U.S. patent application number 10/118797 was filed with the patent office on 2003-06-19 for electroplating solution for copper thin film.
Invention is credited to Hara, Tohru, Ishida, Shoichi, Miyamoto, Mitsuo, Yonezawa, Tetsuo.
Application Number | 20030111354 10/118797 |
Document ID | / |
Family ID | 19187684 |
Filed Date | 2003-06-19 |
United States Patent
Application |
20030111354 |
Kind Code |
A1 |
Hara, Tohru ; et
al. |
June 19, 2003 |
Electroplating solution for copper thin film
Abstract
A plating solution containing 10 to 40 wt % of copper
hexafluorosilicate. With the use of this plating solution, a copper
thin film which has a low film stress and a low resistivity and
which strongly (111)-oriented is plating-deposited on the fine
pattern portion a copper seed layer, and film peeling caused by
deterioration of an adhesion force between an underlying barrier
layer and a copper seed layer even in a heat treatment process and
in a chemical mechanical polishing (CMP) process after plating
deposition is prevented.
Inventors: |
Hara, Tohru; (Tokyo, JP)
; Ishida, Shoichi; (Souraku-gun, JP) ; Miyamoto,
Mitsuo; (Ikoma-shi, JP) ; Yonezawa, Tetsuo;
(Ikoma-shi, JP) |
Correspondence
Address: |
Koda & Androlia
Suite 3850
2029 Century Park East
Los Angeles
CA
90067-3024
US
|
Family ID: |
19187684 |
Appl. No.: |
10/118797 |
Filed: |
April 9, 2002 |
Current U.S.
Class: |
205/291 ;
205/125 |
Current CPC
Class: |
C25D 7/123 20130101;
C25D 3/38 20130101 |
Class at
Publication: |
205/291 ;
205/125 |
International
Class: |
C25D 003/38 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2001 |
JP |
2001-383977 |
Claims
What is claimed is:
1. An electroplating solution for a copper thin film wherein said
solution contains 10 to 40 wt % of copper hexafluorosilicate and is
used as an electrolyte in plating in which a copper thin film is
selectively plating-deposited on a copper seed layer.
2. The electroplating solution according to claim 1, wherein said
solution is used for depositing a copper thin film partially or
entirely on a printed circuit board, a glass substrate, and a
silicon wafer which are provided with or without a pattern.
3. The electroplating solution according to claim 1, wherein said
solution is used in such a condition that a current density during
plating is within a range of 0.5 to 1.5 A/dm.sup.2.
4. The electroplating solution according to claim 1, wherein said
solution is used in such a condition that a plating solution
temperature during plating is within a range of 20 to 40.degree.
C.
5. An electroplating solution according to claim 1, wherein said
solution is used in such a condition that an additive agent in a
range of 0.5 to 1.5 wt % is added thereto during plating.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electroplating solution
used for depositing a copper wiring layer having a film stress
which is important to increase the degree of integration and the
speed of a semiconductor integrated circuit.
[0003] 2. Description of the Prior Art
[0004] It is known that with a development of micropatterns in a
semiconductor integrated circuit the operation speed of such a
circuit is determined by a product (CR: time constant) of an
interlayer capacity (C) of a multilayer interconnection and a
resistance (R) of a micropatterning layer, thus being different
from a conventional semiconductor integrated circuit in which the
circuit is determined by a speed obtained by an electron traveling
time of a MOS transistor.
[0005] A plating technique that uses a copper sulfate aqueous
solution used in a conventional printed circuit board as an
electrolyte is presently used to deposit a copper layer used in a
copper wiring layer of a semiconductor integrated circuit. This
technique is directly used to deposit a copper wiring layer of a
semiconductor integrated circuit that has a difference in level at
a pattern dimension of 0.2 .mu.m or less. In particular, in the
U.S.A., such a technique has been used widely in
microprocessors.
[0006] However, the conventional copper plating technique that uses
a copper sulfate aqueous solution as an electrolyte is developed
for a printed circuit board that has a pattern diameter of about 1
mm. In this technique, the film quality (resistivity and
orientation characteristics of Cu polycrystal) is incomplete, and
the study of Electromigration (EM) resistance is not
sufficient.
