U.S. patent application number 16/236962 was filed with the patent office on 2020-07-02 for composition for tungsten cmp.
The applicant listed for this patent is Cabot Microelectronics Corporation. Invention is credited to Kevin P. DOCKERY, Roman A. IVANOV, Zhao LIU, Na ZHANG.
Application Number | 20200208014 16/236962 |
Document ID | / |
Family ID | 70973117 |
Filed Date | 2020-07-02 |
United States Patent
Application |
20200208014 |
Kind Code |
A1 |
ZHANG; Na ; et al. |
July 2, 2020 |
COMPOSITION FOR TUNGSTEN CMP
Abstract
A chemical mechanical polishing composition includes a water
based liquid carrier, cationic abrasive particles dispersed in the
liquid carrier, a first amino acid compound having an isoelectric
point of less than 7 and a second amino acid compound having an
isoelectric point of greater than 7. The pH of the composition is
in a range from about 1 to about 5. A method for chemical
mechanical polishing a substrate including a tungsten layer
includes contacting the substrate with the above described
polishing composition, moving the polishing composition relative to
the substrate, and abrading the substrate to remove a portion of
the tungsten from the substrate and thereby polish the
substrate.
Inventors: |
ZHANG; Na; (Naperville,
IL) ; DOCKERY; Kevin P.; (Aurora, IL) ; LIU;
Zhao; (Naperville, IL) ; IVANOV; Roman A.;
(Aurora, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cabot Microelectronics Corporation |
Aurora |
IL |
US |
|
|
Family ID: |
70973117 |
Appl. No.: |
16/236962 |
Filed: |
December 31, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09G 1/02 20130101; H01L
21/3212 20130101 |
International
Class: |
C09G 1/02 20060101
C09G001/02; H01L 21/321 20060101 H01L021/321 |
Claims
1. A chemical mechanical polishing composition for polishing a
substrate having a tungsten layer, the composition comprising: a
water based liquid carrier; cationic abrasive particles dispersed
in the liquid carrier; a first amino acid compound having an
isoelectric point of less than 7; a second amino acid compound
having an isoelectric point of greater than 7; and a pH in a range
from about 1 to about 5.
2. The composition of claim 1, having a pH in a range from about 3
to about 5.
3. The composition of claim 1, wherein the first amino acid
compound is selected from the group consisting of alanine,
phenylalanine, glycine, leucine, isoleucine, proline, tyrosine,
valine, glutamic acid, and mixtures thereof.
4. The composition of claim 1, wherein the first amino acid
compound is selected from glycine, valine, alanine, and mixtures
thereof.
5. The composition of claim 1, wherein the second amino acid
compound is selected from the group consisting of histidine,
arginine, lysine, and mixtures thereof.
6. The composition of claim 1, wherein the first amino acid
compound is glycine and the second amino acid compound is
arginine.
7. The composition of claim 1 comprising: from about 0.05 to about
1 weight percent of the first amino acid compound; and from about
0.005 to about 0.2 weight percent of the second amino acid
compound.
8. The composition of claim 1, wherein the cationic abrasive
particles have a zeta potential in a range from about 10 mV to
about 40 mV in the composition.
9. The composition of claim 1, wherein: the cationic abrasive
particles comprise colloidal silica abrasive particles having a
permanent positive charge; the colloidal silica abrasive particles
have a zeta potential in range from about 10 mV to about 40 mV in
the composition; the colloidal silica abrasive particles have an
average particle size greater than about 40 nm; and the composition
has a pH in a range from about 3.5 to about 5.
10. The composition of claim 1, further comprising an iron
containing accelerator.
11. The composition of claim 10, further comprising a stabilizer
bound to the iron containing accelerator, the stabilizer being
selected from the group consisting of phosphoric acid, phthalic
acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic
acid, succinic acid, glutaric acid, pimelic acid, suberic acid,
azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic
acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic
acid, and mixtures thereof.
12. The composition of claim 1, further comprising a hydrogen
peroxide oxidizer.
13. A chemical mechanical polishing composition for polishing a
substrate having a tungsten layer, the composition comprising: a
water based liquid carrier; colloidal silica abrasive particles
having a permanent positive charge and an average particle size
greater than about 40 nm dispersed in the liquid carrier; the
colloidal silica abrasive particles having a zeta potential in a
range from about 10 mV to about 40 mV in the composition. a first
amino acid compound having an isoelectric point less than about 7;
a second amino acid compound having an isoelectric greater than
about 7; and a pH in a range from about 3.5 to about 5.
14. The composition of claim 13, wherein the first amino acid
compound is selected from the group consisting of glycine, valine,
alanine, and mixtures thereof and the second amino acid compound is
selected from the group consisting of histidine, arginine, lysine
and mixtures thereof.
15. The composition of claim 14, comprising: from about 0.05 to
about 1 weight percent of the first amino acid compound; and from
about 0.005 to about 0.2 weight percent of the second amino acid
compound.
16. The composition of claim 13, further comprising an iron
containing accelerator and a stabilizer bound to the iron
containing accelerator, the stabilizer being selected from the
group consisting of phosphoric acid, phthalic acid, citric acid,
adipic acid, oxalic acid, malonic acid, aspartic acid, succinic
acid, glutaric acid, pimelic acid, suberic acid, azelaic acid,
sebacic acid, maleic acid, glutaconic acid, muconic acid,
ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid,
and mixtures thereof.
17. The composition of claim 13, further comprising a hydrogen
peroxide oxidizer.
18. A chemical mechanical polishing composition for polishing a
substrate having a tungsten layer, the composition comprising: a
water based liquid carrier; colloidal silica abrasive particles
having an average particle size greater than about 90 nm dispersed
in the liquid carrier; a cationic surfactant that imparts a
non-permanent positive charge to the colloidal silica abrasive
particles; the colloidal silica abrasive particles having a zeta
potential in a range from about 10 mV to about 40 mV in the
composition; a first amino acid compound having an isoelectric
point less than about 7; a second amino acid compound having an
isoelectric greater than about 7; and a pH in a range from about 3
to about 4.5.
19. The composition of claim 18, wherein the first amino acid
compound is selected from the group consisting of glycine, valine,
alanine, and mixtures thereof and the second amino acid compound is
selected from the group consisting of histidine, arginine, lysine
and mixtures thereof.
20. The composition of claim 19, comprising: from about 0.05 to
about 1 weight percent of the first amino acid compound; and from
about 0.005 to about 0.2 weight percent of the second amino acid
compound.
21. The composition of claim 19, wherein the cationic surfactant
comprises one or a combination of tetrabutylammonium,
tetrapentylammonium, tetrabutylphosphonium,
tributylmethylphosphonium, tributyloctylphosphonium, and
benzyltributylammonium.
22. The composition of claim 19, further comprising an iron
containing accelerator and a stabilizer bound to the iron
containing accelerator, the stabilizer being selected from the
group consisting of phosphoric acid, phthalic acid, citric acid,
adipic acid, oxalic acid, malonic acid, aspartic acid, succinic
acid, glutaric acid, pimelic acid, suberic acid, azelaic acid,
sebacic acid, maleic acid, glutaconic acid, muconic acid,
ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid,
and mixtures thereof.
23. The composition of claim 19, further comprising a hydrogen
peroxide oxidizer.
24. A method of chemical mechanical polishing a substrate including
a tungsten layer, the method comprising: (a) contacting the
substrate with a polishing composition comprising: (i) a water
based liquid carrier; (ii) cationic abrasive particles dispersed in
the liquid carrier; (iii) a first amino acid compound having an
isoelectric point less than about 7; (iv) a second amino acid
compound having an isoelectric point greater than about 7; and (v)
a pH in a range from about 1 to about 5, (b) moving the polishing
composition relative to the substrate; and (c) abrading the
substrate to remove a portion of the tungsten from the substrate
and thereby polish the substrate.
25. The method of claim 24, wherein the first amino acid compound
is selected from the group consisting of glycine, valine, alanine,
and mixtures thereof and the second amino acid compound is selected
from the group consisting of histidine, arginine, lysine and
mixtures thereof.
26. The method of claim 25, wherein the polishing composition
comprises: from about 0.05 to about 1 weight percent of the first
amino acid compound; and from about 0.005 to about 0.2 weight
percent of the second amino acid compound
27. The method of claim 24, wherein: the cationic abrasive
particles comprise colloidal silica abrasive particles having a
permanent positive charge; the colloidal silica abrasive particles
have a zeta potential in range from about 10 mV to about 40 mV in
the composition; the colloidal silica abrasive particles have an
average particle size greater than about 40 nm; and the composition
has a pH in a range from about 3.5 to about 5.
28. The method of claim 24, wherein: the cationic abrasive
particles comprise colloidal silica abrasive particles; the
composition further comprises a cationic surfactant that imparts a
non-permanent positive charge to the colloidal silica abrasive
particles; the colloidal silica abrasive particles have a zeta
potential in range from about 10 mV to about 40 mV in the
composition; the colloidal silica abrasive particles have an
average particle size greater than about 90 nm; and the composition
has a pH in a range from about 3.0 to about 4.5.
29. The method of claim 24, wherein the composition further
comprises an iron containing accelerator; a stabilizer bound to the
iron containing accelerator, the stabilizer being selected from the
group consisting of phosphoric acid, phthalic acid, citric acid,
adipic acid, oxalic acid, malonic acid, aspartic acid, succinic
acid, glutaric acid, pimelic acid, suberic acid, azelaic acid,
sebacic acid, maleic acid, glutaconic acid, muconic acid,
ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid,
and mixtures thereof; and a hydrogen peroxide oxidizer.
