U.S. patent application number 09/867626 was filed with the patent office on 2001-11-01 for apparatus and method for electroplating.
Invention is credited to Maeda, Keiichi.
Application Number | 20010035346 09/867626 |
Document ID | / |
Family ID | 14639173 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010035346 |
Kind Code |
A1 |
Maeda, Keiichi |
November 1, 2001 |
Apparatus and method for electroplating
Abstract
An apparatus and a method for electroplating for forming a metal
film by an electroplating method. The apparatus comprises a plating
bath provided in a non-oxidative atmosphere, and in the method, an
article to be plated is immersed in a plating bath through a
non-oxidative atmosphere.
Inventors: |
Maeda, Keiichi; (Kanagawa,
JP) |
Correspondence
Address: |
Ronald P. Kananen
RADER, FISHMAN & GRAUER, PLLC
1233 20th Street, N.W., Suite 501
Washington
DC
20036
US
|
Family ID: |
14639173 |
Appl. No.: |
09/867626 |
Filed: |
May 31, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09867626 |
May 31, 2001 |
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09296297 |
Apr 22, 1999 |
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6241869 |
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Current U.S.
Class: |
204/277 ;
204/242 |
Current CPC
Class: |
H01L 21/76877 20130101;
C25D 21/04 20130101; C25D 17/001 20130101; H05K 3/241 20130101;
C25D 7/123 20130101; H01L 21/2885 20130101; C25D 5/003 20130101;
H05K 3/423 20130101 |
Class at
Publication: |
204/277 ;
204/242 |
International
Class: |
C25D 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 24, 1998 |
JP |
P10-114494 |
Claims
What is claimed is:
1. An apparatus for electroplating for forming a metal film by an
electroplating method, said apparatus comprising a plating bath
provided in a non-oxidative atmosphere.
2. An apparatus for electroplating as claimed in claim 1, wherein
said non-oxidative atmosphere, in which said plating bath is
provided, is provided in a plating chamber, and said apparatus
further comprises a pre-treating chamber, in which a pre-treatment
of an article to be plated is conducted, and a transportation
chamber connected to said pre-treating chamber and said plating
chamber.
3. An apparatus for electroplating as claimed in claim 1, wherein
said non-oxidative atmosphere is selected from a rare gas
atmosphere, a nitrogen gas atmosphere and a hydrogen gas
atmosphere.
4. An apparatus for electroplating as claimed in claim 2, wherein
said non-oxidative atmosphere is selected from a rare gas
atmosphere, a nitrogen gas atmosphere and a hydrogen gas
atmosphere.
5. A method for electroplating for forming a metal film by an
electroplating method, an article to be plated being immersed in a
plating bath through a non-oxidative atmosphere.
6. A method for electroplating as claimed in claim 5, wherein said
non-oxidative atmosphere is selected from a rare gas atmosphere, a
nitrogen gas atmosphere and a hydrogen gas atmosphere.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an apparatus for
electroplating and a method for electroplating, and particularly it
relates to an apparatus for electroplating and a method for
electroplating, in-which copper is formed into a film in a
semiconductor device by electroplating.
BACKGROUND OF THE INVENTION
[0002] With high integration of an LSI (large scale integrated
circuit), internal interconnection is becoming minute and
multi-layered. Along with such a tendency, development of
flattening technique on formation of interconnection and processing
technique of minute interconnection, and maintenance of reliability
become important problems. As one of the solutions of these
problems, embedded interconnection technique has been investigated.
In particular, copper embedded interconnection technique aiming at
high speed operation and low consumption power is receiving
attention.
[0003] Formation of a copper film by an electroplating method
receives attention as a recent method of copper embedding. In this
method, a barrier metal layer is formed in a groove or a connecting
hole, and then a copper film is formed by an electroplating method
using a copper sulfate solution. In this case, a copper film is
often formed by a sputtering method or a CVD (chemical vapor
deposition) method on the barrier metal layer and used as a glue
layer. The electroplating method realizes embedding in a high
aspect structure at room temperature
[0004] However, the conventional technique described above involves
the following problems. The process of embedding copper in a groove
or a connecting hole by electroplating of copper is described
below. As shown in FIG. 1A, a concave part 112 comprising the
groove and the connecting hole is formed in an interlayer
insulating film 111 by an ordinary RIE (reactive ion etching)
method. As shown in FIG. 1B, a barrier metal layer 113 is formed on
the inner wall of the concave part 112 and on the interlayer
insulating film 111 by forming, for example, a titanium film and a
titanium nitride film, as a laminated film, in this order from the
lower layer, for example, by a sputtering method, and then a glue
layer 114 is further formed thereon. At this time, the barrier
metal layer 113 and the glue layer 114 are formed at the opening
parts of the concave part 112 in the form of overhang.
