U.S. patent application number 10/429774 was filed with the patent office on 2004-01-01 for polishing apparatus, polishing method and method of manufacturing semiconductor device.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Fukushima, Dai, Kurashima, Nobuyuki, Minamihaba, Gaku, Tateyama, Yoshikuni, Yano, Hiroyuki.
Application Number | 20040002292 10/429774 |
Document ID | / |
Family ID | 29774334 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040002292 |
Kind Code |
A1 |
Fukushima, Dai ; et
al. |
January 1, 2004 |
Polishing apparatus, polishing method and method of manufacturing
semiconductor device
Abstract
There is disclosed a polishing method which comprises
positioning a treating substrate held by a substrate holder over a
turntable so as to enable the treating substrate to press-contact
with a polishing region of a polishing surface of the turntable,
the polishing surface having the polishing region where the
treating substrate moves relative thereto, and a non-polishing
region surrounded by the polishing region, introducing a first
liquid and a second liquid into a slurry mixing section disposed at
the non-polishing region of the polishing surface, at least one of
the first and second liquids containing an abrasive component, and
applying a mixed slurry comprising the first and second liquids
which have been mixed together in advance in the slurry mixing
section to the polishing surface while rotating the turntable to
enable the treating substrate to move relative to the polishing
region, thereby polishing the treating substrate.
Inventors: |
Fukushima, Dai;
(Sagamihara-shi, JP) ; Yano, Hiroyuki;
(Yokohama-shi, JP) ; Kurashima, Nobuyuki;
(Yokohama-shi, JP) ; Minamihaba, Gaku;
(Kawasaki-shi, JP) ; Tateyama, Yoshikuni;
(Hiratsuka-shi, JP) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
|
Family ID: |
29774334 |
Appl. No.: |
10/429774 |
Filed: |
May 6, 2003 |
Current U.S.
Class: |
451/41 ;
257/E21.304; 451/285; 451/5 |
Current CPC
Class: |
B24B 57/02 20130101;
H01L 21/3212 20130101; B24B 37/04 20130101; C09G 1/02 20130101 |
Class at
Publication: |
451/41 ; 451/285;
451/5 |
International
Class: |
B24B 049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2002 |
JP |
2002-190659 |
Claims
What is claimed is:
1. A polishing apparatus comprising: a turntable having a polishing
region where a treating substrate moves relative thereto, and a
non-polishing region surrounded by said polishing region; a
substrate holder holding said substrate, thereby enabling said
substrate to press-contact with a polishing surface located within
said polishing region; a first supply pipe feeding a first liquid;
a second supply pipe feeding a second liquid; and a slurry mixing
vessel disposed above said turntable within said non-polishing
region and away from the tip ends of said first supply pipe and
said second supply pipe, said slurry mixing vessel storing and
mixing said first and second liquids to obtain a mixed slurry and
to feed said mixed slurry onto said polishing surface.
2. The polishing apparatus according to claim 1, wherein said
slurry mixing vessel is secured to said turntable through a
polishing cloth adhered to said turntable.
3. A polishing method comprising: positioning a treating substrate
held by a substrate holder over a turntable so as to enable said
treating substrate to press-contact with a polishing region of a
polishing surface of said turntable, said polishing surface having
said polishing region where said treating substrate moves relative
thereto, and a non-polishing region surrounded by said polishing
region; introducing a first liquid and a second liquid into a
slurry mixing section disposed at said non-polishing region of said
polishing surface, at least one of said first and second liquids
containing an abrasive component; and applying a mixed slurry
comprising said first and second liquids which have been mixed
together in advance in said slurry mixing section to said polishing
surface while rotating said turntable to enable said treating
substrate to move relative to said polishing region, thereby
polishing said treating substrate.
4. The polishing method according to claim 3, wherein said mixed
slurry comprising a mixture of said first and second liquids
overflows from said slurry mixing section, thereby feeding said
mixed slurry onto said polishing surface.
5. The polishing method according to claim 3, wherein said slurry
mixing section is a slurry mixing vessel fixed in place to a
polishing cloth adhered to said turntable.
6. The polishing method according to claim 3, wherein said slurry
mixing section is a recessed portion formed in a polishing cloth
adhered to said turntable.
7. The polishing method according to claim 3, wherein said first
liquid comprises abrasive grains and water; while said second
liquid comprises an oxidizing agent and water.
8. The polishing method according to claim 3, wherein said first
liquid comprises abrasive grains and water; while said second
liquid is water diluting said first liquid.
9. The polishing method according to claim 3, wherein said first
liquid and said second liquid are a combination of two liquids
selected from the group consisting of an abrasive grain-containing
dispersion liquid, a solution of an oxidizing agent, and a solution
of a catalyst.
10. The polishing method according to claim 3, wherein said first
liquid comprises abrasive grains and water; while said second
liquid comprises a surfactant and water.
