U.S. patent application number 09/960510 was filed with the patent office on 2002-05-30 for organometallic compounds for chemical vapor deposition and their preparing processes, and processes for chemical vapor deposition of precious-metal films and precious-metal compound films.
This patent application is currently assigned to TANAKA KIKINOZOKU KOGYO K.K.. Invention is credited to Okamoto, Koji.
Application Number | 20020065427 09/960510 |
Document ID | / |
Family ID | 18790455 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020065427 |
Kind Code |
A1 |
Okamoto, Koji |
May 30, 2002 |
Organometallic compounds for chemical vapor deposition and their
preparing processes, and processes for chemical vapor deposition of
precious-metal films and precious-metal compound films
Abstract
A first organometallic compound is an organometallic compound
for manufacturing a ruthenium film or a ruthenium compound film by
a chemical vapor deposition process, wherein the organometallic
compound is alkylcyclopentadienyl(cyclopentadienyl)ruthenium having
a substituent of n-propyl group, iso-propyl group, n-butyl group,
iso-butyl group, tert-butyl group. A second organometallic compound
is an organometallic compound for manufacturing an iridium film or
an iridium oxide film by a chemical vapor deposition process,
wherein the organometallic compound for chemical vapor deposition
is alkylcyclopentadienyl(1,5-cyclooctadiene- )iridium having a
substituent of any alkyl group of n-propyl group, iso-propyl group,
or n-butyl group, iso-butyl group, tert-butyl group.
Inventors: |
Okamoto, Koji; (Kanagawa,
JP) |
Correspondence
Address: |
ARENT FOX KINTNER PLOTKIN & KAHN, PLLC
Suite 600
1050 Connecticut Avenue, N.W.
Washington
DC
20036-5339
US
|
Assignee: |
TANAKA KIKINOZOKU KOGYO
K.K.
|
Family ID: |
18790455 |
Appl. No.: |
09/960510 |
Filed: |
September 24, 2001 |
Current U.S.
Class: |
556/136 ;
427/250 |
Current CPC
Class: |
C07F 17/02 20130101;
C23C 16/18 20130101 |
Class at
Publication: |
556/136 ;
427/250 |
International
Class: |
C23C 016/00; C07F
017/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 11, 2000 |
JP |
2000-310503 |
Claims
1. An organometallic compound for manufacturing a ruthenium film or
a ruthenium compound film by a chemical vapor deposition process,
wherein the organometallic compound for chemical vapor deposition
is alkylcyclopentadienyl(cyclopentadienyl)ruthenium represented by
the following formula: 7wherein the substituent R.sub.1 represents
any one of alkyl groups of n-propyl, iso-propyl, n-butyl,
iso-butyl, and tert-butyl groups.
2. A process for preparing an organometallic compound for chemical
vapor deposition according to claim 1, the process comprising
reacting bis(cyclopentadienyl)ruthenium represented by Formula 2:
8with an alcohol represented by Formula 3: (formula 3) R.sub.1--OH
wherein R.sub.1 represents any one of alkyl groups of n-propyl,
iso-propyl, n-butyl, iso-butyl, and tert-butyl groups.
3. An organometallic compound for manufacturing an iridium film or
an iridium compound film by a chemical vapor deposition process,
wherein the organometallic compound for chemical vapor deposition
is alkylcyclopentadienyl(1,5-cyclooctadiene)iridium represented by
the following formula: 9wherein the substituent R.sub.2 represents
any alkyl group of n-propyl, iso-propyl, or n-butyl, iso-butyl,
tert-butyl group.
4. A process for preparing an organometallic compound for chemical
vapor deposition according to claim 3, the process comprising
reacting bis(1,5-cyclooctadienechloroiridium) having the following
formula: 10with sodium alkylcyclopentadienide having the following
formula: 11wherein the meaning of the substituent R.sub.2 is as
specified above.
5. A process for chemical vapor deposition of a precious-metal film
or a precious-metal compound film, comprising the steps of
vaporizing the organometallic compound according to claim 1 or 3 to
transport it onto a substrate, and decomposing the organometallic
compound by heating.
