A multiple-beam ion-beam assembly consisting of two or more concentrically arranged ring-shaped ion-beam sources having ion-beam slits that emit a plurality of ion beams which overlap on the surface being treated and thus ensure uniformity in distribution of ion currents on the treated surface. Since the ion-beam assembly consists of a plurality of individual source, uniform treatment can be performed on a large surface area. Several embodiments of the invention cover the systems with individual sources adjustable with respect to one another, with an oblique angle of incidence of beams emitted from individual source, and with combination of oblique angles and adjustable sources.

FIELD OF THE INVENTION
 The present invention relates to the field of ion-emission technique,
 particularly to cold-cathode type ion-beam sources having closed-loop
 ion-emitting slits with electrons drifting in crossed electric and
 magnetic fields. More specifically, the invention relates to an ion-beam
 assembly consisting of two or more coaxially arranged ion-beam sources of
 the aforementioned type.
 BACKGROUND OF THE INVENTION
 An ion source is a device that ionizes gas molecules and then focuses,
 accelerates, and emits them as a narrow beam. This beam is then used for
 various technical and technological purposes such as cleaning, activation,
 polishing, thin-film coating, or etching.
 For better understanding the principle of the present invention, it would
 be expedient to describe in detail a known ion-beam source of the type to
 which the invention pertains. Such an ion source is described, e.g., in
 Russian Patent No. 2,030,807 issued in 1995 to M. Parfenyonok, et al. The
 patent describes an ion source that comprises a magnetoconductive housing
 used as a cathode having an ion-emitting slit, an anode arranged in the
 housing symmetrically with respect to the emitting slit, a magnetomotance
 source, a working gas supply system, and a source of electric power
 supply.
 FIGS. 1 and 2 schematically illustrate the aforementioned known ion source
 with a circular ion-beam emitting slit. More specifically, FIG. 1 is a
 sectional side view of an on-beam source with a circular ion-beam emitting
 slit, and FIG. 2 is cross-sectional plan view along line II--II of FIG. 1.
 The ion source 22 of FIGS. 1 and 2 has a hollow cylindrical housing 40 made
 of a magnetoconductive material such as Armco steel (a type of a mild
 steel), which is used as a cathode. The cathode 40 has a cylindrical side
 wall 42, a closed flat bottom 44 and a flat top side 46 with a circular
 ion emitting slit 52.
 A working gas supply hole 53 is formed in the flat bottom 44. The flat top
 side 46 functions as an accelerating electrode. Placed inside the interior
 of the hollow cylindrical housing 40 between the bottom 44 and the top
 side 46 is a magnetic system in the form of a cylindrical permanent magnet
 66 with poles N and S of opposite polarity. An N-pole faces flat top side
 46 and S-pole faces the bottom side 44 of the ion source. The purpose of a
 magnetic system with a closed magnetic circuit formed by parts the 66, 46,
 42, and 44 is to induce a magnetic field in ion emitting slit 52. A
 circular annular-shaped anode 54 which is connected to a positive pole 56a
 of an electric power source 56 is arranged in the interior of housing 40
 around magnet 66 and concentric thereto. The anode 54 is fixed inside
 housing 40 by means of a ring 48 made of a non-magnetic dielectric
 material such as ceramic. The anode 54 has a central opening 55 in which
 aforementioned permanent magnet 66 is installed with a gap between the
 outer surface of the magnet and the inner wall of opening 55. A negative
 pole 56b of electric power source is connected to the housing 40, which is
 grounded at GR.
 Located above the housing 40 of the ion source of FIGS. 1 and 2 is a sealed
 vacuum chamber 57, which has an evacuation port 59 connected to a source
 of vacuum (not shown). An object OB to be treated is supported within the
 chamber 57 above the ion emitting slit 52. The object OB is electrically
 connected via a line 56c to the negative pole 56b of the power source 56.
 Since the interior of the housing 40 communicates with the interior of the
 vacuum chamber 57, all lines that electrically connect the power source 56
 with the anode 54 and the object OB should pass into the interior of the
 housing 40 and the vacuum chamber 57 via conventional
 commercially-produced electrical feedthrough devices which allow
 electrical connections with parts and mechanisms of sealed chambers
 without violation of their sealing conditions. In FIG. 1, these
 feedthrough devices are shown schematically and designated by reference
 numerals 40a, 57a, 57b, and 57c.
 The known ion source of the type shown in FIGS. 1 and 2 is intended for the
 formation of a unilaterally directed tubular ion beam. The source of FIGS.
 1 and 2 forms a tubular ion beam IB emitted in the direction of arrow A
 and operates as follows.
