U.S. patent application number 11/374349 was filed with the patent office on 2006-07-06 for methods for forming ruthenium films with beta-diketone containing ruthenium complexes and method for manufacturing metal-insulator-metal capacitor using the same.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Jung-hee Chung, Suk-jin Chung, Sung-tae Kim, Wan-don Kim, Jin-il Lee, Kwang-hee Lee, Han-Jin Lim, Cha-young Yoo.
Application Number | 20060148193 11/374349 |
Document ID | / |
Family ID | 36641067 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060148193 |
Kind Code |
A1 |
Lee; Kwang-hee ; et
al. |
July 6, 2006 |
Methods for forming ruthenium films with beta-diketone containing
ruthenium complexes and method for manufacturing
metal-insulator-metal capacitor using the same
Abstract
Provided are 1) a method for forming a ruthenium film under a
single process condition, whereby high adhesion of the ruthenium
film to a lower layer is maintained, and 2) a method for
manufacturing an metal-insulator-metal (MIM) capacitor using the
ruthenium film forming method. The method for forming a ruthenium
film includes supplying bis(isoheptane-2,4-dionato)norbornadiene
ruthenium at a flow rate of 0.2-1 ccm and oxygen at a flow rate of
20-60 sccm, and depositing the ruthenium film at a temperature of
330-430.degree. C. under a pressure of 0.5-5 Torr using chemical
vapor deposition (CVD).
Inventors: |
Lee; Kwang-hee; (Seoul,
KR) ; Yoo; Cha-young; (Suwon-city, KR) ; Lim;
Han-Jin; (Seoul, KR) ; Kim; Sung-tae; (Seoul,
KR) ; Chung; Suk-jin; (Suwon-city, KR) ; Kim;
Wan-don; (Yongin-city, KR) ; Chung; Jung-hee;
(Seoul, KR) ; Lee; Jin-il; (Sungnam-city,
KR) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
|
Family ID: |
36641067 |
Appl. No.: |
11/374349 |
Filed: |
March 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10657596 |
Sep 8, 2003 |
7049232 |
|
|
11374349 |
Mar 13, 2006 |
|
|
|
Current U.S.
Class: |
438/396 ;
438/681 |
Current CPC
Class: |
H01L 21/28556 20130101;
H01L 28/65 20130101; H01L 27/11502 20130101; H01L 27/11507
20130101; C23C 16/18 20130101; H01L 27/10852 20130101 |
Class at
Publication: |
438/396 ;
438/681 |
International
Class: |
H01L 21/44 20060101
H01L021/44 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2003 |
KR |
2003-12044 |
Claims
1. A method for manufacturing a metal-insulator-metal (MIM)
capacitor, comprising: (a) forming a first ruthenium film for a
lower electrode on a semiconductor substrate; (b) forming a
dielectric layer on the lower electrode; and (c) forming a second
ruthenium film for an upper electrode on the dielectric layer, step
(a) comprising supplying a two .beta.-diketones-coordinated
ruthenium complex as a ruthenium source at a flow rate of 0.2-1 ccm
and oxygen at a flow rate of 20-60 sccm onto the substrate and
depositing the first ruthenium film using CVD, and step (c)
comprising supplying a two .beta.-diketones-coordinated ruthenium
complex as a ruthenium source at a flow rate of 0.2-1 ccm and
oxygen at a flow rate of 20-60 sccm onto the substrate and
depositing the second ruthenium film using CVD.
2. The method according to claim 1, wherein the ruthenium source is
a two .beta.-diketones and one diene-coordinated ruthenium complex
as represented by the formula 1: ##STR4## wherein R.sub.1 and
R.sub.2 are alkyl groups; the total carbon number of R.sub.1 and
R.sub.2 is 3 to 5; and R.sub.3, R.sub.4 and R.sub.5 are
interconnected to each other to form a chain.
3. The method according to claim 2, wherein the diene is
1,4-cyclohexadiene, norbornadiene, or 1,5-cyclooctadiene.
4. The method according to claim 2, wherein R.sub.1 and R.sub.2 are
asymmetric.
