Note: Descriptions are shown in the official language in which they were submitted.
1077437
The field of the invention is sputtering and the
apparatus which is used in sputtering techniques. Spe-
cifically the invention is concerned with sputtering
machines in which the anode is rotary and a flexible
substrate is led over the anode and required to receive
materials that are deposited thereon.
Apparatus which comprises the environment of the
invention includes a pressure vessel having at least one -~
cathodic target mounted therein, a rotary anode mounted
for rotation within the vessel, a supply of flexible
substrate such as polyester film mounted in the vessel
and a ta~e-up mechanism for coated substrate mounted
also in the vessel. Suitable controls are provided for
operating the apparatus. The substrate is arranged to
be led over the anode and a sputtering plasma established
in the vessel. The material from which the target is made
is sputtered onto the anode, but since the substrate is
carried on the surface of the anode, the material is
coated onto the substrate.
Auxilliary apparatus, supply means and controls are
provided for furnishing the ionizing gas and its mixed com-
ponents and for monitoring and controlling the feed to
the chamber; for furnishing electrical energy to the
apparatus and monitoring and controlling the same and
its effects~ for controlling and monitoring speed,
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10~743~
temperature, thickness of deposit, and many other param-
eters; ~or driving the substrate in its path and moni-
toring and controlling its tension; etc.
It has been found that for the deposit of certain
materials, particularly photoconductors upon thin, fle~-
ible, transparent substrates, the conaitions of deposition
include, among others, the following:
(a) The anode is requlred to rotate,
(b) The power which is supplied is coupled to the
cathode, anode and shielding in the vessel in
an electrical circuit or network in which the
cathode is at maximum negative voltage, the
shielding is at ground potential and the anode :~ -
is at a potential that is also negativla with
respect to ground, but to a much lesser degree
than the cathode,
(c) The anode surface is required to be temperature
controlled to prevent excessive loss of heat
during sputtering,
Certain other re~uirements of the apparatus render
the achievement of the above conditions very difficult
to effect and these include:
(d) Maintaining all of the supporting structure
of the apparatus including the chamber walls,
at ground potential for practicality and
safety,
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1077437
(e) Maintaining the ends of the drum shielded to
prevent excessive deposit thereon,
(f) Moving the substrate-carrying portion or trans- ~ -
port of the apparatus into and out of the
chamber when the sputtering is completed.
The last-mentioned requirement is for the most part
understood to be necessary in the case of a sputtering
apparatus which is to produce quantities of sputtered
substrate and which of necessity is large and cumbersome.
One proposed solution to such problem is to mount the
substrate-carrying portion on the apparatus on a car- ~-
riage along with much of the control and measuring equip-
ment, and to fix the chamber and all of its auxilliary
apparatus to a support which is stationary. ~n such
case the targets are secured within the chamber and the
high voltage connections are associated with the chamber,
along with the controls and instrumentation therefor;
however, this arrangement does not take into considera-
tion that the anode must be maintained at a voltage
different from ground. - ~ccordingly, the invention provides a sputtering
apparatus wherein a sputtering plasma condition is
established and maintained between target means and a
rotary anode mounted within a pressure chamber defined
~5 within an electrically earthed metal vessel and a clo-
sure therefor, flexible strip substrate being transported
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1(:)77437
over said rotary anode interior of the chamber through
the sputtering condition, earthed shielding means
surrounding at least the target means and leaving a
sputtering opening facing the anode and a high voltage
S source coupled to said anode and target means and means
maintaining the anode at a voltage which differs from
that at the shielding means and the target means.
Referring now to the accompanying drawings:
Figure 1 is a side elevational view of the sput-
tering apparatus of the invention in a closed condition,
certain of the connections to exterior apparatus being
illustrated fragmentarily, indicating that such exte-
rior apparatus is associated with the sputtering appa-
ratus;
Figure 2 is a view similar to that of Figure 1 but
in which the sputtering apparatus is in an open condi-
tion;
Figure 3 is a diagrammatic view taken generally
from the plane 3-3 of Figure 2 and looking in the direc-
tion indicated to illustrate the path of movement of the
substrate on the transport arrangement;
Figure 4 is a more or less diagrammatic perspec-
tive view of the transport arrangement;
Figure 5 is a fragmentary sectional view taken gen-
erally through the chamber of the apparatus along the
line 5-5 of Figure 2 and in the indicated direction;
` 1077437
Figure 6 is a fragmentary perspective view of gen-
erally the same portion of the chamber as illustrated
in Figure 5;
Figure 7 is a detailed sectional view taken through
the lower part of the drum anode of the apparatus of
Figure 1 to illustrate the manner in which contact is
made with the same;
Figure 8 is a block diagram illustrating the
electrical circuitry of the sputtering apparatus of
Figure l; and
Figure 9 is a sectional view, more or less diagram-
matic, of a modified apparatus.
