U.S. patent application number 11/117282 was filed with the patent office on 2005-12-01 for method of passivating chemical mechanical polishing compositions for copper film planarization processes.
Invention is credited to Baum, Thomas H., Boggs, Karl E., Darsillo, Michael, King, Mackenzie, Liu, Jun, Roeder, Jeffrey F..
Application Number | 20050263490 11/117282 |
Document ID | / |
Family ID | 32468759 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050263490 |
Kind Code |
A1 |
Liu, Jun ; et al. |
December 1, 2005 |
Method of passivating chemical mechanical polishing compositions
for copper film planarization processes
Abstract
A method of passivating a CMP composition by dilution and
determining the relationship between the extent of dilution and the
static etch rate of copper. Such relationship may be used to
control the CMP composition during the CMP polish to minimize the
occurrence of dishing or other adverse planarization deficiencies
in the polished copper, even in the presence of substantial levels
of copper ions in the CMP composition and at the copper/CMP
composition interface.
Inventors: |
Liu, Jun; (Brookfield,
CT) ; King, Mackenzie; (Southbury, CT) ;
Darsillo, Michael; (Woodbury, CT) ; Boggs, Karl
E.; (Hopewell Junction, NY) ; Roeder, Jeffrey F.;
(Brookfield, CT) ; Baum, Thomas H.; (New
Fairfield, CT) |
Correspondence
Address: |
INTELLECTUAL PROPERTY / TECHNOLOGY LAW
PO BOX 14329
RESEARCH TRIANGLE PARK
NC
27709
US
|
Family ID: |
32468759 |
Appl. No.: |
11/117282 |
Filed: |
April 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11117282 |
Apr 28, 2005 |
|
|
|
10315641 |
Dec 10, 2002 |
|
|
|
Current U.S.
Class: |
216/84 ; 216/88;
257/E21.304; 51/307 |
Current CPC
Class: |
C23F 3/06 20130101; C09G
1/02 20130101; H01L 21/3212 20130101; C23F 3/00 20130101; C23F
11/141 20130101 |
Class at
Publication: |
216/084 ;
051/307; 216/088 |
International
Class: |
B24D 003/02; B44C
001/22; C09C 001/68 |
Claims
What is claimed is:
1. A method of determining a relationship between static etch rate
and chemical mechanical polishing (CMP) composition dilution, said
method comprising: (a) preparing a first CMP composition; (b)
measuring a first static etch rate of a material to be polished
using the first CMP composition; (c) diluting the first CMP
composition with a solvent to produce a second CMP composition; (d)
measuring a second static etch rate of the material to be polished
using the second CMP composition; (e) repeating steps (c) and (d)
to produce a third CMP composition and measuring a third static
etch rate; (f) plotting static etch rate as a function of CMP
composition dilution ratio using a logarithmic scale; and (g)
calculating the non-linear regression equation, wherein said
regression equation is the relationship between static etch rate
and CMP composition dilution.
2. The method of claim 1, further comprising repeating step (e) at
least once.
3. The method of claim 1, wherein the first CMP composition
includes 5-aminotetrazole (ATA).
4. The method of claim 1, wherein the solvent comprises water.
5. The method of claim 3, wherein the first CMP composition further
comprises abrasive, wherein the abrasive comprises at least one
abrasive selected from the group consisting of silica, alumina,
silicon carbide, silicon nitride, iron oxide, ceria, zirconium
oxide, tin oxide, titanium dioxide, alumina-coated colloidal
silica, thermoset resins, thermoplastic resins, and mixtures of two
or more of such components in suitable form.
6. The method of claim 3, further comprising at least one oxidizing
agent, wherein the oxidizing agent comprises at least one compound
selected from the group consisting of ferric nitrate, ferric
ammonium oxalate, ferric ammonium citrate, permanganate salts,
peroxyacids, peroxoborate salts, urea-hydrogen peroxide, iodate
salts, perchlorate salts, persulfate salts, bromate salts,
benzoquinone, chlorate salts, chlorite salts, hypochlorite salts,
hypoiodite salts, oxybromide salts, percarbonate salts, periodate
salts, ceric salts, chromate and dichromate compounds, cupricyanide
and ferricyanide salts, ferriphenanthroline, ferripyridine and
ferrocinium.
7. The method of claim 3, further comprising at least one chelating
agent, wherein the at least one chelating agent comprises at least
one chelant selected from the group consisting of glycine, serine,
proline, leucine, alanine, asparagine, aspartic acid, glutamine,
valine, lysine, ethylenediaminetetraacetic acid,
N-hydroxyethylethylenediaminetriacetic acid, nitrilotriacetic acid,
diethylenetriaminepentaacetic acid, ethanoldiglycinate, phthalic
acid, oxalic acid, malic acid, succinic acid, mandelic acid, and
mellitic acid
8. The method of claim 3, further comprising solvent, wherein the
solvent comprises water.