[0007] In view of these problems, a new plating technique is
desired to be developed in place of the current technique that uses
a copper sulfate plating solution. As a result, in Japanese Patent
Application No. 2000-291585, the present inventors disclosed a
plating method of a copper thin film which is characterized in that
copper hexafluorosilicate is used as an electrolyte so that a
copper thin film having a low resistivity and strongly
(111)-oriented is plated and deposited and the copper thin film is
plated and deposited on a fine pattern portion having a large
aspect ratio with good covering properties.
[0008] However, in copper thin films deposited with the
conventional copper sulfate plating solution and a copper
hexafluorosilicate plating solution of Japanese Patent Application
No. 2000-29185, film stress during plating deposition tend to be
high. Accordingly, an adhesion force between an underlying barrier
layer and a copper seed layer is deteriorated by distortion, thus
causing film peeling in a heat treatment process and in a chemical
mechanical polishing (CMP) process after plating deposition.
Therefore, a further improvement in the film quality is strongly
demanded.
[0009] In order to solve the problem of signal delay derived from
micropatterning of a semiconductor integrated circuit, a metal
copper (Cu) is used as a wiring material in place of aluminum (Al).
It is known that a reduction in sheet resistance of the wiring
layer and an improvement of Electromigration (EM) resistance are
achieved by the employment of the copper wiring layer. However,
when the plating technique that uses a conventional copper sulfate
aqueous solution as an electrolyte is used in wiring of a
semiconductor integrated circuit that has a latest pattern
dimension of 0.2 .mu.m or less and contains a difference in level,
a large number of problems occur. In other words, a further
reduction in resistivity and a further improvement of the
(111)-orientation strength are required.
[0010] The resistivity of a copper wiring layer deposited with
copper sulfate is not lower than expected, and a copper diffusion
barrier film having a thickness of 10 nm or more must be used in
the copper wiring layer that has a small line width. For this
reason, the actual wiring resistance becomes high. In addition, it
is difficult to plate and deposit a copper wiring layer in a
contact hole portion of a semiconductor integrated circuit that has
a contact dimension of 200 nm or less and an aspect ratio of 5 or
more with preferable covering properties. In the deposition using
the copper sulfate plating solution, such dimensions are the lower
limit. Therefore, in order to solve the various problems of the
copper sulfate plating solution, in Japanese Patent Application No.
2000-291585, the present inventors disclosed a copper
hexafluorosilicate plating solution as a new plating solution in
place of the conventional copper sulfate plating solution. This
solution provides a plating method that deposits a copper thin film
that has a low resistivity and strongly (111)-oriented.
[0011] However, in order to form a copper wiring layer on a wiring
layer of a semiconductor integrated circuit, as shown in FIG. 9, a
heat treatment process for stabilization, a chemical mechanical
polishing (CMP) process or the like for flattening, etc. must be
performed after plating deposition. A copper thin film deposited by
the copper sulfate plating solution and the copper
hexafluorosilicate plating solution according to Japanese Patent
Application No. 2000-291585 has drawbacks because of its high film
stress. In other words, an adhesion force between an underlying
barrier layer and a copper seed layer is deteriorated by
distortion, thus causing film peeling in the heat treatment process
of the copper thin film and in the chemical mechanical polishing
(CMP) process performed thereafter.
SUMMARY OF THE INVENTION
[0012] Accordingly, the present invention is to solve the various
problems caused by the copper sulfate plating solution.
[0013] It is, therefore, an object of the present invention to
provide an electroplating solution which can reduce the stress of a
copper thin film deposited by using a copper hexafluorosilicate
plating solution, which does not deteriorate an adhesion force
between a copper seed layer and an underlying barrier layer even in
a heat treatment process and in a chemical mechanical polishing
(CMP) process after plating deposition, and which can plate and
deposit a copper thin film on a fine pattern portion having a large
aspect ratio with good covering properties.
[0014] In other words, the present invention provides an
electroplating solution used for depositing a copper wiring layer
that has a film stress which is important to increase the degree of
integration and the speed of a semiconductor integrated
circuit.
[0015] More specifically, the present invention provides an
electroplating solution that can reduce the stress of a copper thin
film and deposit such a copper thin film on a fine pattern portion,
which has a large aspect ratio, with good covering properties, so
that the copper film does not cause any film peeling derived from
deterioration of an adhesion force between an underlying barrier
layer and a copper seed layer even in a heat treatment process and
in a chemical mechanical polishing (CMP) process after plating
deposition.
