U.S. patent application number 10/785739 was filed with the patent office on 2004-12-30 for method of forming sputtering target assembly and assemblies made therefrom.
Invention is credited to Ford, Robert B., Michaluk, Christopher A., Wickersham, Charles E. JR..
Application Number | 20040262157 10/785739 |
Document ID | / |
Family ID | 32927618 |
Filed Date | 2004-12-30 |
United States Patent
Application |
20040262157 |
Kind Code |
A1 |
Ford, Robert B. ; et
al. |
December 30, 2004 |
Method of forming sputtering target assembly and assemblies made
therefrom
Abstract
A method of forming a sputtering target assembly is described
that involves explosively bonding a target grade plate and a
backing plate member to form a bonded preform having dimensions
such that a large target or several target assemblies can be
obtained. The method includes optionally partitioning the bonded
preform into a plurality of sputtering target assemblies. An
interlayer can optionally be disposed between the target grade
plate and the backing plate member before bonding. A bond quality
test sample can be produced by the method. The sputtering target
assemblies, the bonded preform, and the bond quality test sample
are further described.
Inventors: |
Ford, Robert B.; (Washington
Court House, OH) ; Michaluk, Christopher A.;
(Gilbertsville, PA) ; Wickersham, Charles E. JR.;
(Columbus, OH) |
Correspondence
Address: |
Martha Ann Finnegan, Esq.
Cabot Corporation
157 Concord Road
Billerica
MA
01821-7001
US
|
Family ID: |
32927618 |
Appl. No.: |
10/785739 |
Filed: |
February 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60450196 |
Feb 25, 2003 |
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Current U.S.
Class: |
204/298.12 ;
204/298.13 |
Current CPC
Class: |
C23C 14/3407
20130101 |
Class at
Publication: |
204/298.12 ;
204/298.13 |
International
Class: |
C25B 009/00; C25B
011/00; C25B 013/00 |
Claims
What is claimed is:
1. A method of forming a sputtering target assembly, comprising:
explosively bonding a target grade plate having a bonding surface
and a backing plate member having a bonding surface to form a
bonded preform having a bonded target grade plate and a bonded
backing plate member; and partitioning said bonded preform to form
a plurality of sputtering target assemblies.
2. The method of claim 1, wherein said target grade plate comprises
a valve metal.
3. The method of claim 1, wherein said target grade plate comprises
tantalum, niobium, cobalt, titanium, copper, aluminum, or alloys
thereof.
4. The method of claim 1, wherein said target grade plate comprises
tantalum or an alloy thereof.
5. The method of claim 1, wherein said target grade plate comprises
niobium or an alloy thereof.
6. The method of claim 1, wherein said backing plate member
comprises tantalum, niobium, titanium, copper, aluminum, or alloys
thereof.
7. The method of claim 1, wherein said backing plate member
comprises copper or an alloy thereof.
8. The method of claim 1, wherein said target grade plate comprises
tantalum or an alloy thereof and said backing member comprises
copper or an alloy thereof.
9. The method of claim 1, wherein said backing plate member is
explosively accelerated into said target grade plate.
10. The method of claim 1, wherein a bond strength between said
target grade plate and said backing plate member at a bond
interface of said bonded preform is from about 10,000 p.s.i. to
about 75,000 p.s.i.
11. The method of claim 1, wherein said target grade plate has an
average grain size of less than about 100 microns and a texture
substantially void of (100) textural bands, and wherein said bonded
preform has a sputter target having an average grain size of less
than about 100 microns and a texture substantially void of (100)
textural bands.
12. The method of claim 1, wherein said bonded preform has a
backing plate that has a hardness more than that of said backing
plate member.
13. The method of claim 1, further comprising disposing at least
one interlayer between a portion of said bonding surfaces wherein
said bonded preform has a bonded interlayer.
14. The method of claim 13, wherein said at least one interlayer
comprises niobium or an alloy thereof.
15. The method of claim 13, wherein said at least one interlayer
comprises tantalum or an alloy thereof.
16. The method of claim 13, wherein said at least one interlayer
has a thickness of from about 0.01 to about 0.09 inches.
17. The method of claim 13, wherein said at least one interlayer
covers from about 10 to about 100% of said bonding surface of said
target grade plate or said backing member.
18. The method of claim 1, further comprising removing at least a
portion of a periphery of said bonded target grade plate, said
bonded backing plate member, or a combination thereof to form a
flange on said sputtering target assembly.
19. The method of claim 13, further comprising removing at least a
portion of a periphery of said bonded target grade plate, said
bonded backing plate member, said bonded interlayer, or
combinations thereof to form a flange on said sputtering target
assembly.
20. The method of claim 1, further comprising flattening said
bonded preform.
21. The method of claim 1, wherein said partitioning forms at least
one test sample.
22. A sputtering target assembly comprising: a target having a
bonding surface; a backing member having a bonding surface; and an
interlayer disposed between a portion of said bonding surfaces,
wherein said target, said backing member, and said interlayer are
explosively bonded together.
23. The sputtering target assembly of claim 22, wherein said target
comprises a valve metal.
