U.S. patent application number 17/557131 was filed with the patent office on 2022-04-14 for methods for depositing a transition metal chalcogenide film on a substrate by a cyclical deposition process.
The applicant listed for this patent is ASM IP Holding B.V.. Invention is credited to Markku Leskela, Miika Mattinen, Mikko Ritala.
Application Number | 20220115232 17/557131 |
Document ID | / |
Family ID | |
Filed Date | 2022-04-14 |
United States Patent
Application |
20220115232 |
Kind Code |
A1 |
Mattinen; Miika ; et
al. |
April 14, 2022 |
METHODS FOR DEPOSITING A TRANSITION METAL CHALCOGENIDE FILM ON A
SUBSTRATE BY A CYCLICAL DEPOSITION PROCESS
Abstract
Systems for depositing a transition metal chalcogenide film on a
substrate by cyclical deposition process are disclosed. The methods
may include, contacting the substrate with at least one transition
metal containing vapor phase reactant comprising at least one of a
hafnium precursor, or a zirconium precursor, and contacting the
substrate with at least one chalcogen containing vapor phase
reactant. Semiconductor device structures including a transition
metal chalcogenide film deposited by the methods of the disclosure
are also provided.
Inventors: |
Mattinen; Miika; (Helsinki,
FI) ; Ritala; Mikko; (Espoo, FI) ; Leskela;
Markku; (Espoo, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASM IP Holding B.V. |
Almere |
|
NL |
|
|
Appl. No.: |
17/557131 |
Filed: |
December 21, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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17028066 |
Sep 22, 2020 |
11244825 |
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17557131 |
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16193789 |
Nov 16, 2018 |
10847366 |
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17028066 |
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International
Class: |
H01L 21/02 20060101
H01L021/02; H01L 29/786 20060101 H01L029/786; H01L 29/24 20060101
H01L029/24; H01L 29/04 20060101 H01L029/04 |
Claims
1. A method for depositing a transition metal chalcogenide film on
a substrate by a cyclical deposition process, the method
comprising: contacting the substrate with at least one transition
metal containing vapor phase reactant comprising at least one of a
hafnium precursor and a zirconium precursor; and contacting the
substrate with at least one chalcogen containing vapor phase
reactant.
2. The method of claim 1, wherein the cyclical deposition process
comprises atomic layer deposition.
3. The method of claim 1, wherein the cyclical deposition process
comprises cyclical chemical vapor deposition.
4. The method of claim 1, wherein at least one of the hafnium
precursor and the zirconium precursor comprises at least one of a
halide precursor and a metalorganic precursor.
5. The method of claim 4, wherein the halide precursor comprises at
least one of hafnium tetrachloride (HfCl.sub.4) and zirconium
tetrachloride (ZrCl.sub.4).
6. The method of claim 4, wherein the metalorganic precursor
comprises at least one of an alkylamide precursor and a
cyclopentadienyl-ligand containing precursor.
7. The method of claim 6, wherein the alkylamide precursor
comprises at least one of tetrakis(ethylmethylamido)hafnium
(Hf(NEtMe).sub.4), and tetrakis(ethylmethylamido)zirconium
(Zr(NEtMe).sub.4).
8. The method of claim 6, wherein the cyclopentadienyl-ligand
containing precursor comprises at least one of
tris(dimethylamido)cyclopentadienylhafnium (HfCp(NMe.sub.2).sub.3),
bis(methylcyclopentadienyl)methoxymethylhafnium
((MeCp).sub.2Hf(CH).sub.3(OCH.sub.3)),
tris(dimethylamido)cyclopentadienylzirconium
(ZrCp(NMe.sub.2).sub.3), and
bis(methylcyclopentadienyl)methoxymethylzirconium
((MeCp).sub.2Zr(CH).sub.3(OCH.sub.3)).
9. The method of claim 1, wherein the at least one chalcogen
containing vapor phase reactant comprises hydrogen sulfide
(H.sub.2S), hydrogen selenide (H.sub.2Se), dimethyl sulfide
((CH.sub.3).sub.2S), and dimethyl telluride (CH.sub.3).sub.2Te.
10. The method of claim 1, further comprising flowing the chalcogen
containing vapor phase reactant through a gas purifier prior to
entering the reaction chamber to reduce a concentration of at least
one of water and oxygen within the chalcogen containing vapor phase
reactant.
11. The method of claim 10, wherein the concentration of at least
one of water and oxygen within the chalcogen containing vapor phase
reactant is reduced to less than 1 part per million.
12. The method of claim 1, further comprising flowing a carrier gas
through a vessel containing a source of the transition metal
containing vapor phase reactant to transport the transition metal
containing vapor phase reactant to the reaction chamber and further
comprising flowing the carrier gas through a gas purifier prior to
entering the source of the transition metal containing vapor phase
reactant to reduce a concentration of at least one of water and
oxygen within the carrier gas.
13. The method of claim 12, wherein the concentration of at least
one of water and oxygen within the carrier gas is reduced to less
than 1 part per million.
14. The method of claim 1, further comprising pre-annealing the
reaction chamber prior to film deposition.
15. The method of claim 1, wherein the transition metal
chalcogenide film comprises a predominant (001) crystallographic
orientation.
16. The method of claim 1, further comprising in-situ depositing a
capping layer over the transition metal chalcogenide film.
17. The method of claim 16, wherein in-situ depositing a capping
layer over the transition metal chalcogenide film comprises
depositing the capping layer utilizing non-oxidative precursors or
non-oxygen reactants.
18. The method of claim 16, wherein the capping layer comprises a
metal silicate film.
19. The method of claim 18, wherein the metal silicate film
comprises an aluminum silicate film (Al.sub.xSi.sub.yO.sub.z).
20. A semiconductor device structure comprising a transition metal
chalcogenide film deposited by the method of claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of, and claims priority
to, U.S. patent application Ser. No. 17/028,066 filed Sep. 22, 2020
titled METHODS FOR DEPOSITING A TRANSITION METAL CHALCOGENIDE FILM
ON A SUBSTRATE BY A CYCLICAL DEPOSITION PROCESS; which is a
continuation of U.S. patent application Ser. No. 16/193,789 filed
Nov. 16, 2018 titled METHODS FOR DEPOSITING A TRANSITION METAL
CHALCOGENIDE FILM ON A SUBSTRATE BY A CYCLICAL DEPOSITION PROCESS,
the disclosures of which are hereby incorporated by reference in
their 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. 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.
FIELD OF INVENTION
[0003] The present disclosure relates generally to methods for
depositing a transition metal chalcogenide film on a substrate by a
cyclical deposition process and in particular to the cyclical
deposition of transition metal chalcogenides comprising hafnium or
zirconium. The disclosure also relates to semiconductor device
structures including a transition metal chalcogenide film deposited
by a cyclical deposition process.
BACKGROUND OF THE DISCLOSURE
[0004] The interest in two-dimensional (2D) materials has increased
dramatically in recent years due to their potential in improving
performance in next generation electronic devices. For example,
graphene has been the most studied 2D material to date and exhibits
high mobility, transmittance, mechanical strength, and flexibility.
However, the lack of a band gap in pure graphene has limited its
performance in semiconductor device structures, such as
transistors. Such limitations in graphene have stimulated research
in alternative 2D materials as analogues of graphene. Recently,
transition metal chalcogenides, and particularly transition metal
dichalcogenides, have attracted considerable research attention as
an alternative to graphene. Transition metal dichalcogenides may
have stoichiometry of MX.sub.2, which describes a transition metal
(M) sandwiched between two layers of chalcogen atoms (X), with
strong in-plane covalent bonding between the metal-chalcogen and
weak out-of-plane van der Waals bonding between the layers.
[0005] However, there are few scalable, low temperature methods to
produce 2D materials. Currently, mechanical exfoliation of bulk
crystals is the most commonly used method of formation, but
although this method produces good quality crystals, the method is
unable to produce continuous films and is very labor intensive,
making such a method not viable for industrial production. Chemical
vapor deposition (CVD) has been used to deposit 2D materials, but
current CVD processes for some metal chalcogenides, such as, for
example, hafnium disulfide (HfS.sub.2), operate at temperatures
between 900.degree. C. and 1000.degree. C. and are unable to
produce continuous, large area 2D materials.
[0006] Accordingly, methods are desirable that are capable of
producing 2D materials, at a reduced deposition temperature, and
with atomic level film thickness control.
SUMMARY OF THE DISCLOSURE
[0007] This summary is provided to introduce a selection of
concepts in a simplified form. These concepts are described in
further detail in the detailed description of example embodiments
of the disclosure below. This summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter.
[0008] In some embodiments, methods for depositing a transition
metal chalcogenide film on a substrate by a cyclical deposition
process are provided. The methods may comprise: contacting the
substrate with at least one transition metal containing vapor phase
reactant comprising at least one of a hafnium precursor, or a
zirconium precursor; and contacting the substrate with at least one
chalcogen containing vapor phase reactant, wherein the temperature
of the substrate during the contacting steps is below about
450.degree. C.
[0009] The embodiments of the disclosure also provide semiconductor
device structures comprising a transition metal chalcogenide film
deposited by the methods described herein.
[0010] For the purpose of summarizing the invention and the
advantages achieved over the prior art, certain objects and
advantages of the invention have been described herein above. Of
course, it is to be understood that not necessarily all such
objects or advantages may be achieved in accordance with any
particular embodiment of the invention. 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 or suggested herein
without necessarily achieving other objects or advantages as may be
taught or suggested herein.
[0011] All of these embodiments are intended to be within the scope
of the invention herein disclosed. These and other embodiments will
become readily apparent to those skilled in the art from the
following detailed description of certain embodiments having
reference to the attached figures, the invention not being limited
to any particular embodiment(s) disclosed.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0012] While the specification concludes with claims particularly
pointing out and distinctly claiming what are regarded as
embodiments of the invention, the advantages of embodiments of the
disclosure may be more readily ascertained from the description of
certain examples of the embodiments of the disclosure when read in
conjunction with the accompanying drawings, in which:
[0013] FIG. 1 is a process flow diagram illustrating an exemplary
cyclical deposition method according to the embodiments of the
disclosure;
[0014] FIG. 2 illustrates the growth rate, crystallinity, and
composition of exemplary hafnium chalcogenide films deposited at
various deposition temperatures according to the embodiments of the
disclosure;
[0015] FIG. 3 illustrates the growth rate, crystallinity, and
composition of exemplary zirconium chalcogenide films deposited at
various deposition temperatures according to the embodiments of the
disclosure;
[0016] FIG. 4 illustrates grazing incidence x-ray diffraction
(GIXRD) data for exemplary hafnium chalcogenide films deposited at
various deposition temperatures according to the embodiments of the
disclosure;
[0017] FIG. 5 illustrates grazing incidence x-ray diffraction
(GIXRD) data for exemplary zirconium chalcogenide films deposited
at various deposition temperatures according to the embodiments of
the disclosure;
[0018] FIG. 6 illustrates the ambient stability over time of both a
bare zirconium chalcogenide film and a zirconium chalcogenide film
capped with a metal silicate capping layer according to the
embodiments of the disclosure;
[0019] FIG. 7A illustrates grazing incidence x-ray diffraction
(GIXRD) data for exemplary zirconium chalcogenide films deposited
utilizing a different number of deposition cycles without a capping
layer deposited over the chalcogenide film according to the
embodiments of the disclosure;
[0020] FIG. 7B illustrates grazing incidence x-ray diffraction
(GIXRD) data for exemplary zirconium chalcogenide films deposited
utilizing a different number of deposition cycles with a capping
layer deposited over the chalcogenide film according to the
embodiments of the disclosure;
[0021] FIG. 8 illustrates an exemplary semiconductor device
structure including a transition metal chalcogenide film deposited
according to the embodiments of the disclosure; and
[0022] FIG. 9 illustrates an exemplary reaction system which may be
utilized to deposit a transition metal chalcogenide film according
to the embodiments of the disclosure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0023] Although certain embodiments and examples are disclosed
below, it will be understood by those in the art that the invention
extends beyond the specifically disclosed embodiments and/or uses
of the invention and obvious modifications and equivalents thereof.
