WO2009036218A1

WO2009036218A1 - Apparatus and method for cleaning wafer edge using energetic particle beams

Info

Publication number: WO2009036218A1
Application number: PCT/US2008/076082
Authority: WO
Inventors: John F. Mahoney; James K. Finster; Julius Perel
Original assignee: EHD TECHNOLOGY GROUP Inc
Current assignee: EHD TECHNOLOGY GROUP Inc
Priority date: 2007-09-13
Filing date: 2008-09-11
Publication date: 2009-03-19
Anticipated expiration: 2010-03-13
Also published as: TW200917349A

Abstract

A capillary emitter apparatus adapted to treat top and bottom edge regions of a wafer has at least two capillary emitters arranged in generally opposing configuration and/or at oblique angles, each capillary emitter adapted to generate a beam of high energy particles to impinge upon a different edge region of the wafer. The apparatus also includes a wafer chuck adapted to support and rotate the wafer such that the edge regions are exposed to the beams of high energy particles. It is contemplated that the capillary emitter apparatus can be conductive to receive either a gas or a liquid, or non-conductive to receive a liquid. Where the apparatus receives a liquid, the beam particles comprises primarily multiply-charged particles. Where the apparatus receives a gas, the beam particles comprises primarily singly-charged particles. In either case, the beam particles are adapted to remove thin films and/or particles.

Description

APPARATUS AND METHOD FOR CLEANING WAFER EDGE USING ENERGETIC PARTICLE BEAMS

FIELD OF INVENTION

[0001] The present invention relates in general to an apparatus and method for cleaning and removing process residue material from an edge exclusion and bevel region of semiconductor wafers, flat panel displays or other disc structures.

BACKGROUND OF INVENTION

[0002] During semiconductor wafer processing, various thin films (e.g., metals, oxides, nitrides, carbides and polymeric materials) are applied to a top side of wafers where a two- dimensional array of microchips is fabricated. At the wafer circumference is an "edge exclusion" ring and a bevel, devoid of microchips, which allow robots to handle the wafers. The applied thin films can extend across the edge exclusion of the topside and often "wrap around" the bevel onto a backside of the wafer. Removing the excess film material from the exclusion edge, the bevel and the backside is becoming more important in semiconductor manufacturing. If not removed, residue from the edge and bevel areas can flake off or delaminate and redistribute giving rise to defects on critical wafer surfaces causing yield degradation. It has been demonstrated that cleaning unwanted films or other material from the edge and backside of wafers can decrease cross-contamination and improve wafer yields by 10%. (See, J. D. Morillo, T. Houghton and J. M. Bauer, "Edge and bevel automated defect inspection for 300mm production wafers in manufacturing", 2005 IEEE/SEMI Advanced Semiconductor Manufacturing Conference). In view of the potential for edge or bevel contamination reducing product yield, a need exists to provide a novel and improved method for removing unwanted particulate debris from effected areas. [0003] Configurations employed to clean wafer edges and bevels are known, some of which are discussed in the following U.S. Patents. [0004] U.S. Patent No. 6,874,510 B2 (Reder et al.) discusses a variable power laser beam directed toward a wafer edge at an oblique angle. A concentric channel enclosing the laser beam provides a flow of purge gas to blow away residue removed by the laser beam. [0005] U.S. Patent Publication. No. US 2005/0284576 Al (America et al.) describes a toroidal plasma created at the edge of a wafer. Selective removal of film material is accomplished by proper choice of gases that make up the plasma.

[0006] U.S. Patent No. 6,910,240 Bl (Boyd et al.) teaches a wafer bevel edge cleaning system comprising a system of multiple rollers (drive, stator and cleaning) located at the periphery of a wafer edge which contact selected areas of the wafer circumference. Scrubbing pads, consisting of a variety of polymer materials, line the individual cleaning rollers which clean front and back side edge zones separately. Cleaning and rinse chemicals are dispersed onto the roller pads by a nearby spray nozzle.

[0007] U.S. Patent No. 7,179,154 Bl (Boyd) reveals a cassette configuration consisting of a plurality of rollers (feed, take-up) with a film containing embedded abrasives. The embedded abrasives are forced against the wafer edge using a third roller. Similar to the previous patent, cleaning is assisted by a nozzle used to spray a chemical solution onto the film.