24. The sputtering target assembly of claim 22, wherein said target
comprises tantalum, niobium, cobalt, titanium, copper, aluminum, or
alloys thereof.
25. The sputtering target assembly of claim 22, wherein said target
comprises tantalum or an alloy thereof.
26. The sputtering target assembly of claim 22, wherein said target
comprises niobium or an alloy thereof.
27. The sputtering target assembly of claim 22, wherein said
backing member comprises tantalum, niobium, cobalt, titanium,
copper, aluminum, or alloys thereof.
28. The sputtering target assembly of claim 22, wherein said
backing member comprises copper or an alloy thereof.
29. The sputtering target assembly of claim 22, wherein said
interlayer comprises niobium or an alloy thereof.
30. The sputtering target assembly of claim 22, wherein said
interlayer comprises tantalum or an alloy thereof.
31. The sputtering target assembly of claim 22, wherein said
interlayer has a thickness of from about 0.01 to about 0.09
inches.
32. The sputtering target assembly of claim 22, wherein said
interlayer covers from about 10 to about 100% of said bonding
surface of said target.
33. The sputtering target assembly of claim 22, wherein said
interlayer covers from about 10 to about 100% of said bonding
surface of said backing member.
34. The sputtering target assembly of claim 22, further comprising
a flange comprising a portion of said target, a portion of said
interlayer, a portion of said backing member, or any combinations
thereof.
35. The sputtering target assembly of claim 22, wherein before said
bonding said interlayer is bonded to said target or said backing
member.
36. A bonded preform having dimensions sufficient to be divided to
form a plurality of sputtering target assemblies, comprising: a
target grade plate having a bonding surface; and a backing plate
member having a bonding surface, wherein said target grade plate
and said backing plate member are explosively bonded together.
37. The bonded preform of claim 36, wherein said target grade plate
comprises a valve metal.
38. The bonded preform of claim 36, wherein said target grade plate
comprises tantalum, niobium, cobalt, titanium, copper, aluminum, or
alloys thereof.
39. The bonded preform of claim 36, wherein said target grade plate
comprises tantalum or an alloy thereof.
40. The bonded preform of claim 36, wherein said target grade plate
comprises niobium or an alloy thereof.
41. The bonded preform of claim 36, wherein said backing plate
member comprises tantalum, niobium, cobalt, titanium, copper,
aluminum, or alloys thereof.
42. The bonded preform of claim 36, wherein said backing plate
member comprises copper or an alloy thereof.
43. The bonded preform of claim 36, wherein said backing plate
member is explosively accelerated into said target grade plate.
44. The bonded preform of claim 36, wherein said target grade plate
has an average grain size of less than about 100 microns and a
texture substantially void of (100) textural bands, and wherein
said bonded preform has a sputter target having an average grain
size of less than about 100 microns and a texture substantially
void of (100) textural bands.
45. The bonded preform of claim 36, wherein a bond strength between
said target grade plate and said backing plate member at a bond
interface of said bonded preform is from about 10,000 p.s.i. to
about 75,000 p.s.i.
46. The bonded preform of claim 36, wherein said bonded preform has
a backing plate that has a hardness more than that of said backing
plate member.
47. The bonded preform of claim 36, further comprising at least one
interlayer disposed between a portion of said bonding surfaces.
48. The bonded preform of claim 46, wherein said at least one
interlayer comprises niobium or an alloy thereof.
49. The bonded preform of claim 46, wherein said at least one
interlayer comprises tantalum or an alloy thereof.
50. The bonded preform of claim 46, wherein said at least one
interlayer has a thickness of from about 0.01 to about 0.09
inches.
51. The bonded preform of claim 46, wherein said at least one
interlayer covers from about 10 to about 100% of said bonding
surface of said target grade plate or said backing member.
52. The method of claim 1, wherein a bond strength between said
target grade plate and said backing plate member at a bond
interface of said bonded preform is from about 29,000 p.s.i. to
about 55,000 p.s.i.
53. The method of claim 12, wherein said hardness is at least 10%
greater in said backing plate compared to said backing plate
member.
54. A bonded preform or target assembly comprising a target and a
backing plate bonded together, wherein said bonded preform has a
continuous sputter surface area of greater than 1.5 m.sup.2.
55. The bonded preform or target assembly of claim 54, wherein said
sputter surface area is from 1.5 m to about 10 m.sup.2.
56. The bonded preform or target assembly of claim 54, wherein said
sputter surface area is from about 2 m.sup.2 to about 6
m.sup.2.
57. The bonded preform or target assembly of claim 54, wherein said
target and said backing plate are bonded together by molecular
bonding.
58. A bonded preform or target assembly comprising a target and a
backing plate explosively bonded together, wherein said bonded
preform has a sputter surface area of greater than 400
cm.sup.2.
59. The bonded preform or target assembly of claim 58, wherein said
sputter surface area is from about 500 cm.sup.2 to about 10
m.sup.2.
60. A bonded preform or target assembly comprising a target and a
backing plate bonded together, wherein said bonded preform has a
rectangular dimensions of 1.5 m or greater .times.1.5 m or greater
or a circular diameter of at least 1.5 m.
