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`US 20030029563Al
`
`(19) United States
`(12) Patent Application Publication
`Kaushal et al.
`
`(10) Pub. No.: US 2003/0029563 Al
`Feb. 13, 2003
`(43) Pub. Date:
`
`(54) CORROSION RESISTANT COATING FOR
`SEMICONDUCTOR PROCESSING
`CHAMBER
`
`(75)
`
`Inventors: Tony S. Kaushal, Cupertino, CA (US);
`Chuong Quang Dam, San Jose, CA
`(US)
`
`Correspondence Address:
`APPLIED MATERIALS, INC.
`2881 SCOTT BLVD. M/S 2061
`SANTA CLARA, CA 95050 (US)
`
`(73) Assignee: Applied Materials, Inc.
`
`(21) Appl. No.:
`
`09/927,244
`
`(22) Filed:
`
`Aug. 10, 2001
`
`Publication Classification
`
`Int. Cl.7 ........................................................ C23F 1/02
`(51)
`(52) U.S. Cl. .......................................................... 156/345.1
`
`(57)
`
`ABSTRACT
`
`Resistance to corrosion in a plasma environment is imparted
`to components of a semiconductor processing tool by form(cid:173)
`ing a rare earth-containing coating over component surfaces.
`The plasma-resistant coating may be formed by sputtering
`rare earth-containing material onto a parent material surface.
`Subsequent reaction between these deposited materials and
`the plasma environment creates a plasma-resistant coating.
`The coating may adhere to the parent material through an
`intervening adhesion layer, such as a graded subsurface rare
`earth layer resulting from acceleration of rare earth ions
`toward the parent material at changed energies prior to
`formation of the coating.
`
`GAS
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`RADICALS IN
`
`Page 1 of 20
`
`APPLIED MATERIALS EXHIBIT 1037
`
`

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`Patent Application Publication Feb. 13, 2003 Sheet 1 of 12
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`US 2003/0029563 Al
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`Patent Application Publication Feb. 13, 2003 Sheet 2 of 12
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`US 2003/0029563 Al
`
`Feb. 13,2003
`
`1
`
`CORROSION RESISTANT COATING FOR
`SEMICONDUCTOR PROCESSING CHAMBER
`
`BACKGROUND OF THE INVENTION
`
`[0001] The present invention relates to equipment used in
`the manufacture of semiconductor devices. More specifi(cid:173)
`cally, the present invention relates to formation of a plasma(cid:173)
`resistant coating on the surfaces of selected components of
`semiconductor manufacturing equipment.
`[0002] With the development of high density plasma
`sources and 300 mm-wafer-size reactors, and the growing
`importance of certain high temperature processing steps,
`wear on chamber materials may impact tool performance
`and productivity. Specifically, interaction between corrosive
`plasmas and reactor materials become of critical importance
`to development of future product lines of semiconductor
`manufacturing equipment. Very harsh environments (e.g.,
`NF3 , C2 F 6 , C3F3 , ClF3 , CF4 , SiH4 , TEOS, WF 6 , NH3 , HBr,
`etc.) can be found in plasma etchers and plasma-enhanced
`deposition reactors. Constituents from many of these envi(cid:173)
`ronments may react with and corrode parent anodized mate(cid:173)
`rials such as aluminum oxide.
`[0003] Because of their favorable physical characteristics,
`ceramic materials are commonly used in today's semicon(cid:173)
`ductor manufacturing equipment to meet the high process
`performance standards demanded by integrated circuit
`manufacturers. Specifically, ceramic materials exhibit high
`resistance to corrosion, which helps to increase process kit
`lifetimes and lowers the cost of consumables as compared to
`other materials such as aluminum or quartz. Example of
`components that can be advantageously manufactured from
`ceramic materials include chamber domes for inductively
`coupled reactors, edge rings used to mask the edge of a
`substrate support in certain processing chambers, and cham(cid:173)
`ber liners that protect walls of the chamber from direct
`exposure to plasma formed within the chamber and improve
`plasma confinement by reducing coupling of a plasma with
`conductive chamber walls. In some instances, the chamber
`walls themselves may also be manufactured from ceramic
`materials. Ceramic materials are also used for critical com(cid:173)
`ponents such as high temperature heaters and electrostatic
`chucks.
