U.S. patent application number 10/229779 was filed with the patent office on 2005-07-28 for systems and methods for forming zirconium and/or hafnium-containing layers.
This patent application is currently assigned to MICRON TECHNOLOGY, INC.. Invention is credited to Vaartstra, Brian A..
Application Number | 20050160981 10/229779 |
Document ID | / |
Family ID | 31976314 |
Filed Date | 2005-07-28 |
United States Patent
Application |
20050160981 |
Kind Code |
A9 |
Vaartstra, Brian A. |
July 28, 2005 |
Systems and methods for forming zirconium and/or hafnium-containing
layers
Abstract
A method of forming (and apparatus for forming) a zirconium
and/or hafnium-containing layer on a substrate, particularly a
semiconductor substrate or substrate assembly, using a vapor
deposition process and one or more silicon precursor compounds of
the formula Si(OR).sub.4 with one or more zirconium and/or hafnium
precursor compounds of the formula M(NR'R").sub.4, wherein R, R',
and R" are each independently an organic group and M is zirconium
or hafnium.
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
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 0040501 A1 |
March 4, 2004 |
|
|
Family ID: |
31976314 |
Appl. No.: |
10/229779 |
Filed: |
August 28, 2002 |
Current U.S.
Class: |
118/715;
257/E21.279; 438/240; 438/287; 438/785 |
Current CPC
Class: |
H01L 21/31612 20130101;
C23C 16/45531 20130101; C23C 16/56 20130101; H01L 21/3142 20130101;
H01L 21/02214 20130101; H01L 21/02148 20130101; C23C 16/45553
20130101; H01L 21/02337 20130101; H01L 21/31645 20130101; C23C
16/401 20130101; H01L 21/02159 20130101; H01L 21/31641 20130101;
H01L 21/0228 20130101 |
Class at
Publication: |
118/715; 438/785;
438/240; 438/287 |
International
Class: |
H01L 021/44; H01L
021/31; H01L 021/469; H01L 021/8242; C23C 016/00 |
Claims
What is claimed is:
1. A method of manufacturing a semiconductor structure, the method
comprising: providing a semiconductor substrate or substrate
assembly; providing at least one silicon precursor compound having
the formula Si(OR).sub.4 and at least one precursor compound of the
formula M(NR'R").sub.4, wherein R, R', and R" are each
independently an organic group and M is zirconium or hafnium; and
contacting the precursor compounds to form a metal-containing layer
on one or more surfaces of the semiconductor substrate or substrate
assembly using a vapor deposition process.
2. The method of claim 1 wherein the semiconductor substrate or
substrate assembly is a silicon wafer.
3. The method of claim 1 wherein the metal-containing layer
comprises metal silicates, metal oxides, silicon oxides, and
combinations thereof.
4. The method of claim 3 wherein the metal-containing layer
comprises zirconium silicate, hafnium silicate, zirconium-hafnium
silicate, or combinations thereof.
5. The method of claim 3 wherein the metal-containing layer
comprises a solid solution comprising zirconium oxides, hafnium
oxides, and silicon oxides.
6. The method of claim 1 wherein the metal-containing layer has a
thickness of about 30 .ANG. to about 80 .ANG..
7. A method of manufacturing a semiconductor structure, the method
comprising: providing a semiconductor substrate or substrate
assembly within a deposition chamber; providing at least one
silicon precursor compound having the formula Si(OR).sub.4 and at
least one precursor compound of the formula M(NR'R").sub.4, wherein
R, R', and R" are each independently an organic group and M is
zirconium or hafnium; vaporizing the precursor compounds to form
vaporized precursor compounds; and directing the vaporized
precursor compounds to the semiconductor substrate or substrate
assembly to form a metal-containing dielectric layer on one or more
surfaces of the semiconductor substrate or substrate assembly.
8. The method of claim 7 wherein the precursor compounds are
vaporized in the presence of an inert carrier gas.
9. The method of claim 7 wherein the metal-containing dielectric
layer comprises metal silicates, metal oxides, silicon oxides, and
combinations thereof.