Thus, it is intended that the scope of the invention disclosed
should not be limited by the particular disclosed embodiments
described below.
[0024] The illustrations presented herein are not meant to be
actual views of any particular material, structure, or device, but
are merely idealized representations that are used to describe
embodiments of the disclosure.
[0025] As used herein, the term "substrate" may refer to any
underlying material or materials that may be used, or upon which, a
device, a circuit or a film may be formed.
[0026] As used herein, the term "cyclic deposition" may refer to
the sequential introduction of precursors (reactants) into a
reaction chamber to deposit a film over a substrate and includes
deposition techniques such as atomic layer deposition and cyclical
chemical vapor deposition.
[0027] As used herein, the term "atomic layer deposition" (ALD) may
refer to a vapor deposition process in which deposition cycles,
preferably a plurality of consecutive deposition cycles, are
conducted in a process chamber. Typically, during each cycle the
precursor is chemisorbed to a deposition surface (e.g., a substrate
surface or a previously deposited underlying surface such as
material from a previous ALD cycle), forming a monolayer or
sub-monolayer that does not readily react with additional precursor
(i.e., a self-limiting reaction). Thereafter, if necessary, a
reactant (e.g., another precursor or reaction gas) may subsequently
be introduced into the process chamber for use in converting the
chemisorbed precursor to the desired material on the deposition
surface. Typically, this reactant is capable of further reaction
with the precursor. Further, purging steps may also be utilized
during each cycle to remove excess precursor from the process
chamber and/or remove excess reactant and/or reaction byproducts
from the process chamber after conversion of the chemisorbed
precursor. Further, the term "atomic layer deposition," as used
herein, is also meant to include processes designated by related
terms, such as chemical vapor atomic layer deposition, atomic layer
epitaxy (ALE), molecular beam epitaxy (MBE), gas source MBE, or
organometallic MBE, and chemical beam epitaxy when performed with
alternating pulses of precursor composition(s), reactive gas, and
purge (e.g., inert carrier) gas.
[0028] As used herein, the term "cyclical chemical vapor
deposition" may refer to any process wherein a substrate is
sequentially exposed to two or more volatile precursors, which
react and/or decompose on a substrate to produce a desired
deposition.
[0029] As used herein, the term "chalcogen containing vapor phase
reactant" may refer to a reactant (precursor) containing a
chalcogen, wherein a chalcogen is an element from Group VI of the
periodic table including sulfur, selenium, and tellurium.
[0030] As used herein, the term "film" and "thin film" may refer to
any continuous or non-continuous structures and material deposited
by the methods disclosed herein. For example, "film" and "thin
film" could include 2D materials, nanolaminates, nanorods,
nanotubes, or nanoparticles or even partial or full molecular
layers or partial or full atomic layers or clusters of atoms and/or
molecules. "Film" and "thin film" may comprise material or a layer
with pinholes, but still be at least partially continuous.
[0031] As used herein, the term "2D material" or "two-dimensional
material" may refer to a nanometer scale crystalline material one,
two or three atoms in thickness. In addition, "2D materials" or
"two-dimensional material" may also refer to an ordered nanometer
scale crystalline structure composed of multiple monolayers of
crystalline materials of approximately three atoms in thickness per
monolayer.
[0032] As used herein, the term "halide precursor" may refer to a
transition metal halide precursor comprising a halide component
including at least one of chlorine, iodine, or bromine.
[0033] As used herein, the term "metalorganic precursor" may refer
to a transition metal metalorganic precursor wherein "metalorganic"
or "organometallic" are used interchangeably and may refer to
organic compounds containing a metal species. Organometallic
compounds may be considered to be subclass of metalorganic
compounds having direct metal-carbon bonds.
[0034] A number of example materials are given throughout the
embodiments of the current disclosure; it should be noted that the
chemical formulas given for each of the example materials should
not be construed as limiting and that the non-limiting example
materials given should not be limited by a given example
stoichiometry.
[0035] The embodiments of the disclosure may include methods for
depositing a transition metal chalcogenide on a substrate by a
cyclical deposition process and particularly methods for depositing
transition metal chalcogenide films comprising either a hafnium
component or a zirconium component by atomic layer deposition
processes. As non-limiting examples, hafnium disulfide (HfS.sub.2)
and zirconium disulfide (ZrS.sub.2) are emerging materials, which
have a 2D crystal structure, similar to the well-known transition
metal dichalcogenides (TMDCs), such as, for example, molybdenum
disulfide (MoS.sub.2). In comparison to the most studied 2D
material, graphene, hafnium disulfide and zirconium disulfide may
have a sizable band gap, which makes such exemplary transition
metal chalcogenide films more suitable in semiconductor device
structures, such as, for example, field effect transistors
(FETs).
[0036] Current methods for forming transition metal chalcogenide
films are not suitable for forming high quality, conformal, low
temperature thin films. Transition metal chalcogenide crystals may
be formed by mechanical exfoliation of a bulk transition metal
chalcogenide crystal, but such methods are not suitable for forming
transition metal chalcogenide films to a thickness accuracy on the
atomic scale on suitable substrates. In addition, chemical vapor
deposition of some transition metal chalcogenide films has been
demonstrated but such processes operate at high deposition
temperatures (e.g., greater than 900.degree. C. for HfS.sub.2) and
are unsuitable to produce nanoscale, conformal, thin films.
[0037] Cyclical deposition methods, such as cyclical chemical vapor
deposition and atomic layer deposition techniques, are inherently
scalable and offer atomically accurate film thickness control,
which is crucial in the deposition of high quality 2D materials. In
addition, cyclic deposition methods with surface control in
reactions, such as atomic layer deposition, are characteristically
conformal, thereby providing the ability to uniformly coat three
dimensional structures.
[0038] In addition, transition metal chalcogenide films may be
susceptible to oxidation either during the deposition process or
when exposed to ambient conditions. Therefore cyclical deposition
methods may be desirable, which do not incorporate transition metal
oxide phases into the chalcogenide film during deposition. In
addition, methods are highly desirable to prevent the oxidation of
the transition metal chalcogenide films when exposed to ambient
conditions.
[0039] Accordingly, methods are desired which are capable of
depositing transition metal chalcogenide films at reduced
temperatures, conformally, and with atomic thickness accuracy. In
addition, semiconductor device structures comprising a transition
metal chalcogenide film are desirable.
[0040] A non-limiting example embodiment of a cyclical deposition
process may include ALD, wherein ALD is based on typically
self-limiting reactions, whereby sequential and alternating pulses
of reactants are used to deposit about one atomic (or molecular)
monolayer of material per deposition cycle. The deposition
conditions and precursors are typically selected to provide
self-saturating reactions, such that an adsorbed layer of one
reactant leaves a surface termination that is non-reactive with the
vapor phase reactants of the same reactant. The substrate is
subsequently contacted with a different reactant that reacts with
the previous termination to enable continued deposition. Thus, each
cycle of alternating pulsed reactants typically leaves no more than
about one monolayer of the desired material. However, as mentioned
above, the skilled artisan will recognize that in one or more ALD
cycles more than one monolayer of material may be deposited, for
example, if some gas phase reactions occur despite the alternating
nature of the process.
[0041] In an ALD-type process for depositing a transition metal
chalcogenide film, one deposition cycle may comprise exposing the
substrate to a first vapor phase reactant, removing any unreacted
first reactant and reaction byproducts from the reaction space, and
exposing the substrate to a second vapor phase reactant, followed
by a second removal step. The first reactant may comprise a
transition metal containing precursor, such as a hafnium precursor
or a zirconium precursor, and the second reactant may comprise a
chalcogen containing precursor.
[0042] Precursors may be separated by inert gases, such as argon
(Ar), or nitrogen (N.sub.2), to prevent gas phase reactions between
reactants and enable self-saturating surface reactions. In some
embodiments, however, the substrate may be moved to separately
contact a first vapor phase reactant and a second vapor phase
reactant. Because the reactions self-saturate, strict temperature
control of the substrates and precise dosage control of the
precursor may not be required. However, the substrate temperature
is preferably such that an incident gas species does not condense
into monolayers nor decompose on the substrate surface. Surplus
chemicals and reaction byproducts, if any, are removed from the
substrate surface, such as by purging the reaction space or by
moving the substrate, before the substrate is contacted with the
next reactive chemical. Undesired gaseous molecules can be
effectively expelled from the reaction space with the help of an
inert purging gas. A vacuum pump may be used to assist in the
purging process.
[0043] Reactors capable of being used to deposit or grow thin films
can be used for the deposition. Such reactors include ALD reactors,
as well as CVD reactors equipped with appropriate equipment and
means for providing the precursors. According to some embodiments,
a showerhead reactor may be used. In some embodiments the reactor
is a spatial ALD reactor, in which the substrates moves or rotates
during processing.
[0044] In some embodiments a batch reactor may be used. In some
embodiments, a vertical batch reactor is utilized in which the boat
rotates during processing. Thus, in some embodiments, the wafers
rotate during processing. In other embodiments, the batch reactor
comprises a mini-batch reactor configured to accommodate 10 or
fewer wafers, 8 or fewer wafers, 6 or fewer wafers, 4 or fewer
wafers, or 2 wafers. In some embodiments in which a batch reactor
is used, wafer-to-wafer non-uniformity is less than 3% (1 sigma),
less than 2%, less than 1% or even less than 0.5%.
[0045] The deposition processes described herein can optionally be
carried out in a reactor or reaction chamber connected to a cluster
tool. In a cluster tool, because each reaction chamber is dedicated
to one type of process, the temperature of the reaction chamber in
each module can be kept constant, which improves the throughput
compared to a reactor in which the substrate is heated up to the
process temperature before each run. Additionally, in a cluster
tool it is possible to reduce the time to pump the reaction space
to the desired process pressure levels between substrates.
