SE537187C2 - Microwave plasma apparatus amplified by hollow cathode plasma - Google Patents

Abstract

ABSTRACT A magnetron plasma apparatus boosted by hollow cathode plasma includes at leastone electrically connected pair of a first hollow cathode plate (1) and a second hollowcathode plate (2) placed opposite to each other at a separation distance of at least 0.1mm and having an opening following an outer edge of a sputter erosion zone (3) on amagnetron target (4) so that a magnetron magnetic field (5) forms a perpendícularmagnetic component (6) inside a hollow cathode slit (7) between said hollow cathodeplates, Wherein said plates are connected to a first electric power generator (8)together With said magnetron target to generate a magnetically enhanced hollowcathode plasma (9) in at least one of a first Working gas (10) distributed in said hollowcathode slit and a second Working gas (12) admitted outside said slit in contact With amagnetron plasma (11) generated in at least one of said first Working gas and said second Working gas. (Figure 1)

Description

The hollow cathode effect and related high-density hollow cathode plasma was inventedin 1916 by F. Paschen in his spectroscopy study of the plasma emission. Hollow forms of hiselectrodes (short rectangular tubes) for igniting the plasma led to considerably more lightintensity than in simple planar electrodes at the same direct current (dc) power. Later studiesshowed that the principle of this intense discharge is based on geometry of the hollowelectrode, where electrons emitted from one cathode wall interact with an equivalent electricfield with opposite orientation at the opposite inner wall. Depending on gas pressure anddistance between electrode walls the electrons can oscillate between inner walls and enhancesubstantially the ionization of the present gas or vapor. Such ionization based on pendulummotion of electrons is recognized in the literature as “hollow cathode effect” (P.F. Little et al. 1954). The hollow cathode effect can work also in hollow electrode powered by an alternating current (ac). Typical frequency of ac generators for such purpose is between 105 s* and 108 sl,i.e. including the radio frequency (rt) range. The first rf hollow cathode was described in U.S.Patent 4,521,286 to C. M. Horwitz. It was also found that the anode in the rf hollow cathodes isthe plasma itself (a "virtual anode") in contact with the counter electrode (L. Bárdos et al.1988). The hollow cathode effect can be generated also by pulsed dc power.

The hollow cathode effect is not generated in all negatively biased hollow electrodes. Ahollow electrode can differs substantially from real hollow cathodes; unless its geometry isoptimized to enhance the gas ionization inside its hollow part by 1-3 orders of magnitude due tothe hollow cathode effect. For example, a large-diameter cylindrical electrode where the space-charge sheath thickness is much smaller than the electrode diameter cannot serve as a hollowcathode. Even at lower gas pressures when the sheath is wider, the effect may not take placedue to a low number of ionizing collisions. In order to excite this effect at higher pressures, thedistance between walls must be reduced due to short mean free paths of electrons. The distanced between opposite walls of the hollow cathode must be at least twice the thickness of the spacecharge sheath, which depends on the gas pressure p, but also on the frequency and power of thegenerator used. Moreover, the gas pressure p inside the hollow cathode is typically higher thanoutside the hollow cathode due to higher temperature caused by the high density plasma insidethe hollow cathode and due to a pressure gradient fonned in the flowing gas or by evaporated cathode material. Also, presence of magnetic fields can affect the confinement and properties of the hollow cathode plasma. Therefore, different published empirical formulas for estimationsof the optimal product p-d for the hollow cathode effect in in dc hollow cathodes are generallynot very useful.

A number of patents and publications describe so-called “holloW cathode magnetronsputtering” in systems having targets With holloW geometry, mostly cylinder. The target isalways negative in order to attract ions for bombarding and sputtering, hence the term “holloWcathode target” and “holloW cathode magnetron”. However, Without the holloW cathode effect,e. g. in large diameter targets or in magnetic fields parallel With the Walls of the target Whereelectrons are deflected from their oscillations, such systems are not real hollow cathodes. Forexample, in U.S. patent 4,966,677 to H. Aichert et al. a magnetron sputtering apparatus has aholloW cathode target With a cathode base in Which a holloW target With cylindrical sputteringsurface and cylindrical outer surface is disposed. Neither the parallel magnetic field With thetarget nor the target geometry allows for the hollow cathode effect. Similarly, in U.S. patent5,437,778 to V. L. Hedgcoth, a magnetron sputtering system comprises a holloW longitudinalcathode that is either made from or has its interior Wall coated with a material to be sputtered.No holloW cathode effect can be excited in such systems. Similarly, in U.S. patent 6,283,357 toS. Kulkami et al. a plate of sputter target material is bonded to a sheet of cladding material andthen formed into a “holloW cathode” magnetron target. In U.S. patent 6,887,356 to R.B. Ford etal. a sputtering target is claimed preferably exhibiting uniform grain structure and texture atleast on the sidewalls thereof, but no hollow cathode effect is utilized. Another example is PCTPublication WO 2007/130903 to J. K. Kardokus et al., Where methods of forming "holloWcathode" magnetron sputtering targets are claimed. In these targets, a metallic material isprocessed to produce an average grain size of less than or equal to about 30 microns. Suchsputtering target preferably exhibits substantially uniform sputtering erosion, but no holloWcathode effect is utilized. Basic principles of these so-called “holloW cathode magnetrons” areexplained e. g. by D. A. Glocker (SVC Technical Conference Proceedings 1995).

