U.S. patent application number 10/911372 was filed with the patent office on 2005-01-13 for systems and methods for forming refractory metal oxide layers.
This patent application is currently assigned to MICRON TECHNOLOGY, INC.. Invention is credited to Vaartstra, Brian A..
Application Number | 20050009266 10/911372 |
Document ID | / |
Family ID | 31976283 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050009266 |
Kind Code |
A1 |
Vaartstra, Brian A. |
January 13, 2005 |
Systems and methods for forming refractory metal oxide layers
Abstract
A method of forming (and apparatus for forming) refractory metal
oxide layers, such as tantalum pentoxide layers, on substrates by
using vapor deposition processes with refractory metal precursor
compounds and ethers.
Inventors: |
Vaartstra, Brian A.; (Nampa,
ID) |
Correspondence
Address: |
MUETING, RAASCH & GEBHARDT, P.A.
P.O. BOX 581415
MINNEAPOLIS
MN
55458
US
|
Assignee: |
MICRON TECHNOLOGY, INC.
Boise
ID
|
Family ID: |
31976283 |
Appl. No.: |
10/911372 |
Filed: |
August 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10911372 |
Aug 4, 2004 |
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10229653 |
Aug 28, 2002 |
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6784049 |
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Current U.S.
Class: |
438/240 ;
257/E21.008; 257/E21.274; 257/E21.29; 438/785 |
Current CPC
Class: |
H01L 28/40 20130101;
H01L 21/0228 20130101; C23C 16/405 20130101; H01L 21/02183
20130101; H01L 21/31683 20130101; C23C 16/45553 20130101; H01L
21/02271 20130101; H01L 21/02205 20130101; H01L 21/31604
20130101 |
Class at
Publication: |
438/240 ;
438/785 |
International
Class: |
H01L 021/8242 |
Claims
1-52. (Canceled)
53. A vapor deposition apparatus comprising: a vapor deposition
chamber having a substrate positioned therein; and one or more
vessels comprising one or more refractory metal precursor compounds
of the formula MY.sub.n (Formula I), wherein M is a refractory
metal, each Y is independently a halogen atom, and n is an integer
selected to match the valence of the metal M; and one or more
vessels comprising one or more ethers of the formula
R.sup.1--O--R.sup.2, wherein R.sup.1 and R.sup.2 are each
independently organic groups.
54. The apparatus of claim 53 wherein the substrate is a silicon
wafer.
55. The apparatus of claim 53 further comprising one or more
sources of an inert carrier gas for transferring the precursors to
the vapor deposition chamber.
56. The apparatus of claim 53 further comprising one or more
vessels comprising one or more metal-containing precursor compounds
having a formula different than Formula I.
57. A vapor deposition apparatus comprising: a vapor deposition
chamber; and one or more vessels comprising one or more refractory
metal precursor compounds of the formula MY.sub.n (Formula I),
wherein M is a refractory metal, each Y is independently a halogen
atom, and n is an integer selected to match the valence of the
metal M; and one or more vessels comprising one or more ethers of
the formula R.sup.1--O--R.sup.2, wherein R.sup.1 and R.sup.2 are
each independently organic groups.
58. The apparatus of claim 57 wherein M is tantalum and n is 5.
59. The apparatus of claim 57 wherein Y is independently selected
from the group consisting of F, Cl, I, and combinations
thereof.
60. The apparatus of claim 59 wherein each Y is independently a
fluorine atom.
61. The apparatus of claim 60 wherein M is tantalum and n is 5.
62. The apparatus of claim 57 wherein at least one of R.sup.1 and
R.sup.2 is selected from the group consisting of alkyl groups,
alkenyl groups, aryl groups, silyl groups, and combinations
thereof.
63. The apparatus of claim 57 wherein at least one of R.sup.1 and
R.sup.2 contains one or more functional groups selected from the
group consisting of ether, amino, and carbonyl groups.
64. The apparatus of claim 57 wherein at least one of R.sup.1 and
R.sup.2 is an alkyl group that forms a stable radical or
carbocation.
65. The apparatus of claim 57 wherein at least one of R.sup.1 and
R.sup.2 is selected from the group consisting of benzyl, t-butyl,
dimethylsilyl, and trimethylsilyl groups.
66. The apparatus of claim 65 wherein at least one of R.sup.1 and
R.sup.2 is selected from the group consisting of dimethylsilyl and
trimethylsilyl groups.
67. The apparatus of claim 57 further comprising one or more
vessels comprising one or more metal-containing precursor compounds
having a formula different than Formula I.
68. The apparatus of claim 57 wherein R.sup.1--O--R.sup.2 is
hexamethyldisiloxane.
69. The apparatus of claim 57 wherein R.sup.1--O--R.sup.2 is
tetramethyldisiloxane.
70. A vapor deposition apparatus comprising: a vapor deposition
chamber; and one or more vessels comprising one or more refractory
metal precursor compounds of the formula MY.sub.n (Formula I),
wherein M is a refractory metal, each Y is independently a halogen
atom, and n is an integer selected to match the valence of the
metal M; and one or more vessels comprising one or more ethers of
the formula R.sup.1--O--R.sup.2, wherein R.sup.1 and R.sup.2 are
each independently organic groups, with the proviso that at least
one of the one or more ethers comprises tetramethyldisiloxane.
71. A vapor deposition apparatus comprising: a vapor deposition
chamber; and one or more vessels comprising one or more refractory
metal precursor compounds of the formula MY.sub.n (Formula I),
wherein M is a refractory metal, each Y is independently a halogen
atom, and n is an integer selected to match the valence of the
metal M; and one or more vessels comprising one or more ethers of
the formula R.sup.1--O--R.sup.2, wherein R.sup.1 and R.sup.2 are
each independently organic groups, with the proviso that the one or
more ethers do not comprise disilyl ethers.
Description
FELD OF THE INVENTION
[0001] This invention relates to method of forming a refractory
metal (preferably, tantalum) oxide layer, and particularly to a
method of forming a tantalum pentoxide layer, on a substrate using
a reactive deposition process with a refractory metal precursor
compound with an ether.
BACKGROUND OF THE INVENTION
[0002] In integrated circuit manufacturing, microelectronic devices
such as capacitors are the basic energy storage devices in random
access memory devices, such as dynamic random access memory (DRAM)
devices, static random access memory (SRAM) devices, and
ferroelectric memory (FERAM) devices. Capacitors typically consist
of two conductors, such as parallel metal or polysilicon plates,
which act as the electrodes (i.e., the storage node electrode and
the cell plate capacitor electrode), insulated from each other by a
layer of dielectric material.
