U.S. patent application number 10/689043 was filed with the patent office on 2004-07-15 for abrasive-free chemical mechanical polishing composition and polishing process containing same.
Invention is credited to Small, Robert J., Yao, Li.
Application Number | 20040134873 10/689043 |
Document ID | / |
Family ID | 34549837 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040134873 |
Kind Code |
A1 |
Yao, Li ; et al. |
July 15, 2004 |
Abrasive-free chemical mechanical polishing composition and
polishing process containing same
Abstract
The present invention relates generally to a chemical mechanical
polishing composition for polishing a metal, a metal oxide, and/or
a metal nitride layer of a substrate, which composition is
substantially free of abrasive particles and comprises: a
hydroxylamine derivative; a corrosion inhibitor; and water, wherein
water comprises the majority of the composition. The composition
may optionally include, or alternately be substantially free from,
one or more of the following: hydroxylamine, acid and/or base to
adjust pH, two carbon atom linkage alkanolamine compounds,
quaternary ammonium salts, chelating agents, organic solvents,
non-hydroxyl-containing amine compounds, surfactants, additional
oxidizing agents, and non-abrasive additives. A process for
chemically mechanically polishing a substrate using such a
polishing composition is also provided herein.
Inventors: |
Yao, Li; (Newark, CA)
; Small, Robert J.; (Dublin, CA) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Family ID: |
34549837 |
Appl. No.: |
10/689043 |
Filed: |
October 21, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10689043 |
Oct 21, 2003 |
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09226996 |
Jan 7, 1999 |
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6635186 |
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09226996 |
Jan 7, 1999 |
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09043505 |
Mar 23, 1998 |
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6117783 |
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09043505 |
Mar 23, 1998 |
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PCT/US97/12220 |
Jul 21, 1997 |
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60023299 |
Jul 26, 1996 |
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Current U.S.
Class: |
216/2 |
Current CPC
Class: |
C23F 3/00 20130101; C09G
1/02 20130101; C09G 1/04 20130101; H01L 21/3212 20130101 |
Class at
Publication: |
216/002 |
International
Class: |
C23F 001/00 |
Claims
What is claimed is:
1. A chemical mechanical polishing composition for polishing a
metal, a metal oxide, and/or a metal nitride layer of a substrate,
which composition is substantially free of abrasive particles and
comprises: a hydroxylamine derivative; a corrosion inhibitor; and
water, wherein water comprises the majority of the composition.
2. The chemical mechanical polishing composition of claim 1,
wherein the hydroxylamine derivative comprises hydroxylamine
nitrate, hydroxylamine sulfate, and/or hydroxylamine.
3. The chemical mechanical polishing composition of claim 2,
wherein the hydroxylamine derivative is present in a total amount
from about 1% to about 5% by weight of the composition.
4. The chemical mechanical polishing composition of claim 1,
wherein the corrosion inhibitor comprises benzotriazole.
5. The chemical mechanical polishing composition of claim 4,
wherein the corrosion inhibitor consists essentially of
benzotriazole.
6. The chemical mechanical polishing composition of claim 5,
wherein the corrosion inhibitor is present in a total amount from
about 0.01% to about 0.05% by weight of the composition.
7. The chemical mechanical polishing composition of claim 1,
wherein the water is present in a total amount from about 90% to
about 99% by weight of the composition.
8. The chemical mechanical polishing composition of claim 1,
further comprising a sufficient amount of an acid and/or a base to
adjust the pH of the composition to a desired level.
9. The chemical mechanical polishing composition of claim 8,
wherein the acid and/or base are present in a total amount from
about 0.01% to about 2% by weight of the composition.
10. The chemical mechanical polishing composition of claim 1,
further comprising one or more of the following: a two carbon atom
linkage alkanolamine compound, a quaternary ammonium salt, a
chelating agent, an organic solvent, a non-hydroxyl-containing
amine compound, a surfactant, an additional oxidizing agent, and a
non-abrasive additive.
11. The chemical mechanical polishing composition of claim 1, which
is substantially free of one or more of the following:
hydroxylamine, acid and/or base to adjust pH, two carbon atom
linkage alkanolamine compounds, quaternary ammonium salts,
chelating agents, organic solvents, non-hydroxyl-containing amine
compounds, surfactants, additional oxidizing agents, and
non-abrasive additives.
12. A chemical mechanical polishing composition for polishing a
metal, a metal oxide, and/or a metal nitride layer of a substrate,
which composition is substantially free of abrasive particles and
consists essentially of: about 1% to about 5% by weight of a
hydroxylamine derivative selected from the group consisting of
hydroxylamine, hydroxylamine nitrate, hydroxylamine sulfate, and
mixtures thereof; about 0.01% to about 0.05% by weight of
benzotriazole; about 90% to 99% by weight of water; and less than
about 2% by weight of an acid and/or a base to adjust the pH of the
composition to a desired level.
13. The chemical mechanical polishing composition of claim 12,
which is substantially free of hydroxylamine.
14. A process for chemical mechanical polishing of a substrate
comprising: providing a substantially abrasive-free chemical
mechanical polishing composition that comprises a hydroxylamine
derivative, a corrosion inhibitor, water, and optionally a
sufficient amount of an acid and/or a base to adjust the pH of the
composition to a desired level, wherein the majority of the
composition comprises water; contacting the chemical mechanical
polishing composition with a substrate having a metal oxide layer
surface, upon which metal oxide surface a barrier layer is
disposed, upon which barrier layer a metal layer is disposed; and
chemically mechanically polishing the substrate by contacting the
substrate surface with an abrasive polishing pad at an applied
pressure of not more than about 2 psi and by moving the pad in
relation to the substrate, wherein the removal rate of the barrier
layer greater than about 500 .ANG./min, and wherein the removal
rate of the metal oxide layer is less than about 10 .ANG./min.
15. The process of claim 14, wherein the removal rate of the metal
layer during the chemical mechanical polishing step is less than
about 250 .ANG./min.
16. The process of claim 14, wherein the removal rate of the metal
layer during the chemical mechanical polishing step is greater than
about 10 .ANG./min.
17. The process of claim 14, wherein the removal rate of the
barrier layer during the chemical mechanical polishing step is less
than about 750 .ANG./min.
18. The process of claim 14, wherein the abrasive-free chemical
mechanical polishing composition is substantially free of one or
more of the following: hydroxylamine, acid and/or base to adjust
pH, two carbon atom linkage alkanolamine compounds, quaternary
ammonium salts, chelating agents, organic solvents,
non-hydroxyl-containing amine compounds, surfactants, additional
oxidizing agents, and non-abrasive additives.
19. The process of claim 14, wherein the abrasive-free chemical
mechanical polishing composition consists essentially of: about 1%
to about 5% by weight of a hydroxylamine derivative selected from
the group consisting of hydroxylamine, hydroxylamine nitrate,
hydroxylamine sulfate, and mixtures thereof; about 0.01% to about
0.05% by weight of benzotriazole; about 90% to 99% by weight of
water; and less than about 2% by weight of an acid and/or a base to
adjust the pH of the composition to a desired level.
20. The process of claim 19, wherein the abrasive-free chemical
mechanical polishing composition is substantially free of
hydroxylamine.
21. The process of claim 14, wherein the metal layer of the
substrate comprises copper.
22. The process of claim 21, wherein the barrier layer of the
substrate comprises tantalum nitride.
23. The process of claim 14, wherein the barrier layer of the
substrate comprises tantalum nitride.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 09/226,996, filed Jan. 7, 1999, which is a
continuation-in-part of U.S. application Ser. No. 09/043,505, filed
Mar. 23, 1998, now U.S. Pat. No. 6,117,783, which claims the
priority of International Patent Application No. PCT/US97/12220,
filed Jul. 21, 1997, which in turn claims the priority of U.S.
Provisional Application Serial No. 60/023,299, filed Jul. 26, 1996,
each of which are hereby incorporated by reference in their
entirety.
FIELD OF THE INVENTION
[0002] This invention relates to an improved composition and
process for the chemical mechanical polishing or planarization of
semiconductor wafers. More particularly, it relates to such a
composition and process tailored to meet more stringent
requirements of advanced integrated circuit fabrication.
BACKGROUND OF THE INVENTION
[0003] Chemical mechanical polishing (or planarization) (CMP) is a
rapidly growing segment of the semiconductor industry. CMP provides
global planarization on the wafer surface (millimeters in area
instead of the usual nanometer dimensions). This planarity improves
the coverage of the wafer with dielectric (insulators) and metal
substrates and increases lithography, etching and deposition
process latitudes. Numerous equipment companies and consumables
producers (slurries, polishing pads, etc.) are entering the
market.
[0004] CMP has been evolving for the last ten years and has been
adapted for the planarization of inter-layer dielectrics (ILD) and
for multilayered metal (MLM) structures. During the 80's, IBM
developed the fundamentals for the CMP process. Previously (and
still used in many fabs today) plasma etching or reactive ion
etching. (PIE), SOG ("spin on glass"), or reflow, e.g., with boron
phosphorous spin on glass (BPSG), were the only methods for
achieving some type of local planarization. Global planarization
deals with the entire chip while "local" planarization normally
only covers a 50 square micron area.
[0005] At the 1991 VMIC Conference in Santa Clara, Calif., IBM
presented the first data about CMP processes. In 1993 at the VMIC
Conference, IBM showed that a copper damascene (laying metal lines
in an insulator trench) process was feasible for the MLM
requirements with CMP processing steps. In 1995 the first tungsten
polishing slurry was commercialized.
[0006] The National Technology Roadmap for the Semiconductor
Industries (1994) indicates that the current computer chips with
0.35 micron feature sizes will be reduced to 0.18 micron feature
size in 2001. The DRAM chip will have a memory of 1 gigabit, and a
typical CPU will have 13 million transistors/cm.sup.2 (currently
they only contain 4 million). The number of metal layers (the
"wires") will increase from the current 2-3 to 5-6 and the
operating frequency, which is currently 200 MHZ, will increase to
500 MHZ. This will increase the need for a three dimensional
construction on the wafer chip to reduce delays of the electrical
signals. Currently there are about 840 meters of "wires"/chip, but
by 2001 (without any significant design changes) a typical chip
would have 10,000 meters. This length of wire would severely
compromise the chip's speed performance.
[0007] The global planarization required for today's wafer CDs
(critical dimensions) improves the depth of focus, resulting in
better thin metal film deposition and step coverage and
subsequently increases wafer yields and lowers the cost/device. It
is currently estimated (1996) that it costs .about.$114/layer/wafer
with current limited planarization processes. As the geometries
become smaller than 0.35 micron, the planarity requirements for
better lithography become critical. CMP is becoming important, if
not essential, for multiple metal levels and damascene
processes.
[0008] The CMP process would appear to be the simple rotation of a
wafer on a rotary platen in the presence of a polishing medium and
a polishing pad that grinds (chips away) the surface material. The
CMP process is actually considered to be a two part mechanism: step
one consists of chemically modifying the surface of the material
and then in the final step the altered material is removed by
mechanical grinding. The challenge of the process is to control the
chemical attack of the substrate and the rate of the grinding and
yet maintain a high selectivity (preference) for removing the
offending wafer features without significant damage to the desired
features. The CMP process is very much like a controlled corrosion
process.
[0009] An added complexity is that the wafer is actually a complex
sandwich of materials with widely differing mechanical, electrical
and chemical characteristics, all built on an extremely thin
substrate that is flexible.
[0010] The CMP processes are very sensitive to structural pattern
density which will affect metal structure "dishing" and oxide
erosion. Large area features are planarized slower than small area
features.
[0011] At the recent SEMICON/Southwest 95 Technical program on CMP,
it was stated that "[m]etal CMP has an opportunity to become the
principal process for conductor definition in deep submicron
integrated circuits." Whether or not it does so depends on the
relative success of CMP technologists in achieving the successful
integrated process flow at competitive cost.
[0012] A variety of residue removal compositions and processes
suitable for integrated circuit fabrication have been developed and
marketed by EKC Technology, Inc. (hereinafter "EKC"), the assignee
of the present application. Some of these compositions and
processes are also useful for removing photoresist, polyimide, or
other polymeric layers from substrates in integrated circuit
fabrication, and EKC has also developed a variety of compositions
and processes specifically for removing such polymeric layers from
substrates in integrated circuit fabrication. Additionally, EKC has
developed a variety of compositions and processes to selectively
remove specific substrate compositions from a substrate surface at
a controlled rate. Such compositions and processes are disclosed in
the following commonly assigned issued patents:
[0013] U.S. Pat. No. 6,367,486 to Lee et al., which issued on Apr.
9, 2002, entitled Ethylenediaminetetraacetic acid or its ammonium
salt semiconductor process residue removal process;
[0014] U.S. Pat. No. 6,313,039 to Small et al., which issued on
Nov. 6, 2001, entitled Chemical mechanical polishing composition
and process;
[0015] U.S. Pat. No. 6,276,372 to Lee, which issued on Aug. 21,
2001, entitled Process using hydroxylamine-gallic acid
composition;
[0016] U.S. Pat. No. 6,251,150 to Small et al., which issued on
Jun. 26, 2001, entitled Slurry composition and method of chemical
mechanical polishing using same;
[0017] U.S. Pat. No. 6,248,704 to Small et al., which issued on
Jun. 19, 2001, entitled Compositions for cleaning organic and
plasma etched residues for semiconductors devices;
[0018] U.S. Pat. No. 6,242,400 to Lee, which issued on Jun. 5,
2001, entitled Method of stripping resists from substrates using
hydroxylamine and alkanolamine;
[0019] U.S. Pat. No. 6,235,693 to Cheng et al., which issued on May
22, 2001, entitled Lactam compositions for cleaning organic and
plasma etched residues for semiconductor devices;
[0020] U.S. Pat. Nos. 6,187,730 and 6,221,818, both to Lee, which
issued on Feb. 13, 2001 and on Apr. 24, 2001, respectively,
entitled Hydroxylamine-gallic compound composition and process;
[0021] U.S. Pat. No. 6,156,661 to Small, which issued on Dec. 5,
2000, entitled Post clean treatment;
[0022] U.S. Pat. No. 6,140,287 to Lee, which issued on Oct. 31,
2000, entitled Cleaning compositions for removing etching residue
and method of using;
[0023] U.S. Pat. No. 6,121,217 to Lee, which issued on Sep. 19,
2000, entitled Alkanolamine semiconductor process residue removal
composition and process;
[0024] U.S. Pat. No. 6,117,783 to Small et al., which issued on
Sep. 12, 2000, entitled Chemical mechanical polishing composition
and process;
[0025] U.S. Pat. No. 6,110,881 to Lee et al., which issued on Aug.
29, 2000, entitled Cleaning solutions including nucleophilic amine
compound having reduction and oxidation potentials;
[0026] U.S. Pat. No. 6,000,411 to Lee, which issued on Dec. 14,
1999, entitled Cleaning compositions for removing etching residue
and method of using;
[0027] U.S. Pat. No. 5,981,454 to Small, which issued on Nov. 9,
1999, entitled Post clean treatment composition comprising an
organic acid and hydroxylamine;
[0028] U.S. Pat. No. 5,911,835 to Lee et al., which issued on Jun.
