U.S. patent application number 10/626521 was filed with the patent office on 2004-08-19 for aqueous dispersion for chemical mechanical polishing and production process of semiconductor device.
This patent application is currently assigned to JSR CORPORATION. Invention is credited to Hattori, Masayuki, Kawahashi, Nobuo, Konno, Tomohisa, Motonari, Masayuki.
Application Number | 20040162011 10/626521 |
Document ID | / |
Family ID | 30112992 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040162011 |
Kind Code |
A1 |
Konno, Tomohisa ; et
al. |
August 19, 2004 |
Aqueous dispersion for chemical mechanical polishing and production
process of semiconductor device
Abstract
The invention provides an aqueous dispersion for chemical
mechanical polishing, by which scratches are reduced even for an
article to be polished having a dielectrics low in mechanical
strength, both copper film and barrier metal film can be polished
with high efficiency, and a sufficiently planarized finished
surface with high precision can be provided without overpolishing
the dielectrics, and a production process of a semiconductor
device. The aqueous dispersion for chemical mechanical polishing
comprises abrasive grains, wherein the abrasive grains include (A)
simple particles composed of at least one selected from inorganic
particles and organic particles, and (B) composite particles. It is
preferred that the simple particles (A) are composed of inorganic
particles and composite particles (B) are composed of inorganic
organic composite particles that formed of organic particles and
inorganic particles combined integraly. The production process of a
semiconductor device comprises the step of polishing a surface to
be polished of a semiconductor material with the aqueous dispersion
for polishing.
Inventors: |
Konno, Tomohisa; (Tokyo,
JP) ; Motonari, Masayuki; (Tokyo, JP) ;
Hattori, Masayuki; (Tokyo, JP) ; Kawahashi,
Nobuo; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
JSR CORPORATION
Tokyo
JP
|
Family ID: |
30112992 |
Appl. No.: |
10/626521 |
Filed: |
July 25, 2003 |
Current U.S.
Class: |
451/41 |
Current CPC
Class: |
C09K 3/1463 20130101;
H01L 21/3212 20130101; C09G 1/02 20130101; C09K 3/1436
20130101 |
Class at
Publication: |
451/041 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2002 |
JP |
2002-225906 |
Claims
What is claimed is:
1. An aqueous dispersion for chemical mechanical polishing
comprising abrasive grains, wherein the abrasive grains include:
(A) simple particles composed of at least one selected from
inorganic particles and organic particles, and (B) composite
particles.
2. The aqueous dispersion for chemical mechanical polishing
according to claim 1, wherein the simple particles (A) making up
the abrasive grains are composed of inorganic particles, and the
composite particles (B) are composed of inorganic organic composite
particles obtained by integrally combining organic particles with
inorganic particles.
3. The aqueous dispersion for chemical mechanical polishing
according to claim 1 or 2, wherein the overall content of all the
abrasive grains is 0.11 to 20% by mass, the content of the simple
particles (A) is 0.1 to 19.99% by mass, and the content of the
composite particles (B) is 0.01 to 19.9% by mass.
4. The aqueous dispersion for chemical mechanical polishing
according to any one of claims 1 to 3, wherein a value of a
specific removal rate ratio (RBM/RCu) represented by a ratio of the
removal rate (RBM) of a barrier metal film to the removal rate
(RCu) of a copper film in the case where the copper film and
barrier metal film are polished under the same conditions is 0.5 to
200.
5. The aqueous dispersion for chemical mechanical polishing
according to any one of claims 1 to 3, wherein the value of the
specific removal rate ratio (RBM/RCu) represented by a ratio of the
removal rate (RBM) of a barrier metal film to the removal rate
(RCu) of a copper film in the case where the copper film and
barrier metal film are polished under the same conditions is 10 to
200.
6. The aqueous dispersion for chemical mechanical polishing
according to any one of claims 1 to 3, wherein the value of the
specific removal rate ratio (RBM/RCu) represented by a ratio of the
removal rate (RBM) of a barrier metal film to the removal rate
(RCu) of a copper film in the case where the copper film and
barrier metal film are polished under the same conditions is 0.5 to
3.
7. A process for producing a semiconductor device, comprising the
step of polishing a surface to be polished of a semiconductor
material with the aqueous dispersion for chemical mechanical
polishing according to any one of claims 1 to 6.
8. A process for producing a semiconductor device, comprising the
first polishing treatment step of mainly polishing a copper film of
a surface to be polished of a semiconductor material and the second
polishing treatment step of mainly polishing a barrier metal film
with the aqueous dispersion for chemical mechanical polishing
according to claim 5 or 6, conducted after the first polishing
treatment step.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field of the Invention
[0002] The present invention relates to an aqueous dispersion for
chemical mechanical polishing and a production process of a
semiconductor device making use of this aqueous dispersion, and
particularly to an aqueous dispersion for chemical mechanical
polishing that is useful in a polishing treatment of semiconductor
substrates, in which an inter layer dielectrics low in dielectric
constant exists, in a treatment process that a semiconductor
substrate such as a wafer provided with a wiring pattern is
subjected to chemical mechanical polishing (hereinafter may
referred to as "CMP") in the production of semiconductor devices,
particularly useful in a second polishing treatment step in a
two-step polishing process or a second polishing treatment step in
a three-step polishing process, and a production process of a
semiconductor device making use of this aqueous dispersion.
[0003] 2. Description of the Background Art
[0004] A silicon oxide film (SiO.sub.2 film) formed by a vacuum
process such as chemical vapor deposition (CVD) has heretofore been
often used as an inter layer dielectrics in a semiconductor device
or the like. This SiO.sub.2 film is relatively high in dielectric
constant.
[0005] On the other hand, for the purpose of improving the
performance of ultra LSI, attention has been paid to the formation
of an inter layer dielectrics having a lower dielectric constant in
recent years. In order to achieve this formation of the inter layer
dielectrics lower in dielectric constant, an inter layer
dielectrics composed of a polymer obtained by plasma-polymerizing a
silicon-containing compound such as an alkoxysilane, silane,
alkylsilane, arylsilane, siloxane or alkylsiloxane in the presence
of oxygen, carbon monoxide, carbon dioxide, nitrogen, argon,
H.sub.2O, ozone, ammonia or the like and an inter layer dielectrics
composed of polysiloxane, polysilazane, poly(arylene ether),
polybenzoxazole, polyimide, silses quioxane or the like have been
developed as substitutes for the SiO.sub.2 film.
[0006] Since these dielectrics are low in mechanical strength, soft
and brittle compared with the SiO.sub.2 film, however, a
semiconductor substrate that is an article to be polished may
possibly cause scratches or peeling when a conventional aqueous
dispersion for chemical mechanical polishing containing inorganic
particles is used. In addition, since a great number of scratches
of various shapes may be caused in some cases, a problem arises in
the yield of products.
[0007] In chemical mechanical polishing for forming a damascene
wiring, it is hard to polish a barrier metal film composed of a
metal having high hardness such as tantalum with high efficiency.
On the other hand, since a copper film for forming a wiring portion
is relatively soft and easily polished, dishing may be caused in
the wiring portion in some cases to fail to obtain a planarized
polished surface. In a porous dielectrics low in dielectric
constant in particular, it may be impossible in some cases to form
a good damascene wiring because the dielectrics is
overpolished.
[0008] Although polishing processes for forming a damascene wiring
are various, a two-step polishing treatment comprising of a first
polishing treatment step, in which polishing of a copper film is
mainly conducted, and a second polishing treatment step, in which
polishing of a barrier metal film is mainly conducted, is generally
preferably performed. Either of the first polishing treatment step
and the second polishing treatment step may be conducted with
operations devided into two or more. Further, in the first
polishing treatment step in this two-step polishing treatment,
there are a case where polishing is conducted until the copper film
is being almost completely removed and a case where the substrate
to be polished is subjected to the second polishing treatment step
while the removal of the copper film by the polishing is not
completed. Therefore, in the second polishing treatment step, an
aqueous dispersion for polishing that is different in components
contained from that used in the first polishing treatment step may
be used according to polishing conditions applied in the first
polishing treatment step.
[0009] In each of a plurality of polishing treatment steps
conducted under such different conditions as described above, it is
general to use an aqueous dispersion for polishing suitable for the
purpose of such a polishing treatment step, in other words, an
aqueous dispersion for polishing different in composition from that
other polishing treatment steps. Accordingly, it has been necessary
to provide a number of aqueous dispersions for polishing according
to the number of objects of polishing.