[0008] U.S. Patent No. 6,797,074 B2 (Redeker et al.) discloses an etchant containing, absorbent swab that contacts the edges of a rotating wafer - rotation supplied by a series of v-shaped rollers contacting the wafer edge. A second aspect of the Redeker patent discloses an etchant filled trough (with or without megasonic transducers) in which the edge of a rotating wafer is submerged for cleaning.

[0009] U.S. Patent No. 6,309,981 Bl (Mayer et al.) teaches a method of removing copper metal from the edge and bevel region of a wafer by controlled delivery of a viscous, liquid chemical etchant via a nozzle in close proximity to the wafer edge. Etchant is removed by DI rinse followed by a nitrogen gas blow dry. [0010] U.S. Patent No. 7,256,148 B2 (Kastenmeier et al.) combines plasma, trough (similar to

Redeker patent) and brush cleaning of wafer edges. Kastenmeier discloses both a small area RF plasma source for localized edge cleaning and an extended plasma generating ring source to cover the entire wafer periphery. Typical plasma gases employed are argon, nitrogen and oxygen. In the "brush" embodiment, dispensing channels supply chemicals to the brush contacting the wafer edges.

[0011] U.S. Patent No. 6,837,967 Bl (Berman et al.) teaches a dual purpose toroidal shaped gas manifold, which also serves as a discharge electrode, configured to direct process gases to wafer edges. Magnetic coils are strategically located to aid confinement of the plasma discharge to wafer edge regions. Central portions of the wafer populated with integrated circuit dies are protected from plasma by a hollow top plate. Gas introduced into the hollow plenum provides a back pressure that stops plasma gases from penetrating areas where etching is undesirable.

[0012] U.S. Patent No. 6,186,873 Bl (Becker et al.) discloses a wafer edge cleaning apparatus consisting of a pair of wafer gripper assemblies comprising multiple abrasive wheels, idler gears and a single chemically fed, stationary brush. [0013] U.S. Patent Application No. US 2006/037648 (Kim et al.) teaches a plasma etch method configured to clean bevel edges and wafer backsides. By use of appropriate geometry and placement of RF powered electrodes and dielectric rings, a small area plasma is generated and confined to the bevel region of the wafer. [0014] The existing techniques described in the above prior art can be complex, require a separate resist coating and etch process to clean the wafer edge, or use multiple moving parts with mechanical wear that require frequent component replacement. [0015] Electrohydrodynamic (EHD) apparatus and methods for cleaning surfaces are also known and can avoid problems associated with the aforementioned technologies. EHD atomization is a method for breaking up and dispersing a conducting liquid into an ensemble

(beam) of charged nanodroplets. EHD apparatus and method are described in U.S. Patent Nos. 6,033,484 entitled "Apparatus for Cleaning Contaminated Surfaces Using Energetic Cluster Beams" and 5,796,111 entitled "Method and Apparatus for Cleaning Contaminated Surfaces Using Energetic Cluster Beams," the entire contents of both are hereby incorporated by reference. A charged beam is generated by delivering conductive solution from a sealed, pressurized reservoir along a transfer tube of fused silica, Teflon, PEEK or other suitable material to an electrified nozzle containing a small bore. To initiate the EHD beam, an electrostatic stress is applied to the solution which charges a meniscus interface formed at the small bore of the nozzle. When the applied electrostatic stress exceeds the surface tension holding the meniscus intact, the solution disrupts forming a beam of nanodroplets.

[0016] Despite the many advantages with EHD surface cleaning methods and apparatuses, there exists a need for improved methods and apparatuses that are adapted to clean wafer edges and bevels, that are simpler, more compact, robust, less expensive and more effective than prior methods and apparatus.

SUMMARY OF THE INVENTION

[0017] The present invention recognizes that capillary emitters can be either conductive or nonconductive and thus any of the embodiments of the present invention can incorporate conductive emitters, non-conductive emitters, or even a combination of both, as desired or needed. Where emitters receive a liquid for electrospraying, a beam of primarily highly energized mutiply charged clusters or droplets (including nanodroplets) is generated, which can be particularly suitable for etching, roughening and/or removing. Where emitters receive a gas for ionization, a beam of primarily highly energized singly-charged ions is generated, which can be particularly suitable for sputtering. [0018] In one embodiment of the present invention, a capillary emitter apparatus adapted to treat top and bottom edge regions of a wafer has at least two capillary emitters arranged in generally opposing configuration and/or at oblique angles, each capillary emitter adapted to generate a beam of high energy particles to impinge upon a different edge region of the wafer. The apparatus also includes a wafer chuck adapted to support and rotate the wafer such that the edge regions are exposed to the beams of high energy particles. It is contemplated that the capillary emitter apparatus can be conductive to receive either a gas or a liquid, or non-conductive to receive a liquid. Where the apparatus receives a liquid, the beam particles comprises primarily multiply- charged particles. Where the apparatus receives a gas, the beam particles comprises primarily singly-charged particles. In either case, the beam particles are adapted to remove thin films and/or particles, especially particles of about 1 micron or less in mean diameter. The present invention also contemplates a mask to protect the die area and a neutralizer to reduce electrostatic charging of treated surfaces of the wafer.

