CA1153733A - Magnetically enhanced sputtering device including means for sputtering magnetically permeable targets - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Magnetically enhanced sputtering device including first and second magnets disposed adjacent opposite sides of the target where one of the magnets projects a field over the target surface and through the magnet on the other side, the magnets preferably comprising contacting layers of oriented ferrite impregnated tape. Included is magnetic structure for establishing a magnetic bridge circuit for sputtering magnetically permeable targets. Also included is magnetic structure where a third magnet is disposed beneath the cathode and the fields generated by the first and second magnets pass through the third magnet to enhance the parallelism of the field with respect to the target.

Description

'7~

Il BACKGROUND OF THE INVENTION
I T.-lis i..ver.~ion rela.es .o ra~n2.ically enhanced sputter-ing GeViCeS Gr.~ in particulzr, to i~r~ved r,ea..s Lor imple-~lr.e.l~ing t..e ll,Gsnet c er.hancer.ier,~ Gf such cevices.
5 1I Ge.,erally, crossed mac,.,etic GnL` elec_ric fieias are es~ab-~¦iished in sLtch cev c2s. The elec~ric fieid e~,encs be~teen an zrlo~e (~;.icr, ~cy ~e the cha~.ber wa~ ) and c .arseL, ~QiC~.
! is ~ypically at c~tho~e potent~al ani~ ~n circui~ with the llanGce, w;~tereby elecL.ons are removed rom the ~ar~et. The ¦¦remGv2d elect-cns ioniz~ gas particles to .~ereby produce ¦la plasl..c. The ions are zccel2ratea to ~ne ~a-get ~o dislocg2 ato~.;s GL^ ~he .arSeL ma~erial. The cisloc~ed ~ar~e~ material ther. ty~ically de osi~s as a coctins --iim on alt ob,ecL ~o b2 Icoz.ed. It o-d2r LO ir~p-rove the s~u~er-n~ ~a~ê a~ iow sas '~ I pressur2s, ~n~ c-ossecl ~ia~,te~ic 'ie d -s Jrovided LO le-t~neln ~ le ?a~n Lrave'led ~y the rel.ioved electrcns a.rlc -~:rnts e.,:tance ¦ Lr~2 ior.izir.~ e.liciency o,~ the eleclL~-o~._. ~-. G~r~er .o fur.:her ~ JrGVe ~h2 _cr.iz'n~ eL-iclency o ~he 2 1 eC~:rO ~S r a cios~c ',1 P1aS..-C 'OGr i5 r~referz~ es Labl' 5;^ê_ 50 _hG t G ~.C' ê''ec~
'icurreA.~ circu aLes around .he loop.
! T ê ivn'~-ltg elec.rons .enc ~o co-cê.~ ê _r. ,he r2gior.s ~ :^ere ~hê ..z~.^.2~'c liAnes of '-orce ar2 parc'7~-, _o ...e iarseL
¦Is~r cce. Ir. prio~ c;r~ cl2vices ~,thich c~ploy c closed plzsl.â
,~ 1GO~ ~ ~he -ec i~r. GVCr Wh~ C~t the . C~ - .2_iC I1r.25 Of 'orce c~e ?~ _ê_ .o .:.2 ~ ~ f 5e L S ~ C C 2 L ~ . C S ~ O ~ 2 ; ~ . ~1~ r 5 .1 C 1 1 L i ~ U S
-c.o.~... ..or.-u-.i~~;-~'Ly o_ .zrcêL ercsion a-.a -'-.h bitins _ - ê - e ~ c ~ _ _ ~`. o .' '1 _ c r e r s ~ u . L e-- r c . 2 s .
1' .

, .

BRIEF DESCR:~PTION OF TH~ DRAWING

Figures lA and lB are perspective and cross-sectional views of an earlier, non-published embodiment designed by applican-t for producing a uniform, parallel magnetic field with respect to a targe-t surface.
Figures 2 and 3 are perspective and cross-sectional views of an illustrative embodiment of the invention where magnetic blocks are employed to produce a uniform magnetic field parallel to a target surface.
Figures 4A and 4B are cross-sectional and perspective views of a further illustrative embodiment of the invention where magnetic loops or rings are employed.
Figure 5 is a further illustrative embodiment of the invention for sputtering small targets.
Figures 6 and 6A are further illustrative embodiments of the invention where the orientation of the flux within the field establishing magnets is different from that in Figure 3.
Figure 7 is a diagram illustrating the difficulty associ-ated with establishing an appropriate crossed electric-magnetic field over a magnetically permeable target.
Figure 8A is a further illustrative embodiment of theinvention for sputtering magnetically permeable materials.
Figure 8B is an illustration of electrical analog of the embodiment of Figure 8A.
Figures 8C - 8G are illustrative embodiments of magnetic bridges for use in the present invention.