`[0004]
`Ideally, critical and/or high value ceramic parts of
`a semiconductor processing tool employed in production
`should have a lifetime of at least one year. Depending on the
`particular tool, this can correspond to processing of 50,000
`wafers or more without changing any parts on the tool (i.e.,
`a zero consumable situation), while at the same time main(cid:173)
`taining high process performance standards. For example, to
`meet the requirements of some manufacturers, less than 20
`particles of size of greater than 0.2 µm should be added to
`the wafer during the processing of the wafer in the chamber.
`[0005] However, unwanted particle generation is an issue
`for high temperature applications where processing tem(cid:173)
`peratures exceed 550° C. For example, in highly corrosive
`fluorine and chlorine environments, Al2 0 3 and AlN ceramic
`materials may corrode to form unwanted AlO:F, AlFx, or
`Al Cl films at the component surface. These AlO:F, AlF x• or
`A1c1: films have relatively high vapor pressures and rela(cid:173)
`tively low sublimation temperatures. For example, the sub(cid:173)
`limation temperature of aluminum chloride (AlCl) is
`approximately 350° C. and the sublimation temperature of
`
`aluminum fluoride (AlFJ is approximately 600° C. If a
`ceramic component is employed at a temperature exceeding
`the sublimation temperature, the outer surface of the com(cid:173)
`ponent may be consumed by the process of formation of
`AlO:F, AlFx or AlCl. This consumption of material can
`degrade the chamber component and/or introduce particles
`into the process.
`[0006]
`In light of the above, improvement in the corrosion
`resistance of various substrate processing chamber parts and
`components is desirable.
`
`SUMMARY OF THE INVENTION
`
`[0007] The present invention provides a method for
`improving the corrosion resistance of components of semi(cid:173)
`conductor tools by creating high temperature halogen cor(cid:173)
`rosion resistant surface coatings. Specifically, coatings of
`rare earth-containing materials are formed over the surfaces
`of ceramic tool components. These rare earth-containing
`materials are stable in plasma environments at high tem(cid:173)
`peratures and may be formed onto the chamber components
`by sputter deposition. To promote adhesion of the coating to
`the parent material, an adhesion layer may be first formed on
`the ceramic material by accelerating rare earth ions into the
`surface of the ceramic material at changed energies to form
`an implant layer prior to formation of the surface coating.
`[0008] An embodiment of a substrate processing chamber
`in accordance with the present invention includes at least
`one component bearing a rare earth-containing coating
`bound to a parent material by an intervening adhesion layer,
`such that the component exhibits resistance to etching in a
`plasma environment.
`[0009] An embodiment of a method for treating a parent
`material for resistance to plasma etching comprises forming
`an adhesion layer over a parent material, and forming a rare
`earth-containing coating over the adhesion layer.
`[0010] These and other embodiments of the present inven(cid:173)
`tion, as well as its advantages and features, are described in
`more detail in conjunction with the text below and attached
`figures.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0011] FIG. lA is a simplified cross-sectional view of a
`high density plasma chemical vapor deposition chamber;
`[0012] FIG. 1B is a simplified cross-sectional view of a
`capacitively coupled plasma enhanced chemical vapor depo(cid:173)
`sition chamber;
`
`[0013] FIG. 2A is a cross-sectional view of a coated
`member in accordance with a first embodiment of the
`present invention;
`[0014] FIG. 2B is a cross-sectional view of a coated
`member in accordance with a second embodiment of the
`present invention;
`
`[0015] FIG. 3 is a simplified schematic view of a Metal
`Plasma
`Immersion
`Ion
`Implantation and Deposition
`(MEPIIID) technique;
`
`[0016] FIG. 4 is a graph illustrating the concentration of
`rare earth ions at various depths in a ceramic component
`treated with MEPIIID;
`
`Page 14 of 20
`
`

`

`US 2003/0029563 Al
`
`Feb. 13,2003
`
`2
`
`[0017] FIG. 5 is a simplified cross-sectional view of an
`exemplary metal vapor vacuum arc implanter used in the
`MEPIIID technique;
`
`[0018] FIG. 6 is a simplified schematic view of an Ion
`Bombardment Assisted Deposition (IBAD) technique;
`
`[0019] FIG. 7A shows a magnified (2000x) view of the
`top surface of a first grade of an AlN coupon following
`exposure to a fluorine ambient at high temperature.
