U.S. patent application number 14/101457 was filed with the patent office on 2014-06-12 for electrolytic copper plating solution for filling for forming microwiring of copper for ulsi.
This patent application is currently assigned to JX Nippon Mining & Metals Corporation. The applicant listed for this patent is Akihiro AIBA, Junnosuke SEKIGUCHI, Hirofumi TAKAHASHI. Invention is credited to Akihiro AIBA, Junnosuke SEKIGUCHI, Hirofumi TAKAHASHI.
Application Number | 20140158546 14/101457 |
Document ID | / |
Family ID | 43410924 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140158546 |
Kind Code |
A1 |
SEKIGUCHI; Junnosuke ; et
al. |
June 12, 2014 |
ELECTROLYTIC COPPER PLATING SOLUTION FOR FILLING FOR FORMING
MICROWIRING OF COPPER FOR ULSI
Abstract
An electrolytic copper plating solution for filling for forming
microwiring for ULSI, is characterized in that it has a pH of from
1.8 to 3.0. The electrolytic copper plating solution preferably
contains a saturated carboxylic acid having from 1 to 4 carbon
atoms at a concentration from 0.01 to 2.0 mol/L.
Inventors: |
SEKIGUCHI; Junnosuke;
(Kitaibaraki-shi, JP) ; TAKAHASHI; Hirofumi;
(Kitaibaraki-shi, JP) ; AIBA; Akihiro;
(Kitaibaraki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEKIGUCHI; Junnosuke
TAKAHASHI; Hirofumi
AIBA; Akihiro |
Kitaibaraki-shi
Kitaibaraki-shi
Kitaibaraki-shi |
|
JP
JP
JP |
|
|
Assignee: |
JX Nippon Mining & Metals
Corporation
|
Family ID: |
43410924 |
Appl. No.: |
14/101457 |
Filed: |
December 10, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13378529 |
Dec 15, 2011 |
|
|
|
14101457 |
|
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|
Current U.S.
Class: |
205/122 |
Current CPC
Class: |
C25D 7/0607 20130101;
C25D 3/38 20130101; H01L 21/2885 20130101; H01L 2924/0002 20130101;
H01L 2924/0002 20130101; H01L 21/76877 20130101; H01L 2924/00
20130101; H01L 23/53238 20130101; C25D 7/123 20130101 |
Class at
Publication: |
205/122 |
International
Class: |
C25D 3/38 20060101
C25D003/38; C25D 7/06 20060101 C25D007/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 1, 2009 |
JP |
2009-156929 |
Claims
1. A method for electrolytic copper plating for ULSI microwiring
comprising the step of forming damascene microwiring for ULSI with
an electrolytic copper plating aqueous solution for forming
damascene microwiring for ULSI, characterized in that the plating
solution has a pH of from 1.8 to 3.0, contains copper sulfate at
0.05 to 1.5 mol/L and chloride ions at a concentration of 0.3 to
3.0 mmol/L, and comprises a saturated carboxylic acid at a
concentration of from 0.01 to 2.0 mol/L.
2. The method of claim 1, wherein the plating aqueous solution has
a pH of 2.0 to 2.2.
3. The method of claim 1, wherein the saturated carboxylic acid
contains from 1 to 4 carbon atoms.
4. The method of claim 3, wherein the saturated carboxylic acid is
acetic acid.
5. A ULSI microwiring substrate in which the formation of voids on
inner walls of vias/trenches has been suppressed, characterized in
that USLI microwiring is formed by the method of claim 1.
Description
[0001] This is a division of Ser. No. 13/378 529, filed Dec. 15,
2011, which was the national stage of International Application No.
PCT/JP2010/060545, filed Jun. 22, 2010, which International
Application was not published in English.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an electrolytic copper
plating solution for filling for forming microwiring of copper for
ULSI.
[0004] 2. Description of the Related Art
[0005] Electrolytic copper plating for filling ULSI microwiring is
usually carried out with sulfuric acid-based strongly acidic
plating solutions (pH of 1.2 or lower). Seed layers upon plating
are sputtered copper films, of which thickness in trenches/vias
have become very thin due to miniaturization of wiring. Oxidation
of the outermost layer of the seed layer is unavoidable because the
outermost layer is atmospherically exposed prior to electrolytic
plating. Accordingly, the oxidized parts of the seed layer are
easily dissolved when it is immersed in a strongly acidic
electrolytic plating solution leading to formation of defects on
the thin seed layer. When a copper wiring layer is formed by
electrolytic copper plating thereafter, the copper plating is
unsatisfactorily absent in spots. Particularly, the inner wall of
trenches/vias tends to have problematic voids.
SUMMARY OF THE INVENTION
[0006] An object of the present invention is to provide an
electrolytic copper plating solution which can suppress, upon
electrolytic copper plating on a copper seed layer during
fabrication of ULSI copper microwiring (damascene copper wiring)
having trends to further miniaturization, dissolution of the copper
seed layer and accordingly can suppress occurrence of voids on the
inner wall of vias/trenches.
