U.S. patent application number 12/294947 was filed with the patent office on 2010-09-30 for surface-active conditional inhibitors for the electroplating of copper on a surface.
Invention is credited to Daniel Michelet.
Application Number | 20100243467 12/294947 |
Document ID | / |
Family ID | 37898477 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100243467 |
Kind Code |
A1 |
Michelet; Daniel |
September 30, 2010 |
SURFACE-ACTIVE CONDITIONAL INHIBITORS FOR THE ELECTROPLATING OF
COPPER ON A SURFACE
Abstract
Electrolytes for the electroplating of copper comprising, as
inhibitor, a poly(alkylene-biguanide) salt. The inhibition
developed by poly(alkylene-biguanide) salts is conditioned by the
concentration of an accelerator on the surface of the copper. The
surfactancy of poly(alkylene-biguanide) salts enables them to be
instantly transferred from the electrolyte/air interface to the
electrolyte/copper interface during contact between the cathode and
the electrolyte. The electrolytes according to the invention are
suitable for obtaining smooth and bright electroplated coatings and
for depositing copper on surfaces having submicron-scale
concavities useful in microelectronics.
Inventors: |
Michelet; Daniel; (Nice,
FR) |
Correspondence
Address: |
RENNER OTTO BOISSELLE & SKLAR, LLP
1621 EUCLID AVENUE, NINETEENTH FLOOR
CLEVELAND
OH
44115
US
|
Family ID: |
37898477 |
Appl. No.: |
12/294947 |
Filed: |
April 2, 2007 |
PCT Filed: |
April 2, 2007 |
PCT NO: |
PCT/FR2007/000559 |
371 Date: |
June 18, 2010 |
Current U.S.
Class: |
205/296 |
Current CPC
Class: |
C25D 3/40 20130101; C25D
3/38 20130101 |
Class at
Publication: |
205/296 |
International
Class: |
C25D 3/38 20060101
C25D003/38 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 6, 2006 |
FR |
0603016 |
Claims
1. An electrolyte for the electroplating of copper on a cathode,
characterized in that it contains an effective amount of a poly
(alkylene-biguanide) salt having the general formula (B)
R--NH--C(:NH)--NH--[--(CH.sub.2).sub.p--NH--C(:NH)--NH--C(:NH)--NH--].sub-
.n--(CH.sub.2).sub.p--NH.sub.2, xAH wherein: p is an integer
comprised between 2 and 12 n is an integer comprised between 2 and
100 R-- represents NC-- or H.sub.2N--C(:O)-- AH represents an acid
x is comprised between (n+1) and 2(n+1) if AH is a monoacid, and
between (n+1)/2 and (n+1) if AH is a diacid.
2. The electrolyte for the electroplating of copper on a cathode
according to claim 1, characterized in that in formula (B) of the
poly (alkylene-biguanide) salt, p is equal to 6 n is comprised
between 6 and 20 R-- represents NC--.
3. The electrolyte for the electroplating of copper on a cathode
according to one of claim 1 or 2, characterized in that in formula
(B) AH represents sulfuric acid.
4. The electrolyte for the electroplating of copper on a cathode
according to any of claims 1 to 3, characterized in that the poly
(alkylene-biguanide) salt concentration is comprised between 5
10.sup.-7 mole per liter and 10.sup.-5 mole per liter.
5. The electrolyte for the electroplating of copper on a cathode
according to any of claims 1 to 4, characterized in that it
includes an accelerator of the electrolytic deposition of copper
taken among mercapto-alkyl sulfonic acids and dialkyl disulfide
disulfonic acids, or among their salts.
6. A process for the electroplating of copper on a cathode,
characterized in that the deposit is obtained starting from an
electrolyte according to any of claims 1 to 5.
7. The process for the electroplating of copper on a cathode
according to claim 6, characterized in that the cathode comprises
submicronic concavities.
8. The process for the electroplating of copper on a cathode
according to one of claim 6 or 7, characterized in that a voltage
is applied between the anode and the cathode before said cathode is
contacted with the electrolyte.
9. A copper electrodeposit on a cathode, characterized in that it
has been obtained from an electrolyte according to any of claims 1
to 5.
10. A copper electrodeposit on a cathode, characterized in that it
has been obtained by a process according to any of claims 6 to 8.
Description
[0001] The present invention relates to a new family of additives
for copper electroplating baths. More specifically, the present
invention relates to a new family of surface-active inhibitors for
copper electroplating baths used in the manufacture of smooth and
bright copper electrodeposits and in the manufacture of
semiconductor copper interconnects.
[0002] Each electrolytic copper deposit must present specific
properties according to its utilization. Several mineral or organic
additives are usually added to copper electroplating baths to
intend to obtain deposits having these required properties. The
minor components of copper electroplating baths are often referred
to as additives.
[0003] To obtain a smooth and bright electrolytic copper deposit on
a surface initially comprising grooves, it was empirically found
that it was necessary to add a combination of additives to the
electrolyte such as, an accelerator associated with an inhibitor
and a brightener. Such a combination of additives promotes an
accelerated copper deposition starting from the bottom of
concavities of micronic and submicronic size on the surface, such
as the concave parts of roughness, grooves or microtrenches, which
makes it possible to fill them preferentially. At the same time,
these additives slow down the electrodeposition of copper on the
convex parts of surface. The combination of these two effects makes
it possible to obtain smooth electrolytic copper deposits.
[0004] This result was explained by the fact that when an
accelerator of the deposit is chemically adsorbed on the surface of
copper, its surface concentration increases as this surface rapidly
shrinks as occurs during the filling of a concavity, and that on
the contrary, the surface concentration of this accelerator
decreases as this surface increases as occurs during the deposition
on a convex microstructure. (J. Osterwald and J. Schulz-Harder,
Galvanotechnik, 1975, vol. 66, 360; J. Osterwald,
Oberflache--Surface, 1976, vol. 17, 89).
[0005] The manufacture of semiconductor interconnections also
includes the filling of concavities of submicronic size in the
form, for example, of trenches by electrolytic deposition of
copper. This filling should not leave any void in the concavities.
Such a result was already obtained by a copper deposition which
accelerates starting from the bottom of concavities. Therefore,
obtaining smooth electrolytic copper deposits on the one hand, and
filling concavities of submicronic size by copper electrolytic
deposition on the other hand, set the same technical problem as
already established (T. P. Moffat et al. IBM J. RES & DEV.
