U.S. patent application number 13/766428 was filed with the patent office on 2013-08-22 for target utilization improvement for rotatable magnetrons.
The applicant listed for this patent is Dennis R. Hollars. Invention is credited to Dennis R. Hollars.
Application Number | 20130213805 13/766428 |
Document ID | / |
Family ID | 44708342 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130213805 |
Kind Code |
A1 |
Hollars; Dennis R. |
August 22, 2013 |
TARGET UTILIZATION IMPROVEMENT FOR ROTATABLE MAGNETRONS
Abstract
Rotatable magnetron sputtering apparatuses are described for
depositing material from a target while reducing premature burn
through issues. The rotatable magnetron sputtering apparatus
includes electric coils wound on pole pieces to modulate the
magnetic fields at the ends of the magnetron magnetic assembly.
Changing the direction of electric current moves the sputtering
region alternately around its normal central position to decrease
the rate of erosion depth at the ends of the target material.
Inventors: |
Hollars; Dennis R.; (San
Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hollars; Dennis R. |
San Jose |
CA |
US |
|
|
Family ID: |
44708342 |
Appl. No.: |
13/766428 |
Filed: |
February 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12753814 |
Apr 2, 2010 |
8398834 |
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13766428 |
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Current U.S.
Class: |
204/298.22 |
Current CPC
Class: |
C23C 14/3407 20130101;
C23C 14/35 20130101; H01J 37/3405 20130101; H01J 37/3458 20130101;
H01J 37/3452 20130101 |
Class at
Publication: |
204/298.22 |
International
Class: |
C23C 14/35 20060101
C23C014/35 |
Claims
1. A magnetic assembly for use in a cylindrical rotatable
magnetron, comprising; a first magnet disposed toward a central
portion of the magnetic assembly, the first magnet having a first
magnetic orientation; a second magnet disposed toward an outer
portion of the magnetic assembly, the second magnet having a second
magnetic orientation that is opposite to the first magnetic
orientation; and one or more electromagnetic coils between the
first and second magnets, the one or more electromagnetic coils
wound around one or more pole pieces, the one or more
electromagnetic coils configured to provide a magnetic field having
a third magnetic orientation that is parallel to one of the first
and second magnetic orientations and opposite to the other of the
first and second magnetic orientations.
2. The magnetic assembly of claim 1, wherein the one or more
electromagnetic coils are disposed at end portions of the magnetic
assembly.
3. The magnetic assembly of claim 1, wherein the one or more
electromagnetic coils are arranged in an approximately curved
fashion along a sputtering path at each end of the magnetic
assembly.
4. The magnetic assembly of claim 1, wherein the first and third
magnetic orientations are parallel.
5. The magnetic assembly of claim 1, wherein the second and third
magnetic orientations are parallel.
6. The magnetic assembly of claim 1, wherein the first magnet
comprises a plurality of magnets.
7. The magnetic assembly of claim 1, wherein the second magnet
comprises a plurality of magnets.
8. The magnetic assembly of claim 1, further comprising one or more
magnetic field-shaping pole pieces disposed on top of the one or
more pole pieces.
9. The magnetic assembly of claim 1, wherein one or more of the
first and second magnets are permanent magnets.
10. The magnetic assembly of claim 1, wherein the second magnet
circumscribes at least a portion of the first magnet.
11. The magnetic assembly of claim 1, wherein the first magnet has
a length that is larger than a width of the first magnet.
12. The magnetic assembly of claim 1, wherein the second magnet has
a length that is larger than a width of the second magnet.
13. The magnetic assembly of claim 1, wherein the magnetic assembly
comprises 5 or more electromagnetic coils at each end of the
magnetic assembly.
14. A cylindrical rotatable magnetron sputtering apparatus,
comprising: a magnetic assembly having one or more electromagnetic
coils between a first magnet and a second magnet, the one or more
electromagnetic coils configured to provide a magnetic field having
a magnetic orientation that is parallel to the magnetic orientation
of one of the first and second magnets and opposite the magnetic
orientation of the other of the first and second magnets; one or
more insulated wires in electric contact with the one or more
electromagnetic coils, the one or more insulated wires configured
to provide electric current to the one or more electromagnetic
coils; and a backing tube for housing the magnetic assembly, the
backing tube configured to hold a target material, wherein the
backing tube is configured to rotate while the magnetic assembly
remains stationary.
15. A cylindrical rotatable magnetron sputtering device,
comprising: a magnetic assembly having a first set of
electromagnetic coils and a second set of electromagnetic coils,
each of the first and second sets of electromagnetic coils disposed
between a first magnet and a second magnet, each of the first and
second sets of electromagnetic coils configured to provide a
magnetic field having a magnetic orientation that is parallel to
the magnetic orientation of one of the first and second magnets and
opposite the magnetic orientation of the other of the first and
second magnets; one or more insulated wires in electric contact
with the first and second sets of electromagnetic coils, the one or
more insulated wires configured to provide electric current to each
of the first and second sets of electromagnetic coils; and a
backing tube for housing the magnetic assembly, the backing tube
configured to hold a target material.
16. The cylindrical rotatable magnetron sputtering device of claim
15, wherein the backing tube is configured to rotate while the
magnetic assembly remains stationary.
17. The cylindrical rotatable magnetron sputtering device of claim
15, further comprising a plurality of insulated wires, wherein a
first subset of the plurality of insulated wires is in electric
contact with the first set of electromagnetic coils, and wherein a
second subset of the plurality of insulated wires is in electric
contact with the second set of electromagnetic coils.
18. The cylindrical rotatable magnetron sputtering device of claim
17, wherein each of the first subset and the second subset of the
plurality of insulated wires is in electric contact with a separate
power supply.
19. The cylindrical rotatable magnetron sputtering device of claim
15, wherein the one or more insulated wires include a pair of wires
separately connected in parallel to the first and second sets of
electromagnetic coils.
