U.S. patent application number 08/857944 was filed with the patent office on 2001-07-12 for hybrid coil design for ionized deposition.
Invention is credited to HONG, LIUBO.
Application Number | 20010007302 08/857944 |
Document ID | / |
Family ID | 25327083 |
Filed Date | 2001-07-12 |
United States Patent
Application |
20010007302 |
Kind Code |
A1 |
HONG, LIUBO |
July 12, 2001 |
HYBRID COIL DESIGN FOR IONIZED DEPOSITION
Abstract
A sputtering hybrid coil for a plasma chamber in a semiconductor
fabrication has an enhanced sputtering surface and an internal
coolant carrying channel thermally coupled to the sputtering
surface to cool the sputtering surface and the coil.
Inventors: |
HONG, LIUBO; (SAN JOSE,
CA) |
Correspondence
Address: |
PATENT COUNSEL
APPLIED MATERIALS INC
P O BOX 450A
SANTA CLARA
CA
95052
|
Family ID: |
25327083 |
Appl. No.: |
08/857944 |
Filed: |
May 16, 1997 |
Current U.S.
Class: |
204/192.12 ;
204/192.15; 204/298.06; 204/298.09 |
Current CPC
Class: |
H01J 37/3408 20130101;
H01J 37/321 20130101; C23C 14/358 20130101; C23C 14/3407
20130101 |
Class at
Publication: |
204/192.12 ;
204/192.15; 204/298.06; 204/298.09 |
International
Class: |
C23C 014/34 |
Claims
What is claimed is:
1. An apparatus for sputter deposition of a film layer onto a
substrate comprising: a vacuum chamber; a substrate support
disposed within said vacuum chamber, a target disposed within said
chamber; and a coil disposed within said chamber and extending
within a space defined between said target and substrate support,
said coil having a sputtering surface and a coolant carrying
channel defined within said coil, wherein at least a portion of
said sputtering surface is non-circular in a plane orthogonal to a
longitudinal tangential axis of the coil.
2. The apparatus of claim 1 wherein said coil sputtering surface is
flat in said plane.
3. The apparatus of claim 1, wherein said coil comprises a first
ribbon-shaped coil and a second tubular coil thermally coupled to
said first coil.
4. The apparatus of claim 3, wherein said first ribbon-shaped coil
and second tubular coil are each ring-shaped.
5. The apparatus of claim 4, wherein said first ribbon-shaped coil
defines an outer surface and said second tubular coil is coupled to
said outer surface of said first ribbon-shaped coil.
6. The apparatus of claim 4, wherein said first ribbon-shaped coil
defines an inner surface and said second tubular coil is coupled to
said inner surface of said ribbon-shaped coil.
7. The apparatus of claim 1, wherein said coil is comprised of the
same material as said target.
8. The apparatus of claim 1, wherein said coil is adapted to
radiate RF energy from said coil.
9. An apparatus for sputter deposition of a film layer onto a
substrate comprising: a vacuum chamber; a substrate support
disposed within said vacuum chamber; a target disposed within said
chamber; a first coil disposed within said chamber and extending
through a space defined between said target and substrate support;
and a second coil thermally coupled to said first coil.
10. The apparatus of claim 9, wherein said second coil defines a
coolant carrying channel within said second coil.
11. The apparatus of claim 9, wherein both said first coil and said
second coil are each ring-shaped.
12. The apparatus of claim 11, wherein said first coil defines an
outer surface and second coil is coupled to said outer surface of
said first coil.
13. The apparatus of claim 11, wherein said first coil defines an
inner surface and second coil is coupled to said inner surface of
the said first coil.
14. The apparatus of claim 9, wherein said first coil is adapted to
radiate RF energy from said coil.
15. The apparatus of claim 9, wherein said first coil has width at
least twice as wide as the width of said second coil.
