Samsung Electronics Co., Ltd. v. Demaray LLC
`Samsung Electronic's Exhibit 1051
`Exhibit 1051, Page 1
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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 intermational
`applications under the PCT.
`
`Mongolia Mauritania
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`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
`
`Austria
`Australia
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Cite d'Ivoire
`Cameroon
`China
`Czechoslovakia
`
`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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`Ex. 1051, Page 2
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`Ex. 1051, Page 2
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`WO 96/06203
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`PCT/US95/10597
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`ELECTROCHROMIC MATERIALS AND DEVICES, AND METHOD
`
`1. BACKGROUNDOF THE INVENTION
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`5 A.FieldoftheInvention
`
`The present invention relates to electrochromic and electrochromically active
`materials and devices and to methods and processes for making such materials and
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`devices.
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`B. Description of the Related Technology
`
`Electrochromic or electrochromically active (EC) materials change theirrefractive
`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
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`source. The changein refractive index results in a change in the transmission and/orthe
`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 durationis applied.
`
`Becauseion transfer is required to induce the changein the index of refraction.
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`reversible electrochromic devices contain both a source of ions and a sink. Typically.
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`this necessitates a multiple-material, multi-layer structure comprising electrochromic and
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`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
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`equivalent to those of a rechargeable battery for which the degree ofcoloris an indication
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`of the state of charge. Consequently, many of the electrochromic materials, fabrication
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`methodsandanalysis techniquesare similar or identical to those used for the manufacture
`
`of batteries.
`
`FIGS. 1A and IB (collectively, FIG. 1) schematically depict key components of
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`two commontypesof reversible EC devices. Please note, these figures are not to scale.
`
`Layerthicknesses are chosenin part for ease ofillustration and to help in distinguishing
`
`adjacent layers. Furthermore, except as noted, the cross-hatching is selected primarily
`merely to visually distinguish adjacent layers.
`
`Referringinitially to FIG. 1A, there is shown a typical laminated device 1 which
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`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 onthe interior sides of the substrates apply voltage
`from source 9 across the EC structure which is positioned therebetween. The EC
`structure comprises an EClayer 6 next to the conductor layer 7, a so-called ion storage
`layer 4 next to the conductorlayer 3 and polymer ion conducting layer 5 sandwiched
`between the EC andionstoragelayers. Suitable ion conductor polymer materials include
`proton conducting polymer such as polyAMPS(2-acrylamido-2-methylpropanesulfonic
`acid) , and Li* conducting polymer such as PMMA(poly methyl methacrylate) doped
`
`with LiClO,.
`The EC layer 6 is the primary electrochromic layer in that most of the color
`change occurswithin 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 andas a sourceof ionsfor the primary
`EClayer6. In fact, the ion storage layer 4 often is an EC material whose color change
`augmentsthat of the primary EClayer 6. This can be achieved using an EC layer6 that
`colors as the result of the injection of ions and an ion storage layer 4 ofdifferent EC
`material that colors upon the loss of the transported ions.
`FIG. 1B schematically illustrates a so-called solid state stack EC device 10. (This
`deviceis of the greater interest here, because the components can be formed using the
`techniques developed for formingoptical 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; electrochromiclayer 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. Asindicated 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 ofelectrons (e) and ions (M*) during coloring. Examples of
`suitable ion conductorthin film materials include Ta,O,. MgF., LiNbO,, etc.
`In so-called window (optically transmissive) versions of the devices 1 and 10,
`both conductors 13 and 17, FIG. 1B (also 3 and 7, FIG. 1A) . are transparent layers of
`material such as tin oxide SnO,, indium tin oxide (In,O,:Sn or ITO), fluorine-dopedtin
`oxide (SnO,:F) , aluminum-doped zinc-oxide (ZnO:Al), etc.
`In mirror (reflective)
`devices, one ofthe 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 (electrochromicand ion storage) layers 14 and
`16 (4 and 6) include WO,, MoO,, Nb,O,, V,O,, Cr,0;, TiO,, IrO,, NiO, Rh,O,,etc.
