U.S. patent application number 10/074757 was filed with the patent office on 2003-08-28 for catalytic composition for chemical-mechanical polishing, method of using same, and substrate treated with same.
Invention is credited to Scott, Brandon S., Small, Robert J..
Application Number | 20030162398 10/074757 |
Document ID | / |
Family ID | 27732385 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030162398 |
Kind Code |
A1 |
Small, Robert J. ; et
al. |
August 28, 2003 |
Catalytic composition for chemical-mechanical polishing, method of
using same, and substrate treated with same
Abstract
The present invention provides a composition for
chemical-mechanical polishing which comprises at least one abrasive
particle having a surface at least partially coated by a catalyst.
The catalyst comprises a metal other than a metal of Group 4(b),
Group 5(b) or Group 6(b). The composition further comprises at
least one oxidizing agent. The composition is believed to be
effective by virtue of the interaction between the catalyst coated
on the surface of the abrasive particles and the oxidizing agent,
at the catalyst surface. The invention further provides a method
that employs the composition in the polishing of a feature or
layer, such as a metal film, on a substrate surface. The invention
additionally provides a substrate produced this method.
Inventors: |
Small, Robert J.; (Dublin,
CA) ; Scott, Brandon S.; (Castro Valley, CA) |
Correspondence
Address: |
PARSONS HSUE & DE RUNTZ LLP
655 MONTGOMERY STREET
SUITE 1800
SAN FRANCISCO
CA
94111
US
|
Family ID: |
27732385 |
Appl. No.: |
10/074757 |
Filed: |
February 11, 2002 |
Current U.S.
Class: |
438/692 ; 106/3;
257/E21.304; 51/307; 51/308; 51/309 |
Current CPC
Class: |
G11B 5/3163 20130101;
C23F 3/00 20130101; G11B 5/3169 20130101; C03C 19/00 20130101; Y02P
20/582 20151101; B24B 37/044 20130101; C09K 3/1463 20130101; C23F
3/04 20130101; C09K 3/1445 20130101; C09K 3/1436 20130101; C09G
1/02 20130101; H01L 21/3212 20130101 |
Class at
Publication: |
438/692 ; 106/3;
51/307; 51/308; 51/309 |
International
Class: |
H01L 021/461; 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 |
Claims
1. A composition for chemical-mechanical polishing, comprising: at
least one oxidizing agent; and at least one abrasive particle
having a surface at least partially coated by a catalyst, the
catalyst comprising a metal other than a metal of Group 4(b), Group
5(b) or Group 6(b).
2. The composition of claim 1, wherein the oxidizing agent
comprises a per compound.
3. The composition of claim 1, wherein the oxidizing agent
comprises ozone.
4. The composition of claim 1, wherein the oxidizing agent
comprises an agent selected from a group consisting of a metal
salt, a metal complex, and any combination thereof.
5. The composition of claim 1, wherein the oxidizing agent is
selected from a group consisting of hydroxylamine, a salt of
hydroxylamine, and any combination thereof.
6. The composition of claim 1, wherein the oxidizing agent is in an
amount of from about 0.01 to about 30 weight percent relative to
the composition.
7. The composition of claim 1, wherein the oxidizing agent is in an
amount of from about 0.01 to about 10 weight percent relative to
the composition.
8. The composition of claim 1, wherein the oxidizing agent is in an
amount of from about 0.01 to about 6 weight percent relative to the
composition.
9. The composition of claim 1, wherein the at least one abrasive
particle comprises a metal oxide.
10. The composition of claim 1, wherein the at least one abrasive
particle comprises a material selected from a group consisting of
alumina, ceria, germania, silica, spinel, titania, an oxide of
tungsten, zirconia, and any combination thereof.
11. The composition of claim 1, wherein the at least one abrasive
particle comprises a metal oxide produced by a process selected
from a group consisting of a sol-gel process, a hydrothermal
process, a plasma process, a fuming process, a precipitation
process, and any combination thereof.
12. The composition of claim 1, wherein the at least one abrasive
particle comprises a resinous particle.
13. The composition of claim 1, wherein the at least one abrasive
particle comprises a material selected from a group consisting of a
polyacrylic acid, a polymethylacrylic acid, a polymelamine, a
particle of an ion exchange resin, and any combination thereof.
14. The composition of claim 1, wherein the at least one abrasive
particle comprises a plastic particle.
15. The composition of claim 1, wherein the at least one abrasive
particle comprises a material selected from a group consisting of a
polyacrylic acid, a polymethylacrylic acid, a polyvinyl alcohol,
and any combination thereof.
16. The composition of claim 1, wherein an effective diameter of
the at least one abrasive particle is from about 30 to about 170
nanometers.
17. The composition of claim 1, wherein the at least one abrasive
particle and the catalyst on the surface thereof together are in an
amount of from about 0.01 to about 50 weight percent relative to
the composition.
18. The composition of claim 1, wherein the at least one abrasive
particle and the catalyst on the surface thereof together are in an
amount of from about 0.01 to about 20 weight percent relative to
the composition.
19. The composition of claim 1, wherein the at least one abrasive
particle and the catalyst on the surface thereof together are in an
amount of from about 0.01 to about 10 weight percent relative to
the composition.
20. The composition of claim 1, wherein the catalyst comprises a
metal selected from a group consisting of metals in Group 1 (b) and
Group 8.
21. The composition of claim 1, where the catalyst comprises a
metal having a standard oxidation potential of from about -0.52 to
about -0.25 eV.
22. The composition of claim 1, where the catalyst comprises a
metal having a standard oxidation potential of from about -0.5 to
about -0.4 eV.
23. The composition of claim 1, wherein the catalyst comprises a
metal selected from a group consisting of cobalt, copper, iron, and
any combination thereof.
24. The composition of claim 1, wherein the catalyst comprises a
material selected from a group consisting of an oxide of the metal,
an acetate of the metal, a source of ionic metal, and any
combination thereof.
25. The composition of claim 1, wherein the metal is substantially
insoluble in the composition.
26. The composition of claim 1, wherein the catalyst coats from
about 5 to about 100 percent of the surface of the at least one
abrasive particle.
27. The composition of claim 1, wherein the catalyst coats from
about 5 to about 80 percent of the surface of the at least one
abrasive particle.
28. The composition of claim 1, wherein the catalyst coats from
about 25 to about 50 percent of the surface of the at least one
abrasive particle.
29. The composition of claim 1, further comprising at least one
other abrasive that is free of a catalyst coating.
30. The composition of claim 1, where in the other abrasive is in
an amount of from about 0.01 to about 30 weight percent relative to
the composition.
31. The composition of claim 1, where in the other abrasive is in
an amount of from about 0.01 to about 20 weight percent relative to
the composition.
32. The composition of claim 1, where in the other abrasive is in
an amount of from about 0.01 to about 10 weight percent relative to
the composition.