9. The method of claim 3, wherein the first CMP composition further
comprises abrasive, and wherein ATA, the at least one oxidizing
agent, the at least one chelating agent, and solvent have the
following concentrations by weight, based on total weight of the
composition:
3 ATA 0.001-10 wt. % oxidizing agent 0.1-30 wt. % chelating agent
0.1-25 wt. % solvent 35-99.8 wt. %.
10. The method of claim 1, wherein the first CMP composition is
diluted with solvent in a dilution range from about 1:2 to about
1:100.
11. The method of claim 1, wherein the static etch rate of copper
using the first CMP composition is greater than the static etch
rate of copper using the second CMP composition.
12. The method of claim 1, wherein dilution is effectuated in
steps.
13. The method of claim 1, wherein dilution is effectuated
continuously.
14. The method of claim 1, wherein the regression equation is used
to control the static etch rate of copper.
15. The method of claim 1, wherein solvent is delivered to the
first CMP composition to slow the static etch rate of copper.
16. A kit comprising, in one or more containers, chemical
mechanical polishing (CMP) composition reagents, wherein the CMP
composition comprises 5-aminotetrazole (ATA), at least one
oxidizing agent, at least one chelating agent and solvent, and
wherein the kit is adapted to form a CMP composition suitable to
planarize bulk copper and remove copper overburden from a
microelectronic device having said copper thereon.
17. The kit of claim 16, comprising, in one or more containers, the
following components by weight, based on the total weight of the
combined components:
4 ATA 0.001-10 wt. % oxidizing agent 0.1-30 wt. % chelating agent
0.1-25 wt. % solvent 35-99.8 wt. %.
wherein the total of weight percentages of such components of the
composition does not exceed 100% weight.
18. The kit of claim 16, wherein the CMP composition further
comprises abrasive.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part of U.S. patent application
Ser. No. 10/315,641 for "Passivative Chemical Mechanical Polishing
Composition for Copper Film Planarization" filed on Dec. 10, 2002
in the name of Jun Liu et al., and is co-pending with U.S. patent
application Ser. No. ______, filed Apr. 28, 2005 in the name of Jun
Liu et al. for "Passivative Chemical Mechanical Polishing
Composition for Copper Film Planarization."
FIELD OF THE INVENTION
[0002] The present invention relates to a chemical mechanical
polishing composition and to a method of using same for the
polishing of wafer substrates having copper thereon, e.g., copper
interconnects, electrodes, or metallization, as part of a
microelectronic device structure.
DESCRIPTION OF THE RELATED ART
[0003] Copper is widely employed in semiconductor manufacturing as
a material of construction for components of microelectronic device
structures (e.g., contacts, electrodes, conductive vias, field
emitter base layers, etc.), and it is rapidly becoming the
interconnect metal of choice in semiconductor manufacturing due to
its higher conductivity and increased electromigration resistance
relative to aluminum and aluminum alloys.
[0004] Typically, the process scheme for utilizing copper in
semiconductor manufacturing involves the damascene approach,
wherein features are etched in a dielectric material. In the dual
damascene process a single step is used to form both plugs and
lines. Since copper has a propensity to diffuse into the dielectric
material, leading to leakage between metal lines, barrier layers,
such as Ta or TaN deposited by various deposition methods, are
often used to seal the copper interconnects. Following deposition
of the barrier layer material, a thin seed layer of copper is
deposited on the barrier material via physical vapor deposition,
followed by electrodeposition of copper to fill the features. The
deposited copper must then be planarized to render it of suitable
form to accommodate subsequent process steps in the fabrication of
the finished semiconductor product, and in order to satisfactorily
operate in the microcircuitry in which it is present. The
planarization typically involves chemical mechanical polishing
(CMP), using a CMP composition formulated for such purpose.
[0005] Due to the difference in chemical reactivity between copper
and the barrier layer material, e.g. Ta and/or TaN, two chemically
distinct slurries are often used in the copper CMP process. The
Step I slurry is used to rapidly planarize the topography and
remove the copper, with the Step I polish stopping at the barrier
layer material. The Step II slurry removes the barrier layer
material at a high removal rate and stops at the dielectric layer,
or alternatively at a cap layer that has been applied to protect
the dielectric.
[0006] Step I chemical mechanical polishing (CMP) compositions for
planarization and polishing of copper typically are in the form of
slurries containing an abrasive of suitable type, e.g., an abrasive
selected from among silica, alumina, and other oxides and mineralic
materials, in a solvent medium containing one or more solvent
species, e.g., water, organic solvents, etc. Typically, Step I
slurries have a high copper removal rate, and a copper to barrier
material removal rate selectivity of greater than 100:1.
[0007] One type of CMP composition for planarizing copper surfaces
includes an aqueous slurry of abrasive particles containing
hydrogen peroxide as an oxidizing component and glycine as a
chelating agent. Glycine has been found to react with solution
phase Cu.sup.+2 ions formed by the oxidation of the Cu metal to
form a Cu.sup.2+-glycine complex. The complexing of Cu.sup.+2 ions
through formation of a water soluble Cu.sup.2+-glycine chelate
assists in removal of Cu in protruded regions via a direct
dissolution mechanism, and the Cu.sup.2+-glycine complex decomposes
hydrogen peroxide to yield hydroxyl radicals which have a higher
oxidation potential than hydrogen peroxide itself.
