U.S. patent application number 10/349987 was filed with the patent office on 2003-07-31 for chemical mechanical polishing slurry and method for using same.
This patent application is currently assigned to Cabot Microelectronics Corporation. Invention is credited to Mueller, Brian L., Steckenrider, J. Scott.
Application Number | 20030143848 10/349987 |
Document ID | / |
Family ID | 22303838 |
Filed Date | 2003-07-31 |
United States Patent
Application |
20030143848 |
Kind Code |
A1 |
Steckenrider, J. Scott ; et
al. |
July 31, 2003 |
Chemical mechanical polishing slurry and method for using same
Abstract
An aqueous chemical mechanical polishing slurry useful for
polishing the polysilicon layer of a semiconductor wafer comprising
an aqueous solution of at least one abrasive, and at least one
alcoholamine. The slurry preferably has a pH of from about 9.0 to
about 10.5 and it includes an optional buffering agent.
Inventors: |
Steckenrider, J. Scott;
(Plainfield, IL) ; Mueller, Brian L.; (Aurora,
IL) |
Correspondence
Address: |
Phyllis Turner-Brim
Cabot Microelectronics Corp.
870 Commons Drive
Aurora
IL
60504
US
|
Assignee: |
Cabot Microelectronics
Corporation
|
Family ID: |
22303838 |
Appl. No.: |
10/349987 |
Filed: |
January 23, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10349987 |
Jan 23, 2003 |
|
|
|
09105060 |
Jun 26, 1998 |
|
|
|
6533832 |
|
|
|
|
Current U.S.
Class: |
438/689 ; 106/3;
257/E21.304; 51/307; 51/308; 51/309 |
Current CPC
Class: |
C09G 1/02 20130101; C09K
3/1463 20130101; H01L 21/3212 20130101 |
Class at
Publication: |
438/689 ; 51/307;
51/308; 51/309; 106/3 |
International
Class: |
C09G 001/02; C09G
001/04; C09G 001/00; C08H 001/00; C09D 001/00; C09C 001/68; B24D
003/02; C09K 003/14; H01L 021/302; H01L 021/461 |
Claims
What we claim is:
1. An aqueous chemical mechanical polishing composition for
polishing a substrate containing a metal or silicon layer or thin
film, comprising: at least one abrasive; and at least one
alcoholamine.
2. The aqueous chemical mechanical polishing slurry of claim 1
wherein the slurry has a polysilicon to insulating layer polishing
selectivity greater than about 100.
3. The aqueous chemical mechanical polishing slurry of claim 1
having a slurry pH is from about 9 to about 10.5.
4. The aqueous chemical mechanical polishing slurry of claim 1
including from about 50 ppm to about 2.0 wt % of at least one
alcoholamine.
5. The aqueous chemical mechanical polishing slurry of claim 1
wherein the alcoholamine is a tertiary amine.
6. The aqueous chemical mechanical polishing slurry of claim 1
wherein the alcoholamine is selected from triethanol amine,
dialkylethanol amine, alkyl diethynol amine, and
2-dimethylamino-2-methyl-1-propanol.
7. The aqueous chemical mechanical polishing slurry of claim 1
wherein the alcoholamine is
2-dimethylamino-2-methyl-1-propanol.
8. The aqueous chemical mechanical polishing composition of claim
1, wherein the abrasive is a metal oxide.
9. The aqueous chemical mechanical polishing slurry of claim 8,
wherein the metal oxide abrasive is at least one compound selected
from the group including alumina, titania, zirconia, germania,
silica, ceria or chemical mixture of the metal oxides.
10. The aqueous chemical mechanical polishing slurry of claim 8,
wherein the abrasive is a physical mixture of the elemental oxides
of alumina, titania, zirconia, germania, silica, and ceria
11. The aqueous chemical mechanical polishing slurry of claim 8,
wherein the abrasive has a median particle size less than 1000 nm
and a mean aggregate diameter less than about 400 nm.
