U.S. patent application number 13/546705 was filed with the patent office on 2012-11-01 for sputtering targets, sputter reactors, methods of forming cast ingots, and methods of forming metallic articles.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. Invention is credited to Frederick B. Hidden, Susan D. Strothers, Chi tse Wu, Wuwen Yi.
Application Number | 20120273097 13/546705 |
Document ID | / |
Family ID | 23187081 |
Filed Date | 2012-11-01 |
United States Patent
Application |
20120273097 |
Kind Code |
A1 |
Wu; Chi tse ; et
al. |
November 1, 2012 |
SPUTTERING TARGETS, SPUTTER REACTORS, METHODS OF FORMING CAST
INGOTS, AND METHODS OF FORMING METALLIC ARTICLES
Abstract
The invention encompasses a method of forming a metallic
article. An ingot of metallic material is provided, and such ingot
has an initial thickness. The ingot is subjected to hot forging.
The product of the hot forging is quenched to fix an average grain
size of less than 250 microns within the metallic material. The
quenched material can be formed into a three dimensional physical
vapor deposition target. The invention also includes a method of
forming a cast ingot. In particular aspects, the cast ingot is a
high-purity copper material. The invention also includes physical
vapor deposition targets, and magnetron plasma sputter reactor
assemblies.
Inventors: |
Wu; Chi tse; (Veradale,
WA) ; Yi; Wuwen; (Veradale, WA) ; Hidden;
Frederick B.; (Spokane, WA) ; Strothers; Susan
D.; (Spokane, WA) |
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morristown
NJ
|
Family ID: |
23187081 |
Appl. No.: |
13/546705 |
Filed: |
July 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10759444 |
Jan 14, 2004 |
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13546705 |
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PCT/US2001/045650 |
Oct 9, 2001 |
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10759444 |
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60306836 |
Jul 19, 2001 |
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60493183 |
Aug 7, 2003 |
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Current U.S.
Class: |
148/681 ;
148/559 |
Current CPC
Class: |
B21K 21/00 20130101;
B21J 5/00 20130101; B21J 5/02 20130101; C22F 1/00 20130101; H01J
37/3408 20130101; H01J 37/3423 20130101; B22D 7/00 20130101; C23C
14/3407 20130101; C22F 1/08 20130101; B22D 27/08 20130101; C23C
14/3414 20130101 |
Class at
Publication: |
148/681 ;
148/559 |
International
Class: |
C22F 1/08 20060101
C22F001/08; C21D 8/00 20060101 C21D008/00 |
Claims
1-89. (canceled)
90. A method of forming a three-dimensional physical vapor
deposition target, the method comprising: heating an ingot, the
ingot defining first and second perpendicular directions; forging
the ingot to reduce a thickness of the ingot by 60% to 90% along
the first direction to form a hot-forged product having a reduced
thickness along the first direction and an increased size along a
second direction; quenching the hot-forged product; and forming the
quenched hot-forged product into a three-dimensional physical vapor
deposition target with a press, wherein the three-dimensional
physical vapor deposition target has an average grain size of less
than 250 microns.
91. The method of claim 90, wherein the ingot comprises copper.
92. The method of claim 90, wherein the step of heating the ingot
comprises heating the ingot to a temperature greater than
700.degree. F.
93. The method of claim 90, wherein the ingot contains at least
99.995 weight percent copper.
94. The method of claim 90, wherein the ingot is a copper alloy
ingot.
95. The method of claim 90, wherein the ingot consists essentially
of copper and at least one element selected from the group
consisting of Cd, Ca, Au, Ag, Be, Li, Mg, Al, Pd, Hg, Ni, In, Zn,
B, Ga, Mn, Sn, Ge, W, Cr, O, Sb, Ir, P, As, Co, Te, Fe, S, Ti, Zr,
Sc, Sn and Hf.
96. The method of claim 95, wherein the total amount of the at
least one element is from at least about 100 ppm to less than about
10% by weight.
97. The method of claim 90, wherein the three-dimensional physical
vapor deposition target has an average grain size of less than 200
microns.
98. The method of claim 90, wherein the three-dimensional physical
vapor deposition target has an average grain size of less than 100
microns.
99. The method of claim 90, wherein the step of forging the ingot
comprises forging the ingot along only the first direction.
100. The method of claim 90, wherein the press comprises first and
second portions movable towards one another.
101. A method of forming a three-dimensional physical vapor
deposition target, the method comprising: heating an ingot to a
temperature greater than 700.degree. F., the ingot comprising
copper and having first and second perpendicular directions;
compressing the ingot along only the first direction to form a
hot-forged product; quenching the hot-forged product; and forming
the quenched hot-forged product into a three-dimensional physical
vapor deposition target with a press, wherein the three-dimensional
physical vapor deposition target has an average grain size of less
than 250 microns.
102. The method of claim 101, wherein the ingot is a copper ingot
having a purity of at least 99.995 weight percent.
103. The method of claim 101, wherein the ingot is a copper alloy
ingot.
104. The method of claim 101, wherein the quenched hot-forged
product has is larger in size along the first direction and smaller
in size along the second direction than the ingot.
105. The method of claim 101, wherein the three-dimensional
physical vapor deposition target has an average grain size of less
than 200 microns.
106. The method of claim 101, wherein the three-dimensional
physical vapor deposition target has an average grain size of less
than 100 microns.
107. The method of claim 101, wherein compressing the ingot
comprises compressing the ingot to reduce the thickness by 60% to
90%.
Description
RELATED PATENT DATA
[0001] This patent claims continuation-in-part priority to PCT
application serial number PCT/US01/45650, which was filed Oct. 9,
2001, and which claims priority to U.S. provisional application
Ser. No. 60/306,836, which was filed Jul. 19, 2001. This patent
also claims continuation-in-part priority to U.S. provisional
application Ser. No. 60/493,183, which was filed Aug. 7, 2003.