5. The method according to claim 1, wherein the ruthenium source is
a two .beta.-diketones and one diamine-coordinated ruthenium
complex as represented by the formula 2: ##STR5## wherein R.sub.1
and R.sub.2 are alkyl groups; the total carbon number of R.sub.1
and R.sub.2 is 2 to 5; R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.10
and R.sub.11 are independently hydrogen or alkyl groups; and the
total carbon number of R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.10
and R.sub.11 is 2 to 8.
6. The method according to claim 5, wherein the diamine is
N,N,N',N'-tetramethylethylenediamine.
7. The method according to claim 5, wherein R.sub.1 and R.sub.2 are
asymmetric.
8. The method according to claim 1, wherein the ruthenium source is
a two .beta.-diketones and two organic ligands-coordinated
ruthenium complex as represented by the formula 3: ##STR6##
wherein, R.sub.1 and R.sub.2 are alkyl groups; the total carbon
number of R.sub.1 and R.sub.2 is 2 to 5; and two R.sub.12 are
olefin, amine, nitrile or carbonyl.
9. The method according to claim 8, wherein the olefin is ethylene,
propylene, 2-methylpropylene, butyl, or 1,3-butadiene.
10. The method according to claim 9, wherein the amine is
trimethylamine or triethylamine.
11. The method according to claim 10, wherein the nitirile is
acetonitrile or acrylonitrile.
12. The method according to claim 9, wherein the two
.beta.-diketones are 2,4-hexanedione, 5-methyl-2,4-hexanedione,
2,4-heptanedione, 5-methyl-2,4-heptanedione,
6-methyl-2,4-heptanedione, or 2,4-octanedione.
13. The method according to claim 1, wherein the ruthenium source
is bis(isoheptane-2,4-dionato)norbornadiene ruthenium.
14. The method according to claim 1, wherein the ruthenium film is
deposited at a temperature of 330-430.degree. C.
15. The method according to claim 1, wherein the ruthenium film is
deposited under a pressure of 0.5-5 Torr.
16. The method according to claim 1, wherein the depositing of the
ruthenium film includes supplying an inert gas, including nitrogen
and argon, onto the substrate.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 10/657,596, filed Sep. 8, 2003 which claims priority to Korean
Patent Application No. 2003-12044, filed on Feb. 26, 2003, in the
Korean Intellectual Property Office, the disclosures of which are
incorporated herein by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to film formation in the
manufacturing of metal-insulator-metal (MIM) capacitors.
[0004] 2. Description of the Related Art
[0005] Recently, due to their excellent electrical properties (such
as resistivity), ruthenium and ruthenium compounds are being used
as thin film electrode materials in the production of semiconductor
devices for Dynamic Random Access Memory (DRAM) and Ferroelectric
Random Access Memory (FeRAM).
[0006] Ruthenium or ruthenium compound films are usually formed by
sputtering or chemical vapor deposition (CVD) methods. In
particular, CVD is preferred since thin layers with uniform
thickness are easily formed.
[0007] In order to form ruthenium films using CVD, a ruthenium
source is required. Currently, bis(ethylcyclopentadienyl)ruthenium
[Ru(EtCp).sub.2], as shown in FIG. 1, is the most common ruthenium
source. Such an organic ruthenium compound is obtained by replacing
one hydrogen on each of two cyclopentadiene rings of
bis(cyclopentadienyl)ruthenium with an ethyl group. Because the
bis(ethylcyclopentadienyl)ruthenium has a low melting point, it is
a liquid at room temperature. Therefore,
bis(ethylcyclopentadienyl)ruthenium possesses good handling
properties.
[0008] However, the bis(ethylcyclopentadienyl)ruthenium has
problems in its use as a material for ruthenium films. The main
problem is that it is difficult to carry out the nucleation of the
bis(ethylcyclopentadienyl)ruthenium. In order to solve this
problem, ruthenium films are generally formed under increased
oxygen flow rate and deposition pressure. However, if the oxygen
flow rate and the deposition pressure are increased, the nucleation
rate per unit area is excessively increased. As a result, ruthenium
films form in a needle shape. Formation of such needle-shaped
ruthenium films results in surface morphology, increase of a sheet
resistance, and generation of a leakage current. On the other hand,
if ruthenium films are formed under decreased deposition pressure
and oxygen flow rate, the nucleation rate is excessively lowered.
