U.S. patent application number 10/778630 was filed with the patent office on 2004-11-11 for electroplating composition.
This patent application is currently assigned to Rohm and Haas Electronic Materials, L.L.C. Invention is credited to Binstead, Robert A., Mikkola, Robert D., Wang, Deyan.
Application Number | 20040222104 10/778630 |
Document ID | / |
Family ID | 33032663 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040222104 |
Kind Code |
A1 |
Wang, Deyan ; et
al. |
November 11, 2004 |
Electroplating composition
Abstract
Compositions useful for electrodepositing a metal are provided.
These compositions contain one or more metal salts, electrolyte,
two or more brightener compounds and optionally one or more of
leveler compounds and wetting agents. Also provided are methods of
depositing a metal layer using these compositions.
Inventors: |
Wang, Deyan; (Hudson,
MA) ; Mikkola, Robert D.; (Grafton, MA) ;
Binstead, Robert A.; (Marlborough, MA) |
Correspondence
Address: |
EDWARDS & ANGELL, LLP
P.O. Box 55874
Boston
MA
02205
US
|
Assignee: |
Rohm and Haas Electronic Materials,
L.L.C
Marlborough
MA
|
Family ID: |
33032663 |
Appl. No.: |
10/778630 |
Filed: |
February 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60447411 |
Feb 19, 2003 |
|
|
|
60450283 |
Feb 27, 2003 |
|
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Current U.S.
Class: |
205/291 ;
106/1.13; 257/E21.175 |
Current CPC
Class: |
H01L 21/2885 20130101;
C25D 3/02 20130101; C25D 3/38 20130101; H05K 3/423 20130101 |
Class at
Publication: |
205/291 ;
106/001.13 |
International
Class: |
C25D 003/38 |
Claims
What is claimed is:
1. A composition comprising one or more sources of metal ions, an
electrolyte, and two or more brightening agents, wherein at least
one brightening agent is an organosulfonic acid compound and at
least one brightening agent is a dithiocarbonate-containing
compound.
2. The composition of claim 1 wherein the metal is copper.
3. The composition of claim 1 wherein the organosulfonic acid
compound and the dithiocarbonate-containing compound are present in
a weight ratio of .gtoreq.3:1.
4. A method of depositing a metal layer on a substrate comprising
the steps of contacting the substrate with the composition of claim
1 and applying sufficient current density for a period of time to
deposit the layer of metal.
5. A method of manufacturing an electronic device comprising the
step of depositing a layer of metal on a substrate by contacting
the substrate with the composition of claim 1 and applying
sufficient current density for a period of time to deposit the
layer of metal.
6. The method of claim 5 wherein the electronic device is an
integrated circuit.
7. The method of claim 5 wherein the metal is copper.
8. The method of claim 5 wherein the substrate has one or more
apertures having a size of .ltoreq.2 .mu.m.
9. A method of depositing a copper layer on a substrate having one
or more apertures having a size of .ltoreq.2 .mu.m, comprising the
steps of contacting the substrate with an electroplating
composition comprising one or more sources of metal ions, an
electrolyte, and two or more brightening agents, and applying
sufficient current density for a period of time to deposit the
layer of copper, wherein the copper layer has an arithmetic surface
roughness of .ltoreq.5 nm, as determined by atomic force
microscopy.
10. The method of claim 9 wherein at least one brightening agent is
an organosulfonic acid compound and at least one brightening agent
is a dithiocarbonate-containing compound.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to the field of
electroplating. In particular, the present invention relates to the
field of electrodeposition of copper on substrates.
[0002] Methods for electroplating articles with metal coatings
generally involve passing a current between two electrodes in a
plating solution where one of the electrodes is the article to be
plated. A typical acid copper plating solution comprises dissolved
copper (usually copper sulfate), an acid electrolyte such as
sulfuric acid in an amount sufficient to impart conductivity to the
bath, and proprietary organic additives to improve the uniformity
of the plating and the quality of the metal deposit. Such additives
include brighteners, levelers, surfactants, suppressors, and the
like.
[0003] Electrolytic copper plating solutions are used for many
industrial applications. For example, they are used in the
automotive industry to deposit base layers for subsequently applied
decorative and corrosion protective coatings. They are also used in
the electronics industry, particularly for the fabrication of
printed circuit boards and semiconductors. For circuit board
fabrication, copper is electroplated over selected portions of the
surface of a printed circuit board and onto the walls of through
holes passing between the surfaces of the circuit board base
material, and to fill vias passing from one surface of the printed
circuit board in an interior layer of the board. The walls of a
through hole or via are first metallized to provide conductivity
between the board's circuit layers. For semiconductor fabrication,
copper is electroplated over the surface of a wafer containing a
variety of features such as vias, trenches or a combination
thereof. The vias and trenches are metallized to provide
conductivity between various layers of the semiconductor
device.
[0004] Plating a substrate having irregular topography can pose
particular difficulties. During electroplating a voltage drop
variation typically will exist along an irregular surface which can
result in an uneven metal deposit. Plating irregularities are
exacerbated where the voltage drop variation is relatively extreme,
i.e., where the surface irregularity is substantial. As a result, a
thicker metal deposit, termed overplating, is observed over such
surface irregularities. Consequently, high quality metal plating
(e.g., a metal layer or plate of substantially uniform thickness)
is frequently a challenging step in the manufacture of electronic
devices.