2005, 49, (1) 19-36; G. B. McFadden et al. Journal of The
Electrochemical Society 2003, 150, C591-C599). Consequently,
combinations of additives previously known to generate smooth
electrolytic copper deposits were used to manufacture semiconductor
copper interconnections by filling concavities of submicronic size.
To obtain a copper deposition rate which increases starting from
the bottom of submicronic trenches, one thus proposed to use a
well-known association of polyalkyleneglycols, which act as
inhibitors in the presence of chloride ions i.e. they increase the
copper deposition overvoltage, with thiols bearing a sulfonic acid
group, or with disulfides bearing two sulfonic acid groups, which
act as accelerators, i.e. they decrease the copper deposition
overvoltage.
[0006] This combination of additives presents the disadvantage of
including necessarily chloride ions, generally in the concentration
range of 10.sup.-3 to 10.sup.-2 mole/l. However, in the presence of
chloride ions, the copper surface reacts with Cu.sup.2+ ions to
form cuprous chloride by a disproportionation reaction. (W-P Dow et
al. Journal of The Electrochemical Society, 2005, 152 C67-C76).
This disproportionation reaction, which consumes the already
deposited copper, can partly remove the initial copper layer when
this layer is a thin and divided copper seed layer obtained by
vapor phase deposition of copper, or may change its surface
properties.
[0007] This combination of additives also presents the disadvantage
of generating electrolytes which do not perfectly and
instantaneously wet the initial surface of copper.
[0008] It would thus be desirable to have new compositions of
copper electroplating baths devoid of chloride ions, making it
possible to wet the surface of copper instantaneously, then
preferentially fill the grooves and concavities of submicronic size
present on the copper surface.
[0009] More generally, the additives known to present a useful
activity in acidic copper electroplating baths form, in fact, a
small number of families, known for a long time, such as, for
example, polyethers, thiols or disulfides comprising sulfonic acid
groups, as well as phenazinic nitrogen heterocycles, such as Janus
Green B. It would be thus very desirable to have new families of
active additives for copper electroplating baths in order, for
example, to increase the number of possible combinations when one
seeks to obtain a copper electrodeposit presenting optimal
properties for a particular application.
[0010] The present invention relates to the discovery of the
inhibiting properties of the electrolytic deposition of copper and
of the surface-active properties at the copper-electrolyte
interface of poly (alkylene-biguanide) salts.
[0011] The present invention also relates to copper electroplating
baths devoid of chloride ions, comprising poly (alkylene-biguanide)
salts.
[0012] The present invention also relates to copper electroplating
processes implementing baths comprising poly (alkylene-biguanide)
salts.
[0013] The present invention further relates to smooth copper
electrodeposits and semiconductor interconnects obtained from baths
comprising poly (alkylene-biguanide) salts.
[0014] More specifically, the present invention has as a first
object, poly (alkylene-biguanide) salts used as additives in
neutral or acidic copper electroplating baths, characterized in
that said poly (alkylene-biguanide) salts are represented by the
following general formula:
R--NH--C(:NH)--NH--[(CH.sub.2).sub.p--NH--C(:NH)--NH--C(:NH)--NH--].sub.-
n--(CH.sub.2).sub.p--NH.sub.2, xAH (B)
wherein: [0015] p is an integer of at least 2 up to 12 [0016] n is
an integer of at least 2 up to 100 [0017] R is a group represented
by the formula: NC-- or H.sub.2N--C(:O) [0018] AH is an acid [0019]
x is comprised between (n+1) and 2(n+1) when AH is a monoacid, and
between (n+1)/2 and (n+1) when AH is a diacid.
[0020] Preferably, in the present invention, one implements poly
(alkylene-biguanide) salts having the general formula (B) wherein,
R-- represents NC--, p=4, 6, 8, 10 or 12, and n is comprised
between 5 and 50.
[0021] Most preferably, in the present invention one implements
poly (alkylene-biguanide) salts having the general formula (B)
wherein, R-- represents NC--, p=6, and n is comprised between 6 and
25.
[0022] It is possible to increase the number n of monomers in poly
(alkylene-biguanide) salts in a known way. For example, a solution
of the hydrochloride of an oligomer of general formula (B) in an
alcohol can be heated at a temperature from about 70.degree. C. to
150.degree. C. to produce an oligomer with a higher degree of
condensation by reaction between the amine and cyanamide
endings.
[0023] The preparation of poly (alkylene-biguanide) and of their
salts is well-known and consist, for example, in polycondensing an
.alpha., .omega. alkylene diamine hydrochloride with the sodium
salt of dicyandiamide.
[0024] The structure of poly (alkylene-biguanide) salts depends on
the pH of the solution in which they are dissolved. Their structure
comprises one proton per biguanide group G, i.e. GH' when the pH of
the solution is comprised between approximately 3 and 11, and two
protons, i.e. GH.sub.2.sup.2+ when the pH of the solution is lower
than approximately 3.
[0025] Preferably, poly (alkylene-biguanide) salts are added to the
copper electroplating baths, in the form of aqueous solutions.
Among the preferred salts, one can cite the salts of strong
oxygenated acids, such as sulfates, bisulfates, acidic phosphates
and sulfonates, such as methanesulfonate.
[0026] A poly (alkylene-biguanide) salt in aqueous solution can be
transformed into another salt by known anion exchange processes,
such as electrodialysis, or alternatively, by isolating the poly
(alkylene-biguanide) in the form of the free base and then forming
a solution of a new salt of said free base with a new acid.
[0027] Some poly (alkylene-biguanide) compounds are commercialized
as antiseptics in the form of neutral aqueous solutions of their
hydrochloride, such as poly (hexamethylene-biguanide) hydrochloride
or PHBG.
[0028] Compounds of general formula (B) can be used in copper
electroplating baths within the range of concentration of 10.sup.-7
mole/l to 10.sup.-3 mole/l, preferably of 5.times.10.sup.-7 mole/l
to 10.sup.-5 mole/l. They can be used preferably in association
with copper deposition accelerators taken among mercapto-alkyl
sulfonic acids and dialkyl disulfide disulfonic acids, or among
their salts, such as sodium mercaptopropyl sulfonate (MPS) or
bis-sulfopropyl disulfide (SPS).