[0019] In another detailed embodiment of the present invention, a capillary emitter system adapted to treat top and bottom edge regions of a wafer, has at least two capillary emitters manifolds arranged in a circumferential arrangement around a wafer, wherein at least one manifold has at least two capillary emitters in generally opposing configuration, each capillary emitter adapted to generate a beam of high energy particles to impinge upon a different edge region of the wafer. The capillary emitters can be directed to impinge edge regions and/or bevels of the wafer. [0020] The present invention is also directed to methods of generating EHD beams and ion beams for cleaning wafer edge regions and bevels of thin films and particulates, particularly those with a mean diameter of approximately 1 micron or less. Liquid or gas is delivered to conductive capillary emitters to produce beams of high energy clusters, droplets (including nanodroplets) or ions. Liquid is delivered to non-conductive capillary emitters to produce beams of high energy clusters and/or droplets (including nanodroplets). By varying operating parameters (including the voltage applied to emitters, the immersed electrode and/or extractor electrodes, and the contents the gas or liquid starting ingredient), the nature and size of the beam particles can be varied, as needed or desired.

[0021] These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. It is understood that selected structures and features may have not been shown in certain drawings so as to provide better viewing of the remaining structures and features.

BRIEF DESCRPTION OF THE DRAWINGS [0022] FIG. 1 a is a top plan view of a wafer.

[0023] FIG. Ib is a cross-sectional view of the wafer of FIG. 1, taken along lines A—A.

[0024] FIG. 2a is a side elevational view of an embodiment of a capillary emitter head with a conductive emitter.

[0025] FIG. 2b is a side elevational view of an embodiment of a capillary emitter head with a nonconductive emitter.

[0026] FIG. 3 a is a side elevational view of an embodiment of a capillary emitter apparatus incorporating a plurality of conductive capillary emitter heads.

[0027] FIG. 3b is a side elevational view of an embodiment of a capillary emitter apparatus incorporating a plurality of non-conductive capillary emitter heads. [0028] FIG. 4a is a side elevational view of another embodiment of a capillary emitter apparatus incorporating a plurality of conductive capillary emitter heads. [0029] FIG. 4b is a side elevational view of another embodiment of a capillary emitter apparatus incorporating a plurality of non-conductive capillary emitter heads. [0030] FIG. 5a is a top view of an embodiment of a capillary emitter system incorporating a plurality of conductive capillary emitter manifolds.

[0031] FIG. 5b is a top view of an embodiment of a capillary emitter system incorporating a plurality of non-conductive capillary emitter manifolds.

DETAILED DESCRIPTION OF THE INVENTION

[0032] With reference to FIGS. Ia and Ib, the present invention is directed to capillary emitter apparatuses and methods for cleaning wafers, including certain surface areas and formations of a wafer 155, including circumferential "exclusion" edges 145 and 146 (or peripheral rings) of top and bottom surfaces 135 and 136 and a bevel 147 therebetween, which can have a straight or curved cross section. The wafer may also have a notch 120 or flat edge 123 that is provided for referencing orientation of the wafer. In accordance with the present invention, capillary emitter technology is used to generate electrohydrodynamic (EHD) beams or ion electrodynamic (ED) beams to treat wafer edges, bevels and other formations for surface cleaning of films and/or particulates, especially particulates of 1 micron or less in size (or "mean diameter," used interchangeably with "size" herein). As discussed below, EHD beams are generated through the use of a liquid solution that is dispersed by a capillary emitter, whereas ion ED beams are generated through the use of a gas or vapor that is dispersed by a capillary emitter. Moreover, capillary emitter apparatus can incorporate either a conductive capillary emitter or a nonconductive capillary emitter. (In the former instance where the source ingredient delivered to the capillary emitters is a gas or vapor, the conductive capillary emitter is also referred to as a "capillaritron.")