[0005] It is known in certain areas of plating that the use of
brighteners and/or levelers in the electroplating bath can be
crucial in achieving a uniform metal deposit on a substrate
surface. Conventional copper plating baths typically contain
bis-(sodium sulfopropyl)-disulfide as a brightener. This compound
is generally considered the best in its class for super-conformal
filling of sub-micron vias and trenches in the manufacture of
electronic devices. However, as feature sizes have shrunk, there is
a concern that such brighteners lead to increased surface roughness
during the initial plating stages (ca. .ltoreq.1000-2000 .ANG. of
deposit). Such surface roughness can result in micro-void formation
during the plating of sub-micron sized features such as trenches
and vias.
[0006] Leveling agents are typically in copper plating baths to
provide substantially uniform, or level, copper layers. Such
leveling agents have been proposed in copper plating baths used to
deposit copper in apertures during integrated circuit manufacture.
For example, U.S. Pat. No. 6,444,110 (Barstad et al.) discloses a
method of depositing copper in apertures during integrated circuit
manufacture by electroplating copper from a copper plating bath
containing at least one soluble copper salt, an electrolyte, one or
more brightener compounds having a molecular weight of 1000 or less
and being present in a concentration of at least about 1.5 mg/L,
and preferably one or more leveling agents. The use of leveling
agents in copper plating baths used for semiconductor manufacture
is known to provide poor fill performance of small apertures, such
as vias and trenches. For example, leveling agents that have been
used in semiconductor manufacture form substantially planar
surfaces, however, they also form a substantial number of voids in
the vias or trenches. Such voids can cause electrical open circuits
in the semiconductor. As the geometries of electronic devices get
smaller, the difficulty of plating a uniform copper layer while
completely filling the smaller features becomes more difficult.
[0007] There is a need in the art for copper plating baths that do
not form voids, show reduced surface roughness and are useful for
plating substrates having different sized features. Such copper
plating baths would be particularly useful in printed circuit board
manufacture and in integrated circuit manufacture.
SUMMARY OF THE INVENTION
[0008] The present invention provides a composition including one
or more sources of metal ions, an electrolyte, and two or more
brightening agents, wherein at least one brightening agent is an
organosulfonic acid compound and at least one brightening agent is
a dithiocarbonate-containi- ng compound.
[0009] Also provided by the present invention is a method of
manufacturing an electronic device including the step of depositing
a layer of metal on the substrate by contacting the substrate with
the composition described above and applying sufficient current
density for a period of time to deposit the layer of metal.
[0010] In particular, the present invention provides a method of
manufacturing an integrated circuit including one or more apertures
having a size of .ltoreq.2 .mu.m, including the step of contacting
a substrate with the composition described above and applying
sufficient current density for a period of time sufficient to
deposit a layer of metal.
[0011] A method of depositing a metal layer on a substrate
comprising the steps of contacting the substrate with the
composition of claim 1 and applying sufficient current density for
a period of time to deposit the layer of metal is further
provided.
BRIEF DESCRIPTION OF THE DRAWING
[0012] FIG. 1 is an atomic force micrograph ("AFM") of a 1000 .ANG.
thick copper layer deposited using a conventional copper plating
bath.
[0013] FIG. 2 is an AFM of a 1000 .ANG. thick copper layer
deposited using a copper plating bath of the invention.
[0014] FIGS. 3A and 3B are scanning electron micrographs ("SEMs")
of a cross-section of a 0.5 .mu.m trench on a wafer plated with a
500 .ANG. and 1000 .ANG., respectively, thick copper layer using a
conventional copper plating bath.
[0015] FIGS. 4A and 4B are SEMs of a cross-section of a 0.5 .mu.m
trench on a wafer plated with a 500 .ANG. and 1000 .ANG.,
respectively, thick copper layer using a copper plating bath of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] As used throughout this specification, the following
abbreviations shall have the following meanings, unless the context
clearly indicates otherwise: A=amperes; mA/cm.sup.2=milliamperes
per square centimeter; .degree. C.=degrees Centigrade; g=gram;
mg=milligram; .ANG.=angstrom; L=liter, ppm=parts per million;
ppb=parts per billion; .mu.m=micron=micrometer; cm=centimeter;
RPM=revolutions per minute; DI=deionized; and mL=milliliter. All
amounts are percent by weight and all ratios are by weight, unless
otherwise noted. All numerical ranges are inclusive and combinable
in any order, except where it is clear that such numerical ranges
are constrained to add up to 100%.
[0017] As used throughout the specification, "feature" refers to
the geometries on a substrate, such as, but not limited to,
trenches and vias. "Apertures" refer to recessed features, such as
vias and trenches. The term "small features" refers to features
that are one micron or smaller in size. "Very small features"
refers to features that are one-half micron or smaller in size.