 The vacuum chamber 57 is evacuated, and a working gas is fed into the
 interior of the housing 40 of the ion source via a gas-supply tube 53a. An
 electric field is generated in the ion generation gap 58 and the
 ion-emitting slit 52 due to an electrical potential applied from the
 electric power supply 56 between the anode 54 and the upper cathode plate
 46. As a result, a glow discharge occurs in the gap 58 after the potential
 reaches a predetermined value. A magnetic field is generated by the magnet
 66 across the ion-emitting slit 52 whereby free electrons of the glow
 discharge begin to drift in a closed path within the crossed electrical
 and magnetic fields. When the working gas is passed through the ionization
 gap, the tubular ion beam IB, which is propagated in the axial direction
 of the ion source shown by an arrow A, is formed in the area of the
 ion-emitting slit 52 and in the accelerating gap between the anode 54 and
 the cathode 40.
 The above description of the electron drift is simplified to ease
 understanding of the principle of the invention. In reality, the
 phenomenon of generation of ions in the ion source with a closed-loop
 drift of electrons in crossed electric and magnetic fields is of a more
 complicated nature and consists in the following.
 When, at starting the ion source, a voltage between the anode 54 and
 cathode 40 reaches a predetermined level, a gas discharge occurs in the
 anode-cathode gap. As a result, the electrons, which, under of effect of
 concurrent electrical and magnetic fields, move along complex
 trajectories, are accumulated and held in the area of the ion-emitting
 slit 52 and in the anode-cathode gap 58. In fact, the aforementioned
 electrons drift along the closed-loop slit 52 and exist there over a long
 period of time. After being accelerated by the electric field, the ions
 generated in the anode-cathode gap due to collision of neutral molecules
 with electrons, pass through the ion-emitting slit 52 and are emitted from
 the ion source.
 Strictly speaking, the aforementioned complex trajectories are closed
 cycloid trajectories. The phenomenon of drift of electrons in the crossed
 electric and magnetic fields is known as "magnetization" of electrons. The
 magnetized electrons remain drifting in a closed space between two parts
 of the cathode, i.e., between those facing parts of the cathode 40 which
 form the ion-emitting slit 52. The radius of the cycloids is, in fact, the
 so-called doubled Larmor radius R.sub.L which is represented by the
 following formula:
EQU R.sub.L =m.sub.e V/.vertline.e.vertline.B,
 where m.sub.e is a mass of the electron, B is the strength of the magnetic
 field inside the slit, V is a velocity of the electrons in the direction
 perpendicular to the direction of the magnetic field, and
 .vertline.e.vertline. is the charge of the electron.
 A distinguishing feature of the ion source of the type shown FIGS. 1
 through 3 is that efficient operation of the source is possible only when
 the source has the ion-emitting slit and the anode-cathode gap of
 predetermined geometrical dimensions. More specifically, the width of the
 ion-emitting slit 52 and the height of the gap 58 should be on the same
 order as the aforementioned Larmor radius.
 When a working medium, such as argon which has neutral molecules, is
 injected into the slit, the molecules are ionized by the electrons present
 in this slit and are accelerated by the electric field. As a result, the
 thus formed ions are emitted from the slit towards the object. Since the
 spatial charge of electrons has high density, an ion beam of high density
 is formed. This beam can be converged or diverged by known technique for
 specific applications.
 Thus, the electrons do not drift in a plane, but rather along cycloid
 trajectories across the ion-emitting slit 52. However, for the sake of
 convenience of description, here and hereinafter such expression as
 "electron drifting plane" or "drifting in the plane of ion-beam
 propagation" will be used.
 The diameter of the tubular ion beam formed by means of such an ion source
 may reach 500 mm and more. The ion source of the type shown in FIG. 1 and
 FIG. 2 is not limited to a cylindrical configuration and may have an
 elliptical or an oval-shaped cross.
 A disadvantage of the aforementioned ion source with a closed-loop
 ion-emitting slit is that the position of the tubular ion beam emitted
 from this source remains unchanged with respect to the surface of the
 object OB being treated. Furthermore, the aforementioned tubular beam has
 a non-uniform distribution of the ion beam current in the cross-section of
 the beam and hence on the surface of the object OB. More specifically, the
 ion current density across the tubular beam has two maximums in the areas
 corresponding to the closed-loop slit and one minimum in the center of the
 "tubular" profile of the beam.
 With ever growing demands to the quality and performance characteristics of
 semiconductor devices, uniformity of treatment of semiconductor wafers
 becomes a critical issue. This is because even insignificant variations,
 e.g., in thickness of layers, causes significant variations in parameters
 of semiconductor devices. Therefore, at the present time deviations from
 uniformity within the range 5% (i.e., .+-.2.5%) becomes standard for such
 operations as etching, stripping (removal of resist), overcoating by
 sputtering metals or dielectrics, etc. The above ion-beam source with a
 closed-loop ion-emitting slit and electrons drifting in crossed electric
 and magnetic fields was given only as one specific example. Known in the
 art are ion-beam sources of many other types, e.g., the so-called end-Hall
 type ion-beam source described, e.g., by Kaufman H. R. et al.