[0016] The present inventors attempted to solve the prior art
problems of copper plating performed by a copper sulfate
electrolyte, and such attempts was made by way of optimizing
various plating conditions such as a current density, an electrode
structure, and a plating solution temperature. However, the present
inventors found that the problems are not solved except for an
improvement in covering properties that us obtained by an additive
agent and found also that an improvement of film quality, i.e., a
reduction in resistivity and an improvement of (111)-orientation
strength, is not accomplished by a current copper sulfate
electrolyte. For this reason, the present inventors disclosed in
Japanese Patent Application No. 2000-29185 a plating method of a
copper thin film that uses a copper hexafluorosilicate aqueous
solution as an electrolyte serving as a new plating solution in
place of a copper sulfate plating solution to solve the problems
caused by copper sulfate plating solutions.
[0017] However, with respect to the problem of film peeling caused
by deterioration of an adhesion force between an underlying barrier
layer and a copper seed layer in the heat treatment process and in
the chemical mechanical polishing (CMP) process after plating
deposition, it was found that a film stress in plating deposition
caused by film peeling is not reduced sufficiently by the
conventional copper sulfate plating solution and the copper
hexafluorosilicate plating solution disclosed in Japanese Patent
Application No. 2000-291585.
[0018] So as to solve the problem of film peeling caused by the
deterioration of the adhesion force, the inventors earnestly
continued the study using the copper hexafluorosilicate plating
solution as an electrolyte. As a result, the inventors found that a
copper thin film that has a low stress can be plating-deposited
with a use of an aqueous solution that contains 10 to 40 wt % of
copper hexafluorosilicate as an electrolyte and thus completed the
present invention.
[0019] More specifically, the present invention is characterized in
that an aqueous solution, which is used as an electrolyte, contains
10 to 40 wt % of copper hexafluorosilicate. When the 10 to 40 wt %
copper hexafluorosilicate aqueous solution is used as an
electrolyte, in comparison to the case in which a conventional
copper sulfate and a copper hexafluorosilicate plating solution of
Japanese Patent Application No.2000-291585 are used, a copper thin
film that has a low film stress and a low resistivity and which is
strongly (111)-oriented can be deposited with good covering
properties on a fine pattern of a copper wiring layer of a
semiconductor integrated circuit.
[0020] The electroplating solution of the present invention is
applicable when a copper thin film is partially or entirely
deposited on a printed circuit board, a glass substrate, and a
silicon wafer a pattern formed or not formed on their surfaces.
When the solution of the present invention is employed, a copper
thin film which has a low film stress and a low resistivity and
which is strongly (111)-oriented is partially or entirely deposited
on a printed circuit board, a glass substrate, and a silicon wafer
on which a pattern is formed or not formed.
[0021] The current density during plating is preferably within the
range of 0.5 to 1.5 A/dm.sup.2. When the current density falls
within this range, a copper thin film which is good in
(111)-orientation strength is deposited with good covering
properties. When the current density is less than 0.5 A/dm.sup.2,
the deposition rate is considerably low. When the current density
exceeds 1.5 A/dm.sup.2, then the deposition rate deteriorates
because of generation of hydrogen, and defective introduction of
hydrogen into the film occur, thus decreasing the reliability of
the film.
[0022] The plating solution temperature during plating is
preferably within the range of 20 to 40.degree. C. When the plating
solution temperature falls within this range, (111)-orientation
strength is especially good, and hydrogen is not generated during
the plating. In addition, the deposition rate does not decrease,
and no void is formed in the film. Therefore, the film has good
reliability.
[0023] The amount of an additive agent to be added to the solution
during plating is preferably within the range of 0.5 to 1.5 wt %.
When the plating is performed with an addition of an additive agent
in the amount that falls within this range, a copper thin film
having a low resistivity is formed on the fine contact portion with
good covering properties. When the amount of the additive agent is
smaller than 0.5 wt %, the resistivity increases, and the covering
properties decreases. When the amount of additive agent exceeds 1.5
wt %, a film which is strongly (111)-oriented cannot be obtained,
and the film is not preferable in reliability.