[0003] The continuous shrinkage of microelectronic devices over the
years has led to a situation where the materials traditionally used
in integrated circuit technology are approaching their performance
limits. Silicon (i.e., doped polysilicon) has generally been the
substrate of choice, and silicon dioxide (SiO.sub.2) has frequently
been used as the dielectric material to construct microelectronic
devices. However, when the SiO.sub.2 layer is thinned to about 10
.ANG. (i.e., a thickness of only 4 or 5 molecules), as is desired
in the newest micro devices, the dielectric layer no longer
effectively performs effectively as an insulator due to the
tunneling current running through it. This SiO.sub.2 thin layer
deficiency has lead to a
[0004] search for improved dielectric materials.
[0005] Refractory metal oxides such as tantalum pentoxide
(Ta.sub.2O.sub.5), titanium dioxide (TiO.sub.2), zirconium dioxide
(ZrO.sub.2), and hafnium dioxide (HfO.sub.2), are some of the most
promising SiO.sub.2 replacements for future DRAM devices since they
meet the requirements for large scale processing and fabrication
using conventional microelectronics processing equipment.
Furthermore, these oxides have excellent step coverage, and they
exhibit comparatively low leakage current. Ta.sub.2O.sub.5 is of
particular interest as layers of amorphous Ta.sub.2O.sub.5 have a
dielectric constant of about 25. Ta.sub.2O.sub.5 layers can be
formed using chemical vapor deposition (CVD) processes. For
example, reacting vapors of Ta(OC.sub.2H.sub.5).sub.- 5
(pentaethoxy-tantalum) with oxygen or by reacting vapors of
TaF.sub.5 with an O.sub.2/H.sub.2 plasma can form
Ta.sub.2O.sub.5.
[0006] Annealing can improve the crystallinity and resulting
dielectric constant of refractory metal oxide layers. For example,
the dielectric constant of an amorphous Ta.sub.2O.sub.5 layer can
be increased to at least 40 by annealing the deposited layer at
temperatures over 700.degree. C., causing a change in crystallinity
from an amorphous state to what is believed to be a preferred (001)
orientation of a crystalline hexagonal phase of Ta.sub.2O.sub.5.
Unfortunately, this increase in dielectric constant of annealed
crystalline Ta.sub.2O.sub.5 layers is counterbalanced by higher
leakage currents through the crystal boundaries. High temperature
annealing of a Ta.sub.2O.sub.5 layer on polysilicon also inevitably
produces a thin SiO.sub.2 interfacial layer between the
Ta.sub.2O.sub.5 layer and the polysilicon due to ambient oxidation
during the deposition process and during any post-processing such
as annealing. This SiO.sub.2 layer insures better interfacial
properties but also causes a reduction of the global dielectric
constant of the Ta.sub.2O.sub.5 capacitor. A metal nitride barrier
layer can be applied to the polysilicon substrate prior to
formation of the Ta.sub.2O.sub.5 layer to avoid formation of the
SiO.sub.2 interfacial layer but at the cost of adding another
processing step. Metal nitride barrier layers are also likely to be
oxidized by high temperature anneal processes.
[0007] Changing the nature of the substrate and curing conditions
during CVD processing can improve the dielectric constant of
resulting Ta.sub.2O.sub.5 layers. For example, Kishiro et al.,
"Structure and Electrical Properties of Thin Deposited on Metal
Electrodes," Jpn. J. Appl. Phys., 37:1336-1338 (1998) report
crystalline Ta.sub.2O.sub.5 layers having dielectric constants over
50 made by depositing the layers on platinum and ruthenium
substrates rather than on poly-Si electrodes and annealing at
750.degree. C. For another example, Lin et al., "Ta.sub.2O.sub.5
thin films with exceptionally high dielectric constant," Applied
Physics Newsletter, 74(16):2370-2372 (1999) report that if a
Ta.sub.2O.sub.5 layer is deposited on a Ru/TiN/Ti/SiO.sub.2 layered
substrate, its dielectric constant can be increased up to 90-110
after N.sub.2O plasma treatment and then rapid thermal nitridation
(RTN) at 800.degree. C.
[0008] To date, efforts to improve the dielectric constant of
Ta.sub.2O.sub.5 layers have either required high temperature
processing that has led to various layer deficiencies or have
required specialized processing or substrate considerations. Thus,
there remains a need for a vapor deposition process to form
Ta.sub.2O.sub.5 layers that have high dielectric constants and low
current leakage, and that preferably do not require high
temperature annealing, do not utilize oxidizers that can cause the
formation of SiO.sub.2 interfacial layers on polysilicon
substrates, and do not require specialized processing or substrate
considerations.
SUMMARY OF THE INVENTION
[0009] The present invention is directed toward using a vapor
deposition process using refractory metal precursor compounds and
ethers to form refractory metal oxide layers, especially tantalum
pentoxide (Ta.sub.2O.sub.5) layers, on substrates. The vapor
deposition process is preferably a reactive vapor deposition
process that involves co-reacting the precursor compounds and the
ethers.
[0010] The methods of the present invention involve forming a
refractory metal oxide layer on a substrate by using a vapor
deposition process and one or more refractory metal precursor
compounds of the formula MY.sub.n (Formula I), wherein M is a
refractory metal, each Y is independently a halogen atom, and n is
an integer selected to match the valence of the metal M, and one or
more ethers of the formula R.sup.1--O--R.sup.2, wherein R.sup.1 and
R.sup.2 are each independently organic groups.
[0011] In one embodiment, a method of forming a layer on a
substrate is provided that includes: providing a substrate
(preferably a semiconductor substrate or substrate assembly such as
a silicon wafer); providing a vapor that includes one or more
refractory metal precursor compounds of the formula MY.sub.n,
wherein M is a refractory metal (e.g., tantalum), each Y is
independently a halogen atom (preferably, F, Cl, I, or combinations
thereof, and more preferably, F), and n is an integer selected to
match the valence of the metal M (e.g., n=5 when M=Ta); providing a
vapor that includes one or more ethers of the formula
R.sup.1--O--R.sup.2, wherein R.sup.1 and R.sup.2 are each
independently organic groups (e.g., alkyl groups, alkenyl groups,
aryl groups, silyl groups, and combinations thereof); and directing
the vapors of the one or more refractory metal precursor compounds
and the one or more ethers to the substrate to form a refractory
metal oxide layer on one or more surfaces of the substrate.