 (Characteristics, Capabilities, and Applications of Broad-Beam Sources,
 Commonwealth Scientific Corporation, Alexandria, Va.; Wykoff C. A. et al.,
 50-cm Linear Gridless Source, Eighth International Vacuum Web Coating
 Conference, Nov. 6-8, 1994) This ion source forms conical or belt-like ion
 beams in crossed electrical and magnetic fields. The device consists of a
 cathode, a hollow anode with a conical opening, a system for the supply of
 a working gas, a magnetic system, a source of electric supply, and a
 source of electrons with a hot cathode. Configuration of the electrodes
 used in the ion beam of such sources leads to a significant divergence of
 the ion beam. As a result, uniform distribution of current density across
 the beam can be achieved only in the center of the beam. Furthermore, the
 doze of irradiation with the ions will be essentially reduced
 simultaneously with a significant increase in the treatment time. This is
 because only a small portion of the beam which has uniformity is used. In
 other words, any single-beam ion source will have limits in their
 practical application for uniform treatment of large-area objects. Another
 disadvantage of the aforementioned ion-beam source is that the beam is
 perpendicular to the surface of the object. It is known, however, that
 when the ion beam fells onto the object at an angle different from normal,
 the efficiency of sputtering can be increased by three or more times.
 In general, methods for providing uniformity in distribution of ion-beam
 current density across the beam and on the surface of objects treated with
 ion-beam sources (hereinafter referred to simply as "uniformity") can be
 roughly divided into the following categories:
 1) Uniformity achieved due to beam divergence;
 2) Uniformity achieved due to multiple-cell structure of the ion source;
 3) Uniformity achieved by alternatingly or periodically changing position
 of ion beam with respect to the object.
 An example of an ion source in which uniformity is achieved due to beam
 divergence is a device disclosed in U.S. Pat. No. 6,130,507 issued Oct.
 10, 2000. This patent application discloses a closed-loop slit
 cold-cathode ion source where uniformity of treatment of an object is
 achieved by shifting the anode with respect to the cathode or vice verse.
 Such displacements cause variations in relative positions between the
 object and the beam whereby even with some non-uniformity in the ion
 current density distribution in the beam, the surface of the object is
 treated with an improved uniformity.
 A disadvantage of such a device is that the ion source or the ion-beam
 sputtering system should have movable parts which makes the construction
 of such source or system more complicated and expensive.
 An example of a device in which uniformity achieved due to multiple-cell
 structure is an ion-beam apparatus described in USSR Inventor's
 Certificate No. 865043. As shown in FIG. 3, which is an elevational
 sectional view of the ion-beam source 100 of the aforementioned type, the
 device is made in the form of a multiple-cell source having two cathode
 plates 102 and 104 which function as magnetic poles. An anode plate 106
 with openings is placed between cathode plates 102 and 104. Cathode plate
 104 has rods 108a, 108b, 108c, which extend from cathode plate 104 to
 second cathode plate 102. Second cathode plate 102 has openings 110a,
 110b, 110c coaxial with respective rods 108a, 108b, 108c and with openings
 in anode plate 106. The anode-cathode assembly is supported by a
 cup-shaped housing 112 of a nonconductive material, such as a ceramic,
 which contains an electromagnetic coil 114 for generating the
 aforementioned magnetic field in a anode-cathode space of ion source 100.
 In a conventional manner, entire ion source 100 is placed into a sealed
 vacuum chamber 118. A working medium is supplied to vacuum chamber via a
 working medium supply channel 116.
 Thus, each opening 110a, 110b, 110c in cathode plate 102 and a respective
 coaxial rod 108a, 108b, 108c of the device form an individual ion-beam
 source of the type described above, i.e., of the type disclosed in Russian
 Patent No. 2,030,807. More specifically, the end of each rod and the
 adjacent opening in cathode plate 102 form a closed-loop ion-beam emitting
 slit, so that all rods and the openings in the second cathode plate form a
 plurality of such slits. In the context of the present invention, a
 combination of one rod with a respective opening will be referred to as a
 "cell", and the ion-beam source of this type will be called a
 "multiple-cell type ion-beam source". Cathode plates 102 and 104 are
 electrically isolated from anode plate 106 and can be grounded or
 connected to a source of a negative potential via a conductor 122, and
 anode plate 106 is connected to a source of a positive potential (not
 shown) via a conductor 124.
 In operation, a working medium is supplied through channel 116 to the
 accelerating and ion-generating space between anode plate 106 and cathode
 plates 102, 104, and a potential difference is developed between the
 cathode plates and the anode plate. This generates crossed electric and
 magnetic fields in the anode-cathode space. These fields hold drifting
 electrons which ionize the working medium and compensate for the spatial
 charge of the ion beams IB1, IB2, IB3, which are emitted toward an object
 OB1 via openings in the second cathode plate. Object OB1 is fixed inside
 vacuum chamber 118.