33. The composition of claim 1, further comprising an additive
selected from a group consisting of a polish-enhancement agent, a
stabilization agent, a surfactant, a dispersion agent, a
pH-adjusting agent, and any combination thereof.
34. The composition of claim 33, wherein the additive is present in
an amount of from about 0.001 to about 2 weight percent relative to
the composition.
35. The composition of claim 1, wherein a pH level of the
composition is from about 2 to about 11.
36. The composition of claim 1, wherein a pH level of the
composition is from about 2 to about 8.
37. The composition of claim 1, wherein the oxidizing agent is
present in a prepared composition that lacks a catalyst-coated
abrasive and comprises an oxidizing agent.
38. The composition of claim 1, the composition sufficient for
chemical-mechanical polishing of a substrate surface having a
feature thereon comprising a first material selected from a group
consisting of aluminum, copper, titanium, tungsten, any alloy
thereof, and any combination thereof.
39. The composition of claim 38, the composition sufficient for
chemical-mechanical polishing of the substrate surface comprising a
second material adjacent the feature, the second material selected
from a group consisting of tantalum, tantalum nitride, titanium,
titanium nitride, titanium tungsten, tungsten, and any combination
thereof.
40. A method of polishing a substrate surface having at least one
feature thereon comprising a metal, comprising: providing the
composition of any one of claims 1-5, 9, 12-14, and 20-25; and
chemical-mechanical polishing the feature with the composition.
41. The method of claim 40, wherein said providing comprises
combining the at least one abrasive particle, the surface of which
is at least partially coated with the catalyst, with a prepared
composition, the prepared composition lacking a catalyst-coated
abrasive and comprising an oxidizing agent.
42. The method of claim 40, wherein the metal is selected from a
group consisting of aluminum, copper, titanium, tungsten, any alloy
thereof, and any combination thereof.
43. The method of claim 40, wherein the feature is adjacent a
material selected from a group consisting of tantalum, tantalum
nitride, titanium, titanium nitride, titanium tungsten, tungsten,
and any combination thereof.
44. The method of claim 40, wherein the chemical-mechanical
polishing comprises applying a pressure of from about 1 to about 6
pounds per square inch to the feature.
45. The method of claim 40, said method sufficient to remove the
metal at a rate of from about 100 to about 15,000 Angstroms per
minute.
46. The method of claim 40, said method sufficient to provide the
substrate surface at from about zero to about 40 percent
within-wafer nonuniformity.
47. The method of claim 40, said method sufficient to provide the
substrate surface at from about zero to about 12 percent
within-wafer nonuniformity.
48. The method of claim 40, said method sufficient to provide the
substrate surface wherein any microscratch thereon produced during
the chemical-mechanical polishing is less than about 20
Angstroms.
49. A substrate having a surface comprising at least one feature
thereon comprising a metal, said substrate produced by the method
of claim 40.
50. The substrate of claim 49, wherein the metal is selected from a
group consisting of aluminum, copper, titanium, tungsten, any alloy
thereof, and any combination thereof.
51. The substrate of claim 49, wherein the feature is adjacent a
material selected from a group consisting of tantalum, tantalum
nitride, titanium, titanium nitride, titanium tungsten, tungsten,
and any combination thereof.
52. The substrate of claim 49, the substrate surface having from
about zero to about 40 percent within-wafer nonuniformity.
53. The substrate of claim 49, the substrate surface having from
about zero to about 12 percent within-wafer nonuniformity.
54. The substrate of claim 49, wherein any microscratch on the
substrate surface produced during the chemical-mechanical polishing
is less than about 20 Angstroms.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to a composition that is
usefully employed in chemical-mechanical polishing processes, and
an associated method of polishing a substrate. More particularly,
the invention relates to a composition comprising an abrasive
material that is coated with a catalyst, and an oxidizing agent.
The composition is useful in the polishing of various layers, such
as metal layers, on substrates.
BACKGROUND OF THE INVENTION
[0002] A semiconductor wafer, such as a silicon or a gallium
arsenide wafer, generally has a substrate surface on which one or
more integrated circuits is formed. The substrate surface is
desirably as flat, or planar, as possible before the surface is
processed to form the integrated circuits. A variety of
semiconductor processes are used to form the integrated circuits on
the flat surface, during which the wafer takes on a defined
topography. If this topography is too irregular or includes surface
imperfections, fabrication processes, such as photolithography, are
often compromised, and the resulting semiconductor device is often
inoperable or highly subject to failure. Thus, it is often
necessary to polish the wafer surface to render it as planar or
uniform as possible and to remove surface imperfections.
[0003] Chemical-mechanical polishing or planarization (CMP)
processes are well-known. See, for example, Chemical Mechanical
Polishing in Silicon Processing, Semiconductors and Semimetals,
Vol. 62, Edited by Li, S. et al., which is expressly incorporated
herein by this reference. CMP processes are commonly used to polish
or "planarize" the surfaces of wafers at various stages of
fabrication to improve wafer yield, performance and reliability. In
CMP, typically the wafer is held in place on a carrier using
negative pressure, such as vacuum, or hydrostatic or pneumatic
pressure. The carrier is typically situated over a polishing pad
that is situated on a platen. CMP generally involves applying a
polishing composition or slurry to the polishing pad, establishing
contact between the wafer surface and the polishing pad, and
applying a downward pressure on the wafer carrier while providing
relative motion, typically rotational or orbital motion, between
the wafer surface and the polishing pad. Typically, this relative
motion involves movement of both the carrier and the platen at the
same or different speeds.
[0004] The polishing composition typically contains an abrasive
material, such as silica and/or alumina particles, in an acidic,
neutral, or basic solution. Merely by way of example, a polishing
composition useful in the CMP of tungsten material on a substrate
may contain abrasive alumina (Al.sub.2O.sub.3), also called
aluminum oxide, an oxidizing agent such as hydrogen peroxide
(H.sub.2O.sub.2), and either potassium hydroxide (KOH) or ammonium
hydroxide (NH.sub.4OH). A CMP process employing such a polishing
composition may provide a predictable rate of polishing, while
largely preserving desirable insulation features on the wafer
surface.
[0005] CMP is used in a variety of semiconductor processes to
polish wafers having a variety of surface features, such as oxide
and/or metal layers. By way of example, often the surface of a
semiconductor wafer has insulation or oxide features, the grooves
or stud vias of which are filled with a metal or metal alloy.
Typical filler metals or alloys include aluminum, copper, titanium,
titanium nitride, tantalum, tantalum nitride, tungsten, or any
combination of these metals or alloys. For such a semiconductor
wafer, a typical CMP process involves polishing the metal in a
controlled manner to "stop on" the oxide beneath the metal, such
that the metal is substantially coplanar with the oxide and remains
in the grooves or stud vias of the oxide. After CMP, the
substantially coplanar surface is ready for further processing. CMP
is currently the primary method used to polish or "planarize"
wafers in back end of the line (BEOL) processes.
