U.S. patent application number 12/855268 was filed with the patent office on 2010-12-02 for polishing slurry and method of polishing.
This patent application is currently assigned to HITACHI CHEMICAL CO., LTD.. Invention is credited to Sou ANZAI, Yasuo KAMIGATA, Yasushi KURATA, Hiroki TERAZAKI.
Application Number | 20100301265 12/855268 |
Document ID | / |
Family ID | 29706575 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100301265 |
Kind Code |
A1 |
KURATA; Yasushi ; et
al. |
December 2, 2010 |
POLISHING SLURRY AND METHOD OF POLISHING
Abstract
A polishing slurry comprises a metal-oxidizing agent, a metal
anticorrosive agent, an oxidized metal dissolving agent and water.
The oxidized metal dissolving agent is at least one kind selected
from the group consisting of an acid in which the negative value of
the logarithm of the dissociation constant Ka (pKa) of a first
dissociable acid group is 3.5 or more, an ammonium salt of the acid
and an organic acid ester of the acid. The pH of the polishing
slurry is within the range of 3 to 4. The concentration of the
metal-oxidizing agent is within the range of 0.01 to 3 percent by
weight. In the wiring-formation process of the semiconductor
device, the conductor used for the barrier layer can be polished at
a high polishing rate by using the polishing slurry having the low
polishing particle concentration and the low metal anticorrosive
agent concentration.
Inventors: |
KURATA; Yasushi;
(Hitachi-shi, JP) ; KAMIGATA; Yasuo; (Tsukuba-shi,
JP) ; ANZAI; Sou; (Hitachi-shi, JP) ;
TERAZAKI; Hiroki; (Hitachi-shi, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
HITACHI CHEMICAL CO., LTD.
Tokyo
JP
|
Family ID: |
29706575 |
Appl. No.: |
12/855268 |
Filed: |
August 12, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10517049 |
Dec 3, 2004 |
7799688 |
|
|
PCT/JP2003/006769 |
May 29, 2003 |
|
|
|
12855268 |
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Current U.S.
Class: |
252/79.2 ;
252/79.1 |
Current CPC
Class: |
C09G 1/02 20130101; H01L
21/3212 20130101 |
Class at
Publication: |
252/79.2 ;
252/79.1 |
International
Class: |
C09K 13/04 20060101
C09K013/04; C09K 13/00 20060101 C09K013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 3, 2002 |
JP |
2002-161327 |
Claims
1. A polishing slurry comprising: a metal-oxidizing agent; a metal
anticorrosive agent; an oxidized metal dissolving agent; and water,
wherein the oxidized metal dissolving agent is at least one kind
selected from the group consisting of an acid in which the negative
value of the logarithm of the dissociation constant Ka (pKa) of a
first dissociable acid group is 3.5 or more, an ammonium salt of
the acid and an organic acid ester of the acid, the pH of the
polishing slurry is within the range of 3 to 4, and the
concentration of the metal-oxidizing agent is within the range of
0.01 to 3 percent by weight, wherein the polishing slurry is
capable of polishing a barrier layer.
2. The polishing slurry of claim 1, wherein the concentration of
the oxidizing agent is within the range of 0.01 to 1.5 percent by
weight.
3. The polishing slurry of claim 1, wherein the oxidized metal
dissolving agent is an organic acid.
4. The polishing slurry of claim 3, wherein the organic acid is at
least one kind selected from the group consisting of lactic acid,
succinic acid, adipic acid, glutaric acid, benzoic acid, quinaldic
acid, butyric acid and valeric acid.
5. The polishing slurry of claim 1, wherein the metal anticorrosive
agent is at least one kind selected from the group consisting of a
compound having a triazole skeleton other than benzotriazole, a
compound having a pyrimidine skeleton, a compound having an
imidazole skeleton, a compound having a guanidine skeleton, a
compound having a thiazole skeleton, a compound having a pyrazole
skeleton and benzotriazole.
6. The polishing slurry of claim 1, wherein the metal-oxidizing
agent is at least one kind selected from the group consisting of
hydrogen peroxide, ammonium persulfate, ferric nitrate, nitric
acid, potassium periodate, hypochlorous acid and ozone water.
7. The polishing slurry of claim 1, wherein the polishing slurry
contains polishing particles.
8. The polishing slurry of claim 7, wherein the polishing particles
are at least one kind selected from the group consisting of silica,
alumina, ceria, titania, zirconia and germania.
9. The polishing slurry of claim 7, wherein the polishing particles
are colloidal silica or colloidal alumina having an average
particle diameter of 100 nm or less.
10. The polishing slurry of claim 1, wherein the polishing slurry
contains a water-soluble polymer compound.
11. The polishing slurry of claim 10, wherein the water-soluble
polymer compound is at least one kind selected from the group
consisting of polyacrylic acid and the salt thereof,
polymethacrylic acid and the salt thereof, polyacrylamide,
polyvinyl alcohol, and polyvinylpyrrolidone.
12. (canceled)
13. (canceled)
14. (canceled)
Description
[0001] This application is a continuation application of U.S.
application Ser. No. 10/517,049, filed Dec. 3, 2004, which is a
National Phase filing of PCT/JP2003/06769, filed May 29, 2003,
which is based upon and claims priority under 35 U.S.C. .sctn.119
to Japanese Patent Application No. 2002-161327, filed Jun. 3, 2002,
all of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a polishing slurry, and
particularly, a polishing slurry used for polishing in the
wiring-formation process of a semiconductor device, and a polishing
method using the polishing slurry.
[0004] 2. Description of the Related Art
[0005] Recently, as a Large-Scale Integrated circuit (hereinafter,
referred to as "LSI") of a semiconductor advances to fulfill the
demand of higher integration and performance, new microprocessing
techniques have been developed. The Chemical Mechanical Polishing
(hereinafter, referred to as "CMP") method is one of the new
microprocessing techniques, which is often used in a LSI production
process, especially for flattening interlaminar insulating films,
formation of a metal plug and embedded wires in a multi-layered
wiring-formation process. This technique is disclosed in U.S. Pat.
No. 4,944,836.
[0006] Additionally, in recent years, use of copper and copper
alloy as a wire material has been mainly attempted in order to
enhance the performance of LSI. However, in the case of the copper
and the copper alloy, it is difficult to perform microprocessing
according to dry etching, which has been often used in the
conventional method for forming aluminum alloy wiring. Therefore,
there has been employed what is called Damascene method in which
copper or a thin film of copper alloy is accumulated on and
embedded in an insulating film by way of a groove formed in advance
on the insulating film and then the copper or the copper alloy thin
film remaining at the portions other than the groove portion is
removed by CMP, whereby embedded wiring is formed. For instance,
this technique is disclosed in Japanese Patent Application
Laid-Open (JP-A) No. 2-278822.