15, 1999, entitled Method of removing etching residue;
[0029] U.S. Pat. No. 5,902,780 to Lee, which issued on May 11,
1999, entitled Cleaning compositions for removing etching residue
and method of using;
[0030] U.S. Pat. No. 5,891,205 to Picardi et al, which issued on
Apr. 6, 1999, entitled Chemical mechanical polishing
composition;
[0031] U.S. Pat. No. 5,672,577 to Lee, which issued on Sep. 30,
1997, entitled Cleaning compositions for removing etching residue
with hydroxylamine, alkanolamine, and chelating agent;
[0032] U.S. Pat. No. 5,482,566 to Lee, which issued on Jan. 9,
1996, entitled Method for removing etching residue using a
hydroxylamine-containing composition;
[0033] U.S. Pat. No. 5,399,464 to Lee, which issued on Mar. 21,
1995, entitled Triamine positive photoresist stripping composition
and post-ion implantation baking;
[0034] U.S. Pat. No. 5,381,807 to Lee, which issued on Jan. 17,
1995, entitled Method of stripping resists from substrates using
hydroxylamine and alkanolamine;
[0035] U.S. Pat. No. 5,334,332 to Lee, which issued on Aug. 2,
1994, entitled Cleaning compositions for removing etching residue
and method of using;
[0036] U.S. Pat. No. 5,279,771 to Lee, which issued on Jan. 18,
1994, entitled Stripping compositions comprising hydroxylamine and
alkanolamine;
[0037] U.S. Pat. No. 4,824,763 to Lee, which issued on Apr. 25,
1989, entitled Triamine positive photoresist stripping composition
and prebaking process; and
[0038] U.S. Pat. No. 4,395,348 to Lee, which issued on Jul. 26,
1983, entitled Photoresist stripping composition and method;
[0039] the entire disclosures of all of which are incorporated
herein for all purposes by express reference thereto. These
compositions have achieved substantial success in integrated
circuit fabrication applications.
[0040] Hydroxylamine (HA) formulations have been found to be useful
in the removal of substrate, for example as an etchant used in
chemical-mechanical etching processes, as described in U.S. Pat.
Nos. 6,313,039; 6,251,150; and 6,117,783.
[0041] Hydroxylamine formulations have also been useful in removing
photoresists, such as is found in U.S. Pat. Nos. 5,279,771 and
5,381,807, which describe formulations containing hydroxylamine, an
alkanolamine, and optionally a polar organic solvent. Hydroxylamine
formulations have also been useful in removing etching residue,
such as is found in U.S. Pat. No. 5,334,332, which describes a
formulation containing hydroxylamine, an alkanolamine, water, and a
chelating agent. Hydroxylamine-containing formulations designed to
remove residues are known to be aggressive to metals, particularly
to titanium film and under more aggressive process conditions to
aluminum film.
[0042] As a result, various formulations have been developed to
control the corrosion. The attack of titanium can be moderated by
using different chelator, e.g., such as disclosed in U.S. Pat. No.
6,276,372, and/or by selecting a class of alkanolamine with
2-carbon linkage(s), which is disclosed, e.g., in U.S. Pat. No.
6,121,217. For example, other formulations include those disclosed
in: U.S. Pat. Nos. 6,276,372, 6,221,818, and 6,187,730, which each
describe a hydroxylamine formulation with a gallic compound (as
opposed to catechol) and an alcohol amine; U.S. Pat. No. 6,242,400,
which describes a hydroxylamine formulation with an alcohol amine
and a polar organic solvent; U.S. Pat. Nos. 6,156,661 and
5,981,454, which each describe a buffered hydroxylamine formulation
with an organic acid; U.S. Pat. Nos. 6,140,287 and 6,000,411, which
each describe a hydroxylamine formulation with an alkanolamine and
a chelating agent; U.S. Pat. No. 6,121,217, which describes a
hydroxylamine formulation with an alkanolamine and gallic acid or
catechol; U.S. Pat. No. 6,110,881, which describes a hydroxylamine
formulation with an organic solvent, water, and a chelating agent;
U.S. Pat. No. 5,911,835, which describes a nucleophilic amine
compound formulation with an organic solvent, water, and a
chelating agent; and U.S. Pat. Nos. 5,902,780, 5,672,577, and
5,482,566, which each describe a hydroxylamine formulation with an
alkanolamine, water, and a dihydroxybenzene chelating agent.
[0043] U.S. Pat. No. 5,997,658 to Peters et al. describes a
hydroxlamine-free photoresist stripping and cleaning composition,
for use particularly of copper or titanium
[0044] substrates, having about 70 to 85% by weight of an
alkanolamine, about 0.5 to 2.5% by weight of benzotriazole, about
0.5 to 2.5% by weight of gallic acid and the remainder being water.
Alkanolamines include N-methylethanolamine (NMEA), monoethanolamine
(MEA), diethanolamine, mono-, di-, and tri-isopropanolamine,
2-(2-aminoethylamino)-ethanol, 2-(2-aminoethoxy)-ethanol,
triethanolamine, and the like. The preferred alkanolamine is
N-methylethanolamine (MEA).
[0045] Additionally, U.S. Pat. No. 5,928,430 to Ward et al.,
entitled Aqueous stripping and cleaning compositions containing
hydroxylamine and use thereof, describes an aqueous stripping
composition comprising a mixture of about 55% to 70% by weight of a
polar amine solvent, about 22.5 to 15% by weight of a basic amine,
especially hydroxylamine, gallic acid as a corrosion inhibitor, and
water. U.S. Pat. No. 5,419,779 to Ward describes a stripping
composition containing water, 22.5 to 15% by weight of
hydroxylamine, 55% to 70% monoethanolamine, and preferably up to
about 10% by weight of a corrosion inhibitor, particularly one
selected from the group consisting of catechol, pyrogallol,
anthranilic, acid, gallic acid, and gallic ester.
[0046] Other cleaning-type compositions exist, for example as found
in U.S. Pat. No. 6,261,745 to Tanabe et al., entitled Post-ashing
treating liquid compositions and a process for treatment therewith,
which describes a post-ashing treating liquid composition
comprising a salt of hydrofluoric acid with a base free from metal
ions, a water-soluble organic solvent, water, and an acetylene
alcohol/alkylene oxide adduct.
[0047] Other prior art, e.g., U.S. Pat. Nos. 6,372,050, 6,326,130,
6,268,323, 6,261,745, 5,997,658, 5,417,877, and 4,617,251, inter
alia, have demonstrated the corrosion of the aluminum metal film
caused by various amines and other compounds in photoresist
stripper formulations.
[0048] Slurries
[0049] CMP has been successfully applied to the planarization of
interdielectric levels (IDL) of silicon oxides, BPSG, and silicon
nitride and also metal films. The metal films currently being
studied include tungsten (W), aluminum (Al), and copper (Cu).
[0050] The polishing slurries are a critical part of the CMP
process. The polishing slurries consist of an abrasive suspension
(silica, alumina, etc.) usually in a water solution. The type and
size of the abrasive, the solution pH and presence of (or lack of)
oxidizing chemistry are very important to the success of the CMP
process.
[0051] Metal CMP slurries must have a high selectivity for removing
the unwanted metal compared to the dielectric features on the
wafers. The metal removal rate should be between 1700 to 3500
.ANG./min) without excessive "dishing" of the metal plugs or
erosion of the oxide substrate. The oxide CMP has similar
requirements and polishing rates close to 1700 .ANG./min.
[0052] Metal Polishing
[0053] This type of polishing relies on the oxidation of the metal
surface and the subsequent abrasion of the oxide surface with an
emulsion slurry. In this mechanism, the chemistry's pH is
important. The general equations are (M=metal atom):
M.sub.o.fwdarw.M.sub.n.sup.++n e-
M.sub.n.sup.++[O.sub.x].sub.y.fwdarw.MO.sub.y or [M(OH).sub.x]
[0054] Under ideal conditions the rate of metal oxide (MO.sub.y)
formation (V.sub.f) will equal the rate of oxide polishing
(V.sub.p), (V.sub.f.dbd.V.sub.p). If the pH is too low (acidic)
then the chemistry can rapidly penetrate the oxide and attack the
metal (V.sub.f.dbd.V.sub.p), thus exposing the metal without any
further oxide formation. This means that all metal surfaces, at
high points and in valleys, are removed at the same rate.
Planarization of the surface is not achieved. This could cause
metal plug connectors to be recessed below ("dishing") the
planarization surface which will lead eventually to poor step
coverage and possible poor contact resistance.
[0055] When the pH is too high (caustic), then the oxide layer may
become impenetrable to the chemistry and the metal becomes passive,
(V.sub.f.dbd.V.sub.p) and the metal polishing rate becomes slow.
Metal polishing selectivity to oxide generally ranges from 20 to
100:1, depending on the metal type. Tungsten metal should have
selectivities >50:1 for the metal to oxide, and copper could
have >140:1 metal to oxide selectivity. Etch rates can be up to
7000 .ANG./min. The chemical diffusion rate and the type of metal
oxide surface are important to the successful planarization
process. A detailed mechanism has been proposed by Kaufmnan.
[0056] In practice, the low pH and highly corrosive oxidants
(ferric nitrate) being used with an example metal CMP process has
created corrosion problems with the polishing equipment. Currently
the oxidant used in the metal polishing step has ranged from nitric
acid to hydrogen peroxide, cesium and ferric nitrate solutions and
even ferric cyanide solutions. Because of chemical stability
problems, many slurries are made up at the point of use which means
that there is little or no shelf life.
[0057] Metal planarization needs an oxidizing reagent that is
stable and is not going to contribute to mobile ion contamination,
will not "stain" the equipment, will not affect the slurry
composition and slurry particle distribution and is generally
environmentally friendly. The current hydrogen peroxide systems are
not stable when premixed with the slurry and therefore have to be
delivered to the polishing equipment with separate pumping systems
and mixed at the point of use. The ferric nitrate system requires a
low pH and is known to "stain" the polishing equipment. The
potassium iodate system also requires special handling.
[0058] An emerging area of CMP will deal with the copper damascene
process. The copper metal interconnects (wires) will be required
because of its better conductivity compared to Al. One major
disadvantage with copper is its easy diffusion through silica under
normal operating conditions. The copper damascene process will need
barrier layers to prevent this copper diffusion.
[0059] In the damascene process, "lines" or trenches are etched
into the interdielectric layers, and then the walls of these
trenches are coated with barrier materials. These materials can be
composed of Ta, TaN, Ti or TiN among other materials. Copper metal
is then deposited, by electroless or electrode plating, or PVD or
CVD methods. The excess copper above the trench is then removed by
chemical mechanical polishing. The difficult part of the CMP
process is not to remove excess copper ("dishing") which will
remove the copper metal below the interdielectric layer.
[0060] CMP of the copper metal can be done over a wide pH range (2
to 12). Pourbaix diagrams for copper indicate that copper can only
be passivated (oxide layer) in neutral or basic solutions. In acid
solutions an inhibitor, e.g., benzotriazole (BTA), is usually
needed to control the isotropic etching effects from the
chemistries used in the CMP process. Much of the CMP work has been
done with hydrogen peroxide at various pH ranges.
[0061] Some CMP work has been done with ammonium hydroxide, because
of its ability to form copper complexes though there are problems
with poor selectivity between copper and titanium and silicon
oxide.
[0062] Interlayer Dielectric (Oxide) Polishing
[0063] Recently a group of engineers using ILD (oxide) CMP was
asked to prioritize CMP processing requirements. The major concern
was surface damage (scratching, etc.) followed by wafer (polishing)
nonuniformity (within wafer and wafer to wafer), then polishing
rate and finally planarity. The mechanisms are still being
developed, but the polishing process appears to involve two
concurrent processes; a mechanical process involving plastic
deformation of the surface and, chemical attack by hydroxide (--OH)
to form silanol bonds. 1
[0064] In a slurry (colloidal suspension) the pH is important and
for the silicon oxide system it needs to be in the 10 to 11.5
range. Currently CMP users are using silicon oxide-based slurries
which were "buffered" with sodium hydroxide but now are being
formulated with potassium or ammonium hydroxide solutions. Etch
rates can be in the range of 1700 .ANG./min.
[0065] If the pH is too high the polynuclear species may start to
precipitate in an unpredictable manner. There is also the
possibility of a condensation process to form Si bonds.
[0066] There are other important features of the silicon surface
that will influence the etch rates and final surface conditions;
(metal contamination and possibly micro scratches). As mentioned
above the typical silicon surface is terminated (covered) with --OH
groups under neutral or basic conditions. The silicon surface is
hydrophilic (the surface is "wettable"). These groups activate the
surface to a number of possible chemical or physioabsorbtion
phenomena. The Si--OH groups impart a weak acid effect which allows
for the formation of salts and to exchange the proton (H.sup.+) for
various metals (similar to the ion exchange resins). These
Si--O.sup.- and Si--OH can also act as ligands for complexing Al,
Fe, Cu, Sn, and Ca. Of course the surface is very dipolar and so
electrostatic charges can accumulate or be dissipated depending on
the bulk solution's pH, ion concentration and charge. This
accumulated surface charge can be measured as the Zeta
potential.
[0067] If the silica (Si) surface underneath the oxide layer is
exposed because of an over aggressive polishing process, this could
cause electrochemical problems because silica has a modest redox
potential which will allow Cu, Au, Pt, Pb, Hg and Ag to "plate on"
the silica surface. Exposure to light will also affect the redox
reaction for Cu. The light will "generate" electrons in the
semiconductor Si material which then reduces the copper ion to
Cu.sup.o.
[0068] Post-Clean Processes
[0069] Both the ILD and metal polishing processes must eventually
pass through a final cleaning step to remove traces of slurry and
the chemistry. Though the process appears to be simple, e.g., a
brush scrub and a rinse cycle, considerable effort is being
expended to determine if the process should involve either single
side, double sided scrubbing, single wafer or batch processing,
spray tools or even immersion tanks. Recently an engineering group
working with post-clean CMP ranked wafer cleanliness (from slurry
and pad particles and metallic contamination) as the most important
issue in the post-clean step. Process reliability and defect
metrology were the other two important areas of concern.
[0070] Residual particle levels must be .about.1 particle/20
cm.sup.2, and 90% of these particles with less than >0.2 micron
size. Line widths of 0.35 micron will require the removal of
particles down to 0.035 or less. Incomplete particle removal will
decrease wafer yield. Low defect (scratches) levels and acceptable
planarity will also be very important.
[0071] Most fabs have developed their own in-house technology for
the post-clean CMP steps. Most of the "chemistries" involve DI
water with either added ammonium hydroxide or HF while some fabs
are using the standard RCA SC-1
(NH.sub.4OH:H.sub.2O.sub.2:H.sub.2O) and SC-2
(HC1:H.sub.2O.sub.2:H.sub.2O) cleaning steps traditionally used in
the front end process.
[0072] There are five mechanisms for removing impurities (particles
and/or ions) from wafer surfaces:
[0073] Physical desorption by solvents: replacing a small number of
strongly absorbed material with a large volume of weakly adsorbed
solvent (changing the interaction of the surface charges);
[0074] Change the surface charge with either acids or bases: the
Si--OH or M-OH group can be protonated (made positive) in acid or
made negative with bases by removing the proton;
[0075] Ion competition: removing adsorbed metal ions by adding acid
(e.g., ion exchange);
[0076] Oxidation or decomposition of impurities: oxidation of
metals, organic materials or the surface of slurry particles will
change the chemical bonds between the impurities and substrate
surface. The chemical reaction can either be through redox
chemistry or free radicals; and
[0077] Etching the surface: the impurity and a certain thickness of
the substrate surface is dissolved.
SUMMARY OF THE INVENTION
[0078] One aspect of the present invention relates to a chemical
mechanical polishing composition for polishing a metal, a metal
oxide, and/or a metal nitride layer of a substrate, which
composition is typically substantially free of abrasive particles
and can include: a hydroxylamine derivative; a corrosion inhibitor;
and water. Advantageously, water can be the majority of the
composition. In one embodiment, the water is present in a total
amount from about 90% to about 99% by weight of the
composition.
[0079] In another embodiment, the composition may further contain a
sufficient amount of an acid and/or a base to adjust the pH of the
composition to a desired level. In one preferred embodiment, the
acid and/or base are present in a total amount from about 0.01% to
about 2% by weight of the composition. In another preferred
embodiment, the composition is substantially free of acid and/or
base to adjust the pH.