11. A method for manufacturing a semiconductor device comprising:
forming an insulating film above a surface of a semiconductor
substrate; forming a recessed portion in said insulating film;
depositing a conductive material in said recessed portion as well
as above said insulating film, to form a conductive layer; and
removing the portion of said conductive material that has been
deposited above said insulating film outside said recessed portion
to leave said conductive material in said recessed portion; wherein
at least part of said conductive material deposited above said
insulating film is removed by: positioning said semiconductor
substrate held by a substrate holder over a turntable so as to
enable said semiconductor substrate to press-contact with a
polishing region of a polishing surface of said turntable, said
polishing surface having said polishing region where said
semiconductor substrate moves relative thereto, and a non-polishing
region surrounded by said polishing region; introducing a first
liquid and a second liquid into a slurry mixing section disposed at
said non-polishing region of said polishing surface, at least one
of said first and second liquids containing an abrasive component;
and applying a mixed slurry comprising said first and second
liquids which has been mixed together in advance in said slurry
mixing section to said polishing surface while rotating said
turntable to enable said semiconductor substrate to move relative
to said polishing region, thereby polishing said conductive
material.
12. The method according to claim 11, wherein said mixed slurry
comprising a mixture of said first and second liquids overflows
from said slurry mixing section, thereby feeding said mixed slurry
onto said polishing surface.
13. The method according to claim 11, wherein said slurry mixing
section is a slurry mixing vessel fixed in place to a polishing
cloth adhered to said turntable.
14. The method according to claim 11, wherein said slurry mixing
section is a recessed portion formed in a polishing cloth adhered
to said turntable.
15. The method according to claim 11, wherein said conductive
material comprises a Cu layer disposed through a liner layer.
16. The method according to claim 15, wherein said first liquid
comprises abrasive grains and water; while said second liquid
comprises an oxidizing agent and water.
17. The method according to claim 11, wherein said conductive
material comprises W.
18. The method according to claim 17, wherein said first liquid and
said second liquid are a combination of two liquids selected from
the group consisting of an abrasive grain-containing dispersion
liquid, a solution of an oxidizing agent, and a solution of a
catalyst.
19. The method according to claim 11, wherein said conductive
material comprises Ru or a Ru compound.
20. The method according to claim 19, wherein said first liquid is
an aqueous solution containing a high concentration of a cerium
compound (IV); while said second liquid is water for diluting said
aqueous solution.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2002-190659, filed Jun. 28, 2002, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a polishing apparatus,
polishing method, and to a method of manufacturing a semiconductor
device. In particular, the present invention relates to a polishing
technique employed in forming a damascene wiring of Cu, W, Al,
etc., which is designed to be mounted on a DRAM or a high-speed
logic LSI, or for planarizing an insulating film.
[0004] 2. Description of the Related Art
[0005] In recent years, in order to meet the sophistication in the
manufacture of semiconductor elements or to meet an increased
refinement of semiconductor elements, novel manufacturing
apparatuses are now being developed. Among them, a CMP (Chemical
Mechanical Polishing) apparatus is one of the apparatuses
indispensable in the fabrication of an buried structure such as
buried metal wirings, buried element isolations, etc.
[0006] Meanwhile, in a process employing this CMP apparatus, one of
the main goals is to enhance the polishing speed, to promote the
throughput of polishing. Generally, for polish a metal such as Cu,
a slurry containing an oxidizing agent is employed to denature the
polishing surface into an oxide surface which can be easily
polished, thus enhancing the polishing speed of the metal. However,
the oxidizing agent in a slurry is subject to decomposition or
reaction due to the changes in natures thereof with time, and may
give rise to coalescence or dissolution of abrasive grains. In this
case, various problems such as deterioration of polishing speed and
increase in number of scratches may be caused.
[0007] With a view to avoid the aforementioned problems accompanied
with the employment of an oxidizing agent, a method has been tried
in which a slurry containing the oxidizing agent is kept separately
from a slurry containing abrasive grains, until these two slurries
need to be mixed together, immediately before using them for
polishing. Usually, in two-part supply systems, two slurries kept
separately are mixed together immediately before they are fed
drop-wise, as a single liquid, onto a polishing surface. For
example, two slurries are fed to a polishing surface by a specific
supply system, such as a T-shaped supply or F-shaped. However, a
polishing apparatus employing any of these supply systems has a
drawback in that since the flow rate of slurries, as well as the
length of pipeline are restricted, it is difficult to sufficiently
uniformly mix together two slurries, especially when an additive
which cannot mix with these slurries, such as a nonionic surfactant
or a high-hydrophobicity oxidation inhibitor, is present.
[0008] As mentioned above, even though it may be meaningful to keep
a slurry containing an oxidizing agent by separating it into a
two-part supply system in order to avoid the deterioration of
stability thereof, it may be difficult to derive the inherent
characteristics of the slurry in a stable manner unless two
chemical liquids constituting the two-part system are uniformly
mixed on the occasion of using them for polishing a substrate to be
polished (i.e. polishing substrate).
[0009] In view of the stability of slurry, the chemical liquids
which are separately stored should preferably be mixed together as
close to the time of use as possible. Further, in order to make it
possible to use a slurry immediately after the mixing thereof, the
provision of an auxiliary supply facility for mixing is not
appropriate.
BRIEF SUMMARY OF THE INVENTION
[0010] A polishing apparatus according to one embodiment of the
present invention comprises:
[0011] a turntable having a polishing region where a treating
substrate moves relative thereto, and a non-polishing region
surrounded by the polishing region;
[0012] a substrate holder holding the substrate, thereby enabling
the substrate to press-contact with a polishing surface located
within the polishing region;
[0013] a first supply pipe feeding a first liquid;
[0014] a second supply pipe feeding a second liquid; and
[0015] a slurry mixing vessel disposed above the turntable within
the non-polishing region and away from the tip ends of the first
supply pipe and the second supply pipe, the slurry mixing vessel
storing and mixing the first and second liquids to obtain a mixed
slurry and to feed the mixed slurry onto the polishing surface.