[0029] Compounds of general formula (B) can be used in neutral or
acidic copper electroplating baths, the pH of which being
preferably comprised between 3 and 0. The operating temperature of
these baths is comprised between 0.degree. C. and 100.degree. C.,
preferably between 20.degree. C. and 80.degree. C.
[0030] The applicant discovered that compounds of general formula
(B) inhibited copper electrodeposition at very low concentrations,
within the range from, for example, 5.times.10.sup.-7 mole/l to
10.sup.-5 mole/l as shown by current vs potential curves
corresponding to copper electrodeposition in the presence of these
compounds in examples and Figures. This inhibiting property which
is subject of the present invention can be compared to those of
known inhibitors comprising polyethylene glycol and chloride ions
as shown in FIG. 3.
[0031] On the other hand, a molecule including only one biguanide
group, such as N,N dimethyl biguanide hydrochloride, did not show
inhibiting properties of the electrolytic deposition of copper in
baths containing copper sulfate and sulfuric acid, of pH comprised
between 0.5 to 4.
A second object of the present invention concerns copper
electroplating baths characterized in that they contain at least
one additive of general formula (B).
[0032] It was shown previously, that accelerators such as
3-mercatopropyl sulfonate (MPS) or di n-propyl disulfide 3,3'
disulfonate (bis-sulfopropyl disulfide or SPS) in a copper
electroplating bath were chemisorbed on a copper surface. For
example, in a bath containing copper sulfate, sulfuric acid, a
polyethylene glycol, chloride ions, 10.sup.-3 mole/l and SPS,
5.times.10.sup.-5 mole/l, it was shown that the copper surface
coverage by SPS was 5.4% at equilibrium at room temperature, and
that for SPS concentrations lower than 5.times.10.sup.-5 mole/l the
copper surface coverage by SPS at equilibrium was proportional to
the SPS concentration in solution. The time necessary to fill
concavities of submicronic size by electrolytic deposition of
copper is in general 10 to 30 seconds; this time is less than that
required by the accelerator chemisorbed on the copper surface to
reach an equilibrium with the solution, so that its surface
concentration on the copper surface increases transitionally during
the filling of a concavity of submicronic size because of the fast
reduction of the surface of that concavity. The accelerator, whose
concentration increases, then progressively displaces an inhibitor
of the polyethylene glycol+chloride ion type and the resulting
suppression of inhibition induces an increasingly fast filling
starting from the bottom of the concavity, which makes it possible
to carry out a complete and void-free filling. (T. P. Moffat et al.
The Electrochemical Society Interface, 2004, 46-52).
[0033] An inhibitor likely to be appropriate to fill grooves during
the formation of a smooth electrolytic deposit of copper, or
appropriate for filling concavities of submicronic size during the
manufacture of semiconductor copper interconnections, must thus
show the following properties and characteristics: [0034] Not be
notably displaced from the copper surface by an accelerator of the
MPS or SPS type at low concentration, for instance 10.sup.-5
mole/l. [0035] Be actually displaced from the copper surface by
this same accelerator at higher concentrations in solution, i.e.
multiplied by 4 to 10, i.e. for example at a concentration
comprised between 4.times.10.sup.-5 mole/l and 10.sup.-4 mole/l.
This increased concentration of the accelerator in solution is then
in equilibrium with a concentration of the accelerator on the
surface of copper similar to that which is reached transitionally
during the fast filling of grooves or during the fast filling of
concavities of submicronic size in the manufacture of semiconductor
copper interconnections. [0036] Properties to which is added the
requirement that there must be no chloride ions present.
[0037] The applicant showed that mercaptopropyl sulfonate (MPS) at
a concentration higher than 5.times.10.sup.-5 mole/l suppressed the
inhibition of the electrolytic deposition of copper induced by
compounds of general formula (B) at room temperature as well as at
70-75.degree. C.
[0038] More precisely, the applicant showed that mercaptopropyl
sulfonate (MPS) at a concentration of 10.sup.-5 mole/l did not
oppose to the inhibition of the electrolytic deposition of copper
induced by compounds of general formula (B), whereas at a
concentration of 5.times.10.sup.-5 mole/l to 10.sup.-4 mole/l, MPS
suppressed this inhibition.
[0039] It was shown for example that at room temperature, MPS at a
concentration of 10.sup.-5 mole/l in fact increased the inhibition
of the electrolytic deposition of copper induced by one of the
compounds of general formula (B), whereas at a concentration of
5.times.10.sup.-5 mole/l, MPS suppressed this inhibition.
[0040] Table 1, established from the data of example 4 represented
on FIG. 4, shows the overvoltage for the electrolytic deposition of
copper induced by one of the compounds of general formula (B) at a
concentration of 1.25.times.10.sup.-6 mole/l in the presence of
10.sup.-5 mole/l of MPS at room temperature and the decrease of
this overvoltage resulting from an increase in the concentration of
the accelerator MPS by a factor of 5, i.e from 10.sup.-5 mole/l to
5.times.10.sup.-5 mole/l.
TABLE-US-00001 TABLE 1 i (mA/cm.sup.2) 0 1 2 3 4 5 6 7 8 9 10 MPS =
10.sup.-5 M .eta.(mV) 0 -200 -223 -231 -233 -237 -239 -240 -241 --
-242 MPS = 5 10.sup.-5 M .eta.(mV) 0 -28 -62 -92 -110 -120 -128
-133 -138 -142 -147 .DELTA.(mV) 0 172 161 139 123 117 111 107 103
-- 95
[0041] On a copper surface, flat areas and concavities are
positioned electrically in parallel.
[0042] An electrolyte comprising for example the compound of
formula (B) of the example 4 and 10.sup.-5 mole/l of MPS should
give rise: [0043] To overvoltages for the electrolytic deposition
of copper on flat areas of the surface listed in the first line of
Table 1 according to the current density imposed. [0044] To
overvoltages for the electrolytic deposition of copper in
concavities of the surface listed in the first line of Table 1 at
the beginning of their filling, evolving to the overvoltages listed
in the second line of Table 1 at the end of their filling.
[0045] If the electrolyte is flowing fast enough on the surface so
that the diffusion of copper ions does not limit the deposition
process, the current density is initially identical over the whole
surface, including in the concavities. Table 1 shows that with an
electrolyte containing the compound of formula (B) of example 4 and
10.sup.-5 mole/l of MPS, the current distribution must change
during filling in favor of the bottom of concavities where the
overvoltage becomes lower because of the progressive increase of
the surface concentration of the accelerator.