 Although the multiple-channel ion-beam source of the type described above
 to some extent improves uniformity of ion-current density distribution on
 the surface of an object being treated, adjustment of distribution of the
 beam current density on the surface of the treated object OB1 is
 impossible.
 This problem is partially solved in the apparatus 100' shown in a partial
 side sectional view in FIG. 4 and described in pending U.S. patent
 application Ser. No. 240,469 filed by the same applicants on Jan. 30,
 1999.
 As shown in FIG. 1, each rod 108a', 108b', . . . has means for individually
 adjusting magnetic fields in individual ion-emitting slits 110a', 110b', .
 . . . This, in turn, allows for individually adjusting conditions for
 ionizing electrons in the ion-emitting slits and, hence, the density of
 ions emitted through individual ion-emitting slits.
 However, the ion-beam source of FIG. 4 produces a plurality of ion beams
 all of which have direction essentially normal to the surface being
 treated. In other words, the efficiency of sputtering in this source is
 still much lower than in the case of angle of incidence different from
 90.degree.. Furthermore, the provision of individual electromagnetic coils
 makes the construction of the ion-beam source more complicated and
 expensive.
 An example of an ion-beam apparatus in which uniformity is achieved by
 alternatingly changing positions of the ion beam with respect to the
 object is a device described in U.S. Patent No. 6,037,717 issued on Mar.
 14, 2000. This application describes a cold-cathode ion source with a
 closed-loop ion-emitting slit which is provided with means for generating
 a cyclically-variable, e.g., alternating or pulsating electric field in an
 anode-cathode space. These means may be made in the form of an
 alternating-voltage generator which generates alternating voltage on one
 of the cathode parts that form the ion-emitting slit, whereas the other
 slit-forming part is grounded. The alternating voltage deviates the ion
 beam in the slit with the same frequency as the frequency of the
 alternating voltage. The cold-cathode ion source may be of any type, i.e.,
 with the ion beam emitted in the direction perpendicular to the direction
 of drift of electrons in the ion-emitting slit or with the direction of
 emission of the beam which coincides with the direction of electron drift.
 Displacements of the beam cause variations in relative positions between
 the object and the beam whereby even with some non-uniformity in the ion
 current density distribution in the beam, the surface of the object is
 treated with an improved uniformity.
 A disadvantage of all ion-beam sources described above is that none of them
 allow evacuation of gases from the vacuum chamber through the central
 opening of the ion beam source. Such a demand, however, may occur in some
 applications.
 U.S. patent application Ser. No. 240,468 filed by the same applicants on
 Jan. 30, 1999 describes a combined ion-source and sputtering magnetron
 apparatus having a coldcathode ion source which emits the ion beam in the
 radial inward or outward direction onto the surface of the magnetron
 target at an oblique angle to the target surface. This increases
 efficiency of sputtering. Furthermore, the ion source has a ring-shaped
 configuration so that gases can be evacuated from the vacuum chamber
 through the central opening of the ion beam source.
 Although such a single-beam ion source produces a converging ion beam with
 self-overlapping portions, which to some extent can improve uniformity of
 treatment, the uniform surface area is limited and uniformity is low and
 cannot be adjusted.
 OBJECTS OF THE INVENTION
 It is an object of the present invention to provide an ion-beam source
 which combines in itself simplicity of construction, efficiency of
 operation, and extremely high uniformity in ion-current density
 distribution on the surface of an object being treated with an ion beam.
 Another object is to provide the aforementioned ion-beam source and a
 method of ion-beam treatment which are not limited with regard to the
 dimensions of the objects and allow to adjust the uniformity and
 distribution pattern of ion current on the surface of the object being
 treated. Still another object is to ensure uniformity of treatment on
 large treated areas. Further object is to provide an ion-beam source
 capable of emitting a plurality of ion beams overlapped on the surface
 being treated. Another object is to provide an ion-beam source with
 overlapped ion beams having an angle of incidence on the treated surface
 perpendicular to the surface being treated or different from 90.degree..
 Still another object is to provide a multiple-beam ion-beam source in
 which the beams are emitted onto the surface of the treated object at an
 oblique angle and in which relative positions of the ion-emitting slits
 for different beams can be adjusted with respect to each other. Still
 another object is to provide a method for adjusting uniformity of ion-beam
 treatment by treating the surface of an object simultaneously with a
 plurality of ion beams and by adjusting relative positions of the beams on
 the treated surface. Another object is to provide an ion-beam source
 assembly suitable for evacuation of gases through the central opening of
 the ion-beam source.

SUMMARY OF THE INVENTION
 A multiple-beam ion-beam assembly consisting of two or more concentrically
 arranged ring-shaped ion-beam sources having ion-beam slits that emit a
 plurality of ion beams which overlap on the surface being treated and thus
 ensure uniformity in distribution of ion currents on the treated surface.
