantage of
`being a very high deposition rate process. The '560 patent reports a deposition rate of
`about 4.75A/sec. for tungsten trioxide, WO3 using this technique. The '560 patent
`suggests the PECVD process may be used to coat electrochromic materials on
`temperature sensitive substrates such as plastics, because of the inherently low substrate
`30 heating associated with the process. However, this capability is unlikely. Despite the
`lack of need of "intentional" heating to deposit electrochromic materials, exothermic
`reactions often occur in the deposition chamber during PECVD processing, causing
`substrate heating. Perhaps the primary disadvantage of PECVD is the use of poisonous
`and corrosive gases such as WF6, MoF6, and W(CO)6 whose gaseous byproducts are
`35 hazardous and corrosive, and which thus present problems of equipment design and
`maintenance and are subject to stringent safety regulations.
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`Both RF and DC magnetron reactive sputtering from a metal target have been
`used to form electrochromic films. However, to ensure proper film stoichiometry (for
`example, a composition close to WO3), high oxygen partial pressures are required, which
`cause oxidation and poisoning of the target, thereby slowing film formation. Also, the
`5 reported deposition rates of less than one Angstrom per second are too low for
`commercially viability. See for example, H. Akram, M. Kitao, and S. Yamada in J. Appl.
`Phys. 66(9), 1989 p. 4364.
`U.S. Patent No. 4,451,498 describes the use of RF-excited reactive ion plating for
`forming anodically coloring materials (materials which "color" when a positive voltage
`10 is applied) in oxygen and water vapor atmospheres. Examples of such materials are
`iridium hydroxide and nickel hydroxide. The technique has not been shown to be viable
`at producing the remaining layers of an electrochromic device such as the cathodically
`coloring material, the conductive layers, etc.
`U.S. Patent No. 5,189,550 reports the low temperature formation of crystalline
`15 electrochromic WO3 thin films on glass and plastic substrates by RF ion-assisted
`evaporation. WO3 powder is evaporated onto an unheated substrate that is being
`bombarded with a stream of 200-300 eV oxygen ions. Crystalline WO3 is known in the
`art to show a large infrared reflection upon coloring and therefore is suitable for energy
`efficient electrochromic device applications.
`As should be evident from the above discussion, electrochromic and ion
`conductive materials are not easily formed using the standard deposition processes. In
`part, this is the result of the fact that the structures of electrochromic and ion conductive
`materials simply are not well suited to the standard deposition techniques.
`
`20
`
`25
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`2. SUMMARY OF THE INVENTION
`
`In one aspect, the present invention is embodied in a process suitable for forming
`electrochromic materials on one or more substrates, comprising traversing a substrate
`through physically separated deposition and reaction zones; at the sputter deposition
`30 zone, sputtering depositing at least one layer of material on the traversing substrate; at
`the physically separate reaction zone, reacting the deposited material on the traversing
`substrate, thereby converting the material to a thin coating of an electrochromic material
`or a material useful in an electrochromic device; and repeating the depositing and
`reacting steps to build up the thickness of the coating.
`The process is well suited to the formation of composites or devices which
`include temperature sensitive components such as plastic substrates.
`
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`In another aspect, the present invention is embodied in a process for forming an
`electrochromic structure in situ in a vacuum processing chamber. The process comprises:
`providing a plurality of deposition zones associated with a plurality of sputtering
`cathodes and at least one physically separate reaction zone associated with an ion source
`device; selectively operating the sputtering cathodes for depositing selected materials;
`selectively operating the ion source device for generating a reactive gas plasma for
`chemically reacting with selected ones of the deposited materials; and continuously
`traversing a substrate through the deposition zones and the at least one reaction zone for
`forming a first of an ion storage layer and an EC layer, forming an ion conductor layer,
`and forming the second of the ion storage layer and the electrochromic layer. In another
`aspect, a first conductor layer is formed in situ on the outside of said first layer; and a
`second conductor layer is formed in situ on the outside of said second layer.
`In an optically transmissive (window) embodiment, the conductor layer(s), are
`indium tin oxide, said first and second layers are selected from nickel oxide and tungsten
`oxide, and the ion conducting layer is tantalum oxide. In a reflective (mirror)
`embodiment, one of the conductor layers is reflective material such as the metal
`aluminum.
`Presently preferred process parameters using the throw distances described herein
`and sputtering and reaction gases such as argon and oxygen, are: system pressure of 20-
`80 mtorr (millitorr); and reactive gas partial pressure of 7-40 mtorr.