10. The method of claim 9 wherein the metal-containing dielectric
layer comprises zirconium silicate, hafnium silicate,
zirconium-hafnium silicate, or combinations thereof.
11. The method of claim 10 wherein the metal-containing dielectric
layer comprises a solid solution comprising zirconium oxides,
hafnium oxides, and silicon oxides.
12. The method of claim 7 wherein vaporizing and directing the
precursor compounds is accomplished using a chemical vapor
deposition process.
13. The method of claim 12 wherein the temperature of the
semiconductor substrate or substrate assembly is about 100.degree.
C. to about 600.degree. C.
14. The method of claim 12 wherein the semiconductor substrate or
substrate assembly is in a deposition chamber having a pressure of
about 0.1 torr to about 10 torr.
15. The method of claim 7 wherein vaporizing and directing the
precursor compounds is accomplished using an atomic layer
deposition process comprising a plurality of deposition cycles.
16. The method of claim 15 wherein during the atomic layer
deposition process the metal-containing layer is formed by
alternately introducing the precursor compounds during each
deposition cycle.
17. The method of claim 15 wherein the temperature of the
semiconductor substrate or substrate assembly is about 25.degree.
C. to about 400.degree. C.
18. The method of claim 15 wherein the semiconductor substrate or
substrate assembly is in a deposition chamber having a pressure of
about 10.sup.-4 torr to about 1 torr.
19. The method of claim 15 further comprising a step of annealing
the formed metal-containing layer at a temperature of about
400.degree. C. to about 750.degree. C.
20. A method of forming a metal-containing layer on a substrate,
the method comprising: providing a substrate; providing at least
one silicon precursor compound having the formula Si(OR).sub.4 and
at least one precursor compound of the formula M(NR'R").sub.4,
wherein R, R', and R" are each independently an organic group and M
is zirconium or hafnium; and contacting the precursor compounds to
form a metal-containing layer on the substrate using a vapor
deposition process.
21. The method of claim 20 wherein the metal-containing layer
comprises metal silicates, metal oxides, silicon oxides, and
combinations thereof.
22. The method of claim 20 wherein R, R', and R" are each
independently a (C1-C8)alkyl moiety.
23. The method of claim 22 wherein R is selected from the group
consisting of methyl, ethyl, n-propyl, isopropyl, and butyl, and R'
and R" are each independently selected from the group consisting of
methyl and ethyl.
24. The method of claim 23 wherein the silicon precursor compound
is tetraisopropoxysilane or tetraethoxysilane.
25. A method of forming a metal-containing layer on a substrate,
the method comprising: providing a substrate; providing at least
one silicon precursor compound having the formula Si(OR).sub.4 and
at least one precursor compound of the formula M(NR'R").sub.4,
wherein R, R', and R" are each independently an organic group and M
is zirconium or hafnium; and vaporizing the precursor compounds to
form vaporized precursor compounds; and directing the vaporized
precursor compounds to the substrate to form a metal-containing
layer on the substrate.
26. The method of claim 25 wherein vaporizing and directing the
precursor compounds is accomplished using a chemical vapor
deposition process.
27. The method of claim 25 wherein vaporizing and directing the
precursor compounds is accomplished using an atomic layer
deposition process comprising a plurality of deposition cycles.
28. A method of manufacturing a memory device structure, the method
comprising: providing a substrate having a first electrode thereon;
providing at least one silicon precursor compound having the
formula Si(OR).sub.4 and at least one precursor compound of the
formula M(NR'R").sub.4, wherein R, R', and R" are each
independently an organic group and M is zirconium or hafnium;
vaporizing the precursor compounds to form vaporized precursor
compounds; directing the vaporized precursor compounds to the
substrate to form a dielectric layer on the first electrode of the
substrate; and forming a second electrode on the dielectric
layer.
29. The method of claim 28 wherein the dielectric forms a capacitor
layer.
30. The method of claim 28 wherein the dielectric forms a gate.
31. The method of claim 28 wherein the precursor compounds comprise
at least one compound of the formula Hf(NR'R").sub.4 and at least
one compound of the formula Zr(NR'R").sub.4, wherein R, R', and R"
are each independently an organic group.