[0008] In step I CMP slurries, the compound benzotriazole (BTA) is
often included as a corrosion inhibitor. In theory, 1
[0009] complexes with copper to form an insoluble Cu--BTA complex
on the copper surface. The resulting insoluble protective film is
meant to facilitate the planarization of the topography of the
device structure being fabricated, since the recessed areas on the
wafer surface are protected from dissolution, while mechanical
action of the abrasive species on the protruding areas enables
material removal and planarization to be carried out. Additionally,
the Cu--BTA complex minimizes corrosion and preserves the
functional integrity of the copper device structures for their
intended use.
[0010] It is known that BTA functions well as a copper corrosion
inhibitor in the absence of OH radicals. However, in step I copper
CMP slurries containing hydrogen peroxide and glycine, the
formation of highly oxidizing OH radicals under dynamic CMP
conditions cannot be avoided, since copper metal is readily
oxidized in such slurry environment. Experiments involving the
addition of Cu.sup.2+ to an H.sub.2O.sub.2glycine/BTA system have
shown that the presence of Cu.sup.2+ increases the static etch rate
of Cu dramatically, and at the same time, the Cu corrosion
potential is shifted to less noble ranges.
[0011] The significance of this finding is that in the presence of
H.sub.2O.sub.2 and glycine, BTA is not effective in protecting the
low features of copper wafer surfaces during the CMP process, and
thus undesired "dishing" and erosion occurs in high-density
patterned areas on the wafer substrate.
[0012] Dishing occurs when too much copper is removed such that the
copper surface is recessed relative to the barrier and/or
dielectric surface of the semiconductor wafer. Dishing occurs when
the copper and barrier material removal rates are disparate. Oxide
erosion occurs when too much dielectric material is removed.
[0013] An alternative to the use of BTA as a corrosion inhibitor in
CMP compositions includes 5-aminotetrazole (ATA), which is
compatible with H.sub.2O.sub.2/glycine-based CMP compositions and
effective to passivate copper surfaces when significant amounts of
Cu ions are present in bulk solution and/or near the metal/solution
interface during CMP processing.
[0014] During Step I, bulk copper is rapidly removed followed by
the "soft landing" or "touchdown," whereby the polishing conditions
are altered until the underlying barrier material is exposed, as
determinable using an endpoint detection system such as an in situ
rate monitor (ISRM). Although the endpoint has been detected,
signaling the exposure of the barrier layer material, copper
overburden remains which must be removed and as such, an
over-polishing step is often performed. Unfortunately, the "soft
landing" and the over-polishing steps often result in dishing
and/or erosion into copper features and thus, loss of wafer surface
planarity and uniformity.
[0015] Step I CMP slurries advantageously remove copper rapidly
during the step I CMP process. However, during the soft landing
and/or over-polish, this rapid rate of copper removal may become
disadvantageous as various surface defects such as recesses,
erosion, dishing, etc., form on the copper layer surface. The net
result of the overly aggressive step I slurry during soft landing
and/or over-polish is a wafer substrate having a non-uniform planar
surface, which can render the wafer unusable.
[0016] It would therefore be a significant advance in the art to
provide a method that overcomes the deficiencies of the prior art
relating to the rapid rate of copper removal during the soft
landing and/or overpolishing steps of the step I CMP process.
Specifically, it would be an advance in the art to provide a method
to reduce the static etch rate of copper, and hence copper
corrosion, during the soft landing and/or overpolishing steps of
the step I polishing process.
SUMMARY OF THE INVENTION
[0017] The present invention relates to a chemical mechanical
polishing composition and method of using same for the polishing of
microelectronic device substrates having copper thereon. In
addition, the present invention further relates to a method for
slowing down the rate of copper removal during the soft landing
and/or overpolishing steps of the step I polishing process.
[0018] In one aspect, the present invention relates to a method of
determining a relationship between static etch rate and chemical
mechanical polishing (CMP) composition dilution, said method
comprising:
[0019] (a) preparing a first CMP composition;
[0020] (b) measuring a first static etch rate of a material to be
polished using the first CMP composition;
[0021] (c) diluting the first CMP composition with a solvent to
produce a second CMP composition;
[0022] (d) measuring a second static etch rate of the material to
be polished using the second CMP composition;
[0023] (e) repeating steps (c) and (d) to produce a third CMP
composition and measuring a third static etch rate;
[0024] (f) plotting static etch rate as a function of CMP
composition dilution ratio using a logarithmic scale; and
[0025] (g) calculating the non-linear regression equation, wherein
said regression equation is the relationship between static etch
rate and CMP composition dilution.