[0005] As shown in FIG. 1C, because the coverage of the barrier
metal layer 113 and the glue layer 114 on the concave part 112 does
not become 100%, the resistance of the barrier metal layer 113 and
the glue layer 114 is increased at these parts. Under the
circumstances, when electroplating is conducted by immersing in a
copper electroplating solution 121, current concentration occurs at
the opening part (shown by arrows in the figure). The rate of the
film formation is increased at the part, at which current
concentration occurs. A bubble 115 is formed inside the concave
part 112. As a result, a copper film 116 is formed with a void 115
forming inside the concave part 112, as shown in FIG. 1D. In FIG.
1C, the figure is drawn with the upper surface of the interlayer
insulating film 111 being downward on the contrary to the other
figures.
[0006] FIG. 2 is a schematic cross sectional view showing the voids
actually formed on producing a copper film by electroplating. As
shown in FIG. 2, it has been found that the copper film 116 is
grown in the conditions in that the voids 115 are formed over the
interior to the upper part of the concave parts (grooves) 112
formed in the interlayer insulating film 111.
[0007] In the electroplating apparatus 120 for a wafer currently
available as shown in FIG. 3, in order to prevent the back surface
of the wafer 110 from contacting with a plating solution
(containing copper ion) 121, a face-down structure is employed in
that the front surface of the wafer 110 faces the plating solution
121. The plating solution is stored in a plating bath 122, and an
anode 123 is provided in the plating solution 121.
[0008] In the method described above, there is a case where the
plating solution 121 cannot be spread into minute parts formed on
the surface of the wafer 110 as shown in FIG. 4A. That is, there is
a case where a bubble 117 remains inside the concave part (for
example, a groove) 112 When electroplating is conducted under such
conditions, the copper film 116 is grown in the condition in that
the bubble 117 is remained and a void 115 is formed inside the
concave part 112, as shown in FIG. 4B.
[0009] It has been reported by Y. Harada, et al. in Preprints of
58th Shuki Gakujutu Koenkai of the Japan Society of Applied
Physics, 3p-E-4, p. 776 (1997) that the void thus formed is
disappeared by subjecting to a heat treatment at about
400.degree.C. However, the void generated by forming a film by
electroplating contains the air as different from a void generated
by sputtering under high vacuum. Since the air contains about 20%
of oxygen, there is a possibility that the surroundings of the void
are oxidized, and increase in resistance and deterioration of
reliability may occur.
SUMMARY OF THE INVENTION
[0010] The invention relates to an apparatus for electroplating and
a method for electroplating that solve the problems described
above, and in the apparatus for electroplating, a plating bath is
provided in a non-oxidative atmosphere, such as a rare gas
atmosphere, a nitrogen gas atmosphere and a hydrogen gas
atmosphere.
[0011] Because the plating bath is provided in a non-oxidative
atmosphere in the apparatus for electroplating, even when a bubble
invades into the minute part, such as a groove and a connecting
hole, of the article to be plated on immersing the article into a
plating solution in the plating bath, so as to form a plated layer
with the bubble becoming a void, the void contains a non-oxidative
gas but does not contain oxygen. Therefore, the plated layer is not
oxidized when the gas contained in the void is absorbed by the
plated layer by subjecting the plated layer to the heat treatment
to disappear the void. Thus, increase in resistance and
deterioration of reliability in the plated layer do not occur.
[0012] In the method for electroplating according to the invention,
an article to be plated is immersed in a plating solution through a
non-oxidative atmosphere, such as a rare gas atmosphere, a nitrogen
gas atmosphere and a hydrogen gas atmosphere.