Figures 9A and 9s are plan and cross-sec-tional views of a further lllustrative embodiment of the invention where the magnetic struc-ture is generally disposed within the cathode.
Figure 10 is a cross-sectional view of a further illustra-tive e~bodiment of the invention where a non-sputtering plasma return path is provided over the target surface.
Figures llA and llB are plan and cross-sectional views of a further illustrative embodiment of the inventlon where co-planar loops are employed.
Figure 12 is a cross-sectional view of a further illus-trative embodiment of the invention where auxiliary magnets are used to strengthen the field.
Figure 13 is a further illustrative embodiment of the invention.
Figure 13 appears below Figure 10 on the fourth sheet of drawings.
Figures lA and lB illustrate one technique which was attempted (but not published) by applicant to provide a uniform, parallel magnetic field with respect to the target surface. In these Figures, the target 10 has a configuration of an endless belt and may be provided on a cooling system 12 having a rectangular, ring-like configuration as indicated in Figure lB. Magnets 14 are provided inside the belt-like target 10, all of which are polarized in the direction indicated in Figure lA. Pole plates 16 are connected to opposite ends of the magnets where one of the plates 16 is shown in disassembled relation in Figure lB.

t - 4 -, ~, . . .

~ he resultiny plasma is trappe~ such that it circulates in the oval, belt-like pattern, sputteriny from the top, bottom, and ends of the target. ~he magnetic field seems to emanate from the steel pole plates as if the magnets were adjacen-t the target. The erosion pattern is deepest in the center, and falls to zero at the edges. This is at least partially a function of electrostatic effects and parallel magnetic field intensity. The steel pole plates are able to radiate lines of force into space such that as one moves perpendicular to the pole plates and parallel to the target, the flux is strongly a function of distance from the pole plates. Thus, the field is non-uniform in this respect.
It is thus one primary object of this invention to provide a solution to the above problem and, in particular, an improved magnetically enhanced sputtering device and methods employing a uniform magnetic field which is parallel with respect to a large portion of the target surface.
It is another primary object of this invention to provide an improved magnetically enhanced sputtering device and method for sputtering maynetically permeable targets which may be relatively thick.
Other objects include the provision of (a) very high percentage target utilization while maintaining high sputter rates; (b) very high power densities for very high rates; and (c) smaller target areas than prevlously practical for mini-mizing target inventory of expensive materials.
Other objects and advantages of this invention will be apparent from a reading of the following specification and claims taken with the drawing.

~ , ~

DETAILED DESCRIPTION OF THE PREFERRED EMBODIM5~TS
F THE INVENTION
Reference should be made to the drawing where like reer-ence numerals refer to like parts.
In Figures 2 and 3 a magnetic Lield is generated by block magnets 20 and 22, each o~ which may comprise a plurality or stack o overlapping strips 24 where each strip preferably comprises oriented errite impregnated plastic or rubber tapes such as those manufactured and designated as P~-1.4H by the Minnesota Mining and Manuacturing Co. There is preferably no magnetic connection between the outboard ends 28 and 30 o the magnets. The field between ~he faces 34 and 36 of the block magnets is strongex than i a steel l'UII 32 (shown dotted) were connected between the outboard ends~ The field is al50 unique in that it is almost perfectly constant rom the center of face 34 perpendicularly throuyh space to the center of face 36.
In Figure 3 it can be seen the lines of ~orce that connect ~aces 34 and 36 are very nearly parallel and are substantially, totally encased between the portions of the ~ield that are returning to the opposite ends of the respective block ma~nets.
Thus there is essentially a fixed number of lines o force per unit area in subs~antially all of the center space. The result is an extremely uniform field there. Once this band of flux is trapped, it is possible to increase ox decrease the dis- ¦
tance between magnets 20 and 22 without changing the flux density (within limits). The magnets can even be tipped or bent so the center pattern arches up or down and the flux does not cha e slgnificantly. It appeaxs the protec~ive !