[0046] A stand-alone reactor can be equipped with a load-lock. In
that case, it is not necessary to cool down the reaction chamber
between each run. In some embodiments, a deposition process for
depositing a film comprising a transition metal chalcogenide film
may comprise a plurality of deposition cycles, for example ALD
cycles.
[0047] In some embodiments, cyclical deposition processes are used
to deposit transition metal chalcogenide thin films on a substrate
and the cyclical deposition process may be an ALD type process. In
some embodiments, the cyclical deposition may be a hybrid ALD/CVD
or cyclical CVD process. For example, in some embodiments the
deposition rate of the ALD process may be low compared with a CVD
process. One approach to increase the deposition rate may be that
of operating at a higher substrate temperature than that typically
employed in an ALD process, resulting in a chemical vapor
deposition process, but still taking advantage of the sequential
introduction of precursors, such a process may be referred to as
cyclical CVD. In some embodiments, a cyclical CVD process may
comprise the introduction of two or more precursors into the
reaction chamber wherein there may be a time period of overlap
between the two or more precursors in the reaction chamber
resulting in both an ALD component of the deposition and a CVD
component of the deposition. For example, a cyclical CVD process
may comprise the continuous flow of a first precursor and the
periodic pulsing of a second precursor into the reaction
chamber.
[0048] According to some embodiments of the disclosure, ALD
processes are used to deposit transition metal chalcogenide films
on a substrate, such as an integrated circuit workpiece. In some
embodiments, each ALD cycle may comprise two distinct deposition
steps or phases. In a first phase of the deposition cycle ("the
metal phase"), the substrate surface on which deposition is desired
is contacted with a first vapor phase reactant comprising at least
one of a hafnium precursor, or zirconium precursor, which
chemisorbs onto the substrate surface, forming no more than about
one monolayer of reactant species on the surface of the substrate.
In a second phase of the deposition cycle ("the chalcogen phase"),
the substrate surface on which deposition is desired is contacted
with a second vapor phase reactant comprising at least one
chalcogen containing vapor phase reactant which reacts with the
previously chemisorbed species to form a transition metal
chalcogenide film.
[0049] In some embodiments of the disclosure, the transition metal
containing vapor phase reactant comprises at least one of a hafnium
precursor, or a zirconium precursor. In some embodiments, the
hafnium precursor, or the zirconium precursor, comprises at least
one of a halide precursor, or a metalorganic precursor. In some
embodiments, the metalorganic precursor may comprise at least one
of an alkylamide precursor, or a cyclopentadienyl-ligand containing
precursor. In some embodiments, the hafnium precursor, or zirconium
precursor, may comprise a heteroleptic precursor.
[0050] In some embodiments, the hafnium precursor may comprise at
least one of a hafnium halide precursor, a hafnium metalorganic
precursor, or an organometallic hafnium precursor.
[0051] In some embodiments, the hafnium halide precursor may
comprise at least one halide ligand while the rest of the ligands
are different, such as metalorganic or organometallic ligands as
described later herein. In some embodiments, the hafnium halide
precursor may comprise one, two, three or four halide ligands such
as chloride ligands.
[0052] In some embodiments, the hafnium halide precursor may
comprise at least one of a hafnium chloride, a hafnium iodide, or a
hafnium bromide. In some embodiments, the hafnium chloride may
comprise hafnium tetrachloride (HfCl.sub.4). In some embodiments,
the hafnium iodide may comprise hafnium tetraiodide (HfI.sub.4). In
some embodiments, the hafnium bromide may comprise hafnium
tetrabromide (HfBr.sub.4).
[0053] In some embodiments, the hafnium metalorganic precursor may
comprise at least one of a hafnium alkylamide precursor, a hafnium
cyclopentadienyl-ligand containing precursor, or other metalorganic
hafnium precursors.
[0054] In some embodiments, the hafnium alkylamide precursor may be
selected from the group comprising
tetrakis(ethylmethylamino)hafnium (Hf(NEtMe).sub.4),
tetrakis(dimethylamido)hafnium (Hf(NMe.sub.2).sub.4), or
tetrakis(diethylamido)hafnium (Hf(NEt.sub.2).sub.4).
[0055] In some embodiments of the disclosure, the hafnium
cyclopentadienyl-ligand containing precursor may be selected from
the group comprising (tris(alkylamido)cyclopentadienyl hafnium,
such as (tris(dimethylamido)cyclopentadienylhafnium
HfCp(NMe.sub.2).sub.3, or bis(methylcyclopentadienyl)methoxymethyl
hafnium (MeCp).sub.2Hf(CH).sub.3(OCH.sub.3) or derivatives of
those, such as ones in which there is one or more hydrocarbons,
such as alkyls, attached to the cyclopentadienyl-ligand of those
precursors, or other alkyl groups in alkylamido-ligand.
[0056] In some embodiments, the hafnium precursor may have the
formula;
HfL.sub.1L.sub.2L.sub.3L.sub.4
wherein each of the L ligands through L1-L4 can be independently
selected to be [0057] a) Halide, such as chloride, bromide or
iodide [0058] b) Alkylamido, such as dimethylamido (--NMe.sub.2),
diethylamido (--NEt.sub.2), ethylmethylamido (--NEtMe) [0059] c)
Amidinate, such as N,N'-dimethylformamidinate [0060] d)
Guanidinate, such as N,N'-diisopropyl-2-ethylmethylamidoguanidinate
[0061] e) Cyclopentadienyl or derivatives of those, such as
cyclopentadienyl or methylcyclopentadienyl or other
alkylsubstituted cyclopentadienyl ligands [0062] f)
Cycloheptadienyl or -trienyl-based, such as a cycloheptatrienyl or
cycloheptadienyl [0063] g) Alkyl, such as C1-C5 alkyl, for example
methyl, mostly in case of heteroleptic precursors [0064] h)
Alkoxide, such as methoxide (--OMe), ethoxide (--OEt), isopropoxide
(--O.sup.iPr), n-butoxide (--OBu) or tert-butoxide (--O.sup.tBu)
[0065] i) Betadiketonate, such as
(2,2,6,6-tetramethyl-3,5-heptanedionato) (thd) [0066] j)
Donor-functionalized alkoxide, such as dimethylethanolamine
[0067] In some embodiments of the disclosure, the hafnium precursor
comprises one or more bidentate ligands which are bonded to Hf
through nitrogen and/or oxygen atoms. In some embodiments, the
hafnium precursor comprises one or more ligands which are bonded to
Hf through nitrogen, oxygen, and/or carbon.
[0068] In some embodiments, the zirconium precursor may comprise at
least one of a zirconium halide precursor, a zirconium metalorganic
precursor, or an organometallic zirconium precursor.
[0069] In some embodiments, the zirconium halide precursor may
comprise at least one of a zirconium chloride, a zirconium iodide,
or a zirconium bromide. In some embodiments, the zirconium chloride
may comprise zirconium tetrachloride (ZrCl.sub.4). In some
embodiments, the zirconium halide precursor may comprise at least
one halide ligand while the rest of the ligands are different, such
as metalorganic or organometallic ligands as described later
herein. In some embodiments, the zirconium halide precursor may
comprise one, two, three or four halide ligands such as chloride
ligands. In some embodiments, the zirconium iodide may comprise
zirconium tetraiodide (ZrI.sub.4). In some embodiments, the
zirconium bromide may comprise zirconium tetrabromide
(ZrBr.sub.4).
[0070] In some embodiments, the zirconium metalorganic precursor
may comprise at least one of a zirconium alkylamide precursor, a
zirconium cyclopentadienyl-ligand containing precursor, or other
metalorganic zirconium precursors.
[0071] In some embodiments, the zirconium alkylamide precursor may
be selected from the group comprising
tetrakis(ethylmethylamido)zirconium (Zr(NEtMe).sub.4),
tetrakis(dimethylamido)zirconium (Zr(NMe.sub.2).sub.4), or
tetrakis(diethylamido)zirconium (Zr(NEt.sub.2).sub.4).
[0072] In some embodiments of the disclosure, the zirconium
cyclopentadienyl-ligand containing precursor may be selected from
the group comprising (tris(alkylamido)cyclopentadienylzirconium,
such as (tris(dimethylamido)cyclopentadienyl zirconium
ZrCp(NMe.sub.2).sub.3, or bis(methylcyclopentadienyl)methoxymethyl
zirconium (MeCp).sub.2Zr(CH).sub.3(OCH.sub.3), or derivatives of
those, such as ones in which there is one or more hydrocarbons,
such as alkyls, attached to the cyclopentadienyl-ligand of those
precursors, or other alkyl groups in alkylamido-ligand.
[0073] In some embodiments, the zirconium precursor may have the
formula;
ZrL.sub.1L.sub.2L.sub.3L.sub.4
[0074] wherein each of the L ligands through L1-L4 can be
independently selected to be [0075] k) Halide, such as chloride,
bromide or iodide [0076] l) Alkylamido, such as dimethylamido
(--NMe.sub.2), diethylamido (--NEt.sub.2), ethylmethylamido
(--NEtMe) [0077] m) Amidinate, such as N,N'-dimethylformamidinate
[0078] n) Guanidinate, such as
N,N'-diisopropyl-2-ethylmethylamidoguanidinate [0079] o)
Cyclopentadienyl or derivatives of those, such as cyclopentadienyl
or methylcyclopentadienyl or other alkylsubstituted
cyclopentadienyl ligands [0080] p) Cycloheptadienyl or
-trienyl-based, such as a cycloheptatrienyl or cycloheptadienyl
[0081] q) Alkyl, such as C1-C5 alkyl, for example methyl, mostly in
case of heteroleptic precursors [0082] r) Alkoxide, such as
methoxide (--OMe), ethoxide (--OEt), isopropoxide (--O.sup.iPr),
n-butoxide (--OBu) or tert-butoxide (--O.sup.tBu) [0083] s)
Betadiketonate, such as (2,2,6,6-tetramethyl-3,5-heptanedionato)
(thd) [0084] t) Donor-functionalized alkoxide, such as
dimethylethanolamine
[0085] In some embodiments of the disclosure, the zirconium
precursor comprises one or more bidentate ligands which are bonded
to Zr through nitrogen and/or oxygen atoms. In some embodiments,
the zirconium precursor comprises one or more ligands which are
bonded to Zr through nitrogen, oxygen, and/or carbon.