As a result, ruthenium grains are separated from each other.
[0009] Due to this problem, when
bis(ethylcyclopentadienyl)ruthenium is used as the ruthenium source
for forming films, ruthenium films may sometimes be formed using a
method comprising (a) carrying out nucleation of the
bis(ethylcyclopentadienyl)ruthenium under increased oxygen flow
rate and deposition pressure and (b) depositing the ruthenium films
under decreased oxygen rate and deposition pressure. In this case,
however, due to the different process conditions used, the process
burden is increased. In addition, if the two steps are carried out
in-situ, the process conditions become unstable during the
transitional stage between the two steps. As a result, the
reproducibility and reliability of the process are lowered. On the
other hand, if the two steps are carried out in two separate
chambers, a residue may be left on the surface of a wafer when the
wafer is transferred from one chamber to the other. In addition,
when a gas for cooling the wafer is introduced into a chamber, the
wafer is often displaced due to the change in pressure. As a
result, the ruthenium films on the wafer do not have uniform
thickness.
[0010] Meanwhile, the bis(ethylcyclopentadienyl)ruthenium has
another problem in that ruthenium films made of
bis(ethylcyclopentadienyl)ruthenium have relatively low adhesion to
silicon dioxide films which are commonly used as interlayer
insulating layers.
SUMMARY OF THE INVENTION
[0011] The present invention provides a method for forming a
ruthenium film under a single process condition, whereby high
adhesion of the ruthenium film to a lower layer is maintained.
[0012] The present invention also provides a method for
manufacturing a metal-insulator-metal (MIM) capacitor using the
ruthenium film formation method.
[0013] The present invention discloses a method for forming a
ruthenium film, the method comprising supplying a two
.beta.-diketones-coordinated ruthenium organic matter as a
ruthenium source and oxygen onto a substrate and depositing the
ruthenium film using chemical vapor deposition (CVD).
[0014] According to one embodiment of the present invention, there
is provided a method for forming a ruthenium film, the method
comprising supplying a bis-.beta.-diketones-coordinated ruthenium
complex as the ruthenium source at a flow rate of 0.2 to 0.1 ccm,
and oxygen at a flow rate of 20 to 60 sccm onto a substrate and
depositing the ruthenium film using CVD.
[0015] According to one preferred embodiment of the present
invention, the ruthenium source is a two .beta.-diketones and one
diene-coordinated ruthenium complex, as represented by the general
formula 1: ##STR1## [0016] wherein R.sub.1 and R.sub.2 are alkyl
groups; the total carbon number of R.sub.1 and R.sub.2 is 3 to 5;
and R.sub.3, R.sub.4 and R.sub.5 are interconnected to each other
to form a chain.
[0017] The diene is preferably 1,4-cyclohexadiene, norbornadiene,
or 1,5-cyclooctadiene. Preferably, R.sub.1 and R.sub.2 are
asymmetric.
[0018] In another embodiment, the ruthenium source is a two
.beta.-diketones and one diamine-coordinated ruthenium complex, as
represented by the general formula 2: ##STR2## [0019] wherein
R.sub.1 and R.sub.2 are alkyl groups; the total carbon number of
R.sub.1 and R.sub.2 is 3 to 5; R.sub.6, R.sub.7, R.sub.8, R.sub.9,
R.sub.10 and R.sub.11 are independently hydrogen or alkyl groups;
and the total carbon number of R.sub.6, R.sub.7, R.sub.8, R.sub.9,
R.sub.10 and R.sub.11 is 2 to 8.
[0020] The diamine is preferably
N,N,N',N'-tetramethylethylenediamine. Preferably, R.sub.1 and
R.sub.2 are asymmetric.
