U.S. patent application number 11/737502 was filed with the patent office on 2007-08-16 for polishing medium for chemical-mechanical polishing, and polishing method.
Invention is credited to Tetsuya Hoshino, Akiko Igarashi, Yasuo Kamigata, Yasushi Kurata, Hiroki Terasaki, TAKESHI UCHIDA.
Application Number | 20070190906 11/737502 |
Document ID | / |
Family ID | 27530024 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070190906 |
Kind Code |
A1 |
UCHIDA; TAKESHI ; et
al. |
August 16, 2007 |
POLISHING MEDIUM FOR CHEMICAL-MECHANICAL POLISHING, AND POLISHING
METHOD
Abstract
This invention provides a polishing medium for CMP, comprising
an oxidizing agent, a metal-oxide-dissolving agent, a
protective-film-forming agent, a water-soluble polymer, and water,
and a polishing method making use of this polishing medium. Also,
it is preferable that the water-soluble polymer has a
weight-average molecular weight of 500 or more and the polishing
medium has a coefficient of kinetic friction of 0.25 or more, a
Ubbelode's viscosity of from 0.95 mPas (0.95 cP) to 1.5 mPas (1.5
cP) and a point-of-inflection pressure of 5 kPa (50
gf/cm.sup.2).
Inventors: |
UCHIDA; TAKESHI; (Ibaraki,
JP) ; Kamigata; Yasuo; (Ibaraki, JP) ;
Terasaki; Hiroki; (Ibaraki, JP) ; Kurata;
Yasushi; (Ibaraki, JP) ; Hoshino; Tetsuya;
(Ibaraki, JP) ; Igarashi; Akiko; (Ibaraki,
JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
27530024 |
Appl. No.: |
11/737502 |
Filed: |
April 19, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10069404 |
May 6, 2002 |
7232529 |
|
|
PCT/JP00/05765 |
Aug 25, 2000 |
|
|
|
11737502 |
Apr 19, 2007 |
|
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Current U.S.
Class: |
451/36 ;
257/E21.304; 451/40; 451/60 |
Current CPC
Class: |
C09G 1/02 20130101; C11D
11/0047 20130101; B24B 37/24 20130101; C09G 1/04 20130101; H01L
21/3212 20130101 |
Class at
Publication: |
451/036 ;
451/040; 451/060 |
International
Class: |
B24B 1/00 20060101
B24B001/00; B24C 1/00 20060101 B24C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 1999 |
JP |
HEI11-239777 |
Aug 26, 1999 |
JP |
HEI11-239778 |
Aug 26, 1999 |
JP |
HEI11-239779 |
Aug 26, 1999 |
JP |
HEI11-239780 |
Aug 26, 1999 |
JP |
HEI11-239781 |
Claims
1. A polishing medium for chemical-mechanical polishing, comprising
an oxidizing agent, a protective-film-forming agent, a
water-soluble polymer excluding poly(oxyethylene)lauryl ether,
polyvinyl alcohol, gelatin and carboxymethylcellulose, and
water.
2. The polishing medium for chemical-mechanical polishing according
to claim 1, further comprising a metal-oxide-dissolving agent.
3. The polishing medium for chemical-mechanical polishing according
to claim 1, which has a coefficient of kinetic friction of 0.25 or
more.
4. The polishing medium for chemical-mechanical polishing according
to claim 1, which has a Ubbelode's viscosity of 0.95 mPas (0.95 cP)
or more and 1.5 mPas (1.5 cP) or less.
5. The polishing medium for chemical-mechanical polishing according
to claim 1, which has a point-of-inflection pressure of 5 kPa (50
gf/cm.sup.2) or more.
6. The polishing medium for chemical-mechanical polishing according
to claim 1, wherein said oxidizing agent is at least one of
hydrogen peroxide, nitric acid, potassium periodate, hypochlorous
acid and ozone water.
7. The polishing medium for chemical-mechanical polishing according
to claim 2, wherein said metal-oxide-dissolving agent is at least
one of an organic acid, an organic-acid ester, an organic-acid
ammonium salt and sulfuric acid.
8. The polishing medium for chemical-mechanical polishing according
to claim 1, wherein said protective-film-forming agent is a
nitrogen-containing compound.
9. The polishing medium for chemical-mechanical polishing according
to claim 1, wherein said protective-film-forming agent is at least
one of a mercaptan, glucose and cellulose.
10. A polishing method comprising polishing a polishing object film
of a metal or metal oxide with the polishing medium for
chemical-mechanical polishing according to claim 1.
11. The polishing method according to claim 10, wherein said
polishing object film comprises at least one of copper, a copper
alloy, a copper oxide and a copper alloy oxide.
12. The polishing medium for chemical-mechanical polishing
according to claim 1, which has a coefficient of kinetic friction
of 0.25 or more.
13. The polishing medium for chemical-mechanical polishing
according to claim 12, which has a Ubbelode's viscosity of 0.95
mPas (0.95 cP) or more and 1.5 mPas (1.5 cP) or less.
14. The polishing medium for chemical-mechanical polishing
according to claim 13, which has a point-of-inflection pressure of
5 kPa (50 gf/cm.sup.2) or more.
15. The polishing medium for chemical-mechanical polishing
according to claim 1, which has a Ubbelode's viscosity of 0.95 mPas
(0.95 cP) or more and 1.5 mPas (1.5 cP) or less.
16. The polishing medium for chemical-mechanical polishing
according to claim 1, which has a point-of-inflection pressure of 5
kPa (50 gf/cm.sup.2) or more.