[0016] A polishing method according to one embodiment of the
present invention comprises:
[0017] positioning a treating substrate held by a substrate holder
over a turntable so as to enable the treating substrate to
press-contact with a polishing region of a polishing surface of the
turntable, the polishing surface having the polishing region where
the treating substrate moves relative thereto, and a non-polishing
region surrounded by the polishing region;
[0018] introducing a first liquid and a second liquid into a slurry
mixing section disposed at the non-polishing region of the
polishing surface, at least one of the first and second liquids
containing an abrasive component; and
[0019] applying a mixed slurry comprising the first and second
liquids which have been mixed together in advance in the slurry
mixing section to the polishing surface while rotating the
turntable to enable the treating substrate to move relative to the
polishing region, thereby polishing the treating substrate.
[0020] A method for manufacturing a semiconductor device according
to one embodiment of the present invention comprises:
[0021] forming an insulating film above a surface of a
semiconductor substrate;
[0022] forming a recessed portion in the insulating film;
[0023] depositing a conductive material in the recessed portion as
well as above the insulating film, to form a conductive layer;
and
[0024] removing the portion of the conductive material that has
been deposited above the insulating film outside the recessed
portion to leave the conductive material in the recessed
portion;
[0025] wherein at least part of the conductive material deposited
above the insulating film is removed by:
[0026] positioning the semiconductor substrate held by a substrate
holder over a turntable so as to enable the semiconductor substrate
to press-contact with a polishing region of a polishing surface of
the turntable, the polishing surface having the polishing region
where the semiconductor substrate moves relative thereto, and a
non-polishing region surrounded by the polishing region;
[0027] introducing a first liquid and a second liquid into a slurry
mixing section disposed at the non-polishing region of the
polishing surface, at least one of the first and second liquids
containing an abrasive component; and
[0028] applying a mixed slurry comprising the first and second
liquids which has been mixed together in advance in the slurry
mixing section to the polishing surface while rotating the
turntable to enable the semiconductor substrate to move relative to
the polishing region, thereby polishing the conductive
material.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0029] FIG. 1 is a schematic diagram illustrating the construction
of polishing apparatus according to one embodiment of the present
invention;
[0030] FIGS. 2A to 2C are cross-sectional views each illustrating
the manufacturing process of semiconductor device according to
another embodiment of the present invention;
[0031] FIG. 3 is a graph illustrating the dependency of the
polishing rate of Cu on the number of wafers;
[0032] FIG. 4 is a schematic diagram illustrating the construction
of polishing apparatus according to the prior art;
[0033] FIG. 5 is a schematic diagram illustrating the construction
of polishing apparatus according to the prior art; and
[0034] FIG. 6 is a schematic diagram illustrating the construction
of polishing apparatus employed in a third embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] Next, embodiments according to the present invention will be
explained in detail with reference to drawings.
[0036] FIG. 1 is a schematic diagram illustrating the construction
of polishing apparatus according to one embodiment of the present
invention. As shown in FIG. 1, a turntable 11 has a polishing cloth
13 adhered on the upper surface thereof and is designed to be
revolved horizontally about the central axis 12 thereof in the
direction indicated by an arrow. The revolving speed of the
turntable on this occasion may be within the range of about 30 to
150 rpm. Over the top surface of the turntable 11, there is
disposed a top ring 14 serving as a substrate holder for holding a
semiconductor wafer 16. This top ring 14 is designed to be revolved
horizontally about the central axis 15 thereof in the same
direction as that of the turntable 11. This top ring 14 is enabled
to revolve at a revolving speed of about 30 to 150 rpm. During the
revolution of this top ring 14, a semiconductor wafer 16 held by
the top ring 14 is pressed against the polishing cloth 13 at a
polishing load of 50 to 700 g/cm.sup.2, thereby polishing the
semiconductor wafer 16.
[0037] More specifically, as the turntable 11 is revolves, the
semiconductor wafer 16 held by the top ring 14 is moves along a
circular orbit over the polishing cloth 13 and relative to the
polishing cloth 13, thereby polishing the semiconductor wafer 16. A
region of the polishing cloth 13 which is located on the inner
peripheral side of this circular orbit may be considered as a
non-polishing region, which has nothing to do with the polishing of
the semiconductor wafer 16.
[0038] In this non-polishing region, there is disposed a slurry
mixing vessel 17 functioning as a slurry mixing section in which a
first liquid 20 and a second liquid 21 can be stored and mixed with
each other to create a mixed slurry which is subsequently fed onto
the polishing cloth 13. The first liquid 20 may be a chemical
dispersion liquid containing abrasive grains for example, while the
second liquid 21 may be a chemical liquid containing an oxidizing
agent for example. This first liquid 20 can be stored in a first
storage tank 18 and then fed through a pump 22 and a first supply
pipe 24 to the slurry mixing vessel 17. On the other hand, the
second liquid 21 can be stored in a second storage tank 19 and then
fed through a pump 23 and a second supply pipe 25 to the slurry
mixing vessel 17. These two kinds of liquid may be introduced
respectively into the slurry mixing vessel 17 at a flow rate of 50
to 500 mL/min for example. If desired, it is also possible to
provide the aforementioned slurry-feeding system with a third
storage tank for storing a third liquid containing other kinds of
components, with a pump for feeding this third liquid and with a
third supply pipe.