 Since the ion-beam assembly consists of a plurality of individual sources,
 uniform treatment can be performed on a large surface area. Several
 embodiments of the invention cover the systems with individual sources
 adjustable with respect to one another. The angle of incidence of the
 beams can be within the range from 0 to 90.degree. to the treated surface.
 Some embodiments show a pair of sources with ion beams perpendicular to
 the treated surface and other embodiments show a combination of sources
 with oblique angle and with adjustable positions of individual sources.
 DETAILED DESCRIPTION OF THE INVENTION
 FIGS. 5, 6, and 7--Multiple Ion-Beam Assembly with a Plurality of
 Non-Adjustable Concentric Ion-Beam Sources with Ion Beams Perpendicular to
 the Surface of the Treated Object
 This embodiment of the invention relates to a new principle for achieving
 uniformity of current density distribution by utilizing a multiple-slit
 structure of the ion source. FIGS. 5, 6, and 7 illustrate an embodiment of
 the invention which is a multiple ion-beam assembly with a plurality of
 concentric ion-beam sources having ion beams emitted perpendicular to the
 surface of the treated object. Here, FIG. 5 is a side sectional view of
 the multiple ion-beam assembly of the aforementioned embodiment, FIG. 6 is
 a sectional view along line VI--VI of FIG. 5, and FIG. 7 is a view similar
 to FIG. 6 illustrating an ion-beam assembly of an oval cross-sectional
 configuration.
 In general, a multiple-beam ion source 200 of FIG. 5 is similar to the one
 shown in FIGS. 1 and 2 and differs from it in that it has a plurality of
 concentric emitting slits 252a and 252b, a plurality of concentric rows of
 magnets 266a, 266b, and 266c, operating with a common cathode 240, and a
 plurality of respective concentric anodes 254a and 254b. In the
 illustrated embodiments, only three magnets are shown: magnets 266b and
 266c and 266a. Of those, magnets 266b and 266c are a pair of pluralities
 of magnetic rods arranged a closed circular, elliptical, or oval paths,
 depending on the shape of the ion-beam slit. The magnet 266a is single
 solid magnetic rod (if the aforementioned path is circular) or one of a
 plurality of magnetic rods arranged in line in of an oval path, as shown
 in FIG. 7. Each anode 254a and 254b is fixed to housing 240 by means of
 respective block 265a and 265b of dielectric material and is connected to
 positive poles 256a and 256c of respective power sources 256 and 259.
 Negative poles 256b and 256d of these power sources are connected to
 cathode 240. Reference numerals 253a and 253b designate inlet opening for
 injection of working media (which may be the same or different) into
 individual concentric ion-emitting chambers ICH1 and ICH2. In the
 embodiment illustrated in FIG. 5, chamber ICH2 is located inside of
 chamber ICH1. Both chambers are sealed from each other by respective
 ring-shaped holders 267a and 267b of the respective magnets (FIG. 6).
 In the embodiment of FIG. 5, chamber ICH1 has aforementioned closed-loop
 ion-emitting slit 252b, and chamber ICH2 has aforementioned closed-loop
 slit 252a. Slits 252a and 252b emit concentric diverging ion beams IB1 and
 IB2 which cover the entire surface of an object OB1.
 Similar to the apparatus of FIGS. 1 and 2, ion source 200 is provided with
 a vacuum chamber 257 which is sealingly connected to housing 240 above
 ion-emitting slits or into which the entire ion source is placed. Object
 OB1 is located inside vacuum chamber 257. Object OB1 is grounded via a
 conductor 261 which passes into vacuum chamber 257 via an electric
 feedthrough 263. Object OB1 is electrically isolated from the housing of
 vacuum chamber 257 by a block 265 of dielectric material which is used for
 securing object OB1 inside vacuum chamber 257.
 Ion source 200 of the type shown in FIGS. 5 through 7 is intended for the
 formation of a unilaterally directed concentric tubular ion beams of
 diverging shape.
 The source operates as follows:
 Vacuum chamber 257 is evacuated, and a working gas is fed into the interior
 of individual ion-emitting chambers ICH1 and ICH2 formed inside housing
 240 of the ion source. A magnetic field is generated by concentric magnets
 266a, 266b, and 266c ion emitting slits 252a and 252b and in accelerating
 gaps G1 and G2 between anode 254 and cathode 240, whereby electrons begin
 to drift in a closed path within the crossed electrical and magnetic
 fields. A plasma 258 is formed between anode 254 and cathode 240. When the
 working gas is passed through ionization and acceleration gap G, tubular
 ion beams IB1 and IB2, which propagate in the axial direction of the ion
 source shown by an arrows A1 and A2, are formed in the area of emission
 slits 252b and 252a and in accelerating gaps G1 and G2 between anode 254
 and cathode 240.
 In the embodiment of FIGS. 5, 6, and 7, some uniformity of treatment is
 ensured due to the fact that the diverging ion beams cover the entire
 surface of the object OB1. Such an ion source is suitable for treating
 stationary objects with large surface areas. However, the distribution of
 ion current density on the surface being treated is still not sufficient
 for applications where such uniformity is critical. Furthermore, in the
 ion-beam assembly of FIGS. 5, 6, 7, the pattern of the ion current density
 distribution on the surface of the object is not adjustable.