17. The polishing medium for chemical-mechanical polishing
according to claim 8, wherein said water-soluble polymer is
selected from the group consisting of polysaccharides excluding
carboxymethylcellulose, polycarboxylic acids and esters and salts
thereof, and vinyl polymers excluding polyvinyl alcohol.
18. The polishing medium for chemical-mechanical polishing
according to claim 9, wherein said water-soluble polymer is
selected from the group consisting of pectic acid, agar, polymalic
acid, polymethacrylic acid, polyacrylic acid, polyacrylamide, and
polyvinyl pyrrolidone, and esters and ammonium salts thereof.
19. The polishing medium for chemical-mechanical polishing
according to claim 3, which has a coefficient of kinetic friction
of 0.35 or more.
20. The polishing medium for chemical-mechanical polishing
according to claim 19, which has a coefficient of kinetic friction
of 0.45 or more.
21. The polishing medium for chemical-mechanical polishing
according to claim 4, which has a Ubbelode's viscosity in the range
of 0.96 to 1.3 mPas.
22. The polishing medium for chemical-mechanical polishing
according to claim 21, which has a Ubbelode's viscosity in the
range of 0.97 to 1.0 mPas.
23. The polishing medium for chemical-mechanical polishing
according to claim 5, which has a point-of-inflection pressure of
10 kPa (100 gf/cm.sup.2) or more.
24. The polishing medium for chemical-mechanical polishing
according to claim 5, wherein said water-soluble polymer is
selected from the group consisting of polysaccharides excluding
carboxymethylcellulose, polycarboxylic acids and esters and salts
thereof, and vinyl polymers excluding polyvinyl alcohol.
25. The polishing medium for chemical-mechanical polishing
according to claim 5, wherein said water-soluble polymer is
selected from the group consisting of pectic acid, agar, polymalic
acid, polymethacrylic acid, polyacrylic acid, polyacrylamide, and
polyvinyl pyrrolidone, and esters and ammonium salts thereof.
26. The polishing medium for chemical-mechanical polishing
according to claim 8, wherein said nitrogen-containing compound is
selected from the group consisting of ammonia, alkylamines, amino
acids, imines, azoles, and salts thereof.
27. The polishing medium for chemical-mechanical polishing
according to claim 17, wherein said nitrogen-containing compound is
selected from the group consisting of ammonia, alkylamines, amino
acids, imines, azoles, and salts thereof.
28. The polishing medium for chemical-mechanical polishing
according to claim 2, wherein said protective-film-forming agent is
at least one selected from the group consisting of chitosan,
ethylenediaminetetraacetic acid, L-tryptophane, cuperazone,
triazinedithiol, benzotriazole, 4-hydroxybenzotriazole,
4-carboxyl-1H-benzotriazole butyl ester, tolyltriazole and
naphthotriazole.
29. A polishing medium for chemical-mechanical polishing,
comprising an oxidizing agent, a protective-film-forming agent, a
water-soluble polymer and water, wherein the water-soluble polymer
is at least one selected from the group consisting of
polycarboxylic acids, polycarboxylic esters, and salts thereof.
Description
[0001] This application is a Divisional application of application
Ser. No. 10/069,404, filed May 6, 2002, the contents of which are
incorporated herein by reference in their entirety. Ser. No.
10/069,404 is a National Stage application, filed under 35 USC 371,
of International (PCT) Application No. PCT/JP00/05765, filed Aug.
25, 2000.
TECHNICAL FIELD
[0002] This invention relates to a polishing medium for
chemical-mechanical polishing, especially suited for polishing in
the step of forming wirings of semiconductor devices, and a
polishing method making use of the same.
BACKGROUND ART
[0003] In recent years, as semiconductor integrated circuits
(hereinafter "LSI") are made high-integration and high-performance,
new techniques for fine processing have been developed.
Chemical-mechanical polishing (hereinafter "CMP") is also one of
them. The CMP is often used in LSI fabrication steps, in
particular, in making interlaminar insulating films flat in the
step of forming multilayer wirings, in forming metallic plugs and
in forming buried wirings. This technique is disclosed in, e.g.,
U.S. Pat. No. 4,944,836.
[0004] Recently, in order to make LSIs high-performance, it is also
attempted to utilize copper alloys as wiring materials. It,
however, is difficult for the copper alloys to be finely processed
by dry etching often used in forming conventional aluminum alloy
wirings. Accordingly, what is called the damascene method is
chiefly employed, in which a copper alloy thin film is deposited on
an insulating film with grooves formed previously and is buried
therein, and the copper alloy thin film at the part except the
grooves is removed by CMP to form buried wirings. This technique is
disclosed in, e.g., Japanese Patent Application Laid-open No.
2-278822.
[0005] In a common method of polishing metals by the CMP, a
polishing pad is fastened onto a circular polishing roller
(platen), and the surface of the polishing pad is soaked with a
polishing medium for chemical-mechanical polishing, where a
substrate with a metal film formed thereon is pressed against the
pad on the former's metal film side and a stated pressure
(hereinafter "polishing pressure") is applied thereto on the back
thereof, in the state of which the polishing platen is turned to
remove the metal film at the part of its hills by mechanical
friction acting between the polishing medium and the metal
film.
[0006] The polishing medium used in such CMP is commonly comprised
of an oxidizing agent and solid abrasive grains, to which a
metal-oxide-dissolving agent and/or a protective-film-forming agent
are optionally added. The basic mechanism of CMP making use of this
polishing medium for CMP is considered to be that the metal film
surface is oxidized with the oxidizing agent and the resultant
oxide layer is scraped with the solid abrasive grains. The metal
surface oxide layer at the part of dales does not come into contact
with the polishing pad so much and the effect of scraping
attributable to the solid abrasive grains does not extend thereto.