`In other aspects, the present invention is embodied in a composite which is a solid
`state stack electrochromic device, in a composite which is a stack of components suitable
`for a solid state stack electrochromic device, and in a composite which is a stack of
`components suitable for use in a laminated electrochromic device. In one specific
`embodiment, the composite comprises an ion storage layer and a conductor layer formed
`on a substrate in situ. Another specific composite comprises an electrochromic layer and
`a conductor formed on a substrate in situ. Another specific composite comprises a layer
`of ion storage material, an ion conducting layer and an electrochromic layer formed in
`situ. Still another specific composite comprises a layer of ion storage material, an ion
`conducting layer and an electrochromic layer formed in situ, along with at least one
`conducting layer.
`
`3. BRIEF DESCRIPTION OF THE DRAWING
`
`The above and other aspects of the invention are described with respect to the
`accompanying drawing, in which:
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`FIGS. 1A and IB are simplified cross-sectional schematics of representative
`electrochromic devices constructed respectively using polymer ion conducting material
`and thin film ion conducting material.
`FIG. 2 depicts a magnetron-enhanced sputter system for forming electrochromic
`materials and devices.
`FIG. 3 depicts the optical characteristics (colored or clear) of as-deposited WO3
`as a function of total pressure and oxygen partial pressure.
`FIG. 4 depicts the change of optical density (OD) of as-deposited WO3 films at
`633 nm (nanometers) as a function of total pressure.
`FIG. 5 depicts the distribution of deposition rates for as-deposited WO3 films
`having different changes in optical densities, all measured at 633 nm.
`FIG. 6 is a graph of the coloring and bleaching % transmission response at 633
`nm for WO films formed using either low pressure (8 mtorr, Table Bl) or high pressure
`(45 mtorr, Table B2). The response is determined from the injection of protons in a 0. IN
`HCI solution and at the appropriate coloring and bleaching voltages of -0.5 V and +1.0V
`respectively. Transmission measurements were taken while samples were still in acid.
`The underlying ITO has a sheet resistance of 5 ohms per square. The area tested is <1
`cm,.
`
`FIG. 7 depicts the optical switching response at 550 nm of 3800 A thick WO3
`films prepared according to Example 1. The area tested was 4 cm,; ITO sheet resistance
`was 5 ohms per square. Protonation took place in O.l N HCI solution.
`FIG. 8 depicts the % transmission of the films of FIG. 7 in air, for both colored
`and the bleached states.
`FIG. 9 illustrates the optical switching response at 550 nm of 3500 A thick NiO
`films prepared according to Example 2. The area tested was 4 cm2; the ITO sheet
`resistance was 15 ohms per square. Testing took place in 1.0M KOH solution.
`FIG. 10 depicts the % transmission of the sample of FIG. 9 in air, for both
`colored and bleached states.
`FIG. 11 depicts the optical switching response at 550 nm of 4400 A Nb,O? film
`prepared according to Example 4. The area tested was 4 cm2; ITO sheet resistance was
`5 ohms per square. Protonation/hydration took place in a 0.1 N HCI solution.
`FIGS. 12 and 13 are, respectively, a simplified schematic perspective view,
`partially cut away, and a simplified schematic horizontal cross-sectional view of one type
`of DC linear magnetron sputtering device used in the system and process of the present
`invention.
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`FIGS. 14 and 15 are, respectively, an exploded perspective view and an end view,
`partly in schematic, of one embodiment of a linear magnetron ion source device used in
`the sputtering system and process of the present invention.
`
`5
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`4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
`
`A. System Overview
`The MetaMode® sputtering system and associated processes, which are described
`in detail in commonly assigned U.S. Patent Nos. 4,851,095 and 5,225,057, have been
`used to effect the controlled deposition and formation of refractory metal compounds
`such as oxides, nitrides, carbides, etc. The '095 patent and the '057 patent are
`incorporated by reference.
`This section, Section A, discusses a specific example of a sputtering system,
`constructed and operating in accordance with the present invention, for forming
`electrochromically active materials and devices. The next section, Section B, discusses
`the typical process parameters used for forming optical thin films in the MetaMode®
`sputtering system described in the incorporated '095 and '057 patents, and the
`improvements and discoveries according to the present invention which specially adapt
`the MetaMode® sputtering system for forming exemplary electrochromically active
`materials, specifically WO3, in situ. Section B includes process examples. Section C
`describes additional examples of processes for forming electrochromically active
`materials as well as electrochromically active devices. Sections D and E describe various
`additional embodiments of the present invention. Section F summarizes certain
`advantages of the present invention. Sections G and H disclose details of sputter
`deposition cathodes or devices and ion source devices which are described in the
`incorporated U.S. Patent 4,851,095 and which are suitable for use in the present system
`and process.