12. The aqueous chemical mechanical polishing slurry of claim 1,
wherein the abrasive is present in the range of about 0.5% to 55%
solids by weight.
13. The aqueous chemical mechanical polishing slurry of claim 1,
wherein the abrasive is from about 0.5 to about 3.0 weight percent
fumed silica.
14. The aqueous chemical mechanical polishing slurry of claim 1
including at least one buffering agent.
15. The aqueous chemical mechanical polishing slurry of claim 1
including a buffering agent selected from carbonate and bicarbonate
buffering agents.
16. The aqueous chemical mechanical composition of claim 1
including ammonium bicarbonate.
17. The aqueous chemical mechanical polishing slurry of claim 1,
including from about 0.01 to about 1.0 weight percent of a
buffering agent.
18. An aqueous chemical mechanical polishing slurry comprising:
from about 0.5 to about 15 weight percent fumed silica; from about
50 ppm to about 2.0 weight percent of at least one tertiary
alcoholamine; and from about 0.01 to about 1.0 weight percent of a
buffering agent selected from a carbonate, a bicarbonate, or
mixtures thereof, wherein the slurry has a pH of from about 9.0 to
about 10.5.
19. The aqueous chemical mechanical polishing slurry of claim 18
wherein the tertiary alcoholamine is
2-dimethylamino-2-methyl-t-propanol.
20. The aqueous chemical mechanical polishing slurry of claim 18
wherein the buffering agent is ammonium bicarbonate.
21. The aqueous chemical mechanical polishing slurry of claim 18
having a polysilicon to PETEOS polishing selectivity of at least
500.
22. A method for chemical-mechanical polishing of a substrate
containing an first insulator layer and at least one second layer
selected from at least one conductive or semi-conductive material
the method comprising the steps of: a) providing an aqueous
chemical mechanical polishing slurry comprising an abrasive and a
tertiary amine; b) applying the slurry to the substrate; and c)
removing at least a portion of the second layer by bringing a
polishing pad into contact with the substrate and moving the pad in
relation to the substrate.
23. The aqueous chemical mechanical polishing slurry of claim 22
wherein the second layer is polysilicon and the slurry has a
polysilicon to insulating layer polishing selectivity greater than
about 100.
24. The method of claim 22, wherein the second layer is a
conductive layer that is selected from tungsten, aluminum, copper,
titanium and tantalum.
25. The method of claim 22 wherein the second layer is a
semi-conductive layer selected from the group consisting of
epitaxial silicon and polycrystalline silicon.
26. The method of claim 22 wherein the aqueous chemical mechanical
polishing slurry includes from about 50 ppm to about 2.0 wt % of at
least one alcoholamine.
27. The method of claim 22 wherein the aqueous chemical mechanical
polishing slurry includes at least one tertiary alcoholamine.
28. The method of claim 22 wherein the aqueous chemical mechanical
polishing slurry includes an alcoholamine selected from triethanol
amine, dialkylethanol amine, alkyl diethanol amine, and
2-dimethylamino-2-methyl- -1-propanol.
29. The method of claim 22 wherein the alcoholamine is
2-dimethylamino-2-methyl-1-propanol.
30. The method of claim 22 wherein the aqueous chemical mechanical
polishing composition abrasive is a metal oxide.
31. The method of claim 22 wherein the aqueous chemical mechanical
polishing slurry abrasive is present in the slurry in an amount
ranging from about 0.5% to 55% by weight.
32. The method of claim 22 wherein the abrasive used in the aqueous
chemical mechanical polishing slurry is from about 0.5 to about 3.0
weight percent fumed silica.
33. The method of claim 22 wherein the aqueous chemical mechanical
polishing slurry includes at least one buffering agent.