Since its discovery in 1974 in U.S. Patent 4,166,018 to J. S. Chapin (later described by P.S. McLeod et al. 1977 and R. K. Waits 1978), the magnetron sputtering device underwent anumber of improvements aimed mainly to (i) an increase of the target utilization, (ii) apossibility to sputter magnetic targets, (iii) an increase of an ion flux to the substrate, (iv) anincrease of the sputtering rate, (v) an increase of the ionization level in the Whole magnetronplasma. Substantíal progress in tasks (i) and (ii) has been obtained by optimizing geometry and induction of the magnetic tunnels for plasma confinement, particularly by strong pennanent magnets, but also by using hollow targets as explained above. Such efforts also includeddifferent systems with moving magnets and culminated in an arrangement for target utilizationbased on a rotating cylindrical target (U.S. Patent 4,3 56,073 to H. E. McKelvey, filed 1981, anda number of later patents e. g., U.S. Patent Publication 2009/0260983 to M. A. Berníck, filed in2009). A considerable advance in task (iii) was obtained by partial opening of the magnetictunnel from so-called "closed field magnetrons" to so-called "unbalanced magnetrons" (B.Window et al. 1986). This solution allows for an enhanced presence of ions (plasma) close tothe substrate, efficient biasing of the substrates and controlled growth of e.g. very hard filmsand special film textures. It is noteworthy that so far the progress in task (iv), i.e. in increasingthe sputtering rates, has been obtained by increasing target erosion areas, while different arcevaporators rather than any sputtering devices continued to be relied upon as the fastestphysical vapor deposition (PVD) systems. An increase in the ionization of the magnetronplasma (task (v)) can obviously increase the sputtering rate, such as, for example throughadditional ionization by an rf coil (S. M. Rossnagel et al., 1993). However, recent trends arefocused rather to high power impulse magnetron sputtering (HiPlMS) systems disclosed inU.S. Patent 6,296,742 to Kouznetsov (filed in 1997), where the high power peaks increase theionization dramatically. However due to the pulsed power regime, the average coating ratebarely reaches rates comparable to conventional dc magnetrons. Thus, the advantage offavorable coating properties available in high-density plasma of HiPlMS is outweighed by thenecessity of complicated and expensive pulsed power generators and so far also by anunimpressive deposition rates.

A direct method of increasing the sputtering rate by increasing the ionization in themagnetron plasma using the hollow cathode has been patented by J. J. Cuomo et al. in May1986 in U.S. Patent 4,588,490 “Hollow cathode enhanced magnetron sputtering device”.Cuomo et al. combine a hollow cathode as an electron-emitting device with a plasma sputteretching/deposition device such as a magnetron. The hollow cathode is utilized to provideadditional ionization of the working gas during magnetron operation and can provide mainionization of the working gas at low magnetron powers. The hollow cathode utilizes thermionicelectron emission to inject electrons. For this purpose, it comprises a hollow tubular memberconstructed of a refractory metal and a plurality of layers of electron emissive foils. The hollowcathode is powered by a dc power source independent on the magnetron power generator. Inthe preferred configuration, the axis of the cylindrical hollow cathode is parallel with the planarmagnetron target and positioned above the target close to its edge. In order not to impede the magnetron drift current the radial position of the hollow cathode must be such that the magnetic field lines that it intersects travel to the center pole, rather than the bottom of the magneticassembly. Thus the patent discloses an application of a thermionic hollow cathode emittingelectrons, Without electrical or physical impediment of the magnetron drift current, but alsowithout magnetic enhancement of the hollow cathode plasma. The cathode should be fabricatedfrom refractory metals (e.g. Ta). Low-pressure thermionic regimes of the hollow cathode allowfor about 10-times lowering of the magnetron operation pressure, i.e. down to 4 - 6.7 x 102 Pa(0.3 - 0.5 mTorr). This type of use of the hot hollow cathode arcs as an auxiliary ionizer inmagnetrons is described in the literature as "magnetrons with additional gas ionization" (J.Musil et al., 2006, p. 71-72). An important requirement in such processes is that the cathodemetal should not be released and mixed with the sputtered material from the magnetron target.