6. The process for chemical vapor deposition of a precious-metal
film or a precious-metal compound film according to claim 5,
wherein the organometallic compound vaporized under an atmosphere
containing oxygen gas is decomposed.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to organometallic compounds
for manufacturing precious-metal films or precious-metal compound
films by a chemical vapor deposition process. In particular, the
present invention relates to organometallic compounds for
manufacturing films of ruthenium and iridium, as a precious-metal,
and their compounds. In addition, it relates to a process for
manufacturing precious-metal films or precious-metal compound films
using these organometallic compounds.
[0003] 2. Description of the Related Art
[0004] Recently, there is a continuing need for higher performance
of semiconductor devices, and for DRAMs (dynamic RAMs), researches
are made with the aim of increasing their capacity from Mbit to
Gbit sizes. Following this trend, technologies for densification
and high integration of semiconductor devices are rapidly advanced,
and in order to increase their capacity, attempts are made to
improve not only their structure, but also materials used for these
devices.
[0005] Under these circumstances, materials that receive recent
attention as film electrode materials for DRAMs are precious metals
or precious-metal oxides, and among them, ruthenium or iridium or
oxides thereof. The reason is that these materials have a low
resistivity, and possess superior electric properties when
electrodes are produced. Consequently, these materials receive
attention as becoming one of important materials for film
electrodes in the future. Specifically, in the above-described
DRAMs, these are examined, for example, for uses as materials for
accumulating electrodes of capacitors, and are believed to be able
to make a major contribution to their densification.
[0006] As a method for manufacturing precious-metal or a
precious-metal film is utilized a chemical vapor deposition process
(hereinafter, referred to as a CVD process) in general. This is due
to, according to a CVD process, easy manufacturing of uniform
films, and at the same time superiority in step coverage (ability
to cover differences in level). Additionally, it is likely that a
CVD process will be the mainstream of coming processes for
manufacturing film electrodes which can be adapted to densify
recent circuits and electronic components to a higher extent.
[0007] With respect to ruthenium, as a raw material for ruthenium
films and ruthenium compound films, investigations have been
recently conducted on use of bis(ethylcyclopentadienyl)ruthenium
shown by the following formula. This
bis(ethylcyclopentadienyl)ruthenium is a compound in which one
hydrogen on each of two cyclopentadiene rings in
bis(cyclopentadienyl)ruthenium (commonly called ruthenocene) is
substituted with an ethyl group. 1
[0008] On the other hand, as a raw material for iridium films,
ethylcyclopentadienyl(1,5-cyclooctadiene)iridium shown by the
following formula has been investigated. This
ethylcyclopentadienyl(1,5-cyclooctadi- ene)iridium is a compound in
which one hydrogen on the cyclopentadiene ring in
cyclopentadienyl(1,5-cyclooctadiene)iridium is substituted with an
ethyl group. 2
[0009] These organic precious-metal compounds have a low melting
point and are liquid at room temperature, and thus are handled
easily. Additionally, these compounds have a high vapor pressure,
resulting in superior efficiency in manufacturing films. Therefore,
these organic precious-metal compounds are considered to be
eligible as CVD raw materials.
[0010] However, while the above-described
bis(ethylcyclopentadienyl)ruthen- ium and
ethylcyclopentadienyl(1,5-cyclooctadiene)iridium have superior
properties as CVD raw materials, they display poor stability in the
air, and in particular tend to react with oxygen, so that reaction
with oxygen takes place in the air, resulting in the formation of
various derivatives, such as oxides, hydroxides, and the like, as
impurities. Thus, for these organic compounds, there is a problem
that slight differences in the conditions during manufacturing
steps tends to exert an influence on their purity and easily result
in unevenness among their manufactured lots. If films are
manufactured with the use of such raw materials having a purity
varied from lot to lot, then it is, of course, likely that
properties of the films are also varied, depending upon their raw
materials.