[0080] The chemical mechanical polishing composition according to
the invention may further include, or alternately be substantially
free from one or more of the following: hydroxylamine, acid and/or
base to adjust pH, two carbon atom linkage alkanolamine compounds,
quaternary ammonium salts, chelating agents, organic solvents,
non-hydroxyl-containing amine compounds, surfactants, additional
oxidizing agents, and non-abrasive additives.
[0081] In one embodiment, the hydroxylamine derivative includes
hydroxylamine nitrate, hydroxylamine sulfate, and/or hydroxylamine.
In another embodiment, the hydroxylamine derivative is present in a
total amount from about 1% to about 5% by weight of the
composition.
[0082] In one embodiment, the corrosion inhibitor includes
benzotriazole. In another embodiment, the corrosion inhibitor
consists essentially of benzotriazole. In another embodiment, the
corrosion inhibitor is present in a total amount from about 0.01%
to about 0.05% by weight of the composition.
[0083] In another preferred embodiment, the chemical mechanical
polishing composition according to the invention can be
substantially free of abrasive particles and can consist
essentially of: about 1% to about 5% by weight of a hydroxylamine
derivative selected from the group consisting of hydroxylamine,
hydroxylamine nitrate, hydroxylamine sulfate, and mixtures thereof;
about 0.01% to about 0.05% by weight of benzotriazole; about 90% to
99% by weight of water; and less than about 2% by weight of an acid
and/or a base to adjust the pH of the composition to a desired
level. In an alternate preferred embodiment, the composition is
substantially free of hydroxylamine.
[0084] Another aspect of the invention relates to a process for
chemical mechanical polishing of a substrate including the steps
of: providing a substantially abrasive-free chemical mechanical
polishing composition according to the invention; contacting the
chemical mechanical polishing composition with a substrate having a
dielectric layer surface, upon which dielectric surface a barrier
layer is disposed, upon which barrier layer a metal layer is
disposed; and chemically mechanically polishing the substrate by
contacting the substrate surface with an abrasive polishing pad,
preferably at an applied pressure of not more than about 2 psi, and
by moving the pad in relation to the substrate. In a preferred
embodiment, the metal layer includes copper. In an alternate
embodiment, the metal layer can include tungsten, aluminum,
polysilicon, or the like, or a combination thereof. In a preferred
embodiment, the barrier layer can be based on a refractory metal
such as tantalum and/or may include a metal nitride (and preferably
includes tantalum nitride). In an alternate embodiment, the barrier
layer can be titanium-based.
[0085] Advantageously, at least one or more of the following may
apply to the process according to the invention: the removal rate
during the CMP step of the barrier layer can be greater than about
500 .ANG./min, less than about 750 .ANG./min, or both; the removal
rate during the CMP step of the dielectric layer can be less than
about 10 .ANG./min, preferably less than about 5 .ANG./min, for
example not more than about 1 .ANG./min; and the removal rate of
the metal layer during the CMP step can be less than about 250
.ANG./min, greater than about 10 .ANG./min, or both. In another
embodiment, the removal rate of the metal layer during the CMP step
can be less than about 500 .ANG./min, greater than about 50
.ANG./min, or both.
BRIEF DESCRIPTION OF THE DRAWINGS
[0086] FIGS. 1 and 2 are Pourbaix diagrams for copper and metal,
useful for an understanding of the invention.
DEFINITIONS
[0087] Unless otherwise specified, all percentages expressed herein
should be understood to refer to percentages by weight. Also, the
term "about," when used in reference to a range of values, should
be understood to refer to either value in the range, or to both
values in the range.
[0088] As used herein, the phrases "contains substantially no" and
"is substantially free from," in reference to a composition should
be understood to mean:
[0089] for components such as abrasives, alkanolamines including
AEEA, polar organic solvents including non-hydroxyl-containing
amines, water, organic solvents, hydroxylamine and hydroxylamine
derivatives, the aforementioned phrases should be understood to
mean that the composition contains less than 1.5%, preferably less
than about 1%, more preferably less than about 0.1%, of the
specific element mentioned thereafter;
[0090] for minor components including chelating agents, corrosion
inhibitors, surfactants, and the like, the aforementioned phrases
should be understood to mean that the composition contains less
than 0.2%, preferably less than about 0.1%, most preferably less
than about 0.01%, of the specific element mention thereafter;
and
[0091] for trace contaminants such as metal ions, substantially
free is defined in the specification, e.g., less than 10 ppm metals
and metal ions.
[0092] Preferably, when one of the aforementioned phrases is used,
the composition is completely free of any added element
specifically mentioned thereafter, or at least does not contain the
added element in an amount such that the element affects the
efficacy, storability, usability regarding necessary safety
concerns, or stability of the composition.
[0093] Unless otherwise specified, and wherever possible, a
compound should generally not be characterized under more than one
enumerated element of the composition according to the invention.
If a compound is capable of being characterized under, for example,
two enumerated embodiments of the composition, such a compound may
be characterized herein only under either one of the two enumerated
elements, but not under both. At times, the distinction may be made
based on the content of the compound in the composition. For
instance, catechol or gallic acid can act primarily as a corrosion
inhibitor at "high" concentrations, i.e. about 0.5% to 20%, or
primarily as a metal chelator at "low" concentrations, i.e., in the
ppm to 0.5 wt % range.
[0094] As used herein, hydroxylamine and hydroxyamine derivatives
are not considered organic, despite the organic substituents that
may be present on substituted hydroxylamine.
DETAILED DESCRIPTION OF THE INVENTION
[0095] Now CMP appears to be entering a new growth phase, which
emphasizes a new group of priorities. These priorities include
reducing CMP defects in metal and insulator layers, better
planarity within wafer and wafer to wafer, a premixed concentrate
that avoids point of use mixing; a generic post CMP cleaning an a
high polishing selectivity. There are also environmental, health
and safety issues. These issues are: (1) better vapor handling (or
educed requirement for vapor handling), (2) possible slurry
recycling (or spent slurry residues that are more environmentally
friendly), (3) more stable chemistries to be used with the
abrasives and (4) better end point detection (EPD) during the
polishing steps.
[0096] This invention does not deal with the composition or type of
abrasive (slurry particle size, shape, size distribution % solids)
in the slurry. But the slurries have numerous other components
(oxidizing agents, stabilizers, etc.) that can be improved through
additional experiments. These components include solutions pH, type
of chemistry and chemical and slurry purity. This proposed
invention focuses on the chemistry and its possible pH, Zeta
potential, contact angle ("wetting") and other associated
effects.
[0097] The first phase of the invention focuses on understanding
the CMP chemistry based on hydroxylamine (HDA) and hydroxylamine
derivatives (the chloride, sulfate, nitrate or other salts) under
different pH conditions HDA (NH.sub.2OH) can be viewed a hybrid
between hydrazine (H.sub.2N--NH.sub.2) and hydrogen peroxide
(H.sub.2O.sub.2) in its redox chemistry. HDA is a more selective
(controllable) oxidation and reducing agent. This dual capability
is achieved by shifting the pH from the acid to basic media, as
shown below. 2
[0098] The redox potential for hydrogen peroxide (acidic) and HDA
(in acid and base) (E.sub.v at SHE) are given: 3
[0099] Fortunately few metal ions are reduced to the zero oxidation
state, and this is important in CMP processes to avoid
contamination of the wafer surface with metal particles. Hydrogen
peroxide polishing systems are also not very stable, being easily
decomposed by trace amounts of transition metals. Currently, the
CMP consumable suppliers need to have a two component delivery
system--one for the slurry and the second for the peroxide.
[0100] Besides being a redox agent, HDA, like ammonia, can form
complex salts with many metals including
Al(SO.sub.4).sub.2*NH.sub.2OH*H.sub.2O and
Cu(x).sub.2*NH.sub.2OH*H.sub.2O.
[0101] Another important advantage of using hydroxylamine type
compounds is their decomposition products. Depending on the
solution pH and metal ions and concentration, HDA will decompose to
water, nitrogen, ammonia and N.sub.20. The formation of nitrogen
even takes place through a slow internal redox reaction at pHs
above 8.
[0102] Metal Polishing
[0103] The metals currently being studied for the CMP process
include AI, Cu, and W. Pourbaix diagrams can be used to examine the
best regions (E.sub.v versus pH) for the various polishing rates
(corrosion). No two metal or alloy systems will have the same
regions of chemical activity. Using this data may also allow CMP
polishing conditions to be chosen so that the selectivity of the
polishing rate of one metal is significantly greater than another
metal (or oxide or nitride material) on the same wafer. Pourbaix
diagrams can be obtained for all metals, oxides, nitrides and other
materials appearing on wafer surfaces wherever they are available.
By overlaying the diagrams, pH regions can be roughly determined
which may be corrosive for one material while passivating for
another. This could be one tool that is useful in seeking high
selectivities. FIG. 1 shows the Pourbaix diagram for Cu. This
diagram, based on thermodynamic data, shows that copper, copper (I)
oxide and copper (II) oxide can exist together in the redox
environment of our world (delineated by the sloping parallel dashed
lines). The data also shows that none of these three compounds can
exist at pHs less than 6.8, and at oxidation potentials above
.about.0.2 volts, all of these compounds will dissolve.
[0104] At higher pH values the three compounds can exist in aqueous
solution, including with various anions (Cu(OH).sub.2 and
CuO.sup.2-).
[0105] This invention proposes that usage of HDA or its salts can
be used to remove copper using CMP methods. The advantage of using
the HDA based chemistries is that its oxidation potential
(E.sub.v=-1.05 volts) will allow the Cu to be removed at higher pHs
than conventional chemistries that require a more acidic
environment (lower pH).
[0106] Recent experiments with 10% hydroxylamine nitrate in DI
water showed that 3000 A copper metal on a 300 A Ti metal layer
could be cleanly removed; @ pH 3 .about.100 .ANG./min, pH
4.about.125 .ANG./min and pH 5.about.1000 .ANG./min. This is
exactly the reverse of the expected pH effect from the Pourbaix
diagram and is the result of the oxidation potential.
[0107] When the free base hydroxylamine (5% in DI water) was tested
with the same type of copper wafer, the etching rate dropped to 75
.ANG./min compared to a 10% ammonium hydroxide with a 100 .ANG./min
rate. It is known that ammonium hydroxide solutions will dissolve
copper very slowly, but if oxidizing agents (air or oxygen) are
introduced then the etching rate can be quite measurable. The
hydroxylamine solution is a reducing medium and so the copper etch
is slower. The data does show that HDA could be used for very
controlled (slow) etch rates.
[0108] FIG. 2 shows the Pourbaix diagram for aluminum metal. The
data shows that the pure metal Al cannot exist in the normal redox
regime but only as an oxide coating. Between a pH of 4 and 10 this
oxide layer will not dissolve.
[0109] Experiments with blanket Al metal wafers should again show
the Al metal and its oxide layer can be removed by using either HAN
at a pH of 4 or at 10 since it is necessary to remove the oxide
layer before the metal layer can be polished. Concentration ranges
will vary from 0.5 to 10 wt %.
[0110] Our understanding of HDA and its purification has given us a
unique understanding of HDA's capacities to aid in removing mobile
ions (sodium, potassium, iron and other transition metal ions) from
the wafer's surface. It is critical that all phases of the CMP
process minimize the mobile and transition metal ion concentrations
on the wafer surfaces.
[0111] It is possible to add chelating agents; e.g., alkyl
beta-diketones (2,4 pentanedione, etc.) or EDTA or aromatic
phenolic aldehydes (salicylaldehyde, etc.) or other agents. These
components can be added in concentrations ranging from 2 ppm to 15
wt %. Higher concentrations could be used but there is a
possibility that these chelators could "plate" on the chip's
structures, or would alter the effectiveness of the over all
chemistry. The ketone-based systems may react with the
hydroxylamine based products to form oxime derivatives which are
good chelating agents in their own right.
[0112] Other agents could include bis(hydroxypropyl)hydroxylamine,
anisaldehyde or even alpha hydroxy isobutyric acid as a chelator.
Other compounds could also be aromatic dioxygenated compounds,
benzoin and benzil.
[0113] A recently reported water soluble iron chelator is O-TRENSOX
which can be used in the HDA-based chemistries and should show
promising results.
[0114] Though catechol and catechol derivatives are known to be
good chelating agents at high pH conditions (because of the mono or
dianion) only a little work has been done with this class of
compounds under acidic conditions. There are reports that catechol
will complex with aluminum at pH 3-5.
[0115] Gallic acid is also another compound that under mildly
acidic conditions could have complexing powers with certain Group 3
through 12 metals (IUPAC nomenclature). The catechol and gallic
acid family of compounds can act as either corrosion inhibitors (at
"high" concentrations; i.e. 0.5 to 15-20 wt %) compounds, or as
metal chelators in the ppm to 0.5 wt % range.
[0116] For many oxygenated compounds (phenols, alcohols, some
organic acids, etc.) it is important that the oxygen atoms fill in
vacancies on the metal surfaces. These vacancies are formed because
of poorly organized surface oxide films and/or the pH retards the
reactions or other anions interfere with the film uniformity. If
the chemical environment is too aggressive then the corrosion
inhibitor that is absorbed on the surface will be dissociated from
the surface, but will carry a metal ion with it. Now the corrosion
inhibitor can give the appearance of an attacking species.
[0117] Other benefits to using HDA-based chemistries are the
environment, safety and health aspects. HDA under basic conditions
decomposes to water, nitrogen, and small concentrations of
NH.sub.3. HDA is mildly caustic compared to other nitrogen
containing compounds, i.e., organic amines. Under acidic
conditions, hydroxylamine compounds are very stable in aqueous
solutions.
[0118] CMP users do not like working with sodium or potassium
hydroxide because of the potential mobile ion contamination. Many
users have changed over to ammonium hydroxide which does not have
the same magnitude of a mobile ion problem and does have a lower
surface tension (better surface contact). The main problem with
ammonium hydroxide is its odor which requires very effective
ventilation systems.
[0119] Another important area is to understand and, if possible, to
adjust the slurries' Zeta potential. The Zeta potential is a
electrostatic potential measurement of the interaction of the
electrostatic double layer ions (anions and cations) that exists
around each particle in a solution. The Zeta potential depending on
the type of particle; i.e. aluminum, silica, manganese dioxide
etc., and the solution pH, can be positive or negative. Poorly
designed slurries may have a Zeta potential which leads to settling
of the slurry particles. This can be very detrimental to its
performance during the CMP polishing process.
[0120] Another measure of Zeta potential is the isoelectric point
(IEP) for a particle. The IEP is the pH at which the Zeta potential
value is zero. The chemical composition and source will have
significant effect on the IEP. Some selected values: aluminum oxide
particles can vary between 3.8 to 9.4, while silicon oxide has a
narrower range 1.5 to 3.7.
[0121] Some metal residue IEP values are 9.5 for TiO.sub.2, while
tungsten is somewhere around .about.1. Such wide ranges of values
pose a major challenge to developing chemistries to control the
Zeta potential of the particles that may eventually adhere to the
wafer surface.
[0122] Another concern is that the Zeta potential between the
slurry and metal particles and the wafer will be such that the
particles will be attracted and adhere to the wafer surface. This
will require that a post CMIP clean step remove the adhering
particles.
[0123] The hydroxylamine or hydroxylamine salts can react with the
particle surface through either a redox reaction or a normal
chemical reaction with the terminal groups on the surface. Since
the HDA chemistries can be chemically "tuned" by adjusting the pH
and still be active for metal CMP (see Cu idea above), this will
give us a wider process window to affect the solution slurry Zeta
potential. Concentrations for this effect should be between 1 to 10
wt % because of HDA's single charge.