~,, ~

return flux loops may make this phenomenon possible. Separate auxiliary magnets may also be employed, as will be discussed in more detail hereinafter with respec-t -to Figure 12, making more of the central magnet Elux available to the parallel beam. The trapped band of magnetic flux thus permits the realization of unique behavior.
A unidirectional plasma stream may be established across the surface of target 37. Thus, the central target area of limited erosion, which tends to occur in the prior art as discussed with respect to Figures 1-3 in co-pendingCanadian patent application 325,126 (Morrison, filed 9 April, 1979) is eliminated. Also it is possible to eliminate corners which fail to erode due to the curving plasma stream not being directable into a corner. Very near 50% target utilization is typically realized without the parallel uniform field provision of the present invention. With this provision, the utilization becomes strongly dependent upon the target hold-down method, etc., and has practical values as high as 90%. Target 37 can be fed up into the parallel beam region and all but the clamped part is used. The clamp can provide cooling, etc.
Instead of block magnets 20 and 22, loop magnets 38 and 40 can be used as shown in Figures 4A and 4B. This permits the magnets 38, 40 to be slipped over cooled target 42 or -the target to be slipped through the magnets. As target 42 is eroded to the limit, it may be relatively slipped through the magnet to expose fresh target as indicated in Figure 4A.
This permits very near 100% target utilization. Further, target may be provided on the bottom of cooling plate 44. The loops 38 and 40 would then provide both top and bottom sputtering for ~3~33 higher production rates and efficiency. The power efficienc~
would then be typically 2 to 4 times that o a conventional magnetron cathode. ~n embodiments where target is provided both at 42 and on ~he bottom of cooling plate 44, the cooling plate, for purposes of the following claims, may also be con-sidered part of the cathode.
If only the top face is sputtered as in Figures 4A and 4B, conventional power eficiency can still be attained. Sputter- ¦
ing of magnet loops 38 and 40 is prevented b~ shields 48, which are maintained at anode potential. Confinement o electrons within the plasma is assisted by shield 54, which is maintained at cathode potential where the orientation of the magnetic lines of force with respect to the surface of shield 54 is preferably 9Q or more. Sputtering of the upper inside faces 56 and 58 of magnets and of shield 54 is substantially avoided due to the perpendicular orientation of the lines of orce with respect to these surfaces. ~node 60 establishes the requisite electric field at the return portion of the plasma loop while the chamber wall ~not shown) or some other anode means above target 42 may be employed to establish the requisite electrical field above target 42, where anode 60 may be a rod as shown in Figure 4A!
GeneralIy speaking, reference has been made above to the divisivn o~ the cathode s~ructure into sputtering and non-sputterins sections. It can be defined to a reaso~able degree ~5 the situations where sputtering does not occur to meaninyful extent even in the presence of an intense plasma discharge.
First, in the absence of momentum and cen~riical effects, spu~ter ing will not usually extend beyond the areas where lines of force lorm an angle of about 30 or more with the target surface.

373~

¦The foregoing is discussed in the aforementioned co-pendin~
application where, for example, the use of such angles permits the maintenance of intense discharges without sputtering an angled element. Properly shaped target clamp rings are an example of such elements.
Second, physical-separation between the plasma and the target surface can provide very delicate separation between sputtering and non-sputtering plasmas. Such a separation I is not usually achieved in magnetron technology such as that shown in Figures 1-3 of the aforementioned co-pending applica-tions, in that the trapping magnetic field extends up from the target surface, the field becoming ever stron~er as one moves closer to the target surface. When that relationship with the surface is avoided and a magnetic field parallel to the target Isurface is provided in accordance with the present invention so that its maximum intensity appropriately separates from the target surface, it is possible to approach non-sputtering conditions. ~he plasma tends to center in the intense ield region. I the mean free path of ions from thc plasma ~hat

