Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Description
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MAGNETRON CATHODE SPUTTERING APPARATUS
Back~round_of the Invention
The present invention relates broadly to apparatus for
cathode sputtering and more particularly to an improved
magnetron cathode sputtering system.
Cathode sputtering is widely used for depositing thin
films of material onto substrates. Such a process involves
generally ion bombarding a flat target plate of the material
to be sputtered in an ionized gas atmosphere in an evacuable
coating chamber in whic~ a controlled vacuum is maintained to
cause particles of the target plate material to be dislodged
and deposî-ted as a thin film on the substrate being coated.
The target plate, to which a layer of the coating material to
be sputtered is applied, is generally of elongated, rectangu-
lar form, with the substrate to be coated being moved either
continuously or intermittently therebeneath. The longitudi-
nal axis of the target plate is transverse to the direction
of substrate movement.
In an endeavor to attain increased deposition rates the
use of magnetic enhanced cathodes has been proposed. Such
cathodes are known as planar magnetron cathodes and custo-
marily include an array of permanent magnets arranged in a
closed loop and mounted in a fixed position in relation to
the flat target plate. Thus, the magnetic field is caused to
travel in a closed loop, commonly referred to as a "race
track" which establishes the path or region along which
sputtering or erosion of the target plate material takes
place.
One drawback o~ the conventional flat plate target,
however, is that the race track along which sputtering takes
place is relatively narrow so that erosion occurs in a
relatively narrow ring-shaped region corresponding to the
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shape of the closed loop magnetic field. As a result,
only a relatively sma]l portion of the total target
material in the so-called race track region is consumed
before the target must be replaced.
Summarv of the Invention
The present invention contemplates a new and
novel form o' magnetron cathode which is significantly
different from the planar magnetron cathodes heretofor
proposed and which, while reta:ining the advantages of
high deposition rates, also renders possible an even
more effective and maximum utilization of the target
material thereby substantially increasing the operating
life thereof.
Briefly stated, the present invention is an
apparatus for sputtering thin films of a selected
coating material upon substantially planar substrates.
'rhe apparatus comprises an evacuable coating chamber
a cathode mounted horizontally in the coating chamber
comprising an elongated, cylindrical tubular member
having a layer of the coating material to be sputtered
applied to the outer surface thereof, magnetic means
located in the tubular member for providing a sputtering
zone extending lengthwise thereof, means for rotating
the tubular member about its longitudinal axis to
bring different portions of the coating material into
sputtering position opposite the magnetic means and
within the sputtering zone, and means in the coating
chamber for horizontally supporting the substrates and
for transporting them past the magnetic means to receive
the sputtered material, wherein the means for rotating
the tubular member rotates the same continuously during
the s~utter coating operation.
The present invention is also a method of sputtering
thin Eilms of a selected coating material upon substantially
planar substrates, comprising providi.r1g an elongated,
cylindrical tubular member having a layer of the target
material to be sputtered applied to the outer surface
thereof, provic1ing within the t~bular member a magnetic
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fielcl deflninq the length and width of -the erosion zone
on the target material, rotating the tubular member
continuously about its longitudinal axis cluring the
sputtering operation to bring differen-t portions of the
target material withing the erosion zone for sputtering,
and simultaneously moving the planar substrates past
the erosion zone to receive the material being sputtered.
These and other features and advantages of
the inven-tion will be apparent from the following
description, with reference to the accompanying
drawings.
Brief Description of the Drawings
Fig 1 is a vertical longitudinal section through a
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coating chamber showing in elevation a magrletron cathode con-
structed in accordance with the present invention rnounted
therein,
Fig. 2 is a horizontal longitudinal section taken
substantially on line 2--2 of Fig. 1.
Fig. 3 is an end view of Fig. l,
Fig. 3A is a perspective view of a portion of one of
the magnetic strips,
E'ig. 4 is a view similar to Fig. 1 illustrating another
embodiment of the invention,
Fig. 5 is a horizontal longitudinal section taken sub-
stantially on line 5--5 of Fig. 4,
Fig. 6 is an end view of Fig. 4 and
Fig. 7 and 8 are generally schematic plan views illus-
trating two other modified forms oE the invention.
Fig. 9 is a vertical longitudinal sectional view of
anot:her form of the invention,
Fig. 10 is a vertical section taken substantially on
line 10--10 of Fig. 9,
Fig. 11 is a vertical section taken substantially on
line 11--11 of Fig. 9,
Fig. 12 is a horizontal section taken substantially on
line 12--12 of Fig. 9, and
Fig. 13 is a transverse section taken substantially on
line 13--13 of Fig~ 12.