[0007] In general, a CMP method in metal processing such as copper
and a copper alloy includes the steps of: sticking a polishing pad
on a disc-shaped polishing platen; soaking the surface of the
polishing pad with a polishing liquid for metal; pressing, one
surface of a substrate on which a metal film has been formed,
against the surface of the polishing pad, with applying a
predetermined pressure (hereinafter, referred to as "polishing
pressure") thereon from the back surface of the substrate, and
rotating the polishing platen in that state; and removing the
projected portion of the metal film by utilizing mechanical
friction between the polishing liquid and the projected portion of
the metal film.
[0008] The polishing liquid for metal used for CMP generally
contains a metal-oxidizing agent and solid polishing particles. An
oxidized metal dissolving agent and a metal anticorrosive agent are
further added thereto, according to necessity. With regards to the
basic mechanism of CMP, it is assumed that at first the surface of
the metal film is oxidized by an oxidizing agent; and then the
oxidized layer is scraped off by the solid polishing particles. The
oxidized layer existing at the dented portion of the metal surface
is hardly brought into contact with the polishing pad and thus the
solid polishing particles do not have so much scraping effect
thereon. In other words, the metal layer present at the projected
portion of the substrate surface is removed as CMP is effected,
whereby the substrate surface is made flat and smooth. The details
of the feature described above is disclosed in Journal of
Electrochemical Society, vol. 138, No. 11 (1991), pp.
3460-3464.
[0009] It has been known that addition of an oxidized metal
dissolving agent is effective as a method for increasing the
polishing rate by CMP. It is understood that addition of an
oxidized metal dissolving agent is effective because the scraping
effect by the solid polishing particles is enhanced by dissolving
(hereinafter, referred to as "etching") the particles of metal
oxides, which have been scraped off by the solid polishing
particles, in the polishing liquid. The polishing rate due to CMP
is increased by adding the oxidized metal dissolving agent.
However, if the oxidized layer existing at the dented portion of
the metal film surface is also etched and the metal film surface is
exposed, the metal film surface is further oxidized by the
oxidizing agent. In a case in which such excessive etching is
repeated, the metal film at the dented portion is considerably
etched. Thereby, a phenomenon (hereinafter, referred to as
"dishing") is occurred in which the center portion at the surface
of the embedded metal wiring is recessed like a dish after
polishing, and the flattening effect is damaged.
[0010] In order to prevent such excessive etching from being
occurred, a metal anticorrosive agent for protecting the metal
surface further is added. The metal anticorrosive agent forms a
protective film on the oxidized layer of the metal film surface,
and prevents the oxidized layer from solving in the polishing
slurry. This protective film can be scraped off easily by the solid
polishing particles, and the polishing rate due to CMP is
preferably maintained.
[0011] In order to suppress dishing and etching of copper and
copper alloy during polishing and form highly reliable LSI wiring,
there has been proposed a method for using a polishing liquid for
metal containing: an oxidized metal dissolving agent composed of an
amino acetic acid (such as glycine) or amidosulfuric acid; and BTA
(benzotriazol) as the metal anticorrosive agent. This technique is
disclosed, for example, in JP-A No. 8-83780.
[0012] In the Damascene wiring formation of copper or copper alloy
or the metal-embedding formation such as plug wiring formation of
tungsten or the like, if the polishing rate of the silicon dioxide
film as the interlaminar insulating film formed at the portion
other than the embedded portion is also large, there arises the
phenomenon of "thinning" in which reduction of wiring thickness and
reduction of thickness of the interlaminar insulating film
simultaneously occur. As a result, since there is generated
variation in resistance due to the increase in the wiring
resistance, the pattern density or the like, a characteristic that
the polishing rate of the silicon dioxide film is sufficiently
smaller than that of the metal film to be polished is required.
Therefore, there has been proposed a method in which pH of the
polishing liquid is made higher than the negative value of the
logarithm of the dissociation constant Ka (pKa) of the first
dissociable acid group of an oxidized metal dissolving agent -0.5
by suppressing the polishing rate of silicon dioxide by the action
of an anion produced as a result of dissociation of an acid. This
technique is disclosed, for example, in Japanese Patent No.
2819196.
[0013] As a lower layer beneath metal for wiring portion such as
copper or copper alloy, a barrier layer of a conductor selected
from the group, for example, consisting of tantalum, tantalum
alloy, tantalum nitride and tantalum compounds of other types
(hereinafter, referred to as "tantalums") is formed in order to
prevent copper from diffusing into the interlaminar insulating film
and enhance the adhesion. Accordingly, at the portion other than
the wiring portion at which copper or copper alloy is to be
embedded, the exposed barrier layer must be removed by CMP.
However, as the barrier layer conductor is harder than copper or
copper alloy, a sufficiently high polishing rate is hardly obtained
and flatness often worsens, even if a combination of the polishing
materials for copper or copper alloy is simply employed. Therefore,
there has been studied a two-stage polishing method including the
first step of polishing metal for wiring portion and the second
step of polishing the barrier layer conductor.
[0014] The conductors generally used as the barrier layer, for
example, the above tantalums, titanium and the compound thereof,
tungsten and the compound thereof or the like are chemically
stable. In addition the etching of the conductors is difficult, and
the conductors have high hardness. Thereby, the mechanical
polishing thereof is not so easy as that of copper and a copper
alloy. When the hardness of the polishing particles is increased,
polishing crack is occurred on copper or copper alloy, and the poor
electrical property is caused. When the particle concentration of
the polishing particles is increased, a problem exists in that the
polishing rate of a silicon dioxide film becomes faster, and
thinning is occurred.
[0015] It has been considered that in CMP of the barrier layer as
the second process, the dishing in the embedding wiring portion of
copper or copper alloy must be prevented and the low pH of the
polishing slurry is minus effect so as to suppress the polishing
rate and etching rate of copper or copper alloy. On the other hand,
as the polishing slurry which is effective for polishing the
barrier layer, the following polishing slurry is proposed. The pH
of the polishing slurry is 3 or less and the concentration of the
metal-oxidizing agent is within the range of 0.01 to 3.0 percent by
weight by adjusting the pH of the polishing slurry and the
concentration of the metal-oxidizing agent such that the polishing
of tantalums used as the barrier layer conductor is easily advanced
in a low pH region and in a low metal-oxidizing agent concentration
region (For example, see WO 01/013417).
[0016] However, the polishing rate of the barrier layer due to the
polishing slurry proposed above is not sufficient as compared with
the etching rate and polishing rate of metal for wiring such as
copper and copper alloy. A problem exists in that the state
(hereinafter, referred to as "corrosion") where a foreign matter is
occurred on the oxidized surface to be polished is easily occurred
on the metal surface, particularly on the metal for wiring such as
copper and copper alloy.
[0017] The present inventors have found that the high polishing
rate of the conductor used for the above barrier layer in a region
where the pH is 3 or more is obtained for the above proposal. At
that time, the present inventors have also found that as the kind
of the oxidized metal dissolving agent used for pH adjustment, an
acid in which pKa of a first dissociable acid group is 3.5 or more
and an ammonium salt of the acid are effective.
