U.S. patent application number 11/035847 was filed with the patent office on 2005-07-21 for additive for plating bath.
This patent application is currently assigned to Asahi Denka Co. Ltd.. Invention is credited to Kawamata, Hiromasa, Kobayashi, Hiromitsu, Nito, Hirohisa.
Application Number | 20050155514 11/035847 |
Document ID | / |
Family ID | 34616913 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050155514 |
Kind Code |
A1 |
Kobayashi, Hiromitsu ; et
al. |
July 21, 2005 |
Additive for plating bath
Abstract
A plating bath additive and a plating bath using the said
additive are provided, which plating bath contains a
hydroxyalkanesulfonic acid and which even when applied to an
electronic part such as a semiconductor device does not give rise
to a problem such as circuit-to-circuit insulation becoming
defective. The plating bath additive contains a
hydroxyalkanesulfonic acid as a main component and has an alkali
metal content of less than 0.05 mass % relative to the
hydroxyalkanesulfonic acid. The plating bath incorporates the said
additive therein.
Inventors: |
Kobayashi, Hiromitsu;
(Tokyo, JP) ; Nito, Hirohisa; (Tokyo, JP) ;
Kawamata, Hiromasa; (Tokyo, JP) |
Correspondence
Address: |
DILWORTH & BARRESE, LLP
333 EARLE OVINGTON BLVD.
UNIONDALE
NY
11553
US
|
Assignee: |
Asahi Denka Co. Ltd.
Tokyo
JP
|
Family ID: |
34616913 |
Appl. No.: |
11/035847 |
Filed: |
January 14, 2005 |
Current U.S.
Class: |
106/1.05 |
Current CPC
Class: |
C23C 18/16 20130101;
C25D 3/02 20130101; C25D 3/32 20130101; C23C 18/31 20130101 |
Class at
Publication: |
106/001.05 |
International
Class: |
C23C 018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2004 |
JP |
2004-9284 |
Claims
1. A plating bath additive containing a hydroxyalkylkanesulfonic
acid as a main component, characterized in that the content of an
alkali metal relative to the hydroxyalkylkanesulfonic acid is less
than 0.05 mass %.
2. A plating bath additive as set forth in claim 1, wherein the
hydroxyalkylkanesulfonic acid is isethionic acid.
3. A plating bath additive as set forth in claim 1, wherein the
hydroxyalkylkanesulfonic acid is prepared by oxidizing a
hydroxyalkylmercaptan with use of hydrogen peroxide.
4. A plating bath containing the plating bath additive described in
claim 1.
5. A plating bath containing the plating bath additive described in
claim 2.
6. A plating bath containing the plating bath additive described in
claim 3.
7. A plating bath additive as set forth in claim 2, wherein the
hydroxyalkylkanesulfonic acid is prepared by oxidizing a
hydroxyalkylmercaptan with use of hydrogen peroxide.
8. A plating bath additive as set forth in claim 4, wherein the
hydroxyalkylkanesulfonic acid is prepared by oxidizing a
hydroxyalkylmercaptan with use of hydrogen peroxide.
9. A plating bath additive as set forth in claim 5, wherein the
hydroxyalkylkanesulfonic acid is prepared by oxidizing a
hydroxyalkylmercaptan with use of hydrogen peroxide.
10. A plating bath additive as set forth in claim 6, wherein the
hydroxyalkylkanesulfonic acid is prepared by oxidizing a
hydroxyalkylmercaptan with use of hydrogen peroxide.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a plating bath additive
containing a hydroxyalkanesulfonic acid as a main component, as
well as a plating bath using the said additive.
BACKGROUND OF THE INVENTION
[0002] Hydroxyalkanesulfonic acids have heretofore been used as a
component of various plating baths. For example, in JP 53-14131A, a
hydroxyalkanesulfonic acid is used as a plating bath component for
the formation of tin-lead alloy electroplating so as to serve as a
film for improving solderability or as an etching resist film.
[0003] In JP 11-1792A it is disclosed that a hydroxyalkanesulfonic
acid is used as a plating bath component for plating to an
electronic part or for forming Pb--Sn alloy salient electrodes onto
a surface of a semiconductor wafer.
[0004] In JP 11-279787A it is disclosed that a
hydroxyalkanesulfonic acid is used as a plating bath component for
silver or silver alloy plating.
[0005] In JP 2000-87252A it is disclosed that a
hydroxyalkanesulfonic acid is used as a plating bath component for
an electroless tin-bismuth alloy plating bath.
[0006] However, for example isethionic acid as a conventional
hydroxyalkanesulfonic acid is obtained as sodium salt by subjecting
ethylene oxide to the action of sodium hydrogen sulfite (see
Encyclopaedia Chimica, Vol. 1, page 581), which is then
ion-exchanged to remove the alkali metal for use as an acid.