[0024] As the additive agent, organic compounds (e.g., sodium
mercaptopropane sulfonate (MPSA), polyethylene glycol (PEG), and
ethylene diamine (EDA)) which are conventionally used in
electroplating can be used. In addition, at least one of these
compounds or a mixture of at least two of these compounds can be
used.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a graph showing the relationship between the
stress and resistivity of copper thin films formed when plating is
performed by using the copper hexafluorosilicate plating solution
according to the present invention and a conventional copper
sulfate plating solution;
[0026] FIG. 2 is a graph showing the relationship between the
deposition rate and stress of the copper thin films formed when
plating is performed by using the copper hexafluorosilicate plating
solution according to the present invention and the conventional
copper sulfate plating solution;
[0027] FIG. 3 is a graph showing the relationship between the film
thickness and stress of the copper thin films formed when plating
is performed by using the copper hexafluorosilicate plating
solution according to the present invention and the conventional
copper sulfate plating solution;
[0028] FIG. 4 is a graph showing the manners of changes in stress
of the copper thin films before and after annealing when plating is
performed by using the copper hexafluorosilicate plating solution
according to the present invention and the conventional copper
sulfate plating solution;
[0029] FIG. 5 is a graph showing the relationship between the
deposition rates and adhesion forces of the copper thin films when
plating is performed by using the copper hexafluorosilicate plating
solution according to the present invention and the conventional
copper sulfate plating solution;
[0030] FIG. 6 is a graph showing the relationships between the film
thickness and adhesion force of the copper thin films deposited
when the copper hexafluorosilicate plating solution according to
the present invention and the conventional copper sulfate plating
solution are used;
[0031] FIG. 7 is a graph showing the manner of changes in adhesion
force of the copper thin films before and after annealing when the
copper thin films are deposited by using the copper
hexafluorosilicate plating solution according to the present
invention and the conventional copper sulfate plating solution;
[0032] FIG. 8 is a graph showing the relationship between the
stress and adhesion force of the copper thin films deposited when
the copper hexafluorosilicate plating solution according to the
present invention and the conventional copper sulfate plating
solution are used; and
[0033] FIGS. 9A, 9B and 9C are schematic diagrams showing the steps
in which an insulating interlayer (SiO.sub.2) formed on an Si wafer
is patterned by standard photolithography and dry etching using a
conventional photoresist, the photoresist is removed, a 30-nm
barrier film (Ta) and a 150-nm Cu seed layer are deposited by a
sputtering method on the patterned SiO.sub.2 layer, a copper thin
film is plating-deposited on the Cu seed layer by using the copper
hexafluorosilicate plating solution according to the present
invention, and, thereafter, the resultant structure is subjected to
heat treatment at 400.degree. C. and flattened by a chemical
mechanical polishing (CMP) method to form a copper wiring layer on
the SiO.sub.2 insulating interlayer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] The electroplating solution for a copper thin film according
to the present invention deposits a copper thin film, and in such a
copper thin film, film peeling that would occur on the interface
between an underlying barrier layer and a copper seed layer in a
heat treatment process and in a chemical mechanical polishing (CMP)
process after plating deposition can be avoided.
[0035] For example, an SiO.sub.2 film was deposited on an Si wafer
so as to have a thickness of 200 nm, a TaN film was deposited as a
barrier layer so as to have a thickness of 30 nm, and a copper seed
layer was deposited on the resultant structure by a sputtering
method so as to have a thickness of 100 nm. Thereafter, the
concentration of the copper hexafluorosilicate plating solution
during plating was changed, and a copper thin film was plated and
deposited, and then a heat treatment at 400.degree. C. was
performed for 15 minutes in a nitrogen atmosphere after the plating
deposition. Then, the presence/absence of film peeling is
checked.
[0036] The result, as shown in Table 1 below, indicates that the
problem of film peeling on the interface between the underlying
barrier layer and the copper seed layer did not occur after the
heat treatment when the concentration of the copper
hexafluorosilicate plating solution was set within the range of 10
to 40 wt %. in this study, the plating was performed under the
conditions that the film thickness of the plating copper thin film
was equally set to be 400 nm, 1 wt % of an additive agent (mixture
of sodium mercaptopropane sulfonate (MPSA), polyethylene glycol
(PEG), ethylene diamine (EDA)) was added, the current density was
set to be 1.0 A/dm.sup.2, and the plating bath temperature was set
to be 20.degree. C.
[0037] As seen from the result in Table 1, film peeling did not
occur when a solution having a concentration of 5 wt % or less was
used, but a plating deposition rate was so low that the
concentration was not practical. In addition, the concentration of
45 wt % or higher was found not preferable either. The reason for
this is that with such a concentration not only film peeling
occurred, but also copper hexafluorosilicate which was an
electrolyte was separated due to the solubility of copper
hexafluorosilicate in water when the plating temperature was
17.degree. C. or lower.