[0026] In yet another aspect, the present invention relates to a
kit comprising, in one or more containers, chemical mechanical
polishing (CMP) composition reagents, wherein the CMP composition
comprises 5-aminotetrazole (ATA), at least one oxidizing agent, at
least one chelating agent and solvent, and wherein the kit is
adapted to form a CMP composition suitable to planarize bulk copper
and remove copper overburden from a microelectronic device having
said copper thereon.
[0027] Other aspects, features and embodiments of the invention
will be more fully apparent from the ensuing disclosure and
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a plot of copper corrosion rate, in Angstroms per
minute, as a function of 0.1% ATA/H.sub.2O.sub.2/glycine slurry
dilution ratio (.diamond-solid.) and 0.1%
BTA/H.sub.2O.sub.2/glycine slurry dilution ratio (.box-solid.).
[0029] FIG. 2 is a logarithmic plot of the copper corrosion rate as
a function of the ATA/H.sub.2O.sub.2glycine slurry dilution ratio
and the BTA/H.sub.2O.sub.2/glycine slurry dilution ratio
illustrated in FIG. 1.
[0030] FIG. 3 is a plot of copper corrosion rate, in Angstroms per
minute, as a function of 0.8% ATA/H.sub.2O.sub.2/glycine slurry
dilution ratio (.diamond-solid.) and 0.1% BTA/H.sub.2O.sub.2glycine
slurry dilution ratio (.box-solid.).
[0031] FIG. 4 is a logarithmic plot of the copper corrosion rate as
a function of the ATA/H.sub.2O.sub.2/glycine slurry dilution ratio
and the BTA/H.sub.2O.sub.2/glycine slurry dilution ratio
illustrated in FIG. 3.
[0032] FIG. 5 is a plot of copper corrosion rate, in Angstroms per
minute, as a function of 1.2% ATA/H.sub.2O.sub.2/glycine slurry
dilution ratio (.diamond-solid.) and 0.1%
BTA/H.sub.2O.sub.2/glycine slurry dilution ratio (.box-solid.).
[0033] FIG. 6 is a logarithmic plot of the copper corrosion rate as
a function of the ATA/H.sub.2O.sub.2/glycine slurry dilution ratio
and the BTA/H.sub.2O.sub.2/glycine slurry dilution ratio
illustrated in FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS
THEREOF
[0034] The present invention is based on the discovery that
5-aminotetrazole 2
[0035] is unexpectedly effective as a replacement for BTA as a
copper corrosion inhibitor in Step I CMP compositions for
planarizing copper films. ATA is compatible with CMP compositions
containing hydrogen peroxide as an oxidizer and glycine as a
chelator. The ATA-containing CMP composition achieves active
passivation of copper surfaces even when significant amounts of
copper ions, e.g., Cu.sup.2+ cations, are present in bulk solution
and/or at the metal/solution interface during CMP processing.
[0036] The present invention is further based on the discovery that
dilution of a CMP slurry composition during the soft landing and/or
over polishing step of a CMP process achies active passivation of
exposed copper.
[0037] "Soft landing" or "touchdown," as defined herein,
corresponds to some point in the Step I polishing process whereby
the downforce pressure of the polisher may be decreased and/or the
Step I composition altered to reduce dishing and/or erosion of the
copper lines and plugs. Preferably, soft landing may be effectuated
when the thickness of the layer of copper over the barrier material
has been decreased to a range of from about 0.05 .mu.m to about 0.4
.mu.m.
[0038] "Over-polishing" is performed subsequent to soft landing to
remove the copper overburden from the surface of the barrier
material, while minimizing additional dishing or erosion of the
copper features.
[0039] As used herein, "about" is intended to correspond to .+-.5%
of the stated value.
[0040] "Microelectronic device," as used herein, corresponds to
semiconductor substrates, flat panel displays, and
microelectromechanical systems (MEMS). It is to be understood that
the term "microelectronic device" is not meant to be limiting in
any way and includes any substrate that will eventually become a
microelectronic device.
[0041] As used herein, "suitability" to planarize bulk copper and
remove copper overburden from a microelectronic device having said
copper thereon corresponds to at least partial removal of said
copper from the microelectronic device. Preferably, at least 90% of
the copper is removed from the microelectronic device using the
compositions of the invention, more preferably, at least 99% of the
copper is removed.
[0042] As used herein, dilution of the CMP composition "subsequent"
to the planarization of bulk copper corresponds to the soft landing
step or immediately before the soft landing step.
[0043] The ATA-containing CMP compositions of the invention, in its
broad contemplation, may be formulated with any suitable
constituents, including any appropriate oxidizing agent(s),
chelating agent(s), and corrosion inhibitor(s), abrasive media,
solvent media, and optionally any suitable additives, adjuvants,
excipients, etc., such as stabilizing agents, acids, bases (e.g.,
amines), surfactants, buffering agents, etc.