Description
BACKGROUND OF THE INVENTION
[0001] Chemical mechanical polishing (CMP) compositions and methods
for polishing (or planarizing) the surface of a substrate are well
known in the art. Polishing compositions (also known as polishing
slurries, CMP slurries, and CMP compositions) for polishing metal
layers (such as tungsten) on a semiconductor substrate may include
abrasive particles suspended in an aqueous solution, chemical
accelerators such as oxidizers, chelating agents, and the like, and
corrosion/etch inhibitors for reducing the rate at which the metal
etches in the CMP slurry.
[0002] In tungsten plug and interconnect processes, tungsten is
generally deposited over a dielectric and within openings formed
therein. The excess tungsten over the dielectric layer is then
removed during a CMP operation to form tungsten plugs and
interconnects within the dielectric. As semiconductor device
feature sizes continue to shrink, meeting device requirements
including planarity and defect requirements has become more
difficult in CMP operations such as tungsten CMP operations. For
example, slurry induced defects including excessive localized
corrosion can reduce device yields. Excessive array erosion,
localized erosion, and tungsten plug and line recessing, can also
compromise overall electrical performance and reduce device
yields.
[0003] Commercially available tungsten CMP slurries commonly make
use of a hydrogen peroxide oxidizer. While there are many
advantages to the use of hydrogen peroxide, it is known to
contribute to excessive tungsten etching in certain CMP operations.
There remains a need in the industry for tungsten CMP slurries (or
compositions) that are less corrosive towards tungsten. Moreover,
as is well known in the art, the semiconductor industry is subject
to continuing and severe downward pricing pressure that extends to
the CMP consumables themselves (e.g., to the CMP slurries and
pads). Such pricing pressure poses a challenge to the slurry
formulator as the pressure to reduce costs often conflicts with the
desired slurry performance metrics. Thus, there is also a real need
in the industry for CMP slurries that are stable and that provide
high throughput at reduced overall costs.
BRIEF SUMMARY OF THE INVENTION
[0004] A chemical mechanical polishing composition for polishing a
substrate having a tungsten layer is disclosed. The polishing
composition comprises, consists of, or consists essentially of a
water based liquid carrier and cationic abrasive particles
dispersed in the liquid carrier. The composition further includes a
tungsten corrosion inhibitor having an isoelectric point of less
than 7 and a tungsten corrosion inhibitor having an isoelectric
point of greater than 7. The pH of the composition is in a range
from about 1 to about 5. A method for chemical mechanical polishing
a substrate including a tungsten layer is further disclosed. The
method may include contacting the substrate with the above
described polishing composition, moving the polishing composition
relative to the substrate, and abrading the substrate to remove a
portion of the tungsten from the substrate and thereby polish the
substrate.
DETAILED DESCRIPTION OF THE INVENTION
[0005] A chemical mechanical polishing composition for polishing a
substrate having a tungsten layer is disclosed. The polishing
composition comprises, consists of, or consists essentially of a
water based liquid carrier, cationic abrasive particles dispersed
in the liquid carrier, a first tungsten corrosion inhibitor (e.g.,
a first amino acid compound) having an isoelectric point of less
than 7, and a second tungsten corrosion inhibitor (e.g., a second
amino acid compound different from the first amino acid compound)
having an isoelectric point of greater than 7. The pH of the
composition is in a range from about 1 to about 5. The polishing
composition may further optionally include an iron containing
accelerator, such as a soluble iron accelerator, a stabilizer bound
to the iron containing accelerator, and a hydrogen peroxide
oxidizer. In one embodiment, the first amino acid compound may be
glycine and/or valine and the second amino acid compound may be
histidine, arginine, and/or lysine.
[0006] The disclosed polishing compositions and corresponding (CMP
methods) may confer significant and unexpected advantages. For
example, the disclosed polishing compositions tend to be both
chemically and colloidally stable such that both the pH of the
composition and the average size of abrasive particles in the
composition remain stable with time (e.g., essentially unchanged
with time). The polishing compositions may further provide improved
anti-corrosion performance (e.g., reduced tungsten etching) and
improved shelf and pot life. Moreover, the polishing compositions
and corresponding CMP methods may provide improved planarity
including improved array erosion, localized erosion, and tungsten
plug and line recessing.
[0007] It will be appreciated that the disclosed CMP compositions
may be advantageously utilized for bulk tungsten removal and/or
tungsten buff CMP operations. Bulk removal operations may require
higher tungsten removal rates while buff operations may require
lower defect levels and/or more stringent corrosion control. The
disclosed CMP compositions may also be advantageously utilized for
a single-step tungsten CMP operation. While the disclosed
embodiments may be particularly well suited for tungsten buff
operations, they are not intended to be limited to any particular
tungsten CMP operation.
[0008] The polishing composition contains an abrasive including
metal oxide (abrasive) particles suspended in a liquid carrier. The
abrasive may include substantially suitable metal oxide particles,
for example, including colloidal silica particles and/or fumed
silica particles. As used herein the term colloidal silica
particles refers to silica particles that are prepared via a wet
process rather than a pyrogenic or flame hydrolysis process which
commonly produces structurally different particles. Such colloidal
silica particles may be aggregated or non-aggregated.
Non-aggregated particles are individually discrete particles that
may be spherical or nearly spherical in shape, but can have other
shapes as well (such as generally elliptical, square, or
rectangular cross-sections). Aggregated particles are particles in
which multiple discrete particles are clustered or bonded together
to form aggregates having generally irregular shapes.
[0009] Colloidal silica may be precipitated or
condensation-polymerized silica, which may be prepared using any
method known to those of ordinary skill in the art, such as by the
sol gel method or by silicate ion-exchange.
Condensation-polymerized silica particles are often prepared by
condensing Si(OH).sub.4 to form substantially spherical particles.
The precursor Si(OH).sub.4 may be obtained, for example, by
hydrolysis of high purity alkoxysilanes, or by acidification of
aqueous silicate solutions. Such abrasive particles may be
prepared, for example, in accordance with U.S. Pat. No. 5,230,833
or may be obtained from any of a number of commercial suppliers,
for example, including EKA Chemicals, Fuso Chemical Company, Nalco,
DuPont, Bayer, Applied Research, Nissan Chemical, and Clariant.
[0010] Pyrogenic silica is produced via a flame hydrolysis process
in which a suitable feedstock vapor (such as silicon
tetra-chloride) is combusted in a flame of hydrogen and oxygen.
Molten particles of roughly spherical shapes are formed in the
combustion process, the diameters of which may be varied via
process parameters. These molten spheres, commonly referred to as
primary particles, fuse with one another by undergoing collisions
at their contact points to form branched, three dimensional
chain-like aggregates. Fumed silica abrasives are commercially
available from a number of suppliers including, for example, Cabot
Corporation, Evonic, and Wacker Chemie.
[0011] The polishing composition may include substantially any
suitable amount of the abrasive particles. If the polishing
composition comprises too little abrasive, the composition may not
exhibit a sufficient removal rate. In contrast, if the polishing
composition comprises too much abrasive, then the polishing
composition may exhibit undesirable polishing performance and/or
may not be cost effective and/or may lack stability. The polishing
composition may include about 0.01 wt. % or more abrasive particles
(e.g., about 0.05 wt. % or more). The polishing composition may
include about 0.1 wt. % or more (e.g., about 0.2 wt. % or more,
about 0.3 wt. % or more, or 0.5 wt. % or more) abrasive particles.
The concentration of abrasive particles in the polishing
composition is generally less than about 20 wt. %, and more
typically about 10 wt. % or less (e.g., about 5 wt. % or less,
about 3 wt. % or less, about 2 wt. % or less, or about 1.5 wt. % or
less, or about 1 wt. % or less). It will be understood that the
abrasive particles may be present in the polishing composition at a
concentration bounded by any two of the aforementioned endpoints.
For example, the concentration of abrasive particles in the
polishing composition may be in a range from about 0.01 wt. % to
about 20 wt. %, and more preferably from about 0.05 wt. % to about
10 wt. % (e.g., from about 0.1 wt. % to about 5 wt. %, from about
0.1 wt. % to about 3 wt. %, from about 0.1 wt. % to about 2 wt. %,
from about 0.2 wt. % to about 2 wt. %, from about 0.2 wt. % to
about 1.5 wt. %, or from about 0.2 wt. % to about 1 wt. %).
[0012] The abrasive may include cationic (positively charged)
abrasive particles. For example, the abrasive may include cationic
silica abrasive particles. The cationic silica particles may have a
permanent positive charge or a non-permanent positive charge. For
example, the cationic silica abrasive particles may have a
permanent positive charge. By permanent positive charge it is meant
that the positive charge on the silica particles is not readily
reversible, for example, via flushing, dilution, filtration, and
the like. A permanent positive charge may be the result, for
example, of covalently bonding a cationic compound with the
colloidal silica. A permanent positive charge is in contrast to a
reversible positive charge that may be the result, for example, of
an electrostatic interaction between a cationic compound and the
colloidal silica.
[0013] Notwithstanding, as used herein, a permanent positive charge
of at least 10 mV means that the zeta potential of the colloidal
silica particles remains above 10 mV after the following three step
ultrafiltration test. A volume of the polishing composition (e.g.,
200 ml) is passed through a Millipore Ultracell regenerated
cellulose ultrafiltration disk (e.g., having a MW cutoff of 100,000
Daltons and a pore size of 6.3 nm). The remaining dispersion (the
dispersion that is retained by the ultrafiltration disk) is
collected and replenished to the original volume with pH adjusted
deionized water. The deionized water is pH adjusted to the original
pH of the polishing composition using a suitable inorganic acid
such as nitric acid. This procedure is repeated for a total of
three ultrafiltration cycles (each of which includes an
ultrafiltration step and a replenishing step). The zeta-potential
of the triply ultra-filtered and replenished polishing composition
is then measured and compared with the zeta potential of the
original polishing composition. This three step ultrafiltration
test is described in further detail in Example 10 of commonly
assigned U.S. Pat. No. 9,422,456, which is incorporated herein by
reference in its entirety.