Another way for involving the hollow cathode plasma in the magnetron discharge isformation of grooves or bores directly in the target in order to excite the hollow cathode effectinside these grooves or bores (J. Musil et al., 2006, pp. 91-93). Such arrangements decrease thenecessary voltage for the magnetron discharge, but the sputtering rate decreases as well.Moreover, the targets have rather complicated forms and as the target is consumed duringmagnetron operation the depths of such hollow cathodes are reduced, requiring changes inpower parameters.

In addition to their ability to generate very high~density plasmas (comparable toHiPIMS), due to the hollow cathode effect, hollow cathodes can be used for both ion sputteringand arc evaporation where the cathode itself is a PVD target. Besides dc power, the hollowcathodes can be advantageously powered by pulsed dc or ac electric power (up to the rf range),and can be used to activate gases for fast plasma-enhanced chemical Vapor deposition (PECVD) regimes. Shapes and dimensions of the cathodes can be designed for a wide range ofworking gas pressures from about 1.33 xl0_2 Pa (10-4 Torr) up to atmospheric and higherpressures. Besides conventional tube shaped cathodes, the pendulum motion of electrons canalso occur between parallel conductive “plates” (With rf power even when plates are coated bydielectrics) to produce dense hollow cathode plasma. Moreover, the hollow cathode effect canbe enhanced and focused in selected areas (hot zones) by suitable magnetic fields, as disclosedin U.S. Pat. 5,908,602 to L. Bárdos et al. (1994). Main part of the magnetic induction lines(induction vector B) in the slit between parallel linear plates of the hollow cathodes should beperpendicular to the cathode plates in order not to deflect electrons and prevent theiroscillations between opposite walls. Electrons moving along vector B are not affected by the magnetic force. However, because the vector E of the electric field in the power circuit is oriented towards the anode, i.e. out of the slit, a considerable disadvantage of the staticmagnetic field is the tendency to force the plasma to one side of the slit depending on theorientation of magnetic induction vector B. The drift Velocity of electrons is given be the vectorproduct (E x B)/B2 (E is the vector of electric field perpendicular to a magnetic inductionvector B). The drift Velocity vector is perpendicular to both vectors E and B. This insufficiencycan be compensated in apparatuses having rotating magnets, as disclosed in U.S. Patent6,351 ,075 to H. Baránková et al., Where magnetic induction vector B across the hollow cathodeslit is changed in both its orientation and amplitude. An obvious disadvantage of such apparatuses is the necessity of mechanical means for driving the magnets.

SUMMARY OF THE INVENTION An object of the present invention is therefore to overcome the above describeddrawbacks and to provide magnetron devices boosted by magnetically enhanced dense hollowcathode plasma generated in a parallel-plate hollow cathode placed inside the magnetic field ofthe magnetron for supplying a dense plasma into the magnetron plasma for substrateprocessing.

The invention provides a magnetron plasma apparatus boosted by hollow cathodeplasma for plasma processing on a substrate in a reactor, comprising a parallel plate hollowcathode with a slit Wherein a hollow cathode effect can be excited, a magnetron sputteringapparatus with a magnetron target, an electric power generator for generation of plasma and amagnetic system generating a magnetron magnetic field giving forrn to an erosion zone on themagnetron target surface and spatial shape of the magnetron plasma.

A first aspect of the invention provides a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing Wherein at least one electrically connected pair ofa first hollow cathode plate and a second hollow cathode plate placed opposite to each other ata separation distance of at least 0.1 mm has an opening following an outer edge of a sputtererosion zone on a magnetron target so that a magnetron magnetic field forms a perpendicularmagnetic induction component inside a hollow cathode slit between said first and second plate.Said pair of plates is connected to a first electric power generator together with said magnetrontarget to generate a magnetically enhanced hollow cathode plasma in at least one of a firstworking gas distributed in said hollow cathode slit and a second working gas admitted outsidesaid slit in contact with a magnetron plasma generated in at least one of said first working gasand said second working gas.

A second aspect of the invention relates to a magnetron plasma apparatus boosted by hollow cathode plasma for plasma processing Wherein said second hollow cathode plate isintegrated in said magnetron target and said hollow cathode slit Where said hollow cathodeplasma is formed is created between said first hollow cathode plate and said magnetron target.

A third aspect of the invention relates to a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing Wherein said pair of said first hollow cathodeplate and said second hollow cathode plate are electrically insulated from said magnetron targetand connected to a second electric power generator.

A fourth aspect of the invention relates to a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing Wherein said magnetically enhanced hollowcathode plasma inside said hollow cathode slit forms a first hot zone on said first cathode plateand a second hot zone on said second hollow cathode plate and said first and second hot zonesevaporate material from said first and second hollow cathode plates.

A fifth aspect of the invention relates to a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing Wherein said magnetron target has cylíndricalfonn in a rotatable target magnetron apparatus and said pair of said first hollow cathode plateand said second hollow cathode plate are mechanically decoupled from said magnetron target.