[0039] The first liquid 20 and the second liquid 21 that have been
introduced into the slurry mixing vessel 17 are sufficiently
uniformly mixed together through the effects of the supply pressure
and convection of these liquids, as well as through the effect of
rotation of the turntable, before these liquids are finally applied
to the surface of the polishing cloth 13 through the overflow
thereof.
[0040] Accordingly, the size of the slurry mixing vessel 17 should
such that it is large enough to accommodate the two kinds of liquid
fed thereto, and to carry out mixing of them, but small enough to
be placed within the non-polishing region of the polishing cloth
13. For example, the size in the lateral direction of the slurry
mixing vessel 17 may be within the range of 10 mm to 60 mm. If the
slurry mixing vessel 17 is too small, it may become difficult to
accommodate the two liquids being fed thereto and to carry out
sufficient mixing of them. On the other hand, if the slurry mixing
vessel 17 is too large, it may become impossible to install the
slurry mixing vessel 17 within the non-polishing region of the
polishing cloth 13. Thus, if the size of the slurry mixing vessel
17 is not suitably selected, the fundamental function of the
polishing apparatus to polish a wafer may be severely compromised.
Further, the height of the slurry mixing vessel 17 should
preferably be within the range of 1 mm to 40 mm. If the height of
the slurry mixing vessel 17 is too low, it may become difficult to
accommodate the two liquids being fed thereto and to sufficiently
carry out the mixing of them. On the other hand, if the height of
the slurry mixing vessel 17 is too high, an excess amount of
abrasive grains may remain in the slurry mixing vessel 17, or the
slurry mixing vessel 17 may interfere with the first supply pipe 24
or with the second supply pipe 25. In view of these problems, the
height of the slurry mixing vessel 17 should be determined in such
a way that the brim of the slurry mixing vessel 17 be positioned
lower than and spaced away from the tip end of the supply pipes 24
and 25, while taking the capacity of the slurry mixing vessel 17
into consideration.
[0041] In order to perform uniform mixing of these two kinds of
liquid supplied, and to enable the resultant mixture to overflow
onto the polishing cloth 13, the slurry mixing vessel 17 is
preferably cylindrical. Of course, there is no particular
limitation with regard to the configuration of the slurry mixing
vessel 17.
[0042] The slurry mixing vessel 17 may be manufactured from a
plastic material for example. On the occasion of positioning the
slurry mixing vessel 17 at the non-polishing region of the
polishing cloth 13, the slurry mixing vessel 17 can be secured to
the surface of the polishing cloth 13 by using a double-sided
adhesive tape or screws. If screws are used for the positioning of
the slurry mixing vessel 17, the positioning of the slurry mixing
vessel 17 can be more reliably performed by fixing the slurry
mixing vessel 17 to the turntable 11 with the polishing cloth 13
therebetween. As long as the slurry mixing vessel 17 is positioned
within the non-polishing region and the slurry mixing vessel 17 is
enabled to receive the two kinds of liquid being supplied, there is
no particular limitation with respect to the location of the slurry
mixing vessel 17. Namely, the slurry mixing vessel 17 is not
necessarily positioned coaxial with the center of the polishing
cloth 13.
[0043] In the polishing apparatus according to this embodiment of
the present invention, a slurry which necessitates separate storage
for maintaining the storage stability can be dealt with. One
example of such a slurry is a slurry used in a Cu-CMP procedure. A
slurry used in a Cu-CMP procedure is usually separated, in view of
enhancing storage stability, into an abrasive grain-containing
dispersion liquid, and a solution containing an oxidizing agent. As
for the oxidizing agent useful in this case, there has been
employed ammonium persulfate, which takes a relatively long time
before it becomes compatible with the liquid, as compared with
hydrogen peroxide which is generally employed as an oxidizing
agent. Further, in order to meet various requirements such as high
polishing rate, erosion resistance, non-defectiveness, etc., the
dispersion liquid containing abrasive grains may further contain an
additive such as quinaldinic acid, a surfactant, etc. Since these
additives are highly hydrophobic however, it has been considered
difficult, according to the conventional slurry supply system, to
uniformly mix the aforementioned two liquids on the occasion of
using them.
[0044] Further, a slurry commonly employed in the polishing of W
(tungsten) can be used in the operation of the apparatus according
to this embodiment of the present invention. The slurry employed in
the W-CMP procedure may contain various additives, such as
colloidal silica as an abrasive grain, hydrogen peroxide
(H.sub.2O.sub.2) as an oxidizing agent, Cu.sup.2+ions as a catalyst
for activating hydrogen peroxide, potassium dodecylbenzene
sulfonate as a surfactant for improving the planarizing
characteristics of the slurry, and the like.