`
`[0020] FIG. 7B shows a further magnified (7500x) view
`of the top surface of the AlN coupon of FIG. 7A.
`
`[0021] FIG. 7C shows a magnified (2000x) view of the
`top surface of a second grade of an AlN coupon following
`exposure to a fluorine ambient at high temperature.
`
`[0022] FIG. 7D shows a further magnified (7500x) view
`of the top surface of the AlN coupon of FIG. 7C.
`[0023] FIG. SA shows a magnified (2000x) view of the
`top surface of a first grade of an AlN coupon coated with
`yttrium oxide by reactive sputtering in accordance with an
`alternative embodiment of the present invention.
`
`[0024] FIG. 8B shows a further magnified (7500x) view
`of the top surface of the AlN coupon of FIG. SA.
`
`[0025] FIG. SC shows a magnified (2000x) view of the
`top surface of the AlN coupon of FIGS. 8A-B following
`exposure to a fluorine ambient at high temperature.
`
`[0026] FIG. 8D shows a magnified (7500x) view of the
`top surface of the AlN coupon of FIG. SC.
`[0027] FIG. SE shows a magnified (2000x) view of the
`top surface of a second grade of an AlN coupon coated with
`yttrium oxide by reactive sputtering in accordance with an
`alternative embodiment of the present invention.
`
`[0028] FIG. SF shows a further magnified (7500x) view
`of the top surface of the coated AlN coupon of FIG. SE.
`[0029] FIG. 8G shows a magnified (2000x) view of the
`top surface of anAlN coupon coated with in accordance with
`one embodiment of the present invention, following expo(cid:173)
`sure to a fluorine ambient at high temperature.
`
`[0030] FIG. SH shows a further magnified (7500x) view
`of the top surface of the AlN coupon of FIG. 8G.
`
`[0031] FIG. 9A shows a magnified (2000x) view of the
`top surface of an AlN coupon implanted with yttrium in
`accordance with one embodiment of the present invention.
`
`[0032] FIG. 9B shows a further magnified (7500x) view
`of the top surface of the implanted AlN coupon of FIG. 9A.
`[0033] FIG. 9C shows a further magnified (9000x) view
`of the fractured AlN coupon of FIGS. 9A-9B.
`
`[0034] FIG. 9D shows a magnified (2000x) view of the
`surface of the implanted AlN coupon of FIGS. 9A-9C
`following exposure to a fluorine ambient at high tempera(cid:173)
`ture.
`
`[0035] FIG. 9E shows a further magnified (7500x) view
`of the surface of the implanted AlN coupon of FIG. 9D.
`
`[0036] FIG. lOA shows a magnified (3300x) view of a
`fractured AlN coupon implanted with yttrium oxide follow(cid:173)
`ing exposure to a fluorine ambient at high temperature.
`
`[0037] FIG. 10B shows a further magnified (7500x) view
`of the fractured AlN coupon of FIG. lOA.
`
`[0038] FIG. 11 shows the results of Energy Dispersive
`Spectroscopy (EDS) of the surface of the AlN coupon of
`FIGS. lOA-lOB coated in accordance with an embodiment
`of the present invention, following exposure to a fluorine
`ambient at high temperature.
`
`DESCRIPTION OF THE SPECIFIC
`EMBODIMENTS
`
`[0039] According to the present invention, ceramic com(cid:173)
`ponents of semiconductor fabrication tools, including but
`not limited to electrostatic chucks, gas nozzles, chamber
`domes, heated pedestals, gas distribution manifolds, cham(cid:173)
`ber walls and chamber liners, may be coated with a rare
`earth-containing material and adhesion layer in order to
`improve corrosion resistance. Environments for which the
`coated components can be advantageously used include, but
`are not limited to, highly corrosive plasma etching environ(cid:173)
`ments, and high temperature deposition environments that
`feature corrosive gases.
`
`[0040]
`
`I. Exemplary Substrate Processing Chambers
`
`[0041] FIGS. lA and 1B are simplified cross-sectional
`views of exemplary substrate processing chambers in which
`ceramic components made according to the method of the
`present invention may be employed. FIG. 1A is a simplified
`cross-sectional view of a high density plasma chemical
`vapor deposition (HDP-CVD) chamber 10 such as an Ultima
`HDP-CVD substrate processing chamber manufactured by
`Applied Materials, the assignee of the present invention. In
`FIG. lA, substrate processing chamber 10 includes a
`vacuum chamber 12 in which a substrate support/heater 14
`is housed. Substrate support/heater 14 includes an electro(cid:173)
`static chuck 15 that securely clamps substrate 16 to substrate
`support/heater 14 during substrate processing.