[0007] On the other hand, when plating an electronic part such as a
semiconductor device in a plating bath containing a
hydroxyalkanesulfonic acid, there sometimes has occurred a problem
that circuit-to-circuit insulation in the electronic part is
defective.
SUMMARY OF THE INVENTION
[0008] Accordingly, it is an object of the present invention to
provide a plating bath additive and a plating bath using the said
additive, which plating bath contains a hydroxyalkanesulfonic acid
and which even when applied to an electronic part such as a
semiconductor device does not give rise to a problem such as
circuit-to-circuit insulation becoming defective.
[0009] Having made earnest studies in view of the above-mentioned
point, the present inventors found out that if an alkali metal was
present within a plating bath, the alkali metal remained even if
the surface of a plated article after plating was subjected to
cleaning having such an economical characteristic as falling under
an industrially allowable range, thus sometimes resulting in
circuit-to-circuit insulation in the electronic part becoming
defective. In this way we accomplished the present invention.
[0010] More specifically, the present invention resides in a
plating bath additive containing a hydroxyalkanesulfonic acid as a
main component, characterized in that the content of an alkali
metal relative to the hydroxyalkanesulfonic acid is less than 0.05
mass %.
[0011] The present invention also resides in the above plating bath
additive wherein the hydroxyalkanesulfonic acid is isethionic
acid.
[0012] The present invention further resides in the above plating
bath additive wherein the hydroxyalkanesulfonic acid is obtained by
a method involving oxidizing a hydroxyalkylmercaptan with use of
hydrogen peroxide.
[0013] The present invention further resides in a plating bath
using the above additive.
[0014] According to the present invention there are provided a
plating bath additive and a plating bath using the said additive,
which plating bath contains a hydroxyalkanesulfonic acid and which
even when applied to an electronic part such as a semiconductor
device does not give rise to such a problem as circuit-to-circuit
insualtion in the electronic part becoming defective.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0015] The plating bath additive according to the present invention
contains a hydroxyalkanesulfonic acid as a main component, with the
content of an alkali metal relative to the hydroxyalkanesulfonic
acid being less than 0.05 mass %.
[0016] The hydroxyalkanesulfonic acid component is not specially
limited. Compounds represented by the general formula
HO--R--SO.sub.3H are preferred wherein R is a hydrocarbon group
having 1 to 12 carbon atoms and the hydroxyl group may be located
at any position of R. Concrete examples are
2-hydroxyethane-1-sulfonic acid (isethionic acid),
2-hydroxypropane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid,
3-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid,
4-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid,
2-hydroxyhexane-1-sulfonic acid, and 2-hydroxydecane-1-sulfonic
acid. Particularly, 2-hydroxyethane-1-sulfonic acid (isethionic
acid) is preferred as the plating bath additive.
[0017] How to prepare the hydroxyalkanesulfonic acid is not
specially limited. Reference will now be made to isethionic acid as
an example. Isethionic acid can be obtained by a conventional
method involving subjecting ethylene oxide to the action of sodium
hydrogensulfite to afford sodium salt and subsequent ion exchange
to remove an alkali metal component. In this case, the ion
exchanging operation is repeated until the alkali metal content
becomes less than 0.05 mass % relative to the hydroxyalkanesulfonic
acid.
[0018] The method disclosed in JP 10-204052A, which involves
oxidizing a hydroxyalkylmercaptan with use of hydrogen peroxide, is
preferred because an alkali metal is not used and therefore
ahydroxyalkanesulfonic acid with an alkali metal content of less
than 0.05 mass % can be obtained more effectively.
[0019] The plating bath additive according to the present invention
is useful as a hydroxyalkanesulfonic acid component added to the
plating bath and the hydroxyalkanesulfonic acid content in the
plating bath additive is arbitrary. Any other desired components
than the hydroxyalkanesulfonic acid may be added into the plating
bath of the present invention, provided it is necessary to make a
control so that the alkali metal content relative to the
hydroxyalkanesulfonic acid does not become 0.05 mass % or more.
[0020] Other components which may be added-into the plating
solution are not specially limited. As examples of such other
components there are mentioned antioxidants (e.g., catechol,
hydroquinone, ascorbic acid), brighteners or brightening aids
(e.g., benzaldehyde, formalin, glyoxal), complexing agents (e.g.,
EDTA, ethylenediamine, citric acid), nonionic surfactants as
homogenizers (e.g., polyethylene glycol, oxyethylene-oxypropylene
block copolymer, alkylphenol ethylene oxide adducts, polyhydric
alcohol fatty acid esters, fatty acid alkanol amides), and
antioxidation aids or smoothing agents (e.g., thiourea, ethylene
thiourea, thioglycolic acid).
[0021] The plating bath according to the present invention contains
the plating bath additive described above. As other components than
a hydroxyalkanesulfonic acid, components so far known as components
of a plating path containing a hydroxyalkanesulfonic acid may be
used in respective known ranges.