[0010] On the other hand, any aqueous dispersion for chemical
mechanical polishing, by which occurrence of scratches in a surface
to be polished in an article, on which an inter layer dielectrics
low in mechanical strength and dielectric constant has been formed,
is prevented, has not been proposed.
SUMMARY OF THE INVENTION
[0011] The present invention has been made for the purpose of
solving the above-described problems involved in the prior art and
has as its first object the provision of an aqueous dispersion for
chemical mechanical polishing, by which occurrence of scratches in
a polished surface is greatly prevented even when it is used in a
polishing treatment of an article to be polished composed of a
semiconductor substrate having an inter layer dielectrics low in
mechanical strength and dielectric constant, a ratio of the removal
rate of a copper film to the removal rate of a barrier metal film
can be easily controlled with a great degree of freedom though
basic components are the same thereby both copper film and barrier
metal film can be polished with high efficiency, and a sufficiently
planarized finished surface with high precision can be provided
without overpolishing the dielectrics.
[0012] It is the second object of the present invention to provide
a production process of a semiconductor device including a
polishing treatment step using the above-described aqueous
dispersion for chemical mechanical polishing.
[0013] According to the present invention, there is thus provided
an aqueous dispersion for chemical mechanical polishing comprising
abrasive grains, wherein the abrasive grains include:
[0014] (A) simple particles composed of at least one selected from
inorganic particles and organic particles, and
[0015] (B) composite particles.
[0016] In the aqueous dispersion for chemical mechanical polishing
according to the present invention, it is preferable that the
simple particles (A) making up the abrasive grains be composed of
inorganic particles, and the composite particles (B) be composed of
inorganic organic composite particles obtained by integrally
combining organic particles with inorganic particles.
[0017] In the aqueous dispersion for chemical mechanical polishing
according to the present invention, it is preferable that the
overall content of all the abrasive grains be 0.11 to 20% by mass,
the content of the simple particles (A) be 0.1 to 19.99% by mass,
and the content of the composite particles (B) be 0.01 to 19.9% by
mass.
[0018] In the aqueous dispersion for chemical mechanical polishing
according to the present invention, a value of a specific removal
rate ratio (RBM/RCu) represented by a ratio of the removal rate
(RBM) of a barrier metal film to the removal rate (RCu) of a copper
film in the case where the copper film and barrier metal film are
polished under the same conditions may be 0.5 to 200.
[0019] In the aqueous dispersion for chemical mechanical polishing
according to the present invention, the value of the specific
removal rate ratio (RBM/RCu) may be controlled to 10 to 200. In the
aqueous dispersion for chemical mechanical polishing according to
the present invention, the value of the specific removal rate ratio
(RBM/RCu) may also be controlled to 0.5 to 3.
[0020] According to the present invention, there is also provided a
process for producing a semiconductor device, comprising the step
of polishing a surface to be polished of a semiconductor material
with the aqueous dispersion for chemical mechanical polishing
described above.
[0021] According to the present invention, there is further
provided a process for producing a semiconductor device, comprising
the first polishing treatment step of mainly polishing a copper
film of a surface to be polished in a semiconductor material and
the second polishing treatment step of mainly polishing a barrier
metal film with the aqueous dispersion for chemical mechanical
polishing that the value of the specific removal rate ratio
(RBM/RCu) is 10 to 200 or 0.5 to 3, conducted after the first
polishing treatment step.
[0022] According to the aqueous dispersion for chemical mechanical
polishing of the present invention, occurrence of scratches in a
polished surface is greatly prevented even when it is used in a
polishing treatment of an article to be polished composed of a
semiconductor substrate having an inter layer dielectrics low in
mechanical strength and dielectric constant, a ratio of the removal
rate of a copper film to the removal rate of a barrier metal film
can be easily controlled with a great degree of freedom thereby
both copper film and barrier metal film can be polished with high
efficiency, and a sufficiently planarized finished surface with
high precision can be provided without overpolishing the
dielectrics.
[0023] According to the production process of a semiconductor
device of the present invention, occurrence of scratches in a
polished surface in a polishing treatment is greatly prevented even
with a semiconductor substrate having an inter layer dielectrics
low in mechanical strength and dielectric constant, both copper
film and barrier metal film can be polished with high efficiency,
and a sufficiently planarized finished surface with high precision
can be provided without overpolishing the dielectrics.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The aqueous dispersions for chemical mechanical polishing
according to the present invention will hereinafter be described
specifically.
[0025] The aqueous dispersions (hereinafter also referred to as
polishing slurries or polishing slurry) for chemical mechanical
polishing are in a form of a slurry containing abrasive grains in a
state dispersed in an aqueous medium. The abrasive grains comprise
the following both components:
[0026] (A) simple particles composed of at least one selected from
inorganic particles and organic particles, and
[0027] (B) composite particles.
[0028] The respective components of the abrasive grains will
hereinafter be described.
[0029] (A) Simple Particles
[0030] The polishing slurry according to the present invention
contains simple particles composed of at least one selected from
inorganic particles and organic particles as a component of the
abrasive grains. The simple particles are preferably composed of
inorganic particles.
[0031] As examples of the inorganic particles used as the simple
particles, may be mentioned particles of silicon dioxide, aluminum
oxide, cerium oxide, titanium oxide, zirconium oxide, silicon
carbide, silicon nitride, manganese oxide and the like. Among
these, particles of silicon dioxide are preferred.
[0032] As specific examples of the silicon dioxide particles, may
be mentioned fumed silica synthesized by a fumed process, in which
silicon chloride or the like is reacted with oxygen and hydrogen in
a vapor phase, colloidal silica synthesized by a sol-gel process,
in which a metal alkoxide is hydrolyzed and condensed, and
colloidal silica synthesized by an inorganic colloid process, in
which impurities are removed by purification.
[0033] The colloidal silica synthesized by the sol-gel process or
colloid process is present in an aqueous medium, in a state that
primary particles have associated or aggregated, i.e., in a state
of secondary particles, when the particle diameter thereof is
comparatively small. The inorganic particles in such a state
preferably have an average particle diameter of 1 to 3,000 nm, more
preferably 2 to 1,000 nm in terms of primary particles.
[0034] The average particle diameter of the secondary particles is
preferably 5 to 5,000 nm, more preferably 5 to 3,000 nm,
particularly preferably 10 to 1,000 nm. If inorganic particles, the
average particle diameter of the secondary particles of which is
smaller than 5 nm, are used, the resulting polishing slurry cannot
achieve a sufficiently high removal rate in some cases. On the
other hand, in a polishing slurry using inorganic particles, the
average particle diameter of the secondary particles of which
exceeds 5,000 nm, the prevention of dishing and erosion may become
insufficient in some cases and further, surface defects such as
scratches may be liable to occur. In addition, the polishing slurry
may become low in stability.
[0035] The average particle diameter of the primary particles can
be calculated out from the measurement of the specific surface area
of the intended particles and observation through a transmission
type electron microscope, and the like. The average particle
diameter of the secondary particles can be determined by
measurement by means of a laser scattering diffraction measuring
device, or the like.
[0036] On the other hand, inorganic particles such as silica
synthesized by the fumed process are produced in the form of
secondary particles, and it is very difficult to disperse them in a
state of primary particles in an aqueous medium, and so such
particles are present as secondary particles obtained by
aggregation of primary particles. Accordingly, the inorganic
particles composed of the silica synthesized by the fumed process
are sufficiently identified so far as the secondary particles
thereof are defined.
[0037] The average particle diameter of the secondary particles of
the inorganic particles formed of fumed silica are preferably 10 to
10,000 nm, more preferably 20 to 7,000 nm, particularly preferably
50 to 5,000 nm. By using the inorganic particles formed of fumed
silica, the average particle diameter of the secondary particles of
which falls within this range, there can be provided a polishing
slurry which can achieve high removal rate, sufficiently prevents
dishing and erosion and is high in stability.
[0038] As examples of the organic particles used as the simple
particles in the present invention, may be mentioned polymer
particles respectively composed of (1) polystyrene and styrene
copolymers, (2) (meth)acrylic polymers and (meth)acrylic copolymers
such as polymethyl methacrylate, (3) polyvinyl chloride,
polyacetal, saturated polyester, polyamide, polyimide,
polycarbonate and phenoxy resins, and (4) polyolefins and olefin
copolymers such as polyethylene, polypropylene, poly(1-butene) and
poly(4-methyl-2-pentene), and other thermoplastic resins.