`FIG. 2 is a schematic horizontal cross-sectional view of one suitable embodiment
`30 of a magnetron-enhanced reactive sputtering system, which is derived from the
`MetaMode® sputtering system and is used to form electrochromic coatings in accordance
`with the present invention. FIG. 2 describes a sputtering system having a rotating drum
`34. However, other system geometries can be used to practice the present invention,
`including the in-line system, the disc system and possibly the planetary system described
`in the incorporated '095 and '057 patents. Certainly the electrochromic fabrication
`process can be practiced utilizing the planetary system geometry; the issue is whether
`there is a need to form electrochromic devices on the non-planar substrate geometries
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`such as convex and concave curves and tubes for which this systems are especially well
`suited.
`
`Referring further to FIG. 2, the vacuum system 30 comprises an octahedral
`housing 32 having eight walls which define a vacuum chamber in which the drum 34 is
`5 mounted for rotation, as shown by the arrow, by conventional drive means. For
`convenient reference, we have designated the walls as #l-#8. Mounted in the walls of
`the octahedral housing 32 are as many as five planar magnetron-enhanced sputter
`deposition devices 38-46 or "cathodes" of the type described in detail in the incorporated
`'095 and '057 patents. Preferably, each such cathode comprises a housing equipped with
`10 baffles 43 and with a magnet assembly 45, target 47, and a gas manifold 49 which
`ensures a uniform distribution of the sputtering gas at the target surface and hence a
`uniform coating. Each cathode also comprises a DC power supply capable of delivering
`1-10 kW (kilowatts) power.
`In the illustrated octahedral chamber arrangement, the sputter cathodes are
`15 mounted at positions 1 -4 and 6, and a reactive ion source 48 of the type described in
`detail in the incorporated '095 and '057 patents is mounted in the housing at wall position
`#7. A pair of vacuum source means, preferably turbomolecular vacuum pumps 50 and
`52, backed by mechanical pumps (not shown), are connected into the vacuum chamber,
`respectively, at position #5 (between the sputter cathodes at positions #4 and the ion
`20 source device) and at position #8 (between the reaction ion source and the sputter cathode
`at position #1). The vacuum source means maintain the desired vacuum level in the
`chamber. Throttle valves facilitate control of the vacuum pumping process.
`Please note, the sputtering cathode 46 is mounted at position #6, adjacent to the
`ion source. This positioning facilitates sputtering using metal targets to produce metal
`25 films, or using ceramic targets where no reaction zone is needed. An example of the
`latter use is the formation of electrically conductive indium tin oxide using an indium tin
`oxide target, which does not require ion source operation.
`The region of the vacuum chamber of FIG. 2 adjacent the reaction ion source 48
`is a reaction zone and will be referred to here as the ion source or the ion source zone or
`30 the reaction zone. The chamber regions adjacent the sputter cathode in walls 1 -4 and 6
`are sputter deposition zones. With the exception of deposition zone #6, the deposition
`zones are separated from the reaction zone by the intervening exhaust connections to the
`vacuum pumps 50 and 52, which isolate adjacent regions from one another.
`The rotating drum 34 mounts the substrates 36 and is rotated by motor means (not
`35 shown) at 20-100 rpm in front of the sputtering target(s) and the ion source, that is,
`• sequentially through the deposition and reaction zones. Reactive gas is injected in the
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`vicinity of two long positively biased anode bars mounted in the racetrack region of the
`magnet assembly 45 to form a uniform plasma comprising electrons and ions in the
`reactive gas. Positively charged ions from the plasma are accelerated away from the bars
`and toward the drum 34 and the substrates 36 thereon and react with the metal layer
`previously on the substrates. DC power within the approximate range 50-200 volts (V)
`potential, 1-5 amperes (A) current is supplied by the power supply between the bar
`anodes and system ground.
`During the sequential passage of the substrates through deposition and reaction
`zones, a few monolayer of metal are deposited onto the substrate, then the reactive
`species in the ion source plasma chemically react with the freshly deposited metal.
`Preferably, the thickness of the deposited material is completely reacted, for example, a
`deposited layer of silicon or titanium is completely converted to silicon oxide or titanium
`oxide. However, the process parameters can be adjusted to effect partial reaction of the
`layer.
`
`A major advantage of the present system and process reside in the separation of
`the deposition zone formed in front of the sputtering target from the reaction zone by use
`of differentially pumped regions. The plasma formed in the sputtering zone(s) in front
`of the target(s) is non-reactive and allows sputtering from a metal target with high,
`"metal-like" deposition rates. An intense plasma containing energetic reactive species
`is formed in the reaction zone using a relatively high reactive gas pressure. Film deposi­
`tion and reaction take place by continuously and repetitively traversing (rotating or
`translating) the substrate sequentially through the deposition and reaction zones until the
`desired film thickness is obtained. This repetitive metal deposition-metal reaction
`sequence is one of the main attributes of the MetaMode® sputtering system.