Two desired practical embodiments of the invention
herein are described. One is suitable for commercially
sputtering coatings on relatively wide strips of poly-
ester film. The other is suitable for low production
or experimental wor~ and sputters coatings on narrow
strips. The sizes of the two sputtering apparatuses
are considerably different and the lengths of material
capable of being coated without opening the apparatus
also differ. In the one instance the strip is of the
order of about 50 centimeters wide and in the other it
is of the order of 10 centimeters wide~
The apparatus which shall be detailed initially is
the larger of the two and the more complex, but operat-
ing and constructed in accordance with principles common
to those governing the construction and operation of the
- smaller apparatus.
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1077437
The sputtering apparatus illustrated in Figures 1
through 8 is designated generally by the reference char-
acter 10 and comprises a stationary base or supporting
framework 12 which includes tracks 14 along an upper
edge thereof; a component cabinet 16 mounted on rollers
or wheels 18 engaged on the tracks 14; a pressure vessel
or chamber 20 supported from the framework 12 by fixed
standards 22; and various other parts and structure to
be described~ The cabinet 16 has a transport arrange-
ment 24 mounted to its left hand end supported on a
suitable cantilever subframe 26 which is secured to the
forwardly facing wall 28 of the cabinet 16.
The wall 28 mounts a circular sealing seat 30 and
the transport arrangement 24 and the subframe 26 therefor
are dimensioned and arranged to be encompassed within
the cylinder defined by a projection of the sealing seat
30. The pressure chamber or vessel 20 is closed on all
sides but its right hand end where a flange 32 is pro-
vided adapted to be sealingly engaged against the seat 30.
In Figure 1 the apparatus is shown in its closed condi-
tion, the cabinet 16 having been rolled forward ~to the
left) and thereby having inserted the transport arrange-
ment 24 into the chamber or vessel 20, the joint repre-
sented by the flange 32 and the sealing seat 30 being ren-
dered hermetic by suitable gasket and locking arrangement,
~077437
In Figure 2 the apparatus is shown in its open condition,
the cabinet 16 and the chamber or vessel 20 being sepa-
rated, giving access to the transport arrangement 24 and
any substrate which is carried thereon and to the inte-
rior of the chamber 20,
The tran~port arrangement 24 as illustrated does not
show driving and controlling mechanisms which are con- -
tained in the cabinet 16, these mechanisms for a great
part being mounted on the rear of the wall 28. The
exact nature thereof is subject to wide variation and
such details are not germane to the invention although
presumed to be re~uired for the operation of the appa-
ratus. The cabinet also contains considerable apparatus
and structure needed for the total operation of the
lS apparatus, including speed controls, driving mechanism
pumps and conduits for handling heat exchange liquid, a
large number of measuring instruments for temperatures,
pressures, currents, voltages, etc. The outer wall of
the cabinet 16 is illustrated as having many push-buttons,
meters, lights, and the like but only by way of representa-
tion.
The chamber or vessel 20 is shown having gas connec-
tions at 34 and 36, an electrical panel at 38, pipes and
conduits at 40, electrical lines at 42, push-buttons,
meters, etc. Viewing windows are shown at 44. All of
these are also representative. The apparatus 10 reguires
1077437
considerable control and monitoring well-known to those
skilled in this art and the nature of measurement, opera-
tion and control apparatus will vary with the requirements
of the apparatus.
Basically, there are needs to operate a sputtering
machine which must be furnished, controlled, measured
and often recorded. There are phenomena which must be
measured and observed. The parameters are manifold.
High frequency energy must be furnished to the targets,
requiring matching and control circuits, conduits, and
often cooling devices. In the latter respect, since the
targets are in the chamber or vessel 20, the coolant
for the targets must be provided in the chamber, and
the coolant must be carried and circulated. The
chamber has to be pumped down, requiring vacuum pumps
with accompanying regulation, controls and measurement;
gases for ionization and background have to be intro-
duced requiring regulation, control, measurement and
proportioning.