 FIGS. 8, 8a-8c--Ion-Beam Source Assembly with Ion Beams Perpendicular to
 the Surface of the Object and With Individual Ion-Beam Sources Having
 Positions Adjustable With Respect To Each Other
 FIGS. 8, 8a-8c illustrates another embodiment of a multiple-beam ion source
 assembly which consists of a plurality of annular individual concentric
 ion-beam sources having positions adjustable with respect to each other.
 Although the ion-beam assembly 300 of this embodiment is illustrated as a
 set of two individual ion-beam sources, the assembly may consist of three
 or more individual sources.
 The system of FIG. 8 consists of a first, or an outer ion-beam source 302
 and a second, or an inner ion-beam source 402. The outer ion-beam source
 302 has a hollow cylindrical housing 304. The lower end plate 306 of the
 housing 304 functions as a cathode plate of the ion source. The cathode
 plate 306 has a circular ion-emitting slit 308. Located inside the hollow
 housing 304 above the slit 308 is an annular anode 310 which is spaced
 from the inner wall 304a of the housing 304 and is supported by an block
 312 of an insulating material, e.g., ceramics, glass, etc. The anode 310
 of the first ion-beam source 302 is connected by a conductor 315a to a
 positive terminal 314a of an electric power source 314 via an electric
 feedthrough device 316. A negative terminal 314b of the power source 314
 is grounded at GR1 and is connected via a conductor 315b to the housing or
 cathode 304.
 In the illustrated embodiment, a magnetic-field generating means for the
 first or outer ion-beam source 302 is made in the form of a plurality of
 permanent magnets 318, 320. Although only two of these magnets are shown
 in FIG. 8, it is understood that a plurality of such magnets are arranged
 circumferentially and at equal distances from each other between the inner
 wall 304a of the hollow cylindrical housing 304 and the outer periphery of
 the annular anode 310.
 The inner wall 304a of the first or outer annular ion-beam source 302
 serves as a guide for the second or inner annular ion-beam source 402. The
 inner ion-beam source 402 has a hollow cylindrical housing 404. The lower
 end plate 406 of the housing 404 functions as a cathode plate of the ion
 source. The cathode plate 406 has a circular ion-emitting slit 408.
 Located inside the hollow housing 404 above the slit 408 is an annular
 anode 410 which is spaced from the inner wall 404b of the housing 404 and
 is supported by an block 411 of an insulating material, e.g., ceramics,
 glass, etc. The anode 410 of the first ion-beam source 402 is connected by
 a conductor 415a to a positive terminal 414a of an electric power source
 414 via an electric feedthrough device 416. A negative terminal 414b of
 the power source 414 is grounded at GR1 and is connected via a conductor
 415b to the housing or cathode 404.
 In the illustrated embodiment, a magnetic-field generating means for the
 second or inner ion-beam source 402 is made in the form of a plurality of
 permanent magnets 418, 420. Although only two of these magnets are shown
 in FIG. 8, it is understood that a plurality of such magnets are arranged
 circumferentially and at equal distances from each other between the inner
 wall 404a of the hollow cylindrical housing 404 and the inner periphery of
 the annular anode 410.
 As shown in FIG. 8a, which is fragment C of FIG. 8 shown on a larger scale,
 position of the second or inner ion-beam source 402 with respect to the
 first or outer ion-beam source 302 can be adjusted by means of an
 adjustment screw 412. This screw is threaded into a threaded hole 414 made
 in a flanged portion 404a of the housing 404 of the inner annular ion-beam
 source 402. One end of the screw 412 projects outside the flanged portion
 404a and has a head, while the opposite end of the screw supports a ring
 416 is fixed in a recess 418 of the housing 304 of the outer annular
 ion-beam source 302 so that it can freely rotate inside the recess but is
 restricted against movement in the axial direction of the screw. As a
 result, rotation of the screw 412 will cause the housing 404 of the inner
 annular ion-beam source 402 to move in a vertical direction in the guide
 hole formed by the inner wall 310a of the outer annular ion-beam source
 302.
 An object OB2 to be treated is placed in a vacuum chamber 420 formed by a
 cylindrical body 422 placed between object OB2, which is grounded at
 GR1.sup.1 and the lower side of the outer annular ion-beam source 302. The
 space of the vacuum chamber 420 is sealed by seal ring 426. Sliding
 interface between the outer annular ion-beam source 302 and the inner
 annular ion-beam source 402 along the guide surface 310a is sealed by a
 seal ring 430 which is compressed by means of screws via a flat spacer 434
 (only one of these screws, i.e., a screw 432 is shown). When the seal ring
 430 is compressed, it is deformed outwardly and inwardly in the radial
 direction and is tightly pressed with its inner surface to the outer
 cylindrical surface of the housing 404, whereby the interface between the
 sliding surfaces is sealed.
