U.S. patent application number 10/942358 was filed with the patent office on 2005-06-23 for compensation of spacing between magnetron and sputter target.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Ding, Peijun, Hong, Ilyoung Richard, Lubben, Daniel C., Miller, Michael Andrew, Rengarajan, Suraj, Sundarrajan, Arvind, Yang, Hsien-Lung, Yoshidome, Goichi.
Application Number | 20050133361 10/942358 |
Document ID | / |
Family ID | 37579141 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050133361 |
Kind Code |
A1 |
Ding, Peijun ; et
al. |
June 23, 2005 |
Compensation of spacing between magnetron and sputter target
Abstract
A lift mechanism for and a corresponding use of a magnetron in a
plasma sputter reactor. A magnetron rotating about the target axis
is controllably lifted away from the back of the target to
compensate for sputter erosion, thereby maintaining a constant
magnetic field and resultant plasma density at the sputtered
surface, which is particularly important for stable operation with
a small magnetron, for example, one executing circular or planetary
motion about the target axis. The lift mechanism can include a lead
screw axially fixed to the magnetron support shaft and a lead nut
engaged therewith to raise the magnetron as the lead nut is turned.
Alternatively, the support shaft is axially fixed to a vertically
moving slider. The amount of lift may be controlled according a
recipe based on accumulated power applied to the target or by
monitoring electrical characteristics of the target.
Inventors: |
Ding, Peijun; (Saratoga,
CA) ; Lubben, Daniel C.; (Saratoga, CA) ;
Hong, Ilyoung Richard; (San Jose, CA) ; Miller,
Michael Andrew; (Sunnyvale, CA) ; Yang,
Hsien-Lung; (Campbell, CA) ; Rengarajan, Suraj;
(San Jose, CA) ; Sundarrajan, Arvind; (Santa
Clara, CA) ; Yoshidome, Goichi; (San Jose,
CA) |
Correspondence
Address: |
APPLIED MATERIALS, INC.
Patent/Legal Department
P.O. Box 450A
Santa Clara
CA
95052
US
|
Assignee: |
APPLIED MATERIALS, INC.
|
Family ID: |
37579141 |
Appl. No.: |
10/942358 |
Filed: |
September 16, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60529209 |
Dec 12, 2003 |
|
|
|
Current U.S.
Class: |
204/192.12 ;
204/298.03; 204/298.18; 204/298.2 |
Current CPC
Class: |
H01J 37/3455 20130101;
C23C 14/54 20130101; C23C 14/35 20130101; H01J 37/3408 20130101;
C23C 14/3407 20130101 |
Class at
Publication: |
204/192.12 ;
204/298.2; 204/298.03; 204/298.18 |
International
Class: |
C23C 014/32 |
Claims
1. In a magnetron sputter reactor including a chamber sealable to a
sputtering target, a support in said reactor for holding a
substrate to be processed, and a magnetron placeable on a backside
of said target opposite said support, a magnetron control system
comprising: a lift mechanism affixed to a support of said magnetron
capable of varying a distance of said magnetron from said backside
of said target; and a controller for controlling a degree of said
varying said distance during processing of a sequence of
substrates.
2. The lift mechanism of claim 1, including a motor driving said
lift mechanism in response to said controller.
3. A sputter reactor, comprising: a target affixed to vacuum
chamber; a pedestal within said chamber for support a substrate in
opposition to said target; a magnetron positioned on a back side of
said target; a power supply selectively applying power to said
target to excite a plasma within said chamber to thereby sputter
material from a front side of said target onto said substrate; a
mechanism for varying a spacing between said magnetron and said
target; and a controller controlling said mechanism to adjust said
spacing during a predetermined sequence of depositing said material
onto a plurality of said substrates.
4. The reactor of claim 3, wherein said controller adjusts said
spacing to compensate for an erosion of said front side of said
target by said plasma.
5. A method of sputtering onto a substrate support on a support in
a sputtering reactor chamber including a target fixed to said
chamber and a magnetron disposed on a back of said target opposite
said support, comprising: plural first steps of exciting a plasma
in said chamber and depositing material of said target onto
sequential ones of a plurality of substrates; and plural second
steps of lifting said magnetron away from said backside of said
target performed during or after different ones of said first
steps.
6. The method of claim 5, further comprising rotating said
magnetron about a central axis of said target.
7. The method of claim 5, wherein said rotating step causes said
magnetron to execute planetary motion about said central axis.
8. The method of any claim 5, wherein said second steps lift said
magnetron to compensate for an erosion depth of said target after
said target enters service.
9. A magnetron sputtering method, comprising adjusting a magnetic
field, which is assisting generation of a plasma in sputtering a
target, in compensation for erosion of a front of said target by
particles from said plasma.
10. The method of claim 9, wherein said adjusting comprises moving
a magnetron away from a back of said target.
11. The method of claim 9, wherein said adjusting reduces
variations in said magnetic field at said front of said target
caused by said erosion.
12. The method of claim 9, wherein said adjusting reduces
variations in said plasma at said front of said target caused by
said erosion.
13. The method of claim 9, wherein a degree of said adjusting is
determined according to a recipe for said sputtering.
14. A method for use with a plasma sputter reactor chamber mounting
a target facing an interior of the chamber and with a magnetron
positioned on the backside of said target exteriorly of the
chamber, comprising the steps of: exciting a plasma in said chamber
so as to deposit material of said target onto sequential ones of a
plurality of substrates; lifting said magnetron away from the
backside during or after said exciting of said plasma or deposition
of material; and a controller controlling a degree of said lifting
at an intermediate time of processing of said plurality of
substrates.
15. The method of claim 14, wherein said controller controls said
degree of said lifting according to an amount of erosion of a front
side of said target during processing of said plurality of
substrates.
16. The method of claim 14, wherein there is no substantial
effective movement of said magnetron towards said target during a
sequence of depositions of said material onto different
substrates.
17. The method of claim 16, in which said lifting of said magnetron
is performed during or after any one or more of said exciting of
said plasma or said depositing of material.
18. The method of claim 16, in which said lifting is at performed
plural different times.
19. The method of claims 14, further comprising rotating said
magnetron about a central axis of said target to execute circular
movement about said central axis.
20. The method of claim 14, further comprising rotating said
magnetron to execute planetary motion about said central axis.
21. A hollow cathode sputter reactor, comprising: a vacuum chamber
arranged about a central axis; a support within said chamber for
holding a substrate to be processed; a sputter target sealable to
said chamber and having a right cylindrical vault arranged about
said central axis in opposition to said support formed by a
generally disk-shaped roof and a generally tubular sidewall; a
magnet assembly disposed adjacent a back surface of either said
roof or said sidewall; and a lift mechanism supporting said magnet
assembly and controllably varying a distance between said magnet
assembly and said back surface.