It is assumed that those structures necessary for
accomplishing the functions for a sputtering machine as
described will be provided, hence there is no need to
illustrate them in more detail and describe them further.
The cantilever subframe 26 is illustrated only in
Figure 2 but should be understood to provide the support
for the transport arrangement 24 although not illustrated
1~77437
in other figures. There is an outer plate 46 and posts 48
connected therewith and in turn connected to the wall 28
but within the confines of the seat 30. All of the rollers
and the drum to be described are journalled for roation,
either driven or idling, between the plate 4~ and the wall
28. - -
In Figures 3 and 4 the transport arrangement 24 is
illustrated, but without showing the journals and mount-
ings and also without showing the drive, clutch and brake
mechanisms which can be used therewith, all of the latter
being contained within the cabinet 16 as explained. ~he
substrate which is to be coated is designated 50 and is
shown to be transparent. In the preferred use of the
apparatus, the substrate 50 forms the base for an electro-
photographic fllm which has inorganic coatings sputtered
thereon. In such instance the substrate 50 is synthetic
resin sheeting such as polyester of about .005 to .010
inch thick. Several hundred meters of this material can
be readily mounted on a spool or reel and contained within
the apparatus 10 while being sputtered along its entire
length. Such a spool or reel is shown at 52 and comprises
the supply within the apparatus. It is mounted on a shaft
54 which is preferably driven by a suitable drive motor
but controlled by a tension clutch that receives feedback
information from speed measurement and control apparatus,
all of which is contained in the cabinet 16.
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~077437
The substrate strip 50 passes over an idler roller 56
which guides the reach to the drum 58 which comprises the
anode of the sputtering apparatus 10. Looking for the
moment at Figure 8, it can be seen that the substrate 50
passes around the drum 58 which is also rotating, nor-
mally idling, in close proximity to the targets 60 and
62 which are located in the bottom of the chamber or
vessel 20 as will be described and then passes upward
to another idler roller 64 from which it is led around
a take-up roller 66 that is driven by suitable drive
motors from the interior of the cabinet 16. Since the
diameters of the rolls of substrate on the supply reel 52
and the take-up roller 66 vary inversel~ to one another
during sputtering and it is essential that the speed of
movement of the substrate 50 relative to the targets be
uniform and carefully controlled and a suitable variable
drive to effect this must be provided.
The targets 60 and 62 are shown in Figures 5, 6 and 8.
The chamber or vessel 20 is in the form of a cylindrical
shell 68 with an end bell 70 that couples with the con-
duit 36. All of the parts of the chamber or vessel 20
are formed of stainless steel and maintained at ground
potential for safety. Fabrication of the vessel from
this material is relatively simple compared to making
it from glass or other insulatin~ materials. The tar-
gets 60 and 62 are mounted in target assemblies 72 and 74
1~77437
respectively that comprise shields 76 of metal that are
mechanically mounted to the bottom of the shell 68 by
the brackets 78 and cooled by coolant circulated through
the walls of the shields 76. The conduits for the cool-
ant are passed through the shell 68 by way of housings
80 that also provide for passage of electrical coupling
elements for connecting the targets to the power supply.
The positions of the targets relative to the drum 58
are adjustable as the targets are consumed. Adjustable
structure whereby such adjustments can be effected may be
contained in the housings 80 or can be effected by adjust-
ments on the brackets 78.
Each target 62 is formed of a plurality of plates or
plaques such as best shown in Figure 6 at 82 which are
cemented on a suitable metal backing plate, usually
stainless steel. The target plates 82 can have their
surfaces facing the drum 58 flat planar or arcuately
planar. They are arranged generally to define a cylin-
drical surface that is coaxial with the drum 58 when the
drum is in position adjacent the targets and the appa-
ratus 10 is closed. Each target 60 and 62 is spaced
from its shield 76 leaving a space framing itself.
Background gas is introduced into the hollow behind each
target by way of the pipes 84 that pass through the wall
of the shell 68 and emerge from the spaces around the
targets to bathe the surfaces of the targets. `
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1077437
i~
Preferably, the target plaques are formed as sintered
members of the material which is to be sputtered.
Between the target assemblies there is a standard
86 which mounts one or an assembly of brushes or wiper
contacts at 88. These connect to a part of the power sup-
ply electrical circuit by electrical lines passing through
the shell 68 as will be explained. Preferably these con-
tacts are mounted with resilient supports spring pressing
them to the right as viewed in Figures 2 and 7. They
must be insulated from the shell 68 as are the targets
60 and 62.