`One suitable construction for device 10 uses a glass substrate; an ITO
`conductors); a nickel oxide (NiO)ion storage layer; a tantalum pentoxide (Ta,O,) ion
`conducting layer; and a tungsten oxide (WO,) electrochromic layer.
`Several processes are reported to have been used to manufacture electrochromic
`materials, including the electrochromic components of the exemplary EC devices |
`and/or 10. These processes include sol-gel deposition, electrodeposition, and vacuum
`deposition techniques such as plasma-enhanced chemical vapor deposition (PECVD),
`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
`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 manyplastics and for coating electrochromic layers/devices on plastics.
`USS. 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,
`containing TiO,, Ta,O;. Nb,O;, . V,0;, or B,O;. 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 electrochromictransition metal
`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, WO, using this technique. The '560 patent
`suggests the PECVD process may be used to coat electrochromic materials on
`
`temperature sensitive substrates such asplastics, because of the inherently low substrate
`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 PECVDprocessing, causing
`substrate heating. Perhaps the primary disadvantage of PECVDis the use of poisonous
`and corrosive gases such as WF,, MoF,, and W(CO), whose gaseous byproducts are
`hazardous and corrosive, and which thus present problems of equipment design and
`maintenance andare subject to stringent safety regulations.
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`Both RF and DC magnetronreactive sputtering from a metal target have been
`used to form electrochromic films. However, to ensure properfilm stoichiometry (for
`example, a composition close to WO;), high oxygen partial pressures are required, which
`cause oxidation and poisoningofthe target, thereby slowing film formation. Also, the
`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
`forminganodically coloring materials (materials which "color" whenapositive 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 ofcrystalline
`electrochromic WO, thin films on glass and plastic substrates by RF ion-assisted
`evaporation. WO, powder is evaporated onto an unheated substrate that is being
`bombarded with a stream of 200-300 eV oxygen ions. Crystalline WO; is knownin the
`art to showalarge 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.
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`2. SUMMARYOF THE INVENTION
`
`In one aspect, the present invention is embodied in a processsuitable for forming
`electrochromic materials on one or more substrates, comprising traversing a substrate
`through physically separated deposition and reaction zones; at the sputter deposition
`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 upthe thickness of the coating.
`The process is well suited to the formation of composites or devices which
`include temperature sensitive components suchasplastic substrates.
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`In anotheraspect, the present invention is embodied in a process for forming an
`electrochromicstructurein situ in a vacuum processing chamber. The process comprises:
`providing a plurality of deposition zones associated with a plurality of sputtering
`cathodesandat 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 andthe at least one reaction zone for
`formingafirst of an ion storage layer and an EC layer, forming an ion conductor layer,
`10
`and forming the second ofthe ion storage layer and the electrochromic layer. In another
`aspect, a first conductorlayer is formedin situ on the outsideofsaidfirst layer; and a
`second conductor layer is formedin 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.
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`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 whichis a solid
`state stack electrochromic device, in a composite whichis a stack of componentssuitable
`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 conductorlayer 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 comprisesa 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 respectto the
`accompanying drawing, in which:
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`6
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`FIGS. 1A and 1B 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 WO;
`as a function oftotal pressure and oxygenpartial pressure.
`FIG. 4 depicts the change ofoptical density (OD) of as-deposited WO,filmsat
`633 nm (nanometers) as a function oftotal pressure.
`FIG. 5 depicts the distribution of deposition rates for as-deposited WO,films
`having different changesin optical densities, all measured at 633 nm.
`FIG.6 is a graph of the coloring and bleaching % transmission response at 633
`nm for WOfilms formed using either low pressure (8 mtorr, Table B1) or high pressure
`(45 mtorr, Table B2). The response is determined from the injection of protonsin a 0.1N
`HCIsolution and at the appropriate coloring and bleaching voltages of -0.5V and +1.0V
`respectively. Transmission measurements were taken while samples werestil] in acid.