[0124] Another way to change the Zeta potential is to use
surfactants (nonionic, cationic or anion) to reduce the surface
charge on the wafer. The hydroxylamine chemistries can be matched
with the appropriate surfactant. Experiments with octylphenol
polyethylene (9-10 ethylene oxide units) at pH 9.5 did reduce the
surface tension and also reduced surface roughness. Anionic
surfactants can be used for particles that have positive Zeta
potentials.
[0125] Oxide Polishing
[0126] Some of the films currently being planarized include TEOS,
BPSG, PSG and SOG. Though this area of CMP has matured, EKC's HDA
(50% hydroxylamine) chemistry with its "buffered" pH of 9.5 to
10.5, and low mobile ion concentration (Na and K) could be an
important new chemistry for the current silicon oxide slurries.
[0127] The HDA free base material should be tested at various pH's
(7-11) with a silica slurry. The amount of HDA used in the slurry
should be 2 to 10%. SIMS data should show that the mobile ion
content remained constant or was decreased.
[0128] Though ammonium hydroxide solutions will also polish the
silicon surface, the vapors from the polishing process need to be
handled (removed) in an effective manner. The HDA chemistries do
not have the same smell intensity.
[0129] Work with ammonium salts added to fumed silica, in the pH
range of 6-9 for oxide CMP slurry, shows surprising results. Though
one expects the higher pH (9) to polish silicon oxide faster
(traditional chemical attack of a base on the Si bond), Hayashi et
al. had remarkable success at removing oxide at a pH 6 with a 0.1
molar ammonium salt solution (chloride, sulfate, etc). Even at pH 7
the rate was faster that at pH 9. The results suggest particle
agglomeration (change in the electrical double layer by modifying
the Zeta potential of the fumed silica), forming a "slush" on the
particles and the oxide surface. It was also noticed that the
residual particle count was reduced from 5.times.10.sup.5 to
2.times.10.sup.3 for a 6" wafer. There is no reason that
hydroxylamine salts at this or smaller concentration ranges should
not have a similar effect on the polishing rate. The pK's between
the two groups of salts are different which would allow us again to
"fine tune" the polishing rates.
[0130] One theory is that colloidal silica is very sensitive to pH
and undergoes flocculation at pH values near 8, due to the presence
of insufficient alkali ions.
[0131] Ammonium bifluoride is another important ingredient to be
evaluated in the above matrix. Silica dioxide has several
solubility regions depending on pH. Ammonium bifluoride at low
concentrations (>1.times.10.sup.-3 molar) and low pH (4-6) can
be effective for expanding the "window" for dissolving silica
structures. This chemistry region might open up an entirely new CMP
processing window for ILD. The concentration ranges must be rather
narrow, i.e., 1.times.10.sup.-5 to 1.times.10.sup.-2 molar. At
higher concentrations the chemistries start to act as conventional
HF etching media (in the pH range 4-7) with very rapid etching.
[0132] One important area is the polishing of an oxide/nitride
system and being able to achieve a high oxide to nitride
selectivity. Nitride appears to undergoing slow oxidation to a
silicon oxide type compound which undergoes the standard oxide
polishing process. This reduces the desired polishing
selectivity.
[0133] Since the HDA free base is a saturated nitrogen solution,
and the free base reacts with oxygen thus creating a solution with
very poor oxidizing potentials, it is possible that the nitride
structures will not be readily attacked. Thus the oxide to nitride
polishing selectivity should be enhanced.
[0134] Research would also be directed at determining if the HDA
solutions are stable under the required CMP conditions and whether
there is an enhanced selectivity among various other silicon oxide
systems (SOG, TEOS, BPSG, etc.).
[0135] Post-CMP Clean
[0136] The chemical nature of the wafer surface (hydrophilic or
hydrophobic) will effect the method and type of solution necessary
to remove particles from the wafer surface after the polishing
step. The particle charge relative to the wafer surface will
determine the type of chemistry that will effectively remove the
particles. Zeta potentials of the particles and the effect of the
solution pH on this value will need to be understood. Alumina
particles can be dislodged under acid conditions but silicon oxide
material requires a basic solution.
[0137] At the same time it should be advantageous to use solution
additives to remove metal contaminates from the wafer surface.
Study of residual particle count and metal contamination levels on
wafers from a post-clean procedure allows correlation of this
information with the HDA solution pH and level of additives. These
additives will include water soluble crown ethers and specific
metal chelating agents or buffered citric acid solutions.
[0138] Though HDA and HDA related compounds can effect the particle
and wafer surfaces through pH and redox chemistries, these chemical
species only have a single ionic charge per molecule (though a
reasonable charge density for the size of molecule involved). It
may be necessary to augment the electrostatic double layer around
the particles or on the wafer by adding "polyelectrolytes" which
are highly charged compounds. Normally the polyelectrolytes are
used in high enough concentration to "force" particles to clump
together. In this invention we only want to add enough
polyelectrolytes encourage the particles to repel each other and
away from the wafer surfaces. This will enhance the post CMP
cleaning step. The concentration for this affect could range from 1
part per thousand to 10 wt %.
[0139] There are several other types of redox reagents that also
can be used in CMP applications which could be used by themselves
or in conjunction with other chemistries, including hydroxylamine
and its salts.
[0140] In accordance with another aspect of the invention, ammonium
persulfate (ammonium peroxydisulfate) can be used to remove Al,
copper or tungsten using CMP methods. Though ammonium persulfate
has been used to strip copper metal films from electronic component
boards, this material has not been used to remove Cu in a very
controlled manner. We are not aware of this chemistry being used to
polish Al metal under CMP process conditions.
[0141] The tungsten CMP process appears to operate through the
tungstate (WO.sub.4.sup.=) ion. Though the current CMP processes
are based on ferric nitrate or hydrogen peroxide under acid
conditions another feasible route to obtain this species is to
oxidize the W metal with an oxidizing agent under basic conditions.
The tungstate should have maximum solubility at pH>6.
[0142] Normally ammonium persulfate solutions have a pH in the
range of 2 to 3. This invention illustrates that by adjusting the
oxidizing solution's pH to higher values, the resulting solution
will be a very effective for polishing W metal films.
[0143] Additional Compositions and Processes
[0144] In addition to the aforementioned compositions and processes
discussed above, the following describes preferred compositions and
processes according to the invention. In one preferred embodiment,
for example, a polishing composition is optionally but preferably
substantially abrasive-free and can contain: optionally
hydroxylamine; optionally at least one additive for controlling pH,
e.g., an acid; at least one corrosion inhibitor, preferably a
copper corrosion inhibitor, such as a copper (I) corrosion
inhibitor and/or a copper (II) corrosion inhibitor, more preferably
including benzotriazole or a salt or derivative thereof; water; and
at least one hydroxylamine derivative having the following formula:
4
[0145] wherein R.sub.3 is hydrogen or a linear, branched, or cyclic
hydrocarbon containing from 1 to 7 carbon atoms; and wherein X and
Y are, independently, hydrogen or a linear, branched, or cyclic
hydrocarbon containing from 1 to 7 carbon atoms, or wherein X and Y
are linked together form a nitrogen-containing heterocyclic
C.sub.4-C.sub.7 ring. When X, Y, and R.sub.3 are all hydrogen, the
compound is hydroxylamine.
[0146] Examples of derivatives of hydroxylamine according to the
invention include, but are in no way limited to, hydroxylamine,
N-methyl-hydroxylamine, N,N-dimethyl-hydroxylamine,
N-ethyl-hydroxylamine, N,N-diethyl-hydroxylamine, methoxylamine,
ethoxylamine, N-methyl-methoxylamine, and the like. As used herein,
hydroxylamine is not an organic, and the boiling point and flash
point of hydroxylamine and hydroxylamine derivatives is of no
consequence to the formulation. It should be understood that
hydroxylamine and its derivatives, as defined above, are available
(and may be included in a composition according to the invention)
as salts, e.g., sulfate salts, nitrate salts, phosphate salts, or
the like, or a combination thereof, and the invention includes
these forms of hydroxylamine compounds and their derivatives. These
salts greatly increase the theoretical flash point of hydroxylamine
derivatives. Therefore, in another embodiment, the composition
contains hydroxylamine, a sulfate, nitrate, or phosphate salt of
hydroxylamine, or a combination thereof. Hydroxylamines may not be
desired in a subset of the formulations described herein.
Therefore, in some embodiments, the composition according to the
invention is substantially free from hydroxylamine.
[0147] In one embodiment, the composition according to the
invention contains water. Water is preferred in a majority of
residue removing compositions. Additionally, hydroxylamine is
commercially available in an aqueous, i.e., a 50% aqueous,
solution. Hydroxylamine derivatives are typically available in more
concentrated aqueous forms, for example, 82% solutions with 18%
water (as is the case with HAN, or hydroxylamine nitrate). However,
hydroxylamine and/or hydroxylamine derivatives can be obtained or
manufactured, in some instances and in some concentrations, in a
water-free formulation.
[0148] In one embodiment, the composition can contain an acid,
e.g., to adjust the pH. The acid may be inorganic (e.g.,
hydrochloric, hydrobromic, sulfuric, sulfurous, nitric, nitrous,
phosphoric, phosphorous, or the like, or a combination thereof),
organic (e.g., lactic, acetic, formic, propionic, butyric, benzoic,
ascorbic, carbonic, gluconic, maleic, malonic, oxalic, succinic,
tartaric, citric, gallic, a polycarboxylic acid such as EDTA, or
the like, or a combination thereof), or a combination thereof. In
addition, acids according to the invention may include salts of
acids that still have acid functional moieties, e.g., a hydrogen
ascorbate, a hydrogen carbonate, a hydrogen gluconate, a hydrogen
maleate, a hydrogen malonate, a hydrogen oxalate, a hydrogen
succinate, a hydrogen tartarate, a hydrogen citrate, a dihydrogen
citrate, a hydrogen gallate, a dihydrogen gallate, a mono-, di-, or
tri-substituted salt of EDTA, or the like, or a combination
thereof. In an alternate embodiment, e.g., where higher pH rather
than lower is desired, the composition can contain a base to adjust
the pH. The base may be inorganic (e.g., a completely substituted
salt of an inorganic acid, such as those mentioned above; hydrazine
or a derivative thereof; a hydroxide salt, such as ammonium
hydroxide, sodium hydroxide, lithium hydroxide, potassium
hydroxide, calcium hydroxide, or the like, or a combination
thereof; or the like; or a combination thereof), organic (e.g., a
completely substituted salt of an organic acid, such as those
mentioned above; a non-hydroxyl-containing amine, such as a
substituted or unsubstituted aminobenzene, a substituted or
unsubstituted pyridine, a substituted or unsubstituted pyrrole, a
substituted or unsubstituted pyrrolidine, a substituted or
unsubstituted pyrrolid(in)one, a substituted or unsubstituted
carbazole, a substituted or unsubstituted indole, or the like, or a
salt thereof, or a (co)polymer containing same, or a combination
thereof; or the like; or a combination thereof), or a combination
thereof. In an alternate embodiment, the composition may be
substantially free from acids and/or bases to adjust pH.
[0149] Hydrazines and hydrazine derivatives suitable for use
according to the invention can be represented by the following
formula: 5
[0150] wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are
independently hydrogen; a hydroxyl group; optionally a substituted
C.sub.1-C.sub.6 straight, branched or cyclic hydrocarbon group;
optionally a substituted acyl group, straight or branched alkoxy
group, amidyl group, carboxyl group, alkoxyalkyl group, alkylamino
group, alkylsulfonyl group, or sulfonic acid group; or single or
multiple quaternary ammonium salts of such compounds.
[0151] In one embodiment, the compositions according to the
invention typically contains a corrosion inhibitor. In another
embodiment, the composition according to the invention contains a
single corrosion inhibitor, which is preferably benzotriazole.
[0152] Alternately, corrosion inhibitors useful in the composition
of the invention can be hydroxybenzenes according to the formula:
6
[0153] wherein n=1-4, m=2-5, and each R.sub.m is independently
hydrogen, a substituted C.sub.1-C.sub.7 straight, branched or
cyclic hydrocarbon group; a substituted acyl group, straight or
branched alkoxy group, amidyl group, carboxyl group, alkoxyalkyl
group, aklylamino group, alkylsulfonyl group, or sulfonic acid
group, or the salt of such compounds. In one embodiment, the
corrosion inhibitors can be dihydroxybenzene isomers and/or alkyl
substituted dihydroxybenzenes. In this embodiment, the preferred
corrosion inhibitors are 1,2-dihydroxybenzene and/or
1,2-dihydroxy-4-tert-butylbenzene.
[0154] Additional corrosion inhibitors as known in the art can also
be used in the composition of the present invention. For example,
corrosion inhibitors which are substantially metal-ion-free can be
utilized, such as thiophenol or its derivatives according to the
formula: 7
[0155] where R.sub.1 is preferably a hydrogen, hydroxyl, or
carboxylic acid group; or an ethylenediamine tetracarboxylic acid
(EDTC), or a salt thereof, having the formula: 8
[0156] wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 can be either
H, or NR.sub.5R.sub.6R.sub.7R.sub.8, where R.sub.5, R.sub.6,
R.sub.7, and R.sub.8 are each independently hydrogen or a linear or
branched C.sub.1-C.sub.6 hydrocarbon, or where two or more of
R.sub.5, R.sub.6, R.sub.7, and R.sub.8 together form a heterocyclic
C.sub.4-C.sub.7 ring; wherein R.sub.9 and R.sub.10 may be
independently defined in each repeat unit and each of which are
independently hydrogen or a linear or branched C.sub.1-C.sub.6
hydrocarbon, and wherein each of q, r, s, and t is a whole number
from 0 to 4 (i.e., when q, r, s, or t=0, there is no atom between
the nitrogen and the --COOH group in the formula above). As evident
from the above formula, the EDTC can be mono-, di- or tri-
substituted rather than tetra-substituted. For example, when each
of q, r, s, and t are 1, when each R.sub.9 and R.sub.10 is a
hydrogen, and when each R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are
all hydrogens, the EDTC above is ethylenediamine tetraacetic acid
(EDTA). Metal salts are not believed to be suitable for use, based
upon the understood mechanism of ionic contamination in a
microcircuit as caused by cleaning, as the compositions according
to the invention are preferably free of metals/metal ions.
[0157] Examples of other corrosion inhibitors include, but are not
limited to, nitrate salts of ammonium; hydrocarbon-substituted
ammonium nitrate salts; a choline, bischoline, and/or trischoline
salt, e.g., such as a hydroxide, a bisulfite, or the like;
2,4-pentandione dioxime; 1,6-dioxaspiro[4,4]nonane 2,7-dione
(di-ether); thiourea; ammonium bisulfite; glycerol; sorbitol;
gelatine; starch; phosphoric acid; silicic acid; polyethylene
oxide; polyethylene imine; and the like; or a combination thereof.
Preferably, the corrosion inhibitors are substantially free of
metals and/or metal ions.