A sixth aspect of the invention relates to a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing Wherein multiple pairs of said first hollowcathode plate and said second hollow cathode plate have annular circular openings and create ahollow cylíndrical shape of said magnetron target.

A Seventh aspect of the invention relates to a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing Wherein at least one of said first hollow cathodeplate, said second hollow cathode plate and said magnetron target is fabricated at least in somepart from a different material.

An eighth aspect of the invention relates to a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing Wherein said individual pairs of said first andsecond hollow cathode plates are out of parallel With each other or With respect to saidmagnetron target.

A ninth aspect of the invention relates to a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing Wherein said first hollow cathode plate and saidsecond hollow cathode plate have other than planar shapes and compose uneven forms of saidhollow cathode slit.

A tenth aspect of the invention relates to a magnetron plasma apparatus boosted by hollow cathode plasma for plasma processing, Wherein said magnetically enhanced hollow cathode plasma is generated in said first working gas.

Other goals and advantages of the invention will be further understood and appreciatedin conjunction with the following description and accompanying drawings. While the followingdescription may contain specific details describing particular embodiments of the invention,this should not be construed as limitations to the scope of the invention but rather as anexemplification of preferable embodiments. For each aspect of the invention, many Variationsare possible as suggested herein that are known to those of ordinary skill in the art. A variety ofchanges and modifications can be made within the scope of the invention without departing from the spirit thereof.

REFEREN CES F. Paschen, "2. Bohrs Heliumlinien", Annalen der Physik, IV (50) (1916) 901.

P. F. Little and A. vonEngel, "The hollow-cathode effect and the theory of glow discharges",Proc. Royal Society London, A224 (1954) 209-227.

U.S. Patent 4,521 ,286 "Hollow cathode sputter etcher" filed by C. M. Horwitz in March 1984.

L. Bárdos and V. Dusek, "High rate jet plasma-assisted chemical vapour deposition", Thin Solid Films 158 (1988) 265-270.

U.S. patent 4,966,677 “Cathode sputtering apparatus on the rnagnetron principle with a hollowcathode and a cylindrical target” filed by H. Aichert et al. in April 1989.

U.S. patent 5,437,778 “Slotted cylindrical hollow cathode/magnetron sputtering device” filedby V. L. Hedgcoth in November 1993.

U.S. patent 6,283,357 “Fabrication of clad hollow cathode magnetron sputter targets” filed byS. Kulkarni et al. in August 1999 U.S. patent 6,887,356 “Hollow cathode target and methods of making same” filed by R.B. Fordet al. in November 2001 PCT Publication WO 2007/ 130903 “Hollow cathode magnetron sputtering targets and methodsof forming hollow cathode magnetron sputtering targets” filed by J. K. Kardokus et al. in May2006.

D. A. Glocker, “Principles and Applications of Hollow Cathode Magnetron Sputteríng Sources”, 38th Annual SVC Technical Conference Proceedings (1995), pp. 298-302, ISSN0737-5921.

U.S. Patent 4,166,018 "Sputtering process and apparatus" filed by J. S. Chapin in January 1974.

P. S. McLeod and L. D. Hartsough, "High rate sputtering of aluminum for metallization ofintegrated circuits", J. Vac. Sci. Technol. 14 (1) (1977) 263-265.

R. K. Waits, "Planar magnetron sputtering", J. Vac. Sci. Technol. 15 (2) (1978) 179-187.

U.S. Patent 4,356,073 "Magnetron cathode sputtering apparatus" filed by H. E. McKelvey inFebruary 1981.

U.S. Patent Publication 2009/ 0260983 "Cylindrical magnetron" filed by M. A. Bernick in April2009.

B. Window and N. Savvides, "Charged partícle fluxes from planar magnetron sputteríng sources", J. Vac. Sci. Technol. A4 (2) (1986) 196-202.

S. M. Rossnagel and J. Hopwood, "Magnetron sputter deposition With high levels of metalionization", Appl. Phys. Letters 63 (1993) 3285-3287.

US Patent 6,296,742 "Method and apparatus for rnagnetically enhanced sputtering", filed by V.

Kouznetsov in December 1997.

U.S. Patent 4,588,490 “Hollow cathode enhanced magnetron sputtering device” filed by J. J.Cuomo et al. in May 1986 J. Musil, J. Vlcek and P. Baroch, "Magnetron discharges for thin filrns plasma processing",Chapter 3, pp. 67-110, in "Materials Surface Processing by Directed Energy Techniques", ed.by Yves Pauleau, EMRS Book Series, Elsevíer, 2006 U.S. Patent 5,908,602 “Apparatus for generation of a linear arc discharge for plasmaprocessing”, filed by L. Bárdos and H. Baráiiková, priority November 1994.

