Note: Descriptions are shown in the official language in which they were submitted.
121~337
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Description
1 GAS DISTRIBUTION SYSTEM FOR SPUTTERING CATHOD~S
Field of Invention
The present invention is concerned with the art of
sputtering and in particular with the reactive cathodic
sputtering of metals or metal alloys on the surface of
substrates in an evacuable coating chamber.
Backqround sf the Invention
One method of sputter-coating involves ion bornbarding
a target of the coating material in an ionized gas
atmosphere in a chamber in which a controlled vacuum is
maintained to cause atomic particles of the coating
material to be dislodged and deposited by condensation on
the substrates to be coated. The gas employed is a
non-reactive or inert gas, such as argon.
However, many processes in vacuum deposition utilize
a method known as reactive deposition where a pure metal or
alloy target material is liberated from its bulk and
directed toward a substrate which is intended to collect
the material as or after it has reacted with a gas which is
present in the path of the liberated target ~naterial or at
the substrate surface.
The reactive sputtering is often difficult to
control, rates of deposition are erratic, arcing of the
target occurs due to resistive film build up on the ~arget
face, and yields are often unpredictable.
Outline of the Invention
It is a primary purpose of this invention to provide
a reactive sputtering method which embodies a novel gas
distribution system designed to shield the target material
from the reactive gases employed when an attempt is made to
create a reaction between the target material and a
reactive gas, such as nitrogen or oxygen.
lZ~g837
' -
Broadly speaking the present invention provides
a method of sputtering in which a cathode having a planar
target is mounted in a vacuum chamber for sputter-coating
substantially planar substrates passing therebeneath, com-
prising the steps of: introducing a first gas into the
chamber by way of a gas distribution system located at each
side of the cathode, the first gas being directed by the
system into the upper portion of the chamber adjacent the
target; and introducing a second gas into the chamber by
way of the system, the second gas being directed by the
system into the lower portion of the chamber adjacent the
substrates.
The present invention may also be considered
as providing a gas distribution system for use with a sputtering
cathode, mounted in a vacuum chamber and having a substantially
planar target formed of the material to be sputtered onto
substantially planar substrates located therebeneath, charac-
terized in that a distributor means is located at each side
of the cathode for introducing two separate gases into the
vacuum chamber between the target and the substrates, the
distributor means comprising a support member, a pair of
horizontal porous pipes located within the support member,
and outlets in the support member through which the gases
escape from the porous pipes into the vacuum chamber and
by which the gases are directed in divergent directions,
one toward the target and the other toward the substrate~.
In particular, the gas distribution system of
this invention consists in simultaneously introducing into
the coating chamber, after it has been pumped down, a non-
reactive gas such as argon, and a reactive gas such as nitrogen
or oxygen, and maintaining them substantially separate from
one another, the non-reactive gas being directed toward
and upon the target surface and serving to protect that
surface from the reactive gas which is directed toward and
upon the substrate surface.
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lZ191~37
Such a gas distribution system has assisted
in eliminating many of the problems associated with reactive
deposition. It provides for increased target rate of deposi-
tion; decreases power levels required; eliminates spiking
or arcing; eliminates need to "pulse" gases to keep the
target clean, and efficiency of conversion is high per unit
gas volume, i.e. more efficient usage or reactive gas.
Brief Description of the Drawinqs
Fig. 1 is a cross section of a sputtering cathode
with which the present invention is employed,
Fig. 2 is a side view of the apparatus taken
substantially on line 2--2 of Fig. 1,
Fig. 3 is a plan view of the cathode with the
cover plate removed,
Fig. 4 is an enlarged section of the gas distribu-
tion means of this invention,
Fig. 5 is a view similar to Fig. 1 but showing
another form of the invention,
Fig. 6 is a perspective view of the gas distribution
means shown ln Fig. 5, and
Fig. 7 is a detail section taken substantially
on line 7--7 of Fig. 6.
Detailed Description
Referring to the drawings and particularly to
that form of the invention illustrated in Figs. 1 to 4, the
- 2A -
_ mab/~c
~PG 75207
~Z191337
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1 sputtering apparatus includes an evacuable coating chamber
10 in which is mounted a planar sputtering cathode 11. The
coating chamber is usually part of a continuous sputtering
apparatus through which planar substrates 12, such as glass
sheets or the like, are supported horizontally upon and
carried by conveyor rolls 13 beneath cathode ~ to receive
the coating material sputtered therefrom.
The cathode 11 comprises a housing of substantially
rectangular boxlike form composed of a bottom wall or base
plate 14, side walls 15 and 16, end walls 17 and 18 and a
top or cover plate 19 which define a chamber 20. Applied
to the outer surface of the base plate 14 is a sheet or
layer 21 of the material to be sputtered onto the
substrates and which is generally referred to as the
target.
The base plate 14 of the cathode housing is secured
to the side and end walls 15-16 and 17-18 respectively by
screws 22 which pass upwardly therethrough and are threaded
into elongated metal strips 23 welded or otherwise suitably
secured to the said side and end walls. Pressure tight
seals 24 are provided between the base plate and the side
and end walls, while arranged outwardly of s~id side and
end walls are the insulating shields 25.
~he side walls 15-16 and end walls 17-18 of the
cathode housing terminate at their upper ends in outwardly
directed flanges 26 and 27 respectively which form a
continuous rim surrounding the housing for supporting the
cathode in operative ~osition. More particularly, the top
wall 29 of coating chamber 10 is provided with a transverse
opening 30 through which the cathode is lowered into fiaid
chamber where it is supported by the continuous rim which
overlaps the adjacent portions of the top wall 29.
Strips of insulating material 31 are positioned
between the top wall 29 of the coating chamber and the
supporting rim, while pressure tight seals 32 and 33 are
located at opposite sides of the insulating strips 31.
Similar seals 34 are provided between the supporting rim
and the cover plate 19 of the cathode.
~PG 75207
~1983~
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1 The cathode 11 herein disclosed by way of
illustration is a planar magnetron cathode and to this end
magnetic means 35 are mounted in the cathode chamber 20 and
supported on the base plate 14. The magnetic means 35
consists of two parallel rows of substantially U-shaped
permanent magnets 36 and 37, with the magnets in the two
rows being alternately arranged in overlapping-relation.
The outer legs 38 of the magnets 36 are secured to a
magnetic strip 39 by screws 40, while the outer legs of the
magnets 37 are secured to a similar magnetic strip 42 by
screws 43. The inner legs 44 and 45 of the magnets 36 and
37 are secured to a central magnetic strip 46, extendinq
parallel with the strips 39 and 42, by screws 47 and 48
respectively.
The means for cooling the target are not shown as any
desired means may be provided for this purpose. Likewise,
the electrical means for operating the cathode are not
shown since the operation of magnetron cathodes is well
~nown.
In the operation of a cathode of the above character,
an inert gas, such as argon, is usually admitted to the
vacuum chamber 10 to provide a non-reactive gas atmosphere
after the chamber has been pumped down to the desired
pressure. This pressure is usually in the neighborhood of
to 10 microns. The argon is ionized to establish a
plasma and the argon ions dislodge molecules of the
material from which the target is made, these molecules
then impi~ge upon the substrates that are moved slowly
therebeneath to coat the same.
Such cathodes may also be employed to reactively
sputter a metal oxide coating in a reactive gas atmosphere
containing, for example, oxygen or nitrogen. However, the
use of a reactive gas coming in contact with the target
material is not without objections for the reasons state~
above. Hence, the purpose of this invention is to provide
a reactive sputtering apparatus which can be operated with
greater efficiency and improved results than heretofore.
SPG 75207
lZ19~37
1 According to the present invention, there is provided
a novel gas distribution system in which an inert gas, such
as arg~on, is directed toward and into contact with the
target, while a reactive gas, such as oxygen or nitrogen,
is simultaneiously directed toward and into contact with
the substrate to be coated and in which the two gases are
main~ained substantially separated from one another. This
allows the target to function as it would in a totally
non-reactive environment, while the material liberated from
the ~arget and directed toward the substrate will be acted
upon b~ the reactive gas in its path of movement or at the
surface of the substrate as it would in a reactive
environment.
To accomplish the objects of the invention, there is
provided a gas distribution system including metallic
support members 49 and 50 in the form of elongated
substantially rectangular beams horizontally mounted in the
coating chamber 10 at opposite sides of the cathode 11.
~ach support member is made up of three parallel sections
51, 52, and 53 positioned in contacting relation one above
the other and ~ecured together by screws 54.
