U.S. patent application number 12/427815 was filed with the patent office on 2009-08-13 for organometallic precursor compounds.
Invention is credited to Scott Houston Meiere.
Application Number | 20090202742 12/427815 |
Document ID | / |
Family ID | 38560122 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090202742 |
Kind Code |
A1 |
Meiere; Scott Houston |
August 13, 2009 |
ORGANOMETALLIC PRECURSOR COMPOUNDS
Abstract
This invention relates to organometallic precursor compounds
represented by the formula (L)M(L').sub.2(NO) wherein M is a Group
6 metal, L is a substituted or unsubstituted anionic ligand and L'
is the same or different and is a .pi. acceptor ligand, a process
for producing the organometallic precursor compounds, and a method
for producing a film, coating or powder from the organometallic
precursor compounds.
Inventors: |
Meiere; Scott Houston;
(Williamsville, NY) |
Correspondence
Address: |
PRAXAIR, INC.;LAW DEPARTMENT - M1 557
39 OLD RIDGEBURY ROAD
DANBURY
CT
06810-5113
US
|
Family ID: |
38560122 |
Appl. No.: |
12/427815 |
Filed: |
April 22, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11804814 |
May 21, 2007 |
7547464 |
|
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12427815 |
|
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|
11037085 |
Jan 19, 2005 |
7244858 |
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11804814 |
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Current U.S.
Class: |
427/569 ;
427/227; 427/248.1; 556/58 |
Current CPC
Class: |
C23C 16/18 20130101;
B22F 9/30 20130101 |
Class at
Publication: |
427/569 ;
427/227; 427/248.1; 556/58 |
International
Class: |
C23C 16/14 20060101
C23C016/14; B05D 3/02 20060101 B05D003/02; C07F 11/00 20060101
C07F011/00 |
Claims
1-41. (canceled)
42. A method for producing a film, coating or powder by decomposing
an organometallic precursor compound represented by the formula
(L)M(L').sub.2(NO) wherein M is a Group 6 metal, L is a substituted
or unsubstituted cyclopentadienyl ligand, L' is the same or
different and is a .pi. acceptor ligand, thereby producing the
film, coating or powder.
43. The method of claim 42, where the organometallic precursor
compound is represented by the formula (RL)M(L').sub.2(NO) wherein
M is a Group 6 metal, L is a substituted cyclopentadienyl ligand, R
is an alkyl having from 1 to 8 carbons atoms or SiMe.sub.3; L' is
the same or different and is a .pi. acceptor ligand, thereby
producing the film, coating or powder.
44. The method of claim 42, wherein M is selected from molybdenum,
chromium or tungsten.
45. The method of claim 42 wherein the decomposing of said
organometallic precursor compound is thermal, chemical,
photochemical or plasma-activated.
46. The method of claim of claim 42, wherein said organometallic
precursor compound is evaporated and the vapor is directed into a
deposition reactor housing a substrate.
47. The method of claim 45 wherein said substrate is comprised of a
material selected from the group consisting of a metal, a metal
silicide, a semiconductor, an insulator and a barrier material.
48. The method of claim 46 wherein said substrate is a patterned
wafer.
49. The method of claim 42 wherein said film, coating or powder is
produced by a gas phase deposition.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/804,814, filed May 21, 2007, which is a divisional of
U.S. patent application Ser. No. 11/037,085, filed Jan. 19, 2005,
now U.S. Pat. No. 7,244,858, the contents of which are incorporated
herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to organometallic precursor compounds
represented by the formula (L)M(L').sub.2(NO) wherein M is a Group
6 metal, L is a substituted or unsubstituted anionic ligand and L'
is the same or different and is a .pi. acceptor ligand, a process
for producing the organometallic precursor compounds, and a method
for producing a film or coating from the organometallic precursor
compounds.
BACKGROUND OF THE INVENTION
[0003] Chemical vapor deposition methods are employed to form films
of material on substrates such as wafers or other surfaces during
the manufacture or processing of semiconductors. In chemical vapor
deposition, a chemical vapor deposition precursor, also known as a
chemical vapor deposition chemical compound, is decomposed
thermally, chemically, photochemically or by plasma activation, to
form a thin film having a desired composition. For instance, a
vapor phase chemical vapor deposition precursor can be contacted
with a substrate that is heated to a temperature higher than the
decomposition temperature of the precursor, to form a metal or
metal oxide film on the substrate. Preferably, chemical vapor
deposition precursors are volatile, heat decomposable and capable
of producing uniform films under chemical vapor deposition
conditions.
[0004] The semiconductor industry is currently considering the use
of thin films of various metals for a variety of applications. Many
organometallic complexes have been evaluated as potential
precursors for the formation of these thin films. A need exists in
the industry for developing new compounds and for exploring their
potential as chemical vapor deposition precursors for film
depositions.
[0005] Molybdenum materials are being considered for a number of
applications in the electronics industry for next generation
devices, including electrode, barrier, and lithography. Similar to
the interest in tuning a material by creating an alloy of a n-type
and p-type metal in different ratios (as exemplified by the work by
Misra V. et al. at North Carolina State (IEDM 2001 20.5.1)),
molybdenum can be tuned with nitrogen incorporation and/or
deposition orientation to generate a similar effect (with the
advantage of a single, less expensive source). The work function of
molybdenum can thus be adjusted significantly (Fonseca, L. R. C.,
Fall MRS E4.3, 2003 and Mrovek, M., Fall MRS E4.2, 2003).