[0033] FIG. 2a illustrates an embodiment of a capillary emitter head 10 incorporating a conductive capillary emitter 32. Conductive fluid (gas or liquid) from reservoir 18 flows through fluid conduit 20 and is delivered to the conductive capillary emitter 32 exposed to high vacuum. When the fluid reaches capillary tip 33, it enters an intense electrostatic field region 37 formed by applying high voltage to the conductive capillary emitter 32. A preferred voltage can be in the range of about +8 to +20 kV applied by means of a power supply 17. The electric field 37 is established between the tip 33 and an extractor electrode 30 whose potential is adjustable by means of a power supply 19. The relatively intense fields generated at the tip 33 (> 10⁵ volts/cm) result in electrostatic forces stressing the exposed surface of the conducting fluid. As the voltage applied to the conductive capillary emitter 32 is increased, the electrostatic forces acting on the fluid surface at the tip 33 also increases until a value is reached that exceeds the surface tension force S holding the fluid together. The fluid disrupts into an aggregate of charged clusters forming a beam 34. If a positive high voltage is applied to the capillary 32 by means of power supply 17, particles in the beam 34 will be positively charged. Alternatively, if a negative high voltage is applied to the capillary 32, the beam 34 will consist of negatively charged particles.

[0034] Where the fluid is liquid, the beam of high energy particles comprises primarily of multiply-charged clusters and droplets (including nanodroplets). Where the fluid is gas, the beam of high energy particles comprises primarily of singly charged ions. In either case, the beam particles have a mean diameter of about 1 micron or less. [0035] FIG. 2b illustrates an embodiment of a capillary emitter head 11 incorporating a non- conductive capillary emitter 32. The configuration and operation of the apparatus 11 are generally similar to those of the aforementioned apparatus 10 but with differences including those as discussed below. Conductive solution or liquid 16 is stored in reservoir 18 where it is electrified by an immersed charging electrode 15 by means of power supply 17 with a preferred voltage in the range of about +8 to +20 kV. The electrified fluid flows through fluid conduit 20 and is delivered to the capillary 32 where the electric field 37 is established between the tip 33 and an extractor electrode 30 whose potential is adjustable by means of a power supply 19. As the voltage applied to the immersed electrode 15 is increased, the electrostatic forces acting on the fluid surface at the tip 33 also increases until a value is reached that exceeds the surface tension force S holding the fluid together. The fluid disrupts into an aggregate of charged clusters forming a beam 34.

Likewise, if a positive high voltage is applied to the immersed electrode 15 by means of power supply 17, particles in the beam 34 will be positively charged. Alternatively, if a negative high voltage is applied to the immersed electrode 15, the beam 34 will consist of negatively charged particles. [0036] The apparatus 11 of FIG. 2b is best suited for delivery of a liquid to the non-conductive capillary emitter 32 for generating a beam of high energy particles comprising primarily of multiply-charged clusters and droplets (including nanodroplets), where the particles have a mean diameter of about 1 micron or less. [0037] FIGs. 3a and 3b illustrate embodiments of a capillary emitter apparatus 100 incorporating capillary emitter heads 120 that generate particles of controlled velocity and size for cleaning a target wafer 155. In particular, beams 134 of high energy particles, including ions, clusters and/or droplets (e.g., nanodroplets) are directed toward and impinges on an edge exclusion 145 and 146 of a top and bottom surface of the wafer. The illustrated embodiment of the apparatus 100 comprises at least a pair of emitter heads 120, each having a capillary emitter 160 with a micro-orifice at a distal tip. The tip of each the emitter 160 is disposed generally within a central aperture of a respective extracting electrode 130. The extracting electrodes are connected to a power supply source 116. Fluid stored in reservoir 110 is delivered to the heads 120 via transfer line 100 where the emitters 160 are disposed. Lines 135 distribute the fluid to the heads 120, where, upon reaching the tips of the emitter 160, forms the high energy, directed beams 134 of ions, clusters and/or droplets.

[0038] With reference to FIG. 3a, where the capillary emitters 160 are conductive, reservoir 110 supplies either a gas or a liquid to the emitters 160 to which power source 117 applies a voltage via line 113. With gas as a source ingredient, the beam contains primarily highly energized singly-charged ions. With liquid as a source ingredient, the beams contain highly energized multiply-charged clusters and/or droplets, including nanodroplets.