Hence, with progress of the CMP, the metal layer becomes removed at
its hills and the substrate (with film) surface become flat.
Details on this matter are disclosed in Journal of Electrochemical
Society, Vol. 138, No. 11 (published 1991), pages 3460-3464.
[0007] In order to make higher the rate of polishing by CMP, it is
considered effective to add the metal-oxide-dissolving agent. It
can be explained that this is because the effect of scraping
attributable to the solid abrasive grains comes higher where grains
of metal oxide scraped off by the solid abrasive grains are made to
dissolve in the polishing medium. However, the addition of the
metal-oxide-dissolving agent makes the metal film surface oxide
layer dissolve (hereinafter "etching") also at the part of dales,
and the metal film surface becomes uncovered, so that the metal
film surface is further oxidized by the oxidizing agent. With
repetition of this, the etching of the metal film may proceed at
the part of dales, resulting in a damage of the effect of
flattening.
[0008] In order to prevent this, the protective-film-forming agent
is further added to the metal-polishing medium for CMP. Thus,
adding the metal-oxide-dissolving agent and protective-film-forming
agent adds the effect of chemical reaction, and this brings about
the effect that the CMP rate (the rate of polishing by CMP) is
improved and also any injury (damage) of the metal layer surface to
be polished by CMP may less occur.
[0009] In order to obtain a flat polished surface, it is important
to balance the effect attributable to the metal-oxide-dissolving
agent and protective-film-forming agent used in the polishing
medium for CMP. In the CMP, it is preferable to use a polishing
medium which does not etch the metal film surface oxide layer so
much at the part of dales, dissolves in a good efficiency the
particles of the oxide layer scraped off, and has a high rate of
polishing.
[0010] However, the formation of buried wirings by CMP using a
conventional polishing medium for chemical-mechanical polishing
which contain solid abrasive grains involves the problems such
that; [0011] (1) it may cause a phenomenon that the surface of the
metal wiring having been buried is isotropically corroded at the
middle thereof to become hollow like a dish (hereinafter
"dishing"); [0012] (2) it may cause polishing mars (scratches)
arising from solid abrasive grains; [0013] (3) the wash processing
to remove solid abrasive grains remaining on the substrate surface
after polishing is troublesome; and [0014] (4) a cost increase may
arise because of the prime cost of solid abrasive grains themselves
and the disposal of waste liquor.
[0015] Accordingly, in order to keep the dishing from occurring or
the copper alloy from corroding during the polishing, to form
highly reliable LSI wirings, a polishing method making use of a
polishing medium for CMP which contains a metal-oxide-dissolving
agent comprised of amino acetic acid (e.g., glycine) or
amidosulfuric acid and contains BTA (benzotriazole) is proposed.
This technique is disclosed in, e.g., Japanese Patent Application
Laid-open No. 8-83780.
[0016] However, the BTA has a very high protective-film-forming
effect, and hence it may greatly lower not only the rate of etching
but also the rate of polishing. Accordingly, it is sought to
provide a polishing medium for CMP which lowers the etching rate
sufficiently but does not lower the CMP rate.
DISCLOSURE OF THE INVENTION
[0017] An object of the present invention is to provide a polishing
medium for CMP and a polishing method which can form highly
reliable buried metal film patterns in a good efficiency by making
the etching rate sufficiently low while keeping a high CMP
rate.
[0018] As the protective-film-forming agent, a compound by which a
chelate complex is readily formed with copper is used, such as
ethylenediaminetetraacetic acid or benzotriazole. Such a compound
has a very strong effect of forming a protective film on the
surface to be polished. For example, if it is incorporated in the
polishing medium for CMP in an amount of 0.5% by weight or more,
the copper alloy film comes not subject to CMP, to say nothing of
etching.
[0019] In this regard, the present inventors have discovered that
the use of the protective-film-forming agent in combination with a
water-soluble polymer enables achievement of a high CMP rate while
keeping a sufficiently low etching rate. They have moreover
discovered that the use of such a polishing medium enables the
polishing to be carried out at a practical CMP rate even without
incorporating any solid abrasive grains in the polishing
medium.
[0020] This is considered due to the fact that the scraping by
friction with a polishing pad takes place in place of the effect of
scraping by the friction with solid abrasive grains in conventional
cases. According to the present invention, the water-soluble
polymer is added to a metal polishing medium containing an
oxidizing agent for the polishing object, a metal-oxide-dissolving
agent, a protective-film-forming agent and water, whereby the CMP
rate can be made higher while the etching rate is kept low.
[0021] As to the value of etching rate, it has been found that a
preferable flattening effect can be achieved as long as the etching
rate is controlled to 10 nm/minute or less. As long as the lowering
of CMP rate is within a tolerable range, it is desirable for the
etching rate to be much lower. As long as the etching rate is
controlled to 5 nm/minute or less, the dishing can be kept to a
degree not coming into question even when, e.g., the CMP is
performed in excess by about 50% (i.e., CMP is performed for a time
1.5 times that necessary for removing the polishing object). As
long as the etching rate can further be controlled to 1 nm/minute
or less, the dishing does not come into question even when the CMP
is performed in excess by about 100% or more.
[0022] Accordingly, the present invention provides a polishing
medium for CMP, comprising an oxidizing agent, a
metal-oxide-dissolving agent, a protective-film-forming agent, a
water-soluble polymer, and water, and a polishing method making use
of this polishing medium.