[0013] Because the article to be plated is immersed in the plating
solution through the non-oxidative atmosphere, even when a bubble
invades into the minute part, such as a groove and a connecting
hole, of the article to be plated on immersing the article into a
plating solution, so as to form a plated layer with the bubble
becoming a void, the void does not contain oxygen. Therefore, the
plated layer is not oxidized when the gas contained in the void is
absorbed by the plated layer by subjecting the plated layer to the
heat treatment to disappear the void. Thus, increase in resistance
and deterioration of reliability in the plated layer do not
occur.
BRIEF DESCRIPTION OF DRAWTNGS
[0014] FIGS. 1A to 1D are schematic cross sectional views showing a
conventional embedding process into a groove or a connecting hole
by electroplating of copper.
[0015] FIG. 2 is a schematic cross sectional view showing a void
generated on forming a copper film by electroplating.
[0016] FIG. 3 is a schematic diagram showing a conventional
apparatus for electroplating for a wafer.
[0017] FIGS. 4A and 4B are schematic cross sectional view for
describing the problems associated with the conventional method for
electroplating.
[0018] FIG. 5 is a schematic diagram showing the first embodiment
of the apparatus for electroplating according to the invention.
[0019] FIG. 6 is a schematic diagram showing the second embodiment
of the apparatus for electroplating according to the invention.
[0020] FIGS. 7A to 7C are schematic cross sectional views showing
an embodiment of the method for electroplating according to the
invention.
[0021] FIGS. 8A and 8B are schematic cross sectional views showing
a continued part of the embodiment of the method for electroplating
according to the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] The first embodiment of the apparatus for electroplating
according to the invention will be described with reference to the
schematic diagram shown in FIG. 5.
[0023] As shown in FIG. 5, an apparatus for electroplating 1
comprises a plating chamber 11 having an interior maintained at a
non-oxidative atmosphere, a plating bath 21 provided inside the
plating chamber 11, and means for holding a wafer 41 of a face down
type.
[0024] The plating bath 21 contains a plating solution 31. An anode
22 is provided inside the plating solution 31. The plating bath 21
is also equipped with a supplying part and a discharging part (not
shown in the figure) for the plating solution 31. The plating bath
21 may be a so-called circulating filtering system.
[0025] The means for holding a wafer 41 is tranportably provided by
a driving unit not shown in the figure above the plating solution
31, and is freely movable in the direction A shown by the arrow in
the figure. The means for holding a wafer 41 is equipped with a
cathode 42, and the cathode 42 is connected to the surface to be
plated (the lower surface in the figure) of the wafer 51. The anode
22 and cathode 42 are connected to a power source not shown in the
figure.
[0026] The plating chamber 11 is equipped with a gas supplying part
12 for supplying a non-oxidative gas and a gas evacuation part 13
for evacuating the gas contained in the plating chamber 11. An
argon (Ar) gas, for example, is filled in the plating chamber 11.
The gas to be filled in the plating chamber 11 is not limited to an
argon gas as far as it is a non-oxidative gas, and may be a rare
gas selected from helium, neon, argon, xenon and krypton, a
nitrogen gas or a hydrogen gas. The plating chamber 11 preferably
has an airtight structure, but may have such a constitution in that
the path of the wafer 51 until immersing in the plating solution 31
is in the non-oxidative atmosphere. The plating chamber 11 is
further equipped with a gate valve 14 for loading and unloading the
wafer 51.
[0027] In the apparatus for electroplating 1 described above,
because the plating bath 21 is provided in the plating chamber 11
containing the non-oxidative atmosphere, even when a bubble invades
into the minute part, such as a concave part (not shown in the
figure), e.g., a groove and a connecting hole, of the wafer 51 to
be plated on immersing the wafer 51 into the plating solution 31 in
the plating bath 21, so as to form a plated layer with the bubble
becoming a void, the void contains a non-oxidative gas but does not
contain oxygen. Therefore, the plated layer is not oxidized when
the gas contained in the void is absorbed by the plated layer by
subjecting the plated layer to the heat treatment to disappear the
void. Thus, increase in resistance and deterioration of reliability
in the plated layer do not occur.
[0028] The second embodiment of the apparatus for electroplating
according to the invention will be described with reference to the
schematic diagram shown in FIG. 6.