[0006] Another interest in molybdenum materials is for barrier
applications (e.g., Cu). Molybdenum nitrides are candidates for
this application (Gordon R. et al., Thin Solid Films 1996 288 116).
Molybdenum films also have applications in the area of lithography,
with potential utility for the engineering of projection lens
systems for photolytical patterning of substrates for extreme
ultra-violet lithography (EUVL) at the 45 nm technology node (Van
den hove, L. IEEE 2002).
[0007] The industry movement from physical vapor deposition to
chemical vapor deposition and atomic layer deposition processes due
to the increased demand for higher uniformity and conformality in
thin films has lead to a demand for suitable precursors for future
semiconductor materials. For molybdenum, the traditional chemical
vapor deposition precursors have been Mo(CO).sub.6 and
(Et.sub.xC.sub.6H.sub.6-x).sub.2Mo (a mixture of
bis(ethylbenzene)molybdenum species). The former suffers from being
a solid up to its decomposition point of 150.degree. C., and the
latter, although a liquid, does not have a high vapor pressure
(.about.0.1 torr at 160.degree. C.) and may deliver inconsistently
due to the various species present. (C.sub.7H.sub.8)Mo(CO).sub.3 is
also available, but is a solid (mp=100.degree. C.), and lacks
sufficient thermal stability to be a highly desirable
candidate.
[0008] Building from Mo(CO).sub.6, replacing three CO's with a
cyclopentadienyl (Cp) group seems logical since many Cp systems are
known chemical vapor deposition precursors and Cp allows excellent
tunability for achieving liquid systems. However,
[CpMo(CO).sub.3].sup.- exists as an anion, and therefore is not
sufficiently volatile (note, the dimer of this system is neutral,
but has little volatility due to the increased molecular weight).
Changing Cp to a similar neutral six electron donor would seem a
logical progression, thus yielding the aforementioned
(C.sub.7H.sub.8)Mo(CO).sub.3. Although this compound is neutral
with perhaps adequate volatility, the other issue with these
tricarbonyl systems is their instability. The lack of enough strong
.pi.-acids, like CO, render the material very electron rich, and
make the complex susceptible to premature decomposition. Two
potential pathways are a `ring-slip` for the cycloheptatriene
ligand from an .eta..sup.6 six electron donor to an .eta..sup.4
four electron donor (alleviating the electron density on
molybdenum) or loss of a hydride from the cycloheptatriene ligand
creating an aromatic system and creating a less donating
environment and a molybdenum cation. Another known molecule,
(C.sub.6H.sub.6)Mo(CO).sub.3, suffers from similar instability
issues.
[0009] While the unsubstituted cyclopentadienyl compound, i.e.,
CpMo(CO).sub.2(NO), and the methyl substituted cyclopentadienyl
compound, i.e., (MeCp)Mo(CO).sub.2(NO), are known materials
(Legzdins, P. et al. Inorg. Synth. 1990, 28, 196 and references
therein and Rausch, M. D. et al. Organometallics 1983, 2, 1523 and
references therein), there appear to be no prior teachings or work
relating to the use of these compounds as precursors for chemical
vapor deposition or atomic layer deposition.
[0010] In developing methods for forming thin films by chemical
vapor deposition methods, a need continues to exist for chemical
vapor deposition precursors that preferably exhibit dual metal gate
applications, are liquid at room temperature, have relatively high
vapor pressure and can form uniform films. Therefore, a need
continues to exist for developing new compounds and for exploring
their potential as chemical vapor deposition precursors for film
depositions. It would therefore be desirable in the art to provide
a chemical vapor deposition precursor having dual metal gate
applications, a high vapor pressure and that can form uniform
films.
SUMMARY OF THE INVENTION
[0011] This invention pertains to chemical vapor deposition and
atomic layer deposition precursors for next generation devices,
specifically molybdenum-containing precursors that exhibit dual
metal gate applications. Molybdenum (Mo) is a `mid-gap` material
(i.e., it possesses an intermediate work function between n-type
(.about.4.0 eV) and p-type (5.0 eV) species), and depending on how
it is deposited can serve as both an n- and p-type electrode, as
well as for barrier and lithography applications. The physical
location of molybdenum on the periodic table between n-type
materials on the left (e.g., Ti, Zr, Hf, Ta) and p-type on the
right (e.g., Ni, Pd, Pt, Ir) helps to demonstrate its
flexibility.
[0012] As an advantage over the n-type species, molybdenum metal is
typically easier to deposit than the early transition metals, which
have a higher affinity for forming oxides, carbides, and nitrides.
As an advantage over the p-type species, molybdenum is less
expensive than the `nobel` metals such as palladium and platinum,
and likely easier to etch. Also, using a single metal for both
types presents a processing advantage.
[0013] This invention relates in general to organometallic
precursor compounds represented by the formula (L)M(L').sub.2(NO)
wherein M is a Group 6 metal, L is a substituted or unsubstituted
anionic ligand and L' is the same or different and is a .pi.
acceptor ligand. More particularly, this invention relates to
organometallic precursor compounds represented by the formula
(L)M(CO).sub.2(NO) wherein M is a Group 6 metal and L is a
substituted or unsubstituted anionic ligand. Typically, M is
selected from molybdenum, chromium or tungsten, L is selected from
a cyclopentadienide, diketonate, amide, cyclic amide, alkoxide,
halide or imide, and L' is selected from CO and alkenes. A
preferred organometallic precursor compound is represented by the
formula (RL)Mo(CO).sub.2(NO) wherein L is a substituted
cyclopentadienyl ligand and R is an alkyl having from 2 to about 8
carbon atoms. Typically, R is selected from ethyl, propyl,
isopropyl, butyl, tert-butyl and SiMe.sub.3.