[0012] The present invention also provides a method of
manufacturing a memory device. The method includes: providing a
substrate (preferably a semiconductor substrate or substrate
assembly such as a silicon wafer) having a first electrode thereon;
providing a vapor that includes one or more refractory metal
precursor compounds of the formula MY.sub.n, wherein M is a
refractory metal, each Y is independently a halogen atom, and n is
an integer selected to match the valence of the metal M; providing
a vapor that includes one or more ethers of the formula
R.sup.1--O--R.sup.2, wherein R.sup.1 and R.sup.2 are each
independently organic groups; directing the vapors that include the
one or more refractory metal precursor compounds and the one or
more ethers to the substrate to form a refractory metal oxide
dielectric layer on the first electrode of the substrate; and
forming a second electrode on the dielectric layer.
[0013] The present invention also provides a vapor deposition
apparatus that includes: a vapor deposition chamber having a
substrate (e.g., a silicon wafer) positioned therein; and one or
more vessels that include one or more refractory metal precursor
compounds of the formula MY.sub.n, wherein M is a refractory metal,
each Y is independently a halogen atom, and n is an integer
selected to match the valence of the metal M; and one or more
vessels that include one or more ethers of the formula
R.sup.1--O--R.sup.2, wherein R.sup.1 and R.sup.2 are each
independently organic groups. Optionally, the apparatus includes
one or more sources of an inert carrier gas for transferring the
precursors to the vapor deposition chamber, and/or one or more
vessels that include one or more metal-containing precursor
compounds having a formula different from MY.sub.n.
[0014] The methods of the present invention can utilize a chemical
vapor deposition (CVD) process, which can be pulsed, or an atomic
layer deposition (ALD) process (a self-limiting vapor deposition
process that includes a plurality of deposition cycles, typically
with purging between the cycles). Preferably, the methods of the
present invention use ALD. For certain ALD processes, the tantalum
oxide layer is formed by alternately introducing one or more
precursor compounds and ethers into a deposition chamber during
each deposition cycle.
[0015] "Substrate" as used herein refers to any base material or
construction upon which a metal-containing layer can be deposited.
The term "substrate" is meant to include semiconductor substrates
and also include non-semiconductor substrates such as films, molded
articles, fibers, wires, glass, ceramics, machined metal parts,
etc. "Semiconductor substrate" or "substrate assembly" as used
herein refers to a semiconductor substrate such as a metal
electrode, base semiconductor layer or a semiconductor substrate
having one or more layers, structures, or regions formed thereon. A
base semiconductor layer is typically the lowest layer of silicon
material on a wafer or a silicon layer deposited on another
material, such as silicon on sapphire. When reference is made to a
substrate assembly, various process steps may have been previously
used to form or define regions, junctions, various structures or
features, and openings such as capacitor plates or barriers for
capacitors.
[0016] "Layer" as used herein refers to any metal-containing layer
that can be formed on a substrate from the precursor compounds of
this invention using a vapor deposition process. The term "layer"
is meant to include layers specific to the semiconductor industry,
such as "barrier layer," "dielectric layer," and "conductive
layer." (The term "layer" is synonymous with the term "film"
frequently used in the semiconductor industry.) The term "layer" is
also meant to include layers found in technology outside of
semiconductor technology, such as coatings on glass.
[0017] "Dielectric layer" as used herein is a term used in the
semiconductor industry that refers to an insulating layer
(sometimes referred to as a "film") having a high dielectric
constant that is typically positioned between two conductive
electrodes to form a capacitor. For this invention, the dielectric
layer is a refractory metal oxide layer, preferably a
Ta.sub.2O.sub.5 layer, formed using a reactive deposition
process.
[0018] "Refractory metal" as defined by Webster's New Universal
Unabridged Dictionary (1992) is a metal that is difficult to fuse,
reduce, or work. For the purposes of this invention, the term
"refractory metal" is meant to include the Group IVB metals (i.e.,
titanium (Ti), zirconium (Zr), hafnium (Hf)); the Group VB metals
(i.e., vanadium (V), niobium (Nb), tantalum (Ta)); and the Group
VIB metals (i.e., chromium (Cr), molybdenum (Mo) and tungsten
(W)).
[0019] "Precursor compound" as used herein refers to refractory
metal precursor compounds, tantalum precursor compounds, nitrogen
precursor compounds, silicon precursor compounds, and other
metal-containing precursor compounds, for example. A suitable
precursor compound is one that is capable of forming, either alone
or with other precursor compounds, a refractory metal-containing
layer on a substrate using a vapor deposition process. The
resulting metal-containing layers are typically oxide layers, which
are useful as dielectric layers.
[0020] "Deposition process" and "vapor deposition process" as used
herein refer to a process in which a metal-containing layer is
formed on one or more surfaces of a substrate (e.g., a doped
polysilicon wafer) from vaporized precursor compound(s).
Specifically, one or more metal precursor compounds are vaporized
and directed to one or more surfaces of a heated substrate (e.g.,
semiconductor substrate or substrate assembly) placed in a
deposition chamber. These precursor compounds form (e.g., by
reacting or decomposing) a non-volatile, thin, uniform,
metal-containing layer on the surface(s) of the substrate. For the
purposes of this invention, the term "vapor deposition process" is
meant to include both chemical vapor deposition processes
(including pulsed chemical vapor deposition processes) and atomic
layer deposition processes.
[0021] "Chemical vapor deposition" (CVD) as used herein refers to a
vapor deposition process wherein the desired layer is deposited on
the substrate from vaporized metal precursor compounds and any
reaction gases used within a deposition chamber with no effort made
to separate the reaction components. In contrast to a "simple" CVD
process that involves the substantial simultaneous use of the
precursor compounds and any reaction gases, "pulsed" CVD
alternately pulses these materials into the deposition chamber, but
does not rigorously avoid intermixing of the precursor and reaction
gas streams, as is typically done in atomic layer deposition or ALD
(discussed in greater detail below).
[0022] "Atomic layer deposition" (ALD) as used herein refers to a
vapor deposition process in which numerous consecutive deposition
cycles are conducted in a deposition chamber. Typically, during
each cycle the metal precursor is chemisorbed to the substrate
surface; excess precursor is purged out; a subsequent precursor
and/or reaction gas is introduced to react with the chemisorbed
layer; and excess reaction gas (if used) and by-products are
removed. As compared to the one cycle chemical vapor deposition
(CVD) process, the longer duration multi-cycle ALD process allows
for improved control of layer thickness by self-limiting layer
growth and minimizing detrimental gas phase reactions by separation
of the reaction components. The term "atomic layer deposition" as
used herein is also meant to include the related terms "atomic
layer epitaxy" (ALE) (see U.S. Pat. No. 5,256,244 (Ackerman)),
molecular beam epitaxy (MBE), gas source MBE, organometallic MBE,
and chemical beam epitaxy when performed with alternating pulses of
precursor compound(s), reaction gas and purge (i.e., inert carrier)
gas.