16. An apparatus for sputter deposition of a film layer onto a
substrate comprising: a vacuum chamber; a substrate support
disposed within said vacuum chamber, a target disposed within said
chamber; a coil disposed within said chamber and extending within a
space defined between said target and substrate support, said coil
having a coolant carrying channel within said coil; and a first
flange extending outward from a surface of said coil.
17. The apparatus of claim 16 further comprising a second flange
extending outward from a surface of said coil.
18. The apparatus of claim 17 wherein said first and second flanges
are separate and said coil is positioned between said first and
second flanges.
19. The apparatus of claim 18 wherein said first and second flanges
are welded to said coil.
20. An apparatus for energizing a plasma within a semiconductor
fabrication system to sputter material onto a workpiece, the
apparatus comprising: a semiconductor fabrication chamber having a
plasma generation area within said chamber; a sputtering target
carried within said chamber and made of a first material, said
target being positioned to sputter said target material onto said
workpiece; and a first ring-shaped ribbon coil disposed within said
chamber and extending through a space defined between said target
and substrate support, wherein said first coil is positioned to
couple energy into the plasma generation area and to sputter coil
material onto said workpiece so that both coil material and target
material are deposited on said workpiece to form a layer thereon;
and a second ring-shaped coil thermally coupled to said first coil,
said second coil having a coolant carrying channel defined
therein.
21. A method of depositing material onto a workpiece in a sputter
deposition chamber, comprising: sputtering target material onto
said workpiece from a target positioned in said chamber; and
sputtering material onto said workpiece from a first coil; and
flowing a coolant through a second tubular-shaped coil thermally
coupled to said first coil to cool said first coil.
22. The method of claim 21, wherein said sputtering surface is
ribbon-shaped.
23. An antennae for a sputter deposition apparatus using RF energy,
comprising: a coil adapted to radiate said RF energy, said coil
having a sputtering surface and a coolant carrying channel defined
within said coil, wherein at least a portion of said sputtering
surface is non-circular is a plane orthogonal to a longitudinal
tangential axis of the coil.
24. The antennae of claim 23, wherein said sputtering surface is
flat in said plane.
25. The antennae of claim 23, wherein said coil comprises a first
ribbon-shaped coil and a second tubular coil thermally coupled to
said first coil.
26. The antennae of claim 25, wherein said first ribbon-shaped coil
and second tubular coil are each ring-shaped.
27. The antennae of claim 26, wherein said first ribbon-shaped coil
defines an outer surface and said second tubular coil is coupled to
said outer surface of said first ribbon-shaped coil.
28. The antennae of claim 26, wherein said first ribbon-shaped coil
defines an inner surface and said second tubular coil is coupled to
said inner surface of said ribbon-shaped coil.
29. The antennae of claim 23, wherein said coil is comprised of a
sputter deposition material selected from the group of titanium,
tantalum, copper and aluminum.
30. An antennae for an apparatus for sputter deposition of a film
layer onto a substrate comprising: a first coil; and a second
tubular-shaped coil thermally coupled to said first coil.
31. The antennae of claim 30, wherein said second coil defines a
coolant carrying channel within said second coil.
32. The antennae of claim 30, wherein both said first coil and said
second tubular-shaped coil are each ring-shaped.
33. The antennae of claim 30, wherein said first coil is a
ribbon-shaped coil which defines an outer surface and said second
tubular coil is coupled to said outer surface of said first
ribbon-shaped coil.
34. The antennae of claim 30, wherein said first coil is a
ribbon-shaped coil which defines an inner surface and said second
tubular coil is coupled to said inner surface of the said
ribbon-shaped coil.
35. The antennae of claim 30, wherein said first coil has width at
least twice as wide as the width of said second tubular-shaped
coil.
36. An antennae for an apparatus for sputter deposition of a film
layer onto a substrate comprising: a tubular-shaped coil; and a
first flange extending outward from a surface of said
tubular-shaped coil.
37. The apparatus of claim 36 further comprising a second flange
extending outward from a surface of said coil.