[0007] The present inventors have attempted to suppress dissolution
of copper seed layers upon being immersed in the plating solution
by using carboxylic acids and the like instead of sulfuric acid
usually used for sulfuric acid-based strongly acidic copper plating
solutions and to change pH of the plating solution from
conventional strong acid to around weak acid. As a result, they
have found that formation of voids on the side wall of trenches
which may be generated with the sulfuric acid-based strongly acidic
plating solutions can be avoided with the carboxylic acid-based
plating solution, thereby accomplished the present invention which
solves the above-mentioned problems.
[0008] Thus, the present invention provides the followings: [0009]
(1) an electrolytic copper plating solution for filling for forming
microwiring for ULSI, characterized in that it has a pH of 1.8 or
higher and 3.0 or lower; [0010] (2) the electrolytic copper plating
solution for filling for forming microwiring for ULSI according to
the above (1), wherein it has a pH of 2.0 or higher and 2.2 or
lower; [0011] (3) the electrolytic copper plating solution for
filling for forming microwiring for ULSI according to the above (1)
or (2), wherein it comprises a saturated carboxylic acid having 1
or more and 4 or less carbon atoms at 0.01 mol/L or more and 2.0
mol/L or less; [0012] (4) the electrolytic copper plating solution
for ULSI microwiring according to the above (3), wherein the
carboxylic acid is acetic acid; [0013] (5) a method for
electrolytic copper plating for ULSI microwiring, characterized in
that it uses the electrolytic copper plating solution for filling
for forming microwiring for ULSI according to any of the above (1)
to (4); and [0014] (6) a ULSI microwiring substrate characterized
in that a ULSI microwiring is formed by the method for electrolytic
copper plating for ULSI microwiring according to the above (5).
[0015] In ULSI copper microwiring (damascene copper wiring)
fabrication, formation of a copper wiring layer on a copper seed
layer using the electrolytic copper plating solution of the present
invention can suppress dissolution of the copper seed layer and
accordingly formation of voids on the inner wall of
vias/trenches.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a cross-sectional SEM photograph illustrating that
voids were not formed in the side wall portion of trenches using
the method of the present invention.
[0017] FIG. 2 is a cross-sectional SEM photograph illustrating that
voids were formed in the side wall portion of trenches using the
method of Comparative Example 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The electrolytic copper plating solution for filling for
forming microwiring for ULSI of the present invention has a pH of
1.8 or higher and 3.0 or lower. Conventional sulfuric acid-based
copper plating solutions are strongly acidic at pH 1.2 or lower.
However, the present plating solution can have a pH of 1.8 or
higher and 3.0 or lower because carboxylic acid such as acetic acid
is used instead of sulfuric acid. By employing pH of 1.8 or higher
and 3.0 or lower, dissolution of copper seed layers can be
suppressed and accordingly formation of voids on the inner wall of
vias/trenches can be suppressed. pH is more preferably 2.0 or
higher and 2.2 or lower.
[0019] If pH is lower than 1.8, copper seed layers are easily
dissolved due to low pH and as a result, voids are also easily
formed. If pH is higher than 3.0, copper ions in the plating
solution may be converted to oxides or hydroxides to cause
precipitations.
[0020] The carboxylic acid may be any carboxylic acid that can be
dissolved in the plating solution and adjust pH to the above range,
and is preferably a saturated carboxylic acid having 1 or more and
4 or less carbon atoms such as formic acid, acetic acid, propionic
acid, butyric acid, oxalic acid and the like, with acetic acid
being particularly preferable.
[0021] The plating solution preferably contains the carboxylic acid
at 0.01 to 2.0 mol/L and more preferably 0.2 to 1.0 mol/L. The
concentration of the carboxylic acid in the plating solution
affects filling properties and pH such that the concentration of
carboxylic acid at more than 2.0 mol/L reduces pH of the plating
solution to lower than 1.8, causing increased formation of voids.
When the concentration of carboxylic acid in the plating solution
is less than 0.01 mmol/L, the plating solution has a pH of higher
than 3.0, which may cause precipitations as described above.
[0022] The electrolytic copper plating solution of the present
invention is aqueous and may comprise other components such as
copper salts, chloride ions, trace additives and the like, which
may be well known and are not particularly limited.
[0023] Copper salts may include copper sulfate, copper nitrate,
copper chloride and the like, with copper sulfate being preferable.
The plating solution preferably contains the copper salt at 0.05 to
1.5 mol/L and more preferably 0.2 to 0.8 mol/L.
[0024] The plating solution preferably contains chloride ions at a
concentration of 0.3 to 3.0 mmol/L and more preferably 1.0 to 2.0
mmol/L.