`The underlying ITO has a sheet resistance of 5 ohms per square. Theareatested is <]
`
`cM).
`
`FIG. 7 depicts the optical switching response at 550 nm of 3800 A thick WO,
`films prepared according to Example 1. The area tested was 4 cm,; ITO sheet resistance
`was 5 ohmsper square. Protonation took place in O.1N HCI solution.
`FIG. 8 depicts the %transmission ofthe films of FIG. 7 in air, for both colored
`
`and the bleachedstates.
`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 cm’; the ITO sheet
`resistance was 15 ohmsper square. Testing took place in 1.0M KOHsolution.
`FIG. 10 depicts the % transmission of the sample of FIG. 9 in air, for both
`colored and bleachedstates.
`FIG. 11 depicts the optical switching response at 550 nm of 4400 A Nb.O,film
`prepared according to Example 4. Thearea tested was 4 cm’; ITO sheet resistance was
`5 ohmsper square. Protonation/hydration took place in a 0.1N HCIsolution.
`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
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`invention.
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`7
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`FIGS. 14 and 15 are, respectively, an exploded perspective view and an endview,
`partly in schematic, of one embodimentof a linear magnetron ion source device used in
`the sputtering system and process ofthe present invention.
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`4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
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`A.SystemOverview
`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 accordingto the present invention which specially adapt
`the MetaMode®sputtering system for forming exemplary electrochromically active
`materials, specifically WO,, 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 whichare suitable for use in the present system
`and process.
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`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 andis used to form electrochromiccoatings in accordance
`with the present invention. FIG.2 describes a sputtering system having a rotating drum
`34. However, other system geometries can be usedto 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-planarsubstrate geometries
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`such as convex and concave curvesand tubes for whichthis systemsare especially well
`
`suited.
`
`Referring further to FIG. 2, the vacuum system 30 comprises an octahedral
`housing 32 having eight walls which define a vacuum chamberin which the drum 34is
`mounted for rotation, as shown by the arrow, by conventional drive means. For
`convenient reference, we have designatedthe walls as #1-#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"ofthe type described in detail in the incorporated
`‘095 and '057 patents. Preferably, each such cathode comprises a housing equipped with
`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 powersupply capable of delivering
`1-10 kW (kilowatts) power.
`In the illustrated octahedral chamber arrangement, the sputter cathodes are
`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 pumps50 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 andthe ion
`source device) andat position #8 (between the reaction ion source andthe sputter cathode
`at position #1). The vacuum source means maintain the desired vacuum level in the
`chamber. Throttle valvesfacilitate control of the vacuum pumping process.
`Please note, the sputtering cathode 46 is mountedat position #6, adjacentto the
`ion source. This positioning facilitates sputtering using metal targets to produce metal
`films, or using ceramic targets where noreaction zone is needed. An example of the
`latter use is the formationofelectrically conductive indium tin oxide using an indium tin
`oxide target, which does not require ion source operation.
`Theregion of the vacuum chamber of FIG. 2 adjacent the reaction ion source 48
`is areaction zone andwill be referred to here as the ion source or the ion source zone or
`the reaction zone. The chamberregions 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 zoneby the intervening exhaust connections to the
`vacuum pumps 50 and 52, which isolate adjacent regions from one another.
`The rotating drum 34 mountsthe substrates 36 and is rotated by motor means (not
`shown) at 20-100 rpm in front of the sputtering target(s) and the ion source, thatis,
`- 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 mountedin the racetrack region ofthe
`magnet assembly 45 to form a uniform plasma comprising electrons and ions in the
`reactive gas. Positively charged ions from the plasmaare 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 layerofsilicon or titanium is completely converted to silicon oxideortitanium
`oxide. However, the process parameters can be adjusted to effect partial reaction ofthe
`
`layer.