38. The apparatus of claim 37 wherein said first and second flanges
are separate and said coil is positioned between said first and
second flanges.
39. The apparatus of claim 38 wherein said first and second flanges
are welded to said coil.
40. The antennae of claim 36, wherein said tubular-shaped coil
defines a coolant carrying channel within said coil.
41. An antennae for energizing a plasma within a semiconductor
fabrication system to sputter material onto a workpiece, the
antennae comprising: a first ring-shaped ribbon coil adapted to
sputter coil material onto said workpiece; and a second tubular
ring-shaped coil thermally coupled to said first coil, said
tubular-shaped coil having a coolant carrying channel defined
therein.
42. A method of depositing material on a workpiece in a sputter
deposition chamber, comprising: sputtering target material onto
said workpiece from a target positioned in said chamber; sputtering
coil material onto said workpiece from a coil disposed within the
chamber and extending within a space defined between said target
and substrate support, said coil having a sputtering surface and a
coolant carrying channel defined within said coil, wherein at least
a portion of said sputtering surface is non-circular is a plane
orthogonal to a longitudinal tangential axis of the coil; and
flowing a coolant fluid through said coolant carrying channel.
43. The method of claim 40, further comprising passing RF current
through said coil to energize a plasma in said chamber.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to ionized deposition
processes, and more particularly, to a method and apparatus for
sputtering a coil in the fabrication of semiconductor devices.
BACKGROUND OF THE INVENTION
[0002] To improve bottom coverage of high aspect ratio vias,
channels and other openings in a wafer or other substrate, the
deposition material may be ionized in a plasma prior to being
deposited onto the substrate. The ionized deposition material may
be redirected by electric fields to ensure more material reaches
the bottom areas. It has been found that it is desirable to
increase the density of the plasma to increase the ionization rate
of the sputtered material in order to decrease the formation of
unwanted cavities in the deposition layer. As used herein, the term
"dense plasma" is intended to refer to one that has a high electron
and ion density.
[0003] There are several known techniques for exciting a plasma
with RF fields including capacitive coupling, inductive coupling
and wave heating. In a standard inductively coupled plasma (ICP)
generator, RF current passing through an antenna in the form of a
coil surrounding the plasma induces electromagnetic currents in the
plasma. These currents heat the conducting plasma by ohmic heating,
so that it is sustained in steady state. As shown in U.S. Pat. No.
4,362,632, for example, current through a coil is supplied by an RF
generator coupled to the coil through an impedance matching
network, such that the coil acts as the first windings of a
transformer. The plasma acts as a single turn second winding of a
transformer.
[0004] A high density plasma typically requires the chamber to be
operated at a relatively high pressure. As a result, the frequency
of collisions between the plasma ions and the deposition material
atoms is increased and the scattering of the deposition atoms is
likewise increased. This scattering of the deposition atoms
typically causes the thickness of the deposition layer on the
substrate to be thicker on that portion of the substrate aligned
with the center of the target and thinner in the outlying regions.
Such nonuniformity of deposition is often undesirable in the
fabrication of semiconductor devices. Thus, although ionizing the
deposition material in a high density plasma can facilitate
deposition of material into high aspect ratio channels and vias,
many sputtered contact metals have a tendency to deposit more
thickly in the center of the wafer as compared to the edges.
[0005] The deposition layer can be made more uniform by reducing
the distance between the target and the substrate, which reduces
the effect of plasma scattering. However, decreasing the distance
between the target and the substrate decreases the ionization of
the deposition material and, hence, increases the formation of
unwanted cavities in the deposition layer. For this reason, it is
important to maintain a relatively high plasma ionization rate to
minimize cavity formation in the deposition layer.