[0086] In some embodiments, exposing the substrate to the
transition metal containing vapor phase reactant may comprise,
pulsing the transition metal precursor over the substrate for a
time period between about 0.01 second and about 60 seconds, between
about 0.05 seconds and about 10 seconds, or between about 0.1
seconds and about 5.0 seconds. In addition, during the pulsing of
the transition metal precursor over the substrate the flow rate of
the transition metal precursor may be less than 2000 sccm, or less
than 500 sccm, or even less than 100 sccm. In addition, during the
pulsing of the transition metal precursor over the substrate the
flow rate of the transition metal precursor may be from about 1 to
about 2000 sccm, from about 5 to about 1000 sccm, or from about 10
to about 500 sccm.
[0087] In some embodiments, the purity of the transition metal
containing vapor phase reactants may influence the composition of
the deposited film and therefore high purity sources of the
transition metal containing vapor phase reactants may be utilized.
For example, in some embodiments, the transition metal vapor phase
reactant may comprise a hafnium precursor or a zirconium precursor
with a purity of greater than or equal to 99.99%.
[0088] In some embodiments, the transition metal containing vapor
phase reactant may be contained in a vessel and one or more heaters
may be associated with the vessel to control the temperature of the
metal precursor and subsequently the partial pressure of the metal
precursor. In some embodiments of the disclosure, the metal
precursor within the vessel may be heated to a temperature between
approximately 20.degree. C. and approximately 300.degree. C. For
example, in some embodiments, the metal precursor may be heated to
a temperature from about 30.degree. C. to about 250.degree. C., or
from about 40.degree. C. to about 225.degree. C., or from about
50.degree. C. to about 150.degree. C., depending on the precursor
choice.
[0089] In some embodiments, a vessel containing the metal precursor
may be connected to a source of one or more carrier gases. The
carrier gas may be introduced into the vessel and drawn over the
surface of, or bubbled through, the metal precursor contained
within the vessel. The resulting evaporation of the metal precursor
causes a vapor of the metal precursor to become entrained in the
carrier gas to thereby produce the transition metal vapor phase
reactant which can be dispensed to a reaction chamber.
[0090] In some embodiments, in addition to utilizing high purity
transition metal precursors, the carrier gas may be further
purified to remove unwanted impurities. Therefore, some embodiments
of the disclosure may further comprise, flowing a carrier gas
through a vessel containing a source of the transition metal
containing vapor phase reactant to transport the transition metal
containing vapor phase reactant to the reaction chamber. Further
embodiments of the disclosure may comprise, flowing the carrier
through a gas purifier prior to entering the source of the
transition metal containing vapor phase reactant to reduce the
concentration of at least one of water, or oxygen, within the
carrier gas.
[0091] In some embodiments, the water concentration within the
carrier gas may be reduced to less than 10 parts per million, or
less than 1 part per million, or less than 100 parts per billion,
or less than 10 parts per billion, or less than 1 part per billion,
or even less than 100 parts per trillion.
[0092] In some embodiments, the oxygen concentration within the
carrier gas may be reduced to 10 parts per million, or less than 1
part per million, or less than 100 parts per billion, or less than
10 parts per billion, or less than 1 part per billion, or even less
than 100 parts per trillion.
[0093] In some embodiments, the hydrogen (H.sub.2) concentration
within the carrier gas may be reduced to less than 100 parts per
trillion. In some embodiments, the carbon dioxide (CO.sub.2)
concentration within the carrier gas may be reduced to less than
100 parts per trillion. In some embodiments, the carbon monoxide
(CO) concentration within the carrier gas may be reduced to less
than 100 parts per trillion.
[0094] In some embodiments, the carrier gas may comprise nitrogen
gas (N.sub.2) and the carrier gas purifier may comprise a nitrogen
gas purifier.
[0095] In some embodiments of the disclosure, the transition metal
containing vapor phase reactant may be fed through a gas purifier
prior to entering the reaction chamber in order to reduce the
concentration of at least one of water, or oxygen, within the
transition metal containing vapor phase reactant.
[0096] In some embodiments, the water concentration within the
transition metal containing vapor phase reactant may be reduced to
less than 1 atomic-%, or less than 1000 parts per million, or less
than 100 parts per million, or less than 10 parts per million, or
less than 1 part per million, or less than 100 parts per billion,
or even less than 100 parts per trillion.
[0097] In some embodiments, the oxygen concentration within the
transition metal containing vapor phase reactant may be reduced to
less than 1 atomic-%, or less than 1000 parts per million, or less
than 100 parts per million, or less than 10 parts per million, or
less than 1 part per million, or less than 100 parts per billion,
or even less than 100 parts per trillion.
[0098] Not to be bound be any theory or mechanism, but it is
believed the reduction of at least one of the water concentrations,
or the oxygen concentration, within the carrier gas and/or the
transition metal containing vapor phase reactant may allow for the
deposition of a transition metal chalcogenide film with the desired
composition whilst preventing the deposition of transition metal
oxide phases at an appropriate deposition temperature.
[0099] Excess transition metal vapor phase reactant, such as, for
example, a hafnium precursor, or a zirconium precursor, and
reaction byproducts (if any) may be removed from the substrate
surface, e.g., by pumping with an inert gas. For example, in some
embodiments of the disclosure the methods may include a purge cycle
wherein the substrate surface is purged for a time period of less
than approximately 5.0 seconds, or less than approximately 2.0
seconds, or even less than approximately 1.0 second. In some
embodiments, the substrate surface is purged for a time period
between about 0.01 seconds and about 60 seconds, or between about
0.05 seconds and about 10 seconds, or between about 0.1 seconds and
about 5 seconds. Excess transition metal vapor phase reactant and
any reaction byproducts may be removed with the aid of a vacuum
generated by a pumping system.
[0100] In a second phase of the deposition cycle ("the chalcogen
phase") the substrate is contacted with a second vapor phase
reactant comprising at least one chalcogen containing vapor phase
reactant. In some embodiments of the disclosure, the at least one
chalcogenide containing vapor reactant may comprise hydrogen
sulfide (H.sub.2S), hydrogen selenide (H.sub.2Se), dimethyl sulfide
((CH.sub.3).sub.2S), or dimethyl telluride
((CH.sub.3).sub.2Te).
[0101] It will be understood by one skilled in the art that any
number of chalcogen precursors may be used in the cyclical
deposition processes disclosed herein. In some embodiments, a
chalcogen precursor is selected from the following list: H.sub.2S,
H.sub.2Se, H.sub.2Te, (CH.sub.3).sub.2S, (NH.sub.4).sub.2S,
dimethylsulfoxide ((CH.sub.3).sub.2SO), (CH.sub.3).sub.2Se,
(CH.sub.3).sub.2Te, elemental or atomic S, Se, Te, other precursors
containing chalcogen-hydrogen bonds, such as H.sub.2S.sub.2,
H.sub.2Se.sub.2, H.sub.2Te.sub.2, or chalcogenols with the formula
R--Y--H, wherein R can be a substituted or unsubstituted
hydrocarbon, preferably a C.sub.1-C.sub.8 alkyl or substituted
alkyl, such as an alkylsilyl group, more preferably a linear or
branched C.sub.1-C.sub.5 alkyl group, and Y can be S, Se, or Te. In
some embodiments a chalcogen precursor is a thiol with the formula
R--S--H, wherein R can be substituted or unsubstituted hydrocarbon,
preferably C.sub.1-C.sub.8 alkyl group, more linear or branched
preferably C.sub.1-C.sub.5 alkyl group. In some embodiments a
chalcogen precursor has the formula (R.sub.3Si).sub.2Y, wherein
R.sub.3Si is an alkylsilyl group and Y can be S, Se or Te. In some
embodiments, a chalcogen precursor comprises S or Se. In some
embodiments, a chalcogen precursor comprises S. In some
embodiments, a chalcogen precursor does not comprise S. In some
embodiments the chalcogen precursor may comprise an elemental
chalcogen, such as elemental sulfur. In some embodiments, a
chalcogen precursor does comprise Te. In some embodiments, a
chalcogen precursor does not comprise Te. In some embodiments, a
chalcogen precursor does comprise Se. In some embodiments, a
chalcogen precursor does not comprise Se. In some embodiments, a
chalcogen precursor is selected from precursors comprising S, Se or
Te. In some embodiments, a chalcogen precursor comprises H.sub.2Sn,
wherein n is from 4 to 10.
[0102] In some embodiments, suitable chalcogen precursors may
include any number of chalcogen-containing compounds. In some
embodiments, a chalcogen precursor may comprise at least one
chalcogen-hydrogen bond. In some embodiments the chalcogen
precursor may comprise a chalcogen plasma, chalcogen atoms or
chalcogen radicals. In some embodiments where an energized
chalcogen precursor is desired, a plasma may be generated in the
reaction chamber or upstream of the reaction chamber. In some
embodiments the chalcogen precursor does not comprise an energized
chalcogen precursor, such as plasma, atoms or radicals. In some
embodiments the chalcogen precursor may comprise a chalcogen
plasma, chalcogen atoms or chalcogen radicals formed from a
chalcogen precursor comprising a chalcogen-hydrogen bond, such as
H.sub.2S. In some embodiments a chalcogen precursor may comprise a
chalcogen plasma, chalcogen atoms or chalcogen radicals such as a
plasma comprising sulfur, selenium or tellurium, preferably a
plasma comprising sulfur. In some embodiments, the plasma, atoms,
or radicals comprise tellurium. In some embodiments, the plasma,
atoms or radicals comprise selenium. In some embodiments the
chalcogen precursor does not comprise a tellurium precursor.
[0103] In some embodiments, the purity of the chalcogen containing
vapor phase reactants may influence the composition of the
deposited film and therefore high purity sources of the chalcogen
containing vapor phase reactant may be utilized. In some
embodiments, the chalcogen containing vapor phase reactant may have
a purity of greater than or equal to 99.5%. As a non-limiting
example, the chalcogen containing vapor phase reactant may comprise
hydrogen sulfide (H.sub.2S) with a purity of greater than or equal
to 99.5%.
[0104] In some embodiments, in addition to utilizing high purity
chalcogen containing vapor phase reactants, the chalcogen precursor
gas may be further purified to remove unwanted impurities.
Therefore, some embodiments of the disclosure may further comprise,
flowing a chalcogen containing vapor phase reactant through a gas
purifier prior to entering the reaction chamber to reduce the
concentration of at least one of water, or oxygen, within the
chalcogen containing vapor phase reactant.
[0105] In some embodiments, the water, or oxygen concentration
within the chalcogen containing vapor phase reactant may be reduced
to less than 5 atomic-%, or less than 1 atomic-%, or less than 1000
parts per million, or less than 100 parts per million, or less than
10 parts per million, or less than 1 part per million, or less than
100 parts per billion, or less than 10 parts per billion, or even
less than 1 part per billion.
[0106] Not to be bound be any theory or mechanism, but it is
believed the reduction of at least one of the water concentration,
or the oxygen concentration within the chalcogen containing vapor
phase reactant may allow for the deposition of transition metal
chalcogenide film with the desired composition whilst preventing
the deposition of transition metal oxide phases at an appropriate
deposition temperature.