[0023] In order to achieve much higher CMP rate, higher flattening,
lower dishing level and lower erosion level, the polishing medium
for CMP may preferably satisfy at least one of the following (1) to
(4), and may particularly preferably satisfy all of them.
[0024] (1) That the water-soluble polymer has a weight-average
molecular weight of 500 or more.
[0025] This enables the CMP rate to be made higher while the
etching rate is kept low. The water-soluble polymer may preferably
have a weight-average molecular weight of 500 or more, more
preferably 1,500 or more, and particularly preferably 5,000 or
more. The upper limit of the weight-average molecular weight is not
particularly defined. From the viewpoint of solubility, it may
preferably be 5,000,000 or less.
[0026] As the water-soluble polymer, two or more polymers each
having a weight-average molecular weight of 500 or more but a
weight-average molecular weight different from each other may
preferably be used in combination, which may be water-soluble
polymers of the same type or may be water-soluble polymers of
different types.
[0027] Incidentally, the weight-average molecular weight is
determined by measurement on a GPC (gel permeation chromatography)
column through which an aqueous solution of the water-soluble
polymer is flowed.
[0028] (2) That the polishing medium has a coefficient of kinetic
friction of 0.25 or more.
[0029] Where the protective-film-forming agent is used in
combination with the water-soluble polymer and the polishing medium
has a coefficient of kinetic friction of 0.25 or more, the CMP rate
can be made much higher while the etching rate is kept low. When
compared setting a constant pressure at the time of polishing, a
higher CMP rate can be achieved as a higher coefficient of kinetic
friction the metal polishing medium used has.
[0030] From the results of an experiment made by the present
inventors, it is known that the coefficient of kinetic friction
between a metal film and a metal polishing cloth via the polishing
medium for CMP comes to less than 0.25 when the content of the
protective-film-forming agent in 100 g of the metal polishing
medium without containing the water-soluble polymer is in a range
of 0.0001 mol or more.
[0031] Here, the coefficient of kinetic friction is a coefficient
obtained where the force applied to a wafer carrier when the metal
film on the surface of a wafer is polished, i.e., kinetic
frictional force, is divided by polishing pressure. Stated
specifically, it is determined by calculation from measurements of
tensile stress or the like.
[0032] The polishing medium for CMP of the present invention may
more preferably have a coefficient of kinetic friction of 0.35 or
more, and particularly preferably 0.45 or more.
[0033] (3) That the polishing medium has a viscosity by Ubbelode
viscometer (hereinafter "Ubbelode's viscosity") of from 0.95 mPas
(0.95 cP) to 1.5 mPas (1.5 cP).
[0034] Where the polishing medium has a Ubbelode's viscosity of
from 0.95 mPas (0.95 cP) to 1.5 mPas (1.5 cP), the CMP rate can be
made much higher while the etching rate is kept low. When compared
setting a constant pressure at the time of polishing, a higher CMP
rate can be achieved as a higher Ubbelode's viscosity the metal
polishing medium used has.
[0035] The Ubbelode's viscosity is the value obtained where the
time in which the polishing medium for CMP, kept at a liquid
temperature of 25.degree. C. in a glass tube for measuring
Ubbelode's viscosity, moves over a specified distance is measured
and the resultant movement time is multiplied by a constant (JIS
K2283). The polishing medium may more preferably have a Ubbelode's
viscosity of from 0.96 to 1.3 mPas (0.96 to 1.3 cP), and
particularly preferably from 0.97 mPas (0.97 cP) to 1.0 mPas (1.0
cP). If its Ubbelode's viscosity is less than 0.95 mPas (0.95 cP),
a low CMP rate tends to result. If it is more than 1.5 mPas (1.5
cP), the CMP rate tends to show a poor wafer in-plane
uniformity.
[0036] (4) That the polishing medium has a point-of-inflection
pressure of 5 kPa (50 gf/cm.sup.2) or more.
[0037] Where the polishing medium has a point-of-inflection
pressure of 5 kPa (50 gf/cm.sup.2) or more, the effect of achieving
high flattening, low dishing level and low erosion level can more
effectively be brought out. Here, the point-of-inflection pressure
refers to the polishing pressure at which the CMP rate rises
abruptly. Stated specifically, it is the polishing pressure
(intermediate value) in a region where the CMP rate increases from
10 nm/minute or less to 50 nm/minute or more, and is determined by
measuring the rate of polishing (CMP rate) under various polishing
pressure.
[0038] The polishing medium may preferably have a
point-of-inflection pressure of 5 kPa (50 gf/cm.sup.2) or more, and
more preferably 10 kPa (100 gf/cm.sup.2) or more. If its
point-of-inflection pressure is less than 5 kPa (50 gf/cm.sup.2)
the effect of high flattening tends to be less brought out.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is an illustration showing the steps of polishing a
substrate member in Examples.
BEST MODES FOR PRACTICING THE INVENTION
[0040] A. Composition of Polishing Medium:
[0041] The polishing medium for CMP of the present invention
comprises an oxidizing agent, a metal-oxide-dissolving agent, a
protective-film-forming agent, a water-soluble polymer, and water.
The respective components are described below.
[0042] (1) Oxidizing Agent:
[0043] The oxidizing agent to be contained in the polishing medium
for CMP of the present invention is a compound having oxidizing
power on the polishing object. Stated specifically, it may include
hydrogen peroxide, nitric acid, potassium periodate, hypochlorous
acid and ozone water. Of these, hydrogen peroxide is particularly
preferred. Any one compound of these may be used alone, or two or
more compounds may be used in combination.