[0006] Semiconductor fabrication processes such as photolithography
have evolved significantly, such that advanced devices having very
fine oxide, metal, and other surface features, with sub-0.25 micron
geometries (such as 0.18 micron or less), are now being made.
Process tolerances are necessarily tighter for these advanced
devices, calling for improvements in CMP technology to obtain
desired material removal rates while minimizing wafer defects or
damage. A variety of approaches have been taken in an effort to
improve CMP processes.
[0007] One approach has involved increasing the downward pressure
on the wafer carrier in order to increase material removal rates.
This approach is generally disfavored as the requisite downward
pressure is considered too high and too likely to cause wafer
damage, such as scratching, delamination, or destruction of
material layers on the wafer. When the wafer is fragile, as is
generally the case with substrates layered with films, such as
porous films, having a low dielectric constant, these damage issues
are particularly acute and detrimental in terms of wafer yield and
performance.
[0008] Another approach has involved increasing the amount of
oxidizing agent used in the CMP slurry in an effort to increase
chemical removal of targeted material. This approach is largely
disfavored as the use of increased amounts of oxidizing agents
detrimentally add to the handling issues and environmental issues
associated with many oxidizing agents and thus increase costs.
Attempts to catalyze the oxidizing agent to increase removal rates
have also had limited success. Additional approaches have involved
using a combination of CMP slurries, including for example, a
zirconium slurry, a combination of abrasive particles in a CMP
slurry, and/or using point-of-use mixing techniques. These
approaches are generally undesirable, as they typically complicate
CMP in terms of tooling and process control for example, consume
more process time, and/or increase costs.
[0009] Further developments in the field of CMP technology are
desired.
SUMMARY OF THE INVENTION
[0010] The present invention provides a composition for
chemical-mechanical polishing which comprises at least one abrasive
particle having a surface at least partially coated by a catalyst.
The catalyst comprises a metal other than a metal of Group 4(b),
Group 5(b) or Group 6(b) of the Periodic Table of Elements.
Generally, metals of Group 1(b) or Group 8 are suitable candidates,
as are metals having a standard oxidation of from about -0.52 to
about -0.25 eV. It is believed that the catalyst-coated abrasive
favorably interacts with any one of a number of oxidizing agents
typically employed in chemical-mechanical polishing compositions.
Thus, the composition also comprises such an oxidizing agent. The
oxidizing agent is preferably in the form of an organic or
inorganic per compound, although other oxidizing agents, such as
hydroxylamine for example, may be used.
[0011] The composition may contain a variety of other additives,
such as a typical abrasive (i.e., an abrasive lacking a catalyst
coating), a surfactant, a stabilizing agent, a dispersion agent, a
polish-enhancement agent, and/or a pH-adjusting agent. The pH level
of the composition should be in a range of from about pH 2 to about
pH 11, with a preferred upper level of about pH 8.
[0012] The composition of the present invention is effective in the
CMP of a variety of metal or metal alloy materials on substrates
such as silicon or semiconductor substrates. It is theorized that
the catalyst-coated abrasive and the oxidizing agent react at the
catalyst surface to generate free radicals that are effective
intermediates in the reaction between the oxidizing agent and the
material targeted for removal from the substrate surface. Further,
it is believed that the catalyst-coated abrasive is particularly
effective as it brings the catalyst directly to the targeted
material on the substrate surface, and thus facilitates or
accelerates the removal reaction substantially at the site of the
targeted material.
[0013] The composition provides very desirable material rates, for
example, up to 15,000 Angstroms (.ANG.) per minute, in a CMP
process. This removal rate is so good that it may be desirable to
adjust the composition or the CMP process to bring the rate down to
a level suitable for certain applications, such as the CMP of very
thin films, for example, a copper film of about 3000 .ANG. in
thickness. The composition is effective when used in conventional
CMP processes, as well as CMP processes having relatively low
carrier pressures. Substrates polished using the composition show
good uniformity values, as reflected by relatively low within-wafer
nonuniformity percentages. For example, in one example provided
herein, the within-wafer nonuniformity of the polished substrate
was about 4.57 percent.
[0014] Additional features, aspects and advantages of the present
invention will become apparent from the description of preferred
embodiments and the various examples set forth below.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0015] The composition of the present invention is usefully
employed in the chemical-mechanical polishing (CMP) of a substrate.
The composition or slurry may be used to polish at least one
feature or layer on a substrate such as a silicon substrate, a
gallium arsenide (GaAs) substrate, a thin film transistor-liquid
crystal display ("TFT-LCD") glass substrate, or any other substrate
associated with integrated circuits, thin films, semiconductors,
Micro Electro Mechanical Systems (MEMS) structures, hard disk
platters and heads, and the like. By way of example, the
composition of the present invention may be used in the CMP of a
substrate having one or more layers of aluminum, copper,
copper-aluminum alloy, tantalum, titanium, tungsten, or tantalum-,
titanium-, or tungsten-containing alloys, such as tantalum nitride,
titanium nitride, titanium tungsten, or any combination
thereof.
[0016] Generally, throughout this description, any mention of a
component of the composition refers to at least one such component,
for example, one such component or multiple such components.
Further, any amount of a component of the composition is given as a
weight percent (wt. %) relative to the composition. Additionally,
any amount of a component is given as an approximate amount, for
example, more or less than, or equal to, the precise numerical
amount stated. This convention concerning approximate amounts
applies to any numerical measure stated herein in connection with
the composition, such as a numerical pH level stated for the
composition or a numerical process parameter stated for a CMP
process employing the composition. The foregoing conventions apply
throughout this specification unless specified or clearly intended
or implied otherwise.
[0017] The composition generally comprises at least one oxidizing
agent and at least one abrasive that is at least partially coated
by a catalyst, as further described herein. Typically, the abrasive
component comprises a portion of abrasive that coated with catalyst
(sometimes referred to herein as "coated catalyst") and a portion
of abrasive that is not coated with catalyst (sometimes referred to
herein as "normal abrasive"), although only the former need be
present. For example, the abrasive may comprise a ratio of coated
abrasive to normal abrasive of about 1 to about 9. Each of the
components of the composition and typical, preferred, and more
preferred amounts thereof, in approximate weight percent (wt. %)
relative to the composition, are provided below in Table 1.