[0044] Oxidizing agents employed in the broad practice of the
invention may be of any suitable type, including for example ferric
nitrate, ferric ammonium oxalate, ferric ammonium citrate,
permanganate salts (e.g., potassium permanganate), peroxyacids
(e.g. peracetic acid), peroxoborate salts (e.g., potassium
peroxoborate), urea-hydrogen peroxide, iodate salts (e.g.,
potassium iodate), perchlorate salts (e.g. tetramethylammonium
perchlorate), persulfate salts, bromate salts, benzoquinone,
chlorate salts, chlorite salts, hypochlorite salts, hypoiodite
salts, oxybromide salts, percarbonate salts, periodate salts, ceric
salts (e.g., ammonium ceric sulfate), chromate and dichromate
compounds, cupricyanide and ferricyanide salts,
ferriphenanthroline, ferripyridine and ferrocinium. Preferred
oxidizers include peracetic acid, urea-hydrogen peroxide,
di-t-butyl peroxide, benzyl peroxide, hydrogen peroxide and
compatible mixtures including two or more of such oxidizer
species.
[0045] Chelating agents in the CMP compositions of the invention
may be of any appropriate type, including, for example: amino acids
such as glycine, serine, proline, leucine, alanine, asparagine,
aspartic acid, glutamine, valine, lysine, etc.; polyamine complexes
and their salts, including ethylenediaminetetraacetic acid,
N-hydroxyethylethylenediaminet- riacetic acid, nitrilotriacetic
acid, iminodiacetic acid, diethylenetriaminepentaacetic acid, and
ethanoldiglycinate; polycarboxylic acids, including phthalic acid,
oxalic acid, malic acid, succinic acid, mandelic acid, and mellitic
acid; and compatible mixtures including two or more of the
foregoing species. Preferred chelating agents include amino acids,
with glycine being most preferred.
[0046] The corrosion inhibitor component in the CMP composition of
the invention comprises ATA, and may additionally include other
corrosion inhibitor components in combination with ATA, in specific
embodiments of the invention. Such other corrosion inhibitor
components may be of any suitable type, including for example,
imidazole, benzotriazole, benzimidazole, amino, imino, carboxy,
mercapto, nitro, alkyl, urea and thiourea compounds and
derivatives, etc. Preferred inhibitors include tetrazoles and their
derivatives, and the invention therefore contemplates the provision
of ATA alone or in combination with other tetrazole (or other
corrosion inhibitor) species, as the corrosion inhibitor in
compositions according to the present invention.
[0047] ATA is employed in CMP compositions of the invention in any
suitable concentration. Suitable concentrations of ATA in a
specific formulation are readily empirically determinable within
the skill of the art, based on the disclosure herein, to provide a
CMP composition with suitable copper surface passivation
characteristics even in CMP environments containing high levels of
copper cations. In one preferred embodiment of the invention, the
amount of ATA in the CMP composition is in a range of from about
0.001 to about 10% by weight, based on the total weight of the CMP
composition, with an amount of ATA in a range of from about 0.01 to
about 5% by weight being more preferred, and an amount of ATA in a
range of from about 0.10 to about 1.5% by weight being most
preferred, based on the same total weight basis, although greater
or lesser percentages may be employed to advantage in specific
applications within the broad scope of the present invention.
[0048] The abrasive may be of any suitable type, including, without
limitation, metal oxides, silicon nitrides, carbides, etc. Specific
examples include silica, alumina, silicon carbide, silicon nitride,
iron oxide, ceria, zirconium oxide, tin oxide, titanium dioxide,
and mixtures of two or more of such components in suitable form,
such as grains, granules, particles, or other divided form.
Alternatively, the abrasive may include composite particles formed
of two or more materials, e.g., NYACOL.RTM. alumina-coated
colloidal silica (Nyacol Nano Technologies, Inc., Ashland, Mass.).
Alumina is a preferred inorganic abrasive and may be employed in
the form of boehmite or transitional .delta., .theta. or .gamma.
phase alumina. Organic polymer particles, e.g., including thermoset
and/or thermoplastic resin(s), may be utilized as abrasives. Useful
resins in the broad practice of the present invention include
epoxies, urethanes, polyesters, polyamides, polycarbonates,
polyolefins, polyvinylchloride, polystyrenes, polyolefins, and
(meth)acrylics. Mixtures of two or more organic polymer particles
may be used as the abrasive medium, as well as particles comprising
both inorganic and organic components.
[0049] Bases may be optionally employed for pH adjustment in
compositions of the invention. Illustrative bases include, by way
of example, potassium hydroxide, ammonium hydroxide and
tetramethylammoniumhydroxide (TMAH), tetraethylammonium hydroxide,
trimethyl hydroxyethylammonium hydroxide, methyl
tri(hydroxyethyl)ammonium hydroxide, tetra(hydroxyethyl)ammonium
hydroxide, and benzyl trimethylammonium hydroxide.