[0021] In another embodiment, the ruthenium source is a two
.beta.-diketones and two organic ligands-coordinated ruthenium
complex, as represented by the general formula 3: ##STR3## [0022]
wherein R.sub.1 and R.sub.2 are alkyl groups; the total carbon
number of R.sub.1 and R.sub.2 is 2 to 5; and two R.sub.12 groups
are olefin, amine, nitrile or carbonyl.
[0023] As used as the organic ligand, the olefin is preferably
ethylene, propylene, 2-methylpropylene, butyl, or 1,3-butadiene;
the amine is preferably trimethylamine or triethylamine; and the
nitirile is preferably acetonitrile or acrylonitrile. The two
.beta.-diketones are preferably 2,4-hexanedione,
5-methyl-2,4-hexanedione, 2,4-heptanedione,
5-methyl-2,4-heptanedione, 6-methyl-2,4-heptanedione, or
2,4-octanedione.
[0024] The ruthenium source is preferably
bis(isoheptane-2,4-dinato)norbornadiene ruthenium.
[0025] The ruthenium film is deposited at a temperature of
330-430.degree. C. under a pressure of 0.5-5 Torr. When the
ruthenium film is deposited, an inert gas such as nitrogen or argon
is supplied onto the substrate.
[0026] According to another embodiment of the present invention,
there is provided a method for forming a ruthenium film, the method
supplying bis(isoheptane-2,4-dionato)norbornadiene ruthenium as the
ruthenium source at a flow rate of 0.2 to 1 ccm and oxygen at a
flow rate of 20 to 60 sccm onto a substrate and depositing the
ruthenium film using CVD at a temperature of 330-430.degree. C.
under a pressure of 0.5-5 Torr.
[0027] According to yet another aspect of the present invention,
there is provided a method for manufacturing an MIM capacitor, the
method comprising (a) forming a first ruthenium film for a lower
electrode on a semiconductor substrate; (b) forming a dielectric
layer on the lower electrode; and (c) forming a second ruthenium
film for an upper electrode on the dielectric layer. Step (a)
comprises supplying a two .beta.-diketones-coordinated ruthenium
complex as the ruthenium source at a flow rate of 0.2-1 ccm and
oxygen at a flow rate of 20-60 sccm onto the substrate and
depositing the first ruthenium film using CVD. Step (c) comprises
supplying a two .beta.-diketones-coordinated ruthenium complex as a
ruthenium source at a flow rate of 0.2-1 ccm and oxygen at a flow
rate of 20-60 sccm onto the substrate and depositing the second
ruthenium film using CVD.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The above and other features and advantages of the present
invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
[0029] FIG. 1 is a general formula of a conventional ruthenium
source for forming ruthenium films;
[0030] FIG. 2 is a cross sectional view of a ruthenium film formed
on a semiconductor substrate according to the present
invention;
[0031] FIGS. 3 to 5 are formulas of ruthenium sources for forming
ruthenium films according to embodiments of the present
invention;
[0032] FIG. 6 is a graph showing variation in a deposition rate
with temperature using a ruthenium source according to the present
invention;
[0033] FIG. 7 is a graph showing variation in resistivity with
temperature using a ruthenium source according to the present
invention;
[0034] FIG. 8 is a graph showing variation in deposition rate with
pressure using a ruthenium source according to the present
invention;
[0035] FIG. 9 is a graph showing variation in resistivity with
pressure using a ruthenium source according to the present
invention;
[0036] FIG. 10 is a graph showing variation in each of resistivity,
deposition rate, and step coverage with oxygen flow rate using a
ruthenium source according to the present invention;
[0037] FIGS. 11A, 11B and 11C are photographs of ruthenium films
formed at an oxygen flow rate of 16 sccm using a ruthenium source
according to the present invention; (A) a ruthenium film after
deposition, (B) a ruthenium film that was annealed at 450.degree.