[0045] Although hydrogen peroxide is effective in enhancing the
polishing rate of W, as the hydrogen peroxide is activated into HO*
by the action of Cu.sup.2+ion, the life of HO* is very short,
meaning that hydrogen peroxide cannot be stored as a mixture with
Cu.sup.2+ions. Colloidal silica is liable to flocculate and
precipitate due to the salting-out effect thereof as colloidal
silica is contacted with Cu.sup.2+ion, so that colloidal silica
cannot be stored as a mixture with Cu.sup.2+ion. On the other hand,
under a specific pH region (pH=5 or less) where hydrogen peroxide
cannot be decomposed, silica is potentially unstable and hence
liable to flocculate and precipitate, making colloidal silica
cannot be stored as a mixture with hydrogen peroxide. Therefore,
the polishing slurry is generally separated, for the purpose of
storage, into three kinds of liquid, i.e. an abrasive
grain-containing dispersion liquid containing colloidal silica, an
oxidizing agent solution containing hydrogen peroxide, and a
catalyst solution containing Cu.sup.2+ions. On the occasion of
using these three kinds of liquid, they are mixed together
immediately before the polishing operation.
[0046] A metal film containing Ru or an Ru compound can be polished
by using a polishing slurry which is formed of an aqueous solution
containing, as an abrasive component, a cerium compound (IV) such
as cerium nitrate, cerium diammonium nitrate, etc. Generally,
cerium compound (IV) is stable, as it exists as a solution in high
concentration. However, once cerium compound (IV) is diluted into a
solution of low concentration, cerium compound (IV) is caused to
change with time, thereby deteriorating the oxidizing power thereof
and hence deteriorating the polishing performance thereof.
Accordingly, if a polishing is to be performed by using an aqueous
solution containing cerium compound (IV), the solution of cerium
compound (IV) should be put to use without leaving it stand for a
long period of time after the dilution thereof. More preferably,
the solution of cerium compound (IV) should be used immediately
after the dilution thereof, most preferably concurrent with the
dilution thereof. Therefore, the cerium compound (IV) should be
stored as an aqueous solution of high concentration separately to
the dilution water.
[0047] Further, when ceria is used as an abrasive grain in a slurry
for polishing an oxide film, a surfactant may be added to the
slurry for the purpose of enhancing the planarizing characteristics
of the slurry. However, when ceria particles are kept contacted
with the surfactant for a long period of time, the surfactant
adheres to the surface of ceria particles, thereby making it
difficult for the ceria particles to exhibit the inherent
characteristics thereof. Therefore, it is desirable to separate the
slurry into two liquids, i.e. an abrasive grain-containing
dispersion liquid containing ceria as an abrasive grain, and a
liquid containing a surfactant, these two liquids being
subsequently mixed together immediately before using them for a
polishing procedure.
[0048] Generally speaking, when a dispersion containing abrasive
grains is stored as a solution of high concentration, it can be
stored without generating the flocculation of the abrasive grains.
Therefore, it is preferable that an abrasive grain-containing
dispersion is preliminarily prepared by dispersing abrasive grains
therein at a higher concentration than that of an abrasive
grain-containing dispersion which is actually employed, the
abrasive grain-containing dispersion containing a higher
concentration of abrasive grains being subsequently diluted with
water to a desired concentration immediately before the actual use
thereof for polishing. For example, in the case of a slurry for
polishing an oxide film, a dispersion containing silica at a
concentration of 30% by weight may be prepared at first and
subsequently, diluted with water immediately before use to obtain a
diluted dispersion having a volume which is three times as large as
that of the initial volume. Even in a case where a dispersion
containing a high concentration of abrasive grains is prepared at
first and subsequently, diluted with water before use, the
polishing apparatus according to this embodiment of the present
invention can be suitably employed.
[0049] The slurry described above may further contain, as desired,
any additives usually employed, such as an oxidizing agent, a
surfactant, an oxidation inhibitor, a pH adjustor, etc. at a ratio
which is usually employed.
[0050] As for the oxidizing agent, it is possible to employ
H.sub.2O.sub.2, (NH.sub.4).sub.2S.sub.2O.sub.8,
K.sub.2S.sub.2O.sub.8, iron nitrate, cerium ammonium nitrate,
etc.
[0051] As for the surfactant, it is possible to employ dodecyl
sulfonate, dodecyl benzene sulfonate, polyoxyethylene lauryl ether,
fatty ester, polyoxyethylene alkylamine, etc.
[0052] As for the oxidation inhibitor, it is possible to employ BTA
(benzotriazole), amine having carboxylic group, etc. As for the pH
adjustor, it is possible to employ aqueous ammonia, KOH, nitric
acid, citric acid, oxalic acid, succinic acid, etc.
[0053] In the polishing apparatus according to this embodiment of
the present invention, the slurry employed therein is separated in
advance into a first liquid and a second liquid, at least one of
them containing an abrasive component, and these liquids are
separately supplied, making it possible to avoid the slurry from
being damaged in stability of quality. Moreover, since these two
kinds of separately supplied liquid are uniformly mixed at a
use-point, and the resultant mixed slurry is immediately employed
for polishing, the effects of enhancing the polishing performance
of slurry can be sufficiently exhibited. As a result, it is now
possible to stably perform high performance polishing which is
almost free from defects such erosion and scratches.
EXAMPLE 1
[0054] Next, one example for forming a Cu damascene wiring by using
the polishing apparatus according to this embodiment of the present
invention will be explained.
[0055] FIGS. 2A to 2C show cross-sectional views each illustrating
a process for forming a Cu damascene wiring.