Descri~tion of the Preferred~Embodiments
One form of the invention is illustrated in Figs. 1 to
8 of the invention and a ~econd form illustrated in Figs. 9
to 13. Referring to the drawings and particularly to the em-
bodiment of the invention illustrated in Figs. 1, 2 and 3,
the cathode assembly is designated by the numeral 20 and is
mounted in an evacuable coating chamber 21. The coating
chamber is rectanglllar and is composed of a bottom wall 22,
top wall 23, opposite side walls 24 and 25 and end walls (not
shown). The bottom and top walls 22 and 23 are suitably
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joined to the side walls 24 and 25 at the hermetic seals 26
.. . . . .. . . .. . . . .
and 27 respectively. The end walls are sirnilarly sealed to
the .op and bottom and side walls. A vacuum pump 28 is pro-
vided to evacuate the coating chamber 21 to the desired
pressure. Should it be desired to inject gases into the
chamber, it may be done through conduit 2~ controlled by a
valve 30.
The cathode assembly 20 comprises generally an elonga-
ted cylindrical tube 31 mounted in the coating chamber 21 and
in the lower portion of which is mounted the magnetic means
32. The tube 31 is formed of a suitable non-magnetic ma-
terial such as, for exarnple, brass or stainless steel and
is of a diameter, wall thickness and length required for the
operation to be perforrned.
~ pplied to the outer surface o, the -tube 31 is a layer
33 of a selected coating or target material to be deposited
onto the substrates being coated. Thus, the tube 31 and
layer of coating material 33 constitute a tubular target or
sputtering source as distin~uished from the conventional
planar target.
The tube 31 is supported in a horizontal position in
the coating chamber 21 and is mounted for rotation about its
longitudinal axis. For this purpose, the tube is supported
at its inner end b~ a trunnion 34 secured the closecl inner
end 35 of the tube and ~ournaled in a bearing block 36 car-
ried by a bracket 37 secured to the side wall 25 of the
coating chamber by screws 38.
The tube 31 is open at its outer end and extends
through an opening in the side wall 24 of the coating chamber
21, where it is supported in an annular ring 39 surrounded by
a collar 40 secured to said side wall 24 be screws 41. The
interior of the coating chamber is sealed frorn the atmosphere
by O-rings 42 and 43 engaging the tube 31 and side wall 24 of
the coating chamber respectively.
To provide the requisite cooling of the cathode assemr
bly there is provided a coo:Lant conduit 44 also of a suitable
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nOn-magnetic materlal extending longitudinally in the ~ower
portlon of the tube 31. The inner end of said conduit is
closed and spaced from the closed inner end 35 of tube 31,
while the outer end thereof extends beyond the tube as indi-
cated at 45. A suitable coolant, such as water, i5 intro-
duced into-the outer end of the conduit 44 and, after passing
through openings 46 therein, circulates throughout the tube
31 and exits at the outer end t:hereof.
The magnetic means 32 comprises an array of U-shaped
permanent magnets 47 arranged in two straight parallel rows A
and B that extend lengthwise within the tube 31. The magnets
47 in each row are aligned with one another, with the magnets
in one row being disposed alternately with and overlappin~
the magnets in the otiher row. Also the magnets in the two
rows A and B are arranged at an angle relative to one anoth-
er, as shown in Fig. 3, and are secured to the conduit 44 by
suitable brackets or the like.
The outer legs 48 of the magnets 47 in row A engage a
longi-tudinally extending, relative narraw strip 49 of a suit-
able magnetic material, such as hot rolled mild steel, while
the outer legs 50 of the magnets in row B engage a similar
magnetic strip 51 arranged parallel with magnetic strip 49.
The inner legs 52 and 53 of the magnets in rows A and B over-
lap one another and engage a central longitudinally extending
magnetic strip 54 that extends parallel with the outer mag-
netic strips 49 and 51. The magnets 47 are secured to the
respective magnetic strips by screws 55 passing therethrough
to tie them together as a unit. The bottom surfaces 59 of
the magnetic strips 49, 51 and 54 are shaped to conform to
the curvature of the inner surface of the tube 31. The cen-
tral magnetic strip 54 is notched on a slant alternately
first to one side and then the other, as indicated at 54a in
Fig. 3A, such that the inner legs 52 and 53 of the magnets
will Eace-to-face contact with said strip.
The magnets 47 are preferably disposed so that the
north poles thereof engage ~he outer magnetic strips 49 and
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51, while the south poles of the ma~nets engage the central
magnetic strip 54 'Fhis arrangement of ~he magnets and
ma~netic strips establishe5 two straight magnetic Eields
along wich erosion of the target material 33 takes place.