[0023] "Chemisorption" as used herein refers to the chemical
adsorption of vaporized reactive precursor compounds on the surface
of a substrate. The adsorbed species are irreversibly bound to the
substrate surface as a result of relatively strong binding forces
characterized by high adsorption energies (>30 kcal/mol),
comparable in strength to ordinary chemical bonds. The chemisorbed
species are limited to the formation of a monolayer on the
substrate surface. (See "The Condensed Chemical Dictionary", 10th
edition, revised by G. G. Hawley, published by Van Nostrand
Reinhold Co., New York, 225 (1981)). The technique of ALD is based
on the principle of the formation of a saturated monolayer of
reactive precursor molecules by chemi sorption. In ALD one or more
appropriate reactive precursor compounds are alternately introduced
(e.g., pulsed) into a deposition chamber and chemisorbed onto the
surfaces of a substrate. Each sequential introduction of a reactive
precursor compound is typically separated by an inert carrier gas
purge. Each precursor compound co-reaction adds a new atomic layer
to previously deposited layers to form a cumulative solid layer.
The cycle is repeated, typically for several hundred times, to
gradually form the desired layer thickness. It should be
understood, however, that ALD can use one precursor compound and
one reaction gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIGS. 1-3 are exemplary capacitor constructions.
[0025] FIG. 4 is a perspective view of a vapor deposition coating
system suitable for use in the method of the present invention.
DETALED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0026] The present invention provides a method of forming metal
oxide layers on substrates by using vapor deposition processes
using one or more refractory metal precursor compounds and one or
more ethers. The refractory metal precursor compounds are of the
formula MY.sub.n, wherein M is a refractory metal, each Y is
independently a halogen atom, and n is an integer selected to match
the valence of the metal M. The one or more ethers are of the
formula R.sup.1--O--R.sup.2, wherein R.sup.1 and R.sup.2 are each
independently organic groups. Preferably, M is tantalum and the
formed refractory metal oxide layer is a tantalum pentoxide
layer.
[0027] The layers or films formed can be in the form of refractory
metal oxide-containing films, wherein the layer includes one or
more refractory metal oxides optionally doped with other metals.
Thus, the term "refractory metal oxide" films or layers encompass
just refractory metal oxide as well as doped films or layers
thereof (i.e., mixed metal oxides). Such mixed metal species can be
formed using one or more metal-containing precursor compounds of a
formula different from Formula I, which can be readily determined
by one of skill in the art.
[0028] The refractory metal oxide layers typically have a thickness
of about 10 .ANG. to about 100 .ANG.. A preferred layer is a
Ta.sub.2O.sub.5 layer. Preferred tantalum pentoxide layers include
a combination of amorphous material and at least some crystalline
hexagonal phase, preferably with patterned (001) orientation. Such
Ta.sub.2O.sub.5 layers do not require high temperature annealing
(i.e., heating to temperatures of at least 700.degree. C.) as is
normally required to crystallize fully amorphous layers but
surprisingly exhibit a desirable combination of high dielectric
constants, typically in the range of 50 to 100, and low leakage
currents, typically in the range of 10.sup.-7 to 10.sup.-9
A/cm.sup.2, soon after completion of the vapor deposition
processing.
[0029] The substrate on which the metal-containing layer is formed
is preferably a semiconductor substrate or substrate assembly. Any
suitable semiconductor material is contemplated, such as for
example, conductively doped polysilicon (for this invention simply
referred to as "silicon"). A substrate assembly may also contain a
layer that includes platinum, iridium, rhodium, ruthenium,
ruthenium oxide, titanium nitride, tantalum nitride,
tantalum-silicon-nitride, silicon dioxide, aluminum, gallium
arsenide, glass, etc., and other existing or to-be-developed
materials used in semiconductor constructions, such as dynamic
random access memory (DRAM) devices and static random access memory
(SRAM) devices, for example.
[0030] Substrates other than semiconductor substrates or substrate
assemblies can be used in methods of the present invention. These
include, for example, fibers, wires, etc. If the substrate is a
semiconductor substrate or substrate assembly, the layers can be
formed directly on the lowest semiconductor surface of the
substrate, or they can be formed on any of a variety of the layers
(i.e., surfaces) as in a patterned wafer, for example.
[0031] Refractory metal precursor compounds useful in the practice
of this invention include any reactive refractory metal compounds.
Preferably, the refractory metal precursor compounds are of the
formula MY.sub.n (Formula I), wherein M is a refractory metal, Y is
independently a halogen atom, and n is an integer selected to match
the valence of the metal M (e.g., n would be 5 for a pentavalent
metal). More preferably, each Y is a fluorine atom. More
preferably, M is Ti, Nb, Ta, Mo, or W. Most preferably, M is Ti or
Ta.
[0032] Preferably, M is tantalum and n is 5, so that the refractory
metal precursor compound is a tantalum precursor compound of the
formula TaY.sub.5 wherein Y is defined as above. More preferably, Y
is fluorine and the tantalum precursor compound is TaF.sub.5.
Useful tantalum precursor compounds include TaF.sub.5, TaCl.sub.5,
and TaBr.sub.5 (all available from Sigma-Aldrich Chemical Company,
Milwaukee, Wis.).
[0033] Ether compounds useful in this invention are of the formula
R.sup.1--O--R.sup.2 wherein R.sup.1 and R.sup.2 is each
independently an organic group. As used herein, the term "organic
group" is used for the purpose of this invention to mean a
hydrocarbon group that is classified as an aliphatic group, cyclic
group, or combination of aliphatic and cyclic groups (e.g., alkaryl
and aralkyl groups). In the context of the present invention,
suitable organic groups for precursor compounds of this invention
are those that do not interfere with the formation of a
metal-containing layer using vapor deposition techniques. In the
context of the present invention, the term "aliphatic group" means
a saturated or unsaturated linear or branched hydrocarbon group.
This term is used to encompass alkyl, alkenyl, and alkynyl groups,
for example. The term "alkyl group" means a saturated linear or
branched monovalent hydrocarbon group including, for example,
methyl, ethyl, n-propyl, isopropyl, t-butyl, amyl, heptyl,
2-ethylhexyl, dodecyl, octadecyl, and the like. The term "alkenyl
group" means an unsaturated, linear or branched monovalent
hydrocarbon group with one or more olefinically unsaturated groups
(i.e., carbon-carbon double bonds), such as a vinyl group. The term
"alkynyl group" means an unsaturated, linear or branched monovalent
hydrocarbon group with one or more carbon-carbon triple bonds. The
term "cyclic group" means a closed ring hydrocarbon group that is
classified as an alicyclic group, aromatic group, or heterocyclic
group. The term "alicyclic group" means a cyclic hydrocarbon group
having properties resembling those of aliphatic groups. The term
"aromatic group" or "aryl group" means a mono- or polynuclear
aromatic hydrocarbon group. The term "heterocyclic group" means a
closed ring hydrocarbon in which one or more of the atoms in the
ring is an element other than carbon (e.g., nitrogen, oxygen,
sulfur, etc.).