[0158] In one embodiment, the composition can optionally include at
least one two carbon atom linkage alkanolamine compound. The
generic two carbon atom linkage alkanolamine compounds suitable for
inclusion in the invention have the structural formula, 9
[0159] wherein R.sub.1, R.sub.1', R.sub.2, R.sub.2', and R.sub.3
are, independently in each case, hydrogen or a linear, branched, or
cyclic hydrocarbon containing from 1 to 7 carbon atoms; wherein Z
is a group having the formula
-(-Q-CR.sub.1R.sub.1'--CR.sub.2R.sub.2'--).sub.m--, such that m is
a whole number from 0 to 3 (i.e., when m=0, there is no atom
between the --CR.sub.2R.sub.2'-- group and the --OR.sub.3 group in
the formula above), R.sub.1, R.sub.1', R.sub.2, and R.sub.2' may be
independently defined in each repeat unit, if m>1, within the
parameters set forth for these moieties above, and Q may be
independently defined in each repeat unit, if m>1, each Q being
independently either --O-- or --NR.sub.3--; and wherein X and Y
are, independently in each case, hydrogen, a C.sub.1-C.sub.7
linear, branched, or cyclic hydrocarbon, or a group having the
formula --CR.sub.1R.sub.1'--CR.sub.2 R.sub.2'-Z-F, with F being
either --O--R.sub.3 or --NR.sub.3R.sub.4, where R.sub.4 is defined
similarly to R.sub.1, R.sub.1', R.sub.2, R.sub.2', and R.sub.3
above, and with Z, R.sub.1, R.sub.1', R.sub.2, R.sub.2', and
R.sub.3 defined as above, or wherein X and Y are linked together
form a nitrogen-containing heterocyclic C.sub.4-C.sub.7 ring.
[0160] Many two-carbon atom linkage alkanolamine compounds have
relatively low boiling points and relatively low flash points. The
two carbon atom linkage alkanolamine compounds that may be useful
in the present invention preferably have relatively high boiling
points (e.g., 185.degree. C. or above, preferably 200.degree. C. or
above, alternately 215.degree. C. or above) and preferably have
relatively high flash points (e.g., 95.degree. C. or above,
preferably 100.degree. C. or above, alternately 110.degree. C. or
above). Preferred specific examples of such two carbon atom linkage
alkanolamine compounds include AEEA and 2-(2-aminoethoxy)ethanol
("DGA"). AEEA, or N-hydroxyethyl-ethylenediamine- , is the most
preferred of the two carbon atom linkage alkanolamine compounds,
though it may be admixed with other two carbon atom linkage
alkanolamine compounds to achieve a particular result, such as
increased etching or lower cost.
[0161] Examples of other two-carbon atom linkage alkanolamine
compounds include, but are in no way limited to, 2-aminoethanol
("monoethanolamine" or "MEA"), 2-(N-methylamino)ethanol
("monomethyl ethanolamine" or "MMEA"), 2-amino-1-propanol
("monoisopropanolamine" or "MIPA"),
2-(N-hydroxyethyl-amino)-ethanol ("diethanolamine" or "DEA"),
2-[(2-aminoethyl)-(2-hydroxyethyl)-amino]-ethanol
("N,N-bis-hydroxyethyl-- ethylenediamine"),
N,N,N-tris-(2-hydroxyethyl)-ammonia ("triethanolamine" or "TEA"),
N-aminoethyl-N'-hydroxyethyl-ethylenediamine,
N,N'-dihydroxyethyl-ethylenediamine,
2-[2-(2-aminoethoxy)-ethylamino]-eth- anol,
2-[2-(2-aminoethylamino)-ethoxy]-ethanol,
2-[2-(2-aminoethoxy)-ethox- y]-ethanol,
tertiarybutyldiethanolamine, isopropanolamine, diisopropanolamine,
3-amino-1-propanol ("n-propanolamine" or "NPA"), isobutanolamine,
2-(2-aminoethoxy)-propanol; 1-hydroxy-2-aminobenzene; or the like,
or any combination thereof.
[0162] In one embodiment, the composition can contain a two-carbon
atom linkage alkanolamine compound, in which m is greater than or
equal to 1. In another embodiment, the composition can contain a
two-carbon atom linkage alkanolamine compound, in which m is 1 and
R.sub.1, R.sub.1', R.sub.2, R.sub.2', and R.sub.3 are all hydrogen
or a C.sub.1-C.sub.4 linear or branched hydrocarbon. In an
alternate embodiment, the composition can contain a two-carbon atom
linkage alkanolamine compound, in which: m is 1; R.sub.1, R.sub.1',
R.sub.2, R.sub.2', and R.sub.3 are all hydrogen or a
C.sub.1-C.sub.4 linear or branched hydrocarbon; and Q is
--NR.sub.3. In another alternate embodiment, the composition can
contain a two-carbon atom linkage alkanolamine compound, in which:
m is 1; R.sub.1, R.sub.1', R.sub.2, R.sub.2', and R.sub.3 are all
hydrogen; X and Y are, independently, hydrogen or a linear or
branched C.sub.1-C.sub.4 hydrocarbon; and Q is --NH--,
--NCH.sub.3--, or --N[(C.sub.2-C.sub.4) linear or branched
hydrocarbon]-. In an alternate embodiment, the composition may be
substantially free from two carbon atom linkage alkanolamine
compounds.
[0163] In practice, it appears that, when present, the corrosion
inhibitor (particularly in the form of an EDTC, catechol, or gallic
acid) enhances the ability of the two carbon atom linkage
alkanolamine compound (when present) to clean/polish the substrate.
At the same time, when present, the EDTC, catechol, gallic acid, or
other corrosion inhibitor can help to prevent attack on the metal
or metal alloy substrate, e.g., copper.
[0164] In one embodiment, the composition can contain a quaternary
ammonium salt, e.g., as represented by the following formula:
10
[0165] wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are
independently hydrogen; optionally a substituted C.sub.1-C.sub.6
straight, branched or cyclic hydrocarbon group; optionally a
substituted acyl group, straight or branched alkoxy group, amidyl
group, carboxyl group, alkoxyalkyl group, alkylamino group, or
alkylsulfonyl group, sulfonic acid group; or the salt of such
compounds; and wherein the [counterion].sup.- may be a monovalent,
divalent, trivalent, or tetravalent anion and is preferably a
monovalent anion. In an alternate embodiment, the composition may
be substantially free from quaternary ammonium salts.
[0166] Examples of monovalent anions for use as a counterion to a
quaternary ammonium salt according to the invention include, but
are not limited to, hydroxyl groups, nitrate groups, bisulfite
groups, bicarbonate groups, carboxylate groups having structures
based on singly de-protonated carboxylic acid groups (e.g.,
formate, acetate, propionate, butyrate, isobutyrate, benzoate,
naphthoate, or the like, or singly de-protonated forms of multiply
protic carboxylic acids, such as lactate, ascorbate, glyconate,
oxalate, malonate, fumarate, maleate, phthalate, isophthalate,
terephthalate, gluconate, succinate, glutarate, tartrate,
salicylate, glycerate, citrate, gallate, subgallate, or the like),
or other acids listed herein, or the like, or a combination
thereof. For a list of pKa's of various carboxylic acids and their
relative likelihood of being mono-, di-, or tri-valent anions, see
the Table below.
1 pK.sub.a1 pK.sub.a2 pK.sub.a3 Monobasic formic 3.8 acetic 4.8
propionic 4.9 n-butyric 4.9 isobutyric 4.8 benzoic 4.2 Dibasic
ascorbic 4.2 11.6 gluconic 3.5 4.7 malic 3.4 5.1 malonic 2.8 5.7
oxalic 1.3 4.3 succinic 4.1 5.6 tartaric 2.9 4.2 Tribasic citric
3.1 4.8 6.9 gallic 4.2 8.9
[0167] In one embodiment, the composition according to the
invention optionally contains a chelating agent. In another
embodiment, the composition according to the invention contains a
single chelating agent, which is preferably EDTA (or a non-metallic
salt thereof), another organic polyacetic acid compound (or a
non-metallic salt thereof), gallic acid, or catechol. Catechol has
a boiling point of 245.degree. C., and a flash point of 127.degree.
C. In another embodiment, the composition according to the
invention contains a mixture of two chelating agents, such as
catechol and gallic acid. In another embodiment, the composition
according to the invention contains a mixture of two chelating
agents, preferably catechol and a polyacetic acid such as EDTA, or
its corresponding salt. In an alternate embodiment, the composition
is substantially free from chelating agents.
[0168] Examples of chelating agents include, but in no way limited
to, mono-, di-, or multi- hydroxybenzene-type compounds, e.g., such
as catechol, resorcinol, butylated hydroxytoluene ("BHT"), and the
like, or a combination thereof. In one embodiment the chelators
include three or more carboxylic acid-containing moieties, e.g.,
such as ethylenediamine tetraacetic acid ("EDTA"), non-metallic
EDTA salts, and the like, or a combination thereof Compounds
containing a two carboxylic acid moieties, such as citric acid, are
less preferred. Compounds containing both hydroxyl and carboxylic
acid moieties, e.g., such as gallic acid and the like, are useful
in one embodiment. Aromatic compounds containing thiol groups,
e.g., such as thiphenol; amino-carboxylic acids; diamines, e.g.,
such as ethylene diamine; polyalcohols; polyethylene oxide;
polyamines; polyimines; or a combination thereof, are useful in one
embodiment. In one embodiment, two or more chelating agents can be
used in one composition, where the chelating agents are selected
from groups described above. Alternately or additionally, some
chelating agents are described in U.S. Pat. No. 5,417,877, issued
May 23, 1995 to Ward, and in commonly assigned U.S. Pat. No.
5,672,577, issued Sep. 30, 1997 to Lee, the disclosures of each of
which are incorporated herein by reference.
[0169] Catechol can, in one embodiment, act as both a chelating
agent and as a corrosion inhibitor.
[0170] In one embodiment, the composition according to the
invention optionally contains a polar organic solvent. In an
alternate embodiment, the compositions is substantially free of
polar organic solvent. Examples of polar organic solvents for the
composition according to the invention include, but are in no way
limited to, dimethyl sulfoxide, ethylene glycol, ethylene glycol
alkyl ether, diethylene glycol alkyl ether, triethylene glycol
alkyl ether, propylene glycol, propylene glycol alkyl ether,
dimethyl sulfoxide, N-substituted pyrrolidone such as
N-methyl-2-pyrrolidone (NMP), sulfolanes, dimethylacetamide, and
the like, or any combination thereof. Dimethylsulfone, CAS No.
126-33-0, with a boiling point of 237.degree. C., is preferred in
some embodiments of the invention. NMP, with a boiling point of
199-202.degree. C. and a flash point of only 96.degree. C., may be
useful in some embodiments because of low cost. NMP does, however,
tend to lower the flash point of mixtures of the present invention.
Similarly, DMSO, with a boiling point of 189.degree. C. and a flash
point of only 95.degree. C., is less preferred in some embodiments
of the invention. 2,4-dimethylsulfolane, with a boiling point of
280.degree. C. and a flash point of 143.degree. C., is preferred in
some embodiments of the invention. Care must be taken because, in
the absence of alkanolamines and the like, 2,4-dimethylsulfolane is
only slightly miscible with water.
[0171] According to the present invention, amines, particularly
alkanolamines and also particularly low molecular weight amines,
are separate from, and are not classified as, a polar organic
solvent. Other additional polar organic solvents as known in the
art, other than those specifically excluded, can also be used in
the composition of the present invention. In an alternate
embodiment, the composition according to the invention is
substantially free from polar organic solvents as defined
herein.
[0172] Generally, non-polar organic solvents are not preferred,
though high boiling alcohols and the like may be used.
[0173] Organic solvents, including polar organic solvents, that
have a boiling point less than about 100.degree. C. are undesirable
in the composition according to the invention, as they tend to
evaporate over a period of more than about 24-48 hours at operating
conditions. Thus, generally the composition according to the
invention can be substantially free of organic solvents,
particularly that have a boiling point less than about 100.degree.
C. It is more preferred that the composition according to the
invention be substantially free of organic solvents that have a
boiling point less than about 150.degree. C. It is even more
preferred that the composition according to the invention be
substantially free of organic solvents that have a boiling point
less than about 199.degree. C.
[0174] In one embodiment, the composition according to the
invention optionally contains an amine compound that is not a
hydroxyl-containing amine and is not an alkanolamine. In an
alternate embodiment, the composition is substantially free of
amines that are not hydroxyl-containing amines and that are not
alkanolamines. Examples of such amine compounds include, but are in
no way limited to, o-diaminobenzene, p-diaminobenzene,
N-(2-aminoethyl)-ethylenediamine ("AEEDA"), piperazine,
N-substituted piperazine derivatives, piperidine, N-substituted
piperidine derivatives, diethylene triamine,
2-methyleneaminopropylenediamine, hexamthylene tetramine, and the
like, or a combination thereof. In a preferred embodiment, when
present, the non-hydroxyl-containing amine compound(s) has(have) a
boiling point no less than about 100.degree. C., or alternately no
less than about 150.degree. C. Amines may increase corrosion of
certain sensitive metals. In an alternate embodiment, the
composition according to the invention can be substantially free
from non-hydroxyl-containing amine compounds, or
non-hydroxyl-containing amine compounds having boiling points no
less than about 100.degree. C., or alternately no less than about
150.degree. C.
[0175] In one embodiment, the composition according to the
invention also contains a surfactant. In an alternate embodiment,
the composition is substantially free of surfactant. Examples of
surfactants include, but are in no way limited to, sodium laurel
sulfate, sodium stearate, and the like, or a combination
thereof.
[0176] In one embodiment, the composition according to the
invention also contains an additional oxidizing agent (i.e., other
than any hydroxylamine, hydroxylamine derivatives, pH-controlling
acids/bases, two carbon atom linkage amine compounds,
non-hydroxyl-containing amines, quaternary ammonium salts, and/or
other components present in the composition that may serve to
oxidize at least a portion of one or more of the layers on the
substrate). In an alternate embodiment, the composition is
substantially free of additional oxidizing agents.
[0177] Examples of additional oxidizing agents include, but are not
limited to: acids and/or salts having halide ions, i.e., including
ammonium and alkyl substituted ammonium halides; acids and/or salts
having halate (e.g., HalO.sub.4.sup.-x ions, where Hal is a halogen
atom and (-x) is the ionic charge) ions, i.e., including ammonium
and alkyl substituted ammonium halates; acids and/or salts having
metalate (e.g., MO.sub.4.sup.-x ions, where M is a metal atom, such
as chromium, manganese, copper, gallium, molybdenum, or the like,
and wherein (-x) is the ionic charge) ions, i.e., including
ammonium and alkyl substituted ammonium metalates; acids and/or
salts having borate ions, i.e., including ammonium and alkyl
substituted ammonium borates (e.g., sodium borate, potassium
borate, iron borate, copper borate, boric acid, or the like, or a
combination thereof); acids and/or salts having nitrate ions, i.e.,
including ammonium and alkyl substituted ammonium nitrates (e.g.,
ferric nitrate, sodium nitrate, calcium nitrate, copper nitrate,
nickel nitrate, aluminum nitrate, potassium nitrate, nitric acid,
or the like, or a combination thereof); acids and/or salts having
nitrite ions, i.e., including ammonium and alkyl substituted
ammonium nitrites (e.g., ferric nitrite, sodium nitrite, calcium
nitrite, copper nitrite, nickel nitrite, aluminum nitrite,
potassium nitrite, nitrous acid, or the like, or a combination
thereof); acids and/or salts having phosphate ions, i.e., including
ammonium and alkyl substituted ammonium phosphates (e.g., iron
phosphate, sodium phosphate, calcium phosphate, copper phosphate,
nickel phosphate, magnesium phosphate, aluminum phosphate,
potassium phosphate, phosphoric acid, or the like, or a combination
thereof); acids and/or salts having phosphite ions, i.e., including
ammonium and alkyl substituted ammonium phosphites (e.g., iron
phosphite, sodium phosphite, calcium phosphite, copper phosphite,
nickel phosphite, magnesium phosphite, aluminum phosphite,
potassium phosphite, phosphorous acid, or the like, or a
combination thereof); acids and/or salts having hypophosphite ions,
i.e., including ammonium and alkyl substituted ammonium
hypophosphites (e.g., iron hypophosphite, sodium hypophosphite,
calcium hypophosphite, copper hypophosphite, nickel hypophosphite,
magnesium hypophosphite, aluminum hypophosphite, potassium
hypophosphite, hypophosphoric acid, or the like, or a combination
thereof); acids and/or salts having sulfate ions, i.e., including
ammonium and alkyl substituted ammonium sulfates (e.g., iron
sulfate, sodium sulfate, calcium sulfate, copper sulfate, nickel
sulfate, magnesium sulfate, aluminum sulfate, potassium sulfate,
sulfuric acid, or the like, or a combination thereof); acids and/or
salts having sulfite ions, i.e., including ammonium and alkyl
substituted ammonium sulfites (e.g., iron sulfite, sodium sulfite,
calcium sulfite, copper sulfite, nickel sulfite, magnesium sulfite,
aluminum sulfite, potassium sulfite, sulfurous acid, or the like,
or a combination thereof); acids and/or salts having hyposulfite
ions, i.e., including ammonium and alkyl substituted ammonium
hyposulfites (e.g., iron hyposulfite, sodium hyposulfite, calcium
hyposulfite, copper hyposulfite, nickel hyposulfite, magnesium
hyposulfite, aluminum hyposulfite, potassium hyposulfite,
hyposulfuric acid, or the like, or a combination thereof); a
compound containing at least one oxygen-oxygen bond, but not
gaseous O.sub.2 or O.sub.3 (e.g., a peroxide such as hydrogen
peroxide, benzoyl peroxide, or the like; a peracid such as
peracetic acid, periodic acid, perboric acid, perchloric acid,
perbromic acid, perchromic acid, or the like; a perhalate such as
perchlorate, perbromate, periodate, or the like; a permetalate such
as perborate, permanganate, perchromate, or the like; a
di-permetalate such as di-perchromate, di-permanganate, or the
like; a persulfate; a di-persulfate; a percarbonate, or the like;
or a combination thereof); a compound containing at least one
nitrogen-nitrogen bond, but not gaseous N.sub.2 (e.g., hydrazine
and/or a hydrazine derivative such as described above, an azo
compound such as AIBN, a diazo compound, an azide such as sodium
azide, or the like, or a combination thereof); or the like; or a
combination thereof.