[0014] This invention also relates to a process for producing an
organometallic precursor compound which comprises reacting a Group
6 metal-carbonyl and/or alkene source compound, a hydrocarbon or
heteroatom-containing compound and a nitrosyl source compound under
reaction conditions sufficient to produce said organometallic
precursor compound. Typically, the hydrocarbon or
heteroatom-containing compound comprises a lithiated
cyclopentadienide, diketonate, amide, cyclic amide, alkoxide,
halide or imide.
[0015] This invention also relates to a method for producing a
film, coating or powder by decomposing an organometallic precursor
compound represented by the formula (L)M(L').sub.2(NO), preferably
an organometallic precursor compound represented by the formula
(L)M(CO).sub.2(NO), wherein M is a Group 6 metal, L is a
substituted or unsubstituted anionic ligand and L' is the same or
different and is a .pi. acceptor ligand, thereby producing the
film, coating or powder. Typically, the decomposing of said
organometallic precursor compound is thermal, chemical,
photochemical or plasma-activated.
[0016] The invention has several advantages. For example, the
method of the invention is useful in generating organometallic
compound precursors that have varied chemical structures and
physical properties. Films generated from the organometallic
compound precursors can be deposited with a short incubation time,
and the films deposited from the organometallic compound precursors
exhibit good smoothness.
[0017] A preferred embodiment of this invention is that the
organometallic precursor compounds may be liquid at room
temperature. In some situations, liquids may be preferred over
solids from an ease of semiconductor process integration
perspective.
[0018] As can be seen from this invention, the solution to the
problems encountered with the molybdenum-containing precursors of
the prior art stems from the addition of a nitrosyl ligand.
Although similar to carbonyl (CO) in structure, nitrosyl (NO) is a
notably stronger .pi.-acid (by .about.1V) when binding in its
NO.sup.+ form. This fact leads to the second key advantage. Not
only does NO stabilize the precursor, e.g., CpMo(CO).sub.2(NO), by
removing excess electron density from the metal center, but the
ligand's cationic nature balances the anionic cyclopentadienyl
ligand, rendering the overall molecule neutral. This compound is
thermally stable, and is only slightly air sensitive (i.e., it can
be manipulated for short periods in air). Although the
unsubstituted cyclopentadienyl system is a solid, the substituted
cyclopentadienyl system is a liquid. Finally, the substituted
cyclopentadienyl system appears to have a higher volatility than
the bis(ethylbenzene)molybdenum mixture or Mo(CO).sub.6.
[0019] In comparison with the methyl substituted cyclopentadienyl
compound, i.e., (MeCp)Mo(CO).sub.2(NO), of the prior art, the
organometallic precursor compounds of this invention are typically
easier to purify, while the unsubstituted cyclopentadienyl
compound, i.e., CpMo(CO).sub.2(NO), of the prior art forms a solid
molybdenum complex. In addition, the organometallic precursor
compounds of this invention may be more conducive to the deposition
of pure metal films versus compounds such as the molybdenum amides,
which have been used for nitrides. However nitrides and oxides may
still be accessible with these systems with the proper choice of
co-reactant (e.g., ammonia, oxygen, respectively).
DETAILED DESCRIPTION OF THE INVENTION
[0020] As indicated above, this invention relates to organometallic
precursor compounds represented by the formula (L)M(L').sub.2(NO),
preferably organometallic precursor compounds represented by the
formula (L)M(CO).sub.2(NO), wherein M is a Group 6 metal, L is a
substituted or unsubstituted anionic ligand, and L' is the same or
different and is a .pi. acceptor ligand. Typically, M is selected
from molybdenum, chromium or tungsten, L is selected from a
cyclopentadienide, diketonate, amide, cyclic amide, alkoxide,
halide or imide, and L' is selected from CO and alkenes. A
preferred organometallic precursor compound is represented by the
formula (RL)Mo(CO).sub.2(NO) wherein L is a substituted
cyclopentadienyl ligand and R is an alkyl having from 2 to about 8
carbon atoms. Typically, R is selected from ethyl, propyl,
isopropyl, butyl, tert-butyl and SiMe.sub.3.
[0021] Illustrative organometallic precursor compounds of this
invention include, for example, (EtCp)Mo(CO).sub.2(NO),
(PrCp)Mo(CO).sub.2(NO), (iPrCp)Mo(CO).sub.2(NO),
(BuCp)Mo(CO).sub.2(NO), (tBuCp)Mo(CO).sub.2(NO), and the like ,
wherein Et is ethyl, Pr is propyl, iPr is isopropyl, Bu is butyl
and tBu is tert-butyl.
[0022] As also indicated above, this invention also relates to a
process for producing an organometallic precursor compound which
comprises reacting a Group 6 metal-carbonyl and/or alkene source
compound, e.g., Mo(CO).sub.6 and
Mo(CO).sub.3(C.sub.2H.sub.4).sub.3, a hydrocarbon or
heteroatom-containing compound, and a nitrosyl source compound
under reaction conditions sufficient to produce said organometallic
precursor compound. Typically, the hydrocarbon or
heteroatom-containing compound comprises a lithiated
cyclopentadienide, diketonate, amide, cyclic amide, alkoxide,
halide or imide.