The details of construction of the drum 58 are being
passed for the present to explain the operation of the
circuit of the power supply that is used in the apparatus
10. Reference now is made to Figure 8 for an explanation
of the circuit of the power supply. The construction of
the drum 58 is better appreciated when one understand~
the power circuit.
In Figure 8, the power or energy supply for the
apparatus 10 is shown in most basic diagrammatic form.
There is a high voltage power source shown at the left
as the block 90~ The source 90 is coupled to the appa-
ratus 10 by way of a matching network 92 that is shown
having two lines at 94 and 96 for its output. The high~
est voltage, say of the order of 3000 volts at a fre-
quency of 13.56 megahertz appears at the line 9~ and
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1077437
is applied to the targets 60 and 62, appearing as a
voltage to ground. The line 96 is at ground potential.
All of the shielding in the apparatus 10 (represented
here only by the drum 58, shields 76 and the drum shields)
is at ground potential, but the drum itself is not.
Thus, the output from the matching network 92 is applied ~ -
to a voltage divider which comprises in this simple ex-
ample two impedances Zl and Z2 connected across the lines
94 and 96. In the practical example these are capacitors
and a part of the voltage divider can take into account ~-
parasitic capacitance paths which could have some sig-
nificance at this frequency. The lines can be high fre-
quency plumbing, coaxial cable, shielded leads, etc.
The voltage is divided in accordance with the re-
spective reactance of the two impedances Zl and Z2. ~he
drum 58 is connected by way of a line 98 to the terminal
100 between the impedances Zl and z2. In order to enable
the drum 58 to rotate, the contacts 88 previously de-
scribed are provided to enable the drum to remain at a
voltage which is not ground. The electronic effect in
sputtering in apparatus 10 is that of a diode, such that
there is an effective rectifying action. The cathodes
are the targets 60 and 62 and these are maintained at a
very high negative voltage, which for the example given
is -3000 volts. This is below ground which assumes the
maximum positive voltage for the system, being zero volts.
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iO77437
Conventionally, the anode is at ground potential and
the substrate is laid upon it. Herein, only the shield-
ing is at ground potential. The anode is the drum 58
and it is maintained at a voltage which is also below
ground, but not to the same extent as the targets 60 and
62. In the practical example, the voltage of the drum
was maintained at some value about 50 volts or less below
ground, that is -50 volts. This was achieved by proper
design of the voltage divider string Zl and z2 and other
parts of the circuit. Those skilled in designing power
supplies for r.f. energized sputtering apparatus will
understand this type of circuit and the nature thereof~
The drum 58 is required to be rotary, it is required
to be made out of metal so that it can be easily fabri-
cated and will have the necessary strength to stand up
to the requirements of the sputtering apparatus, it is
required to be journalled using mechanically durable bear-
ings, shafts and supports, and yet at least its outer skin
is required to be at a voltage that differs from its sur-
roundings. Another requirement for the drum is that its
outer skin must be subjected to temperature control by
means of heat exchange liquids. Thus, in the practical
example of the invention, it was deemed necessary to
heat the outer skin of the drum by means of oil to main-
tain the same at a temperature of about 150 C.
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1077~37
All of these requirements are achieved using the drum
as shown in Figure 7. The body of the drum 58 is formed
of an inner metal cylinder 102 with end flanges or rings
104 welded thereto. The metal end caps or discs 106 are
secured to the-cylinder 102 by the circumferentially
spaced screws 108. An outer coaxial metal cylinder llO
forms the circumferential skin of the drum 58 and it is
welded to a telescopically arranged coaxial metal cylinder
112 of smaller diameter to form a chamber 114 between
them. The cylinders 110 and 112 are connected by metal
end rings 116 welded in place at each and the left hand
metal end is exposed as shown.
The chamber 114 carries the heat exchange liquid 118
either in a bulk form which fills the entire chamber or by
way of coils wrapped around the interior of the chamber
(not shown), These are connected by way of suitable
conduits such as shown at 120 to the hollow shaft 122 by
way of which they are connected to a source of such
liquid. Conduits are shown at 120'. Since the liquid
will normally be oil or other insulating fluid there is
no problem with providing an insulating coupling or
couplings for the conduits 120 or 120' so that the skin
110 is electrically insulated from the remainder of the
drum 58, the shaft 122, etc.