[0039] These organic particles can be prepared by a method of an
emulsion polymerization process, suspension polymerization process,
emulsion dispersion polymerization process, grinding a resin
obtained by bulk polymerization process or the like, or other
methods. The organic particles may also be particles of a copolymer
having a crosslinked structure obtained by a copolymerization with
a crosslinkable monomer such as divinylbenzene or ethylene glycol
in the above-described polymerization process.
[0040] The organic particles used as the simple particles are
preferably particles of a resin selected from (1) polystyrene and
styrene copolymers and (2) (meth)acrylic polymers and (meth)acrylic
copolymers such as polymethyl methacrylate among the resin
mentioned above, and their copolymers having a crosslinked
structure.
[0041] Almost all of the such organic particles as described above
generally present as single particles in the polishing slurry. The
average particle diameter of these organic particles is preferably
10 to 5,000 nm, more preferably 15 to 3,000 nm, particularly
preferably 20 to 1,000 nm. By using the organic particles having an
average particle diameter within this range as the simple
particles, there can be provided a polishing slurry which can
achieve high removal rate, sufficiently prevents dishing and
erosion and is high in stability.
[0042] (B) Composite Particles
[0043] The composite particles (B) are contained in the polishing
slurry according to the present invention as particles making up
the abrasive grains together with the simple particles (A).
[0044] In the present invention, as specific examples of the
composite particles, may be mentioned inorganic organic composite
particles obtained by integrally combining organic particles with
inorganic particles, and modified particles obtained by bonding a
modifying substance to surfaces of organic particles.
[0045] The composite particles composed of the inorganic organic
composite particles are those obtained by integrally combining
organic particles with inorganic particles in the extent that these
particles are not easily separated. No particular limitation is
imposed on the kinds of these organic particles and inorganic
particles. For example, the same organic particles and inorganic
particles as those forming the simple particles described above may
be used.
[0046] No particular limitation is also imposed on the specific
structure of the composite particles. For example, those obtained
by combining the organic particles composed of polymer particles
with the inorganic particles by a proper method are preferably
used.
[0047] More specifically, particles in a state that organic
particles and inorganic particles, which are different in polarity
of zeta potential from each other, have been combined by
electrostatic force in, for example, an aqueous medium may be used
as the composite particles.
[0048] The zeta potential of the organic particles is often
negative in the whole pH range or a wide pH range exclusive of a
low pH range. In particular, organic particles composed of a
polymer having a carboxyl group, sulfonic group or the like surely
have a negative zeta potential, and organic particles composed of a
polymer having an amino group or the like have a positive zeta
potential in a specific pH range.
[0049] On the other hand, the zeta potential of the inorganic
particles have high dependency on pH, and some inorganic particles
have an isoelectric point, at which a zeta potential is zero, at a
characteristic pH. In such inorganic particles, the polarity of the
zeta potential thereof is reversed before and after this point.
[0050] Therefore, a specific kind of organic particles are combined
with a specific kind of inorganic particles, and both particles are
mixed in such a pH range that their zeta potentials become reverse
polarities to each other, whereby inorganic organic composite
particles in a state that such organic particles and inorganic
particles have been integrally combined by electrostatic force can
be obtained.
[0051] Even when the zeta potentials of organic particles and
inorganic particles mixed are the same polarity upon mixing,
inorganic organic composite particles in a state that the organic
particles and inorganic particles have been integrally combined can
also be obtained by changing the pH after the mixing to create a
state that the zeta potentials thereof become reverse polarities to
each other.
[0052] In the present invention, the composite particles may be
modified organic particles in a state that a proper modifying
substance has been bonded to the surfaces of organic particle
composed of, for example, polymer particles. As examples of the
polymer particles, may be mentioned particles of polystyrene and
polymethyl methacrylate. The polymer particles, to which the
modifying substance has been bonded, can be obtained by, for
example, a method in which a reactive material for modifying
substance, such as an alkoxysilane, aluminum alkoxide or titanium
alkoxide, is polycondensed in the presence of the polymer particles
to form the modifying substance on the surfaces of the polymer
particles.
[0053] When the material for the modifying substance is an
alkoxysilane, modified organic particles that polysiloxane is
bonded to the surfaces of the polymer particles can be obtained.
When the material for the modifying substance is an aluminum
alkoxide or titanium alkoxide, modified organic particles that an
aluminum or titanium atom is bonded to the surfaces of the polymer
particles through a siloxane bond can be obtained. In the method
described above, the surfaces of the polymer particles may also be
treated with a silane coupling agent or the like in advance.
[0054] In the present invention, the composite particles may also
be inorganic organic composite particles combined by bonding
inorganic particles such as silica particles or alumina particles
to the surfaces of organic particles composed of proper polymer
particles. In this case, the inorganic particles may be bonded by
being physically held by a bonding component such as siloxane on
the surfaces of the polymer particles or be chemically bonded by a
functional group such as a hydroxyl group existing on the surfaces
of the polymer particles.
[0055] Those in a state that the inorganic organic composite
particles obtained by the above-described integral bonding by
electrostatic force have been modified by a modifying substance by
a polycondensation reaction of, for example, an alkoxysilane,
aluminum alkoxide, titanium alkoxide or the like in the presence of
such inorganic organic composite particles can also be used as the
composite particles.
[0056] When the composite particles are composed of the inorganic
organic particles, such composite particles exist in any of the
following States 1 to 3 according to the particle diameters and
component proportions of the respective organic particles and
inorganic particles forming the composite particles or exist in a
condition that a plurality of states are mixed.
[0057] State 1: a state that the inorganic particles have adhered
as shell particles to the surfaces of core particles composed of
the organic particles.
[0058] State 2: a state that the organic particles have adhered as
shell particles to the surfaces of core particles composed of the
inorganic particles.
[0059] State 3: a state that the organic particle and inorganic
particles have aggregated to each other without forming a clear
core-shell structure.
[0060] Among the above-described states, State 1 or 2 is
preferred.
[0061] In each of States 1 to 3, the inorganic particles may be in
any state of primary particles and secondary particles, or both
particles may be mixed.
[0062] With respect to the component proportions of the inorganic
particle and organic particles forming the inorganic organic
composite particles, the proportion of the inorganic particles is
preferably 1 to 2,000 parts by weight, more preferably 10 to 1,000
parts by weight per 100 parts by weight of the organic
particles.
[0063] In the present invention, the average particle diameter of
the composite particles is preferably 20 to 20,000 nm, more
preferably 50 to 10,000 nm, particularly preferably 50 to 5,000
nm.
[0064] By containing the composite particles satisfying the
above-described conditions, there can be provided a polishing
slurry which can achieve high removal rate, sufficiently prevents
dishing and erosion and is high in stability.
[0065] In the polishing slurry according to the present invention,
the proportion of the abrasive grains contained is such that the
overall content of the simple particles (A) composed of at least
one selected from the inorganic particles and organic particles and
the composite particles (B) amounts to 0.11 to 20% by mass based on
100% by mass of the polishing slurry.
[0066] If the proportion of the abrasive grains contained is lower
than 0.11% by mass, the resulting polishing slurry cannot achieve
any sufficient removal rate. If the proportion contained exceeds
20% by mass on the other hand, the resulting polishing slurry
becomes high in cost and may be deteriorated in shelf stability in
some cases.
[0067] The content of the simple particles (A) composed of at least
one selected from the inorganic particles and organic particles is
preferably 0.1 to 19.99% by mass, more preferably 0.1 to 10% by
mass, particularly preferably 0.5 to 10% by mass based on 100% by
mass of the polishing slurry.
[0068] The content of the composite particles (B) is preferably
0.01 to 19.9% by mass, more preferably 0.01 to 10% by mass,
particularly preferably 0.01 to 5% by mass based on 100% by mass of
the polishing slurry.
[0069] A relative ratio of the simple particles (A) composed of at
least one selected from the inorganic particles and organic
particles to the composite particles (B) is preferably 1:10 to 10:1
by mass, more preferably 1:10 to 5:1, particularly preferably 1:5
to 5:1.
[0070] When the proportion of the abrasive grains contained falls
within the above range, a polishing slurry which can prevent
occurrence of surface defects such as scratches even for a surface
to be polished, in which a fragile inter layer dielectrics exists,
and achieves sufficient removal rate can be provided.