[0056] First of all, as shown in FIG. 2A, an interlayer insulating
film 31 comprising a low-K material, etc. was deposited on the
surface of a semiconductor substrate 30, thereby forming therein a
groove having a depth of 3000 .ANG.. Incidentally, the
semiconductor substrate 30 may be a bulk substrate or an SOI
substrate, and semiconductor elements (not shown) were integrally
formed therein in advance. Then, a liner 32 constituted by Ta/TaN
and having a thickness of about 300 .ANG. was deposited on the
substrate 30 by sputtering. Thereafter, a Cu layer having a
thickness of about 7000 .ANG. was deposited as a wiring material 33
on the substrate 30 by sputtering (seed layer) and plating
method.
[0057] A redundant portion of the Cu layer as a wiring material 33
was removed as shown in FIG. 2B by CMP using the apparatus shown in
FIG. 1. Thereafter, as shown in FIG. 2C, the liner 32 that was
deposited on the interlayer insulating film 31 was removed by CMP
to form a buried wiring in the groove.
[0058] On the occasion of this Cu-CMP procedure in this example,
IC1000 (Rodel Nitta Co., Ltd.) was employed as the polishing cloth
13, and the slurry mixing vessel 17 made of plastic and having a
radius of 20 mm and a height of 20 mm was fixed in place at the
central portion of the non-polishing region of this polishing cloth
13, thereby constructing the polishing apparatus shown in FIG. 1.
In the positioning of the slurry mixing vessel 17, the center of
the slurry mixing vessel 17 was made coaxial with the center of the
polishing cloth 13.
[0059] The slurry employed herein was formed of a mixture of two
kinds of liquid, i.e. a first liquid which was a dispersion
containing abrasive grains, and a second liquid which was a
solution containing an oxidizing agent. This abrasive
grain-containing dispersion was prepared by mixing in pure water 2%
by weight of silica as a polishing grain, 1% by weight of
quinaldinic acid as an oxidation inhibitor, and 0.4% by weight of a
nonionic surfactant. The solution of oxidizing agent was prepared
by dissolving 2% by weight of ammonium persulfate as an oxidizing
agent in pure water.
[0060] In this polishing procedure, the turntable 11 was rotated at
a speed of 100 rpm, during which two kinds of liquid were
introduced dropwise into the slurry mixing vessel 17 at flow rate
of 150 mL/min, respectively. Concurrently, while the top ring 14
holding a wafer 16 was rotated at a speed of 100 rpm, the top ring
14 was pressed down onto the polishing cloth 13 at a polishing load
of 400 g/cm.sup.2. Under these conditions, polishing was performed
for 100 seconds to remove a redundant portion of the Cu layer, as
shown in FIG. 2B.
[0061] Incidentally, the feeding flow rates of the first and second
liquids, the rotational speeds of the turntable and the top ring,
the polishing load can be suitably modified depending on the kind
of polishing material, and of the chemical liquids, on the
polishing conditions, etc.
[0062] Five seconds later, as measured from the initiation of the
supply of these liquids, these two liquids were accumulated, as a
uniform slurry which had been sufficiently mixed, up to the top of
the slurry mixing vessel 17, thereby allowing these liquids to
overflow from the slurry mixing vessel 17 and to be applied over
the polishing cloth 13. Since this uniformly mixed slurry is
enabled to spread over the polishing cloth 13 immediately before
the polishing, it was possible to sufficiently derive the polishing
performance which the slurry inherently had. More specifically, by
using a conventional slurry (polishing rate: about 10000 .ANG./min;
erosion: 300 .ANG. or less) which was conventionally considered as
having a high performance but having problems with respect to
stability and life, it was possible to form a damascene wiring at a
scale of mass production level.
[0063] The dependency of the polishing rate of Cu on the number of
wafers is indicated by a curve "a" in FIG. 3. It is apparent from
the curve "a" that when the apparatus of this example was employed,
the non-uniformity of the polishing rate of Cu could be confined
within .+-.250 .ANG./min or so even if 40 sheets of wafers were
polished.
[0064] For the purpose of comparison, a Cu damascene wiring was
formed in the same manner as described above by using the
conventional apparatuses as shown in FIGS. 4 and 5. In the
apparatus shown FIG. 4, two kinds of liquid were respectively fed
onto the polishing cloth 13 and mixed together through the rotation
of the turntable 11, thus rendering two kinds of liquid available
for polishing. The apparatus shown in FIG. 5, on the other hand,
illustrates an example wherein two kinds of liquid were supplied by
using a T-shaped pipe. In this case, the tip ends of supply pipes
24 and 25 for feeding the liquids, respectively, were connected
with the T-shaped pipe 51, thereby permitting a mixed slurry 52 to
be dropped onto the polishing cloth 13. In this case, the flow rate
of the mixed slurry 52 was the total of the supply flow rates of
these two liquids.
[0065] In these conventional apparatuses, the polishing performance
such as polishing rate and erosion was very poor in stability,
making it sometimes impossible to perform polishing of Cu at all.
The reason for this may be attributed to the fact that the two
liquids were not sufficiently mixed, thus an insufficiently stable
slurry was supplied to the polishing surface.