61. A bonded preform or target assembly comprising a target and
backing plate explosively bonded together, wherein said bonded
preform has a continuous sputter surface area of 400 cm.sup.2 or
greater.
62. The bonded preform or target assembly of claim 61, further
comprising an interlayer located between said target and backing
plate.
63. The bonded preform or target assembly of claim 54, further
comprising an interlayer located between said target and backing
plate.
64. The bonded preform or target assembly of claim 54, wherein said
target comprises a valve metal.
65. The bonded preform or target assembly of claim 54, wherein said
target comprises tantalum, niobium, cobalt, titanium, copper,
aluminum, or alloys thereof.
66. The bonded preform or target assembly of claim 54, wherein said
target comprises tantalum or an alloy thereof.
67. The bonded preform or target assembly of claim 54, wherein said
target comprises niobium or an alloy thereof.
68. The bonded preform or target assembly of claim 54, wherein said
backing plate member comprises tantalum, niobium, titanium, copper,
aluminum, or alloys thereof.
69. The bonded preform or target assembly of claim 54, wherein said
backing plate member comprises copper or an alloy thereof.
70. The bonded preform or target assembly of claim 54, wherein said
target grade plate comprises tantalum or an alloy thereof and said
backing member comprises copper or an alloy thereof.
71. The bonded preform or target assembly of claim 58, wherein said
target grade plate comprises a valve metal.
72. The bonded preform or target assembly of claim 58, wherein said
target grade plate comprises tantalum, niobium, cobalt, titanium,
copper, aluminum, or alloys thereof.
73. The bonded preform or target assembly of claim 58, wherein said
target grade plate comprises tantalum or an alloy thereof.
74. The bonded preform or target assembly of claim 58, wherein said
target grade plate comprises niobium or an alloy thereof.
75. The bonded preform or target assembly of claim 58, wherein said
backing plate member comprises tantalum, niobium, titanium, copper,
aluminum, or alloys thereof.
76. The bonded preform or target assembly of claim 58, wherein said
backing plate member comprises copper or an alloy thereof.
77. The bonded preform or target assembly of claim 58, wherein said
target grade plate comprises tantalum or an alloy thereof and said
backing member comprises copper or an alloy thereof.
78. The bonded preform or target assembly of claim 60, wherein said
target grade plate comprises a valve metal.
79. The bonded preform or target assembly of claim 60 wherein said
target grade plate comprises tantalum, niobium, cobalt, titanium,
copper, aluminum, or alloys thereof.
80. The bonded preform or target assembly of claim 60, wherein said
target grade plate comprises tantalum or an alloy thereof.
81. The bonded preform or target assembly of claim 60, wherein said
target grade plate comprises niobium or an alloy thereof.
82. The bonded preform or target assembly of claim 60, wherein said
backing plate member comprises tantalum, niobium, titanium, copper,
aluminum, or alloys thereof.
83. The bonded preform or target assembly of claim 60, wherein said
backing plate member comprises copper or an alloy thereof.
84. The bonded preform or target assembly of claim 60, wherein said
target grade plate comprises tantalum or an alloy thereof and said
backing member comprises copper or an alloy thereof.
85. The bonded preform or target assembly of claim 61, wherein said
target grade plate comprises a valve metal.
86. The bonded preform or target assembly of claim 61, wherein said
target grade plate comprises tantalum, niobium, cobalt, titanium,
copper, aluminum, or alloys thereof.
87. The bonded preform or target assembly of claim 61, wherein said
target grade plate comprises tantalum or an alloy thereof.
88. The bonded preform or target assembly of claim 61, wherein said
target grade plate comprises niobium or an alloy thereof.
89. The bonded preform or target assembly of claim 61, wherein said
backing plate member comprises tantalum, niobium, titanium, copper,
aluminum, or alloys thereof.
90. The bonded preform or target assembly of claim 61, wherein said
backing plate member comprises copper or an alloy thereof.
91. The bonded preform or target assembly of claim 61, wherein said
target grade plate comprises tantalum or an alloy thereof and said
backing member comprises copper or an alloy thereof.
92. The bonded preform or target assembly of claim 63, wherein said
interlayer is formed by striping material from an anvil and
depositing said material at the bond interface using an explosion
bonding plasma jet.
93. The bonded preform or target assembly of claim 92, wherein at
least one coating of a bond enhancing material is applied to the
anvil.
Description
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of prior U.S. Provisional Patent Application No.
60/450,196 filed Feb. 25, 2003, which is incorporated in its
entirety by reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a method of forming a
sputtering target assembly. More specifically, the method includes
the preferred use of explosion bonding to form a sputtering target
assembly.