[0178] In one embodiment, the composition according to the
invention also contains an additional non-abrasive additive. These
additional additives may be spherical, discotic, elliptical,
irregular, or any other shape, dense, porous, hollow, e.g., in the
form of a particle, agglomerate, foam, flake, fiber/whisker, or the
like, or any combination thereof), but must be substantially
non-abrasive to the substrate and/or layer(s) (e.g., metal oxide,
metal nitride, etc.) disposed thereon. Examples of additional
non-abrasive particulate additives include, but are not limited to:
polymeric additives such as rubber particles, polyurethane foams,
or the like; sources of carbon such as carbon black particles,
mica, or the like; relatively soft metal oxides such as iron oxide
or the like; hydrated metal oxides (e.g., metal hydroxides and/or
oxide hydroxides) such as aluminum hydroxides and/or oxide
hydroxides (e.g., gibbsite, bayerite, nordstrandite, doyleite,
boehmite, diaspore, carboirite, rankamite, simpsonite, bahianite,
alumotungstite, meixnerite, hydrocalumite, kuzelite, and the like),
iron hydroxides and/or oxide hydroxides (e.g., including bemalite,
goethite, lepidocrocite, feroxyhyte, ferritungstite, akaganeite,
derbylite, tomichite, graeserite, hemolite, kleberite,
carmichaelite, yttrocrasite, bamfordite, jamborite, iowaite,
muskoxite, montroseite, and the like), manganese hydroxides and/or
oxide hydroxides (e.g., including manganite, groutite,
feitknechtite, nsutite, janggunite, vemadite, cianciulliite,
quenselite, and the like), chromium hydroxides and/or oxide
hydroxides (e.g., including woodallite, bracewellite, guyanaite,
grimaldiite, and the like), tin hydroxides and/or oxide hydroxide
(e.g., hydroromarchite), antimony hydroxides and/or oxide
hydroxides (e.g., including partzite, stetefeldtite, romeite,
stibiconite, bismutostibiconite, bindheimite, jixianite,
scheteligite, brandholzite, bottinoite, cyanophyllite, cualstibite,
shakhovite, and the like), niobium hydroxides and/or oxide
hydroxides (e.g., including betafite, stibiobetafite,
yttrobetafite, plumbobetafite, calciobetafite, pyrochlore,
kalipyrochlore, strontiopyrochlore, bariopyrochlore,
yttropyrochlore, ceriopyrochlore, plumbopyrochlore,
bismutopyrochlore, uranpyrochlore, fersmite, and the like),
tantalum hydroxides and/or oxide hydroxides (e.g., including
microlite, stannomicrolite, stibiomicrolite, bariomicrolite,
parabariomicrolite, plumbomicrolite, bismutomicrolite,
uranmicrolite, and the like), calcium hydroxides and/or oxide
hydroxides, titanium hydroxides and/or oxide hydroxides (e.g.,
including portlandite, kassite, kobeite, lucasite, aeschynite,
niobo-aeschynite, and the like), or the like, or combinations
thereof; relatively soft minerals such as talc, gypsum, magnesium
sulfate, or the like; or the like, or combinations thereof. In an
alternate embodiment, the composition is substantially free of
additional non-abrasive particulate additives.
[0179] Advantageously, the amount of hydroxylamine derivatives
(including hydroxylamine, when present) in the composition
according to the invention can be from about 0.1% to about 50%,
preferably from about 0.2% to about 20%, alternately from about
0.5% to about 10%, for example from about 0.5% to about 5% or from
about 5% to about 10%.
[0180] When present, the amount of hydroxylamine in the composition
according to the invention can be expressed in a ratio, relative to
the amount of hydroxylamine derivative(s) present in the
composition according to the invention. In one embodiment, the
hydroxylamine:hydroxylamine derivative weight ratio can be from
about 1:20 to about 20:1, for example from about 1:20 to about 1:1
or from about 1:1 to about 1:20, alternately from about 1:5 to
about 1:1 or from about 1:10 to about 1:2. In another embodiment,
the hydroxylamine:hydroxylamine derivative molar ratio can be from
about 1:54 to about 8:1, alternately from about 1:54 to about 1:2.7
or from about 1:2.7 to about 8:1, for example from about 1:13.5 to
about 1:2.7 or from about 1:2.7 to about 1.9:1.
[0181] Advantageously, the amount of corrosion inhibitor in the
composition according to the invention can be from about 0.01% to
about 10%, preferably from about 0.01% to about 2%, more preferably
from about 0.01% to about 1%, for example, from about 0.01% to
about 0.05% or from about 0.01% to about 0.1%, or alternately from
about 0.1% to about 1%.
[0182] Advantageously, the amount of water in the composition
according to the invention can advantageously be the majority of
the composition, e.g., from about 50% to about 99%, preferably from
about 60% to about 98%, for example from about 75% to about 97% or
from about 65% to about 90%, alternately from about 80% to about
98% or from about 90% to about 99%.
[0183] When present, the amount of acid and/or base added into the
composition according to the invention can advantageously be
sufficient to adjust the pH of the composition to the desired
level. A particular amount of acid and/or base to adjust the pH is
not specified herein, although it is generally less than about 5%,
for example, less than about 2%, alternately from about 0.01% to
about 2% or from about 0.01% to about 1%.
[0184] When present, the amount of two-carbon atom linkage
alkanolamine compound in the composition according to the invention
can advantageously be from about 0.1% to about 15%, alternately
from about 0.01% to about 5%, from about 0.2% to about 10%, from
about 0.1% to about 1%, or from about 0.5% to about 5%.
[0185] When present, the amount of chelating agent in the
composition according to the invention can advantageously be from
about 0.01% to about 15%, for example, from about 0.1% to about
10%, alternately from about 0.01% to about 1%, from about 0.01% to
about 0.1%, from about 2% to about 8%, or from about 1% to about
5%.
[0186] When present, the amount of quaternary ammonium salt in the
composition according to the invention can advantageously be from
about 0.01% to about 15%, for example, from about 0.1% to about
10%, alternately from about 0.01% to about 1%, from about 0.01% to
about 0.1%, from about 2% to about 8%, or from about 1% to about
5%.
[0187] When present, the amount of organic solvent in the
composition according to the invention can advantageously be from
about 0.1% to about 25%, for example from about 0.5% to about 15%,
alternately from about 0.1% to about 10% or from about 5% to about
20%.
[0188] When present, the amount of polar organic solvent in the
composition according to the invention can advantageously be from
about 0.1% to about 20%, for example, from about 0.1% to about 10%,
alternately from about 0.5% to about 10%, from about 2% to about
8%, or from about 1% to about 5%.
[0189] When present, the amount of non-hydroxyl-containing amine in
the composition according to the invention can advantageously be
from about 0.01% to about 15%, for example, from about 0.1% to
about 10%, alternately from about 0.01% to about 1%, from about
0.01% to about 0.1%, from about 2% to about 8%, or from about 1% to
about 5%.
[0190] When present, the amount of surfactant in the composition
according to the invention can advantageously be from about 0.01%
to about 10%, for example, from about 0.1% to about 5%, or
alternately from about 0.01% to about 1% or from about 1% to about
10%.
[0191] When present, the amount of additional oxidizing agent in
the composition according to the invention can advantageously be
from about 0.1% to about 10%, for example, from about 0.5% to about
5%, alternately from about 1% to about 10%, from about 2% to about
8%, or from about 1% to about 5%.
[0192] When present, the amount of non-abrasive additives in the
composition according to the invention can advantageously be from
about 0.1% to about 25%, for example from about 0.5% to about 15%,
alternately from about 0.1% to about 10% or from about 5% to about
20%.
[0193] Preferably, all of the compositions according to the
invention have very low metal impurity/ion contents, i.e., not more
than about 10 ppm total. In a preferred embodiment, the
compositions according to the invention have not more than about 5
ppm total metal content, preferably not more than about 1 ppm total
metal impurity and metal ion content.
[0194] In a preferred embodiment, the composition according to the
invention contains: substantially no abrasive particles, a
hydroxylamine derivative, a corrosion inhibitor, water, optionally
hydroxylamine, optionally an acid and/or a base (e.g., to adjust
pH), optionally a two carbon atom linkage alkanolamine compound,
optionally a quaternary ammonium salt, optionally a chelating
agent, optionally an organic solvent, optionally a
non-hydroxyl-containing amine compound, optionally a surfactant,
optionally an additional oxidizing agent, and optionally a
non-abrasive additive. In another preferred embodiment, the
composition according to the invention can be substantially free of
one or more of the following: abrasive particles, hydroxylamine,
acid and/or base to adjust pH, two carbon atom linkage alkanolamine
compounds, quaternary ammonium salts, chelating agents, organic
solvents (polar and/or non-polar), non-hydroxyl-containing amine
compounds, surfactants, additional oxidizing agents, and
non-abrasive additives.
[0195] While the compositions according to the invention are
preferably substantially free of abrasive particles, the processes
according to the invention may advantageously include the use of an
abrasive (e.g., an abrasive pad or the like), but preferably not
abrasive particles.
[0196] In a preferred embodiment, the present invention relates to
a process for chemical mechanical polishing of a substrate
including: providing a substantially abrasive-free chemical
mechanical polishing composition as described above; contacting the
chemical mechanical polishing composition with a substrate having a
dielectric material surface (e.g., a metal oxide layer), upon which
dielectric material a barrier layer is disposed, upon which barrier
layer a metal layer is disposed; and chemically mechanically
polishing the substrate by contacting the substrate surface with an
abrasive polishing pad, preferably at an applied pressure of not
more than about 2 psi and by moving the pad in relation to the
substrate. In another preferred embodiment, the metal layer
includes copper. In an alternate embodiment, the metal layer can
include tungsten, aluminum, polysilicon, or the like, or a
combination thereof. In another preferred embodiment, the barrier
layer can be based on a refractory metal such as tantalum and/or
may include a metal nitride (and preferably includes tantalum
nitride). In an alternate embodiment, the barrier layer can be
titanium-based.
[0197] Advantageously, at least one or more of the following may
apply to the process according to the invention: the removal rate
during the CMP step of the barrier layer can be greater than about
500 .ANG./min, less than about 750 .ANG./min, or both; the removal
rate during the CMP step of the dielectric layer can be less than
about 10 .ANG./min, preferably less than about 5 .ANG./min, for
example not more than about 1 .ANG./min; and the removal rate of
the metal layer during the CMP step can be less than about 250
.ANG./min, greater than about 10 .ANG./min, or both. In another
embodiment, the removal rate of the metal layer during the CMP step
can be less than about 500 .ANG./min, greater than about 50
.ANG./min, or both.
EXAMPLES
[0198] The following non-limiting examples represent best modes
contemplated by the inventors and describe the invention further.
In these examples, solution chemistry was tested as follows:
Example 1
[0199] Test: Solutions of ammonium persulfate were prepared and
then added to a 5% alumina slurry. The pHs were adjusted with NaOH
just before use.
[0200] The CMP experiments were with 10,000 .ANG. tungsten wafers,
at 33 rpm and 2 psig. The pad was a Rodell RC 1000 on a Logitech
P5M polisher. Base line polishing experiments with only an alumina
slurry have determined that there is an 8.times. to 10.times.
polishing factor between the Logitech and the IPEC/Westech
industrial size CMP polisher.
2 10% solution pH 3 removal rate 112 .ANG./min 10% solution pH 6
removal rate 105 .ANG./min 10% solution pH 7.7 removal rate 196
.ANG./min 10% solution pH 7.9 removal rate 198 .ANG./min 5%
solution pH 9 removal rate 176 .ANG./min
[0201] Notice that there appears to be a maximum value at a pH
around 7.9.
Example 2
[0202] Test: Mother composition that was tested was composed of
ammonium persulfate (APS) with varying concentrations of malonic
acid (MA). The pH was adjusted with sodium hydroxide. Ammonium
hydroxide will be oxidized to nitrogen and water.
3 APS MA pH Etch Rate (.ANG./min) 10% 1% 6 162 10% 1% 8.1 460 10%
0.4% 8 291 5% 1% 8.8 265 10% 0% 8 162
[0203] Notice that the best etch rates are seen at pH values above
8 and that malonic acid does have a positive effect (10% APS, 0%
MA, etch rate 162 .ANG./min), compared to the 5%, 1% MA solution
(265 .ANG./min).
[0204] There are other additives that can be added to oxidizers
that can also be used in the CMP process. These additives can
include oxalic acid, lactic acid, gluconic acid, malonamide, and
citric acid. These organic acids should have pKa lower than the pH
of the planarization solution. It is desirable to have these acids
in their corresponding anion form, which should be the most
effective chelation species.
[0205] In addition to malonic acid (HO.sub.2CCH.sub.2CO.sub.2H),
APS can be used effectively for W CMP when combined with other
organic acids, including but not limited to: succinic acid
(HO.sub.2CCH.sub.2CH.sub.2CO.- sub.2H), tartaric acid
(HO.sub.2CCH(OH)CH(OH)CO.sub.2H), citric acid
(HO.sub.2CCH.sub.2C(OH)(CO.sub.2H)CH.sub.2CO.sub.2H), and oxalic
acid (HO.sub.2CCO.sub.2H).
[0206] Bases that can be used to adjust the oxidizing solution's
pH, include sodium hydroxide, potassium hydroxide, magnesium
hydroxide, magnesium carbonate, and imidazole, among others.
[0207] There are other potential oxidizer compounds that can be
included; e.g., peroxy-monosulfuric acid (Caro's acid)
(H.sub.2SO.sub.5) or its salts are very strong oxidizing agents,
(E.sup.o=-1.44V). The acid form has one proton with a dissociation
constant similar to sulfuric acid while the second proton has a pKa
of only 9.4.