[0039] With reference to FIG. 3b, where the emitters 160 are nonconductive, reservoir 110 supplies to the emitters 160 a liquid that is charged by an immersed electrode 115 powered by power source 117 via line 112. The beams produced thereby contain highly energized clusters and droplets, including nanodroplets. The electrode 115 can be constructed of mono atomic metallic elements, binary metallic alloys, tertiary metallic alloys, quaternary metallic alloys, and vitreous carbon, or combinations thereof.

[0040] It is understood by one of ordinary skill in the art that by varying the operating parameters (including the voltage applied to the emitters 160, the immersed electrode 115 and/or the extractor electrodes 130, and the contents the gas or liquid starting ingredient), the nature and size of the beam particles can be varied, as needed or desired. Moreover, as an alternative to the pressurized reservoir method of delivering solution to the emitters, a direct drive mechanism such as a syringe pump can used for solution transport.

[0041] As illustrated in FIGs. 3a and 3b, the capillary emitters 160 are in a generally opposing configuration to face each other such that respective directed beams 134 impact the edges 145 and 146 of the wafer 155 positioned therebetween. It is understood by one of ordinary skill in the art that etching and ballistic kinetic interactions of the beam with the wafer edge surface act to remove film and debris. Accordingly, the wafer 155 can be mounted on one of many types of wafer chucks 140 well-known to practitioners in the industry and moved in a circular motion by a rotating spindle mechanism 150 allowing the wafer edge to pass under the beam. [0042] As illustrated, the emitters 160 are angled at about zero degrees from the vertical for normal incidence to the wafer and are vertically aligned for contemporaneous cleaning of corresponding top and bottom edges 145 and 146. However, the present invention provides for the emitters 160 to impact the wafer edges 145 and 145 at angles of incidence ranging between about 40 to 60 degrees from normal, although each emitter may have a different angle of incidence from the other emitters as needed or desired. The beams may be directed at an oblique angle to the wafer edge to insure that the beams sweep debris off and away from a central portion of the wafer. Thus with both emitters 160 in operation (including contemporaneous operation), there is no need to flip the wafer for cleaning the edges of the front and back surfaces. In one embodiment, spacing between the tip of the emitters 160 and the wafer edge ranges between about 0.250 and 0.750 inches.

[0043] To prevent debris removed from the wafer edges from collecting on sensitive surfaces of the wafer, a mask 125 is mounted in close proximity to the wafer top side exposing only the peripheral edge 145. [0044] The electrosprayed liquid solution can consist of a single component organic or inorganic liquid or a mixture of one or more chemically different components. Examples of electrosprayed liquids include but are not limited to : water, alcohols (methanol, 2-propanol (IPA), ethanol), glycerol, hydroxylamine, ethylene glycol, formamide, n-methylpyrrolidone (NMP), hydrogen peroxide, TMAH, nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid, hydrofluoric acid and ammonium hydroxide. It is understood by one of ordinary skill in the art that many of the aforementioned chemicals can be combined in many ways to prepare solution mixtures sufficient to generate stable EHD beams. In some applications, the conductivity of the liquid may be too low or too high to achieve the desired beam properties of particle size and velocity. In these cases, amounts of added acidic or basic chemical agents are increased or lowered to achieve the desired beam properties. Conductive additives can also include volatile salts (e.g. ammonium acetate).

[0045] Impact energy transferred in collision of the high energy particles with the wafer edge results in removal of contaminated films and debris from the surface of the wafer edge. For example, studies have demonstrated that a directed EHD beam can remove polymer and other residues from wafer edges. A fluoropolymer film deposited on a wafer edge after plasma processing was completely removed after exposure to a 20 kV, 0.5μA formamide nanodroplet beam. The rate of film removal was shown to depend on the distance separating the EHD nanodroplet source from the wafer edge, beam current and accelerating voltage. Wafer edge cleaning times are reduced by decreasing the EHD nanodroplet source-target distance and by increasing the nanodroplet beam current. To further exemplify the capability, versatility and range of EHD beam for removal of material, Table 1 shows etching rates of various thin film materials from semiconductor wafers. [0046] Table 1. EHD Beam Etching Rates

Film Etching rate Etching rate Etching rate

Material (nanometer/min) (nanometer/min) (nanometer/min)

Removed Solution A Solution B Solution C

From Wafer

Al 97 60 27

Cu 40 48.6 38.5

Nitride 37.5 51.7 72

Oxide 135.7 41.8 85

TiW 20 58.3 47

Photoresist 1400 2000 1950 wherein,

Solution A includes a mixture of hydrogen peroxide and nitric acid, wherein one such mixture has about 30 ml of 30% H₂O₂ and about 60 microliters of 70% HNO₃.