[0046] In submicronic structures in the form of trenches, the
trench surface is in general 4 to 10 times larger than that of the
trench opening. With respect to the surface occupied by the trench
on the surface, the current densities listed in Table 1 would be
multiplied by 4 to 10 at the beginning of the filling.
[0047] Generally, the inhibition of copper electrodeposition by the
compounds of the invention is a partial inhibition, the magnitude
of which is conditioned by respective concentrations of the
compounds of general formula (B) and of accelerator of MPS or SPS
type, as well as by the potential of the copper electrode and by
temperature.
[0048] More precisely, a concentration of 10.sup.-5 mole/l of
mercaptopropyl sulfonate (MPS) did not suppress, or only slightly
suppressed, to the partial inhibition of the electrolytic
deposition of copper induced by one of the compounds of general
formula (B), whereas a concentration of 5.times.10.sup.-5 to
10.sup.-4 mole/l of MPS suppressed most of this inhibition. This
was observed by the applicant over a wide range of electrode
potential ranging from 0 to -140 mV/Ag/AgCl at 70-75.degree. C. For
a given concentration of an accelerator of the MPS or SPS type, for
example 10.sup.-5 mole/l, and a given concentration of one of the
compounds of general formula (B), ranging for example between
5.times.10.sup.-7 mole/l and 2.5.times.10.sup.-6 mole/l, one can
choose the deposition rate on the flat areas of the surface by
varying the current which makes the electrode potential change over
the range 0 to -140 mV/Ag/AgCl at 70-75.degree. C.; the cathode
potential vs electrolyte being all the more negative as the
intensity is higher.
[0049] In submicronic concavities of the surface, the increase of
the accelerator concentration must result in a progressive
suppression of the inhibition and in a deposition rate increase
with filling whatever the cathode potential in a range of 0 to -140
mV/Ag/AgCl.
[0050] Compounds of general formula (B) associated with an
accelerator of the mercaptopropyl sulfonate (MPS) or sulfopropyl
disulfide (SPS) type thus present the properties of conditional
inhibitors required to induce a process of accelerated filling
starting from the bottom of submicronic concavities by progressive
suppression of inhibition during filling.
[0051] Copper electroplating baths implementing compounds of
general formula (B) and an accelerator of the mercaptopropyl
sulfonate (MPS) or sulfopropyl disulfide (SPS) type thus present
the required properties to obtain smooth and bright copper deposits
or to fill submicronic concavities in the manufacture of
interconnections in micro-electronics.
[0052] Another object of this invention is to provide
electroplating baths able to wet the surface of copper
instantaneously.
[0053] The applicant showed that compounds of general formula (B)
are partially localized at the electrolyte-air interface and cover
instantaneously a significant part of the copper surface during the
immersion of a copper electrode in the electrolyte.
[0054] The injection of a compound of general formula (B) in the
electrolyte during the electrolytic deposition of copper at a
constant electrode potential resulted in a progressive inhibition
of this electrodeposition. The decrease of current vs time which
resulted from the arrival of the inhibitor of general formula (B)
on the electrode made it possible to measure precisely the rate at
which this inhibitor reached the surface of the electrode by
diffusion from the bulk of the electrolyte. For example, when a
compound of general formula (B), p=6; n=8; R.dbd.NC--;
AH.dbd.H.sub.2SO.sub.4 was injected, the necessary time to observe
a 50% decrease of the current was about 18 seconds at room
temperature for an amount of this inhibitor injected corresponding
to a concentration of 6.25.times.10.sup.-7 mole/l, whereas it was
about 8 seconds for an amount corresponding to a concentration of
1.25.times.10.sup.-6 mole/l, and about 2 seconds for an amount
corresponding to a concentration of 5.times.10.sup.-6 mole/l.
[0055] By using a small auxiliary copper wire and a potentiostat,
one can make the potential of a copper electrode equal to an
imposed potential vs a reference electrode as of the very first
instant of its contact with the electrolyte. By recording the
current every 0.005 second during the immersion of a copper
electrode in electrolytes, the applicant found that, for example,
when the electrolyte contained one of the inhibitors of general
formula (B) at a concentration of 5.times.10.sup.-6 mole/l, the
current was already not more than 61% of the value it had in the
absence of this inhibitor after only 0.02 second. This ratio was
55% after 0.05 second, 52% after 0.1 second and then decreased up
to 18% after 20 seconds.
[0056] An amount of the inhibitor of general formula (B),
sufficient to decrease the copper ions reduction rate by half was
thus present instantaneously on the copper surface during its
immersion in the electrolyte, followed by the slow diffusion of an
additional amount of this inhibitor. The amount of this inhibitor
which was instantaneously present on the copper surface was
therefore already present at the electrolyte-air interface, since
its diffusion from the bulk of the electrolyte would have required
approximately two seconds.
[0057] This result can be explained by the fact that compounds of
general formula (B) are amphiphilic oligomers and for this reason
present surface-active properties, i.e. these compounds present a
concentration excess at the interface of their solutions with air
compared to their concentration in the electrolyte.
[0058] During the immersion of a copper electrode in an aqueous
solution containing one of the compounds of general formula (B),
the initial electrolyte-air interface, which presented a
concentration excess of this compound compared to its concentration
in the electrolyte, was instantaneously transformed into an
electrolyte-copper interface, which consequently presented
approximately the same concentration of the compound of general
formula (B) which existed at the electrolyte-air interface
initially.
[0059] The discovery of the process of instantaneous transfer of
compounds of general formula (B) from the electrolyte-air interface
to the electrolyte-copper interface by the applicant is likely to
favor an instantaneous wetting of the copper surface by
electrolytes containing compounds of general formula (B).
[0060] The amphiphilic character of compounds of general formula
(B) can be modified according to known general rules which describe
the surface-active properties of amphiphilic compounds, in
particular by modifying the length of the hydrophobic chain
(CH.sub.2).sub.p or by modifying the concentration of mineral salts
and of the acid present in the electrolyte, as well as the
temperature.
[0061] The use of compounds of general formula (B) as inhibitors in
copper electroplating baths thus makes it possible to deliver
instantaneously a given and adjustable amount of these inhibitors
to the copper surface as soon as this surface is immersed in the
electrolyte. This instantaneous initial input of these inhibitors
to the copper surface is followed by an additional amount
controlled by their diffusion which can take from a few seconds to
a few tens of seconds according to the concentration of these
inhibitors in the electrolyte, the geometry of the concavity to be
filled and the temperature.