TECHNICAL FIELD
[0002] The invention pertains to methods of forming cast ingots,
and also pertains to methods of forming high-purity metallic
articles. Additionally, the invention pertains to methods of
forming sputtering targets, and pertains to sputtering target
constructions. Also, the invention pertains to sputter reactor
assemblies. In particular aspects, the invention pertains to
sputtering target constructions comprising, consisting essentially
of, or consisting of, non-magnetic materials.
BACKGROUND OF THE INVENTION
[0003] Physical vapor deposition (PVD) is a commonly used method
for forming thin layers of material in semiconductor fabrication
processes. PVD includes sputtering processes. In an exemplary PVD
process, a cathodic target is exposed to a beam of high-intensity
particles. As the high-intensity particles impact a surface of the
target, they force materials to be ejected from the target surface.
The materials can then settle on a semiconductor substrate to form
a thin film of the materials across the substrate.
[0004] Difficulties are encountered during PVD processes in
attempting to obtain a uniform film thickness across the various
undulating features that can be associated with a semiconductor
substrate surface. Attempts have been made to address such
difficulties with target geometry. Accordingly, numerous target
geometries are currently being commercially produced. Exemplary
geometries are described with reference to FIGS. 1-8. FIGS. 1 and 2
illustrate an isometric view and cross-sectional side view,
respectively, of an Applied Materials Self Ionized Plasma Plus.TM.
target construction 10. FIGS. 3 and 4 illustrate an isometric view
and cross-sectional side view, respectively, of a Novellus Hollow
Cathode Magnetron.TM. target construction 12. FIGS. 5 and 6
illustrate an isometric and cross-sectional side view,
respectively, of a Honeywell, International Endura.TM. target
construction 14. Finally, FIGS. 7 and 8 illustrate an isometric and
cross-sectional side view, respectively, of a flat target
construction 16.
[0005] Each of the cross-sectional side views of FIGS. 2, 4, 6 and
8 is shown comprising horizontal dimensions "X" and vertical
dimensions "Y". The ratio of "Y" to "X" can determine if the target
is a so-called three-dimensional target, or a two-dimensional
target. Specifically, each of the targets will typically comprise a
horizontal dimension "X" of from about 15 inches to about 17
inches. The Applied Materials.TM. target (FIG. 2) will typically
comprise a vertical dimension "Y" of about five inches, the
Novellus.TM. target (FIG. 4) will typically comprise a vertical
dimension of about 10 inches, the Endura.TM. target (FIG. 6) will
typically comprise a vertical dimension of from about two inches to
about six inches, and the flat target will typically comprise a
vertical dimension of less than or equal to about 1 inch. For
purposes of interpreting this disclosure and the claims that
follow, a target is considered to be a three dimensional target if
the ratio of the vertical dimension "Y" to the horizontal dimension
"X" is greater than or equal to 0.15. In particular aspects of the
present invention, a three dimensional target can have a ratio of
the vertical dimension "Y" to the horizontal dimension "X" of
greater than or equal to 0.5. If the ratio of the vertical
dimension "Y" to the horizontal dimension "X" is less than 0.15,
the target is considered a two-dimensional target.
[0006] The Applied Materials.TM. target (FIG. 2) and Novellus.TM.
target (FIG. 4) can be considered to comprise complex three
dimensional geometries, in that it is difficult to fabricate
monolithic targets having the geometries of such targets. The
Applied Materials.TM. target (FIG. 2) and Novellus.TM. target (FIG.
4) both share the geometrical characteristic of comprising at least
one cup 11 having a pair of opposing ends 13 and 15. End 15 is open
and end 13 is closed. The cups 11 have hollows 19 extending
therein. Further, each cup 11 has an internal (or interior) surface
21 defining a periphery of the hollow 19, and an exterior surface
23 in opposing relation to the interior surface. The exterior
surface 23 extends around each cup 11, and wraps around the closed
ends 13 at corners 25. Targets 10 and 12 each have a sidewall 27
defined by the exterior surface and extending between the ends 13
and 15. The targets of 10 and 12 of FIGS. 2 and 4 further share the
characteristic of a flange 29 extending around the sidewall 27. A
difference between the target 12 of FIG. 4 relative to the target
10 of FIG. 2 is that target 10 has a cavity 17 extending downwardly
through a center of the target to narrow the cup 11 of target 10
relative to the cup of target 12.
[0007] Exemplary sputtering apparatuses which can utilize Applied
Materials.TM. target 10 of FIG. 2 are described in U.S. Pat. No.
6,251,242. One of such apparatuses is shown diagrammatically in
FIG. 9. Specifically, FIG. 9 illustrates a magnetron plasma sputter
reactor 200 having sputtering target 10 provided therein. The
target 10 will be described in FIG. 9 utilizing alternative
language and numbering relative to that utilized in FIG. 2 in order
to illustrate an alternative description of the target.
[0008] The reactor 200 comprises a magnetron 202 symmetrically
arranged about a central axis 204. The target 10, or at least its
interior surface, is composed of a material to be
sputter-deposited. The target can comprise, for example, Ti, Ta or
high purity copper. Target 10 comprises an annularly-shaped
downwardly facing vault 206 (i.e., the hollow 19 described with
reference to FIG. 2) facing a wafer 208 being sputter-coated. Vault
206 may be alternatively characterized as an annular downwardly
facing trough. Vault 206 can have an aspect ratio of its depth to
radial width of at least 1:2, and in particular applications, at
least 1:1. The vault has an outer sidewall 210 outside of the outer
periphery of the wafer 208, an inner sidewall 212 overlying the
wafer 208, and a generally flat vault top wall or roof 216. Target
10 includes a central portion forming a post 218 including the
inner sidewall 212 and a generally planar face 220 in parallel
opposing relation to wafer 208. Flange 29 of target 10 forms a
vacuum seal to a body 222 of reactor 200.
[0009] The magnetron reactor 200 includes one or more central
magnets 224 having a first vertical magnetic polarization, and one
or more outer magnets 226 of a second vertical magnetic
polarization opposite the first polarization and arranged in an
annular pattern. The magnets 224 and 226 can be permanent magnets,
and accordingly can be composed of strongly ferromagnetic material.
