U.S. patent application number 09/845549 was filed with the patent office on 2003-06-05 for chemical mechanical polishing slurry composition for polishing conductive and non-conductive layers on semiconductor wafers.
This patent application is currently assigned to ARCH SPECIALTY CHEMICALS, INC.. Invention is credited to Jenkins, Richard J., LaFollette, Larry A., Mahulikar, Deepak, Pasqualoni, Anthony Mark.
Application Number | 20030104770 09/845549 |
Document ID | / |
Family ID | 25295487 |
Filed Date | 2003-06-05 |
United States Patent
Application |
20030104770 |
Kind Code |
A1 |
Pasqualoni, Anthony Mark ;
et al. |
June 5, 2003 |
Chemical mechanical polishing slurry composition for polishing
conductive and non-conductive layers on semiconductor wafers
Abstract
The invention relates to a novel CMP slurry composition used for
polishing metals, the composition comprising: (a) a dispersion
solution comprising an abrasive; and (b) an oxidizer. The slurry
composition has a large particle count of less than about 150,000
particles having a particle size greater than 0.5 .mu.m in 30 .mu.L
of slurry, which is achieved by filtering the slurry composition
prior to use. Also, the inclusion of a chemical activity enhancer,
such as, an amine and a corrosion inhibitor, results in the
appropriate copper removal rate without increasing static etch
rates.
Inventors: |
Pasqualoni, Anthony Mark;
(Hamden, CT) ; Mahulikar, Deepak; (Madison,
CT) ; LaFollette, Larry A.; (Maumee, OH) ;
Jenkins, Richard J.; (Dundee, MI) |
Correspondence
Address: |
Paul D. Greeley, Esq.
Ohlandt, Greeley, Ruggiero & Perle, L.L.P.
One Landmark Square, 10th Floor
Stamford
CT
06901-2682
US
|
Assignee: |
ARCH SPECIALTY CHEMICALS,
INC.
NORWALK
CT
|
Family ID: |
25295487 |
Appl. No.: |
09/845549 |
Filed: |
April 30, 2001 |
Current U.S.
Class: |
451/60 |
Current CPC
Class: |
C09K 3/1463 20130101;
H01L 21/31053 20130101; C09G 1/02 20130101; H01L 21/3212
20130101 |
Class at
Publication: |
451/60 |
International
Class: |
B24B 001/00; B24B
007/19 |
Claims
What is claimed is:
1. A slurry composition for chemical and mechanical polishing
comprising: a dispersion comprising an abrasive; and an oxidizer;
wherein said dispersion has a large particle count of less than
about 150,000 particles having a particle size of greater than
about 0.5 .mu.m in a 30 .mu.L sample.
2. The composition of claim 1, wherein said dispersion is selected
from the group consisting of: fumed silica, colloidal silica,
alumina, ceria, and mixtures thereof.
3. The composition of claim 2, wherein said dispersion is a fumed
silica dispersion.
4. The composition of claim 3, wherein said fumed silica dispersion
is between about 6 wt. % to 8 wt. % fumed silica.
5. The composition of claim 1, wherein said oxidizer is selected
from the group consisting of: hydrogen peroxide, potassium
ferricyanide, potassium dichromate, potassium iodate, potassium
bromate, vanadium trioxide, hypochlorous acid, sodium hypochlorite,
potassium hypochlorite, calcium hypochlorite, magnesium
hypochlorite, ferric nitrate, various ammonium salts such as
ammonium persulfate, potassium permanganate, and mixtures
thereof.
6. The composition of claim 5, wherein said oxidizer is present in
an amount between about 0.05% to 10% of the total weight of the
slurry composition.
7. The composition of claim 5, wherein said oxidizer is hydrogen
peroxide.
8. The composition of claim 7, wherein said hydrogen peroxide is
present in an amount between about 0.05% to 0.50% of the total
weight of the slurry composition.
9. The composition of claim 1, further comprising a corrosion
inhibitor.
10. The composition of claim 9, wherein said corrosion inhibitor is
selected from the group consisting of: benzotriazole,
6-tolylytriazole, 1-(2,3,dicarboxypropyl)benzotriazole, carboxylic
acids, and mixtures thereof.
11. The composition of claim 10, wherein said corrosion inhibitor
is present in amount between about 0.003% to 0.10% of the total
weight of the slurry composition.
12. The composition of claim 10, wherein said corrosion inhibitor
is benzotriazole.
13. The composition of claim 12, wherein said benzotriazole is
present in an amount between about 0.005% to 0.015% of the total
weight of the slurry composition.
14. The composition of claim 1, further comprising a chemical
activity enhancer, which increases the copper removal rate.
15. The composition of claim 14, wherein said chemical activity
enhancer is an amine, which is selected from the group consisting
of: ammonia, hydroxylamine, monoethanolamine, diethanolamine,
triethanolamine, diethyleneglycolamine, N-hydroxylethylpiperazine,
and mixtures thereof.
16. The composition of claim 15, wherein said amine is present in
an amount between about 0.005% to 10% of the total weight of the
slurry composition.
17. The composition of claim 15, wherein said chemical activity
enhancer is ammonia.
18. The composition of claim 17, wherein said ammonia is present in
an amount between about 0.01% to 0.03% of the total weight of the
slurry composition.
19. The composition of claim 1, further comprising a pH
adjuster.
20. The composition of claim 10, wherein said pH adjuster is
selected from the group consisting of: formic acid, acetic acid,
propanoic acid, butanoic acid, pentanoic acid, hexanoic acid,
heptanoic acid, octanoic acid, nonanoic acid, lactic acid,
hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid,
hydrofluoric acid, malic acid, tartaric acid, gluconic acid, citric
acid, phthalic acid, pyrocatechoic acid, pyrogallol carboxylic
acid, gallic acid, tannic acid and mixtures thereof.
21. The composition of claim 20, wherein said pH adjuster is
present in an amount between about 0.10% to 2% of the total weight
of the slurry.
22. The composition of claim 20, wherein said pH adjuster is
propanoic acid.
23. The composition of claim 22, wherein said propanoic acid is
present in an amount between about 0.20% to 0.50% of the total
weight of the slurry composition.
24. The composition of claim 1, wherein said slurry composition has
a pH between about 8 to 10.5.
25. The composition of claim 1, further comprising at least one
additional chemical component selected from the group consisting
of: stabilizing agents, surfactants, fluorine-containing compounds,
chelating agents, salts, and mixtures thereof.
26. A slurry composition for the chemical mechanical polishing of
metal layers, the composition comprising: (a) a silica dispersion;
(b) an oxidizer; (c) a chemical activity enhancer; (d) a pH
adjuster; and (e) a corrosion inhibitor, wherein said silica
dispersion has a large particle count of less than about 150,000
particles having a particle size greater than about 0.5 .mu.m in a
30 .mu.L sample.
27. A method of preparing a chemical mechanical polishing slurry
composition, comprising the steps of: (a) admixing a chemical
mechanical polishing slurry composition comprising: a silica
dispersion and an oxidizer; and (b) filtering said chemical
mechanical polishing slurry composition such that the large
particle count in said composition is less than about 150,000
particles having a particle size greater than about 0.5 .mu.m in
about 30 .mu.L of sample.
28. The method of claim 27, wherein said slurry composition is
filtered at least once prior to its use.
29. The method of claim 28, wherein said slurry composition is
filtered at least three times prior to its use.
30. A method of reducing defects on a metal layer, comprising the
steps of: (a) applying to a metal layer a slurry composition
comprising a silica dispersion and an oxidizer, wherein said silica
dispersion has a large particle count of less than about 150,000
particles having a particle size of greater than about 0.5 .mu.m in
a 30 .mu.L sample; and (b) chemically mechanically polishing said
metal layer with said slurry composition.
31. The method of claim 30, wherein said metal layer is selected
from the group consisting of: copper, tungsten, tantalum, aluminum,
titanium, and combinations thereof.
Description
[0001] The present invention relates to a chemical mechanical
polishing slurry system used in semiconductor manufacturing. More
particularly, the present invention relates to a chemical
mechanical polishing slurry system that has a lower incidence of
defects.
BACKGROUND OF THE INVENTION
[0002] Semiconductors are typically made up of millions of active
devices that are connected together via metal interconnections to
form circuits and components. The active devices are interconnected
by a well-known multilayer interconnect process. In a typical
interconnect process, alternating layers of metal and dielectric
are put on the silicon wafer by a variety of processes. After each
layer is applied, a means is used to remove excess amounts of these
layers and to assure both local and global planarity of the surface
in preparation for the application of the next layer.