20. The cylindrical rotatable magnetron sputtering device of claim
15, wherein the one or more insulated wires include pairs of wires,
each of the pairs of wires being connected to one of the first set
and second set of electromagnetic coils.
21. The cylindrical rotatable magnetron sputtering device of claim
20, wherein each of the pairs of wires is in electric contact with
a separate power supply.
Description
CROSS-REFERENCE
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/753,814, filed Apr. 2, 2010, which
application is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] Sputter deposition is a physical vapor deposition ("PVD")
method for depositing thin films by sputtering, i.e., ejecting,
material from a "target" (or source) onto a "substrate", such as a
silicon wafer. Sputtering sources can be magnetrons that use strong
electric and magnetic fields to trap electrons close to the surface
of the magnetron. The electrons follow helical paths around the
magnetic field lines undergoing more ionizing collisions with
gaseous neutrals species near the target surface than would
otherwise occur. The sputter gas is an inert, such as argon (Ar).
The extra Ar ions created as a result of these collisions leads to
a higher deposition rate. The plasma can be sustained at a lower
pressure.
[0003] U.S. Pat. No. 4,356,073 to McKelvey ("McKelvey '073"), which
is entirely incorporated herein by reference, teaches a rotatable
magnetron sputtering apparatus. McKelvey '073 teaches a
backing/target tube that is a straight cylinder of constant
diameter. U.S. Pat. No. 4,445,997 to McKelvey ("McKelvey '997"),
which is entirely incorporated herein by reference, teaches a
rotatable magnetron with a non-cylindrical backing/target tube that
is somewhat barrel shaped having a larger diameter over a portion
of the center region. The teachings of McKelvey '997 can be applied
to coating curved substrates, like the windshields of automobiles.
U.S. Pat. No. 4,466,877 to McKelvey ("McKelvey '887"), which is
entirely incorporated herein by reference, teaches a dual rotatable
magnetron as a pair of single cylindrical magnetrons mounted in
close proximity to each other, and powered simultaneously. With
this arrangement two different metals (i.e., one on each magnetron)
can be "co-sputtered" to form a coating on a substrate that was an
alloy of the metals.
[0004] There have been improvements in the art, both in
construction details and methods of incorporation in sputtering
processes. For example, U.S. Pat. No. 6,365,010 to Hollars
("Hollars"), which is entirely incorporated herein by reference,
teaches construction methods and process embodiments for the use of
dual rotatable magnetrons for the deposition of dielectric
coatings.
[0005] One issue with current single rotatable magnetrons and dual
rotatable magnetrons is that the utilization of the target material
is limited by excess material erosion at the ends of the target,
leading to premature end of target life and inefficient utilization
of the often expensive target material.
[0006] Reference will now be made to the figures, wherein like
numerals refer to like parts throughout. It will be appreciated
that the figures are not necessarily drawn to scale.
[0007] FIG. 1 shows a perspective cutaway view 1a illustrating the
design of a typical rotatable magnetron and a top planar view 1b of
the magnetic closure at each end of the device. In view 1a of FIG.
1 target material 1 is bonded to a carrier tube 2, which tube can
normally be reused a number of times with the same or different
target material. A pair of concentric pipes or tubes, 3a and 3b,
are used to provide pressurized cooling water in and out of the
magnetron as well as to support a magnetic assembly 4. In its basic
form the magnetic assembly consists of a set of permanent magnets 5
arranged in straight rows with the middle row having opposite
magnetic polarity to those on each side, as indicated by the north
(N) and south (S) pole labels. The device can function with all of
the magnets inverted with respect to the orientation in the
illustration. The magnets sit on a highly permeable elongated plate
or bar 6, which provides a closure path for the magnetic flux on
the back side of the assembly. Mild steel and iron/nickel alloys
can be used for this purpose. Mounting bar 7 supports the magnets
and permeable plate and provides a means of attachment to tube 3b.
A thin enclosing cover 8 protects the magnets from water damage. In
operation the tubes and magnetic assembly can be held fixed while
the target material and backing tube can be rotated past the
magnetic assembly as indicated by the arrow. A negative direct
current ("DC") voltage or an alternating voltage can be applied to
the target, and the arched magnetic field (not shown) between the
magnet poles provides a region of increased electron trapping which
allows the device to sputter the target material at relatively low
pressures compared to diode sputtering.
[0008] The magnetic assembly must terminate near each end of the
target. View 1b of FIG. 1 shows a top planar view of the most
common construction where the outer set of magnets are connected by
a roughly circular segment of magnets 9 oriented in the same sense
with the spacing `W` between the straight segments approximately
preserved around the end. View 1b also illustrates that magnetic
assemblies are generally constructed using individual magnets.
Often permeable continuous pole pieces are used as a cap on the
individual magnets to both concentrate the magnetic flux and smooth
the magnitude of the flux generated from individual magnets that
usually have somewhat unequal strength. The pole pieces can be so
effective in smoothing the flux that small gaps between the
individual magnets can also be tolerated. This allows an additional
way of adjusting magnetic field strength. These optional pole
pieces have not been shown in this figure. Dashed line 10 shows the
path of the central region of the arched magnetic field where
sputtering of the target material proceeds at the most rapid rate.
The target material erodes faster at each end because the
turn-around region of the magnetic field there presents a somewhat
longer sputtering path length to the direction of rotation of the
target tube than do the straight sections. This effect is
illustrated in FIG. 2 in views 2a and 2b. View 2a shows that target
material 1 on backing tube 2 has uniform thickness before
sputtering begins. View 2b shows the target at end of life after
sputtering. The common problem is that the material is exhausted
down to the backing tube 2 at region 11 on the ends of the target,
while a significant thickness of material (about 25 to 30% in some
cases) remains unused over the majority of the tube length. This
premature "burn through" results in poor net utilization of target
materials that are often very expensive.