The rings 116 and the discs 106 are spaced radially
apart to pro~ide an annular space at each end of the
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,
~077437
drum 58 as shown at 124. A cylinder 126 of polytetrafluoro
ethylene or other stable insulating material is formed
as for example by machining and is positioned between
the cylinder 102 and the cylinder 112. It has its ends
S machined to a lesser thickness than its body so'that the
shoulders 128 and 130 are formed. The resulting axial
ends 132 are made to have a thickness the same as the
annular space 124 and the axial length of the cylinder 126
is made to be identical to the overall length of the drum
58 so that it is flush with the outer ends of the discs
106 and the rings 116. There is thus provided a compos-
ite cylindrical member in which the outer skin 110 is
insulated from the remainder of the drum 58. The drum
is held in assembly by a plurality of screws 134 that
engage through washers 136 of the same insulating mate- '
rial and are spaced circum~erentially around the ends '
of the drum. The washers 136 are,set into deep recesses
138 that are bored into the ends of the drum 58, each ~ -
recess 138 having a portion thereof in each of a disc
106, a ring 116 and an axial end 132. In this way, in
addition to the washers 136 and screws 134 clamping the
parts together axially, the parts are locked against
relative movement circumferentially.
The ring 116 on the left hand end of the drum 58 is ~ '
located in such a manner that when the apparatus 10 is in
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, . . .
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1077437
closed condition, the contacts 88 will engage and wipe
the same thereby establishing electrical contact there-
with.
The ends of the drum 58 are shielded as shown at
140, 142, 144 to prevent material from being sputtered
onto any other parts of the drum while the substrate 50
is passing around the bottom of the skin 110 and being
coated thereat. The plasma representing the sputtering
is indicated at 146. Such shielding is supported from
the wall 28 and subframe 46 as for example by connecting
brackets indicated at 147 in Figures 2, 3 and 4. It
should be clear from Figure 7 that the shielding members
140, 142 and 144 close off the ends of the drum 58 except
to allow passage of the substrate strip 50 and to provide
an opening to admit contacts 88 to wipe the ring 116.
Also, these shielding members are at ground potential
and nowhere touch the drum skin 110.
A modified form of the invention is illustrated in
Figure 9 which is especially useful for small projects.
The sputtering apparatus 200 comprises a chamber 210
which has a cover member 212 adapted to be engaged onto
the flange 214 of the chamber 210 and locked in place.
Sealing is provided by the gasket 216 engaged between
. the flange 214 and the flange 218.
The cover member carries a supply reel 220 and a
take-up reel 222 mounted on shafts 224 and 226
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il~77437
respectively. The shafts are driven by motors 228 and 230
respectively controlled from the exterior of the appa-
ratus 200,
The cover 212 mounts a coupling 232 from which the
drum 236 is suspended. In this case the drum is metal
and the entire drum is insulatea from the chamber 210
and the cover 212 by suitable insulation provided in the
coupling 232. It is mounted on a shaft 238 which passes
through the coupling 232 driven by the motor 240 mounted
on the top of the cover 212. A sprocket chain and
sprocket wheels such as 242 provides the coupling to the
shaft 238 without short-circuiting the drum to ground.
Suitable insulation is provided for this. A ring 244 on
the shaft 238 connects to the drum 236 electrically and
is isolated from all other parts of the apparatus 200.
Electrical connection 246 with the contacts 248 corre-
spond to the line 98 and the contacts 88 of Figure 8.
The drum is hollow and has a central hollow conduit
250 providing coaxial chambers 252 and 254 which connect
with the pipe 256 that passes around the skin 258 o~ the
drum 236 on the interior thereof. Heat exchange liquid
enters and circulates by way of the chambérs 252 and 254.
At the top of the view one can see where suitable cou-
plings are attached to enable rotation of the shaft 250
through the use of rotary fluid couplings. These need
not be shown.
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1077437
The target 260 in this apparatus 200 is a simple disc
of the photoconductive material mounted on a holder 262
which is connected by way of the member 264 through the
wall of the chamber 210 to a source of high voltage radio
fre~uency 266. There is no need to show the circuitry of
Figure 8 since it is assumed to be used in connection
with the apparatus 200.
Shielding at 268, 270 and 272 at ground potential is
provided adjacent the drum 236, the drum mounting on the
shaft 238 and the target 260. Sputtering plasma is pro-
duced in the same manner as in the case of the apparatus
10 through the use of suitable high frequency energy and
a suitable background gas admitted as for example by the
conduit 274 in the gap 276 between the s~in 258 of the
drum 236 and the face of the target 260.
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