[0022] Thus, arbitrary components may be selected for the plating
bath of the invention as desired by a user, with no special
limitation being placed thereon. As examples of such components,
mention may be made of compounds (e.g., copper, tin, silver, and
their salts and oxides, each alone or in combination of two or
more) which supplies ions of a metal to be plated, inorganic acids,
organic acids, oxidizing agents, reducing agents, surfactants, pH
adjustors, pH controllers, buffer agents, smoothing agents, stress
relaxation agents, stabilizers, complexing agents (chelating
agents), brighteners, semibrighteners, antioxidants, dispersants,
homogenizers, and other additives known to be incorporated in
plating baths. Arbitrary components which may be incorporated in
the plating bath additive of the present invention are also capable
of being incorporated in the plating bath of the invention.
EXAMPLES
[0023] The present invention will be further described below by way
of working Examples thereof, but it is to be understood that the
present invention is not limited by the following Examples.
Example 1
[0024] 357 g (6.3 mol) of 60 mass % hydrogen peroxide was charged
into a glass reactor equipped with an internal condenser, an
agitator, a condenser having an opening/closing cock for solvent
distillation, and a liquid introducing device, and thereafter 156 g
(2.0 mol) of 2-mercaptoethanol was fed continuously from a liquid
inlet at a rate of 0.4 mL/min under agitation. During this
operation, the liquid temperature was held at 45.degree. C. by
adjusting the amount of cooling water fed to the condenser. After
the end of the addition of 2-mercaptoethnaol, the agitation was
continued at room temperature for 10 hours. Then, nitrogen gas was
blown into the reaction solution through a sample inlet pipe and
the reaction solution was held for 5 hours under heating at
110.degree. C. and at the atmospheric pressure, with agitation,
while a portion of vapor was allowed to be discharged to the
exterior of the reaction system. This reaction solution was then
passed through a 35 mm dia. tower charged with 200 mL of an ion
exchange resin (Duolite A-561, a product of Sumitomo Chemical Co.),
from the top of the tower and is thereby purified to afford 54.0
mass % of an isethionic acid solution (yield 241.6 g: percent yield
95.9%). No alkali metal was detected from this acqeuous isethionic
acid solution (detection limit 10 ppb).
[0025] The aqueous isethionic acid solution was used as a plating
bath additive (1).
[0026] Comparative Example 1 & Example 2
[0027] A 43 mass % aqueous solution of commercially available
sodium isethionate (a product of Aoki Yushi Kogyo Co.) was prepared
and was then passed through a 30 mm dia. tower charged with 82 mL
of an ion exchange resin (MONOSPHIA 630C_H, a product of The Dow
Chemical Co.), at a (down-flow) SV1.0, from the top of the tower,
and was thereby purified to afford 10 mass % of an aqueous
isethionic acid solution having a sodium content of 5 mass %
relative to isethionic acid. The aqueous isethionic acid solution
was then concentrated to an isethionic acid concentration of 40
mass % and the thus-concentrated aqueous solution was used as a
comparative plating bath additive (1).
[0028] After regeneration of the ion exchange resin by a
conventional method, the same purifying operation as above was
repeated twice for the comparative plating bath additive (1) to
afford a 7.0 mass % aqueous isethionic acid solution having a
sodium content of 0.03 mass %. This aqueous isethionic acid
solution was then concentrated to 40 mass % to afford a plating
bath additive (2) according to the present invention.
Example 3
[0029] A 49.2 mass % aqueous 2-hydroxypropane-1-sulfonic acid
solution was prepared in the same way as in Example 1 except that
2-mercaptoethanol was substituted by 2-mercaptopropanol. No alkali
metal was detected from the aqueous 2-hydroxypropane-1-sulfonic
acid solution.
[0030] The aqueous 2-hydroxypropane-1-sulfonic acid solution thus
prepared was used as a plating bath additive (3) according to the
present invention.
Example 4 & Comparative Example 2
[0031] Using the plating bath additives prepared in Examples 1 to 3
according to the present invention and the comparative bath
additive prepared in Comparative Example 1, aqueous solutions of
the composition shown in Table 1 were prepared as plating baths (Sn
plating baths).
1 TABLE 1 SnO 30 g/L Thiourea 8 g/L Additive for the plating baths
100 g/L (as hydroxyalkanesulfonic acid) p-Cumylphenol ethylene
oxide 10 g/L (10 mol) adduct Glyoxazole 1 g/L Catechol 1 g/L
Balance Water
[0032] On the other hand, when two systems of adjacent copper
circuits were formed on a silicon wafer and were each Sn-plated
using each of the plating baths prepared above, then tested for
circuit-to-circuit insulation. As a result, a satisfactory
insulation was attained in case of using the plating baths prepared
according to the present invention, but the insulation was poor in
the case of the plating bath using the comparative plating bath
additive prepared in Comparative Example 2.
* * * * *