[0071] In the polishing slurry according to the present invention,
a value of a ratio (RBM/RCu) (hereinafter also referred to as
"specific removal rate ratio") of a removal rate (RBM) of a barrier
metal film obtained by polishing the barrier metal film with this
polishing slurry to a removal rate (RCu) of a copper film obtained
by polishing the copper film under the same conditions as the case
of the barrier metal film amounts to 0.5 to 200.
[0072] In the above, "copper film" includes films of copper alloys
having a copper content of at least 95% by mass, such as
copper-silicon and copper-aluminum, in addition to films composed
of pure copper.
[0073] "Barrier metal film" is formed by a metal having high
hardness, such as tantalum or titanium, a nitride or oxide thereof,
or the like. The metal forming the barrier metal film is not
limited to a pure metal, and may be an alloy, for example,
tantalum-niobium. When the barrier metal film is formed by a
nitride, tantalum nitride, titanium nitride or the like is also not
necessarily a pure substance. The material of this barrier metal
film is particularly preferably tantalum and/or tantalum
nitride.
[0074] The barrier metal film is often formed by only one material
such as tantalum or titanium. However, films of different
materials, for example, both tantalum film and tantalum nitride
film may be formed on the same substrate as a barrier metal film in
some cases.
[0075] "The same conditions" related to the specific removal rate
ratio means that a polishing apparatus of a specified type is used,
and the rotating speeds of the platen and head thereof, polishing
pressure, polishing time, the kind of a polishing pad used, and the
feeding rate of a polishing slurry per unit time are the same. The
specific removal rate ratio can be calculated out from the values
of respective removal rates of a copper film and a barrier metal
film when both films are separately polished under "the same
conditions". The polishing of these films can be conducted by using
wafers equipped with the copper film and the barrier metal film,
respectively.
[0076] In the polishing slurries according to the present
invention, the specific removal rate ratio (RBM/RCu) can be
optionally controlled within a range of 0.5 to 200. In order to
control the specific removal rate ratio (RBM/RCu), the polishing
slurries according to the present invention may contain a
heterocyclic compound.
[0077] As examples of such a heterocyclic compound, may be
mentioned quinolinecarboxylic acids, indolizines, compounds having
a 5-membered heterocycle and compounds having a 6-membered
heterocycle.
[0078] As examples of the quinolinecarboxylic acids, may be
mentioned 2-quinolinecarboxylic acid (quinaldinic acid) and
2,3-pyridinedicarboxyli- c acid (quinolinic acid).
[0079] As examples of the indolizines, may be mentioned
7-hydroxy-5-methyl-1,3,4-triazaindolizine.
[0080] As examples of the compounds having a 5-membered
heterocycle, may be mentioned benzotriazoles such as
1,2,3-benzotriazole,
1-(N,N-bis(2-ethylhexyl)aminomethyl)-benzotriazole,
carboxybenzotriazole, 1-(2',3'-dihydroxy-propyl)benzotriazole,
1-(2',3'-dicarboxyethyl)-benzotr- iazole and
1-(2-ethylhexylaminomethyl)benzotriazole; benzothiazoles such as
2-aminobenzothiazole, 2-amino-6-methylbenzothiazole and
2-mercaptobenzothiazole; triazoles such as 4-amino-1,2,4-triazole,
4-amino-3-hydrazino-5-mercapto-1,2,4-triazole,
3-mercapto-1,2,4-triazole and
3-mercapto-4-methyl-4H-1,2,4-triazole; tetrazoles such as
5-amino-1H-tetrazole, 1-phenyl-5-mercapto-1H-tetrazole,
1H-tetrazole, 1H-tetrazole-1-acetic acid and
1-(2-dimethylaminoethyl)-5-mercaptotetrazo- le; and
2-mercaptothiazoline, 4,5-dicyanoimidazole,
2-amino-4,5-dicyano-1H-imidazole and
3H-1,2,3-triazolo[4,5-b]pyridin-3-ol- .
[0081] As examples of the compounds having a 6-membered
heterocycle, may be mentioned triazines such as
3-amino-5,6-dimethyl-1,2,4-triazine,
2,4-diamino-6-diallylamino-1,3,5-triazine and
3-amino-5,6-dimethyl-1,2,4-- triazine; and benzoguanamine,
thiocyanuric acid, melamine, phthalazine and
2,3-dicyano-5-methylpyrazine.
[0082] As the heterocyclic compound, may also be used a derivative
of a compound having both 5-membered heterocycle and 6-membered
heterocycle. As such derivatives, may be mentioned adenine and
guanine.
[0083] The content of such a heterocyclic compound may be
controlled to 0.0001 to 5% by mass, preferably 0.001 to 1% by mass,
more preferably 0.01 to 0.5% by mass based on 100% by mass of the
polishing slurry. If the content of the heterocyclic compound is
lower than 0.0001% by mass, the removal rate of a copper film
and/or a barrier metal film cannot be made sufficiently high. In
particular, when such a polishing slurry is used in polishing of
the barrier metal film, it takes a long time to polish this film.
On the other hand, there is no need to contain this heterocyclic
compound in an amount exceeding 5% by mass.
[0084] As described above, the specific removal rate ratio
(RBM/RCu) of the polishing slurries according to the present
invention can be freely controlled within the range of 0.5 to
200.
[0085] The polishing slurries according to the present invention
are thereby useful as aqueous dispersions for polishing in a second
or third polishing treatment in the case where a chemical
mechanical polishing step for a copper film in particular is
conducted by the so-called 2-step polishing or 3-step
polishing.
[0086] In the 2-step polishing, are conducted a first polishing
treatment step that any other copper than copper filled in a wiring
groove formed on a substrate is removed by polishing and a second
polishing treatment step that a barrier metal film exposed by this
first polishing treatment step is polished to form a wiring. In the
3-step polishing, after the 2-step polishing of above, a third
polishing treatment step that a dielectrics exposed after the
barrier metal film has been removed by polishing in the second
polishing treatment step is polished is conducted as needed.
[0087] More specifically, the 2-step polishing is polishing process
composed of 2 steps of a first polishing treatment step, in which a
copper film is mainly polished, and a second polishing treatment
step, in which a barrier metal film is mainly polished. The 2
polishing treatment steps may be performed independently of each
other, and continuity with time and continuity related to a
polishing apparatus between 2 steps are not required.
[0088] The first polishing treatment step and second polishing
treatment step can be continuously conducted by successively
changing and feeding a polishing slurry in the same polishing
apparatus. In the same polishing apparatus, a semiconductor
substrate that is an article to be polished may also be taken out
after completion of the first polishing treatment step and perform
the second polishing treatment step after changing the polishing
slurry.
[0089] The first polishing treatment step and second polishing
treatment step may also be conducted by separate polishing
apparatus. A polishing apparatus having a plurality of polishing
pads in its interior is used to conduct the first polishing
treatment step by one polishing pad and the second polishing
treatment step by the other polishing pad, whereby the first
polishing treatment step and second polishing treatment step can
also be continuously performed for an article to be polished.
[0090] Either of the first polishing treatment step and the second
polishing treatment step can be achieved with operations divided
into two or more.
[0091] In the first polishing treatment step in such a 2-step
polishing treatment or 3-step polishing treatment as described
above, for example, a polishing slurry whose specific removal rate
ratio (RBM/RCu) is at most 0.1 may preferably be used.
[0092] As the aqueous dispersion for chemical mechanical polishing
used in the first polishing treatment step, a polishing slurry
containing abrasive grains, an oxidizing agent and an organic acid
and containing a surfactant or the like as needed may be
specifically used.
[0093] As the abrasive grains, may be used, for example, those
composed of at least one of inorganic particles and organic
particles. The proportion thereof is 0.01 to 10% by mass,
preferably 0.01 to 5% by mass based on 100% by mass of the
polishing slurry.
[0094] As the oxidizing agent, may be used, for example, a
persulfate (ammonium salt, potassium salt or the like),
heteropoly-acid (for example, silicomolybdic acid, phosphomolybdic
acid, silicotungstic acid, phosphotungstic acid or the like),
permanganic acid compound (potassium salt or the like), bichromic
acid compound (potassium salt or the like) or hydrogen peroxide.
The proportion thereof is 0.01 to 10% by mass, preferably 0.05 to
5% by mass, particularly preferably 0.1 to 3% by mass based on 100%
by mass of the polishing slurry.
[0095] As the organic acid, may be used, for example, one or at
least two of quinolinic acid, quinolinecarboxylic acid, fumaric
acid, phthalic acid, malic acid, tartaric acid and citric acid. The
proportion thereof is 0.0001 to 7% by mass, preferably 0.001 to 5%
by mass, more preferably 0.01 to 1% by mass based on 100% by mass
of the polishing slurry.