A cathode potential sufiicient to cause sputtering to
occur is supplied to the tubular target from a D.C. pcwer
source (not shown) through a power line 60 having sliding
contact with the tube 31. 'Fhe apparatus is grounded in any
sutable manner.
The substrates S to be coated are supported on and
carried throu~h the coating chamber 21 and beneath the
cathode 20 by rollers 62 and 63 keyed to a horizontal shaft
64 journaled in bearing blocks G5 and 65a supported on the
bottom of the coating chamber.
As stated above, the outer surface of the tube 31 is
provided with a layer 33 of the material to be sputtered on
the substrates S as they pass therebeneath. By means of the
handle 66 secured to the outer end of the tube 31 the tube
can be rotated either clockwise or counter-clockwise about
its longitudinal axis to position a selected portion ~f the
coating material to be sputtered directly opposite ths mag-
nets and within the magnetic field. When this portion ~f the
coating material has been depleted, the tube can agcin be
rotated to bring another and fresh portion of the c~ating
material into sputtering position. This procedure can be
repeated until a maximum amount of the coating materi-l has
been utilized.
Also be applying different coati`ng materia s to
different portions of the outer surface oE the rotatabl- tube
a particular selected coating material can be brough into
sputtering position. In this way, it is possible to ~~utter
different coating materials onto the substrates from a ~ingle
target.
The magnetic means 32 are supported on the tu~ 31,
with the magnetic ~trips 49, 51 and 54 in direct contact-~ith
the inner surEace thereof. . With such an arrangement, upon
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rotation of the tube 31, and clue to the frictional contact
between the tube and the magnetic str:Lps, the ma~nets may be
moved slightly with the tube from their original position
relative to that portion of the coating material to be sput-
tered. Should this occur, it can be readily corrected and
the magnets returned to their original position by turning
the conduit 44, by means of the handle 67 secured to the
outer end thereof, to move the magnets in the reverse
direction.
Figs. 4, 5 and 6 are views similar to Figs. 1, 2 and 3
respectively but disclose an alternate form of magnetic means
70. Otherwise, the construction and operation of the appara-
tus are the same as above described with reference to Figs.
1, 2 and 3 and the same numerals are used to designate like
parts.
In this form of the invention, the magnetic means 70 is
composed of a single row C of permanent U-shaped magnets 71,
the legs 72 and 73 Gf which engage spaced, longitudinally ex-
tending magnetic strips 74 and 75 respectively and are secur-
ed thereto by screws 76 and 77. The bottom surfaces 78 and
79 of the magnetic strips 74 and 75 are shaped to conform to
the curvature of the inner surface of the tube 31. In this
embodiment, the established magnetic field also follows a
straight path to create a straight erosion pattern on the
target material.
Extending longitudinally within the tube 31 and beneath
the row of magnets 71 is a coolant conduit 80 to which the
magnets are secured. ~ cooling liquid, such as water, is
introduced into the outer end of the conduit and discharged
therefrom through openings 81 into the tube. The cooling
liquid, after circulating within the tube 31, exits therefrom
through the outer end thereof.
The tube 31 can also be rotated by means of the handle
66 to selectivel~ position different portions of the coating
material opposite the ~gnets and within the magnetic field.
Likewise, a~ter the tube has been -turned to place the selec-
ted unused portion of the coating material in sputtering
~33~
position the magnetic means can be adjusted, if necessary,
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by means of the handle 67 to again bring the-magnets into
proper position relati~e to that portion of the coating
material to be sputtered.
In Figs. 7 and 8 are illustrated in somewhat schematic
form two other modified ernbodiments of the invention, in each
of which a plurality of rotatable cathodes of the type shown
in Figs. 4, 5 and 6 are employecl.
l~ith reference to Fig. 7 & 8, two cathode assemblies 82
and 83 are horizontally disposecl in spaced parallel side-by-
side relation in an evacuable coating chamber 84. Eachcathode assembly comprises an elongated, c~lindrical tube 85
having a layer of the coating material 85a to be sputtered,
applied to the outer surface thereof. Located within the
tube 85 are the magnetic means 86 composed of a single row of
permanent U-shaped magnets 87, the opposite legs of which
engage longitudinally extending magnetic strips 88 and 89 and
are secured thereto by screws 90 and 91 respectively.