[0003] Numerous bonding techniques are used to bond sputtering
target assembly components (e.g., a sputter target or target blank
and a backing plate) together, such as soldering, brazing,
diffusion bonding, mechanical fastening, epoxy bonding, friction
welding, explosion bonding, etc. Each of the bonding techniques has
its own advantages and disadvantages. A common disadvantage of
conventional bonding techniques is the individual bonding of a
target and a backing plate, i.e., sputtering target assemblies are
formed one at a time. Singularly forming sputtering target
assemblies has several drawbacks. First, it can be quite
time-consuming and resource intensive, owing to the batch nature of
production and inherent costs of the bonding process. Another
drawback concerns quality control. Currently, a representative
sample of sputtering target assemblies is typically dedicated for
purposes of evaluating bond quality or bond integrity. However,
variables in the bonding process affecting bond integrity can lead
to uncertainty as to the relatedness of the bond quality of one
sputtering target assembly to that of another. Moreover,
sacrificing a certain percentage of otherwise usable sputtering
target assemblies for quality control purposes adds to the overall
cost of sputtering target assembly production.
[0004] Another disadvantage of conventional bonding techniques is
that they are feasible only for a sputtering target of limited
size. That is due, in part, to the fact that shear failure of
conventional bonds increases with increasing temperatures reached
during use (i.e., in the sputtering process). The debonding risk is
even more possible as the size of the target increases.
Accordingly, thin films deposited on large area substrates, e.g.,
glass panels used for fabricating flat panel displays, are
typically formed by sputtering a sputtering target assembly
comprised of a mosaic of several conventional-sized targets. The
sputtering behavior of the edges of the individual target "tiles"
may differ from that of the bulk of the target array, resulting in
a deposited film having diminished thickness uniformity. The
ability to produce a single sputtering target having a large area
and a high strength, high integrity bond to a backing plate
represents an improvement to the current sputtering target
fabrication technology.
[0005] The present invention shows that explosion bonding or
explosive bonding produces a bond of superior strength and is
accomplished without subjecting the bonding materials to elevated
temperatures. Accordingly, explosive bonding produces a durable
bond while avoiding many of the undesirable effects of heating the
sputtering target assembly components during bonding such as
mechanical stress, grain growth, and in the case of components
having dissimilar coefficients of thermal expansion, warping.
However, in the past, several technical and manufacturing related
issues had prevented explosive bonding from being used for the
fabrication of sputtering targets. First, the properties of the
sputtering target can be altered after being subjected to an
explosive shock wave. Specifically, in the case of tantalum, it is
known that explosive shocking of the material generates
"deformation twins" throughout the microstructure. In addition,
explosive bonding has been deemed a relatively costly bonding
technique compared to conventional bonding processes. At least some
of the additional cost of explosion bonding is attributed to added
material costs associated with what is commonly referred to as the
"edge effect." Explosive bonding can require that the starting
target materials be oversized to compensate for predictable damage
at the periphery of the sputtering target assembly, i.e., the edge
effect. An alternative solution is to incorporate a "momentum trap"
along the edge of the explosive bonded workpiece. The momentum trap
is comprised of a metal having a similar density and impedance to
that of the target material, and acts to absorb the trailing
compressive shock wave with minimal reflection of a tensile
wave.
[0006] Accordingly, a need exists for a method to improve upon the
bonding process to reduce the cost of and improve the quality
control process in forming bonded sputtering target assemblies,
generally, as well as to minimize the effective unusable area of an
explosively bonded sputtering target assembly.
SUMMARY OF THE PRESENT INVENTION
[0007] It is therefore a feature of the present invention to
provide an improved method of bonding a target and a backing plate
to form a sputtering target assembly.
[0008] Another feature of the present invention is to provide a
method for forming multiple sputtering target assemblies
simultaneously.
[0009] A further feature of the present invention is to provide a
method of bonding a target and a backing plate in which a bond
quality test sample is formed in the process.
[0010] Another further feature of the present invention is to
provide a method of manufacturing a sputtering target and backing
plate assembly having a large sputtering surface area.
[0011] An additional feature of the present invention is to provide
a method to explosively bond a target grade plate and backing plate
whereby the metallurgical properties of the target plate are not
significantly altered by the bonding process.
[0012] Yet another feature of the present invention is to provide a
method to explosively bond a target plate and a backing plate so as
to minimize the defectively bonded area resulting from the
explosive bonding process.
[0013] Additional features and advantages of the present invention
will be set forth in part in the description that follows, and in
part will be apparent from the description, or may be learned by
practice of the present invention. The objectives and other
advantages of the present invention will be realized and attained
by means of the elements and combinations particularly pointed out
in the description and appended claims.
[0014] To achieve these and other advantages, and in accordance
with the purposes of the present invention, as embodied and broadly
described herein, the present invention relates to a method of
forming a sputtering target assembly comprising explosively bonding
a target grade plate and a backing plate member to form a bonded
preform having dimensions sufficient to be divided into two or more
targets. The method then involves partitioning the bonded preform
to form a plurality of sputtering target assemblies. The method
optionally includes disposing an interlayer between the target
grade plate and the backing plate member before bonding.
[0015] The present invention further relates to a bonded preform
having dimensions such that it can be partitioned to form a
plurality of sputtering target assemblies.
[0016] The present invention also relates to a sputtering target
assembly including a target, a backing member, and an interlayer
disposed therebetween, wherein the sputtering target assembly is
preferably formed by partitioning a bonded preform.