2~ are accelerated toward the ~arget is short com~ared with the distance to the target, only rather low energy ions will reach the target surface. The ions will have lost most of their voltage caused energy through repeated collisions. When the energy of these ions is below the sputter threshold value, no sputtering can occur. To sput~er, individual bombarding ions must possess sufficient energy to knock individual target atoms out of the target structure. When they fall below ~his energy, they ~rovide only a heating action and possib1y an ~1 i~ , ~3l53~3 1l increase in the electron emission.
In an intentionally non-sput~ering area, an attempt should be made to (a) keep all cathode potential items at 90 or more with respect to the lines of force such as illustrated at shield 54 of Figure 4A and (b) provide a large separation relative to the mean free ion path of items not at these anyles with respect \ \ to the lines of force. Providing higher gas pressures in these areas also makes the distances less critical. In tunnel systems, such as that of Figure 4A where the plasma passes over the top and under the bottom of the target, this can be achieved by in-troducing the sputter gas via the tunnel as illustrated in Figure ¦ 4A where gas source 61 is connected to the tunnel 63 by line 65, the gas being removed by pump 67 which is connected to the space over target 42. As is conventional, source 61 and pump 67 are located outside the vacuum chamber containing the structure of Figure 4A. The introduction of sputter gas into the tunnel gives hiyh tunnel pressure while permitting much lower pressures at the sputter areas of target 42. Fur~her, this ~urther inhibits con-tamination of the plasma with non-target ions during its passage through the tunnel as it returns to ~he target surface.
In accordance with a further aspect o~ the invention, it is possible to narrow the target area as in Figure 5 such that small inventories of expensive target materials may be main-I tained. Thus, a small volume ~ar~et 62 may be clamped as shown in Figure 5 by a cooling member 64 to e~fect sputtering thereof, the magnetic lines of force being substantially parallel over t'ne entire surface of the small target and cathode potential surfaces 69 and 71 being provided to assist in plasma conLine~
ment.

3~733 Magnet orientation can be changed 90 adjacent target 70 so that the field projects out OL one end o magnet 66 and thence ¦
over the target to maynet 68, as shown in Figure 6. The orienta-tion of the magnets may also be changed to angles between those !shown in Figures 5 and 6. Even tipping outboard (where the separ-ation between the upper portions of loop magnets 66 and 62 is less¦
than that between the lower portions thereof) can provide some effective ield projection. In act, any of the field projection methods of ~igures 2-6 can be employed without concern about cen- ¦
ter void problems of the type hereinbe~ore discussed With respect to Figures 1-3 of the above mentioned co~pending applications.
Thus, by changing the direction of the rotational axis, this concern has been eliminated~ It is also possible to remain uniplanar with an intentional center void area.
Further, as can be seen in Figure 6~, the loop magnets 66 and 68 of Figure 6 can be bent 90, for example, as indicated at 71 and 73 whereby target 70 can be moved under the control of mov-ing means 75 through the sputtering plasma indicated at 77. The return plasma inaicated at 79 is removed from the path traversed by the target and hence does not sputter the target, This is in contradistinction to the embodiment of Figure 6 where the target should not extend below the loops 66 and 68 into the return plasma lest the target be sputtered both by the sputtering portion o~ the plasma above the loops 66 and 68 and by the return plasma.
Reference should now be made to ~igure 7 regarding mag-netically enhanced sputtering o magnetically permeable materials I
in accordance with a very important further aspect of the in- ¦
vention. When a permeable target is placed over the conventional magnetic structures, the preferential flux ~low is via the target, ~;37'3~3 i~ not being projecLed through and above the tar~et to provide ~he required flu~ pa~tern above it. Llmited spu~ter rates have been obtained by using very thin -target,~aterial~and~or placing this in only the "race track" area of the target, which is not an ade~uate solution to the problem.
If it is assumed the structure in Figure 6 is fitted with a permeable target 72, the ~ield picture shown in ~igure 7 re-sults. The high permeability of target 72 cau~es the flux that previously arched over the target area to be drawn into the tar-get. The parallel field at the cxitical height of 1/8 - 3~4"
above ~he target surface is almost zero rather than the 80-100 gauss level typically needed for support of a plasma. Thus the embodiments illustrated thus far are not di,ectly applicable to the sputtering at high power levels of high permeability materials .
The permeability of target 72 may be seen as conductance for magnetic lines of force, Flux only goes where it wants to go - or is ~orced to go. The question thus arises as to how the environs o high permeability target 42 can be changed such that the ~lux that must be above it cannot enter the target. The classical terminology of magnetics is less familiar than that o~
electxicity. ~ence, there is illustrated in Figure 8B an elec-trical analog of a magnetic solution to the problem shown in Figure 8A, If it were an electrical field that target 72 were to be inserted into withQut substantially disturbing it, the potential o the target would have to be adjusted to be the same as that of the field at the position the target was to occupyf It is thereore necessary to place the target at a "magnetic potential" the same as that midway between the north pole magnet 66 and the south pole of magnet 68. This is effected by magnets ~ 3 l l 74 and 76 which stop ~he flux flow thxough the "meter" (that is, target 72) in the bridge circuit where the magnets are prefer-ably connected by pole plates 75 and 77. A flux ield is thus eskablished above permeable targek 72 that is almost totally oblivious to the target's presence - just as balanced bridge 78 of Figure 8B is oblivious to the presence o meter 80.
This above may be also viewed as removing the ~lux paths from point A of magnet 66 to point B of magnet 74 and from . point C of magnet 68 to point D OL magneJL 76, just as creating le~ual electrical potentials at E and F in bridge 80 prevents current flow through meter 80. There is some small difference in "magnetic potential" over the width o target 72 so that the field shape is not quite perfect over the target, but the improvement brought about by this magnetic bridge is such that sputtering o~ magnetically permeable materials becomes practicable.
There are many possible magnet con~igurations for the bridge o~ Figure 8A. It is only necessary that the tendency ~or flux to flow through the target be substantially reduced.
2~ It should also be noted lower magnets 74 and 76 can provide the return plasma path rather than be part of the figure of rota- ¦
tion and extension shown in Figure 8A. Configurations of various ¦
bracXet-like combinations as shown in Figures 8C-8G can serve this double function or be extended and rotated as in Figure 8A -or involve tunnel returns, e~c. Note that the pole piece of such embodiments as that of Figure 8C may be eliminated whereby lll I