Solution B includes a mixture of hydrogen peroxide and ammonium hydroxide, wherein one such mixture has about 30 ml of 30% H₂O₂ and about 30 microliters of 30% NH₄OH/ Solution C includes a mixture of phosphoric acid, water and nitric acid, wherein one such mixture has about 26.3 ml of water, about 3.75 ml of 80% H₃PO₄ and about 187 microliters of 70% HNO₃.

[0047] As understood by one of ordinary skill in the art, the EHD beam etching rates of Table 1 are not limited to the values displayed in Table 1 and higher rates are anticipated by optimizing the process configuration, beam current, beam impact energy and EHD etching solution. [0048] For wafer surface cleaning, the electrostatic stress between the capillary tip and the extractor plates is applied by a voltage source in a preferred range of about 10 to 20 kV. However, it is understood that applied potentials outside the stated range can be used without compromising the spirit or intent of the present invention. [0049] In the illustrated embodiments of FIGs. 3a and 3b, the apparatus 100 includes a neutralizer 135 to prevent electrostatic charging of the wafer edge 145 and 146 and bevel 147 that can cause a reduction in the energy of the impacting species. A common technique used for beam neutralization uses a thermionic 40 or hot filament technique (see FIGs. 2a and 2b). However, filaments 44 tend to be fragile (thus need special handling). They also exhibit lifetime limitations due to burn-out and are a potential source of contamination due to filament evaporation. [0050] Neutralization can also be achieved using microchannel plate technology that provides a uniform, high density flux of electrons well-suited for target or substrate neutralization. For example, an electron generator array (EGA) 135 can produce a beam of neutralizing electrons to prevent wafer charge buildup with less than one-milliwatt input. LQ one commercial configuration, a single EGA is capable of providing a 10 μA electron beam using only 0.02 watts. [0051] As a "cold" electron source, the EGA uses millions of micro-pore glass tubes fused into a mechanically rigid structure. When a voltage (e.g., up to a few kilovolts) is applied at the EGA input, i.e., across the thickness of the EGA which is typically about lmm, each pore produces a beam of electrons. The EGA needs little, if any, no warm-up time and tends to avoid burn out which can plague filaments. As understood by one of ordinary skill in the art, the EGA operates on the principle of field emission by generating electrons at the input of the EGA. As the initial burst of electrons travel down the pores of the EGA, the emission is multiplied by the principle of microchannel plate operation.

[0052] FIGs. 4a and 4b illustrate other embodiments of a capillary emitter apparatus 200 incorporating a plurality (e.g., at least three) capillary emitters 230, each having a conically shaped tip 240 with a micro-orifice preferably with a circular opening having a diameter in the range 1 to 100 microns. A capillary nozzle tip 240 having a micro-orifice of about 50 microns has been proven to perform satisfactorily, especially where a gas is delivered for ionization by the conductive emitters 230 (or "capillaritrons"). In such instance, with reference to FIG. 4a, the conductive emitters are electrically connected to high positive voltage source 217. Gas (e.g., argon) to be ionized at the capillary tip 240 is fed from a gas inlet 200 through a gas flow channel

231 confined within a manifold 225 until it reaches the capillary tip 240. The gas to be ionized is fed therethrough at a predetermined pressure.

[0053] hi operation, a plasma is formed inside the nozzle tip 240 by virtue of the collision of atoms in the gas to be ionized with electrons liberated from the capillary wall (and/or from within the plasma itself). Ions which reach the nozzle orifice are accelerated outward by the strong divergent electric field generated between the tip 240 and the wafer 155 . A resultant ion beam 265 of primarily singly-charged ions impinges on, sputters and etches away material from contaminated edge regions 145 and 146 on the top and bottom sides of the wafer 155. The illustrated embodiment of the apparatus 200 has the capillary emitters 230a and 230b configured to impact the wafer edges 145 and 146 at an angle ranging between about 40 to 60 degrees from the normal. Moreover, a third capillary emitter 230c is configured to impact a bevel surface 147 with a generally normal angle of incidence, although this angle may also range between about 40 to 60 degrees from the vertical. Any of the capillary emitters, and especially the third emitter 230c, can be mounted on a movable platform or the like such that the angle of incidence varies during operation for cleaning bevels with curved cross-sections. One of ordinary skill in the art appreciates that the wafer 155 can be mounted on one of many types of wafer chucks 140 and moved in a circular motion by a rotating spindle mechanism 150 allowing the edges 145 and 146 and the bevel 147 to pass under the ion beams 215. [0054] Capillary tips or emitters fabricated from metallic conductors result in superior performance, although ceramic or quartz nozzle tips with an electrode wire extending through the bore to the tip operate satisfactorily.