34. A method for chemical-mechanical polishing of a substrate
containing an insulator layer and a polysilicon layer, the method
comprising the steps of: a) providing an aqueous chemical
mechanical polishing slurry comprising from about 0.5 to about 15
weight percent fumed silica, from about 50 ppm to about 2.0 weight
percent 2-dimethylamino-2-methyl-1-propa- nol, and at least one
buffering agent wherein the slurry has a pH of from about 9.0 to
about 10.5; b) applying the slurry to the substrate; and c)
removing at least a portion of the polysilicon layer by bringing a
polishing pad into contact with the substrate and moving the pad in
relation to the substrate.
35. The method of claim 34 wherein the buffering agent used in the
aqueous chemical mechanical polishing slurry is from about 0.01 to
about 1.0 weight percent ammonium bicarbonate.
36. The method of claim 34 wherein the polysilicon to insulating
layer polishing selectivity of the slurry is greater than about
100.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a chemical mechanical
polishing slurry for semiconductor integrated circuit manufacturing
and, more particularly, to improved chemical mechanical polishing
slurries that are useful for polishing polycrystalline silicon
(Poly-Si) and various interconnect layers, metals, and thin-films
used in semiconductor integrated circuit manufacturing with
especially high selectivity to interlayer dielectric materials.
[0003] 2. Background of the Related Art
[0004] A semiconductor wafer typically includes a substrate, such
as a silicon or gallium arsenide wafer, on which a plurality of
transistors have been formed. Transistors are chemically and
physically connected to the substrate by patterning regions in the
substrate and layers on the substrate. The transistors and layers
are separated by interlevel dielectrics (ILDs), comprised primarily
of some form of silicon oxide (SiO.sub.2). The transistors are
interconnected through the use of well known multilevel
interconnects to form functional circuits. Typical multilevel
interconnects are comprised of stacked thin-films consisting of one
or more of the following materials: titanium (Ti), titanium nitride
(TiN), tantalum (Ta), aluminum-copper (Al-Cu), aluminum-silicon
(Al-Si), copper (Cu), tungsten (W), doped poly-silicon (Poly-Si),
and various combinations thereof. In addition, transistors or
groups of transistors are isolated from one another, often through
the use of trenches filled with an insulating material such as
SiO.sub.2, SiN.sub.4, or Poly-Si
[0005] The traditional technique for forming interconnects has been
improved by the method disclosed in U.S. Pat. No. 4,789,648 to Chow
et al. which relates to a method for producing coplanar multilevel
metal/insulator films on a substrate. The new technique, which has
gained wide interest and produces multilevel interconnects, uses
chemical mechanical polishing (CMP) to planarize the surface of the
metal layers or thin-films during the various stages of device
fabrication.
[0006] In general CMP involves the concurrent chemical and
mechanical polishing of an overlying first layer to expose the
surface of a non-planar second layer on which the first layer is
formed. One such process is described in U.S. Pat. No. 4,789,648 to
Beyer et al., the specification of which is incorporated herein by
reference. Briefly, Beyer et al, discloses a CMP process using a
polishing pad and a slurry to remove a first layer at a faster rate
than a second layer until the surface of the overlying first layer
of material becomes coplanar with the upper surface of the covered
second layer. A more detailed explanation of chemical mechanical
polishing is found in U.S. Pat. Nos. 4,671,851, 4,910,155 and
4,944,836, the specifications of which are incorporated herein by
reference.
[0007] The composition of CMP slurries is an important factor in
providing an optimal chemical mechanical polishing process. Typical
polishing slurries available for CMP processes contain an abrasive
such as silica or alumina in an acidic or basic solution. For
example, U.S. Pat. No. 4,789,648 to Beyer et al. discloses a slurry
formulation including alumina abrasives, an acid such as sulfuric,
nitric and acetic acid and deionized water. Similarly, U.S. Pat.
No. 5,209,816 to Yu et al. discloses an aqueous slurry including
abrasive particles and an anion which controls the rate of removal
of silica.
[0008] Other CMP polishing slurries are described in U.S. Pat. Nos.