[0011] In addition, even if manufacturing is designed so that the
product is not in contact with the air at all during the
manufacturing steps, it is likely that these compounds easily
undergo oxidation in the course of transportation of substrates,
since oxygen gas is employed as a reaction gas in order to
accelerate a film-forming reaction during the manufacturing of
films.
[0012] In this case, various derivatives of these compounds act as
impurities, and will exert an influence on purity and electric
property of the films, and what is considered as having a greater
influence is morphology such as surface roughness and the like. The
influence on morphology due to these impurities is on the order of
nanometers, and thus seems to be extremely small as numerical
values. However, in the area of DRAMs requiring densification in
these days, even such small values will be responsible for whether
use can be made as electrodes.
[0013] The present invention has been achieved under the background
as described above, and has an object of providing an
organometallic compound for chemical vapor deposition which
possesses superior properties as CVD raw materials possessed by the
conventional bis(ethylcyclopentadienyl)ruthenium and
ethylcyclopentadienyl(1,5-cyclooc- tadiene)iridium and which has
high stability to oxygen.
SUMMARY OF THE INVENTION
[0014] The inventors have conducted extensive research and made
investigations on organometallic compounds capable of solving the
above-described problems. As a result, it has been found that the
following organometallic compounds with respect to ruthenium and
iridium are suitable, thereby leading to the present invention.
[0015] First, there is given an explanation of organic ruthenium
compounds related to the present application. A first invention
related to the present application is directed to an organometallic
compound for manufacturing a ruthenium film or a ruthenium compound
film by a chemical vapor deposition process, wherein the
organometallic compound for chemical vapor deposition is
alkylcyclopentadienyl(cyclopentadienyl)ruthe- nium represented by
the following formula: 3
[0016] wherein the substituent R.sub.1 represents any one of alkyl
groups of n-propyl, iso-propyl, n-butyl, iso-butyl, and tert-butyl
groups.
[0017] The organic ruthenium compounds related to the present
invention have higher oxidative stability at room temperature and
is not easily oxidized in the air, when compared with the
conventional bis(ethylcyclopentadienyl)ruthenium. Therefore, the
organic ruthenium compounds related to the present invention are
not contaminated with impurities due to their partial oxidation,
even if they have come in contact with the air during manufacturing
and when introduced into a CVD apparatus after manufacturing. In
this regard, it can be said that the organic ruthenium compounds
related to the present invention are organometallic compounds
allowing easier handling in manufacturing consistent films than
before.
[0018] These alkylcyclopentadienyl(cyclopentadienyl)ruthenium
compounds can react with oxygen and be decomposed under an
atmosphere at elevated temperatures, so that these compounds will
be not decomposed until they are introduced into a CVD apparatus
and heated on a substrate. The rate of decomposition at high
temperatures is almost the same as that of the conventional
bis(ethylcyclopentadienyl)ruthenium, causing no problem in forming
films.
[0019] In addition, these
alkylcyclopentadienyl(cyclopentadienyl)ruthenium compounds,
similarly to bis(ethylcyclopentadienyl)ruthenium, have a low
melting point, resulting in easy handling, and a high vapor
pressure, allowing efficient manufacturing of films, and thus are
compounds having properties required as CVD raw material.
[0020] Furthermore, these
alkylcyclopentadienyl(cyclopentadienyl)ruthenium compounds are
synthesized with relative ease, and can be prepared by reacting
bis(cyclopentadienyl)ruthenium represented by Formula 4 with an
alcohol represented by formula 5. 4
[0021] (formula 5)
R.sub.1--OH
[0022] Wherein R.sub.1 represents any one of alkyl groups of
n-propyl, iso-propyl, n-butyl, iso-butyl, and tert-butyl
groups.
[0023] In this reaction, it is preferable to use a catalyst, in
order to promote the reaction of bis(cyclopentadienyl)ruthenium
with various alcohols. As a catalyst in this case, it is preferable
to employ aluminum chloride.