`
`[0042] When substrate support/heater 14 is in a processing
`position (indicated by dotted line 18), deposition and carrier
`gases are flowed into chamber 10 via gas injection nozzles
`20. Nozzles 20 receive gases through gas supply lines,
`which are not shown. Chamber 10 can be cleaned by the
`introduction of fluorine radicals or other etchant radicals that
`are dissociated in a remote microwave plasma chamber (not
`shown) and delivered to chamber 10 through a gas feed port
`22. Unreacted gases and reaction byproducts are exhausted
`from the chamber 10 by a pump 24 through an exhaust port
`on the bottom of the chamber. Pump 24 can be isolated from
`chamber 10 by a gate valve 26.
`
`[0043] The rate at which deposition, carrier and clean
`gases are supplied to chamber 10 is controlled by a mass
`flow controllers and valves (not shown), which are in turn
`controlled by computer processor (not shown). Similarly, the
`rate at which gases are exhausted from the chamber is
`controlled by a throttle valve 28 and gate valve 26, which are
`also controlled by the computer processor.
`
`[0044] A plasma can be formed from gases introduced into
`chamber 10 by application of RF energy to independently
`controlled top coil 30 and side coil 32. Coils 30 and 32 are
`mounted on a chamber dome 34, which defines the upper
`boundary of vacuum chamber 12. The lower boundary of
`vacuum chamber 12 is defined by chamber walls 36. Sub-
`
`Page 15 of 20
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`

`

`US 2003/0029563 Al
`
`Feb. 13,2003
`
`3
`
`strates can be loaded into chamber 10 and onto chuck 15
`through an opening 38 in chamber wall 36.
`
`[0045] According to the present invention, any or all of
`electrostatic chuck 15, gas nozzles 20, and chamber dome 34
`of substrate support/heater 14 may be fabricated from mate(cid:173)
`rial implanted with rare-earth ions.
`
`[0046] FIG. 1B is a simplified cross-sectional view of a
`capacitively-coupled plasma enhanced chemical vapor
`deposition chamber (PECVD) 50 such as the CxZ CVD
`substrate processing chamber manufactured by Applied
`Materials, the assignee of the present invention. In FIG. lB,
`substrate processing chamber 50 includes a vacuum cham(cid:173)
`ber 52 in which a heated pedestal 54 and a gas distribution
`manifold 56 are housed. During processing, a substrate 58
`(e.g., a semiconductor wafer) is positioned on a flat or
`slightly convex surface 54Aof pedestal 54. The pedestal can
`be controllably moved between a substrate loading position
`(depicted in FIG. 1B) and a substrate processing position
`(indicated by dashed line 60 in FIG. 1B), which is closely
`adjacent to manifold 56.
`
`[0047] Deposition, carrier and cleaning gases are intro(cid:173)
`duced into chamber 52 through perforated holes 56A of a gas
`distribution faceplate portion of manifold 56. More specifi(cid:173)
`cally, gases input from external gas sources (not shown) flow
`into the chamber through the inlet 62 of manifold 56,
`through a conventional perforated blocker plate 64 and then
`through holes 56A of the gas distribution faceplate. Gases
`are exhausted from chamber 52 through an annular, slot(cid:173)
`shaped orifice 70 surrounding the reaction region and then
`into an annulate exhaust plenum 72. Exhaust plenum 72 and
`slot-shaped orifice 70 are defined by ceramic chamber liners
`74 and 76 and by the bottom of chamber lid 57.
`
`[0048] The rate at which deposition, carrier and clean
`gases are supplied to chamber 50 is controlled by mass flow
`controllers and valves (not shown), which are in turn con(cid:173)
`trolled by computer processor (not shown). Similarly, the
`rate at which gases are exhausted from the chamber is
`controlled by a throttle valve (not shown and also controlled
`by the computer processor) connected to exhaust port 66,
`which is fluidly-coupled to exhaust plenum 72.