Likewise, "small apertures" refer to apertures that are one micron
or smaller (.ltoreq.1 .mu.m) in size and "very small apertures"
refer to apertures that are one-half micron or smaller (.ltoreq.0.5
.mu.m) in size. As used throughout this specification, the term
"plating" refers to metal electroplating, unless the context
clearly indicates otherwise. "Deposition" and "plating" are used
interchangeably throughout this specification. "Halide" refers to
fluoride, chloride, bromide and iodide. Likewise, "halo" refers to
fluoro, chloro, bromo and iodo. The term "alkyl" includes linear,
branched and cyclic alkyl. "Brightener" refers to an organic
additive that increases the plating rate of the electroplating
bath. The terms "brightener," "brightening agent" and "accelerator"
are used interchangeably throughout this specification.
"Suppressors", which are also known as "carriers", refer to organic
additives that suppresses the plating rate of a metal during
electroplating. "Leveler" refers to an organic compound that is
capable of providing a substantially planar metal layer. The terms
"levelers" and "leveling agents" are used interchangeably
throughout this specification.
[0018] The present invention provides a composition including one
or more sources of metal ions, an electrolyte, and two or more
brightening agents, wherein at least one brightening agent is an
organosulfonic acid compound and at least one brightening agent is
a dithiocarbonate-containi- ng compound. Such composition is
suitable for electroplating a layer of metal, particularly copper,
on a conductive substrate.
[0019] Any substrate upon which a metal, particularly copper, can
be electroplated is useful in the present invention. Such
substrates include, but are not limited to, printed wiring boards,
integrated circuits, semiconductor packages, lead frames,
interconnects, and the like. Particularly useful substrates are any
used in the manufacture of electronic devices, such as integrated
circuits, and more particularly wafers used in dual damascene
manufacturing processes. Such substrates typically contain a number
of features, particularly apertures, having a variety of sizes. For
example, integrated circuit substrates may contain apertures
ranging from 100 .mu.m to as little as 50 nm or 25 nm or less. In
one embodiment, it is preferred that the substrate contains small
apertures, and preferably very small apertures. Such small
apertures may be present in the substrate along with larger
apertures, such as 100 .mu.m apertures. For example, an integrated
circuit substrate may contain one or more 0.2 .mu.m as well as one
or more 2 .mu.m, or even larger, apertures. It is further preferred
that the apertures that are filled by copper deposited from the
instant plating baths are free of voids. It will be appreciated by
those skilled in the art that other substrates to be plated, such
as lead frames and printed wiring boards, may have larger features
or smaller features or no features at all. The present invention is
particularly suitable for filling apertures of varying aspect
ratios, such as low aspect ratio apertures and high aspect ratio
apertures. By "low aspect ratio" is meant an aspect ratio of from
0.1:1 to 4:1. The term "high aspect ratio" refers to aspect ratios
of 4:1 or greater such as 10:1 or 20:1. Thus, apertures having a
wide variety of aspect ratios, such as 0.5:1, 1:1, 2:1, 2.5:1, 3:1,
4:1, 5:1, 6:1, 8:1, 10:1 or even higher, may be plated with copper
according to the present invention. In one embodiment, the present
compositions are useful for filling both high and low-aspect ratio
apertures on a substrate.
[0020] Any metal ion source that is at least partially soluble in
the electroplating bath and which metal can be deposited
electrolytically is suitable for use in the present invention. It
is preferred that the metal ion source is soluble in the plating
bath. Suitable metal ion sources are metal salts and include, but
are not limited to, metal sulfates, metal halides, metal acetates,
metal nitrates, metal fluoroborates, metal alkylsulfonates, metal
arylsulfonates, metal sulfamates, metal gluconates and the like.
Suitable metal salts include, but are not limited to, tin salts,
copper salts, silver salts, bismuth salts and the like. Copper is a
particularly suitable metal. Typical sources of copper ions
include, without limitation, copper sulfate, copper chloride,
copper acetate, copper nitrate, copper fluoroborate, copper methane
sulfonate, copper phenyl sulfonate and copper p-toluene sulfonate.
Copper sulfate pentahydrate is particularly suitable. Such metal
salts are generally commercially available and may be used without
further purification.
[0021] The metal salts may be used in the present invention in any
amount that provides sufficient metal ions for electroplating on a
substrate. When the metal is copper, the copper salt is typically
present in an amount sufficient to provide an amount of copper
metal of 10 to 80 g/L of plating solution. It will be appreciated
that mixtures of sources of metal ions may be used in the present
invention. Thus, alloys, such as copper-tin having up to 2 percent
by weight tin, may be advantageously plated according to the
present invention. Other suitable copper alloys include, but are
not limited to copper-silver, tin-copper-silver,
tin-copper-bismuth, and the like. The amounts of each of the
sources of metal ions in such mixtures depends upon the particular
alloy to be plated and is well known to those skilled in the art.
Typically, the amount of such alloying metal ion is up to 5% by
weight of the total amount of metal ions in the composition.
[0022] The present metal electroplating baths include an
electrolyte, typically an acidic electrolyte. Such baths are
typically aqueous. Suitable acidic electrolytes include, but are
not limited to, sulfuric acid, acetic acid, fluoroboric acid,
alkylsulfonic acids such as methanesulfonic acid, ethanesulfonic
acid, propanesulfonic acid and trifluoromethane sulfonic acid,
arylsulfonic acids such as phenyl sulfonic acid, phenol sulfonic
acid and toluenesulfonic acid, sulfamic acid, hydrochloric acid,
phosphoric acid and the like. Mixtures of acids may be
advantageously used in the present metal plating baths. Typically
suitable acids include sulfonic acid, methanesulfonic acid,
ethanesulfonic acid, propanesulfonic acid, and mixtures thereof.