[0018] Since the corrosion operations of the metal for wiring such
as copper and copper alloy and the conductor used for the barrier
layer are respectively small in a region wherein the pH is or more
in the invention, the corrosion of the metal wiring portion is not
easily occurred, and the highly reliable LSI wiring can be formed.
In addition, in the region where the pH is 3 or more, the etching
rate and polishing rate of the metal of the wiring portion can be
sufficiently reduced as compared with the polishing rate of the
barrier layer, and thereby, dishing or thinning is effectively
reduced. The concentration of the metal anticorrosive agent to the
metal surface can be also reduced.
[0019] It is an object of the invention to provide a polishing
slurry which can realize the high polishing rate of the conductor
used for the barrier layer in low polishing particle concentration,
and can form the embedding pattern of a highly reliable metal film
by suppressing the etching operation of the metal for wiring such
as copper and copper alloy by reducing the dishing and thinning of
the metal wiring. It is another object of the invention to provide
a polishing method using the polishing slurry.
SUMMARY OF THE INVENTION
[0020] The polishing slurry of the invention relates to the
following polishing slurry and polishing method.
[0021] (1), That is, the invention relates to a polishing slurry
comprising: a metal-oxidizing agent; a metal anticorrosive agent
for protecting metal surface; an oxidized metal dissolving agent;
and water, the oxidized metal dissolving agent being at least one
kind selected from the group consisting of an acid in which the
negative value of the logarithm of the dissociation constant Ka
(pKa) of a first dissociable acid group is 3.5 or more, an ammonium
salt of the acid and an organic acid ester of the acid, the pH of
the polishing slurry being within the range of 3 to 4, the
concentration of the metal-oxidizing agent being within the range
of 0.01 to 3 percent by weight.
[0022] (2) The invention relates to the polishing slurry of the
(1), wherein the concentration of the oxidizing agent is within the
range of 0.01 to 1.5 percent by weight.
[0023] (3) The invention relates to the polishing slurry of the (1)
or (2), wherein the oxidized metal dissolving agent is an organic
acid.
[0024] (4) The invention relates to the polishing slurry of the
(3), wherein the oxidized metal dissolving agent is at least one
kind selected from the group consisting of lactic acid, succinic
acid, adipic acid, glutaric acid, benzoic acid, quinaldic acid,
butyric acid and valeric acid.
[0025] (5) The invention relates to the polishing slurry of any one
of (1) to (4), wherein the metal anticorrosive agent is at least
one kind selected from the group consisting of a compound having a
triazole skeleton other than benzotriazole, a compound having a
pyrimidine skeleton, a compound having an imidazole skeleton, a
compound having a guanidine skeleton, a compound having a thiazole
skeleton, a compound having a pyrazole skeleton and
benzotriazole.
[0026] (6) The invention relates to the polishing slurry of any one
of the (1) to (5), wherein the metal-oxidizing agent is at least
one kind selected from the group consisting of hydrogen peroxide,
ammonium persulfate, ferric nitrate, nitric acid, potassium
periodate, hypochlorous acid and ozone water.
[0027] (7) The invention relates to the polishing slurry of any one
of (1) to (6), wherein the polishing slurry contains polishing
particles.
[0028] (8) The invention relates to the polishing slurry of the
(7), the polishing particles are at least one kind selected from
the group consisting of silica, alumina, ceria, titania, zirconia
and germania.
[0029] (9) The invention relates to the polishing slurry of the (7)
or (8), wherein the polishing particles are colloidal silica or
colloidal alumina having an average particle diameter of 100 nm or
less.
[0030] (10) The invention relates to the polishing slurry of any
one of the (1) to (9), wherein the polishing slurry contains a
water-soluble polymer compound.
[0031] (11) The invention relates to the polishing slurry of the
(10), wherein the water-soluble polymer compound is at least one
kind selected from the group consisting of polyacrylic acid and the
salt thereof, polymethacrylic acid and the salt thereof,
polyacrylamide, polyvinyl alcohol, and polyvinylpyrrolidone.
[0032] (12) The invention relates to a polishing method comprising:
a first polishing step of polishing a conductive substance layer of
a substrate having an interlaminar insulating film of which the
surface consists of dented portions and projected portions, a
barrier conductor layer coating the interlaminar insulating film
along the surface thereof, and the conductive substance layer with
which the dented portions are filled up and coats the barrier
conductor layer to expose the barrier conductor layer of the
projected portions; and a second polishing step of polishing
chemically and mechanically polishing at least the barrier
conductor layer and the conductive substance layer of the dented
portions while supplying the polishing slurry of any one of the (1)
to (11) to expose the interlaminar insulating film of the projected
portions.
[0033] (13) The invention relates to the polishing method of the
(12), wherein the barrier conductor layer prevents the conductive
substance from diffusing to the interlaminar insulating film, and
the conductive substance is at least one of copper and a copper
alloy.
[0034] (14) The invention relates to the polishing method of the
(12) or (13), wherein the barrier conductor layer is a single layer
made of one kind or a lamination layer made of two kinds or more
selected from the group consisting of tantalum, tantalum nitride, a
tantalum alloy, titanium, titanium nitride, a titanium alloy,
tungsten, tungsten nitride and a tungsten alloy.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] Hereinafter, the invention will be explained in detail. The
polishing slurry of the invention contains the metal-oxidizing
agent, the metal anticorrosive agent for protecting metal surface,
the oxidized metal dissolving agent and water as a main
constituent.
[0036] Hereinafter, It will be noted that the composition of the
conductor used for the barrier layer polished by the polishing
slurry is tantalums and the metal composition for wiring is copper
or a copper alloy. However, the polishing slurry is similarly
applied for the case that other composition usually used, for
example, the conductor is titanium compounds such as titanium,
titanium nitride, a titanium alloy, tungsten compounds such as
tungsten, tungsten nitride and a tungsten alloy, and the case that
the metal for wiring is a copper oxide, a copper alloy oxide,
tungsten, a tungsten alloy, silver and gold or the like.
[0037] Examples of the metal-oxidizing agents in the polishing
slurry of the invention include hydrogen peroxide, ammonium
persulfate, ferric nitrate, nitric acid, potassium periodate,
hypochlorous acid and ozone water. Particularly, hydrogen peroxide
is preferable. These may be used alone or combination of more kinds
thereof. In the case in which the substrate is a silicon substrate
containing an element for a integrated circuit, an oxidizing agent
which does not contain nonvolatile components is preferable, so
that undesirable pollution caused by alkali metal, alkali earth
metal, halides or the like can be avoided. Ozone water exhibits
rapid change in the composition thereof in a period of time.