Example 3
[0208] A commercial product Caroat (potassium peroxomonosulfate
compound, including the potassium salt of Caro's acid; empirical
formula 2KHSO.sub.6KHSO.sub.4K.sub.2SO.sub.4) is a good oxidizer in
aqueous system at low pH, but combined with APS, it shows promising
results for W CMP at higher pH values. CAROAT is a registered
product of Degussa Corporation. The following removal rates are for
the Logitech PM5 polisher (33 rpm, 12" IC1000 pad, 2 psig) on 3"
wafers (10,000 A sputtered W), with 5% alumina slurry (50 parts of
10% alumina+90% water slurry), chemistry addition rate of 100
mL/min, and slurry addition rate of 20 mL/min:
4 APS (pph) CAROAT (pph) pH Removal Rate (.ANG./min) 10 1.0 5.5 90
10 1.0 7.5 139 10 1.0 8.7 349
[0209] Conclusion: Synergism between APS and Caroat enhances W
removal rates, with removal rates increasing with increasing pH
over the range 5.5 to 8.7.
[0210] Oxone peroxymonsulfate has a standard electrode potential
similar to peroxymonosulfate, with a wider range of pH stability
(between 2-6 and at 12). This material has .about.4.5% "active"
oxygen.
Example 4
[0211] APS combined with malonamide (H.sub.2NCOCH.sub.2CONH.sub.2)
shows W removal rates comparable with those of APS+malonic acid
using the Logitech PM5 polisher (33 rpm, 12" IC1000 pad, 2 psig) on
3" wafers (10,000 .ANG. sputtered W), with 5% alumina slurry (50
parts of 10% alumina+90% water slurry), chemistry addition rate of
90 mL/min, and slurry additional rate of 20 mL/min:
5 Malonamide Removal APS (pph) (pph) pH Rate (.ANG./min) 5 0 9.0
176 10 1.0 9.0 429 10 2.5 8.9 385 10 2.0 7.9 250 10 0 7.9 198
[0212] Conclusion: malonamide enhances the W removal rate when
combined with APS in an aqueous system over the W removal rate of
APS alone. Removal rates increase with pH.
[0213] Though the use of hydrogen peroxide is well known in the
metal CMP field it does suffer from poor long term stability when
mixed with slurry mixtures. The CMP users have made adjustments to
this problem by segregating the peroxide solution from the slurry
until just prior to usage on the polisher. This means that the CMP
user must have dual dispensing systems which increases the cost of
ownership which directly affects the CMP cost per wafer.
[0214] In accordance with another aspect of the invention,
perborates such as sodium perborate tetrahydrate are good compounds
which are indirect sources for hydrogen peroxide. The teraborate
has a 10.5% active oxygen content. This compound has a different
stability than hydrogen peroxide and therefore could be an
important compound for CMP metal etching applications. The dry form
of the perborate salt is used in many bleaching applications,
including detergent formulations, tooth powders and denture
cleaners.
[0215] Because of the sodium perborate's low solubility it could
also be used as a slurry or coslurry component. This could be very
beneficial to the CMP process since the chemistry is not only
acting as an abrasive but also as an oxidant. Its low solubility
but direct contact with the metal/metal oxide could give better
etch control.
[0216] Other compounds such as sodium carbonate peroxhydrate
(2Na.sub.2CO.sub.3*3H.sub.2O.sub.2) contain .about.14 wt % active
oxygen. This compound also has a better stability than hydrogen
peroxide and therefore could be an important material for metal
CMP.
[0217] Test: experiments with blanket Al metal (5000 .ANG.) wafer
showed that a 5 wt % hydroxylamine solution will remove 2 .ANG./min
of the metal, but a 5 wt % sodium percarbonate removed 6.4
.ANG./min. The polishing conditions were with a Logitech P5M
polisher with a Politex felt cloth at 33 rpm and 2 psi pressure on
the 3" wafer. No slurry was used during the test.
Example 5
[0218] Experiments with blanket W metal (10,000 .ANG.) wafer showed
that a 10 wt % hydroxylamine solution will remove 3.3 .ANG./min of
the metal, but a 5 wt % sodium percarbonate removed 168 .ANG./min.
Experiments also showed that a 2 wt % ferric nitrate solution will
remove only 34 .ANG./min of metal. The polishing conditions were
with Logitech P5M polisher with a Politex felt cloth at 33 rpm and
2 psig pressure on the 3" wafer. No slurry was used during the
test.
[0219] In accordance with a further aspect of the invention,
another compound that will be of interest will be the urea hydrogen
peroxide complex which will permit a more controlled introduction
of the oxidizing chemistry into the slurry system.
Example 6
[0220] Experiments with blanket W metal (10,000 .ANG.) wafer showed
that a 15 wt % hydrogen perioxide solution with 5% alumina slurry
removed 109 .ANG./min of the metal, yet only a 2 wt % urea hydrogen
peroxide with only a 2 wt % alumina slurry removed 83 .ANG./min. It
is interesting that a solution seven times more dilute and less
slurry removes almost as much metal as the hydrogen peroxide
solution. The polishing conditions were with a Logitech P5M
polisher with a Politex felt cloth at 33 rpm and 2 psig pressure on
the 3" wafer.
[0221] This combination of chemicals will generate environmentally
"friendly" waste products (urea and oxygen).
[0222] In accordance with still another aspect of the invention,
another commercially available oxidizing agent that could effective
for planarization tungsten or copper metal is peracetic acid. The
decomposition products include only oxygen and acetic acid
(vinegar).
[0223] Test: Experiments with blanket W metal (10,000 .ANG.) wafer
showed that a 15 wt % hydrogen peroxide solution with a 5% alumina
slurry removed 109 .ANG./min of the metal, yet only a 3.5 wt %
peracetic acid with only a 2 wt % alumina slurry removed 166
.ANG./min. It is interesting that a solution four time mores dilute
and less slurry removes 50% more metal as the hydrogen peroxide
solution. The polishing conditions were with a Logitech P5M
polisher with a Politex felt cloth at 33 rpm and 2 psig pressure on
the 3" wafer.
[0224] In accordance with a further aspect of the invention,
another unique idea is to blend two different chemistries to
achieve synergistic interactions. Two possible chemicals that could
be blended are hydrogen peroxide and hydroxylamine.
Example 7
[0225] Experiments with blanket W metal (10,000 .ANG.) wafer showed
that a 1 wt % hydrogen peroxide solution with a 5% alumina slurry
removed 109 .ANG./min of the metal, yet a 10 wt % H.sub.2O.sub.2
mixed with a 10% hydroxylamine with only a 5 wt % alumina slurry
removed 731 .ANG./min. The pH was adjusted to 8.7. The polishing
conditions were with a Logitech P5M polisher with a Politex felt
cloth at 33 rpm and 2 psig pressure on the 3" wafer.
Example 8
[0226] Experiments with blanket W metal (10,000 .ANG.) wafer showed
that a 10 wt % hydroxylamine solution will remove 3.3 .ANG./min of
the metal, but a 5 wt % H2O2 and 5 wt % hydroxylamine (pH 7.5)
removed 380 .ANG./min. Experiments also showed that a 2 wt % ferric
nitrate solution will remove only 34 .ANG./min. of metal. The
polishing conditions were with a Logitech P5M polisher with a
Politex felt cloth at 33 rpm and 2 psig pressure on the 3" wafer.
No slurry was used during the test.
[0227] Another aspect of the invention is to blend two different
chemistries to achieve synergistic interactions. Two possible
chemical that could be blended are ammonium persulfate and
potassium periodate. Potassium periodate has a higher oxidation
level compared to the potassium iodate.
Example 9
[0228] Experiments with blanket W metal (10,000 A) wafer showed
that a 10 wt % ammonium persulfate solution with a 5% alumina
slurry removed 162 .ANG./min of the metal (pH 8), yet a 10 wt %
ammonium persulfate mixed with a 2% KIO.sub.4 with only a 5 wt %
alumina slurry removed 637 .ANG./min. The pH was adjusted to
6.9.
[0229] When a 2 wt % potassium iodate (KIO.sub.3) was substituted
into the ammonium persulfate solution, the polishing rate decreased
to 246 .ANG./min. The polishing conditions were with a Logitech P5M
polisher with a Politex felt cloth at 33 rpm and 2 psi pressure on
the 3" wafer.
[0230] In another aspect of the invention, a similar chemistry to
that of the previous aspect uses a synergism between ammonium
persulfate (APS) and periodic acid (rather than potassium
periodate) for polishing tungsten.
Example 10
[0231] Removal rates of W generally increase with pH for the
periodic acid (H.sub.5IO.sub.6) in water without APS on 3" wafers
coated with sputtered W (10,000 .ANG.) using 1% or 2.5% alumina (10
or 25 parts of 10% alumina+90% water slurry), 0-3 parts NH.sub.4OH
to adjust pH, chemistry and slurry combined together at a
chemistry/slurry addition rate of 50-100 mL/min, and the Logitech
PM5 polisher (33 rpm, 12" IC1000 pad, 2 psig):
6 Periodic Removal Rate Alumina (pph) Acid (pph) pH (.ANG./min) 1.0
2.0 1.4 130 1.0 2.0 1.9 274 1.0 2.0 2.1 326 2.5 2.0 2.5 252 2.5 2.0
6.8 4.26
[0232] Conclusion: tungsten removal rates increase at higher pH
values over a pH range of 1 to 7 with a constant concentration of
periodic acid.
Example 11
[0233] Periodic acid in water added to APS increases the removal
rate of W over APS alone at pH 1; increasing the amount of periodic
acid used with 10 parts APS also increases the W removal rate using
the Logitech PM5 polisher (33 rpm, 12" IC1000 pad, 2 psig), 3"
wafers (10,000 .ANG. sputtered W), 0-3 parts NH4OH to adjust pH, 1%
alumina (10 parts of 10% alumina+90% water slurry), and
chemistry/slurry addition rate of 100 mL/min:
7 Periodic Removal Rate APS (pph) Acid (pph) pH (.ANG./min) 0 2.0
2.4 130 10 2.0 1.1 386 10 0.5 3.5 118 10 2.0 5.2 388 10 0 6 112
[0234] Conclusion: there is a synergistic effect that enhances W
removal rate when APS and periodic acid are used together.
Increased removal rates are observed over a pH range of 1-7.
Example 12
[0235] Constant removal rates were observed for several days in an
aqueous periodic acid/NH.sub.4OH system without APS using 0-3 parts
NH.sub.4OH to adjust pH, 2.5% alumina (25 parts of 10% alumina+90%
water slurry) added to the chemistry immediately prior to polishing
3" wafers (10,000 .ANG. sputtered W), chemistry/slurry addition
rate of 100 mL/min, and the Logitech PM5 polisher (33 rpm, 12" IC
1000 pd, 2 psig):
8 Period Acid Removal Time (days) (parts per 100) Rate (.ANG./min)
0 2.0 252 3 2.0 255
[0236] Conclusion: periodic acid has a very good polishing rate
when used alone, and, unlike hydrogen peroxide, has a good chemical
stability over several days.
Example 13
[0237] A comparison of removal rates for the aqueous periodic acid
system is shown below between the Logitech polisher (2 psig) with
3" wafers (10,000 .ANG. sputtered W) and the Strasbaugh 6EC
polisher (5-7 psig) with 200 mm wafers (10,000 .ANG. sputtered W).
Operating conditions were pH 6-7, 2.5% alumina (25 parts of 10%
alumina+90% water slurry), no APS, chemistry/slurry addition rate
of 200 mL/min for the Strasbaugh 6EC (40-50 rpm, 22" perforated
IC1000 over SUBA IV pads) and 100 mL/min for the Logitech PM5 (33
rpm, 12" ICI000 pad). The comparison suggests that the removal
rates determined used the larger Strasbaugh polisher are 6 to 8.6
times larger than those obtained using the smaller Logitech
polisher.
9 Table Removal Period Downforce Speed Rate Acid (pph) pH (psig)
(rpm) Polisher (.ANG./min) 2.0 6.8 2 33 Logitech PM5 426 2.0 6 5 40
Strasbaugh 6EC 2535 2.0 6 5 40 Strasbaugh 6EC 2727 2.0 6 5 50
Strasbaugh 3174 2.0 6 7 50 Strasbaugh 6EC 3666
[0238] Conclusion: these results for W polishing show that when
comparing removal rates determined using the Logitech planarizer to
larger planarizers such as the Strasbaugh 6EC, the removal rates
must be scaled up by a factor of 6 to 8.6.
[0239] Expanding on the last two aspects of the invention, a
comparison of polishing rates for the periodate salts potassium
periodate (KIO.sub.4) and the lithium periodate (LiH.sub.4IO.sub.6)
was accomplished, as well as for potassium iodate (KIO.sub.3) that
was used in Wang et al., published PCT application WO 97/13889,
dated 17 Apr. 1997. The KIO.sub.4 system proved to have higher
removal rates for W than did the KIO.sub.3 system; W removal rates
are enhanced when synergistically combining KIO.sub.4 and APS; and
both K and Li periodate may be used to oxidize W in near-neutral pH
regimes, thus getting away from corrosion problems associated with
very low pH CMP systems. In mixtures of K and Li periodates with
APS, systems with higher proportions of Li:K provide higher W
removal rates.
Example 14
[0240] Addition of APS to KIO.sub.3 in water increases the W
removal rate, and increasing amounts of KIO.sub.3 added to APS also
increase W removal rates over a pH range of 5.8 to 7.8 (pH adjusted
with 0-3 parts NaOH) using the Logitech PM5 polisher (33 rpm, 12"
IC1000 pad, 2 psig), 3" wafers (10,000 .ANG. sputtered W), 5%
alumina (50 parts of 10% alumina+90% water slurry), and separate
addition of chemistry and slurry with a chemistry addition rate of
90 mL/min, and slurry addition rate of 20 mL/min:
10 APS (pph) KIO.sub.3 (pph) pH Removal Rate (.ANG./min) 0 2.0 7.0
193 10 2.0 7.2 246 10 2.0 5.8 208 10 2.0 7.2 339 10 2.0 7.8 350
[0241] Conclusion: adding APS to KIO.sub.3 increases the W removal
rate, increasing pH of the combined APS/KIO.sub.3/water system
increases the W removal rate, and increasing the concentration of
KIO.sub.3 in the combined system increases the W removal rate.
Example 15
[0242] The aqueous potassium periodate (KIO.sub.4) system, with the
same polishing parameters as above, also shows a synergistic effect
when combined with APS and shows even a greater removal rate for W
than the potassium iodate system. NaOH (0-3 parts) was used to
adjust pH. Operating conditions included using the Logitech PM5
polisher (33 rpm, 12" IC 1000 pad, 2 psig), 3" wafers (10,000 A
sputtered W), 5% alumina (50 parts of 10% alumina+90% water
slurry), chemistry addition rate of 90 mL/min, and slurry addition
rate of 20 mL/min:
11 Removal Rate APS (pph) KIO.sub.4 (pph) pH (.ANG./min) 0 0.2 7.9
142 10 0.2 7.7 405 10 2.0 6.9 637 (supersaturated solution)
Example 16
[0243] Mixtures of Li and K periodate show improved removal rates
for higher proportions of Li:K. There is also an effect of pH noted
in the table below: increased removal rate with increasing pH.