[0006] As described in copending application Ser. No. 08/680,335,
entitled "Coils for Generating a Plasma and for Sputtering," filed
Jul. 10, 1996 (Attorney Docket # 1390CIP/PVD/DV) and assigned to
the assignee of the present application, which application is
incorporated herein by reference in its entirety, it has been
recognized that the coil itself may provide a source of sputtered
material to supplement the deposition material sputtered from the
primary target of the chamber. Application of an RF signal to the
coil can cause the coil to develop a negative bias which will
attract positive ions which can impact the coil causing material to
be sputtered from the coil. Because the material sputtered from the
coil tends to deposit more thickly at the periphery of the wafer,
the center thick tendency for material sputtered from the primary
target can be compensated by the edge thick tendency for material
sputtered from the coil. By shaping the coil in the form of a
ribbon, it has been found that uniformity can be improved.
[0007] However, because relatively large currents are passed
through the coil to energize the plasma, the coil often undergoes
significant resistive heating. In addition, ions impacting the coil
can further heat the coil if the coil is used as a sputtering
source. As a result, the coil can reach relatively high
temperatures which can have an adverse effect on the wafer, the
wafer deposition process or even the coil itself. Moreover, the
coil will cool once the deposition is completed and the current to
the coil is removed. Each heating and subsequent cooling of the
coil causes the coil to expand and then contract. This thermal
cycling of the coil can cause target material deposited onto the
coil to generate particulate matter which can fall onto and
contaminate the wafer.
[0008] To reduce coil heating, it has been proposed in some
applications to form the coil from hollow tubing through which a
coolant such as water is passed. However, such tubing typically has
a relatively poor sputtering rate and therefore is not well suited
to sputtering. As a consequence, improvements in uniformity may be
more difficult to achieve, particularly if a relatively high rate
of coil sputtering is needed.
SUMMARY OF THE PREFERRED EMBODIMENTS
[0009] It is an object of the present invention to provide an
improved method and apparatus for sputtering which obviates, for
practical purposes, the above-mentioned limitations, particularly
in a manner requiring a relatively uncomplicated arrangement. 5
These and other objects and advantages are achieved by, in
accordance with one aspect of the invention, an RF coil disposed
within a vacuum chamber, between a target and substrate support,
wherein the coil has both a coolant carrying channel and a
sputtering surface shaped to enhance sputtering of the coil. The
coil sputtering surface provides for sputtering at sufficiently
high rates to reduce non-uniformity in the deposition layer on the
substrate. At the same time, a coolant carrying channel defined
within the coil facilitates heat transfer from the sputtering
surface to the coolant to prevent the coil from reaching
undesirably high temperatures during the sputtering process and
prevent thermal cycling.
[0010] In one embodiment, the coil comprises two coils joined
together to form a hybrid coil. A first RF coil, which sputters
deposition material onto a substrate, is disposed within the vacuum
chamber and extends through a space defined between the target and
substrate. This first coil may be a ribbon-shaped coil which is
especially suited for providing edge-thick sputter depositing of
material at a rate sufficient to offset the center-thick deposition
from the target, thereby enhancing the uniformity of the deposition
layer. A second tubular-shaped coil is thermally and electrically
coupled to the first coil to absorb heat from the first coil. Such
an arrangement facilitates economical manufacture of the hybrid
coil as discussed below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective, partial cross-sectional view of a
plasma generating chamber having a hybrid coil in accordance with
one embodiment of the present invention.
[0012] FIG. 2 is a schematic diagram of the electrical
interconnections to the plasma generating chamber of FIG. 1.
[0013] FIG. 3 is a partial perspective view of the hybrid coil of
FIG. 1.
[0014] FIG. 3a is a cross-sectional view of the coil of FIG. 3.
[0015] FIG. 4 is a partial perspective view of a hybrid coil in
accordance with another embodiment of the present invention.
[0016] FIG. 5 is a partial perspective view of a hybrid coil in
accordance with yet another embodiment of the present
invention.
[0017] FIG. 6 is a partial perspective view of a hybrid coil in
accordance with another embodiment of the present invention.
[0018] FIG. 6a is a cross-sectional view of the coil of FIG. 6.
DETAILED DESCRIPTION OF THE DRAWINGS
[0019] Referring to FIGS. 1 and 2, a plasma generator in accordance
with a first embodiment of the present invention comprises a
substantially cylindrical plasma chamber 100 which is received in a
vacuum chamber 102 (shown schematically in FIG. 2). The plasma
chamber 100 of this embodiment has a one-turn or multiple-turn
hybrid antenna or coil 104 which includes a first RF ribbon coil
106 encircling an interior plasma generation area 108. Radio
frequency (RF) energy from an RF generator 110 is radiated from the
first RF coil 106 of the hybrid coil 104 into the interior area 108
of the deposition system 100, which energizes a plasma within the
deposition system 100. A second, tubular coil 112 of the hybrid
coil 104 is thermally and electrically coupled to the outer surface
of the first coil 106 to cool the first coil 106 by absorbing heat
therefrom. This second coil 112 may also radiate RF energy.
[0020] An ion flux strikes a negatively biased target 114
positioned at the top of the chamber 102. The target 114 is
preferably negatively biased by a DC power source 116. The first
coil 106 also develops a negative bias to attract ions. The plasma
ions eject material from the target 114 and first coil 106 onto a
substrate 118 which may be a wafer or other workpiece which is
supported by a pedestal 120 at the bottom of the deposition system
100. A rotating magnet assembly 122 provided above the target 114
produces magnetic fields which sweep over the face of the target
114 to promote uniform erosion of the target.
[0021] The atoms of material ejected from the target 114 and first
coil 106 are in turn ionized by the plasma being energized by the
first coil 106 which is inductively coupled to the plasma. The RF
generator 1 10 is preferably coupled to the first coil 106 through
an amplifier and impedance matching network 124. The other end of
the first RF coil 106 is coupled to ground, preferably through a
capacitor 126 which may be a variable capacitor. The ionized
deposition material is attracted to the substrate 118 and forms a
deposition layer thereon. The pedestal 120 may be negatively biased
by an AC (or DC or RF) source 128 so as to externally bias the
substrate 118. Also, the substrate 118 may self bias in some
applications such that external biasing of the substrate 118 may
optionally be eliminated.
[0022] As will be explained in greater detail below, in accordance
with one aspect of the present invention, material is sputtered
from the ribbon-shaped first RF coil 106 of the water-cooled hybrid
coil 104, onto the substrate 118, while the first coil 106 is
cooled by the second, tubular-shaped coil 112 of the hybrid coil
104. As best seen in FIG. 3A which is a cross-sectional view in the
radial plane orthogonal to the longitudinal tangential axis 130
(FIG. 3), the first RF coil 106 preferably has a relatively flat
face 132 facing the interior of the chamber for sputtering material
to offset substantially the center-thick deposition from the target
114 and, hence, improve the uniformity of the deposition.
[0023] To cool the first coil 106, the second coil 112 coupled to
the first coil 106 is preferably a tubular coil to facilitate
absorbing heat from the first coil. The use of the term "tubular"
hereinafter refers to any tubed shaped object, wherein the radial
cross-section of the outer surface may be comprised of any suitable
shape, including circular (as shown in FIG. 3A) or any non-circular
shape such as rectangular. The second tubular coil 112 defines an
internal channel 134 which permits the flow of a coolant such as
water through the coil 112. The water is preferably circulated
through the coil 112 in a closed system having a heat exchanger
(not shown) to facilitate heat transfer from the coil. In preferred
embodiments, the first coil 106 and second tubular coil 112 of the
hybrid coil 104 are fastened together so that the coils are
thermally and electrically coupled together. The electrical
coupling of the first and second coils permits both coils to
radiate RF energy from a single source. Thermal coupling
facilitates heat transfer from the RF coil 106 to the cooling coil
112. The coils 106 and 112 may be fastened in a variety of
processes including e-beam welding at high vacuum (UV) or UHV
environments to minimize contamination during welding. Other
methods to join the first ribbon coil 106 and second tubular coil
112 may also be used, preferably those that minimize contamination,
and provide suitable structural strength and heat and electrical
conductivity between the two coils.
[0024] In accordance with another aspect of the present invention,
the cooling coil 112 is positioned on an outer face 136 of the RF
ribbon coil 106 so that the ribbon coil 106 is positioned between
the cooling coil 112 and the central plasma generation area 108. As
explained below, such an arrangement has several advantages. In the
illustrated embodiment, the hybrid coil 104 is insulatively carried
by standoffs 138 (FIG. 1) and RF feedthroughs 140 which position
the coil 104 close to a grounded shield wall 142. Because there is
relatively little space between the coil 104 and the shield wall
142, there are relatively few ions between the coil 104 and the
wall 142. Hence, most of the plasma ions available to sputter the
hybrid coil 104 are located in the central plasma generation area
108 which is faced by the inner face 132 of the ribbon coil 106. It
is believed that the inner face 132 of the ribbon coil 106 will
tend to shield the outer face 136 of the ribbon coil and hence the
cooling coil 112 as well, which is carried on the coil outer face
136. Consequently, it is believed that the majority of the material
sputtered from the hybrid coil 104 will be sputtered from the inner
face 132 together with the top and bottom faces 144a and 144b of
the coil 106 and relatively little, if any, will be sputtered from
the cooling coil 112. As a result, the cooling coil 112 may be
fabricated from less expensive materials than the sputtering coil
106 which is preferably made of the same high quality material as
the target 114.
[0025] For example, the first coil 106 of the illustrated
embodiment in FIG. 3 may be comprised of a heavy duty bead blasted
solid high-purity (preferably 99.995% pure) titanium ribbon formed
into a single turn coil having a width of 1/8to {fraction
(1/16)}inches (3 to 1.5 mm), a height from 1 to 2 inches (25 to 50
mm), and a diameter of 10-12 inches (250-300 mm). However, other
highly conductive materials and shapes may be utilized depending on
the material being sputtered and other factors. For instance, if
the material to be sputtered is aluminum, both the target and the
coil may be made of high purity aluminum. Still further, instead of
the ribbon-shaped coil, a multiple turn coil may be implemented
with flat, open-ended annular rings. The advantage of a multiple
turn coil is that the required current levels can be substantially
reduced for a given RF power level. However, multiple turn coils
tend to be more complicated and hence more costly and difficult to
fabricate, support and clean as compared to single turn coils.
Multiple turn coils may also be shaped as spirals or helixes, for
example.
[0026] The second tubular coil 112 coupled to the first coil 106
may be round and have an outer diameter of 3/8or 1/4inches (10 or
44 mm). The first coil 106 and second tubular coil 112 can be made
of the same type of high purity material to minimize contamination.
Because there is little or no net sputtering from the second
tubular coil 112, the second tubular coil 112 could also be made of
a lesser grade material but of the same type as the ribbon coil.
Alternatively, the cooling coil 112 may be formed of other types of
materials with high thermal conductivity (such as CU) and coated
with a thick layer of high purity material of the same type as the
first ribbon coil 106.
[0027] In the illustrated embodiment, RF current is supplied to the
hybrid coil 104 by the RF feedthroughs 140 which are attached to
the open ends of the ribbon coil 106. The tubular coil 112 is
connected to a source of water or other coolant which maintains a
continuous flow of coolant through the tubular coil 112. Also, a
tubular conductive conduit may be used to supply both RF current
and coolant to the tubular coil 112.
[0028] For example, conductive conduits may be used to pass the RF
current and coolant water from the exterior of the chamber, through
the apertures in walls of the vacuum chamber and through apertures
in the shield wall 142 to the coil. Ceramic insulators insulate the
conduits from the walls of the chamber and the shield which are
typically at ground. If the RF current is supplied directly to the
tubular coil 112 instead of the ribbon coil 106, it is preferred
that the welding or other method used to attach the tubular coil
112 to the ribbon coil 106 provide a good electrical contact as
well as thermal contact. On the other hand, if RF current is
supplied directly by the feedthroughs to the ribbon coil 106 which
is employed as the primary RF and sputtering coil, good electrical
contact between the ribbon coil 106 and the cooling coil 112 is
less of a concern.
[0029] FIG. 4 illustrates an alternative embodiment in which a
tubular cooling coil 112a is coupled to the inner side 132a of a
ribbon coil 106a. Because positioning the tubular coil 112a on the
inner side 132a of the first ribbon coil 106 as shown in FIG. 4
provides a greater surface area facing the ionization area, it is
believed that the sputtering rate of the hybrid coil 104a may be
enhanced. Since the cooling coil 112a could provide a substantial
source of sputtered material, the tubular coil 112a is preferably
made of the same high grade target material as the ribbon coil
106a. However, it is recognized that such an arrangement may also
lead to an increase in the generation of undesirable particulate
matter.
[0030] FIG. 5 shows a hybrid coil 146 which includes a tubular
cooling coil 148 having an upper flange 150 and lower flange 152
extending from the tubular cooling coil 148. During the ionization
process, material is sputtered from both flanges 150 and 152 as
well as the cooling coil 148 onto the substrate. Because the
flanges 150,152 are thermally coupled to the cooling coil 148, the
flanges 150, 152 are cooled by heat transfer from the flanges 150,
152 to the tubular coil 148. The flanges 150, 152 may be formed
integrally with the cooling coil 148 by various processes including
machine rolling or casting processes, for example. Alternatively,
the flanges 150 and 152 can be fastened to the tubular coil 148 by
welding the flanges to the upper and lower sides, respectively, of
the tubular coil 148. The tubular coil 148 preferably has an
internal coolant carrying channel 154 for cooling the flanges
150,152.
[0031] It is also contemplated that a coil in accordance with the
present invention may comprise a single contiguous coil having an
inner, solid, sputtering region and an outer, hollow cooling
region. For example, FIG. 6 shows an alternative hybrid coil 156
which is generally tubular-shaped with a non-circular exterior
cross-section as shown in the radial cross-sectional view of FIG.
6A. More particularly, this embodiment has a relatively flat inner
sputtering surface 158 which faces the ionization area 108 (FIG.
2). It is believed that this non-circular cross-section of the coil
increases the total sputtering surface of the sputtering region of
the coil to increase the sputtering rate of the tubular coil 156. A
channel of the hollow, outer cooling region 160 permits the passage
of a coolant such as water. It is recognized that other
non-circular exteriors, such as ovals, may also be utilized to
increase the sputtering rate of the water cooling coil.
[0032] The preferred coil embodiments discussed herein can be used
to deposit many different types of metals, such as Al, Ti, Ta, Cu,
etc., and metal nitrates, such as TiN, TaN, etc. If one or more
additional coils are used with the tubular coil, then the tubular
coil and additional coils may be comprised of the same material or,
alternatively, different materials. Still further, additional
tubular cooling coils as well as sputtering coils may be added to
the embodiments discussed herein. The use of multiple coils is
disclosed in the aforementioned copending application Ser. No.
08/680,335, entitled "Coils for Generating a Plasma and for
Sputtering."
[0033] It will, of course, be understood that modifications of the
present invention, in its various aspects, will be apparent to
those skilled in the art, some being apparent only after study
others being matters of routine mechanical and electronic design.
Other embodiments are also possible, their specific designs
depending upon the particular application. As such, the scope of
the invention should not be limited by the particular embodiments
herein described but should be defined only by the appended claims
and equivalents thereof.
* * * * *