C. under a hydrogen atmosphere for 30 minutes after deposition, and
(C) a ruthenium film that was annealed at 700.degree. C. under a
nitrogen atmosphere for 30 minutes after deposition;
[0038] FIGS. 12A, 12B and 12C are photographs of ruthenium films
formed at an oxygen flow rate of 40 sccm using a ruthenium source
according to the present invention; (A) a ruthenium film after
deposition, (B) a ruthenium film that was annealed at 450.degree.
C. under a hydrogen atmosphere for 30 minutes after deposition, and
(C) a ruthenium film that was annealed at 700.degree. C. under a
nitrogen atmosphere for 30 minutes after deposition;
[0039] FIGS. 13A, 13B and 13C are photographs of ruthenium films
formed at an oxygen flow rate of 70 sccm using a ruthenium source
according to the present invention; (A) a ruthenium film after
deposition, (B) a ruthenium film that was annealed at 450.degree.
C. under a hydrogen atmosphere for 30 minutes after deposition, and
(C) a ruthenium film that was annealed at 700.degree. C. under a
nitrogen atmosphere for 30 minutes after deposition;
[0040] FIG. 14 is a graph showing variation in deposition rate with
a flow rate of a ruthenium source according to the present
invention;
[0041] FIG. 15 is a graph showing variation in resistivity with a
flow rate of a ruthenium source according to the present
invention;
[0042] FIG. 16 is a graph showing variation in leakage current
density with applied voltage using a ruthenium source according to
the present invention; and
[0043] FIGS. 17A and 17B are cross sectional views of a
semiconductor substrate in successive steps in a method for
manufacturing a metal-insulator-metal (MIM) capacitor according to
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0044] Hereinafter, exemplary embodiments of the present invention
will be described with reference to the accompanying drawings.
However, the present invention is not limited to these embodiments
and various modifications can be carried out. The embodiments of
the present invention are provided to assist ordinary persons
skilled in the art to more clearly understand the present
invention. In this regard, each constitutional element on drawings
is graphically expressed for proper understanding. The same
numerals are used for the corresponding constitutional elements in
drawings. As used herein, the expression "a first layer is formed
`on` a second layer or a semiconductor substrate" includes the case
where the first layer indirectly contacts with the second layer due
to a third layer between the first layer and the second layer, in
addition to direct contact of the first layer and the second
layer.
[0045] Referring to FIG. 2, first, a semiconductor substrate 100 is
placed in a chamber. The substrate 100 may be a silicon substrate.
An MOS transistor (not shown) and an interlayer insulating layer
(not shown) may be formed on the substrate. Although not clearly
shown in FIG. 2, a silicon dioxide film as an interlayer insulating
layer is formed on the uppermost surface of the substrate 100. In
accordance with the present invention, a ruthenium film 110 is
formed on the substrate 100 from a ruthenium source of the present
invention using chemical vapor deposition (CVD).
[0046] In one embodiment of the present invention, a ruthenium
source for forming the ruthenium film 110 is a two .beta.-diketones
and one diene-coordinated ruthenium complex (see FIG. 3). R.sub.1
and R.sub.2 as substituents of each .beta.-diketone may be alkyl
groups. The total carbon number of R.sub.1 and R.sub.2 is 3 to 5.
Preferably, R.sub.1 and R.sub.2 may be asymmetric. The diene may be
1,4-cyclohexadiene, norbornadiene or 1,5-cyclooctadiene.
[0047] In another embodiment of the present invention, a ruthenium
source for forming the ruthenium film 110 is a two .beta.-diketones
and one diamine-coordinated ruthenium complex (see FIG. 4). R.sub.1
and R.sub.2 as substituents of each .beta.-diketone may be alkyl
groups. The total carbon number of R.sub.1 and R.sub.2 may be 2 to
5. Preferably, R.sub.1 and R.sub.2 may be asymmetric. The two
.beta.-diketones may be 2,4-hexanedione, 5-methyl-2,4-hexanedione,
2,4-heptanedione, 5-methyl-2,4-heptanedione,
6-methyl-2,4-heptanedione, or 2,4-octanedione. R.sub.6, R.sub.7,
R.sub.8, R.sub.9, R.sub.10 and R.sub.11 as substituents of the
diamine are independently hydrogen or alkyl groups. Total carbon
number of these substituents may be 2 to 8. The diamine may be
N,N,N',N'-tetramethylethylenediamine.