[0003] A common process used to accomplish these goals is chemical
mechanical planarization (CMP). In this process, an aqueous
solution containing various chemicals and suspended abrasive
particles, namely, a slurry, is interposed between the wafer and a
moving pad while pressure is applied. The combination of the
mechanical effects of the abrasive particles, applied pressure,
imposed relative velocity and the chemical effects which result
from chemical reaction between the material being polished and
constituents in the solution result in a synergistic enhancement of
the polishing rate or material removal rate. That is, the material
removal rate is higher than that produced by either the mechanical
effects or chemical effects alone.
[0004] There are two general types of layers that can be polished.
The first layer is interlayer dielectrics (ILD), such as, silicon
oxide and silicon nitride. The second layer is metal layers, such
as, tungsten, copper, aluminum, etc., which are used to connect the
active devices.
[0005] In the case of CMP of metals, the chemical action is
generally considered to take one of two forms. In the first
mechanism, the chemicals in the solution react with the metal layer
to continuously form an oxide layer on the surface of the metal.
This generally requires the addition of an oxidizer to the
solution, such as, hydrogen peroxide, ferric nitrate, etc.
Thereafter, the mechanical abrasive action of the particles
continuously and simultaneously removes this oxide layer. A
judicious balance of these two processes obtains optimum results in
terms of removal rate and polished surface quality.
[0006] In the second mechanism, no protective oxide layer is
formed. Instead, the constituents in the solution chemically attack
and dissolve the metal, while the mechanical action is largely one
of mechanically enhancing the dissolution rate by such processes as
continuously exposing more surface area to chemical attack, raising
the local temperature (which increases the dissolution rate) by the
friction between the particles and the metal, enhancing the
diffusion of reactants and products to and away from the surface by
mixing, and by reducing the thickness of the boundary layer.
[0007] A number of systems for chemical-mechanical polishing of
copper have been disclosed. Kumar et al. in an article entitled
"Chemical-Mechanical Polishing of Copper in Glycerol Based
Slurries" (Materials Research Society Symposium Proceedings 1996)
disclose a slurry that contains glycerol and abrasive alumina
particles. An article by Gutmann et al. entitled
"Chemical-Mechanical Polishing of Copper with Oxide and Polymer
Interlevel Dielectrics" (Thin Solid Films, 1995) discloses slurries
based on either ammonium hydroxide or nitric acid that may contain
benzotriazole (BTA) as an inhibitor of copper dissolution. Luo et
al. in an article entitled "Stabilization of Alumina Slurry for
Chemical-Mechanical Polishing of Copper" (Langmuir, 1996) discloses
alumina-ferric nitrate slurries that contain polymeric surfactants
and BTA. Carpio et al. in an article entitled "Initial Study on
Copper CMP Slurry Chemistries" (Thin Solid Films, 1995) disclose
slurries that contain either alumina or silica particles, nitric
acid or ammonium hydroxide, with hydrogen peroxide or potassium
permanganate as an oxidizer.
[0008] There are a number of theories as to the mechanism for
chemical-mechanical polishing of copper. An article by Zeidler et
al. (Microelectronic Engineering, 1997) proposes that the chemical
component forms a passivation layer on the copper, changing the
copper to a copper oxide. The copper oxide has different mechanical
properties than metallic copper, such as, density and hardness, and
passivation changes the polishing rate of the abrasive portion. The
above article by Gutmann et al. discloses that the mechanical
component abrades elevated portions of copper and the chemical
component then dissolves the abraded material. The chemical
component also passivates recessed copper areas minimizing
dissolution of those portions.
[0009] Planar Solutions has developed a basic slurry for the CMP of
copper, tantalum and TEOS layers. This is described in a
publication titled "Development of a 1:1:1 TA: Copper layer: TEOS
layer slurry for Tantalum layer polishing" in the proceedings of
the CMP MIC conference, February 1999. In a two step process to CMP
the copper layer, in the first step the slurry polishes the copper
layer rapidly, while in the second step, the slurry polishes the
tantalum layer, the copper layer, and the TEOS layer
simultaneously. The prior art slurry was designed to have no
selectivity towards these layers and the topography performance was
excellent. The topography has been reported to be in the 100-300 A
range. However, the prior art slurry has two distinct disadvantages
associated with it, namely, defectivity and oxide thinning or total
copper loss.