Polishing parameters are for the Logitech PM5 polisher (33 rpm, 12"
IC1000 pad, 2 psig), 3" wafers (10,000 .ANG. sputtered W), 1%
alumina (10 parts of 10% alumina+90% water slurry), and
chemistry/slurry addition rate of 100 mL/min:
12 LiH.sub.4IO.sub.6 Removal APS (pph) (pph) KIO.sub.4 (pph) pH
Rate (.ANG./min) 10 0.4 0.0 7.2 382 10 0.3 0.1 7.2 215 10 0.2 0.2
6.5 175 10 0.1 0.3 6.1 170
[0244] Conclusion: addition of Li and/or K periodate to an aqueous
APS system enhances W removal at near-neutral pH. In mixed Li/K
periodate+APS systems, higher proportions of Li:K provide higher W
removal rates at near-neutral pH.
Example 17
[0245] Tungsten removal rates using the 10 parts APS+0.4 parts Li
periodate are stable for a period of several days when combined
with alumina slurry. The pH was not adjusted, but stayed
near-neutral, between pH 6.4 and 7.6, during the course of the
test. Polishing was done used the Logitech PM5 polisher (33 rpm,
12" IC1000 pad, 2 psig), 3" wafers (10,000 .ANG. sputtered W), 5%
alumina (50 parts of 10% alumina+90% water slurry), and
chemistry/slurry addition rate of 100 mL/min:
13 Time (days) Removal Rate (.ANG./min) 15 218 7 244 15 218
[0246] Conclusion: even when combined with alumina slurry, the
APS/LiH.sub.4IO.sub.6 water system has high and stable removal
rates for more than 2 weeks, providing a better shelf life than the
acidic ferric nitrate/water alumina system which must be combined
at point-of-use.
EXAMPLE 18
[0247] A quantity of 500 ml of two comparative chemical solutions
was each placed in a 600 ml beaker equipped with a magnetic
stirring rod. The first ammonium persulfate solution consisted of
114 parts of ammonium persulfate in deionized water to give total
of 1000 parts of solution having a pH of 3.1. The second ferric
(III) nitrate solution consisted of 40 parts of ferric (III)
nitrate nanohydrate dissolved in deionized water to give a total of
1000 parts of solution having a pH of 1.5. These solutions were
tested with silicon wafers at room temperature as follows:
[0248] Three inch wafers with a 300 .ANG. Ti metal adhesion layer
and 3000 .ANG. sputtered Cu were used. At selected time intervals,
the wafer sample was removed, rinsed with DI water and then dried
with nitrogen gas. A conventional four point probe was used to
determine the metal film thickness. The etch rates were:
14 Ammonium persulfate 3000 .ANG./min Ferric (III) nitrate 1287
.ANG./min
[0249] One would have expected the chemistry with the lowest pH
(more acidic), i.e., the ferric (III) nitrate solution, to etch the
Cu the fastest.
Example 19
[0250] In this series of tests, the effectiveness of hydroxylamine
nitrate at various pH levels was tested for etch wafers with 3000
.ANG. sputtered Cu and a 300 .ANG. Ti adhesion layer. The apparatus
was as used in Example 1. The solution was composed of 24 parts by
weight of 82 weight percent hydroxylamine nitrate in 176 parts by
weight of DI water. The pH was adjusted with small quantities of
hydroxylamine, as the free base. The hydroxylamine free base was
composed of 20 parts by weight of its commercially available
approximately 50 percent by weight aqueous solution and 80 parts by
weight deionized water. Also used was an ammonium hydroxide
solution composed of 80 parts by weight of a 25 percent by weight
aqueous ammonium hydroxide solution and 120 parts by weight of
deionized water.
[0251] After a certain interval, the wafer was rinsed with
deionized water and dried with nitrogen. The wafer was then
weighed. A separate blank Ti wafer was etched in a 10 percent by
weight H.sub.2O.sub.2 solution to determine the amount of Cu on
each 3 inch wafer. The results obtained are shown in the table
below.
15 Chemistry pH Etch rate (.ANG./min) Hydroxylamine nitrate 3 120
Hydroxylamine nitrate 4 150 Hydroxylamine nitrate 5 600
Hydroxylamine (free base) 11.7 75 Ammonium hydroxide 12.7 100
[0252] It is well known that Cu metal will be etched with inorganic
and organic amines at pHs above 9. It is also known that Cu metal
will be etched at very low pHs (below 3). The above results are
quite surprising, since a significant etch rate was seen at ph
5.
[0253] In a further aspect of the invention, other chemistries that
have given good CMP process results are based on hydroxylamine
nitrate (HAN) and other hydroxylamine salts. Besides several
examples with HAN, one example examines the use of citric acid in
combination with HAN. Other combinations could include mono-, di-
and tri-organic acids. Examples of such acids include, but are not
limited to acetic acid, malonic acid and citric acid,
respectively.
Example 20
[0254] Amines (and ammonia compounds) are more effective in neutral
or basic solutions for polishing (etching) copper. Some ammonium
compounds have only moderate success at polishing copper at low
pHs. Hydrogen peroxide chemistries are usually used at low pHs. The
following example shows that hydroxylamine nitrate (HAN, a mild
oxidizing agent) will effectively polish copper. Hydroxylamine and
its salts are not amines but do contain the NH2-group found in
inorganic and organic amines. Hydroxylamine's NH.sub.2 group is
attached to a hydroxyl (HO-group) which is not found in "amines"
and does influence its oxidation-reduction potential.
[0255] These results were obtained by immersing a copper wafer
(10,000 .ANG.) in stirred 10% hydroxylamine nitrate solutions (12.2
parts of 82% HAN in 87.8 parts water) for various time periods. At
certain time periods the wafers were removed, rinsed with DI water,
dried with nitrogen and then weighed to the nearest 0.1 mg. Another
wafer from the same group was etched with an ammonium
peroxydisulfate solution (10 parts peroxydisulfate and 90 parts
water) until there was no further weight loss. It was possible to
use weight ratios to determine the metal loss in .ANG./min. The
hydroxylamine nitrate results were compared to a 10% ammonium
hydroxide solution (10 parts 27% ammonium hydroxide in 90 parts
water) under similar conditions.
16 pH Removal Rate (.ANG./min) HAN 3.1 120 HAN 4.0 150 HAN 5.0 600
NH.sub.4OH 12.7 100
[0256] This example shows that hydroxylamine compound will remove
copper metal and that there is a definite optimum pH. The ammonium
hydroxide had the poorest etch rate even though this is an optimum
pH region for etching copper with amines.
Example 21
[0257] In this example the hydroxylamine nitrate chemistry is used
in a slurriless polishing system. A Logitech PM5 polishing system
(used for CMIP modeling experiments) was used with a Politex felt
pad at 33 rpm with 2 psig pressure on the 3" copper wafer. The 5%
chemistry (6.1 parts HAN with 95.9 parts water) was added to the
polishing table at 50 mL/min. The removal rate was determined by a
Four Dimensions four point probe used for determining metal film
thickness on wafers.
17 pH Removal Rate (.ANG./min) 4.2 18 6.0 218
[0258] This example shows that there is a pH effect with the HAN
solutions. The metal film had a very bright finish.
Example 22
[0259] In this example a 10% hydroxylamine nitrate solution (12.2
parts of HAN in 87.8 parts water) mixed with a 2.5% silicon oxide
slurry was used with a Politex pad on the Logitech PM5 polisher was
33 rpm with 2 psig pressure on the 3" copper wafer. The chemistry
was added to the polishing pad at 90 mL/min. The removal rate was
determined by a Four Dimensions four point probe for determining
metal film thickness on wafers.
18 pH Removal Rate (.ANG./min) 2.6 1270 4.0 1014
[0260] This example shows that the use of a silicon oxide slurry
will shift the effective polishing rate to very low pHs with very
good copper removal rates. This example also shows that the HAN
chemistry works well with slurries with the Logitech modeling
equipment. The metal film had a very bright finish.
Example 23
[0261] In this example a commercial alumina slurry is used with
various chemistries. The slurry concentration was 2.5% used with a
Politex pad on the Logitech PM5 polisher at 33 rpm with 2 psig
pressure on the 3" copper water. The hydrogen peroxide solution was
composed of 15 parts of a 30% H.sub.20.sub.2 solution mixed with 85
parts of water.
19 pH Removal Rate (.ANG./min) 5% HAN 5 950+ 5% HAN 5 950+ 5% HAN 6
575+ 15% H.sub.2O.sub.2 4 65 H.sub.2O 4.8 44
[0262] This example shows that the polishing rate for HAN is
reproducible and is polishing better than the traditional hydrogen
peroxide chemistry for copper CMP. The water experiment shows that
the copper polishing rate is not solely a pH effect. The metal
films polished with HAN had very bright finishes, but the hydrogen
peroxide polished wafer was "cloudy" and the water polished wafer
was dull.
Example 24
[0263] Another important feature is a good shelf life after the
slurry and chemistry are mixed together. Currently the hydrogen
peroxide/slurry systems are so unstable that the industry currently
mixes the slurry and the chemistry only at the point of use.
Premixed hydrogen peroxide/slurry solutions only have several hours
of useful life.
[0264] In this example a 0.5 wt % hydroxylamine nitrate solution
(0.6 parts of HAN in 99.4 parts water) mixed with a 2.5% alumina
slurry. A master batch was made and stored in a plastic container.
Samples of the chemistry/slurry were then removed after certain
number of days and used in the polishing experiment. The pH of the
slurry varied only between 4 and 4.1 during the 22 day trial. The
slurry mixture was used with a Politex pad on the Logitech PM5
polisher at 33 rpm with 2 psig pressure on the 3" copper wafer. The
chemistry was added to the polishing pad at 50 mL/min. The removal
rate was determined by a Four Dimensions four point probe for
determining metal film thickness on wafers.
20 Day Removal Rate (.ANG./min) 0 637 4 1064 22 558
[0265] Except for the fourth day result which increased by
.about.40%, the 22nd day result clearly shows that the chemistry is
still giving good polishing rates. The metal films had very bright
finishes.
EXAMPLE 25
[0266] Another feature is the selectivity of the polishing rate
between different materials on the wafer. It is important that all
materials (metals and the surrounding IDL layers) are not polished
at the same rate, otherwise it would be difficult to stop at a
specific layer.
[0267] The following example shows the selectivity between the
copper metal and a BPSG film. In this example a 0.5 wt %
hydroxylamine nitrate solution (0.6 parts of HAN in 99.4 parts
water) is mixed with a 2.5% alumina slurry. The pH of the slurry
varied between 4 and 4.4. The slurry mixture was used with a
Politex pad on the Logitech PM5 polisher at 33 rpm with 2 psig
pressure on the 3" copper wafer. The chemistry was added to the
four point probe for determining metal film thickness on wafers,
and the BPSG film thickness was determined by ellipsometer.
[0268] The copper film removal rate was 637 .ANG./min while the
BPSG film was only polished at a 37 .ANG./min rate. The selectivity
of Cu to BPSG was 17.2. This means that the polishing process will
"stop" when the BPSG layer is reached, since it has a much slower
polishing rate.
[0269] In a further aspect of the invention, another way to polish
copper is to use a combination of chelating agents (polyfunctional
organic acids) with the conjugate hydroxylamine salts.
Example 26
[0270] In this example a solution of citric acid (8.8 parts citric
acid adjusted with hydroxylamine to a pH 4.2 to 4.4, the remainder
is water) is mixed with various concentration of hydroxylamine
(HDA) to obtain solutions with pHs close to neutral. These
chemistries were used in a slurry polishing system. A Logitech PM 5
polishing system was used with a Politex felt pad at 33 rpm with 2
psig pressure on the 3" copper wafer. The chemistries were added to
the polishing table between 20 to 90 mL/min. The removal rate was
determined by a Four Dimensions four point probe for determining
metal film thickness on wafers.
21 Parts Citric Parts Removal Rate Acid Sol. HDA pH (.ANG./min) 100
0 4.2 58 95 5 6.6 64 90 10 954 80 20 7.0 1100
[0271] This example shows that even though the pH is only varied
over a 0.4 pH range (for the HDA salt solutions) there was a
significant increase in the copper etch rate, related to the
increase in the hydroxylamine salt of the citric acid.
Examples 27-41
[0272] In these Examples, compositions were made containing:
hydroxylamine and/or hydroxylamine salts; benzotriazole; optionally
added acid, such as sulfuric or nitric, to control pH; and DI
water, as shown in the Table below. In that Table, 82% HAN is 82 wt
% hydroxylamine nitrate (NH.sub.2OH*HNO.sub.3) in water; 50%
HDA.RTM. is 50 wt % hydroxylamine (NH.sub.2OH) in water; BTZ
solution is 0.2 wt % benzotriazole in water; 25% TMAH is 25wt %
tetramethylammonium hydroxide in water; and 15% IPHA is 15 wt %
isopropylhydroxylamine in water. Comparative Example #1, as shown
in the Table below, is commercially available from EKC
Technologies, Inc., of Maynard, Calif.
22 wt % wt % BTZ wt % acid Water Example hydroxylamine solution
(added) (added) pH Comparative #1 1.23 (82% HAN) 8 0.006 (nitric)
90.8 2.3-2.7 #27 2 (82% HAN) 8 0.006 (nitric) 90 2.8-3.5 #28 2 (82%
HAN) 13 0.006 (nitric) 85 2.8-3.5 #29 3 (82% HAN) 8 0.006 (nitric)
89 2.8-3.5 #30 3 (82% HAN) 12 0.006 (nitric) 85 2.8-3.5 #31 3 (82%
HAN) 19.5 0.006 (nitric) 77.5 2.8-3.5 #32 5 (82% HAN) 8 0.006
(nitric) 87 2.8-3.5 #33 5 (82% HAN) 12 0.006 (nitric) 83 2.8-3.5
#34 5 (82% HAN) 20 0.006 (nitric) 75 2.8-3.5 #35 5 (82% HAN) 32.5
0.006 (nitric) 62.4 2.8-3.5 #36 2 (82% HAN) 8 <0.006 (sulfuric)
.about.88 .about.4 2 (50% HDA) #37 2 (82% HAN) 8 1.8 (sulfuric)
86.3 .about.2.5 2 (50% HDA) #38 1.23 (82% HAN) 10 none 88.6 5.2-5.7
0.2 (50% HDA) #39 1.23 (82% HAN) 10 none 88.4 5.3-5.4 0.4 (50% HDA)
#40 1.23 (82% HAN) 10 none 88.6 .about.5.5 0.2 (25% TMAH) #41 1.23
(82% HAN) 10 none 88.6 .about.5.5 0.2 (15% IPHA)
[0273] For Example #39, when using a 1 psi downforce, the
composition exhibited an etch rate for TaN of about 200-400
.ANG./min. However, when the composition of Example 49 was used
with a fixed pad, commercially available from 3M of St. Paul, Minn.
(and with the following process conditions: .about.2 psi downforce;
.about.70 RPM TS; .about.75 RPM CS; .about.175 mL/min flow rate;
.about.4-15 second wash, e.g., for cleaning; and a temperature of
about 70.degree. F.), it etched the layers of a Cu/TaN/Metal oxide
substrate as follows:
[0274] Cu: 118 .ANG./min
[0275] TaN: 580 .ANG./min
[0276] MO: .about.0 .ANG./min
[0277] The average TaN etch rates for the compositions of Examples
38 and 40-41 on substrates similar to the one used above are
delineated as follows:
23 Example pH Avg TaN etch rate (1 psi) pH Adjusted by using #38
.about.5.5 714 .ANG./min HDA50 #40 .about.5.5 740 .ANG./min TMAH
#41 .about.5.5 770 .ANG./min IPHA
[0278] It was noted that use of Example 41 (containing IPHA)
resulted in heavy scratches at first but a comparable end product
to the other compositions. It was also noted that the composition
of Example 40 (containing TMAH) exhibited better performance than
the composition of Example 38 (containing HDA50).
[0279] The invention now being fully described, it will be apparent
to one of ordinary skill in the art that many changes and
modifications can be made thereto without departing from the spirit
or scope of the invention.
* * * * *