5,354,490 to Yu et al., 5,340,370 to Cadien et al., 5,209,816 to Yu
et al., 5,157,876 and 5,137,544 to Medellin, and 4,956,313 to Cote
et al., the specifications of each which are incorporated herein by
reference.
[0009] Although many of the slurry compositions are suitable for
limited purposes, the slurries described above tend to exhibit
unacceptable polishing rates and corresponding selectivity levels
to insulator materials used in wafer manufacture. In addition,
known polishing slurries tend to produce poor film removal traits
for the underlying films or produce deleterious film-corrosion
which leads to poor manufacturing yields.
[0010] Accordingly, a need remains for new and improved polishing
slurries and processes having high selectivity to the insulator
media surrounding the trenches or interconnects, e.g., silica,
spin-on-glass, and low k dielectric material which are not
hazardous or corrosive. A further need remains for a single slurry
which is capable of providing both high and uniform removal rates
of the first layer and high selectivities to the insulator
films.
SUMMARY OF THE INVENTION
[0011] This invention is a chemical mechanical polishing slurry
that is especially useful for polishing semi-conductive layers of a
semiconductor integrated circuit at high rates.
[0012] This invention is also a chemical mechanical polishing
slurry that exhibits a high selectivity towards polishing a
dielectric layer in comparison to an interlevel dielectric layer
(ILD) layer of an IC circuit.
[0013] Furthermore, this invention is a chemical mechanical
polishing slurry that has good storage stability.
[0014] This invention is also a method for using a chemical
mechanical polishing slurry to polish at least one layer of a
substrate such as an integrated circuit.
[0015] In one embodiment, this invention is an aqueous chemical
mechanical polishing composition for polishing a substrate
containing a metal or silicon layer or thin film. The aqueous
chemical mechanical polishing slurry includes at least one abrasive
and at least one alcoholamine wherein the alcoholamine is
preferably a tertiary alcoholamine.
[0016] In another embodiment, this invention is an aqueous chemical
mechanical polishing slurry. The aqueous chemical mechanical
polishing slurry comprises from about 0.5 to about 15 weight
percent fumed silica, from about 50 ppm to about 2.0 weight percent
2-dimethylamino-2-methyl-1-- propanol, and from about 0.01 to about
1.0 weight percent ammonium bicarbonate buffering agent. The
aqueous chemical polishing slurry preferably has a pH of from about
9.0 to about 10.5 and exhibits a polysilicon to PETEOS polishing
selectivity of at least 500.
DESCRIPTION OF THE CURRENT EMBODIMENT
[0017] The present invention is directed to chemical mechanical
polishing slurries for polishing conductive and semi-conductive
layers and thin-films with high selectivity to ILD materials. The
polishing slurry is an aqueous medium including at least one
abrasive and at least one alcoholamine. The slurry may also include
optional additives such as a buffering agent.
[0018] The first component of the slurry of this invention is at
least one abrasive. The abrasive is typically a metal oxide
abrasive. The metal oxide abrasive may be selected from the group
including alumina, titania, zirconia, germania, silica, ceria and
mixtures thereof. The CMP slurry of this invention may include from
about 0.1 to about 55 weight percent or more of an abrasive. It is
more preferred, however, that the CMP slurry of this invention
includes from about 0.5 to about 15 weight percent abrasive and
most preferably, 0.5 to about 3.0 wt % of an abrasive.
[0019] The metal oxide abrasive may be produced by any techniques
known to those skilled in the art. Metal oxide abrasives can be
produced using any high temperature process such as sol-gel,
hydrothermal or, plasma process, or by processes for manufacturing
fumed or precipitated metal oxides. Preferably, the metal oxide is
a fumed or precipitated abrasive and, more preferably it is a fumed
abrasive such as fumed silica or fumed alumina. For example, the
production of fumed metal oxides is a well-known process which
involves the hydrolysis of suitable feedstock vapor (such as
aluminum chloride for an alumina abrasive) in a flame of hydrogen
and oxygen. Molten particles of roughly spherical shapes are formed
in the combustion process, the diameters of which are varied
through process parameters. These molten spheres of alumina or
similar oxide, typically referred to as primary particles, fuse
with one another by undergoing collisions at their contact points
to form branched, three dimensional chain-like aggregates. The
force necessary to break aggregates is considerable. During cooling
and collecting, the aggregates undergo further collision that may
result in some mechanical entanglement to form agglomerates.