[0055] The apparatus 200 also includes a neutralizer 235 to prevent charging of the wafer edges 145 and 146 and bevel 147 that can cause a reduction in the energy of the impacting species. [0056] Although the embodiment of FIG. 4a has been described above in the context of a gas as the source ingredient to produce ion beams, it is understood by one of ordinary skill in the art that the apparatus can also use a liquid as a source ingredient to produce EHD beams. Moreover, the capillary emitter apparatus can also be adapted to use electrospray a liquid using nonconducting emitters, as illustrated in FIG. 4b, wherein two emitters are configured to generate beams that impinge on edge regions 145 and 146 and a third emitter is configured to generate a beam that impinges on bevel region 147. An electrode 215 powered by the power supply 217 is provided to charge the liquid in the reservoir 210.

[0057] FIGs.5a and 5b illustrate embodiments of a capillary emitter system 300 incorporating a plurality of capillary emitter manifolds 320 (for example, a plurality of two, three, four or more) configured generally equidistant from each other in circumferential arrangement around wafer 155. Each manifold 320 contains two or more heads 342 (conducting in FIG. 5a and non-conducting in

FIG. 5b) using the aforementioned head configurations of FIGs. 3 or 4 to treat the wafer edges 145 and 146 and bevel 147. One of ordinary skill in the art appreciates that additional manifolds can be added to meet the necessary throughput requirements. A neutralizer apparatus 335 is also included to provide a source of electrons preventing buildup of charge at the wafer edges 145 and 146 and/or bevel 147.

[0058] In the embodiment of FIG. 5a, conducting emitters 342 are powered by power supply 317. Gas or liquid is supplied by reservoir 310 to each emitter 342. In the embodiment of FIG 5b, liquid is supplied by reservoir 310, the liquid being charged by an electrode 315 powered by the power supply 317. [0059] For optimum cleaning, the chuck can rotate the wafer in a manner such that the entirety of the edge region of a side of the wafer passes under all emitters directed to that side of the wafer. However, where time or other factors are constraints, the chuck can rotate the wafer in a manner such that any portion of an edge region on a side of the wafer passes under one emitter or a limited predetermined number of emitters only. Other patterns and manners of rotation are possible, as understood by one of ordinary skill in the art.

[0060] Any of the foregoing embodiments of the present invention may also be adapted to clean features or formations in the edge or bevel of the wafer, such as a flat edge 123 or a notch 120 (see FIG. Ia) formed for wafer reference and orientation purposes. One or more capillary emitters can be movably oriented to treat and clean around or in the flat edge or notch, as needed or desired.

[0061] In accordance with another feature of the present invention, a method is provided for treating the edge, notch and bevel regions of a wafer or disc using a confined, well-directed, high energy EHD or ED beam of highly energized particles, including clusters, droplets and ions. Clusters and droplets are generated by flowing a liquid species through a capillary nozzle or emitter that is conductive or nonconductive. EHD beam initiates upon application of a voltage to a conductive nozzle or the liquid species itself. The liquid solution can consist of a single component organic or inorganic liquid or a mixture of one or more chemically different components. Examples of electrosprayed liquids include but are not limited to : water, alcohols (methanol, 2- propanol (IPA), ethanol), glycerol, hydroxylamine, ethylene glycol, formamide, n- methylpyrrolidone (NMP), hydrogen peroxide, TMAH, nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid, hydrofluoric acid and ammonium hydroxide. It is understood by one of ordinary skill in the art that many of the aforementioned chemicals can be combined in many ways to prepare solution mixtures sufficient to generate stable EHD beams [0062] The ions on the other hand are generated by flowing a gas or vapor species through a conductive capillary nozzle (including those rendered conductive by means of an electrode wire), whose orifice diameter is about 50 microns or less. Ion ED beam initiation is instantaneous upon application of a voltage to the metal nozzle (for operational theory and apparatus configurations see: "Capillaritron: A new, versatile ion source", Appl. Phys. Lett. 38, 320 , 1981 and U.S. Patent No. 4,318,028 to Perel et al ). The ion source can produce ions beams from any gaseous species (e.g., argon, helium, nitrogen, oxygen, xenon and hydrogen) including reactive gases and molecular complexes.