[0096] The polishing slurry according to the present invention,
whose specific removal rate ratio (RBM/RCu) is controlled to 10 to
200, preferably 15 to 200, more preferably 20 to 200, is
particularly useful in the second polishing treatment step
performed for a surface to be polished after polishing is conducted
until the copper film is almost completely removed by the first
polishing treatment step, since the removal rate of the barrier
metal film is high, and the removal rate of the copper film is low
when this polishing slurry is used.
[0097] As a heterocyclic compound used for providing the polishing
slurry whose specific removal rate ratio (RBM/RCu) is 10 to 200,
are preferred the benzotriazoles among the above-mentioned
heterocyclic compounds. 1,2,3-Benzotriazole, carboxybenzotriazole,
1-(2',3'-dicarboxyethyl)benzot- riazole and
1-(2-ethylhexyl-aminomethyl)benzotriazole are more preferred, with
1,2,3-benzotriazole being particularly preferred. The proportion
contained is preferably 0.001 to 0.1% by mass, more preferably
0.005 to 0.05% by mass.
[0098] On the other hand, the polishing slurry according to the
present invention, whose specific removal rate ratio (RBM/RCu) is
controlled to 0.5 to 3, preferably 0.7 to 2, more preferably 0.8 to
1.5, is usefully used in the second polishing treatment step
performed for an article to be polished that the polishing of the
copper film is not complete in the first polishing treatment step,
or the second or third polishing treatment step in the 3-step
polishing treatment, since sufficient removal rate is achieved for
both copper film and barrier metal film.
[0099] As a heterocyclic compound used for providing the polishing
slurry whose specific removal rate ratio (RBM/RCu) is 0.5 to 3, are
preferred the quinolinecarboxylic acids and indolizines among the
above-mentioned heterocyclic compounds. Quinaldinic acid and
quinolinic acid and 7-hydroxy-5-methyl-1,3,4-triazaindolizine are
more preferred, with quinaldinic acid and
7-hydroxy-5-methyl-1,3,4-triazaindolizine being particularly
preferred. The proportion contained is preferably 0.001 to 5% by
mass, more preferably 0.01 to 1% by mass.
[0100] As described above, the polishing slurries according to the
present invention contain (A) simple particles composed of at least
one selected from inorganic particles and organic particles and (B)
composite particles as abrasive grains and may contain a suitable
heterocyclic compound for controlling the specific removal rate
ratio (RBM/RCu). Further, the polishing slurries according to the
present invention may contain additives such as an oxidizing agent,
a surfactant and an organic acid as needed.
[0101] The oxidizing agent is added for the purpose of improving
the removal rate. As the oxidizing agent, may be used, for example,
a persulfate, hydrogen peroxide, inorganic acid, organic peroxide,
polyvalent metal salt or the like.
[0102] As examples of the persulfate, may be mentioned ammonium
persulfate and potassium persulfate. As examples of the inorganic
acid, may be mentioned nitric acid and sulfuric acid. As examples
of the organic peroxide, may be mentioned peracetic acid,
perbenzoic acid and tert-butyl hydroperoxide.
[0103] As examples of the polyvalent metal salt, may be mentioned
permanganic acid compound and bichromic acid compounds. The
permanganic acid compound may include potassium permanganate, and
the bichromic acid compounds may include potassium bichromate.
[0104] Among these, hydrogen peroxide, persulfates and inorganic
acids are preferred as the oxidizing agent.
[0105] The proportion of the oxidizing agent contained may be
controlled to at most 10% by mass, preferably 0.01 to 10% by mass,
particularly 0.05 to 5% by mass, especially 0.1 to 3% by mass based
on 100% by mass of the polishing slurry. It is not necessary to
contain the oxidizing agent in a proportion exceeding 10% by
mass.
[0106] The surfactant is added for the purpose of controlling the
removal rate and reducing scratches, and any of a cationic
surfactant, an anionic surfactant and a nonionic surfactant may be
used. The anionic surfactant is particularly preferred.
[0107] As examples of such an anionic surfactant, may be mentioned
carboxylic acid salts, sulfonic acid salts, sulfate salts and
phosphate salts.
[0108] As examples of the carboxylic acid salts, may be mentioned
fatty acid soap and alkyl ether carboxylic acid salts. As examples
of the sulfonic acid salts, may be mentioned alkyl benzene sulfonic
acid salts, alkyl naphthalene sulfonic acid salts and
.alpha.-olefinsulfonic acid salts. As examples of the sulfate
salts, may be mentioned higher alcohol sulfate salts, alkyl ether
sulfate salts and polyoxyethylene alkyl phenyl ether sulfate salts.
As examples of the phosphate salts, may be mentioned alkyl
phosphate salts.
[0109] Among these anionic surfactants, sulfonic acid salts are
preferred, alkyl benzene sulfonic acid salts are more preferred,
with potassium dodecylbenzenesulfonate being particularly
preferred.
[0110] The proportion of the surfactant contained may preferably be
controlled to at most 5% by mass, more preferably at most 1% by
mass, particularly preferably at most 0.5% by mass based on the
100% by mass of the polishing slurry. If this content exceeds 5% by
mass, the removal rate of the copper film in particular is greatly
decreased. It is hence not preferable to contain the surfactant in
such a high proportion.
[0111] In the present invention, the organic acid is added for the
purpose of improving the removal rate. For this purpose, wide kinds
of organic acid, such as monobasic acids, dibasic acids, hydroxy
acids and carboxylate acids, may be used. For example, saturated
acids, unsaturated acids and aromatic acids may be mentioned.
[0112] As examples of the saturated acids, may be mentioned formic
acid, acetic acid, butyric acid, oxalic acid, malonic acid,
succinic acid, glutaric acid, adipic acid and hydroxy acids. As
examples of the unsaturated acid, may be mentioned maleic acid and
fumaric acid. As examples of the aromatic acids, may be mentioned
benzoic acid and phthalic acid. As examples of the hydroxy acids,
may be mentioned lactic acid, malic acid, tartaric acid and citric
acid.
[0113] Among these organic acids, malonic acid, succinic acid,
maleic acid, lactic acid and citric acid are preferred.
[0114] The proportion of the organic acid contained may be
controlled to at most 10% by mass, preferably 0.01 to 10% by mass,
particularly 0.1 to 5% by mass, especially 0.3 to 3% by mass based
on 100% by mass of the polishing slurry. It is not necessary to
contain the organic acid in a proportion exceeding 5% by mass.
[0115] The polishing slurries according to the present invention
are obtained by dispersing or dissolving the abrasive grains,
heterocyclic compound and additives described above in an aqueous
medium. As the aqueous medium, may be mentioned water, mixed medium
of water and alcohol, and the like. As examples of the alcohol, may
be mentioned methanol and ethanol. Among these media, water is
preferred as the aqueous medium.
[0116] The pH of the polishing slurries according to the present
invention may be controlled to a value of a suitable region within
a range of 2 to 12, with pH 3 to 11 being particularly preferred.
When the pH falls within this range, sufficient removal rate can be
realized, and occurrence of surface defects such as scratches can
be prevented even when a fragile dielectrics is polished.
[0117] The pH of the polishing slurry whose specific removal rate
ratio (RBM/RCu) is controlled to 10 to 200 is preferably 7 to 12,
more preferably 8 to 11 when the polishing slurry is used in the
second polishing treatment step performed for an article to be
polished that the copper film has been almost completely removed in
the first polishing treatment step of the 2-step polishing
treatment. When the pH falls within this range, the removal rate of
the barrier metal film becomes sufficient, and occurrence of
surface defects such as scratches can be prevented even when a
fragile dielectrics is polished.
[0118] The pH of the polishing slurry whose specific removal rate
ratio (RBM/RCu) is controlled to 0.5 to 3 is preferably 5 to 10,
more preferably 6 to 9 when the polishing slurry is used in the
second polishing treatment step performed for an article to be
polished that the copper film is not completely removed in the
first polishing treatment step of the 2-step polishing treatment,
or used in the second or third polishing treatment step of the
3-step polishing treatment. When the pH falls within this range,
both removal rates of the barrier metal film and copper film
becomes sufficient, and occurrence of surface defects such as
scratches can be prevented even when a fragile dielectrics is
polished.
[0119] The adjustment of the pH can be conducted by means that a
proper amount of the inorganic acid or organic acid described above
is added, and also by means that a suitable basic substance is
contained in a proper amount.