1TABLE 1 Chemical-Mechanical Polishing Composition More Component
Typical Amount Preferred Amount Preferred Amount Oxidizing 0.01 to
30 wt. % 0.01 to 10 wt. % 0.01 to 6 wt. % Agent Normal 0.01 to 30
wt. % 0.01 to 20 wt. % 0.01 to 10 wt. % Abrasive Coated 0.01 to 50
wt. % 0.01 to 20 wt. % 0.01 to 10 wt. % Abrasive
[0018] The oxidizing agent of the CMP composition assists in the
chemical removal of targeted material on the substrate surface. The
oxidizing agent component is thus believed to enhance or increase
the material removal rate of the composition. Preferably, the
amount of oxidizing agent in the composition is sufficient to
assist the chemical removal process, while being as low as possible
to minimize handling, environmental, or similar or related issues,
such as cost. The various amounts of oxidizing agent provided in
Table 1 are all effective and suitable, while the more preferred
amount of from about 0.01 to about 6 weight percent relative to the
composition, is particularly preferred in terms of minimizing the
potential issues mentioned above.
[0019] The oxidizing agent is preferably an inorganic or organic
per-compound. A per-compound is generally defined as a compound
containing an element in its highest state of oxidation, such as
perchloric acid; a compound containing at least one peroxy group
(--O--O--), such as peracetic acid and perchromic acid; or a
compound having exhaustive substitution or addition, such as
perchloroethylene. The Condensed Chemical Dictionary, Tenth
Edition, Revised by Hawley, G. Suitable per-compounds containing at
least one peroxy group include, but are not limited to, hydrogen
peroxide, urea hydrogen peroxide, a monopersulfate
(SO.sub.5.sup.dbd), a dipersulfate (S.sub.2O.sub.8.sup.dbd- ),
peracetic acid, a percarbonate, an organic peroxide, such as
benzoyl peroxide, di-t-butyl peroxide, any acid thereof, any salt
thereof, any adduct thereof, and any combination of the foregoing.
Suitable per-compounds that do not contain a peroxy group include,
but are not limited to, periodic acid, any periodiate salt,
perbromic acid, any perbromate salt, perchloric acid, any
perchlorate salt, perboric acid, any perborate salt, permanganate,
any pennanganate salt, and any combination of the foregoing. Most
preferably, the oxidizing agent is a per-compound or a compound
possessing a reactive peroxy functional group, such as
monopersulfate, di-persulfate, peracetic acid, urea hydrogen
peroxide, hydrogen peroxide, any acid, salt, or adduct thereof, and
any combination of the foregoing.
[0020] Other oxidizing agents are also suitable components of the
composition of the present invention. For example, ozone is a
suitable oxidizing agent either alone or in combination with one or
more other suitable oxidizing agents. Further by way of example,
the oxidizing agent may be a metal salt, a metal complex or
coordination compound, or any combination thereof An organic or
inorganic hydroxylamine compound or salt is yet another possible
oxidizing agent component for the composition.
[0021] A sampling of suitable oxidizing agents includes iron salts,
aluminum salts, sodium salts, potassium salts, as well as ammonium
salts, quaternary ammonium salts, phosphonium salts, peroxides,
chlorates, perchlorates, permanganates, persulfates, and any
combination thereof. In general, the various oxidizing agents
described herein may be used either alone or in combination with
one another, although any combination that might undesirably
complicate the CMP process is preferably avoided.
[0022] In addition to the oxidizing agent component, the
composition also comprises an abrasive that is at least partially
coated by a catalyst. The abrasive is effective in the mechanical
removal of targeted material on the substrate surface. Suitable
amounts of catalyst-coated abrasive, such as the preferred range of
from about 0.01 to about 20 weight percent relative to the
composition, are listed in Table 1 above. Suitable amounts of
normal abrasive, if any, are also listed in Table 1.
[0023] The abrasive is generally in the form of an abrasive
particle, and typically many abrasive particles, of one material or
a combination of different materials. Generally, a suitable
abrasive particle is more or less spherical and has an effective
diameter of about 30 to about 170 nanometers (nm), although
individual particle size may vary. Abrasive in the form of
aggregated or agglomerated particles are preferably processed
further to form individual abrasive particles.
[0024] The abrasive particle may be a metal oxide particle, a
resinous particle, or a plastic particle, and is preferably a metal
oxide particle. A suitable metal oxide abrasive includes, but is
not limited to, alumina, ceria, germania, silica, spinel, titania,
an oxide of tungsten, zirconia, and any combination thereof. The
metal oxide abrasive may be produced by any of a variety of
techniques, including sol-gel, hydrothermal, hydrolytic, plasma,
fuming and precipitation techniques, and any combination thereof.
Preferably, the metal oxide abrasive is a precipitated or fumed
abrasive, and preferably a fumed abrasive. By way of example, the
metal oxide abrasive may be a fumed abrasive such as fumed silica
or fumed alumina. In general, the above-mentioned metal oxide
abrasives may be used either alone or in combination with one
another, although any combination that might undesirably complicate
the CMP process is preferably avoided.
[0025] As mentioned above, other abrasives, such as plastic or
resinous abrasives, are suitable components of the composition of
the present invention. For example, a suitable plastic abrasive
particle may be composed of a polyacrylic acid, a polymethylacrylic
acid, a polyvinyl alcohol, or any combination thereof. Further by
way of example, a suitable resinous abrasive particle may be
composed of a polyacrylic acid, a polymethylacrylic acid, a
polymelamine, or any combination thereof, or any particle of a ion
exchange resin, such as a plastic ion exchange resin.
[0026] According to the present invention, the abrasive is at least
partially coated by a catalyst. The catalyst enhances, or
increases, the rate of the chemical reaction between the oxidizing
agent of the composition and the targeted material, particularly
metal material, on the substrate surface during a CMP process. The
catalyst is believed to assist in the formation of activated
oxidizing species, such as activated peroxy groups, at reaction
sites on the material targeted for removal. Preferably, the
catalyst is substantially insoluble in the composition such that it
remains for the most part on the abrasive particle during the CMP
process.
[0027] Care should be taken as to the amount of catalyst-coated
abrasive used, as using too much catalyst may compromise control of
the CMP process. The amount of catalyst-coated abrasive should
generally not exceed 50 weight percent of the composition. Where
catalyst concentration is a concern, an increased amount of normal
abrasive, absent a catalyst coating, may be used to dilute the
catalyst in the composition and facilitate control of the CMP
process.
[0028] As mentioned above, the abrasive material of the composition
is at least partially coated with the catalyst. As used herein,
"coating" and its various linguistic or grammatical forms or
counterparts generally refer to forming a physical connection
between the abrasive and the catalyst, such as by forming at least
a partial layer of catalyst material on at least a portion of the
abrasive, absorbing or adsorbing the catalyst material on at least
a portion of the abrasive, forming adhesion between the catalyst
material and at least a portion of the abrasive, and the like, by
any suitable means or method. By way of example, a method of
producing a silica sol coated with iron acetate is provided in U.S.
Pat. No. 4,478,742 of Payne, the entire contents of which are
incorporated herein by this reference. The catalyst may coat from
about 5 to about 100 percent of the surface of the abrasive
particle, such as from about 5 to about 80 percent of the particle
surface, or preferably, from about 25 to about 50 percent of the
particle surface.