1TABLE 1 Concentration of Presence/Absence of Film Presence/Absence
copper Peeling on Interface of Brilliance hexafluorosilicate
between Underlying Barrier of Copper Thin Aqueous Solution Layer
and Copper Seed Film during Plating during Plating (wt %) Layer
deposition 5 Absent Present 10 Absent Present 20 Absent Present 30
Absent Present 40 Absent Present 45 Present Absent
[0038] Embodiments of the present invention will be described
below.
[0039] As plating conditions for a copper thin film, an SiO.sub.2
film was deposited on an Si wafer so as to have a thickness of 200
nm, a TaN film was deposited as a barrier metal so as to have a
thickness of 30 nm, and a copper seed layer was deposited on the
resultant structure by a sputtering method so as to have a
thickness of 100 nm. A copper hexafluorosilicate (CuSiF.sub.6)
aqueous solution having a concentration of 20 wt % of the present
invention was used as a plating solution. For the comparison
purposes, deposition was performed also using a conventional copper
sulfate (CuSO.sub.4) plating solution. The film thickness of the
plating copper thin film was equally set to be 400 nm, 1 wt % of an
additive agent (mixture of sodium mercaptopropane sulfonate (MPSA),
polyethylene glycol (PEG), ethylene diamine (EDA)) was added, the
current density was set to be 1.0 A/dm.sup.2, and the plating bath
temperature was set to be 20.degree. C. Under the conditions,
plating was performed.
[0040] The present invention will be described in more detail
below. As a matter of course, the present invention is not limited
to the shown examples.
EXAMPLE 1
[0041] FIG. 1 shows the relationships between the stress and
resistivity of plating copper thin films deposited under the same
conditions by using the copper hexafluorosilicate plating solution
of the present invention and the conventional copper sulfate
plating solution. The resistivity of plating copper thin films
strongly depends on a film stress. When the stress is low, then the
resistivity decreases. A low-resistivity film can be realized by
reducing the film stress. With the use of the copper
hexafluorosilicate plating solution according to the present
invention, a copper thin film that has especially a low stress and
a low resistivity is obtained as indicated by white circles. The
(111)-orientation of the copper thin film is also improved by the
reduction in stress.
EXAMPLE 2
[0042] FIG. 2 shows the relationships between the deposition rate
and stress of plating copper thin films, the film thickness of
which being equally set to be 400 nm. The stress of a copper thin
film deposited at a deposition rate of 3 nm/s by using the
conventional copper sulfate plating solution is 41.2 Mpa as
indicated by black circles. However, the film stress can be reduced
to 39.0 MPa when the copper hexafluorosilicate plating solution
according to the present invention is used as indicated by white
circles. As is apparent from the result of FIG. 2, a low-stress
film can be plated by the copper hexafluorosilicate plating
solution. Therefore, it is apparent that the copper
hexafluorosilicate plating solution is effective to reduce the
stress of a plating copper thin film. In FIG. 2, "Min." means "the
minimum value."
EXAMPLE 3
[0043] FIG. 3 shows the relationships between the film thickness
and stress of plating copper thin films deposited under the same
conditions by using the copper hexafluorosilicate plating solution
of the present invention and the conventional copper sulfate
plating solution. When the copper hexafluorosilicate plating
solution of the present invention is used, the stress is reduced by
an increase in film thickness, and a film having a stress which is
lower than that of a film obtained by using a copper sulfate
plating solution of the prior art is obtained. When the copper
hexafluorosilicate plating solution is used, the stress decreased,
as shown by white circles, from 38.5 MPa to 36.0 MP because of the
increase in film thickness. The reason for this is that the stress
generated by the difference between crystal lattices on the
interface between the copper thin film and the barrier film becomes
moderate by an increase in plating film thickness. In FIG. 3,
"Min." means "the minimum value."
EXAMPLE 4
[0044] FIG. 4 shows changes in stress of plating copper thin films
before and after annealing when the plating copper thin films are
deposited under the same conditions by using the copper
hexafluorosilicate plating solution of the present invention and
the conventional copper sulfate plating solution. Annealing was
performed at 400.degree. C. for 15 minutes. The stress of the
copper thin film formed using the copper hexafluorosilicate plating
solution decreased from 38.5 MPa to 12.5 MPa by the annealing. The
stress decreases from 41.3 MPa to 20.0 MPa by annealing in the
copper thin film formed using the copper sulfate plating solution.