[0044] Where the substrate member is a silicon substrate member
including devices for integrated circuits, it is undesirable for it
to be contaminated with alkali metals, alkaline earth metals,
halides and so forth. Hence, it is preferable for the oxidizing
agent not to contain any involatile component. The ozone water may
undergo a great compositional change with time. Hence, the hydrogen
peroxide is most suited for the present invention. However, where
the substrate member to be polished is a glass substrate member not
including any semiconductor devices, an oxidizing agent containing
an involatile component may be used without any problem.
[0045] The oxidizing agent component may preferably be mixed in an
amount of from 0.003 mol to 0.7 mol, more preferably from 0.03 mol
to 0.5 mol, and particularly preferably from 0.2 mol to 0.3 mol,
based on the total weight 100 g of the oxidizing agent,
metal-oxide-dissolving agent, protective-film-forming agent,
water-soluble polymer and water. If it is mixed in an amount of
less than 0.003 mol, the metal may insufficiently be oxidized. If
it is more than 0.7 mol, the polishing surface tends to be
roughed.
[0046] (2) Metal-Oxide-Dissolving Agent:
[0047] As the metal-oxide-dissolving agent to be contained in the
polishing medium for CMP of the present invention, at least one of
an organic acid, an organic-acid ester, an organic-acid ammonium
salt and sulfuric acid is preferred.
[0048] The metal-oxide-dissolving agent may preferably be
water-soluble, and may also be mixed in the state of an aqueous
solution. As examples of metal-oxide-dissolving agents preferable
for the present invention they may include organic acids such as
formic acid, acetic acid, propionic acid, butyric acid, valeric
acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric
acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic
acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid,
benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic
acid, malonic acid, succinic acid, glutaric acid, adipic acid,
pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid
and citric acid; esters of these organic acids; salts (such as
ammonium salts) of these organic acids; sulfuric acid; nitric acid;
ammonia; ammonium salts (e.g., ammonium persulfate, ammonium
nitrate and ammonium chloride); and chromic acid. Any one compound
of these may be used alone, or two or more compounds may be used in
combination.
[0049] Of these, in view of easy balancing with the
protective-film-forming agent, formic acid, malonic acid, malic
acid, tartaric acid and citric acid are preferred. The polishing
medium for CMP which makes use of any of these is suited for
layered films having conductor (which may also be semiconductor)
layers formed of copper, a copper alloy, a copper oxide and/or a
copper alloy oxide (hereinafter these are generically termed
"copper alloy" in some cases). In particular, malic acid, tartaric
acid and citric acid are preferred in view of an advantage that the
etching rate can effectively be controlled while practical CMP
polishing rate is maintained.
[0050] The metal-oxide-dissolving agent component in the present
invention may preferably be mixed in an amount of from 0 mol to
0.005 mol, more preferably from 0.00005 mol to 0.0025 mol, and
particularly preferably from 0.0005 mol to 0.0015 mol, based on the
total weight 100 g of the oxidizing agent, metal-oxide-dissolving
agent, protective-film-forming agent, water-soluble polymer and
water. If it is mixed in an amount of more than 0.005 mol, the
etching tends to be controlled with difficulty.
[0051] (3) Protective-Film-Forming Agent:
[0052] The protective-film-forming agent is a compound which forms
a protective film on the surface of the polishing object, and
nitrogen-containing compounds (e.g., ammonia, alkylamines, amino
acids, imines, azoles, and salts of these) mercaptans, glucose and
cellulose are preferred.
[0053] As examples of protective-film-forming agents preferable for
the present invention, they may include ammonia; alkylamines such
as dimethylamine, trimethylamine, triethylamine, propylenediamine,
ethylenediaminetetraacetic acid (EDTA), sodium
diethyldithiocarbamate and chitosan; amino acids such as glycine,
L-alanine, .beta.-alanine, L-2-aminobuyric acid, L-norvaline,
L-valine, L-leucine, L-norleucine, L-isoleucine, L-alloisoleucine,
L-phenylalanine, L-proline, sarcocine, L-ornithine, L-lysine,
taurine, L-serine, L-threonine, L-allothreonine, L-homoserine,
L-tyrosine, 3,5-diiodo-L-tyrosine,
.beta.-(3,4-dihydroxyphenyl)-L-alanine, L-thyroxine,
4-hydroxy-L-proline, L-cystine, L-methionine, L-ethionine,
L-lanthionine, L-cystathionine, L-cysteine, L-cysteic acid,
L-aspartic acid, L-glutamic acid, S-(carboxymethyl)-L-cystine,
4-aminobutyric acid, L-asparagine, L-glutamine, azaserine,
L-alginine, L-canavanine, L-citrulline, .delta.-hydroxy-L-lysine,
creatine, L-kynurenine, L-histidine, 1-methyl-L-histidine,
3-methyl-L-histidine, ergothioneine, L-tryptophane, actinomycin C1,
apamine, anguiotensin I, anguiotensin II and antipains; imines such
as dithizone, cuproin (2,2'-biquinoline), neocuproin
(2,9-dimethyl-1,10-phenanthroline), basocuproin
(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and
cuperazone(biscyclohexanoneoxalylhydrazone); azoles such as
benzimidazole-2-thiol, triazinedithiol, triazinetrithiol,
2-[2-(benzothiazolyl)]thiopropionic acid,
2-[2-(benzothiazolyl)]thiobutyric acid, 2-mercaptobenzothiazole,
1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole,
benzotriazole, 1-hydroxybenzotriazole,
1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole,
4-hydroxybenzotriazole, 4-carboxyl-1H-benzotriazole,
4-carboxyl-1H-benzotriazole methyl ester,
4-carboxyl-1H-benzotriazole butyl ester,
4-carboxyl-1H-benzotriazole octyl ester, 5-hexylbenzotriazole,
[1,2,3-benzotriazolyl-1-methyl][1,2,4-triazolyl-1-methyl][2-ethylhexyl]am-
ine, tolyltriazole, naphthotriazole and
bis[(1-benzotriazolyl)methyl]phosphonic acid; mercaptans such as
nonylmercaptan and dodecylmercaptan; and saccharides such as
glucose and cellulose. Any one compound of these may be used alone,
or two or more compounds may be used in combination.