[0120] As examples of the basic substance, may be mentioned
hydroxides of alkali metals and ammonia. As the hydroxide of an
alkali metal, may be used sodium hydroxide, potassium hydroxide,
rubidium hydroxide or cesium hydroxide.
[0121] In order to perform a chemical mechanical polishing
treatment of a semiconductor substrate or the like with the
polishing slurry according to the present invention, it is only
necessary to use a commercially available chemical mechanical
polishing.apparatus, for example, "EPO-112" or "EPO-222"
manufactured by Ebara Corporation, "LGP-510" or Model "LGP-552"
manufactured by Lap Master SFT Corp., "Mirra" manufactured by
Applied Materials Inc., or the like to conduct the polishing
treatment under prescribed conditions.
[0122] After completion of the polishing treatment, the abrasive
grains remaining on the polished surface are preferably removed.
The removal of the abrasive grains can be conducted by an ordinary
cleaning method. For example, cleaning is conducted with an
alkaline washing solution containing ammonia, hydrogen peroxide and
water in a ratio of about 1:1:5 in terms of weight after
brush-scrubbing, whereby the abrasive grains adhered to the surface
to be polished can be removed.
[0123] In order to remove impurity metal species adsorbed on the
polished surface, cleaning may be conducted with a cleaning
solution composed of, for example, an aqueous solution of citric
acid, a mixed aqueous solution of hydrofluoric acid and citric acid
or a mixed aqueous solution of hydrofluoric acid and
ethylenediamine-tetraacetic acid (EDTA).
[0124] The polished surface may also be heated to a high
temperature in the presence of oxygen, thereby burning and removing
the organic particles on the polished surface. As examples of a
specific method of burning, may be mentioned an ashing treatment by
causing oxygen plasma to act or with plasma by supplying oxygen
radical by down flow. By this method, the organic particles
remaining on the polished surface can be easily removed.
[0125] According to the present invention, a semiconductor
substrate provided with a copper film and a barrier metal film and
also with an inter layer dielectrics of, for example, a low
dielectric constant is provided as an article to be polished, and
chemical mechanical polishing is performed for the intended surface
thereof to be polished with the aqueous dispersion for chemical
mechanical polishing, thereby producing a semiconductor device is
produced.
[0126] A copper film in the semiconductor substrate, which is an
article to be polished, is not limited to that composed of pure
copper and may be a film composed of a copper alloy having a copper
content of at least 95% by mass, such as copper-silicon or
copper-aluminum.
[0127] A barrier metal film is formed by a metal having high
hardness, such as tantalum or titanium, a nitride or oxide thereof,
or the like. The metal forming the barrier metal film is not
limited to a pure metal, and may be an alloy, for example,
tantalum-niobium. When the barrier metal film is formed by a
nitride, tantalum nitride, titanium nitride or the like is also not
necessarily a pure substance. The material of this barrier metal
film is particularly preferably tantalum and/or tantalum
nitride.
[0128] The barrier metal film is often formed by only one material
selected from tantalum or titanium and the like. However, films of
different materials, for example, both tantalum film and tantalum
nitride film may be formed on the same substrate as a barrier metal
film.
[0129] As examples of the inter layer dielectrics, may be mentioned
a SiO.sub.2 film, a boro phospho silicate film (BPSG film) in which
a small amount of boron and phosphorus is added to SiO.sub.2, a
dielectrics called FSG (fluorine-doped silicate glass) in which
fluorine is doped in SiO.sub.2 and a silicon oxide dielectrics of
low dielectric constant.
[0130] As examples of silicon oxide, may be mentioned a thermal
oxide film, a PETEOS film (plasma enhanced-TEOS film), an HDP film
(high density plasma enhanced-TEOS film) and a silicon oxide film
obtained by a thermal CVD process.
[0131] The thermal oxide film can be formed by exposing silicon
heated to a high temperature to an oxidative atmosphere to
chemically react the silicon with oxygen or water. The PETEOS film
can be formed by a chemical vapor phase epitaxy process using
tetraethyl orthosilicate (TEOS) as a raw material and utilizing
plasma as accelerating conditions. The HDP film can be formed by a
chemical vapor phase epitaxy process using tetraethyl orthosilicate
(TEOS) as a raw material and utilizing high density plasma as
accelerating conditions.
[0132] The silicon oxide film obtained by the thermal CVD process
can be obtained by an atmospheric pressure CVD process (AP-CVD
process) or low pressure CVD process (LP-CVD process). The boro
phospho silicate film (BPSG film) can be obtained by the
atmospheric pressure CVD process (AP-CVD process) or low pressure
CVD process (LP-CVD process). The dielectrics called FSG
(fluorine-doped silicate glass) can be formed by a chemical vapor
phase epitaxy process utilizing high density plasma as accelerating
conditions.
[0133] The silicon oxide dielectrics of low dielectric constant can
be obtained by applying a raw material on to a substrate by, for
example, a spin coating method and then heating it under an
oxidative atmosphere. As examples of the silicon oxide dielectrics
of low dielectric constant obtained in such a manner, may be
mentioned an HSQ film (hydrogen silsesquioxane film) using
triethoxysilane as a raw material, an MSQ film (methyl
silsesquioxane film) using tetraethoxysilane and a small amount of
methyltrimethoxysilane as raw materials, and dielectrics of low
dielectric constant using other silane compounds as raw materials.
As these dielectrics of low dielectric constant, dielectrics
obtained by mixing proper organic polymer particles with the raw
material and using the mixture, thereby burning out the polymer to
form voids in a heating step to make the dielectric constant lower
may also be used. Dielectrics of a low dielectric constant using an
organic polymer such as polyarylene polymer, polyallylene ether
polymer, polyimide polymer or benzocyclobutene polymer as a raw
material may also be mentioned.
EXAMPLES
[0134] The present invention will hereinafter be described in more
detail by the following Examples. All designations of "part" or
"parts" as will be used in the following examples mean part or
parts by mass unless expressly noted.
[0135] (1) Preparation of Aqueous Dispersion DA1 Containing
Inorganic Particles:
[0136] (1-1) Preparation of Aqueous Dispersion DA1 Containing Fumed
Silica Particles A1:
[0137] Fumed silica particles (product of Nippon Aerosil Co., Ltd.;
trade name "Aerosil #90"; average primary particle diameter: 20 nm)
in an amount of 2 kg were dispersed in 6.7 kg of ion-exchanged
water by means of an ultrasonic dispersing machine, and the
dispersion was filtered through a filter having a pore size of 5
.mu.m to prepare Aqueous Dispersion DA1 containing Fumed Silica
Particles Al. The average secondary particle diameter of the silica
particles in Aqueous Dispersion DA1 was 220 nm.
[0138] (1-2) Preparation of Aqueous Dispersion DA2 Containing
Colloidal Silica Particles A2:
[0139] A rotating type dispersing machine was charged with 70 parts
of aqueous ammonia having a concentration of 25% by mass, 40 parts
of ion-exchanged water, 35 parts of ethanol and 15 parts of
tetraethoxysilane, and the mixture was heated to 60.degree. C. with
stirring at 180 rpm. After the mixture was continuously stirred for
2 hours at this temperature, it was cooled to obtain an alcohol
dispersion of colloidal silica particles. A process of removing an
alcohol component by means of an evaporator while adding
ion-exchanged water at 80.degree. C. was repeated several times to
remove the alcohol component in the dispersion, thereby preparing
Aqueous Dispersion DA2 containing Colloidal Silica Particles A2 at
a solid concentration of 8% by mass. The average primary particle
diameter of Colloidal Silica Particles A2 in Aqueous Dispersion DA2
was 30 nm, while the average secondary particle diameter was 45
nm.
[0140] (2) Preparation of Aqueous Dispersion Containing Composite
Particles B:
[0141] (2-1) Preparation of Aqueous Dispersion Db1 Containing
Organic Particles:
[0142] A flask was charged with 90 parts of methyl methacrylate, 5
parts of methoxypolyethylene glycol methacrylate (product of
Shin-Nakamura Chemical Co., Ltd.; trade name "NK Ester M-90G",
#400), 5 parts of 4-vinylpyridine, 2 parts of an azo type
polymerization initiator (product of Wako Pure Chemicals
Industries, Ltd.; trade name "V50") and 400 parts of ion-exchanged
water, and the mixture was heated to 70.degree. C. with stirring
under a nitrogen gas atmosphere to conduct polymerization for 6
hours, thereby obtaining an aqueous dispersion containing organic
particles having an average particle diameter of 150 nm composed of
a polymethyl methacrylate polymer having a cation of an amino group
and a polyethylene glycol chain as functional groups. This aqueous
dispersion was diluted with water, thereby obtaining an aqueous
dispersion the organic particle content in which was adjusted to
10% by mass. The yield of the polymerization was 95%.