[0029] The catalyst comprises a metal other than a metal from
Groups 4(b), 5(b) and 6(b) of the Periodic Table of the Elements.
See, for example, Handbook of Chemistry and Physics, 64.sup.th
Edition, Periodic Table of the Elements, Inside Front Cover, which
is fully incorporated herein by this reference. A suitable metal
includes, but is not limited to cobalt, copper, iron, nickel,
silver, and any combination thereof. Further examples of suitable
metals include those from Group 1(b) and Group 8 of the Periodic
Table of the Elements.
[0030] Catalysts having a standard oxidization potential of from
about -0.52 to about -0.25 eV are also contemplated as having
suitable catalytic activity for compositions of the present
invention. Examples of metal catalysts with oxidation potentials in
this range include copper (-0.52 eV), iron (-0.44 eV), cobalt
(-0.28 eV), and nickel (-0.25 eV). Further, it is believed that
catalysts having a standard oxidation potential of from about -0.5
to about -0.4 eV have an optimal or preferred catalytic activity.
An example of a metal catalyst with an oxidation potential in this
range is iron, a preferred catalyst or catalyst component herein.
As mentioned previously, there are a variety of suitable metal
catalysts, such as any comprising a metal from Group 1(b) and Group
8 of the Periodic Table of the Elements.
[0031] The catalyst may be in a variety of forms, such as an oxide,
a nitrate, a halide, such as chloride, a perchlorate, or an acetate
of the metal, a source of ions of the metal, and any combination
thereof. By way of example, suitable metal oxides include iron
oxide, copper oxide, and cobalt oxide. Further by way of example,
the catalyst may be a source of mulivalent metal, such as a source
of divalent iron. Preferably, the catalyst is a metal acetate, such
as copper acetate ("CuAc") or iron acetate ("FeAc").
[0032] It is believed that the composition of the present invention
is particularly advantageous by virtue of the interaction between
the catalyst surface and the oxidizing agent. That is, it is
believed that a reaction takes place between the catalyst that is
coated on the abrasive, and the oxidizing agent, such as a peroxide
or hydroperoxide, at the catalyst surface. It is believed that this
reaction generates free radicals or active reaction intermediates,
such as hydroxyl free radicals (HO.), at the catalyst surface,
which favorably interact with the targeted material on the
substrate when the catalyst coating on the abrasive contacts the
substrate surface. Descriptions of redox systems involving
catalysts that generate free radicals in the presence of oxidizing
agents are provided in Walling, C., Free Radicals in Solution
(1957), pp. 564-579, and Bacon, R., The Initiation of
Polymerisation Processes by Redox Catalysts, Quart. Revs., Vol. IX
(1955), pp.287-310, the entire contents of which are fully
incorporated herein by this reference. Such catalysts are candidate
coatings for the abrasive used in the composition.
[0033] The pH of the composition is desirably on the order of from
about pH 2 to about pH 11, and preferably, from about pH 2 to about
pH 8. These pH levels, and particularly the preferred levels, are
believed to facilitate control of the CMP process. A composition
having a pH that is too low, such as below pH 2, may present
problems in terms of the handling of the composition and the
quality of the polishing itself. A composition having a pH that is
too high, such as above pH 11, may detrimentally contribute to
corrosion or other attack on the metal layer, such as copper or
tungsten, on the substrate surface, depending on the nature of the
metal layer. This may not be an issue in the polishing of metal
layers such as aluminum or exotic metals, which may tolerate a CMP
composition of relatively high pH without ill effect.
[0034] The pH of the composition may be adjusted using an
appropriate pH-adjusting agent, such as a suitable acid, base,
amine, or any combination thereof. The pH-adjusting agent may
contain metal ions. Examples include metal hydroxides, such as
NaOH, KOH and the like, containing sodium, potassium, and like
metal ions, respectively. Preferably, the pH-adjusting agent used
in the composition does not contain any undesirable metal ions,
such that undesirable metal components are not introduced into the
composition. Suitable pH-adjusting agents include amines, ammonium
hydroxide, nitric acid, phosphoric acid, sulfuric acid, organic
acids, and any combination thereof.
[0035] The composition may also include one or more of various
optional additives. Suitable optional additives include
surfactants, stabilization agents, dispersion agents, and the like.
These optional additives are generally employed to facilitate or
promote stabilization of the composition against settling,
flocculation (including precipitation, aggregation or agglomeration
of particles, and the like), decomposition, and the like. Examples
of these optional additives include sulfuric acid, phosphoric acid,
nitric acid, ammonium salts, potassium salts, sodium salts, or
other cationic salts of sulfates and phosphates, and any
combination thereof.
[0036] In general, any of these optional additives should be
present in an amount sufficient to substantially stabilize the
composition. The necessary amount varies depending on the
particular additive selected and the particular make-up of the CMP
composition, such as the nature of the surface of the abrasive
component. If too little of the additive is used, the additive will
have little or no effect on the stability of the composition. On
the other hand, if too much of the additive is used, the additive
may contribute to the formation of undesirable foam and/or
flocculent in the composition. Generally, suitable amounts of these
optional additives range from about 0.001 to about 2 weight percent
relative to the composition, and preferably from about 0.001 to
about 1 weight percent. These optional additives may be added
directly to the composition or applied to the surface of the
abrasive component of the composition.
[0037] While there are many suitable surfactant additives for the
composition, preferred surfactant additives include dodecyl sulfate
sodium salt, sodium lauryl sulfate, dodecyl sulfate ammonium salt,
and any combination thereof. Suitable commercially available
surfactants include TRITON DF-16 manufactured by Union Carbide and
SURFYNOL manufactured by Air Products and Chemicals.
[0038] Stabilization agents may be used to stabilize the catalyst
in the presence of the oxidizing agent of the composition. For
example, stabilizers may be needed to stabilize a metal ion
catalyst in the presence of an oxidizing agent, such as hydrogen
peroxide. If a stabilization agent is not used, the oxidizing agent
and the catalyst may react in a manner that rapidly degrades the
oxidizing agent and thus compromises the CMP process. On the other
hand, the presence of a stabilization agent in the composition may
compromise the efficacy of the catalyst. Thus, for optimal CMP
performance, careful consideration should be given as to whether or
not to use a stabilizing agent in the composition, and as to the
selection and amount of any stabilization agent added to the
composition.
[0039] Suitable stabilizing agents include organic acids, such as
adipic acid, carboxylic acid, citric acid, malonic acid,
orthophthalic acid, and ethylenediaminetetraacetic acid, phosphoric
acid, phosphonate compounds, nitrites, and other ligands, such as
those that bind the catalyst material and thus reduce reactions
that degrade the oxidizing agent, and any combination of the
foregoing agents. As used herein, an acid stabilizing agent refers
to both the acid stabilizer and its conjugate base. That is, the
various acid stabilizing agents may also be used in their conjugate
form. By way of example, herein, an adipic acid stabilizing agent
encompasses adipic acid and/or its conjugate base, a carboxylic
acid stabilizing agent encompasses carboxylic acid and/or its
conjugate base, carboxylate, and so on for the above-mentioned acid
stabilizing agents. A suitable stabilizer, used alone or in
combination with one or more other stabilizers, decreases the rate
at which an oxidizing agent such as hydrogen peroxide decomposes
during a CMP process.