[0048] In yet another embodiment of the present invention, a
ruthenium source for forming the ruthenium film 110 is a two
.beta.-diketones and two organic ligands-coordinated ruthenium
complex (see FIG. 5). R.sub.1 and R.sub.2 as substituents of each
.beta.-diketone may be alkyl groups. The total carbon number of
R.sub.1 and R.sub.2 may be 2 to 5. Two R.sub.12 groups as the
organic ligands are olefin, amine, nitrile or carbonyl. As used as
the organic ligand, the olefin may be ethylene, propylene,
2-methylpropylene, butyl, or 1,3-butadiene; the amine may be
trimethylamine or triethylamine; and the nitirile may be
acetonitrile or acrylonitrile.
[0049] Hereinafter, optimal process condition for forming a
ruthenium film will be described using
bis(isoheptane-2,4-dionato)norbornadiene ruthenium
[Ru(C.sub.7H.sub.8)(C.sub.7H.sub.11O.sub.2).sub.2, simply referred
to as "bis norbornadiene ruthenium", hereinafter] as a ruthenium
source.
[0050] In order to determine a relationship between the deposition
rate and temperature, the deposition rate of a ruthenium film was
measured as a function of temperature (330-440.degree. C.) while
varying the ruthenium source flow rate (0.2-1 ccm) and oxygen flow
rate (8-100 sccm). As shown in FIG. 6, the deposition rate showed
little change over the temperature range when the ruthenium source
flow rate and oxygen flow rate was held constant.
[0051] Under the same variable values as mentioned above, the
resistivity was measured as a function of temperature while varying
the ruthenium source flow rate and the oxygen flow rate. As shown
in FIG. 7, it can be seen that resistivity does not depend on
temperature when the ruthenium source flow rate and oxygen flow
rate are constant.
[0052] In order to determine a relationship between the deposition
rate and pressure, the deposition rate of a ruthenium film as a
function of pressure (100-700 Torr) was measured while varying the
ruthenium source flow rate (0.2-1 ccm) and the oxygen flow rate
(8-100 sccm). As shown in FIG. 8, the deposition rate showed little
change over the pressure range. Rather, the deposition rate varied
with the ruthenium source flow rate and the oxygen flow rate.
[0053] Under the same variable values as mentioned above,
resistivity as a function of pressure was measured while varying
the ruthenium source flow rate and the oxygen flow rate. As shown
in FIG. 9, pressure only slightly affects resistivity.
[0054] Therefore, it can be said that temperature and pressure have
minimal effects on the physical properties of ruthenium sources
according to the present invention. However, with reference to the
deposition temperature, ruthenium sources according to the present
invention, such as the bis norbornadiene ruthenium, spontaneously
decompose and react with other compounds at a temperature range of
250-500.degree. C. Therefore, preferably, the film deposition is
carried out at 250-500.degree. C.
[0055] Next, resistivity, deposition rate and step coverage were
measured while varying the oxygen flow rate and keeping the flow
rate of the ruthenium source constant. Oxygen was supplied over the
range of 0-100 sccm, and the ruthenium source was supplied at a
constant rate of 1 ccm. The deposition temperature was 350.degree.
C. and the deposition pressure was 1 Torr. In the case of
depositing the ruthenium film under the conditions mentioned above,
as the oxygen flow rate was increased, resistivity was remarkably
decreased, but the deposition rate (deposition speed) was
increased. Step coverage was gradually decreased after the oxygen
flow rate exceeded 60 sccm.
[0056] FIGS. 11 to 13 show scanning electron microscope (SEM)
photographs of ruthenium films of the present invention.
[0057] FIGS. 11A, 11B and 11C show images of ruthenium films formed
at an oxygen flow rate of 16 sccm using a ruthenium source of the
present invention; (A) a ruthenium film after deposition, (B) a
ruthenium film that was annealed at 450.degree. C. under a hydrogen
atmosphere for 30 minutes after deposition, and (C) a ruthenium
film that was annealed at 700.degree. C. under a nitrogen
atmosphere for 30 minutes after deposition.