[0143] A flask was charged with 100 parts of the thus-obtained
aqueous dispersion containing the organic particles in a proportion
of 10% by mass and, 1 part of methyltrimethoxysilane was added, the
mixture was stirred at 40.degree. C. for 2 hours, and nitric acid
was then added to adjust the pH thereof to 2, thereby obtaining
Aqueous Dispersion Db1. The zeta potential of the organic particles
contained in Aqueous Dispersion Db1 was +17 mV.
[0144] (2-2) Preparation of Aqueous Dispersion Db2 Containing
Inorganic Particles:
[0145] Colloidal silica dispersion (product of Nissan Chemical
Industries, Ltd.; trade name "Snowtex O", average primary particle
diameter: 12 nm) was dispersed in water, and an aqueous solution of
potassium hydroxide was added to the dispersion to adjust a pH of
the dispersion,. thereby obtaining Aqueous Dispersion Db2 having a
pH of 8 and containing 10% by mass of inorganic particles composed
of colloidal silica. The zeta potential of the silica particles
contained in Aqueous Dispersion Db2 was -40 mV.
[0146] (2-3) Preparation of Composite Particles B:
[0147] While stirring 100 parts of Aqueous Dispersion Db1, 50 parts
of Aqueous Dispersion Db2 were gradually added thereto over 2
hours, and the resultant mixture was additionally stirred for 2
hours to obtain Aqueous Dispersion Db containing Composite
Particles B with the inorganic particles composed of silica bonded
to the surfaces of the organic particles composed of the polymethyl
methacrylate polymer. To Aqueous Dispersion Db, were added 2 parts
of vinyltriethoxysilane, and the mixture was stirred for 1 hour.
Thereafter, 1 part of tetraethoxysilane was added, and the mixture
was heated to 60.degree. C., continuously stirred for 3 hours and
then cooled, thereby obtaining Aqueous Dispersion DB containing
Composite Particle B having an average particle diameter of 180 nm
in a proportion of 10% by mass. Composite Particles B were such
that the silica particles adhered to the outer surfaces of the
polymethyl methacrylate polymer particles so as to cover 80% of the
surface area thereof.
[0148] (3) Production of Dielectrics of Low Dielectric
Constant:
[0149] (3-1) Preparation of Polysiloxane Sol:
[0150] A mixed solution composed of 101.5 g of
methyltrimethoxysilane, 276.8 g of methyl methoxypropionate and 9.7
g of tetraisopropoxytitanium/- ethyl acetoacetate complex was
heated to 60.degree. C., and a mixture of 92.2 g of
.gamma.-butyrolactone and 20.1 g of water was added dropwise to
this mixed solution over 1 hour. After completion of the addition,
a reaction was conducted at 60.degree. C. for 1 hour to obtain
polysiloxane sol.
[0151] (3-2) Production of Polystyrene Particles:
[0152] A flask was charged with 100 parts of styrene, 2 parts of an
azo type polymerization initiator (product of Wako Pure Chemicals
Industries, Ltd.; trade name "V60"), 0.5 parts of potassium
dodecylbenzenesulfonate and 400 parts of ion-exchanged water, and
the mixture was heated to 70.degree. C. under the nitrogen
atmosphere with stirring to conduct polymerization for 6 hours,
thereby obtaining polystyrene particles having an average particle
diameter of 150 nm.
[0153] (3-3) Production of Dielectrics of Low Dielectric
Constant:
[0154] Fifteen grams of the polysiloxane sol obtained in the step
(3-1) were mixed with 1 g of the polystyrene particles obtained in
the step (3-2), and the resultant mixture was coated on to a
thermal oxide film-coated silicon substrate having a diameter of 8
inch by a spin coating method to form a coating film. Thereafter,
the substrate was heated at 80.degree. C. for 5 minutes and then at
200.degree. C. for 5 minutes in an oven. The substrate was then
heated at 340.degree. C. for 30 minutes, at 360.degree. C. for 30
minutes, at 380.degree. C. for 30 minutes and additionally at
450.degree. C. for 1 hour under reduced pressure, thereby forming a
colorless transparent film having a thickness of 2,000 .ANG..
[0155] The section of this film was observed through a scanning
electron microscope. As a result, it was confirmed that a great
number of fine voids are formed. The relative dielectric constant,
modulus of elasticity and voids thereof were 1.98, 3 GPa and 15%,
respectively.
Example 1
[0156] [Preparation of Polishing Slurry]
[0157] A polyethylene-made bottle was charged 2 parts by mass, in
terms of solids, of Aqueous Dispersion A1 containing the fumed
silica particles prepared in the step (1-1) and 0.5 parts by mass,
in terms of solids, of Aqueous Dispersion B containing the
composite particles prepared in the step (2), 0.02 parts by mass of
1,2,3-benzotriazole (BTA), 1 part by mass of maleic acid, 0.05
parts by mass of potassium dodecylbenzenesulfonate (PDBS) and 1
part by mass of hydrogen peroxide were successively contained, and
the resultant mixture was stirred for 15 minutes. The pH of the
mixture was adjusted to 9 with potassium hydroxide, ion-exchanged
water was added in such a manner that the total mass of all the
components is 100 parts by mass, and the thus-adjusted mixture was
filtered through a filter having a pore size of 5 .mu.m to obtain a
polishing slurry having a pH of 9.5. This slurry is called "Slurry
1".
[0158] [Evaluation of Removal Rate]
[0159] Slurry 1 prepared above was used, and a wafer having various
kinds of films was placed on a chemical mechanical polishing
apparatus (CMP apparatus, Model "EPO112", manufactured by Ebara
Corporation) to perform polishing for 1 minute by means of a
polishing pad (product of Rodel Nitta, Ltd.; trade name "IC1000")
made of porous polyurethane under the following conditions to
evaluate a removal rate.
[0160] Head rotating speed: 70 rpm
[0161] Head load: 250 g/cm.sup.2
[0162] Table rotating speed: 70 rpm
[0163] Polishing slurry-feeding rate: 300 ml/min
[0164] Articles to be polished for evaluation are the following
wafers.
[0165] (1) Wafer Sample 1 for evaluating removal rate on copper
film:
[0166] A wafer obtained by forming a copper film having a thickness
of 15,000 .ANG. on a silicon substrate 8-inch in diameter having a
thermal oxide film.
[0167] (2) Wafer Sample 2 for evaluating removal rate on barrier
metal film:
[0168] A wafer obtained by forming a tantalum nitride film having a
thickness of 1,500 .ANG. on a silicon substrate 8-inch in diameter
having a thermal oxide film.
[0169] (3) Wafer Sample 3 for evaluating removal rate on
dielectrics:
[0170] A wafer obtained by forming a plasma TEOS film having a
thickness of 10,000 .ANG. on a silicon substrate 8-inch in
diameter.
[0171] (4) Wafer Sample 4 for evaluating removal rate on
dielectrics of low dielectric constant:
[0172] The thermal oxide film-coated silicon substrate 8 inch in
diameter produced in the step (3-3), on which a dielectrics of law
dielectric constant having a thickness of 2,000 .ANG. was
formed.
[0173] The film thickness after the polishing treatment was
measured in accordance with the following method to calculate out
the removal rate. The results are shown in Table 1. More
specifically, the thickness of the copper film and tantalum nitride
film were measured by means of an electroconduction type film
thickness meter (manufactured by KLA-Tencor Co., model "OMNIMAP
RS75") . The thickness of the TEOS film and dielectrics of low
dielectric constant were measured by means of a light interference
type film meter (manufacture by SENTEC Co., model "FPT500").
[0174] [Evaluation]
[0175] Peeling of an outer peripheral portion of the dielectrics of
low dielectric constant and the number of scratches after the
polishing treatment were evaluated. More specifically, after a
dielectrics of low dielectric constant was formed on a silicon
substrate in the same manner as in the step (3-3), and this
substrate was polished under the same conditions as described
above, it was cleaned and dried, and separation at the outer
peripheral portion was then observed visually and through an
optical microscope.
[0176] The whole surface of the polished surface was observed
visually, through an optical microscope and by a pattern-free wafer
surface dust particle inspection apparatus (manufactured by
KLA-Tencor Co., model "Surfscann SP1") to evaluate the number of
scratches.