`This method of deposition and reaction, although certainly not limited to the
`formation of oxides, is particularly advantageous in the formation of oxides. As is well
`known, the presence of oxide on the surface of a metal sputter target reduces the rate of
`metal sputtered from the target. In the system 30, minimal target oxidation occurs and
`therefore, high metal sputter rates are maintained. In addition, the substrate rotation and
`the separation of the metal target from the reactive gas results in low deposition
`temperatures so that heat sensitive substrates such as plastics can be coated.
`In accordance with the present invention, a substrate-to-target distance of about
`3 in. (inches) is preferred. In a present embodiment, the two turbomolecular vacuum
`pumps each have 2200 liters/seconds pumping speed and, as mentioned, are backed by
`a mechanical pump. With appropriate adjustment of pumping speeds, the system can
`produce electrochromic materials of excellent optical qualities. The working gas
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`15
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`WO 96/06203
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`PCT7US95/10597
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`10
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`5
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`10
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`pressures vary over the range of about 20-80 mtorr, depending on the material to be
`deposited. Cathodic and anodic coloring materials have been successfully and
`reproducibly deposited. The deposition rates using this MetaMode® sputtering system-
`derived system are higher than with conventional reactive sputtering techniques.
`The system 30, FIG. 2, and the process described herein can be used to form
`individual layers, groups of layers and solid state stack devices such as the solid state
`stack device 10 in situ within the chamber without breaking vacuum, for example, by
`forming the constituent layers sequentially on the substrate. The solid state stack often
`comprises five layers (plus substrate(s)). As alluded to previously, for a transmissive EC
`structure, the two conductor layers of the five layer stack (conductor/IS layer/IC layer/EC
`layer/conductor) can be the same transmissive material and therefore where the other
`three layers are different materials, four (sputter) targets of the different materials are
`used. If all layers are different materials, five (sputter) targets are needed. Furthermore,
`the system 30 and present process can be used to form individual layers and groups of
`15 layers of laminated devices such as the device 1. For example, the ion storage layer and
`associated conductor can be formed in situ on the associated substrate, and/or the EC
`layer and associated conductor layer be formed in situ on their associated substrate,
`preparatory to forming the ion conducting layer using other techniques and assembling
`the device.
`As alluded to above, up to five targets can be accommodated in the octagonal
`machine 30 shown in FIG. 2. A key aspect of the present invention is the ability to
`fabricate electrochromic layers of either of the above types using the modified
`MetaMode® sputtering technique. High switching speeds, high coloration efficiency,
`good adhesion, and high durability films can be obtained by the present system and
`25 process. In addition, films show a long memory, i.e., films remain in the
`electrochemically induced colored or bleached state for a long time, typically for 24
`hours with minimum loss in optical density.
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`20
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`B. Evaluation of Characteristic Process Parameters for WO,
`Typical process parameters used in the MetaMode® sputtering system to form
`optical thin films — total pressure, P < 5 mtorr; oxygen partial pressure < 30%; and high
`ion (reaction) source current -- are not suitable for forming electrochromically active
`materials such as WO3. It was difficult to obtain clear WO3 films in the as-deposited
`state. Also, the WO3 films colored and bleached poorly.
`Unfortunately, the effects of total pressure, oxygen partial pressure, argon partial
`pressure, ion source current and other process parameters, such as power to the sputter
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`WO 96/06203
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`PCT/US95/10597
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`11
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`target cathode, are interdependent. Changing one parameter to improve particular
`process or device characteristics may degrade other characteristics. For example, the
`clarity of the as-deposited film is enhanced by lowering the sputtering power and
`increasing the oxygen flow. However, lowering the sputtering power decreases the
`deposition rate. Increasing the oxygen flow tends to poison the sputter target and thereby
`decrease the deposition rate.
`It has been discovered that the use of high total pressure, typically > 20 mtorr
`(typically measured in a deposition zone) , enables the use of relatively low ion gun
`source current and the combination of high oxygen flows and low oxygen partial
`pressures, thereby obtaining (1) clear as-deposited films; (2) high deposition rates,
`because the target remains unpoisoned and operates in or near metal mode conditions;
`and (3) improved optical density.
`FIG. 3 summarizes the two critical parameters, total power and oxygen partial
`pressure, which affect the WO3 formation process. The open squares represent WO,
`films that were "clear" as-deposited. The dark squares represent WO, films that were
`colored blue as-deposited. The as-deposited coloring was the result of these films being
`substoichiometric tungsten oxide due to oxygen deficiency, not hydrated or protonated