Inner magnets 224 are disposed within a cylindrical central well
228 (i.e., the cavity 17 of FIG. 2) formed between opposed portions
of the inner target sidewall 212, and the outer magnets 226 are
disposed generally radially outside of the outer target sidewall
210. A circular magnetic yoke 230 magnetically couples tops of the
inner and outer magnets 224 and 226. The yoke can be composed of a
magnetically soft material, such as, for example, a paramagnetic
material, that can be magnetized to form a magnetic circuit for the
magnetism produced by magnets 224 and 226.
[0010] A cylindrical inner pole piece 232 of magnetically soft
material abuts the lower ends of inner magnets 224 and extends deep
within target well 228 adjacent the inner target sidewall 212.
Magnetic pieces 230 and 232 can be configured in size to emit a
magnetic field (illustrated by dashed arrows within vault 206) that
is substantially perpendicular to the magnetic field of the
corresponding associated magnets 224 and 226. The magnetic field
is, accordingly, also substantially perpendicular to the target
vault sidewalls 210 and 212.
[0011] Reactor 200 includes a vacuum chamber body 222 which can
have a dielectric target isolator (not shown) provided therein.
Wafer 208 is clamped to a heater pedestal electrode 250 by
appropriate mechanisms, such as, for example, a clamp ring (not
shown). An electrically grounded shield (not shown) is typically
provided to act as an anode with respect to the cathode target, and
a power supply (not shown) is provided to negatively bias the
cathode target. Various shields and power supplies which can be
utilized with the apparatus of FIG. 9 are described in, for
example, U.S. Pat. No. 6,251,242.
[0012] A port 252 is provided to extend through body 222, and a
vacuum pumping system 254 is utilized to pump a vacuum within
chamber 200 through port 252. An RF power supply 256 is utilized to
RF bias pedestal 250, and a controller 258 is provided to regulate
various aspects of apparatus 200, including, for example, the RF
controller 256 and the vacuum pump 254, as shown.
[0013] It can be desired to form sputtering targets having a small
average grain size. It is frequently found that targets having a
smaller average grain size of the materials utilized therein will
produce more uniform deposited films than will targets having the
same materials with a larger grain size. A postulated mechanism for
the effect of the smaller grain size on uniformity of deposited
films is that small grain sizes can reduce micro-arcing problems
relative to large grain sizes. The improvement in deposited film
uniformity that can be achieved with materials having smaller grain
sizes has led to a desire to incorporate small grain size materials
into sputtering targets. It is found that small grain size
materials can be formed within two-dimensional sputtering targets
simply by subjecting the target materials to high compression
during formation of the materials. Since the two-dimensional
targets are essentially flat, high-compression technology can be
readily incorporated into the processes of forming two dimensional
targets. In contrast, it has proven difficult to form three
dimensional targets having small grain sizes therein. It would be
particularly desired to form monolithic copper targets having the
complex geometries of the FIG. 2 and FIG. 4 target shapes, while
also having a small average grain size.
[0014] Numerous materials can be utilized in forming sputtering
targets, with exemplary materials being metallic materials (such
as, for example, materials comprising one or more of Cu, Ni, Co,
Mo, Ta, Al, and Ti), of which some materials can be non-magnetic.
One of the materials that can be particularly desired for
utilization in sputtering targets is high-purity copper (with the
term "high purity" referring to a copper material having a purity
of at least 99.995 weight percent). High-purity copper materials
are frequently utilized in semiconductor fabrication processes for
forming electrical interconnects associated with semiconductor
circuitry. It would be desirable to develop processing which could
form three-dimensional high-purity copper targets having an average
grain size of less than or equal to about 250 microns.
SUMMARY OF THE INVENTION
[0015] In one aspect, the invention encompasses a method of forming
a metallic article, such as, for example, a sputtering target. The
metal of the metallic article can comprise, for example, one or
more of Cu, Ni, Co, Ta, Al, and Ti, and in particular embodiments
can comprise Ta, Ti, or Cu. In a particular aspect, the invention
encompasses a method of forming a high-purity copper article. An
ingot of copper material is provided, with such ingot having a
copper purity of at least 99.995 weight percent, and further having
an initial grain size greater than 250 microns, and an initial
thickness. The ingot is subjected to hot forging at a temperature
of from about 700.degree. F. to about 1,100.degree. F. under
sufficient pressure and time to reduce a thickness of the ingot by
from about 40% to about 90% of the initial thickness. The product
of the hot forging is quenched to fix an average grain size of less
than 250 microns within the high-purity copper material. The
average grain size can be fixed to be less than 200 microns, and
even to be less than 100 microns. In particular aspects, the
quenched material is formed into a three dimensional physical vapor
deposition target.
[0016] In another aspect, the invention encompasses a method of
forming a cast ingot. A mold is provided. Such mold has an interior
cavity. The interior cavity is partially filled with a first charge
of molten material. The first charge is cooled within the interior
cavity to partially solidify such first charge. While the first
charge of molten material is only partially solidified, a remaining
portion of the interior cavity is at least partially filled with a
second charge of the molten material. The first and second charges
are cooled within the interior cavity to form an ingot comprising
the first and second charges of the material. In particular
aspects, the cast ingot is a high-purity copper material.
[0017] In yet another aspect, the invention encompasses various
target constructions having particular geometries, and/or having an
average grain size of less than about 250 microns.
[0018] In yet another aspect, the invention encompasses various
monolithic copper target constructions in which the average grain
size of the copper is less than 250 microns.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Preferred embodiments of the invention are described below
with reference to the following accompanying drawings.
[0020] FIG. 1 is an isometric view of a prior art Applied
Materials.TM. sputtering target.
[0021] FIG. 2 is a cross-sectional side view of the sputtering
target of FIG. 1.
[0022] FIG. 3 is an isometric view of a prior art Novellus.TM.
hollow cathode sputtering target.