[0054] Of these, chitosan, ethylenediaminetetraacetic acid,
L-tryptophane, cuperazone, triazinedithiol, benzotriazole,
4-hydroxybenzotriazole, 4-carboxyl-1H-benzotriazole butyl ester,
tolyltriazole and naphthotriazole are preferred in order to achieve
both a high CMP rate and a low etching rate.
[0055] The protective-film-forming agent may be mixed in an amount
of from 0.0001 mol to 0.05 mol, more preferably from 0.0003 mol to
0.005 mol, and particularly preferably from 0.0005 mol to 0.0035
mol, based on the total weight 100 g of the oxidizing agent,
metal-oxide-dissolving agent, protective-film-forming agent,
water-soluble polymer and water. If it is mixed in an amount of
less than 0.0001 mol, the etching tends to be controlled low with
difficulty. If it is in an amount of more than 0.05 mol, a low CMP
rate tends to result.
[0056] (4) Water-Soluble Polymer:
[0057] As water-soluble polymers preferable for the present
invention, they may include polysaccharides such as alginic acid,
pectic acid, carboxymethyl cellulose, agar, curdlan and pullulan;
polycarboxylic acids such as polyaspertic acid, polyglutamic acid,
polylysine, polymalic acid, polymethacrylic acid, ammonium
polymethacrylate, sodium polymethacrylate, polymaleic acid,
polyitaconic acid, polyfumaric acid, poly(p-styrenecarboxylic
acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide,
methyl polyacrylate, ethyl polyacrylate, ammonium polyacrylate,
sodium polyacrylate, polyamic acid, polyamic acid ammonium salt and
polyamic acid sodium salt and polyglyoxylic acid, polycarboxylic
esters, and salts thereof; and vinyl polymers such as polyvinyl
alcohol, polyvinyl pyrrolidone and polyacrolein. Any one compound
of these may be used alone, or two or more compounds may be used in
combination.
[0058] Where, however, the substrate member to be polished is a
silicon substrate member for semiconductor integrated circuits,
acids or ammonium salts are preferred because it is undesirable for
it to be contaminated with alkali metals, alkaline earth metals,
halides and so forth. Where the substrate member is a glass
substrate member, this does not necessarily apply.
[0059] Of these compounds, pectic acid, agar, polymalic acid,
polymethacrylic acid, polyacrylic acid, polyacrylamide, polyvinyl
alcohol and polyvinyl pyrrolidone, esters of these and ammonium
salts of these are particularly preferred.
[0060] The water-soluble polymer may be mixed in an amount of from
0.001 to 0.3% by weight, more preferably from 0.003 to 0.1% by
weight, and particularly preferably from 0.01 to 0.08% by weight,
based on the total weight 100 g of the oxidizing agent,
metal-oxide-dissolving agent, protective-film-forming agent,
water-soluble polymer and water. If it is mixed in an amount of
less than 0.001% by weight, the effect attributable to its use in
combination with the protective-film-forming agent tends not to be
brought out in low etching control. If it is in an amount of more
than 0.3% by weight, a low CMP rate tends to result.
[0061] (5) Others:
[0062] The polishing medium for CMP of the present invention may
optionally appropriately contain additives. The solid abrasive
grains need not substantially be contained, or may be contained.
Also, in the case of the polishing medium for CMP of the present
invention which does not contain any abrasive grains, the CMP
proceeds by the action of the friction with a polishing pad which
is mechanically much softer than the solid abrasive grains, and
hence the polishing defects can be made to dramatically less
occur.
[0063] B. Characteristic Features of Polishing Medium:
[0064] Different from conventional polishing mediums making use of
only the protective-film-forming agent, the polishing medium of the
present invention can flatten polishing objects by CMP without
relying on any strong mechanical friction caused by solid abrasive
grains, but by the action of the friction with the polishing pad
which is much softer than them.
[0065] In the polishing medium for CMP of the present invention,
since the protective-film-forming agent is used in combination with
the water-soluble polymer, the etching is controlled but, in the
friction with the polishing pad, the protective-film-forming agent
does not function and the CMP proceeds, as so presumed.
[0066] In general, in CMP, the degree at which the polishing mars
occur depends on the particle diameter, particle size distribution
and shape of the solid abrasive grains. The decrease in layer
thickness (hereinafter "erosion") due to the scrape of insulating
film and the deterioration of flattening effect also depends on the
particle diameter of the solid abrasive grains and the physical
properties of the polishing pad.
[0067] When the surface of metal film, in particular, copper film
is treated with BTA, the dishing of the metal film is considered to
depend on the hardness of the polishing pad and the chemical
properties of the polishing medium. More specifically, hard solid
abrasive grains are necessary for the progress of CMP, but are
undesirable for the improvement of flattening effect in CMP and
perfectness (free of any damage such as polishing mars) of CMP
surface. From this fact, it is seen that in fact the flattening
effect depends on the properties of the polishing pad which is
softer than the solid abrasive grains.
