Note: Descriptions are shown in the official language in which they were submitted.
COPPER ELECTRODEPOSITION WITH SUBSTITUTED
PHTHALOCYANINE AND AN APO SAFRAMINE
ckground of the Invention
The present invention broadly relates to an aqueous
electrolyte ccmposition and process for electrodepositing cop~r
on a conductive substrate, and more particularly, to an improved
aqueous acidic copper platiny bath containing a r.ovel ccmbination
of brightening agents to provide a cop~er plate which is ductile,
level and bright particularlv in the low current densi.y recess
areas.
A variety of aqueous electrolyte CGmpOSitions ar.d
processes have heretofore been used or proposed for use for
electrodepositing bright, level ductile copper depositsO Typical
of such prior art cc~positions and processes are those describe~
in U.S. Patent Nos. 2,707,166; 2,707,167; 2,738,318; 2,882,209;
3,267,010; 3,328,273; 3,770,598; 4,110,176 ar~ 4,2l2,335. T~
accordance with the teachings oE ~rited St2tes Patent ~o.
4,272,335 an improved aqueous acidic copper elect~olyte is
provided which contains a substituted phthalocy~nir.e radical as a
brightening agent ~hich in accordance with the preferred
disclosure further incorporates supplemental secondary
brightening agents such as polysulfides, sulfides and/or
polyether ccm¢our.ds. While the aqueous acidic electrolyte as
described in the afore~entioned United States patent provides for
improvements in the briyhtness, leveling and cuc.ility of copper
platings, under certain operating parameters and ccmposition
variations, less than optimum brightness of the copper plate has
been obtained in the low current density recess areas of articles
being plated.
On the other hand, when an apo safranine brightening
ccmpound has been employed alone or in further cGmbination ~"ith
supplemental brightening agents such as polysulfides, organic
sulfides and/or polyether ccmpounds, unsatisfactory brightness
and leveling of the deposit has been obtained under certain
conditions in low current density areas. An increase in the
concentration of the apo safranine brightening co~pound to
overc~me the low current density problem resulted in the
formation of dark striations in the low current density areas
producing an unacceptable deposit.
mere, accordingly, has been a need for a still further
improvement in aqueous acidic copper electrolytes to provide
exceptional brightness of copper deposits in the low current
density recess areas of articles being plated which can be
consistently attained over a broad range of composi-tion and
processing conditions. The aqueous acidic electro]yte of the
present invention incorporates a selected combination of
brightening agents providing for a synergistic brightening
effect, particularly in such low current density recess areas
over a relatively broad range of concentrations and bath operating
conditions.
Summary of the Invention
The benefits and advantages of the present inv~ntion
are achieved by an electrolyte CQmposition and process for
eleetrod~positing copper from an aqueous acidic plating bath
containing a brightening.amount of a ccmbination of compounds
including a bath soluble substituted phthalocyanine c~?ound and
an apo safran m e compound present in cont.rolled amounts. ~ore
particularly, the aqueous acidic electrolyte is preferably of the
copper sulfate or fluoroborate type and incorporates copper in an
amount sufficient to electrodeposit CQpper~ and a brightening
amount of the substituted phthalocyanine eompound represented by
the formula:
Pc-~X)n
~herein:
Pe is a phthalocyanine radical;
X is -SO2NR2~-s03M~-cH2gc(NR2)2
R is H, alkyl containing 1-6 carbon atoms, aryl
containing 6 carbon atcms, aralkyl containing
6 carbon atcms in the aryl portion and 1 to
6 carbon atQms in the aLkyl portion,
- heterocyclic containing 2 to 5 carbon atoms
and at least 1 nitrogen, oxygen, sulfur or
phosphorus atom, and aLkyl, aryl, araIkyl and
heterocyclie, as defined abcve, containing
1 to 5 amino, hydroxy, sulfonic or phosphonic
groups;
:,~
- \
n is 1-6;
Y is halogen or alkyl sulfate containing 1 to 4
carbon atoms in the alkyl portion; and
M is H, Li, Na, K or Mg,
in further ccmbination with a ccmpound represented by Formula A.
FORMULA A
(R'.)~N .
X' ~
¢3
Wherein the R' are the same or differen-t and c~amprise
-CH3, -C2H5 or -C3H7, and X' is an anion selected
from the group consisting of chloride, bromide, iodide,
fluoride, sulfate, bisulfate and nitrate.
,~ ,
~,.
~5~
The phthalocyanine brightering agent may be ~etal-free
or may contain a stable divalent or trivalent metal, such as
cobalt, nickel, chromium, iron, or copper, as well as nuxtures of
these of which copper constitutes the preferred ~etal.
Phthalocyanine brightening agents suitable for use in the
practice of the present invention have a bath solubility of at
least about 0.1 milligrams per liter (mg/1).
In accordance with a preferred practice of the present
inventiOn~ the phthalocyanine and apo safranine
brightening agerts are supplemented by the addition of secor.dary
brightening agents including aliphatic polysulfides, organic
sulfides and/or polyether compounds to further enhance the
brightness and physical properties of the copper deposit.
In accordance with the process aspects of the presen~
invention, the aqueous acidic electroplating bath can be operated
at temperatures ranging from about 15 up to about 50C and at
current densities ranging from about 0.5 to about 400 an~eres per
square foot (ASF).
Additional benefits and advantages of the present
invention will become apparent upon a reading of the Description
of the Preferred ~mbcd1ments taken in conjunction with the
accompanying examples.
,~
Description of the Preferred Embodiments
In accordance with the practice of the process of tne
present invention, an aqueous acidic electrolyte is pr~ided
which may be of the sulfate type typically containing about 180
to about 250 g/l of copper sulfa-te as the pentahydrate and about
30 to about 80 g/l of sulfuric acid. Alternatively, fluoroborate
baths can be prepared typically containing from about 200 to
about 600 g/l of copper fluoroborate and up to about 60 g/l of
fluoboric acid. It is also contemplated that copper nitrate salts
can be employed in approximately equivalent proportions for copper
sulfate and the electrolyte can be acidified employing equivalent
~mounts of phosphoric acid, nitric acid or sulfuric acid. In
accordance with the preferred practice of the present invention,
sulfate-type copper baths are employed.
The aqueous electroly-te may further incorporate halide
ions such as chloride and/or bromide ions in an amount up to
about 0.5 g/l.
~ he exceptional brightening obtained in the low current
density recess areas is achieved by employing a synergistic
ccmbination of the substituted phthalocyanine brightening
agent and the apo safranine brightening agent in controlled
conoentrations and proportions, preferably in further ccmbination
with supplemental organic brightening agents. The substituted
phthalocyanine ccmpound which may be metal-free or which may
contain a stable divalent or trivalent metal bound by
coordination of the lsoindole nitrogen atoms of the molecule,
which metal is selected from the group consisting of cobalt,
nickel, chrcmium, iron or copper, as well as mixtures of the
foregoing of which copper is the more typical and preferred
metal. Such phthalocyanine compounds suitable for use in the
practice of the present process are those having a bath
solubility of at least about 0.1 mg/l and correspond to the
structural formula:
~s~
t~)b
~9 '
1. 1
( X ) ~ N ~ Z ~ ( X b
N ~
~\~
(X) 3b
l~herein:
X is as has ~een heretofore defined;
Z is Ni, Co, Cr, Fe or Cu;
a is 0-1; and
- b is 0-2, provided however that the total
number of X substituents is 1-6.
Suhstituted phthalocyanine compounds suitable for use
in the practioe of the present invention further include those as
described in United States Patent No. 4,272,335. A particularly
preferred ph~halocyanine cc~pound ccmprises Alcian Blue.
3S~
The c~nbil~ed brightening agents corresponding to
Forrnula A and the substituted phthalocyanine brightening
agent are employed at a bath concentration of frcm about 0.0005
g/l up to about 1 g/l with concentrations of about 0.002 g/l to
about 0.01 g/l being preferred. The substituted phthalocyanirle
brightening agent should ccmprise frorn about 35 up to
about 80 percent by weight of the ccmbined weight of the t~
brightening agents ernployed. A particularly satisfaetory
ccrnbination ccmprises ernploying Methie Turquoise as the
substituted phthalcxcyanine brightening agent at a concentration
of 3 rng/l in cornbination with an apo safranine brightening agent
represented by Formula A in which R'cc~rises ethyl also present
at a concentra-tion of 3 rng/l.
In addition to the substituted phthalocyanine and apo
safranine brightening agents, it has been found advantageous in
accordance with the practi oe of the present invention to
incorporate at least one additional supplemental brighténing
agent of the types known in the art to further enhance the
brightness, ductility and leveling of the electrodeposited
copper. Included among such supplernental brightening agents are
polyether compounds and organic sulfide and disulfide ccmpounds.
The preferred organie polyether ccmpounds are bath
soluble and c~npatible polyethers containing at least 4 ether
oxygen atoms and having an average leeular weight ranging from
about 180 up to 1,000,000. Partieularly satisfaetory results are
obtained with polypropylene and polyethylene glycols ineluding
mixtures of th~ foreyoing of an avera~e molecular weight of about
600 to about 6,000, and aIkoxylated arcm~tic alcohols ha~ing a
molecular weight ranging from about 300 to 2500. Ex~mplary of
such preferred polyether bri~htening compounds which can
satisfactorily be en~loyed are polyethylene glycols of an average
molecular weight of from about 400 to about 1,000,000;
ethoxylated naphthols containing 5 to 45 mols ethylene oxide
groups; pr~poxylated naphthols containing 5 to 15 mols of
propylene oxide groups; ethoxylated nonyl phenol containing 5 to
30 nmols ethylene oxide groups; propylene glycols of an average
molecular weigh-t of about 350 to about 1,000; block polymers of
polyoxyethylene and polyoxypropylene glycols of an average
mole~ular weight of abou-t 350 to 250,000; ethoxylated phenols
containing 5 to 100 mols of ethylene oxide groups; propoxylated
phenols containing 5 to 15 mols of propylene oxide groups, and
ethylene diamune block polymers having a molecular weight of
about 1600 -to about 30,000. Additional polyether compounds
suitable for use in the practice of the present process are those
disclosed in United States Patent No. 4,272,335.
me polyether brightening compounds are employed in a
range of about 0.001 up to about 5 g/l with the lower
concentrations generally being used with the higher molecular
weight polyethers.
Organic sulfide brightening compounds which can be
satisfactorily employed in the practice of the present process
include the various sulfonate organic sulfide compounds as
described in United Sta-tes PaTENT ~o. 3,267,010, and particularly
Table I thereof; organic sulfur compounds as disclosed in United
States Patent No. 4,181,582 and particularly Table III thereof;
and the organic polysulfide compounds as disclosed in United States
Patent No. 3,328,273 and particularly Table I thereof. The
organic sulfide compcunds containing sulfonic or phosphonic
groups may also contain various substituent groups, such as
methyl, chloro, bromo, methoxy, ethoxy, carboxy or hydroxy, on
the m~lecules, especially on the aromatic and heterocyclic
sulfide-sulfonic or phosphonic acids. Such ccm~ounds may be used
as the free acids r the alkali metal salts, organic amune salts,
or the like.
Cther suitable organic divalent sulfur cc~ounds which
can be satisfactorily used include HO3P-(CH2)3-S-S-(CH2)3-PO3H,
as well as merca~tans, thiocarbHmates, thiolcarbamates,
thioxanthates, and thiocarbonates which contain at least one
sulfonic or phosphonic group.
A particularly preferred group of organic divalent
sulfur compounds as described in U.S. Patent No. 3,328,273 are
the organic polysulfide compounds of the formula
XRl~(S)nR2S3H or ~ ~~S)n~2P3H wherein ~ and
~ are the same or different aIkylene group containing from
,~
about 1 to 6 cæbon atoms, X is hydrogen, SO3H or PO3H and n
is a number frcm about 2 to 5. mese organic divalent sulfur
compounds are aliphatic polysulfides wherein at least t~,~
divalent sulfur atoms are vicinal and wherein the molecule has
one or two terminal sulfonic or phosphonic acid groups. The
alkylene portion of the molecule may be substituted with groups
such as methyl, ethyl, chloro, bromo, ethoxy, hydroxy, and the
like. mese ccmpounds may be added as the free acids or as the
aIkali metal or amine salts.
me organic sulfide brightening compound or mixture of
compounds are present in the electrolyte within a range of about
0.0005 to about 1 g/l.