[0009] An approach to resolving this problem is taught by U.S. Pat.
No. 5,364,518 to Hartig et al. ("Hartig"), entitled "Magnetron
Cathode for a Rotating Target". FIG. 3a and FIG. 3b illustrate
certain teachings of Hartig. FIG. 3a shows the arched magnetic
fields that exist between magnetic poles of opposite sense. When a
voltage is applied, sputtering proceeds most rapidly at the mid
point of the arched field. The shape of the sputtering groove 12
that results is approximately the inverse of the shape of the
arched magnetic field as implied by FIG. 3a. More precisely
sputtering proceeds most rapidly where the component of the
magnetic field that is perpendicular to the local surface of target
material 1 goes to zero. This is commonly referred to as the
vertical component of the field. For a curved or arched magnetic
field this point is also where the tangent to the magnetic field
line arch is parallel to the local target material surface. FIG. 3b
shows the improvement. A magnetic shunt 13 is placed across one
side of the magnets. This would correspond to the outside array of
magnets on the turn around indicated as 9 in FIG. 1 (view 1b). The
shunt causes the arched magnetic field to become skewed as
indicated. When target material 1 has full thickness, sputtering
proceeds most rapidly somewhat offset towards the shunt. But as the
target material gets thinner, the maximum sputtering region shifts
towards the center of the magnets, thus broadening or smearing the
sputtering region over a larger area. This effectively slows the
erosion in the burn through region with respect to the remainder of
the target. With this arrangement the length of the sputtering
groove at the beginning of sputtering is somewhat longer than it is
when the sputtering is finished. As a consequence, the uniformity
of the deposited coating on the substrate changes slightly over the
life of the target.
[0010] Other magnetic arrangements around the ends of the magnetic
assembly can be used to minimize the premature burn through
problem. One is to make use of magnets with variations in strength
along with (usually) smaller magnets and/or highly permeable
elements placed between the primary magnets to reshape the magnetic
fields. Using these methods it is possible to flatten the tops of
the arched fields, which also results in a broader and flatter
erosion groove on the target ends. It is also possible by magnet
arrangement to "split" the end groove into two grooves spaced a
certain distance apart. This also helps remedy the burn through
problem.
[0011] U.S. Pat. No. 6,146,509 to Aragon ("Aragon"), entitled
"Inverted Field Circular Magnetron Sputtering Device", which is
entirely incorporated herein by reference, teaches an inverted
field circular magnetron sputtering device with no moving
mechanical parts. FIG. 4 shows an isometric cut-away view of an
inverted field circular planar magnetron of Aragon. The features of
the magnetron of Aragon are axially symmetric, and if it were cut
in each half would resemble an end region of a typical cylindrical
rotatable magnetron as previously described. FIG. 5 illustrates the
symmetric cross sectional layout of Aragon in greater detail. The
primary permanent magnets at the center pole 14a and around the
outer pole 14b are orientated in the same magnetic sense, as
indicated by the arrows. In a "normal" magnetron the inner and
outer magnets have opposite sense. The inner and outer poles of the
magnetron of Aragon have the same sense, i.e., one of the poles has
been inverted with respect to the "normal" sense. The magnetron of
Aragon can be referred to as an "inverted field" magnetron. In
addition to the permanent magnets, Aragon teaches use of a pair of
independent circular coils 43 and 44 situated between the primary
poles. Each coil has an associated permeable pole piece 41 and 42
respectively. The permanent magnets are capped with permeable pole
pieces 16a and 16b, which cab help to concentrate the flux from the
magnets as well as to smooth the flux from non-uniform magnets.
This can be a common feature of most magnetrons.
[0012] By a proper selection of DC currents through the coils,
magnetic poles of opposite sense to the primary poles can be
created which cause the formation of two magnetic electron trapping
fields 17a and 17b. Thus two concentric sputtering grooves instead
of the usual single groove can be created. By varying the currents
in the coils and alternately powering them, the magnetic strengths
and directions of the induced magnetic poles can be changed. This
will cause the sputtering grooves to move a small radial distance
either in or out, improving both the target utilization and the
uniformity of the deposited coating on a stationary circular
substrate.
[0013] While there are approaches to resolving the burn through
problem, such approaches can have their limitations. For example,
magnetic arrangements for overcoming the burn through problem are
rather difficult to construct correctly. Individual magnets never
have exactly the same strength, so that each setup has to be
individually "tweaked" into its final configuration. Also, magnets
may loose magnetic strength with time, especially from over heating
if the magnetron is improperly cooled, or if the cooling is
interrupted during operation. If a magnetic material such as nickel
is used for sputtering, the target material must be relatively thin
to allow enough magnetic flux to leak through to support
sputtering. In this case the shunting solution in FIG. 3b does not
give ample sputtering groove movement to avert the burn through
problem, and other magnetic "fixes" change with time as the target
material gets thinner. A solution is to move the entire magnetic
assembly in and out of the target tube by about 0.5 inches during
the sputtering operation. However, this solution is impractical as
it is very complicated to couple linear motion through the wall of
a vacuum chamber. Most sealing arrangements can lead to leakage,
and bearing surfaces have to be elongated to accept the motion.
While desirable in concept, this method is difficult to accomplish
in practice.
[0014] Accordingly, there is a need in the art for magnetron
sputtering devices and methods that overcome the burn through
problem of current sputtering devices and methods.
SUMMARY OF THE INVENTION
[0015] In one aspect of the invention, rotatable magnetron
sputtering devices and methods for preventing the premature burn
through of a target material are provided. In embodiments,
rotatable magnetron sputtering devices that do not utilize any
physically moving parts are provided.