[0068] This matter is described taking the case of BTA from among
protective-film-forming agents. It is considered that, upon
exposure of the copper alloy film surface to a liquid containing
BTA, a film of a polymer-like complex compound having a structure
of Cu(I)BTA or Cu(II)BTA as the chief skeleton is formed by the
reaction of copper or an oxide thereof with BTA. This film is
fairly strong. Hence, where a polishing medium for CMP which
contains 1% by weight of BTA is used, the film is usually little
polished away even when solid abrasive grains are contained in this
polishing medium. Also, where only the water-soluble polymer is
mixed in the polishing medium for CMP and any
protective-film-forming agent is not added, it is difficult
especially to control etching rate low, resulting in an
insufficient protective effect. It is conventionally known that a
protective film of a different type is thus formed depending on the
type of the protective-film-forming agent. However, the combination
of the protective-film-forming agent with the water-soluble polymer
as shown in the present invention enables achievement of both a
high CMP rate and a low etching rate and moreover makes unnecessary
any strong friction caused by solid abrasive grains.
[0069] Thus, the polishing medium for CMP of the present invention
is very favorable for the CMP of copper alloys and furthermore the
formation of buried patterns making use of the same.
[0070] C. Polishing Method:
[0071] The present invention provides a polishing method comprising
polishing a polishing object film of a metal or metal oxide by the
use of the above polishing medium for CMP of the present invention
to remove at least part of the polishing object film. The polishing
medium for CMP of the present invention can achieve high flattening
at a high speed, even when the polishing object film is a layered
film comprised of copper, a copper alloy, a copper oxide and/or a
copper alloy oxide.
[0072] The polishing method of the present invention can polish the
polishing object film by feeding the polishing medium for CMP of
the present invention to a polishing cloth on a polishing platen,
and simultaneously bringing a substrate having the polishing object
film thereon, into contact with the polishing cloth, in the state
of which the polishing platen and the substrate (with film) are
relatively moved.
[0073] In the present invention, a metal film comprised of copper
or a copper alloy (such as copper/chromium) is formed on a
substrate having dales at its surface, filling the dales with the
metal film. This substrate member is subjected to CMP using the
polishing medium according to the present invention, whereupon the
metal film at the part of hills of the substrate member is
selectively polished away by CMP and the metal film at the part of
dales is left therein, thus the desired conductor pattern is
obtained.
[0074] In the polishing method of the present invention, a commonly
available polishing apparatus may be used which has a holder for
holding the polishing object such as a semiconductor substrate
member and a platen to which a polishing cloth (pad) has been
fastened (fitted with, e.g., a motor whose number of revolutions is
variable). As the polishing cloth, commonly available nonwoven
fabric, foamed polyurethane, porous fluorine resin and so forth may
be used without any particular limitations.
[0075] There are no particular limitations on polishing conditions.
It is preferable to rotate the platen at a low revolution of 200
rpm or less so that the substrate does not rush out therefrom. The
semiconductor substrate member having the polishing object film may
preferably be pressed against the polishing cloth at a pressure of
from 10 to 100 kPa (100 to 1,000 gf/cm.sup.2), and more preferably
from 10 to 50 kPa (100 to 500 gf/cm.sup.2) in order to satisfy the
wafer in-plane uniformity of polishing rate and the flatness of
patterns.
[0076] In the course of the polishing, the polishing medium for CMP
is continuously fed to the polishing cloth by means of a pump or
the like. There are no particular limitations on this feed
quantity. It is preferable for the polishing-cloth surface to be
always covered with the polishing medium.
[0077] The semiconductor substrate member on which the polishing
has been completed may preferably be washed thoroughly in running
water and thereafter be set on a spin dryer or the like to blow off
any drops of water adhering onto the semiconductor substrate
member, followed by drying.
[0078] The polishing method of the present invention is suited for
the polishing of copper alloy wirings in semiconductor devices. For
example, as shown in FIG. 1, on the surface of a silicon wafer 10
[FIG. 1(a)], a silicon dioxide film 11 is formed [FIG. 1(b)], a
resist layer 12 having a stated pattern is formed on the surface
thereof [FIG. 1(c)], a dale 13 is formed in the silicon dioxide
film 11 by dry etching and then the resist layer 12 is removed
[FIG. 1(d)], a metal such as copper is deposited by vacuum
deposition, plating or CVD in such a way that it covers the surface
of the silicon dioxide film 11 and the uncovered part of the
silicon wafer 10, to provide a wiring layer 15 [FIG. 1(e)], and
thereafter its surface is polished by CMP. Thus, as shown in FIG.
1(f), a semiconductor substrate member 14 having buried wirings 15
of copper is obtained.
EXAMPLES
[0079] The present invention is specifically described below by
giving Examples. The present invention is by no means limited by
these Examples.
[0080] (1) Preparation of Polishing Medium for CMP
[0081] To 0.15 part by weight of DL-malic acid (a guaranteed
reagent), 70 parts by weight of water was added to effect
dissolution, and a solution prepared by dissolving 0.2 part by
weight of benzotriazole in 0.8 part by weight of methanol was added
thereto. Further, 0.05 part by weight (solid-matter weight) of a
water-soluble polymer was added (but, in only Comparative Example
3, the water-soluble polymer was mixed in an amount of 1.5 parts by
weight). Finally, 33.2 parts by weight of hydrogen peroxide water
(a guaranteed reagent, an aqueous 30% by weight solution) was
added. Thus, polishing mediums for CMP were obtained. Surface
protective agents and water-soluble polymers used in Examples and
Comparative Examples are shown in Tables 1 to 3.