[0023] FIG. 4 is a cross-sectional side view of the FIG. 3
sputtering target.
[0024] FIG. 5 is an isometric view of a prior art Honeywell
International Endura.TM. sputtering target.
[0025] FIG. 6 is a cross-sectional side view of the FIG. 5
sputtering target.
[0026] FIG. 7 is an isometric view of a prior art flat sputtering
target.
[0027] FIG. 8 is a cross-sectional side view of the FIG. 7
sputtering target.
[0028] FIG. 9 is diagrammatic, cross-sectional view of a prior art
magnetron sputter reactor.
[0029] FIG. 10 is an isometric view of an ingot at a preliminary
processing step of a method of the present invention.
[0030] FIG. 11 is a view of the ingot of FIG. 10 being compressed
by a hot forge.
[0031] FIG. 12 is a view of a hot forge product resulting from the
hot forge compression of FIG. 11.
[0032] FIG. 13 is a cross-sectional side view through the product
of FIG. 12, illustrating a three dimensional target profile that
can be machined from the product of FIG. 12.
[0033] FIG. 14 is a view of the FIG. 12 product placed within a
press configured for formation of a three dimensional target shape
from the FIG. 12 product.
[0034] FIG. 15 is a view of the FIG. 14 apparatus shown at a
processing step subsequent to that of FIG. 14, and illustrating a
three dimensional target shape formed from the FIG. 12 hot forge
product.
[0035] FIG. 16 is a diagrammatic, cross-sectional view of a first
embodiment sputtering target geometry encompassed by the present
invention.
[0036] FIG. 17 is a diagrammatic, cross-sectional view of a second
embodiment sputtering target geometry encompassed by the present
invention.
[0037] FIG. 18 is a diagrammatic, cross-sectional view of a third
embodiment sputtering target geometry encompassed by the present
invention.
[0038] FIG. 19 is diagrammatic, cross-sectional view of a magnetron
sputter reactor comprising the first embodiment sputtering target
geometry encompassed by the present invention.
[0039] FIG. 20 is a diagrammatic, cross-sectional view through a
prior art cast ingot.
[0040] FIG. 21 is a diagrammatic, cross-sectional view of an
apparatus utilized in forming a cast ingot in accordance with a
method of the present invention.
[0041] FIG. 22 is a view of the FIG. 21 apparatus shown at a
processing step subsequent to that of FIG. 21.
[0042] FIG. 23 is a view of the FIG. 21 apparatus shown at a
processing step subsequent to that of FIG. 22.
[0043] FIG. 24 is a diagrammatic cross-sectional side view of a
cast ingot formed in accordance with methodology of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] In one aspect, the invention encompasses a method of forming
a metallic article having a grain size of less than about 250
.mu.m, preferably less than about 200 .mu.m, and even more
preferably less than about 100 .mu.m. Such embodiment is described
with reference to FIGS. 10-15. Referring initially to FIG. 10, an
ingot 20 of metallic material is illustrated. Ingot 20 can, in
particular embodiments, comprise a cast material. Exemplary
metallic components of ingot 20 are one or more of Cu, Ni, Co, Ta,
Al, and Ti; with a suitable material being copper having a purity
of at least 99.995 weight percent. The metallic materials can
include alloys which include one or more of Cu, Ni, Co, Ta, Al, and
Ti; such as, for example, a Ti/Zr alloy having a purity of at least
99.9995 weight percent. Ingot 20 comprises a substantially
cylindrical shape with a diameter "0" and a thickness `T`.
Thickness `T` can be referred to as an initial thickness of ingot
20. The shape of ingot 20 is referred to as a "substantially"
cylindrical shape to indicate that there may be minor deviation of
the shape from a true cylinder. Ingot 20 further comprises opposing
ends 22 and 24. End 22 can be referred to as a first end, and end
24 can be referred to as a second end.
[0045] Referring to FIG. 11, ingot 20 is placed within a forging
apparatus 30. Apparatus 30 can be considered to be a hot forge, in
that it is preferably configured to compress ingot 20 while the
ingot is at a temperature higher than room temperature. Ingot 20
will be typically be compressed while a bulk of the ingot is at a
temperature of from about 700.degree. F. to about 1,100.degree. F.,
and more preferably, while the bulk of the ingot is at a
temperature of from about 850.degree. F. to about 1,050.degree. F.,
(with the term "bulk" meaning greater than or equal to 95% of a
mass of the ingot).
[0046] Apparatus 30 can be considered to comprise a press
configured to press against the opposing ends 22 and 24 of ingot
20. Apparatus 30 comprises a first portion 32, and an opposing
second portion 34. In operation, ingot 20 is placed between
portions 32 and 34, with first end 22 proximate and facing first
portion 32, and second end 24 proximate and facing second portion
34. Portions 32 and 34 are then displaced relative to one another
to compress ingot 20 between them. The displacement of portions 32
and 34 is illustrated by arrow 37 in FIG. 11, with such arrow
indicating that portion 32 is moved toward portion 34. It is to be
understood that the displacement of portions 32 and 34 can
alternatively comprise movement of portion 34 toward portion 32, or
can comprise movement of both of portions 32 and 34 toward one
another. The compression of ingot 20 is preferably under sufficient
pressure, and for a sufficient duration of time, to reduce a
thickness of the ingot by from about 40% to about 90% of the
initial thickness, (i.e., to reduce the ingot to a thickness that
is from about 10% to about 60% of the initial thickness).
[0047] The hot forging converts ingot 20 into a hot-forged product
(shown in FIG. 12). A suitable pressure for compression of ingot 20
is less than or equal to about 10,000 pounds per square inch (psi),
with an exemplary pressure being about 9,700 psi. In a particular
process of the present invention, ingot 20 will have a diameter "D"
of about 10 inches, and a pressure of about 1,100 tons will be
applied across an entirety of the surfaces of ends 22 and 24.