[0058] FIGS. 12A, 12B and 12C show images of ruthenium films formed
at an oxygen flow rate of 40 sccm using a ruthenium source of the
present invention; (A) a ruthenium film after deposition, (B) a
ruthenium film that was annealed at 450.degree. C. under a hydrogen
atmosphere for 30 minutes after deposition, and (C) a ruthenium
film that was annealed at 700.degree. C. under a nitrogen
atmosphere for 30 minutes after deposition.
[0059] FIGS. 13A, 13B and 13C show images of ruthenium films formed
at an oxygen flow rate of 70 sccm using a ruthenium source of the
present invention; (A) a ruthenium film after deposition, (B) a
ruthenium film that was annealed at 450.degree. C. under a hydrogen
atmosphere for 30 minutes after deposition, and (C) a ruthenium
film that was annealed at 700.degree. C. under a nitrogen
atmosphere for 30 minutes after deposition.
[0060] As shown in FIGS. 11 to 13, when a ruthenium film is
subjected to annealing at 450.degree. C., the ruthenium source is
sufficiently decomposed by the oxygen, resulting in the reduction
of impurities in the ruthenium film. In the ruthenium film surfaces
from which impurities are removed, grain growth and agglomeration
are partially caused. On the other hand, when a ruthenium film is
annealed at 700.degree. C., surface areas on which a small amount
of oxygen is provided have smooth surfaces. In surface areas on
which a large amount of oxygen is provided, excess grain growth and
agglomeration result (see FIG. 13C).
[0061] As apparent from the above description, in order to form a
ruthenium film with optimal resistivity, deposition rate and step
coverage, the oxygen flow rate is preferably 20 to 60 sccm.
[0062] Next, the deposition rate and resistivity as a function of
the ruthenium source flow rate according to the present invention
will be described. FIG. 14 is a graph showing variation in
deposition rate with the flow rate of a ruthenium source of the
present invention. As shown in FIG. 14, the deposition rate is
increased as the flow rate of a ruthenium source is increased. In
particular, as both of the oxygen flow rate and the ruthenium
source flow rate are increased, the deposition rate is remarkably
increased. Similarly, as the flow rate of a ruthenium source is
increased, resistivity is increased (FIG. 15). However, resistivity
is decreased as the oxygen flow rate is increased. Therefore, in
order to form a ruthenium film with optimal resistivity, deposition
rate and step coverage, it is preferable to provide ruthenium
sources of the present invention at a flow rate of about 0.2 to 1
ccm, and more preferably at 0.4 to 0.8 ccm.
[0063] In summary, the ruthenium film 110 with optimal resistivity,
deposition rate, and step coverage according to the present
invention can be formed under the following conditions: an oxygen
flow rate of 20 to 60 sccm, a ruthenium source flow rate of 0.2 to
1 ccm, a deposition temperature of 200 to 500.degree. C. (and
preferably 330 to 430.degree. C.) and a deposition pressure of 0.1
to 30 Torr (and preferably 0.5 to 5 Torr). Decomposition of a
ruthenium source is maximized at the aforementioned deposition
temperature and pressure range.
[0064] Under the aforementioned conditions, the ruthenium seed is
uniformly distributed on the surface of an interlayer insulating
layer and a high quality ruthenium film 110 is formed without
altering the process condition. Furthermore, because the
aforementioned two-step CVD process is not used, the process burden
is reduced and device reliability is improved. In order to improve
process efficiency, an inert gas such as nitrogen and argon may be
supplied onto a substrate.