32. The method of claim 31 wherein vaporizing and directing the
precursor compounds is accomplished using a chemical vapor
deposition process.
33. The method of claim 31 wherein vaporizing and directing the
precursor compounds is accomplished using an atomic layer
deposition process comprising a plurality of deposition cycles.
34. A vapor deposition apparatus comprising: a vapor deposition
chamber having a substrate positioned therein; one or more vessels
comprising one or more silicon precursor compounds having the
formula Si(OR).sub.4; and one or more vessels comprising one or
more one precursor compounds of the formula M(NR'R").sub.4, wherein
R, R', and R" are each independently an organic group and M is
zirconium or hafnium.
35. The apparatus of claim 34 wherein the substrate is a silicon
wafer.
36. The apparatus of claim 34 further comprising one or more
sources of an inert carrier gas for transferring the precursors to
the vapor deposition chamber.
Description
FIELD OF THE INVENTION
[0001] This invention relates to methods of forming a layer on a
substrate using one or more silicon precursor compounds and one or
more zirconium and/or hafnium precursor compounds during a vapor
deposition process. The precursor compounds and methods are
particularly suitable for the formation of a metal silicate
dielectric layer, particularly a zirconium and/or hafnium silicate
dielectric layer, onto a semiconductor substrate or substrate
assembly.
BACKGROUND OF THE INVENTION
[0002] Capacitors are the basic energy storage devices in random
access memory devices, such as dynamic random access memory (DRAM)
devices and static random access memory (SRAM) devices. They
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 dielectric material.
[0003] The continuous shrinkage of microelectronic devices such as
capacitors and gates 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 with silicon to construct microelectronic
devices. However, when the SiO.sub.2 layer is thinned to 1 nm
(i.e., a thickness of only 4 or 5 molecules), as is desired in the
newest micro devices, the layer no longer effectively performs as
an insulator due to the tunneling current running through it.
[0004] Thus, new high dielectric constant materials are needed to
extend device performance. Such materials need to demonstrate high
permittivity, barrier height to prevent tunneling, stability in
direct contact with silicon, and good interface quality and film
morphology. Furthermore, such materials must be compatible with the
gate material, semiconductor processing temperatures, and operating
conditions.
[0005] High quality dielectric materials based on ZrO.sub.2 and
HfO.sub.2 have high dielectric constants, so are being investigated
as replacements in memories for SiO.sub.2 where very thin layers
are required. These high crystalline multivalent metal oxide layers
are thermodynamically stable in the presence of silicon, minimizing
silicon oxidation upon thermal annealing, and appear to be
compatible with metal gate electrodes.
[0006] This discovery has led to an effort to investigate various
deposition processes to form layers, especially dielectric layers,
based on zirconium and hafnium silicates. Such deposition processes
have included vapor deposition, metal thermal oxidation, and high
vacuum sputtering. Vapor deposition processes, which includes
chemical vapor deposition (CVD) and atomic layer deposition (ALD),
are very appealing as they provide for excellent control of
dielectric uniformity and thickness on a substrate. But vapor
deposition processes typically involve the co-reaction of reactive
metal precursor compounds with an oxygen source such as oxygen or
water, either of which can cause formation of an undesirable
SiO.sub.2 interfacial layer. Thus, an effort is underway to develop
water- and oxygen-free vapor deposition processes.
[0007] Ritala et al., "Atomic Layer Deposition of Oxide Thin Films
with Metal Alkoxides as Oxygen Sources," SCIENCE, 288:319-321
(2000) describe a chemical approach to ALD of thin oxide films. In
this approach, a metal alkoxide, serving as both a metal source and
an oxygen source, reacts with another metal compound such as a
metal chloride or metal alkyl to deposit a metal oxide on silicon
without creating an interfacial silicon oxide layer. However,
undesirable chlorine residues can also be formed. Furthermore,
zirconium and hafnium alkyls are generally unstable and not
commercially available. They would also likely leave carbon in the
resultant films.
[0008] Despite these continual improvements in semiconductor
dielectric layers, there remains a need for a vapor deposition
process utilizing sufficiently volatile metal precursor compounds
that can form a thin, high quality zirconium silicate and/or
hafnium silicate (or SiO.sub.2 stabilized zirconium oxide and/or
hafnium oxide) layer, particularly on a semiconductor substrate
using a vapor deposition process.
SUMMARY OF THE INVENTION
[0009] This invention provides methods of vapor depositing a
metal-containing layer on a substrate. These vapor deposition
methods involve forming the layer by combining one or more
zirconium and/or hafnium diorganoamide (e.g., dialkylamide)
precursor compounds with one or more tetraorganooxysilane (e.g.,
tetraalkoxysilane) precursor compounds. Significantly, the methods
of the present invention do not require the use of water or a
strong oxidizer, thus reducing (and typically avoiding) the problem
of producing an undesirable interfacial oxide layer between the
desired metal-containing layer and the substrate. Typically and
preferably, the layer is a dielectric layer that is primarily
composed of zirconium silicate, hafnium silicate, zirconium-hafnium
silicate, or related SiO.sub.2-stabilized zirconium oxide and/or
SiO.sub.2-stabilized hafnium oxide.
[0010] The methods of the present invention involve forming a
metal-containing layer on a substrate. Such methods include:
providing a substrate (preferably a semiconductor substrate or
substrate assembly such as a silicon wafer); providing at least one
silicon precursor compound having the formula Si(OR).sub.4 and at
least one precursor compound of the formula M(NR'R").sub.4, wherein
R, R', and R" are each independently an organic group and M is
zirconium or hafnium; and contacting the precursor compounds to
form a metal-containing layer (preferably a dielectric layer) on
one or more surfaces of the substrate using a vapor deposition
process.
[0011] Preferably, a method of the present invention involves:
providing a substrate (preferably a semiconductor substrate or
substrate assembly such as a silicon wafer) within a deposition
chamber; providing at least one silicon precursor compound having
the formula Si(OR).sub.4 and at least one precursor compound of the
formula M(NR'R").sub.4, wherein R, R', and R" are each
independently an organic group and M is zirconium or hafnium;
vaporizing the precursor compounds to form vaporized precursor
compounds; and directing the vaporized precursor compounds toward
the substrate to form a metal-containing layer (preferably a
dielectric layer) on one or more surfaces of the substrate.
[0012] Another preferred method involves manufacturing a memory
device structure, wherein the method includes: providing a
substrate (preferably a semiconductor substrate or substrate
assembly such as a silicon wafer) having a first electrode thereon;
providing at least one silicon precursor compound having the
formula Si(OR).sub.4 and at least one precursor compound of the
formula M(NR'R").sub.4, wherein R, R', and R" are each
independently an organic group and M is zirconium or hafnium;
vaporizing the precursor compounds to form vaporized precursor
compounds; directing the vaporized precursor compounds to the
substrate to form a layer (preferably a dielectric layer) on the
first electrode of the substrate; and forming a second electrode on
the dielectric layer. Preferably, the dielectric forms a capacitor
layer, although a gate is also possible.
[0013] 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 precursor
compounds can be alternately introduced into a deposition chamber
during each deposition cycle.
[0014] For certain embodiments, the metal-containing layer can
include metal silicates (e.g., zirconium silicate, hafnium
silicate, zirconium-hafnium silicate), metal oxides, silicon
oxides, and combinations thereof. For certain embodiments, the
metal-containing layer can include a solid solution that includes,
for example, zirconium oxide, hafnium oxide, and silicon
oxides.
[0015] The present invention also provides a vapor deposition
apparatus that includes: a vapor deposition chamber having a
substrate positioned therein; one or more vessels comprising one or
more silicon precursor compounds having the formula Si(OR).sub.4;
and one or more vessels comprising one or more one precursor
compounds of the formula M(NR'R").sub.4, wherein R, R', and R" are
each independently an organic group and M is zirconium or
hafnium.
[0016] "Semiconductor substrate" or "substrate assembly" as used
herein refers to a semiconductor substrate such as a 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.
[0017] "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.
[0018] "Dielectric layer" as used herein refers to a layer (or
film) having a high dielectric constant containing primarily
zirconium silicate and/or hafnium silicate (or SiO.sub.2 stabilized
zirconium oxide and/or hafnium oxide). Zirconium and hafnium
silicates can be depicted by the simple condensed formulas
ZrSiO.sub.4 and HfSiO.sub.4, respectively, but for this invention
the terms "zirconium silicate" and "hafnium silicate" are meant to
also include other stoichiometric reaction products of SiO.sub.2,
ZrO.sub.2 and HfO.sub.2 having the general formulas
Zr.sub.aSi.sub.bO.sub.c and Hf.sub.aSi.sub.bO.sub.c, respectively,
wherein c=2 (a+b), which is meant to also include SiO.sub.2
stabilized zirconium oxide and/or hafnium oxide. Metal-containing
layers containing mixed zirconium/hafnium silicates of the general
formula Zr.sub.aHf.sub.bSi.sub.cO.sub.d, wherein d=2 (a+b+c), are
also contemplated to be included within the scope of this
invention.
[0019] "Precursor compound" as used herein refers to a zirconium,
hafnium, or silicon compound, for example, capable of forming,
either alone or with other precursor compounds, a metal-containing
layer on a substrate in a vapor deposition process. The zirconium,
hafnium, and silicon precursor compounds are all preferably liquid
at the vaporization temperature, and more preferably at room
temperature. Preferably, the precursor compounds are organometallic
compounds that form volatile by-products upon reacting.
[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), molecular beam epitaxy (MBE), gas source MBE,
organometallic MBE, and chemical beam epitaxy when performed with
alternating pulses of precursor compound(s), reaction gas(es), 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 (e.g., >30 kcal/mol),
comparable in strength to ordinary chemical bonds. The chemisorbed
species typically form a mononolayer 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 chemisorption. In ALD one or more appropriate precursor
compounds or reaction gases are alternately introduced (e.g.,
pulsed) into a deposition chamber and chemisorbed onto the surfaces
of a substrate. Each sequential introduction of a reactive compound
(e.g., one or more precursor compounds and one or more reaction
gases) 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
that ALD can alternately utilize one precursor compound, which is
chemisorbed, and one reaction gas, which reacts with the
chemisorbed species.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a cross-sectional view of a transistor made
according to the present invention.
[0025] FIG. 2 is a perspective view of a vapor deposition coating
system suitable for use in the method of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0026] The present invention provides methods of forming a layer
(preferably a zirconium and/or hafnium silicate layer) on a
substrate (preferably a semiconductor substrate or substrate
assembly) using one or more silicon precursor compounds of the
formula Si(OR).sub.4 and one or more zirconium and/or hafnium
precursor compounds of the formula M(NR'R").sub.4, wherein R, R',
and R" are each independently an organic group and M is zirconium
or hafnium.
[0027] The layers or films formed can be in the form of
metal-containing films, which is used herein to refer to zirconium
silicate, hafnium silicate, or zirconium-hafnium silicate, as well
as solid solutions of oxides of zirconium, hafnium, and silicon
(e.g., SiO.sub.2 stabilized zirconium oxide and/or hafnium oxide).
Various combinations of silicates and oxides arc also possible.
[0028] 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.
[0029] 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.
[0030] The precursor compounds useful in this invention are of the
formulas Si(OR).sub.4 and M(NR'R").sub.4, wherein R, R', and R" is
each independently an organic group and M is zirconium or
hafnium.
[0031] 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, 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.).
[0032] 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 0, 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.
[0033] For all the precursor compounds of this invention, R is an
organic group (preferably, an organic moiety), preferably a
(C1-C10)alkyl group (preferably, an alkyl moiety), more preferably
a (C1-C8)alkyl group (preferably, an alkyl moiety), even more
preferably a (C1-C6)alkyl group (preferably, an alkyl moiety), and
most preferably a "lower" (i.e., C1-C4) alkyl group (preferably, an
alkyl moiety).
[0034] For the silicon precursor compounds of this invention having
the formula Si(OR).sub.4, R is preferably a (C1-C8)alkyl group
(preferably, an alkyl moiety), more preferably a (C1-C6)alkyl group
(preferably, an alkyl moiety), and most preferably a "lower" (i.e.,
C1-C4) alkyl group (preferably, an alkyl moiety--methyl, ethyl,
n-propyl, isopropyl, or butyl). Preferably, all of the R groups are
the same. A compound represented by the formula Si(OR).sub.4 has
two commonly used equivalent names: either tetraorganoxysilane
(e.g., tetraalkoxysilane) or tetraorgano orthosilicate (e.g.,
tetraalkyl orthosilicate). Examples of suitable silicon precursor
compounds include tetramethyl orthosilicate, tetraethyl
orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate,
tetrakis(2-butoxyethyl) orthosilicate, and tetraallyl
orthosilicate, all available from Sigma-Aldrich Chemical Co.,
Milwaukee, Wis.
[0035] The silicon precursor compounds can also be prepared by
reacting one mole of tetrachlorosilane with four moles of the
alcohol needed to provide the desired R groups. For example,
tetraisopropoxysilane, a preferred silicon precursor compound, can
be prepared by reacting tetrachlorosilane with isopropyl alcohol
followed by distillation of the crude reaction product. Preferably,
the silicon precursor compound is tetraisopropoxysilane or
tetraethoxysilane.
[0036] For the zirconium precursor compounds of the formula
Zr(NR'R").sub.4, R' and R" are preferably both methyl, both ethyl,
or one each of methyl and ethyl. Examples of suitable zirconium
precursor compounds include tetrakis(dimethylamino) zirconium,
tetrakis(diethylamino) zirconium and tetrakis(ethylmethylamino)
zirconium, all available from Sigma-Aldrich Chemical Co.
[0037] For the hafnium precursor compounds of the formula
Hf(NR'R").sub.4, R', and R" are preferably both methyl, both ethyl,
or one each of methyl and ethyl. Examples of suitable hafnium
precursor compounds include tetrakis(dimethylamino) hafnium and
tetrakis(ethylmethylamino) hafnium, the latter available from
Sigma-Aldrich Chemical Co.
[0038] The zirconium and hafnium dialkylamide compounds offer the
advantages (compared to other zirconium and hafnium precursor
compounds) of high reactivity with surface groups, high volatility,
volatile by-products, and optimized reactivity with
tetraalkoxysilanes, for example.
[0039] The zirconium and hafnium dialkylamide compounds can be
prepared using standard techniques. For example, zirconium and
hafnium chlorides can be reacted with lithium dialkylamides.
Alternatively, such compounds are commercially available. For
example, tetrakis(dimethylamino) zirconium and
tetrakis(dimentylamino)hafnium are available from Strem Chemical
Co.
[0040] 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.
[0041] 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, nitrites, 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.
[0042] For this invention, preferably no reaction gas is employed
to minimize oxidation of the substrate (typically silicon) to its
oxide (typically silicon dioxide); instead, the orthosilicate
precursor compound provides the source of both the oxygen and the
silicon to form the desired metal silicate layer.
[0043] 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 combinations thereof. In the context of the
present invention, an inert carrier gas is one that does not
interfere with the formation of the metal-containing layer. Whether
done in the presence of a inert carrier gas or not, the
vaporization is preferably done in the absence of oxygen to avoid
oxygen contamination of the layer (e.g., oxidation of silicon to
form silicon dioxide).
[0044] 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.
[0045] The final layer (preferably, a dielectric layer) formed
preferably has a thickness in the range of about 10 A 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..
[0046] In most vapor deposition processes, the precursor
compound(s) are typically reacted with an oxidizing or reducing
reaction gas (e.g., water vapor, oxygen or ammonia) at elevated
temperatures to form the metal-containing layer. However, in the
practice of this invention, no such reaction gas is needed as the
silicon precursor compound(s) provide the source of oxygen needed
in the vapor deposition process when reacting with the zirconium
and/or hafnium precursor compound(s) to form the zirconium and/or
hafnium silicate layer (i.e., no oxidizing or hydrolyzing
coreactant is needed). However, oxidizing gases, such as O.sub.2,
O.sub.3, H.sub.2O, and H.sub.2O.sub.2, can be used if desired.