22. The reactor of claim 21, wherein said lift mechanism includes
an actuator controllably moving a support member of said magnet
assembly.
Description
RELATED APPLICATIONS
[0001] This application claims benefit of U.S. provisional
application Ser. No. 60/529,209, filed Dec. 12, 2003. It also is
related to concurrently filed U.S. patent application entitled
MECHANISM FOR VARYING THE SPACING BETWEEN SPUTTER MAGNETRON AND
TARGET.
FIELD OF THE INVENTION
[0002] The invention relates generally to sputter deposition of
materials. In particular, the invention relates to a movable
magnetron that creates a magnetic field to enhance sputtering.
BACKGROUND ART
[0003] Sputtering, alternatively called physical vapor deposition
(PVD), is the most prevalent method of depositing layers of metals
and related materials in the fabrication of integrated circuits.
The more conventional type of sputtering, as originally applied to
integrated circuits as well as to other applications, deposits upon
a workpiece a planar layer of the material of the target. However,
the emphasis has recently changed in the use of sputtering for the
fabrication of integrated circuits because vertical interconnects
through inter-level dielectrics having the high aspect ratios now
being used present a much greater challenge than the horizontal
interconnects. Furthermore, the horizontal interconnects are being
increasingly implemented by electrochemically plating copper into
horizontally extending trenches while sputtering is being reserved
for liner layers deposited onto the sidewalls in the holes in which
the vertical interconnects are formed or also deposited onto the
walls of the horizontal trenches.
[0004] It has long been known that sputtering rates can be
increased by the use of a magnetron 10, illustrated in the
schematic cross-sectional view of FIG. 1, positioned in back of a
sputtering target 12. The magnetron projects a magnetic field 14
across the face of the target 12 to trap electrons and hence
increase the plasma density. The magnetron 10 typically includes at
least two magnets 16, 18 of anti-parallel magnetic polarities
perpendicular to the face of the target 12. A magnetic yoke 20
supports and magnetically couples the two magnets 16, 18. The
resultant increased plasma density is very effective at increasing
the sputtering rate adjacent the parallel components of the
magnetic field 14. However, as illustrated in the cross-sectional
view of FIG. 2, an erosion region 22 develops adjacent the magnetic
field, which brings a front surface 24 of the target 12 closer to
the magnetron 10, which front surface 24 is the surface being
currently sputtered. The erosion illustrated in FIG. 2 emphasizes
an erosion pit adjacent the magnetron 10. In typical operation, the
magnetron 10 is scanned over the back of the target 12 to produce a
more uniform erosion pattern. Nonetheless, even if a target eroded
to a planar surface, the fact remains that after erosion the
surface of the target being sputtered is closer to the magnetron 10
than before erosion.
[0005] The target erosion presents several problems if the lifetime
of the target 12 is to be maximized. First, the erosion pattern
should be made as uniform as possible. In conventional planar
sputtering, uniformity is improved by forming the magnets 16, 18 in
a balanced, relatively large closed kidney-shaped ring and rotating
the magnetron about the central axis of the target. Secondly, the
erosion depth can be compensated by adjusting the spacing between
the target and the wafer being sputter deposited, as disclosed by
Tepman in U.S. Pat. No. 5,540,821. Futagawa et al. disclose a
variant in U.S. Pat. No. 6,309,525. These schemes have primarily
addressed the dependence of deposition rate on the separation
between the wafer and the effective front face of the target 12.
These approaches do not address how the erosion affects the
magnetic enhancement of sputtering.
[0006] The erosion problem has been complicated by the need to
produce a highly ionized sputter flux so that the ionized sputter
atoms can be electrostatically attracted deep within high
aspect-ratio holes and be magnetically guided, as has been
explained for an SIP reactor by Fu et al. in U.S. Pat. No.
6,306,265, incorporated herein by reference in its entirety. The
apparatus described therein uses a small triangularly shaped
magnetron to effect self-ionized sputtering, taking into account
three factors. First, it is advantageous to reduce the size of the
magnetron in order to concentrate the instantaneous sputtering to a
small area of the target, thereby increasing the effective target
power density. Secondly, the concentrated magnetic field of the
small magnetron increases the plasma density adjacent the portion
of the target being sputtered, thereby increasing the ionization
fraction of the target atoms being sputtered. The ionized sputter
flux is effective at being attracted deep within high aspect-ratio
holes in the wafer. However, the target erosion affects the
effective magnetic field at the target face being sputtered,
thereby changing the sputtering rate and the ionization fraction.
Thirdly, the small magnetron makes uniform target sputtering that
much more difficult. Various magnetron shapes, e.g., triangular
have been used to increase the uniformity of sputtering, but their
uniformity is not complete. Instead, annular troughs are eroded
into the target even in the case of rotary magnetrons.
[0007] Two major operational effects are readily evident in the use
of conventional rotary magnetrons, particularly small magnetrons.
First, as illustrated in the plot 26 of the graph of FIG. 3, the
deposition rate falls from its initial rate with target usage, here
measured in target kilowatt-hours of cumulative power applied to
the target since it was fresh. The target usage corresponds to both
the amount of target that has been eroded since the target was put
into service with a substantially planar and uneroded surface and
to the number of wafers that have been deposited in a repetitive
process. We believe that the decrease is believed arises at least
indirectly from the target erosion in which the target surface
being sputtered is no longer optimized for the magnetic field since
its separation from the magnetron is varying. The sputtering
degradation can be compensated by either increasing the length or
sputtering or increasing the target power. Secondly, the
non-uniformity of sputtering reduces the lifetime of the target to
a number N.sub.1 at which the erosion trough maximum approaches the
target backing plate or, in the case of an integral target, a
minimum thickness of the target. At this point, to prevent either
sputter deposition of the backing material or breakthrough of the
target, the target must be discarded even though substantial target
material survives away from the erosion troughs. Costs would be
saved for target purchase, operator time, and production throughput
if the target lifetime is increased.