[0040] Optionally, certain additives or polish-enhancement agents
may be added to the composition to enhance or improve the polishing
rate of targeted material on the substrate surface, such as
tantalum and titanium material often present in the form of barrier
layers on the substrate surface. An example of a polish-enhancement
agent is hydroxylamine, which is particularly effective when the
targeted material is tantalum. Polishing-enhancement agents other
than hydroxylamine, such as fluoride-based agents, are generally
preferred for use with peroxide-containing compositions. The
optional polishing-enhancement agent, if any, is generally present
in an amount of from about 0.001 to about 2 weight percent, or
preferably, from about 0.001 to about 1 weight percent, relative to
the composition.
[0041] The CMP composition or slurry of the present invention may
be prepared using conventional techniques. Typically, the water and
abrasive components are combined, catalyst-coated abrasive is then
added, oxidizer is then added, and the pH is adjusted.
Alternatively, according to one aspect of the present invention,
the catalyst-coated abrasive may be added to an existing CMP
composition, such as a commercially available CMP composition that
contains an oxidizing agent. For example, the catalyst-coated
abrasive may be added to a previously formulated peroxide
composition to provide a CMP composition of this invention.
[0042] In some CMP processes, particularly some of the advanced
polishing processes, the composition is prepared by adjusting the
amount of each composition component in real time, just prior to a
re-mixing of the composition at the point of use. For most CMP
processes, the prepared composition is re-mixed at the point of
use, whereupon it is poured onto the polishing pad. Typically, the
composition is poured onto the pad as it is moved or rotated. As
the CMP process proceeds, additional slurry may be added or excess
slurry may be removed, as desired or necessary.
[0043] Examples of the composition according to the present
invention are provided below. A first example concerns two CMP
compositions, Composition A and Composition B, which are
particularly suited to CMP of a wafer, such as a silicon wafer,
having a tungsten layer or feature on its surface. The components
of the two compositions and the approximate amounts thereof, as
well as the approximate pH of the compositions, are set forth in
Table 2.
2TABLE 2 Chemical-Mechanical Polishing Compositions A and B
Hydrogen Peracetic Mirasol Mirasol 3070 Composition Peroxide Acid
3070 with Catalyst pH Composition A 3 wt. % 0 wt. % 5 wt. % 0.5 wt.
% 2 Composition B 0 wt. % 5 wt. % 5 wt. % 0.5 wt. % 2
[0044] In Composition A, hydrogen peroxide (H.sub.2O.sub.2) served
as an oxidizing agent, Mirasol 3070, a commercially available
aqueous solution of abrasive silica particles, served as an
abrasive, Mirasol 3070 with a cationic iron catalyst absorbed onto
at least a portion of the surface of the silica particles, served
as an abrasive coated with a catalyst, and deionized water made up
the remainder of the composition. Composition B differed from
Composition A in that peracetic acid (CH.sub.3COOOH), rather than
hydrogen peroxide, served as an oxidizing agent. For both
Composition A and Composition B, the Mirasol 3070 component, as
opposed to the oxidizing agent or the catalyst, was believed to be
predominantly responsible for determining the pH of the
composition.
[0045] Mirasol 3070, commercially available from Precision
Colloids, LLC of Cartersville, Ga., contains approximately 30
weight percent silica (SiO.sub.2) particles, which generally have
an effective diameter of approximately 70 nanometers. Mirasol 3070
coated with catalyst contains the above-described Mirasol 3070 with
iron acetate catalyst coated on about 70 percent of the surface
area of each silica particle.
[0046] Each of the Compositions A and B were used in a conventional
CMP process performed on a silicon substrate at least partially
layered with a tungsten film of about 8000 Angstroms (A) in
thickness. The process parameters included a carrier pressure of
about 6 pounds per square inch (psi), a carrier speed of about 90
revolutions per minute (rpm), a platen speed of about 90 rpm, and a
flow rate for the CMP composition used of about 175 milliliters per
minute (ml/min), as set forth in Table 3 below. The processes
differed only in terms of which CMP composition was used. The
results of each CMP process in terms of the approximate material
(tungsten) removal rate in Angstroms per minute (A/min) and the
approximate within-wafer nonuniformity percentage (% WIWNU) are set
forth in Table 4.
3TABLE 3 Chemical-Mechanical Polishing Process Using Composition A
or Composition B Carrier Carrier Platen Composition Pressure Speed
Speed Flow Rate Composition (psi) (rpm) (rpm) (ml/min) Composition
A 6 90 90 175 Composition B 6 90 90 175
[0047]
4TABLE 4 Chemical-Mechanical Polishing Results Using Composition A
or Composition B Removal Rate Nonuniformity Composition (.ANG./min)
(% WIWNU) Composition A 5040 10.9 Composition B 5077 7.42
[0048] As mentioned previously, in CMP processes, and particularly
modern or advanced CMP processes, it is desirable to obtain
acceptable or optimal, such as increased, material removal rates
while using acceptable or optimal, such as not unduly high, carrier
pressures. In the CMP of tungsten-layered wafers, a good carrier
pressure is about 9 psi or less, such as about 6 psi, and a good
outcome at a pressure of about 6 psi is a removal rate of greater
than about 5000 .ANG./min. Further, obtaining polished wafers with
uniformity values of from about 3 to about 12% WIWNU percent is
considered a good result. While the foregoing examples of process
parameters, outcomes and results are often desirable, other
suitable outcomes and results are contemplated herein.
[0049] In the CMP processes performed with Composition A and
Composition B, desirable tungsten removal rates of about 5040 and
5077 .ANG./min, respectively, were obtained. Additionally, the
surfaces of the polished wafers were substantially uniform, having
10.9 and 7.42% WIWNU, respectively. Composition B is generally
preferred over Composition A, given its higher removal rate and
better uniformity value (lower % WIWNU). It should be noted that
while there is a general preference for compositions that provide
high removal rates, other factors, such as good uniformity values
(for example, low % WIWNU), efficient use of oxidizer, and good
storage and handling characteristics, are also important
considerations in the evaluation of a composition of the present
invention.
[0050] A second example of the composition of the present invention
concerns two CMP compositions, Composition C and Composition D,
which were used in the CMP of a silicon wafer that had a copper
layer or feature on its surface. In this example, the copper layer
had a thickness of about 15,000 .ANG.. The components of the two
compositions and the approximate amounts thereof, as well as the
approximate pH of the compositions, are set forth in Table 5.