¦¦the facing south poles of ma~nets 6~ and 74 would be held in ¦Iclose proximity to one another or in contacting relationship.
¦~A1SO note the return portion of the plasma need not extend llfully around the target to form a tunnel return. Rather, it ¦ can be bent to curve to the side and optionally return close to the sput~er surface, the bending of the magnetics beiny generally indicated hereinbefore with respect to Figure 6A.
This permits targets to be long and move quite independently of the magnetics.
The double unction bracket system types at first appear ¦
to be very simple - yet they make possible the sputtering of high permeability materials. It should also be noted that the target need not be permeable in the above embodiments of Figures 8A - 8G.
Generally speaking, the principles discussed hereinbefore I for establishing a magnetic bridge circui-t within which a permeable target is disposed are applicable to most, if not all, magnetically enhanced sputtering devices regardless o~
the location of (a) the primary magnetic structure employed to establish the magnetic field in the sputtering portion of the plasma-with respect to (b) the target surface. Further, the lines of foxce produced by the auxiliary magnetic structure to complete the magnetic bridge circuit behind the target surface may pass through the permeable target as indicated in ~igure 8A.
In the embodiment o Figures 2-8, the target is relatively located within the magnet system. However, in the embodiment of Figures 9A and 9B, the magnet loops 38 and 40 are relatively located within endless belt-like target 82. An anode 84 IL il 115;~'733 is placed within the masnet loop to establish the vol~age relationsh,ips needed or crossed field plasma trapping. ~his system sputters inward. Shields (not shown) at cathode potential should be disposed against the inner magnet faces.
These will no~ sputter because of the perpendicular lines o~
force. If target 82 were to be removed, but not the shields, the remaining,structure is ~enerally similar to the magnetron vacuum gauge. ~his device is a very effective plasma trap.
It is possible to employ only the bottom segment 86 of the target., A sputter-up system results with its plasma return through,the open space over the target as shown in Figure 10. The loops 38 and 40 can be tipped or b~nt to give a larger opening at top B8 such that the flow o sputtered material is not impeded. A cathode with single direction plasma flow across the target resul~s bu~ no plasma tunnel under th,e target is,re~uired. Further, the target support , system and ,cathode structure is significantly simplified.
Also the embodiment o~ F1gure 10 markedly decreases the chance of plasma contamination. Further, the return portion 38, 40 may be bent under target 90 or adjacent it, the bending of the magnetics being generally indicated hereinbe~ore with respect to ~igure 6A~ It may also have auxiliary lower magnets for use with hlgh permeability targets as indicated at 92 and 94.
Anode 84 should be c~ossed at its ends. Optional pole plates 96 and 98 may also be included. ~uxther~ cooling plate 100 may also be employed to clamp ~ar~et 90 in place.
The loops,formed by the magnetic s~ructure may also be such ,that they,are,substantially co-planar as indicated by magnets .
~ ll 102 and 104 in Fisures llA and llB. Taryet 106 thus takes the form of a planar ring or rectangular tube, etc. This type o system also has practical applications. The target can be Ifed up through the s~ace between the magnet rinys 102 and 104.
~ There are also many obvious combinations and permutations o the above embodiments that are advantageous. Combinations of magnets as shown in ~igure 12 appear to be effective where additional ring magnet 108 under gap 110 causes the flux ~alue in the gap to be higher than available with the two loops 38 and 40 alone. If ring 108 is not employed, additional inner rings 112 can be employed for magnetic targets.
Referring to Figure 13, there is shown a further illus-trative embodiment of the invention where the magnets 114 and 116 are disposed adjacent the sides of target 120 as in other embodiments of the invention discussed hereinbefore. However, the lines of force projected by magnets 114 and 116 are in general opposition to one another and pass through the target to a magnet 118 located below the target, the flux in magne~
118 being generally perpendicular to the target surface. Hence, the embodiment of Figure 13 tends to combine eatures of the embodiments of Figures 1-12 of the present invention with those described in the aforementioned, co-pending Canadian application whereb~ ~he parallelism o~ a field which passes through the ; target is enhanced by magnets ad~acent the sides of the target.
The desired strength uniformity and parallelism of the magnetic field is preferably obtained with the ferrite magnets described hereinbefore where the rubber or plastic tapes ¦impregnated ILth orierted ~errite particles are particularly -16~

l l , 1 ~53 ~ 3,~ 1 advantageous. The presence of these particles, which are capable of producing a very strong magnetic ~ield, in a low permeability binder such as rubber or plastic, is a~parently effective in generating fields having the requisite characteristics.
Further, the oriented ferrite imp~egnated plastics make prac-tical multi-part magnet systems in which there is no need for interconnecting high permeability connections. In fact, such items as steel interconnecting plates o~ten detract from the flux levels obtained.
Many of the embodiments of this invention may use ferrite magnets in whole or in part such as those ferrite magnets made by Arnold Magnetics, Inc. or Crucible Iron and Steel Co. Also, many of the embodiments described herein may use more conventional magnets such as alnico ferromagnetic mag~-nets in whole or in part but seldom with the convenience and practicality of the preferred ma~erials. Electromagnets may also be employea, but they also are subject to the same ob- ¦
jection. In any event, the above magnet means such as perman~ ¦
ent magnets or electromagnets are preferably used in the subject application although magnetic means such as pole plates may also be used in conjunction wlth the magnet means discussed hereinbefore with respect to Figures lA and 13 and other fiyures of the drawing.
The magnetic structures of the present invention may be employed with planar cathodes which are circular or oblong~
Oblong cathodes may be rectangular, elliptical or oval. Also, the planar cathode may be annular as in Figure llA. Further~
th~ planar cathode may include non~linear por~ions such as ~ ~;3~3~

¦~the concave portions shown in ~he cathodes of Figures 5 and 7 ¦~ OL U. S. Patent 3,878,085. In addition to planar cathodes, cylindrical, concial, endless belt, etc. cathodes may also be l employed. Also, as the cathode is sputtered, there may be a ¦ tendency for it to erode univenly. Nevertheless, the cathode may still be considered planar, cylindrical or whatevex its original shape was. Further, contoured surfaces may be im-parted to the cathode so that it is thicker in areas of greatest expected erosion whereby the tarset will sputter relatively uniformly. Again, such a cathode is to be considered planar, cylindrical, etc. dependin~ upon its ~eneral coniguration prior to sputtering thereof.
The target material to be sputtered may or may not be the cathode of the device. If not, it may be clamped to the cathode by a clamp similar to those illustrated for various ; embodiments o ~he invention where the clamp may also be employed to secure the cathode within the sputtering device.
Regarding the anode referred to hereinbefore, it is usually so-called because sputtering systems are typically self-rectifying when an AC potential is applied. Hence, al-though the term anode is employed in the following claims~ it is to be understood that it may be any other equivalent electrode in the system, Further, ~he anode can be the container wall of the sputtering device. DC, lo~J frequency AC (60 Hz, for example) or industrial radio frequencies, such as 13.56 MHz or 27.12 MHz, may be applied across the anode and cathode. To effect RF isolation, the anode is almost always the container ~wall when th le high frequencies ara emplo~ed although it is 1l.

~ 3~ ;

quite often employed as the anode when DC is emplo~ed.
~s to the gas employed in the system, it may be either active or inert depending upon the type of sputtered layer desired.
It should be urther noted that the principles of the present inVention can be applied to sputter etching.

Claims (31)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A magnetically enhanced sputtering device comprising a cathode, at least a portion of which is provided with a sputtering surface;
anode means spaced from said cathode for establishing an electric field therebetween;
first and second magnet means for establishing a first magnetic field crossed with respect to said electric field so that at least a portion of a closed plasma loop is established adjacent said sputtering surface, at least a portion of said first and second magnetic means being so disposed above or to the side of said sputtering surface that some of the lines of force of said first magnetic field are projected over said sputtering surface from said first magnet means through said second magnet means, the strength of said field being approximately uniform over a substantial portion of the distance between said first and second magnet means.

2. A sputtering device as in Claim 1 where at least a portion of said first magnet means is disposed adjacent one side of said sputtering surface and at least a portion of said second magnet means is disposed adjacent a side of said sputtering surface opposite said one side.

3. A sputtering device as in Claim 1 or 2 where said first and second magnet means are each ferrite magnets.

4. A sputtering device as in Claim 1 or 2 where said first and second magnet means are each ferrite magnets and where said ferrite magnets each include a plurality of layers of oriented ferrite impregnated tape where at least one of the layers at least partially overlaps one of the layers adjacent thereto.

5. A sputtering device as in Claim 1 or 2 where the magnetic flux in said first and second magnet means is dis-posed at an angle with respect to a plane containing at least a portion of said sputtering surface so that said lines of force arch over said sputtering surface.

6. A sputtering device as in Claim 1 or 2 where the magnetic flux in said first and second magnet means is dis-posed at an angle with respect to a plane containing at least a portion of said sputtering surface so that said lines of force arch over said sputtering surface, and where said flux in the first and second magnet means is substantially perpendicular to said plane.

7. A sputtering device as in Claim 1 or 2 where the magnetic flux in said first and second magnet means is approx-imately parallel to said sputtering surface so that said lines of force are projected parallel to said sputtering surface.

8. A sputtering device as in Claim 2 wherein said first and second magnet means are each annular and are substantially disposed in different planes.

9. A sputtering device as in Claim 8 where at least one of said first and second annular magnet means are bent so that said one annular magnet means includes a first por-tion disposed in one plane and a second portion disposed in another plane inclined with respect to said one plane.

10. A sputtering device as in Claim 8 where said planes are substantially parallel to one another.

11. A sputtering device as in Claim 8 where said sputter-ing surface is substantially disposed between said first and second annular magnet means.

12. A sputtering device as in Claim 11 including means for relatively moving said sputtering surface between said first and second magnet means in a third plane disposed between the planes containing said first and second annular magnet means.

13. A sputtering device as in Claim 8 where said sputtering surface is disposed in the open spaces of said first and second annular magnet means so that a first portion of said plasma loop sputters said sputtering surface and a return portion of the plasma loop extends below the side of said cathode opposite said sputtering surface to return the plasma to said first portion.

14. A sputtering device as in Claim 13 where said return portion of the plasma loop is sufficiently removed from the side of said cathode opposite said sputtering surface that said opposite side is not sputtered.

15. A sputtering device as in Claim 13 including means for introducing an ionizable sputter gas into said device where the return portion of the plasma loop extends below said opposite side of the cathode.

16. A sputtering device as in Claim 13 where the side of said cathode opposite said sputtering surface is also provided with a second sputtering surface over at least a portion thereof, said second sputtering surface being sputtered by said return portion of the closed plasma loop.

17. A sputtering device as in Claim 13 including cooling means for cooling and supporting the cathode.

18. A sputtering device as in Claim 13 including auxiliary magnet means disposed on the side of said cathode opposite said sputtering surface, said auxiliary magnet means strenghen-ing the magnetic field between said first and second magnet means.

19. A sputtering device as in Claim 13 including means for relatively moving said sputtering surface with respect to said open spaces.

20. A sputtering device as in Claim 8 where said first and second annular magnet means are both disposed above said sputter-ing surface so that a first portion of said closed plasma loop sputters said sputtering surface and a return portion of said plasma loop is also disposed above said sputtering surface, the return portion of the plasma loop returning the plasma to said first portion.

21. A sputtering device as in Claim 20 where the por-tions of said first and second magnet means closest to said sputtering surface are closer to one another than the opposite portions thereof to thereby facilitate the transfer of sputtered material away from said sputtering surface.

22. A sputtering device as in Claim 8 where said cathode is annular and said sputtering surface extends around at least a portion of the interior surface of the cathode and where said first and second magnet means are disposed in the proximity of the opposite open ends of the annular cathode so that said closed plasma loop extends at least partially around said sputtering surface.

23. A sputtering device as in Claim 1 or 2 where said first and second magnet means are each annular and concen-trically co-planar.

24. A sputtering device as in Claim 1 or 2 where said first and second magnet means are each annular and concen-trically co-planar, and where said cathode is annular.

25. A sputtering device as in Claim 1 or 2 where said first and second magnet means are each annular and concentrically co-planar and where said cathode is annular including means for relatively moving said annular sputtering surface between said first and second magnet means.

26. A sputtering device as in Claim 1 or 2 where said sputtering surface comprises a magnetically permeable material and where said device includes further magnet means for estab-lishing a second magnetic field so disposed with respect to said first magnetic field and said sputtering surface that the tendency for said first magnetic field to pass through said magnetically permeable sputtering surface is substantially reduced.

27. A sputtering device as in Claim 1 or 2 where said sputtering surface comprises a magnetically permeable material and where said device includes further magnet means for estab-lishing a second magnetic field so disposed with respect to said first magnetic field and said sputtering surface that the tendency for said first magnetic field to pass through said magnetically permeable sputtering surface is substantially reduced, and where said first and second magnetic fields are disposed on opposite sides of said sputtering surface.

28. A sputtering device as in Claim 1 or 2 where said sputtering surface comprises a magnetically permeable material and where said device includes further magnet means for estab-lishing a second magnetic field so disposed with respect to said first magnetic field and said sputtering surface that the tendency for said first magnetic field to pass through said magnetically permeable sputtering surface is substantially reduced, where said first and second magnetic fields are disposed on opposite sides of said sputtering surface, and where the lines of force of said first and second magnetic fields are substantially parallel with respect to one another.

29. A magnetically enhanced sputtering device comprising a cathode, at least a portion of which is provided with a sputtering surface;
anode means spaced from said cathode for establishing an electric field therebetween;
first and second magnet means for establishing a first magnetic field crossed with respect to said electric field so that a plasma is established adjacent said sputter-ing surface, at least a portion of said first and second magnet means being so disposed above said sputtering surface that some of the lines of force of said first magnetic field are projected over said sputtering surface from said first magnet means through said second magnet means, the strength of said field being approximately uniform over a substantial portion of the distance between said first and second magnet means, said first and second magnet means each comprising a plurality of layers of oriented ferrite impregnated tape where at least one of the layers at least partially overlaps one of the layers adjacent thereto.

30. A magnetically enhanced sputtering device comprising a cathode, at least a portion of which is provided with a sputtering surface;
anode means spaced from said cathode for establishing an electric field therebetween;
first and second magnet means for respectively estab-lishing first and second magnetic fields crossed with res-pect to said electric field so that a plasma is established adjacent said sputtering surface;
third magnet means disposed on the side of said cathode opposite said sputtering surface; and at least a portion of said first and second magnet means being so disposed above said sputtering surface that some of the lines of force of said first and second magnetic fields are projected over said sputtering surface from said first and second magnet means through said cathode and said magnet means.

31. A sputtering device as in Claims 1, 29 or 30, where said sputtering surface comprises a magnetically permeable material and where at least a further portion of said lines of said first magnetic field are projected through the magnetically permeable material.