'rhe outer magnetic strip 88 of each cathode assembly
constitutes the north pole piece and the inner magnetic strip
89 the south pole piece. 'rhe outer magnetic strips 88 extend
beyond the inner magnetic strips 89 and are turned inwardly
toward one another as indicated at 92. Positioned between
the cathodes 82 and 83 at the opposite ends thereof are the
additional permanent U-shaped magnets 93 and 94 which ~ridge
the gap between the inturned ends 92 of the magnetic strips
88 and in conjunction therewith establish a magnetic field in
the form of a closed loop or race track. 'rhe ca~hodes 82 and
83 are internally cooled by the introduction of a cooling
liquid into the coolant conduits 95 as above described with
reference to Figs. 1, 2, and 3.
'Fhe tubes 85 oE the cathodes 82 and 83 are rotatable
independently of one another to bring the desired unused
portion of the coating material on the outer surface thereof
into proper registration with the respective row of magnets.
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Either the same or different types of coating materials can
be applied to the tubes.
The embodiment of the invention illustrated in Fig. 8
distinguishes from that disclosed in Fig. 7 in that four cath-
ode assemblies 96, 97, 98 and 99 are mounted in horizontally
spaced, parallel relation in the coating chamber 100. ~lese
cathode assemblies are preferably of the same type as show in
Fig. 7, with each comprising an elongated, cylindrical rotata-
ble tube 101 having a layer of the material to be sputtered
applied to the outer surface thereof. Also, the magnetic
rneans with the tube 85 of each cathode is composed of a
single row of permanent U-shaped magnets 102, the opposite
legs of ~hich engage and are secured to the magnetic strips
103 and 104 by screws 105 and 106 respectively.
The magnetic strips 103 constitute north pole pieces,
while the magnetic strips 104 constitute south pole pieces.
The magnetic strips 103 of cathodes 96-97 and 98-99 extend at
one end beyond the associated strips 104 and are turned in-
wardly as indica-ted at 107 and 108 respectivelyO On the
o-ther hand, the magnetic strips 104 of the magnets 97 and 98
extend beyond the associated magnetic strips 103 at the other
end of the rows of magnets and are turned inwardly toward one
another as indicated at 109.
Located between the inturned ends 107 of rnagnetic
strips 103 of cathodes 96 and 97 is a permanent U-shaped
magnet 110 ~nd a similar magnet 111 is positioned between the
inturned ends 108 of the magnetic strips 103 of cathodes 98
and 99. Also positioned between the inturned ends 109 of the
rnagnetic strips 104 of magnets 97 and 98 is a like perrnanent
rnagnet 112. The individual magnets 110, 111 and 112 at the
opposite ends of the cathodes serve to bridge the gaps be-
tween the associated magnetic strips and in conjunction
therewith act to complete the rnagnetic field which follows a
serpentine pal:h
The tubes 101 of the cathodes 96, 97, 98 and 99 are
mounted in the coating chamber 100 for individual rotation
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rela-tive to one another and may be provlded with the sarne or
different types of coating materials. The cathodes are also
adapted to be internally cooled as described above through
the coolant corlduits 113, 114, 115 and 116 to which the
associated magnets are secured.
A second form of the invention is illustrated in Figs.
9-13 and distinguishes, in essence, from the previous embodi-
ments in that, whereàs in those embodiments the tubular tar-
get is rotated about its longitudinal axis in a step-by-step
fashion, this embodiment contemplates a tubular target that
is continuously rotated durlng the sputter-coating operation.
With reference par-ticularly to E`igs. 9 to 13, the cath-
ode therein disclosed comprises an elongated, cylindrical
tube or tubular member 120 mounted for horizontal rotation
about its longitudinal axis in the upper portion O f an
evacuable coating chamber 121 and Aaving applied to the outer
surface thereof a layer 122 of the coating material to be
sputtered. The tube 120 is provided at its opposite ends
with the end walls 123 and 124 and constitutes a rotatable
target.
Mounted in the tubular target 120, in spaced concentric
relation thereto, is a relatively smaller elongated, cylindri-
cal tubular member 125, in which the magnetic means 126 are
located. The inner tube 125 is closed at its opposite ends
by the end walls 127 and 128 which are provided with
trunnions 129 and 130 respectively, said trunnions projecting
through openings in the end walls 123 and 124 respectively of
the tube 120.
The trunnions 12g and 130 are provided with reduced
squared end por-tions 131 and 132 respectively that are
supported in correspondingly shaped recesses 133 (Fig. 11)
formed in supporting brackets 134 and 135. These brackets
have porti.ons 136 and 137 respectively that extend outwardly
beneath horizontal walls 138 and 139 forming a part of the
coating chamber lZl and are secured thereto by screws 140 and
141. With such an arrangement, the inner tube 125 is main-
tained in a ~.ixed position and rotation thereof prevented,
while the outer target tube 120 is rotated relative thereto.