[0107] In some embodiments, exposing the substrate to the chalcogen
containing vapor phase reactant may comprise, pulsing the chalcogen
precursor (e.g., hydrogen sulfide) over the substrate for a time
period of between 0.1 seconds and 2.0 seconds, or from about 0.01
seconds to about 10 seconds, or less than about 20 seconds, or less
than about 10 seconds, or less than about 5 seconds. During the
pulsing of the chalcogen precursor over the substrate the flow rate
of the chalcogen precursor may be less than 2000 sccm, or less than
500 sccm, or even less than 100 sccm. In addition, during the
pulsing of the chalcogen precursor over the substrate the flow rate
of the chalcogen precursor may be from about 1 sccm to about 2000
sccm, or from about 5 sccm to about 1000 sccm, or from about 10
sccm to about 500 sccm.
[0108] The second vapor phase reactant comprising a chalcogen
containing precursor may react with the metal-containing molecules
left on the substrate. In some embodiments, the second phase
chalcogen precursor may comprise hydrogen sulfide and the reaction
may deposit a transition metal disulfide on the surface of the
substrate.
[0109] Excess second source chemical and reaction byproducts, if
any, may be removed from the substrate surface, for example, by a
purging gas pulse and/or vacuum generated by a pumping system.
Purging gas is preferably any inert gas, such as, without
limitation, argon (Ar), nitrogen (N.sub.2), or helium (He). A phase
is generally considered to immediately follow another phase if a
purge (i.e., purging gas pulse) or other reactant removal step
intervenes.
[0110] The deposition cycle in which the substrate is alternatively
contacted with the first vapor phase reactant (i.e., the transition
metal containing precursor) and the second vapor phase reactant
(i.e., the chalcogen containing precursor) may be repeated one or
more times until a desired thickness of a transition metal
chalcogenide is deposited. It should be appreciated that in some
embodiments of the disclosure, the order of the contacting of the
substrate with the first vapor phase reactant and the second vapor
phase reactant may be such that the substrate is first contacted
with the second vapor phase reactant followed by the first vapor
phase reactant. In addition, in some embodiments, the cyclical
deposition process may comprise contacting the substrate with the
first vapor phase reactant (i.e. the transition metal containing
precursor) one or more times prior to contacting the substrate with
the second vapor phase reactant (i.e., the chalcogen containing
precursor) one or more times and similarly may alternatively
comprise contacting the substrate with the second vapor phase
reactant one or more times prior to contacting the substrate with
the first vapor phase reactant one or more times.
[0111] In addition, some embodiments of the disclosure may comprise
non-plasma reactants, e.g., the first and second vapor phase
reactants are substantially free of ionized reactive species. In
some embodiments, the first and second vapor phase reactants are
substantially free of ionized reactive species, excited species or
radical species. For example, both the first vapor phase reactant
and the second vapor phase reactant may comprise non-plasma
reactants to prevent ionization damage to the underlying substrate
and the associated defects thereby created.
[0112] The cyclical deposition processes described herein,
utilizing a transition metal containing precursor and a chalcogen
containing precursor to form a transition metal chalcogenide film,
may be performed in an ALD or CVD deposition system with a heated
substrate, i.e., the temperature of the substrate during the
process of contacting the substrate with the chemical precursors
may be controlled.
[0113] For example, in some embodiments, methods may comprise
heating the substrate to temperature of between approximately
200.degree. C. and approximately 500.degree. C., or even heating
the substrate to a temperature of between approximately 350.degree.
C. and approximately 450.degree. C. Of course, the appropriate
temperature window for any given cyclical deposition process, such
as for an ALD reaction, will depend upon the surface termination
and reactant species involved. Here, the temperature varies
depending on the precursors being used and is generally at or below
about 700.degree. C. In some embodiments, the deposition
temperature is generally at or above about 100.degree. C. for vapor
deposition processes. In some embodiments the deposition
temperature is between about 100.degree. C. and about 600.degree.
C., and in some embodiments the deposition temperature is between
about 300.degree. C. and about 500.degree. C. In some embodiments
the deposition temperature is below about 500.degree. C., or below
about 475.degree. C., or below about 450.degree. C., or below about
425.degree. C. or below about 400.degree. C., or below about
375.degree. C., or below about 350.degree. C., or below about
325.degree. C. or below about 300.degree. C. In some instances the
deposition temperature can be below about 250.degree. C., or below
about 200.degree. C., or below about 150.degree. C., or below about
100.degree. C., for example, if additional reactants or reducing
agents are used in the process. In some instances the deposition
temperature can be above about 20.degree. C., above about
50.degree. C. and above about 75.degree. C. In some embodiments of
the disclosure, the deposition temperature, i.e., the temperature
of the substrate during deposition is approximately 400.degree.
C.
[0114] In some embodiments the growth rate of the transition metal
chalcogenide film is from about 0.005 .ANG./cycle to about 5
.ANG./cycle, or from about 0.01 .ANG./cycle to about 2.0
.ANG./cycle. In some embodiments the growth rate of the film is
more than about 0.05 .ANG./cycle, or more than about 0.1
.ANG./cycle, or more than about 0.15 .ANG./cycle, or more than
about 0.20 .ANG./cycle, or more than about 0.25 .ANG./cycle, or
even more than about 0.3 .ANG./cycle. In some embodiments the
growth rate of the film is less than about 2.0 .ANG./cycle, or less
than about 1.0 .ANG./cycle, or less than about 0.75 .ANG./cycle, or
less than about 0.5 .ANG./cycle, or less than about 0.2
.ANG./cycle. In some embodiments of the disclosure, the growth rate
of the transition metal chalcogenide is approximately 0.10
.ANG./cycle.
[0115] The embodiments of the disclosure may comprise a cyclical
deposition process which may be illustrated in more detail by the
exemplary method 100 of FIG. 1. The exemplary method 100 may begin
with a process block 110 which comprises, providing a substrate
into a reaction chamber and heating the substrate to the deposition
temperature.
[0116] In some embodiments of the disclosure, the substrate may
comprise a planar substrate or a patterned substrate including high
aspect ratio features, such as, for example, trench structures
and/or fin structures. The substrate may comprise one or more
materials including, but not limited to, silicon (Si), germanium
(Ge), germanium tin (GeSn), silicon germanium (SiGe), silicon
germanium tin (SiGeSn), silicon carbide (SiC), or a group III-V
semiconductor material, such as, for example, gallium arsenide
(GaAs), gallium phosphide (GaP), or gallium nitride (GaN). In some
embodiments, the substrate may comprise one or more dielectric
materials including, but not limited to, oxides, nitrides, or
oxynitrides. For example, the substrate may comprise a silicon
oxide (e.g., SiO.sub.2), a metal oxide (e.g., Al.sub.2O.sub.3), a
silicon nitride (e.g., Si.sub.3N.sub.4), or a silicon oxynitride.
In some embodiments of the disclosure, the substrate may comprise
an engineered substrate wherein a surface semiconductor layer is
disposed over a bulk support with an intervening buried oxide (BOX)
disposed there between.
[0117] Patterned substrates may comprise substrates that may
include semiconductor device structures formed into or onto a
surface of the substrate, for example, a patterned substrate may
comprise partially fabricated semiconductor device structures, such
as, for example, transistors and/or memory elements. In some
embodiments, the substrate may contain monocrystalline surfaces
and/or one or more secondary surfaces that may comprise a
non-monocrystalline surface, such as a polycrystalline surface
and/or an amorphous surface. Monocrystalline surfaces may comprise,
for example, one or more of silicon (Si), silicon germanium (SiGe),
germanium tin (GeSn), germanium (Ge), or a III-V material.
Polycrystalline or amorphous surfaces may include dielectric
materials, such as oxides, oxynitrides, or nitrides, such as, for
example, silicon oxides and silicon nitrides.
[0118] The reaction chamber utilized for the exemplary cyclical
deposition process 100 may be an atomic layer deposition reaction
chamber, or a chemical vapor deposition reaction chamber, or any of
the reaction chambers as previously described herein. In some
embodiments of the disclosure, the reaction chamber may be
subjected to a pre-annealing process prior to loading the substrate
within the reaction chamber or with the substrate pre-loaded into
the reaction chamber. For example, the pre-annealing process may be
utilized to reduce the concentration of at least one of water,
and/or oxygen, within the reaction chamber. Therefore, some
embodiments of the disclosure may further comprise, pre-annealing
the reaction chamber prior to film deposition at temperature of
greater than 400.degree. C., or greater than 500.degree. C., or
greater than 600.degree. C., or even greater than 700.degree. C. In
some embodiments, the pre-annealing of the reaction chamber at high
temperature may be performed for time period of less than 60
minutes, or less than 30 minutes, or less than 15 minutes, or less
than 10 minutes, or even less than 5 minutes.
[0119] The process block 110 (of FIG. 1) may continue by heating
the substrate to a desired deposition temperature, as previously
disclosed herein. As a non-limiting example, the substrate may be
heated to deposition temperature between approximately 300.degree.
C. and approximately 450.degree. C., or to a temperature of
approximately 400.degree. C.
[0120] The exemplary method 100 may continue with cyclical
deposition phase 140 which may commence by means of a process block
120 which comprises, contacting the substrate with a transition
metal containing vapor phase reactant, as previously disclosed
herein. As a non-limiting example, the substrate may be contacted
with hafnium tetrachloride (HfCl.sub.4) or zirconium tetrachloride
(ZrCl.sub.4), for a time period of approximately 1 second. Upon
contacting the substrate with the transition metal containing
precursor, the excess transition metal containing precursor and any
byproducts may be removed from the reaction chamber by a purge/pump
process.
[0121] The cyclical deposition phase 140 of the exemplary method
100 may continue by means of a process block 130 which comprises,
contacting the substrate with a chalcogen containing vapor phase
reactant, as previously disclosed herein. As a non-limiting
example, the substrate may be contacted with hydrogen sulfide
(H.sub.2S) for a time period of approximately 1 second. Upon
contacting the substrate with the chalcogen containing precursor,
the excess chalcogen containing precursor and any byproducts may be
removed from the reaction chamber by purge/pump process.
[0122] The method wherein the substrate is alternately and
sequentially contacted with at least one transition metal
containing vapor phase reactant and contacted with at least one
chalcogen containing vapor phase reactant may constitute one unit
deposition cycle. For example, a unit deposition cycle may
comprise, contacting substrate with the transition metal vapor
phase reactant, purging the reaction chamber, contacting the
substrate with the chalcogen containing vapor phase reactant, and
again purging the reaction chamber.
[0123] In some embodiments of the disclosure, the method of
depositing a transition metal chalcogenide may comprise repeating
the unit deposition cycle one or more times. For example, the
cyclic deposition phase 140 of exemplary method 100 may continue by
means of a decision gate 150 which determines if the cyclical
deposition phase 140 of exemplary method 100 continues or exits.