[0008] Hong et al. have presented a planetary magnetron as a
solution to the uniformity problem for a high-density plasma
reactor in U.S. patent application Ser. No. 10/152,494, filed May
21, 2002, now published as Application Publication 2003-0217913,
and incorporated herein by reference in its entirety. As
illustrated in the cross-sectional view of FIG. 4, a plasma reactor
30 has a fairly conventional lower reactor including a reactor wall
32 which supports a sputtering target 34 through an adapter 36 and
isolator 38 in opposition to a pedestal electrode 40 supporting the
wafer 42 to be sputter deposited with the material of the target
34. A vacuum pump system 44 pumps the vacuum chamber to a level of
a few milliTorr or less while a gas source 46 supplies a working
gas such as argon through a mass flow controller 48. A clamp ring
50 holds the wafer 42 to the pedestal electrode 40 although an
electrostatic chuck may alternatively be used. An electrically
grounded shield 52 protects the reactor walls 32 and further acts
as an anode in opposition to the target 34 while a DC power supply
54 negatively biases the target 34 to a few hundred volts to excite
the argon working gas into a plasma. The positively charged argon
ions are accelerated to the negatively biased target 34, which they
strike and dislodge or sputter atoms of the target material. The
sputtered atoms are ejected from the target 34 with fairly high
energy in a wide beam pattern and thereafter strike and stick to
the wafer 42. With sufficiently high target power and high plasma
density, a substantial fraction of the sputtered atoms are ionized.
Preferably, an RF power supply 58, for instance oscillating at
13.56 MHz, biases the pedestal electrode 40 through a capacitive
coupling circuit 60 such that a negative DC self-bias develops on
the wafer 42, which accelerates the positively charged sputter ions
deep within high-aspect ratio holes being sputter coated.
[0009] According to the invention, a magnetron 70 positioned in
back of the target 34 projects its magnetic field in front of the
target 34 to create a high-density plasma region 72, which greatly
increases the sputtering rate of the target 34. If the plasma
density is high enough, a substantial fraction of sputtered atoms
are ionized, which allows additional control over the sputter
deposition. Ionization effects are particularly pronounced in
sputtering copper, which has a high self-sputtering yield, as
copper ions are attracted back to the copper target and sputter
further copper. The self-sputtering allows the argon pressure to be
reduced, thereby reducing wafer heating by argon ions and reducing
argon scattering of copper atoms, whether ionized or neutral, as
they travel from the target 34 to the wafer 42.
[0010] In the described embodiment, the magnetron 70 is
substantially circular and includes an inner magnetic pole 74 of
one magnetic polarization with respect to and extending along a
central axis 76 of the chamber 32 as well as the target 34 and
pedestal electrode 40. It further includes an annular outer pole 78
surrounding the inner pole 74 and of the opposed magnetic polarity
along the central axis 76. A magnetic yoke 80 magnetically couples
the two poles 74, 78 and is supported on a carrier 81. The total
magnetic intensity of the outer pole 78 is substantially greater
than that of the inner pole 74, for example by a factor of greater
than 1.5 or 2.0, to produce an unbalanced magnetron which projects
its unbalanced magnetic portion towards the wafer 42 to thereby
confine the plasma and also guide sputtered ions towards the wafer
42. Typically, the outer pole 78 is composed of plural cylindrical
magnets arranged in a circle and having a common annular pole piece
on the side facing the target 34. The inner pole 74 may be composed
of one or more magnets, preferably with a common pole piece. Other
forms of magnetrons are encompassed by the invention.
[0011] The high plasma densities achieved by this configuration as
well as that of Fu et al. are achieved in part by minimizing the
area of the magnetron 70. The encompassing area of the magnetron 70
is typically less than 10% of the area of the target 34 being
scanned by the magnetron 70. The magnetron/target area ratio may be
less than 5% or even less than 2% if uniform sputtering is
otherwise maintained. As a result, only a small area of the target
34 is subject to an increased target power density and resultant
intensive sputtering. That is, the sputtering at any instant of
time is highly non-uniform. To compensate for the non-uniformity, a
rotary drive shaft 82 rotated by a drive source 84 and supporting
the magnetron 70 circumferentially scans the magnetron 70 about the
chamber axis 76. However, as has been described with respect to the
reactor of Fu et al., the resultant annular troughs in the target
may produce significant radial non-uniformity in the
sputtering.
[0012] Hong et al. significantly reduce the sputtering
non-uniformity by the use of a planetary scanning mechanism 90 to
cause the magnetron 70 to move along a planetary or other epicyclic
path over the back of the target 34 with respect to the central
axis 76. Their preferred planetary gear mechanism 90 for achieving
planetary motion includes, as additionally and more completely
illustrated in FIG. 5, a fixed gear 92 fixed to a housing 94 and a
drive plate 96 fixed to the rotary shaft 82. In the reactor of Hong
et al., the housing 94 is stationary. The drive plate 96 rotatably
supports an idler gear 98 which engages the fixed gear 92. The
drive plate 96 also rotatably supports a follower gear 100 engaged
with the idler gear 98. A shaft 102 of the follower gear 100 is
fixed also to the carrier 81 so that the magnetron 70 supported on
the carrier 81 away from the follower shaft 102 rotates with the
follower gear 100 as it rotates about the fixed gear 92 to execute
the planetary motion. Counterweights 110, 112 are fixed to the
non-operative ends of the drive plate 96 and the carrier 81 to
reduce bending and shimmy on the rotary drive shaft 82 and the
follower shaft 102. Particularly in copper sputtering which
achieves a high ionization ratio Cu.sup.+/Cu.sup.0 of sputtered
copper ions, the sputter reactor 30 of FIG. 4 advantageously
includes a magnetic coil or magnet ring 114 annular about the
central axis 76 to guide the copper ions to the wafer 42.
[0013] Because the DC power supply 54 delivers a significant amount
of power to the target 34 and a high flux of energetic ions bombard
the target 34 thereby heating the target 34, it is conventional to
immerse the magnetron 70 as well as the planetary mechanism 90 in a
cooling water bath 116 enclosed in a tank 118 sealed to the target
34 and the fixed drive-shaft housing 94. Unillustrated fluid lines
connect the bath 116 with a chiller to recirculate chilled
deionized water or other cooling fluid to the bath 118.
[0014] The planetary magnetron scanning, because of its convolute
path across the target 34, greatly improves the uniformity of
target erosion so that the target 34 is more uniformly eroded and
results in a nearly planar sputtering surface even as the target is
eroded. As a result, the target utilization is greatly improved.
Nonetheless, as the target 34 erodes generally uniformly, the
magnetic field at its sputtering face is changing and apparently on
average decreasing. The change affects the sputtering rate, which
as described above has been observed to decrease. The plots
presented in FIG. 3 are speculative. Actual experimental data are
presented in FIG. 6. Plot 120 presents the measured deposition rate
for copper in the planetary magnetron chamber of FIG. 4 having an
axially fixed magnetron and with 28 kW of DC target power and 600W
of RF bias power as a function of target usage in kilowatt-hours.