 The vacuum chamber 420 is evacuated through an exhaust pipe 436 which forms
 an extension of the central opening of the inner annular ion-beam source
 402 and is connected to a vacuum pump (not shown).
 In a typical operation required for uniform treatment of a large surface
 area of the object, both ion beam sources, i.e., the outer annular
 ion-beam source 302 and inner annular ion-beam source 402 are used
 simultaneously. In principle, each ion-beam source operates in the same
 manner as the known ion beam source 22 shown in FIG. 1 and the ion-beam
 source 200 shown in FIG. 6, with the only difference that the outer
 annular ion-beam source 302 and inner annular ion-beam source 402 have
 hollow cylindrical, elliptical, or oval shaped housings. Each source has
 its one gas supply, magnetic field generation, and electric power supply
 systems described above.
 During operation, the outer annular ion-beam source 302 emits a tubular
 diverging ion beam IB3 through its closed-loop ion-beam emitting slit 308.
 The beam IB3 falls onto an annular surface 440 of the object OB2.
 Similarly, the inner annular ion-beam source 402 emits a tubular diverging
 ion beam IB4 through its closed-loop ion-beam emitting slit 408. The beam
 IB4 falls onto an annular surface 442 of the object OB2.
 FIG. 8b is a diagram illustrating distribution of ion currents from
 individual ion sources 302 and 402 on the surface of the treated object
 OB2, and FIG. 8c is a diagram illustrating the resulting distribution of
 ion currents obtained from both individual ion sources. In FIGS. 8b and
 8c, the abscissa axis X shows radial positions of the points on the object
 OB2, and the ordinate axis I shows densities of the ion-beam currents on
 the surface of the object OB2. Curve Ia corresponds to the outer annular
 ion-beam source 302, and curve Ib corresponds to the inner annular
 ion-beam source 402. It can be seen from FIGS. 8a and 8b that each curve
 Ia and Ib corresponds to distribution in the radial direction according to
 the normal law, whereas interposition of the beams IB3 and IB4 "smoothens"
 the peaks of the Gaussian curves into a more uniform shape shown in FIG.
 8c. The pattern of the resulting current density curve IR can be adjusted
 by displacing the inner annular ion-beam source 402 with respect to the
 outer annular ion-beam source 302 by means of the adjusting screw 412.
 FIG. 9--Multiple Ion-Beam Assembly with a Plurality of Concentric Ion-Beams
 Having an Oblique Angle to the Surface of the Treated Object
 FIG. 9 illustrates another embodiment of a multiple-beam ion source
 assembly 500 which differs from the embodiment of FIG. 8 mainly in that it
 generates a plurality of concentric ion beams having an oblique angle to
 the surface of the treated object.
 For simplicity of the drawings and explanation, the multiple-beam ion
 source assembly 500 is shown as a combination only of two separate
 ion-beam sources 502 and 602, although a greater amount of the individual
 sources is possible. In the embodiment shown in FIG. 9, positions of both
 ion-beam sources 502 and 602 with respect to each other remain unchanged
 and both sources share the same single magnetic field generating system
 made in the form of a plurality of permanent magnets (only two of which,
 i.e., 504, 506 are shown).
 The multiple-beam ion source assembly 500 has a ring-shaped housing with a
 cylindrical outer surface 510 (which, in fact, may have any convenient
 shape, since it does not effect the principle of the invention and is
 shown cylindrical only for the simplicity) and an upwardly broadening
 tapered central opening. The ring-shaped housing 508 is hollow and its
 interior is sealingly separated by a ring-shaped magnet holder 512 into
 two isolated working chambers 514 and 516. The ring-shaped magnet holder
 512 is made in the form of a tapered toroidal ring fit into the inner
 space of the hollow housing 508. Magnet holder 512 has a plurality of
 uniformly spaced through holes for insertion of permanent magnets 504,
 506, etc. The inner surface of the housing 508 is coated with three
 ring-shaped bodies 518a, 518b, and 518c made in the form of truncated
 conical rings which are attached to the appropriately shaped inner wall of
 the housing 508, e.g., by screws 520, 522, 524, 526, 528, and 530. Rings
 518a, 518b, and 518c have such dimensions and are attached to the housing
 508 so that two closed-loop ion-emitting slits 532 and 534 are formed.
 The working chamber 516 of the ion-beam sources 502 contains a ring-shaped
 anode 536 which is supported inside the working chamber 516 by a ring 540
 of an insulating material such as ceramic. Similarly, the working chamber
 514 of the ion-beam sources 602 contains a ring-shaped anode 536 which is
 supported inside the working chamber 514 by a ring 542 of an insulating
 material such as ceramic. Both anodes are shown as rings of a polygonal
 cross-section suitable for fitting into the inner space of the respective
 working chambers so as to form respective ionization and ion-accelerating
 gaps 544 (in the working chamber 516) and 546 (in the working chamber
 514).