[0017] Also, the present invention relates to a bond quality test
sample that is produced as a byproduct of an explosive bonding
method of forming a sputtering target assembly.
[0018] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are intended to provide a further
explanation of the present invention, as claimed.
[0019] The accompanying drawings, which are incorporated in and
constitute a part of this application, illustrate various aspects
of the present invention and, together with the description, serve
to explain the principles of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a perspective view of a target grade plate in the
shape of a rectangle before bonding.
[0021] FIG. 2 is a perspective view of a backing plate member in
the shape of a rectangle before bonding.
[0022] FIG. 3 is a perspective view of an optional interlayer in
the shape of a rectangle before bonding.
[0023] FIG. 4 is a perspective view of a bonded preform having a
bonded target grade plate and a bonded backing plate member of
similar shape and dimensions.
[0024] FIG. 5 is a perspective view of a bonded preform having a
bonded target grade plate, a bonded backing plate member, and a
bonded interlayer.
[0025] FIG. 6 is a perspective view of a sputtering target assembly
having a flange comprising a portion of the backing plate.
[0026] FIG. 7 is a perspective view of a sputtering target assembly
having an optional interlayer and with a flange comprising a
portion of the backing plate.
[0027] FIG. 8 is a perspective view of a sputtering target assembly
having an optional interlayer and with a flange comprising a
portion of the backing plate and a portion of the interlayer.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0028] A method according to the present invention for forming a
sputtering target assembly involves explosively bonding a target
grade plate and a backing plate member to form a bonded preform,
and optionally partitioning the bonded preform to form a plurality
of sputtering target assemblies. An interlayer can optionally be
disposed between the target grade plate and the backing plate
member before bonding. The present invention further relates to
forming a large target which is bonded onto a backing plate. This
bonded target is larger than conventional target sizes and can be
useful in applications where a series or mosaic of targets are
needed to form a large sputter surface area.
[0029] In more detail, the preform that is optionally divided into
multiple target assemblies preferably includes two components,
namely, a backing plate member having a bonding surface and a
sputter target grade plate or target grade plate having a bonding
surface and having a sputter surface. The backing plate member can
be any suitable metal material usable as a backing plate in
sputtering applications. The target or target materials can be any
material capable of being sputtered. Examples of the backing plate
member material include, but are not limited to, copper, or a
copper alloy, tantalum, niobium, titanium, aluminum, and alloys
thereof, such as TaW, NbW, TaZr, NbZr, TaNb, NbTa, TaTi, NbTi,
TaMo, NbMo, and the like. Examples of target grade plate materials
that can be bonded by the method of the present invention, include,
but are not limited to, tantalum, niobium, cobalt, titanium,
copper, aluminum, and alloys thereof.
[0030] No limitation exists as to the type of materials used in the
target grade plate and the backing plate member. The thicknesses of
the backing plate and the target grade plate can be any suitable
thickness used for forming sputtering target assemblies. For
purposes of the present invention, the target grade plate or
sputter target grade plate can include a plate having dimensions
larger than the dimensions for a finished sputter target. In more
detail, the target grade plate refers to the starting material
which has dimensions totaling the combined dimensions of two or
more conventional finished targets and preferably three or more or
four or more conventional targets. In other words, the dimensions
of the target grade plate are such that multiple finished targets
can optionally be cut from the target grade plate after bonding
onto the backing plate member. As can be understood from the
description of the invention, the target grade plate is a large
plate. Similarly, the backing plate member for purposes of the
present invention has similar dimensions to the target grade plate.
Examples of suitable thicknesses of the backing plate member and of
the target grade plate include, but are not limited to, a backing
plate with a thickness of from about 0.25 or less to about 2 inches
or more, and a target grade plate with a thickness ranging from
about 0.06 inches to about 1 inch or more. In the present
invention, the target grade plate materials to be bonded with the
backing plate member can be target grade material, for instance, as
described in U.S. Pat. No. 6,348,113 (Michaluk et al.),
incorporated in its entirety by reference herein. This patent shows
examples of plate that can be prepared from starting ingots, plates
or billets. The purity, texture, and/or grain size and other
properties, including size and the like are not critical to the
present invention. The powder used to make the target grade plate
as well as the target itself can have any purity with respect to
the metal. For instance, the purity can be 99% or greater such as
from about 99.5% or greater and more preferably 99.95% or greater
and even more preferably 99.99% or greater, or 99.995% or greater
or 99.999% or greater. The target grade plate can have any suitable
grain size (e.g., average grain sizes of less than 300 microns,
less than 100 microns, less than 50 microns, less than 20 microns)
and/or texture. For instance, the texture can be random, a primary
(111) texture, or a primary (100) texture that can be on the
surface or throughout the entire thickness of the target.
Preferably, the texture is uniform. Also, the target can have a
mixed (111):(110) texture throughout the surface or throughout the
entire thickness of the target. In addition, the target can be
substantially void of textural banding, such as substantially void
of (100) textural banding.