Plot 121 presents the deposition rate for a small axially fixed
magnetron executing simple rotary motion, as described by Fu et
al., with 56 kW of DC target power. Although the fall off in the
simple rotary chamber is not as great in the planetary chamber, it
is still significant. It is pointed out, however, that it may be
advantageous to more heavily sputter the outer regions of the
target 34, particularly when the target/wafer spacing is relatively
small in order to compensate for the geometric effect of greater
deposition at the wafer center. Such intended non-uniformity can be
achieved by adjusting the length of the rotation arms in a
planetary chamber or by changing the shape or radial position of
the magnetron in a simple rotary chamber. Even in this case, the
deposition rate decreases with target usage.
[0015] A second set of non-uniformity problems is not immediately
addressed by the planetary scanning mechanism. The small area of
the magnetron 70 advantageously produces a high target power
density and high plasma density and hence increases sputtering rate
and increases the fraction of ionized sputter atoms which are drawn
deep within high aspect-ratio holes to coat the sides and bottom of
via holes. However, the magnetic field and hence the plasma density
depend upon the distance between the target sputtering surface and
the magnetron. As a result, as the target 34 is being sputtered,
even if uniformly, the plasma density is changing and hence the
sputtering rate and the ionization rate upon which the via sidewall
coverage depends are changing. The effect is exacerbated for a
small magnetron because the gradient of the magnet field is
greater. As a result, the changing magnetic field and plasma
density destabilizes the process causing variation in bottom and
sidewall coverages across the lifetime of the target. It has
generally been accepted that the high-performance sputtering is
different at the end of the lifetime of the target than at the
beginning. Plot 122 in FIG. 7 shows the measured target voltage and
plot 123 in FIG. 8 shows the measured mean bias voltage with
respect to target usage for the axially fixed planetary magnetron
with the aforementioned values of target and bias power. There is a
significant rise in the target voltage and the magnitude of the
bias voltage with increased sputtering. However, the bias voltage
is subject to fluctuations of about +20V with the maximum magnitude
greatly increasing to about 150V at maximum usage. The instability
is readily apparent from the plot 122 of FIG. 7 for target voltage
and the plot 123 of FIG. 8 for bias power. The change of sputtering
rate can be compensated by increasing the sputtering duration, but
this does not address the sidewall coverage. In any case, the
increased sputtering period decreases throughput and introduces
another variable into the queuing plan. The variation in plasma
density because of reduced magnetic field can be partially
compensated by increasing the target power. Such power compensation
however involves an ad hoc relationship which needs to be
determined for each set of conditions and also reduces the ability
to maximize plasma densities and sputtering rates with limited
power supplies.
[0016] Halsey et al. in U.S. Pat. No. 5,855,744 show an apparatus
for deforming a linear magnetron as it scans across a rectangular
target. In one embodiment, multiple actuators moving shafts along
multiple respective axes deform the magnetron. Mizouchi et al. in
U.S. Pat. No. 6,461,485 discloses a single vertical actuator for
compensating for end effects in linear scanning.
[0017] Demaray et al. in U.S. Pat. No. 5,252,194 discloses a slider
mechanism for vertically moving a large magnetron to adjust the
magnetic field at the front of the target.
[0018] Schultheiss et al. in U.S. Pat. No. 4,927,513 discloses a
magnetron lift mechanism to control magnetic properties of
sputtered layers.
SUMMARY OF THE INVENTION
[0019] The invention includes the method and apparatus for
compensating erosion of a plasma sputtering target by moving the
magnetron away from the back of the target as the front of the
target is eroded. The compensation provides a more constant
magnetic field and plasma density at the surface of the target
being sputtered and results in a more stable sputtering
process.
[0020] The lift mechanism may include a lead screw mechanism
including a lead screw and lead nut. The lead screw may be axially
fixed to the magnetron and a lead nut threadably engaged with the
lead screw. Rotation of the lead nut vertically moves the
magnetron. The lead screw may be azimuthally fixed while the lead
nut is axially fixed. The lead nut may be manually moved or moved
under the control of a motor or other actuator coupled to the lead
nut by a gear or a linear lead screw mechanism or linear
actuator.
[0021] The amount of lift my be dictated by a predetermined recipe
or by a measured cumulative power applied to the target.
Alternatively, the target resistance or power characteristic or the
physical erosion depth may be monitored to determine when
additional lift is required.
[0022] The magnetron lift mechanism may also be used to control the
magnetic field at the face of the sputtering target for control of
the sputtering process other than simple compensation of target
erosion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIGS. 1 and 2 are cross-sectional views functionally
illustrating the effect of magnetron sputtering as the target is
being eroded.
[0024] FIG. 3 is a graph illustrating the dependencies in the prior
art and according to the invention of the sputtering deposition
rate as a function of the target usage.
[0025] FIG. 4 is a schematic cross-sectional view of a plasma
sputter reactor with a planetary magnetron.
[0026] FIG. 5 is an isometric view of a planetary magnetron.
[0027] FIG. 6 is a graph illustrating the experimentally determined
dependencies in the prior art of the sputtering deposition rate as
a function of target usage.
[0028] FIG. 7 is a graph illustrating the experimentally determined
dependencies in the prior art and in the practice of the invention
of target voltage as a function of target usage.
[0029] FIG. 8 is a graph illustrating the experimentally determined
dependencies in the prior art and in the practice of the invention
of bias voltage as a function of target usage.
[0030] FIG. 9 is a graph illustrating as a function of target usage
both a sequence of target spacings used in an experiment verifying
the invention and the resultant sputtering deposition rate.
[0031] FIG. 10 is a cross-sectional view of a lead screw lift
mechanism for raising the magnetron.
[0032] FIG. 11 is an orthographic view of the exterior portions of
the lead screw lift mechanism of FIG. 10 and a spur gear mechanism
for driving the spacing between target and magnetron.
[0033] FIG. 12 is an orthographic view of a first embodiment of a
lead screw mechanism for driving the spacing compensation.
[0034] FIG. 13 is an orthographic view of a dual slider mechanism
for driving the spacing compensation to be used in the lead screw
mechanism of FIG. 10.
[0035] FIG. 14 is an orthographic view of a collar, slider and its
case to be used in the slider mechanism of FIG. 13.
[0036] FIG. 15 is an orthographic view of a bracket used with the
slider mechanism of FIG. 13.
[0037] FIG. 16 is an orthographic view of the slider mechanism of
FIG. 13 additionally including a magnetron rotation motor.