[0016] In an aspect of the invention, a magnetic assembly for use
in a cylindrical rotatable magnetron is provided. The magnetic
assembly comprises a first magnet disposed toward a central portion
of the magnetic assembly, the first magnet having a first magnetic
orientation. The magnetic assembly further comprises a second
magnet disposed toward an outer portion of the magnetic assembly,
the second magnet having a second magnetic orientation that is
opposite to the first magnetic orientation. The magnetic assembly
further comprises one or more electromagnetic coils between the
first and second magnets, the one or more electromagnetic coils
wound around one or more pole pieces. The one or more
electromagnetic coils are configured to provide a magnetic field
having a third magnetic orientation that is parallel to one of the
first and second magnetic orientations and opposite to the other of
the first and second magnetic orientations.
[0017] In another aspect of the invention, a cylindrical rotatable
magnetron sputtering apparatus is provided. The cylindrical
rotatable magnetron sputtering apparatus comprises a magnetic
assembly having one or more electromagnetic coils between a first
magnet and a second magnet, the one or more electromagnetic coils
configured to provide a magnetic field having a magnetic
orientation that is parallel to the magnetic orientation of one of
the first and second magnets and opposite the magnetic orientation
of the other of the first and second magnets. The cylindrical
rotatable magnetron sputtering apparatus further comprises one or
more insulated wires in electric contact with the one or more
electromagnetic coils, the one or more insulated wires configured
to provide electric current to the one or more electromagnetic
coils. The cylindrical rotatable magnetron sputtering apparatus
further comprises a backing tube for housing the magnetic assembly,
the backing tube configured to hold a target material. The backing
tube is configured to rotate while the magnetic assembly remains
stationary.
[0018] In another aspect of the invention, a cylindrical rotatable
magnetron sputtering device is provided. The cylindrical rotatable
magnetron sputtering device comprises a magnetic assembly having a
first set of electromagnetic coils and a second set of
electromagnetic coils, each of the first and second sets of
electromagnetic coils disposed between a first magnet and a second
magnet, each of the first and second sets of electromagnetic coils
configured to provide a magnetic field having a magnetic
orientation that is parallel to the magnetic orientation of one of
the first and second magnets and opposite the magnetic orientation
of the other of the first and second magnets. The cylindrical
rotatable magnetron sputtering device further comprises one or more
insulated wires in electric contact with the first and second sets
of electromagnetic coils, the one or more insulated wires
configured to provide electric current to each of the first and
second sets of electromagnetic coils. The cylindrical rotatable
magnetron sputtering device further comprises a backing tube for
housing the magnetic assembly, the backing tube configured to hold
a target material.
[0019] Various objects, features and advantages of the present
invention will become apparent to those skilled in the art after
having read the following detailed description of preferable
embodiments, which are illustrated in the several figures of the
drawing.
INCORPORATION BY REFERENCE
[0020] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent, or patent
application was specifically and individually indicated to be
incorporated by reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized, and the accompanying drawings, which are not
necessarily drawn to scale, and of which:
[0022] FIG. 1 is a perspective cutaway schematic view of a
cylindrical rotatable magnetron, and a planar view of a typical
magnetic assembly at the ends of the magnetron;
[0023] FIG. 2 is a cross sectional view of a cylindrical rotatable
target on a backing tube illustrating the premature burn through at
the end of the target;
[0024] FIG. 3a is a prior art schematic showing the sputtering
erosion pattern for the typical magnetic field geometry for a
cylindrical rotatable magnetron;
[0025] FIG. 3b is a prior art illustration of a magnetic shunt
method of minimizing the burn through at the ends of a cylindrical
rotatable magnetron;
[0026] FIG. 4 is an isometric cut-away schematic diagram showing
the construction and layout of a prior art inverted field circular
planar magnetron;
[0027] FIG. 5 is a detailed cross sectional view of a prior art
inverted field circular planar magnetron that is symmetrical about
the center line;
[0028] FIG. 6 is a detailed cross sectional view of a modified
prior art inverted field circular planar magnetron that becomes
appropriate for application to the ends of a cylindrical rotatable
magnetron, in accordance with an embodiment of the invention;
[0029] FIG. 7 is a schematic illustration showing the principle of
joining the halves of a modified circular planar magnetron to the
ends of an arbitrarily long straight magnetic assembly of a
cylindrical rotatable magnetron, in accordance with an embodiment
of the invention;
[0030] FIG. 8 shows a practical embodiment of the invention for the
ends of the magnetic assemblies of cylindrical rotatable
magnetrons, in accordance with an embodiment of the invention;
[0031] FIG. 9 illustrates the change in the position of maximum
sputtering for opposite directions of the DC current through the
coils of the embodiment of the invention, in accordance with an
embodiment of the invention; and
[0032] FIG. 10 depicts an embodiment where a pair of wires supplies
the DC current in parallel to the coils at each of the ends of a
cylindrical rotatable magnetron, in accordance with an embodiment
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0033] While preferable embodiments of the invention have been
shown and described herein, it will be obvious to those skilled in
the art that such embodiments are provided by way of example only.
Numerous variations, changes, and substitutions will now occur to
those skilled in the art without departing from the invention. It
should be understood that various alternatives to the embodiments
of the invention described herein can be employed in practicing the
invention.
[0034] In aspects of the invention, magnetron sputtering devices
and methods are provided. Magnetron sputtering devices of
embodiments of the invention are configured to operate with
physical vapor deposition ("PVD") systems, including ultrahigh
vacuum ("UHV") chambers having a material on which deposition of a
particular target material is desired. In embodiments, cylindrical
rotatable magnetrons for preventing premature burn through of a
target material are provided. In various embodiments, solutions to
premature burn through that do not utilize any physically moving
parts are provided.