[0048] Ingot 20 will typically initially comprise an average grain
size of about 10,000 .mu.m if the ingot is a cast material, and
such grain size can be reduced to less than or equal to 250 .mu.m,
200 .mu.m, or even 100 .mu.m with hot-forging of the present
invention. For instance, in an exemplary process in which a
thickness of a high purity copper ingot 20 is reduced to about 30%
of an initial thickness in a time of less than about one hour, the
resulting hot-forged product had a measured average grain size of
from about 85 microns to 90 microns after quenching to a
temperature of about 70.degree. F.
[0049] Among the parameters that can affect a grain size ultimately
formed within the hot-forged product obtained by the compression of
FIG. 11 is a duration of the compression. Specifically, it can be
preferred that ingot 20 be subjected to the relatively high
temperatures associated with the hot-forging for a period of time
of from about 15 minutes to about three hours, and preferably from
about 30 minutes to about one hour. Also, the amount of reduction
of the thickness of ingot 20 can have an effect on the resulting
average grain size. Specifically, it is found that if the thickness
of ingot 20 is reduced by less than 60%, a resulting grain size can
increase beyond 100 .mu.m. For instance, it has been found that if
the thickness of a high purity copper material is reduced by 50%, a
resulting grain size is 200 .mu.m, while a thickness reduction by
from about 60% to 90% can achieve a resulting average grain size of
about 100 .mu.m or less. The temperatures associated with hot
forging can include a step of heating the ingot 20 to a desired
temperature of greater than 700.degree. F. (preferably greater than
800.degree. F.) in an oven, and then hot pressing the ingot 20
while maintaining the temperature of the bulk of the ingot 20 (with
the "bulk" of the ingot being considered to be greater than or
equal to about 95% of the mass of the ingot) at greater than
700.degree. F. (preferably greater than 800.degree. F.). The
duration of the hot forging temperature is considered to include
the time that the ingot 20 is in the oven at the desired
temperature, as well as the time that the ingot is being hot
pressed at the desired temperature.
[0050] In the shown preferred embodiment, lubricating materials 36
and 38 are provided between ingot 20 and the portions 32 and 34,
respectively, of apparatus 30. Lubricating materials 36 and 38
preferably comprise a solid lubricant, such as, for example,
graphite foil. The solid lubricant can be preferred over liquid
lubricants, as solid lubricants are found to be more suitable for
the high temperatures employed in the hot forging process of the
present invention. In less preferred embodiments, liquid lubricants
can be utilized.
[0051] However, it is found that liquid lubricants typically burn
under the processing conditions of the present invention.
[0052] The graphite foil 36 is preferably provided to a thickness
of from about 0.01 inches to about, 0.100 inches, with a preferred
thickness being from about 0.030 inches to about 0.060 inches.
Graphite foil 38 has similar preferred thickness ranges. It is
found that if either graphite foil 36 or foil 38 is thinner than
0.01 inches, it tears during processing of the present invention,
and if the foil is thicker than 0.100 inches it can interfere with
the forging process by contributing its own mechanical properties
to the processing. Such contribution of mechanical properties of
the lubricating foil to the processing can disrupt reproducibility
of the processing conditions, and further can cause an average
grain size associated with the ends of ingot 20 to be different
than an average grain size within an interior region (i.e., a
region between the ends) of ingot 20. The graphite foil can be
provided to a desired thickness by stacking several thin sheets of
graphite foil on top of one another to achieve the thickness of
from about 0.030 inches to about 0.060 inches. Alternatively, a
single sheet of solid lubricant having the desired thickness can be
utilized.
[0053] After the compression of ingot 20 within apparatus 30, the
resulting hot-forged product is quenched to fix an average grain
size of less than 250 .mu.m, 200 .mu.m, or even 100 .mu.m within
the product. The term "fix" is used to indicate that the average
grain size stops changing within the material after the quench, and
more specifically, that the average grain size remains fixed within
the material provided that the material is kept at temperatures
below 100.degree. F. If the material is reheated to temperatures
above 100.degree. F., and particularly to temperatures in excess of
150.degree. F., an average grain size within the material can begin
to increase. The quenching of the hot-forged product typically
occurs within about 15 minutes of removing the hot-forged product
from press 30, and typically comprises reducing a temperature of an
entirety of the hot-forged product to less than or equal to about
150.degree. F. Such can be accomplished by immersing the hot-forged
product within a tank of fluid maintained at about room temperature
(about 70.degree. F.). In preferred embodiments of the present
invention, an entirety of the hot-forged product is reduced to a
temperature of less than or equal to about 70.degree. F. within
about 15 minutes of removing the hot-forged product from press
30.
[0054] FIG. 12 illustrates a hot-forged product resulting from
compression of ingot 20 (FIG. 10) within apparatus 30 (FIG. 11).
Product 40 comprises a substantially cylindrical shape having a
diameter "E" and a thickness "W". Thickness "W" is preferably from
about 10% to about 40% of the original thickness "T" of ingot 20
(FIG. 10). Product 40 comprises the opposing ends 22 and 24 of
ingot 20, with such ends now having a diameter "E" which is larger
than the diameter "D" of ingot 20.
[0055] Hot-forged product 40 can be formed into a'' sputtering
target. An exemplary method of forming product 40 into a sputtering
target is described with reference to FIG. 13. Specifically,
product 40 is shown in cross-sectional side view, and a target
construction 42 is illustrated contained within product 40. Target
construction 42 corresponds approximately to the three dimensional
target 10 of FIGS. 1 and 2. It is to be understood, however, that
target construction 42 can correspond to other constructions, such
as, for example, a two dimensional target construction, or the
three dimensional target constructions 12 and 14 of FIGS. 3-6.
Product 40 comprises a mass of material 44 surrounding the target
construction 42. Mass 44 can be removed by machining processes to
leave the target construction 42.
[0056] Another method for forming a target construction from
product 40 is described with reference to FIGS. 14 and 15.