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I'o e.ffect rotation o~ the tubular target 120 the end
walls 123 and 124 thereof are, as previously mentioned, pro-
vided centrally thereof with openings through which the
trunnions 129 and 130 of the inner tube 125 pass. Surround-
ing these openings are the outwardly directed annular flanges
142 and -14~ that recei~e the bearing sleeves 144 and 145
fitting over the trunnions 129 and 130. Endwise moyement of
the tubular target 120 is prevented by the rings 146 engaging
the annular flanges 142 and 143, while hermetic seals 147 àre
provided inwardly of said bearing sleeves 144 and 145.
As noted above, the tubular target member 120 is moun-
ted for continuous rotation during the coating operation.
The drive means there-~or inc.ludes a motor 148 mounted upon
the top wall 149 of the coating chamber 121, said top wall
being supported at its opposite sides by the vertical walls
150 and 151 `of the coating chamber. The top wall is also
supported by the coatiny charnber end walls 152 and 153.
0-ri,ngs 154 and 155 are located between the top wall 149 and
said vertical side and end walls as well as between said
vertical walls 150 and 151 and the horizontal walls 138 and
139 of the coating chamber.
.. Keyed to the drive shaft of the motor is a sprocket
gear 156 about which is trained a sprocket chain-157 which is
also trained about a sprocket gear 158 keyed to a horizontal
shaft 159. ThiB shaft is journaled in bearings 160 mounted
in a bearing block 161 secured to the vertical wall 151 of
the coating chamber by machine screws 162 (Fig. 10). The
shaft 159 projects through an opening in the vertical wall
151 and has ]ceyed to the inner end thereof a gear 162 meshing
with a gear 163 keyed to the annular flange 143 on vertical
wall 124 of the tubular target 120. Upon operation of the
motor 148 the target member will be rotated thro~gh the gears
162 and 163, while the inner tube 125 remains stationery.
The rnagnetic means 126 are supported in the inner tube
125 and comE~rises an array of substantially U-shaped per-
rnanent magnet:s 164 arranged~ in two straight parall.el rows D
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and ~ extenaing leng-thwise o~ the tube 125- ~le form and
arrangernent of these magnets are the same as described above
with reference to Figs. 1, 2 and 13 and such disclos~re is
included here by reference. Similar numerals are U~ed to
designate like parts.
The cathode is adapted to be intexnally cooled and for
this purpose a cooling rnedium, such as water, is circulated
throu~h the space 165 between the outer and inner tubular
members 120 and 125 alon~ their length and also at the ends
thereof. The incoming cooling me~ium is supplied by a feed
pipe 166 supported by the top w~ll 149 of the coating chamber
as irldicated at 167 (Fig. 11). The feed pipe feeds into the
outer end of a passageway 168 formed in the trunnion 130 and
is discharged in-to the space 165 at the adjacent end of the
cathode. After circulating within the space 165 the coolinq
medium is discharged at the opposite end of the cathode
through a passageway 169 in trunnion 129 which leads to a
discharge pipe 170 supported by the tip wall 149 of the
coating chamber as indicated at 172.
The planar substrates 17~ to be sputter-coated are
supported on and carried horizontally through the coating
chamber 121 and beneath the cathode by the conveyor rollers
173 keyed to horizontal shafts 174 journaled in bearing
blocks 175 and 176 supported on the bottom 177 of the coating
chamber. A vacuum pump 178 is provided to evacuate the
coating chamber to the desired pressure. Should it be
desired to inject gasses into the chamber it may be done
through conduit 179 controlled by a valve 180.
As pointed out above, the outer tubular member 120 is
adapted to be rotated continuously during the sputtering
operation. Simultaneously, the substrates 172 will be passed
horizontally beneath the cathode to receive the coating
material sput-tered from the target 120. The longitudinal
axis of the tubular targe~ 120 is transverse to the direction
of substrate ~movement. A cathode potential sufficient to
cause sput-tering to occur in supplied to the target material
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from a D.C. power source (not shown) through a power llne 181
secured to a contract 182 having s~idlng engagement with the
-target 120.
Whlle there has been il]ustrated and described herein
preferred embodlment of the in~ention, lt will be understood
that changes and rnodlflcations may be made without departing
from the splrit and scope of the claims. By way oE example,
diferent types of perrnanent magnets as well as electromag-
nets may be employed in lleu of U-shaped permanent magnets.
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