The decision gate of the process block 150 may be determined based
on the thickness of the transition metal chalcogenide film
deposited. For example, if the thickness of the transition metal
chalcogenide film is insufficient for the desired application, then
the cyclical deposition phase 140 of the exemplary method 100 may
return to the process block 120 and the processes of contacting the
substrate with a transition metal containing vapor phase reactant
and contacting the substrate with a chalcogen containing vapor
phase reactant may be repeated one or more times. Once the
transition metal chalcogenide film has been deposited to a desired
thickness the exemplary method 100 may exit via a process block 160
and the transition metal chalcogenide film may be subjected to
additional processes to form a device structure.
[0124] In some embodiments of the disclosure, the deposition
temperature of the transition metal chalcogenide film may affect
the growth rate of the chalcogenide film, the crystallinity of the
chalcogenide film, and the composition the chalcogenide film. As a
non-limiting example, FIG. 2 illustrates the growth rate,
crystallinity, and composition, of exemplary hafnium disulfide
films deposited at various deposition temperatures utilizing
hafnium tetrachloride (HfCl.sub.4) and hydrogen sulfide (H.sub.2S)
as the precursor chemicals. Examination of FIG. 2 illustrates that
between a deposition temperature of approximately 200.degree. C.,
up to a deposition of approximately 350.degree. C., the deposition
rate of the exemplary hafnium disulfide films decreases and the
crystal structure of the hafnium disulfide films is amorphous,
i.e., there is no long range ordering of the crystal structure
which would normally be associated with a crystalline material.
Between a deposition temperature of approximately 350.degree. C.
and approximately 400.degree. C. there is an increase the growth
rate of the exemplary hafnium disulfide films and the crystal
structure of the hafnium disulfide films becomes crystalline, i.e.,
there is long range ordering of the crystalline structure of the
chalcogenide film. In addition, between a deposition temperature of
approximately 350.degree. C. and approximately 400.degree. C., the
exemplary hafnium disulfide film exhibits a composition of hafnium
disulfide (HfS.sub.2). However, as the deposition temperature is
further increased above a temperature of approximately 400.degree.
C., the growth rate of the exemplary films again decreases and the
composition of the deposited film becomes that of a mixture between
a hafnium sulfide and a hafnium oxide. The deposition of hafnium
oxide phases above a temperature of approximately 400.degree. C.
may result from residual oxygen and/or water remaining in the
reaction chamber utilized in the above non-limiting examples. In
further non-limiting examples, the residual oxygen and/or water
concentration within the reaction chamber may be further reduced
and deposition above a temperature of approximately 400.degree. C.
may result in deposition of a hafnium disulfide (HfS.sub.2) film
without the deposition of hafnium oxide phases.
[0125] Therefore, in some embodiments of the disclosure, the
transition metal chalcogenide film may comprise a hafnium sulfide
and particularly hafnium disulfide (HfS.sub.2). In addition, in
some embodiments, the transition metal chalcogenide film may be
crystalline with a composition comprising hafnium disulfide
(HfS.sub.2) at a deposition temperature between approximately
350.degree. C. and approximately 400.degree. C., and particular at
a deposition temperature of approximately 400.degree. C. In some
embodiments, a crystalline hafnium disulfide (HfS.sub.2) film may
be deposited at a deposition temperature greater than 400.degree.
C.
[0126] As a further non-limiting example, FIG. 3 illustrates the
growth rate, crystallinity, and composition, of exemplary zirconium
sulfide films deposited at various deposition temperatures
utilizing zirconium tetrachloride (ZrCl.sub.4) and hydrogen sulfide
(H.sub.2S) as the precursor chemicals. Examination of FIG. 3
illustrates that between a deposition temperature of approximately
200.degree. C., up to a deposition of approximately 350.degree. C.,
the deposition rate of the exemplary zirconium sulfide films
increases and the crystal structure of the zirconium sulfide films
is amorphous, i.e., there is no long range ordering in the crystal
structure which would normally be associated with a crystalline
material. Between a deposition temperature of approximately
350.degree. C. and approximately 400.degree. C. there is a further
increase in the growth rate of the exemplary zirconium sulfide
films and the crystal structure of the zirconium sulfide films
becomes crystalline, i.e., there is long range ordering of the
crystalline structure of the chalcogenide film. In addition,
between a deposition temperature of approximately 350.degree. C.
and approximately 400.degree. C., the exemplary zirconium sulfide
film exhibits a composition of zirconium disulfide (ZrS.sub.2).
However, as the deposition temperature is further increased above a
temperature of approximately 400.degree. C., the growth rate of the
exemplary films initially decreases and then again increases and
the composition of the deposited film becomes that of a mixture
between a zirconium sulfide and a zirconium oxide. The deposition
of zirconium oxide phases above a temperature of approximately
400.degree. C. may result from residual oxygen and/or water
remaining in the reaction chamber utilized in the above
non-limiting examples. In further non-limiting examples, the
residual oxygen and/or water concentration within the reaction
chamber may be further reduced and deposition above a temperature
of approximately 400.degree. C. may result in deposition of a
zirconium disulfide (ZrS.sub.2) film without the deposition of
zirconium oxide phases.
[0127] Therefore, in some embodiments of the disclosure, the
transition metal chalcogenide film may comprise a zirconium sulfide
and particularly zirconium disulfide (ZrS.sub.2). In addition, in
some embodiments, the transition metal chalcogenide film may be
crystalline with a composition comprising zirconium disulfide
(ZrS.sub.2) at a deposition temperature between approximately
350.degree. C. and approximately 400.degree. C., and particular at
a deposition temperature of approximately 400.degree. C. In some
embodiments, a crystalline zirconium disulfide (ZrS.sub.2) film may
be deposited at a deposition temperature greater than 400.degree.
C.
[0128] As further non-limiting examples of the transition metal
chalcogenide films deposited according to the embodiments of the
disclosure, FIG. 4 and FIG. 5 illustrate grazing incidence x-ray
diffraction (GIXRD) data for hafnium sulfide films deposited
utilizing hafnium tetrachloride (HfCl.sub.4) and hydrogen sulfide
(H.sub.2S) as chemical precursor (FIG. 4) and zirconium sulfide
films deposited utilizing zirconium tetrachloride (ZrCl.sub.4) and
hydrogen sulfide (H.sub.2S) as chemical precursors (FIG. 5)
deposited at various deposition temperature between 200.degree. C.
and 500.degree. C.
[0129] Examination of FIG. 4 illustrates that for a deposition
temperature of 200.degree. C., up to a deposition temperature of
350.degree. C., the GIXRD data does not include any discernable
peaks in the data, corresponding to a non-crystalline film, i.e.,
the exemplary hafnium sulfide films are amorphous. For a deposition
temperature of 400.degree. C., up to a deposition temperature of
450.degree. C., the GIXRD data has a discernable primary peak
corresponding to a crystalline hafnium sulfide film and in
particular a hafnium disulfide film with a composition (HfS.sub.2).
In addition, for a deposition temperature between 400.degree. C.
and 450.degree. C. the exemplary hafnium disulfide films have a
predominate (001) crystallographic orientation as demonstrated by
the location of the peak in the GIXRD data. For a deposition
temperature of 500.degree. C. the peak in the GIXRD data related to
hafnium disulfide is not discernable but rather a number of smaller
peaks corresponding to a hafnium oxide (e.g., HfO.sub.2) are
present indicating the deposited film comprises a hafnium oxide
film. As previously described herein, the presence of hafnium oxide
phases at a deposition of 500.degree. C. may be due to residual
water and/or oxygen within the reaction chamber utilized to deposit
the exemplary hafnium sulfide films of FIG. 4. In additional
non-limiting examples, the reaction chamber utilized to deposit the
hafnium sulfide films may have a reduced concentration of water
and/or oxygen and deposition at a temperature of 500.degree. C. and
above may result in crystalline hafnium sulfide films without the
presence of hafnium oxide phases.
[0130] Therefore, in some embodiments of the disclosure, the
transition metal chalcogenide film may comprise a hafnium sulfide
and particularly hafnium disulfide (HfS.sub.2). In addition, in
some embodiments, the transition metal chalcogenide film may
comprise crystalline hafnium disulfide (HfS.sub.2) with a
predominant (001) crystallographic orientation for a deposition
temperature between approximately 350.degree. C. and approximately
400.degree. C., and particular at a deposition temperature of
approximately 400.degree. C. In some embodiments, the transition
metal chalcogenide film may comprise crystalline hafnium disulfide
(HfS.sub.2) with a predominant (001) crystallographic orientation
for a deposition temperature greater than 400.degree. C.
[0131] In addition, GIXRD data from exemplary zirconium sulfide
films are illustrated in FIG. 5 and examination of FIG. 5
illustrates that for a deposition temperature of 200.degree. C., up
to a deposition temperature of 300.degree. C., the GIXRD data does
not include any discernable peaks in the data, corresponding to a
non-crystalline film, i.e., the exemplary zirconium sulfide films
are amorphous. For a deposition temperature of 350.degree. C., up
to a deposition temperature of 450.degree. C., the GIXRD data has a
single discernable peak corresponding to a crystalline zirconium
sulfide film and in particular a zirconium disulfide film with a
composition (ZrS.sub.2). In addition, for a deposition temperature
between 350.degree. C. and 450.degree. C. the exemplary zirconium
disulfide films have a predominate (001) crystallographic
orientation as demonstrated by the location of the peak in the
GIXRD data. For a deposition temperature of 500.degree. C. the peak
in the GIXRD data related to zirconium disulfide is present but
also a number of smaller peaks corresponding to a zirconium oxide
(e.g., ZrO.sub.2) are present indicating the deposited film
comprises a mixture of both a zirconium sulfide and a zirconium
oxide. As previously described herein, the presence of zirconium
oxide phases at a deposition temperature of 500.degree. C. may be
due to residual water and/or oxygen within the reaction chamber
utilized to deposit the exemplary zirconium sulfide films of FIG.
5. In additional non-limiting examples, the reaction chamber
utilized to deposit the zirconium sulfide films may have a reduced
concentration of water and/or oxygen and deposition at a
temperature of 500.degree. C. and above may result in crystalline
zirconium sulfide films without the presence of zirconium oxide
phases.
[0132] Therefore, in some embodiments of the disclosure, the
transition metal chalcogenide film may comprise a zirconium sulfide
and a particularly zirconium disulfide (ZrS.sub.2). In addition, in
some embodiments, the transition metal chalcogenide film may
comprise crystalline zirconium disulfide (ZrS.sub.2) with a (001)
crystallographic orientation for a deposition temperature between
approximately 300.degree. C. and approximately 450.degree. C., and
particular at a deposition temperature of approximately 400.degree.
C. In some embodiments, the transition metal chalcogenide film may
comprise crystalline zirconium disulfide (ZrS.sub.2) with a
predominant (001) crystallographic orientation for a deposition
temperature of greater than 400.degree. C.