[0014] Cationic silica abrasive particles having a permanent
positive charge may be prepared via treating the silica particles
with an aminosilane compound as disclosed in commonly assigned U.S.
Pat. Nos. 7,994,057 and 9,028,572 or in U.S. Pat. No. 9,382,450,
each of which is incorporated by reference herein in its entirety.
Example cationic silica particles may be treated using any suitable
treating method to obtain the cationic particles. For example, a
quaternary aminosilane compound and the colloidal silica may be
added simultaneously to some or all of the other components in the
polishing composition. Alternatively, the silica particles may be
treated with a quaternary aminosilane compound (e.g., via a heating
a mixture of the colloidal silica and the aminosilane) prior to
mixing with the other components of the polishing composition.
Colloidal silica particles having a permanent positive charge may
also be obtained by incorporating a chemical species, such as an
aminosilane compound, in the colloidal silica particles as
disclosed in in commonly assigned U.S. Pat. No. 9,422,456.
[0015] Cationic silica abrasive particles having a non-permanent
positive charge may be prepared via introducing a cationic
surfactant into the polishing composition, for example, as
disclosed commonly assigned U.S. Pat. No. 9,631,122, which is
incorporated by reference herein in its entirety. Such cationic
surfactants may include, for example, one or a combination of
tetrabutylammonium, tetrapentylammonium, tetrabutylphosphonium,
tributylmethylphosphonium, tributyloctylphosphonium, and
benzyltributylammonium.
[0016] As noted above, the abrasive particles (such as silica
particles) may have a positive charge in the polishing composition.
The charge on dispersed particles is commonly referred to in the
art as the zeta potential (or the electrokinetic potential). The
zeta potential of a particle refers to the electrical potential
difference between the electrical charge of the ions surrounding
the particle and the electrical charge of the bulk solution of the
polishing composition (e.g., the liquid carrier and any other
components dissolved therein). The zeta potential generally depends
on the pH of the aqueous medium. For a given polishing composition,
the isoelectric point of the particles is defined as the pH at
which the zeta potential is zero. As the pH is increased or
decreased away from the isoelectric point, the surface charge (and
hence the zeta potential) is correspondingly decreased or increased
(to negative or positive zeta potential values). The zeta potential
of a dispersion such as a polishing composition may be obtained
using commercially available instrumentation such as the Zetasizer
available from Malvern Instruments, the ZetaPlus Zeta Potential
Analyzer available from Brookhaven Instruments, and/or an
electro-acoustic spectrometer available from Dispersion
Technologies, Inc.
[0017] In certain embodiments, the cationic silica abrasive
particles have a zeta potential of about 10 mV or more (e.g., about
15 mV or more, about 20 mV or more, about 25 mV or more, or about
30 mV or more) in the polishing composition (e.g., in a pH range
from about 1 to about 5 and in the presence of the first and second
amino acid compounds disclosed below and other optional additives).
The cationic silica abrasive particles may have a zeta potential of
about 50 mV or less (e.g., about 45 mV or less or about 40 mV or
less) in the polishing composition. It will be understood that the
cationic silica abrasive particles may have a zeta potential in a
range bounded by any two of the aforementioned endpoints. For
example, the cationic silica abrasive particles may have a zeta
potential in a range from about 10 mV to about 50 mV (e.g., about
10 mV to about 45 mV, or about 20 mV to about 40 mV) in the
polishing composition.
[0018] The abrasive particles may have substantially any suitable
particle size. The particle size of a particle suspended in a
liquid carrier may be defined in the industry using various means.
For example, the particle size may be defined as the diameter of
the smallest sphere that encompasses the particle and may be
measured using a number of commercially available instruments, for
example, including the CPS Disc Centrifuge, Model DC24000HR
(available from CPS Instruments, Prairieville, La.) or the
Zetasizer.RTM. available from Malvern Instruments.RTM.. The
abrasive particles may have an average particle size of about 5 nm
or more (e.g., about 10 nm or more, about 20 nm or more, or about
30 nm or more). The abrasive particles may have an average particle
size of about 250 nm or less (e.g., about 200 nm or less, about 150
nm or less, about 120 nm or less, or about 100 nm or less, or about
80 nm or less). It will thus be understood that the abrasive
particles may have an average particle size in a range bounded by
any two of the aforementioned endpoints. For example, the abrasive
particles may have an average particle size in a range from about 5
nm to about 250 nm (e.g., from about 10 nm to about 200 nm, from
about 20 nm to about 150 nm, from about 20 nm to about 120 nm, or
from about 30 nm to about 100 nm).
[0019] In embodiments in which the abrasive particles include
cationic silica particles having a permanent positive charge, the
cationic silica particles may advantageously have a particle size
greater than about 40 nm (e.g., in a range from about 40 nm to
about 200 nm, from about 40 nm to about 150 nm, from about 40 nm to
about 120 nm, or from about 40 nm to about 80 nm). In embodiments
in which the abrasive particles include cationic silica particles
having a non-permanent positive charge, the cationic silica
particles may advantageously have a particle size greater than
about 90 nm (e.g., in a range from about 90 nm to about 250 nm,
from about 90 nm to about 200 nm, from about 90 nm to about 150 nm,
or from about 90 nm to about 120 nm).
[0020] A liquid carrier is used to facilitate the application of
the abrasive and any optional chemical additives to the surface of
the substrate to be polished (e.g., planarized). The liquid carrier
may be any suitable carrier (e.g., a solvent) including lower
alcohols (e.g., methanol, ethanol, etc.), ethers (e.g., dioxane,
tetrahydrofuran, etc.), water, and mixtures thereof. Preferably,
the liquid carrier comprises, consists essentially of, or consists
of water, more preferably deionized water.
[0021] The polishing composition is generally acidic having a pH of
less than about 7. The polishing composition may have a pH of about
1 or more (e.g., about 2 or more, about 2.5 or more, about 3 or
more, or about 3.5 or more). Moreover, the polishing composition
may have a pH of about 6 or less (e.g., about 5 or less, about 4.5
or less, or about 4 or less). It will be understood that the
polishing composition may have a pH in a range bounded by any two
of the aforementioned endpoints, for example, in a range from about
1 to about 5 (e.g., from about 2 to about 5, from about 2 to about
4, from about 2.5 to about 5, from about 3 to about 5, from about 3
to about 4.5, or from about 3.5 to about 5). In embodiments in
which the abrasive particles include cationic silica particles
having a permanent positive charge, the pH may advantageously be in
a range from about 3.5 to about 5. In embodiments in which the
abrasive particles include cationic silica particles having a
non-permanent positive charge, the pH may advantageously be in a
range from about 3 to about 4.5.
[0022] It will be understood that the pH of the polishing
composition may be achieved and/or maintained by any suitable
means. The polishing composition may include substantially any
suitable pH adjusting agents or buffering systems. For example,
suitable pH adjusting agents may include nitric acid, sulfuric
acid, phosphoric acid, phthalic acid, citric acid, adipic acid,
oxalic acid, malonic acid, maleic acid, ammonium hydroxide, and the
like while suitable buffering agents may include phosphates,
sulfates, acetates, malonates, oxalates, borates, ammonium salts,
and the like. The disclosed embodiments are not limited in this
regard.
[0023] Optional embodiments of the polishing composition may
further include an iron containing accelerator. An iron containing
accelerator as used herein is an iron containing chemical compound
that increases the removal rate of tungsten during a tungsten CMP
operation. For example, the iron containing accelerator may include
a soluble iron containing catalyst such as is disclosed in U.S.
Pat. Nos. 5,958,288 and 5,980,775. Such an iron containing catalyst
may be soluble in the liquid carrier and may include, for example,
ferric (iron III) or ferrous (iron II) compounds such as iron
nitrate, iron sulfate, iron halides, including fluorides,
chlorides, bromides, and iodides, as well as perchlorates,
perbromates and periodates, and organic iron compounds such as iron
acetates, carboxylic acids, acetylacetonates, citrates, gluconates,
malonates, oxalates, phthalates, and succinates, and mixtures
thereof.
[0024] An iron containing accelerator may also include an iron
containing activator (e.g., a free radical producing compound) or
an iron containing catalyst associated with (e.g., coated or bonded
to) the surface of the colloidal silica particle such as is
disclosed in U.S. Pat. Nos. 7,029,508 and 7,077,880. For example,
the iron containing accelerator may be bonded with the silanol
groups on the surface of the colloidal surface particle.
[0025] The amount of iron containing accelerator in the polishing
composition may be varied depending upon whether or not an
oxidizing agent used and the chemical form of the accelerator and
optional oxidizing agent. When a hydrogen peroxide oxidizer (or one
of its analogs) is used and a soluble iron containing catalyst is
used (such as ferric nitrate), the catalyst may be present in the
composition in an amount sufficient to provide a range from about
0.5 to about 3000 ppm Fe based on the total weight of the
composition. The polishing composition may include about 1 ppm Fe
or more (e.g., about 2 ppm or more, about 5 ppm or more, or about
10 ppm or more). The polishing composition preferably includes
about 500 ppm Fe or less (e.g., about 200 ppm or less, about 100
ppm or less, or about 50 ppm or less). The polishing composition
may thus include a range from about 1 to about 500 ppm Fe (e.g.,
from about 2 to about 200 ppm, from about 5 to about 100 ppm, or
from about 10 to about 50 ppm). Polishing compositions used for
bulk tungsten removal may include from about 5 to about 50 ppm Fe
(e.g., from about 10 to about 40 ppm Fe). Polishing compositions
used for a tungsten buffing operation may include from about 0.5 to
about 20 ppm Fe (e.g., from about 1 to about 10 ppm Fe).