Agglomerates are thought to be loosely held together by van der
Waals forces and can be reversed, i.e., de-agglomerated, by proper
dispersion in a suitable media.
[0020] Precipitated abrasives may be manufactured by conventional
techniques such as by coagulation of the desired particles from an
aqueous medium under the influence of high salt concentrations,
acids or other coagulants. The particles are filtered, washed,
dried and separated from residues of other reaction products by
conventional techniques known to those skilled in the art.
[0021] A preferred metal oxide will have a surface area, as
calculated from the method of S. Brunauer, P. H. Emmet, and I.
Teller, J. Am. Chemical Society, Volume 60, Page 309 (1938) and
commonly referred to as BET, ranging from about 5 m.sup.2/g to
about 430 m.sup.2/g and preferably from about 30 m.sup.2/g to about
170 m.sup.2/g. Due to stringent purity requirements in the IC
industry the preferred metal oxide should be of a high purity. High
purity means that the total impurity content, from sources such as
raw material impurities and trace processing contaminants, is
typically less than 1% and preferably less than 0.01% (i.e., 100
ppm).
[0022] The metal oxide abrasive useful in the dispersion of this
invention may consist of metal oxide aggregates or individual
single sphere particles. The term "particle" as it is used herein
refers to both aggregates of more than one primary particle and to
single particles.
[0023] It is preferred that the metal oxide abrasive consists of
metal oxide particles having a size distribution less than about
1.0 micron, a mean particle diameter less than about 0.4 micron and
a force sufficient to repel and overcome the van der Waals forces
between abrasive aggregates themselves. Such metal oxide abrasive
has been found to be effective in minimizing or avoiding
scratching, pit marks, divots and other surface imperfections
during polishing. The particle size distribution in the present
invention may be determined utilizing known techniques such as
transmission electron microscopy (TEM). The mean particle diameter
refers to the average equivalent spherical diameter when using TEM
image analysis, i.e., based on the cross-sectional area of the
particle. By force is meant that either the surface potential or
the hydration force of the metal oxide particles must be sufficient
to repel and overcome the van der Waals attractive forces between
the particles.
[0024] In another preferred embodiment, the metal oxide abrasive
may consist of discrete, individual metal oxide particles having a
primary particle diameter less than 0.4 micron (400 nm) and a
surface area ranging from about 10 m.sup.2/g to about 250
m.sup.2/g.
[0025] Preferably, the metal oxide abrasive is incorporated into
the aqueous medium of the polishing slurry as a concentrated
aqueous dispersion of metal oxides. The concentrated aqueous
dispersion of metal oxides comprising from about 3% to about 45%
solids, and preferably between 10% and 20% solids. The aqueous
dispersion of metal oxides may be produced utilizing conventional
techniques, such as slowly adding the metal oxide abrasive to an
appropriate media, for example, deionized water, to form a
colloidal dispersion. The dispersion is typically completed by
subjecting it to high shear mixing conditions known to those
skilled in the art. The pH of the slurry may be adjusted away from
the isoelectric point to maximize colloidal stability.
[0026] A most preferred abrasive of this invention is fumed
silica.
[0027] The chemical mechanical polishing slurry of this invention
includes at least one alcoholamine. It has been found that the
addition of an alcoholamine to the polishing slurry enhances the
polishing rate of the polysilicon compound in comparison to the
underlying ILD layer. Any alcoholamines may be used in the
compositions of this invention. Examples of useful alcoholamines
include ethanol amines, propanol amines, primary alcoholamines,
secondary alcoholamines, tertiary alcoholamines and so forth. A
most preferred type of alcoholamines useful in the compositions of
this invention are tertiary alcoholamines. Examples of useful
tertiary alcoholamines include triethynol amine, dialkylethynol
amine, alkyl diethynol amine and the like. It is preferred that the
tertiary alcoholamine include two methyl groups and one isopropyl
group. A most preferred tertiary alcoholamine is
2-dimethylamino-2-methyl-1-propanol.