[0050] Acids may also be optionally employed for pH adjustment in
compositions of the invention. The acids used may be of any
suitable type, including, by way of example, formic acid, acetic
acid, propanoic acid, butanoic acid, pentanoic acid, isovaleric
acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid,
lactic acid, hydrochloric acid, nitric acid, phosphoric acid,
sulfuric acid, hydrofluoric acid, malic acid, fumaric acid, malonic
acid, glutaric acid, glycolic acid, salicylic acid,
1,2,3-benzenetricarboxylic acid, tartaric acid, gluconic acid,
citric acid, phthalic acid, pyrocatechoic acid, pyrogallol
carboxylic acid, gallic acid, tannic acid, and mixtures including
two or more acids of the foregoing or other types.
[0051] Amines when present may be of any suitable type, including,
by way of example, hydroxylamine, monoethanolamine, diethanolamine,
triethanolamine, diethyleneglycolamine, N-hydroxylethylpiperazine,
N-methylethanolamine, N,N-dimethylethanolamine,
N-ethylethanolamine, N,N-diethylethanolamine, propanolamine,
N,N-dimethylpropanolamine, N-ethylpropanolamine,
N,N-diethylpropanolamine, 4-(2-hydroxyethyl)morphol- ine,
aminoethylpiperazine, and mixtures including two or more of the
foregoing or other amine species.
[0052] Surfactants when optionally employed in compositions of the
invention may be of any suitable type, including non-ionic,
anionic, cationic, and amphoteric surfactants, and polyelectrolytes
including, for example: salts of organic acids; alkane sulfates
(e.g., sodium dodecyl sulfate); alkane sulfonates; substituted
amine salts (e.g., cetylpyridium bromide); betaines; polyethylene
oxide; polyvinyl alcohol; polyvinyl acetate; polyacrylic acid;
polyvinyl pyrrolidone; polyethyleneimine; and esters of
anhydrosorbitols, such as those commercially available under the
trademarks Tween.RTM. and Span.RTM., as well as mixtures including
two or more of the foregoing or other surfactant species.
[0053] The pH of CMP compositions of the invention may be at any
suitable value that is efficacious for the specific polishing
operation employed. In one embodiment, the pH of the CMP
composition may be in a range of from about 2 to about 11, more
preferably in a range of from about 2 to about 7, and most
preferably in a range of from about 3 to about 6.
[0054] The solvents employed in CMP compositions of the invention
may be single component solvents or multicomponent solvents,
depending on the specific application. In one embodiment of the
invention, the solvent in the CMP composition is water. In another
embodiment, the solvent comprises an organic solvent, e.g.,
methanol, ethanol, propanol, butanol, ethylene glycol, propylene
glycol, glycerin, etc. In yet another embodiment, the solvent
comprises a water-organic solvent solution. A wide variety of
solvent types and specific solvent media may be employed in the
general practice of the invention to provide a solvating/suspending
medium in which the abrasive is dispersed and in which the other
components are incorporated to provide a composition of appropriate
character, e.g., of slurry form, for application to the platen of
the CMP unit to provide a desired level of polishing of the copper
on the wafer substrate.
[0055] In one embodiment, the invention provides a Step I CMP
composition useful for chemical mechanical polishing of substrates
having copper thereon, e.g., copper interconnects, metallization,
device structural elements, etc., in which the composition includes
hydrogen peroxide, glycine, ATA, and solvent.
[0056] In another embodiment, the invention provides a Step I CMP
composition useful for chemical mechanical polishing of substrates
having copper thereon, e.g., copper interconnects, metallization,
device structural elements, etc., in which the composition includes
hydrogen peroxide, glycine, ATA, abrasive and solvent.
[0057] In another embodiment, the CMP composition of the invention
is an aqueous abrasive composition, and includes an aqueous medium,
abrasive, ATA, H.sub.2O.sub.2 and glycine, wherein ATA,
H.sub.2O.sub.2 and glycine have the following composition by
weight, based on the total weight of the composition:
1 ATA 0.001-10 wt. % H.sub.2O.sub.2 0.1-30 wt. % Glycine 0.1-25 wt.
% Water 35-99.8 wt. %.
[0058] In a further specific illustrative embodiment, the CMP
composition comprises the following components by weight, based on
the total weight of the composition:
2 ATA 0.001-10 wt. % H.sub.2O.sub.2 0.1-30 wt. % Glycine 0.1-25 wt.
%. Abrasive 0.1-30 wt. % Water 5-99.7 wt. %
[0059] with the total wt. % of all components in the composition
totaling to 100 wt. %.
[0060] The CMP compositions of the invention may be provided as a
single package formulation or a multi-part formulation that is
mixed at the point of use or in a storage tank upstream of the
tool. The advantage of a multi-part formulation resides in its
extended shelf life relative to single-package formulations. A
single package formulation is more susceptible to decomposition and
change of its properties over time, in relation to a multi-part
formulation, due to the presence of the oxidizer in the
single-package CMP composition. The concentrations of the
single-package formulation or the individual packages of the
multi-part formulations may be widely varied in specific multiples,
i.e., more dilute or more concentrated, in the broad practice of
the invention, and it will be appreciated that the CMP compositions
of the invention can variously and alternatively comprise, consist
or consist essentially of any combination of ingredients consistent
with the disclosure herein.