[0038] FIG. 17 is a schematic representation of a computerized lift
control system.
[0039] FIGS. 18 and 19 are schematic cross-sectional view of two
hollow cathode magnetrons incorporated the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] The erosion of the front of the target in magnetron
sputtering can be compensated by moving the magnetron away from the
back of the target. As illustrated in FIG. 4, a lift mechanism 124
controllably raises the magnetron 70 with respect to the back of
the target 34, preferably in an amount commensurate to the amount
of the front surface of the target 34 that has been eroded since
the target 34 was installed with a flesh planar front surface. The
compensation should focus on the areas of the target 34 being more
heavily eroded since they contribute a higher fraction of sputtered
atoms. While the conventional design criterion minimizes the
distance between the magnetron 70 and the back of the target 34 and
maintains the separation at this initial spacing, one preferred
criterion of the invention maintains an approximately constant
spacing between the magnetron 70 and the front of the target 34
facing the wafer 42. The nearly constant spacing maintains a
substantially constant magnetic field at the surface of the target
34 being sputtered. The nearly constant magnetic field removes one
variable from the process conditions determining sputtering
performance, not just sputtering rate but also ionization fraction
among other effects. Thereby, sputtering time or target voltage do
not need to be adjusted for target usage. Movement of the magnetron
to maintain a substantially constant magnetic field at the front
face of the target 34 stabilizes the sputtering process over the
life of the target and enables a substantially constant deposition
rate despite target usage, as schematically illustrated in plot 126
of FIG. 3. Also, the sidewall and bottom coverages may be
maintained substantially constant over the life of the target.
Furthermore, the lifetime of the target considerably increases to a
value N.sub.2 as the target is nearly uniformly eroded almost to
its backing plate.
[0041] Although other implementations are possible, the lift
mechanism 124 can be easily incorporated into the conventional
design by allowing the housing 94 to be axially movable by the lift
mechanism while still maintaining its fluid seal to the tank
118.
[0042] A first embodiment of the invention used to verify the
effects of compensating the magnetron-to-target spacing uses a
series of shims of varying thickness placed between the magnetron
70 of FIG. 5 and the carrier 81. As the target erodes, the previous
shim is replaced by a thinner shim. As a result, the magnetron 70
is being moved away from the back of the target 34 along a single
axis at the center of the magnetron 70 although that axis is moving
as the magnetron 70 is moved along a planetary path. As a result, a
nearly constant magnetic field can be maintained at the sputtering
surface of the target 34 over the target life thereby stabilizing
the sputtering process. The manual shimming process may be
alternatively effected by shims placed between the otherwise
stationary housing 94 and the roof of the tank 118.
[0043] Actual experimental data using a copper target and a
planetary magnetron in the reactor of FIG. 4 are presented in FIG.
9. Plot 125 shows the magnet-to-target (MTS) spacing, specifically
to the back of the target as the shim thickness was occasionally
increased while plot 126 in shows the measured deposition rate.
Even in these preliminary experiments, the deposition rate is
maintained nearly constant. With the use of the invention, a copper
target may be used to deposit thin copper seed layers on up to
20,000 wafers. Plot 121 in FIG. 6 also shows actual data for the
moderated change of deposition rate as a function of target usage
as the shims were being replaced. Plot 127 in FIG. 7 shows the
dependence of measured target voltage as a function of target
usage. Plot 128 in FIG. 8 shows the dependence of the mean of the
measured bias voltage as a function of target usage. Further,
although not illustrated, the deviations of the maximum and mean
bias voltage from the mean do not significantly change with target
usage.
[0044] These results could be improved particularly for target and
bias power by more frequently moving the magnetron with a finer
resolution. These results also show that target and bias voltages
are sensitive indicators of the amount of erosion and hence the
need for spacing compensation. These voltages are easy to monitor
during production. Current is another sensitive measurement for
electrical supplies generating constant power. Alternatively, if
the power supplies are set to generate constant voltage or current,
the complementary quantity or power may be measured. These
electrical measurements typically amount to monitoring the
resistance of the plasma under some set electrical condition.
Therefore, the compensation can be dynamically controlled by
measuring one or both of these voltages (or other quantities)
during production and comparing them to baseline values. When the
deviation exceeds a threshold, the compensation may be performed to
bring the measured value closer to the baseline value. It is also
possible to optically or otherwise measure the physical depth of
erosion of the target and use the depth measurement to initiate the
compensation. Nonetheless, it has proven satisfactory to keep track
of cumulative target power and move the magnetron at values
experimentally determined for a given sputter recipe.
[0045] Although the first embodiment relying on shims is effective,
it clearly presents operational difficulties as the sputter reactor
needs to be shut down and the magnetron removed from the water bath
to allow manual replacement of its shims. It is greatly desired to
perform the spacing compensation from outside the water bath and
preferably under computerized electrical control.
[0046] One set of embodiments is based on converting the stationary
housing 94 to a vertically movable but in large part azimuthally
fixed housing 94 driven by a lead screw mechanism 130, as
illustrated in the cross-sectional view of FIG. 10. The rotary
drive shaft 82 includes a central bore 132 for flowing chilled
cooling water to the center of the tank 118 of FIG. 4 near the back
of the target 34. The cooling water flows out of the water bath
through an unillustrated outlet in a roof 142 or other wall of the
tank 118. The top of the drive shaft 82 is coupled by yet further
unillustrated belts or other means to the motor 84. The drive plate
96 of the planetary mechanism is fixed to the bottom of the drive
shaft 82 and rotates with it. Two ring bearings 134, 136 rotatably
support a boss 138 of the drive shaft 82 within the housing 94. An
annular dynamic seal 139 the seals the fluid within the bath 116
from the bearings 134, 136 and the exterior.
[0047] A tail 140 of the housing 94 axially passes through an
aperture in the tank roof 142 but is azimuthally fixed by other
means. The fixed gear 92 of the planetary mechanism is fixed to the
end of the housing tail 140. As a result, when the housing 94 is
vertically moved, the fixed gear 92, the drive plate 96, and the
rest of the planetary mechanism 90 and magnetron 70 are also
vertically moved along the central axis 76.