`
`[0049] The deposition process in chamber 50 can be either
`a thermal or a plasma-enhanced process. In a plasma(cid:173)
`enhanced process, an RF power supply (not shown) provides
`electrical energy between the gas distribution faceplate and
`an electrode 68A within pedestal 54 so as to excite the
`process gas mixture to form a plasma within the generally
`cylindrical region between the faceplate and pedestal. This
`is in contrast to an inductive coupling of RF power into the
`gas, as is provided in the chamber configuration shown in
`FIG. lA. In either a thermal or a plasma process, substrate
`58 can be heated by a heating element 68B within pedestal
`54.
`
`[0050] According to the present invention, any or all of
`pedestal 54, heating element 68B gas distribution manifold
`56, and chamber liners 74 and 76 may be constructed from
`a ceramic material implanted with rare-earth ions according
`to the present invention. The embodiments ofFIGS. lAand
`1B are for exemplary purposes only, however. A person of
`skill in the art will recognize that other types of ceramic
`parts in these and other types of substrate processing cham(cid:173)
`bers in which highly corrosive environments are contained
`
`( e.g., reactive ion etchers, electron cyclotron resonance
`plasma chambers, etc.) may benefit from the teaching of the
`present invention.
`
`[0051]
`
`II. Coating Formation
`
`[0052]
`In accordance with embodiments of the present
`invention, parent materials of components of semiconductor
`fabrication apparatuses are protected against corrosion by a
`surface coating containing a rare earth metal, the coating
`exhibiting low reactivity to a halogen gas environment at
`elevated temperatures. For purposes of this patent applica(cid:173)
`tion, yttrium is considered a rare earth metal.
`
`[0053] Surface coatings in accordance with embodiments
`of the present invention maintain adhesion to the parent
`material at high operating temperatures (up to 1000° C.).
`The surface coatings may include yttrium fluoride, yttrium
`oxides, yttrium-containing oxides of Aluminum (YA103 ,
`Y3Al5 0 12, Y 4Al2 0 9 ), Erbium oxides, Neodymium oxide,
`and other rare earth oxides.
`
`[0054] The high operating temperatures of many plasma
`processes can create problems arising from a lack of adhe(cid:173)
`sion between a parent material and an overlying coating.
`Accordingly, it is useful to form an adhesion layer between
`the coating and parent material.
`
`[0055] This is illustrated in FIG. 2A, which is a cross(cid:173)
`sectional view of coated member 215 in accordance with an
`embodiment of the present invention. As shown in FIG. 2A,
`adhesion layer 212 overlies parent material 214, and coating
`216 is formed over adhesion layer 212. Parent material 214
`may comprise AlN, Al2 0 3 , or some other material. In
`accordance with one embodiment of the present invention,
`rare earth-containing coating 216 may be deposited over
`adhesion layer 212 by sputtering techniques. Sputtering may
`take place in a particular ambient, for example by reactive
`sputtering of a target of the rare earth material in an oxygen
`ambient to create a rare earth oxide coating.
`
`[0056] Adhesion layer 212 may exhibit a coefficient of
`thermal expansion intermediate that of parent material 214
`and coating 216, such that coating 216 adheres to parent
`material 214 over a wide temperature range. The adhesion
`layer may be formed over the substrate by deposition prior
`to formation of the coating.
`
`[0057]
`In alternative embodiments in accordance with the
`present invention, the adhesion layer may be formed by
`accelerating rare earth ions toward the parent material at
`changed energies prior to formation of the surface coating.
`For example, adhesion layer 212 of structure 215 of FIG. 2A
`may result from ion-implantation, with reduction over time
`in the energy of implantation of rare earth metals into parent
`material 214 creating
`layer 212.
`implanted adhesion
`Implanted adhesion layer 212 may be graded, with the rare
`earth metal concentration gradient determined by duration of
`implantation at particular energy levels.
`
`[0058] Acceleration of rare-earth ions to a depth into the
`target parent material may be accomplished using a variety
`of techniques. In one implantation approach, rare earth ions
`are introduced into the parent material utilizing metal
`plasma
`ion
`immersion
`implantation and deposition
`(MEPIIID). FIG. 3 shows a simplified schematic view of the
`MEPIIID technique.
`
`Page 16 of 20
`
`

`

`US 2003/0029563 Al
`
`Feb. 13,2003
`
`4
`
`[0059] As shown in FIG. 3, single or dual-source
`MEPIIID source 300 is used to implant and deposit a layer
`of rare-earth ions over the component 300 being treated.