Accordingly, hydrogen peroxide is the most preferable as the
oxidizing agent. However, if the substrate to be polished is a
glass substrate which does not contain a semiconductor element, an
oxidizing agent containing nonvolatile components may also be
acceptable.
[0038] The concentration of the metal-oxidizing agent of the
invention must be within the range of 0.01 to 3 percent by weight
in the polishing slurry, more preferably 0.01 to 1.5 percent by
weight, and most preferably 0.1 to 1.0 percent by weight. When the
concentration of the oxidizing agent is less than 0.01 percent by
weight, the effect of addition is reduced, and the sufficient
polishing rate of tantalums cannot be obtained. On the other hand,
when the concentration is more than 3 percent by weight, the
etching rate of metal such as copper and a copper alloy is
increased, and thereby, the problem of corrosion is easily
generated. Also, the polishing rate of tantalums also tends to be
reduced.
[0039] Generally, when the pH is low, the etching rates of copper
film and a copper alloy film are large, and it is difficult to
suppress the etching due to the metal anticorrosive agent. However,
since the concentration of the metal-oxidizing agent is
sufficiently low in the invention, the etching can be suppressed
due to the metal anticorrosive agent.
[0040] The oxidized metal dissolving agent of the invention is at
least one kind selected from the group consisting of an acid in
which the negative value of the logarithm of the dissociation
constant Ka (pKa) of a first dissociable acid group is 3.5 or more,
an ammonium salt of the acid and an organic acid ester of the acid.
There are no particular limitations as long as the oxidized metal
dissolving agent is water-soluble. However, organic acids are
preferable in view of the etching properties of the metal, and
examples of the organic acids include lactic acid, succinic acid,
acid acid, adipic acid, glutaric acid, benzoic acid, quinaldic
acid, butyric acid, valeric acid, salicylic acid, glyceric acid and
pimelic acid. Of these, lactic acid, succinic acid, adipic acid,
glutaric acid, benzoic acid, quinaldic acid, butyric acid and
valeric acid or the like are more preferable. The other examples
include the ammonium salt of these acids and the organic acid ester
thereof. It is also effective to use together at least two kinds of
acids, ammonium salts or organic acid esters because the etching
rate can be effectively suppressed with maintaining a high,
practically acceptable CMP rate.
[0041] Preferable examples of the organic acid esters include alkyl
ester such as methyl ester, ethyl ester, 1-propyl ester, 2-propyl
ester, 1-butyl ester, 2-butyl ester, 3-butyl ester, tert-butyl
ester. Methyl ester, ethyl ester, 1-propyl ester and 2-propyl ester
are more preferable. The practical polishing rate of tantalums can
be obtained in the region where the pH of the polishing slurry is
within the range of 3 to 4 by using the acid in which the
dissociation constant (pKa) of the first dissociable acid group is
3.5 or more, the ammonium salt of the acid or the organic acid
ester of the acid.
[0042] The pH of the polishing slurry of the invention must be
within the range of 3 to 4. In order to obtain a higher polishing
rate of tantalums, the pH is preferably within the range of 3 to
3.75, and the pH is more preferably within the range of 3 to 3.5.
In order to suppress the etching rate of metal such as copper and a
copper alloy as compared with the polishing rate of tantalums,
superior characteristic is obtained in the range where the pH is
within the range of 3 to 4 than the range where the pH is less than
3. Though the region where the pH is more than 4 is very effective
for suppressing the etching operation, the practical polishing rate
of tantalums is not obtained.
[0043] When the pH is set to higher than 4 by the concentration or
the like of the oxidized metal dissolving agent, the decomposition
of the oxidizing agent such as hydrogen peroxide is promoted, and a
secondary oxidized layer which is harder to be polished than a
primary oxidized layer is formed on the film surface of the
tantalums. Thereby, the polishing rate is easily reduced.
[0044] The pH of the polishing slurry of the invention can be
adjusted by the amount of addition of the acid. The pH can be also
adjusted by adding alkali components such as ammonia, sodium
hydroxide and tetramethylammonium hydroxide (TMAH).
[0045] The pH of the polishing slurry of the invention is measured
by a pH meter (for example, Model PH81 (trade name: manufactured by
Yokogawa Electric Co.)). After a two-point calibration is performed
by using a standard buffer solution (the pH of a phthalic acid salt
pH buffer solution: 4.21 (25.degree. C.) and the pH of a neutral
phosphoric acid salt pH buffer solution: 6.86 (25.degree. C.)), an
electrode is put into the polishing slurry, and a stabilized value
after elapse of 2 minutes or more is measured.
[0046] There are no particular limitations as long as the metal
anticorrosive agent of the invention forms the protective film on
the oxidized layer of the surface of the metal film, and prevents
the oxidized layer from solving in the polishing slurry. At least
one kind is preferably selected from the group consisting of a
compound having a triazole skeleton other than benzotriazole, a
compound having a pyrimidine skeleton, a compound having an
imidazole skeleton, a compound having a guanidine skeleton, a
compound having a thiazole skeleton, a compound having a pyrazole
skeleton and benzotriazole (BTA). It is also effective to use kinds
of two or more together from these.
[0047] Examples of the compounds having the triazole skeleton
include 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole,
benzotriazole, 1-hydroxybenzotriazole,
1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole,
4-hydroxybenzotriazole, 4-carboxyl(-1H-)benzotriazole,
4-carboxyl(-1H-)benzotriazole methyl ester,
4-carboxyl(-1H-)benzotriazole buryl ester,
4-carboxyl(-1H-)benzotriazole octyl ester, 5-hexyl benzotriazole,
[1,2,3-benzotriazolyl-1-methyl][1,2,4-triazolyl-1-methyl][2-ethylhexyl]am-
ine, tolyltriazole, naphthotriazole,
bis[(1-benzotriazolyl)methyl]phosphonic acid, 3-aminotriazole and
5-methyl benzotriazole. Of these, in view of the polishing rate and
the etching rate, 1,2,3-triazole, 1,2,4-triazole,
3-amino-1H-1,2,4-triazole, 4-amino-4H-1,2,4-triazole,
benzotriazole, 1-hydroxybenzotriazole and 5-methybenzotriazole are
more preferable. These may be used alone or combination of more
kinds thereof.
[0048] Examples of the compounds having the imidazole skeleton
include 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole,
2-propylimidazole, 2-butylimidazole, 4-methylimidazole,
2,4-dimethylimidazole, 2-ethyl-4-methylimidazole,
2-undecylimidazole and 2-aminoimidazole. These may be used alone or
combination of more kinds thereof.