[0048] A support collar 146 is fixed to the tank roof 142 and
sealed to it with an O-ring placed in an O-ring groove 147. An
annular bellows 148 surrounding the upper portion of the housing
tail 140 is sealed on opposed ends to the housing 94 and to the
inner portion of the support collar 146 to slidably seal the fluid
in the bath 116 from the exterior as well as from most of the
mechanical parts of the lift mechanism 130 while allowing axial
movement between the housing 94 and drive shaft 82 on one hand and
the tank roof 142 on the other. The bellows 148 should accommodate
a movement of about 3/4" (2 cm) corresponding to the usable
thickness of the target 34. Other types of slidable fluid seals are
possible. The fixed collar 146 rotatably supports an internally
threaded lead nut 150 through two ring bearings 152, 154. An inner
retainer ring 156 fixed to the lead nut 150 and an outer retainer
ring 158 fixed to the collar 146 trap the upper bearing 152 against
the lead nut 150 and the collar 146. Another similar retainer ring
configuration beneath the lead nut 150 traps the lower bearing 154.
The lead nut 150 can thus rotate about the central axis 76 but is
axially fixed to the tank top 142.
[0049] The external threads of a azimuthally fixed but vertically
movable lead screw 164 engage the internal threads of the lead nut
150. The lead screw 164 supports the housing 94 on its upper
surface. The housing 94 may be fixed to the lead screw 164 or guide
pins may couple them to prevent relative rotational movement. A
plurality of screws 166 hold the lead screw 164 to the tank top 142
through compression springs 168. As a result, the lead screw 164 is
rotationally fixed as it engages the rotatable lead nut 150 but the
compression springs 168 accommodate limited vertical motion of the
lead screw 164. The axial fixing of the lead nut 150 to the tank
top 142 provides a wide mechanical base for the heavy rotating
magnetron, thereby reducing shimmy and allowing the reduction of
the clearance between the magnetron 70 and the back of the target
34.
[0050] In operation, if the lead nut 150 is rotated clockwise, the
azimuthally fixed lead screw 164 rises and lifts the housing 94 and
the attached rotary shaft 82 and magnetron 70 away from the target
34. Counter-clockwise rotation of the lead nut 150 produces the
opposite axial movement of lowering the magnetron 70 toward the
target 34. The lift drive mechanism for rotating the lead nut 150
is easily formed outside of the cooling bath 116. Two types of lift
drive mechanisms will be described.
[0051] A first embodiment of a rotational lift drive includes a
spur gear drive 170 illustrated in the orthographic view of FIG.
11. The outer rim of the inner retainer ring 156 is partially
formed with a toothed gear 172 in a gear ledge 173 extending from
only part of the inner retainer ring 156. The toothed gear 172
engages with a lift drive gear 174 controllably driven by a lift
motor 176, which maybe mounted on the tank roof 142 with a
vertically oriented drive shaft to which the toothed gear 172 is
fixed. The lift motor 176 is preferably a stepper motor rotating a
fixed angle for each motor pulse with a separate control signal
controlling the direction of rotation. Thereby, the lead nut 150 of
FIG. 10 is controllably rotated to raise or lower the lead screw
164 and hence the housing 94 and attached drive shaft 82 and
magnetron 70.
[0052] An optical position sensor 175 includes two arms 175a, 175b
spaced to accommodate the gear ledge 173 as it rotates in lifting
the magnetron. One arm 175a contains an optical emitter, such as an
light emitting diode, while the other arm 175b contains a light
detector, such as a photodiode. The position sensor 175 is used to
calibrate the rotation of the gear 172 using the gear ledge 173 as
a flag. The lift motor 176 rotates the gear 172 toward the position
sensor 175 until the gear ledge 173 enters between the arms 175a,
175b of the position sensor 175 and blocks the emitted light from
the optical detector. The controller notes that position as a home
position. The stepper motor 176 is then stepped in the opposite
direction by a controlled number of pulses to a desired rotation
location of the gear 172 and hence vertical position of the
magnetron. Other position sensors may be used.
[0053] The drive shaft motor 84 may be vertically mounted on the
tank roof 142 through a motor mount 180. The drive shaft motor 84
drives a motor drive gear 182 through optional unillustrated
gearing to reduce the rotation rate. A shaft drive gear 186 is
formed in a capstan 188 fixed to the drive shaft 82. A ribbed belt
190 is wrapped over both the motor drive gear 182 and the shaft
drive gear 186 so that the motor 84 rotates the drive shaft 82 in
executing the planetary motion of the magnetron 70. Because the
drive shaft 82 and the attached shaft drive gear 186 are raised and
lowered in operation relative to the motor mount 180 and attached
motor drive gear 182, the teeth of at least the shaft drive gear
186 must be wide enough to accommodate the slip or axial movement
of the belt 190 relative to teeth of that gear 186 and the motor
drive gear 182 may be formed with two rims to limit the axial
movement of the belt 190 on that gear 182. A rotary fluid coupling
194 is mounted on the top of the drive shaft 82 to allow cooling
water lines to be connected to the central bore 132 of the rotating
drive shaft 82.
[0054] A second embodiment of a rotational lift drive includes a
lead screw mechanism 200 illustrated in the orthographic, partially
sectioned view of FIG. 12. A support collar 202 is fixed to the
tank roof 142 and rotatably supports the lead nut 150 through a
ring bearing 204 trapped by an upper retainer ring 206. A lead nut
lever 208 extends radially outwardly from the lead nut 150 and has
two parallel arms 210 formed at its end. A pivot connection
including two arms 212 at the back of the lift motor 176, an
unillustrated pivot pin through them, and a mount for the pin,
pivotally mounts the lift motor 176 to the tank roof 142 in a
horizontal orientation. The horizontally oriented lift motor 176
rotates a shaft 216 having a lead screw formed on its distal end. A
nut box 220 threadably captures the lead screw of the drive shaft
216 and is pivotally supported by a pin 218 fixed to the arms 210
of the lead nut lever 208. Thereby, rotation of the lift motor 176
rotates the lead nut 150 to raise or lower along the central axis
72 the lead screw 164 and hence the housing tail 140 and attached
drive shaft 82 and magnetron 70.
[0055] The second embodiment of FIG. 12 can be easily modified to
replace the lift motor 176 with a hydraulic or pneumatic linear
actuator driving a shaft pivotally coupled at its end to the arms
210 of the lead nut lever 208. Yet further, the second embodiment
could be manually controlled by the operator manually rotating the
lead nut lever 208. Other combinations of gears, levers, and
actuators or motors can be used to implement the lead nut lift
mechanism.
[0056] The lead nut lift mechanism offers several advantages. It is
concentric about the lift axis and the support shaft for the
magnetron. The magnetron is supported on an azimuthally fixed lead
screw threaded into a larger lead nut that is axially fixed to a
yet larger structure. Hence, the lead nut lift mechanism offers low
vibration and flexing of the relatively heavy rotating magnetron.