[0029] An apparatus for electroplating 2 has a constitution of a
so-called multi-chamber type comprising a transportation chamber
61, as a central part, containing a transportation robot 62 for
transporting a wafer 51, and-further comprises a wafer container on
the loading side 71 containing a wafer 51 before treatment, a
pre-treating chamber 72, a plating chamber 11 having the similar
constitution as in the first embodiment, a post-treating chamber
73, and a wafer container on the unloading side 74, which are
connected to the transportation chamber 61 via gate valves 81 to
85, for example. In this constitution, at least the plating chamber
11, the transportation chamber 61 and the pre-treating chamber 72
each are equipped with a supplying part and an evacuation part of
the non-oxidative gas not shown in the figure to maintain the
interior thereof at the non-oxidative atmosphere.
[0030] The non-oxidative atmosphere may comprise a rare gas
selected from helium, neon, argon, xenon and krypton, a nitrogen
gas or a hydrogen gas, as similar to the first embodiment.
[0031] In the apparatus for electroplating 2 described above,
because the interior of the plating chamber 11, the transportation
chamber 61 and the pre-treating chamber 72 is maintained at the
non-oxidative atmosphere, the wafer having been subjected to the
pre-treatment is transported to the plating chamber 11 without
suffering oxidation, and subjected to the formation of a plated
layer by electroplating. Therefore, even in the case where a plated
layer comprising copper or a copper alloy, which are liable to be
oxidized, oxidation does not occur from the pre-treatment to the
electroplating, and thus a plated layer having high reliability can
be produced.
[0032] One embodiment of the method for electroplating according to
the invention will be described with reference to FIGS. 7A to 7C,
8A and 8B. In these figures, for example, the method of forming a
copper interconnection is shown.
[0033] As shown in FIG. 7A, the formation of elements, for example,
is conducted on a silicon substrate (not shown in the figure) by an
ordinary LSI process, an interlayer insulating film 52 is the
formed. Thereafter, a groove 53 is formed by an ordinary
lithography technique and an etching technique (for example, an RIE
(reactive ion etching)). In this embodiment, for example, the
groove 53 has a width of 0.4 .mu.m and a depth of 0.5 82 m.
[0034] As shown in FIG. 7B, a barrier metal layer 54 as an
underlayer is formed on the inner wall of the groove 53 and on the
interlayer insulating film 52 by a magnetron sputtering method in
high vacuum. The barrier metal layer 54 may be formed, for example,
by forming a titanium film to a thickness of 20 nm and then a
titanium nitride film is formed to a thickness of 50 nm.
[0035] As an example of the conditions for forming the titanium
film, argon is used as a process gas (the supplying flow amount of
which is 100 sccm, for example), the direct current power of the
magnetron sputtering apparatus is 5 kW, the pressure of the
sputtering atmosphere is 0.4 Pa, and the substrate temperature is
150.degree.C. Hereinafter, the unit sccm means a volume flow amount
(cm.sup.3/min) under the normal state.
[0036] As an example of the conditions for forming the titanium
nitride film, argon (the supplying flow amount of which is 30 sccm,
for example) and nitrogen (the flow amount of which is 80 sccm, for
example) are used as a process gas, the direct current power of the
magnetron sputtering apparatus is 5 kW, the pressure of the
sputtering atmosphere is 0.4 Pa, and the substrate temperature is
150.degree. C.
[0037] Subsequent to the formation of the barrier metal layer 54, a
copper layer to be a glue layer 55 is formed to a thickness of, for
example, 20 nm by a magnetron sputtering method in high vacuum. As
an example of the conditions for forming the glue layer 55, argon
is used as a process gas (the supplying flow amount of which is 100
sccm, for example), the direct current power of the magnetron
sputtering apparatus is 5 kW, the pressure of the sputtering
atmosphere is 0.4 Pa, and the substrate temperature is 20.degree.
C.
[0038] The wafer 51 having been subjected to the process described
above is transferred to the apparatus for electroplating 1
described with reference to FIG. 5, to conduct plating of copper on
the wafer 51. In the following description, the same symbols will
be used as in FIG. 5. Into the plating chamber 11 of the apparatus
for electroplating 1, an argon gas, for example, is supplied in a
flow amount of 10 dm.sup.3/min. While an argon gas is used for
forming the non-oxidative atmosphere, it may be a rare gas, such as
helium and neon, a nitrogen gas or a hydrogen gas. The wafer 51 is
subjected to copper plating in the plating solution 31 exposed to
the non-oxidative atmosphere.
