Note: Descriptions are shown in the official language in which they were submitted.
10816S6
PHN 8456
The invention relates to a sputtering device
comprising in an envelope a cathode which comprises at
its surface the material to be sputtered, a magnet device
for generating one or more magnetic fields by which at
least one electron trap before the surface is determined,
and an anode.
The invention also relates to a method of
sputtering material by means of such a device.
An electron trap is formed by magnetic field
lines which extend from the cathode surface and describe
an arc thereabove and return thereto again. Said field
lines thus form a magnetic mirror for the electrons
originating from the cathode surface. In this manner
the electrons are retained near the cathode.
Such a device and method are known from the
published ~etherlands patent application 7,211,911, Telic
Corporation, filed September 1, 1972. Such a device is
used in providing thin films on flat and curved sub-
strates, layers for the manufacture of integrated cir-
cuits, layers having magnetic properties, optical layers,
in providing internal coatings in hollow spaces, during
the manufacture of resistors and all sputtering processes
in which a low substrate temperature is desired.
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10816S6
PHN 8456
It is known from the published German patent
application 2,417,288, Airco Inc., filed March 9, 1974
that by a magnet device an electron trap ~an be obtained
which retains the electrons originating from the cathode
until they have consumed their energy in ionizing col-
lisions so that extra plasma is formed. This results
in a higher sputtering rate. However, it is also known
from Physical Vapour Deposition, pages 114 and 115, Airco
Inc., U.S.A. 1976, that said sputtering takes place very
unevenly and results in a channel-like cavity of the
cathode. This has a number of disadvantages. The
cathode has to be replaced when only a small part of
the cathode has sputtered. In addition, the channel-
like cavity of the cathode detrimentally influences
the direction in which the particles of material move
away from the cathode and the reproduceability of the
sputtering process.
It is therefore an object of the invention
to provide a device and a method which does not ex-
hibit the said disadvantages and in which a very
uniform and efficient consumption of the cathode mater-
ial can take place.
Another object of the invention is to pro-
vide a device and a method with which several types
of material can be sputtered in a simple manner and
without exchanging the whole cathode.
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101~16S6
P~IN 8456
16.3.77
According to the invention, a device of the
kind described in the preamble is characterized in
that the electron trap can be moved along the surface.
As a result of this it is possible, periodically or
continuously, to always expose another part of the
surface of the cathode to the discharge, so that a
very uniform sputtering is possible.
Such a cathode may be constructed so as
; to be flat, the magnet device being movable substan-
tially parallel to the cathode surface and prefer-
ably in one direction. Preferably, however, the
cathode is tubular and a number of mutually spaced
magnets facing each other with their north or south
poles and forming the magnet device are arranged so
as to be movable axially in or around said tubular
cathode in the axial direction.
Such a tubular cathode may have a square
or circular cross-section or may have any other
shape with which the direction in which the sputter-
ed particles move can be influenced. It is, of course,
alternatively possible to move the tubular envelope
with respect to the magnet device.
By manufacturing the cathode surface from
a number of different materials to be sputtered,
any desired composition of materials can be realized
by moving the electron trap(s~ in a simple manner.
Such a cathode made of titanium can be used
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~081656 PI-IN 8456
16.3.77
as a sputter source in a titanium sallimation pump.
The device is suitable for high frequency
and direct current applications.
The sputtering device in which in a tubular
cathode a number of spaced magnets forming the magnet
device and facing each other with their north or
south poles in the axial direction are arranged so
as to be movable axially, is particularly suitable
for providing a very uniform coating in a hollow
space, for example, a metal mirror in a lamp or
tube.
The invention will be described in greater
detail with reference to a drawing, in which:
Figure 1 shows diagrammatically a flat
cathode for a device according to the invention
having a movable electron trap,
Figures 2 and 3 are sectional view of
parts of tubular cathodes having several movable
electron traps,
Figure 4 is a sectional view of a tubular
cathode for a device according to the invention,
Figures 5 and 6 are possible sectional
views of such a cathode,
Figure 7 shows diagrammatically a device
according to the invention,and
Figure 8 is a sectional view of a tubular
cathode for a device according to the invention.
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108~6S6 PHN 8456
Figure 1 shows diagrammatically a flat cathode
1 for a device according to the invention. The direc-
tionof the field lines 2 generated by the magnet de-
vice is shown. Said field lines form an electron trap
because a magnetic mirror is created before the
cathode surface 3. In the elliptical region 4 below
the field lines a channel-shaped cavity will be
formed by the sputtering of the cathode material,
By moving the electron trap, preferably in the direc-
t~on of the arrow 33, said erosion can be distributed
over the whole surface 3. When the cathode surface is
composed of several types of material, any desired
composition of materials can be realized by moving
the electron trap. During sputtering, the cathode
1 has a negative potential with respect to the anode
5 of approximately 800 Volts. In practice voltages
are used of a few hundred Volts up to a few kVolts.
In the sputtering space a pressure of 10 3 to 10
Torr usually prevails. As a sputtering gas may be
used, for example, argon, neon, or reactive gases
such as 2' N2 or mixtures thereof.