[0133] In some embodiments of the disclosure, the as-deposited
transition metal chalcogenide films may be subjected to a
post-deposition annealing process to improve the crystallinity of
the transition metal chalcogenide thin films. For example, in some
embodiments, the method of depositing the transition metal
chalcogenide film may further comprise, a post-deposition annealing
of the metal chalcogenide at a temperature above the deposition
temperature of the transition metal chalcogenide film. For example,
in some embodiments, annealing of the transition metal chalcogenide
may comprise, heating the transition metal chalcogenide film to a
temperature of approximately less than 800.degree. C., or
approximately less than 600.degree. C., or approximately less than
500.degree. C., or even approximately less than 400.degree. C. In
some embodiments, the post-deposition annealing of the transition
metal chalcogenide thin film may be performed in an atmosphere
comprising a chalcogen, for example, the post-deposition annealing
process may be performed in an ambient comprising a chalcogenide
compound, for example sulfur compounds, such as a hydrogen sulfide
(H.sub.2S) atmosphere. In some embodiments, the post-deposition
annealing of the metal chalcogenide thin film may be performed for
a time period of less than 1 hour, or less than 30 minutes, or less
than 15 minutes, or even less than 5 minutes. In some embodiments,
the post-deposition annealing of the transition metal chalcogenide
thin film may be performed in an atmosphere not comprising
chalcogens, such as S, Se, or Te, for example, in inert gas ambient
such as N.sub.2, or noble gas, such as Ar or He, or in hydrogen
containing ambient such as H.sub.2 or H.sub.2/N.sub.2 ambient.
[0134] Transition metal chalcogenide films, such as, for example,
hafnium disulfide and zirconium disulfide films, deposited
according to some of the embodiments of the disclosure may be
continuous films comprising a 2D material. In some embodiments the
films comprising a transition metal chalcogenide film deposited
according to some of the embodiments disclosure may be continuous
at a thickness below about 100 nanometers, or below about 60
nanometers, or below about 50 nanometers, or below about 40
nanometers, or below about 30 nanometers, or below about 25
nanometers, or below about 20 nanometers, or below about 15
nanometers, or below about 10 nanometers, or below about 5
nanometers or lower.
[0135] In some embodiments, the transition metal chalcogenide films
deposited according to the embodiments of the disclosure may be
continuous over a substrate having a diameter greater than 100
millimeters, or greater than 200 millimeters, or greater than 300
millimeters, or even greater than 400 millimeters. The continuity
referred to herein can be physical continuity or electrical
continuity. In some embodiments the thickness at which a film may
be physically continuous may not be the same as the thickness at
which a film is electrically continuous, and the thickness at which
a film may be electrically continuous may not be the same as the
thickness at which a film is physically continuous.
[0136] In some embodiments of the disclosure, the transition metal
chalcogenide films deposited by the methods disclosed herein may
comprise at least one of a hafnium sulfide, a hafnium selenide, a
hafnium telluride, a zirconium sulfide, a zirconium selenide, or a
zirconium telluride.
[0137] In some embodiments of the disclosure, the transition metal
chalcogenide films deposited by the methods disclosed herein may
comprise a hafnium chalcogenide and particularly a hafnium sulfide
having the general formula HfS.sub.x, wherein x may range from
approximately 0.75 to approximately 2.8, or wherein x may range
from approximately 0.8 to approximately 2.5, or wherein x may range
from 0.9 to approximately 2.3, or alternatively wherein x may range
from approximately 0.95 to approximately 2.2. The elemental
composition ranges for HfS.sub.x may comprise Hf from about 30
atomic % to about 60 atomic %, or from about 35 atomic % to about
55 atomic %, or even from about 40 atomic % to about 50 atomic %.
Alternatively the elemental composition ranges for HfS.sub.x may
comprise S from about 25 atomic % to about 75 atomic %, or S from
about 30 atomic % to about 60 atomic %, or even S from about 35
atomic % to about 55 atomic %.
[0138] In some embodiments of the disclosure, the transition metal
chalcogenide films deposited by the methods disclosed herein may
comprise a zirconium chalcogenide and particularly a zirconium
sulfide having the general formula ZrS.sub.x, wherein x may range
from approximately 0.75 to approximately 2.8, or wherein x may
range from approximately 0.8 to approximately 2.5, or wherein x may
range from 0.9 to approximately 2.3, or alternatively wherein x may
range from approximately 0.95 to approximately 2.2. The elemental
composition ranges for ZrS.sub.x may comprise Zr from about 30
atomic % to about 60 atomic %, or from about 35 atomic % to about
55 atomic %, or even from about 40 atomic % to about 50 atomic %.
Alternatively the elemental composition ranges for ZrS.sub.x may
comprise S from about 25 atomic % to about 75 atomic %, or S from
about 30 atomic % to about 60 atomic %, or even S from about 35
atomic % to about 55 atomic %.
[0139] In additional embodiments, the transition metal chalcogenide
films of the present disclosure may comprise, less than about 20
atomic % oxygen, or less than about 10 atomic % oxygen, or less
than about 5 atomic % oxygen, or even less than about 2 atomic %
oxygen. In further embodiments, the transition metal chalcogenide
films may comprise, less than about 25 atomic % hydrogen, or less
than about 10 atomic % hydrogen, or less than about 5 atomic % of
hydrogen, or less than about 2 atomic % of hydrogen, or even less
than about 1 atomic % of hydrogen. In yet further embodiments, the
transition metal chalcogenide films may comprise, less than about
20 atomic % carbon, or less than about 10 atomic % carbon, or less
than about 5 atomic % carbon, or less than about 2 atomic % carbon,
or less than about 1 atomic % of carbon, or even less than about
0.5 atomic % carbon. In the embodiments outlined herein, the atomic
concentration of an element may be determined utilizing Rutherford
backscattering (RBS) and/or elastic recoil detection analysis
(ERDA).
[0140] In some embodiments of the disclosure, the transition metal
chalcogenide films may be deposited on a three-dimensional
structure. In some embodiments, the step coverage of the transition
metal chalcogenide films may be equal to or greater than about 50%,
or greater than about 80%, or greater than about 90%, or about 95%,
or about 98%, or about 99% or greater in structures having aspect
ratios (height/width) of more than about 2, more than about 5, more
than about 10, more than about 25, more than about 50, or even more
than about 100.
[0141] In some embodiments, the transition metal chalcogenide film
of the present disclosure, such as hafnium and zirconium
dichalcogenide films, may be deposited to a thickness from about 20
nanometers to about 100 nanometers. In some embodiments, a
transition metal chalcogenide thin film deposited according to some
of the embodiments described herein may have a thickness from about
20 nanometers to about 60 nanometers. In some embodiments, a
transition metal chalcogenide thin film deposited according to some
of the embodiments described herein may have a thickness greater
than about 20 nanometers, or greater than about 30 nanometers, or
greater than about 40 nanometers, or greater than about 50
nanometers, or greater than about 60 nanometers, or greater than
about 100 nanometers, or greater than about 250 nanometers, or
greater than about 500 nanometers, or even greater. In some
embodiments a transition metal chalcogenide thin film deposited
according to some of the embodiments described herein may have a
thickness of less than about 50 nanometers, or less than about 30
nanometers, or less than about 20 nanometers, or less than about 15
nanometers, or less than about 10 nanometers, or less than about 5
nanometers, or less than about 3 nanometers, or less than about 2
nanometers, or less than about 1.5 nanometers, or even less than
about 1 nanometer.
[0142] In some embodiments a transition metal chalcogenide film,
such as a hafnium or zirconium dichalcogenide film deposited
according to some of the embodiments described herein may have a
thickness of equal to or less than about 10 monolayers of
transition metal chalcogenide material, or equal to or less than
about 7 monolayers of transition metal chalcogenide material, or
equal to or less than about 5 monolayers of transition metal
chalcogenide material, or to equal or less than about 4 monolayers
of transition metal chalcogenide material, or equal to or less than
about 3 monolayers of transition metal chalcogenide material, or
equal to or less than about 2 monolayers of transition metal
chalcogenide material, or even equal to or less than about 1
monolayer of transition metal chalcogenide material.
[0143] In some embodiments of the disclosure, the transition metal
chalcogenide films deposited according the methods disclosed herein
may include a protective capping layer to substantially prevent, or
even prevent, the unwanted oxidation of the transition metal
chalcogenide film. For example, upon completion of the deposition
of the transition metal chalcogenide the chalcogenide film may be
unloaded from the reaction chamber and exposed to ambient
conditions wherein oxygen and/or water within the ambient
environment may oxidize the deposited transition metal chalcogenide
film.
[0144] Therefore, in some embodiments, a capping layer may be
deposited over the transition metal chalcogenide film and
particularly deposited directly over the transition metal
chalcogenide film. In addition, to prevent any potential oxidation
of the transition metal chalcogenide film, the capping layer may be
deposited within the same reaction chamber utilized to deposit the
transition metal chalcogenide, i.e., the capping layer may be
deposited in-situ within the same reaction chamber utilized to
deposit the transition metal chalcogenide film. Therefore, in some
embodiments of the disclosure, the methods may further comprise,
in-situ depositing a capping layer over the transition metal
chalcogenide film to substantially prevent oxidation of the
transition metal chalcogenide film when exposed to ambient
conditions.
[0145] In some embodiments, the capping layer may comprise a metal
silicate film. In some embodiments, the metal silicate film may
comprise at least one of an aluminum silicate
(Al.sub.xSi.sub.yO.sub.x), a hafnium silicate
(Hf.sub.xSi.sub.yO.sub.x), or a zirconium silicate
(Zr.sub.xSi.sub.yO.sub.x). More detailed information regarding the
deposition of metal silicate films may be found in U.S. Pat. No.
6,632,279, filed on Oct. 13, 2000, titled "METHOD FOR GROWING THIN
OXIDE FILMS," all of which is hereby incorporated by reference and
made a part of this specification.
[0146] In some embodiments, the capping layer may be deposited
directly on the transition metal chalcogenide film by a cyclical
deposition process, such as an atomic layer deposition process, or
a cyclical chemical vapor deposition process, as disclosed herein
previously. As a non-limiting example, the capping layer may
comprise a metal silicate and the metal silicate may be deposited
by cyclical deposition process, such as atomic layer deposition,
for example. In some embodiments, the capping layer may be
deposited using processes comprising non-oxidative
reactants/precursors, or non-oxygen reactants (for example without
O.sub.2, H.sub.2O, O.sub.3, H.sub.2O.sub.2, O-containing plasmas,
radicals or atoms) containing processes. Therefore, in some
embodiments, the capping layer may be deposited without utilizing
H.sub.2O, O.sub.3, or H.sub.2O.sub.2. In some embodiments, the
capping layer may be deposited without utilizing an oxygen based
plasma, i.e., without O-containing plasmas, oxygen radicals, oxygen
atoms, or oxygen excited species. The capping layer may be
deposited using processes comprising non-oxidative
reactants/precursor, or non-oxygen reactants to prevent, or
substantially prevent, the oxidation of the underlying transition
metal chalcogenide film. Therefore, in some embodiments, in-situ
depositing a capping layer over the transition metal chalcogenide
film may be performed without additional oxidation of the
transition metal chalcogenide film.