[0023] This invention also involves a process for producing an
organometallic compound comprising (i) reacting a hydrocarbon or
heteroatom-containing material with a base material in the presence
of a solvent and under reaction conditions sufficient to produce a
first reaction mixture comprising a hydrocarbon or
heteroatom-containing compound, (ii) adding a metal-carbonyl and/or
alkene source compound and a nitrosyl source compound to said first
reaction mixture, (iii) reacting said hydrocarbon or
heteroatom-containing compound with said metal-carbonyl and/or
alkene source compound and nitrosyl source compound under reaction
conditions sufficient to produce a second reaction mixture
comprising said organometallic compound, and (iv) separating said
organometallic compound from said second reaction mixture. The
method is particularly well-suited for large scale production since
it can be conducted using the same equipment, some of the same
reagents and process parameters that can easily be adapted to
manufacture a wide range of products. The method provides for the
synthesis of organometallic compounds using a process where all
manipulations are carried out in a single vessel, and which route
to the organometallic compounds does not require the isolation of
an intermediate complex. This method is more fully described in
U.S. patent application Ser. No. 10/678,074, filed Oct. 6, 2003,
which is incorporated herein by reference.
[0024] The organometallic precursor compounds of this invention may
also be prepared by conventional methods such as described in
Legzdins, P. et al. Inorg. Synth. 1990, 28, 196 and references
therein.
[0025] The metal-carbonyl and/or alkene source compound, e.g.,
Mo(CO).sub.6 and Mo(CO).sub.3(C.sub.2H.sub.4).sub.3, starting
material may be selected from a wide variety of compounds known in
the art. The invention herein most prefers the Group 6 metals such
as molybdenum, chromium and tungsten. The CO ligands are preferred
.pi. acceptor ligands. Other suitable .pi. acceptor ligands include
alkenes.
[0026] The concentration of the Group 6 metal-carbonyl and/or
alkene compound starting material can vary over a wide range, and
need only be that minimum amount necessary to react with the
hydrocarbon or heteroatom-containing compound and the nitrosyl
source compound and to provide the given metal concentration
desired to be employed and which will furnish the basis for at
least the amount of metal necessary for the organometallic
compounds of this invention. In general, depending on the size of
the reaction mixture, metal-carbonyl and/or alkene source compound
starting material concentrations in the range of from about 1
millimole or less to about 10,000 millimoles or greater, should be
sufficient for most processes.
[0027] The nitrosyl source compound may be selected from a wide
variety of compounds known in the art. Illustrative nitrosyl source
compounds include diazald (i.e.,
N-methyl-N-nitroso-p-toluenesulfonamide), nitrosonium
tetrafluoroborate and nitric oxide.
[0028] The concentration of the nitrosyl source compound starting
material can vary over a wide range, and need only be that minimum
amount necessary to react with the metal-carbonyl compound starting
material and the hydrocarbon or heteroatom-containing compound. In
general, depending on the size of the reaction mixture, nitrosyl
source compound starting material concentrations in the range of
from about 1 millimole or less to about 10,000 millimoles or
greater, should be sufficient for most processes.
[0029] The hydrocarbon or heteroatom-containing starting material
may be selected from a wide variety of compounds known in the art.
Illustrative hydrocarbon or heteroatom-containing compounds
include, for example, amines, alcohols, diketones,
cyclopentadienes, imines, hydrocarbons, halogens and the like.
Preferred hydrocarbon or heteroatom-containing starting materials
include alkyl substituted cyclopentadienes including their alkali
metal salts, for example, LiEtCp.
[0030] The concentration of the hydrocarbon or
heteroatom-containing starting material can vary over a wide range,
and need only be that minimum amount necessary to react with the
base starting material. In general, depending on the size of the
reaction mixture, hydrocarbon or heteroatom-containing starting
material concentrations in the range of from about 1 millimole or
less to about 10,000 millimoles or greater, should be sufficient
for most processes.
[0031] The base starting material may be selected from a wide
variety of compounds known in the art. Illustrative bases include
any base with a pKa greater than about 10, preferably greater than
about 20, and more preferably greater than about 25. The base
material is preferably n-BuLi, t-BuLi, MeLi, NaH, CaH, lithium
amides and the like.
[0032] The concentration of the base starting material can vary
over a wide range, and need only be that minimum amount necessary
to react with the hydrocarbon or heteroatom-containing starting
material. In general, depending on the size of the first reaction
mixture, base starting material concentrations in the range of from
about 1 millimole or less to about 10,000 millimoles or greater,
should be sufficient for most processes.
[0033] In one embodiment, the hydrocarbon or heteroatom-containing
compound may be generated in situ, for example, lithiated amides,
alkoxides, diketonates, cyclopentadienides, imides and the like.
Generating the hydrocarbon or heteroatom-containing compound in
situ in the reaction vessel immediately prior to reaction with the
metal source compound is beneficial from a purity standpoint by
eliminating the need to isolate and handle any reactive solids. It
is also less expensive.