The design is mechanically simple, thereby increasing reliability
and reducing cost.
[0057] A second type of lift mechanism is a double slider mechanism
230 illustrated orthographically in FIG. 13. It includes an
elongated collar 232, also illustrated orthographically in FIG. 14,
adapted to be fixed and sealed to the tank roof 142. A vertically
oriented slider case 234 fixed to the collar 232 includes two
vertically extending and horizontally stacked tracks, one of which
is formed on one side by rails 235. The two tracks respectively
trap two sliders 236, which are fixed together and can together
vertically move along the rails 235. Only the exterior slider 236
is illustrated. Two sliders fixed to each other provide greater
stiffness in supporting the relatively heavy load. A vertically
extending back 238 is fixed to the collar 232 to provide a rigid
mount for the slider case 234 and other parts. A vertically
oriented drive shaft 240 is rotatably supported in the top end of
the slider case 234. The lower end of the drive shaft 240 is
threaded as a lead screw and engages corresponding threads formed
in an unillustrated lead box axially supporting both sliders 236.
As a result, when the drive shaft 240 rotates, the sliders 236 move
up or down within the slider case 234.
[0058] A bracket 250 illustrated orthographically in FIG. 15 has a
base 252 sized to fit onto the exterior slider 234. A plurality of
through holes 254 drilled through the bracket base 252 pass screws
256 threaded into the exterior slider 234 to snugly hold the
bracket base 252. Locating pins 258 may be inserted into the
exterior slider 234 to engage corresponding holes formed in the
bottom of the bracket base 252. The bracket 250 further includes a
tubular collar 260 having an aperture 262 sized to closely hold the
housing 94 of FIG. 10, with suitable modifications of that housing
94, and an upper axial end 264 to support the housing 94. The
housing 94 may be fixed to the tubular collar 260 or engage it
through pins so that the housing 94 does not rotate.
[0059] Returning to FIG. 13, a shaft gear 270 is fixed to the
magnetron drive shaft 82 of FIG. 10, which is rotatable within but
vertically fixed in the housing 94. The housing 94 itself is not
rotatable but can move vertically with respect to the collar 232
and the tank roof 142. The vertically movable housing 94 maybe
sealed to the tank roof 142 by an assembly including the bellows
148 of FIG. 10 to be axially movable with respect to the tank roof
142 over a limited throw. The shaft gear 270 is similar to the
shaft gear 186 of FIG. 11 and may be driven by the belt 190 driven
by the vertically oriented motor 84. The belt 190 as applied to
FIG. 13 should be able to vertically slide along the teeth of the
shaft gear 270.
[0060] A slider drive mechanism includes a plate 276 fixed to end
of the slider case 234 which passes the end of the slider shaft 240
to be fixed to a slider gear 278. The plate 276 also supports below
a vertically oriented slider motor 280 having a drive shaft fixed
to a motor gear 282. A ribbed belt 284 is wrapped around the slider
and motor gears 278, 282 so that the slider motor 280 can move the
slider 234 up and down within the slider case 250 to thereby
vertically move the housing 94 and attached magnetron 70 relative
to the tank roof 142 and the back of the target 34.
[0061] A modified double slider mechanism 290 illustrated
orthographically in FIG. 16 includes a modified bracket 292 having
a shelf 294 extending outward from the top of the tubular collar
260. A shaft drive motor 296 and gear box 298 are supported on the
bottom of the shelf 294 to drive a motor gear 300. A ribbed belt
302 engages both the motor gear 300 and the shaft gear 270 to
thereby rotate the magnetron shaft 82 and cause the attached
magnetron 70 to execute planetary motion. Because the motor 296 and
motor gear 300 are axially fixed to the housing 94 and hence moves
with the magnetron shaft 82, the belt 270 does not need to slip
along the teeth of the gears 270, 300.
[0062] The described compensation mechanisms may be used in a
number of ways for compensating target erosion. It is possible to
perform the lifting and compensating during the plasma excitation
and sputter deposition, but it is preferable instead to perform it
after one wafer is processed and before the next one is processed.
Even though motor controlled, the mechanisms may be essentially
manually controlled by on occasion instructing the lift motor to
move a set amount corresponding to a desired lift of the magnetron.
However, the lift compensation algorithm is advantageously
incorporated into the recipe for which a machine is being used and
a computerized controller performs the compensation as well as
controls the other chamber elements according to the recipe. In
view of the limited axial throw of about 2 cm and the large number
of wafers which maybe deposited with a single target over many
weeks of even continuous processing, it is reasonable to compensate
the spacing on only an occasional basis, for example, once an hour
or once a day or more specifically after a large number of wafers
have been processed.
[0063] In a control procedure emphasizing the optimized process in
which the reactor is being used, the amount of displacement may be
determined empirically for a given combination of target,
magnetron, initial target/magnetron spacing, and general operating
conditions developed for a step in the fabrication of a chip design
A convenient unit of target usage is total kilowatt-hours of use
since the target was fresh so that the process recipe keeps a
running total of kilo-watt hours and adjusts the spacing as a
function of the total kilowatt-hours according to a compensation
algorithm incorporated into the process recipe and set during
development of the recipe. The compensation may be controlled once
a set period for this unit has passed. For a given process, wafer
count is nearly as good a usage unit.
[0064] A dynamic control algorithm may also be effective. As is
evident from the plots 122, 127 of FIG. 7, the measured target
voltage can be tracked and correlated with deviations from a
predetermined value set by the recipe. when the measured voltage
deviates by a set voltage increment, the magnetron maybe moved
upwardly by a set spacing increment experimentally determined
beforehand to largely compensate the voltage increment. In fact,
the empirical algorithm may be obtained in corresponding fashion
during development of the process in which the development engineer
tracks changes in the target voltage as a function of target usage
and experimentally determines what spacing compensation is
necessary to bring the target voltage back to a set value.
[0065] It is also possible to directly measure the position of the
sputtering surface of the target by optical or other means or to
measure the thickness of the target by separate electrical means,
both approaches providing a measurement of target erosion.
[0066] It is desirable that the compensation be directly measurable
by a feedback measurement, for example, the angular position of the
set nut or of the linear position of the slider or an angular
displacement of one of the rotary parts, all measured from a known
position. For example, the position sensor 175 of FIG. 11 acts as a
limit indicator useful for resetting after a power outage or
computer glitch.
[0067] It is noted that the baseline magnetron-to-target spacing
may vary from one recipe to another and the described lift
mechanisms may be used to initially obtain the baseline spacing for
a fresh target as well as to maintain it during extended target
usage.