[0028] The alcoholamine is present in the compositions of this
invention in the amount that improves the polysilicon polishing
rate. The amount of alcoholamine used in the compositions of this
invention will vary from about 50 ppm to about 2 wt % or more. More
preferably, the alcoholamine should be present in the composition
of this invention in an amount ranging from about 500 ppm to about
1.0 wt %.
[0029] A buffering agent may be added to the compositions of this
invention as an optional ingredient. The buffer functions in the
compositions of this invention to make the slurries more resistant
in pH change. In addition, the polysilicon rate is slightly
enhanced by adding a buffer to the compositions of this invention.
Any buffer which possesses an acid/conjugate base with a pKa close
to the desired composition pH is preferred as a composition buffer.
The actual pH can be approximated with the equation:
pH=pKa++log [conjugate base]/[acid]
[0030] which may be used in the compositions of this invention. It
is preferred however that the buffer does not contain metallic
ions. Especially useful buffers include carbonate and bicarbonate
buffers such as ammonium bicarbonate.
[0031] The buffer, if used, should be present in the compositions
of this invention in amounts ranging from about 0.01 to about 1.0
wt %. It is most preferred that the buffer is present in the
compositions of this invention in an amount ranging from about 0.01
to about 0.15 wt %.
[0032] Other well known polishing slurry additives may be
incorporated into the chemical mechanical polishing slurry of this
invention. Useful optional additives include surfactants,
stabilizers, complexing agents, film forming agents and the like
compositions. An example of one class of optional additives are
inorganic acids and/or salts thereof which may be added to the
polishing slurry to further improve or enhance the polishing rate
of the barrier layers in the wafer, such as titanium and tantalum.
Useful inorganic additives include sulfuric acid, phosphoric acid,
nitric acid, HF acid, ammonium fluoride, ammonium salts, potassium
salts, sodium salts or other cationic salts of sulfates, phosphates
and fluorides.
[0033] It is desirable to maintain the pH of the CMP slurry of this
invention within a range of from about 7.0 to about 12.0, more
preferably within a range of from about 8.0 to about 12.0, and most
preferably within a range of from about 9.0 to about 10.5 in order
to facilitate control of the CMP process. Substrate polishing
quality problems are encountered when the pH of the CMP slurry of
this invention is too low, e.g., less than about 8. The pH of the
CMP slurry of this invention may be adjusted using any known acids
or bases. However, the use of an acid or base that contains no
metal ions, such as ammonium hydroxide or nitric, phosphoric,
sulfuric, or organic acids are preferred to avoid introducing
undesirable metal components into the CMP slurry of this
invention.
[0034] The CMP slurry of this invention may be used to polish any
type of conductive layer including, for example, tungsten,
aluminum, copper, titanium, tantalum, and mixtures thereof.
However, the chemical mechanical polishing slurry of this invention
has been found to be most useful for polishing conductive and
semi-conductive layers of integrated circuit wafers including, but
not limited to titanium nitride, tantalum nitride, and polysilicon
layers. The polysilicon layers can include both epitaxial silicon
and polycrystalline silicon.
[0035] The chemical mechanical polishing slurries of this invention
have high polysilicon (Poly-Si) polishing rate. In addition, the
chemical mechanical polishing slurries of this invention exhibits
desirable low polishing rates towards the dielectric (PETEOS)
insulating layer. As a result, the polishing slurries of this
invention exhibit [Poly-Si]/[PETEOS] polishing selectivities of at
least greater than 100, and preferably greater than about 500.