Referring initially to FIG. 14, hot-forged product 40 is provided
within a press 50. Press 50 comprises a first portion 52 and a
second portion 54. Portions 52 and 54 are displaced relative to one
another to compress product 40 between them. In the shown
embodiment, the displacement of portions 52 and 54 is illustrated
by arrows 56 and 58, which indicate that both of portions 52 and 54
are moved relative to one another. It is to be understood, however,
that the invention encompasses other embodiments wherein only one
of portions 52 and 54 is moved during the displacement of portions
52 and 54 relative to one another.
[0057] FIG. 15 illustrates apparatus 50 after product 40 is
compressed between portions 52 and 54. Product 40 is shown molded
into a three dimensional target configuration corresponding
approximately to the shape of target 10 (FIGS. 1 and 2). It is
noted that product 40 is not exactly in the shape of target 10, and
the shown embodiment excess material 60 is shown extruding
outwardly from sides of the target material. Such excess material
can be removed by appropriate machining. Also, to any other extent
that product 40 is not formed exactly into a desired target shape,
the product can be machined to refine a shape of the product into a
desired target shape. Generally, press 50 will not be utilized to
form target 40 into an exact target shape, but rather will be
utilized to form target 40 into a shape which approximates the
desired target shape, with excess material remaining over that of
the desired target shape. The excess material is then removed by
appropriate machining to form the desired target shape.
[0058] Press 50 is preferably operated under conditions in which
product 40 is held within a temperature range of from about
1,300.degree. F. to about 1,700.degree. F. for a duration of time
of less than or equal to about five minutes, and preferably of less
than or equal to about three minutes, to allow the material of
product 40 to extrude into the desired target shape. Product 40 can
be initially pre-heated in an oven to a temperature greater than
1,300.degree. F., and then subject to pressing within press 50. The
oven pre-heating is generally preferred, as it is typically not
practical to heat product 40 to a desired temperature in excess of
1,300.degree. F. with press 50 alone.
[0059] After the material of product 40 is compressed into the
desired target shape by press 50, it can be quenched under
identical conditions to those discussed above for hot quenching of
a forged product from apparatus 30 (FIG. 11). Accordingly, the
target shape resulting from compression of product 40 within press
50 can be quenched such that an entirety of the target shape is
reduced to a temperature of less than or equal to about 150.degree.
F. (and preferably less than or equal to about 70.degree. F.)
within about 15 minutes of removing the target shape from within
press 50.
[0060] An advantage of utilizing the embodiment of FIGS. 14 and 15,
relative to that discussed above with reference to FIG. 13, is that
the embodiment of FIGS. 14 and 15 can comprise less waste of
material than does that of FIG. 13. A hot-forged product utilized
in the embodiment of FIG. 13 will typically comprise a shape of
about five inches in thickness by about 17 inches in diameter,
whereas that utilized for the embodiment of FIGS. 14 and 15 can be
smaller, and in particular embodiments can be on the order of about
four inches in thickness by about 15 inches in diameter to form the
same product as that formed by a material having five inches in
thickness and 17 inches in diameter and subjected to the FIG. 13
processing. This can enable about a 40% to 50% reduction in
material processed according to the embodiment of FIGS. 14 and 15,
relative to the material processed according to the embodiment of
FIG. 13. For instance, a high-purity copper material subjected to
processing to form a three dimensional target can comprise a mass
of several hundred pounds when utilized to form three dimensional
sputtering targets. The utilization of the embodiment of FIGS. 14
and 15 has been found to save about 180 pounds of copper material
relative to the utilization of the embodiment of FIG. 13.
[0061] A lubricant can be applied to surfaces of product 40 during
the processing of FIGS. 14 and 15. A preferred lubricant can be a
liquid lubricant, in spite of the high temperatures utilized during
such processing, because a liquid lubricant can flow within the
various undulations of press 50 better than a solid lubricant. In
particular embodiments, a high temperature cooking oil is utilized
as the lubricant.
[0062] The methodology of FIGS. 14 and 15 can be utilized to form
numerous complex target geometries. Exemplary target geometries are
described with reference to FIGS. 16-18. Referring initially to
FIG. 16, a target 300 is illustrated. Target 300 comprises a
geometry similar to that of the target 10 of FIG. 2 (i.e., geometry
similar to an Applied Materials.TM. target). Target 300 comprises a
shape which includes a cup 301 having a hollow 302 extending
therein. An interior surface 308 defines a periphery of the hollow,
and an exterior surface 309 is in opposing relation to the interior
surface. Cup 301 has a first end 305 and an opposing second end
307. End 305 is open, and in the shown embodiment end 307 is
closed. It is to be understood, however, that end 307 could
comprise an opening extending therethrough.
[0063] Exterior surface 309 extends around end 307 (in the shown
embodiment the exterior surface extends entirely around the closed
end, but it is to be understood that the invention encompasses
other embodiments (not shown) wherein the exterior surface extends
only partially around an open end 307). Exterior surface 309 wraps
around end 307 at rounded corners 304. Such rounded corners have a
radius of curvature about a point (with an exemplary point 311
illustrated) of at least about 1 inch. In particular embodiments,
the radius of curvature around corners 304 can be at least about
1.25 inches, 1.5 inches, 1.75 inches, 2 inches, or greater. It is
preferred that the radius of curvature be small enough to avoid
excess thinning of the target material at locations proximate
curved regions 304. Excess thinning can be understood as thinning
which detrimentally influences target performance.
[0064] Target 300 can comprise an inner shape defined by peripheral
surface 308 which is substantially identical to, or in particular
embodiments exactly identical to, a prior art Applied Materials.TM.
target; and yet comprises an outer shape defined by peripheral
surface 309 which is different than the prior Applied Materials.TM.
target.
[0065] An advantage of forming curved corners 304 is that such can
simplify the process of FIGS. 14 and 15 relative to formation of
more square or angled corners. Specifically, it is found that the
compression within press 50 of FIGS. 14 and 15 can be difficult
relative to substantially square corners, in that there can be poor
material flow around such square corners. However, utilization of
curved corners can enhance material flow, and thus improve the
quality of a product formed by the compression of FIGS. 14 and 15.