[0068] FIG. 17 schematically illustrates an example of a control
system for adjusting the spacing S between the front face of the
magnetron 70 and the back surface of the target 34 as well as
controlling other parts of the sputter reactor. The lift motor 176
is preferably implemented in a stepper motor that is connected
through a schematically illustrated mechanical drive 310 (for
example that of FIGS. 10 and 11) which can selectively raise or
lower the magnetron 70. A flag 312 attached to the mechanical drive
310, and a position sensor 314 detects the position of the flag
312, for example, at the extreme of the travel of the mechanical
drive 310 in which the magnetron 70 is farthest from the target
34.
[0069] A computerized controller 316 is conventionally used to
control the sputtering operation according to a process recipe
stored within the controller 316 on a recordable medium 318, such
as a recordable disk. The controller 316 conventionally controls
the target power supply 54 as well as other conventional reactor
elements 44, 48, 58, 84, and 114. Additionally according to the
invention, the controller 316 controls the stepper motor 176 with a
controlled series of pulses and a directional signal to drive the
magnetron 70 a controlled distance in either direction. The
controller 316 stores the current position of the magnetron 70 and,
if additional movement is desired, can incrementally move the
magnetron 70. However, on startup or after some unforseen
interrupt, the controller 316 raises the magnetron 70 away from the
target 34 until the position sensor 314 detects the flag 312. The
setting of the stepper motor 176 at this flagged position
determines a home position. Thereafter, the controller 316 lowers
the magnetron 70 to a desired position or spacing S from the target
34. This limit detection maybe implemented by the position sensor
175 of FIG. 11.
[0070] The recipe stored within the controller 316 may contain the
desired compensation rate, for example, as a function of kilowatt
hours of power applied to the target 34 from the power supply 54 or
alternatively as a compensation for variation in target voltage.
The controller 316 can monitor the applied power through a watt
meter 320 connected between the power supply 54 and the target.
However, the power supply 54 is often designed to deliver a
selectable constant amount of power. In this case, the total power
consumption can be monitored by software within the controller 316
with no direct power measurement. The controller 316 may also
monitor the target voltage with a voltmeter 322 connected to the
power supply line to the target 34. As mentioned previously, target
voltage is a sensitive indicator of the need to compensate the
spacing between magnetron and target.
[0071] The spacing compensation may be advantageously applied to
the roof magnetron used with a target having an annular vault
formed in its surface, as has been described by Gopalraja et al. in
U.S. Pat. No. 6,451,177, incorporated herein by reference in its
entirety. The invention can also be applied to a sputter reactor
having a hollow cathode magnetron 330 schematically illustrated in
FIG. 18, such as disclosed by Lai et al. in U.S. Pat. No.
6,193,854, incorporated herein by reference in its entirety. The
hollow cathode magnetron 330 includes a target 332 formed with a
single right circular cylindrical vault extending about a central
axis 334 and facing an unillustrated pedestal supporting the wafer.
Unillustrated biasing means applied to the target 332 relative to
an anode excites the sputtering working gas into a plasma to
sputter the portions of the target 332 inside the vault to thereby
coat a layer onto the wafer of the material of the target 332.
[0072] Permanent magnets 336, usually axially aligned, are placed
around the exterior of a circumferential sidewall 338 of the target
332 to serve several functions including intensifying the plasma
adjacent the sidewall 338. However, in some implementations, the
magnets are horizontally aligned to create a bucking field within
the vault adjacent the sidewall 338. According to the invention,
motors or other types of actuators 340 selectively move the magnets
336 radially with respect to the central axis 334 to compensate for
sputtering erosion of the target sidewalls 338. The hollow cathode
magnetron 330 may additionally include a roof magnetron 342
positioned in back of a disk-shaped roof 342 of the target 332. The
roof magnetron 342 may be stationary or be rotated about the
central axis 334. According to the invention, a motor or other
actuator 346 maybe used to axially move the roof magnetron 342
along the central axis 334 to compensate for erosion of the target
roof 344. However, as has been previously discussed, the various
magnet movements may be used alternatively to tune the sputtering
process to an initial state as well as to maintain it there.
[0073] An alternative hollow cathode magnetron 350 schematically
illustrated in FIG. 19 uses a sidewall coil 352 wrapped around the
target sidewall 338 to produce an axial magnetic field inside the
target vault. According to the invention, an adjustable power
supply 354 supplying the coil current is adjusted, for among other
reasons, to compensate for target erosion such that a more constant
magnetic field is produced adjacent the interior surface of the
eroding target.
[0074] The compensation mechanism is not limited to those which
have been described. For example, especially in the case that the
magnetron executes only simple rotary motion, the rotary shaft
supporting the magnetron can be directly lifted if an additional
dynamic or slidable seal allows leak-free axial movement of the
rotary shaft. Other types of lift mechanisms and lift drives may be
used in achieving the control or compensation of the
target/magnetron spacing However, the lead-screw lift mechanism 130
of FIG. 10 has effectively been used for compensating an SIP
magnetron of the Fu patent which executes simple rotary motion.
[0075] Although the above described lift mechanisms have been
described for raising a magnetron away from the target backside,
they may be used as well to lower the magnetron. Also, the
apparatus maybe used for purposes other than compensating for
target erosion.
[0076] Although the invention has been developed for copper
sputtering, it may be used for sputtering other materials dependent
on the target material and whether a reactive gas is admitted to
the chamber. Such materials include nearly all metals and metal
alloys and their reactive compounds used in sputter deposition,
including but not limited to Cu, Ta, Al, Ti, W, Co, Ni, NiV, TiN,
WN, TaN, Al--Cu alloys, Cu--Al, Cu--Mg, etc.
[0077] The invention may be also applied to other magnetrons such
as the more conventional large kidney-shaped magnetrons and to
other magnetrons not intended to ionize the sputtered atoms. Nested
magnetrons are not required. Long-throw sputter reactors can
benefit from the invention. Inductive RF power may be coupled into
the magnetron sputter reactor to increase the source power.
Although the invention is particularly useful with scanned
magnetrons, it may also be applied to stationary magnetrons. It may
also be applied to magnets used more for confining the plasma and
guiding ions rather than strictly for increasing the plasma
density.
[0078] Accordingly, the invention greatly stabilizes a sputtering
process over the lifetime of the target with relatively minor
additions to the sputter apparatus.
[0079] The above described embodiments do not encompass all
possible implementations and uses of the invention. The coverage of
the invention should be determined primarily by the specific
language of the claims.
* * * * *