[0039] As the conditions for the electroplating of copper, copper
sulfate (the supplying flow amount of which is 67 g/dm.sup.3, for
example), sulfuric acid (the supplying flow amount of which is 170
g/cm.sup.3, for example) and hydrochloric acid (the supplying flow
amount of which is 70 ppm, for example) are used as the plating
solution 31, and a surface active agent, as an additive, is added
to the plating solution. The temperature of the plating solution 31
is 20.degree. C., and the current is a direct current of 9 A (in
the case of an 8-inch wafer).
[0040] It is an important factor of the presence of a void
remaining inside the groove or connecting hole on the
electroplating as to whether or not the plating solution 31 is
spread through the minute part (the interior of the groove or
connecting hole). By using the apparatus for electroplating 1
according to the invention, even when a copper film 57 is formed
with a void 56 remaining in the groove 53 as shown in FIG. 7C, the
void 56 is filled with an inert gas.
[0041] Accordingly, it becomes possible that the void can be
disappeared by the subsequent heat treatment of the copper film 57
with out oxidation of the copper film 57, so as to bury the copper
film 57 in the groove 53 as shown in FIG. 8A.
[0042] The copper film 57 (including the glue layer 55) and the
barrier metal layer 54 at the position other than the part to be an
interconnection groove are ground by chemical mechanical polishing
(hereinafter referred to as CMP), to form an interconnection part
58 in the groove 53 as shown in FIG. 8B. As an example of the
conditions for the CMP, a grinding pad comprising a non-woven cloth
laminated with a polyurethane closed-cell foamed body (for example,
IC1000/SUBA-IV Laminate, a trade name) is used, a slurry comprising
alumina abrasive grain for grinding added with a hydrogen peroxide
aqueous solution is used as a grinding slurry, the grinding
pressure is 100 g/cm.sup.2, the rotation number of the surface
table is 30 rpm, the supplying amount of the grinding slurry is 100
cm.sup.3/min, and the grinding temperature is from 25 to 30.degree.
C.
[0043] While copper is used as the interconnection material in this
embodiment, gold, silver, aluminum, a gold alloy, a silver alloy, a
copper alloy and an aluminum alloy may be used as the
interconnection material.
[0044] The electroplating in this embodiment may be conducted by
using the apparatus 2 for electroplating apparatus of a
multi-chamber type described with reference to FIG. 6. Accordingly,
by using the non-oxidative atmosphere as not only the atmosphere of
the plating chamber but also the atmospheres of the pre-treating
chamber, the transportation chamber and the plating chamber,
oxidation of the surface of the wafer after the pre-treatment can
be prevented, and the adhesion property between the glue layer
comprising copper and the copper film formed by the electroplating
can be improved.
[0045] In this case, an argon gas, for example, is used as the
non-oxidative gas, and its flow amount is 10 dm.sup.3/min. As the
non-oxidative gas, a gas containing no oxygen, such as a rare gas
other then an argon gas, a nitrogen gas and a hydrogen gas may be
used.
[0046] As described in the foregoing, according to the apparatus
for electroplating of the invention, because the plating bath is
provided in a non-oxidative atmosphere, even when a bubble invades
into the minute part, such as a concave part, e.g., a groove and a
connecting hole, of the article to be plated on immersing the
article into a plating solution in the plating bath, so as to form
a plated layer with the bubble becoming a void, the bubble is
composed of an non-oxidative gas, and thus the void contains the
non-oxidative gas. Therefore, the plated layer is not oxidized when
the gas contained in the void is absorbed by the plated layer by
the heat treatment, and increase in resistance and deterioration of
reliability in the plated layer can be prevented.
[0047] According to the method for electroplating of the invention,
because the article to be plated is immersed in the plating bath
through a non-oxidative atmosphere, even when a bubble invades into
the minute part, such as a concave part, e.g., a groove and a
connecting hole, of the article to be plated on immersing the
article into a plating solution in the plating bath, the bubble is
composed of an non-oxidative gas. Therefore, when a plated layer
with the bubble becoming a void, the void contains the
non-oxidative gas. Therefore, the plated layer is not oxidized when
the gas contained in the void is absorbed by the plated layer by
the heat treatment, and increase in resistance and deterioration of
reliability in the plated layer can be prevented.
* * * * *