[0034] As a means of simplifying the discussion and the recitation
of certain terminology used throughout this application, the terms
"group" and "moiety" are used to differentiate between chemical
species that allow for substitution or that may be substituted and
those that do not so allow for substitution or may not be so
substituted. Thus, when the term "group" is used to describe a
chemical substituent, the described chemical material includes the
unsubstituted group and that group with nonperoxidic O, N, S, Si,
or F, atoms, for example, in the chain as well as carbonyl groups
or other conventional substituents. Where the term "moiety" is used
to describe a chemical compound or substituent, only an
unsubstituted chemical material is intended to be included. For
example, the phrase "alkyl group" is intended to include not only
pure open chain saturated hydrocarbon alkyl substituents, such as
methyl, ethyl, propyl, t-butyl, and the like, but also alkyl
substituents bearing further substituents known in the art, such as
hydroxy, alkoxy, alkylsulfonyl, halogen atoms, cyano, nitro, amino,
carboxyl, etc. Thus, "alkyl group" includes ether groups,
haloalkyls, nitroalkyls, carboxyalkyls, hydroxyalkyls, sulfoalkyls,
etc. On the other hand, the phrase "alkyl moiety" is limited to the
inclusion of only pure open chain saturated hydrocarbon alkyl
substituents, such as methyl, ethyl, propyl, t-butyl, and the
like.
[0035] In the ether compounds, preferably at least one of R.sup.1
and R.sup.2 is selected from the group of alkyl groups, alkenyl
groups, aryl groups, silyl groups, or combinations thereof (any of
which may be branched or unbranched). At least one of R.sup.1 and
R.sup.2 can optionally contain functional groups such as ether,
amino, and carbonyl groups. More preferably, at least one of
R.sup.1 and R.sup.2 is an alkyl, alkenyl, aryl, or silyl group
(preferably an alkyl group) that forms a stable radical or
carbocation, such as a benzyl, allyl, t-butyl, dimethylsilyl or
trimethylsilyl group. Most preferably, at least one of R.sup.1 and
R.sup.2 is a group also capable of abstracting halide groups from
MY.sub.n. Examples of such halide-abstracting groups are
dimethylsilyl and trimethylsilyl groups. Examples of useful ether
compounds include (CH.sub.3).sub.3Si--O--Si(CH.sub.3).sub.3
(1,1,1,3,3,3-hexamethyldisiloxane),
(CH.sub.3).sub.2(H)Si--O--Si(H)(CH.su- b.3).sub.2
(1,1,3,3-tetramethyldisiloxane), (CH.sub.3).sub.3C--O--C(CH.sub-
.3).sub.3 (di-tert-butyl ether) and
C.sub.6H.sub.5CH.sub.2--O--CH.sub.2C.s- ub.6H.sub.5 (dibenzyl
ether).
[0036] Various precursor compounds can be used in various
combinations, optionally with one or more organic solvents
(particularly for CVD processes), to form a precursor composition.
The precursor compounds may be liquids or solids at room
temperature (preferably, they are liquids at the vaporization
temperature). Typically, they are liquids sufficiently volatile to
be employed using known vapor deposition techniques. However, as
solids they may also be sufficiently volatile that they can be
vaporized or sublimed from the solid state using known vapor
deposition techniques. If they are less volatile solids, they are
preferably sufficiently soluble in an organic solvent or have
melting points below their decomposition temperatures such that
they can be used in flash vaporization, bubbling, microdroplet
formation techniques, etc. Herein, vaporized precursor compounds
may be used either alone or optionally with vaporized molecules of
other precursor compounds or optionally with vaporized solvent
molecules, if used. As used herein, "liquid" refers to a solution
or a neat liquid (a liquid at room temperature or a solid at room
temperature that melts at an elevated temperature). As used herein,
"solution" does not require complete solubility of the solid but
may allow for some undissolved solid, as long as there is a
sufficient amount of the solid delivered by the organic solvent
into the vapor phase for chemical vapor deposition processing. If
solvent dilution is used in deposition, the total molar
concentration of solvent vapor generated may also be considered as
a inert carrier gas.
[0037] The solvents that are suitable for this application
(particularly for a CVD process) can be one or more of the
following: aliphatic hydrocarbons or unsaturated hydrocarbons
(C3-C20, and preferably C5-C10, cyclic, branched, or linear),
aromatic hydrocarbons (C5-C20, and preferably C5-C10), halogenated
hydrocarbons, silylated hydrocarbons such as alkylsilanes,
alkylsilicates, ethers, polyethers, thioethers, esters, lactones,
ammonia, amides, amines (aliphatic or aromatic, primary, secondary,
or tertiary), polyamines, nitriles, cyanates, isocyanates,
thiocyanates, silicone oils, alcohols, or compounds containing
combinations of any of the above or mixtures of one or more of the
above. The compounds are also generally compatible with each other,
so that mixtures of variable quantities of the precursor compounds
will not interact to significantly change their physical
properties.
[0038] The precursor compounds can be vaporized in the presence of
an inert carrier gas if desired. Additionally, an inert carrier gas
can be used in purging steps in an ALD process. The inert carrier
gas is typically selected from the group consisting of nitrogen,
helium, argon, and mixtures thereof. In the context of the present
invention, an inert carrier gas is one that is generally unreactive
with the complexes described herein and does not interfere with the
formation of the desired metal-containing film (i.e., layer).
[0039] The deposition process for this invention is a vapor
deposition process. Vapor deposition processes are generally
favored in the semiconductor industry due to the process capability
to quickly provide highly conformal layers even within deep
contacts and other openings. Chemical vapor deposition (CVD) and
atomic layer deposition (ALD) are two vapor deposition processes
often employed to form thin, continuous, uniform, metal-containing
(preferably dielectric) layers onto semiconductor substrates. Using
either vapor deposition process, typically one or more precursor
compounds are vaporized in a deposition chamber and optionally
combined with one or more reaction gases to form a metal-containing
layer onto a substrate. It will be readily apparent to one skilled
in the art that the vapor deposition process may be enhanced by
employing various related techniques such as plasma assistance,
photo assistance, laser assistance, as well as other
techniques.