[0026] Embodiments of the polishing composition including an iron
containing accelerator may further include a stabilizer. Without
such a stabilizer, the iron containing accelerator and an oxidizing
agent, if present, may react in a manner that degrades the
oxidizing agent rapidly over time. The addition of a stabilizer
tends to reduce the effectiveness of the iron containing
accelerator such that the choice of the type and amount of
stabilizer added to the polishing composition may have a
significant impact on CMP performance. The addition of a stabilizer
may lead to the formation of a stabilizer/accelerator complex that
inhibits the accelerator from reacting with the oxidizing agent, if
present, while at the same time allowing the accelerator to remain
sufficiently active so as to promote rapid tungsten polishing
rates.
[0027] Useful stabilizers include phosphoric acid, organic acids,
phosphonate compounds, nitriles, and other ligands which bind to
the metal and reduce its reactivity toward hydrogen peroxide
decomposition and mixture thereof. The acid stabilizers may be used
in their conjugate form, e.g., the carboxylate can be used instead
of the carboxylic acid. The term "acid" as it is used herein to
describe useful stabilizers also means the conjugate base of the
acid stabilizer. For example the term "adipic acid" means adipic
acid and its conjugate base. Stabilizers can be used alone or in
combination and significantly decrease the rate at which oxidizing
agents such as hydrogen peroxide decompose.
[0028] The stabilizer may include phosphoric acid, acetic acid,
phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid,
aspartic acid, succinic acid, glutaric acid, pimelic acid, suberic
acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid,
muconic acid, ethylenediaminetetraacetic acid (EDTA),
propylenediaminetetraacetic acid (PDTA), and mixtures thereof. Such
stabilizers may be added to the disclosed compositions in an amount
ranging from about 1 equivalent per iron containing accelerator to
about 3.0 weight percent or more (e.g., from about 3 to about 10
equivalents). As used herein, the term "equivalent per iron
containing accelerator" means one molecule of stabilizer per iron
ion in the composition. For example 2 equivalents per iron
containing accelerator means two molecules of stabilizer for each
iron ion.
[0029] The polishing composition may optionally further include an
oxidizing agent. Such an optional oxidizing agent may be added to
the polishing composition during the slurry manufacturing process
or just prior to the CMP operation (e.g., in a tank located at the
semiconductor fabrication facility). Preferable oxidizing agents
include inorganic or organic per-compounds. A per-compound as
defined herein is a compound containing at least one peroxy group
(--O--O--) or a compound containing an element in its highest
oxidation state. Examples of compounds containing at least one
peroxy group include but are not limited to hydrogen peroxide and
its adducts such as urea hydrogen peroxide and percarbonates,
organic peroxides such as benzoyl peroxide, peracetic acid, and
di-t-butyl peroxide, monopersulfates (SO.sub.5.sup.=),
dipersulfates (S.sub.2O.sub.8.sup.=), and sodium peroxide. Examples
of compounds containing an element in its highest oxidation state
include but are not limited to periodic acid, periodate salts,
perbromic acid, perbromate salts, perchloric acid, perchlorate
salts, perboric acid, and perborate salts and permanganates. The
most preferred oxidizing agents is hydrogen peroxide.
[0030] When used, an oxidizing agent may be present in the
polishing composition in an amount ranging, for example, from about
0.1 to about 10 weight percent. In embodiments in which a hydrogen
peroxide oxidizing agent and a soluble iron containing accelerator
are used, the oxidizing agent may be present in the polishing
composition in an amount ranging from about 0.1 to about 6 weight
percent (e.g., from about 0.2 to about 5 weight percent, from about
0.3 to about 4 weight percent, or from about 0.5 to about 3 weight
percent).
[0031] The disclosed polishing compositions further include at
least first and second tungsten corrosion inhibitors including
zwitterionic chelating compounds such as amino acid compounds in
solution in the liquid carrier. The first tungsten corrosion
inhibitor is a neutral zwitterionic chelating compound at the pH of
the polishing composition. The second tungsten corrosion inhibitor
is a cationic zwitterionic chelating compound at the pH of the
polishing composition. The first and second tungsten corrosion
inhibitors may be characterized by their corresponding isoelectric
points. It will be understood that the isoelectric point (pi) of an
organic acid compound is the pH at which the compound as a whole is
neutral (uncharged) such that the zwitterion form is dominant. The
isoelectric point is also referred to in the art as the
isoelectronic point and the isoionic point.
[0032] The first and second tungsten corrosion inhibitors may
advantageously be amino acid compounds due in part to the
availability, affordability, and low toxicity of amino acids. In
one embodiment, the first tungsten corrosion inhibitor may be a
first amino acid compound that has an isoelectric point of less
than 7 (e.g., less than 6). For example, the first amino acid
compound may include alanine, phenylalanine, glycine, leucine,
isoleucine, proline, tyrosine, valine, and glutamic acid. The first
amino acid compound may also have an isoelectric point in a range
from about 4 to about 7 (e.g., in a range from about 5 to about 6).
For example, the first amino acid compound may be selected from
glycine, valine, alanine, and mixtures thereof.
[0033] In certain embodiments, the first amino acid compound may
include amino acid compounds having non-polar side chains. In such
embodiments, the first amino acid compound may be selected from
glycine, alanine, valine, leucine, isoleucine, methionine, proline,
phenylalanine, tryptophan, and mixtures thereof (e.g., including
glycine, alanine, valine, and mixtures thereof).
[0034] The second tungsten corrosion inhibitor may be a second
amino acid compound that has an isoelectric point of greater than 7
(e.g., greater than 8, or greater than 9). It will be understood
that the second amino acid compound is necessarily different than
the first amino acid compound. The second amino acid compound may
include amino acid compounds having basic side chains. In such
embodiments, the second amino acid compound may be selected from
lysine, arginine, histidine, and mixtures thereof.
[0035] In certain preferred embodiments, the first amino acid
compound may be glycine and the second amino acid compound may be
lysine, arginine, and/or histidine. In other preferred embodiments,
the first amino acid compound may be valine and the second amino
acid compound may be lysine, arginine, and/or histidine.
[0036] The first and second amino acid compounds may further
include polymers compounds having an amino acid monomer unit (also
referred to in the art as a polyamino acid). For example, the first
amino acid compound may include a polyamino acid having monomer
units selected from glycine, alanine, valine, leucine, isoleucine,
methionine, proline, phenylalanine, tryptophan, and mixtures
thereof. Likewise, the second amino acid may include a polyamino
acid having monomer units selected from lysine, arginine,
histidine, ornithine, and mixtures thereof. In embodiments,
including polymer compounds, the polyamino acid may be a
homopolymer or a copolymer. Copolymers include two or more
different monomer units. In suitable copolymers at least one of the
monomer units is an amino acid.
[0037] The polishing composition may include substantially any
suitable amount of the first and second tungsten corrosion
inhibitors (e.g., amino acid compounds). As described in more
detail below, polishing composition may advantageously include a
greater amount of the first inhibitor than the second inhibitor
(e.g., from about 3 times to about 30 times more of the first
inhibitor than the second inhibitor), although the disclosed
embodiments are not limited in this regard. If the polishing
composition includes too much inhibitor, it may exhibit undesirable
polishing performance (e.g., reduced removal rates) and/or may not
be cost effective, and/or may lack stability. The polishing
composition may include about 0.01 weight percent or more of the
first inhibitor (e.g., about 0.02 weight percent or more, about
0.03 weight percent or more, about 0.04 weight percent or more, or
about 0.05 weight percent or more). For example, the polishing
composition may include about 0.08 weight percent or more (e.g.,
about 0.1 weight percent or more, about 0.12 weight percent or
more, about 0.14 weight percent or more, or about 0.2 weight
percent or more) of the first inhibitor. The polishing composition
may also include about 2 weight percent or less of the first
inhibitor (e.g., about 1.5 weight percent or less, about 1 weight
percent or less, or about 0.5 weight percent or less). It will be
understood that the first tungsten corrosion inhibitor may be
present in the polishing composition at a concentration bounded by
any two of the aforementioned endpoints. For example, the
concentration of the first inhibitor in the polishing composition
may be in a range from about 0.01 weight percent to about 2 weight
percent (e.g., from about 0.05 weight percent to about 1 weight
percent, from about 0.8 weight percent to about 1 weight percent,
or from about 0.1 weight percent to about 1 weight percent).
[0038] The polishing composition may also include about 0.001
weight percent or more of the second tungsten corrosion inhibitor,
(e.g., about 0.002 weight percent or more, about 0.003 weight
percent or more, or about 0.004 weight percent or more). For
example, the polishing composition may include about 0.005 weight
percent or more (e.g., about 0.008 weight percent or more, about
0.01 weight percent or more, about 0.02 weight percent or more,
about 0.03 weight percent or more, or about 0.05 weight percent or
more) of the second inhibitor. The polishing composition may also
include about 1 weight percent or less of the second inhibitor
(e.g., about 0.5 weight percent or less, about 0.2 weight percent
or less, about 0.1 weight percent or less, or about 0.05 weight
percent or less). It will be understood that the second tungsten
corrosion inhibitor may be present in the polishing composition at
a concentration bounded by any two of the aforementioned endpoints.
For example, the concentration of the second corrosion inhibitor in
the polishing composition may be in a range from about 0.001 weight
percent to about 1 weight percent (e.g., from about 0.002 weight
percent to about 0.5 weight percent, from about 0.005 weight
percent to about 0.2 weight percent, or from about 0.005 weight
percent to about 0.1 weight percent).
[0039] One aspect of the disclosed embodiments is the surprising
discovery that the use of a combined tungsten inhibitor system
including first and second different tungsten inhibitor compounds
as described above provides (i) suitable anti-corrosion performance
(tungsten corrosion inhibition) and (ii) chemical and colloidal
stability such that both the pH of the composition and the average
size of abrasive particles in the composition remain essentially
stable with time. It was further discovered that the disclosed
polishing compositions may further provide suitable throughput,
improved shelf and pot life, and improved planarity including
improved array erosion, localized erosion, and tungsten plug and
line recessing during a tungsten CMP operation.
[0040] The polishing composition may optionally further include a
biocide. The biocide may include any suitable biocide, for example
an isothiazolinone biocide. The amount of biocide in the polishing
composition typically is in a range from about 1 ppm to about 50
ppm, and preferably from about 1 ppm to about 20 ppm.
[0041] The polishing composition may be prepared using any suitable
techniques, many of which are known to those skilled in the art.
The polishing composition may be prepared in a batch or continuous
process. Generally, the polishing composition may be prepared by
combining the components thereof in any order. The term "component"
as used herein includes the individual ingredients (e.g., the
abrasive particles, the iron containing accelerator, the first and
second amino acid compounds, etc.)
[0042] For example, the silica may be dispersed in the aqueous
liquid carrier. Other components such as an iron containing
accelerator, a stabilizer, the first and second amino acid
compounds, and a biocide may then be added and mixed by any method
that is capable of incorporating the components into the polishing
composition. An optional oxidizing agent may be added at any time
during the preparation of the polishing composition. For example,
the polishing composition may be prepared prior to use, with one or
more components, such as a hydrogen peroxide oxidizing agent, being
added just prior to the CMP operation (e.g., within about 1 minute,
or within about 10 minutes, or within about 1 hour, or within about
1 day, or within about 1 week of the CMP operation). The polishing
composition also may also be prepared by mixing the components at
the surface of the substrate (e.g., on the polishing pad) during
the CMP operation.
[0043] The polishing composition of the invention may also be
provided as a concentrate which is intended to be diluted with an
appropriate amount of water prior to use. In such an embodiment,
the polishing composition concentrate may include abrasive
particles, the first and second amino acid compounds, the optional
iron containing accelerator and stabilizer, the optional biocide,
and water, with or without an oxidizing agent, in amounts such
that, upon dilution of the concentrate with an appropriate amount
of water, and an oxidizing agent if not already present in an
appropriate amount, each component of the polishing composition
will be present in the polishing composition in an amount within
the appropriate range recited above for each component. For
example, abrasive particles, the first and second amino acid
compounds, and the optional iron containing accelerator and
stabilizer, may each be present in the polishing composition in an
amount that is about 2 times (e.g., about 3 times, about 4 times,
or about 5 times) greater than the concentration recited above for
each component so that, when the concentrate is diluted with an
equal volume of (e.g., 1 equal volume of water, 2 equal volumes of
water, 3 equal volumes of water, or even 4 equal volumes of water
respectively), along with an optional oxidizing agent in a suitable
amount, each component will be present in the polishing composition
in an amount within the ranges set forth above for each component.
Furthermore, as will be understood by those of ordinary skill in
the art, the concentrate may contain an appropriate fraction of the
water present in the final polishing composition in order to ensure
that other components are at least partially or fully dissolved in
the concentrate.
[0044] Although the polishing composition of the invention may be
used to polish any substrate, the polishing composition is
particularly useful in the polishing of a substrate comprising at
least one metal including tungsten and at least one dielectric
material. The tungsten layer may be deposited over one or more
barrier layers, for example, including titanium and/or titanium
nitride (TiN). The dielectric layer may be a metal oxide such as a
silicon oxide layer derived from tetraethylorthosilicate (TEOS),
porous metal oxide, porous or non-porous carbon doped silicon
oxide, fluorine-doped silicon oxide, glass, organic polymer,
fluorinated organic polymer, or any other suitable high or low-k
insulating layer.
[0045] The polishing method of the invention is particularly suited
for use in conjunction with a chemical mechanical polishing (CMP)
apparatus. Typically, the apparatus includes a platen, which, when
in use, is in motion and has a velocity that results from orbital,
linear, or circular motion, a polishing pad in contact with the
platen and moving with the platen when in motion, and a carrier
that holds a substrate to be polished by contacting and moving
relative to the surface of the polishing pad. The polishing of the
substrate takes place by the substrate being placed in contact with
the polishing pad and the polishing composition of the invention
and then the polishing pad moving relative to the substrate, so as
to abrade at least a portion of the substrate (such as tungsten,
titanium, titanium nitride, and/or a dielectric material as
described herein) to polish the substrate.
[0046] A substrate can be planarized or polished with the chemical
mechanical polishing composition with any suitable polishing pad
(e.g., polishing surface). Suitable polishing pads include, for
example, woven and non-woven polishing pads. Moreover, suitable
polishing pads can comprise any suitable polymer of varying
density, hardness, thickness, compressibility, ability to rebound
upon compression, and compression modulus. Suitable polymers
include, for example, polyvinylchloride, polyvinylfluoride, nylon,
fluorocarbon, polycarbonate, polyester, polyacrylate, polyether,
polyethylene, polyamide, polyurethane, polystyrene, polypropylene,
co-formed products thereof, and mixtures thereof.
[0047] It will be understood that the disclosure includes numerous
embodiments. These embodiments include, but are not limited to, the
following embodiments.
[0048] In a first embodiment a chemical mechanical polishing
composition for polishing a substrate having a tungsten layer
includes a water based liquid carrier, cationic abrasive particles
dispersed in the liquid carrier, a first amino acid compound having
an isoelectric point of less than 7, a second amino acid compound
having an isoelectric point of greater than 7, and a pH in a range
from about 1 to about 5.
[0049] A second embodiment may include the first embodiment having
a pH in a range from about 3 to about 5.
[0050] A third embodiment may include any one of the first and
second embodiments wherein the first amino acid compound is
selected from the group consisting of alanine, phenylalanine,
glycine, leucine, isoleucine, proline, tyrosine, valine, glutamic
acid, and mixtures thereof.
[0051] A fourth embodiment may include any one of the first three
embodiments wherein the first amino acid compound is selected from
glycine, valine, alanine, and mixtures thereof.
[0052] A fifth embodiment may include any one of the first four
embodiments wherein the second amino acid compound is selected from
the group consisting of histidine, arginine, lysine, and mixtures
thereof.
[0053] A sixth embodiment may include any one of the first five
embodiments wherein the first amino acid compound is glycine and
the second amino acid compound is arginine.
[0054] A seventh embodiment may include any one of the first six
embodiments wherein the composition comprises from about 0.05 to
about 1 weight percent of the first amino acid compound and from
about 0.005 to about 0.2 weight percent of the second amino acid
compound.
[0055] An eighth embodiment may include any one of the first seven
embodiments wherein the cationic abrasive particles have a zeta
potential in a range from about 10 mV to about 40 mV in the
composition.
[0056] A ninth embodiment may include any one of the first eight
embodiments wherein the cationic abrasive particles comprise
colloidal silica abrasive particles having a permanent positive
charge, the colloidal silica abrasive particles have a zeta
potential in range from about 10 mV to about 40 mV in the
composition, the colloidal silica abrasive particles have an
average particle size greater than about 40 nm, and the composition
has a pH in a range from about 3.5 to about 5.
[0057] A tenth embodiment may include any one of the first eight
embodiments wherein the cationic abrasive particles comprise
colloidal silica abrasive particles and the composition further
comprises a cationic surfactant that imparts a non-permanent
positive charge to the colloidal silica abrasive particles.
[0058] An eleventh embodiment may include the tenth embodiment
wherein the cationic surfactant comprises one or a combination of
tetrabutylammonium, tetrapentylammonium, tetrabutylphosphonium,
tributylmethylphosphonium, tributyloctylphosphonium, and
benzyltributylammonium.
[0059] A twelfth embodiment may include the tenth embodiment
wherein the colloidal silica abrasive particles have a zeta
potential in range from about 10 mV to about 40 mV in the
composition, the colloidal silica abrasive particles have an
average particle size greater than about 90 nm, and the composition
has a pH in a range from about 3.0 to about 4.5.
[0060] A thirteenth embodiment may include any one of the first
twelve embodiments wherein the composition further includes an iron
containing accelerator.
[0061] A fourteenth embodiment may include the thirteenth
embodiment wherein the composition further includes a stabilizer
bound to the iron containing accelerator, the stabilizer being
selected from the group consisting of phosphoric acid, phthalic
acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic
acid, succinic acid, glutaric acid, pimelic acid, suberic acid,
azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic
acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic
acid, and mixtures thereof.
[0062] A fifteenth embodiment may include any one of the first
fourteen embodiments wherein the composition further includes a
hydrogen peroxide oxidizer.
[0063] In a sixteenth embodiment a chemical mechanical polishing
composition for polishing a substrate having a tungsten layer
includes a water based liquid carrier, colloidal silica abrasive
particles having a permanent positive charge and an average
particle size greater than about 40 nm dispersed in the liquid
carrier, the colloidal silica abrasive particles having a zeta
potential in a range from about 10 mV to about 40 mV in the
composition, a first amino acid compound having an isoelectric
point less than about 7, a second amino acid compound having an
isoelectric point greater than about 7, and a a pH in a range from
about 3.5 to about 5.
[0064] A seventeenth embodiment may include the sixteenth
embodiment wherein the first amino acid compound is selected from
the group consisting of glycine, valine, alanine, and mixtures
thereof and the second amino acid compound is selected from the
group consisting of histidine, arginine, lysine and mixtures
thereof.