U.S. Patent 6,35l,075 "Plasma processing apparatus having rotating magnets", filed by H.Baránková and L. Bárdos, priority November 1997.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features of the invention are set forth with particularity in the appendedclaims. A better understanding of the features and advantages of the present invention will beobtained by reference to the following detailed description that sets forth illustrativeembodiments, in which the principles of the invention are utilized, and the accornpanyingdrawings of which: FIG. 1 is a schematic view of a first embodiment and explanation of a secondembodiment according to the present invention showing an example of magnetron plasmaapparatus boosted by hollow cathode plasma for plasma processing on a substrate in a reactorat gas pressure below 6.65 x 103 Pa (50 Torr).

FIG. 2 is a view of magnetized hollow cathode plasma generated by different parallel-plate hollow cathodes in a perpendicular magnetic field explaining preferred embodimentsaccording to the present invention.

FIG. 3 is a schematic view of an example of third embodiment according to the presentinvention, where the parallel plate hollow cathode is electrically insulated from the magnetrontarget.

FIG. 4 is a schematic view of an example of a fourth embodiment according to thepresent invention, where the magnetron target has cylindrical form in a rotatable targetmagnetron apparatus.

FIG. 5 is a schematic view of an example of a fifth embodiment according to thepresent invention, where multiple pairs of hollow cathode plates create a hollow cylindrical magnetron target.

FIG. 6 is a schematic view of two examples of another alternatives according to thepresent invention, Where hollow cathode plates are not in parallel with each other and/or with the magnetron target.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Throughout the drawings, the same reference numbers are used for similar orcorresponding elements.

The invention provides systems and methods for the plasma processing on substrates,such as, for example sputtering and dry etching. The invention provides also systems andmethods with contribution of arc evaporation and/or sputtering of the hollow cathode platematerial into the magnetron plasma and for processing on the substrates. Ionized and activatedparticles in the apparatus according to this invention can be used in various regimes for ionplating, activated reactive evaporation, reactive sputtering, evaporation and combined regimes,etc. It is possible to utilize direct processes incorporating sputtered and evaporated materialsfrom magnetron target and from hollow cathode plates with or without an inert Working gas, aswell as reactive processes incorporating chemical reactions of these materials with activatedreactive Working gases, different chemical precursors, vapors, etc. Various aspects of theinvention described herein may be applied to any of the particular applications set forth belowor in any other type of plasma processing including, but not limited to combinations of severalapparatuses according to this invention, or combinations with other types of plasma systems,like microwave plasma systems, arc evaporators, laser plasma sources, etc. It shall be alsounderstood that different aspects of the invention can be appreciated individually, collectively,or in combination with each other.