[0061] In one embodiment, each single ingredient of the CMP
composition is individually delivered to the polishing table for
combination at the table, to constitute the CMP composition for
use. In another embodiment, the CMP composition is formulated as a
two-part composition in which the first part comprises abrasive and
corrosion inhibitor in aqueous medium, and the second part
comprises oxidizing agent and chelating agent. In still another
embodiment, the CMP composition is formulated as a two-part
composition in which the first part comprises abrasive, corrosion
inhibitor and chelating agent in an aqueous medium, and the second
part comprises the oxidizer. In all of these various embodiments,
the mixing of ingredients or parts to form the final composition
occurs at the point of use, with mixing at the polishing table,
polishing belt or the like, in an appropriate container shortly
before reaching the polishing table, or at the CMP composition
manufacturer and/or supplier.
[0062] Accordingly, another aspect of the invention relates to a
kit including, in one or more containers, the components adapted to
form the compositions of the invention as described
hereinabove.
[0063] The copper CMP composition of the invention may be utilized
in a conventional manner in the CMP operation, by application of
the CMP composition to the copper surface on the microelectronic
device substrate in a conventional fashion, and polishing of the
copper surface may be carried out using a conventional polishing
element such as a polishing pad, polishing belt, or the like.
[0064] The CMP composition of the invention is advantageously
employed to polish surfaces of copper elements on microelectronic
device substrates, without the occurrence of dishing or other
adverse planarization deficiencies in the polished copper, even
when significant amounts of copper ions, e.g., Cu.sup.2+ ions, are
present in the bulk CMP slurry composition and/or at the copper/CMP
slurry interface during CMP processing.
[0065] Step I CMP slurries advantageously remove copper rapidly
during the step I CMP process. However, as the step I process
enters the soft landing and/or overpolishing phases, this rapid
rate of copper removal may become disadvantageous as various
surface defects such as recesses, erosion, dishing, etc., form on
the copper layer surface.
[0066] To limit the overly aggressive CMP slurry composition during
the soft landing and/or overpolishing steps of the Step I polishing
step, the Step I CMP slurry of the invention may be diluted in a
serial fashion. Accordingly, another embodiment of the present
invention relates to a process of using a CMP composition to
efficiently and uniformly planarize copper-containing
microelectronic device substrates. Following rapid removal of the
bulk copper layer using a more concentrated CMP composition, the
CMP composition is diluted, either by in-line mixing or directly at
the platen, to form a diluted CMP composition(s) for the soft
landing and over-polishing steps. The diluting media most
preferably corresponds to the solvent of the Step I CMP composition
of the invention.
[0067] To demonstrate the effect of dilution on copper corrosion
rates, Step I CMP compositions were diluted twice in a step-wise
fashion and the Cu corrosion rates determined using electrochemical
methods. As defined herein, "Cu corrosion rate" is equivalent to
"static etch rate." By way of example, the initial Step I CMP
compositions included 5 wt. % H.sub.2O.sub.2, 6 wt. % glycine, 1
wt. % abrasive, varying concentrations of ATA, and the balance
water. To simulate the acceleration effect of corrosive copper ions
in the solution, i.e., the formation of the Cu.sup.2+-glycine
complex which decomposes H.sub.2O.sub.2 to form the highly
oxidizing OH radicals, 0.5 wt. % CuSO.sub.4.5 H.sub.2O was added to
the initial Step I CMP compositions. In each case, the Step I CMP
composition including ATA was compared to a Step I CMP composition
including 5 wt. % H.sub.2O.sub.2, 6 wt. % glycine, 1 wt. %
abrasive, 0.1 wt. % BTA, and the balance water
[0068] The initial Step I CMP composition (hereinafter Slurry1) was
diluted step-wise with water to yield a second CMP slurry (1 part
Slurry1 to 5 parts water; hereinafter Slurry2), and a third CMP
slurry (1 part Slurry1 to 50 parts water; hereinafter Slurry3). The
Cu corrosion rates in Angstroms per minute, were measured and the
average Cu corrosion rate plotted as a function of CMP slurry
dilution using both a linear and logarithmic scale.
[0069] Importantly, the number of serial dilutions of Slurry1,
i.e., the most concentrated CMP slurry, is not limited to the
aforementioned two dilutions. The number of dilutions depend on the
desired end result of the Step I CMP polish and may vary from one
step-wise dilution to ten step-wise dilutions. Alternatively, the
dilution may be effectuated in a continuous manner whereby diluting
solvent is continuously added to the CMP slurry during the
soft-landing and/or over-polishing steps. In yet another
alternative, Slurryl is not diluted per se, but rather diluted CMP
compositions are prepared for delivery of clean, diluted
chemistries to the tool subsequent to the polish using Slurry1.