[0035] Methods and devices of embodiments of the invention reduce,
if not eliminate, target burn through by providing a uniform
sputtering rate across the target. In an embodiment, this is
accomplished by providing a sputtering rate that is higher at
certain locations than others. For example, the sputtering rate
away from the ends of the target can be higher, thus providing for
nearly uniform or substantially uniform sputtering across the
target.
[0036] Methods and systems of embodiments of the invention are
based on the realization that there are issues associated with
current magnetron sputtering systems and methods. One issue with
current systems and methods is that during sputtering the target
depletes more quickly at certain points (e.g., the ends) than
others, leading to the so-called "burn trough" problem. This can
lead to high processing costs.
[0037] In embodiments, non-mechanical magnetron sputtering
apparatuses and methods are provided. Apparatuses and methods of
embodiments of the invention reduce, if not eliminate the burn
through issues associated with current magnetron sputtering
apparatuses and methods.
Magnetron Sputtering Apparatuses
[0038] In an aspect of the invention, a magnetron sputtering
apparatus is provided. In embodiments, the magnetron sputtering
apparatus includes a magnetic assembly. In embodiments, the
magnetic assembly is configured for use in a rotatable magnetron,
such as a cylindrical rotatable magnetron. In an embodiment, the
magnetic assembly of the magnetron sputtering apparatus comprises a
first magnet disposed toward a central portion of the magnetic
assembly, the first magnet having a first magnetic orientation. The
magnetic assembly further comprises a second magnet disposed toward
an outer portion of the magnetic assembly, the second magnet having
a second magnetic orientation that is opposite to the first
magnetic orientation. The magnetic assembly further comprises one
or more electromagnetic coils (also "electric coils" herein)
between the first and second magnets. In embodiments, the one or
more electromagnetic coils are wound around one or more pole
pieces. The one or more electromagnetic coils are preferably
configured to provide a magnetic field having a third magnetic
orientation that is parallel to one of the first and second
magnetic orientations and opposite (or anti-parallel or
inverse-parallel) to the other of the first and second magnetic
orientations.
[0039] In embodiments, the electromagnetic coils (also "coils"
herein) can be formed of a conductor. In embodiments, the coils can
be formed of one or more electrically conductive metals, such as
copper (Cu). In an embodiment, the coils can be formed of insulated
Cu wires. In embodiments, winding a conductive wire around a pole
piece (or core) provides an inductor or electromagnet configured to
produce a magnetic (or electromagnetic) field upon the flow of
electric current (e.g., DC current) through the conductive
wire.
[0040] In an embodiment, the magnetic assembly further comprises
one or more magnetic field-shaping pole pieces disposed on top of
the one or more pole pieces. The magnetic field-shaping pole pieces
can be configured to produce a net magnetic field having a
predetermine shape.
[0041] In an embodiment, the one or more electromagnetic coils are
disposed at end portions of the magnetic assembly. In an
embodiment, the one or more electromagnetic coils are arranged in
an approximately or nearly curved fashion along a sputtering path
at each end of the magnetic assembly. In another embodiment, the
one or more electromagnetic coils are arranged in a substantially
curved fashion along the sputtering path at each end of the
magnetic assembly.
[0042] In an embodiment, the magnetic assembly has a length that is
longer than a width of the magnetic assembly. In such a case, the
magnetic assembly is cylindrical or nearly cylindrical.
[0043] In an embodiment, the first and third magnetic orientations
of the magnetic assembly are parallel. In another embodiment, the
second and third magnetic orientations are parallel.
[0044] In an embodiment, the first magnet of the magnetic assembly
comprises a plurality of magnets. In such a case, the plurality of
magnets can be arranged so as to produce a predetermined magnetic
field. In another embodiment, the second magnet of the magnetic
assembly comprises a plurality of magnets. In embodiments, one or
more of the first and second magnets are permanent magnets.
[0045] In an embodiment, the second magnet circumscribes at least a
portion of the first magnet.
[0046] In a preferable embodiment, the second magnet circumscribes
the entire first magnet. In an embodiment, the first magnet has a
length that is larger than a width of the first magnet. In
embodiments, the first and second magnets can be comprises of
individual smaller magnets. In certain embodiments, individual
magnets can be between about 0.5 inches and 2 inches in length, and
between about 0.1 inches and 1 inch in width. In an embodiment,
individual magnets can have a length of about 1 inch and a width
less than about 0.5 inches.
[0047] In an embodiment, the magnetic assembly comprises, at each
end, 1 or more electromagnetic coils, 2 or more electromagnetic
coils, 3 or more electromagnetic coils, 4 or more electromagnetic
coils, 5 or more electromagnetic coils, 6 or more electromagnetic
coils, 7 or more electromagnetic coils, 8 or more electromagnetic
coils, 9 or more electromagnetic coils, 10 or more electromagnetic
coils, 11 or more electromagnetic coils, 12 or more electromagnetic
coils, 13 or more electromagnetic coils, 14 or more electromagnetic
coils, 15 or more electromagnetic coils, 16 or more electromagnetic
coils, 17 or more electromagnetic coils, 18 or more electromagnetic
coils, 19 or more electromagnetic coils, 20 or more electromagnetic
coils, or 30 or more electromagnetic coils.
[0048] In embodiments, a rotatable magnetron sputtering apparatus
(or device) is provided having a magnetic assembly comprising one
or more electromagnetic coils between a first magnet and a second
magnet. In an embodiment, the rotatable magnetron sputtering
apparatus is cylindrical at least along one cross-section of the
rotatable magnetron sputtering apparatus, in which case the
rotatable magnetron sputtering apparatus be referred to as a
cylindrical rotatable magnetron sputtering apparatus. In an
embodiment, one or both of the first and second magnets can be
permanent magnets. In embodiments, the one or more electromagnetic
coils are preferably configured to provide a magnetic field having
a magnetic orientation that is parallel to the magnetic orientation
of one of the first and second magnets and opposite the magnetic
orientation of the other of the first and second magnets. In
embodiments, the magnetic assembly further comprises one or more
insulated wires in electric contact (also "electrical contact"
herein) with the one or more electromagnetic coils. The one or more
insulated wires are configured to provide electric current to the
one or more electromagnetic coils. In an embodiment, the one or
more insulated wires are in electric communication with one or more
power supplies, such as a direct current ("DC") power supply. In an
embodiment, the magnetic assembly further comprises a backing tube
for housing the magnetic assembly, the backing tube configured to
hold a target material. In an embodiment, the backing tube is
configured to rotate while the magnetic assembly remains
stationary.