[0031] The target grade plate and the backing plate member can have
any shape and/or dimensions. Preferably, the target grade plate and
the backing plate member are substantially of the same shape and
the same dimensions. Optionally, the backing plate member can have
dimensions in excess of the dimensions of the target, or,
alternatively the target grade plate can have dimensions in excess
of the dimensions of the backing plate member. In a preferred
embodiment, both the target grade plate and the backing plate
member are substantially rectangular or circular in shape, having a
length of from about 1 ft or less to about 5 ft or more, and a
width of from about 1 ft or less to about 5 ft or more, or
diameters of from 6 inches or less to 5 feet or more. Any
dimensions or ranges therein can be used. Other shapes of the
target grade plate and the backing plate member can have similar
surface areas. Other dimensions for the bonded preform or bonded
target/backing plate includes sputter surface areas of about 1.5
m.sup.2 or greater. Preferred sputter surface areas are from about
1.5 m.sup.2 to about 10 m.sup.2 and more preferably from about 2
m.sup.2 to about 6 m.sup.2. Another way to describe one aspect of
the invention is a bonded target/backing plate wherein the bonded
target/backing plate has a rectangular dimension of 1.5 m or
greater for the length and 1.5 m or greater for the width or if the
bonded target/backing plate is circular, a circular diameter of at
least 1.5 m. Preferred dimensions are 1.5 m to about 3 m in length
and from about 1.5 m to about 3 m in width. Similarly, the circular
diameter can be from about 1.5 m to about 3 m or more. Preferably,
the bonded target is a molecular bond, and more preferably is
explosion bonded. When explosion bonded targets are formed, the
bonded target/backing plate can have a surface area of 400 cm.sup.2
or higher, such as from about 500 cm.sup.2 to about 1.5 m.sup.2.
With respect to diameters, with explosion bonded target/backing
plates of the present invention, the dimensions can be a length of
from greater than 20 cm, and more preferably greater than 25 cm in
length to about 3 m in length with the width being greater than 20
cm, and preferably greater than 25 cm to about 3 m. As indicated
above, with such large sputter surface areas, the need for mosaic
sputter targets or a series of sputter targets placed next to each
other can be avoided or minimized. By using a single target or less
targets to formed the mosaic, a more uniform sputtered thin film
can be achieved for a variety of uses including the capacitor area,
plasma screen area, and the like. The explosion bonding of the
present invention makes the preparation of large targets especially
useful since a uniform bond exists throughout the bonded surfaces
of the target and backing plate and explosion bonding permits the
formation of a large bonded target where other bonding techniques
would have great difficulty in forming a bonded target having such
a continuous sputter surface area.
[0032] As to explosively bonding, the target grade plate and the
backing plate member are arranged so that the bonding surfaces of
each are facing each other. Preferably, the periphery of the target
grade plate corresponds to the periphery of the backing plate
member. The target grade plate and the backing plate member can be
fixed in place using any conventional technology, such as clamps,
bands of metal strips, vices, and other locking devices. The target
grade plate and the backing plate member can be fixed in place such
that a gap is created and maintained between them before bonding.
Optionally, the target grade plate and the backing plate member can
be placed one atop the other, preferably with a standoff device
disposed therebetween, for example, as described in U.S. Pat. No.
6,164,519 (Gilman et al), which is incorporated in its entirety by
reference herein. An explosive charge can be located behind the
target grade plate, the backing plate member, or both to achieve
explosion bonding. Preferably, an explosive charge is located
behind the backing plate member while the target grade plate
remains stationary, for example, against a steel anvil, so that the
backing plate is accelerated or exploded into the target grade
plate.
[0033] Generally, the amount of explosive charge is a charge
sufficient to provide a bond between the target grade plate and the
backing plate member. Generally, the amount of explosive charge for
a 1 inch thick backing member with a gap of about 0.25 inch ranges
from about 0.018 pounds/in..sup.2 for C10100 copper backing plate
to about 0.024 pounds/in..sup.2 for C18200 copper alloy backing
plate using dynamite packed to a density of 1 g/cc. Other
explosives such as Pentolite, TNT, Trimonite No. 1, C4 or other
suitable explosives may be used, and the explosive charge is
preferably adjusted for the explosive energy. For additional
information on the calculation of the explosive charge see the
article by R. J. Carlson, V. D. Linse and R. H. Wittman, Materials
Engineering 68, 70 (1968), incorporated in its entirety by
reference herein.
[0034] In explosion bonding, it is preferred to maintain a gap
between the bonding members, i.e., the exploded members, or the
exploded member and the stationary member, before detonating the
explosive. In the absence of such a gap, the bond may not
adequately form, or, may not form at all. Furthermore, surface
impurities that are removed from the bonding surfaces by the
jetting that occurs during bonding can escape via the gap and thus
are not trapped between the bonded members. Accordingly, in one
embodiment of the present invention, a gap can exist between the
backing plate member and the target grade plate. Any manner in
which to create a gap between the backing plate member and target
grade plate can be used.
[0035] Having a gap permits either the target grade plate or the
backing plate member upon explosion to reach its optimal velocity
before impact with the stationary member. On the other hand,
placing the bonding members at a less than optimal distance from
each other achieves a less than optimal bonding velocity, and thus
a superior bond is not achieved. Alternatively, if the distance
between the bonding members is too great, then the accelerated or
exploded member is at less than maximum velocity when it impacts
the stationary member, and thus a superior bond is not
achieved.