[0034] With the in situ generated hydrocarbon or
heteroatom-containing compound in place, addition of the
metal-carbonyl source compound, e.g., Mo(CO).sub.6, can be
performed through solid addition, or in some cases more
conveniently as a solvent solution or slurry. Although certain
metal-carbonyl source compounds are moisture sensitive and are used
under an inert atmosphere such as nitrogen, it is generally to a
much lower degree than the hydrocarbon or heteroatom-containing
compounds, for example, lithiated amides, alkoxides, diketonates,
cyclopentadienides, imides and the like. Furthermore, many
metal-carbonyl source compounds such as Mo(CO).sub.6 are denser and
easier to transfer.
[0035] The hydrocarbon or heteroatom-containing compounds prepared
from the reaction of the hydrocarbon or heteroatom-containing
starting material and the base starting material may be selected
from a wide variety of compounds known in the art. Illustrative
hydrocarbon or heteroatom-containing compounds include, for
example, lithiated amides, alkoxides, diketonates,
cyclopentadienides, imides and the like.
[0036] The concentration of the hydrocarbon or
heteroatom-containing compounds can vary over a wide range, and
need only be that minimum amount necessary to react with the
metal-carbonyl source compounds and nitrosyl-source compounds to
give the organometallic compounds of this invention. In general,
depending on the size of the reaction mixture, hydrocarbon or
heteroatom-containing compound concentrations in the range of from
about 1 millimole or less to about 10,000 millimoles or greater,
should be sufficient for most processes.
[0037] The solvent employed in the method of this invention may be
any saturated and unsaturated hydrocarbons, aromatic hydrocarbons,
aromatic heterocycles, alkyl halides, silylated hydrocarbons,
ethers, polyethers, thioethers, esters, thioesters, lactones,
amides, amines, polyamines, nitriles, silicone oils, other aprotic
solvents, or mixtures of one or more of the above; more preferably,
diethylether, pentanes, or dimethoxyethanes; and most preferably
hexanes or THF. Any suitable solvent which does not unduly
adversely interfere with the intended reaction can be employed.
Mixtures of one or more different solvents may be employed if
desired. The amount of solvent employed is not critical to the
subject invention and need only be that amount sufficient to
solubilize the reaction components in the reaction mixture. In
general, the amount of solvent may range from about 5 percent by
weight up to about 99 percent by weight or more based on the total
weight of the reaction mixture starting materials.
[0038] Reaction conditions for the reaction of the base starting
material with the hydrocarbon or heteroatom-containing material,
such as temperature, pressure and contact time, may also vary
greatly and any suitable combination of such conditions may be
employed herein. The reaction temperature may be the reflux
temperature of any of the aforementioned solvents, and more
preferably between about -80.degree. C. to about 150.degree. C.,
and most preferably between about 20.degree. C. to about 80.degree.
C. Normally the reaction is carried out under ambient pressure and
the contact time may vary from a matter of seconds or minutes to a
few hours or greater. The reactants can be added to the reaction
mixture or combined in any order. The stir time employed can range
from about 0.1 to about 400 hours, preferably from about 1 to 75
hours, and more preferably from about 4 to 16 hours, for all
steps.
[0039] Reaction conditions for the reaction of the hydrocarbon or
heteroatom-containing compound with the metal-carbonyl and/or
alkene source compound and the nitrosyl source compound, such as
temperature, pressure and contact time, may also vary greatly and
any suitable combination of such conditions may be employed herein.
The reaction temperature may be the reflux temperature of any of
the aforementioned solvents, and more preferably between about
-80.degree. C. to about 150.degree. C., and most preferably between
about 20.degree. C. to about 80.degree. C. Normally the reaction is
carried out under ambient pressure and the contact time may vary
from a matter of seconds or minutes to a few hours or greater. The
reactants can be added to the reaction mixture or combined in any
order. The stir time employed can range from about 0.1 to about 400
hours, preferably from about 1 to 75 hours, and more preferably
from about 4 to 16 hours, for all steps. In the embodiment of this
invention which is carried out in a single pot, the hydrocarbon or
heteroatom-containing compound is not separated from the first
reaction mixture prior to reacting with the metal-carbonyl and/or
alkene source compound. In a preferred embodiment, the
metal-carbonyl source compound is added to the first reaction
mixture at ambient temperature or at a temperature greater than
ambient temperature.
[0040] The organometallic compounds prepared from the reaction of
the hydrocarbon or heteroatom-containing compound, the
metal-carbonyl and/or alkene source compound and the nitrosyl
source compound may be selected from a wide variety of compounds
known in the art. For purposes of this invention, organometallic
compounds include compounds having a metal-carbon atom bond as well
as compounds having a metal-heteroatom bond. Illustrative
organometallic compounds include, for example, Group 6
metal-containing amides, alkoxides, diketonates,
cyclopentadienides, halides, imides and the like.
[0041] For organometallic compounds prepared by the method of this
invention, purification can occur through recrystallization, more
preferably through extraction of reaction residue (e.g., hexane)
and chromatography, and most preferably through sublimation and
distillation.
[0042] Furthermore, this process is not limited to
molybdenum-cyclopentadiene based systems. It can also be extended
to other metals as well as other anionic ligands. Examples of other
metals include, but are not limited to, chromium and tungsten.
Other ligands include, but are not limited to, alkoxides,
betadiketonates, imides, nitrates, anionic hydrocarbons, halides,
carbonates and the like.
[0043] Those skilled in the art will recognize that numerous
changes may be made to the method described in detail herein,
without departing in scope or spirit from the present invention as
more particularly defined in the claims below.
[0044] Examples of techniques that can be employed to characterize
the organometallic compounds formed by the synthetic methods
described above include, but are not limited to, analytical gas
chromatography, nuclear magnetic resonance, thermogravimetric
analysis, inductively coupled plasma mass spectrometry,
differential scanning calorimetry, vapor pressure and viscosity
measurements.
[0045] Relative vapor pressures, or relative volatility, of
organometallic compound precursors described above can be measured
by thermogravimetric analysis techniques known in the art.
Equilibrium vapor pressures also can be measured, for example by
evacuating all gases from a sealed vessel, after which vapors of
the compounds are introduced to the vessel and the pressure is
measured as known in the art.
[0046] Many organometallic compound precursors described herein are
liquid at room temperature and are well suited for preparing
in-situ powders and coatings. For instance, a liquid organometallic
compound precursor can be applied to a substrate and then heated to
a temperature sufficient to decompose the precursor, thereby
forming a metal or metal oxide coating on the substrate. Applying a
liquid precursor to the substrate can be by painting, spraying,
dipping or by other techniques known in the art. Heating can be
conducted in an oven, with a heat gun, by electrically heating the
substrate, or by other means, as known in the art. A layered
coating can be obtained by applying an organometallic compound
precursor, and heating and decomposing it, thereby forming a first
layer, followed by at least one other coating with the same or
different precursors, and heating.
[0047] Liquid organometallic compound precursors such as described
above also can be atomized and sprayed onto a substrate.
Atomization and spraying means, such as nozzles, nebulizers and
others, that can be employed are known in the art.
[0048] In preferred embodiments of the invention, an organometallic
compound, such as described above, is employed in gas phase
deposition techniques for forming powders, films or coatings. The
compound can be employed as a single source precursor or can be
used together with one or more other precursors, for instance, with
vapor generated by heating at least one other organometallic
compound or metal complex. More than one organometallic compound
precursor, such as described above, also can be employed in a given
process.
[0049] Deposition can be conducted in the presence of other gas
phase components. In an embodiment of the invention, film
deposition is conducted in the presence of at least one
non-reactive carrier gas. Examples of non-reactive gases include
inert gases, e.g., nitrogen, argon, helium, as well as other gases
that do not react with the organometallic compound precursor under
process conditions. In other embodiments, film deposition is
conducted in the presence of at least one reactive gas. Some of the
reactive gases that can be employed include but are not limited to
hydrazine, oxygen, hydrogen, air, oxygen-enriched air, ozone
(O.sub.3), nitrous oxide (N.sub.2O), water vapor, organic vapors,
ammonia and others. As known in the art, the presence of an
oxidizing gas, such as, for example, air, oxygen, oxygen-enriched
air, O.sub.3, N.sub.2O or a vapor of an oxidizing organic compound,
favors the formation of a metal oxide film.
[0050] As indicated above, this invention also relates in part to a
process for producing a film, coating or powder. The process
includes the step of decomposing at least one organometallic
compound precursor, thereby producing the film, coating or powder,
as further described below.
[0051] Deposition processes described herein can be conducted to
form a film, powder or coating that includes a single metal or a
film, powder or coating that includes a single metal oxide. Mixed
films, powders or coatings also can be deposited, for instance
mixed metal oxide films. A mixed metal oxide film can be formed,
for example, by employing several organometallic precursors, at
least one of which being selected from the organometallic compounds
described above.
[0052] Gas phase film deposition can be conducted to form film
layers of a desired thickness, for example, in the range of from
about 1 nm to over 1 mm. The precursors described herein are
particularly useful for producing thin films, e.g., films having a
thickness in the range of from about 10 nm to about 100 nm. Films
of molybdenum, for instance, can be considered for fabricating
metal electrodes, in particular as n-channel metal electrodes in
logic, as capacitor electrodes for DRAM applications, and as
dielectric materials.
[0053] The process also is suited for preparing layered films,
wherein at least two of the layers differ in phase or composition.
Examples of layered film include metal-insulator-semiconductor, and
metal-insulator-metal.
[0054] In an embodiment, the invention is directed to a process
that includes the step of decomposing vapor of an organometallic
compound precursor described above, thermally, chemically,
photochemically or by plasma activation, thereby forming a film on
a substrate. For instance, vapor generated by the compound is
contacted with a substrate having a temperature sufficient to cause
the organometallic compound to decompose and form a film on the
substrate.
[0055] The organometallic compound precursors can be employed in
chemical vapor deposition or, more specifically, in metalorganic
chemical vapor deposition processes known in the art. For instance,
the organometallic compound precursors described above can be used
in atmospheric, as well as in low pressure, chemical vapor
deposition processes. The compounds can be employed in hot wall
chemical vapor deposition, a method in which the entire reaction
chamber is heated, as well as in cold or warm wall type chemical
vapor deposition, a technique in which only the substrate is being
heated.
[0056] The organometallic compound precursors described above also
can be used in plasma or photo-assisted chemical vapor deposition
processes, in which the energy from a plasma or electromagnetic
energy, respectively, is used to activate the chemical vapor
deposition precursor. The compounds also can be employed in
ion-beam, electron-beam assisted chemical vapor deposition
processes in which, respectively, an ion beam or electron beam is
directed to the substrate to supply energy for decomposing a
chemical vapor deposition precursor. Laser-assisted chemical vapor
deposition processes, in which laser light is directed to the
substrate to affect photolytic reactions of the chemical vapor
deposition precursor, also can be used.
[0057] The process of the invention can be conducted in various
chemical vapor deposition reactors, such as, for instance, hot or
cold-wall reactors, plasma-assisted, beam-assisted or
laser-assisted reactors, as known in the art.
[0058] Examples of substrates that can be coated employing the
process of the invention include solid substrates such as metal
substrates, e.g., Al, Ni, Ti, Co, Pt, Ta; metal silicides, e.g.,
TiSi.sub.2, CoSi.sub.2, NiSi.sub.2; semiconductor materials, e.g.,
Si, SiGe, GaAs, InP, diamond, GaN, SiC; insulators, e.g.,
SiO.sub.2, Si.sub.3N.sub.4, HfO.sub.2, Ta.sub.2O.sub.5,
Al.sub.2O.sub.3, barium strontium titanate (BST); barrier
materials, e.g., TiN, TaN; or on substrates that include
combinations of materials. In addition, films or coatings can be
formed on glass, ceramics, plastics, thermoset polymeric materials,
and on other coatings or film layers. In preferred embodiments,
film deposition is on a substrate used in the manufacture or
processing of electronic components. In other embodiments, a
substrate is employed to support a low resistivity conductor
deposit that is stable in the presence of an oxidizer at high
temperature or an optically transmitting film.
[0059] The process of the invention can be conducted to deposit a
film on a substrate that has a smooth, flat surface. In an
embodiment, the process is conducted to deposit a film on a
substrate used in wafer manufacturing or processing. For instance,
the process can be conducted to deposit a film on patterned
substrates that include features such as trenches, holes or vias.
Furthermore, the process of the invention also can be integrated
with other steps in wafer manufacturing or processing, e.g.,
masking, etching and others.
[0060] Chemical vapor deposition films can be deposited to a
desired thickness. For example, films formed can be less than 1
micron thick, preferably less than 500 nanometer and more
preferably less than 200 nanometers thick. Films that are less than
50 nanometer thick, for instance, films that have a thickness
between about 1 and about 20 nanometers, also can be produced.
[0061] Organometallic compound precursors described above also can
be employed in the process of the invention to form films by atomic
layer deposition (ALD) or atomic layer nucleation (ALN) techniques,
during which a substrate is exposed to alternate pulses of
precursor, oxidizer and inert gas streams. Sequential layer
deposition techniques are described, for example, in U.S. Pat. No.
6,287,965 and in U.S. Pat. No. 6,342,277. The disclosures of both
patents are incorporated herein by reference in their entirety.
[0062] For example, in one ALD cycle, a substrate is exposed, in
step-wise manner, to: a) an inert gas; b) inert gas carrying
precursor vapor; c) inert gas; and d) oxidizer, alone or together
with inert gas. In general, each step can be as short as the
equipment will permit (e.g. milliseconds) and as long as the
process requires (e.g. several seconds or minutes). The duration of
one cycle can be as short as milliseconds and as long as minutes.
The cycle is repeated over a period that can range from a few
minutes to hours. Film produced can be a few nanometers thin or
thicker, e.g., 1 millimeter (mm).
[0063] The process of the invention also can be conducted using
supercritical fluids. Examples of film deposition methods that use
supercritical fluid that are currently known in the art include
chemical fluid deposition; supercritical fluid transport-chemical
deposition; supercritical fluid chemical deposition; and
supercritical immersion deposition.
[0064] Chemical fluid deposition processes, for example, are well
suited for producing high purity films and for covering complex
surfaces and filling of high-aspect-ratio features. Chemical fluid
deposition is described, for instance, in U.S. Pat. No. 5,789,027.
The use of supercritical fluids to form films also is described in
U.S. Pat. No. 6,541,278 B2. The disclosures of these two patents
are incorporated herein by reference in their entirety.
[0065] In an embodiment of the invention, a heated patterned
substrate is exposed to one or more organometallic compound
precursors, in the presence of a solvent, such as a near critical
or supercritical fluid, e.g., near critical or supercritical
CO.sub.2. In the case of CO.sub.2, the solvent fluid is provided at
a pressure above about 1000 psig and a temperature of at least
about 30.degree. C.
[0066] The precursor is decomposed to form a metal film on the
substrate. The reaction also generates organic material from the
precursor. The organic material is solubilized by the solvent fluid
and easily removed away from the substrate. Metal oxide films also
can be formed, for example by using an oxidizing gas.
[0067] In an example, the deposition process is conducted in a
reaction chamber that houses one or more substrates. The substrates
are heated to the desired temperature by heating the entire
chamber, for instance, by means of a furnace. Vapor of the
organometallic compound can be produced, for example, by applying a
vacuum to the chamber. For low boiling compounds, the chamber can
be hot enough to cause vaporization of the compound. As the vapor
contacts the heated substrate surface, it decomposes and forms a
metal or metal oxide film. As described above an organometallic
compound precursor can be used alone or in combination with one or
more components, such as, for example, other organometallic
precursors, inert carrier gases or reactive gases.
[0068] In a system that can be used in producing films by the
process of the invention, raw materials can be directed to a
gas-blending manifold to produce process gas that is supplied to a
deposition reactor, where film growth is conducted. Raw materials
include, but are not limited to, carrier gases, reactive gases,
purge gases, precursor, etch/clean gases, and others. Precise
control of the process gas composition is accomplished using
mass-flow controllers, valves, pressure transducers, and other
means, as known in the art. An exhaust manifold can convey gas
exiting the deposition reactor, as well as a bypass stream, to a
vacuum pump. An abatement system, downstream of the vacuum pump,
can be used to remove any hazardous materials from the exhaust gas.
The deposition system can be equipped with in-situ analysis system,
including a residual gas analyzer, which permits measurement of the
process gas composition. A control and data acquisition system can
monitor the various process parameters (e.g., temperature,
pressure, flow rate, etc.).
[0069] The organometallic compound precursors described above can
be employed to produce films that include a single metal or a film
that includes a single metal oxide. Mixed films also can be
deposited, for instance mixed metal oxide films. Such films are
produced, for example, by employing several organometallic
precursors. Metal films also can be formed, for example, by using
no carrier gas, vapor or other sources of oxygen.
[0070] Films formed by the methods described herein can be
characterized by techniques known in the art, for instance, by
X-ray diffraction, Auger spectroscopy, X-ray photoelectron emission
spectroscopy, atomic force microscopy, scanning electron
microscopy, and other techniques known in the art. Resistivity and
thermal stability of the films also can be measured, by methods
known in the art.
[0071] Various modifications and variations of this invention will
be obvious to a worker skilled in the art and it is to be
understood that such modifications and variations are to be
included within the purview of this application and the spirit and
scope of the claims.
EXAMPLE 1
[0072] In a glovebox, Mo(CO).sub.6 (31.9 grams, 121 mmol) was
placed into a three-neck 500 milliliter round-bottom flask
containing a stir bar. Also in the glovebox, Li(EtCp) (11.5 grams,
115 mmol) was placed into a one-neck 250 milliliter round-bottom
flask. To each flask was added 150 milliliters of anhydrous
inhibitor-free THF, and each was capped with septa. The flasks were
removed from the box and placed in a fume hood. The flask
containing the molybdenum reagent was placed into a heating mantle
above a stir plate and clamped into position. A nitrogen inlet and
an exhaust line (through an oil bubbler at the top rear of the
hood) were placed into the side-neck septum via needles. Under a
heavy nitrogen purge (i.e., vigorous bubbling in the oil bubbler)
the center-neck septa was removed and a water condenser was
attached. Water flow was initiated (through a `fail-safe` turn
wheel device hooked up to the variac for the heating mantle to
discontinue heating if water fails), and the inlet and outlet lines
were copper wired. The top of the condenser was fitted with a 24/40
t-joint. After a few minutes, the nitrogen/exhaust lines were
removed from the septum and attached (with no needles) to the two
t-joint hose barbs (using copper wire). Stirring was commenced.
[0073] The Li(EtCp) solution was transferred to the reaction flask
by cannula via pressure transfer. After addition was complete, the
two flask septa were replaced with pennyhead stoppers under a heavy
purge. Heating was commenced, and the mixture was brought to reflux
under a slow purge of nitrogen through the t-joint. Reflux was
continued for 43 hours (during which time CO gas will evolve and
exhaust through the bubbler). The mixture was then allowed to cool
to room temperature. While the mixture was cooling, in the glovebox
was prepared a solution of Diazald (i.e.,
N-methyl-N-nitroso-p-toluenesulfonamide) (25.0 grams, 115 mmol) in
THF (100 milliliters) within a one-neck 150 milliliter round bottom
flask. The flask was capped with a septum and brought into the fume
hood. The contents of the flask were transferred slowly (45
minutes) to the stirring room temperature reaction mixture by
pressure transfer via cannula (note: CO evolution will occur
quickly, releasing approximately 3 liters of CO). Once the Diazald
addition was complete, stirring was continued for 1 hour, after
which the condenser was removed, and the contents of the flask were
filtered in the fume hood through a medium porosity frit.
[0074] The remaining solids were rinsed with THF (4.times.25
milliliters). The filtrate was placed into a 1 liter round-bottom
flask and the solvent removed in vacuo (rotovap with N.sub.2
refill). The remaining liquid was loaded onto a 500 milliliter frit
loaded halfway with silica gel with a 2 centimeter layer of sand on
top. The plug was eluted with pentane. After an initial 500
milliliter of colorless pentane was recovered, 2 liters of orange
product solution was collected (note: the pentane solution
`filtrate` was still orange when collection was halted). The
solvent was removed from the product solution in-vacuo (rotovap
with N.sub.2 refill) and the remaining liquid was transferred to a
100 milliliter round-bottom flask for distillation (crude yield
28.5 grams, 90%). The product was vacuum distilled on a short path
apparatus. An early sublimate fraction (crystalline pale yellow
solid) was recovered initially and discarded (after NMR analysis).
The desired product was then collected in a new receiver flask (pot
temperature 120.degree. C., head temperature 70.degree. C., 0.15
torr line gauge). (EtCp)Mo(CO).sub.2(NO), 25.8 grams (82%), is a
vivid orange liquid. (EtCp)Mo(CO).sub.2(NO) may be handled for
short periods in air, but is best stored under nitrogen. The
compound was characterized and proven to be >99% pure by NMR,
GC-MS/FID, and TGA. Melting point (-10.degree. C.) was determined
by DSC.
* * * * *