[0025] Trace additives may include promoters, inhibitors, leveling
agents and the like.
[0026] Promoters may include bis(3-sulfopropyl)-disulfide, disodium
salt, 3-mercaptopropanesulfonic acid and the like, which are
preferably contained in the plating solution at 1 to 30 mg/L.
[0027] Inhibitors may include polyethylene glycol, polypropylene
glycol, copolymers thereof and the like, which are preferably
contained in the plating solution at 10 to 500 mg/L.
[0028] Leveling agents may include Janus Green B,
polyethyleneimine, polyvinylpyrrolidone and the like, which are
preferably contained in the plating solution at 0.1 to 50 mg/L.
[0029] Plating operations using the electrolytic copper plating
solution of the present invention are preferably carried out at a
bath temperature of 20 to 30.degree. C. in view of stability of
bath and deposition speed of copper. The cathode current density is
preferably 0.1 to 5 A/dm2.
[0030] A material to be plated by electrolytic copper plating is a
microwiring substrate such as semiconductor wafers and is
preferably a silicon substrate having ULSI microwiring such as
trenches/vias onto which a copper seed layer is provided.
[0031] The copper seed layer may be formed by well-known methods
such as sputtering and electroless plating.
[0032] The electrolytic copper plating solution of the present
invention allows to carry out plating without voids even when the
copper seed layer in trenches/vias has a thickness of 2 nm or
less.
Examples
Example 1
[0033] A silicon substrate having ULSI microwiring was subjected to
electrolytic copper plating using the following plating solution.
The silicon substrate, which is to be plated, has fine trench
patterns (line width: 180 nm and depth: 500 nm) and a Cu seed layer
is provided on its outermost surface by sputtering. The Cu seed
layer had a thinnest thickness of 2 nm in trenches.
[0034] Composition of plating solution:
TABLE-US-00001 Copper (copper sulfate) 0.63 mol/L; Acetic acid 0.5
mol/L HCl 1.4 mmol/L Bis(3-sulfopropyl)-disulfide, disodium salt 10
mg/L Polypropylene glycol 80 mg/L Polyvinylpyrrolidone 10 mg/L pH
2.1
[0035] Plating was carried out at 25.degree. C. and 1 A/dm.sup.2
for 30 seconds.
[0036] Cross-sectional SEM observation is shown in FIG. 1. Void was
not formed at anywhere including the side wall part of
trenches.
Example 2
[0037] A silicon substrate having ULSI microwiring was subjected to
electrolytic copper plating using the following plating solution.
The silicon substrate to be plated was the same as the one used in
Example 1, in which Cu seed layer had a thinnest thickness of 2 nm
in trenches.
[0038] Composition of plating solution:
TABLE-US-00002 Copper (copper sulfate) 0.63 mol/L; Formic acid 1.0
mol/L HCl 1.4 mmol/L Bis(3-sulfopropyl)-disulfide, disodium salt 10
mg/L Polypropylene glycol 80 mg/L Polyvinylpyrrolidone 10 mg/L pH
1.9
[0039] Plating was carried out at 25.degree. C. and 1 A/dm.sup.2
for 30 seconds.
[0040] Cross-sectional SEM observation showed that void was not
formed at anywhere including the side wall part of trenches.
Example 3
[0041] A silicon substrate having ULSI microwiring was subjected to
electrolytic copper plating using the following plating
solution.
[0042] The silicon substrate to be plated was the same as the one
used in Example 1 except that its Cu seed layer had a thinnest
thickness of 1.8 nm in trenches.
[0043] Composition of plating solution:
TABLE-US-00003 Copper (copper sulfate) 0.63 mol/L; Oxalic acid 0.1
mol/L HCl 1.4 mmol/L Bis(3-sulfopropyl)-disulfide, disodium salt 10
mg/L Polypropylene glycol 80 mg/L Polyvinylpyrrolidone 10 mg/L pH
2.5
[0044] Plating was carried out at 25.degree. C. and 1 A/dm.sup.2
for 30 seconds.
[0045] Cross-sectional SEM observation showed that void was not
formed at anywhere including the side wall part of trenches.
[0046] Comparative example 1
[0047] Electrolytic copper plating was carried out in the same
manner as Example 1 except that composition of the plating solution
was changed as follows.
[0048] Composition of plating solution:
TABLE-US-00004 Copper (copper sulfate) 0.63 mol/L Sulfuric acid 0.5
mol/L HCl 1.4 mmol/L Bis(3-sulfopropyl)-disulfide, disodium salt 10
mg/L Polypropylene glycol 80 mg/L Polyvinylpyrrolidone 10 mg/L
<pH 1.0
[0049] Cross-sectional SEM observation is shown in FIG. 2. Voids
(dark shadowy parts in circles) were observed in at least some of
the side wall part of trenches.
* * * * *