[0036] The CMP slurry of this invention may be produced using
conventional techniques known to those skilled in the art.
Typically, the non-abrasive components such as the alcoholamine,
are mixed into an aqueous medium, such as deionized or distilled
water, at predetermined concentrations under low shear conditions
until such components are completely dissolved in the medium. A
concentrated dispersion of the metal oxide abrasive, such as fumed
silica, is added to the medium and diluted to the desired loading
level of abrasive in the final CMP slurry prior to slurry use.
[0037] The silica and the alcoholamines used in the compositions of
this invention form a stable slurry. Therefore, the CMP slurries of
the present invention will typically be supplied as one package
system (abrasive and alcoholamine in a stable aqueous medium).
[0038] In a typical chemical mechanical polishing process that uses
the CMP slurries of this invention, the substrate or wafer to be
polished will be placed in direct contact with a rotating polishing
pad. A carrier applies pressure against the backside of the
substrate. During the polishing process, the pad and table are
rotated while a downward force is maintained against the substrate
back. A chemical mechanical polishing slurry of this invention is
applied to the pad during polishing. The slurry initiates the
polishing process by reacting with the film being polished either
mechanically, chemically, or both. The polishing process is
facilitated by the rotational movement of the pad relative to the
substrate as slurry is provided to the wafer/pad interface.
Polishing is continued in this manner until a least a portion of
the desired film on the insulator is removed.
EXAMPLE 1
[0039] This Example investigates the effect of adding a tertiary
alcoholamine to a conventional low-metals silica-based polishing
slurry on polishing rates and selectivity to PETEOS.
[0040] A base polishing slurry including 2 wt % of L90 fumed silica
having an average surface area of about 90 m.sup.2/g, manufactured
by Cabot Corporation and water adjusted to a pH of 10.5 using
ammonium hydroxide (NH.sub.4OH) was prepared by admixing the
ingredients. A second polishing slurry was made including 2 wt % of
L90 fumed silica manufactured by Cabot Corporation and water
adjusted to a pH of 10.5 using 0.15 wt % of
2-dimethylamino-2-methyl-1-propanol which is a tertiary
alcoholamine.
[0041] Both polishing slurries were used to polish Poly-Si and
PETEOS 8" wafers using an IPEC 472 polisher loaded with a
perforated IC1000/Suba IV pad manufactured by Rodel. The polishing
conditions used were a 5.5 psi down-force, a 1.8 psi back-pressure,
a 30 rpm platen speed, a 24 rpm carrier speed and a 140 ml/min
slurry flow rate.
[0042] The polishing results are reported in Table I below.
1TABLE I Poly-Si PETEOS Poly wt % Rate Rate Si/PETEOS Run Silica
Additive pH .ANG./min .ANG./min Selectivity 1 2 NH.sub.4OH 10.5
1868.4 48.0 38.92 2 2 T-AMINE 10.5 3003.4 9.36 320.9
[0043] The polishing results indicate that the Poly-Si polishing
rate is enhanced and the PETEOS polishing rate is reduced by using
a slurry including a tertiary alcoholamine.
EXAMPLE 2
[0044] This Example investigates the effect of amount and type of
amine added to a conventional low-metals silica-based polishing
slurry on polishing rates and selectivity to PETEOS.
[0045] A base polishing slurry was prepared including 2 wt % of L90
fumed silica having an average surface area of about 90 m.sup.2/g,
manufactured by Cabot Corporation and water. Varying amounts and
types of alcoholamines or ammonium salts were added to the slurry
as set forth in Table II, below. The alcoholamines and ammonium
salts combined with the base slurry included ammonium salts
tetramethylammonium hydroxide ("TMAH"), methyltertiarybutylammonium
hydroxide ("MTBAH"), and the alcoholamines
2-amino-2-methyl-1-proponol ("AMP-95") and
2-dimethylamino-2-methyl-1-propanol ("T-AMINE").