[0024] The following will give an explanation of organic iridium
compounds related to the present application. A second invention
related to the present invention is directed to an organometallic
compound for manufacturing an iridium film or an iridium compound
film by a chemical vapor deposition process, wherein the
organometallic compound for chemical vapor deposition is
alkylcyclopentadienyl(1,5-cyclooctadiene)iri- dium represented by
the following formula: 5
[0025] In this formula, the substituent R.sub.2 in the
alkylcyclopentadienyl(1,5-cyclooctadiene)iridium related to the
present invention is propyl or butyl group, the propyl group
including n-propyl group, iso-propyl group, and the butyl group
including any one of n-butyl group, iso-butyl group, and tert-butyl
group. In the present invention, these substituents are specified,
since the results of inventors' investigations show that
alkylcyclopentadienyl(1,5-cyclooctadiene)iridium in which an alkyl
group having 5 or more carbons is introduced has an increased
melting point, and thus will become unfit as CVD raw material. In
case of introducing an ethyl group having two carbons, on the other
hand, ethylcyclopentadienyl(1,5-cyclooctadiene)iridium as mentioned
above is a substance that is already known as a raw material for
iridium films, and also this prior art has poor stability to the
air.
[0026] These organic iridium compounds related to the present
invention also have higher stability to oxygen at room temperature
and do not undergo oxidation in the air, so that there is no
possibility of contamination with impurities, even if they come
into contact with the air before introduced into a CVD
apparatus.
[0027] In addition, the organic iridium compounds related to the
present invention, similarly to the conventional
ethylcyclopentadienyl(1,5-cycloo- tadiene)iridium, have a low
melting point and a high vapor pressure. Therefore, the organic
iridium compounds related to the present invention are handled with
ease and capable of efficiently manufacturing films. Thus, it can
be said that these organic iridium compounds are compounds having
properties required as CVD raw material.
[0028] Furthermore, these
alkylcyclopentadienyl(1,5-cyclooctadiene)iridium compounds related
to the present invention can be prepared with relative ease. That
is, these compounds can be prepared by reacting
bis(1,5-cyclooctadiene)iridium represented by the following formula
with sodium alkylcyclopentadienide represented by the following
formula: 6
[0029] wherein the meaning of the substituent R.sub.2 is as
specified above.
[0030] As explained above, the organic ruthenium compounds and
organic iridium compounds related to the present invention can be
said to be suitable substances as raw materials for ruthenium and
iridium, and compound films thereof by a CVD process. A CVD process
in which these organic precious-metal compounds are applied will
allow stable manufacturing of films having good morphology. In
consequence, as a chemical vapor deposition process related to the
present invention is utilized a chemical vapor deposition process
of a precious-metal or precious-metal compound film in which these
organic precious-metal compounds are vaporized, transferred onto a
substrate, and decomposed by heating the substrate to laminate the
precious-metal.
[0031] Regarding the substrate temperature in this case, with
respect to each of compounds it is preferable that temperatures are
controlled to 200.degree. C. to 300.degree. C. to decompose an
organic precious-metal compound. Also, in this CVD step, it is
preferable that the inside of a reactor is under an atmosphere at
reduced pressure. Reducing the pressure in a reactor can improve
the uniformity of the film-thickness distribution and step-coverage
(ability to cover differences in level). The preferred range of the
pressure in a reactor is 140 to 1400 Pa.
[0032] As mentioned above, any organic precious-metal compound
related to the present invention has a property of easily
undergoing decomposition by mixing oxygen gas into the reaction
system. Therefore, in a CVD step utilizing these compounds, it is
preferable that an organic precious-metal compound vaporized in an
atmosphere containing oxygen gas is decomposed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Preferable embodiments of the present invention will be
described in conjunction with Comparative Examples. In this
section, butylcyclopentadienyl(cyclopentadienyl)ruthenium and
alkylcyclopentadienyl(1,5-cyclooctadiene)iridium related to the
present invention were prepared, and ruthenium and iridium films
were manufactured by a CVD process employing these organometallic
compounds. Then, these films were compared with films manufactured
with conventionally used raw materials.