[0063] The ion beam etching rate is a function of the nozzle (acceleration) voltage, angle of incidence, species of gas employed and the nature of the etched material. For most wafer films, a preferred ion beam angle of incidence for maximum etching ranges between about 40-60 degrees from the normal. Published etch rates for over 50 different materials using a 500 volt argon ion beam range from about 20 to 400 nrn/min. (See Commonwealth Scientific Corporation, Bulletin #137-78) These etch rates can be substantially increased by increasing the ion energy and should be as high as possible within the limitations imposed by apparatus configuration and arcing considerations. Although the ionization efficiency of the capillaritron ion source is relatively small, about 5-10% of the input gas is ionized, the un-ionized high velocity gas plume is a propitious source of purge gas for removing sputtered debris. [0064] The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. Features disclosed in one embodiment may be used in another embodiment as needed or desired. [0065] Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.

Claims

WHAT IS CLAIMED IS:

1. A capillary emitter apparatus adapted to treat top and bottom edge regions of a wafer, comprising: at least two capillary emitters arranged in generally opposing configuration, each capillary emitter adapted to generate a beam of high energy particles to impinge upon a different edge region of the wafer; and a wafer chuck adapted to support and rotate the wafer such that the edge regions are exposed to said beams of high energy particles.

2. A capillary emitter apparatus of claim 1, wherein the capillary emitters are nonconductive.

3. A capillary emitter apparatus of claim 1, wherein the capillary emitters are conductive.

4. A capillary emitter apparatus of claim 1 , wherein the particles comprises primarily multiply-charged particles.

5. A capillary emitter apparatus of claim 1, wherein the particles comprises primarily singly- charged particles.

6. A capillary emitter apparatus of claim 1, further comprising a source adapted to provide a liquid for electrospraying by the capillary emitters.

7. A capillary emitter apparatus of claim 1, further comprising a source adapted to provide a gas for ionization by the capillary emitters.

8. A capillary emitter apparatus of claim 6, wherein the liquid is electrically charged in the source by an electrode.

9. A capillary emitter apparatus of claim 3, further comprising: a source supplying the apparatus with an ingredient that is one of the group consisting of gas and liquid, and a power supply to electrically charged the conductive capillary emitters.

10. A capillary emitter apparatus of claim 2, further comprising: a source supplying the apparatus with a liquid; an electrode charging the liquid stored in the source; and a power supply applying a voltage to the electrode.

11. A capillary emitter apparatus of claim 1 , wherein the particles are of about 1 micron or less in mean diameter.

12. A capillary emitter apparatus of claim 1 , further comprising a third capillary emitter adapted to generate a beam of high energy particles to impinge a bevel region of the wafer.

13. A capillary emitter apparatus of claim 1, further comprising a mask to cover a top surface of the wafer inside the edge region.

14. A capillary emitter apparatus of claim 1, further comprising a neutralizer to reduce electrostatic charging of the wafer edge regions.

15. A capillary emitter system adapted to treat top and bottom edge regions of a wafer, comprising: at least two capillary emitters manifolds arranged in a circumferential arrangement around a wafer, at least one manifold comprising: at least two capillary emitters in generally opposing configuration, each capillary emitter adapted to generate a beam of high energy particles to impinge upon a different edge region of the wafer; and a wafer chuck adapted to support and rotate the wafer such that the edge regions are exposed to said beams of high energy particles.

16. A capillary emitter system of claim 15, wherein the capillary emitters are conductive.

17. A capillary emitter system of claim 15, wherein the capillary emitters are nonconductive.

18. A capillary emitter system of claim 15, wherein at least one manifold further comprises a capillary emitter adapted to generate a beam of high energy particles to impinge upon a bevel of the wafer.

19. A capillary emitter system of claim 15, further comprising a source to provide a gas to the system for generating the beams.

20. A capillary emitter system of claim 15, further comprising a source to provide a liquid to the system for generating the beams.

21. A capillary emitter system of claim 19, further comprising a power supply to apply a voltage to the conductive emitters.

22. A capillary emitter system of claim 20, further comprising: an electrode configured to charge the liquid; and a power supply to apply a voltage to the electrode.