 Reference numerals 548 and 550 designate channels for the supply of working
 gases to respective working chambers 516 and 514 of the individual
 ion-beam sources 502 and 602, respectively. Grounding and electric power
 supply circuits and power sources are not designated, as they are the same
 as in the previous embodiment of the invention.
 An object OB3 is supported in a vacuum chamber 552 which is shown only
 partially.
 In operation, the ion-beam source 502 emits ion beam IB5, and the ion-beam
 source 602 emits the ion-beam IB6 so that both ion beams overlap and
 ensure uniform distribution of the ion-beam current density on the surface
 of an object OB3.
 An advantage of the ion-beam source assembly 500 shown in FIG. 9, as
 compared to the embodiment shown in FIG. 8, is that the ion beams IB5 and
 IB6 impinge the surface of the object OB3 at angles oblique to the surface
 of the object. As has been mentioned above, such direction of the beams
 ensure higher efficiency of sputtering of particles from the surface of
 the object.
 FIG. 10--Ion-Beam Source Assembly with Individual Ion-Beam Sources Having
 Oblique Ion Beams and Positions Adjustable with Respect to Each Other
 FIG. 10 illustrates ion-beam assembly 700 of another embodiment, which, in
 fact, is a combination of the embodiments of FIGS. 8 and 9. In other
 words, this assembly consists of two individual ion-beam sources, i.e., an
 inner ion-beam source 702 and an outer ion-beam source 802. The inner
 ion-beam source 702 is slidingly installed in the central opening 704 of
 the outer ion-beam source 802, and the sliding interface between the
 sources is sealed by a seal ring 706 compressible by the end face of a
 flanged sleeve 708. The sleeve 708 is pressed against the seal ring 706 by
 threading a screw 709 into the threaded opening 710 of the outer ion-beam
 source 802.
 The inner ion-beam source 702 is shifted with respect to the outer ion beam
 source 802 by means of an adjustment screw of the type similar to the case
 of FIG. 8a (not shown in FIG. 10). Each ion-beam source 702 and 802 has an
 individual gas supply channel, an electric power supply system (not
 shown), and a magnetic field generation system. In the inner ion-beam
 source 702 the magnetic field generation system is shown as a plurality
 magnets 716, 718, etc., located on the inner side of the ion-beam source
 702, whereas in the outer ion-beam source 802 the magnetic field
 generation system is shown as a plurality of magnets 816, 818, etc.,
 located on the outer side of the outer ion-beam source 802. The rest of
 the construction is similar to the elements of both embodiments of FIGS. 8
 and 9, and therefore their detailed description is omitted.
 The ion-beam source assembly of FIG. 10 operates in the same manner as the
 devices of the previous embodiments and is characterized by the fact that
 individual ion-beam sources not only have oblique angles of their ion
 beams IB7 and IB8, but also are adjustable with respect to each other,
 thus combining advantages of both previous embodiments.
 Thus it has been shown that the invention provides a multiple-beam ion-beam
 assembly which is simple in construction, efficient in operation, provides
 extremely high uniformity in ion-current density distribution on the
 surface an object being treated, is not limited with regard to the
 dimensions of the objects and allows to adjust the uniformity and
 distribution pattern of ion current on the surface of the object, ensures
 uniformity of treatment on large treated areas, is capable of emitting a
 plurality of ion beams overlapped on the surface of the object, provides
 overlapped ion beams which have angle of incidence on the treated surface
 different from 90.degree., provides adjustment in relative positions of
 different ion beams with respect to each other. The invention also
 provides a method for adjusting uniformity of ion-beam treatment by
 treating the surface of an object simultaneously with a plurality of ion
 beams and by adjusting relative positions of the beams on the treated
 surface. The invention provides an ion-beam source assembly suitable for
 evacuation of gases through the central opening of the ion-beam source.
 Although the invention was shown and described with reference to specific
 embodiments having specific materials and shapes of the parts and units of
 the apparatus and method, it is understood that these embodiments were
 given only as examples and that any modifications and changes are
 possible, provided they do not depart from the scope of the patent claims
 attached below. For example, the ion-beam assembly may comprise a
 combination of sources with ion beams perpendicular and inclined to the
 surface of the object. Three or more than three ion beam sources of the
 same or different types can be used in a single multiple-beam assembly. In
 operation, individual ion-beam sources can be used simultaneously, in
 alternating order, or in any sequence required for the process. The inner
 annular ion-beam source can be stationary and the outer annular ion-beam
 source can be moveable. The mechanism for shifting ion sources with
 respect to each other can be different from the screw-type mechanism. For
 example, it can be a rack-and-pinion mechanism, a hydraulic mechanism, a
 mechanism driven from a stepper-motor, etc. The ion source assembly can be
 used for coating, etching, activation, cleaning, etc.