The meeting faces of the sections 51 and 52 of each
support member 49 and 50 are provided with semi-circular
grooves 60 and 61 respectvely which together form an
- 25 annular opening extending longitudinally of said support
member and in which is mounted a pipe 62 formed of a
suitable porous material. The meetin~ faces of the support
sections S2 and 53 are provided with similar semi-circular
grooves ~3 and 64 in which is mounted a pipe 65 also of
porous material. As shown in Fig. 3, the porous pipes 62
at opposite sides of the cathode are closed at one end as
at 162 while, at their opposite ends, they are joined to
pipes 163 that extend inwardly and are connected to a gas
inlet pipe 67. The porous pipes 65 at opposite sides of
the cath~de are closed at one end as at 165 and connected
at their opposite ends to a gas inlet pipe 68. The porous
pipe 62 is adapted to receive a non-reactive gas, such as
SPG 75207
lZ~98~37
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1 argon, while the porous pipe 65 receives a reactive gas,
such as oxygen or nitrogen.
The meeting faces of the sections 51 and 52 of each
support member 49 and 50, inwardly of the porous pipe 62,
are slanted upwardly and inwardly as at 69 and 70 and
spaced slightly from one another to provide a slit 71 (Fig.
4) through which the non-reactive or inert gas escaping
through the porous pipe 62 will be directed tGward and upon
the target 21. Similarly, the meeting faces of the
sections 52 and 53 of each support member inwardly of the
porous pipe 65 slant inwardly and downwardly as at 72 and
73 and are spaced slightly from one another to provide a
- slit 74 through which the reactive gas escaping through the
porous pipe 65 will be directed toward and upon the
substrate 12. In this way, the target face will be
shielded from the reactive gas by the layer of non-reactive
~as which is next to the target. Thus, the sputtering from
the target face takes place in a non-reactive gas
atmosphere, while the reaction desired takes place in a
reactive gas atmosphere at or adjacent to the substrate.
In practice, the coating chamber is first pumped down
to the desired pressure and an inert gas, such as argon,
introduced into the upper portion thereof through the
porous pipes 62. The reactive gas, such as oxygen or
nitrogen, is then introduced through the porous pipe 65
into the lower portion of the chamber. The gas introduced
into the upper portion of the chamber is usually 100~ inert
gas, such as argon, while the gas introduced into the lower
- portion of the chamber is not necessarily 100~ reactive
gas. This gas may be a mixture of argon and oxygen or
nitrogen; for example 80% oxygen or nitrogen and 20% argon.
The presence of the argon gas above the reactive gas will
prevent the reactive gas from passing upwardly into contact
with the target face.
The target may be formed of a pure metal such as
titanium or tantalum. When the reactive gas used is oxygen
and the molecules of titanium or tantalum are sputtered
from the target they will be converted into titanium oxide
SP~, 752~7
lZ198~3~7
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l or tantalum oxide respectively when they hit the oxygen.
Likewise, when nitrogen gas is used the titanium ~nd
tantalllm molecules will be converted into titanium nitride
and tantalum nitride.
To control the amount of gas introduced into the
vacuum chamber lO, set screws 75 and 76 are threaded
through the top and bottom sections 51 and 53 of each
support member 49 and 50 and are received within openings
97 and 98 in the central section 52. Upon rotation o~ the
set screws, the meeting faces 69-70 and 72-73 can be sprung
slightly toward or away from one another to increase or
decrease the width of the slits and thus regulate the
amount of gas passing therethrough.
In Figs. 5 to 7 is illustrated an alternate form of
gas distribution system embodying the basic feature of the
invention as described above. The cathode illustrated in
Fig. 5 is the same as in Figs. l to 3 so that like numeral~s
have been used to designate like parts.
The gas distribution system herein disclosed
comprises a rectangular frame 97 which encircles the lower
portion of the cathode ll within vacuum chamber lO and is
secured to the underside of the top wall 29 of said chamber
by brackets 98. The frame is composed of upper and lower
horizontal tubular side members 79 and 80 integral with the
tubular end members 81 and 82. The upper and lower side
and end members are joined together by the side and end
metal plate members 83 and 84 respectively,
The gases are introduced into the upper and lower
tubular side members 79 and 80 through feed pipes 85 and 86
and exit therefrom and from the end members 81 and 82
through aperatures 87 and 88 respectively. The openings 87
in the upper tubular members are positioned to direct an
inert yas upwardly and inwardly toward the target 21, while
the openings 88 in the lower tubular members are positioned
to direct a re-active gas, or a mixture of inert and
reactive gases, downwardly and inwardly toward the
substrate 12 as explained above.
SPG 75207
12~ 37
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1 The operation and advantages of this form of the
invention are the same as those above described with
relation to that form of the invention illustrated in Figs.
1 to 4.
Modifications may be made without departing from the
spirit or scope of the invention as defined in the appended
claims.