However, even after the annealing, the stress of the copper thin
film formed using the copper sulfate plating solution is higher
than the stress of the copper thin film formed using the copper
hexafluorosilicate plating solution of the present invention. In
FIG. 4, "Min." means "the minimum value."
EXAMPLE 5
[0045] FIG. 5 shows the relationships between the deposition rates
and adhesion forces of plating copper thin films when the film
thickness is equally set to be 400 nm. The adhesion force of the
copper thin film formed with the copper hexafluorosilicate plating
solution increases from 28.5 gf to 31.3 gf as the deposition rate
decreases as indicated by white circles. Even in the case in which
the copper sulfate plating solution is used, the adhesion force
likewise increases with the decrease in deposition rate as
indicated by black circles. However, an adhesive force which is
almost equal to that obtained when the copper hexafluorosilicate
plating solution is used is not obtained when the copper sulfate
plating solution is used. In FIG. 2, "Max." means "the maximum
value."
EXAMPLE 6
[0046] FIG. 6 shows the relationships between the film thickness
and adhesion force of plating copper thin films deposited under the
same conditions by using the copper hexafluorosilicate plating
solution of the present invention and the conventional copper
sulfate plating solution. The adhesion force of the copper thin
film formed with the copper hexafluorosilicate plating solution
increases from 28.8 gf to 35.1 gf with an increase in film
thickness as indicated by white circles. Even in the case in which
the copper sulfate plating solution is used, the adhesion force
likewise increases with an increase in film thickness; however, an
adhesive force which is higher than that obtained when the copper
hexafluorosilicate plating solution is used is not obtained when
the copper sulfate plating solution is used.
EXAMPLE 7
[0047] FIG. 7 shows changes in stress of plating copper thin films
before and after annealing when the plating copper thin films are
deposited under the same conditions by using the copper
hexafluorosilicate plating solution of the present invention and
the conventional copper sulfate plating solution. Annealing was
performed at 400.degree. C. for 15 minutes. Film peeling in
annealing poses a serious problem. The adhesion force decreases
from 33.0 gf to 30.0 gf in the copper thin film formed by the
copper hexafluorosilicate plating solution. When the copper sulfate
plating solution is used, the adhesion force decreases from 30.0 gf
to 26.7 gf. Accordingly, it is clear that even after annealing the
adhesion force obtained with the copper hexafluorosilicate plating
solution is higher than the adhesion force obtained with the copper
sulfate plating solution.
EXAMPLE 8
[0048] FIG. 8 shows the relationships between the stress and
adhesion force of plating copper thin films deposited under the
same conditions by using the copper hexafluorosilicate plating
solution of the present invention and the conventional copper
sulfate plating solution. In the copper thin film formed with the
copper hexafluorosilicate plating solution, the adhesion force
increases from 31.3 gf to 33.0 gf as the stress decreases from 41.0
gf to 38.0 gf as indicated by white circles. Even in the case in
which the copper thin film formed with the copper sulfate plating
solution, the adhesion force likewise increases with a decrease in
stress. However, when the copper hexafluorosilicate plating
solution is used, a copper thin film having a low stress and a high
adhesion force is obtained in comparison with the case in which the
copper sulfate plating solution is used. In order to solve the
problem of film peeling of a plating copper thin film occurring in
chemical mechanical polishing (CMP) and annealing, the decrease in
film stress and the increase in adhesion force are extremely
important.
EXAMPLE 9
[0049] As shown in FIGS. 9A through 9C, an insulating interlayer
(SiO.sub.2) formed on an Si wafer was patterned by standard
photolithography and dry etching using a conventional photoresist.
Thereafter, the photoresist was removed, and a 30-nm barrier film
(Ta) and a 150-nm Cu seed layer were deposited by a sputtering
method on the patterned SiO.sub.2 layer, and then a copper thin
film was plating-deposited on the Cu seed layer by using the copper
hexafluorosilicate plating solution according to the present
invention. As a result, the copper thin film was deposited on a
fine pattern with good covering properties. After the plating
deposition, even though the resultant structure was subjected to
heat treatment at 400.degree. C. and flattened by a chemical
mechanical polishing (CMP) method, film peeling did not occur, and
a copper wiring layer was formed on the SiO.sub.2 insulating
interlayer.
* * * * *