Referring to FIG. 1, a first embodiment of a magnetron plasma apparatus boosted byhollow cathode plasma for plasma processing on a substrate in a reactor according to thepresent invention will be described. In practically implemented embodiments gas pressuresbelow about 6.65 xl03 Pa (50 Torr) can be used. In the present embodiment, at least oneelectrically connected pair of a first hollow cathode plate 1 and a second hollow cathode plate 2placed parallel and opposite to each other at a separation distance of 0.5 mm between them hasan opening along an outer edge of a sputter erosion zone 3 on a magnetron target 4. Theseparation of 0.5 mm is considered as a typical practical lowest limit, even if separationdistances down to about 0.1 mm would be possible to make the apparatus operable. The pair ofcathode plates is placed so that a magnetron magnetic field 5 forms a perpendicular magnetic induction component 6, in this embodiment of at least 102 Tesla, inside a hollow cathode slit 7 11 between plates 1 and 2, and the pair of plates 1 and 2 is electrically connected to a first electricpower generator 8 together with target 4 to generate a magnetically enhanced hollow cathodeplasma 9 in a first working gas 10 distributed in the hollow cathode slit 7 in contact with amagnetron plasma 11 generated in the first working gas 10 and in a second working gas 12admitted outside slit 7. Thus the apparatus according to the present embodiment utilizes themagnetic field 5 of the magnetron for generation of the magnetically enhanced hollow cathodeplasma 9 inside slit 7. For further improved performance of the magnetically enhanced hollowcathode plasma 9 the depth of the slit 7 given by the widths of plate 1 and plate 2 should be atleast of twice the distance between plate 1 and 2. The magnetron magnetic field 5 can havedifferent shapes. A typical tunnel-Shaped part of the field confines in the present embodimentthe plasma above the target and defines the shape of the sputter erosion zone 3 on the target 4.The magnetic induction at the outer edge of the erosion zone 3 is close to one pole of amagnetron magnetic system 17 and can in the present embodiment generate the perpendicularmagnetic induction component 6 of at least 10"2 Tesla inside the hollow cathode slit 7 to formthe magnetically enhanced hollow cathode plasma 9. In so-called unbalanced magnetrons, themagnetic system 17 contains also means for partial unbalancing of the tunnel magnetic field toallow more ions to escape the magnetic tunnel and travel to a substrate 19. The unbalancing ofthe field can be provided also without use of the additional means by positioning of magnets inthe system 17 under the target 4. Depending on power of the electric generator 8, an ionbombardment inside the hollow cathode slit 7 from the magnetically enhanced hollow cathodeplasma can form first and second hot zones 14 and 15 at respective cathode plates 1 and 2. Thetemperature of the respective hot zones depends on the cooling effect from the magnetrontarget, thickness of the respective plates, as well as on the thermal conductivity of the plates.Therefore, in various embodiments, the hot zone 15 at the second plate 2 at the magnetrontarget can acquire lower temperature than the first hot zone 14 at the first plate 1. Themagnetically enhanced hollow cathode plasma 9 expands from the slit 7 and interacts with themagnetron plasma 11 to compose a resulting processing plasma 18 that can contain at least oneof ionized material of the magnetron target 4, ionized first working gas 10, ionized secondworking gas 12 and ionized sputtered and/or evaporated material particles from the hollowcathode plates 1 and 2. In different embodiment, the resulting processing plasma can containany combination or subset of these components. In a typical embodiment, the resultingprocessing plasma 18 comprises ionized material of the magnetron target 4, ionized firstworking gas 10 and ionized second working gas 12. In the particular embodiment of Fig. l, the magnetically enhanced hollow cathode plasma ca be generated in the first Working gas. ln other 12 embodiments, the rnagnetically enhanced hollow cathode plasma is generated in the secondworking gas. The working gases may also in different embodiment be composed from severalcomponents. In a typical embodiment, the first hollow cathode plate 1, the second hollowcathode plate 2 and the magnetron target 4 can be fabricated in the same material. However, inother embodiments, at least one of the first hollow cathode plate 1, the second hollow cathodeplate 2 and the magnetron target 4 can be fabricated at least in some part from a differentmaterial. In other words, the first hollow cathode plate 1, the second hollow cathode plate 2and/or the magnetron target 4 may be composed of parts of different materials, or one or two ofthe first hollow cathode plate 1, the second hollow cathode plate 2 and/or the magnetron target4 may be composed of a different material compared to the other ones. In such a way, differentcompositions of the resulting processing plasma 18 can be achieved. Thus the processingplasma 18 contains high density of ions for plasma processing on the substrate 19. If suitable ina simple modification of the first embodiment in FIG. 1 (not shown) the second hollow cathodeplate 2 can be integrated directly into the magnetron target 4. However in many practical casesthe second hollow cathode plate 2 can be used for a mechanical holding of the magnetron target4 on a cooled holder (not shown) of the target 4. In such embodiments, there is a directmechanical attachment between the second hollow cathode plate 2 and the target 4.

FIG. 2 is a view of magnetized hollow cathode plasma generated by different parallel-plate hollow cathodes in a perpendicular magnetic field. It is shown that the perpendicularmagnetic induction component 6 in a slit 7 of a parallel-plate hollow cathode composed of plate1 (shown in a semi-transparent manner) and plate 2, described for example in U.S. Patents5,908,602 and 6,35l,075, causes side drifts of the magnetically enhanced hollow cathodeplasma 9 depending on orientation of the component 6. If the plates form a closedcircumferential shape of the hollow cathode slit 7 the magnetically enhanced hollow cathodeplasma 9 has a uniform circumferential shape independent on orientation of the perpendicularcomponent 6, e.g. shape of a circle or a racetrack, as shown in FIG. 2. This property allows forutilization of the magnetron magnetic field 5 and incorporation of these circumferentialparallel-plate hollow cathodes with the magnetron target 4 according to the present invention,as shown in FIG. 1. Thus the apparatus according to the invention can be applied to arbitrary forms of the planar magnetrons (Circular, rectangular triangular, polygonal, etc.).

EXAMPLESReferring to FIG. 3, a schematic view of an example of a third embodiment according to the present invention is explained. In this embodiment, at least one electrically connected 13 pair of the first hollow cathode plate 1 and the second hollow cathode plate 2 is electricallyinsulated from the magnetron target 4, for example by an insulator 20. Plates 1 and 2 are placedopposite to each other at a separation distance of at least 0.5 mm and have an openingfollowing an outer edge of the sputter erosion zone 3 on a magnetron target 4 so that themagnetron magnetic field 5 forms a perpendicular magnetic induction component 6 of at leastl0'2 Tesla inside a hollow cathode slit 7 between plates 1 and 2. The plates 1 and 2 areelectrically connected to a second electric power generator 13 independent from the firstelectric power generator 8 powering the magnetron target 4. The magnetically enhanced hollowcathode plasma 9 is generated in a first working gas 10 distributed in the hollow cathode slit 7in contact with a magnetron plasma 11 generated in the first working gas 10 and in a secondworking gas 12 admitted outside slit 7. Generator 13 supplies enough power for an ionbombardment inside the hollow cathode slit 7 by the magnetically enhanced hollow cathodeplasma 9 which forms first and second hot zones 14 and 15 at respective cathode plates 1 and 2.An advantage of this embodiment is an independent control of the magnetron plasma 11 andthe magnetically enhanced hollow cathode plasma 9 and consequently respective yields ofsputtered and evaporated materials in the resulting processing plasma 18 at the substrate 19.