It is noted that although only some of the square corners
associated with the external periphery 309 of target 300 have been
rounded, other corners (such as, for example, the corners labeled
as 310 and 312) can be rounded in other embodiments of the
invention. An advantage of not rounding corners 310 and 312 can be
that a target apparatus comprising substantially square corners 310
and 312 will fit within a prior art Applied Materials.TM.
sputtering apparatus without modification to either the target or
the apparatus. An advantage of rounding at least some of the
corners of a three-dimensional target construction is that such can
reduce an amount of material incorporated into the target
construction, and thus reduce an expense associated with the
material of the target construction.
[0066] The shown target has orifices 316 extending through flanges
318, and configured for attaching the target to a sputtering
apparatus. It is to be understood, however, that the illustrated
flanges 318 and orifices 316 are exemplary, and that other
configurations can be utilized in target constructions of the
present invention.
[0067] Target 300 can consist essentially of a material which
comprises one or more of Ni, Co, Ta, Al, and Ti; and in particular
embodiments that material can consist essentially of Cu or Ti.
[0068] FIGS. 17 and 18 show additional embodiments of target
constructions that can be formed in accordance with the present
invention. Specifically, FIG. 17 shows a target 350 similar to the
Novellus.TM. target of FIG. 4, but having rounded corners 352 along
an outer periphery 354 of the target. The target 350 comprises an
inner periphery 356 which is identical to the inner periphery of
the prior art Novellus.TM. target. A radius of curvature of rounded
corners 352 can be identical to the radius described above with
reference to target 300 of FIG. 16.
[0069] Referring to FIG. 18, a target 360 is illustrated. Target
360 is also similar to the Novellus.TM. target of FIG. 4, but
comprises rounded corners along an inner periphery 362, as well as
along an outer periphery 364. More specifically, inner periphery
362 comprises rounded corners 366 and outer periphery 364 comprises
rounded corners 368. In the shown embodiment, rounded corners 368
and 366 comprise a same radius of curvature as one another; and
interior rounded corners 366 are radially within exterior rounded
corners 368. The radius of curvature of corners 366 and 368 can be,
for example, identical to that described previously with reference
to FIG. 16. It is to be understood that the invention encompasses
other embodiments (not shown) wherein inner corners 366 comprise a
different radius of curvature than outer corners 368.
[0070] Referring to FIG. 19, a magnetron sputter reactor 400 is
illustrated to comprise a target 300 of the type described with
reference to FIG. 16. Similar numbering will be utilized in
describing reactor to 400 as was used above in describing the
reactor 200 of FIG. 9, where appropriate. Reactor 400 comprises
magnets 226 and 224. A difference between the utilization of target
300 versus target 10 (FIG. 9) is that curved corners 304 cause gaps
402 to occur between outer periphery 306 of target 300 and the
magnets 224 and 226. Gaps 402 are generally not problematic, in
that a magnetic permeability associated with the gaps does not
appreciably affect the magnetic flux through the material of target
300. It can, however, be problematic to have a target 300 with a
different thickness in between a magnet and sputtering surface at
one portion of a cup shape of the magnet than within another
portion of the cup shape of the magnet. For instance, the shown
target 300 has a first thickness "A" extending through a lower
portion of a sidewall, and a second, larger thickness, "B"
extending through a second portion of sidewall. The relative ratio
of "A" to "B" can cause different magnetic permeabilities
associated with different portions of the target, and thus alter
sputtering performance of one portion of the target relative to
another. However, in embodiments in which the target comprises
non-magnetic materials (such as, for example, copper), there can be
negligible effect from having different thicknesses around the cup
of the target construction. In embodiments in which the different
thicknesses of the target construction are found to be problematic,
a target construction can be formed having curved corners, with a
radius of curvature and geometrical proportion being chosen to
minimize or eliminate differences in magnetic flux associated with
different regions of the target during a sputtering operation.
[0071] A difficulty which has been found in utilizing the
processing of FIGS. 10-19 is in obtaining a suitable starting ingot
for the processing. FIG. 20 illustrates a prior art ingot 70 in
cross-sectional view, and shows a problem with conventional casting
processes. Specifically, ingot 70 comprises a thickness "R", and a
shrinkage cavity 72 extending a significant depth into the ingot
material to reduce a usable amount of the thickness "R". A dashed
line 74 is shown across ingot 70 to divide the ingot into an
unusable portion 76 above the dashed line and a usable portion 78
below the dashed line. In practice, ingot 70 would be cut along
dashed line 74, and accordingly the thickness would be reduced to a
second thickness "X" which corresponds to the thickness of usable
portion 78 of the ingot. In traditional casting processes, a high
purity copper ingot 70 formed with an initial thickness "R" of
about 15 inches will have a shrinkage cavity 72 typically extending
to a thickness of greater than two inches. Such shrinkage cavity
will reduce the usable portion of ingot 70 to a thickness "X" of
less than about 13 inches. In other words; at least about 13% of
the original thickness "R" is sacrificed due to the shrinkage
defect 72.
[0072] Shrinkage defect 72 occurs during cooling of the material of
ingot 70 in a casting process. In applications of the present
invention, it can be preferred that an ingot have a usable portion
which is at least 14 inches in thickness, and in some applications
it can be desired that the ingot initially be about 17 inches in
usable thickness. One method of achieving such ingots would be to
initially form ingots which are much thicker than is desired, and
to then cut a significant amount of the ingot away to remove a
shrinkage defect. However, it would be preferred to develop methods
of forming ingots which substantially alleviate the formation of a
shrinkage defect within the ingots.
[0073] A method of forming ingots in accordance with the present
invention is described with reference to FIGS. 21-24. Referring
initially to FIG. 21, a mold 100 is shown in cross-sectional view.