`
`A major advantageofthe present system and process reside in the separation of
`the deposition zone formedin frontofthe sputtering target from the reaction zone by use
`of differentially pumped regions. The plasma formedin 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 zoneusing 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 zonesuntil the
`desired film thickness is obtained. This repetitive metal deposition-metal reaction
`sequenceis 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 advantageousin the formation of oxides. As is well
`known,the presence of oxide on the surface of a metal sputter target reducesthe rate of
`metal sputtered from thetarget. 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
`temperaturesso 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
`pumpseach 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 elextrochromic .materials of excellent optical qualities. The working gas
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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
`
`comprisesfive layers (plus substrate(s)). As alluded to previously, for a transmissive EC
`structure, the two conductorlayersofthe 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
`layers of laminated devices such as the device 1. For example, the ion storage layer and
`associated conductor can be formed insitu 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
`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 lossin optical density.
`
`B. Evaluati
`
`f
`
`racteristic Process Parameters for W
`
`Typical process parameters used in the MetaMode® sputtering system to form
`optical thin films-- total pressure, P < 5 mtorr; oxygenpartial pressure < 30%; and high
`ion (reaction) source current -- are not suitable for forming electrochromically active
`materials such as WO.
`It wasdifficult to obtain clear WO,films in the as-deposited
`state. Also, the WO, 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 powerto the sputter
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`target cathode, are interdependent. Changing one parameter to improve particular
`processor 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 tendsto poisonthe sputter target and thereby
`decrease the deposition rate.
`It has been discovered that the use of high total pressure, typically > 20 mtorr
`(typically measuredin 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 andoperates in or near metal mode conditions;
`and (3) improved optical density.
`FIG. 3 summarizesthe twocritical parameters, total power and oxygenpartial
`pressure, which affect the WO, 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 wasthe result of these films being
`substoichiometric tungsten oxide due to oxygen deficiency, not hydrated or protonated
`tungsten oxide dueto residual water vapor in the coating system. These films showed
`poor to no optical modulation when protoninjection/extraction was attempted.
`FIG. 4 summarizes optical density valuesforall films. A normalized change in
`optical density calculation was used in which the optical density. OD, was divided by
`film thickness, d, to account for thickness: OD/d = (logig Tyicached/Tcoiorea/d. The data
`depicted in the figure illustrate that films depositedat total pressures of less than 10 mtorr
`have low values of OD/d, while those deposited at higher pressures, over the approximate
`range 20 mtorr - 75 mtorr, have much higher normalized optical densities, on the order
`of 4.2-6.2.
`It is theorized that the pressure affects the structure ofthe films: the W atoms
`may be thermalized at the high pressures (>20 mtorr total pressure), forming a more
`open,
`less dense structure than is attained at the lower pressures (<20 mtorr total
`pressure).
`
`FIG. 5 summarizes the distribution of deposition rates for films of different
`optical densities, deposited at different (high and low) pressures, using typical process
`parameters which are shown below,in Tables B1 and B2. Asindicated in this figure,
`high depositionrates still obtain at high pressures. The hightotal or system pressures
`allow the use of high oxygen flow rates in combination with relatively overall low
`oxygenpartial pressures. The high oxygen flowsprovide sufficient oxygen to completely
`react the deposited film, while the low oxygen partial pressures (high argon partial
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`pressures) allow the sputter target to operate unpoisoned,at or near the metal mode
`condition.
`Theelectrochromicproperties listed in Tables B1 and B2 were obtained usingthe
`step voltammetry technique, which is well known to those of usual skill in the art. The
`WO,films, which were coated on 5 ohms per square ITO/glass, were tested in 0.1N
`hydrochloric acid solution. A coloring voltage of -0.5V vs a saturated calomelelectrode
`(SCE) was applied through the ITO layer to induce charge injection and hence color the
`film; and 1.0V vs SCE was applied through the ITO to extract charge and bleachthe film.
`Each voltage wasapplied for a period of 10 seconds. A platinum wire was used as a
`counterelectrodein this and the other examples that follow. FIG. 6 depicts the optical
`transmission response(at 633 nm) for the samp