[0049] Examples of the compounds having the pyrimidine skeleton
include pyrimidine, 1,2,4-triazolo[1,5-a]pyrimidine,
1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine,
1,3-diphenyl-pyrimidine-2,4,6-trione, 1,4,5,6-tetrahydropyrimidine,
2,4,5,6-tetraaminopyrimidinesulfate, 2,4,5-trihydroxypyrimidine,
2,4,6-triaminopyrimidine, 2,4,6-trichloropyrimidine,
2,4,6-trimethoxypyrimidine, 2,4,6-triphenylpyrimidine,
2,4-diamino-6-hydroxylpyrimidine, 2,4-diaminopyrimidine,
2-acetamidepyrimidine, 2-aminopyrimidine,
2-methyl-5,7-diphenyl-(1,2,4) triazolo(1,5-a)pyrimidine,
2-methylsulfanilyl-5,7-diphenyl(1,2,4)triazolo(1,5-a)pyrimidine,
2-methylsulfanilyl-5,7-diphenyl-4,7-dihydro-(1,2,4)triazolo (1,5-a)
pyrimidine and 4-aminopyrazolo[3,4-d]pyrimidine. Particularly, in
view of the polishing rate and the etching rate,
4-aminopyrazolo[3,4-d]pyrimidine, 1,2,4-triazolo(1,5-a) pyrimidine,
2-methyl-5,7-diphenyl-(1,2,4) triazolo(1,5-a) pyrimidine,
2-methylsulfanilyl-5,7-diphenyl-(1,2,4) triazolo(1,5-a)pyrimidine
are preferable. These may be used alone or combination of more
kinds thereof.
[0050] Examples of the compounds having the guanidine skeleton
include 1,3-diphenyl guanidine and 1-methyl-3-nitroguanidine.
Examples of the compounds having the thiazole skeleton include
2-mercaptobenzothiazole. These may be used alone or combination of
more kinds thereof.
[0051] The polishing slurry of the invention may contain polishing
particles, and the polishing rate of tantalums can be improved by
containing the polishing particles. A silicon dioxide film is used
as the insulating film layer of copper or a copper alloy wiring
such as LSI, in this case, when the silicon dioxide film is
polished by using the polishing slurry of the invention after
polishing the tantalums as the barrier layer, the polishing slurry
preferably contains the polishing particles.
[0052] As the polishing particles used in the invention, inorganic
polishing particles such as silica, alumina, zirconia, ceria,
titania, germania and silicon carbide, and organic polishing
particles such as polystyrene, polyacryl and polyvinyl chloride may
be used. At least one kind selected from silica, alumina, ceria,
titania, zirconia and germania is preferable. Colloidal silica and
colloidal alumina which have excellent dispersion stability in the
polishing slurry, have the few number of polishing cracks
(scratches) generated by CMP and have an average particle diameter
of 150 nm or less are preferable. Herein, the average particle
diameter of 100 nm or less which increases the polishing rate of
the barrier layer is more preferable, and most preferably 70 nm or
less. It is noted that the colloidal silica is manufactured by
hydrolysis of silicon alcoxide or ion exchange of sodium silicate
and the colloidal alumina is manufactured by hydrolysis of
aluminium nitrate.
[0053] The particle diameter of the polishing particles of the
invention is measured by an optical diffraction scattering particle
size distribution meter (for example, trade name: COULTER N4SD,
manufactured by COULTER Electronics). The measurement conditions of
the particle size distribution meter (COULTER N4SD) are the
following. The measurement temperature is set to 20.degree. C., and
the solvent refractive index is set to 1.333 (water). The particle
refractive index is set to Unknown (set), and the solvent viscosity
is set to 1.005 cP (water). The Run Time is set to 200 sec, and the
laser incidence angle is set to 90 degrees. When the Intensity
(corresponding to scattering intensity and turbidity) is higher
than 4E+05, the polishing slurry is diluted by water and measured
such that the Intensity is within the range of 5E+04 to 4E+05.
[0054] The polishing slurry of the invention may contain a
water-soluble polymer compound. As the water-soluble polymer
compound used in the invention, at least one kind is suitably
selected from the group consisting of a polymer which contains a
monomer having a carboxyl group such as polyacrylic acid,
polyacrylic acid ammonium salt, polyacrylic acid sodium salt,
polymethacrylic acid, polymethacrylic acid ammonium salt,
polymethacrylic acid sodium salt and polyacrylamide as the basic
constitutional unit; and a polymer which contains a monomer having
a vinyl group such as polyvinyl alcohol and polyvinylpyrrolidone as
the basic constitutional unit. Particularly, the water-soluble
polymer compound is preferably at least one kind selected from the
group consisting of polyacrylic acid and the salt thereof,
polymethacrylic acid and the salt thereof, polyacrylamide,
polyvinyl alcohol and polyvinylpyrrolidone.
[0055] In the case in which the substrate is a silicon substrate
for a semiconductor integrated circuit, a water-soluble polymer is
preferably an acid or an ammonium salt thereof, such that
undesirable pollution caused by alkali metal, alkali earth metal,
halides or the like can be avoided. However, when the substrate is
a glass substrate or the like, such restriction as described above
is unnecessary.
[0056] By adding these water-soluble polymer compounds, the dishing
characteristic can be improved by the etching restraining effect
due to the metal anticorrosive agent.
[0057] The content the metal anticorrosive agent used in the
invention is preferably within the range of 0.001 to 5.0 percent by
weight based on the total weight of the polishing slurry, more
preferably 0.01 to 1.0 percent by weight, and particularly
preferably 0.01 to 0.5 percent by weight. When the content is less
than 0.001 percent by weight, it tends to be difficult to suppress
the etching of the metal. Even when the content is more than 5
percent by weight, there is no difference in the effect, and a
problem in that the metal anticorrosive agent is easily re-eluted
may be occurred.
[0058] The content of the oxidized metal dissolving agent used in
the invention is preferably within the range of 0.001 to 10.0
percent by weight based on the total weight of the polishing
slurry, more preferably 0.01 to 5.0 percent by weight, and
particularly preferably 0.01 to 2.0 percent by weight. When the
content is less than 0.001 percent by weight, it is difficult to
set the polishing slurry to a predetermined pH value. When the pH
is high, the polishing rate tends to be reduced. When the content
is more than 10.0 percent by weight, the etching rate is increased
while the pH is reduced, and a problem of the corrosion of the
metal wiring tends to be occurred.
[0059] The content of water may be the remainder, and there are no
particular limitations as long as water is contained. The
water-soluble polymer compound and the polishing particles are
arbitrary ingredients as described above.
[0060] When the water-soluble polymer compound is blended, the
content of the water-soluble polymer compound is preferably within
the range of 0.001 to 0.5 percent by weight based on the total
weight of the polishing slurry, and more preferably 0.01 to 0.2
percent by weight. When the content is less than 0.001 percent by
weight, the combined use effect with the metal anticorrosive agent
tends not to be exhibited for the suppression of etching. When the
content is more than 0.5 percent by weight, the polishing rate due
to CMP tends to be reduced.
[0061] The weight average molecular weight of the water-soluble
polymer compound is preferably 500 or more. Though the maximum of
the weight average molecular weight is not particularly specified,
the weight average molecular weight is preferably 5 million or less
are preferred in view of the solubility. When the weight average
molecular weight is less than 500, the polishing rate of tantalums
tends to be easily reduced. In respect of the etching of copper and
a copper alloy, a copolymer obtained by reacting with a polymer
compound of which the weight average molecular weight is small
having a hydrophobic group is effective.
[0062] When the polishing particles are blended, the concentration
of the polishing particles is preferably within the range of 0.01
to 20.0 percent by weight based on the total weight of the
polishing slurry, more preferably 0.05 to 15.0 percent by weight,
and most preferably 0.1 to 8.0 percent by weight. When the
concentration of the polishing particles is less than 0.01 percent
by weight, the polishing particles adding effect is lost. When the
concentration of the polishing particles is more than 20.0 percent
by weight, not only the polishing particles are easily flocked, but
also there is no difference in the polishing rate.
[0063] In the polishing slurry of the invention, when the
concentration of the oxidizing agent based on the total weight of
the polishing slurry is about 0.15 percent by weight, the polishing
rate of tantalums becomes maximized. A primary oxidized layer which
is polished easily and mechanically is formed on the film surface
of tantalums by the oxidizing agent, and the high polishing rate is
obtained.
[0064] On the other hand, when the concentration of the oxidizing
agent used in the invention is more than 3 percent by weight, the
etching rate of metal such as copper and a copper alloy is
increased, and thereby, dishing or the like is easily generated. In
addition, since the secondary oxidized layer which is harder to be
polished than the primary oxidized layer is formed on the film
surface of tantalums, the polishing rate is reduced. When the
concentration of the oxidizing agent is less than 0.01 percent by
weight, the oxidized layer is not sufficiently formed. Thereby, the
polishing rate is reduced, and the exfoliation or the like of the
film of tantalums may be generated.
[0065] The polishing slurry of the invention may contain suitably
dispersing agents such as a surface-active agent; pH buffers;
colorants such as dyes such as Victoria pure blue, pigments such as
phthalocyanine green; and organic solvents such as methanol and
ethylene glycol if needed other than the materials described
above.
[0066] The polishing slurry of the invention can be applied, for
example to the formation of a metal wiring layer in a semiconductor
device, and can be used for chemical mechanical polishing (CMP) of
the conductive substance layer, the conductor layer used as the
barrier layer and the interlaminar insulating film.
[0067] That is, the polishing method of the invention comprises: a
first polishing step of polishing a conductive substance layer of a
substrate having an interlaminar insulating film of which the
surface consists of dented portions and projected portions, a
barrier conductor layer (barrier layer) coating the interlaminar
insulating film along the surface thereof, and the conductive
substance layer with which the dented portions are filled up and
coats the barrier layer to expose the barrier layer of the
projected portions; and a second polishing step of polishing
chemically and mechanically polishing at least the barrier layer
and the conductive substance layer of the dented portions while
supplying the polishing slurry of the invention to expose the
interlaminar insulating film of the projected portions.
[0068] Examples of the conductive substances include substances in
which the metal is a main ingredient such as copper, a copper
alloy, a copper oxide, an oxide of a copper alloy, tungsten, a
tungsten alloy, silver and gold. The conductive substance in which
copper is a main ingredient such as copper, a copper alloy, a
copper oxide and an oxide of a copper alloy is preferable, and more
preferably, at least one of copper and a copper alloy. As the
conductive substance layer, a film obtained by forming the
substance by the known spatter method and plating method can be
used.
[0069] The barrier layer applied for the invention is preferably
for the above conductive substance, particularly the barrier layer
for copper and a copper alloy. The barrier layer is formed in order
to prevent the conductive substance from diffusing into an
insulating film and enhance the adhesion between the insulating
film and the conductive substance. Examples of the composition of
the conductor forming the barrier layer include tantalum compounds
such as tantalum, tantalum nitride and a tantalum alloy, titanium
compounds such as titanium, titanium nitride and a titanium alloy,
and tungsten compounds such as tungsten, tungsten nitride and a
tungsten alloy. The composition of the conductor is preferably
selected from tantalum, tantalum nitride, a tantalum alloy,
titanium, titanium nitride, a titanium alloy, tungsten, tungsten
nitride and a tungsten alloy. The barrier layer may have a single
layer structure consisting of one kind or a lamination layer
structure consisting of two kinds or more.
[0070] Examples of the interlaminar insulating films include a
silicone based coating film and an organic polymer film. Examples
of the silicone based coating films include silicon dioxide, fluoro
silicate glass, organosilicate glass obtained by using
trimethylsilane and dimethoxydimethylsilane as a starting material,
siliconoxynitride, silica based coating films such as hydrogenated
silsesquioxane, silicon carbide and silicon nitride. Examples of
the organic polymer films include all aromatic low dielectric
constant interlaminar insulating film. Particularly, organosilicate
glass is preferable. These films are formed by a CVD method, a spin
coat method, a dip coat method or a spray method.
[0071] In the polishing method of the invention, as a polishing
machine, a generally-used polishing machine which includes a holder
for holding a substrate having the surface to be polished and a
polishing platen having a polishing pad stacked thereon and a motor
or the like mounted thereon whose speed of rotation is adjustable
can be used when the substrate is polished by the polishing
pad.
[0072] The material of the polishing pad stacked on the polishing
platen is not particularly restricted, and common nonwoven fabric,
foamed polyurethane, porous fluororesin and the like can be used as
the polishing pad. It is preferable that a groove is formed on the
polishing pad such that the polishing slurry is collected.
[0073] Though there is no particular restriction on the polishing
condition, the rotational speed of the platen is preferably kept
low (no higher than 200 rpm) such that the substrate does not come
off. The polishing pressure (processing load) at which the surface
to be polished, of the substrate, is pressed against the polishing
pad is preferably 1 to 100 kPa, and in order to achieve the
homogeneity of the polishing rate on the surface to be polished and
pattern-flatness in the satisfactory manner, is more preferably 5
to 50 kPa. The polishing slurry of the invention is continually
supplied in the space between the polishing pad and the surface to
be polished by a pump or the like during polishing. Though there is
no restriction on the amount, to be supplied, of the polishing
slurry, it is preferable that the surface of the polishing pad is
constantly covered with the polishing slurry.
[0074] Particularly, a surface to be polished, of a substrate, can
be polished by moving a polishing pad relative to the substrate in
the state in which the surface to be polished of the substrate is
pressed against a polishing pad, while the polishing slurry is
supplied onto the polishing pad stacked on the polishing platen. In
order to move the polishing pad relative to the substrate, the
substrate may be polished by the rotation and fluctuation of the
holder in addition to the rotation of the polishing platen. There
can be mentioned a polishing method for rotating epicyclically a
polishing platen and a polishing method for moving rectilinearly a
belt-like polishing pad in one direction of the longitudinal
direction. The holder may be in the fixing, rotating or fluctuating
state. These polishing methods can be suitably selected by the
surface to be polished or the polishing machine as long as the
polishing pad is moved relative to the substrate.
[0075] When the polishing of the substrate is completed, the
substrate is thoroughly washed with flowing water, water drops
attached on the substrate were removed by using spin dry or the
like, and dried.
[0076] Hereinafter, the embodiment of the polishing method of the
invention will be explained along with the formation of the wiring
layer in the semiconductor device.
[0077] First, an interlaminar insulating film made of silicon
dioxide or the like are laminated on a silicon substrate. A
specified pattern of dented portions (the exposed portion of the
substrate) is then formed on the surface of the interlaminar
insulating film by the known means such as the formation of a
resist layer and etching, and thereby the interlaminar insulating
film consisting of the projected portions and the dented portions
is formed. The barrier layer such as tantalums coating the
interlaminar insulating film along the unevenness of the surface
thereof on this interlaminar insulating film is formed by a vapor
deposition method or a CVD method or the like. The conductive
substance layer such as copper coating the barrier layer such that
the dented portions are filled up with the conductive substance is
formed by the vapor deposition method, the plating method or the
CVD method or the like. It is preferable that the forming thickness
of the interlaminar insulating film, the barrier layer and the
conductive substance, generally, is about within the range of 0.01
to 2.0 .mu.m, 1 to 100 nm and 0.01 to 2.5 .mu.m.
[0078] Next, the conductive substance layer formed on the surface
of the semiconductor substrate is polished by CMP using the
polishing slurry for the conductive substance of which the
polishing rate ratio of the conductive substance/the barrier layer
is sufficiently large, for example (first polishing process).
Thereby, the barrier layer of the projected portions formed on the
substrate is exposed to the surface, and a desired wiring pattern
is obtained by leaving the conductive substance layer in the dented
portions. The obtained pattern surface can be polished as the
surface to be polished for the second polishing process in the
polishing method using the polishing slurry of the invention.
[0079] In the second polishing process, the polishing slurry of the
invention which can polish the conductive substance, the barrier
layer and the interlaminar insulating film is used, and at least
the exposed barrier layer and the conductive substance formed in
the dented portions are polished by chemical machical polishing.
The polishing is completed when a desired pattern is obtained in
which the section of the barrier layer is exposed to the boundary
between the dented portion and the projected portion, the whole of
interlaminar insulating film under the barrier layer of the
projected portions is exposed, and the conductive substance layer
as the wiring layer at the dented portions is left. In order to
secure more superior flatness at the time of the polish completion,
a part of the interlaminar insulating film of the projected
portions may be further polished as over-polishing (when time until
a desired pattern can be obtained by the second polishing process
is 100 seconds, 50% over-polishing means polishing executed by
adding the polishing for 50 seconds to the polishing for 100
seconds).
[0080] Thus, an interlaminar insulating film and a second metal
wiring are further formed on the metal wiring such as copper formed
as described above. After an interlaminar insulating film is formed
between the wirings and on the wiring again, similarly, the entire
surface of the semiconductor substrate is polished, and is formed
as a smooth plane. The semiconductor device having the desired
number of wiring layers can be manufactured by repeating the
process at a predetermined number.
EXAMPLES
[0081] The present invention will be explained further in detail by
the following examples hereinafter. It should be noted that the
present invention is not restricted by any means to these
examples.
Examples 1 to 5, Comparative Examples 1 to 3
Method for Producing Polishing Slurry
[0082] 3.0 percent by weight of colloidal silica polishing
particles having an average particle diameter of 70 nm, 1.0 percent
by weight of hydrogen peroxide solution (a guaranteed reagent, an
aqueous solution of 30 percent by weight), BTA (benzotriazole) as
the metal anticorrosive agent and oxidized metal dissolving agent
shown in Table 1, in the concentrations (unit: percent by weight)
shown in Table 1, and pure water were blended such that the total
amount became 100 percent by weight based on the total weight of
the polishing slurry. An ammonia water (25%) was added and adjusted
such that the pH of the resultant solution was set to pH specified
in Table 1, and the polishing slurry used in Examples 1 to 5 and
Comparative Examples 1 to 3 was produced.
[0083] Polishing substrates were chemically and mechanically
polished on following conditions using each polishing slurry
produced above.
[Polishing Substrate]
[0084] Substrate (A): Silicon substrate having no pattern and
having a diameter of 5 inch (12.5 cm)
[0085] (a) Silicon substrate on which a tantalum film having a
thickness of 200 nm was formed (Film structure: Silicon
substrate/Silicon dioxide having a film thickness 300 nm/Tantalum
film having a film thickness of 200 nm)
[0086] (b) Silicon substrate on which a tantalum nitride film
having a thickness of 100 nm was formed (Film structure: Silicon
substrate/Silicon dioxide having a film thickness of 300
nm/Tantalum nitride film having a film thickness of 100 nm)
[0087] (c) Silicon substrate on which a silicon dioxide film having
a thickness of 1 .mu.m was formed (Film structure: Silicon
substrate/Silicon dioxide film having a film thickness of 1
.mu.m)
[0088] (d) Silicon substrate on which a copper film having a
thickness of 1.2 .mu.m was formed (Film structure: Silicon
substrate/Silicon dioxide having a film thickness of 300 nm/Barrier
layer: Tantalum nitride having a film thickness of 25 nm/Copper
having a film thickness of 1.2 .mu.m)
[0089] Substrate (B): Silicon substrate having a pattern and having
a diameter of 5 inch (12.5 cm) (Silicon substrate on which grooves
having a depth of 0.5 .mu.m were formed/Silicon dioxide having a
film thickness of 300 nm/Barrier layer: Tantalum nitride having a
film thickness of 50 nm/Copper having a film thickness of 1.2
.mu.m)
[0090] The above substrate (B) was produced by the following
method. Grooves having a wiring density of 50%, wiring width of
0.35 to 100 .mu.m and a depth of 0.5 .mu.m were formed on a silicon
substrate, and a silicon dioxide film having a thickness of 300 nm
was formed by the known plasma CVD method. A tantalum nitride film
having a thickness of 50 nm as the barrier layer was formed by the
known spatter method. Similarly, a copper film of 1.2 .mu.m was
formed by the spatter method, and the resultant substrate was
subjected to the known heat treatment.
[0091] As the specific resistance values of the above copper and
conductor used for evaluation of the polishing rate and etching
rate, a copper film of 1.83 .mu..OMEGA.cm, a tantalum nitride film
of 263 .mu..OMEGA.cm and a tantalum film of 184 .mu..OMEGA.cm were
used.
[Polishing Condition]
[0092] Supply of polishing slurry: 50 cc/minute
[0093] Polishing machine: deadweight load type polishing machine
for experiment (the diameter of a polishing platen: .phi.40 cm)
[0094] Polishing pad: Foamed polyurethane resin (IC1000,
manufactured by Rodel Inc.)