Mold 100 comprises an interior cavity 102 which, in preferred
embodiments, can comprise a cylindrical shape. A first charge of a
molten metallic material 104 is provided within cavity 102 to only
partially fill the cavity. In a preferred embodiment, the first
charge will be provided to fill less than or equal to about 50% of
the volume of interior cavity 102. Material 104 is cooled while
agitating mold 100. The agitation is preferably a mechanical
agitation, as illustrated by the arrow 106. The agitation can be in
the side-to-side motion shown, or can comprise other motions. The
agitation helps to expel gas from within molten material 104 during
the cooling of the material. In a particular embodiment, material
104 comprises high-purity copper initially provided within mold 100
at a temperature of from about 2200.degree. F. to about
2800.degree. F., and mold 100 is held at a cooling temperature less
than a melting point of material 104. Material 104 is allowed to
cool for a time of from about 30 seconds to about 40 seconds, so
that an upper surface of material 104 becomes partially
solidified.
[0074] Referring to FIG. 22, a second charge of material 104 is
provided over the partially solidified first charge. Mold 100 is
then agitated while second charge 104 is allowed to cool for from
about 30 seconds to about 40 seconds.
[0075] Referring to FIG. 23, a third charge of material 104 is
provided over the second charge, and mold 100 is agitated while the
first, second and third charges completely cool and solidify. A
reason for having the earlier charges of material 104 only
partially solidified during addition of the later charges is to
avoid forming a solid interface between the various charges.
Although FIGS. 22 and 23 show interfaces between the first, second
and third charges, such are provided for illustration purposes
only, and in practice such interfaces are avoided by having the
various charges only partially solidified. Accordingly, the
resulting ingot has a homogeneous composition from a lowermost
portion of the ingot to an uppermost portion.
[0076] FIG. 24 illustrates a cross-sectional side view of an ingot
130 formed in accordance with the present invention. Ingot 130
comprises a thickness "R", and a shrinkage cavity 132 extending
partially along the thickness "R". However, shrinkage cavity 132 is
significantly smaller than the shrinkage cavity 72 of the prior art
ingot 70 shown in FIG. 20. Accordingly, a usable portion "X" of
ingot 130 is much larger than the usable portion "X" of the prior
art ingot 70. In particular applications, ingots have been formed
having a cavity depth of less than 0.25 inches in a total thickness
"R" of 15 inches, and also having a cavity depth of less than 0.25
inches in a total thickness of 18 inches. Accordingly, ingot 130
can be formed to have a shrinkage cavity that extends to less than
or equal to about 10% of a total thickness "R" of the ingot, and in
particular embodiments to less than or equal to about 5% of a total
thickness "R" of the ingot, and in yet other embodiments to less
than or equal to about 2% of a total thickness "R" of the
ingot.
[0077] In particular embodiments, each of the successive charges of
molten material provided within interior cavity 102 after the first
charge fill a volume corresponding to about 10% of the original
volume of the interior cavity. Accordingly, if a first charge fills
about 50% of a volume of the original cavity, each additional
charge will fill about 10% of such volume of the original cavity,
and there will be about five such additional charges utilized to
entirely fill the ingot mold. In another particular embodiment, a
first charge fills about 90% of the original volume of the interior
cavity, and the remaining volume is filled with a single subsequent
charge. The casting of the present invention can comprise vacuum
casting which is performed in a vacuum chamber and under a pressure
of about 200 mTorr.
[0078] Methodology of the present invention can be utilized to form
three-dimensional targets having an average grain size of less than
or equal to 250 microns, 200 microns, or even 100 microns. For
instance, methodology of the present invention can be utilized to
form monolithic copper targets having a copper purity of at least
99.995 weight percent, and having complex three dimensional shapes
of the types exemplified in FIGS. 2 and 4. As another example,
methodology of the present invention can be utilized to form
monolithic targets comprising Ta or Ti, and having complex three
dimensional shapes of the types exemplified in FIGS. 2 and 4.
[0079] Although particular metals and alloys are described above
for the exemplary aspects of the invention being discussed, it is
to be understood that any suitable composition can be utilized in
the methodology and target constructions of the present invention.
Among the numerous alloys and metal-containing compositions that
can be utilized are compositions comprise copper together with one
or more of Cd, Ca, Au, Ag, Be, Li, Mg, Al, Pd, Hg, Ni, In, Zn, B,
Ga, Mn, Sn, Ge, W, Cr, O, Sb, Ir, P, As, Co, Te, Fe, S, Ti, Zr, Sc,
and Hf. Exemplary compositions can consist essentially of less than
or equal to about 99.99% copper by weight and at least one element
selected from the group consisting of Cd, Ca, Au, Ag, Be, Li, Mg,
Al, Pd, Hg, Ni, In, Zn, B, Ga, Mn, Sn, Ge, W, Cr, O, Sb, Ir, P, As,
Co, Te, Fe, S, Ti, Zr, Sc, Sn and Hf. In particular instances, the
at least one element can preferably be selected from Ag, Al, In,
Zn, B, Ga, Mn, Sn, Ge, Ti and Zr. A total amount of the at least
one element present in the constructions can preferably be from at
least about 100 ppm by weight to less than about 10% by weight.
More preferably, the at least one element can be present at from at
least 1000 ppm to less than about 2%, by weight. Typically the at
least one element will be present to about 0.5 atomic percent.
[0080] A specific composition which can be utilized in the various
targets described herein is a composition comprising, consisting
essentially of, or consisting of CuSn, with the Sn being present to
from about 100 ppm (by weight) to about 3 atomic percent, and with
a typically amount of Sn being about 0.5 atomic percent.
[0081] Another specific composition which can be utilized in the
various targets described herein is a composition comprising,
consisting essentially of, or consisting of CuAl, with the Al being
present to from about 100 ppm (by weight) to about 3 atomic
percent, and with a typically amount of Al being about 0.5 atomic
percent.
[0082] Another specific composition which can be utilized in the
various targets described herein is a composition comprising,
consisting essentially of, or consisting of CuAg, with the Ag being
present to from about 100 ppm (by weight) to about 3 atomic
percent, and with a typically amount of Ag being about 0.5 atomic
percent.
* * * * *