In accordance with the process aspects of the present
nvention, an aqueous acidic copper electrolyte of the foregoing
composition is employed in which an electrically conductive
substrate is immersed and is cathodically charged for a period of
time to deposit the desired thickness of copper thereon. During
the electroplating operation, the bath is controlled at a
temperature of frcm about 15 up to about 50C and at cathode
current densities ranging from as low as about 0.5 to as high as
about 400 ASF, preferably from about 10 to about 100 ASF.
Particularly satisfactory results are obtained at bath
temperatures of about 20 to about 36C at current densities of
about 10 to about 50 ASF.
~5~
In order to further illustrate the present in~Jention,
the follc~ing typical examples are provided. It will be
appreciated that the examples are provided for illustrative
purposes and are not intended to be limiting of the scope of the
present invention as herein described and as set forth in the
subjoined claims.
EX~LE 1
An aqueous acidic copper electrolyte is prepared
containing akout 165 to about 225 g/l copper sulfate
pentahydrate, about 42 to about 75 g/l sulfuric acid and about
O.04 to about 0.1 g/l chloride ions. Tb the foregoing aqueous
solution, 3 mg/l of Methic Ttrq~loise comprising the
phthalocyanine brightening agent is added along with 3 mg/l of
diethyl apo safranine. As supplemental brightening agents, the
bath further contains 50 mg/l of polypropylene glycol of an
average molecular weight of 700 and 20 mg/l of Bis (3-sulfopropyl
disulfide disodium salt).
An operation of the bath at a current density of from
about 0.5 to about 100 ASF at a temperature of from about 70 to
about 80F produced highly leveled, fine-grained copper desposits
with no physical defects.
EXPMæLE 2
An aqueous acidic copper electrolyte is prepared
containing about 165 to about 225 g/l copper sulfate
pentahydrate, about 42 to about 75 g/l sulfuric acid and about
14
s~
0.04 to about 0.1 g/1 chloride ions. To the foregoing aqueous
solution, 3 mg/l of Methic Turquoise cGmprising the
phthalocyanine brightening agent is added along with 60 mg/1 of a
block polymer of ethylene propylene oxide (mol wt. 3000), 20 mg/l
of Bis (3-sulfopropyl disulfide disodium salt) and 1.5 mg/l of
the reaction product of polyethylene imine (mol wt. 600) with
benzyl chloride as supplemental brightening agents.
The operation of the bath at a temperature of from
about 70 to about 80F and at current densities of about 20 to
about 80 ASF produces bright, leveled copper deposits. The
further addition of 3 mg/l of diethyl apo safranine to the
electrolyte results in a dramatic improvement in the leveling
characteristics of the deposit and also substantially improves
the brightness in the low current density areas of test panels
employing ~he same plating parameters.
EXAMæLE 3
An aqueous acidic copper electrolyte is prepared
containing about 165 to about 225 g/1 copper sulfate
pentahydrate, about 42 to about 75 g/l sulfuric acid and about
0.04 to about 0.1 g/l chloride ions. To the foregoing aqueous
solution, 2 mg/l of diethyl apo safranine is added in further
ccmbination with supplemental brightening agents ccmprising 20
mg/l Bis (3-sulfcpropyl disulfide disodium salt), 200 mg~l
polyethylene oxide (mol wt. 6000) and 1.5 mg/1 of a reaction
product of polyethyleneimine (mol wt. 600) reacted with ben~yl
chloride.
The foregoing electrolyte produces a bright, leveled
copper deposit when plated on a J-shaped test panel at an average
current density of about 50 ASF for a period of 15 minutes but
t~e deposit is striated in the low curxent density area. The
addition of 3 mg/l of Methic Turquoise ccmprising the substituted
phthalocyanine radical brightening agent to the electxolyte
results in the elimlnation of the striations in the lcw current
density area of the J-type test panel plated under the same
conditions without any loss of brightness and leveling of the
copper deposit.
While it will be apparent that the preferred
embodiments of the invention disclosed are well calculated to
fulfill the objects above stated, it will be appreciated that the
invention is susceptible to modification, variation and change
without departing frcm the proper scope or fair meaning of the
subjoined claims.
16