[0177] The results are shown in Table 1.
Examples 2 to 5, and Comparative Examples 1 and 2
[0178] Six polishing slurries "Slurry 2" to "Slurry 7" were
evaluated as to polishing performance in the same manner as in
Example 1 except that the polishing slurries were prepared by
changing the abrasive grains, other additives and pH in accordance
with their corresponding formulations shown in Table 1, and used
respectively. The results are shown in Table 1.
[0179] In Table 1, "BTA" in the line of Heterocyclic compound means
1,2,3-benzotriazole, and "HMT" means
7-hydroxy-5-methyl-1,3,4-triazaindol- izine. "PDBS" in the line of
Surfactant means potassium dodecylbenzenesulfonate.
1 TABLE 1 Compara- Compara- tive tive Example 1 Example 2 Example 3
Example 4 Example 5 Example 1 Example 2 Aqueous dispersion for
Slurry 1 Slurry 2 Slurry 3 Slurry 4 Slurry 5 Slurry 6 Slurry 7
polishing Abra- Parti- Kind Fumed Colloidal Colloidal Fumed Fumed
Fumed Colloidal sive cles silica silica silica silica silica silica
silica grains (1) A1 A2 A2 A1 A1 A1 A2 Contained 2.0 2.0 2.0 1.0
4.0 3.0 2.0 proportion (part) Parti- Kind Composite Composite
Composite Composite Composite None None cles parti- parti- parti-
parti- parti- (2) cles B cles B cles B cles B cles B Contained 0.5
0.5 0.5 1.0 1.0 -- -- proportion (part) Heterocyclic Kind BTA BTA
HMT Quinal- BTA BTA BTA compound dinic acid Contained 0.02 0.02 0.1
0.2 0.05 0.02 0.02 proportion (part) Organic Kind Maleic Succinic
Maleic Succinic Maleic Maleic Maleic acid acid acid acid acid acid
acid acid Contained 1.0 1.0 1.0 1.5 1.0 1.0 1.0 proportion (part)
Surfactant Kind PDBS PDBS PDBS PDBS None PDBS PDBS Contained 0.05
0.05 0.05 0.05 -- 0.05 0.05 proportion (part) Oxidising Kind
Hydrogen Hydrogen Hydrogen Hydrogen Hydrogen Hydrogen Hydrogen
agnet peroxide peroxide peroxide peroxide peroxide peroxide
peroxide Contained 1.0 1.0 1.0 1.0 1.0 1.0 1.0 proportion (part) pH
9.5 9.4 7.5 7.2 9.5 9.5 9.5 Removing Copper 60 55 600 850 2 70 55
rate film (.ANG./min) Tantalum 1100 1300 920 800 1200 1150 1250
nitride TEOS film 20 50 50 60 850 50 40 Dielectrics 15 40 15 30 450
40 35 of low dielectric constant Removing rate ratio 18.3 23.6 1.5
0.9 60.0 16.4 22.7 (RBM/Rcu) Condition of Peeling of None None None
None None Occured Occured dialectrics of an outer at some at some
low dialectric peripheral part part constant after portion
polishing Number of 1 0 0 1 2 10 or 10 or scratches more more
[0180] It is understood from the results shown in Table 1 that
according to the polishing slurries of Comparative Examples 1 and 2
containing only the inorganic particles as the abrasive grains, the
number of scratches on the surface of the dielectrics of low
dielectric constant is increased, and peeling partially occurs
though the removal rate of the barrier metal film is high.
[0181] On the other hand, it is understood that according to the
polishing slurries of Examples 1 to 5 containing both composite
particles and inorganic particles, sufficiently high removal rate
as to the barrier metal film is achieved, the removal rate ratio of
the copper film to the barrier metal can be optionally controlled
by changing the kind and amount of the heterocyclic compound added,
and scratches on the surface of the dielectrics of low dielectric
constant are not caused at all or extremely little.
Examples 6 to 10
[0182] In these examples, a 2-step polishing treatment was
performed.
[0183] [Preparation of Polishing Slurry]
[0184] (1) Preparation of Slurry 8.
[0185] A polishing slurry (Slurry 8) containing 1 part of fumed
silica, 1 part of quinolinic acid, 0.7 parts of oxalic acid, 0.05
parts of potassium dodecylbenzene-sulfonate and 1 part of hydrogen
peroxide per 100 parts of the polishing slurry and adjusted to pH 9
with potassium hydroxide was prepared in a similar manner to
Example 1.
[0186] (2) Preparation of Slurry 9.
[0187] A polishing slurry (Slurry 9) containing 1 part of fumed
silica, 0.5 parts of quinaldinic acid, 0.05 parts of potassium
dodecylbenzene-sulfonate and 1 part of ammonium persulfate per 100
parts of the polishing slurry and adjusted to pH 9.5 with potassium
hydroxide was prepared in a similar manner to Example 1.
[0188] A patterned substrate (831CMP001 substrate, product of
International SEMATECH) was used as a sample for evaluation, and
this substrate was subjected to a polishing treatment under the
following conditions to measure the sizes of dishing at a copper
wiring portion of a line width of 100 .mu.m and erosion at an
alternate wiring site, in which a copper wiring 4.5 .mu.m wide and
a dielectrics portion 0.5 .mu.m wide are alternately formed, by
means of a probe type step height meter (HRP240 manufactured by
KLA-Tencor Co.)
[0189] [Polishing Treatment]
[0190] (1) First Polishing Treatment Step:
[0191] The same polishing apparatus and polishing pad as those used
in Example 1 were used. In a treatment using Slurry 8, the
polishing treatment was performed under the conditions that head
rotating speed of 100 rpm, head load of 105 g/cm.sup.2, table
rotating speed of 100 rpm, polishing slurry-feeding rate of 300
ml/min, and polishing time of 192 seconds.
[0192] Dishing at the copper wiring portion of a line width of 100
.mu.m was 750 .ANG., and erosion at the alternate wiring site was
380 .ANG..
[0193] In a treatment using Slurry 9, the polishing treatment was
performed under the conditions, that head rotating speed of 100
rpm, head load of 250 g/cm.sup.2, table rotating speed of 100 rpm,
polishing slurry-feeding rate of 300 ml/min and polishing time of
165 seconds. Dishing at the copper wiring portion of a line width
of 100 .mu.m was 300 .ANG., and erosion at the alternate wiring
site was 390 .ANG..
[0194] (2) Second Polishing Treatment Step:
[0195] The same polishing apparatus and polishing pad as those used
in Example 1 were used. Slurry 1 to Slurry 5 were respectively used
to conduct the polishing treatment under the conditions that head
rotating speed of 70 rpm, head load of 250 g/cm.sup.2, table
rotating speed of 70 rpm, polishing slurry-feeding rate of 300
ml/min and polishing time of 45 or 60 seconds.
[0196] The results are shown in Table 2.
2 TABLE 2 Example 6 Example 7 Example 8 Example 9 Example 10 First
Slurry Slurry 8 Slurry 8 Slurry 9 Slurry 9 Slurry 9 polishing
Polishing 192 192 165 165 165 treatment time step (sec) Second
Slurry Slurry 1 Slurry 2 Slurry 3 Slurry 4 Slurry 5 polishing
Polishing 45 45 60 60 60 treatment time step (sec) Dishing (.ANG.)
450 480 205 200 280 Erosion (.ANG.) 200 210 250 215 190
[0197] [Effects of the Invention]
[0198] According to the aqueous dispersions for chemical mechanical
polishing of the present invention, occurrence of scratches in a
polished surface is greatly prevented. even when it is used in a
polishing treatment of an article to be polished composed of a
semiconductor substrate having an inter layer dielectrics low in
mechanical strength and dielectric constant, a ratio of the removal
rate of a copper film to the removal rate of a barrier metal film
can be easily controlled with a great degree of freedom to polish
both copper film and barrier metal film with high efficiency, and a
sufficiently planarized finished surface with high precision can be
provided without overpolishing the dielectrics.
[0199] According to the production process of a semiconductor
device of the present invention, occurrence of scratches in a
polished surface in a polishing treatment is greatly prevented even
in a semiconductor substrate having an inter layer dielectrics low
in mechanical strength and dielectric constant, both copper film
and barrier metal film can be polished with high efficiency, and a
sufficiently planarized finished surface with high precision can be
provided without overpolishing the dielectrics.
* * * * *