[0040] The final layer (preferably, a dielectric layer) formed
preferably has a thickness in the range of about 10 .ANG. to about
500 .ANG.. More preferably, the thickness of the metal-containing
layer is in the range of about 30 .ANG. to about 80 .ANG..
[0041] In most vapor deposition processes, the precursor
compound(s) are typically reacted with an oxidizing or reducing
reaction gas at elevated temperatures to form the refractory
metal-containing layer. However, in the practice of this invention,
no such reaction gas is needed as the ether provides the source of
oxygen needed in the vapor deposition process when reacting with
the refractory metal precursor compound(s) to form the refractory
metal-containing layer.
[0042] Chemical vapor deposition (CVD) has been extensively used
for the preparation of metal-containing layers, such as dielectric
layers, in semiconductor processing because of its ability to
provide highly conformal and high quality dielectric layers at
relatively fast processing times. The desired precursor compounds
are vaporized and then introduced into a deposition chamber
containing a heated substrate with optional reaction gases and/or
inert carrier gases. In a typical CVD process, vaporized precursors
are contacted with reaction gas(es) at the substrate surface to
form a layer (e.g., dielectric layer). The single deposition cycle
is allowed to continue until the desired thickness of the layer is
achieved.
[0043] Typical CVD processes generally employ precursor compounds
in vaporization chambers that are separated from the process
chamber wherein the deposition surface or wafer is located. For
example, liquid precursor compounds are typically placed in
bubblers and heated to a temperature at which they vaporize, and
the vaporized liquid precursor compound is then transported by an
inert carrier gas passing over the bubbler or through the liquid
precursor compound. The vapors are then swept through a gas line to
the deposition chamber for depositing a layer on substrate
surface(s) therein. Many techniques have been developed to
precisely control this process. For example, the amount of
precursor material transported to the deposition chamber can be
precisely controlled by the temperature of the reservoir containing
the precursor compounds and by the flow of an inert carrier gas
bubbled through or passed over the reservoir.
[0044] Preferred embodiments of the precursor compounds described
herein are particularly suitable for chemical vapor deposition
(CVD). The deposition temperature at the substrate surface is
preferably held at a temperature in a range of about 100.degree. C.
to about 600.degree. C., more preferably in the range of about
200.degree. C. to about 500.degree. C. The deposition chamber
pressure is preferably maintained at a deposition pressure of about
0.1 torr to about 10 torr. The partial pressure of precursor
compounds in the inert carrier gas is preferably about 0.001 torr
to about 10 torr.
[0045] Several modifications of the CVD process and chambers are
possible, for example, using atmospheric pressure chemical vapor
deposition, low pressure chemical vapor deposition (LPCVD), plasma
enhanced chemical vapor deposition (PECVD), hot wall or cold wall
reactors or any other chemical vapor deposition technique.
Furthermore, pulsed CVD can be used, which is similar to ALD
(discussed in greater detail below) but does not rigorously avoid
intermixing of percursor and reactant gas streams. Also, for pulsed
CVD, the deposition thickness is dependent on the exposure time, as
opposed to ALD, which is self-limiting (discussed in greater detail
below).
[0046] A typical CVD process may be carried out in a chemical vapor
deposition reactor, such as a deposition chamber available under
the trade designation of 7000 from Genus, Inc. (Sunnyvale, Calif.),
a deposition chamber available under the trade designation of 5000
from Applied Materials, Inc. (Santa Clara, Calif.), or a deposition
chamber available under the trade designation of Prism from
Novelus, Inc. (San Jose, Calif.). However, any deposition chamber
suitable for performing CVD may be used.
[0047] Alternatively, and preferably, the vapor deposition process
employed in the methods of the present invention is a multi-cycle
ALD process. Such a process is advantageous (particularly over a
CVD process) in that in provides for optimum control of
atomic-level thickness and uniformity to the deposited layer (e.g.,
dielectric layer) and to expose the metal precursor compounds to
lower volatilization and reaction temperatures to minimize
degradation. Typically, in an ALD process, each reactant is pulsed
sequentially onto a suitable substrate, typically at deposition
temperatures of about 25.degree. C. to about 400.degree. C.
(preferably about 150.degree. C. to about 300.degree. C.), which is
generally lower than presently used in CVD processes. Under such
conditions the film growth is typically self-limiting (i.e., when
the reactive sites on a surface are used up in an ALD process, the
deposition generally stops), insuring not only excellent
conformality but also good large area uniformity plus simple and
accurate thickness control. Due to alternate dosing of the
precursor compounds and/or reaction gases, detrimental vapor-phase
reactions are inherently eliminated, in contrast to the CVD process
that is carried out by continuous coreaction of the precursors
and/or reaction gases. (See Vehkamaki et al, "Growth of SrTiO.sub.3
and BaTiO.sub.3 Thin Films by Atomic Layer Deposition,"
Electrochemical and Solid-State Letters, 2(10):504-506 (1999)).
[0048] A typical ALD process includes exposing an initial substrate
to a first chemical species (e.g., refractory metal precursor
compound of the formula MY.sub.n) to accomplish chemisorption of
the species onto the substrate. Theoretically, the chemisorption
forms a monolayer that is uniformly one atom or molecule thick on
the entire exposed initial substrate. In other words, a saturated
monolayer. Practically, chemisorption might not occur on all
portions of the substrate. Nevertheless, such an imperfect
monolayer is still a monolayer in the context of the present
invention. In many applications, merely a substantially saturated
monolayer may be suitable. A substantially saturated monolayer is
one that will still yield a deposited layer exhibiting the quality
and/or properties desired for such layer.
[0049] The first species is purged from over the substrate and a
second chemical species (e.g., a different compound of the formula
MY.sub.n, a metal-containing precursor compound or a formula
different than MY.sub.n, or an ether compound) is provided to react
with the first monolayer of the first species. The second species
is then purged and the steps are repeated with exposure of the
second species monolayer to the first species. In some cases, the
two monolayers may be of the same species. As an option, the second
species can react with the first species, but not chemisorb
additional material thereto. That is, the second species can cleave
some portion of the chemisorbed first species, altering such
monolayer without forming another monolayer thereon. Also, a third
species or more may be successively chemisorbed (or reacted) and
purged just as described for the first and second species.
[0050] Purging may involve a variety of techniques including, but
not limited to, contacting the substrate and/or monolayer with a
carrier gas and/or lowering pressure to below the deposition
pressure to reduce the concentration of a species contacting the
substrate and/or chemisorbed species. Examples of carrier gases
include N.sub.2, Ar, He, etc. Purging may instead include
contacting the substrate and/or monolayer with any substance that
allows chemisorption by-products to desorb and reduces the
concentration of a contacting species preparatory to introducing
another species. The contacting species may be reduced to some
suitable concentration or partial pressure known to those skilled
in the art based on the specifications for the product of a
particular deposition process.