[0095] Polishing pressure: 14 kPa
[0096] Relative speed of the substrate with respect to the
polishing platen: 36 m/min
[0097] Rotating rate of a polishing platen: 60 rpm
[0098] A resistance meter Model RT-80 (trade name, manufactured by
Napson Company) was used for measuring the sheet resistance value
for calculating the film thickness before and behind CMP and
etching process.
[Evaluation Item of Polishing Slurry]
[0099] (1) Etching rate: The etching rate was obtained from the
difference in film thickness of the copper layer before or after
the immersion of a substrate having a copper film and no pattern in
the polishing slurries of Examples and Comparative Examples which
were being stirred (room temperature of 25.degree. C., the stirring
rate of 100 rpm), which difference in film thickness being
converted from the electric resistance.
[0100] (2) Polishing rate due to CMP: The difference in film
thickness before or after the above substrate (A) (Substrate having
no pattern: Silicon substrate having a copper film, tantalum
nitride, a tantalum film or a silicon dioxide film) was chemically
and mechanically polished for 1 minute was obtained by being
converted from the electric resistance.
[0101] (3) Magnitude of dishing: Copper was chemically and
mechanically polished by using a polishing slurry (trade name:
HS.cndot.4000, manufactured by Hitachi Chemical Co., Ltd.) until
the barrier layer made of tantalum nitride was exposed on the
entire surface of the above substrate (B) (first polishing
process). The polishing slurry has a sufficiently large polishing
rate ratio of copper to tantalum nitride, and is a polishing slurry
for copper which contains no polishing particle.
[0102] The magnitude of dishing measured at a 100/100 .mu.m pattern
portion was 50 nm in the state that the barrier layer was exposed
on an insulated film portion after the above first polishing
process, and the magnitude of thinning measured at a 4.5/0.5 .mu.m
pattern portion was 20 nm. Then, the surface was polished by the
polishing slurries of Examples and Comparative Examples until
tantalum nitride on the insulated film portion was lost (second
polishing process). The substrate was polished for the time
obtained by adding 1 minute to the polishing time of tantalum
nitride of 50 nm in the polishing rate conversion evaluated by CMP
of a tantalum nitride substrate having no pattern.
[0103] The reduction in film thickness (magnitude of dishing) of
the wiring metal portion to the insulated film portion was then
obtained, by using a surface profilometer, from the surface
configuration of the stripe-like pattern portion in which the
wiring metal portions of 100 .mu.m width and the insulating film
portions of 100 .mu.m width were alternately arranged.
[0104] (4) Magnitude of thinning: The surface configuration of the
stripe-like pattern portion having a total width of 2.5 mm in which
wiring metal portions of 4.5 .mu.m width and insulating film
portions of 0.5 .mu.m width arranged alternately formed on the
substrate in which the above (3) magnitude of dishing was evaluated
was measured by using the surface profilometer. The reduction in
film thickness of the insulated film portion near the center of the
pattern to the insulating film field portion around the stripe-like
pattern was then obtained.
[0105] (5) Corrosion: The surface to be polished after evaluating
the above (4) magnitude of thinning was observed with 1000
magnifications using a microscope (trade name: AL-2000,
manufactured by Olympus Optical Co., Ltd.), and presence/absence of
generation of foreign matterlike projections was evaluated.
[0106] The evaluation results (the polishing rate of the various
films by CMP, the etching rate of copper, the magnitude of dishing,
the magnitude of thinning and presence/absence of corrosion) in
Examples 1 to 5 and Comparative Examples 1 to 3 were shown in Table
1.
TABLE-US-00001 TABLE 1 Example oxidized metal CMP polishing
rate(nm/min) No. dissolving agent BTA pH Tantalum Silicon unit wt %
wt % -- Cupper Tantalum nitride dioxide Exam- 1 succinic 0.15 3.13
16.0 45.0 63.5 15.5 ple acid 0.6 2 lactic 0.15 3.05 8.0 24.3 38.0
15.0 acid 0.05 3 adipic 0.10 3.23 12.0 35.5 53.5 16.0 acid 0.6 4
glutaric 0.10 3.18 14.0 39.5 56.5 14.8 acid 0.6 5 glutaric 0.15
3.55 12.5 29.5 48.5 15.0 acid 0.6 Compar- 1 oxalic 0.2 2.40 33.5
31.5 42.5 15.2 ative acid 0.15 Exam- 2 malic 0.2 3.70 17.0 15.0
29.8 14.8 ple acid 0.5 3 succinic 0.15 4.10 3.5 10.0 19.5 14.5 acid
0.6 Example oxidized metal Cupper Magnitude Magnitude Corrosion of
No. dissolving agent etching rate of dishing of thinning Cupper
wiring unit wt % nm/min nm nm -- Exam- 1 succinic 0.3 20 30 absence
ple acid 0.6 2 lactic 0.6 35 30 absence acid 0.05 3 adipic 0.1 25
25 absence acid 0.6 4 glutaric 0.2 25 25 absence acid 0.6 5
glutaric 0.0 40 30 absence acid 0.6 Compar- 1 oxalic 30.0 80 60
presence ative acid 0.15 Exam- 2 malic 0.2 65 40 absence ple acid
0.5 3 succinic 0.1 55 35 absence acid 0.6
[0107] An organic acid of which the pKa was small was used in the
Comparative Example 1. Since the pH of the polishing slurry was
low, the polishing rate of copper was large, and the flatness
characteristic such as dishing and thinning was inferior. In
addition, when the substrate having the pattern was polished,
corrosion was found at the copper wiring portion. Since an organic
acid of which the pKa was comparatively small was used and the pH
was adjusted to pKa or more in the Comparative Example 2, the
polishing rate of the tantalum system conductor was small and the
flatness characteristic was also inferior. Though an acid of which
the pKa was 3.5 or more was used in the Comparative Example 3,
since the pH was adjusted to 4 or more, the polishing rate of the
tantalum system conductor was small and flatness efficiency was
also inferior.
[0108] On the other hand, in Examples 1 to 5, the high polishing
rate, excellent dishing and thinning characteristics of the
tantalum system conductor were obtained.
INDUSTRIAL APPLICABILITY
[0109] According to the invention, in the wiring-formation process
of the semiconductor device, the high polishing rate of the
conductor used for the barrier layer can be realized by the
polishing slurry having low polishing particle concentration and
low metal anticorrosive agent concentration. The occurrence of the
dishing and thinning of the metal wiring is reduced by suppressing
the etching of the metal for wiring, and highly reliable embedding
wiring pattern of the metal film can be formed. According to the
polishing slurry and polishing method of the invention, the
high-reliability semiconductor device and apparatus which are
excellent in miniaturization, thin film, dimensional accuracy and
electrical characteristic can be suitably manufactured.
* * * * *