[0065] An eighteenth embodiment may include the sixteenth or
seventeenth embodiments wherein the composition includes from about
0.05 to about 1 weight percent of the first amino acid compound and
from about 0.005 to about 0.2 weight percent of the second amino
acid compound.
[0066] A nineteenth embodiment may include any one of the sixteenth
through the eighteenth embodiments wherein the composition further
includes an iron containing accelerator and a stabilizer bound to
the iron containing accelerator, the stabilizer being selected from
the group consisting of phosphoric acid, phthalic acid, citric
acid, adipic acid, oxalic acid, malonic acid, aspartic acid,
succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic
acid, sebacic acid, maleic acid, glutaconic acid, muconic acid,
ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid,
and mixtures thereof.
[0067] A twentieth embodiment may include any one of the sixteenth
through the nineteenth embodiments wherein the composition further
includes a hydrogen peroxide oxidizer.
[0068] In a twenty-first embodiment a polishing composition for
polishing a substrate having a tungsten layer includes a water
based liquid carrier, colloidal silica abrasive particles having an
average particle size greater than about 90 nm, a cationic
surfactant that imparts a non-permanent positive charge to the
colloidal silica abrasive particles, the colloidal silica abrasive
particles having a zeta potential in a range from about 10 mV to
about 40 mV in the composition, a first amino acid compound having
an isoelectric point less than about 7, a second amino acid
compound having an isoelectric point greater than about 7, and a pH
in a range from about 3 to about 4.5.
[0069] A twenty-second embodiment may include the twenty-first
embodiment wherein the first amino acid compound is selected from
the group consisting of glycine, valine, alanine, and mixtures
thereof and the second amino acid compound is selected from the
group consisting of histidine, arginine, lysine and mixtures
thereof.
[0070] A twenty-third embodiment may include any one of the
twenty-first through the twenty-second embodiments wherein the
composition further includes from about 0.05 to about 1 weight
percent of the first amino acid compound and from about 0.005 to
about 0.2 weight percent of the second amino acid compound.
[0071] A twenty-fourth embodiment may include any one of the
twenty-first through the twenty-third embodiments wherein the
cationic surfactant comprises one or a combination of
tetrabutylammonium, tetrapentylammonium, tetrabutylphosphonium,
tributylmethylphosphonium, tributyloctylphosphonium, and
benzyltributylammonium.
[0072] A twenty-fifth embodiment may include any one of the
twenty-first through the twenty-fourth embodiments wherein the
composition further includes an iron containing accelerator and a
stabilizer bound to the iron containing accelerator, the stabilizer
being selected from the group consisting of phosphoric acid,
phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid,
aspartic acid, succinic acid, glutaric acid, pimelic acid, suberic
acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid,
muconic acid, ethylenediaminetetraacetic acid,
propylenediaminetetraacetic acid, and mixtures thereof.
[0073] A twenty-sixth embodiment may include any one of the
twenty-first through the twenty-fifth embodiments wherein the
composition further includes a hydrogen peroxide oxidizer.
[0074] In a twenty-seventh embodiment a method for chemical
mechanical polishing a substrate including a tungsten layer
includes (a) contacting the substrate with a polishing composition
comprising a water based liquid carrier, cationic abrasive
particles dispersed in the liquid carrier, a first amino acid
compound having an isoelectric point less than about 7, a second
amino acid compound having an isoelectric point greater than about
7, and a pH in a range from about 1 to about 5. The method further
includes (b) moving the polishing composition relative to the
substrate and (c) abrading the substrate to remove a portion of the
tungsten from the substrate and thereby polish the substrate.
[0075] A twenty-eighth embodiment may include the twenty-seventh
embodiment wherein the first amino acid compound is selected from
the group consisting of glycine, valine, alanine, and mixtures
thereof and the second amino acid compound is selected from the
group consisting of histidine, arginine, lysine and mixtures
thereof.
[0076] A twenty-ninth embodiment may include any one of the
twenty-seventh through the twenty-eighth embodiments wherein the
composition includes from about 0.05 to about 1 weight percent of
the first amino acid compound and from about 0.005 to about 0.2
weight percent of the second amino acid compound.
[0077] A thirtieth embodiment may include any one of the
twenty-seventh through the twenty-ninth embodiments wherein the
cationic abrasive particles comprise colloidal silica abrasive
particles having a permanent positive charge, the colloidal silica
abrasive particles have a zeta potential in range from about 10 mV
to about 40 mV in the composition, the colloidal silica abrasive
particles have an average particle size greater than about 40 nm,
and the composition has a pH in a range from about 3.5 to about
5.
[0078] A thirty-first embodiment may include any one of the
twenty-seventh through the twenty-ninth embodiments wherein the
cationic abrasive particles comprise colloidal silica abrasive
particles, the composition further comprises a cationic surfactant
that imparts a non-permanent positive charge to the colloidal
silica abrasive particles, the colloidal silica abrasive particles
have a zeta potential in range from about 10 mV to about 40 mV in
the composition, the colloidal silica abrasive particles have an
average particle size greater than about 90 nm, and the composition
has a pH in a range from about 3.0 to about 4.5.
[0079] A thirty-second embodiment may include any one of the
twenty-seventh through the thirty-first embodiments wherein the
composition further includes a hydrogen peroxide oxidizer, an iron
containing accelerator, and a stabilizer bound to the iron
containing accelerator, the stabilizer being selected from the
group consisting of phosphoric acid, phthalic acid, citric acid,
adipic acid, oxalic acid, malonic acid, aspartic acid, succinic
acid, glutaric acid, pimelic acid, suberic acid, azelaic acid,
sebacic acid, maleic acid, glutaconic acid, muconic acid,
ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid,
and mixtures thereof.
[0080] The following examples further illustrate the invention but,
of course, should not be construed as in any way limiting its
scope.
Example 1
[0081] A number of polishing compositions were prepared in order to
evaluate chemical stability (pH stability) of the compositions.
Each composition included 3 weight percent PL-5 colloidal silica
(available from Fuso Chemical Company), 0.09 weight percent
tetrabutylammonium hydroxide, 0.002 weight percent ferric nitrate
nonahydrate, 0.004 weight percent malonic acid, 0.0008 weight
percent Kathon LX biocide, and 1 millimolar of an amino acid
corrosion inhibitor. Example 1A included no amino acid inhibitor.
Examples 1B-1J included the following amino acids as indicated in
Table 1; arginine (1B), lysine (1C), histidine (1D), glutamic acid
(1E), isoleucine (1F), valine (1G), aspartic acid (1H), proline
(1I), and glutamine (1J).
[0082] Each composition was prepared as follows: a dispersion was
prepared including the PL-5 colloidal silica, tetrabutylammonium
hydroxide, ferric nitrate nonahydrate, malonic acid, Kathon LX and
amino acid corrosion inhibitor. The pH was adjusted to 3.4 with
nitric acid or potassium hydroxide.
[0083] The polishing compositions, corresponding amino acid
corrosion inhibitor, amino acid type (group A or group B), and pH
drift after seven days are provided in Table 1. Note that group A
amino acids have an isoelectric point of less than 7 and group B
amino acids have an isoelectric point of greater than 7.
TABLE-US-00001 TABLE 1 Polishing Amino Acid Amino Acid pH Drift
Composition (1 mM) Type (seven days) 1A None 0.7 1B Arginine B
>1 1C Lysine B >1 1D Histidine B 1.4 1E Glutamic Acid A 0.5
1F Isoleucine A 0.13 1G Valine A 0.16 1H Aspartic Acid A -0.1 1I
Proline A 0.4 1J Glutamine A 0.3
[0084] The data in Table 1 highlight one of the problems with CMP
compositions. Note that the pH of the compositions including
arginine, lysine, and histidine drifts significantly in just 7 days
(the pH of the composition rises over 1 pH unit) as compared to a
composition with no tungsten inhibitor. The pH of compositions
including glutamic acid, isoleucine, valine, aspartic acid,
proline, or glutamine does not drift as significantly.
Example 2
[0085] The tungsten static etch rate was evaluated for 22
compositions. Each composition included 3 weight percent PL-5
colloidal silica, 0.09 weight percent tetrabutylammonium hydroxide,
0.002 weight percent iron nitrate nonahydrate, 0.004 weight percent
malonic acid, 0.0008 weight percent (8 ppm) Kathon LX biocide, 0.35
weight percent hydrogen peroxide, and 1 mM of an amino acid
corrosion inhibitor. The pH was adjusted to 3.4 with nitric acid or
potassium hydroxide. In compositions including first and second
amino acids corrosion inhibitors, the total concentration of the
amino acid combination was 1 mM, with the first and second amino
acids included in a 1:1 molar ratio. The compositions were prepared
as described above in Example 1.
[0086] To obtain the tungsten etch rate for each polishing
composition, the composition was first heated to 60 degrees C.
after which the hydrogen peroxide was added to a concentration of
0.35 weight percent. After waiting 5 minutes for the temperature to
return to 60 degrees, a Silyb tungsten wafer (a 1-inch square
coupon) having an 8000 .ANG. thick tungsten layer was submersed in
the polishing composition for 5 minutes. Tungsten removal rates
were determined via resistivity measurements made before and after
immersion of the wafer in the polishing compositions. The amino
acid compound(s), amino acid type (group A or group B), and the
static etch rate of tungsten are provided in Table 2. Composition
2A included no inhibitor.
TABLE-US-00002 TABLE 2 Polishing Amino Acid Amino W Etch Rate
Composition (1 mM) Acid Type (Ang/min) 2A None 288 2B Lysine B 123
2C Glutamic Acid A 286 2D Histidine B 36 2E Isoleucine A 273 2F
Valine A 254 2G Aspartic Acid A 305 2H Proline A 293 2I Arginine B
29 2J Glutamine A 279 2K Isoleucine and A + B 62 Histidine 2L
Isoleucine and A + B 50 Arginine 2M Isoleucine and A + A 221
Aspartic Acid 2N Isoleucine and A + A 184 Glutamic Acid 2O Valine
and A + B 51 Histidine 2P Valine and A + B 39 Arginine 2Q Valine
and A + A 269 Aspartic Acid 2R Valine and A + A 221 Glutamic Acid
2S Glutamine and A + B 51 Histidine 2T Glutamine and A + B 41
Arginine 2U Glutamine and A + A 219 Aspartic Acid 2V Glutamine and
A + A 168 Glutamic Acid
[0087] As is apparent from the results set forth in Table 2,
compositions including type B amino acid compounds (particularly
arginine and histidine) exhibited low tungsten etch rates at 60
degrees C. (e.g., less than or equal to about 60 Angstroms per
minute). The compositions including type A and type B amino acids
also exhibited low tungsten etch rates.
Example 3
[0088] There are multiple tungsten deposition methods used in the
semiconductor industry and the deposition method has been observed
to impact tungsten corrosion. In this example, the tungsten static
etch rate was evaluated for 26 compositions (3A through 3Z). Each
composition included 4 weight percent Fuso PL-5 colloidal silica,
0.09 weight percent tetrabutylammonium hydroxide, 0.0018 weight
percent iron nitrate nonahydrate, 0.004 weight percent malonic
acid, 8 ppm Kathon LX biocide, 0.15 weight percent hydrogen
peroxide, and one or more amino acid compounds. The pH was adjusted
to 3.5 with nitric acid. The compositions were prepared as
described above in Example 1.
[0089] To obtain the tungsten etch rate for each polishing
composition, the composition was first heated to 60 degrees C.
after which the hydrogen peroxide was added to a concentration of
0.15 weight percent. After waiting 5 minutes for the temperature to
return to 60 degrees, a Silyb tungsten wafer (a 1-inch square
coupon) having a 2000 .ANG. thick tungsten layer was submersed in
the polishing composition for 5 minutes. Tungsten removal rates
were determined via resistivity measurements made before and after
immersion of the wafer in the polishing compositions. The amino
acid compound(s) and their corresponding concentration, amino acid
type (group A and/or group B) and concentration in parts per
million, and the static etch rate of tungsten are provided in Table
3. Composition 3A included no inhibitor.
TABLE-US-00003 TABLE 3 Polishing Amino W Etch Rate Composition
Amino Acid (ppm) Acid Type (Ang/min) 3A None 249 3B Glycine (1400)
A 25 3C Valine (1400) A 73 3D Isoleucine (1400) A 50 3E Histidine
(200) B 15 3F Lysine (200) B 72 3G Arginine (200) B 11 3H Arginine
(100) B 17 3I Glutamic Acid (1400) A 18 3J Glycine (1400) A + B 11
Histidine (200) 3K Glycine (1400) A + B 7 Histidine (100) 3L Valine
(1400) A + B 10 Histidine (200) 3M Valine (1400) A + B 10 Histidine
(100) 3N Isoleucine (1400) A + B 9 Histidine (200) 3O Glycine
(1400) A + B 17 Lysine (200) 3P Valine (1400) A + B 27 Lysine (200)
3Q Isoleucine (1400) A + B 21 Lysine (200) 3R Glycine (1400) A + B
7 Arginine (200) 3S Glycine (1400) A + B 11 Arginine (100) 3T
Valine (1400) A + B 11 Arginine (200) 3U Valine (1400) A + B 14
Arginine (100) 3V Isoleucine (1400) A + B 8 Arginine (200) 3W
Glutamic Acid (1400) A + B 5 Histidine (200) 3X Glutamic Acid
(1400) A + B 5 Histidine (100) 3Y Glutamic Acid (1400) A + A 173
Valine (200) 3Z Glutamic Acid (1400) A + A 248 Valine (100)
[0090] As is apparent from the results set forth in Table 3,
compositions including type B amino acid compounds (particularly
arginine and histidine) exhibited low tungsten etch rates at 60
degrees C. (e.g., less than or equal to about 30 Angstroms per
minute). The compositions including type A and type B amino acids
also exhibited low tungsten etch rates.
Example 4
[0091] Twenty two polishing compositions (4A through 4V) were
prepared to evaluate chemical and colloidal stability of polishing
compositions including amino acid compounds, particularly
compositions including a combination of type A and type B amino
acid compounds as compared with compositions including only type B
amino acid compounds. Each of the polishing compositions was
prepared as a 3.times. concentrate and included 12 weight percent
of the indicated colloidal silica (Fuso PL-2, PL-5, or PL-7), 0.27
weight percent tetrabutylammonium hydroxide, 0.0054 weight percent
iron nitrate nonahydrate, 0.012 weight percent malonic acid, and 15
ppm Kathon LX biocide. Table 4A indicates the amino acid
compound(s) and their corresponding concentration prior to
dilution, the pH and the silica included in each composition.
TABLE-US-00004 TABLE 4A Polishing Amino Silica Composition Amino
Acid (ppm) Acid Type pH (size) 4A Glycine (4200) A + B 3.5 PL-5
Histidine (300) (100 nm) 4B Glycine (4200) A + B 3.5 PL-5 Arginine
(300) (100 nm) 4C Glycine (4200) A + B 3.5 PL-5 Lysine (300) (100
nm) 4D Valine (4200) A + B 3.5 PL-5 Histidine (300) (100 nm) 4E
Valine (4200) A + B 3.5 PL-5 Arginine (300) (100 nm) 4F Valine
(4200) A + B 3.5 PL-5 Lysine (300) (100 nm) 4G Glycine (4200) A + B
2.3 PL-5 Histidine (300) (100 nm) 4H Glycine (4200) A + B 3.5 PL-2
Arginine (300) (40 nm) 4I Glycine (4200) A + B 3.5 PL-7 Arginine
(300) (120 nm) 4J Glycine (4200) A + B 3.5 PL-5 Histidine (600)
(100 nm) 4K Glycine (4200) A + B 3.5 PL-5 Lysine (600) (100 nm) 4L
Valine (4200) A + B 3.5 PL-5 Lysine (600) (100 nm) 4M Valine (4200)
A + B 3.5 PL-5 Arginine (600) (100 nm) 4N Valine (4200) A + B 3.5
PL-5 Histidine (600) (100 nm) 4O Glycine (4200) A + A 3.5 PL-5
Glutamic Acid (4200) (100 nm) 4P Valine (4200) A 3.5 PL-5 (100 nm)
4Q Histidine (300) B 3.5 PL-5 (100 nm) 4R Arginine (300) B 3.5 PL-5
(100 nm) 4S Lysine (300) B 3.5 PL-5 (100 nm) 4T Histidine (600) B
3.5 PL-5 (100 nm) 4U Arginine (600) B 3.5 PL-5 (100 nm) 4V Lysine
(600) B 3.5 PL-5 (100 nm)
[0092] As indicated in Table 4A, composition 4H included Fuso PL-2
(40 nm). Composition 41 included Fuso PL-7 (120 nm). The remainder
of the compositions (4A-4G and 4J-4V) included Fuso PL-5 (100 nm).
The pH of composition 4G was adjusted to 2.3 using nitric acid. The
pH of the remaining compositions was adjusted to 3.5 using nitric
acid. The compositions were prepared as described above in Example
1.
[0093] Diluted polishing compositions were prepared by diluting the
above described compositions with deionized water (1 part polishing
composition to 2 parts water). The diluted compositions represent
example point-of-use polishing compositions as used in a CMP
operation. These diluted compositions were monitored for chemical
and colloidal stability (pH, particle size, and zeta potential)
after 3 weeks at room temperature. The abrasive particle size and
zeta potential were measured using a Zetasizer.RTM. available from
Malvern Instruments. The amino acid compound(s) and their
corresponding concentration after dilution, amino acid type (group
A and/or group B), pH, particle size, and zeta potential are
provided in Table 4.
TABLE-US-00005 TABLE 4B Particle Zeta Polishing Amino Size
Potential Composition Amino Acid (ppm) Acid Type pH (nm) (mV) 4A
Glycine (1400) A + B 3.6 101 13.6 Histidine (100) 4B Glycine (1400)
A + B 3.6 104 13.4 Arginine (100) 4C Glycine (1400) A + B 3.7 106
13.8 Lysine (100) 4D Valine (1400) A + B 4.1 103 12.8 Histidine
(100) 4E Valine (1400) A + B 3.9 104 13.7 Arginine (100) 4F Valine
(1400) A + B 3.9 105 13.9 Lysine (100) 4G Glycine (1400) A + B 2.5
101 12.4 Histidine (100) 4H Glycine (1400) A + B 3.5 46 11.3
Arginine (100) 4I Glycine (1400) A + B 3.7 128 15.3 Arginine (100)
4J Glycine (1400) A + B 3.8 103 13.4 Histidine (200) 4K Glycine
(1400) A + B 3.7 103 13.5 Lysine (200) 4L Valine (1400) A + B 4.0
102 13.0 Lysine (200) 4M Valine (1400) A + B 3.9 103 13.3 Arginine
(200) 4N Valine (1400) A + B 3.6 103 11.8 Histidine (200) 4O
Glycine (1400) A + A 3.6 102 13.6 Glutamic Acid (1400) 4P Valine
(1400) A 3.8 98 12.6 4Q Histidine (100) B 5.0 145 7.8 4R Arginine
(100) B 5.3 1160 7.5 4S Lysine (100) B 5.4 2990 15.6 4T Histidine
(200) B 4.9 107 9.2 4U Arginine (200) B 5.2 1290 8.4 4V Lysine
(200) B 5.2 1030 12.2
[0094] It is evident from the data set forth in Table 4 that the
polishing compositions including a combination of type A and type B
amino acid compounds have superior chemical and colloidal stability
to the polishing compositions including only type B amino acid
compounds. By comparing further comparing the data set forth in
Tables 2 and 3 it is evident that only the polishing compositions
including a combination of type A and type B amino acid compounds
have suitable chemical and colloidal stability and acceptably low
tungsten etch rates. In particular, the polishing compositions
including only type A inhibitors exhibit high tungsten static etch
rates, while those including only type B inhibitors are chemically
and colloidally unstable.