`With this technique, component 302 is inserted into plasma
`304 after plasma 304 has been deflected with magnetic filter
`304. Sheath edge 311 represents a concentrated plasma zone
`near biased target component 302, where most reactions and
`rearrangements of materials occur.
`
`[0060] The treated component 302 is then subjected to
`implantation by biasing component 302 with a negative
`voltage utilizing electrode 307 in communication with
`power supply 306. When target component 302 is unbiased,
`it is subject to the initial deposition phase of the treatment
`process. When target component 302 is negatively biased
`( e.g., at -50 ke V), ions 310 from plasma 304 are accelerated
`toward target component 302 at high velocities so that target
`component 302 is subjected to ion implantation to a depth
`into the material. The magnitude of the negative bias of the
`target material, and hence the energy of bombardment, is
`then reduced to produce a gradient of concentration of rare
`earth material to a depth in the material.
`
`[0061] A more detailed description of a single-source
`MEPIIID system is set forth in U.S. Pat. No. 5,476,691
`issued to Ian Brown et al., hereby incorporated by reference
`in its entirety. In a technique employing a dual-source
`MEPIIID implanter, the treatment process is similar except
`that plasmas from two separate plasma guns are brought
`together through independent magnetic channels, in order to
`deposit a thin film over the parent component.
`
`[0062] The MEPIIID approach to implantation of rare
`earth metals requires that the component be subject to an
`electrical bias. However, such biasing is not possible with
`parent materials that are poor conductors. This issue can be
`resolved if an electrode is embedded within the component,
`the embedded electrode capable of being biased during the
`implantation step. Such is the case for heaters and electro(cid:173)
`static chucks.
`
`[0063] FIG. 4 is a graph that shows the concentration of
`rare-earth ions and aluminum nitride at various depths of an
`aluminum nitride component treated with a MEPIIID tech(cid:173)
`nique. As can be seen in FIG. 4 the upper surface of the
`treated component comprises a layer M of rare-earth mate(cid:173)
`rial formed from the deposition phases of the treatment
`process. Beneath layer M, the concentration of rare-earth
`ions decreases with depth until point N, where the concen(cid:173)
`tration of rare-earth ions reaches background levels ( essen(cid:173)
`tially zero).
`
`[0064] Because of this profile of implanted material, a
`graded interface is obtained between the coated surface and
`the bulk of the parent material. An interface of this type
`provides a gradual transition of surface properties such as
`physical and chemical properties, and results in improved
`adhesion as compared to more abrupt, stepped profile dis(cid:173)
`tributions. Such a graded interface also eliminates limita(cid:173)
`tions of adhesion due to thermal mismatch--{)ften a limiting
`factor of corrosion resistant coatings having an abrupt
`interface.
`
`[0065]
`In components having an abrupt transition between
`coating and parent material, the protective coating deposited
`over chamber materials may crack in response to environ(cid:173)
`mental stresses. For example, during high temperature ther-
`
`mal cycles the temperature change during and/or between
`various cycles can be as high 700° C. for ceramic heater
`applications. Another example of an environmental stress
`that may induce cracking of a coating are the mechanical
`stresses associated with wafer handling.
`[0066] Once a crack in a coating is initiated, in a corrosive
`environment aggressive and corrosive free radicals may
`penetrate the film coating and erode the underlying wall
`material. This penetration may cause film delamination and
`particulate contamination.
`[0067] By contrast, corrosion-resistant coatings in accor(cid:173)
`dance with embodiments of the present invention may serve
`as a barrier to the diffusion of reactive species into the parent
`material. In this respect, implanted structures may have
`superior performance and versatility as compared with struc(cid:173)
`tures formed by plasma spray, CVD, laser ablation or PVD
`deposition techniques.
`[0068] FIG. 5 is a simplified cross-sectional view of an
`exemplary MEPIIID™ ion implanter 500 useful to implant
`ceramic components with rare-earth metals according to this
`embodiment of the present invention. Implanter 500
`includes a cathode 502 of the desired metal atoms or alloy
`to be implanted, an anode 504, a plasma extractor 506, a
`trigger 508, a cavity 510, and an insulative bushing 512 all
`surrounded by an outer frame 514.