Referring to FIG. 4, a schematic view of an example of a fourth embodiment accordingto the present invention is explained. In this embodiment the magnetron target 4 has cylindricalform in a rotatable target magnetron apparatus and the pair of the first hollow cathode plate 1and second hollow cathode plate 2 is mechanically decoupled from rotating magnetron target 4.In this embodiment, the magnetically enhanced hollow cathode plasma 9 can be generated bythe second electric power generator 13 independently from the magnetron target 4, but alsotogether with the magnetron target from the same first electric power generator 8. ln thisschematic view all reference numbers are listed in the LIST OF THE USED REFERENCENUMBERS below. i Referring to FIG. 5 a schematic view of an example of a fourth embodiment accordingto the present invention is explained. In this embodiment multiple pairs of the first hollowcathode plate 1 and second hollow cathode plate 2 have annular circular openings and create ahollow cylindrical magnetron target 4 wherein the second hollow cathode plate 2 is the firsthollow cathode plate 1 of the adjacent pair of plates. The target is electrically connected to thefirst electric power generator 8 and is electrically insulated from the anode 16 by an insulator20. Anode 16 locks the target and the insulator 20 on the sides by side closures 21. In thisembodiment the first working gas 10 is distributed into all individual hollow cathode slits 7 by at least one gas distributor channel 22. A feasible modification of this embodiment (not shown) 14 is a multiple magnetron target 4 consisting of multiple target segments each containing one ormore pairs of the first hollow cathode plate 1 and second hollow cathode plate 2, wherein eachtarget segrnent is encapsulated in a corresponding segment of the insulator 20 and locked into acorresponding segment of the anode 16 with closures 21. In this modification, a common firstelectric power generator 8 can be used simultaneously in all parallel segrnents, or multiplegenerators can be used for powering of each target segment separately. In this embodiment theapparatus is suitable for processing of axially positioned cylindrical or round types of substrate19. In this schematíc view all reference numbers are listed in the LIST OF THE USEDREFERENCE NUMBERS below.

Referring to FIG. 6, schematíc views of examples of still more embodiments accordingto the present invention are explained. In these examples, the pairs of plates 1 and 2 are not inparallel with the magnetron target 4 and can form an angle 23 with respect to the target 4.Angle 23 can have also an opposite orientation to that shown in FIG. 6. Also, hollow cathodeplates 1 and 2 may not be positioned in parallel with each other and can fonn an angle 24 inboth orientations, where the hollow cathode slit 7 is either more opened or more closed towards the target 4. The options explained schematically in Fig. 6 can be used in different combinations Anotheríoption is that the first hollow cathode plate 1 and the second hollow cathode plate 2 have other than planar shapes and compose uneven forms of the hollow cathodeslit 7. Still other options are based on different combinations of working gases, as well as onpossibility to operate the magnetically enhanced hollow cathode plasma 9 in the slit 7 withoutuse of the first working gas 10 (the inlet of the gas 10 may be closed) and only in the secondworking gas 12. Thus the magnetically enhanced hollow cathode plasma 9 and/or themagnetron plasma 11 can be generated only in the first working gas 10 or only in the secondworking gas 12 where any of the working gases 10 and 12 can be composed from severalcomponents. In this schematíc view all reference numbers are listed in the LIST OF THEUSED REFERENCE NUMBERS below.

High-density plasmas generated by hollow cathodes in accordance with the presentinvention can advantageously be used in processing procedures requiring very dense plasmas,like in the HiPIMS. However, the plasma generated by the apparatus according to the presentinvention brings more advantages, for example possibility of high processing and depositionrates, high activation degree, rapid plasma chemical reactions and generation of radicals, highrate etching, an improved stability and control of plasma processes, an efficient control ofproperties of deposited films including new film properties like superhard or superelastic films, etc. The plasma processing according to the present invention enables also different hybrid processes when combining for example sputtering and evaporation regimes, PE CVD andsputtering and/or evaporation regimes, incorporation of particles from different materials,deposition of different composite films, etc. The invention may offer significant advantageswith respect to HiPIMS, including, but not limited to possibility of continuous processing anduse of more simple and cheaper power generators, such as for example dc, pulsed dc, ac and rf.Moreover, as the HiPIlVIS represents a generation mode of the magnetron plasma rather thanthe magnetron itself the magnetron plasma apparatus according to the present invention can beused also in HiPlMS regimes. A further advantage of different embodiments of the apparatusaccording to this invention is capability of Operating at relatively high pressures as compared totypical pressures of 0.13 - 1.3 Pa (l - 10 mTorr) for magnetron sputtering or etching. This isenabled by the magnetically enhanced hollow cathodes, which can Work at high pressures andsupply high-density plasma into the magnetron. It is necessary, however, to adjust the geometryof the hollow cathode and the whole system, the position of the substrate and the gas flow ratesaccording to the required gas pressure due to differences in the mean free paths of plasmaparticles.