[0049] In embodiments, a cylindrical rotatable magnetron sputtering
device comprises a magnetic assembly having a first set of
electromagnetic coils and a second set of electromagnetic coils.
Each of the first and second sets of electromagnetic coils is
disposed between a first magnet and a second magnet. In an
embodiment, one or both of the first and second magnets can be
permanent magnets. In embodiments, each of the first and second
sets of electromagnetic coils is configured to provide a magnetic
field having a magnetic orientation that is parallel to the
magnetic orientation of one of the first and second magnets and
opposite the magnetic orientation of the other of the first and
second magnets. The cylindrical rotatable magnetron sputtering
device further comprises one or more insulated wires in electric
contact with the first and second sets of electromagnetic coils.
The one or more insulated wires are configured to provide electric
current to each of the first and second sets of electromagnetic
coils. In an embodiment, the cylindrical rotatable magnetron
sputtering device further comprises a backing tube for housing the
magnetic assembly. The backing tube is configured to hold a target
material. In an embodiment, the backing tube is configured to
rotate while the magnetic assembly remains stationary.
[0050] In an embodiment, the cylindrical rotatable magnetron
sputtering device further comprises a plurality of insulated wires.
A first subset of the plurality of insulated wires can be in
electric contact with the first set of electromagnetic coils. A
second subset of the plurality of insulated wires can be in
electric contact with the second set of electromagnetic coils. In
an embodiment, each of the first subset and the second subset of
the plurality of insulated wires can be in electric contact with a
separate power supply. In an alternative embodiment, the first
subset and the second subset of the plurality of insulated wires
can be in electric contact with the same power supply.
[0051] In an embodiment, the one or more insulated wires of the
cylindrical rotatable magnetron sputtering device can include a
pair of wires separately connected in parallel to the first and
second sets of electromagnetic coils. In another embodiment, the
one or more insulated wires can include pairs of wires, each of the
pairs of wires being connected to one of the first set and the
second set of electromagnetic coils. In an embodiment, each of the
pairs of wires can be in electric contact with a separate power
supply.
[0052] With reference to FIG. 6, in an embodiment, a magnetron
sputtering apparatus (or device) is shown. The magnetron sputtering
apparatus includes permanent magnets 14a and 14b, or center pole
and outer pole, respectively, capped with permeable pole pieces 16a
and 16b. In embodiments, the sputtering apparatus includes a single
electromagnetic coil (also "coil" herein) 15 wound
circumferentially around a highly permeable pole piece 17. The
magnetic orientation of the center pole 14a and outer pole 14b are
orientated in an opposite magnetic sense, as indicated by the
arrows. In the illustrated embodiment of FIG. 6, the two central
coils 43 and 44 of Aragon and their associated pole pieces are
replaced with the single coil 15.
[0053] With continued reference to FIG. 6, in an embodiment, the
pole piece 17 helps concentrate the field produced upon the flow of
current (e.g., direct current) through the single coil 15. In an
embodiment, the height of the pole piece 17 can be varied to adjust
the total field strength. In an embodiment, the height of the pole
piece 17 can be selected so as to provide a desired (or
predetermined) field strength. In an embodiment, the height can be
about the same as the permanent magnets 14a and 14b and pole pieces
in order to make the most efficient use of the available magnetic
field strength.
[0054] With continued reference to FIG. 6, in an embodiment,
orienting the permanent magnet 14b such that it has an opposite
sense (or orientation) with respect to the permanent magnet 14a
causes magnetic field lines 17a from permanent magnet 14a to seek a
closed path through outer pole 14b. However, depending upon the
direction of the DC current through coil 15, the induced direction
of the combined magnetic field in pole piece 17 and the field from
the coil 15 itself can be changed to match the field direction of
one of pole 14a and pole 14b and opposite to the other of pole 14a
and pole 14b. In the illustrated embodiment, the direction of the
field in pole piece 17 matches that in center pole 14a (and
opposite the field lines in outer pole 14b) so that field lines 17b
(emanating from pole piece 17) also may seek closure at 14b. This
causes the center of the magnetic field to be skewed away from its
central position to a new position 18, where the maximum sputtering
rate can occur. In an alternative embodiment (not shown), the
direction of the current in coil 15 can be reversed such that the
induced direction of the combined magnetic field in pole piece 17
is parallel to that of outer pole 14b and opposite to the field
direction of pole 14a. In such a case, the position of maximum
sputtering rate can move to the other side of pole piece 17. In
embodiments, by changing the direction of current through coil 15,
the position of maximum sputtering can be swept to either side of
pole piece 17 and coil 15 at a rate equal to the alternating
frequency of the applied DC current, which can be selected
arbitrarily. In an embodiment, DC current is alternated at a
frequency selected to average the deposition over the time of
substrate passage through the deposition chamber. This new
arrangement would also improve the target utilization of an
ordinary circular planar magnetron, but the uniformity of the
deposited coating on a stationary circular substrate will not be as
good as for the original inverted field embodiment.