`[0069] The vacuum arc is a plasma discharge that takes
`place between cathode 502 and the grounded anode 504. The
`plasma is generated at a number of tiny points on the surface
`of the cathode, called cathode spots and having a dimension
`of few microns. The arc is concentrated to an extremely high
`current density, in the order of 108 -1012 A/cm2
`. The metal
`ions are extracted from the plasma using perforated extrac(cid:173)
`tion grids 506 which are polarized at appropriate conditions
`to accelerate the extracted ions toward the ceramic compo(cid:173)
`nent target. Such MEPIIID™ ion sources are efficient and do
`not require a background gas-the plasma generation pro(cid:173)
`cess is neither an evaporative nor a sputtering process. A
`more detailed description of a MEPIIID™ ion implanter
`similar to the one shown in FIG. 5 is given in U.S. Pat. No.
`5,013,578 issued to Ian Brown et al. The '578 patent is
`hereby incorporated by reference in its entirety.
`[0070]
`In the past, MEPIIID™ implanters have typically
`been used for metal surface treatment in the automotive
`industry ( e.g., piston surface treatment) and the tooling
`industry for increased hardness. However, one limitation of
`such commercially available implanters is their anisotropy,
`e.g., the limitation to implant flat surfaces only. This is
`perfectly acceptable to implant the exposed face of flat
`ceramic heaters or electrostatic chucks, but it is a limitation
`in treating complex-shaped ceramic parts.
`
`[0071] Manufacturability of a commercially feasible
`MEPIIID™ implanter based on a design similar to that
`shown in FIG. 5 has been established, however, in which
`large-area or complex-shaped parts could be treated in an
`industrial scale, high dose implanter. A description of such
`implanter is set forth by Ian Brown in Brown, et al., "Metal
`Ion Implantation for Large Scale Surface Modification," J.
`Vac. Sci. Tech., A 11(4), July 1993, which is hereby incor(cid:173)
`porated by reference in its entirety.
`
`[0072] While the MEPIIID technique is described above
`in conjunction with formation of an adhesion layer for a
`
`Page 17 of 20
`
`

`

`US 2003/0029563 Al
`
`Feb. 13,2003
`
`5
`
`rare-earth contammg coating in accordance with one
`embodiment of the present invention, the present invention
`is not limited to use of any particular fabrication technique.
`For example, an alternative embodiment for forming a
`corrosion-resistant coating in accordance with embodiments
`of the present invention utilizes Ion Bombardment Assisted
`Deposition (IBAD) to accelerate rare earth metals into the
`parent material.
`
`[0073] Specifically, FIG. 6 shows rare earth metal 601
`such as Yttrium sputtered onto the surface of parent material
`604 while ion gun 600 accelerates ion beam 602 of inert
`Argon ions at high (-10-12 ke V) energies against coated
`target parent material 604. As a result of the high energy of
`ion bombardment, deposited metal 601 is driven to a depth
`within parent material 604. Over time, the energy of the ion
`beam is then reduced to a lower level (-0.5 ke V), such that
`deposited rare earth remains on the surface as a coating
`rather than being driven into the parent material. In this
`manner a graded adhesion layer may be formed, with the
`concentration of rare earth metals in the adhesion layer
`determined by the duration of bombardment at a particular
`reduced energy level.
`
`[0074] As a result of deposition of rare earth metal under
`these conditions, graded subsurface rare earth layer 612 lies
`between coating 608 and parent material 604, promoting
`adhesion between coating 608 and parent material 604.
`Performing such deposition in an oxygen ambient can cause
`the rare earth metal to react with oxygen to form rare earth
`oxide coating 608 over parent material 604.
`
`[0075] Having fully described several embodiments in
`accordance with the present invention, many other equiva(cid:173)
`lent or alternative embodiments of the present invention will
`be apparent to those skilled in the art. For example, in
`accordance with an alternative embodiment of the present
`invention, a coating and/or adhesion layer may be formed by
`a chemical vapor deposition (CVD) process rather than a
`physical vapor deposition process.
`
`[0076] Moreover, in accordance with yet another alterna(cid:173)
`tive embodiment of the present invention, a plasma resistant
`coating may take the form of a multi-layer structure. This is
`shown in FIG. 2B, which depicts a cross-sectional view of
`a coated member 219 in accordance with yet another alter(cid:173)
`native embodiment in accordance with the present inven-
`
`tion. In FIG. 2B, coating 220 overlies adhesion layer 222
`which in turn overlies parent material 224. Coating 220 itself
`is comprised