[0147] In other embodiments, the capping layer may comprise a
metal, such as a transition metal, for example. In some
embodiments, the capping layer may comprise, a nitride, a sulfide,
a carbide, or mixtures thereof, or for example a silicon containing
layer such as an amorphous silicon layer. In other embodiments, the
capping layer can be a dielectric layer. In other embodiments, the
capping layer can be a conductive layer. In other embodiments, the
capping layer can be a semiconductor layer.
[0148] An exemplary ALD process for depositing the capping layer
may comprise one or more repeated unit deposition cycles, wherein a
unit deposition cycle may comprise, contacting the substrate with a
metal vapor phase reactant, purging the reaction chamber of excess
metal precursor and reaction by-products, contacting the substrate
with a precursor comprising both a silicon component and an oxygen
component, and purging the reaction chamber for a second time. As a
non-limiting example, the capping layer may comprise an aluminum
silicate film (Al.sub.xSi.sub.yO.sub.z) and the metal vapor phase
reactant may comprise aluminum trichloride (AlCl.sub.3) whereas the
precursor comprising both a silicon component and an oxygen
component may comprise tetra-n-butoxysilane Si(O.sup.nBu).sub.4. In
some embodiments of the disclosure, the capping layer may comprise
a metal silicate deposited without the use of an oxidizing
precursor, such as, for example, O.sub.2, H.sub.2O, O.sub.3,
H.sub.2O.sub.2, O-containing plasmas, radicals or atoms.
[0149] In some embodiments, the capping layer may be deposited at
the same temperature utilized to deposit the transition metal
chalcogenide film. For example, the capping layer may be deposited
at a temperature of less than 500.degree. C., or less than
450.degree. C., or less than 400.degree. C., or less than
300.degree. C., or less than 200.degree. C. In some embodiments,
the capping layer may be deposited at a temperature between
approximately 200.degree. C. and 500.degree. C., and particularly
at a deposition temperature of approximately 400.degree. C.
[0150] In some embodiments, the capping layer may be deposited to a
thickness of less than 50 nanometers, or less than 40 nanometers,
or less than 30 nanometers, or less than 20 nanometers, or less
than 10 nanometers, or less than 7 nanometers, or less than 5
nanometers, or less than 3 nanometers, or less than 2 nanometers,
or even less than 1 nanometer. In some embodiments, the capping
layer is a continuous film and is disposed directly over the metal
chalcogenide film to substantially prevent oxidation of the metal
chalcogenide film.
[0151] As a non-limiting example, FIG. 6 illustrates the ambient
stability over time of both a bare zirconium chalcogenide film and
a zirconium chalcogenide film capped with an aluminum silicate
capping layer deposited according to the embodiments of the
disclosure. In more detail, FIG. 6 illustrates the change in the
normalized x-ray diffraction (XRD) intensity of the primary (001)
peak over exposure time to ambient conditions for both an aluminum
silicate capped zirconium disulfide film (represented by the
triangular data markers) and an uncapped, bare zirconium disulfide
film (represented by the square data marks). Examination of the
data for the bare zirconium disulfide film illustrates that the
intensity of the (001) peak in the XRD data decreases over time
indicating the bare zirconium disulfide oxidizes over the time
exposed to the ambient conditions. In contrast, examination of the
data for the aluminum silicate capped zirconium disulfide film
illustrates no decrease in the intensity of the (001) peak in the
XRD data over time, indicating substantially no oxidation of the
capped zirconium disulfide film.
[0152] In some embodiments of the disclosure, the in-situ
deposition of the capping layer directly on the surface of the
transition metal chalcogenide film may be beneficial in improving
the quality of thin transition metal chalcogenide films as the
capping layer may prevent oxidation of the chalcogenide film during
reaction chamber cool down after the deposition.
[0153] In more detail, FIG. 7A illustrates grazing incidence x-ray
diffraction (GIXRD) data for exemplary zirconium disulfide films
deposited utilizing a different number of deposition cycles without
a capping layer and FIG. 7B illustrates grazing incidence x-ray
diffraction (GIXRD) data for exemplary zirconium chalcogenide films
deposited utilizing a different number of deposition cycles with an
in-situ capping layer deposited directly over the chalcogenide
film. Examination of FIG. 7A, i.e., the uncapped zirconium
disulfide, illustrates that the XRD peak corresponding to
crystalline zirconium disulfide does not appear until 1000
deposition cycle have been completed, which corresponds to a
thickness of approximately 8 nanometers. In contrast, examination
of FIG. 7B, i.e., the capped zirconium disulfide, illustrates that
the XRD peak corresponding to crystalline zirconium disulfide
appears at 500 deposition cycles, which corresponds to a thickness
of approximately 4 nanometers. Therefore, in some embodiments of
the disclosure, the metal chalcogenide film may be covered by an
in-situ capping layer and the metal chalcogenide film may be
crystalline below a thickness of less than approximately 5
nanometers, or less than approximately 4 nanometers, or less than
approximately 2 nanometers, or less than 1.5 nanometers, or even
less than 1 nanometer.
[0154] The metal chalcogenide films deposited by the cyclical
deposition processes disclosed herein may be utilized in a variety
of contexts, such as in the formation of semiconductor device
structures. One of skill in the art will recognize that the
processes described herein are applicable to many contexts,
including, but not limited to, the fabrication of transistors.
[0155] As a non-limiting example, and with reference to FIG. 8, a
semiconductor device structure 800 may comprise a field effect
transistor (FET) which may include a silicon substrate 802 and a
silicon dioxide (SiO.sub.2) layer 804 disposed over the silicon
substrate 802. The semiconductor device structure 800 may further
comprise a source region 806 and a drain region 808. Disposed
between the source and drain regions is a transition metal
chalcogenide film 810 deposited according to the embodiments of the
disclosure. The transition metal chalcogenide film 810 may comprise
a film of hafnium disulfide or zirconium disulfide and may consist
of the channel region of the FET structure. In some embodiments of
the disclosure, the transition metal chalcogenide film 810 may have
thickness of less than 10 nanometers, or less than 5 nanometers, or
even less than 1 nanometer. Disposed directly over the transition
metal chalcogenide film 810 may be a capping layer 811. For
example, the capping layer 811 may comprise a metal silicate film
and in particular an aluminum silicate film. The semiconductor
device structure 800 may further comprise a gate dielectric layer
812 disposed over the transition metal chalcogenide film 810,
wherein the gate dielectric layer 812 may comprise hafnium dioxide
(HfO.sub.2). The semiconductor device structure 800 may further
comprise a gate electrode 814 disposed over the transition metal
chalcogenide film 810.
[0156] Embodiments of the disclosure may also include a reaction
system configured for depositing the transition metal chalcogenide
films of the present disclosure. In more detail, FIG. 9
schematically illustrates a reaction system 900 including a
reaction chamber 902 that further includes mechanism for retaining
a substrate (not shown) under predetermined pressure, temperature,
and ambient conditions, and for selectively exposing the substrate
to various gases. A precursor reactant source 904 may be coupled by
conduits or other appropriate means 904A to the reaction chamber
902, and may further couple to a manifold, valve control system,
mass flow control system, or mechanism to control a gaseous
precursor originating from the precursor reactant source 904. A
precursor (not shown) supplied by the precursor reactant source
904, the reactant (not shown), may be liquid or solid under room
temperature and standard atmospheric pressure conditions. Such a
precursor may be vaporized within a reactant source vacuum vessel,
which may be maintained at or above a vaporizing temperature within
a precursor source chamber. In such embodiments, the vaporized
precursor may be transported with a carrier gas (e.g., an inactive
or inert gas) and then fed into the reaction chamber 902 through
conduit 904A. In other embodiments, the precursor may be a vapor
under standard conditions. In such embodiments, the precursor does
not need to be vaporized and may not require a carrier gas. For
example, in one embodiment the precursor may be stored in a gas
cylinder. The conduit 904A may further comprise a gas purifier 905A
for substantially removing unwanted contaminants from the vapor fed
to the reaction chamber 902.
[0157] The reaction system 900 may also include additional
precursor reactant sources, such as precursor reactant source 906
which may also be coupled to the reaction chamber 902 by mean of
conduits 906A and additional gas purifier 905B, as described
above.
[0158] A purge gas source 908 may also be coupled to the reaction
chamber 902 via conduits 908A, and selectively supplies various
inert or noble gases to the reaction chamber 902 to assist with the
removal of precursor gas or waste gasses from the reaction chamber.
The various inert or noble gasses that may be supplied may
originate from a solid, liquid or stored gaseous form.
[0159] The reaction system 900 of FIG. 9 may also comprise a system
operation and control mechanism 910 that provides electronic
circuitry and mechanical components to selectively operate valves,
manifolds, pumps and other equipment included in the reaction
system 900. Such circuitry and components operate to introduce
precursors, purge gasses from the respective precursor sources 904,
906, and purge gas source 908. The system operation and control
mechanism 910 also controls timing of gas pulse sequences,
temperature of the substrate and reaction chamber, and pressure of
the reaction chamber and various other operations necessary to
provide proper operation of the reaction system 900. The operation
and control mechanism 910 can include control software and
electrically or pneumatically controlled valves to control flow of
precursors, reactants and purge gasses into and out of the reaction
chamber 902. The control system can include modules such as a
software or hardware component, e.g., a FPGA or ASIC, which
performs certain tasks. A module can advantageously be configured
to reside on the addressable storage medium of the control system
and be configured to execute one or more processes.
[0160] Those of skill in the relevant arts appreciate that other
configurations of the present reaction system are possible,
including different number and kind of precursor reactant sources
and purge gas sources. Further, such persons will also appreciate
that there are many arrangements of valves, conduits, precursor
sources, purge gas sources that may be used to accomplish the goal
of selectively feeding gasses into reaction chamber 902. Further,
as a schematic representation of a reaction system, many components
have been omitted for simplicity of illustration, and such
components may include, for example, various valves, manifolds,
purifiers, heaters, containers, vents, and/or bypasses.
[0161] The example embodiments of the disclosure described above do
not limit the scope of the invention, since these embodiments are
merely examples of the embodiments of the invention, which is
defined by the appended claims and their legal equivalents. Any
equivalent embodiments are intended to be within the scope of this
invention. Indeed, various modifications of the disclosure, in
addition to those shown and described herein, such as alternative
useful combination of the elements described, may become apparent
to those skilled in the art from the description. Such
modifications and embodiments are also intended to fall within the
scope of the appended claims.
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