[0065] Meanwhile, adhesion of ruthenium films were tested using a
ruthenium source of the present invention and the conventional
bis(ethylcyclopentadienyl)ruthenium. The adhesion test refers to a
"peeling test". For the peeling test, ruthenium films were formed
on wafers with a size of 20 cm.times.20 cm. Each wafer was cut into
a total of 1600 grids with specimen sizes of 5 mm.times.5 mm. Then,
cellophane tapes were attached to the specimens. After the
cellophane tapes were removed from the specimens, the number of
specimens of ruthenium films that were peeled off from wafers was
measured. In most specimens of the present invention, ruthenium
films were not peeled off from wafers. However, in the conventional
ruthenium films, 35 specimens were peeled off from wafers. Based on
this test, it can be seen that ruthenium films formed using
ruthenium sources of the present invention have superior adhesion
to an interlayer insulating layer than those formed using a
conventional ruthenium source.
[0066] FIG. 16 is a graph showing the leakage current density of a
ruthenium film according to the present invention. It can be seen
from FIG. 16 that ruthenium films of the present invention exhibit
stable leakage current.
[0067] Hereinafter, a method for manufacturing an MIM capacitor
using the aforementioned ruthenium film forming method will be
described in detail.
[0068] Reference is made to FIG. 17A, an interlayer insulating
layer 210 in which a storage node plug 205 is contained is formed
on a semiconductor substrate 200. A mold oxide layer 215 is
deposited on the interlayer insulating layer 210. An etch stopper
(not shown) may be placed between the interlayer insulating layer
210 and the mold oxide layer 215.
[0069] Then, the mold oxide layer 215 is etched to expose the
storage node plug 205, thereby forming a lower electrode area 218.
A first ruthenium film 220 is formed on the mold oxide layer 215
and the lower electrode area 218. The first ruthenium film is
preferably formed by a method comprising supplying a ruthenium
source at a flow rate of 0.2-1 ccm and oxygen at a flow rate of
8-100 sccm and preferably 20-60 sccm onto a substrate and
depositing the ruthenium film at a temperature of 330-430.degree.
C. under a pressure of 0.5-5 Torr using CVD. The ruthenium source
is a two .beta.-diketones-coordinated ruthenium complex such as bis
norbornadiene ruthenium. In the case of using such a ruthenium
source under the aforementioned single process condition, a
ruthenium film of uniform thickness can be formed.
[0070] Reference is now made to FIG. 17B. In FIG. 17B, the
ruthenium film 220 (from FIG. 17A) was subjected to chemical and
mechanical polishing (CMP) to expose the mold oxide layer 215,
resulting in formation of a lower electrode 225. Before the CMP
process, a buffer oxide layer may be formed on the first ruthenium
film 220. Then, the mold oxide layer 215 is removed in a
conventional manner. Then, a dielectric layer 230, for example
tantalum oxide layer (Ta.sub.2O.sub.5) is formed on the lower
electrode 225 and the interlayer insulating layer 210. A second
ruthenium film is formed on the dielectric layer 230 in the same
manner as when forming the first ruthenium film 220 to thereby form
an upper electrode 235. As a result, capacitor 240 is produced.
[0071] Therefore, in case of manufacturing an MIM capacitor using
the ruthenium film forming method of the present invention, a
process step is simplified and excellent ruthenium electrodes can
be obtained.
[0072] As apparent from the above description, according to the
ruthenium film forming method of the present invention, a ruthenium
source is a two .beta.-dikentone-coordinated ruthenium complex such
as bis norbornadiene ruthenium. An oxygen flow rate, temperature,
and pressure are optimally adjusted. Therefore, a ruthenium film
which has excellent resistivity, deposition rate and step coverage
is formed.
[0073] In addition, homogeneous nucleation occurs and a ruthenium
film with uniform thickness is formed.
[0074] Furthermore, because a ruthenium film is formed under a
single process condition, the process is simplified. As a result,
process reproducibility and device reliability are improved. In
addition, because a vacuum is not generated during the formation of
the ruthenium film due to the constant pressure, a ruthenium film
with uniform thickness is formed.
[0075] Still furthermore, ruthenium films formed using ruthenium
sources of the present invention have excellent adhesion to an
interlayer insulating layer. As a result, the leakage current that
results from the peeling of a ruthenium film from an interlayer
insulating layer is prevented.
[0076] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *