Note: Descriptions are shown in the official language in which they were submitted.
'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'
.
,
.
733
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 -
, ~, . . .
33
~ 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.
~ , ~
- 5 -
33
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
!
~,, ~
733
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
-- 7
~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
-14-
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
-15-
.
~ 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
-18-
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.