[0051] ALD is often described as a self-limiting process, in that a
finite number of sites exist on a substrate to which the first
species may form chemical bonds. The second species might only bond
to the first species and thus may also be self-limiting. Once all
of the finite number of sites on a substrate are bonded with a
first species, the first species will often not bond to other of
the first species already bonded with the substrate. However,
process conditions can be varied in ALD to promote such bonding and
render ALD not self-limiting. Accordingly, ALD may also encompass a
species forming other than one monolayer at a time by stacking of a
species, forming a layer more than one atom or molecule thick.
[0052] The described method indicates the "substantial absence" of
the second precursor (i.e., second species) during chemisorption of
the first precursor since insignificant amounts of the second
precursor might be present. According to the knowledge and the
preferences of those with ordinary skill in the art, a
determination can be made as to the tolerable amount of second
precursor and process conditions selected to achieve the
substantial absence of the second precursor.
[0053] Thus, during the ALD process, numerous consecutive
deposition cycles are conducted in the deposition chamber, each
cycle depositing a very thin metal-containing layer (usually less
than one monolayer such that the growth rate on average is from
about 0.2 to about 3.0 Angstroms per cycle), until a layer of the
desired thickness is built up on the substrate of interest. The
layer deposition is accomplished by alternately introducing (i.e.,
by pulsing) refractory metal precursor compound(s) and ether
compound(s) into the deposition chamber containing a semiconductor
substrate, chemisorbing the precursor compound(s) as a monolayer
onto the substrate surfaces, and then reacting the chemisorbed
precursor compound(s) with the other co-reactive precursor
compound(s). The pulse duration of precursor compound(s) and inert
carrier gas(es) is sufficient to saturate the substrate surface.
Typically, the pulse duration is from about 0.1 to about 5 seconds,
preferably from about 0.2 to about 1 second.
[0054] In comparison to the predominantly thermally driven CVD, ALD
is predominantly chemically driven. Accordingly, ALD is often
conducted at much lower temperatures than CVD. During the ALD
process, the substrate temperature is maintained at a temperature
sufficiently low to maintain intact bonds between the cherisorbed
precursor compound(s) and the underlying substrate surface and to
prevent decomposition of the precursor compound(s). The temperature
is also sufficiently high to avoid condensation of the precursor
compounds(s). Typically the substrate temperature is kept within
the range of about 25.degree. C. to about 400.degree. C.
(preferably about 150.degree. C. to about 300.degree. C.), which is
generally lower than presently used in CVD processes. Thus, the
first species or precursor compound is chemisorbed at this
temperature. Surface reaction of the second species or precursor
compound can occur at substantially the same temperature as
chemisorption of the first precursor or, less preferably, at a
substantially different temperature. Clearly, some small variation
in temperature, as judged by those of ordinary skill, can occur but
still be a substantially same temperature by providing a reaction
rate statistically the same as would occur at the temperature of
the first precursor chemisorption. Chemisorption and subsequent
reactions could instead occur at exactly the same temperature.
[0055] For a typical ALD process, the pressure inside the
deposition chamber is kept at about 10.sup.-4 torr to about 1 torr,
preferably about 10.sup.-4 torr to about 0.1 torr. Typically, the
deposition chamber is purged with an inert carrier gas after the
vaporized precursor compound(s) have been introduced into the
chamber and/or reacted for each cycle. The inert carrier gas(es)
can also be introduced with the vaporized precursor compound(s)
during each cycle.
[0056] The reactivity of a precursor compound can significantly
influence the process parameters in ALD. Under typical CVD process
conditions, a highly reactive compound may react in the gas phase
generating particulates, depositing prematurely on undesired
surfaces, producing poor films, and/or yielding poor step coverage
or otherwise yielding non-uniform deposition. For at least such
reason, a highly reactive compound might be considered not suitable
for CVD. However, some compounds not suitable for CVD are superior
ALD precursors. For example, if the first precursor is gas phase
reactive with the second precursor, such a combination of compounds
might not be suitable for CVD, although they could be used in ALD.
In the CVD context, concern might also exist regarding sticking
coefficients and surface mobility, as known to those skilled in the
art, when using highly gas-phase reactive precursors, however,
little or no such concern would exist in the ALD context.
[0057] After layer formation on the substrate, an annealing process
can be optionally performed in situ in the deposition chamber in a
nitrogen atmosphere or oxidizing atmosphere. Preferably, the
annealing temperature is within the range of about 400.degree. C.
to about 1000.degree. C. Particularly after ALD, the annealing
temperature is more preferably about 400.degree. C. to about
750.degree. C., and most preferably about 600.degree. C. to about
700.degree. C. The annealing operation is preferably performed for
a time period of about 0.5 minute to about 60 minutes and more
preferably for a time period of about 1 minute to about 10 minutes.
One skilled in the art will recognize that such temperatures and
time periods may vary. For example, furnace anneals and rapid
thermal annealing may be used, and further, such anneals may be
performed in one or more annealing steps.
[0058] As stated above, the use of the complexes and methods of
forming films of the present invention are beneficial for a wide
variety of thin film applications in semiconductor structures,
particularly those using high dielectric materials or ferroelectric
materials. For example, such applications include capacitors such
as planar cells, trench cells (e.g., double sidewall trench
capacitors), stacked cells (e.g., crown, V-cell, delta cell,
multi-fingered, or cylindrical container stacked capacitors), as
well as field effect transistor devices.
[0059] A specific example of where a dielectric layer is formed
according to the present invention is a capacitor construction.
Exemplary capacitor constructions are described with reference to
FIGS. 1-3. Referring to FIG. 1, a semiconductor wafer fragment 10
includes a capacitor construction 25 formed by a method of the
present invention. Wafer fragment 10 includes a substrate 12 having
a conductive diffusion area 14 formed therein. Substrate 12 can
include, for example, monocrystalline silicon. An insulating layer
16, typically borophosphosilicate glass (BPSG), is provided over
substrate 12, with a contact opening 18 provided therein to
diffusion area 14. A conductive material 20 fills contact opening
18, with material 20 and oxide layer 18 having been planarized as
shown. Material 20 might be any suitable conductive material, such
as, for example, tungsten or conductively doped polysilicon.
Capacitor construction 25 is provided atop layer 16 and plug 20,
and electrically connected to node 14 through plug 20.
[0060] Capacitor construction 25 includes a first capacitor
electrode 26, which has been provided and patterned over node 20.