[0062] The present invention has for third object, copper
electroplating processes characterized in that they use baths
containing at least one additive of general formula (B).
[0063] The electrolytic deposition of copper from baths
implementing molecules of general formula (B) can be done by
application of a direct current with a current density ranging from
0.1 to 100 mA/cm.sup.2 at the cathode, preferably ranging from 1 to
60 mA/cm.sup.2.
[0064] In an embodiment preferred by the applicant, a voltage is
first applied between the anode, immersed beforehand in the
electrolyte, and the cathode, not yet in contact with the
electrolyte. Then, the cathode and the electrolyte are put in
contact.
[0065] The present invention has for fourth object, electrolytic
copper deposits characterized in that they were obtained by using
baths containing at least one additive of general formula (B).
[0066] The electrolytic copper deposits obtained, for example, from
baths containing poly (hexamethylene biguanide) sulfate have a
smooth and bright aspect and an old rose color.
[0067] The following examples illustrate the invention.
EXAMPLE 1
Preparation of a poly (hexamethylene-biguanide) sulfate
Solution
[0068] 100 grams of a 20% w/w commercial solution of poly
(hexamethylene biguanide) hydrochloride comprising mainly eight
biguanide groups per polymer molecule were placed in a flask and
concentrated under a 20 mm Hg vacuum at 50.degree. C. The resulting
residue was dissolved in absolute ethanol, then the ethanol was
evaporated under vacuum. This operation was repeated twice. The
residue was then dissolved in 100 ml of anhydrous methanol and the
resulting solution degassed with nitrogen. 20 grams of a 25% w/w
solution of sodium methylate in anhydrous methanol previously
degassed with nitrogen were then added dropwise to this methanolic
solution upon stirring under nitrogen. The resulting solution with
a fine suspension of sodium chloride was then left at 4.degree. C.
overnight, and then centrifuged to eliminate the sodium chloride. A
titration showed that the resulting methanolic solution contained
0.6 mole/l of a strong base corresponding to 0.066 mole/l of the
compound of formula (B) (p=6; n=8) as the free base.
[0069] 0.17 ml of the preceding methanolic solution were added to
10 ml of 0.005 mole/l aqueous sulfuric acid. Approximately one gram
of this solution was evaporated under vacuum to remove the
methanol, then the volume of the solution was adjusted to 10 ml
with distilled water.
[0070] This solution contained 0.001 mole/l of poly
(hexamethylene-biguanide) sulfate of formula (B) (p=6; n=8; x=4.5;
AH.dbd.H.sub.2SO.sub.4) that will be designated by the abbreviation
In1 the following examples.
EXAMPLE 2
Copper Electrodeposition Overvoltage Induced by In1
[0071] A 20 ml electrochemical cell with a magnetic stirrer was
used. It was equipped with an Ag/AgCl reference electrode, a
platinum grid as the counter-electrode, and the section of a 3.1 mm
diameter copper wire surrounded by Teflon as the working electrode.
The copper electroplating baths were degassed with nitrogen before
carrying out measurements.
[0072] The cell was connected to a potentiostat. The copper cathode
potential was scanned linearly over time towards negative
potentials at a scanning rate of 1.66 mV/second, and the resulting
current measured in milliamperes was recorded.
[0073] FIG. 1 shows the current vs potential curves obtained with
the three following baths: [0074] a05d: 0.25 mole/l SO.sub.4Cu
solution; pH adjusted to 0.5 with H.sub.2SO.sub.4 [0075] m05: idem
a05d+In1: 1.25.times.10.sup.-6 mole/l [0076] d05: idem a05d+In1:
5.times.10.sup.-6 mole/l [0077] Temperature: Room temperature
[0078] The copper electrodeposition overvoltage induced by compound
In1 from example 1 was about 80 mV for an In1 concentration of
1.25.times.10.sup.-6 mole/l, and about 140 mV for an In1
concentration of 5.times.10.sup.-6 mole/l.
EXAMPLE 3
Copper Electrodeposition Overvoltage Induced by poly (hexamethylene
biguanide) hydrochloride at Various pHs
[0079] By dilution of the 20% commercial solution of poly
(hexamethylene biguanide) hydrochloride comprising mainly eight
biguanide groups per polymer molecule, one prepared a 0.001 mole/l
solution of poly (hexamethylene biguanide) hydrochloride of formula
(B) (p=6; n=8; x=9; AH.dbd.HCl) designated hereafter by the
abbreviation In2.
[0080] The test protocol described in example 1 was repeated with
the four following baths: [0081] E3: 0.25 mole/l SO.sub.4Cu
solution; In2: 5.times.10.sup.-6 mole/l; pH adjusted to 3 with
H.sub.2SO.sub.4 [0082] E2: idem E3 but pH adjusted to 2 with
H.sub.2SO.sub.4 [0083] E1: idem E3 but pH adjusted to 1 with
H.sub.2SO.sub.4 [0084] E05: idem E3 but pH adjusted to 0.5 with
H.sub.2SO.sub.4 [0085] Temperature: Room temperature
[0086] FIG. 2 shows the current vs potential curves obtained.
[0087] The copper electrodeposition overvoltage induced by a
5.times.10.sup.-6 mole/l concentration of compound In2 was about
200 mV. It was almost independent of pH from pH=3 to pH=0.
[0088] The copper electrodeposition overvoltage induced by
compounds In1 and In2 can be compared with the overvoltage induced
in a known way by polyethylene glycol in the presence of chloride
ions. For comparison, the test protocol of example 2 was repeated
with the two following baths: [0089] og05: 0.25 mole/l SO.sub.4Cu
solution+PEG 3400: 88.times.10.sup.-6 mole/l+Cl.sup.-: 10.sup.-3
mole/l; pH=0.5 [0090] og05 mps: idem og05+sodium mercaptopropyl
sulfonate: 10.sup.-5 mole/l
[0091] FIG. 3 shows the corresponding current vs potential
curves.