[0070] FIGS. 1 and 2 correspond to linear and logarithmic plots of
the average Cu corrosion rate as a function of CMP slurry dilution
for a Step I CMP slurry having an ATA concentration of 0.1 wt. %,
respectively. Non-linear regression of the best-fit straight line
in FIG. 2 yields a power relation between corrosion rate and slurry
dilution of y=14.396.times..sup.-0.4881.
[0071] FIGS. 3 and 4 correspond to linear and logarithmic plots of
the average Cu corrosion rate as a function of CMP slurry dilution
for a Step I CMP slurry having an ATA concentration of 0.8 wt. %,
respectively. Non-linear regression of the best-fit straight line
in FIG. 4 yields a power relation between corrosion rate and slurry
dilution of y=10.306.times..sup.-0.5024.
[0072] FIGS. 5 and 6 correspond to linear and logarithmic plots of
the average Cu corrosion rate as a function of CMP slurry dilution
for a Step I CMP slurry having an ATA concentration of 1.2 wt. %,
respectively. Non-linear regression of the best-fit straight line
in FIG. 6 yields a power relation between corrosion rate and slurry
dilution of y=8.0513.times..sup.-0.5517.
[0073] In each example, the copper corrosion rate decreases with
increasing slurry dilution. This may prove advantageous during the
soft-landing and over-polishing steps to slow the copper corrosion
rate and concomitantly minimize the dishing and erosion of the
copper lines and plugs. Further, compared to compositions including
BTA, ATA leads to a lower overall corrosion rate as well as a more
rapid corrosion decrease with increasing dilution, as evidenced by
the slopes of the regression lines.
[0074] These power relationships between copper corrosion rate and
slurry dilution provide a means to control the static etch of Cu
during Step I CMP polishing. In order to achieve acceptable
planarization of the wafer surface at an efficient etch rate with
the minimum amount of dishing, Slurry1 may be diluted at some point
prior to the soft-landing, during the soft-landing and/or during
the over-polishing steps of the Step I CMP polish, as readily
determined by one skilled in the art. As defined herein, "bulk
layer" represents the copper layer that is rapidly removed by the
Step I CMP composition of the invention, e.g., Slurry1, and
"residual layer" represents the copper layer that remains following
the removal of the bulk layer, including the copper overburden,
which is intended to be removed at a slower rate, e.g., by Slurry2,
Slurry3, etc. By diluting the overly aggressive Slurryl at the
appropriate point in the CMP polish, polishing defects such as
dishing and erosion are substantially eliminated.
[0075] The diluting solvent, e.g., water, may be delivered to the
polishing table at the appropriate time and in the appropriate
amount based on the regression equation specific to the slurry
composition of choice, as readily determinable by one skilled in
the art. In practice, Slurry1 may be diluted in a serial manner and
the Cu corrosion rate of each composition measured using Tafel or
some equivalent measurement. Thereafter, a logarithmic plot of the
Cu corrosion rate as a function of the slurry dilution may be
plotted and the non-linear regression equation calculated. Using
the regression equation and knowledge of the wafer to be polished,
e.g., thickness of the film, removal rate, etc., one skilled in the
art may determine the appropriate time and in the appropriate
amount of diluting solvent to deliver to the polishing table to
slow the static etch rate of copper to a rate that minimizes the
formation of polishing defects such as dishing.
[0076] The CMP composition of the invention may be diluted in a
serial manner to effectuate substantial removal of the residual
layer of copper while simultaneously minimizing dishing and erosion
of the copper lines and plugs, as readily determined by one skilled
in the art. As defined herein, "substantial removal" corresponds to
at least 80%, preferably at least 90%, most preferably at least 95%
of the residual layer of copper is removed using the series of Step
I CMP compositions.
[0077] It is also contemplated herein that the dilution process may
be automated whereby the polishing table and a programmable logic
control (PLC) unit may be communicatively connected and the
regression equation for the CMP slurry of choice input into the
PLC. At the appropriate time, the appropriate amount of diluting
solvent will be delivered to the polishing table, as controlled by
the PLC.
[0078] Following completion of the Step I CMP process, the platen
and substrate are rinsed with solvent. Preferably, the solvent is
the same as that used in the Step I CMP compositions described
herein, e.g., water. The rinse time may be in a range from about 5
sec to about 30 sec, preferably about 10 sec to about 20 sec.
Thereafter, the wafer substrate may be transferred to another
platen for Step II polishing thereon.
[0079] While the invention has been described herein in reference
to specific aspects, features and illustrative embodiments of the
invention, it will be appreciated that the utility of the invention
is not thus limited, but rather extends to and encompasses numerous
other variations, modifications and alternative embodiments, as
will suggest themselves to those of ordinary skill in the field of
the present invention, based on the disclosure herein.
Correspondingly, the invention as hereinafter claimed is intended
to be broadly construed and interpreted, as including all such
variations, modifications and alternative embodiments, within its
spirit and scope.
* * * * *