While preferable embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided as an example only. Numerous Variations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understood that various alternativesto the embodiments of the invention described herein could be employed in practicing theinvention. It is intended that the following claims define the scope of the invention and thatmethods and structures within the scope of these claims and their equivalents be covered thereby. 16 LIST OF THE USED REFERENCE NUMBERS 1 ~ first cathode plate 2 - second cathode plate 3 ~ sputter erosion zone 4 - magnetron target 5 ~ magnetic ñeld 6 - perpendicular magnetic induction component7 ~ hollow cathode slit 8 - first electric power generator 9 - magnetically enhanced hollow cathode plasma10 - first Working gas 11 - magnetron plasma 12 - second working gas 13 - second electric power generator 14 - first hot zone 15 - second hot zone 16 - anode 17 - magnetic system 18 ~ processing plasma 19 - substrate 20 - insulator 21 - anode side closures 22 - gas distributor channel 23 - angle between hollow cathode plates 1 and 2 and the magnetron target 4 24 - angle between cathode plate 1 and 2

Claims (10)

What is claimed is:

1. A magnetron plasma apparatus boosted by hollow cathode plasma for plasmaprocessing on a substrate in a reactor, comprising a parallel plate hollow cathode with a slitwherein a hollow cathode effect can be excited, magnetron sputtering apparatus With amagnetron target, an electric power generator for generation of plasma and a magnetic systemgenerating a magnetron magnetic field giving form to an erosion zone on the magnetron targetsurface and spatial shape of the magnetron plasma, Wherein at least one electrically connected pair of a first hollow cathode plate (1) and a secondhollow cathode plate (2) placed opposite to each other at a separation distance of at least 0.1mm has an opening following an outer edge of a sputter erosion zone (3) on magnetron target(4) so that a magnetron magnetic field (5) forms a perpendicular magnetic induction component(6) inside a hollow cathode slit (7) between said plates (1) and (2); said pair of plates (1) and (2) is connected to a first electric power generator (8) togetherwith said target (4) to generate a magnetically enhanced hollow cathode plasma (9) in at leastone of a first working gas (10) distributed in said hollow cathode slit (7) and a second workinggas (12) admitted outside said slit (7) in contact with a magnetron plasma (11) generated in at least one of said first working gas (10) and said second working gas (12).

2. The apparatus according to claim 1, characterized in that said second hollow cathodeplate (2) is integrated in said magnetron target (4) and said hollow cathode slit (7) where saidhollow cathode plasma (9) is formed is created between said first hollow cathode plate (1) and said target (4).

3. The apparatus according to claiml, characterized in that said pair of said first hollowcathode plate (1) and said second hollow cathode plate (2) are electrically insulated from said magnetron target (4) and connected to a second electric power generator (13).

4. The apparatus according to any of the claims 1 to 3, characterized in that saidmagnetically enhanced hollow cathode plasma (9) inside said hollow cathode slit (7) forms afirst hot zone (14) on said first cathode plate (1) and a second hot zone (15) on said second hollow cathode plate (2) and said hot zones (14) and (15) evaporate material from said hollow 18 cathode plates ( 1) and (2).

5. The apparatus according to any of the preceding claims, characterized in that saidmagnetron target (4) has cylindrical form in a rotatable target magnetron apparatus and saidpair of said first hollow cathode plate (1) and said second hollow cathode plate (2) are mechanically decoupled from said magnetron target (4).

6. The apparatus according to any of the claims l - 4, characterized in that multiple pairsof said first hollow cathode plate (1) and said second hollow cathode plate (2) have annular circular openings and create a hollow cylindrical shape of said magnetron target (4).

7. The apparatus according to any of the preceding claims, characterized in that at leastone of said first hollow cathode plate (1), said second hollow cathode plate (2) and said magnetron target (4) is fabricated at least in some part from a different material.

8. The apparatus according to any preceding claims characterized in that said individualpairs of said hollow cathode plates (1) and (2) are out of parallel With each other or With respect to said magnetron target (4).

9. The apparatus according to any preceding claims characterized in that said first hollowcathode plate (1) and said second hollow cathode plate (2) have other than planar shapes and compose uneven forms of said hollow cathode slit (7).

10. The apparatus according to any preceding claims characterized in that said magnetically enhanced hollow cathode plasma (9) is generated in said first working gas (10).