EXAMPLE 4
Progressive Suppression of the Inhibiting Effect of In1 by
Mercaptopropyl Sulfonate (MPS)
[0092] The inhibition of copper electrodeposition by the compound
In1 can be suppressed by increasing concentrations of
mercaptopropyl sulfonate (MPS) as shown when the protocol of
example 2 was repeated with the three following baths:
Temperature: Room temperature m 05: 0.25 mole/l SO.sub.4Cu
solution; In1: 1.25.times.10.sup.-6 mole/l; pH adjusted to 0.5 with
H.sub.2SO.sub.4 o05: idem m05+MPS: 10.sup.-5 mole/l n05: idem
m05+MPS: 5.times.10.sup.-5 mole/l
[0093] FIG. 4 shows the corresponding current vs potential
curves.
[0094] A 10.sup.-5 mole/l concentration of MPS increased the copper
electrodeposition overvoltage induced by 1.25.times.10.sup.-6
mole/l of In1 whereas a concentration of 5.times.10.sup.-5 mole/l
of MPS suppressed this inhibition.
EXAMPLE 5
Progressive Suppression of the Inhibiting Effect of In1 by
Mercaptopropyl Sulfonate (MPS) at 70-75.degree. C.
[0095] Example 4 was repeated with the following baths:
Temperature: 71.degree. C.
[0096] tx05: 0.25 mole/l SO.sub.4Cu solution; pH adjusted to 0.5
with H.sub.2SO.sub.4 tx05b: idem tx05+1 nl: 5.times.10.sup.-6
mole/l tx05d: idem tx05b+MPS: 5.times.10.sup.-5 mole/l tx05e: idem
tx05b+MPS: 10.sup.-4 mole/l
[0097] FIG. 5 shows the corresponding current vs potential
curves.
[0098] The addition of 5.times.10.sup.-5 mole/l of MPS almost
suppressed the inhibition induced by In1. The experiment was
repeated with a double concentration of In1 with the three
following baths:
Temperature: 74.degree. C.
[0099] tb05: 0.25 mole/l SO.sub.4Cu solution; In1: 10.sup.-5 mol/l;
pH adjusted to 0.5 with H.sub.2SO.sub.4 tb05e: idem tb05+MPS:
5.times.10.sup.-5 mole/l tb05g: idem tb05+MPS: 10.sup.-4 mole/l
[0100] FIG. 6 shows the corresponding current vs potential curves.
A concentration of 5.times.10.sup.-5 mole/l of MPS suppressed the
inhibition induced by In1 at 74.degree. C.
EXAMPLE 6
Inhibiting Effect of In1 in the Presence of Mercaptopropyl
Sulfonate (MPS) at 70-75.degree. C.
Measurement by Chronoamperometry
[0101] Using the cell of Example 1, the current corresponding to
the electrodeposition of copper was recorded as a function of time
for a given and constant copper electrode potential with respect to
the reference electrode. The solution was stirred by a small
magnetic bar. After 70 to 80 seconds the inhibitor In1 was
introduced in the bath and the resulting inhibition was
recorded.
Temperature: 74.degree. C.
[0102] Imposed potential: E=-40 mV/Ag/AgCl Baths composition:
[0103] cata 14: 0.25 mole/l SO.sub.4Cu solution; MPS: 10.sup.-5
mole/l; pH adjusted to 0.5 with H.sub.2SO.sub.4 [0104] At 70
seconds: Injection of 6.25.times.10.sup.-7 mole/l of In1 [0105]
cata 10: 0.25 mole/l SO.sub.4Cu solution; MPS: 5.times.10.sup.-5
mole/l; pH adjusted to 0.5 with H.sub.2SO.sub.4 [0106] At 80
seconds: Injection of 6.25.times.10.sup.-7 mole/l of In1
[0107] FIG. 7 shows the corresponding current vs time curves. The
abscissa represents the time starting with the setting of the
potential which was established about two seconds after the copper
electrode immersion in the bath. The ordinate represents the
current in milliamperes.
[0108] At 74.degree. C. and for a copper electrode potential E=-40
mV/Ag/AgCl, a concentration of 10.sup.-5 mole/l of MPS did not
prevent the inhibition induced by a concentration of
6.25.times.10.sup.-7 mole/l of In1, whereas a concentration of
5.times.10.sup.-5 mole/l of MPS effectively prevented the
inhibition induced by a concentration of 6.25.times.10.sup.-7
mole/l of In1.
EXAMPLE 7
Inhibiting Effect of In1 as a Function of In1 and MPS
Concentrations
[0109] Example 6 conditions were applied to the following two
baths:
Temperature: 74.degree. C.
[0110] Imposed potential: E=-40 mV/Ag/AgCl [0111] cata 11: 0.25
mole/l SO.sub.4Cu solution; MPS: 5.times.10.sup.-5 mole/l; pH
adjusted to 0.5 with H.sub.2SO.sub.4 [0112] At 70 seconds:
Injection of 1.25.times.10.sup.-6 mole/l of In1 [0113] cata 23:
0.25 mole/l SO.sub.4Cu solution; MPS: 10.sup.-4 mole/l; pH adjusted
to 0.5 with H.sub.2SO.sub.4 [0114] At 70 seconds: Injection of
1.25.times.10.sup.-6 mole/l of In1
[0115] Curves corresponding to examples 6 and 7 have been combined
in FIG. 8.
[0116] At 74.degree. C. and for a copper electrode potential E=-40
mV/Ag/AgCl, a concentration of 5.times.10.sup.-5 mole/l of MPS did
not suppress the inhibition induced by a concentration of
1.25.times.10.sup.-6 mole/l of In1, but suppressed the inhibition
induced by 6.25.times.10.sup.-7 mole/l of In1. A concentration of
10.sup.-4 mole/l of MPS only partially suppressed the inhibition
induced by 1.25.times.10.sup.-6 mole/l of In1.
EXAMPLE 8
Influence of the Copper Cathode Potential in the Competition
Between Inhibitor In1 and Accelerator MPS
[0117] Experiments of examples 6 and 7 were repeated with a cathode
potential E=-140 mV/AgCl instead of E=-40 mV/Ag/AgCl
Temperature: 74.degree. C.