Figure 2 shows a part of a tubular cathode
6 for a device according to the invention. Said tu-
bular cathode comprises-a number of magnets 7 which
are arranged at a distance from each other and have
thelr corresponding poles facing 6ach other. Said
magnets 7 are permanent magnets in this case. How-
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10816S6 16~3.77
ever, they may also be electromagnets. In this case,
soft iron discs 8 are provided between the magnets
and influence the direction of the entrance and e~it
of the field lines. However, said discs may also be
absent or be manufactured from a material other than
soft iron. As a result of the magnets, electron traps
9 situated around the cathode are formed. The magnets
can be moved wlth respect to the cathode surface so
that the formation of channel-like grooves around the
cathode can be prevented by periodic or continuous
displacement of the magnet device in the direction
of the arrow 33. It is, of course, alternatively
possible to move the cathode surface with respect
to the magnet devioe. The anode 10 is in the form
of a ring.
Figure 3 also shows a tubular cathode. In
this case the magnets consist of permanent magnetic
rings 11 and the electron traps are situated on the
inside of the tubular cathode. In this case the anode
12 is in the form of a rod.
. .,
Figure 4 is a sectional view of a tubular
cathode for a device according to the invention.
The cathode surface is determined by a tube 13 hav-
ing an inside diameter of 28 mm and an outside dia-
meter of 32 mm and is closed on one side. Said tube,
300 mm long, comprises a number of 6 mm thick an-
nular magnets 14 which are situated around a water
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P~l~ 8456
16.3.77
- 10816S6
inlet tube 15 for cooling water. The cooling water
flows along the wall of the tube 13 via the spaces
16 to the water outlet 17. The water is admitted
via the inlet aperture 18. By means of an 0-ring
seal 19 the magnet device 20 is placed in the holder
21 so as to be movable. The said holder 21 is arrang-
ed so as to be insulated with respect to the housing
23 of the device by means of a glass plate 22. When
a large number of magnets are used, a large number
of electron traps are obtained. The kno~n cylindri-
.cal sputtering systems require very strong and large
magnets, since the magnetic field must be constant
and parallel to the surface of the cathode through-
out the length of the cylindrical cathode.
Figures 5 and 6 show possible cross-sections
of such a cathode. The space 16 for passing the cool-
ing water is situated between a magnet 14 and the in-
ner wall of the tube 13. The magnets 14 are situated
around the cooling water tube 15. The electrons
trapped by the electron trap will cover a cycloidal
track 32 as is shown in Figure 6.
It is alternatively possible to construct
the tube 13 so as to be double-jacketed so that the
inner tube constantly serves as a holder for the
magnet device and the outer tube can or cannot be
; moved around the inner tube and serves as a cathode
surface which can easily be replaced.
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PHN 8456
10~6S6 16.3.77
~igure 7 shows diagrammatically a device ac-
cording to the invention. The cathode 24 is secured
in the housing 23 by means of a glass plate 22 and
is connected to a high frequency or direct current
supply 25 for applying the desired potential between
the cathode 24 and the anode 26 which in this case
is annular. After evacuating the housing 23 via gas
outlet aperture 27, the housing 23 is filled with
argon to a pressure of 10 3 Torr via the gas inlet
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aperture 28. The cathode 24 is cooled by cooling
water, as described, via the connections 29 and 30.
i The material sputtered from the cathode is deposit-
ed on the substrate 31 as a layer or a thin film.
The mag~et device is reciprocated continuously or
periodically by means of a driving mechanism 34. As
was to be expeoted, the sputtering rate for a device
according to the invention is substantially equally
large as for the known devices. For example, a sput-
tering rate for copper of 10~000 ~/minute was measur-
ed with a direct current discharge with a supplied
power of 2 kW and a distance between the cathode and
the substrate of 5 cm. With a high frequency dis-
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charge the sputtering rate was approximately 5000 ~/
minute with the same power and electrode/substrate
arrangement. However, the cathode according to the
invention could be used 3 to 5 x longer than when
the magnet device was not moved. Hence, the use
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PI~N 8L~56
10816S6 1 6.3.77
of the invention means that the sputtering process
need be interrupted less frequently and that the
cathode material to be sputtered is used more effi-
ciently.
Figure 8 is a sectional view of a tubular
cathode according to the invention in which the
cathode surface consists of chromium 35 and copper
36. By moving the magnet device 20 a choice can be
made from chromium and copper or a mixture thereof.
In the position shown of the magnet device, copper
36 is sputtered which is deposited on the inner wall
` of the glass tube 37 and forms a:thin coating. Of
course, it is alternatively possible not to com-
pose the magnet device from one group of magnets
as is shown in Figure 8, but of several groups.
It is also possible to compose the cathode surface
of more than two different materials, This type
of cathodes is particularly suitable for coating
the inside of tubes of metal or glass or of en-
velopes o,f, for example, lamps. The whole cathode
with the associated anode 38, in this case amlular,
can be moved through a tube while sputtering so
that said tube is coated on its side. By means of
a cathode as shown in Figure 3, rods or tubes can
be coated on the outside.
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