[0055] With reference to FIG. 7, a top view of a circular planar
magnetron sputtering apparatus is depicted, in accordance with an
embodiment of the invention. Separate half segments of circular
magnetron are shown, with each half being attached to the end of an
arbitrarily long straight section of the magnetic assembly of a
cylindrical rotatable magnetron. FIG. 6 is a cross-sectional side
view of the half segment shown at the bottom right of FIG. 7. The
circular magnetron of FIG. 7 includes magnets 5. In an embodiment,
the magnets 5 can be the same as those shown in views 1a and 1b of
FIG. 1, and the other elements are labeled consistently with those
of FIG. 6. The skilled artisan will understand that a magnetic
field (and subsequent sputtering) cannot be generated if the coil
15 is cut in as this would prevent current flow.
[0056] With reference to FIG. 8, a construction for the end of a
cylindrical rotatable magnetron magnetic assembly that will
accomplish the same field switching function as in the circular
planar design of FIG. 6 is shown, in accordance with an embodiment
of the invention. Magnetic assembly 8a can be like that described
in FIG. 1 view 1b except that pole pieces 21 with coils 22 are
added along sputtering path 10 in the turn around region. In an
embodiment, the coils 22 are wound around the pole pieces 21. In
embodiments, each of the pole pieces 21 is configured to generate a
magnetic field. In an embodiment, each of the pole pieces 21 can
function like the pole piece 17 of FIG. 6. The number and size of
the pole pieces and coils may be adjusted to best fit the geometry
of the end section of the magnetic assembly to accomplish the
approximately half circular geometry derived from the circular
planar case. For instance, if the assembly were wider as shown in
assembly 8b, central pole piece 24 can be made longer with respect
to the other pole pieces. Alternately, central pole piece 24 can be
made from two shorter pole pieces. In either case, in a preferable
embodiment, the coils should all be wound in the same sense as
indicated by arrows 25 such that, upon the application of direct
current, the resulting magnetic field vectors from pole pieces 21
are parallel to one another. In an embodiment, pole pieces 21 can
be electrically connected in series to simplify the wiring to the
current source. In an embodiment, a series connection can allow all
five coils to be powered conveniently by a single pair of wires. If
the coils are independent and powered by several sets of wires, the
flow of current though all the coils can be in the same direction
to produce the proper magnetic field. In an embodiment (not shown),
optional continuously curved pole pieces can be added on top of the
coils (top pole pieces), below the coils (bottom pole pieces), or
both to smooth and shape the field further. Top and/or bottom pole
pieces can provide a permanent field shape that need not exactly
follow the piecewise pattern of the coils.
[0057] In embodiments, the magnetic assembly can comprise, at each
end, 1 or more, or 2 or more, or 3 or more, or 4 or more, or 5 or
more, or 6 or more, or 7 or more, or 8 or more, or 9 or more, or 10
or more, or 15 or more, or 20 or more pole pieces. In the
illustrated embodiment of FIG. 8, the magnetic assembly comprises 5
pole pieces 21 and coils 22 at each end portion of the magnetic
assembly. Magnetic assemblies (and magnetrons) of embodiments of
the invention have two ends (also "end portions" herein). In an
embodiment, the pole pieces 21 can be circumferentially disposed in
relation to central magnet 5.
[0058] FIG. 9 is a planar schematic view illustrating a cylindrical
rotatable magnetron magnetic assembly with DC current applied to
the coils of the pole pieces 21, in accordance with an embodiment
of the invention. Only one end of the magnetron is depicted since
the opposite end is symmetrical in construction. In an embodiment,
the direction of the DC current is changed (e.g., with the aid of a
control or computer system) such that the sputtering region is
moved alternately around its normal central position, thereby
decreasing the rate of erosion depth at the ends of the target
material. In view 9a the direction of the DC current is selected to
produce poles that match the outer set of magnets, that is north
poles in pole pieces 21. This skews the magnetic field inward
toward the center south pole as indicated by sputtering path 10.
When the current direction is reversed, the induced poles are
inverted, becoming south poles as shown in view 9b. This skews the
magnetic field in the opposite direction, i.e., it is forced
outward toward the outer pole as indicated by new sputtering path
10. In an embodiment, the strength of the magnetic field at
position 26 in both of the illustrated embodiments (9a and 9b) are
approximately the same as they are without the coils in place.
Thus, the sputtering rate at the ends of the cylindrical rotatable
magnetron magnetic assembly does not change with position as it
does in Hartig, where the field strength at the start of sputtering
increasing with erosion but moves to a different position by the
time the target is sputtered through.
[0059] With continued reference to FIG. 9, the orientation of the
permanent magnets 5 is fixed--the inner magnet has an orientation
that is inverted with respect to the orientation of the outer
magnet. While the orientation of the magnets (outside inward), as
illustrated, is north-north-south (view 9a) and north-south-south
(view 9b), other orientations are possible. For example, the
magnets can be oriented such that the polarities (outside inward)
are south-south-north or south-north-north.
[0060] In an embodiment, a control system is provided for
controlling the supply of power (e.g., DC power) to the
electromagnetic coils of magnetic assemblies of embodiments of the
invention. The control system can alternate (or modulate) the
supply of DC power to one or more coils. In addition, the control
system can change the direction of the DC current to the coils. The
control system can further control the rate at which a target
disposed on a backing tube of the rotatable magnetron rotates. In
addition, the control system can control the current and/or voltage
supplied to the coils. In an embodiment, the control system can
control the supply of power to the coils by turning "on" and "off"
one or more power supplies in electric contact with the coils.
Sputtering
[0061] In an aspect of the invention, sputtering apparatus are
provided using the magnetic arrangements of embodiments of the
invention.