[0118] cata 13: 0.25 mole/l SO.sub.4Cu solution; MPS: 10.sup.-5
mole/l; pH adjusted to 0.5 with H.sub.2SO.sub.4 [0119] At 55
seconds: Injection of 6.25.times.10.sup.-7 mole/l of In1 [0120]
cata 12: 0.25 mole/l SO.sub.4Cu solution; MPS: 5.times.10.sup.-5
mole/l; pH adjusted to 0.5 with H.sub.2SO.sub.4 [0121] At 60
seconds: Injection of 6.25.times.10.sup.-7 mole/l of In1 [0122]
cata 19: 0.25 SO.sub.4Cu solution; MPS: 10.sup.-5 mole/l; pH
adjusted to 0.5 with H.sub.2SO.sub.4 [0123] At 70 seconds:
Injection of 1.25.times.10.sup.-6 mole/l of In1 [0124] cata 20:
0.25 mole/l SO.sub.4Cu solution; MPS: 10.sup.-4 mole/l; pH adjusted
to 0.5 with H.sub.2SO.sub.4 [0125] At 80 seconds: Injection of
1.25.times.10.sup.-6 mole/l of In1 [0126] cata 21: 0.25 mole/l
SO.sub.4Cu solution; MPS: 10.sup.-5 mole/l; pH adjusted to 0.5 with
H.sub.2SO.sub.4 [0127] At 75 seconds: Injection of
2.5.times.10.sup.-6 mole/l of In1 [0128] cata 22: 0.25 mole/l
SO.sub.4Cu solution; MPS: 10.sup.-4 mole/l; pH adjusted to 0.5 with
H.sub.2SO.sub.4 [0129] At 75 seconds: Injection of
2.5.times.10.sup.-6 mole/l of In1
[0130] FIGS. 9 and 10 show the curves corresponding to these six
experiments.
[0131] At 74.degree. C. and for a copper electrode potential E=-140
mV/Ag/AgCl, [0132] A concentration of 10.sup.-5 mole/l of MPS did
not suppress the inhibition induced by 6.25.times.10.sup.-7 mole/l
of In1, whereas a concentration of 5.times.10.sup.-5 mole/l of MPS
completely suppressed this inhibition (cata13/cata12) [0133] A
concentration of 10.sup.-5 mole/l of MPS did not suppress the
inhibition induced by 1.25.times.10.sup.-6 mole/l of In1, whereas a
concentration of 10.sup.-4 mole/l of MPS totally suppressed this
inhibition (cata19/cata20) contrary to what was observed for E=-40
mV/Ag/AgCl (cata23) [0134] However, a concentration of 10.sup.-4
mole/l of MPS only partially suppressed the inhibition induced by
2.5.times.10.sup.-6 mole/l of In1 (cata21/cata22)
[0135] This indicated that the displacement of the inhibitor In1 by
MPS was therefore easier at an electrode potential of E=-140 mV
than at a potential of E=-40 mV/Ag/AgCl
EXAMPLE 9
Influence of the Copper Cathode Potential on the Competition
Between the Inhibitor In1 and the Accelerator MPS
[0136] The influence of the copper cathode potential is illustrated
by the recording of the inhibition obtained with two identical
baths at different potentials.
[0137] Temperature: 70.degree. C. [0138] cata 11: 0.25 mole/l
SO.sub.4Cu solution; MPS: 5.times.10.sup.-5 mole/l; pH adjusted to
0.5 with H.sub.2SO.sub.4 Cathode potential: E=-40 mV/Ag/AgCl At 70
seconds: Injection of 1,25.times.10.sup.-6 mole/l of In1 [0139]
cata 8 0.25 mole/l SO.sub.4Cu solution; MPS: 5.times.10.sup.-5
mole/l; pH adjusted to 0.5 with H.sub.2SO.sub.4 Cathode potential:
E=-80 mV/Ag/AgCl At 70 seconds: Injection of 1.25.times.10.sup.-6
mole/l of In1
[0140] FIG. 11 shows the corresponding curves.
[0141] The inhibiting effect of In1 was observed at both
potentials, but the inhibition is less for a copper cathode
potential E=-80 mV than for a potential E=-40 mV/Ag/AgCl.
EXAMPLE 10
Inhibition of the Copper Deposition by In1 Followed by the
Suppression of this Inhibition by an Increased Concentration of
Accelerator MPS at 70-75.degree. C.
[0142] Starting from a bath containing 10.sup.-5 mole/l of MPS, an
inhibition was induced by addition of In1, then suppressed by
addition of an additional amount of MPS.
Temperature: 74.degree. C.
[0143] Imposed potential: E=-40 mV/Ag/AgCl [0144] cata 31: 0.25
mole/l SO.sub.4Cu solution; MPS: 10.sup.-5 mole/l; pH adjusted to
0.5 with H.sub.2SO.sub.4 [0145] At 40 seconds: Injection of
6.25.times.10.sup.-7 mole/l of In1 [0146] At 95 seconds: Injection
of 9.times.10.sup.-5 mole/l of MPS [0147] cata 32: 0.25 mole/l
SO.sub.4Cu solution; MPS: 10.sup.-5 mole/l; pH adjusted to 0.5 with
H.sub.2SO.sub.4 [0148] At 40 seconds: Injection of
1.25.times.10.sup.-6 mole/l of In1 [0149] At 95 seconds: Injection
of 9.times.10.sup.-5 mole/l of MPS
[0150] FIG. 12 shows the corresponding current vs time curves. A
concentration of 10.sup.-5 mole/l of MPS did not prevent the
inhibition induced by a concentration of 6.25.times.10.sup.-7
mole/l of In1 or of 1.25.times.10.sup.-6 mole/l of In1 at
74.degree. C. whereas a total concentration of MPS of 10.sup.-4
mole/l of MPS effectively suppressed the inhibition induced by a
concentration of 6.25.times.10.sup.-7 mole/l of In1 or of
1.25.times.10.sup.-5 mole/l of In1 at 74.degree. C.
EXAMPLE 11
Inhibition of the Copper Deposition by In1 Followed by the
Suppression of this Inhibition by an Increased Concentration of
Accelerator MPS at 70-75.degree. C. Diluted Copper Sulfate
Solution
[0151] The experiment of example 10 was repeated with solution
comprising 0.1 mole/l of copper sulfate at two different imposed
potentials:
Temperature: 74.degree. C.