[0066] The dependency of the polishing rate of Cu on the number of
wafers when the apparatus shown in FIG. 4 was employed is indicated
by a curve "b" in FIG. 3. It is apparent from the curve "b" that
when this conventional apparatus was employed, the polishing rate
of Cu considerably fluctuated, and at the same time, gradually
lowered as a whole as the number of wafers treated increased.
Moreover, an erosion having a dimension of 500 .ANG. or more was
recognized on the surface of wafer after polishing. Even in the
case where the apparatus of FIG. 5 was employed, almost the same
results as those of the apparatus of FIG. 4 were obtained.
[0067] It was confirmed from this example that it was possible to
perform a stable polishing when the apparatus of this example was
employed.
EXAMPLE 2
[0068] In this example, a W damascene wiring was formed by using a
slurry comprising a mixture of three kinds of liquid, i.e. an
abrasive grain-containing dispersion as a first liquid, a solution
of oxidizing agent as a second liquid, and a solution of a catalyst
as a third liquid.
[0069] First of all, as shown in FIG. 2A, an interlayer insulating
film 31 comprising of a low-K material, etc. was deposited on the
surface of a semiconductor substrate 30, thereby forming therein a
groove having a depth of 3000 .ANG.. Incidentally, the
semiconductor substrate 30 may be a bulk substrate or an SOI
substrate, and semiconductor elements (not shown) were integrally
formed therein in advance. Then, a liner 32 constituted by Ta/TaN
and having a thickness of about 200 .ANG. was deposited on the
substrate 30 by sputtering. Thereafter, a W layer having a
thickness of about 3500 .ANG. was deposited as a wiring material 33
on the substrate 30 by sputtering.
[0070] A redundant portion of the W layer as a wiring material 33
was removed as shown in FIG. 2B by CMP using the apparatus shown in
FIG. 1. The apparatus employed herein was the same as the apparatus
shown in FIG. 1 except that a storage tank, a pump and a supply
pipe, were additionally provided for the third liquid. Thereafter,
as shown in FIG. 2C, the liner 32 that was deposited on the
interlayer insulating film 31 was removed by CMP to form a buried
wiring in the groove.
[0071] In this W-CMP procedure in this example, IC1000 (trade name;
Rodel Nitta Co., Ltd.) was employed as the polishing cloth 13 in
the same manner as in the aforementioned Example 1, and the slurry
mixing vessel 17 made of plastic and having a radius of 20 mm and a
height of 20 mm was screwed in place, at the non-polishing region
of this polishing cloth 13, thereby constructing the polishing
apparatus shown in FIG. 1. In the positioning of the slurry mixing
vessel 17, the center of the slurry mixing vessel 17 was offset by
a distance of about 5 mm from the center of the polishing cloth
13.
[0072] The slurry employed herein was prepared as follows.
[0073] Namely, a first liquid which was a dispersion containing
abrasive grains was prepared by mixing in pure water 5% by weight
of silica as a polishing grain, and 1% by weight of potassium
dodecylbenzene sulfonate as a surfactant for enhancing the
planarizing performance of the slurry. A second liquid which was a
solution of an oxidizing agent was prepared by dissolving 1% by
weight of hydrogen peroxide as an oxidizing agent in pure water.
Further, copper sulfate was dissolved in pure water to obtain a
0.05 wt % aqueous solution thereof, thereby obtaining a third
liquid containing Cu.sup.2+ion functioning as a catalyst for
activating the hydrogen peroxide.
[0074] In this polishing procedure, the turntable 11 was rotated at
a speed of 100 rpm, during which three kinds of liquid, i.e. the
abrasive grain-containing dispersion, the oxidizing agent
dispersion and the catalyst solution, were introduced dropwise into
the slurry mixing vessel 17 at flow rate of 150 mL/min,
respectively. Concurrently, while rotating the top ring 14 holding
a wafer 16 at a speed of 120 rpm, the top ring 14 was pressed down
onto the polishing cloth 13 at a polishing load of 400 g/cm.sup.2,
thereby removing a redundant portion of the W layer, as shown in
FIG. 2B.
[0075] Five seconds later, as measured from the initiation of the
supply of these liquids, these three kinds of liquid were
accumulated, as a uniform slurry which had been sufficiently mixed,
up to the brim of the slurry mixing vessel 17, thereby allowing
these liquids to overflow from the slurry mixing vessel 17 and to
be provided over the polishing cloth 13. It was possible in this
slurry mixing vessel 17 to sufficiently mix potassium
dodecylbenzene sulfonate in the slurry. Since this uniformly mixed
slurry is enabled to be provided over the polishing cloth 13
immediately before the polishing, it was possible to sufficiently
derive the polishing performance inherent to the slurry.
[0076] After the polishing was performed for two minutes (Just +30%
over), the polishing rate of W was found to be about 3000
.ANG./min, and a damascene wiring of excellent quality exhibiting
an erosion of 300 .ANG. or less was obtained with high
stability.
Example 3
[0077] The slurry mixing vessel functioning as a slurry mixing
section for storing and mixing two kinds of liquid which have been
separately introduced therein and for feeding a mixed slurry to the
surface of the polishing cloth can be substituted by a recessed
portion formed in the polishing cloth. FIG. 6 illustrates an
example.