[0036] According to one embodiment, explosively bonding the target
grade plate and the backing member forms a bonded preform. FIG. 4
is an example of a bonded preform. The bonded preform can have any
shape and/or dimensions depending upon the shapes and dimensions of
the target grade plate and the backing plate member, the
orientation of the bonding members before the explosion, and any
deformation of the periphery after the explosion. Preferably, the
bonded preform is of sufficient dimensions to be divided or
partitioned to form a plurality of sputtering target assemblies.
Preferably, the periphery of the bonded preform is substantially
defined by both the target grade plate and the backing plate
member. Optionally, the periphery of the bonded preform can be
substantially defined by the periphery of the backing plate member
or the target grade plate. The bonded preform can be in any form,
such as, a plate, a sheet, a slab, or the like. In a preferred
embodiment, the surface area of the bonded preform is substantially
rectangular or circular in shape, having a length of from about 1
ft or less to about 5 ft or more, and a width of from about 1 ft or
less to about 5 ft or more, or similar circular diameters. Other
shapes of the bonded preform can have similar surface areas.
[0037] Preferably, the bonded preform has a sputter target having
metallurgical properties that are similar to the target grade
plate. For example, explosively bonding a target grade plate having
an average grain size of less than about 100 microns and a texture
substantially void of (100) textural bands according to the present
invention preferably forms a bonded preform having a sputter target
having an average grain size of less than about 100 microns and a
texture substantially void of (100) textural bands. In addition, as
a result of the explosive bonding, the bonded preform preferably
has a backing plate that is harder than the backing plate member
prior to being bonded, as measured quantitatively, for example, in
Rockwell B scale. For instance, the hardness is increased by 5% or
more, such as 10% or more, and 30%-60% or more. In one specific
example, a backing plate, like C46400 went from a Rockwell B scale
hardness of 63 before explosion bonding to a bulk hardness of 85
and an interface hardness of 100 after bonding.
[0038] The bond preform preferably has a bond interface between the
target grade plate and the backing plate member, the bond interface
having superior strength. For example, the bond strength can be
from 10,000 p.s.i. to about 75,000 p.s.i. or higher, which is
approximately twice the typical bond strength achieved by, for
example, diffusion bonding. Other ranges include from about 25,000
p.s.i. to about 55,000 p.s.i., and from about 40,000 p.s.i. to
about 56,000 p.s.i., and the like. This bond strength is preferably
uniform through the bonded surface. As stated above, increased bond
strength is particularly important as the diameter of the sputter
target increases. The bond interface formed by the present
invention can include or not include interdiffusion of the target
grade plate and the backing plate member. With less interdiffusion,
the sputter target and the backing plate member can be more easily
separated for recycling after use, for example, by reducing the
amount of the reclaimed metal of either being contaminated with the
other.
[0039] As to partitioning (which is completely optional),
partitioning involves dividing or sectioning the bonded preform to
form a plurality of sputtering target assemblies. The formed
sputtering target assemblies can have any shape, and the shapes may
vary from one sputtering target assembly to another. Sectioning the
bonded preform can be accomplished by any conventional cutting and
machining technique. Examples of such cutting techniques can
include, but are not limited to, boring, milling, grinding,
electrode discharge machining, waterjet abrasive cutting, laser
cutting, plasma cutting, flame-cutting, sawing, use of a punch
press, or other suitable method. The cutting pattern or cutting
design for the bonded preform can be predetermined. A surface of
the bonded preform can be marked or scribed with the predetermined
cutting pattern. Preferably, the cutting pattern maximizes the
usable or viable area of the bonded preform. In other words, the
unused area of the bonded preform is minimized. A suitable computer
program can be used to generate the cutting pattern. The cutting
pattern may be programmed into a cutting device adapted to
automatically control the cutting process. For example, an abrasive
waterjet device can be programmed to cut the bonded preform.
[0040] Areas of the bonded preform that are too small or otherwise
unsuitable for producing a sputtering target assembly can be cut
into bond quality test samples. Preferably, the test samples are
taken from areas adjacent to the bonded sputtering target
assemblies formed. Cutting the bonded preform to form the test
samples can be accomplished by any conventional cutting and
machining technique previously discussed. A test sample can be
identified such that its location relative to a formed sputtering
target assembly can be recorded. Such test samples can then be used
for purposes of bond evaluation and quality control analyses and
the like. The test sample can serve as a historical record for bond
integrity of one or more sputtering target assemblies that are cut
from an area of the bonded preform approximate the test sample. The
test sample can have any size and/or dimensions (e.g. 1 inch or
less to 5 inches or more in diameter).
[0041] After the individual sputtering target assemblies are
optionally cut from the bonded preform, the desired shape and
dimensions of the finished sputtering target assembly can be formed
using the cutting and machining techniques previously described.