[0010] The defectivity issue revolves around several chatter mark
defects revealed in the copper layer after CMP. After polishing
with the prior art slurry, the polished substrate, when viewed at
200.times. magnification at nine sites, had several hundred chatter
mark defects (hereafter referred to as a normalized defectivity of
100). The chatter mark defects were deep and were cosmetically
unacceptable.
[0011] The oxide thinning is primarily associated with the high
removal rate of the TEOS layer. The prior art slurry removed the
TEOS layer more rapidly than the tantalum layer or the copper
layer. For example, typical removal rates were TEOS layer: 1500
.ANG./min, tantalum layer: 600 .ANG./min, and copper layer: 900
.ANG./min. As a result of the high oxide thinning, thicker TEOS
layers will have to be deposited, which will result in subsequent
increased costs.
[0012] The present invention overcomes the disadvantages of the
current metal slurry compositions so that defectivity and oxide
thinning or total copper loss are significantly reduced and/or
eliminated. The present invention also provides many additional
advantages, which shall become apparent as described below.
SUMMARY OF THE INVENTION
[0013] The present invention relates to a novel CMP slurry
composition used for polishing metals comprising (a) a dispersion
solution comprising an abrasive; and (b) an oxidizer. The slurry
composition has a large particle count of less than about 150,000
particles having a particle size greater than 0.5 .mu.m in 30 .mu.L
of slurry, which is achieved by filtering the slurry composition
prior to use. By controlling the particle size of the abrasive
dispersion, through either filtration of the dispersion itself or
the slurry composition before use, defectivity and oxide
thinning/total copper loss problems are significantly reduced
and/or eliminated. Also, the inclusion of a chemical activity
enhancer, such as, an amine and a corrosion inhibitor, results in
the appropriate copper removal rate without increasing static etch
rates, which cause increased topography.
[0014] The slurry composition may also comprise at least one other
component selected from the group consisting of: acids, chelating
agents, fluorine-containing compounds, buffering agents, salts, and
biological agents.
DETAILED DESCRIPTION OF THE INVENTION
[0015] It has been found that by reducing the number of abrasive
large particles, in combination with optimizing chemical activity,
in a CMP slurry composition, defectivity and oxide thinning/total
copper loss on the substrate being polished is significantly
reduced and/or eliminated. The defectivity and oxide thinning/total
copper loss depends on two critical factors: (1) the number of
large particles present in the slurry composition, and (2) the
chemical activity of the slurry composition.
[0016] For the purpose of this patent application, the term
"particle" includes, but is not limited to, colloids, aggregates
and other fused combinations of particles, as well as agglomerates
and other solely mechanically interwoven combinations of particles.
"Large particle count" is intended to mean a count of particles
where the particles have a particle size greater than about 0.5
.mu.m. The term "particle size" is intended to mean an average
diameter size of a distribution of particles.
[0017] To count particles and measure particle size, there are many
suitable methods known in the art. Preferably, the particle count
and size is measured by an Accusizer, manufactured, for example, by
Particle Sizing Systems. To measure particle count and size using
an Accusizer, an amount of sample containing particles is diluted
with about 1 milliliter (mL) of water and then introduced into the
Accusizer. The Accusizer then measures the particle count and size
of the particles contained in the sample. The particle count is
proportional to the amount of sample analyzed. For example, when
analyzing about 30 microliters (.mu.L) of the slurry of the present
invention, diluted with about 1 mL of water, in an Accusizer, less
than about 150,000 particles having a particle size greater than
about 0.5 (micrometers).mu.m are measured. If 60 .mu.L of the same
slurry of the present invention were diluted with 1 mL of water,
the Accusizer would measure less than about 300,000 particles
having a particle size greater than about 0.5 .mu.m.
[0018] The CMP slurry of the present invention comprises an
abrasive dispersion and an oxidizer. The abrasive particles may be
any material that is effective at removing metal and silicon
layers. Silica is the abrasive material used in the present
invention. The silica may be, for example, colloidal silica, fumed
silica and other silica dispersions; however, the preferred silica
is fumed silica. Preferably, the silica is present in the slurry in
a concentration of about 4% to 10% of the total weight of the
slurry. More preferably, the silica is present in a concentration
of about 5% to 9% of the total weight of the slurry.
[0019] Most preferably, the silica is present in a concentration of
about 6.5% to 8% of the total weight of the slurry.
[0020] In addition, other ceramics, such as, for example, alumina
(A1.sub.2O.sub.3), ceria (CeO.sub.2), and mixtures thereof may also
be utilized as an abrasive in the slurry composition.
[0021] To reduce the number of large particles contained in the
slurry composition, the slurry composition is filtered before its
use. Preferably, the slurry composition is filtered at least once
prior to its use. More preferably, the slurry composition is
filtered at least three times prior to its use. Alternatively, the
abrasive dispersion can be filtered prior to being admixed with the
other chemical components that make up the slurry composition.
[0022] The slurry composition can be filtered using any filtration
process known in the art. By way of example, the filtration process
may include one or more stages of filtration in series starting
with coarse filters (i.e., bag filters) followed by cartridge type
filters. Typically, filtration could begin with one or more very
coarse (i.e., 50 micron) filters and then be followed by one or
more fine pore size filters (i.e., 0.5 micron). Filtration time can
vary depending on the amount of the slurry composition to be
filtered. For example, the slurry can be filtered at a flow rate
between about 0.5 to 10 gallons per minute.
[0023] As a result of the filtration, chatter mark defects on a
polished substrate are significantly reduced, as shown in Tables 1
and 2 below.
1TABLE 1 Chatter mark defects versus large particle counts Large
Particle Counts Normalized Chatter mark defects 100 >100 10
.about.100 5 20-40 2 <10
[0024]
2TABLE 2 Results of test polishes # Particles > 0.5 .mu.m #
Chattermark Test Condition (Accusizer) Defects Fumed Silica Slurry
150,000 0 Agitated K1020 737,000 33230 Unagitated K1020 356,000
6820 Unfiltered K1020 670,000 6800 Filtered K1020 360,000 4700
Colloidal SiO.sub.2 (Klebesol 50,000 900 1501) A5012 Ta Slurry
360,000 550
[0025] The slurries listed in Table 2, with the exception of the
colloidal silica slurry, are fumed silica based slurries. All of
the slurries, except for the A5012 Ta slurry, are KOH stabilized
and include hydrogen peroxide and BTA. The A5012 Ta slurry is fumed
silica based, but ammonia stabilized. The ammonia ion attacks
copper reducing chatter mark defects. Unless noted otherwise, each
slurry was filtered, resulting in different large particle counts
in the slurry compositions.
[0026] When there is a lack of significant chemical activity, the
defects varied directly with the number of coarse particles
(>0.5 .mu.m) present. A slurry with a higher chemical activity,
such as an acidic slurry or an ammonia based slurry, such as A5012,
reduced the chatter mark defects significantly. A single patterned
wafer exhibiting few chatter mark defects was polished using a
fumed silica slurry, which was filtered several times and had a
very low particle count, i.e., less than about 150,000 particles
having a particle size greater than about 0.50 .mu.m, in a 30 .mu.L
sample. This resulted in zero chatter mark defects on the polished
wafer.
[0027] By reducing the fumed silica concentration in the slurry
composition to about 6.5% to 8% of the total weight of the slurry,
the TEOS layer removal rate dropped from 1500 .ANG./min to about
1200 .ANG./min. In addition, the copper and tantalum removal rates
were reduced. To combat these reductions, the oxidizer
concentration was systematically reduced, which resulted in an
increased tantalum layer removal rate, as demonstrated by Table 3
below.
3TABLE 3 Tantalum and copper removal rates versus oxidizer
concentration Oxidizer Concentration Tantalum layer removal Copper
layer Normalized rate .ANG./min. removal rate .ANG./min. 100 250
800 50 400 250 0 1000 50
[0028] Hydrogen peroxide (H.sub.2O.sub.2) is used as the oxidizing
agent in the present invention. Preferably the concentration of the
H.sub.2O.sub.2 is from about 0.01% to 10% of the total weight of
the slurry. When used with fumed silica, the H.sub.2O.sub.2 is
present in a concentration from about 0.05% to 0.50% of the total
weight of the slurry.
[0029] Other suitable oxidizing agents may be utilized. For
example, potassium ferricyanide, potassium dichromate, potassium
iodate, potassium bromate, vanadium trioxide, hypochlorous acid,
sodium hypochlorite, potassium hypochlorite, calcium hypochlorite,
magnesium hypochlorite, ferric nitrate, various ammonium salts such
as ammonium persulfate, potassium permanganate and mixtures
thereof, are suitable oxidizing agents.
[0030] In order to further enhance the chemical activity of the
slurry composition, additional chemicals may be added to the CMP
slurry composition, including, for example, corrosion inhibitors,
amines, stabilizing agents, surfactants, acids, fluorine-containing
compounds, chelating agents, and salts.
[0031] Suitable corrosion inhibitors that may be added to the
slurry composition include, for example, benzotriazole,
6-tolylytriazole, 1-(2,3-dicarboxypropyl)benzotriazole, carboxylic
acids and mixtures thereof. The corrosion inhibitor may be present
in the slurry in a concentration of about 0.001% to 10% and is
preferably present in a concentration of about 0.003% to 0.05% of
the total weight of the slurry. The preferred corrosion inhibitor
is benzotriazole (BTA) and is most preferably present in a
concentration of about 0.005% to 0.015% of the total weight of the
slurry.
[0032] Suitable amines that may be added to the slurry composition
include, for example, ammonia, hydroxylamine, monoethanolamine,
diethanolamine, triethanolamine, diethyleneglycolamine,
N-hydroxylethylpiperazine, and mixtures thereof. The amines may be
present in the slurry composition in a concentration of about
0.001% to 10%, and are preferably present in a concentration of
about 0.005% to 5% of the total weight of the slurry. The preferred
amine is ammonia and is most preferably present in a concentration
of about 0.01% to 0.03% of the total weight of the slurry.
[0033] It has been found that the inclusion of small amounts of a
chemical activity enhancer, such as, ammonia and a corrosion
inhibitor, such as, BTA, in the slurry composition results in the
appropriate adjustment of the copper layer removal rate without any
increase in static etch rates, which causes the topography to
increase. This is demonstrated in Table 4 below for a slurry
composition having about 6.5 wt. % abrasive particles, normalized
50 H.sub.2O.sub.2, and a pH of about 10.
4TABLE 4 Copper layer removal rate versus ammonia and BTA
concentrations Copper layer Ammonia content BTA content removal
rate, Static Etch rate, % % .ANG./min .ANG./min 0 0 250 .about.0
0.01 0 500 Not measured 0.02 0.01 2000 .about.0 0.02 0.0125 1000
.about.0
[0034] In order to maintain the pH of the slurry composition, a
stabilizing agent may be added so that the pH of the slurry is
about 8 to 10.5. Suitable stabilizing agents include, for example,
ammonium hydroxide and potassium hydroxide. These stabilizing
agents may be present in the slurry in a concentration of about
0.1% to 5%, and more preferably in a concentration of about 0.2% to
1% of the total weight of the slurry.
[0035] Suitable surfactant compounds that may be added to the
slurry composition include, for example, any of the numerous
nonionic, anionic, cationic, or amphoteric surfactants known to
those skilled in the art. The surfactant compounds may be present
in the slurry composition in a concentration of about 0.05% to 1%
and are preferably present in a concentration of about 0.07% to
0.5% of the total weight of the slurry. The preferred types of
surfactants are nonionic, anionic, and mixtures thereof and are
most preferably present in a concentration of about 0.075% to 0.4%
of the total weight of the slurry.
[0036] Suitable acid compounds that may be added to the slurry
composition, to adjust the pH of the composition, include, for
example, formic acid, acetic acid, propanoic acid, butanoic acid,
pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid,
nonanoic acid, lactic acid, hydrochloric acid, nitric acid,
phosphoric acid, sulfuric acid, hydrofluoric acid, malic acid,
tartaric acid, gluconic acid, citric acid, phthalic acid,
pyrocatechoic acid, pyrogallol carboxylic acid, gallic acid, tannic
acid, and mixtures thereof. The acid compound may be present in the
slurry composition in a concentration of about 0.1% to 2% of the
total weight of the slurry. The preferred acid is propanoic acid,
most preferably in a concentration of about 0.2% to 0.5% of the
total weight of the slurry.
[0037] It has been found that carboxylic acids, if added, may also
impart corrosion inhibition properties to the slurry composition,
in addition to adjusting the pH of the composition.
[0038] To increase the selectivity of tantalum and tantalum
compounds relative to silicon dioxide, fluorine-containing
compounds may be added to the slurry composition. Suitable
fluorine-containing compounds include, for example, hydrogen
fluoride, perfluoric acid, alkali metal fluoride salt, alkaline
earth metal fluoride salt, ammonium fluoride, tetramethylammonium
fluoride, ammonium bifluoride, ethylenediammonium difluoride,
diethylenetriammonium trifluoride, and mixtures thereof. The
fluorine-containing compounds may be present in the slurry
composition in a concentration of about 0.1% to 5%, and are
preferably present in a concentration of about 0.25% to 1% of the
total weight of the slurry. The preferred fluorine-containing
compound is tetramethylammonium fluoride, most preferably in a
concentration from about 0.3% to 0.8% of the total weight of the
slurry.
[0039] Suitable chelating agents that may be added to the slurry
composition include, for example, ethylenediaminetetracetic acid
(EDTA), N-hydroxyethylethylenediaminetriacetic acid (NHEDTA),
nitrilotriacetic acid (NTA), diethylklenetriaminepentacetic acid
(DPTA), ethanoldiglycinate, and mixtures thereof. The chelating
agents may be present in the slurry composition in a concentration
of about 0.05% to 1%, and are preferably present in a concentration
of about 0.1% to 0.75% of the total weight of the slurry. The
preferred chelating agent is EDTA and is most preferably present in
a concentration of about 0.15% to 0.5% of the total weight of the
slurry.
[0040] Suitable salts that may be added to the slurry composition
include, for example, ammonium persulfate, potassium persulfate,
potassium sulfite, potassium carbonate, potassium propionate,
ammonium nitrate, potassium hydrogen phthalate, hydroxylamine
sulfate, and mixtures thereof. The salts may be present in the
slurry composition in a concentration of about 0.1% to 5%, and are
preferably present in a concentration of about 0.25% to 1% of the
total weight of the slurry. The preferred salt is ammonium
persulfate and is most preferably present in a concentration of
about 0.3% to 0.75% of the total weight of the slurry.
[0041] The CMP method of the present invention involves a two step
process wherein the CMP slurry composition is used to polish a
substrate with at least one metal layer, such as, copper, tungsten,
tantalum, aluminum, titanium, and combinations thereof. The CMP
method reduces both the amount of defects and oxide thinning/total
copper loss on the metal layers polished, as compared to a process
employing a high copper removal rate slurry alone.
[0042] The substrate polishing process comprises the steps of:
applying to a metal layer a slurry composition comprising a silica
dispersion and an oxidizer, wherein the silica dispersion has a
large particle count of less than about 150,000 particles having a
particle size of greater than about 0.5 .mu.m in a 30 .mu.L sample;
and chemically mechanically polishing the metal layer with the
slurry composition.
[0043] This invention is explained below in further detail with
reference to Example 1, which is not by way of limitation, but by
way of illustration.
EXAMPLE 1
[0044] A filtered CMP slurry composition, which reduces the TEOS
layer removal rate (oxide thinning) and the chatter mark defect
rate, was prepared having the following components and properties:
about 6.5% to 8% fumed silica dispersion, about 0.005% to 0.015%
H.sub.2O.sub.2, about 0.005% to 0.015% BTA, about 0.01% to 0.03%
ammonia, and a pH of about 8 to 10.5. For these ranges, several
wafers were polished and the following results, shown in Table 5
below, were achieved versus the prior art, unfiltered control
slurry, which comprised 10% fumed silica dispersion, 0.2%
H.sub.2O.sub.2, and 0.005% BTA.
5TABLE 5 Properties of a filtered CMP slurry composition versus an
unfiltered prior art slurry composition. Control Slurry Improved
slurry Copper layer removal rate 800-1000 800-1000 .ANG./min
Tantalum layer removal rate 550-750 450-600 .ANG./min TEOS layer
removal rate 1350-1700 1000-1200 .ANG./min Static etch rate 0 0
Chatter mark defects 25 <10 Dishing 50 micron lines 100-300
.ANG. 500 .ANG. max Erosion Fine Lines max 50-200 .ANG. 400 .ANG.
max
[0045] As is evident by the results summarized in Table 5 above,
the slurry of the present invention achieved fewer chatter mark
defects, and a reduced TEOS layer removal rate, over the prior art
control slurry. This was achieved while still maintaining
comparable and acceptable copper and tantalum removal rates and
erosion fine line characteristics compared to the prior art control
slurry.
[0046] The present invention has been described with particular
reference to the preferred forms thereof. It will be obvious to one
of ordinary skill in the art that changes and modifications may be
made therein without departing from the spirit and scope of the
present invention as defined by the following claims.
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