[0062] In an embodiment, if the coils of the cylindrical rotatable
magnetron magnetic assembly are wound in the same sense on each
end, and if each end is powered in parallel from one pair of input
wires, then for a given direction of the DC current both sputtering
grooves will move either inward or outward, but together at the
same time (and rate). Accordingly, the total length of the
sputtering groove will get somewhat longer then shorter as the
current changes direction. In another embodiment, if the coils of
the cylindrical rotatable magnetron magnetic assembly are wound in
an opposite sense with respect to each other and powered in the
same way, then the total sputtering groove will remain constant in
length but will shift back and forth along the length of the
magnetron as the current direction changes. The amount of motion of
the groove is dependent upon the level of the current through the
coils up to the limit of the wire rating.
[0063] While certain symmetrical groove motions have been
described, it will be appreciated that such symmetrical groove
motions can be obtained in other ways. For example, each set of
coils may be powered by separated sources that could be operated in
ways to produce the two symmetrical motions. However, any number of
asymmetrical motions could also be achieved, but they might not be
as useful as the symmetrical ones. The frequency of change of
current direction is somewhat arbitrary, but it should be selected
to insure adequate averaging during the time it takes a substrate
to pass through the coating area of the magnetron.
[0064] FIG. 10 illustrates a cylindrical magnetron sputtering
apparatus, in accordance with an embodiment of the invention. The
illustrated embodiment shows one approach in bringing the DC
current source to the coils of the cylindrical magnetron. Certain
elements of FIG. 10 are described above in the context of FIGS. 1
and 2. End caps 27 and 28 seal the ends of backing tube 2. Cap 27
with the its extension tube 27a provides structural and rotational
support through vacuum wall 29, while end cap 28 may be
cantilevered or supported on a bearing at location 30 depending on
the length and weight of the magnetron. Target material 1 along
with its backing tube and end caps (hatched) rotate while tubes 3a
and 3b and magnetic assembly 4 remain stationary. The split view
shows the target material 1 before (left) and at a certain point
after (right) the application of DC current to the coils.
[0065] With continued reference to FIG. 10, insulated wires 30 are
used to carry the current to the coils. In an embodiment, two
insulated wires 30 are used to carry current to the coils. In an
embodiment, the wires and coils are insulated to the level of the
operational voltage of the magnetron, which can be less than or
equal to about 1000 volts (V). In an embodiment, the wires can fit
readily into the cavity between stationary tubes 3a and 3b without
any significant interference with the water flow, whose typical
pattern is indicated by the arrows. Water (or any other cooling
fluid) generally flows into and down inner tube 3a and out into
backing tube 2 at the far end of the device. Tube 3b is sealed
around the end of tube 3a so that water returns at the opposite end
though one or several apertures 31 in outer tube 3b. In an
embodiment, the cross sectional area of the annulus between the
tubes is generally larger than the cross sectional area of tube 3a.
In such a case, the addition of the wires in this annulus area does
not limit the water flow through the device. The pair of wires 30
can have a parallel split at the first encountered set of coils.
The split off pair of wires are then made to pass through small
holes made in tube 3b and plates 6 and 7 to connect to the first
set of coils. The main wires would then pass down the annulus to
the end of the magnetic assembly where they are connected to the
second set of coils through similar passages. Either of the
symmetrical motions of the sputtering groove may be selected by the
direction that wires 30 are attached to the coils, regardless of
whether the coils are wound in the same or opposite sense. Clearly
two individual pairs of wires could be used to power each set of
coils separately, since there is ample space in the annulus between
the tubes. This may be desirable in some applications if upon
careful measurement of the way a particular magnetron is
functioning, it becomes advantageous to have slightly different
currents in each coil to make the groove motion more precisely
identical on each end of the device. Since this part of the
construction of the magnetron does not rotate, the wires will not
be twisted during operation.
Example
[0066] Two opposite polarity rows of high energy density SmCo
magnets were placed 1.5 inches apart on a mild steel backing plate.
A 100-turn coil was constructed on a steel pole piece that was 2
inches long, 0.75 inches high, and 0.125 inches thick using 24
gauge copper transformer wire. The completed coil was approximately
0.25 inches thick and fit easily between the two rows of magnets.
The tops of the magnets and the coil and pole piece were
approximately co-planar. In a plane 0.5 inches above the plane of
the tops of magnets the field strength measured about 350 gauss,
well within the usual range for sputtering. A low voltage DC
current of 3 amps passing through the coil was provided to move the
sputtering groove 0.25 inches. Reversing the current direction
moved the groove an equal amount in the opposite direction for a
total movement of 0.5 inches. This much movement of the sputtering
groove was enough to remove completely the premature burn through
region 11 depicted in FIG. 2.
[0067] Those skilled in the art will recognize that coils made with
larger gauge wire would carry higher currents and thus create
larger magnetic fields. Incorporating more turns would also create
higher magnetic fields for the same current. These modifications
can be readily implemented if larger motion of the sputtering
groove is needed or desired.
[0068] It should be understood from the foregoing that, while
particular implementations have been illustrated and described,
various modifications can be made thereto and are contemplated
herein. It is also not intended that the invention be limited by
the specific examples provided within the specification. While the
invention has been described with reference to the aforementioned
specification, the descriptions and illustrations of the preferable
embodiments herein are not meant to be construed in a limiting
sense. Furthermore, it shall be understood that all aspects of the
invention are not limited to the specific depictions,
configurations or relative proportions set forth herein which
depend upon a variety of conditions and variables. Various
modifications in form and detail of the embodiments of the
invention will be apparent to a person skilled in the art. It is
therefore contemplated that the invention shall also cover any such
modifications, variations and equivalents.
[0069] While preferable embodiments of the present invention have
been shown and described herein, it will be obvious to those
skilled in the art that such embodiments are provided by way of
example only. Numerous variations, changes, and substitutions will
now occur to those skilled in the art without departing from the
invention. It should be understood that various alternatives to the
embodiments of the invention described herein can be employed in
practicing the invention. It is intended that the following claims
define the scope of the invention and that methods and structures
within the scope of these claims and their equivalents be covered
thereby.
* * * * *