[0034] A. Ruthenium Compounds
[0035] First Embodiment: 8.0 g of bis(cyclopentadienyl)ruthenium,
3.0 g of aluminum chloride, and 80 g of polyphosphoric acid were
mixed. The mixed solution was heated to 100.degree. C. under a
nitrogen atmosphere, to which 3.0 g of tert-butyl alcohol was added
dropwise over 30 minutes, and then the mixture was heated to
120.degree. C. to carry out the reaction for 4 hours. After the
reaction, hot water was added to the solution to remove
polyphosphoric acid, and then distillation treatment gave 2.0 g of
tert-butylcyclopentadienyl(cyclopentadienyl)ruthenium. Five lots of
tert-butylcyclopentadienyl(cyclopentadienyl)ruthenium were prepared
by this preparing method, and subjected to film production as
described later.
COMPARATIVE EXAMPLE 1
[0036] For comparison with the
tert-butylcyclopentadienyl(cyclopentadienyl- )ruthenium prepared in
the first embodiment, bis(ethylcyclopentadienyl)rut- henium was
prepared. In a flask with an argon atmosphere by vacuum
substitution, 200 ml of ethanol was placed, in which 25.0 g of
ruthenium chloride trihydrate was dissolved, and the solution was
cooled to -30.degree. C. Then, to the solution was added 40 g of
ethylcyclopentadiene, followed by 9.55 g of zinc powder (purity
99.999%, 200 meshes) in seven portions at an interval of 10
minutes. After the reaction was completed, the liquid phase was
collected, from which bis(ethylcyclopentadienyl)ruthenium was
extracted with hexane. As in the first embodiment, five lots of
bis(ethylcyclopentadienyl)ruthenium were prepared by this preparing
method, and subjected to film production.
[0037] Next, ruthenium films were manufactured by a CVD process
employing five lots prepared of
tert-butylcyclopentadienyl(cyclopentadienyl)rutheni- um and
bis(ethylcyclopentadienyl)ruthenium, and examined for properties of
the ruthenium films among the lots. The conditions for
manufacturing the films were as follows:
[0038] Vaporization temperature: 100.degree. C.,
[0039] Substrate temperature: 250.degree. C.,
[0040] Reaction chamber pressure: 200 Pa,
[0041] Carrier gas/reaction gas: argon/oxygen,
[0042] Gas flow rate: 200/200 sccm.
[0043] The manufactured films were measured for the average
roughness (Rms) with an AFM (atomic force microscope) , whose
results are shown in Table 1.
1 TABLE 1 Lot No. 1 2 3 4 5 First 1.0 nm 1.2 nm 1.0 nm 1.1 nm 1.0
nm Embodiment Comparative 2.0 nm 1.2 nm 3.0 nm 1.0 nm 2.0 nm
Example 1
[0044] From these results, it has been confirmed that the ruthenium
films manufactured using
tert-butylcyclopentadienyl(cyclopentadienyl)ruthenium related to
the first embodiment had superior roughness, regardless of the lots
of the raw material. In the case of Comparative Example,
bis(ethylcyclopentadienyl)ruthenium, on the other hand, the values
of the surface roughness varied from lot to lot. It is believed
that this is due to slight differences in the purity among the
lots, because even if manufacturing have been carried out in the
same steps, the time of contacting the prepared
bis(ethylcyclopentadienyl)ruthenium with the air may vary
delicately during the steps, or the oxygen that is the reaction gas
can result in oxidation during its transportation to a substrate in
manufacturing films.
[0045] Second Embodiment: 8.0 g of bis(cyclopentadienyl)ruthenium,
3.0 g of aluminum chloride, and 80 g of polyphosphoric acid were
mixed. The mixed solution was heated to 100.degree. C. under a
nitrogen atmosphere, to which 4.0 g of n-propyl alcohol was added
dropwise over 30 minutes, and then the mixture was heated to
120.degree. C. to carry out the reaction for 4 hours. After the
reaction was completed, hot water was added to the solution to
remove the polyphosphoric acid, and then distillation treatment
gave 1.8 g of n-propylcyclopentadienyl(cyclopentad-
ienyl)ruthenium.
[0046] Five lots of
n-propylcyclopentadienyl(cyclopentadienyl)ruthenium were prepared
in this way, and films were manufactured under the same conditions
as those of the first embodiment. As a result, it has been
confirmed as in the first embodiment that films can be stably
manufactured which have superiority in surface roughness,
regardless of the lots of the raw material.
[0047] B. Iridium Compounds
[0048] Third Embodiment: Under an atmosphere of nitrogen gas, in
350 mL of tetrahydrofuran as a solvent was dissolved 17 g of
bis(1,5-cyclooctadienechloroiridium). With cooling the solution to
-80.degree. C., a solution in which 8 g of sodium
n-propylcyclopentadieni- de was dissolved in 35 mL of
tetrahydrofuran was added. The mixed solution was then reacted at
-80.degree. C. for 30 minutes, and after that the solvent was
distilled off from the reaction solution, followed by hexane
extraction and vacuum distillation to give 18 g of
n-propylcyclopentadienyl(1,5-cyclooctadiene)iridium. Five lots of
n-propylcyclopentadienyl(1,5-cyclooctadiene)iridium were prepared
by this preparing method, and subjected to film production as
described later.
[0049] Forth Embodiment: Using 8.5 g of sodium
iso-propylcyclopentadienide instead of sodium
n-propylcyclopentadienide in the third embodiment, 20 g of
iso-propylcyclopentadienyl(1,5-cyclooctadiene)iridium was prepared
in an otherwise similar procedure as in the second embodiment.
Also, five lots of
iso-propylcyclopentadienyl(1,5-cyclooctadiene)iridium were
manufactured.
[0050] Fifth Embodiment: Using 8.2 g of sodium
tert-butylcyclopentadienide instead of sodium
n-propylcyclopentadienide in the third embodiment, 17 g of
tert-butylcyclopentadienyl(1,5-cyclooctadiene)iridium was prepared
in an otherwise similar procedure to that in the second embodiment.
Also, five lots of
tert-butylcyclopentadienyl(1,5-cyclooctadiene)iridium were
prepared.
COMPARATIVE EXAMPLE 2
[0051] For comparison to organic iridium compounds prepared in the
above-described third to fifth embodiments,
ethylcyclopentadienyl(1,5-cyc- looctadiene)iridium was prepared. In
this Comparative Example, using 8.5 g of sodium
ethylcyclopentadienide instead of sodium n-propylcyclopentadienide
in the first embodiment,
ethylcyclopentadienyl(1,5-cyclooctadiene)iridium was prepared in an
otherwise similar procedure to that in the second embodiment.
[0052] Next, iridium films were manufactured by a CVD process
employing five lots of each of organic iridium compounds prepared
in the third to fifth embodiments and in Comparative Example, and
examined for properties of the iridium films among the lots. The
conditions for manufacturing the films were set in the same
conditions as in the film production carried out in the first
embodiment.
[0053] The manufactured films were measured for the average
roughness (Rms) with an AFM (atomic force microscope), whose
results are shown in Table 2.
2 TABLE 2 Lot No. 1 2 3 4 5 Third 1.0 nm 1.2 nm 1.1 nm 1.0 nm 1.2
nm Embodiment Fourth 0.9 nm 1.0 nm 1.1 nm 0.9 nm 1.2 nm Embodiment
Fifth 1.0 nm 1.0 nm 1.2 nm 1.1 nm 1.0 nm Embodiment Comparative 2.0
nm 1.5 nm 1.0 nm 0.8 nm 2.5 nm Example 2
[0054] From these results, it has turned out that the iridium films
manufactured using the organic iridium compounds prepared in the
third to fifth embodiments had superior surface roughness,
regardless of the lots of the raw material. In contrast, it has
been confirmed that the iridium films manufactured using the
ethylcyclopentadienyl(1,5-cyclooctadiene)iri- dium of Comparative
Example had a surface roughness varied from lot to lot, and as a
result, it is difficult to stably manufacture uniform films.
* * * * *