Such electrolytes are generally commercially available from a
variety of sources and may be used without further purification.
The acids are typically present in an amount in the range of from 1
to 300 g/L, preferably from 5 to 250 g/L, and more preferably from
10 to 180 g/L.
[0023] For certain applications, such as in the plating of wafers
having very small apertures, it may be desired that the total
amount of added acid be low. By "low acid" is meant that the total
amount of added acid in the electrolyte is less than or equal to 20
g/L, and typically less than or equal to 10 g/L.
[0024] Such electrolytes may optionally contain a source of halide
ions, such as chloride ions such as copper chloride or hydrochloric
acid. A wide range of halide ion concentrations may be used in the
present invention. Typically, the halide ion concentration is in
the range of from 0 to 100 ppm based on the plating bath, and
typically from 10 to 75 ppm. A particularly useful amount of halide
ion is 20 to 75 ppm and more particularly 20 to 50 ppm. Such halide
ion sources are generally commercially available and may be used
without further purification.
[0025] Two or more brightening agents are used in the present
compositions, wherein at least one brightening agent is an
organosulfonic acid compound and at least one brightening agent is
a dithiocarbonate-containing compound. Any organosulfonic acid may
be used as the first brightening agent. As used herein, the term
"organosulfonic acid" includes salts thereof. Suitable
organosulfonic acids are those compounds having the formula
R--SO.sub.3X, where R is optionally substituted alkyl, optionally
substituted heteroalkyl, optionally substituted aryl, or optionally
substituted heterocyclic and X is hydrogen or a counter ion such as
sodium, potassium or ammonium. Typically, the alkyl groups are
(C.sub.1-C.sub.16)alkyl and more typically (C.sub.3-C.sub.12)alkyl.
Heteroalkyl groups typically have one or more heteroatoms, such as
nitrogen, sulfur or oxygen, in the alkyl chain. Suitable aryl
groups include, but are not limited to, phenyl, benzyl, biphenyl
and naphthyl. Suitable heterocyclic groups typically contain from 1
to 3 heteroatoms, such as nitrogen, sulfur or oxygen, and 1 to 3
separate or fused ring systems. Such heterocyclic groups may be
aromatic or non-aromatic. Particularly useful organosulfonic acid
compounds are those further containing a thiol or disulfide moiety.
Specific organosulfonic acid brighteners suitable for use in the
present invention include, but are not limited to,
3-mercapto-propylsulfonic acid-(3-sulfopropyl)ester;
3-mercapto-propylsulfonic acid sodium salt; carbonic
acid-dithio-o-ethylester-s-ester with 3-mercapto-1-propane sulfonic
acid potassium salt; bis-sulfopropyl disulfide;
3-(benzothiazolyl-s-thio)propyl sulfonic acid sodium salt;
pyridinium propyl sulfobetaine;
1-sodium-3-mercaptopropane-1-sulfonate; 3-mercapto-ethyl
propylsulfonic acid-(3-sulfoethyl)ester; 3-mercapto-ethylsulfonic
acid sodium salt; bis-sulfoethyl disulfide;
3-(benzothiazolyl-s-thio)ethyl sulfonic acid sodium salt;
pyridinium ethyl sulfobetaine;
1-sodium-3-mercaptoethane-1-sulfonate; N,N-dimethyl-dithiocarbamic
acid-(3-sulfopropyl)ester; N,N-dimethyl-dithiocarbamic
acid-(3-sulfoethyl)ester; and the like. Mixtures of organosulfonic
acid brightening agents may be used.
[0026] Any dithicarbonate-containing compound may be used as the
second brightening agent. In one embodiment, the
dithiocarbonate-containing compound further contains one or more
sulfonic acid or sulfonic acid ester moieties. Suitable
dithiocarbonate-containing compounds are those having the formula
R.sup.1--S--C(.dbd.S)--O--R.sup.2, where R.sup.1 and R.sup.2 are
independently optionally substituted alkyl, optionally substituted
heteroalkyl, optionally substituted aryl, or optionally substituted
heterocyclic. Typically, the alkyl groups are
(C.sub.1-C.sub.16)alkyl and more typically (C.sub.1-C.sub.6)alkyl.
Suitable heteroalkyl, aryl and heterocyclic moieties are those
described above. Exemplary dithiocarbonate-containing compounds
include, without limitation,
(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester potassium salt,
(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester sodium salt,
(O-ethyldithiocarbonato)-S-(3-propanesulfonic acid)-ester, and the
like. Mixtures of dithiocarbonate-containing brightening agents may
be used.