[0082] (2) Polishing
[0083] Using the polishing mediums for CMP thus obtained, CMP was
carried out under conditions shown below. Substrate member to be
polished: Silicon substrate with a copper film formed thereon in a
thickness of 1 .mu.m. [0084] Polishing pad: IC1000 (available from
Rodel Inc.). [0085] Polishing pressure: 21 kPa (210 gf/cm.sup.2)
(point-of-inflection [0086] pressure: 0 to 50 kPa (0 to 500
gf/cm.sup.2). [0087] Relative speed of substrate member to
polishing platen: 36 m/minute.
[0088] (3) Polished-Product Evaluation Items
CMP Rate:
[0089] Determined by calculation from electrical resistance value
in respect of the difference in layer thickness before and after
the copper film was polished by CMP.
Etching Rate:
[0090] Determined by calculation from electrical resistance value
in respect of the difference in copper layer thickness before and
after immersion in the polishing medium having been stirred.
[0091] (4) Evaluation Results
[0092] The results of evaluation on the above items in Examples and
Comparative Examples are shown in Tables 1 to 3. TABLE-US-00001
TABLE 1 Example 1 2 3 4 5 6 Protective-film- benzotriazole forming
agent Water-soluble pectic agar- polyacrylic acid polymer acid agar
(molecular (50000) (40000) (300) (5000) (12000) (90000) weight MW)
CMP rate 160 132 85 147 153 321 (nm/minute) Etching rate 1.0 1.1 1
0.9 0.9 0.9 (nm/minute) Point-of- 3 3 2 30 15 6 inflection pressure
(kPa) Ubbelode's 0.95 0.95 0.94 0.94 0.95 0.98 viscosity (mPa s)
Coefficient of 0.34 0.37 0.19 0.27 0.30 0.50 kinetic friction
[0093] TABLE-US-00002 TABLE 2 Example 7 8 9 10 11 12 Protective-
benzotriazole film-forming agent Water- polyacrylamide polyvinyl
alcohol soluble (1500) (10000) (800000) (23000) (66000) (88000)
polymer (molecular weight MW) CMP rate 162 124 162 132 135 135
(nm/minute) Etching rate 1.0 1.0 1.0 0.9 0.9 0.9 (nm/minute)
Point-of- 6 5 5 9 7 6 inflection pressure (kPa) Ubbelode's 0.94
0.96 0.99 0.97 0.98 0.98 viscosity (mPa s) Coefficient 0.27 0.32
0.35 0.48 0.54 0.57 of kinetic friction
[0094] TABLE-US-00003 TABLE 3 Example Comparative Example 13 14 1 2
3 4 Protective- benzotriazole none film-forming agent Water
polyvinyl none poly- none soluble pyrrolidone acrylamide polymer
(40000) (1200000) (800000) (molecular weight MW) CMP rate 91 99 80
112 20 145 (nm/minute) Etching rate 0.8 0.8 0.7 39.6 5.0 50.6
(nm/minute) Point-of- 8 6 2 none none None inflection pressure
(kPa) Ubbelode's 0.95 0.96 0.94 0.99 1.6 0.94 viscosity (mPa s)
Coefficient 0.40 0.45 0.16 0.42 0.25 0.23 of kinetic friction
[0095] To evaluate actual CMP performance, a silicon substrate
member in which grooves of 0.5 .mu.m in depth were formed in the
insulating layer and a copper film was formed by known sputtering
and was buried in the grooves by known heat treatment was subjected
to CMP. After the CMP, whether or not any erosion and polishing
mars occurred was examined by visual observation,
optical-microscope observation and electron-microscope observation
of the substrate member. As the result, the erosion and the
polishing mars were not seen to have occurred in all Examples.
[0096] In Comparative Example 1, in which only the
protective-film-forming agent was mixed in the polishing medium and
the water-soluble polymer was not added, the CMP rate was low.
Also, in Comparative Examples 2 and 3, in which only the
water-soluble polymer was mixed and the protective-film-forming
agent was not added, and in Comparative Example 4, in which both
the protective-film-forming agent and the water-soluble polymer
were not mixed, the etching rate was so high that the dishing
occurred in a large level.
[0097] On the other hand, in Examples 1 to 14, in which the
protective-film-forming agent and the water-soluble polymer were
used in combination, the CMP rate was high although the etching
rate was low, making it possible to shorten the polishing time.
Moreover, the dishing was only in a small level, and the high
flattening was achievable. Also, Examples 4 to 6, in which the
molecular weight of the water-soluble polymer was 500 more, showed
a higher CMP rate than Example 3, in which it was not more than
500, thus it was found preferable for the water-soluble polymer to
have a molecular weight of 500 or more.
[0098] In Comparative Example 1, in which the polishing medium had
a coefficient of kinetic friction of 0.16, which was lower than
0.25, the CMP rate was low. Also, the polishing medium of
Comparative Example 4, too, having a low coefficient of kinetic
friction of 0.23, showed a higher etching rate than the CMP rate,
and hence caused the dishing in a large level. In Comparative
Examples 1 and 4, having a Ubbelode's viscosity of 0.94 mPas (0.94
cP), which was lower than 0.95, the CMP rate was low. Also, in
Comparative Example 1, having a point-of-inflection pressure of 2
kPa (20 gf/cm.sup.2), which was lower than 5 kPa (50 gf/cm.sup.2),
the CMP rate was low. Still also, in Comparative Examples 2 to 4,
in which the point-of-inflection pressure was not present, the
etching rate was so high that the dishing occurred in a large
level.
POSSIBILITY OF INDUSTRIAL APPLICATION
[0099] As described above, according to the polishing medium for
CMP of the present invention, highly reliable buried metal film
patterns can be formed in a good efficiency.
* * * * *