[0152] cata 36: 0.1 mole/l SO.sub.4Cu solution; MPS: 10.sup.-5
mole/l; pH adjusted to 0.5 with H.sub.2SO.sub.4 Electrode
potential: E=0 V/Ag/AgCl [0153] At 60 seconds: Injection of
6.25.times.10.sup.-7 mole/l of In1 [0154] At 110 seconds: Injection
of 9.times.10.sup.-5 mole/l of MPS [0155] cata 40: 0.1 mole/l
SO.sub.4Cu solution; MPS: 10.sup.-5 mole/l; pH adjusted to 0.5 with
H.sub.2SO.sub.4 Electrode potential: E=-0.40 V/Ag/AgCl [0156] At 20
seconds: Injection of 6.25.times.10.sup.-7 mole/l of In1 [0157] At
70 seconds: Injection of 9.times.10.sup.-5 mole/l of MPS
[0158] FIG. 13 shows the corresponding current vs time curves.
Conclusions of example 10 also apply to solutions comprising
containing 0.1 mole/l of copper sulfate.
EXAMPLE 12
Chronoamperometric Recording of the Electrode Immersion in a Bath
Containing In1 and Comparison with the Case where In1 is Added
During the Deposition
[0159] The effect of In1 is compared according to whether it is
present during the electrode immersion or added during the copper
deposition.
Immersion of the electrode at a controlled potential: (cata41) In
order that the copper electrode be at the imposed potential as of
its first contact with the electrolyte, a small fine copper wire
was attached to the part of the electrode which will not be
immersed. The small copper wire was then immersed in the
electrolyte, and then the potentiostat was started in order to
impose a potential E=-40 mV/Ag/AgCl to the small copper wire
against the electrolyte. Then, the copper electrode was immersed
and was placed at a potential E=-40 mV/Ag/AgCl as of its first
contact, and the resulting current was recorded as a function of
time at the rate of one point every 0.005 second.
Temperature 71.degree. C.
[0160] Imposed potential: E=-40 mV/Ag/AgCl [0161] cata 30: 0.25
mole/l SO.sub.4Cu solution; MPS: 10.sup.-5 mole/l; pH adjusted to
0.5 with H.sub.2SO.sub.4 [0162] At 20 seconds: Injection of
6.25.times.10.sup.-7 mole/l of In1 [0163] At 95 seconds: Injection
of 9.times.10.sup.-5 mole/l of MPS [0164] cata 41: 0.25 mole/l
SO.sub.4Cu solution; MPS: 10.sup.-5 mole/l; In1:
6.25.times.10.sup.-7 mole/l pH adjusted to 0.5 with H.sub.2SO.sub.4
[0165] At 130 seconds: Injection of 9.times.10.sup.-5 mole/l of
MPS
[0166] FIG. 14 shows the corresponding curves.
[0167] After 20 seconds, In1 induced the same inhibition whatever
its mode of introduction in a bath containing 10.sup.-5 mole/l of
MPS, and this inhibition was suppressed in the same way by an
additional amount of MPS.
[0168] One observed that the initial current at the very first
instant of the immersion in the bath comprising In1 was only about
one half of the current observed during the immersion in a bath
which did not comprise In1. The increase of the current which was
multiplied by a factor of 1.8 during the first 4 to 5 seconds was
interpreted as resulting from a faster diffusion of MPS than of In1
to the electrode surface. This was followed by a decrease until a
constant current was reached, after about 15 seconds, resulting
from the equilibrium between MPS and In1 at the electrode
surface.
EXAMPLE 13
Kinetics of In1 Inhibition During the Immersion of a Copper
Electrode at Controlled Potential
[0169] The chronoamperometric recording procedure of the electrode
immersion in the bath described in example 12 was used.
Temperature: Room temperature Imposed potential (small wire, then
electrode): E=-100 mV/Ag/AgCl Recording of the resulting current vs
time at the rate of one point every 0.005 second.
Electrolytes:
[0170] a05b: 0.25 mole/l SO.sub.4Cu solution; pH adjusted to 0.5
with H.sub.2SO.sub.4 d05d: Idem a05b+5.times.10.sup.-5 mole/l of
In1 d05f2: Idem a05b+10.sup.-5 mole/l of In1
[0171] FIG. 15 shows the I(t) curves corresponding to a 20-second
recording.
[0172] FIG. 16 shows the I(t) curves corresponding to the first
second following the immersion.
Table 2 below gives the ratio between the current observed during
the immersion in the presence of In1: d05d or d05f2 and the current
observed in the absence of In1: a05b.
TABLE-US-00002 TABLE 2 T(seconds): 0.02 0.05 0.1 0.2 0.3 0.4 0.5
0.6 0.8 1.0 20 I d05d/I a05b: 0.618 0.55 0.52 0.503 0.5 0.494 0.487
0.483 0.468 0.467 0.181 I d05f2/I a05b: 0.476 0.407 0.388 0.36
0.344 0.344 0.326 0.319 0.302 0.302 0.087
[0173] The initial decrease of the current during about 0.2 second
in FIG. 16 corresponds to the establishment of the Cu.sup.2+
concentration gradient. Table 2 and FIGS. 15 and 16 show that 0.05
second after the immersion, the initial inhibition was 45% and 60%
for concentrations of 5.times.10.sup.-6 mole/l and 10.sup.-5 mole/l
of In1, respectively. Then, the inhibition increased slowly during
the next 20 seconds.
EXAMPLE 14
[0174] Conditions of example 2 were repeated except that, in the
bath composition In2 was replaced by N,N dimethyl biguanide
hydrochloride at a concentration of 10.sup.-4 mole/l. The
overvoltage for the copper electrodeposition was not notably
modified compared to the same bath devoid of inhibitor for all pHs
examined: pH=3, 2, 1 and 0.5 The same conclusion was reached with a
bath containing 2.times.10.sup.-4 mole/l of N,N dimethyl biguanide
hydrochloride.
EXAMPLE 15
Copper Electrolytic Deposition from Baths Containing In1
[0175] Two identical copper sheets were used as cathode and anode,
each face of the sheets had an area of 1.45 cm.sup.2. In1 was added
at a concentration of 4.8 10.sup.-6 mole/l in an electrolyte
comprising 0.5 mole/l of copper sulfate and 1 mole/l of sulfuric
acid and a 30 mA electrolytic current was applied during 15 minutes
at room temperature. The copper electrolytic deposit observed with
a microscope was smooth, bright and of old rose color.
EXAMPLE 16
[0176] The experiment described in example 15 was repeated after
adding 2.1.times.10.sup.-5 mole/l of sodium 3-mercaptopropyl
sulfonate to the electrolyte. The copper deposit obtained, observed
with a microscope, was smooth, mid-bright and of old rose
color.
* * * * *