[0027] Both the first and second brightening agents are generally
commercially available and may be used without further
purification. The first organosulfonic acid brightening agent and
the second dithiocarbonate-containing compound brightening agent
may be used in a wide range of amounts, such as any suitable weight
ratio such as from 99:1 to 1:99. Typically, the weight ratio of the
first organosulfonic acid brightening agent and the second
dithiocarbonate-containing compound brightening agent is
.gtoreq.3:1, more typically .gtoreq.4:1, and even more typically
.gtoreq.5:1. Even higher weight ratios of organosulfonic acid
brightening agent to dithiocarbonate-containing compound
brightening agent provide deposits having greatly reduced void
formation in small or very small apertures compared to copper
deposits from conventional electroplating baths. Suitable higher
ratios are from 25:1 to 150:1, and more typically from 40:1 to
125:1, and still more typically from 50:1 to 100:1. In one
embodiment, particularly suitable ranges are from 20:1 to 1:20 and
more typically from 10:1 to 1:10. The total amount of brightening
agents used in the present compositions may vary over a wide range
but is typically at least 0.01 mg/L, based on the bath. More
typically, the total amount of brightening agents is at least 0.05
mg/L, still more typically at least 0.5 mg/L, and even more
typically at least about 1 mg/L. For example, the brighteners may
be present in an amount of from 0.01 mg/L to 200 mg/L. Particularly
suitable amounts of brightener are at least 0.01 mg/L, and more
particularly at least 4 g/L. Even higher brightener concentrations
may be used, such as at least 10, 15, 20, 30, 40 or 50 mg/L, based
on the bath. In one embodiment, a particularly useful range of such
brightener concentrations is from 0.01 to 50 mg/L. In another
embodiment, the dithicarbonate-containing brightener is present in
an amount of 0.01 to 10 ppm and more typically from 1 to 10
ppm.
[0028] The present compositions may further include one or more
other organic additives such as leveling agents and suppressor
compounds. For example, although they are not necessary, one or
more leveling agents may be used. Suitable leveling agents include,
but are not limited to, one or more of nigrosines,
pentamethyl-para-rosaniline hydrohalide, hexamethyl-para-rosaniline
hydrohalide, reaction products of an amine with an epihalohydrin,
or compounds containing a functional group of the formula N--R--S,
where R is a substituted alkyl, unsubstituted alkyl, substituted
aryl or unsubstituted aryl. Typically, the alkyl groups are
(C.sub.1-C.sub.6)alkyl and preferably (C.sub.1-C.sub.4)alkyl. In
general, the aryl groups include (C.sub.6-C.sub.20)aryl, preferably
(C.sub.6-C.sub.10)aryl. Such aryl groups may further include
heteroatoms, such as sulfur, nitrogen and oxygen. It is preferred
that the aryl group is phenyl or napthyl. The compounds containing
a functional group of the formula N--R--S are generally known, are
generally commercially available and may be used without further
purification.
[0029] In such above compounds containing the N--R--S functional
group, the sulfur ("S") and/or the nitrogen ("N") may be attached
to such compounds with single or double bonds. When the sulfur is
attached to such compounds with a single bond, the sulfur will have
another substituent group, such as but not limited to hydrogen,
(C.sub.1-C.sub.12)alkyl, (C.sub.2-C.sub.12)alkenyl,
(C.sub.6-C.sub.20)aryl, (C.sub.1-C.sub.12)alkylthio,
(C.sub.2-C.sub.12)alkenylthio, (C.sub.6-C.sub.20)arylthio and the
like. Likewise, the nitrogen will have one or more substituent
groups, such as but not limited to hydrogen,
(C.sub.1-C.sub.12)alkyl, (C.sub.2-C.sub.12)alkenyl,
(C.sub.7-C.sub.10)aryl, and the like. The N--R--S functional group
may be acyclic or cyclic. Compounds containing cyclic N--R--S
functional groups include those having either the nitrogen or the
sulfur or both the nitrogen and the sulfur within the ring
system.
[0030] By "substituted alkyl" is meant that one or more of the
hydrogens on the alkyl group is replaced with another substituent
group, such as, but not limited to, cyano, hydroxy, halo,
(C.sub.1-C.sub.6)alkoxy, (C.sub.1-C.sub.6)alkylthio, thiol, nitro,
and the like. By "substituted aryl" is meant that one or more
hydrogens on the aryl ring are replaced with one or more
substituent groups, such as, but not limited to, cyano, hydroxy,
halo, (C.sub.1-C.sub.6)alkoxy, (C.sub.1-C.sub.6)alkyl,
(C.sub.2-C.sub.6)alkenyl, (C.sub.1-C.sub.6)alkylthio, thiol, nitro,
and the like. "Aryl" includes carbocyclic and heterocyclic aromatic
systems, such as, but not limited to, phenyl, naphthyl and the
like.
[0031] When such leveling agents are used, they are typically used
in an amount of from 0.5 ppm to 50 ppm based on the total weight of
the plating bath, although greater amounts may be used. More
typically, the total amount of leveling agent is from 1 to 25 ppm
and even more typically from 2 to 20 ppm. In one embodiment, as the
amount of leveling agent is increased in the plating bath that the
amount of brightener is also increased. Amounts of leveling agent
greater than about 1 ppm are particularly useful in certain plating
baths.
[0032] Suitable suppressors are generally known in the art. It will
be clear to one skilled in the art which suppressors to use and in
what amounts. One of the advantages of the present invention is
that such additional suppressors, while they might be beneficial in
certain applications, are not required. Suppressors useful in the
present invention include, but are not limited to, polymeric
materials, particularly those having heteroatom substitution, and
more particularly oxygen substitution. Typically the suppressor is
a high molecular weight polyether, such as those of the
formula:
R--O--(CXYCX'Y'O).sub.nH
[0033] where R is H, (C.sub.2-C.sub.20)alkyl group or
(C.sub.6-C.sub.10)aryl group; each of X, Y, X' and Y' is
independently selected from hydrogen, alkyl such as methyl, ethyl
or propyl, aryl such as phenyl, or aralkyl such as benzyl; and n is
an integer from 5 to 100,000. It is preferred that one or more of
X, Y, X' and Y' is hydrogen. In one embodiment, n is greater than
12,000. Particularly suitable suppressors include commercially
available polyethylene glycol copolymers, including ethylene
oxide-propylene oxide copolymers and butyl alcohol-ethylene
oxide-propylene oxide copolymers. Suitable butyl alcohol-ethylene
oxide-propylene oxide copolymers are those having a weight average
molecular weight of 1800. When such suppressors are used, they are
typically present in an amount in the range of from 1 to 10,000 ppm
based on the weight of the bath, and more typically from 5 to 2,000
ppm.
[0034] It will be appreciated that a single dual-functioning
organic additive may be used in the present plating baths. Such
"dual-function" additives are capable of functioning as a leveling
agent or a suppressor or as both a leveling agent and a suppressor
in a copper plating bath. Dual-function additives (or compounds) of
the invention typically contain a first moiety capable of providing
a level copper deposit, a second moiety capable of suppressing
copper plating and optionally a spacer group. The dual-functioning
reaction products of the present invention may be used in a copper
plating bath in any suitable amount. The particular amount used
will depend upon the particular reaction product selected, the
concentration of the copper and the acid in the plating bath and
the current density used to deposit the copper, as well as whether
a leveling function, a suppressing function or both functions is
desired. In general, the dual-function compounds are used in a
total amount of from 0.5 ppm to 10,000 ppm based on the total
weight of the plating bath, although greater or lesser amounts may
be used.
[0035] Particularly suitable compositions contain one or more
sources of metal ions, electrolyte, water, two or more brightening
agents, wherein at least one brightening agent is an organosulfonic
acid compound and at least one brightening agent is a
dithiocarbonate-containing compound, and one or more suppressors.
In another embodiment, the composition further contains one or more
suppressors and one or more leveling agents.
[0036] The compositions of the present invention can be prepared by
combining one or more sources of metal ions, electrolyte, water,
two or more brightening agents and any optional organic additives
in any order. It is preferred that the inorganic components such as
metal salts, water, acid and optional halide ion source, are first
added to the bath vessel followed by the organic components such as
leveling agents, brighteners, suppressors, surfactants and the
like.
[0037] Typically, the plating baths of the present invention may be
used at any temperature from 10.degree. C. to 65.degree. C. or
higher. More typically, the temperature of the plating baths is
from 10.degree. C. to 35.degree. C. and even more typically from
15.degree. to 30.degree. C.
[0038] In general, when the present invention is used to deposit
metal on a substrate such as a wafer used in the manufacture of an
integrated circuit, the plating baths are agitated during use. Any
suitable agitation method may be used with the present invention
and such methods are well-known in the art. Suitable agitation
methods include, but are not limited to, air sparging, work piece
agitation, impingement and the like.
[0039] When the present invention is used to plate an integrated
circuit substrate, such as a wafer, the wafer may be rotated such
as from 1 to 150 RPM and the plating bath contacts the rotating
wafer, such as by pumping or spraying. In the alternative, the
wafer need not be rotated where the flow of the plating bath is
sufficient to provide the desired metal deposit.
[0040] Typically, substrates are electroplated by contacting the
substrate with the plating baths of the present invention. The bath
is typically subjected to a current density for a period of time
sufficient to deposit a copper layer on the substrate. Suitable
current densities, include, without limitation, the range of 1 to
100 mA/cm.sup.2. Typically, the current densities are from 1 to 60
mA/cm.sup.2. The specific current density depends upon the
substrate to be plated, the plating bath composition selected and
the like. Such current density choice is well within the skill of
one in the art.
[0041] The present invention is useful for depositing a layer of
metal, such as copper, on a variety of substrates, particularly
those having variously sized apertures. Accordingly, the present
invention provides a method of depositing copper on a substrate
including the steps of: contacting a substrate to be plated with a
metal, such as copper, with a metal plating bath composition
described above; and then applying a current density for a period
of time sufficient to deposit a copper layer on the substrate. For
example, the present invention is particularly suitable for
depositing copper on integrated circuit substrates, such as
semiconductor devices, with one or more small diameter vias,
trenches, or other apertures or any combinations of these. In one
embodiment, it is preferred that semiconductor devices are plated
according to the present invention. Such semiconductor devices
include, but are not limited to, wafers used in the manufacture of
integrated circuits.
[0042] In particular, the present invention provides a method for
manufacturing an electronic device, such as an integrated circuit,
including the steps of: contacting an electronic device substrate
with a metal plating bath composition described above; and then
applying a current density for a period of time sufficient to
deposit a metal layer on the substrate. More particularly, the
present invention provides a method for manufacturing an integrated
circuit comprising the steps of: contacting an electronic device
substrate with a copper plating bath; and then applying a current
density for a period of time sufficient to deposit a copper layer
on the substrate, wherein the copper plating bath includes 10 to 80
g/L as copper metal of one or more soluble copper salts, 5 to 250
g/L of one or more acids, 15 to 75 ppm of a halide ion, and 1 to 50
mg/L of two or more brighteners, wherein at least one brightening
agent is an organosulfonic acid compound and at least one
brightening agent is a dithiocarbonate-containing compound.
[0043] Copper is deposited in apertures without substantially
forming voids according to the present methods. By the term
"without substantially forming voids" it is meant that >95% of
the plated features are void-free. Typically, >97% of the plated
features are void-free and more typically the plated features are
void-free.
[0044] An advantage of the present invention is that it provides
metal deposits that are smoother, i.e. having less surface
roughness, as measured by atomic force microscopy ("AFM"), as
compared to conventional electroplating baths. By "smoother copper
deposit" it is meant that the average surface roughness ("Ra") and
the minimum to maximum height differential ("Z") of the copper
deposit (as measured from an atomic force micrograph) having a
certain thickness are lower than those achieved using conventional
copper plating baths. For example, layers of copper deposited from
the present plating baths typically have an arithmetic average
roughness ("Ra") of .ltoreq.5 nm, and more typically .ltoreq.4 nm.
For copper layers having a thickness of >10,000 .ANG. deposited
from the present electroplating baths, suitable Ra values are
.ltoreq.4 nm and more typically .ltoreq.3 nm. These copper layers
also have a low Z-value, such as .ltoreq.100 nm. For copper layers
having a thickness of 1000 .ANG., the value of Z is typically
.ltoreq.90 nm and more typically .ltoreq.86 nm. For copper layers
having a thickness of 10,000 .ANG., the value of Z is typically
.ltoreq.50 nm and more typically .ltoreq.40 nm. The "Z-value" is
the difference in heights in nm of the average of the 10 highest
and 10 lowest points examined. The lower the Z-value, the more
uniform the surface of the copper layer. It has been found that the
present invention provides a smoother copper deposit during initial
electroplating stages (i.e. .ltoreq.1000-2000 .ANG. of deposit
thickness), as well as during the later stages of plating (i.e.
.ltoreq.10,000 .ANG. of deposit thickness), as compared to
conventional copper electroplating baths. It will be appreciated by
those skilled in the art that deposit thicknesses formed during the
middle stages of plating (i.e. approximately 2000-10,000 .ANG. of
deposit thickness) will also benefit from the present
invention.
[0045] For example, FIG. 1 is an atomic force micrograph ("AFM") of
a 1000 .ANG. thick copper layer deposited using a conventional
copper plating bath. FIG. 2 is an AFM of a 1000 .ANG. thick copper
layer deposited using a copper plating bath of the invention. These
figures clearly show the present plating baths provide a metal
deposit having a smoother surface that that obtained using
conventional plating baths.
[0046] In another embodiment, the present invention provides a
method of depositing a copper layer on a substrate having one or
more apertures having a size of .ltoreq.2 .mu.m, including the
steps of contacting the substrate with an electroplating
composition comprising one or more sources of metal ions, an
electrolyte, and two or more brightening agents, and applying
sufficient current density for a period of time to deposit the
layer of copper, wherein the copper layer has an arithmetic surface
roughness of .ltoreq.5 nm, as determined by atomic force
microscopy.
[0047] A further advantage of the present invention is that
smoother metal deposits are provided, which means less time and
effort is spent in removing metal, such as copper, during
subsequent chemical-mechanical polishing ("CMP") process,
particularly copper removal during integrated circuit manufacture.
A further advantage of the present invention is that a wide range
of apertures sizes may be filled within a single substrate with
substantially no suppressed local plating. Thus, the present
invention is particularly suitable to substantially filling
apertures in a substrate having a variety of aperture sizes, such
as from 0.18 .mu.m to 100 .mu.m.
[0048] While the process of the present invention has been
generally described with reference to semiconductor manufacture, it
will be appreciated that the present invention may be useful in any
electrolytic process where an essentially level or planar metal
deposit such as a layer of copper having high reflectivity is
desired, and where reduced overplating and metal filled small
apertures that are substantially free of voids are desired. Such
processes include printed wiring board manufacture, advanced
packaging, micro-electrical-mechanical devices, and the like. For
example, the present plating baths may be useful for the plating of
vias, pads or traces on a printed wiring board, as well as for bump
plating on wafers. Other suitable processes include packaging and
interconnect manufacture. Accordingly, suitable substrates include
lead frames, interconnects, printed wiring boards, and the
like.