[0047] 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.
[0048] 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 compound and by the flow of an inert carrier gas
bubbled through or passed over the reservoir.
[0049] 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.
[0050] 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).
[0051] 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.
[0052] 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)).
[0053] A typical ALD process includes exposing an initial substrate
to a first chemical species (e.g., a silicon precursor compound) 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.
[0054] The first species is purged from over the substrate and a
second chemical species (e.g., a different silicon precursor
compound or a zirconium or hafnium precursor 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 chemi sorbed 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.
Optionally, the second species (or third or subsequent) can include
at least one reaction gas if desired.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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) silicon precursor compound(s) and zirconium/hafnium
precursor compound(s) (i.e., tetraalkoxysilane(s) or
zirconium/hafnium dialkylamide(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.
[0059] 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 chemisorbed
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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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. 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.
[0064] A specific example of where a metal-containing layer formed
according to the present invention would be useful is as a gate
dielectric with either silicon-based gates or novel metal gates.
Referring now to FIG. 1, a patterned gate structure 66 is shown
over substrate 50 and gate dielectric 54. This includes a gate
polysilicon film 56, a barrier film 58 (e.g., nitrogen-doped
polysilicon), a metallic layer 60, insulating cap 62 (e.g., silicon
dioxide or silicon nitride), and sidewall spacers 68 (e.g., silicon
dioxide or silicon nitride).
[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. 2. 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 in this process, precursor compounds 160 (e.g., a
silicon precursor compound) 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.
[0066] 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. Unless specified otherwise, all
percentages shown in the examples are percentages by weight.
EXAMPLES
Example 1
Synthesis of Tetraisopropoxysilane,
Si[OCH(CH.sub.3).sub.2].sub.4
[0067] A dry argon-purged flask equipped with stirrer and
thermometer was charged with 100 mL of anhydrous isopropyl alcohol
(having a water content of 230 ppm as determined by Karl Fischer
Analysis). Then 25 mL of silicon tetrachloride (available from
Sigma-Aldrich Co., Milwaukee, Wis.) was added slowly to the alcohol
at ambient temperature over a 25 minute period by syringe. During
the reaction the contents of the flask formed an emulsion and
exothermed to 35.degree. C.
[0068] After standing at ambient conditions for 24 hours, the
contents of the flask had formed two layers. The lower layer along
with some of the upper layer were transferred to a flask connected
to a one-piece distillation apparatus. The isopropyl alcohol was
removed from the reaction mixture by distilling at 78.degree. C.
and atmospheric pressure using an argon purge. During the
distillation, by-product hydrogen chloride gas was vented from the
system. Following alcohol and HCl removal, the crude reaction
product was distilled at 166.degree. C. without the argon purge to
recover the purified reaction product,
Si[OCH(CH.sub.3).sub.2].sub.4, whose purity and identification was
verified using GCMS analysis.
Example 2
Atomic Layer Deposition of (Hf,Si)O.sub.2
[0069] Using an ALD process, precursor compounds hafnium
dimethylamide, Hf(N(CH.sub.3).sub.2]).sub.4 (Strem Chemicals,
Newbury Port, Mass.), and tetraisopropoxysilane,
Si[OCH(CH.sub.3).sub.2].sub.4, were alternately pulsed for 200
cycles into a deposition chamber containing a silicon substrate
with a top layer composed of 1500 Angstroms of p-doped polysilicon.
A 350 .ANG. layer of (Hf,Si)O.sub.2 was deposited, containing 25
atom % Hf, 10 atom % Si and oxygen. X-ray diffraction analysis
(XRD) showed the layer to be amorphous, as measured immediately
after the ALD process was completed and also after a 750.degree.
C./1 minute anneal in oxygen.
[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.
* * * * *