Example 5
[0095] The polishing performance of polishing compositions 4A
through 4V (defined above in Table 4A of Example 4) and
compositions 5A through 5H was evaluated. With the exception of
composition 5B, each of the polishing compositions was prepared as
a 3.times. concentrate and included 12 weight percent colloidal
silica, 0.27 weight percent tetrabutylammonium hydroxide, 0.0054
weight percent iron nitrate nonahydrate, 0.012 weight percent
malonic acid, and 15 ppm Kathon LX biocide. Polishing composition
5B was prepared as a 1.5.times. concentrate and included 6 weight
percent colloidal silica, 0.14 weight percent tetrabutylammonium
hydroxide, 0.0027 weight percent iron nitrate nonahydrate, 0.006
weight percent malonic acid, and 8 ppm Kathon LX biocide. Each
composition was adjusted to pH 3.5 using nitric acid. Table 5A
indicates the amino acid compound(s) and their corresponding
concentration prior to dilution and the particular silica included
in each composition.
TABLE-US-00006 TABLE 5A Polishing Amino Composition Amino Acid
(ppm) Acid Type Silica (size) 5A Proline (4200) A + B PL-5 Arginine
(300) (100 nm) 5B Glutamic Acid (2100) A + B PL-5 Arginine (150)
(100 nm) 5C Proline (4200) A + B PL-5 Arginine (3000) (100 nm) 5D
Alanine (4200) A + B PL-5 Lysine (300) (100 nm) 5E Glycine (4200) A
+ B PL-7 Arginine (300) (120 nm) 5F Glycine (4200) A + B DVSTS006
Arginine (300) (60 nm) 5G Glycine (4200) A + B Tama 14 Arginine
(300) (72 nm) 5H Glycine (4200) A + B NexSil Arginine (300) 85K-40
(75 nm)
[0096] As indicated in Table 5A, compositions 5A-5D included Fuso
PL-5 (100 nm). Composition 5E included Fuso PL-7 (120 nm).
Composition 5F included DVSTS006 (60 nm) available from Nalco.
Composition 5G included Tama 14 (72 nm). Composition 5H included
NexSil.RTM. 85K-40 (75 nm) available from Nyacol Nano Technologies.
This example illustrates certain advantages of the disclosed
embodiments in tungsten buffing CMP. Polishing compositions found
to be unstable, such as by exhibiting particle growth (>15%) or
pH drift (>1 unit), were not considered suitable for polishing
(see Example 4). Tungsten pattern wafers (Silyb W854 L&S
patterns) were prepared by polishing to endpoint+10% using an
Applied Materials Mirra polishing tool and W8051 tungsten CMP
slurry available from Cabot Microelectronics Corp. These
pre-polished wafers were buff polished using diluted polishing
compositions selected from Tables 4A and 5A. Each of the
pre-polished wafers was buff polished using a Mirra polishing tool,
a NexPlanar E6088 polishing pad (available from Cabot
Microelectronics), a Saesol C1 conditioner (in-situ mode at 6 lbs.)
using a down force of 2.5 psi, a platen speed of 100 rpm, a head
speed of 101 rpm, and a slurry flow rate of 180 ml/min. Blanket
tungsten wafers (8000 .ANG. available from Novati) and TEOS wafers
(20000 .ANG. available from WRS Materials) were also polished for
60 seconds at the same conditions. The patterned wafers were
polished for corresponding times based on the blanket TEOS removal
rates with a target of 600 .ANG. TEOS removal.
[0097] Table 5B presents blanket and patterned wafer polishing data
for polishing compositions 4A-4C, 4F-4J, and 5A-5H. Each polishing
composition was diluted prior to polishing (to 3 weight percent
silica) and included 0.3 weight percent hydrogen peroxide. Table 5B
lists the blanket TEOS removal rate (RR), the blanket tungsten
removal rate (RR), the field oxide removed from the patterned
wafer, localized erosion (sometimes referred to as fang in the
industry) on a 1 .mu.m isolated tungsten line, array oxide erosion
on a 1.times.9 .mu.m array (10% W), and tungsten line protrusion on
a 1.times.9 .mu.m array (10% W) for each polishing composition.
TABLE-US-00007 TABLE 5B W Line Polishing TEOS Field Local Array
Pro- Compo- RR W RR Oxide Erosion Erosion trusion sition
(.ANG./min) (.ANG./min) (.ANG.) (.ANG.) (.ANG.) (.ANG.) 4A 513 265
562 Not Detected 14 171 4B 532 269 605 Not Detected 57 254 4C 499
317 643 Not Detected 17 220 4F 499 283 551 Not Detected 48 189 4G
590 212 651 55 70 300 4H 1407 302 665 53 82 444 4I 366 265 624 Not
Detected 65 160 4J 508 270 552 Not Detected 57 224 5A 517 254 594
Not Detected 13 264 5B 533 266 594 Not Detected 34 240 5C 561 208
629 Not Detected 44 322 5D 505 299 648 Not Detected 27 197 5E 367
211 619 Not Detected 23 181 5F 1176 232 559 Not Detected 1 285 5G
998 239 565 Not Detected 13 278 5H 1385 251 543 Not Detected 13
268
[0098] As is evident from the data set forth in Table 5B, the
disclosed polishing compositions including a group A amino acid
compound and a group B amino acid compound exhibit low array oxide
erosion and W line protrusion and undetected localized erosion on
an isolated line.
Example 6
[0099] The polishing performances of two polishing compositions
employing cationic silica having a permanent positive charge were
evaluated. Each polishing composition was prepared as a 3.times.
concentrate and included 12 weight percent colloidal silica, 0.27
weight percent tetrabutylammonium hydroxide, 0.0054 weight percent
iron nitrate nonahydrate, 0.012 weight percent malonic acid, 15 ppm
Kathon LX biocide, 4200 ppm Proline, and 300 ppm Arginine. The
cationic silica particles were prepared as described in Example 13
of commonly assigned U.S. Pat. No. 9,422,456. The pH of polishing
composition 6A was adjusted to 4.5 using nitric acid. The pH of
composition 6B was adjusted to 3.5 using nitric acid.
[0100] Tungsten patterned wafers, tungsten blanket wafers, and TEOS
blanket wafers were polished as described above with respect to
Example 5. Table 6 presents blanket and patterned wafer polishing
data for polishing compositions 6A and 6B. Each polishing
composition was diluted prior to polishing (to 3 weight percent
silica) and included 0.3 weight percent hydrogen peroxide. Table 6
lists the same metrics as shown in Table 5B.
TABLE-US-00008 TABLE 6 W Line Polishing TEOS Field Local Array Pro-
Compo- RR W RR Oxide Erosion Erosion trusion sition (.ANG./min)
(.ANG./min) (.ANG.) (.ANG.) (.ANG.) (.ANG.) 6A 1393 354 565 Not
Detected 1 286 6B 518 328 1212 104 115 561
[0101] As is evident from the data set forth in Table 6, the
disclosed polishing compositions including a group A amino acid
compound and a group B amino acid compound and a permanently
charged cationic silica exhibit low array erosion and W line
protrusion and undetected localized erosion on an isolated W line,
particularly at pH greater than 3.5.
Example 7
[0102] Eight polishing compositions were prepared to evaluate pH
drift and static etch rate as a function of amino acid
concentration in the polishing composition. Each polishing
composition included 4.5 weight percent Fuso PL-5 colloidal silica,
0.09 weight percent tetrabutylammonium hydroxide, 0.0018 weight
percent iron nitrate nonahydrate, 0.004 weight percent malonic
acid, 8 ppm Kathon LX biocide. The pH was adjusted to 3.5 using
nitric acid. Compositions 7A-7D included valine (type A) and
compositions 7E-7H included histidine (type B). Hydrogen peroxide
was added to each composition to a concentration of 0.15 weight
percent. The static etch rates were obtained as described above in
Example 3 (using the W wafer coupons described above in Example
2).
[0103] Table 7 discloses the amino acid, the amino acid
concentration, the static etch rate, and the pH drift (after two
days) for each composition.
TABLE-US-00009 TABLE 7 Polishing Amino [Amino Acid] WSER
Composition Acid ppm) (.ANG./min) pH drift 7A Valine 100 100 0.8 7B
Valine 400 110 0.4 7C Valine 800 98 0.2 7D Valine 1400 100 0.1 7E
Histidine 25 28 0.7 7F Histidine 50 6 0.4 7G Histidine 100 4 0.6 7H
Histidine 500 5 0.4
[0104] As is evident in the data set forth in Table 7, minimal pH
drift can be achieved using higher concentrations of type A amino
acids (e.g., greater than 1000 ppm) and significantly reduced
static etch rates can be achieved at greater than about 25 ppm of
type B amino acids.
[0105] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. Recitation of ranges of values herein are
merely intended to serve as a shorthand method of referring
individually to each separate value falling within the range,
unless otherwise indicated herein, and each separate value is
incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the invention and does not
pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0106] Preferred embodiments of this invention are described
herein, including the best mode known to the inventors for carrying
out the invention. Variations of those preferred embodiments may
become apparent to those of ordinary skill in the art upon reading
the foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
* * * * *