The finished sputtering target assembly can be of any shape and/or
dimensions, such as a disc, and preferably conforming to original
equipment manufacturer specifications. Optionally, at least a
portion of the periphery of the bonded target, the bonded backing
member, or a combination thereof, can be removed to form a flange
on the sputtering target assembly. A portion of the periphery of
the bonded target can be removed such that the flange comprises
both the target and the backing member. Leaving a portion of the
target in the flange area has the effect of providing a protective
sputtering layer over the flange which reduces the unintended or
incidental sputtering of the backing plate material. A portion of
the periphery of the bonded target can be removed down to the bond
such that the flange comprises the backing member, as shown, for
example, in FIG. 6. A portion of the periphery of the bonded target
can be removed down to the bond and a portion of the periphery of
the backing member can be removed such that the flange comprises
the backing member. At this point, any conventional processing and
finishing of the sputtering target assembly can be done, such as
polishing and the like. These same or some of these steps can be
used even if the large bonded target is not cut.
[0042] As an option, at least one interlayer can be disposed
between the target grade plate and the backing plate member before
bonding. The interlayer layer can be bonded between the target
grade plate and backing plate member by explosive bonding, thereby
forming a bonded preform having a bonded interlayer, as shown, for
example, in FIG. 5. The interlayer can be any conventional
interlayer material, such as, but not limited to, in the case of
tantalum bonding to copper alloy backing plates, niobium,
zirconium, titanium, or vanadium or other materials that can
enhance the bond quality. The technical paper by berg et al.,
Metallurgical Transactions A, 16, 841 (1985), incorporated in its
entirety by reference herein, provides a description of the
thermodynamic principles for choosing a suitable bonding
interlayer. The interlayer can have any shape, regular or
irregular, and/or dimensions. A periphery of the interlayer can be
less than or greater than the periphery of either the target grade
plate or the backing plate member. The interlayer can cover from
about 10 to about 100% of the bonding surface of the target grade
plate. The interlayer can cover from about 10 to about 100% of the
bonding surface of the backing plate member. The interlayer can
have a thickness of from about 0.01 to about 0.09 inches, and
preferably has a thickness of from about 0.02 to about 0.06 inches.
More than one interlayer can be used.
[0043] An interlayer can also be created by having a plasma jet
created during the explosive bonding so as to transport materials
from the anvil into the bond interface area. This plasma jet is
created from the explosion and the movement of air in between the
plate and backing plate. The plasma jet is capable of removing
material from the anvil surface and then getting trapped in between
the plate and backing plate. In one example, a steel anvil was used
with a tantalum target and C18200 backing plate. Iron from the
anvil was detected in the tantalum-C18200 bond interface. For
instance, the interlayer is formed by striping material from an
anvil and depositing the material at the bond interface using the
explosion bonding plasma jet. If the anvil material does not
provide improved interlayer bonding, then a coating (or
multi-coatings) on the anvil can be used to enhance bonding. For
example, any material that is capable of enhancing the bond
strength between the target and backing plate can be used to
enhance bonding. Specific examples include titanium, nickel, and
other metals or any alloys thereof that are conventionally used as
interlayers and other examples are the materials previously
mentioned herein. The coating can be any thickness.
[0044] The interlayer can be fixed in place before bonding of the
target grade plate and the backing plate member using any suitable
method, including attaching the interlayer to either the target
grade plate or the backing plate member. For example, the
interlayer can be friction welded, spot welded, stir welded,
explosively bonded, or diffusion bonded to either of the bonding
members. Alternatively, the interlayer can be located atop the
bonding surface of one of the bonding members without attaching the
interlayer to either bonding member. Alternatively, the interlayer
can be maintained in a position between the bonding members such
that a gap is created between the interlayer and both bonding
surfaces. After bonding, as described above, a portion of the
periphery of the interlayer can be machined and cut away in the
flange areas of the sputtering target assembly, or, alternatively,
can remain intact on the flange areas of the target material. FIG.
7 is an example of a sputtering target assembly formed according to
the method of the present invention wherein a portion of the
periphery of the target and a portion of the periphery of the
interlayer have been completely removed such that the flange
comprises a portion of the backing plate. FIG. 8 is an example of a
sputtering target assembly formed according to the method of the
present invention wherein a portion of the periphery of the target
has been completely removed and a portion of the periphery of the
interlayer remains intact such that the flange comprises a portion
of the interlayer as well as a portion of the backing plate.
[0045] Optionally, the bonded preform can be leveled or flattened,
for example, by level rolling before optional partitioning.
Flattening the preform can produce a substantially stress-free
plate and a nearly planar bonding interface. Preferably, the bonded
preform is flattened before the desired cutting pattern is
determined, and preferably before the desired cutting pattern is
marked on the surface of the bonded preform.
[0046] The method described above permits the formation of large
targets or the bonding of multiple targets onto a backing plate in
one bonding process and thus achieves a greater output of target
materials bonded onto backing plates and further achieves a
consistent bonding of the multiple sputtering target
assemblies.
[0047] Other embodiments of the present invention will be apparent
to those skilled in the art from consideration of the present
specification and practice of the present invention disclosed
herein. It is intended that the present specification and examples
be considered as exemplary only with a true scope and spirit of the
invention being indicated by the following claims and equivalents
thereof.
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