[0049] Thus, electronic devices such as semiconductor devices,
semiconductor packages, printed circuit boards and the like, are
formed according to the present invention having substantially
planar copper layers and filled features that are substantially
free of added defects, wherein the copper layer has not been
subjected to polishing processes, such as a CMP process,
electropolishing or silmultaneous plating and planarization
techniques. By "substantially planar copper layer" is meant that
the step height difference between areas of dense very small
features and areas free of or substantially free of dense very
small features is less than 1 .mu.m, preferably less than 0.5
.mu.m, more preferably less than 0.2 .mu.m, and even more
preferably less than 0.1 .mu.m. "Substantially free of added
defects" refers to the leveling agent not increasing the number or
size of defects, such as voids, in very small features as compared
to control plating baths not containing such leveling agent. A
further advantage of the present invention is that a substantially
planar metal layer may be deposited on a substrate having
non-uniformly sized small features, wherein the features are
substantially free of added voids, with the use of a single
leveling agent. "Non-uniformly sized small features" refer to small
features having a variety of sizes in the same substrate. Thus, the
need to tailor the leveling agent to the size of the feature to be
filled is avoided.
[0050] The following examples are intended to illustrate further
various aspects of the present invention, but are not intended to
limit the scope of the invention in any aspect.
EXAMPLE 1
[0051] Two copper plating baths are prepared by combining 40 g/L
copper as copper sulfate, 10 g/L sulfuric acid, 20 ppm chloride
ion, 175 ppm of an ethylene oxide-propylene oxide copolymer having
a molecular weight of approximately 2500 as suppressor, 2 ppm of an
imidazole-epihalohydrin reaction product as leveling agent, 12 ppm
of bis-(sodium sulfopropyl)-disulfide as brightener and water to
1L. Nothing else is added to the first copper plating bath
(Comparative). To the second plating bath (Inventive) is added 4.8
ppm of (O-ethyldithiocarbonato)-S-(- 3-sulfopropyl)-ester,
potassium salt as a second brightener.
[0052] Layers of copper are electroplated onto wafer substrates by
contacting a spinning wafer segment (4 cm.times.4 cm) at 200 RPM
with one of the above plating baths at 25.degree. C. A current
density ramp of 10 mA/cm2 (for 0-1000 .ANG. of deposit thickness),
20 mA/cm2 (1000-2000 .ANG.), 30 mA/cm2 (2000-3000 .ANG.), 40 mA/cm2
(3000-4000 .ANG.), 50 mA/cm2 (4000-5000 .ANG.), and 60 mA/cm2
(5000-10,000 .ANG.), is applied and a copper layer is deposited on
each wafer to a thickness of either 0.1 .mu.m or 1 .mu.m. The
layers of copper are analyzed by AFM to determine the arithmetic
average roughness ("Ra") and height differential ("Z"). FIG. 1
shows the AFM of the 0.1 .mu.m (1000 .ANG.) thick copper deposit
obtained from the Comparative plating bath. FIG. 2 shows the AFM of
the 0.1 .mu.m (1000 .ANG.) thick copper deposit obtained from the
Inventive plating bath. These results are reported in Table 1.
1 TABLE 1 Ra Z Plating Bath Copper Thickness (.ANG.) (nm) (nm)
Comparative 1000 8.91 141 " 10,000 4.33 66.3 Inventive 1000 3.4
85.8 " 10,000 2.82 34.6
[0053] The lower the value of Ra is, the smoother the surface is.
Lower values of Z indicate a more uniform surface height across the
evaluated area. Thus, layers of copper having low Ra and Z-values
are desired. As can be seen from the above data, the copper layers
deposited from the bath of the invention show a 50% reduction in
average surface roughness as compared to the copper layers
deposited from the Comparative plating bath. For a given thickness
of metal deposit the present plating baths provide smoother
surfaces than those obtained from conventional copper baths.
EXAMPLE 2
[0054] The procedure of Example 1 is repeated except that the wafer
substrates have 0.5 .mu.m trenches. The wafers are plated for a
time sufficient to deposit either a 500 .ANG. or 1000 .ANG. thick
copper layer. After plating, the wafers are cross-sectioned and
analyzed by scanning electron microscopy. FIGS. 3A and 3B are
scanning electron micrographs ("SEMs") of a cross-section of a 0.5
.mu.m trench on a wafer plated with a 500 .mu. and 1000 .mu.,
respectively, thick copper layer using the Comparative copper
plating bath. FIGS. 4A and 4B are SEMs of a cross-section of a 0.5
.mu.m trench on a wafer plated with a 500 .ANG. and 1000 .ANG.,
respectively, thick copper layer using the Inventive copper plating
bath. These data clearly show that the copper layer deposited from
the Inventive plating bath has less surface roughness that that
obtained from the Conventional copper plating bath.
EXAMPLES 3-11
[0055] The procedure of Example 1 is repeated except that a
dithiocarbonate-containing following formula is used instead of
(O-ethyldithiocarbonato)-S-(3-, sulfopropyl)-ester, potassium
salt:
R--O--C(.dbd.S--R.sup.1--SO.sub.3X
2 Example R R.sup.1 X 3 Ethyl Propyl Sodium 4 Ethyl Propyl Hydrogen
5 Methyl Propyl Potassium 6 Methyl Ethyl Potassium 7 Ethyl Ethyl
Hydrogen 8 Propyl Propyl Potassium 9 Ethyl Butyl Hydrogen 10 Ethyl
Butyl Potassium 11 Methyl Butyl Sodium
* * * * *