5TABLE 5 Chemical-Mechanical Polishing Compositions C and D
Hydroxyl- Peracetic Mirasol Mirasol 3070 Composition amine Acid
3070 and Catalyst pH Composition C 0 wt. % 1.5 wt. % 5 wt. % 0.5
wt. % 2 Composition D 4 wt. % 0 wt. % 5 wt. % 0.5 wt. % 6.7
[0051] In Composition C, peracetic acid (CH.sub.3COOOH) served as
an oxidizing agent, Mirasol 3070 (described above) served as an
abrasive, Mirasol 3070 coated with catalyst (described above)
served as an abrasive coated with a catalyst, and deionized water
made up the remainder of the compositon. Composition D differed
from Composition C in that hydroxylamine (NH.sub.2OH), rather than
peracetic acid, served as an oxidizing agent. The two compositions
also differed in terms of pH, Composition C having a pH of about 2
and Composition D having a pH of about 6.7.
[0052] Each of the Compositions C and D were used in a conventional
CMP process performed on a silicon wafer at least partially layered
with copper. When Composition C was used, the process parameters
included a carrier pressure of about 4 psi, a carrier speed of
about 40 rpm, a platen speed of about 40 rpm, and a flow rate for
the Composition C of about 100 ml/min. When Composition D was used,
the process parameters included a carrier pressure of about 4 psi,
a carrier speed of about 75 rpm, a platen speed of about 75 rpm,
and a flow rate for the Composition D of about 175 ml/min. The
parameters of each CMP process are set forth in Table 6 and the
results thereof in terms of the approximate material (copper)
removal rate and the approximate within-wafer nonuniformity
percentage are set forth in Table 7.
6TABLE 6 Chemical-Mechanical Polishing Process Using Composition C
or Composition D Carrier Carrier Platen Composition Pressure Speed
Speed Flow Rate Composition (psi) (rpm) (rpm) (ml/min) Composition
C 4 40 40 100 Composition D 4 75 75 175
[0053]
7TABLE 7 Chemical-Mechanical Polishing Results Using Composition C
or Composition D Removal Rate Nonuniformity Composition (.ANG./min)
(% WIWNU) Composition C 15,000 Not measurable Composition D 7797
8.87
[0054] As mentioned previously, in CMP processes, and particularly
modern or advanced CMP processes, it is desirable to obtain
acceptable or optimal, such as increased, material removal rates
while using acceptable or optimal, such as not unduly high, carrier
pressures. In the CMP of copper-layered wafers, a good carrier
pressure is about 9 psi or less, such as about 4 psi, and a good
outcome at a pressure of about 4 psi is a removal rate of greater
than about 7500 .ANG./min. While the foregoing examples of process
parameters, outcomes and results are often desirable, other
suitable outcomes and results are contemplated herein.
[0055] In the CMP process performed with Composition C, an
unusually high copper removal rate was obtained, such that all of
the copper was removed. This result prevented measurement of a
uniformity value. In the CMP process performed with Composition D,
a desirable copper removal rate was obtained. Additionally, the
surface of the wafer polished using Composition D was substantially
uniform. Composition D is thus a desirable composition of the
present invention. Composition C is also a useful composition of
the present invention, although it may be a bit too aggressive in
terms of removal rate for some applications, such as in the
polishing of very thin layers on a substrate. Accordingly, for some
applications, a CMP process using Composition C may be altered by
diluting the composition, diluting the catalyst-coated abrasive
and/or oxidizing agent components of the composition, changing the
composition flow rate, or the like.
[0056] A third example concerns two CMP compositions of the present
invention, Composition B, from the first example above, and
Composition E, each of which were used in the CMP of a silicon
wafer that had a tungsten layer on its surface, the layer being of
about 8000 .ANG. in thickness. Composition B was compared to a
similar composition, Composition 1, and Composition E was compared
to a similar composition, Composition 2. Neither of Compositions 1
and 2 contained catalyst-coated abrasive. The pH of all four
compositions was about 2. The components of the four compositions
and the approximate amounts thereof are set forth in Table 8 below.
Composition E and Composition 2 contained ethylene glycol, the
purpose of which was to boost the removal rate. It is believed that
this ethylene glycol additive acts as a catalyst promoter or an
inhibitor as to the polishing of the oxide.
8TABLE 8 Chemical-Mechanical Polishing Compositions B and E and
Compositions 1 and 2 Pera- Mirasol Hydrogen cetic Mirasol 3070 with
Ethylene Composition Peroxide Acid 3070 Catalyst Glycol Composition
B 0 wt. % 5 wt. % 5 wt. % 0.5 wt. % 0 wt. % Composition 1 0 wt. % 5
wt. % 5 wt. % 0 wt. % 0 wt. % Composition E 3 wt. % 0 wt. % 5 wt. %
0.5 wt. % 0.25 wt. % Composition 2 3 wt. % 0 wt. % 5 wt. % 0 wt. %
0.25 wt. %
[0057] Each of the four compositions were used in a conventional
CMP process having the same process parameters as previously
described in the first example and set forth in Table 3 above. Each
of Compositions 1 and 2 were tested twice, in a Trail A and a Trial
B, respectively. The results of each CMP process in terms of the
approximate material (tungsten) removal rate in A/min and the
approximate % WIWNU are set forth in Table 9.
9TABLE 9 Chemical-Mechanical Polishing Results Using Composition B
or E or Composition 1 or 2 Removal Rate Nonuniformity Composition
(.ANG./min) (% WIWNU) Composition B 5077 7.42 Composition 1: Trial
A 2215 6.96 Trial B 2466 6.94 Composition E 4476 4.57 Composition
2: Trial A 1556 3.42 Trial B 1582 3.34
[0058] In terms of the tungsten removal rate, Composition B
outperformed Composition 1 by over 200 percent (up to about 229%)
and Composition E outperformed Composition 2 by over 280 percent
(up to about 288%). The CMP performances of Composition B and
Composition E are impressive, even when the moderate decreases in
surface uniformity are considered. These results demonstrate that
the catalyst-coated abrasive is an effective, if not potent,
component in the compositions of this invention.
[0059] This effective catalyst-coated abrasive component functions
optimally when it is relatively, if not substantially, stable.
Catalyst stability is a desirable characteristic in the
composition, as it facilitates control of the CMP process. Thus,
tests were conducted to determine the relative stability of the
catalyst-coated abrasive used in the composition of the present
invention, as compared with that of a soluble catalyst, in the
presence of an oxidizing agent, in two other compositions. In these
tests, the "coated catalyst" composition was composed of the
catalyst-coated abrasive in the form of iron-coated (FeAc-coated)
silica particles, and an oxidizing agent in the form of
hydroxylamine, and had a pH of about 7. The first "free catalyst"
composition was composed of normal abrasive in the form of silica
particles, soluble catalyst in the form of iron nitrate, and
oxidizing agent in the form of hydroxylamine, and had a pH of about
7. The second "free catalyst" composition was composed of all of
the components of the first "free catalyst" composition except for
the abrasive component.