Examplary materials include conductively doped polysilicon, Pt, Ir,
Rh, Ru, RuO.sub.2, IrO.sub.2, RhO.sub.2. A capacitor dielectric
layer 28 is provided over first capacitor electrode 26. The
materials of the present invention can be used to form the
capacitor dielectric layer 28. Preferably, if first capacitor
electrode 26 includes polysilicon, a surface of the polysilicon is
cleaned by an in situ HF dip prior to deposition of the dielectric
material. An exemplary thickness for layer 28 in accordance with
256 Mb integration is 100 Angstroms.
[0061] A diffusion barrier layer 30 is provided over dielectric
layer 28. Diffusion barrier layer 30 includes conductive materials
such as TiN, TaN, metal silicide, or metal silicide-nitride, and
can be provided by CVD, for example, using conditions well known to
those of skill in the art. After formation of barrier layer 30, a
second capacitor electrode 32 is formed over barrier layer 30 to
complete construction of capacitor 25. Second capacitor electrode
32 can include constructions similar to those discussed above
regarding the first capacitor electrode 26, and can accordingly
include, for example, conductively doped polysilicon. Diffusion
barrier layer 30 preferably prevents components (e.g., oxygen) from
diffusing from dielectric material 28 into electrode 32. If, for
example, oxygen diffuses into a silicon-containing electrode 32, it
can undesirably form SiO.sub.2, which will significantly reduce the
capacitance of capacitor 25. Diffusion barrier layer 30 can also
prevent diffusion of silicon from metal electrode 32 to dielectric
layer 28.
[0062] FIG. 2 illustrates an alternative embodiment of a capacitor
construction. Like numerals from FIG. 1 have been utilized where
appropriate, with differences indicated by the suffix "a". Wafer
fragment 10a includes a capacitor construction 25a differing from
the construction 25 of FIG. 2 in provision of a barrier layer 30a
between first electrode 26 and dielectric layer 28, rather than
between dielectric layer 28 and second capacitor electrode 32.
Barrier layer 30a can include constructions identical to those
discussed above with reference to FIG. 1.
[0063] FIG. 3 illustrates yet another alternative embodiment of a
capacitor construction. Like numerals from FIG. 1 are utilized
where appropriate, with differences being indicated by the suffix
"b" or by different numerals. Wafer fragment 10b includes a
capacitor construction 25b having the first and second capacitor
plate 26 and 32, respectively, of the first described embodiment.
However, wafer fragment 10b differs from wafer fragment 10 of FIG.
2 in that wafer fragment 10b includes a second barrier layer 40 in
addition to the barrier layer 30. Barrier layer 40 is provided
between first capacitor electrode 26 and dielectric layer 28,
whereas barrier layer 30 is between second capacitor electrode 32
and dielectric layer 28. Barrier layer 40 can be formed by methods
identical to those discussed above with reference to FIG. 1 for
formation of the barrier layer 30.
[0064] In the embodiments of FIGS. 1-3, the barrier layers are
shown and described as being distinct layers separate from the
capacitor electrodes. It is to be understood, however, that the
barrier layers can include conductive materials and can
accordingly, in such embodiments, be understood to include at least
a portion of the capacitorr electrodes. In particular embodiments
an entirety of a capacitor electrode can include conductive barrier
layer materials.
[0065] A system that can be used to perform vapor deposition
processes (chemical vapor deposition or atomic layer deposition) of
the present invention is shown in FIG. 4. The system includes an
enclosed vapor deposition chamber 110, in which a vacuum may be
created using turbo pump 112 and backing pump 114. One or more
substrates 116 (e.g., semiconductor substrates or substrate
assemblies) are positioned in chamber 110. A constant nominal
temperature is established for substrate 116, which can vary
depending on the process used. Substrate 116 may be heated, for
example, by an electrical resistance heater 118 on which substrate
116 is mounted. Other known methods of heating the substrate may
also be utilized.
[0066] In this process, precursor compounds 160 (e.g., a refractory
metal precursor compound and an ether) are stored in vessels 162.
The precursor compounds are vaporized and separately fed along
lines 164 and 166 to the deposition chamber 110 using, for example,
an inert carrier gas 168. A reaction gas 170 may be supplied along
line 172 as needed. Also, a purge gas 174, which is often the same
as the inert carrier gas 168, may be supplied along line 176 as
needed. As shown, a series of valves 180-185 are opened and closed
as required.
[0067] The following examples are offered to further illustrate the
various specific and preferred embodiments and techniques. It
should be understood, however, that many variations and
modifications may be made while remaining within the scope of the
present invention, so the scope of the invention is not intended to
be limited by the examples.
EXAMPLES
Example 1
Atomic Layer Deposition of Tantalum Pentoxide
[0068] Using an ALD process, precursor compounds tantalum
pentafluoride, (TaF5), and 1,1,3,3-tetramethyldisiloxane,
(CH.sub.3).sub.2(H)Si--O--Si(H- )(CH.sub.3).sub.2, (both available
from Sigma-Aldrich Chemical Co., Milwaukee, Wis.) were
alternatively pulsed into a deposition chamber containing a
platinum electrode having a surface temperature of about
260.degree. C. After 800 cycles, a Ta.sub.2O.sub.5 layer having a
thickness of 400 .ANG. was achieved, the layer having no silicon or
carbon contamination and a only trace of fluorine contamination (no
more than 2 atom %) as determined by atomic emission spectroscopy
(AES) analysis. X-ray diffraction analysis (XDA) showed the layer
to be mainly amorphous with some (001) oriented hexagonal phase
present, which remained the preferred crystalline orientation after
the layer was annealed at 750.degree. C. in an oxygen
atmosphere.
[0069] A capacitor was formed by using physical vapor deposition to
sputter platinum top electrodes through a hard mask on the
as-deposited Ta.sub.2O.sub.5 layer. Dielectric constants of near 60
were obtained on 0.4 mm.sup.2 capacitors, measured at frequencies
between 0.1 kHz and 100 kHz. Leakage was 6.times.10.sup.-7
A/cm.sup.2. Excellent step coverage was obtained on structured
wafers with containers having a 10:1 aspect ratio.
[0070] The complete disclosures of the patents, patent documents,
and publications cited herein are incorporated by reference in
their entirety as if each were individually incorporated. Various
modifications and alterations to this invention will become
apparent to those skilled in the art without departing from the
scope and spirit of this invention. It should be understood that
this invention is not intended to be unduly limited by the
illustrative embodiments and examples set forth herein and that
such examples and embodiments are presented by way of example only
with the scope of the invention intended to be limited only by the
claims set forth herein as follows.
* * * * *