[0046] The polishing slurries were used to polish both Poly-Si and
PETEOS 8" wafers using an IPEC 472 polisher loaded with a
perforated IC1000/Suba IV pad manufactured by Rodel. The polishing
conditions used were a 5.5 psi down-force, a 1.8 psi back-pressure,
a 30 rpm speed, a 24 rpm carrier speed and a 140 ml/min slurry flow
rate.
[0047] The polishing results are reported in Table II below.
2TABLE II Poly-Si PETEOS Selectivity Additive Additive Rate Rate
Poly- Run % solids pH type ppm .ANG./min .ANG./min Si/PETEOS 3 2
10.5 .multidot. TMAH 430 2968 10.16 292.dwnarw. 4 2 10.5 .multidot.
MTBAH 875 3085 2.62 1177? 5 2 10.3 AMP-95 1500 2367 2.88 822 6 2
10.5 T-AMINE 1500 2995 2.67 1122 7 2 10.6 T-AMINE 1500 2909 0.80
3636 8 2 10.0 T-AMINE 730 2716 3.17 857 9 2 10.0 T-AMINE 500 2218
1.25 1774 10 2 10.5 T-AMINE 1500 3232 2.50 1293 11 2 10.6 T-AMINE
5000 2987 4.32 692 12 2 11.2 T-AMINE 15000 2236 2.25 994 13 2 11.3
T-AMINE 25000 2056 2.35 875
[0048] The polishing results indicate that a silica slurry
including alcoholamines i.e., (runs 5-13), exhibit a superior
[Poly-Si]/[PETEOS] polishing selectivity in comparison to the same
silica slurry including similar amounts of ammonium salts.
EXAMPLE 3
[0049] This Example investigates the effect of adding buffers to a
polishing slurry including a fumed silica abrasive and at least one
tertiary amine on polishing rates and defectivity.
[0050] A base polishing slurry including 2 wt % of L90 fumed silica
having an average surface area of about 90 m.sup.2/g, manfactured
by Cabot Corporation and water was prepared by admixing the
ingredients. Varying amounts of ammonium bicarbonate and the
tertiary alcoholamine, 2-dimethylamino-2-methyl-1-propanol, were
added to the slurry in the amounts set forth in Table III
below.
[0051] The polishing slurries were used to polish both Poly-Si and
PETEOS 8" wafers using an IPEC 472 polisher loaded with a
perforated IC 1000/Suba IV pad. The polishing conditions used were
a 5.5 psi down-force, a 1.8 psi back-pressure, a 30 rpm platen
speed, a 24 rpm carrier and a 140 ml/min slurry flow rate.
[0052] The polishing results are reported in Table III, below.
3TABLE III T-Amine Buffer Poly Si PETEOS Poly-Si/PETEOS Run wt %
ppm Rates Rate Selectivity 1 0.15 0 3197.83 2 0.15 0 3231.71 2.5
1293 3 0.15 700 3526.36 4 0.15 700 3564.93 5.12 696 5 0.5 0 2960.8
6 0.5 0 2987.39 4.32 691 7 0.5 700 3474.3 8 0.5 700 3467.33 4.28
810 9 1.5 0 2213.34 10 1.5 0 2235.9 2.25 994 11 1.5 700 2367.87 12
1.5 700 2344.33 4.25 552 13 2.5 0 2055.3 14 2.5 0 2055.73 2.35 875
Went into pad wet for 30 min delay 15 2.5 700 2135.48 16 2.5 700
2131.76 3.94 541 17 0.15 0 3218.72 2.79 1154
[0053] The polishing results show that the addition of a buffering
agent to the alcoholamine containing slurries of this invention
enhances the slurry Poly-Si polishing rate without significantly
altering the Poly-Si/PETEOS polishing selectivity.
[0054] While the present invention has been described by means of
specific embodiments, it will be understood that modifications may
be made without departing from the spirit of the invention. The
scope of the invention is not to be considered as limited by the
description of the invention set forth in the specification and
examples, but rather as defined by the following claims.
* * * * *