[0060] The three test compositions were prepared as set forth
below. A "coated catalyst" preparation was obtained by adding an
appropriate amount of the catalyst-coated abrasive to 50
milliliters of water, while a first "free catalyst" preparation was
obtained by adding the silica particles to 50 ml of water, and then
adding an appropriate amount of the iron nitrate to the
water-abrasive mixture. The amount of abrasive in the first "free
catalyst" preparation was similar to the amount of catalyst-coated
abrasive used in the "coated catalyst" preparation. A second "free
catalyst" preparation containing only iron nitrate dissolved in 50
ml of water (i.e., no abrasive) was also prepared.
[0061] The same designated amount of 50% hydroxylamine was added to
each of these preparations to obtain the three test compositions.
At a pH of over 6, hydroxylamine is a good reducing agent, the
stability of which is extremely sensitive to trace metals in
solution. Hydroxylamine reacts easily with many transition metal
ions, such as cobalt, copper and iron ions, resulting in the
reduction of the metal ions by at least one oxidation level and the
formation of by-products including nitrogen gas, ammonia
(NH.sub.3), water, and possibly heat, depending on the
concentration of the hydroxylamine. A high level of reactivity, or
a very fast reaction rate, is a sign of relative instability.
[0062] When the hydroxylamine component was added to obtain the
"coated catalyst" composition, little color change, little or no
outgassing, and little or no precipitation were observed. When the
first "free catalyst" composition containing silica abrasive was
formed, an immediate color change (light orange to brown),
substantial outgassing, and precipitation were observed. When the
second "free catalyst" composition containing no abrasive was
formed, a more immediate color change (light orange to very dark
brown) and similar outgassing, as compared to the first "free
catalyst" composition, were observed. The "coated catalyst"
composition was clearly more stable than the two relatively
unstable "free catalyst" compositions tested. The compositions of
the present invention are all of the "coated catalyst" variety,
comprising a catalyst-coated abrasive rather than solely a free,
soluble catalyst such as iron nitrate. As demonstrated above, this
relatively stable, catalyst-coated abrasive is an extremely
effective component of the composition of this invention.
[0063] The composition of the present invention is advantageously
used in conventional CMP processes, and more particularly, in CMP
processes that call for reduced carrier pressures. Generally,
carrier pressures of from about 0.5 to about 2 psi are considered
low carrier pressures, although this pressure range depends on the
particular CMP process under consideration. Low carrier pressures
are often desirable because they reduce the risk of wafer damage,
such as scratching, delaminating, or destroying of material layers,
particularly metal layers, on the wafer surface. When the
composition of the present invention is used in a
low-carrier-pressure process, desirable material removal rates are
obtainable even though the carrier pressure is low. Appropriate use
of the composition in CMP processes may reduce the risk of wafer
damage and improve wafer yield and performance.
[0064] Additionally, the composition of the present invention may
be advantageously used in the CMP of wafers layered with relatively
fragile films, such as porous films, that have low dielectric
constants. At the pressures used in typical CMP processes, these
films are particularly vulnerable to delamination, crushing, or
other damage. In advanced CMP processes used for these wafers,
carrier pressures of about 2 psi are desirable and carrier and
platen speeds are about the same as, or often greater than, those
used in typical CMP processes. For a wafer layered with a porous
material of relatively low dielectric constant, such as from about
1.5 or about 1.7 to about 2.3, and of about 0.1 micron in
thickness, a removal rate of greater than about 5000 .ANG./min is
desirable. As demonstrated herein, these removable rates are
obtainable when the composition of the present invention is used in
CMP, even when the carrier pressure is relatively low. The
compositions of the present invention are believed suitable for use
in CMP processes having even lower carrier pressures, such as the
low carrier pressures described above.
[0065] As demonstrated herein, the composition of the present
invention may be used in CMP processes to obtain desirable material
removal rates and within-wafer nonuniformity values. Merely by way
of example, the composition may be used in the CMP of a substrate
surface having a feature, layer or film thereon, such as a film of
aluminum, copper, titanium, tungsten, an alloy thereof, or any
combination thereof. Further by way of example, the composition may
be used in the CMP of such a substrate surface, where the film has
an adjacent or an underlying feature, layer or film, such as a film
of tantalum, tantalum nitride, titanium, titanium nitride, titanium
tungsten, tungsten, and any combination thereof.
[0066] Accordingly, the present invention includes a method of
polishing a substrate surface having at least one feature thereon
that comprises a metal, such as metal or metal alloy feature. The
substrate undergoing polishing may be any suitable substrate, such
as any of the substrates described herein. According to the method
of the invention, a composition of the invention is provided and
the feature on the substrate surface is polished. The polishing is
chemical-mechanical polishing, such as that associated with any
conventional or known CMP process, any suitable later-developed CMP
process, or any CMP process described herein. The polishing process
parameters may be any suitable parameters, such as any of the
parameters described herein. For example, the carrier pressure
applied to the substrate surface, or the feature thereon, may be
from about 1 to about 6 psi.
[0067] Generally, the polishing of the substrate surface continues
until the targeted feature or layer is substantially coplanar with
surrounding material, such as an oxide material, on the substrate.
For example, the polishing of a metal-featured substrate may
continue until any metal excess is sufficiently removed to provide
a substantially uniform profile across the substrate surface. By
way of example, suitable surface uniformity (typically measured
using known wafer profiling techniques) is reflected by
within-wafer nonuniformity (WIWNU) values of less than about 12%,
and preferably, from about 4% to about 6%, the lower values
typically reflecting better process control. Appropriate WIWNU
values may vary depending on the characteristics of the CMP process
and the substrates undergoing polishing.
[0068] The inventive method may be used to remove targeted
material, such as metal or metal alloy, from the substrate surface
at a rate of from about 100 to about 10,000 or to about 15,000
.ANG./min. The present method may be used to provide a polished
substrate surface of good uniformity, such as a substrate surface
having from about zero to about 40 percent, preferably, from about
zero to about 12 percent, or more preferably, from about zero to
about 10 percent, within-wafer nonuniformity. Further, the present
method may be used to provide a polished substrate surface wherein
any microscratch on the surface that is associated with the
polishing is less than about 20 .ANG.. The present invention
further encompasses a substrate produced by the inventive method,
including any of the substrates described herein, and any of the
substrates having any of the qualities, such as desirable
uniformity values and surface characteristics, described
herein.
[0069] Various aspects and features of the present invention have
been explained or described in relation to beliefs or theories,
although it will be understood that the invention is not bound to
any particular belief or theory. Further, although the various
aspects and features of the present invention have been described
with respect to preferred embodiments and specific examples herein,
it will be understood that the invention is entitled to protection
within the full scope of the appended claims.
* * * * *