[0078] The polishing apparatus shown in FIG. 6 is substantially the
same as the apparatus shown in FIG. 1 except that a slurry mixing
recess 41 is provided, in place of the slurry mixing vessel 17, in
the non-polishing region of the polishing cloth 13. The horizontal
dimension of this recess 41 may be within the range of 10 mm to 60
mm in radius. If the size of this recess 41 is too small, it may
become difficult to accommodate the two liquids being fed thereto,
and to sufficiently carry out the mixing of them. On the other
hand, if the size of the slurry mixing recess 41 is too large, it
may become difficult to install the slurry mixing recess 41 within
the non-polishing region of the polishing cloth 13, thereby
obstructing the fundamental function of the polishing apparatus to
polish a wafer. Further, in order to accommodate two liquids, and
to enable these liquids to be sufficiently mixed together therein,
the depth of the recess 41 should preferably be at least 1 mm. On
the other hand, although there is no particular limitation with
respect to the upper limit of the depth of the recess 41, the depth
of the recess 41 should desirably be limited, unless the surface of
the turning table 11 is specifically protected by a suitable means,
to such an extent that the recess 41 is not deep enough to pass
through the polishing cloth 13, in order to avoid corrosion of the
turntable 11.
[0079] Further, as for the configuration of the recess 41, although
there is no particular limitation, the configuration of the recess
41 should preferably be cylindrical for the same reason as set
forth in the explanation of the aforementioned slurry mixing
vessel.
[0080] This recess 41 can be formed in the polishing cloth 13 by
dimpling work or recessing work, for instance. As for the polishing
cloth 13, it is possible to employ a 2-ply laminate structure
consisting of SUBA400 (trade name; Rodel Nitta Co., Ltd.) and
IC1000 (trade name; Rodel Nitta Co., Ltd.) for instance. In this
case, the recess 41 can be formed by cutting a predetermined
portion of the laminate structure, which corresponds to the
non-polishing region, into a desired configuration by using a
cutter or a mold before or after laminating these sheets.
[0081] There is no particular limitation with respect to the
location at which the slurry mixing recess 41, as long as the
location is confined within the non-polishing region and suited for
receiving and accommodating the aforementioned two kinds of slurry.
Further, the center of the slurry mixing recess 41 is not
necessarily aligned with the center of the polishing cloth 13.
[0082] By using the polishing apparatus shown in FIG. 6, the
polishing of the oxide film (SiO.sub.2 film) having a step portion
originating from an underlying wiring pattern was performed. As for
the polishing cloth 13 to be employed herein, a 2-ply laminate
polishing cloth consisting of SUBA400 and IC1000 was prepared. The
central portion of this laminate polishing cloth was worked by a
cutter, to form a cylindrical recess having a radius of 40 mm and a
depth of 1 mm.
[0083] As for the slurry employed herein, an abrasive
grain-containing dispersion wherein 0.5% by weight of ceria
particles was dispersed as abrasive grains in pure water, as well
as an additive-containing solution wherein 30% by weight of
polycarboxylic acid-based surfactant was dissolved in pure water
were employed as a first liquid and a second liquid,
respectively.
[0084] In this polishing procedure, the turntable 11 was permitted
to rotate at a speed of 100 rpm, during which the aforementioned
two liquids were introduced dropwise into the slurry mixing recess
41 at a flow rate of 150 mL/min, respectively. Concurrently, while
rotating the top ring 14 holding a wafer 16 at a speed of 107 rpm,
the top ring 14 was pressed down onto the polishing cloth 13 at a
polishing load of 500 g/cm.sup.2, thereby polishing the oxide
film.
[0085] When the polishing was performed for two minutes, the
polishing rate of the SiO.sub.2 film was found about 3000 .ANG./min
or more, thus making it possible to planarize the initial stepped
portion having a height of 6000 .ANG.. The erosion on the surface
of oxide film after the polishing was confirmed to be limited to
500 .ANG. or less.
[0086] Although the embodiments of the present invention have been
explained taking several of them as examples, the present invention
should not be construed as limited to such embodiments. For
example, the slurry mixing vessel and the slurry mixing recess,
both employed as a slurry mixing section, may be suitably selected
in combination with the slurries which require a separate storage
as mentioned above. In any combination thereof, it is possible to
realize the effects which make it possible to perform a stabilized
polishing with a sufficiently large polishing rate.
[0087] As explained above, according to one embodiment of the
present invention, it is possible to provide a polishing apparatus
which is capable of polishing any desired layer of a treating
substrate at a sufficiently large polishing rate while making it
possible to extremely minimize the generation of defects, such as
erosion and scratches of the treating substrate, and also making it
possible to retain the stability and life of slurry without
necessitating the provision of an auxiliary supply facility.
Further, according to another embodiment of the present invention,
it is possible to provide a polishing method which is capable of
polishing any desired layer of a treating substrate at a
sufficiently large polishing rate while making it possible to
extremely minimize the generation of defects such as the erosion
and scratches of the treating substrate and also making it possible
to retain the stability and life of slurry. Moreover, according to
a further embodiment of the present invention, it is possible to
provide a method of manufacturing a semiconductor device provided
with a damascene wiring of high performance.
[0088] The present invention is very useful in the formation of a
damascene wiring of Cu, W, Al, etc., which is designed to be
mounted on a DRAM or a high-speed logic LSI, and therefore, the
present invention is very valuable from an industrial view
point.
[0089] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention is its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *