U.S. patent application number 13/034564 was filed with the patent office on 2011-12-01 for precursors and methods for atomic layer deposition of transition metal oxides.
Invention is credited to Timo Hatanpaa, Suvi Haukka, Markku Leskela, Jaakko Niinisto, Mikko Ritala.
Application Number | 20110293830 13/034564 |
Document ID | / |
Family ID | 45022355 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110293830 |
Kind Code |
A1 |
Hatanpaa; Timo ; et
al. |
December 1, 2011 |
PRECURSORS AND METHODS FOR ATOMIC LAYER DEPOSITION OF TRANSITION
METAL OXIDES
Abstract
Methods are provided herein for forming transition metal oxide
thin films, preferably Group IVB metal oxide thin films, by atomic
layer deposition. The metal oxide thin films can be deposited at
high temperatures using metalorganic reactants. Metalorganic
reactants comprising two ligands, at least one of which is a
cycloheptatriene or cycloheptatrienyl (CHT) ligand are used in some
embodiments. The metal oxide thin films can be used, for example,
as dielectric oxides in transistors, flash devices, capacitors,
integrated circuits, and other semiconductor applications.
Inventors: |
Hatanpaa; Timo; (Espoo,
FI) ; Niinisto; Jaakko; (Vantaa, FI) ; Ritala;
Mikko; (Espoo, FI) ; Leskela; Markku; (Espoo,
FI) ; Haukka; Suvi; (Helsinki, FI) |
Family ID: |
45022355 |
Appl. No.: |
13/034564 |
Filed: |
February 24, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61308263 |
Feb 25, 2010 |
|
|
|
Current U.S.
Class: |
427/255.7 |
Current CPC
Class: |
C01P 2006/40 20130101;
C23C 16/45553 20130101; C23C 16/405 20130101; C01G 25/02 20130101;
C01G 27/02 20130101; C01G 23/07 20130101; C23C 16/45527 20130101;
C23C 16/45536 20130101 |
Class at
Publication: |
427/255.7 |
International
Class: |
C23C 16/455 20060101
C23C016/455 |
Claims
1. A method for forming a transition metal oxide thin film on a
substrate in a reaction chamber by atomic layer deposition, the
method comprising: providing a vapor phase pulse of a first
metalorganic reactant comprising a CHT ligand and a transition
metal to the reaction chamber such that it forms no more than a
monolayer on the substrate; removing excess first reactant from the
reaction chamber; providing a vapor phase pulse of a second
reactant comprising oxygen to the reaction chamber; and removing
excess second reactant and any reaction byproducts from the
reaction chamber; wherein the providing and removing steps are
repeated until a thin metal oxide film of a desired thickness and
composition is obtained, wherein the substrate temperature during
the providing and removing steps is above about 300.degree. C.
2. The method of claim 1, wherein the metalorganic reactant
comprises a Group IVB metal.
3. The method of claim 1, wherein the substrate temperature during
the providing and removing steps is above about 350.degree. C.
4. The method of claim 1, wherein the metalorganic reactant
comprises one or more of hafnium, titanium, and zirconium.
5. The method of claim 1, wherein the metalorganic reactant is an
organometallic reactant.
6. The method of claim 1, wherein the metalorganic reactant
comprises two ligands, one of which is the cycloheptatrienyl (CHT,
C.sub.7H.sub.7) ligand.
7. The method of claim 6, wherein the metalorganic reactant
comprises two CHT ligands.
8. The method of claim 6, wherein the metalorganic reactant
comprises one CHT ligand and one cyclopentadienyl (Cp) ligand.
9. The method of claim 6, wherein the metalorganic reactant does
not comprise a halide.
10. The method of claim 4, wherein the deposited thin film
comprises ZrO.sub.2.
11. The method of claim 4, wherein the deposited thin film
comprises TiO.sub.2.
12. The method of claim 4, wherein the deposited thin film
comprises HfO.sub.2.
13. A method for forming a transition metal oxide thin film by
atomic layer deposition on a substrate in a reaction chamber
comprising: alternately and sequentially contacting the substrate
with a vapor phase reactant pulse comprising a metal reactant and a
vapor phase reactant pulse comprising an oxygen reactant, wherein
the metal reactant comprises a transition metal and two ligands,
one of which is a cycloheptatrienyl (CHT) ligand.
14. The method of claim 13, wherein the metal reactant comprises a
Group IVB metal.
15. The method of claim 13, wherein the metal reactant is selected
from reactants having the formula (I) R.sub.xCp-M-CHT, where RxCp
represents substituted or unsubstituted cyclopentadienyl, CHT is
cycloheptatrienyl and M is selected from Ti, Zr and Hf.
16. The method of claim 13, wherein the metal reactant is selected
from reactants having the formula (II)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-Cp(R.sub.8R.sub.-
9R.sub.10R.sub.11R.sub.12), where M is selected from Ti, Zr and Hf,
and R.sub.1-12 can independently be H or an alkyl group.
17. The method of claim 13, wherein the metal reactant is selected
from reactants having the formula (III)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-CHT(R.sub.8R.sub-
.9R.sub.10R.sub.11R.sub.12R.sub.13R.sub.14), where M is selected
from Ti, Zr and Hf, and R.sub.1-14 can independently be H or an
alkyl group.
18. The method of claim 13, wherein the metal reactant is selected
from reactants having the formula (IV)
R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-L, where M
is selected from Ti, Zr and Hf; R.sub.1-7 can independently be H or
an alkyl group; and L is a mono or bidentate alkyl, cycloalkyl,
alkoxy, amide or imido group or acyclic or cyclic dienyl
ligand.
19. The method of claim 13, wherein the metal reactant is selected
from reactants having the formula (V)
R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-CHD(R.sub.8R.sub.-
9R.sub.10R.sub.11R.sub.12R.sub.13R.sub.14R.sub.15R.sub.16), where M
is selected from Ti, Zr and Hf; R.sub.1-16 can independently be H
or an alkyl group, and CHD is cyloheptadiene (C.sub.7H.sub.9).
20. The method of claim 13, wherein the metal reactant is selected
from reactants having the formula (VI)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7R.sub.8)X-M-X(R.sub.9R.-
sub.10R.sub.11R.sub.12R.sub.13R.sub.14R.sub.15R.sub.16), where M is
selected from Ti, Zr and Hf, R.sub.1-14 can independently be H or
an alkyl group and X is cycloheptatriene (C.sub.7H.sub.8).
21. The method of claim 13, wherein the oxygen reactant is selected
from the group consisting of O.sub.2, O.sub.3, H.sub.2O, NO,
NO.sub.2, N.sub.2O, and H.sub.2O.sub.2.
22. The method of claim 13, wherein the substrate temperature
during the pulses is from about 100 to about 500.degree. C.
23. The method of claim 13, wherein the substrate temperature
during the pulses is above about 300.degree. C.
24. The method of claim 13, wherein the metal precursor comprises
Ti.
25. The method of claim 13, wherein the metal precursor comprises
Hf.
26. The method of claim 13, wherein the metal precursor comprises
Zr.
27. A method for forming a thin film comprising a transition metal
by atomic layer deposition on a substrate in a reaction space
comprising: alternately and sequentially contacting the substrate
with a first vapor phase metal reactant pulse and a second vapor
phase reactant pulse; wherein the alternate and sequential pulses
are repeated until a thin film of a desired thickness and
composition is obtained and wherein the metal reactant comprises a
compound comprising a transition metal and two cycloheptatriene
(C.sub.7H.sub.8) ligands.
28. The method of claim 27, wherein the metal reactant comprises a
Group IVB metal.
29. The method of claim 28, wherein the metal reactant comprises
one of Ti, Hf and Zr.
30. The method of claim 27, wherein the substrate temperature
during the pulses is above about 300.degree. C.
31. The method of claim 27, wherein the thin film comprises a metal
oxide.
32. The method of claim 31, wherein the second reactant is an
oxygen source.
33. The method of claim 32, wherein the second reactant comprises
one or more of O.sub.2, H.sub.2O, O.sub.3, NO, NO.sub.2, N.sub.2O,
and H.sub.2O.sub.2.
34. The method of claim 27, wherein the thin film comprises a metal
nitride.
35. The method of claim 34, wherein the second reactant is a
nitrogen source.
36. The method of claim 35, wherein the nitrogen source is selected
from NH.sub.3, N.sub.2H.sub.2, and nitrogen containing plasma.
37. A method of synthesizing a CHT metal reactant comprising a
transition metal, the method comprising forming a reaction mixture
by combining a transition metal reactant with ferric chloride,
cycloheptatriene and tetrahydrofuran (THF) in a flask containing
magnesium chips.
38. The method of claim 37, wherein the reaction mixture is stirred
overnight.
39. The method of claim 37, wherein the ferric chloride,
cycloheptatriene and THF are first combined and then the transition
metal chloride is added.
40. The method of claim 39, wherein the transition metal chloride
is added while warming the mixture.
41. The method of claim 39, wherein the transition metal reactant
is a transition metal chloride.
42. The method of claim 37, wherein the transition metal reactant
is a Group IVB metal chloride.
43. The method of claim 37, wherein the Group IVB metal chloride is
TiCl.sub.4.
44. The method of claim 37, wherein the CHT metal reactant
comprises (C.sub.7H.sub.7)M(C.sub.7H.sub.9)/M(C.sub.7H.sub.8)
(CHT-M-CHD).
Description
REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. provisional
application No. 61/308,263, filed Feb. 25, 2010. The priority
application is hereby incorporated by reference in its
entirety.
PARTIES OF JOINT RESEARCH AGREEMENT
[0002] The invention claimed herein was made by, or on behalf of,
and/or in connection with a joint research agreement between the
University of Helsinki and ASM Microchemistry Oy signed on Nov. 14,
2003 and renewed in 2008. The agreement was in effect on and before
the date the claimed invention was made, and the claimed invention
was made as a result of activities undertaken within the scope of
the agreement.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present application relates generally to methods and
compositions for depositing transition metal oxide thin films, such
as titanium, zirconium and hafnium oxide thin films, by atomic
layer deposition using metalorganic precursors. The metalorganic
precursors comprise at least one cycloheptatriene (CHT) ligand.
[0005] 2. Description of the Related Art
[0006] Atomic layer deposition (ALD) is a self-limiting process,
whereby alternated pulses of reactants saturate a substrate
surface. The deposition conditions and precursors are selected such
that an adsorbed layer of precursor in one pulse leaves a surface
termination that is non-reactive with the gas phase reactants of
the same pulse. A subsequent pulse of different reactants reacts
with the previous termination to enable continued deposition. Thus,
each cycle of alternated pulses typically leaves no more than about
one molecular layer of the desired material. The principles of ALD
type processes have been presented by T. Suntola, e.g. in the
Handbook of Crystal Growth 3, Thin Films and Epitaxy, Part B:
Growth Mechanisms and Dynamics, Chapter 14, Atomic Layer Epitaxy,
pp. 601-663, Elsevier Science B.V. 1994, the disclosure of which is
incorporated herein by reference. Variations of ALD have been
proposed that allow for modulation of the growth rate. However, to
provide for high conformality and thickness uniformity, these
reactions are still more or less self-saturating.
[0007] While ALD processes can be used to deposit films at lower
temperatures, typically CVD processes have been used for higher
temperature growth because the reactions occur more rapidly at
higher temperatures. In addition, some ALD processes can lose their
self limiting nature at high temperatures. In some cases, higher
temperatures can cause undesirable decomposition of some
precursors. Some precursor decomposition can disrupt the self
limiting nature of the ALD process, for example if the products of
the decomposition reaction react with each other and/or react with
the adsorbed species to deposit material on the substrate
surface.
[0008] Atomic layer deposition (ALD) of Group IVB metal oxides,
such as TiO.sub.x, ZrO.sub.2 and HfO.sub.2, has been studied for
years. However, higher temperature ALD options for these metal
oxides are quite limited. Metal halide reactants are typically
used; however, metal halides are incompatible with some materials
and processes. Some metal-organic precursors have also been used.
However, these reactants have not been well suited for higher
temperature deposition processes.
SUMMARY OF THE INVENTION
[0009] In accordance with one aspect of the present invention,
methods for forming transition metal oxide thin films on a
substrate in a reaction chamber by atomic layer deposition using
metalorganic reactants are provided. Organometallic reactants are
used in some embodiments. In some embodiments the transition metal
oxide thin films are Group IVB metal oxide thin films. In some
embodiments, the methods comprise providing a vapor phase pulse of
a first reactant comprising a first Group IVB metalorganic
precursor to a reaction chamber such that it forms no more than a
monolayer on a substrate in the reaction chamber; removing excess
first reactant from the reaction chamber; providing a vapor phase
pulse of a second reactant comprising oxygen to the reaction
chamber such that it converts the adsorbed Group IVB metal reactant
to a metal oxide; and removing excess second reactant and any
reaction byproducts from the reaction chamber. The providing and
removing steps are repeated until a thin metal oxide film of a
desired thickness and composition is obtained. The substrate
temperature during the providing and removing steps may be above
about 300.degree. C., more preferably above about 350.degree. C. In
some embodiments the metalorganic precursor is an organometallic
precursor, comprising a carbon-metal bond.
[0010] In accordance with another aspect of the present invention,
methods for forming transition metal oxide films, preferably Group
IVB metal oxide films, by atomic layer deposition comprise
alternately and sequentially contacting a substrate with vapor
phase pulses of a cycloheptatrienyl or cycloheptatriene (CHT) metal
reactant and an oxygen source. The alternate and sequential pulses
are repeated until a thin film of a desired thickness is
obtained.
[0011] CHT metal reactants are metalorganic, typically
organometallic compounds, comprising at least one
chycloheptatrienyl or cycloheptatriene ligand (a CHT ligand). In
some embodiments the CHT metal reactant comprises only two ligands,
including at least one cycloheptatrienyl or cycloheptatriene (CHT)
ligand. In some embodiments the CHT metal reactant comprises two
CHT ligands. In some embodiments the CHT metal reactant comprises
two cycloheptatrienyl ligands. In other embodiments the CHT metal
reactant comprises one CHT ligand and one cyclopentadienyl ligand
(Cp). In some embodiments, the CHT reactant does not comprise a
halide. In some embodiments, the CHT reactant comprises one
cycloheptadienyl (CHD) ligand. In some embodiments, the CHT
reactant comprises two C.sub.7H.sub.8 cycloheptatriene ligands.
[0012] In some embodiments, a CHT metal reactant is selected from
the group consisting of reactants of the formula: [0013] (I)
R.sub.xCp-M-CHT, where R.sub.xCp represents substituted or
unsubstituted cyclopentadienyl, CHT is cycloheptatrienyl
(C.sub.7H.sub.7) and M is selected from Ti, Zr and Hf.
[0014] In other embodiments, a CHT metal reactant is selected from
the group consisting of reactants of the formula: [0015] (II)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-Cp(R.sub.8R.sub.-
9R.sub.10R.sub.11R.sub.12), where M is selected from Ti, Zr and Hf,
R.sub.1-12 can independently be H or an alkyl group.
[0016] In other embodiments, a CHT metal reactant is selected from
the group consisting of reactants of the formula: [0017] (III)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-CHT(R.sub.8R.sub-
.9R.sub.10R.sub.11R.sub.12R.sub.13R.sub.14), where M is selected
from Ti, Zr and Hf, R.sub.1-14 can independently be H or an alkyl
group.
[0018] In other embodiments, a CHT metal reactant is selected from
the group consisting of reactants of the formula: [0019] (IV)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-L, where M
is selected from Ti, Zr and Hf, R.sub.1-7 can independently be H or
an alkyl group and L is a mono or bidentate alkyl, cycloalkyl,
alkoxy, amide or imido group. L may also be a acyclic or cyclic
dienyl ligand.
[0020] In other embodiments, a CHT metal reactant is selected from
the group consisting of reactants of the formula: [0021] (V)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-CHD(R.sub.8R.sub-
.9R.sub.10R.sub.11R.sub.12R.sub.13R.sub.14R.sub.15R.sub.16), where
M is selected from Ti, Zr and Hf, R.sub.1-16 can independently be H
or an alkyl group and CHD is a cyloheptadienyl
(C.sub.7H.sub.9).
[0022] In other embodiments a CHT reactant it is selected from the
group consisting of reactants of the formula: [0023] (VI)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7R.sub.8)X-M-X(R.sub.9R.-
sub.10R.sub.11R.sub.12R.sub.13R.sub.14R.sub.15R.sub.16), where M is
selected from Ti, Zr and Hf, R.sub.1-14 can independently be H or
an alkyl group and X is cycloheptariene (C.sub.7H.sub.8).
[0024] In some embodiments, a CHT metal reactant can take different
forms depending on the conditions. For example, in some embodiments
a CHT metal reactant may have formula (V) under some conditions,
but may be in the form of formula (VI) under other conditions.
[0025] In the formulas (I)-(VI) CHT, CHD or X, denote the structure
of the ligand i.e. C.sub.7 ring structure with double bonds or
delocalized electrons, where different groups R.sub.1-R.sub.16 can
attach. For example, according to formula (IV) the compound can be
C.sub.7H.sub.7-M-L or ((CH.sub.3).sub.3C.sub.7H.sub.4)-M-L, not
H.sub.7C.sub.7H.sub.7-M-L or
(H.sub.4(CH.sub.3).sub.3C.sub.7H.sub.7)-M-L, respectively.
[0026] In another aspect of the invention, transition metal nitride
thin films, such as Group IVB metal nitride films, are deposited by
ALD using a transition metal CHT reactant and a nitrogen containing
reactant. In some embodiments the metal CHT reactant comprises two
CHT ligands. In some embodiments the CHT reactant does not comprise
a Cp group. In some embodiments, the CHT reactant comprises two
C.sub.7H.sub.8 cycloheptatriene ligands.
[0027] In still another aspect of the invention, transition metal
carbide thin films, such as Group IVB metal carbide films, are
deposited by ALD using a metal CHT reactant. In some embodiments
the metal CHT reactant comprises two CHT ligands. In some
embodiments, the CHT reactant does comprise two C.sub.7H.sub.8
cycloheptatriene ligands.
[0028] In another aspect of the invention, methods of synthesizing
transition metal precursors comprising one or more CHT ligands are
provided. In some embodiments, methods of synthesizing
(C.sub.7H.sub.8)M(C.sub.7H.sub.8), where M is a transition metal,
preferably a Group IVB metal, are provided. The methods may
comprise forming a reaction mixture by combining a transition metal
reactant with ferric chloride, cycloheptatriene and tetrahydrofuran
(THF) in a flask containing magnesium chips. The transition metal
reactant may be, for example, a Group IVB transition metal
reactant, preferably a metal halide. Exemplary reactants include
transition metal chlorides. In one embodiment, the transition metal
reactant is TiCl.sub.4.
[0029] These and other embodiments will become readily apparent to
those skilled in the art from the following detailed description,
the invention not being limited to any particular preferred
embodiments disclosed.
[0030] Certain objects and advantages of the disclosed precursors
and methods have been described herein. Of course, it is to be
understood that not necessarily all such objects or advantages may
be achieved in accordance with any particular embodiment. Thus, for
example, those skilled in the art will recognize that the invention
may be embodied or carried out in a manner that achieves or
optimizes one advantage or group of advantages as taught herein
without necessarily achieving other objects or advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 shows the structure of CpTiCHT (left) and (MeCp)ZrCHT
(right).
[0032] FIG. 2 shows the TGA curves measured for CpTiCHT and
(MeCp)ZrCHT.
[0033] FIG. 3 is a graph of growth rate at various temperatures
(top) and a graph of saturation as measured by growth rate for
different metal reactant pulse lengths (bottom).
[0034] FIG. 4 shows TofERDA data for ZrO.sub.2 films deposited
using (MeCp)ZrCHT and O.sub.3 at various temperatures.
[0035] FIGS. 5a, 5b and 5c show XRD data for ZrO.sub.2 films
deposited using (MeCp)ZrCHT and O.sub.3 at various
temperatures.
[0036] FIG. 6 represents graphs of GIXRD data for ZrO.sub.2 films
deposited using (MeCp)ZrCHT and O.sub.3.
[0037] FIG. 7 illustrates experiments to characterize the
electrical properties of ZrO.sub.2 films deposited using
(MeCp)ZrCHT and O.sub.3.
[0038] FIG. 8 is a flow chart of an embodiment of an ALD process
for depositing a Group IVB metal oxide using a CHT metal
precursor.
[0039] FIG. 9 is a schematic of the crystal structure of
Ti(C.sub.7H.sub.8).sub.2. The formulation may also be
(C.sub.7H.sub.7)Ti(C.sub.7H.sub.9) i.e. (CHT)Ti(CHD).
[0040] FIG. 10 shows TG, DTG and SDTA curves measured for
(CHT)Ti(CHD).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0041] Methods and compositions for forming transition metal oxide
films using metalorganic precursors are described herein. While
primarily illustrated in the context of forming Group IVB metal
oxide films, other transition metals can be substituted for the
Group IVB metals in some embodiments, as will be recognized by the
skilled artisan. In addition, although the thin films are generally
described with respect to the formation of an integrated circuit,
such as a capacitor or transistor, the skilled artisan will readily
appreciate the application of the principles and advantages
disclosed herein to various contexts in which metal oxide thin
films are useful. For example, transparent titanium oxide films can
be used in flat panel displays, LEDs, and solar cells.
[0042] In addition, although illustrated primarily in terms of
deposition of transition metal oxide thin films, in some
embodiments transition metal nitride or metal carbide films, such
as Group IVB metal nitride and carbide films, can be deposited by
ALD using the disclosed metal precursors.
[0043] As used herein, the term metal oxide film refers to a
transition metal oxide film unless otherwise stated. Preferred
transition metal oxide films are Group IVB metal oxide films. Group
IVB metal oxide thin films include oxide films comprising titanium
(Ti), zirconium (Zr) and/or hafnium (Hf). Exemplary Group IVB metal
oxide films that are specifically discussed herein include
TiO.sub.2, ZrO.sub.2 and HfO.sub.2. Other Group IVB metal oxide
films will be apparent to the skilled artisan. In addition, as
noted above, in some embodiments the Group IVB metals can be
substituted with other transition metals, as will be understood by
the skilled artisan.
[0044] In some embodiments, transition metal oxide films are
deposited on a substrate by atomic layer deposition (ALD) type
processes utilizing one or more metalorganic precursors. In some
embodiments the metalorganic precursor is an organometallic
precursor and thus comprises a carbon-metal bond. As discussed
below, in some embodiments deposition temperatures of greater than
300.degree. C. are used. In other embodiments, deposition
temperatures of greater than 350.degree. C. are used.
[0045] In particular embodiments, CHT metal reactants are utilized.
CHT metal reactants are metal reactants comprising at least one CHT
ligand. The CHT metal reactant may be a metalorganic compound and
in some embodiments is an organometallic compound. CHT ligands are
cycloheptatrienyl and cycloheptatriene ligands. Thus, CHT metal
reactants comprise at least one cycloheptatrienyl ligand or, in
some cases, at least one cycloheptatriene ligand. The CHT metal
reactants used herein typically comprise only two ligands, one of
which is a CHT ligand (cycloheptatrienyl or cycloheptatriene). In
some embodiments, the reactants comprise either two CHT ligands or
one CHT ligand and one cyclopentadienyl (Cp) ligand. In some
embodiments the CHT reactant comprises two cycloheptatrienyl
ligands. In some embodiments, the CHT reactant comprises two
C.sub.7H.sub.8 cycloheptatriene ligands. In other embodiments the
CHT metal reactants comprise one CHT ligand and another ligand such
as a mono or bidentate alkyl, cycloalkyl, alkoxy, amide or imido
group. In other embodiments the CHT metal reactants comprise one
CHT ligand and another ligand such as a dienyl ligand. In some
embodiments the CHT metal reactant comprises a transition metal.
However, the CHT metal reactants typically comprise one or more
Group IVB metals. In some embodiments, the CHT reactants do not
comprise a halide.
[0046] In some embodiments, CHT metal reactants have the general
formula: [0047] (I) RxCp-M-CHT, where RxCp represents substituted
or unsubstituted cyclopentadienyl, CHT is cycloheptatrienyl
(C.sub.7H.sub.7) and M is selected from Ti, Zr and Hf.
[0048] In other embodiments, CHT metal reactants have the general
formula: [0049] (II)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-Cp(R.sub.8R.sub.-
9R.sub.10R.sub.11R.sub.12), where M is selected from Ti, Zr and Hf,
R.sub.1-12 can independently be H or an alkyl group, and may be a
bridged or substituted alkyl. Exemplary alkyl groups include, but
are not limited to Me, Et, Pr, .sup.iPr, Bu, .sup.tBu and other
C.sub.1-C.sub.10 alkyls. Other alkyl groups that may be used will
be apparent to the skilled artisan.
[0050] In still other embodiments, the CHT metal reactants have the
general formula: [0051] (III)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-CHT(R.sub.8R.sub-
.9R.sub.10R.sub.11R.sub.12R.sub.13R.sub.14), where M is selected
from Ti, Zr and Hf, R.sub.1-14 can independently be H or an alkyl
group, and may be a bridged or substituted alkyl. Exemplary alkyl
groups include, but are not limited to Me, Et, Pr, .sup.iPr, Bu,
.sup.tBu and other C.sub.1-C.sub.10 alkyls. Other alkyl groups that
may be used will be apparent to the skilled artisan.
[0052] In still other embodiments, the CHT metal reactants have the
general formula: [0053] (IV)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-L, where M
is selected from Ti, Zr and Hf; R.sub.1-7 can independently be H or
an alkyl group, and may be a bridged or substituted alkyl; and L is
either a mono or bidentate alkyl, cycloalkyl, alkoxy, amide or
imido group. L may also be a acyclic or cyclic dienyl ligand.
Exemplary alkyl groups include, but are not limited to Me, Et, Pr,
.sup.iPr, Bu, .sup.tBu and other C.sub.1-C.sub.10 alkyls. Other
alkyl groups that may be used will be apparent to the skilled
artisan. Exemplary alkoxy groups include OMe, OEt, O.sup.iPr,
O.sup.tBu, O.sub.2CMe and O.sub.2C.sup.tBu. Exemplary amide groups
include N(Me).sub.2, N(MeEt) and N(Et).sub.2. Exemplary dienyl
ligands include 2,4-dimethylpenta-1,4-dienyl and
hepta-2,5-dienyl.
[0054] In other embodiments, a CHT metal reactant is selected from
the group consisting of reactants of the formula: [0055] (V)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7)CHT-M-CHD(R.sub.8R.sub-
.9R.sub.10R.sub.11R.sub.12R.sub.13R.sub.14R.sub.15R.sub.16), where
M is selected from Ti, Zr and Hf; R.sub.1-16 can independently be H
or an alkyl group, and may be a bridged or substituted alkyl.
Exemplary alkyl groups include, but are not limited to Me, Et, Pr,
.sup.iPr, Bu, .sup.tBu and other C.sub.1-C.sub.10 alkyls. Other
alkyl groups that may be used will be apparent to the skilled
artisan. CHD is a cyloheptadiene (C.sub.7H.sub.9).
[0056] In other embodiments, a CHT metal reactant is selected from
the group consisting of reactants of the formula: [0057] (VI)
(R.sub.1R.sub.2R.sub.3R.sub.4R.sub.5R.sub.6R.sub.7R.sub.8)X-M-X(R.sub.9R.-
sub.10R.sub.11R.sub.12R.sub.13R.sub.14R.sub.15R.sub.16), where M is
selected from Ti, Zr and Hf; R.sub.1-16 can independently be H or
an alkyl group, and may be a bridged or substituted alkyl.
Exemplary alkyl groups include, but are not limited to Me, Et, Pr,
.sup.iPr, Bu, .sup.tBu and other C.sub.1-C.sub.10 alkyls. Other
alkyl groups that may be used will be apparent to the skilled
artisan. X is cycloheptatriene (C.sub.7H.sub.8).
[0058] In some embodiments, a CHT metal reactant can take different
forms depending on the conditions. For example, in some embodiments
a CHT metal reactant may have formula (V) under some conditions,
but may be in the form of formula (VI) under other conditions.
[0059] In the formulas (I)-(VI) CHT, CHD or X, denote the structure
of ligand i.e. C.sub.7 ring structure with double bonds or
delocalized electrons, where different groups R.sub.1-R.sub.16 can
attach. For example, according to formula (IV) the compound can be
C.sub.7H.sub.7-M-L or ((CH.sub.3).sub.3C.sub.7H.sub.4)-M-L, not
H.sub.7C.sub.7H.sub.7-M-L or
(H.sub.4(CH.sub.3).sub.3C.sub.7H.sub.7)-M-L, respectively.
[0060] In some embodiments one or more of the alkyl groups in
R.sub.1-R.sub.16 mentioned in formulas (I)-(VI) may be
C.sub.1-C.sub.2 alkyls, such as Me or Et, while in other
embodiments one or more of the alkyl groups in R.sub.1-R.sub.16
mentioned in formulas (I)-(VI) may be C.sub.3-C.sub.10 alkyls, such
as Pr, .sup.iPr, Bu and .sup.tBu.
[0061] In some embodiments one or more of the R.sub.1-R.sub.14
substituents mentioned in formulas (I)-(VI) are other than
hydrogen. In yet other embodiments two or more of the
R.sub.1-R.sub.14 substituents mentioned in formulas (I)-(VI) are
other than hydrogen. In yet other embodiments three or more of the
R.sub.1-R.sub.16 substituents mentioned in formulas (I)-(VI) are
other than hydrogen.
[0062] FIG. 1 illustrates the structures of two exemplary
reactants, CpTiCHT and (MeCp)ZrCHT.
Atomic Layer Deposition Processes
[0063] ALD processes are generally based on controlled,
self-limiting surface reactions of precursor chemicals. Gas phase
reactions are avoided by feeding the precursors alternately and
sequentially into the reaction chamber. Vapor phase reactants are
separated from each other in the reaction chamber, for example, by
removing excess reactants and/or reactant byproducts from the
reaction chamber between reactant pulses.
[0064] Briefly, a substrate is loaded into a reaction chamber and
is heated to a suitable deposition temperature, generally at
lowered pressure. Deposition temperatures are typically maintained
below the thermal decomposition temperature of the reactants but at
a high enough level to avoid condensation of reactants and to
provide the activation energy for the desired surface reactions.
However, in some embodiments some minor decomposition may take
place without significantly disrupting the step coverage and
uniformity of the ALD process. Of course, the appropriate
temperature window for any given ALD reaction will depend upon a
variety of factors, including without limitation the surface
termination and the particular reactant species involved.
[0065] In some embodiments, thin films are deposited at deposition
temperatures of about 100 to about 500.degree. C., more preferably
about 150 to about 400.degree. C. and in some embodiments about 300
to about 400.degree. C. Particular deposition temperatures for some
specific embodiments are provided below.
[0066] In some embodiments, metal oxide films are deposited on a
substrate by atomic layer deposition (ALD) type processes utilizing
one or more metalorganic precursors at temperatures greater than
about 300.degree. C. or at temperatures greater than about
350.degree. C. In some of these embodiments, the metalorganic
precursors are organometallic precursors. In some embodiments the
precursors are metal CHT precursors as described herein.
[0067] A first transition metal reactant is conducted or pulsed
into the chamber in the form of vapor phase pulse and contacted
with the surface of the substrate. Conditions are preferably
selected such that no more than about one monolayer of the first
reactant is adsorbed on the substrate surface in a self-limiting
manner. Excess first reactant and reaction byproducts, if any, are
removed from the reaction chamber, such as by purging with an inert
gas. The appropriate pulsing and purging times can be readily
determined by the skilled artisan based on the particular
circumstances.
[0068] Purging the reaction chamber means that vapor phase
precursors and/or vapor phase byproducts are removed from the
reaction chamber such as by evacuating the chamber with a vacuum
pump and/or by replacing the gas inside the reactor with an inert
gas such as argon or nitrogen. Typical purging times are from about
0.05 to 20 seconds, more preferably between about 0.5 and 10, and
still more preferably between about 1 and 5 seconds. However, other
purge times can be utilized if necessary, such as where highly
conformal step coverage over extremely high aspect ratio structures
or other structures with complex surface morphology is needed.
Also, batch ALD reactors can utilize longer purging times because
of increased volume and surface area.
[0069] A second gaseous reactant is pulsed into the chamber where
it reacts with the first reactant bound to the surface. Excess
second reactant and gaseous byproducts of the surface reaction are
removed from the reaction chamber, preferably by purging with the
aid of an inert gas and/or evacuation. The steps of pulsing and
purging are repeated until a thin film of the desired thickness has
been formed on the substrate, with each cycle leaving typically
less than or no more than a molecular monolayer. The second
reactant may be, for example, an oxygen containing reactant, such
that a metal oxide is formed. In other embodiments the second
reactant may comprise nitrogen or carbon, in order to form metal
nitrides or metal carbides, respectively.
[0070] As mentioned above, each pulse or phase of each cycle is
preferably self-limiting. An excess of reactants is supplied in
each phase to saturate the susceptible structure surfaces. Surface
saturation ensures reactant occupation of all available reactive
sites (subject, for example, to physical size or "steric hindrance"
restraints) and thus ensures excellent step coverage. However, in
some embodiments, some minor non-self-limiting deposition may occur
which does not significantly disturb the unique properties of ALD
process.
[0071] According to some embodiments, a transition metal oxide thin
film, preferably a Group IVB metal oxide thin film, is formed on a
substrate by an ALD type process comprising multiple metal oxide
deposition cycles, each metal oxide deposition cycle
comprising:
[0072] providing a first vapor phase reactant pulse comprising a
first metalorganic reactant to the reaction chamber such that it
forms no more than a monolayer on the substrate,
[0073] wherein the metalorganic reactant comprises a transition
metal, preferably a Group IVB metal;
[0074] removing excess first reactant from the reaction
chamber;
[0075] providing a second vapor phase reactant pulse comprising a
second reactant to the reaction chamber, wherein the second
reactant comprises oxygen; and removing excess second reactant and
any reaction byproducts from the reaction chamber.
[0076] The providing and removing steps are repeated until a thin
film of a desired thickness and composition is obtained. In some
embodiments, the deposition cycle is carried out at a temperature
of at least 300.degree. C. or even at least 350.degree. C.
[0077] Further, in some embodiments the metalorganic reactant is an
organometallic reactant.
[0078] In some embodiments the same metalorganic precursor is
utilized in each cycle. However, in other embodiments, different
reactants can be utilized in one or more different cycles. In
addition, the ALD process may begin with any phase of the
deposition cycle.
[0079] In one embodiment illustrated in FIG. 8, a vapor phase
reactant pulse comprising a Group IVB metal CHT reactant is
provided to the reaction chamber where it contacts a substrate.
Preferably the reactant is selected such that if it decomposes at
the given process conditions it does not adversely affect the
deposition process. Preferably the metal reactant comprises one or
more of Ti, Hf, and Zr. In some embodiments, reactants are selected
from the reactants of formula's (I), (II), (III), (IV), (V) and
(VI).
[0080] Preferably, the metal CHT reactant is provided such that it
forms no more than about a single molecular layer on the substrate.
If necessary, any excess metal reactant can be purged or removed
from the reaction space. In some embodiments, the purge step can
comprise stopping the flow of metal reactant while still continuing
the flow of an inert carrier gas such as nitrogen or argon.
[0081] Next, a vapor phase reactant pulse comprising an oxygen
source or precursor is provided to the substrate and reaction
chamber. Any of a variety of oxygen precursors can be used,
including, without limitation: oxygen, plasma excited oxygen,
atomic oxygen, ozone, water, nitric oxide (NO), nitrogen dioxide
(NO.sub.2), nitrous oxide (N.sub.2O), hydrogen peroxide
(H.sub.2O.sub.2), etc. A suitable oxygen precursor can be selected
by the skilled artisan such that it reacts with the molecular layer
of the metal reactant on the substrate to form a metal oxide under
the particular process conditions. In some embodiments, ozone is
used with a metal CHT reactant.
[0082] The oxygen source may be an oxygen-containing gas pulse and
can be a mixture of an oxygen precursor and inactive gas, such as
nitrogen or argon. In some embodiments the oxygen source may be a
molecular oxygen-containing gas pulse. One source of oxygen may be
air. In some embodiments, the oxygen source or precursor is water.
In some embodiments the oxygen source comprises an activated or
excited oxygen species. In some embodiments the oxygen source
comprises ozone. The oxygen source may be pure ozone or a mixture
of ozone and another gas, for example an inactive gas such as
nitrogen or argon. In other embodiments the oxygen source is oxygen
plasma.
[0083] The oxygen precursor pulse may be provided, for example, by
pulsing ozone or a mixture of ozone and another gas into the
reaction chamber. In other embodiments, ozone (or other oxygen
precursor) is formed inside the reactor, for example by conducting
oxygen containing gas through an arc. In other embodiments an
oxygen containing plasma is formed in the reactor. In some
embodiments the plasma may be formed in situ on top of the
substrate or in close proximity to the substrate. In other
embodiments the plasma is formed upstream of the reaction chamber
in a remote plasma generator and plasma products are directed to
the reaction chamber to contact the substrate. As will be
appreciated by the skilled artisan, in the case of remote plasma
the pathway to the substrate can be optimized to maximize
electrically neutral species and minimize ion survival before
reaching the substrate.
[0084] Each metal oxide deposition cycle typically forms no more
than about one molecular layer of metal oxide. If necessary, any
excess reaction byproducts or oxygen precursor can be removed from
the reaction space. In some embodiments, the purge step can
comprise stopping the flow of oxygen precursor while still
continuing the flow of an inert carrier gas such as nitrogen or
argon. Preferably the oxygen precursor has a decomposition
temperature above the substrate temperature during deposition. In
some embodiments the oxygen precursor may decompose at the
substrate deposition temperature but does not disrupt the self
limiting nature of the ALD process.
[0085] The metal oxide deposition cycle is typically repeated a
predetermined number of times 150 to form a metal oxide of the
desired thickness and composition. In some embodiments, multiple
molecular layers of metal oxide are formed by multiple deposition
cycles. In other embodiments, a molecular layer or less of metal
oxide is formed.
[0086] Removing excess reactants can include evacuating some of the
contents of the reaction space or purging the reaction space with
argon, helium, nitrogen or any other inert gas. In some embodiments
purging can comprise turning off the flow of the reactive gas while
continuing to flow an inert carrier gas to the reaction space.
[0087] The precursors employed in the ALD type processes may be
solid, liquid or gaseous material under standard conditions (room
temperature and atmospheric pressure), provided that the precursors
are in vapor phase before it is conducted into the reaction chamber
and contacted with the substrate surface. "Pulsing" a vaporized
precursor onto the substrate means that the precursor vapor is
conducted into the chamber for a limited period of time. Typically,
the pulsing time is from about 0.05 to 10 seconds. However,
depending on the substrate type and its surface area, the pulsing
time may be even higher than 10 seconds. Preferably, for a 300 mm
wafer in a single wafer ALD reactor, a metal precursor, such as a
Ti, Hf, or Zr precursor, is pulsed for from 0.05 to 20 seconds,
more preferably for from 0.1 to 10 seconds and most preferably for
about 0.3 to 5.0 seconds. An oxygen-containing precursor is
preferably pulsed for from about 0.05 to 10 seconds, more
preferably for from 0.1 to 5 seconds, most preferably for from
about 0.2 to 3.0 seconds. However, pulsing times can be on the
order of minutes in some cases, for example, if the process is
applied to reactors having large surface area, such batch ALD
reactors. The optimum pulsing time can be readily determined by the
skilled artisan based on the particular circumstances.
[0088] The mass flow rate of the precursors can also be determined
by the skilled artisan. In one embodiment, for deposition on 300 mm
wafers the flow rate of metal precursors is preferably between
about 1 and 1000 sccm without limitation, more preferably between
about 100 and 500 sccm. The mass flow rate of the metal precursors
is usually lower than the mass flow rate of the oxygen source,
which is usually between about 10 and 10000 sccm without
limitation, more preferably between about 100-2000 sccm and most
preferably between 100-1000 sccm.
[0089] The pressure in the reaction chamber is typically from about
0.01 to about 20 mbar, more preferably from about 1 to about 10
mbar. However, in some cases the pressure will be higher or lower
than this range, as can be readily determined by the skilled
artisan. Atmospheric pressure could also be used for these high
temperature reactions.
[0090] Before starting the deposition of the film, the substrate is
typically heated to a suitable growth temperature. Growth
temperatures are described above and typically range from about 100
to about 400.degree. C. In some embodiments growth temperatures of
greater than 300.degree. C. or even 350.degree. C. are used.
[0091] The deposition cycles can be repeated a predetermined number
of times or until a desired thickness is reached. Preferably, the
thin films are between about 5 .ANG. and 200 nm thick, more
preferably between about 10 .ANG. and 100 nm thick.
[0092] In other embodiments, transition metal nitride thin films
are deposited using a transition metal CHT reactant, preferably a
Group IVB metal CHT reactant. The reaction conditions can be
essentially as described above for deposition of transition metal
oxide, except that a nitrogen-containing reactant is used in place
of the oxygen reactant. Nitrogen containing reactants may be, for
example, NH.sub.3, nitrogen plasma, N.sub.2H.sub.2, hydrogen azide,
hydrazine and/or hydrazine derivatives, amines, nitrogen radicals,
and other excited species of nitrogen.
[0093] In other embodiments, transition metal carbide thin films
are deposited using a transition metal CHT reactant, preferably a
Group IVB metal CHT reactant. Again, the reaction conditions can be
essentially as described above for deposition of transition metal
oxides, except that a carbon-containing reactant is used in place
of the oxygen reactant. In some embodiments, the carbon source is a
hydrocarbon such as an alkane, alkene, and/or alkyne.
Deposition of Thin Films Comprising Zirconium Oxide
[0094] In some embodiments, methods are provided for depositing
thin films comprising zirconium oxide. A vapor phase pulse of a
zirconium CHT precursor is provided to the reaction chamber. The
zirconium precursor may be selected from the group consisting of
the compounds of formulas (I), (II), (III), (IV), (V) and (VI)
above, where M is Zr. In some embodiments the precursor is
(MeCp)ZrCHT. The zirconium precursor can be provided such that it
forms no more than one monolayer of material on the substrate.
Next, a vapor phase reactant pulse comprising an oxygen precursor
is provided to the reaction chamber. The oxygen precursor can be
provided such that it reacts with the zirconium precursor on the
substrate surface. Preferred oxygen precursors include atomic
oxygen, oxygen plasma, O.sub.2, H.sub.2O, O.sub.3, NO, NO.sub.2,
N.sub.2O, and H.sub.2O.sub.2. In some embodiments the oxygen
precursor is O.sub.3. Preferably the substrate temperature during
pulses of zirconium and oxygen precursors is above about
300.degree. C. The cycle can be generally referred to as a
zirconium oxide deposition cycle. The deposition cycle can be
repeated until the thin film reaches the desired thickness.
[0095] The process conditions for the zirconium oxide deposition
can be essentially as described above in reference to the metal
oxide deposition cycle.
Deposition of Thin Films Comprising Titanium Oxide
[0096] In some embodiments, methods are provided for depositing
thin films comprising titanium oxide. A vapor phase pulse of a
titanium CHT precursor is provided to the reaction chamber. The
titanium precursor may be selected from the group consisting of the
compounds of formulas (I), (II), (III), (IV), (V) and (VI) above,
where M is Ti. In some embodiments the precursor is CpTiCHT. The
titanium precursor can be provided such that it forms no more than
one monolayer of material on the substrate. Next, a vapor phase
reactant pulse comprising an oxygen precursor is provided to the
reaction chamber. The oxygen precursor can be provided such that it
reacts with the titanium precursor on the substrate surface.
Preferred oxygen precursors include atomic oxygen, oxygen plasma,
O.sub.2, H.sub.2O, O.sub.3, NO, NO.sub.2, N.sub.2O, and
H.sub.2O.sub.2. In some embodiments the oxygen precursor is
O.sub.3. Preferably the substrate temperature during pulses of
titanium and oxygen precursors is above about 300.degree. C. The
cycle can be generally referred to as a titanium oxide deposition
cycle. The deposition cycle can be repeated until the thin film
reaches the desired thickness.
[0097] The process conditions for the titanium oxide deposition can
be essentially as described above in reference to the metal oxide
deposition cycle.
Deposition of Thin Films Comprising Hafnium Oxide
[0098] In some embodiments, methods are provided for depositing
thin films comprising hafnium oxide. A vapor phase pulse of a
hafnium CHT precursor is provided to the reaction chamber. The
hafnium precursor may be selected from the group consisting of the
compounds of formulas (I), (II), (III), (IV), (V) and (VI) above,
where M is Hf. The hafnium precursor can be provided such that it
forms no more than one monolayer of material on the substrate.
Next, a vapor phase reactant pulse comprising an oxygen precursor
is provided to the reaction chamber. The oxygen precursor can be
provided such that it reacts with the hafnium precursor on the
substrate surface. Preferred oxygen precursors include atomic
oxygen, oxygen plasma, O.sub.2z H.sub.2O, O.sub.3, NO, NO.sub.2,
N.sub.2O, and H.sub.2O.sub.2. In some embodiments the oxygen
precursor is O.sub.3. Preferably the substrate temperature during
pulses of hafnium and oxygen precursors is above about 300.degree.
C. The cycle can be generally referred to as a hafnium oxide
deposition cycle. The deposition cycle can be repeated until the
thin film reaches the desired thickness.
[0099] The process conditions for the hafnium oxide deposition can
be essentially as described above in reference to the metal oxide
deposition cycle.
Applications
[0100] Metal oxide films may be used, for example, as dielectric
layers between top and bottom electrodes in capacitors. In some
embodiments, a capacitor suitable for use in an integrated circuit
is formed by a method comprising:
[0101] depositing a bottom electrode;
[0102] depositing a dielectric oxide layer over the bottom
electrode by an atomic layer deposition process comprising
alternating and sequential pulses of a metal CHT source and pulses
of an oxygen source as described herein; and
[0103] depositing a top electrode directly over and contacting the
dielectric layer.
[0104] The metal oxides can also be used as dielectric layers in
transistors. In one embodiment of a method for forming a transistor
in an integrated circuit, a dielectric oxide layer is first
deposited over one or more gate electrodes on a substrate by an ALD
process. The deposition of the dielectric oxide layer can include
any of the methods described herein. Preferably the dielectric
oxide layer comprises one or more of hafnium, zirconium, and
titanium. Next, a semiconductor is deposited on the dielectric
oxide layer. In some embodiments the semiconductor comprises one or
more of silicon and germanium. Next, electrically conductive source
and drain electrodes are deposited on top of the semiconductor such
that the drain electrodes align with the gate electrodes.
[0105] The skilled artisan will appreciate that the metal oxide
thin films described herein have many other uses, such as a
floating gate dielectric layer in a flash device, as a blocking
oxide in charge trapping flash devices, as a gate dielectric in
memory stacks, as a dielectric oxide in other semiconductor
devices, etc. The thin films described herein can also be useful in
optical areas, for example, titanium dioxide can be a transparent
conducting oxide used in optical components, flat panel displays,
LEDs, solar cells and chemical sensors.
Precursor Synthesis
[0106] Methods are also provided for synthesizing the metal CHT
precursors used in the ALD processes described herein. In
particular, CHT precursors of formulas (I), (II), (III), (IV), (V)
and (VI) above, can be synthesized.
[0107] In some embodiments the CHT precursor that is synthesized is
CpTiCHT and in other embodiments the precursor (MeCp)ZrCHT is
synthesized, as described in the Examples below.
[0108] In other embodiments, transition metal precursors of formula
(III) are synthesized, such as (C.sub.7H.sub.8)M(C.sub.7H.sub.8),
where M is a transition metal, preferably a group IVB metal such as
Ti, Zr, Hf. In a container containing magnesium chips, anhydrous
FeCl.sub.3, cycloheptatriene, and tetrahydrofuran (THF) are
combined. A transition metal precursor, such as a transition metal
halide THF adduct is added to the reaction mixture, preferably over
a long period of time and while stirring. The reaction is
exothermic thus, for example, the transition metal precursor may be
added over a 1-h period to avoid possible overheating of the
stirred reaction mixture. The transition metal precursor comprises
a Group IVB metal in some embodiments, and may be, for example, a
transition metal chloride. The transition metal precursor may be in
solution, such as in solution with THF.
[0109] The mixture may be stirred over night, for example at room
temperature. Following stirring, the volatile products may be
evaporated under vacuum.
[0110] Synthesis of C.sub.7H.sub.8--Ti--C.sub.7H.sub.8 using
TiCl.sub.4 is described in Example 8 below.
EXAMPLES
[0111] All complex preparations were done under exclusion of air
and moisture using standard Schlenk and glove box techniques.
Toluene and xylene were dried and stored over 4 .ANG. molecular
sieves. THF was freshly distilled from sodium benzophenone ketyl.
Anhydrous Zirconium(IV) chloride (Aldrich 99.999%), Titanium(IV)
chloride (Fluka >99.0%), Dicyclopentadienyl Titanium(IV)
dichloride (Aldrich 97%), ferric chloride (Riedel-de Haen),
magnesium turnings and cycloheptariene (Aldrich 90%) were used as
received. Methylcyclopentadiene dimer was cracked to corresponding
monomer just before usage.
[0112] .sup.1H and .sup.13C NMR spectra were recorded with a Varian
Gemini 2000 instrument at ambient temperature. Chemical shifts were
referenced to SiMe.sub.4 and are given in ppm. Thermogravimetric
analyses were carried out on a Mettler Toledo Star.sup.e system
equipped with a TGA 850 thermobalance using a flowing nitrogen
atmosphere at 1 atm. The heating rate was 10.degree. C./min and the
weights of the samples prepared to 70 .mu.l pans were between 10-11
mg. Melting points were taken from the SDTA data measured by the
thermobalance. Mass spectra were recorded with a JEOL JMS-SX102
operating in electron impact mode (70 eV) using a direct insertion
probe and sublimation temperature range of 50-370.degree. C.
Example 1
[0113] Synthesis of (C.sub.5H.sub.5)Ti(C.sub.7H.sub.7): The
synthesis was done using the method of Demerseman et al. (Inorg.
Chem. 1982, 21, 3942). CpTiCl.sub.3 had to be synthesized initially
and two different methods were employed synthesizing different
batches. First the method of Sloan at al. (J. Am. Chem. Soc. 1959,
81, 1364.) was employed. The method of Hitchcock et al. (Dalton
Trans., 1999, 1161.) was also used as Cp.sub.2TiCl.sub.2 is readily
available.
[0114] In a 1-L flask containing 20 g of magnesium chips were added
2 g of anhydrous FeCl.sub.3, 50 ml of cycloheptatriene, 50 ml of
THF, and, over a 3-h period to allow the warming of the stirred
reaction mixture, a solution of 57.45 g (0.26 mol) of CpTiCl.sub.3
in 400 ml of THF. The mixture was stirred at room temperature over
night and the volatile products were evaporated under vacuum.
Sublimation of the residue (130.degree. C./0.05 mmHg) gave a blue
solid: 85.8% yield (45.9 g); .sup.1H NMR (C.sub.6D.sub.6):), 4.91
(s, 5H, CH), 5.43 (s, 7H, CH); .sup.13C{.sup.1H}
NMR(C.sub.6D.sub.6): 97.35 (CH, C.sub.7-ring), 86.71 (CH, Cp ring);
MS (EI, 70 eV) m/z: 204 (M.sup.+) with the correct isotopic
distribution.
[0115] FIG. 1 shows the structure of CpTiCHT and FIG. 2 provides
the TGA curve measured for CpTiCHT.
Example 2
[0116] Synthesis of (MeC.sub.5H.sub.4)Zr(C.sub.7H.sub.7): The
synthesis was performed in a fashion similar to that described for
CpZrCHT by Tamm et al. (Organometallics 2005, 3163). The method is
also similar with that presented for CpTiCHT in Example 1 above.
MeCpZrCl.sub.3 needed in the synthesis was synthesized using the
method of Hitchcock et al. (Polyhedron 1995, 14, 2745). A Schlenk
flask was charged with magnesium turnings (6 g, 247 mmol),
catalytic amounts of ferric chloride (0.6 g, 3.7 mmol),
cycloheptatriene (15 ml), and THF (50 ml). This reaction mixture
was treated dropwise with a solution of MeCpZrCl.sub.3 (17.3 g,
62.4 mmol) in THF (150 ml) over a period of 1 h. After the mixture
was stirred overnight at room temperature, all volatiles were
removed in vacuo. The air-sensitive residue was sublimed at
140.degree. C./0.05 mbar to obtain 13.0 g (79.6%) of
(MeC.sub.5H.sub.4)Zr(C.sub.7H.sub.7) as a purple crystalline solid.
Anal. calcd. for Zr.sub.1C.sub.13H.sub.14: C, 33.65; H, 6.35.
Found: C, 26.963; H, 5.03. Mp. 174-176.degree. C., .sup.1H NMR
(C.sub.6D.sub.6) 1.81 (s, 3H, CH.sub.3), 5.14 (t, 2H, CH)), 5.23
(m, 2H, CH) 5.24 (s, 7H, CH); .sup.13C{.sup.1H} NMR
(C.sub.6D.sub.6) 14.61 (CH.sub.3), 41.74 (Cp ring), 81.39
(C.sub.7-ring), 100.92 (Cp ring), 103.34 (Cp ring). MS (EI, 70 eV)
m/z: 260 (M.sup.+) with the correct isotopic distribution.
[0117] FIG. 1 shows the structure of (MeCp)ZrCHT and FIG. 2
provides the TGA curve measured for this compound. (MeCp)ZrCHT is a
solid precursor at 100.degree. C.
Example 3
[0118] The thermal stability of the CpTiCHT synthesized in Example
1 was tested on an extremely high surface area silica substrate and
found to be good. The compound saturated the silica surface at
400.degree. C., although the ligands are most likely decomposed.
CpTiCHT was observed to be a blue solid that vaporized at
130.degree. C.
Example 4
[0119] (MeCp)ZrCHT was synthesized as described above. (MeCp)ZrCHT
was used in combination with O.sub.3 in an ALD process essentially
as described herein. An ozone concentration of 100 g/m.sup.3 was
used. Smooth, uniform zirconium oxide films were deposited at
temperatures up to about 450.degree. C. Saturation was confirmed at
350.degree. C., and at 400.degree. C. only slight decomposition was
observed as the growth rate increased from 0.7 .ANG./cycle with 1 s
pulses of the metal precursor to 0.8 .ANG./cycle with 2 s pulses.
FIG. 3. According to ERDA, the films deposited at 350.degree. C.
were exceptionally pure (no H detected, <0.06 at. % C). FIG. 4.
XRD data is presented in FIGS. 5a, 5b and 5c. GIXRD data is
presented in FIG. 6. Similar characteristics were observed as with
films deposited from (CpMe).sub.2Zr(OMe)Me and O.sub.3.
[0120] Several of the deposited ZrO.sub.2 films were tested for
their electrical properties. Preliminary results shown in FIG. 7
verify that the films act as dielectrics. A film deposited at
400.degree. C. showed a CET of 0.67-1.17 nm (6.2 nm/5.58
g/cm.sup.3).
Example 5
[0121] ZrO.sub.2 is deposited by ALD from alternating pulses of
(MeCp)ZrCHT or another CHT metal precursor and an oxygen source,
such as O.sub.3 The substrate temperature is above 300.degree.
C.
Example 6
[0122] HfO.sub.2 is deposited on a substrate by ALD using
alternating pulses of a Hf CHT precursor and an oxygen source, such
as O.sub.3 at a substrate temperature of above 300.degree. C.
Example 7
[0123] TiO.sub.2 is deposited on a substrate by ALD using
alternating pulses of CpTiCHT and O.sub.3 at a substrate
temperature of above 300.degree. C.
Example 8
[0124] Synthesis of CHT metal reactant: In a 1-L flask containing 5
g of magnesium chips were added 0.5 g of anhydrous FeCl.sub.3, 30
ml of cycloheptatriene, 30 ml of THF, and, over a 1-h period to
allow the warming of the stirred reaction mixture, a solution of 12
g (0.063 mol) of TiCl.sub.4 in 200 ml of THF. The mixture was
stirred at room temperature over night, and the volatile products
were evaporated under vacuum. Sublimation of the residue
(130.degree. C./0.05 mmHg) gave a dark solid: 24.4% yield (3.54 g);
mp. 177-200.degree. C.; .sup.1H NMR (C6D6): 1.2-1.5 (m, CH),
1.9-2.1 (m, CH), 2.1-2.2 (m, CH), 4.2-4.4 (m, CH), 4.9-5.1 (CH, m),
5.32 (s, 7H, CH), 5.6-5.8 (m, CH); 13C{1H} NMR (C6D6): 37.34 (CH,
C7-ring), 88.67 (CH, .eta.7-C7-ring), 101.53 (CH, C7-ring), 102.33
(CH, C7-ring), 113.39 (CH, C7-ring); MS (EI, 70 eV) m/z: 278, 232,
230 [M]+, 91 [C7H7]+. The chemical structure of the synthesized CHT
compound was determined to be
(C.sub.7H.sub.7)Ti(C.sub.7H.sub.9)/Ti(C.sub.7H.sub.8).sub.2. While
this is believed to be accurate, identification of the structure
was difficult and it was initially identified differently. Crystal
structure of the synthesized precursors is shown in FIG. 9. TG, DTG
and SDTA curves measured for (CHT)Ti(CHD) are shown in FIG. 10.
[0125] Other transition metals precursors of formula (III), such as
(C.sub.7H.sub.7)M(C.sub.7H.sub.9)/M(C.sub.7H.sub.8).sub.2, where M
is a transition metal, preferably group IVB metal such as Ti, Zr,
Hf, can be synthesized using essentially the method described above
for synthesis of
(C.sub.7H.sub.7)Ti(C.sub.7H.sub.9)/M(C.sub.7H.sub.8).sub.2.
[0126] It will be appreciated by those skilled in the art that
various modifications and changes can be made without departing
from the scope of the invention. Similar other modifications and
changes are intended to fall within the scope of the invention, as
defined by the appended claims.
* * * * *